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| Discrete Regulated power supply |
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| techguru:
Hi to all, I got this circuit from youtube , I cannot understand current control action . 1) what are the transistor which will control the current because there is a preset in collector of T7 transistor and potentiometer in base of T7? 2)correct me if i am wrong, T1,T2,T3 form single transistor compund configuration(sziklai pair). 3)what is the function of T4 transistor? My answer is T4 transistor supplies current to the base of compund transistor. 4)how current limiting function is implemented? Thank you all... |
| ledtester:
FWIW, here's the youtube video about this supply: The video says the circuit was published in Elektor Electronics around 20 years ago. The explanation of how current limiting works begins at around 4:10 in the video. |
| AG7CK:
T4 is a driver. As you say, based on the signal from the error amplifier T5-T6, it regulates the series element T1-T2-T3 by draining current from bias resistor R1. T1-T2 is a pure PNP Sziklai pair. Add T3 to this, and it becomes a NPN compound transistor. D1 keeps T1 biased. T7 is the current limiter. It acts by inhibiting the driver T4. It measures the voltage from base of T3 to output, and when the current is large enough, it turns on and raises the voltage on R2 which makes the driver drain current from R1, lowering the base of T3 and hence lowering the ouput voltage. |
| schmitt trigger:
Many years ago, an electronics magazine had a section called "DANDY": Discretes are not dead yet. There were many simple but clever discrete circuits, like this one, that would perform surprisingly well. |
| cellularmitosis:
--- Quote from: techguru on June 06, 2018, 05:46:54 pm ---Hi to all, I got this circuit from youtube , I cannot understand current control action . 1) what are the transistor which will control the current because there is a preset in collector of T7 transistor and potentiometer in base of T7? 2)correct me if i am wrong, T1,T2,T3 form single transistor compund configuration(sziklai pair). 3)what is the function of T4 transistor? My answer is T4 transistor supplies current to the base of compund transistor. 4)how current limiting function is implemented? Thank you all... --- End quote --- Thanks for starting a thread, I had seen that video recently and was quite curious to try this circuit out. |
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