I want to make an AC to DC regulated power supply. I don't have an overcurrent protection circuit yet. Please give me some advice.

菁华如风

I want to make an AC to DC regulated power supply. I don't have an overcurrent protection circuit yet. Please give me some advice. [Copy link]

I want to make a voltage-stabilizing circuit board by myself. The preliminary simulation diagram and the indicators I want to achieve are as follows: Performance indicators: lRated input AC voltage220V, no-load output (open circuit) voltage5.0V, rated output current0.67A lRated input AC voltage[font=Arial, 220V, from no-load to rated load (7.5Ω), the output voltage fluctuation is not more than 0.2V. Under rated load (7.5Ω), output ripple (peak-to-peak value) ≦50mV. Under rated load (7.5Ω), if the input voltage is within the rated value, 200V～240 Vfluctuation, output voltage fluctuation is not greater than0.1V lLEDWorking status indication (Normal light is green, fault light is red) lUse industrial frequency power transformer (220V/9V 20W), step down the voltage to 9V AC and then rectify and stabilize the voltage I was thinking of using a single-chip microcomputer to make a digital display digital tube to display fault codes or control the automatic reset of the overload protection circuit. There is still an overcurrent protection circuit that has not been built, and I don’t know how to add the microcontroller. I would like to ask the masters for help to give me some suggestions, please be more specific (I am just getting started in electronics~~) To summarize the questions I want to ask: 1. What are the improvements to the circuit? 2. How to build an overload protection circuit? 3. How to use a single-chip microcomputer (I have STC's 89C52RC) to receive overload signals and display fault codes? 3. How to set the automatic reset of the overload protection after the circuit returns to normal? Thank you undefined

maychang

1. If there is any room for improvement in the circuit, don't just "improve" it. Just give up. Let's not talk about the fact that the TIP41C you are using has a withstand voltage of only 100V and cannot be used in 220V AC rectification (the voltage after rectification can reach more than 300V). First, calculate the efficiency of reducing more than 300V to 5V. It is less than 2%. More than 98% of the energy is wasted. How big a heat sink do you need to dissipate this heat?

菁华如风

maychang posted on 2017-11-15 15:29 1. If there is any improvement in the circuit, don't "improve" it, just give up. Not to mention that the TIP41C you are using has a withstand voltage of only 100V, so it can't be used in 220V AC...

"Use an industrial frequency power transformer (220V/9V 20W), step down the voltage to 9V AC, and then rectify and stabilize the voltage"

maychang

Jinghua Rufeng published on 2017-12-6 09:05 "Use an industrial frequency power transformer (220V/9V 20W), step down the voltage to 9V AC, and then rectify and stabilize the voltage"

This diagram is feasible using an industrial frequency transformer. However: 1. Q2 does not need to use the same type of tube as Q1, and can use a small power tube, such as 8050. This is cheaper. 2. R1 is 7.5kΩ, which is too large. Assuming that the voltage across R1 is 5V, the current passing through it is only 0.67mA, which is not enough for Q2 and U1.

菁华如风

maychang posted on 2017-12-6 12:05 This diagram is feasible using a power frequency transformer. However: 1. Q2 does not have to use the same type of tube as Q1, and a small power tube can be used, such as 8050...

Hmm, thank you for your advice