Title of Invention	DEVICE FOR DRIVING AT LEAST ONE ELECTROMAGNETIC LOAD
Abstract	A device for driving at least one electromagnetic load which includes a first switching means device arranged between a first terminal of a supply voltage and a first terminal of at least one load, and a second switching device arranged between a first terminal of an assigned load and the second terminal of the supply voltage. The energy released during the transition from a first higher. current to a second lower current is stored in a storage device.

Title of Invention

DEVICE FOR DRIVING AT LEAST ONE ELECTROMAGNETIC LOAD

Abstract

A device for driving at least one electromagnetic load which includes a first switching means device arranged between a first terminal of a supply voltage and a first terminal of at least one load, and a second switching device arranged between a first terminal of an assigned load and the second terminal of the supply voltage. The energy released during the transition from a first higher. current to a second lower current is stored in a storage device.

Full Text	Device for driving at--l-ea-sfe—one elect roroacmotirG load -pyirog art The invention relates to a device for driving at least one electromagnetic load according to the preambles of the independent claims. Such a device for driving an electromagnetic load is disclosed, for example, in DE-A 44.13 240, which has not been previously published. In the case of this device, the energy released during turn-off is stored in a capacitor. In this case, the energy released during the transition from a holding current to the current 0 is transferred to a capacitor. The energy released during the transition from the energizing current to the holding current is lost in the case of this device• Object of the invention The invention is based on the object, in the case of a device for driving an electromagnetic load, of providing a device having the most simple structure possible, in which the turn-on operation is accelerated and the total energy consumption is minimized. Advantagos-i^f—the- invention The arrangement according to the invention, having the features of the independent claims, has the advantage that it is possible to recover the energy which is released during the transition from the energizing current to the holding current. A particularly advantageous embodiment makes it possible to drive two loads simultaneously in a different manner using the same output stage. That is to say that injection operations which overlap in time are possible. Drawing The device according to the invention is explained below using the embodiments illustrated in the drawing, in which Figure 1 shows a first circuit arrangement of the device according to the invention, Figure 2 shows a second circuit arrangement and Figure 3 shows various signals plotted against time. Description of the exemplary embodiments The device according to the invention is preferably used in internal combustion engines, in particular in self-ignition internal combustion engines. In that case, the metering of fuel is controlled by means of electromagnetic valves. These electromagnetic valves are referred to below as loads. The invention is not restricted to this application, it can be used wherever rapidly switching electromagnetic loads are required. In the case of the application in internal combustion engines, in particular in self-ignition internal combustion engines, the opening and closing times of the electromagnetic valve define the beginning of inj ection and the end of inj ection, respectively, of the fuel into the cylinder. Figure 1 illustrates the most essential elements of the device according to the invention. The embodiment illustrated is concerned with a four-cylinder internal combustion engine. In this case, each load is assigned an injection valve and each injection valve is assigned a cylinder of the internal combustion engine. When the internal combustion engine has higher numbers of cylinders, correspondingly more valves, switching means and diodes are to be provided. 100, 101, 102 and 103 represent four loads. One connection of each of the loads 100 to 103 is connected to a voltage supply 105 via a switching means 115 and a diode 110. The diode 110 is arranged in such a way that its anode is connected to the positive pole and its cathode is connected to the switching means 115. The switching means 115 is preferably a field-effect transistor. The second connection of each of the loads 100 to 103 is connected via a respective second switching means 120, 121, 122 and 123 to a resistor means 125. The switching means 120 to 123 are preferably field-effect transistors, too. The switching means 120 to 123 are referred to as low-side switches and the switching means 115 is referred to as a high-side switch. The second connection of the resistor means 125 is connected to the second connection of the voltage supply. Each load 100 to 103 is assigned a diode 130, 131, 132 and 133. The anode connection of the diodes is in contact with the respective junction point between the load and the low-side switch. The cathode connection is connected to a capacitor 145 and to a further switching means 140. The second connection of the switching means 140 is in contact with the first connections of the loads 100 to 103. The switching means 140 is preferably a field-effect transistor, too. This switching means 140 is also referred to as a booster switch. The second connection of the capacitor 145 is likewise connected to the second connection of the supply voltage 105. A drive signal AH is applied to the high-side switch 115 by a control unit 160. The control unit 160 applies a drive signal AL1 to the switching means 120, a drive signal AL2 to the switching means 121, a drive signal AL3 to the switching means 122, a drive signal AL4 to the switching means 123 and a drive signal AC to the switching means 140. A diode 150 is connected between the second connection of the voltage supply 105 and the junction point between the switching means 115 and the first connections of the loads 100 to 103. In this case, the anode of the diode is connected to the second connection of the voltage supply 105. The current flowing through the load can be determined by means of the resistor 125. Using the arrangement illustrated, current can be measured by means of the current measuring resistor 125 only when one of the switching means 120 to 123 is closed. In order to be able to detect the current when the low-side switches are open, too, the current measuring resistor may also be arranged at a different point. For example, the second connection of the capacitor 145 can be connected to the junction point between the current measuring means 125 and the switching means 120 to 123. In this case, current can also be measured when the low-side switch is in the off state. Furthermore, the current measuring means may be arranged between the voltage supply and the high-side switch or between the high-side switch and the loads. Figure 2 illustrates a corresponding device, in which the loads 100 to 103 are divided into two groups. The loads 100 and 101 form a first group, and the loads 102 and 103 form a second group of loads. The loads are assigned to the individual groups in such a way that loads which must be driven simultaneously under specific operating states are assigned to different groups. Elements which have already