Hi,
i was working on an SMPS .... from ""mean well"" which provides an o/p og 7.5V and 3A....I would like to modify the circuit so that it wold provide 5V.....Please help me to change the voltage....
SMPS uses TOP223 PWM controller and an PC 817 opto coupler series....In regulation loop has a Az431 Shunt regulator to control the o/p voltage...
After tracing the circuit , the control loop almost looks like below....
I could find R4 = 20k and R3 = 10k so that o/p voltage is 7.5V......I changed R4 to 10K, now the output was stuck at 5.7V...... I tried different values for R4 like 6.8,8.2k but Vout was stuck at 5.7 ......I could observe the opto coupler Forward current to be at abt 25mA at this stage..... In normal case (7.5V out) the opto coupler I forward current was restricted to 3mA.....
I tried increasing the series resistance but the o/p voltage just increases above 5.7V......
How to bring down the 5.7V to the range of 4.5V to 5V for an SMPS.........
i was working on an SMPS .... from ""mean well"" which provides an o/p og 7.5V and 3A....I would like to modify the circuit so that it wold provide 5V.....Please help me to change the voltage....
SMPS uses TOP223 PWM controller and an PC 817 opto coupler series....In regulation loop has a Az431 Shunt regulator to control the o/p voltage...
After tracing the circuit , the control loop almost looks like below....
I could find R4 = 20k and R3 = 10k so that o/p voltage is 7.5V......I changed R4 to 10K, now the output was stuck at 5.7V...... I tried different values for R4 like 6.8,8.2k but Vout was stuck at 5.7 ......I could observe the opto coupler Forward current to be at abt 25mA at this stage..... In normal case (7.5V out) the opto coupler I forward current was restricted to 3mA.....
I tried increasing the series resistance but the o/p voltage just increases above 5.7V......
How to bring down the 5.7V to the range of 4.5V to 5V for an SMPS.........