aramosfet
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Hi All,
I recently purchased a Regulated power supply kit from (https://www.banggood.com/0-30V-2mA-3A-Adjustable-DC-Regulated-Power-Supply-DIY-Kit-p-958308.html).
The schematic of the design is also provided.
![Regulated Supply.jpg Regulated Supply.jpg](https://www.edaboard.com/data/attachments/53/53139-9e86140d8d01df2861d049f0f80a52c9.jpg)
My goal is to control the setting of output voltage and current limit with a microcontroller, LCD/LED display and rotary encoders. To that end, I tried to understand the functioning of the supply and have a few doubts.
From the schematic, I understand
1. R7 is used as the current sense resistor.
2. P1 controls the output voltage through U2 opamp. which drives the darlington pair Q2 and Q4.
3. P2 sets the current limit through U3. When current limit is exceeded D9 pulled to negative by U3 which reduces the drive to output transistors.
4. Q3 and D12 serve as current limit indication.
Questions.
1. what is the purpose of U1?
Both inputs of U1 are tied to ground (before the current sense resistor).
2. Why is U1 negative supply connected to ground instead of negative supply. Further, most references in the schematic are connected to load ground before the sense resistor rather than the input supply ground or bridge rectifier ground. why is this so?
3. As per the BOM, the negative supply is regulated by a 5.7V Zener. So the opamps have a positive rail that goes to 32V or more and the negative rail to -5.7V. Is this fine?
Finally, the intent is to drive the P1 and P2 potentiometer points with voltages to set the output voltage and current limit digitally with a microcontroller. What would be the best way to achieve it?
Thanks
I recently purchased a Regulated power supply kit from (https://www.banggood.com/0-30V-2mA-3A-Adjustable-DC-Regulated-Power-Supply-DIY-Kit-p-958308.html).
The schematic of the design is also provided.
![Regulated Supply.jpg Regulated Supply.jpg](https://www.edaboard.com/data/attachments/53/53139-9e86140d8d01df2861d049f0f80a52c9.jpg)
My goal is to control the setting of output voltage and current limit with a microcontroller, LCD/LED display and rotary encoders. To that end, I tried to understand the functioning of the supply and have a few doubts.
From the schematic, I understand
1. R7 is used as the current sense resistor.
2. P1 controls the output voltage through U2 opamp. which drives the darlington pair Q2 and Q4.
3. P2 sets the current limit through U3. When current limit is exceeded D9 pulled to negative by U3 which reduces the drive to output transistors.
4. Q3 and D12 serve as current limit indication.
Questions.
1. what is the purpose of U1?
Both inputs of U1 are tied to ground (before the current sense resistor).
2. Why is U1 negative supply connected to ground instead of negative supply. Further, most references in the schematic are connected to load ground before the sense resistor rather than the input supply ground or bridge rectifier ground. why is this so?
3. As per the BOM, the negative supply is regulated by a 5.7V Zener. So the opamps have a positive rail that goes to 32V or more and the negative rail to -5.7V. Is this fine?
Finally, the intent is to drive the P1 and P2 potentiometer points with voltages to set the output voltage and current limit digitally with a microcontroller. What would be the best way to achieve it?
Thanks