Pulse electrochemical machining can improve the machining accuracy and surface quality of parts. It has been widely recognized by people. However, the early pulse power supply frequency is low and the controllability is poor, and the pulse current processing cannot be fully utilized. Therefore, pulse electrochemical machining technology is mostly used for part forming processing, but it is rarely used in precision machining and finishing. With the development of modern power electronics technology, the emergence of power electronic devices such as bipolar high-power transistors (GTR), power FETs, and insulated gate bipolar transistors (IGBTs), pulse width modulation (PWM) control technology The adoption of this kind of power supply provides conditions for the development of this kind of power supply. However, the GTR is driven by current, and the required driving power is large and generally only reaches a pulse frequency below 5 kHz. The power of the MOSFET device is small, and when it is used to manufacture a large power pulse power supply, it is necessary to use a parallel connection of a plurality of tubes, which is bound to increase. The complexity of the power supply.
Based on this, this paper selects IGBT as the core component to design the pulse power supply. Is the principle block diagram of the power supply. On one hand, the pulse signal generated by the waveform generator is optically isolated, and then the power switching device IGBT is turned on and off after power amplification; on the other hand, the power frequency voltage signal is sequentially passed through a voltage regulator, a transformer, and a rectification and filtering circuit. After that, the output voltage (0~30V) adjustable DC voltage signal is input to both ends of the power switching device; the protection circuit is used to protect the power switching device and its driving circuit. In this way, by controlling the turn-on and turn-off of the IGBT module, the DC voltage signal is passed through the IGBT to obtain a pulse voltage signal that changes according to the pulse control signal.
The pulse signal generation pulse signal is generated by the waveform generator. The waveform generator can be composed of a discrete component, a single junction transistor, an integrated operational amplifier, a time base integrated circuit 555, an integrated pulse width modulator TLP494, a UC3842, an SG3524, and the like, and a single chip microcomputer. The pulse signal generating circuit composed of integrated pulse width modulator is simple and fully functional, and can generate pulse signals with frequencies higher than 100 kHz, and the frequency and pulse width are independently adjustable. This paper adopts integrated pulse width modulator SG3524 as the core of pulse signal generation. element.
Once the current is confirmed as an overcurrent, the low speed cut-off circuit can turn off the IGBT slowly. The circuit schematic for driving and protecting the IGBT is applied to the application-specific hybrid integrated drive module EXB841. Based on the EXB841 driver module, this circuit adds a small number of components to make the drive and protection of the IGBT more perfect, work more reliable and more stable [7, 8].
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