What is the specific principle of adding two resistors and two transistors to this resistor buck circuit? I haven't figured it out.
Rick 发表于 July 3, 2020
These two transistors seem to be 400V-resistant tubes. The purpose here is first-level buck and first-level voltage regulation. One piece of this triode, used in 220Vac circuit, has the risk of withstand voltage.
When the circuit satisfies several conditions, it can be used - 0 load, two 47K has a certain risk. At full load, two 56Ks have a greater risk of breakdown (two 15Ks in series or three in series with appropriate resistance) should be used. The specific safety range needs to be calculated.
Beyonce 发表于 July 3, 2020
This is not a resistance-capacitance buck. The resistance-capacitance buck capacitor is connected inside. The feeling is to use a triode to build a high-voltage LDO.
Henrik 发表于 July 3, 2020
Two and 56K share a part of the power, and then use two transistors to share the power and share 5V. Why do you use a transistor to share the power without a resistor? Because the transistor has a current expansion effect, the load capacity of the output 5V voltage is enhanced .