12V switching power supply to raise the voltage to 14V?

1: First, the computer power supply ON/OFF that line shorted to ground, so that the switching power supply has been turned on, but do not power up first.

2: Find the TL494 IC on the circuit board of the computer power supply. The model number on some power supplies may be 7500, find its first leg, connect the 100K potentiometer to the ground in the first leg, and adjust the potentiometer to the maximum resistance value.

3: In the output +12V, there is connected to a voltmeter, now energized. Pay attention to the voltage on the table, now about 12V or so. Slowly adjust the potentiometer so that the voltage output is stable at about 15.5V. If there is no output when adjusting the voltage higher, that is the power protection. After the power failure, remove the TL494 fourth pin to the LM339 resistor to the reservation’s ground line. After adjusting the potentiometer resistance value, then connect a series of the same large resistor on the potentiometer to adjust the output will not exceed this voltage. At the same time, a fixed potentiometer is put on the instructions, adjust to what position is how much voltage.

4: Output +12V line in series with a sufficient current diode; charge the battery and set the power supply voltage to about 14.4V. After 2 – 4 hours to adjust to the maximum voltage output, the switching power supply output voltage is stable, so after charging is complete, it will automatically set the current to be small. After the voltage limit, do not worry about overcharging. You can fill the 32A battery in about 10 hours. The so-called constant current is just the beginning of the current limit, so start to turn down the voltage; the purpose is to limit the current. The best is that the diode series can be touched by hand; when the voltage is adjusted to the maximum, the series diode does not heat up; it is charged fully. You will know how long it takes to fill up after a few times; setting a little longer will not affect the battery.

The computer power supply above the TL431 you can not move; it is the standby circuit.


Ena Leung

Ena Leung


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