A new type of electroplating power supply equipment - high frequency switching power supply. It combines the advantages of waveform smoothness of silicon rectifiers and the convenience of voltage regulation of thyristor rectifiers. It has the highest current efficiency (up to 90%) and the smallest volume. It is a promising rectifier. Manufacturing technology has solved the power problem, and thousands of amps to tens of thousands of amps of high-power switching power supplies have entered the practical stage of production.
It converts the AC power grid through the EMI anti-electromagnetic interference line filter, directly rectifies and filters, converts the DC voltage into a high-frequency square wave of tens or hundreds of kHz through the converter, and is isolated and stepped down by the high-frequency transformer. The frequency filter outputs a DC voltage. After sampling, comparing, amplifying and controlling, driving the circuit, the duty cycle of the power tube in the converter is controlled to obtain a stable output voltage (or output current).
The adjusting tube of the high-frequency switching rectifier works in the switching state, the power loss is small, the efficiency can reach 75%~90%, the volume is small, the weight is light, and the precision and ripple coefficient are better than the silicon rectifier, and the whole output range can be Meet the precision required for production. It has self-protection ability and can start and stop at any time with load. It can be easily connected to a computer, which brings great convenience to automated production and is widely used in the PCB plating industry.
The main conversion structure of high-frequency switching rectifier for electroplating has a forward, half-bridge, full-bridge, etc., which has both a pulse-width modulation (PWM) "hard switching" circuit and a popular phase shifting control "soft switching". "Power circuit.
Pulse Width Modulation (PWM) high frequency switching rectifiers, operating at frequencies below 50 kHz, are controlled by voltage or current feedback. It adjusts the output current by changing the drive voltage pulse width by interrupting the power flux and adjusting the duty cycle, so that the device operates in a "hard switching" state, that is, forced conduction (when the voltage is not zero) or forced shutdown ( When the current is not zero, the switching power tube has a high voltage and a large current at the same time, so the switching loss is large and the peak interference is strong. The high-voltage spikes caused by the leakage inductance of the transformer and the rate of change of the large current not only damage the power tube, but also generate significant electromagnetic radiation, which reduces reliability and power efficiency.
The switching power supply has reached the frequency of audio, and it is easier to achieve low ripple output by filtering. Moreover, functions such as steady current and voltage regulation are easier to implement.