Problem 1: Voltage failure
Cause:
A common failure mode caused by the MOSFET drain-source voltage exceeding its specified voltage value and reaching a certain energy limit
Solution:
1. Reasonable derating use,
2. Reasonable transformer reflection voltage,
3. Reasonable RCD and TVS absorption circuit design,
4. Large current wiring should adopt thick and short layout structure to minimize wiring parasitic inductance,
5. Choose a reasonable gate resistor Rg,
6. In high-power power supply, you can add RC shock absorber or Zener diode to absorb
Problem 2: Electrostatic failure
Causes:
absorb dust, change the impedance between lines, due to the action of electric field or current, the insulation layer and conductor of the component are damaged, so that the component cannot work (completely damaged), due to the instantaneous soft breakdown of the electric field or overheating of the current, the component is damaged damage
Solution:
The protection diode at the input of the MOS circuit has a current tolerance of 1 mA when powered. When there may be too large instantaneous input current (greater than 10mA), the input protection resistor should be connected in series. At the same time, due to the limited instantaneous energy absorbed by the protection circuit, excessive transient signals and excessive electrostatic voltage will cause the protection circuit to fail. Therefore, during the soldering process, the soldering iron must be reliably grounded to prevent leakage from the input terminals of the equipment. In general use, after the power is cut off, the residual heat of the soldering iron can be used for soldering, and the grounding pin should be soldered first.
Question 3: Current failure
Cause:
It refers to the destruction mode caused by the abnormal high current and voltage superimposed on the MOSFET at the same time when the power supply is running, resulting in instantaneous local heating
Solution:
1. Limited by the maximum rated current and pulse current
2. RDSON limited by maximum junction temperature.
3. Limited by the maximum power dissipation of the device.
4. Limited by the maximum single pulse current.
5. Breakdown voltage BVDSS restricted area.
