I have a 19.5V 11.8A 230W laptop/touchscreen desktop PSU. It's for HP machines but is branded Bestec, and seems to be the same one as Dell PA-19.
I'd like to use it for a project that requires 24.0V, so I'd like to modify the PSU's voltage divider according to https://polonai.se/smps/tosh/ and https://hackaday.io/project/3469-mod...k-power-supply
The output caps are rated at 25V, so I'll be close, but not over their limit.
I've identified the opamp/comparator and voltage reference as ST's TSM103 in red, and pin 2 is the inverting input and pin 3 is the 2.5V reference. I don't have a variable PSU with me right now, so I can't identify when the optocouplers turn off and the voltage divider to the output voltage.
1. Can someone help me identifying the voltage divider?
2. The PSU has two optocouplers separating mains from the secondary. Why two, not one?
3. There's a 50k trimpot in the area highlighted in yellow on the other side of the board. I've tweaked it, and the output voltage is constant at exactly 20.00V, regardless of the trimpot position. Since it's not affecting voltage, could it be used to set the OCP current limit?
Thanks!
I'd like to use it for a project that requires 24.0V, so I'd like to modify the PSU's voltage divider according to https://polonai.se/smps/tosh/ and https://hackaday.io/project/3469-mod...k-power-supply
The output caps are rated at 25V, so I'll be close, but not over their limit.
I've identified the opamp/comparator and voltage reference as ST's TSM103 in red, and pin 2 is the inverting input and pin 3 is the 2.5V reference. I don't have a variable PSU with me right now, so I can't identify when the optocouplers turn off and the voltage divider to the output voltage.
1. Can someone help me identifying the voltage divider?
2. The PSU has two optocouplers separating mains from the secondary. Why two, not one?
3. There's a 50k trimpot in the area highlighted in yellow on the other side of the board. I've tweaked it, and the output voltage is constant at exactly 20.00V, regardless of the trimpot position. Since it's not affecting voltage, could it be used to set the OCP current limit?
Thanks!
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