been described in Figure 1 are designated in Figure 2 by corresponding reference symbols. A respective high-side switch 115 and 116 is provided for each group. The diode 111 corresponds to the diode 110 of the first group. Correspondingly, the booster transistor 140 likewise has to be designed in a duplicated manner. The booster transistor of the second group is designated by 141. The capacitor 145 in the second group is correspondingly designated by 146. Furthermore, two further drive lines for the switching means 116 and 141 are provided. The signal AH1 is applied to the high-side switch 115 of the first group and AH2 is applied to the high-side switch 116 of the second group. The signal AC1 is applied to the booster switch 140 of the first group and the signal AC2 is applied to the booster switch 141 of the second group. Correspondingly, the resistor 125 also has to be designed in a duplicated manner, and in the second group it is designated by 126. The drive signal AC for the booster transistor 140 and 141 is plotted in Figure 3a. The drive signal AH for the high-side switches 115, 116 is plotted in Figure 3b • Figure 3c shows the drive signal AL of one of the low-side switches. The current I flowing through the load is plotted against time in Figure 3d, and the voltage UC applied to the capacitor 145 is plotted against time in Figure 3e. One metering cycle for an electromagnetic valve is illustrated here. Various phases are distinguished in each metering cycle. In a phase 0, prior to the driving of the load, the output stage is switched off. The drive signals AC, AH and AL are at a low potential. This means that the high-side switch 115, the low-side switches 120 to 123 and the booster switch 140 block the flow of current. No current flows through the loads. The capacitor 145 is charged to its maximum voltage UC. This voltage assumes, for example, a value of approximately 80 volts, whereas the voltage of the voltage supply assumes a value of approximately 12 V. In the first phase, at the beginning of the driving, which is referred to as the booster mode, the low-side switch assigned to the load which is to meter fuel is driven. This means that the signal AL assumes a high level starting at phase 1. At the same time, a high signal which drives the switch 140 is output onto the line AC. The high-side switch 115 is not driven, it continues to be in the off state. This driving of the switching means causes a current to flow from the capacitor 145 via the booster switch 140, the corresponding load, the low-side switch assigned to the load and the current measuring means 125. In this phase, the current I rises very rapidly as a result of the high voltage across the load. Phase 1 ends when the voltage applied to the capacitor 145 falls below a specific value U2. In the second phase, which is referred to as energizing current regulation, the inrush current is received by the high-side switch 115 and the booster is inactivated. In the second phase, the drive signal for the booster switch 140 is withdrawn, so that the switch 140 is in the off state. The drive signals AH and AL for the high-side switch 115 and the low-side switch assigned to the load are set to a high level, in order that these switches enable the flow of current. As a result of this, a current flows from the voltage supply 105 via the diode 110, the high-side switch 115, the load, the corresponding low-side switch, the current measuring resistor 125 back to the voltage source 105. By clocking the high-side switch, the current which is detected by means of the current measuring resistor 125 can be regulated to a predeterminable value for the energizing current IA. That is to say that when the desired current IA for the energizing current is reached, the high-side switch 115 is driven into the off state. When the current falls below a further threshold, the said high-side switch 115 is enabled again. A freewheeling circuit acts when the high-side switch 115 is in the off state. The current flows from the load through the low-side switch, the resistor 125 and the freewheeling diode 150. The second phase ends when the control unit 160 identifies the end of the energizing phase. This may be the case, for example, when a switching instant identification arrangement affirms that the armature of the electromagnetic valve has reached its new end position. If the switching instant identification arrangement does not affirm within a predetermined time that the armature of the electromagnetic valve has reached its new end position, then a fault is identified. In the third phase, which is also referred to as the first rapid turn-off, the drive signal for the corresponding low-side switch is withdrawn. This causes a current to flow from the respective load through the diode 130 to 133 assigned to the load into the capacitor 145 and the energy stored in the load to be transferred to the capacitor 145. In the embodiment illustrated, the high-side switch 115 is at the same time driven in such a way that it remains closed. In this phase, the current decreases from the energizing current IA to the holding current IH. At the same time, the voltage applied to the capacitor 145 rises to a value U3 which is, however, considerably less than the value Ul. The third phase is concluded when the desired value IH for the holding current is reached. The energy released during the transition from the energizing current IA to the holding current IH is stored in the capacitor. It is particularly advantageous here that the transition from the energizing current to the holding current takes place rapidly on account of the rapid turn-off. The third phase is followed by the fourth phase, which is also referred to as holding current regulation. In a manner corresponding to that in the second phase, the drive signal for the low-side switch remains at its high level, that is to say the low-side switch assigned to the load remains closed. The current which flows through the load is adjusted to the desired value for the holding current by opening and closing the high-side switch 115. A freewheeling circuit acts when the high-side switch 115 is in the off state. The current flows from the load through the low-side switch, the resistor 125 and the freewheeling diode 150. Phase 4 is concluded when the injection operation is complete. In the subsequent fifth phase, which is also referred to as the second rapid turn-off and checking of the rapid turn-off, the corresponding low-side switch is switched off and the high-side switch 115 is driven. In this phase, the current which flows through the load likewise falls rapidly to the value zero. At the same time, the voltage U which is applied to the capacitor 145 rises by a smaller value than in the third phase. In the 3rd and 5th phases, the desired value for the current I changes from a high to a low value. In these phases, the low-side switch assigned to the load is in each case driven in such a way that it blocks the flow of current. The energy released is transferred to the capacitor 145, 146 in the process. Rapid turn-off takes place in these phases. This causes the current to reach its new desired value rapidly. In phases two and four, current regulation is implemented by clocking the high-side switch. The freewheeling diode 150 is active when the high-side switch is in the off state. The current falls slowly in these phases. This leads to