Title of Invention

A FIRING PULSE GENERATION DEVICE FOR A SINGLE PHASE PULSE WIDTH MODULATED INVERTER FOR GENERATING THE CONTROLLED SIGNAL FOR CONTROLLING THE OUTPUT VOLTAGE OF THE INVERTER AND THE METHOD OF GENERATION

Abstract

A firing pulse generation device for a single phase pulse width modulated inverter for generating the controlled signal for controlling the output voltage of the inverter comprising an operating amplifier integrated circuit based square wave generator (3) for generating variable amplitude square wave, a 'RC' filter circuit (4) for transforming variable amplitude square wave to variable amplitude sine wave, a comparator for comparing fixed amplitude triangular wave with variable amplitude sine wave, a constant amplitude triangle wave generator (8) for generating fixed amplitude triangle wave called pulse width modulated gating signals, a gating logic and interlock circuit (6) for protecting the Top and Bottom switching device of inverter bridge; and an inverter bridge (7) having power semiconductor transistor switches, wherein a control signal generator (1) is disposed in the circuit for generating the control signal for varying the amplitude of the square wave applied as controlled auxiliary power supply voltate parameter (AUXVCC) wherein VSA reference electronic circuit (VSAR) (2) is disposed for generating the VCP signal.

Full Text

FIELD OF INVENTION The invention relates to a method and circuit for generation of firing pulse of single phase pulse width modulated (PWM) inverter. BACKGROUND OF THE INVENTION In order to convert a dc voltage into an ac voltage, inverters are used as electrical power converters. There are many types of inverters. Today, Pulse Width Modulated (PWM) Voltage Source Inverters (VSI) are most widely used to produce an output ac voltage of pure sine wave shape from a DC voltage source. These inverters are also used to get a voltage wave of variable amplitude and variable frequency. These inverters have many applications, like power supplied for lights, ac motors fans, pumps, controllers for variable speed operation of ac motors, controllers for induction heating furnaces and other equipment. Every PWM inverter requires a control circuit to produce a pre- determined output voltage wave of a desired amplitude and desired frequency. One of the essential parts of this control circuit is a firing pulse generation circuit. There are many methods of firing pulse generation circuits for a single phase Pulse Width Modulated (PWM) inverter. The sine-triangle method of firing pulse generation circuit is one of the most widely used method. In this invention a sine wave with variable voltage and variable frequency is required to produce a voltage wave of variable amplitude and variable frequency at the output of the inverter. Presently, in many sine-triangle methods of firing pulse generation circuits the required sine wave with variable voltage and variable frequency is produced in different ways. One method is to produce a sine wave signal with fixed amplitude and variable frequency with a function generation circuit and then amplifying this sine wave signal in a Operational Amplifier (OPAMP) based voltage amplifier with a fixed gain. This gain is adjusted, whenever the amplitude is required to be increased / decreased for the desired sine wave. Another method is based on the use of special purpose Memory Integrated Circuits (ICs) called "EEPROMs". In this Memory ICs based circuits digital values corresponding to the desired sine wave are loaded, by generating these values with a special software program tailor made for this function. The voltage amplitude and frequency of this sine wave is controlled through special complicated interface circuits or through special dedicated software programs. The Memory ICs like "EEPROMS" / interface circuits / specially developed or tailor made software programs / loading tools and other associated or supporting hardware / software involve higher complexity in implementation and also involve higher cost. Hence, these methods are relatively costlier and more complicated in comparison to the present invention. OBJECTS OF THE INVENTION An object of the invention is to develop a novel method and circuit for generation of firing pulse of single phases pulse width modulated (FWM) inverter. - Another object of the invention is to deveiop a method to vary only the amplitude of the sine wave while other parameter i.e frequency is kept constant and undisturbed at the pre-set value. - A further object of the invention is to develop a novel circuit for the precise control of speed/voltage/torque/current through inverter which is easier and simpler - A still further object of the invention is to precisely control the output voltage of the inverter. SUMMARY OF THE INVENTION Accordingly there is a provision of a simple, easy and low cost method of firing pulse generation circuit used as a part of the "Electronic Controller" for controlling the output voltage of a single phase Pulse Width Modulated (PWM) inverter. In this method, a variable amplitude constant frequency sine wave is generated. The amplitude of the sine wave is controlled by a control voitage which can be varied from zero to ten volts (dc) in order to get a variable amplitude of the sine wave of zero to ten volts, which controls the modulation index of the PWM waveform. This results in appropriate change in the output voltage of the inverter, without changing the set output frequency of the inverter. The novelty of this firing pulse generation circuit is that a control signal (VCON) is used to change the amplitude of the square wave to a desired level. The change in control signal (VCON) amplitude, results in the variation of power supply voltage (AUXVCC) fed to the OPAMP integrated circuit (IC) generating the square wave. This results in getting the desired amplitude of the sine wave (VSC), without changing the set frequency of the sine wave. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Fig.1 shows the Block Schematic of the Novel firing pulse generation circuit and the various components in this circuit along with their interconnection details. Flg.2 shows the Adjustable Amplitude Sine Wave Generation with change in the amplitude of the control signal (VCON). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In this Invention a novel method of firing pulse generation for a single phase pulse width modulated (PWM) Inverter Is presented. In this, a sine-triangle method of firing pulse generation circuit Is used. The required sine wave with variable voltage and fixed frequency is produced. This sine wave is called as "reference wave". This required sine wave is produced by developing a special analog circuit. As illustrated in Fig (1) the control signal generated through control signal generator (1) for varying the amplitude of the square wave is a dc voltage signal. The variation of the amplitude of the square wave results in the variation in the amplitude of the "Reference Sine Wave (VSC)". The variable amplitude reference sine wave (VSC) is then compared with a fixed amplitude and fixed frequency triangle wave generated through a constant amplitude triangle generator (8) to produce the required PWM gating signals. This triangle wave is called as "Carrier Wave". These PWM gating signals are fed to special logic circuits to protect the TOP and Bottom switching devices (like IGBT-Transistor, BJT- Transistor, MOSFET-Transistor, GTO-Thyristor, SCR-Thyristors) which are in the various arms of an inverter bridge. These protected signals are sent through buffer circuits and finally they are fed to the gates of the semiconductor switches. By controlling the "Frequency" and "Amplitude" of the reference sine wave signal, the frequency and amplitude of the output voltage wave of the inverter are controlled. In Fig. 1, block (2) is a Square Wave Amplitude Reference Generator (VSAR). This new development is presented along with its component systems in the Fig.-1: Block Schematic of the Novel firing pulse generation circuit for a single phase pulse width modulated (PWM) inverter. The Fig-1 shows the Block Schematic of the Novel firing pulse generation circuit and the various components in this circuit along with their Interconnection details. In this firing pulse generation circuit, a sine wave (VSC) is generated by passing a square wave (VSQW) through a RC filter (4). This sine wave has an adjustable amplitude. The sine wave (VSC) is compared with a fixed amplitude triangular wave (VT) in a comparator (5) this comparison produces the Pulse Width Modulated (PWM) signals. These PWM signals (VPWM) are passed through a gating logic and a interlock circuit (6). Then, these signals are fed to the Power semiconductor transistor switches like Insulated Gate Bipolar Transistor (IGBTs) / MOSFETS / BJTs (7). The Fig.2 shows the Adjustable Amplitude Sine Wave Generation with change in the amplitude of the control signal (VCON). In this firing pulse circuit, a control signal (VCON) generated through control signal generator (1) is used to change the amplitude of the square wave to a desired level. The amplitude of the square wave (VSQW) is adjusted to get the desired amplitude of the sine wave (VSC). In this novel firing circuit, a square wave of fixed frequency is produced through operational amplifier based square wave generator (3) as illustrated in fig (1). This results in a wave of a fixed frequency. The change in control signal (VCON) amplitude, results in the variation of the power supply voltage (AUXVCC) fed to the Operational amplifier based integrated circuit (IC) (3) generating the square wave. This results in the amplitude of the square wave to be controlled to the desired level. By the variation of the +ve (VCP) or -ve (VCN) signals fed as power supply voltages (+AUXVCC / - AUXVCC) of the square wave generator IC circuit (3) an independent variation can be done of either the +ve top half OR -ve bottom half of the desired sine wave. Also, these +ve (VCP) or -ve (VCN) signals can be varied to shape the desired sine wave for exactly matching the amplitude of the top and bottom halves of the sine wave, thus tuning the wave shape to produce a perfect sine wave. This method gives a sine wave (VSC) where only the amplitude is varied by a control signal (VCON) without affecting the other parameter- frequency, which is kept constant and undisturbed at the pre-set value. So, by choosing the control voltage to vary the power supply fed to amplifier IC circuit (3) generating the square wave, the +ve and -ve halves of the square wave generating circuit is varied. This changes