Circuit diagram and maintenance skills of CONVO VSD switch power supply

This is the circuit diagram of the switch power supply for the GVF-G type of the CONVO drivers, with a power of 5.5KW and version number 002-E-P00-01 8.6kVA 13A. This circuit is not considered a very classic switch power supply circuit, but it does not mean that it is a poorly performing circuit, and its failure rate is not high in actual operation.

The input of the circuit is approximately 550V DC voltage at both ends of the autonomous DC home energy storage capacitor. The oscillation and driving are carried out using commonly used power chips 38440, which provide the circuit’s starting voltage and current from R40, R41, and Z8. The Z8 voltage stabilization value has not been measured yet, and is estimated to be around 13V. Here, the LED also serves as a power indicator. After the vibration of 3844, the 7-pin power supply voltage of 3844 is established through rectification and filtering circuits such as D13, Dl4, C30, and C31 through the BT winding. At the same time, this power supply also undertakes the functions of output voltage sampling and voltage feedback. After being divided by R1 and R2, it is sent to the 2 pins of 3844 for feedback voltage input. This is different from the voltage feedback method of switch power supply circuits in other brands of frequency converters. Due to the fact that voltage sampling is not directly taken from the secondary power supply branch of the transformer, it can only be considered as an indirect sampling of the output voltage of each channel, so the control strain rate and accuracy are not too high. However, the+18V and -18V power supply of the secondary winding were introduced into the CPU motherboard, and voltage stabilizing links of 7815 and 7915 were added respectively. The circuit was slightly cumbersome, and its power supply performance was correspondingly improved. After the+8V power supply was introduced into the motherboard, 7805 voltage stabilization processing was added as the power supply for the CPU.
The sampling of the switching tube current is obtained from the resistor R37 connected in series with the K2225 source of the switching tube as usual. Sent to the 3-pin current detection terminal of 3844. 1. The feedback component of the internal voltage amplifier is connected between the two pins, which determines the amplification rate of the sampling voltage. The 8-pin is the Vref terminal, which outputs a 5V reference voltage during normal operation, providing a current path for the external R and C oscillation timing components of the 4-pin, ensuring the stability of the oscillation frequency. The 6 pins are pulse output pins, also known as drive output terminals. Introduced into the gate of switch K2225 through R36.
The 24V output power supply not only provides 24V control voltage for the frequency converter control terminal, but also supplies power to two cooling fans. It can be seen that the operating mode of this fan is controlled by the CPU motherboard signal and determined by parameter settings. There are generally three operating modes: running after power on, running during operation, and running when the radiator temperature reaches a certain value.
Maintenance tips: When the switch tube K2225 is damaged due to breakdown, a high voltage impulse is introduced from pin 3 of 3844, which often causes damage to the R5 resistor. The resistor may also have opened or increased in value:

Maintenance tips: When the switch tube k2225 is damaged due to breakdown, 3844 is often damaged simultaneously due to the introduction of high voltage surge from three pins; The r5 resistor may also be open or the resistance value may have increased; Most of the current sampling resistors r37 connected to the source have also been opened. Before replacing the switch tube, it is necessary to conduct a comprehensive inspection. The switch tube k2225 can be directly replaced with k1317 tube.