a lower switching frequency. In the sixth phase, the output stage is inactive, that is to say that no fuel is metered. This means that the drive signal AC for the booster switch 140, the drive signal AH for the high-side switch and the drive signal AL for the low-side switches all assume a low level and all of these switches are in the off state. The current which flows through the load remains at 0 and the value of the voltage across the capacitor 145 remains constant. In the seventh phase after driving, which is also referred to as reclocking, the high-side switch 115 is switched on again by the drive signal AH. A current flow is initialized in one of the loads by closing a low-side switch. The current flows, for example, via the diode 110, the switch 115, the load 100, the switching means 12 0 and the current measuring means 125 back into the voltage source. When the current reaches a desired value which is selected in such a way that the electromagnetic valve still does not react, the low-side switch is driven in such a way that it opens. This once again effects a rapid turn-off for the current path comprising the load, one of the diodes 130 to 133 and the capacitor 145. The voltage applied to the capacitor 145 rises as a result. As soon as the current reaches its zero value again, the low-side switch 120 is activated again. This process is repeated until the voltage across the capacitor 145 incrementally reaches the value Ul again. Phase 8 subsequently takes place, in which all of the drive signals are withdrawn and all of the switches are switched off. This phase corresponds to phase 0. If it is envisaged that each cylinder has only one injection interval per metering cycle, then there are no difficulties in the case of a device according to Figure 1. If, on the other hand, it is envisaged that pre-injection takes place before the actual main injection or post-injection takes place after the actual main injection, then the situation may arise where the electromagnetic valves of two cylinders have to be driven simultaneously. In particular the main injection and the pre-injection of the following cylinder and/or the post-injection and the pre-injection of the following cylinder may overlap in time. The consequence of this in a circuit arrangement according to Figure 1 is that two loads are selected by means of the low-side switches, but only joint current regulation is possible by means of the high-side switch 115. Two valves cannot be driven differently at the same time by means of this arrangement. It is thus not possible, for example, to regulate the current to the holding current in one electromagnetic valve and to the energizing current in the other electromagnetic valve. Furthermore, the capacitor 145 must be charged before the next valve can be driven. If the turn-off times and the turn-on times of two valves are very close together, it is not possible to charge the capacitor 145. Driving such that two electromagnetic valves are energized differently at the same time and the capacitor 145 is charged is possible, on the other hand, with a device according to Figure 2. In this arrangement, the loads are divided into two groups. Each group of loads is assigned a high-side switch 115, 116, a booster switch 140, 141, a measuring resistor 125, 126 and a capacitor 145, 146. A respective group of loads can be selected by means of the respective high-side switch 115 and 116. According to the invention, it is provided that the loads are in each case assigned to different groups which are assigned to the cylinders into which fuel is successively metered. The device according to the invention has been illustrated using the example of an internal combustion engine having four cylinders. The procedure can also be applied to internal combustion engines having a different number of cylinders. A corresponding number of loads, switching means and further elements must be provided for this purpose. Provision may also be made for dividing the loads into a larger number of groups . This is particularly practical in the case of relatively high numbers of cylinders. In the case of the previously described embodiment, a transition from a high current level to a lower current level takes place after the current regulating phase, some of the stored electrical energy being used partly to charge the capacitor. The capacitor is charged further at the end of driving during the rapid turn-off of the load current. If, after this, the charge of the capacitor is still insufficient for renewed turning on, a further voltage increase is achieved by periodically switching the load current on and off (reclocking) between two injection operations and storing the electrical energy. High engine speeds mean that the time intervals which can be utilized for stepping up the voltage by means of reclocking become shorter. At high speeds, stepping up in the time between two injection operations is not possible, with the result that the capacitor cannot be charged to the required voltage. According to the invention, therefore, it is proposed in a further embodiment that the stepping up of the voltage be carried out as early as during the current regulation and the capacitor be completely charged again during driving. Reclocking during the break in driving can be omitted as a result of this. Furthermore, the risk of undesired injection occurring is reduced, since the load is not energized between the two injection operations. Plotted against time in a manner corresponding to that in Figure 3 are the drive signals AC for the booster transistor 41 in Figure 4a, the drive signal AH for the high-side switch in Figure 4b, the drive signal AL of a low-side switch in Figure 4c, a control signal AS which takes account of the charge state of the capacitor in Figure 4d, the current I flowing through the load in Figure 4e and the voltage U dropping across the capacitor in Figure 4f. Various phases are distinguished in a manner corresponding to that in the case of the driving method according to Figure 3. In a phase 0, which is prior to the driving of the load, the output stage is switched off. The drive signals AC, AH, AL and the signal AS are at a low potential. This means that the high-side switch 115, the low-side switches 120 - 123 and the booster switch 140 block the flow of current. No current flows through the loads. The capacitor 145 is charged to its maximum voltage U10. This voltage assumes a value of approximately 80 volts, whereas the voltage supply-assumes values of approximately 12 volts. The first phase at the beginning of driving corresponds to the first phase of the procedure according to Figure 3 . The signal AS rises to its high level during phase 1. This indicates that the voltage dropping across the capacitor is less than a predetermined threshold value US. In the 2nd phase, which can also be referred to as energizing current regulation, the inrush current is received by the high-side switch 115 and the booster is inactivated. This means that the drive signal AT for the booster switch 140 is withdrawn in the 2nd phase, with the result that the switch 140 is in the off state. The drive signals AH and AL for the high-side switch 115 and the low-side switch assigned to the load assume a high level, in order that these switches enable the flow of current. A current consequently flows from the voltage supply 105 via the diode 110, the high-side