ltc3707egn power burner

(1) I have a switching power supply, which always burns the power tube, why

The industry recognized one is that the magnetic flux imbalance is easy to cause damage to the power tube, but it always burns out Does it mean that the power tube will overheat as soon as it is powered on? If so, it may be that the input is short-circuited or the output is short-circuited, and it is also possible that the inductive reactance of the transformer is not enough. For the absorption circuit, if you want to rule out this possibility, you can try to reduce the switching frequency to the minimum, or choose a power tube with high performance. I think this might be small.

(2) What is the reason for the switching power supply to burn the switch tube?

Frequent burning of the switch tube should be the place where the circuit is overloaded, such as the breakdown of the resonant capacitor, Whether the resistance used for the protection around the switch tube, the diode and other components are broken down, and the output transformer is short-circuited between turns.

㈢ What is the reason why the switching power supply always likes to burn the switch tube

There are these reasons why the switching power supply always burns the switch tube

1 , soft start circuit failure

2, switch tube integrated circuit board anti-peak absorption circuit failure

3, positive feedback too strong

4, timing capacitor failure leakage

5. The decoupling capacitor in the voltage regulator circuit fails

6. The negative feedback open loop of the voltage regulator circuit

7. The current limiting resistor of the switching tube emission Too small

8, the switching voltage is damaged

9, the rectifier bridge is damaged

10, the insulation between the switch tube and the heat sink is poor

11. The performance of the switch tube is poor or the power is too small

12. The B+ rectifier diode is damaged

13. The input AC voltage is too high or too low

Switching power supply, also known as switching power supply, switching converter, is a high-frequency electric energy conversion device. Its function is to convert a level of voltage into the voltage or current required by the user through different forms of architecture.

Switching power supply is a power supply that uses modern power electronic technology to control the time ratio of switching on and off to maintain a stable output voltage. Switching power supply is generally controlled by pulse width modulation (PWM) IC and MOSFET constitute. With the development and innovation of power electronic technology, switching power supply technology is also constantly innovating. At present, switching power supply is widely used in almost all electronic equipment due to its small size, light weight and high efficiency. It is an indispensable power supply method for the rapid development of today’s electronic information industry.

㈣ Which components will be burned out by the short circuit of the switching power supply

1. Most of the fuses burn out due to the high current in the rear circuit, that is to say, the latter circuit has Short circuit, such as switching tube short circuit, current limiting resistor burnout, chip damage, and bridge stack short circuit large filter capacitor damage will cause the fuse to burn out, and the fault phenomenon is no response to power-on.
2. 300V large filter capacitor is damaged: serious leakage will cause no response to boot, and slight damage will cause flashing and crashing problems. Generally, the capacitor bulge can be seen from the appearance.
3. Output filter capacitor: the fault is roughly the same as above
4. Switch tube: After damage, the insurance will generally be burned, and at the same time, the current limiting resistor will be damaged. No response to power on.
5. Zener diode: no response after power-on after damage, generally because the protection circuit works or the output voltage is directly pulled down, causing the load to not work.
6. Optical coupling and 431: The damage of these two components will generally cause unstable output voltage or no voltage output (damage of sampling resistor will also cause similar problems).
7. Start-up resistance and start-up capacitor: The damage of these two components will cause 300V no-voltage output, and the whole machine will not respond.
8. Current limiting resistor: This resistor damages the operation of the overcurrent protection circuit, and will also cause no output voltage of 300V.
9. Composite diode: After damage, the output voltage is unstable or can not carry the load.
10. PWM control chip: If it is serious, it will repeatedly burn the switch and fuse, and if it is slightly damaged, it will cause 300V no output voltage. You can judge the quality of the ground resistance value. Generally, the ground resistance value is divided by the ground pin. Other pins are a few hundred ohms.
11. Timing resistors and capacitors: Serious damage will cause no voltage output, and a little bit will cause the output voltage to be incorrect.

㈤ The reason why the FET of the mainboard power supply is burned out

It is caused by the unstable voltage of the external power supply. In addition, the parameters of the mainboard components are too conservative.

㈥ Why does the switching power supply always burn the switch tube?

Is the output voltage normal~~~~ or the conduction time of the tube is too long (this will make the tube more more time in the “amplified” state)

㈦ What is the reason why the switching power supply burns the switch tube

The reasons for the switching power supply burning the switch tube are:
Breakdown of rectifier devices, loss of capacitance of filter capacitors, failure of switching transformer primary winding peak absorption circuit, etc.
Should focus on inspection and replace defective components to eliminate faults.

㈧ 24V switchThe power supply repeatedly burns the switch tube. I don’t know why. Attach the circuit diagram.

This problem is probably caused by the switching transformer. You need to confirm whether the inductance and number of turns of the switching transformer are correct, and also confirm the The parameters are correct, the no-load should not heat up when you debug, I suggest you keep only one winding output voltage (3.3 or 5V) to test whether it is normal.

㈨ What is the problem of Tongjia ld7531 power supply burning switch tube

The power supply part is damaged and there is a large silicon rectifier in front to see if it is damaged or the tube is burning The circuit is directly regarded as a short circuit, so it is protected.

㈩ Why does the switching power supply always like to burn the switching tube?

Look I can’t analyze it until your drawings are specific. If you can’t solve the answer from the previous friend, it is probably caused by this problem.
1. Check whether the rising and falling edges of the control pole waveform of the tube are too long, which causes the tube to lose too much heat and fry the machine for a long time.
2. Check whether the duty cycle is too large, and it will also be caused by too long conduction time.
3. Check whether the transformer enters the critical saturation state or the transient pulse current is too large due to the excessive parasitic capacitance.
It is estimated that these two causes are more likely. See if it can help you.


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