Using 40W fluorescent lamp electronic ballast to convert into VCD player switching power supply

In view of the problem that the assembled VCD machine in the current market has poor disc reading ability and cannot work normally when the power supply voltage is lower than 200V, the switching power supply modified by the 40W fluorescent lamp electronic ballast replaces the original machine transformer power supply, and achieves unexpected results. The modified VCD machine can not only work within a wide range of power supply voltage of 130V~250V, but also has a much improved disc reading ability. The discs that were difficult to play before can now be played smoothly without freezing. The following is a special introduction.

The modification of the switching power supply is very simple. As shown in the figure, the ballast is the Yongan 98-2 type produced in Dongguan, with an operating voltage of AC130V-265V, a rated current of 185mA, a harmonic type of H, and a power factor of 0.98. The circuit is equipped with delayed start and multiple protection functions.

When modifying, only the heat sinks on the original V1 and V2 need to be removed, and no changes are made to other circuits. Take an E-type magnetic core of the same size as the original ballast, remove the original winding, and use 0.19mm enameled wire to tightly wind 135 turns on its frame as the primary. After insulation, use the removed enameled wire to wind 12 turns for audio amplifier (5V) power supply; wind 48 turns with a center tap to supply the mainboard (9Vx2); double wind 24 turns to supply the panel (9V) and decompression (5V) circuits respectively. See the attached diagram for the electrical principle.

Then use screws and thin wires to fix the finished transformer to the gap at one end of the original ballast, connect the primary coil to points A and B in the figure, remove the original VCD machine transformer, and connect the secondary of the homemade transformer to the corresponding rectifier circuit. Also pay attention to replacing each rectifier diode with a high-frequency tube, and replace the 2200μF/16V capacitor on the mainboard with a 3300μF/25V capacitor. After checking everything is correct, you can turn on the power.

Since the working current of the whole machine is very small, there is no need to add heat sinks to V1 and V2. Even if the machine is turned on for more than ten hours continuously, the temperature of VI and V2 will rise very little.