switch 115, the load, the corresponding low-side switch, the current measuring resistor 125 back to the voltage source 105. In contrast to phase 2 according to Figure 3, the current which is detected by means of the current measuring resistor 125 is regulated to a predeterminable value for the energizing current IA by clocking the low-side switch. That is to say that when the desired current IA for the energizing current is reached, the low-side switch 120 to 125 is driven into the off state. When the current falls below a further threshold, the said low- side switch 120 to 125 is enabled again. The consequence of this is that when the low-side switch 12 0 to 125 is open, a current flows from the respective load through the diode 130 to 133, assigned to the load, into the capacitor 145 and the energy stored in the load is transferred to the capacitor 145. At the same time, the voltage U applied to the capacitor 145 rises. The second phase ends when the control unit 160 identifies the end of the energizing phase. This may be the case, for example, when a switching instant identification arrangement affirms that the armature of the electromagnetic valve has reached its new end position. In the third phase, which is also referred to as the first rapid turn-off, the drive signal for the corresponding low-side switch is withdrawn in a manner corresponding to the third phase according to the first embodiment. This causes a current to flow from the respective load through the diode 130-133, assigned to the load, into the capacitor 145. The energy stored in the load is at the same time transferred to the capacitor 145. The current decreases from the energizing current IA to the holding current IH in this phase. At the same time, the voltage U applied to the capacitor 145 rises. The third phase is concluded when the desired value for the holding current is reached. The energy released during the transition from the energizing current to the holding current is stored in the capacitor. The third phase is followed by the fourth phase, which is also referred to as holding current regulation. In a manner corresponding to that in the second phase, the drive signal for the high-side switch remains at its high level, that is to say the high-side switch remains closed. The current which flows through the load is adjusted to the desired value for the holding current during the opening and closing of the low-side switch. When the low-side switch is in the off state, the current flows from the respective load through the diode 13 0-133, assigned to the load, into the capacitor 145. The energy stored in the load is thereby transferred to the capacitor. As soon as the voltage IT dropping across the capacitor has reached a predetermined threshold value US, the signal AS changes to a low potential. The first part 4a of the fourth phase is thus concluded. From this point in time, the current is no longer regulated by means of the low-side switch, but by means of the high-side switch. This means that the low-side switch is constantly in its on position and the high-side switch alternates between its closed and its open position. A freewheeling circuit acts when the high-side switch 115 is in the off position. The current flows from the load through the low-side switch, the resistor 125 and the freewheeling diode 150. The fourth phase is concluded when the inj ection operation is complete. The subsequent fifth phase corresponds to the fifth phase of the procedure according to Figure 3. Phases six and seven according to Figure 3 are not necessary with this type of driving. As long as the signal AS is at its high level, that is to say the voltage across the capacitor has not yet reached the predetermined threshold value US, the output stage arrangement operates as a current-regulating step-up converter. The high-side switch is permanently enabled in this operating state. The current is regulated by the low-side switch, which is assigned to the individual load and is periodically switched on and off for the purpose of current regulation. If the voltage U dropping across the capacitor 145 has reached a predetermined value US, there is a changeover to another operating mode. The capacitor is not charged any further in this operating mode. The current is regulated by means of the high-side switch in a manner corresponding to that in the exemplary embodiment in Figure 3• The threshold value US for the capacitor voltage is preferably selected in such a way that the voltage at the end of phase 4a, together with the voltage rise in the fifth phase, produces a voltage value which is required for rapid turning on. The circuit arrangement operates as a step-up converter in phase 4a. The current is regulated in phase 4b by means of the high-side switch. Claim1• Device for driving at least one electromagnetic load, in particular an electromagnetic valve for controlling the metering of fuel into an internal combustion engine, having a first switching means (115, 116), which is arranged between a first connection of a supply voltage and a first connection of at least one load (100, 101, 102, 103), having second switching means (120, 121, 122, 123), which are arranged between a second connection of an assigned load (100, 101, 102, 103) and the second connection of the voltage supply, characterized in that means are provided which drive the switching means in such a way that it is possible to store in a storage means (145, 146) at least the energy released during the transition from an energizing current value (IA) to a holding current value (IH). 2. Device according to Claim 1, characterized in that, in a first driving phase, the first connection of the load can be connected to the storage means (145, 146) by means of a third switching means (140, 141) . 3. Device according to Claim 1 or 2, characterized in that the energy released during the opening of the second switching means can be stored in the storage means. 4. Device according to one of the preceding claims, characterized in that the energy released during the transition from the holding current value (IA) to the value zero can be stored in the storage means (145). 5. Device according to one of the preceding claims, characterized in that a freewheeling circuit acts in a phase in which the current can be regulated to a desired value. 6. Device according to one of Claims 1 to 4, characterized in that, in a phase in which the current can be regulated to a desired value, the released energy can be stored in the storage means (145)• 7. Device according to one of the preceding claims, characterized in that the second switching means are momentarily driven in a phase following the driving in such a way that the load does not react, and in that the energy released during the opening of the second switching means can be stored in the storage means. 8. Device according to one of the preceding claims, characterized in that the storage means is connected in parallel with the second switching means. 9. Device according to one of the preceding claims, characterized in that the loads can be divided into at least two groups, a first switching means (115, 116), a third switching means (140, 141) and/or a storage means (145, 146) being assigned to each of the said groups. 10. Device for driving at least one electromagnetic load substantially as hereinbefore described with reference to the accompanying drawings.

