EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: Efe_114 on May 26, 2022, 09:46:23 am
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Basically the title. I have no clue how this power supply works and what "D/A Width" is supposed to mean in a power supply. Please help me out with understanding this. |O
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D/A width appears to refer to a knob with that name on the front panel, and the knob is depicted in the schematic as potentiometer VR1.
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From my very quick look:
- T1 forms a flyback converter to change +9V into a positive and negative voltage of some sort which is isolated
- D4 is used as a basic voltage reference, and then opamp 1b does some filtering and gain on this to generate the main analog voltage rail
- the main rail is then divided down using R5 and R6 into various voltage references, and then buffered through opamps 1A and 2A
- opamp 2B converts the unknown negative voltage into a regulated -5V based on the main analog voltage rail and an inverting configuration
So basically a flyback makes an isolated +/- supply, then some reference voltages are made using resistor dividers, and then these reference voltages are buffered by some opamps.
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From my very quick look:
- T1 forms a flyback converter to change +9V into a positive and negative voltage of some sort which is isolated
- D4 is used as a basic voltage reference, and then opamp 1b does some filtering and gain on this to generate the main analog voltage rail
- the main rail is then divided down using R5 and R6 into various voltage references, and then buffered through opamps 1A and 2A
- opamp 2B converts the unknown negative voltage into a regulated -5V based on the main analog voltage rail and an inverting configuration
So basically a flyback makes an isolated +/- supply, then some reference voltages are made using resistor dividers, and then these reference voltages are buffered by some opamps.
Thanks for answering, I have 2 more questions if you could answer.
How does that flyback circuit actually oscillate? I thought the same but I decided otherwise because I couldn't spot an oscillator.
Why do they have the transistor outside of the 1b amplifier feedback loop?
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https://electronics.stackexchange.com/questions/377753/understanding-a-single-transistor-flyback-transformer-driver might be of help here.
As for the BJT outside of 1b, perhaps it is for power supply sequencing? Not really sure.