The U5 reference voltage is 2.5V, RP4 is 50 ohms, and the switch S1 is regarded as a load connected to achieve a constant current DC10ma. Now the problem is: when the VCC voltage is DC70V, the circuit works normally after S1 is short-circuited. When VCC increases to DC120V, the MOS tube IRF740 will burn out after S1 is closed. What is wrong?
Fitzgerald 게시 날짜 October 7, 2020
guess:
1. Some components have insufficient voltage
2. Some components have insufficient power or heat dissipation
Freida 게시 날짜 October 7, 2020
With the increase of the power supply voltage, the output power of the power supply increases under the same current. This part of the power is carried by two parts, the load and the MOS. Because the load is subjected to a constant current, the power is constant. The power received by MOS is I*VDS
Kana 게시 날짜 October 7, 2020
irf740 can withstand 400v 10A, why does it burn out when it is connected to 120V?
Phil 게시 날짜 October 7, 2020
The former 400V refers to the withstand voltage, and the latter refers to the maximum current, not the maximum power.