Full Text

Device for driving at--l-ea-sfe—one elect roroacmotirG load
-pyirog art
The invention relates to a device for driving at least one electromagnetic load according to the preambles of the independent claims.
Such a device for driving an electromagnetic load is disclosed, for example, in DE-A 44.13 240, which has not been previously published. In the case of this device, the energy released during turn-off is stored in a capacitor. In this case, the energy released during the transition from a holding current to the current 0 is transferred to a capacitor.
The energy released during the transition from the energizing current to the holding current is lost in the case of this device•
Object of the invention
The invention is based on the object, in the case of a device for driving an electromagnetic load, of providing a device having the most simple structure possible, in which the turn-on operation is accelerated and the total energy consumption is minimized.
Advantagos-i^f—the- invention
The arrangement according to the invention, having the features of the independent claims, has the advantage that it is possible to recover the energy which is released during the transition from the energizing current to the holding current. A particularly advantageous embodiment makes it possible to drive two loads simultaneously in a different manner using the same output stage. That is to say that injection operations which overlap in time are possible.

Drawing
The device according to the invention is explained below using the embodiments illustrated in the drawing, in which Figure 1 shows a first circuit arrangement of the device according to the invention, Figure 2 shows a second circuit arrangement and Figure 3 shows various signals plotted against time.
Description of the exemplary embodiments
The device according to the invention is preferably used in internal combustion engines, in particular in self-ignition internal combustion engines. In that case, the metering of fuel is controlled by means of electromagnetic valves. These electromagnetic valves are referred to below as loads. The invention is not restricted to this application, it can be used wherever rapidly switching electromagnetic loads are required.
In the case of the application in internal combustion engines, in particular in self-ignition internal combustion engines, the opening and closing times of the electromagnetic valve define the beginning of inj ection and the end of inj ection, respectively, of the fuel into the cylinder.
Figure 1 illustrates the most essential elements of the device according to the invention. The embodiment illustrated is concerned with a four-cylinder internal combustion engine. In this case, each load is assigned an injection valve and each injection valve is assigned a cylinder of the internal combustion engine. When the internal combustion engine has higher numbers of cylinders, correspondingly more valves, switching means and diodes are to be provided.
100, 101, 102 and 103 represent four loads. One connection of each of the loads 100 to 103 is connected to a voltage supply 105 via a switching means 115 and a diode 110.
The diode 110 is arranged in such a way that its anode is connected to the positive pole and its cathode is connected to the switching means 115. The switching

means 115 is preferably a field-effect transistor.
The second connection of each of the loads 100 to 103 is connected via a respective second switching means 120, 121, 122 and 123 to a resistor means 125. The switching means 120 to 123 are preferably field-effect transistors, too. The switching means 120 to 123 are referred to as low-side switches and the switching means 115 is referred to as a high-side switch. The second connection of the resistor means 125 is connected to the second connection of the voltage supply.
Each load 100 to 103 is assigned a diode 130, 131, 132 and 133. The anode connection of the diodes is in contact with the respective junction point between the load and the low-side switch. The cathode connection is connected to a capacitor 145 and to a further switching means 140. The second connection of the switching means 140 is in contact with the first connections of the loads 100 to 103. The switching means 140 is preferably a field-effect transistor, too. This switching means 140 is also referred to as a booster switch. The second connection of the capacitor 145 is likewise connected to the second connection of the supply voltage 105.
A drive signal AH is applied to the high-side switch 115 by a control unit 160. The control unit 160 applies a drive signal AL1 to the switching means 120, a drive signal AL2 to the switching means 121, a drive signal AL3 to the switching means 122, a drive signal AL4 to the switching means 123 and a drive signal AC to the switching means 140.
A diode 150 is connected between the second connection of the voltage supply 105 and the junction point between the switching means 115 and the first connections of the loads 100 to 103. In this case, the anode of the diode is connected to the second connection of the voltage supply 105.
The current flowing through the load can be determined by means of the resistor 125.
Using the arrangement illustrated, current can be measured by means of the current measuring resistor 125

only when one of the switching means 120 to 123 is closed. In order to be able to detect the current when the low-side switches are open, too, the current measuring resistor may also be arranged at a different point. For example, the second connection of the capacitor 145 can be connected to the junction point between the current measuring means 125 and the switching means 120 to 123. In this case, current can also be measured when the low-side switch is in the off state. Furthermore, the current measuring means may be arranged between the voltage supply and the high-side switch or between the high-side switch and the loads.
Figure 2 illustrates a corresponding device, in which the loads 100 to 103 are divided into two groups. The loads 100 and 101 form a first group, and the loads 102 and 103 form a second group of loads. The loads are assigned to the individual groups in such a way that loads which must be driven simultaneously under specific operating states are assigned to different groups.
Elements which have already been described in Figure 1 are designated in Figure 2 by corresponding reference symbols. A respective high-side switch 115 and 116 is provided for each group. The diode 111 corresponds to the diode 110 of the first group. Correspondingly, the booster transistor 140 likewise has to be designed in a duplicated manner. The booster transistor of the second group is designated by 141. The capacitor 145 in the second group is correspondingly designated by 146. Furthermore, two further drive lines for the switching means 116 and 141 are provided. The signal AH1 is applied to the high-side switch 115 of the first group and AH2 is applied to the high-side switch 116 of the second group. The signal AC1 is applied to the booster switch 140 of the first group and the signal AC2 is applied to the booster switch 141 of the second group. Correspondingly, the resistor 125 also has to be designed in a duplicated manner, and in the second group it is designated by 126.
The drive signal AC for the booster transistor 140 and 141 is plotted in Figure 3a. The drive signal AH

