Hi,
I am in school learning about linear and switching power supplies ... I have already built multiple switching regulators and would like to learn more about linear regulators and op-amps.
I have created a power supply similar in fashion to the one below except I didn't include the IC3B op-amp or the circuitry with the 78L12 - 12V voltage regulator since I don't understand why they are included.
I have one really big issue! other then 1) everything else works!
1) The short circuit is being regulated to 1.5A output(tested with 0.33 ohms on output) however the pass transistor TIP3055 heats up very fast and the regulated 1.5A looses control over time! If you keep it on long enough the short circuit CC regulation fails and 5A! comes out. However, when I remove R48 and R52, to increase the short circuit CC limit, the output goes higher ~ 6A and the pass transistor isn't heating up as fast! It seems like it only heats up when the CC limit is regulated to 1.5A! Therefore the heating on TIP3055 has nothing to do with the load current, only when the CC is at it's limit it causes the TIP3055 transistor to heat up really fast(I don't understand!!).
The other issues:
1) I don't understand what the 78L12 - 12 volt regulator circuit is there and why it is connected to -Vs?
2) Is IC3B needed for better current regulation?
52
Thank you for your help!
I am in school learning about linear and switching power supplies ... I have already built multiple switching regulators and would like to learn more about linear regulators and op-amps.
I have created a power supply similar in fashion to the one below except I didn't include the IC3B op-amp or the circuitry with the 78L12 - 12V voltage regulator since I don't understand why they are included.
I have one really big issue! other then 1) everything else works!
1) The short circuit is being regulated to 1.5A output(tested with 0.33 ohms on output) however the pass transistor TIP3055 heats up very fast and the regulated 1.5A looses control over time! If you keep it on long enough the short circuit CC regulation fails and 5A! comes out. However, when I remove R48 and R52, to increase the short circuit CC limit, the output goes higher ~ 6A and the pass transistor isn't heating up as fast! It seems like it only heats up when the CC limit is regulated to 1.5A! Therefore the heating on TIP3055 has nothing to do with the load current, only when the CC is at it's limit it causes the TIP3055 transistor to heat up really fast(I don't understand!!).
The other issues:
1) I don't understand what the 78L12 - 12 volt regulator circuit is there and why it is connected to -Vs?
2) Is IC3B needed for better current regulation?
52
Thank you for your help!