Analysis of the Principle of Kaiyu Intelligent Switching Power Supply Module

Kaiyu brand intelligent switching power supply (also known as universal power supply module). It can be used for the maintenance and replacement of 14-inch to 34-inch color TV, VCD, DVD and satellite receiver switching power supply. The original machine only needs to retain the rectification filter, peak pulse absorption circuit and secondary rectification circuit. It can significantly improve work efficiency during on-site maintenance. The actual object is shown in Figure 1 (omitted).

In order to understand the working principle of the power module, the author disassembled the module and drew its schematic diagram, as shown in Figure 2. From the schematic diagram, it can be seen that the module is very similar to the switching power supply in the color display, that is, it adopts the typical uc3842+field effect tube solution. The difference is that when the blue line is not connected, the error sampling is taken from the primary. uC3842 is a PWM switching power supply integrated controller with excellent performance, wide application and relatively simple structure. Since it has only one output terminal, it is mainly used for switching power supplies controlled at one end.

Debugging method: Connect the module to the circuit as shown in Figure 3, that is, connect the red wire to the original switch tube C pole position, the black wire to the ground, and the blue wire to the optocoupler ④ pin, which can be used for remote control standby (if the original machine is a step-down standby, a 5kΩ~10kΩ adjustable resistor needs to be connected in series). Disconnect all loads in the original circuit and connect a 60w--100w bulb to the output end as a dummy load. After checking that everything is correct, turn on the power, and use a multimeter to monitor the output voltage at the same time, and debug the fine-tuning resistor on the module. Make the output voltage consistent with the original machine, and the other groups of voltages will automatically adapt.

Common troubleshooting methods:

1. When a non-operating fault occurs, check whether the 300V filter and transformer are normal, whether the load is short-circuited, and whether the remote control shutdown related circuits are normal.

2. If overheating, interference or even howling occurs, improve the original machine's absorption circuit. R should be around 39Ω/3W and C should be 470pF~1000PF.

3. In rare cases where the switch transformer does not match the module, the problem can be solved by doubling the main winding of the original transformer. Try not to disassemble the core to avoid damage.

4. The blue line also has a precise voltage stabilization function. Connecting it to the optocoupler will make the working voltage more stable. If it does not meet the requirements, check whether the original voltage stabilization circuit is normal.