for the high-side switches 115, 116 is plotted in Figure 3b • Figure 3c shows the drive signal AL of one of the low-side switches. The current I flowing through the load is plotted against time in Figure 3d, and the voltage UC applied to the capacitor 145 is plotted against time in Figure 3e. One metering cycle for an electromagnetic valve is illustrated here.
Various phases are distinguished in each metering cycle. In a phase 0, prior to the driving of the load, the output stage is switched off. The drive signals AC, AH and AL are at a low potential. This means that the high-side switch 115, the low-side switches 120 to 123 and the booster switch 140 block the flow of current. No current flows through the loads. The capacitor 145 is charged to its maximum voltage UC. This voltage assumes, for example, a value of approximately 80 volts, whereas the voltage of the voltage supply assumes a value of approximately 12 V.
In the first phase, at the beginning of the driving, which is referred to as the booster mode, the low-side switch assigned to the load which is to meter fuel is driven. This means that the signal AL assumes a high level starting at phase 1. At the same time, a high signal which drives the switch 140 is output onto the line AC. The high-side switch 115 is not driven, it continues to be in the off state. This driving of the switching means causes a current to flow from the capacitor 145 via the booster switch 140, the corresponding load, the low-side switch assigned to the load and the current measuring means 125. In this phase, the current I rises very rapidly as a result of the high voltage across the load. Phase 1 ends when the voltage applied to the capacitor 145 falls below a specific value U2.
In the second phase, which is referred to as energizing current regulation, the inrush current is received by the high-side switch 115 and the booster is inactivated. In the second phase, the drive signal for the booster switch 140 is withdrawn, so that the switch

140 is in the off state. The drive signals AH and AL for the high-side switch 115 and the low-side switch assigned to the load are set to a high level, in order that these switches enable the flow of current. As a result of this, a current flows from the voltage supply 105 via the diode 110, the high-side switch 115, the load, the corresponding low-side switch, the current measuring resistor 125 back to the voltage source 105. By clocking the high-side switch, the current which is detected by means of the current measuring resistor 125 can be regulated to a predeterminable value for the energizing current IA. That is to say that when the desired current IA for the energizing current is reached, the high-side switch 115 is driven into the off state. When the current falls below a further threshold, the said high-side switch 115 is enabled again.
A freewheeling circuit acts when the high-side switch 115 is in the off state. The current flows from the load through the low-side switch, the resistor 125 and the freewheeling diode 150.
The second phase ends when the control unit 160 identifies the end of the energizing phase. This may be the case, for example, when a switching instant identification arrangement affirms that the armature of the electromagnetic valve has reached its new end position. If the switching instant identification arrangement does not affirm within a predetermined time that the armature of the electromagnetic valve has reached its new end position, then a fault is identified.
In the third phase, which is also referred to as the first rapid turn-off, the drive signal for the corresponding low-side switch is withdrawn. This causes a current to flow from the respective load through the diode 130 to 133 assigned to the load into the capacitor 145 and the energy stored in the load to be transferred to the capacitor 145. In the embodiment illustrated, the high-side switch 115 is at the same time driven in such a way that it remains closed. In this phase, the current decreases from the energizing current IA to the holding

current IH. At the same time, the voltage applied to the capacitor 145 rises to a value U3 which is, however, considerably less than the value Ul. The third phase is concluded when the desired value IH for the holding current is reached. The energy released during the transition from the energizing current IA to the holding current IH is stored in the capacitor. It is particularly advantageous here that the transition from the energizing current to the holding current takes place rapidly on account of the rapid turn-off.
The third phase is followed by the fourth phase, which is also referred to as holding current regulation. In a manner corresponding to that in the second phase, the drive signal for the low-side switch remains at its high level, that is to say the low-side switch assigned to the load remains closed. The current which flows through the load is adjusted to the desired value for the holding current by opening and closing the high-side switch 115. A freewheeling circuit acts when the high-side switch 115 is in the off state. The current flows from the load through the low-side switch, the resistor 125 and the freewheeling diode 150. Phase 4 is concluded when the injection operation is complete.
In the subsequent fifth phase, which is also referred to as the second rapid turn-off and checking of the rapid turn-off, the corresponding low-side switch is switched off and the high-side switch 115 is driven. In this phase, the current which flows through the load likewise falls rapidly to the value zero. At the same time, the voltage U which is applied to the capacitor 145 rises by a smaller value than in the third phase.
In the 3rd and 5th phases, the desired value for the current I changes from a high to a low value. In these phases, the low-side switch assigned to the load is in each case driven in such a way that it blocks the flow of current. The energy released is transferred to the capacitor 145, 146 in the process. Rapid turn-off takes place in these phases. This causes the current to reach its new desired value rapidly.

In phases two and four, current regulation is implemented by clocking the high-side switch. The freewheeling diode 150 is active when the high-side switch is in the off state. The current falls slowly in these phases. This leads to a lower switching frequency.
In the sixth phase, the output stage is inactive, that is to say that no fuel is metered. This means that the drive signal AC for the booster switch 140, the drive signal AH for the high-side switch and the drive signal AL for the low-side switches all assume a low level and all of these switches are in the off state. The current which flows through the load remains at 0 and the value of the voltage across the capacitor 145 remains constant.
In the seventh phase after driving, which is also referred to as reclocking, the high-side switch 115 is switched on again by the drive signal AH. A current flow is initialized in one of the loads by closing a low-side switch. The current flows, for example, via the diode 110, the switch 115, the load 100, the switching means 12 0 and the current measuring means 125 back into the voltage source. When the current reaches a desired value which is selected in such a way that the electromagnetic valve still does not react, the low-side switch is driven in such a way that it opens. This once again effects a rapid turn-off for the current path comprising the load, one of the diodes 130 to 133 and the capacitor 145. The voltage applied to the capacitor 145 rises as a result. As soon as the current reaches its zero value again, the low-side switch 120 is activated again. This process is repeated until the voltage across the capacitor 145 incrementally reaches the value Ul again.
Phase 8 subsequently takes place, in which all of the drive signals are withdrawn and all of the switches are switched off. This phase corresponds to phase 0.
If it is envisaged that each cylinder has only one injection interval per metering cycle, then there are no difficulties in the case of a device according to Figure 1. If, on the other hand, it is envisaged that pre-injection takes place before the actual main