the amplitude of the sine wave to the desired level. This in- turn, varies the output voltage of the inverter to the desired value, without changing the set output frequency. Also, this circuit offers easy to operate and accurately shaped Sine wave reference signal, which in turn results in accurate PWM gate pulses for firing (triggering) the Power semiconductor transistor switches like Insulated Gate Bipolar Transistors (IGBTs)/ MOSFERTS / BJTs (7). This results in accurate and precise control of the output voltage of the inverter. The output voltage of the inverter can be automatically controlled by generating the control signal (VCON) at the desired level by using a closed loop control system for voltage control. This circuit offers advantages like novel, simple, easy and low cost circuit configuration for the generation of the crucial reference sine wave signal with adjustable amplitude. REFERENCES: 1. Mohan, Ned., Undeland, Tore M., and. Robbins, W.P., "Power Electronics - converters, applications and design", John Wiley & Sons, Cananda (1989). 2. Murphy, J.M.D., and Turnbull, F.G., "Power electronic control of ac motors", Pergaman Press, England (1988). 3. Bose, B.K., "Power electronics and ac drives", Prentice Hall (1986). 4. Dubey, G.K., "Power semiconductor controlled drives", Prentice Hall (1989). 5. Rashid, Muhammad H., "Power electronics - circuits, devices and applications", Prentice-Hall, India, 2nd Edition (1993). 6. Bose, B.K., "Power electronics and variable frequency drives - technology and applications", IEEE Press (1996). 7. Rashid, Muhammad H., "Power electronics - circuits, devices and applications", Prentice-Hall, India, 3rd Edition (2004). WE CLAIM 1. A firing pulse generation device for a single phase pulse width modulated inverter for generating the controlled signal for controlling the output voltage of the inverter comprising; an integrated circuit based square wave generator (3) for generating variable amplitude square wave; a 'RC' filter circuit (4) for transforming variable amplitude square wave to variable amplitude sine wave; a comparator for comparing fixed amplitude triangular wave with variable amplitude sine wave; a constant amplitude triangle wave generator (8) for generating fixed amplitude triangle wave called pulse width modulated gating signals; a gating logic and interlock circuit (6) for protecting the Top and Bottom switching device of inverter bridge; and an inverter bridge (7) having power semiconductor transistor switches; Characterized in that, a control signal generator (1) is disposed in the circuit for generating the control signal for varying the amplitude of the square wave applied as controlled auxiliary power supply voltate parameter (AUXVCC) wherein VSA reference electronic circuit (VSAR) (2) is disposed for generating the VCP signal. 2. A method generation of firing pulse of single phase pulse width modulated (PWM) inverter, the said method comprising; generating a control signal (VCON) through a control signal generator (1) for changing the amplitude of a square wave to a desired level; adjusting the square wave (VSQW) by passing the said wave through a RC filter (4) to get the desired amplitude of the sine wave (VSC); varying the +ve (VCP) or -ve (VCN) signals fed as power supply voltages (+AUXVCC/- AUXVCC) of the square wave generator IC circuit (3) to obtain an independent variation of either the +ve top half or -ve bottom half of the desired sine wave; shaping the desired sine wave for exactly matching the amplitude of the top and bottom valves; tuning the wave shape to produce a perfect sine wave; comparing the sine wave (VSC) "with a fixed amplitude triangular wave (VT) in a comparator (5) to produce the pulse width Modulated (PWM) signals; passing the said PWM signals (VPWM) through a gating logic and a interlock circuit (6) and then feeding to the power semiconductor transistor switches to control precisely and accurately the output voltage of the inverter. ABSTRACT A FIRING PULSE GENERATION DEVICE FOR A SINGLE PHASE PULSE WIDTH MODULATED INVERTER FOR GENERATING THE CONTROLLED SIGNAL FOR CONTROLLING THE OUTPUT VOLTAGE OF THE INVERTER AND THE METHOD OF GENERATION A firing pulse generation device for a single phase pulse width modulated inverter for generating the controlled signal for controlling the output voltage of the inverter comprising an operating amplifier integrated circuit based square wave generator (3) for generating variable amplitude square wave, a 'RC' filter circuit (4) for transforming variable amplitude square wave to variable amplitude sine wave, a comparator for comparing fixed amplitude triangular wave with variable amplitude sine wave, a constant amplitude triangle wave generator (8) for generating fixed amplitude triangle wave called pulse width modulated gating signals, a gating logic and interlock circuit (6) for protecting the Top and Bottom switching device of inverter bridge; and an inverter bridge (7) having power semiconductor transistor switches, wherein a control signal generator (1) is disposed in the circuit for generating the control signal for varying the amplitude of the square wave applied as controlled auxiliary power supply voltate parameter (AUXVCC) wherein VSA reference electronic circuit (VSAR) (2) is disposed for generating the VCP signal.

