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Power Inverter Power Supply Design and Implementation of Adjustable

Print View , by: iSee ,Total views: 32 ,Word Count: 1116 ,Date: Sun, 23 Aug 2009 Time: 10:02 PM

1 Introduction

Sinusoidal pulse width modulation and frequency conversion technology in the field of industrial control applications become increasingly widespread. Many electrical test instruments require high power, high-performance to meet the test requirements of electrical equipment. At present, high-power switching power supply on the market, the core of power devices were powered by MOSFET semiconductor field-effect transistors and bipolar power transistors, they can not meet the small-scale, high-frequency, high-efficiency requirements. MOSFET field-effect transistor with a switching speed and voltage mode control features, but its on-state resistance of large and difficult to meet the high-voltage high-current requirements; bipolar power transistors will satisfy the requirements of high-voltage high-current, but not fast switching speed, is a current-controlled devices, which require considerable power drive. Insulated gate bipolar power crystal field-effect transistor MOSFET and IGBT set of bipolar power transistors in one, with voltage-mode control, input impedance large, drive power is small, switching speed, operating frequency, high-capacity and so on. With a high-performance insulated gate bipolar power of crystals for switching IGBT inverter components, using technology developed by AM frequency inverter power supply, with high efficiency, reliable performance, small size, and so on.

2 Works

The power supply uses high-frequency inverter technology, digital signal generator, sinusoidal pulse width modulation and frequency modulation, timing control and the series-resonant power output. Power supply with high efficiency and high output power, small size, etc., the overall block diagram shown in Figure 1.

By the digital signal generator sine wave is modulated 25kHz triangle wave modulation, pulse width modulation to get a sine wave inverter driven by the driving circuit elements IGBT. To change the sine wave frequency, amplitude modulation can be achieved FM output, the output for the series-resonant inverter output will be filtered out high-frequency carrier signal, thereby to obtain the required frequency of the sinusoidal signal. Timing control circuitry used to control the power source when the power supply in the slow power-power to ensure stable power supply current in power, while also avoiding the impact of zero-crossing switch; in the control circuit is also designing a fault lock function, Once the power failure, lock function will be banned from opening IGBT, when the fault occurs, IGBT open locked point, when large-capacity filter capacitors will store a high energy. Therefore, power failure protection Automatic cut off part of a work of power and auto-discharge function, the whole design has a dual over-current, over voltage and thermal protection features such as sound.

Power Inverter Power Supply Design and Implementation of Adjustable

Power Inverter Power Supply Design and Implementation of Adjustable

3 Control and drive circuit

Control circuitry means the control circuit, including the sine-wave pulse width modulation generation, duty cycle regulation and fault latch. Sine wave modulation control circuit can be adjusted according to the actual application of its frequency. Drive circuit is produced using Mitsubishi IGBT driver module specific EXB840, the driver module can drive up to 150A/600V and 75A/1200V of the IGBT, the module within the drive circuit so that signal delay ≤ 1μs, it applies to the switching operation of up to 40kHz. Use this module to note, IGBT gate-emitter circuit wiring must be less than 1M, gate-emitter drive Stranded wire should be used. EXB840 the drive circuit shown in Figure 2.

4 inverter and snubber circuit

The power supply uses half-bridge series resonant inverter circuit structure, the main circuit principle shown in Figure 3. In the high-power IGBT resonant inverter circuit, the main circuit of the structural design is essential, since there is lead in the circuit parasitic inductance, IGBT switching action when the peak inductor voltage surges on the inspired Ldi / dt can not be ignored, as the power supply uses a half-bridge inverter circuit, a relatively full-bridge circuit, will produce a greater than full-bridge circuit di / dt. Proper design that is a buffer over-voltage protection circuit, the normal work of the IGBT is very important. If the buffer circuit design properly, will result in increased loss snubber circuit will cause the circuit fever severe enough to damage the components, is not conducive to long-term work.

Power Inverter Power Supply Design and Implementation of Adjustable

Power Inverter Power Supply Design and Implementation of Adjustable

Process is: When VT2, when opened, with the current rise in the line under the effect of stray inductance Lm, making Uab down to Vcc-Ldi/dt, this time before a work cycle to be charged to Vcc buffer capacitor C1, by VT1 anti-parallel diode VD1, VT2 and the buffer discharge resistor R2. In the buffer circuit, flow through the anti-parallel diode VD1 instantaneous turn-on current ID1 flows through the line for stray inductor current IL and the flow through the buffer capacitor C1 and the current IC. That ID1 = IL + IC, thus IL, and di / dt relative to the non-buffer circuit is much smaller. When VT1 off, due to circuit stray inductance Lm role in making Uce rising rapidly, and larger than the bus voltage Vcc, then the buffer diode VD1 forward bias, Lm in the storage (LmI2 / 2) to the buffer circuit transfer, snubber circuit absorbs energy storage will not cause a significant increase Uce.

5 Calculation and selection of buffer components

Power Inverter Power Supply Design and Implementation of Adjustable

Where: f-switching frequency; Rtr-switch current rise time; IO-Maximum switching current; Ucep-transient voltage peaks.

Component selection in the buffer circuit, the capacitor to choose a higher voltage capacitors, diodes the best choice for high-performance, fast recovery diodes, resistors to use without a sense resistor.

6 Conclusion

The power supply has been successfully applied to high-power electrical testing equipment, as compared with the traditional methods, not only high accuracy but also improve work efficiency, increase safety, reduce labor intensity.

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