injection or post-injection takes place after the actual main injection, then the situation may arise where the electromagnetic valves of two cylinders have to be driven simultaneously. In particular the main injection and the pre-injection of the following cylinder and/or the post-injection and the pre-injection of the following cylinder may overlap in time. The consequence of this in a circuit arrangement according to Figure 1 is that two loads are selected by means of the low-side switches, but only joint current regulation is possible by means of the high-side switch 115. Two valves cannot be driven differently at the same time by means of this arrangement. It is thus not possible, for example, to regulate the current to the holding current in one electromagnetic valve and to the energizing current in the other electromagnetic valve. Furthermore, the capacitor 145 must be charged before the next valve can be driven. If the turn-off times and the turn-on times of two valves are very close together, it is not possible to charge the capacitor 145.
Driving such that two electromagnetic valves are energized differently at the same time and the capacitor 145 is charged is possible, on the other hand, with a device according to Figure 2. In this arrangement, the loads are divided into two groups. Each group of loads is assigned a high-side switch 115, 116, a booster switch 140, 141, a measuring resistor 125, 126 and a capacitor 145, 146. A respective group of loads can be selected by means of the respective high-side switch 115 and 116. According to the invention, it is provided that the loads are in each case assigned to different groups which are assigned to the cylinders into which fuel is successively metered.
The device according to the invention has been illustrated using the example of an internal combustion engine having four cylinders. The procedure can also be applied to internal combustion engines having a different number of cylinders. A corresponding number of loads, switching means and further elements must be provided for

this purpose. Provision may also be made for dividing the loads into a larger number of groups . This is particularly practical in the case of relatively high numbers of cylinders.
In the case of the previously described embodiment, a transition from a high current level to a lower current level takes place after the current regulating phase, some of the stored electrical energy being used partly to charge the capacitor. The capacitor is charged further at the end of driving during the rapid turn-off of the load current. If, after this, the charge of the capacitor is still insufficient for renewed turning on, a further voltage increase is achieved by periodically switching the load current on and off (reclocking) between two injection operations and storing the electrical energy.
High engine speeds mean that the time intervals which can be utilized for stepping up the voltage by means of reclocking become shorter. At high speeds, stepping up in the time between two injection operations is not possible, with the result that the capacitor cannot be charged to the required voltage. According to the invention, therefore, it is proposed in a further embodiment that the stepping up of the voltage be carried out as early as during the current regulation and the capacitor be completely charged again during driving. Reclocking during the break in driving can be omitted as a result of this. Furthermore, the risk of undesired injection occurring is reduced, since the load is not energized between the two injection operations.
Plotted against time in a manner corresponding to that in Figure 3 are the drive signals AC for the booster transistor 41 in Figure 4a, the drive signal AH for the high-side switch in Figure 4b, the drive signal AL of a low-side switch in Figure 4c, a control signal AS which takes account of the charge state of the capacitor in Figure 4d, the current I flowing through the load in Figure 4e and the voltage U dropping across the capacitor in Figure 4f.

Various phases are distinguished in a manner corresponding to that in the case of the driving method according to Figure 3. In a phase 0, which is prior to the driving of the load, the output stage is switched off. The drive signals AC, AH, AL and the signal AS are at a low potential. This means that the high-side switch 115, the low-side switches 120 - 123 and the booster switch 140 block the flow of current. No current flows through the loads. The capacitor 145 is charged to its maximum voltage U10. This voltage assumes a value of approximately 80 volts, whereas the voltage supply-assumes values of approximately 12 volts.
The first phase at the beginning of driving corresponds to the first phase of the procedure according to Figure 3 . The signal AS rises to its high level during phase 1. This indicates that the voltage dropping across the capacitor is less than a predetermined threshold value US.
In the 2nd phase, which can also be referred to as energizing current regulation, the inrush current is received by the high-side switch 115 and the booster is inactivated. This means that the drive signal AT for the booster switch 140 is withdrawn in the 2nd phase, with the result that the switch 140 is in the off state. The drive signals AH and AL for the high-side switch 115 and the low-side switch assigned to the load assume a high level, in order that these switches enable the flow of current. A current consequently flows from the voltage supply 105 via the diode 110, the high-side switch 115, the load, the corresponding low-side switch, the current measuring resistor 125 back to the voltage source 105.
In contrast to phase 2 according to Figure 3, the current which is detected by means of the current measuring resistor 125 is regulated to a predeterminable value for the energizing current IA by clocking the low-side switch. That is to say that when the desired current IA for the energizing current is reached, the low-side switch 120 to 125 is driven into the off state. When the current falls below a further threshold, the said low-