Documents:

00574-kol-2007-claims.pdf

00574-kol-2007-correspondence others 1.1.pdf

00574-kol-2007-correspondence others.pdf

00574-kol-2007-description complete.pdf

00574-kol-2007-drawings.pdf

00574-kol-2007-form 1.pdf

00574-kol-2007-form 18.pdf

00574-kol-2007-form 2.pdf

00574-kol-2007-form 3.pdf

00574-kol-2007-gpa.pdf

574-KOL-2007-(28-09-2012)-ABSTRACT.pdf

574-KOL-2007-(28-09-2012)-AMANDED CLAIMS.pdf

574-KOL-2007-(28-09-2012)-CORRESPONDENCE.pdf

574-KOL-2007-(28-09-2012)-DESCRIPTION (COMPLETE).pdf

574-KOL-2007-(28-09-2012)-DRAWINGS.pdf

574-KOL-2007-(28-09-2012)-FORM-1.pdf

574-KOL-2007-(28-09-2012)-FORM-2.pdf

574-KOL-2007-(28-09-2012)-OTHERS.pdf

574-KOL-2007-(28-09-2012)-PA.pdf

574-KOL-2007-CORRESPONDENCE 1.1.pdf

574-KOL-2007-CORRESPONDENCE.pdf

574-KOL-2007-EXAMINATION REPORT.pdf

574-KOL-2007-FORM 18.pdf

574-KOL-2007-GPA.pdf

574-KOL-2007-GRANTED-ABSTRACT.pdf

574-KOL-2007-GRANTED-CLAIMS.pdf

574-KOL-2007-GRANTED-DESCRIPTION (COMPLETE).pdf

574-KOL-2007-GRANTED-DRAWINGS.pdf

574-KOL-2007-GRANTED-FORM 1.pdf

574-KOL-2007-GRANTED-FORM 2.pdf

574-KOL-2007-GRANTED-FORM 3.pdf

574-KOL-2007-GRANTED-SPECIFICATION-COMPLETE.pdf

574-KOL-2007-REPLY TO EXAMINATION REPORT.pdf