If I use a chip with a regulated output of 5V3A, the input uses AC 220V, the transformer and the rectifier bridge output 12V, and then the regulator chip is connected. If the transformer uses such a small high-frequency transformer, how should the transformer determine the voltage and current? How should the input voltage and current of the voltage regulator chip be determined?
Celia 發表於 October 19, 2020
1 The [high frequency transformer] you mentioned is suitable for your voltage stabilizer chip;
2 Your voltage regulator chip is suitable for [low frequency transformer], as long as the capacity is greater than 20 ~ 25W.
Fraser 發表於 October 19, 2020
The train of thought feels a bit strange.
To design a voltage stabilizing circuit, it is necessary to determine the voltage stabilizing chip according to the needs of the output, such as audio use, you can use 7805, adjustable voltage can be used for analog devices 317, low-heat analog circuits use LDO, low-heat large current, ripple\interference It doesn't matter to use 2596.
Also consider the pressure difference, 8V input to 5V, small current, you can use 7805, 6V to 5V requires LDO, if you want to switch from 12V to 5V, you can use 2596 instead of 7805.
The input voltage, output voltage and output current of the voltage regulator chip itself are determined, and then the input current is calculated according to the characteristics of the voltage regulator chip.
For example, 7805 is series regulator, input current = output current, if it is 5V 3A, use series regulator, 12V input 5V output, (assuming 3A can be output)
Then input power 12*3=36 watts,,,, output power=5*3=15 watts. Then 21 watts of power will be completely sent to the voltage regulator chip to heat up! Smoke will be emitted in minutes.
The 2596 is a switch chip with much higher efficiency. The input and output currents are different. The efficiency can be 90%. Input 10 watts of power can output 9 watts of power, and only 10% of the power generates heat.
Pearl 發表於 October 19, 2020
Switch AC220V to 12V switching power supply with flyback BUCK topology. The transformer of this circuit has general models corresponding to switching frequency and power. There are a lot of Taobao, and you can buy power modules directly. 12V to 5V 3A is not recommended to use voltage regulator IC, low efficiency and high heat, using DCDC step-down circuit is more efficient.