side switch 120 to 125 is enabled again. The consequence of this is that when the low-side switch 12 0 to 125 is open, a current flows from the respective load through the diode 130 to 133, assigned to the load, into the capacitor 145 and the energy stored in the load is transferred to the capacitor 145. At the same time, the voltage U applied to the capacitor 145 rises.
The second phase ends when the control unit 160 identifies the end of the energizing phase. This may be the case, for example, when a switching instant identification arrangement affirms that the armature of the electromagnetic valve has reached its new end position.
In the third phase, which is also referred to as the first rapid turn-off, the drive signal for the corresponding low-side switch is withdrawn in a manner corresponding to the third phase according to the first embodiment. This causes a current to flow from the respective load through the diode 130-133, assigned to the load, into the capacitor 145. The energy stored in the load is at the same time transferred to the capacitor 145. The current decreases from the energizing current IA to the holding current IH in this phase. At the same time, the voltage U applied to the capacitor 145 rises. The third phase is concluded when the desired value for the holding current is reached. The energy released during the transition from the energizing current to the holding current is stored in the capacitor.
The third phase is followed by the fourth phase, which is also referred to as holding current regulation. In a manner corresponding to that in the second phase, the drive signal for the high-side switch remains at its high level, that is to say the high-side switch remains closed. The current which flows through the load is adjusted to the desired value for the holding current during the opening and closing of the low-side switch. When the low-side switch is in the off state, the current flows from the respective load through the diode 13 0-133, assigned to the load, into the capacitor 145. The energy

stored in the load is thereby transferred to the capacitor.
As soon as the voltage IT dropping across the capacitor has reached a predetermined threshold value US, the signal AS changes to a low potential. The first part 4a of the fourth phase is thus concluded. From this point in time, the current is no longer regulated by means of the low-side switch, but by means of the high-side switch. This means that the low-side switch is constantly in its on position and the high-side switch alternates between its closed and its open position. A freewheeling circuit acts when the high-side switch 115 is in the off position. The current flows from the load through the low-side switch, the resistor 125 and the freewheeling diode 150. The fourth phase is concluded when the inj ection operation is complete.
The subsequent fifth phase corresponds to the fifth phase of the procedure according to Figure 3. Phases six and seven according to Figure 3 are not necessary with this type of driving.
As long as the signal AS is at its high level, that is to say the voltage across the capacitor has not yet reached the predetermined threshold value US, the output stage arrangement operates as a current-regulating step-up converter. The high-side switch is permanently enabled in this operating state. The current is regulated by the low-side switch, which is assigned to the individual load and is periodically switched on and off for the purpose of current regulation.
If the voltage U dropping across the capacitor 145 has reached a predetermined value US, there is a changeover to another operating mode. The capacitor is not charged any further in this operating mode. The current is regulated by means of the high-side switch in a manner corresponding to that in the exemplary embodiment in Figure 3•
The threshold value US for the capacitor voltage is preferably selected in such a way that the voltage at the end of phase 4a, together with the voltage rise in

the fifth phase, produces a voltage value which is required for rapid turning on. The circuit arrangement operates as a step-up converter in phase 4a. The current is regulated in phase 4b by means of the high-side switch.

Claim1• Device for driving at least one electromagnetic load, in particular an electromagnetic valve for controlling the metering of fuel into an internal combustion engine, having a first switching means (115, 116), which is arranged between a first connection of a supply voltage and a first connection of at least one load (100, 101, 102, 103), having second switching means (120, 121, 122, 123), which are arranged between a second connection of an assigned load (100, 101, 102, 103) and the second connection of the voltage supply, characterized in that means are provided which drive the switching means in such a way that it is possible to store in a storage means (145, 146) at least the energy released during the transition from an energizing current value (IA) to a holding current value (IH).
2. Device according to Claim 1, characterized in that, in a first driving phase, the first connection of the load can be connected to the storage means (145, 146) by means of a third switching means (140, 141) .
3. Device according to Claim 1 or 2, characterized in that the energy released during the opening of the second switching means can be stored in the storage means.
4. Device according to one of the preceding claims, characterized in that the energy released during the transition from the holding current value (IA) to the value zero can be stored in the storage means (145).
5. Device according to one of the preceding claims, characterized in that a freewheeling circuit acts in a phase in which the current can be regulated to a desired value.
6. Device according to one of Claims 1 to 4, characterized in that, in a phase in which the current

can be regulated to a desired value, the released energy can be stored in the storage means (145)•
7. Device according to one of the preceding claims, characterized in that the second switching means are momentarily driven in a phase following the driving in such a way that the load does not react, and in that the energy released during the opening of the second switching means can be stored in the storage means.
8. Device according to one of the preceding claims, characterized in that the storage means is connected in parallel with the second switching means.
9. Device according to one of the preceding claims, characterized in that the loads can be divided into at least two groups, a first switching means (115, 116), a third switching means (140, 141) and/or a storage means (145, 146) being assigned to each of the said groups.

10. Device for driving at least one electromagnetic load substantially as hereinbefore described with reference to the accompanying drawings.

Documents:

« Previous Patent

Next Patent »

Patent Number

229032

Indian Patent Application Number

145/MAS/1996

PG Journal Number

12/2009

Publication Date

20-Mar-2009

Grant Date

13-Feb-2009

Date of Filing

30-Jan-1996

Name of Patentee

ROBERT BOSCH GMBH

Applicant Address

POSTFACH 30 02 20, 70442 STUTTGART,

Inventors:

#	Inventor's Name	Inventor's Address
1	KLAUS DRESSLER,	WEINSTR. 45, 74369 LOCHGAU,
2	RAINER, BURKEL	BRUHLSTR. 5, 71679 ASPERG,
3	ENGELBERT TILLHON	RIESLINGSTR. 17, 74369 LAUFFEN,
4	ANDREAS WERNER	WEINBERGSTR. 54, 73262 REICHENBACH,
5	UDO SCHULZ,	AUSTR. 18, 71665 VAIHINGEN,
6	WOLFGANG KRAMPE	NARZISSENWEG 7, 71272 RENNINGEN,
7	WILHELM EYBERG	ALBERTUS-MAGNUS-STR. 37, 71229 LEONBERG,
8	ANDREAS KOCH	FREIDRICH-SILCHERSTR. 12, 74321 BIETIGHEIM-BISSINGEN,

PCT International Classification Number

F02M51/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA