Retrofitting Stabilized Power Supply with Computer Switching Power Supply
1. Why use a computer switching power supply to modify a regulated power supply?
1) It is cheap and easy to obtain materials. A second-hand 200-watt computer switching power supply is about 30 yuan.
2) The output current is large, and it is no problem to output 4 or 5 amperes. When the output current of the general linear regulated power supply is slightly larger, the heat will be obvious, and heat dissipation becomes a difficult problem. The advantage of the switching power supply is high efficiency and less heat generation. . It is especially suitable for battery chargers and car radios.
31) is a small ripple, which can meet the requirements of general use.
4) Compared with the linear regulated power supply of the same power, it is light in weight and small in size.
There are also deficiencies:
1) The stability of the output voltage is not as good as the linear regulated power supply.
2) There is certain electromagnetic radiation interference.
3) It is not easy to adjust the output voltage from 0 volts.
2. How to modify the regulated power supply with a computer switching power supply?
Computer power supply circuits are varied, and it is inconvenient to repeat them one by one. Let me introduce the modification idea.
1) Remove the original rectifier filter and feedback loop.
2) Redesign the rectification filter circuit according to the output voltage and current. Pay special attention to use Schottky diodes, and fix them on the heat sink where the diodes were originally installed, and add insulating gaskets.
3) Connect a suitable bleeder resistor at both ends of the filter capacitor, pay attention to the resistance value and power.
4) Select several pins as taps according to the secondary winding of the original transformer, and the number of taps and the voltage are determined according to the output voltage. This is a skillful job.
5) Redesign the feedback loop so that the output voltage can be adjusted with a variable resistor. In this case, it may be necessary to consult the pin function of the relevant integrated circuit.
3. Several issues that should be paid attention to:
1) It is also possible to disassemble the transformer and rewind the coil. It is not easy to control the inductance under amateur conditions. It is more difficult to wind a single-ended flyback transformer. However, the half-wave conversion circuit does not have strict requirements on the inductance. It is better to wrap the primary section around.
2) If it is designed as multiple outputs, only one set of output voltages can be relatively controlled.
3) Design the circuit for adjusting the output voltage: if the variable resistance contact is disconnected, the output voltage is the lowest. Prevent the output voltage from increasing instantaneously due to the contact of the variable resistance contact point.
