Power supply circuits, or power supply circuits in the field of propulsion, inevitably use MOSFETs, which are of many types and have many functions. For switching power supply or propulsion applications, it is natural to use its switching function.
Regardless of N-type or P-type MOSFET, the principle is essentially the same, MOSFET is added to the gate of the bonding end of the current to regulate the output side of the drain current, MOSFET is a voltage-controlled device it is based on the current added to the gate on the manipulation of the device's characteristics, is not prone to switching like a transistor due to base current caused by the positive charge storage effect, and therefore, in the switching application, the MOSFET switching rate should be faster than the transistor. The switching rate should be faster than the triode.
MOSFET small-current heating causes
1, the circuit principle of the problem is to let the MOSFET work in the linear state of operation, rather than in the switching situation. This is also a cause of MOSFET heat. If the N-MOS switching, G-level operating voltage than the switching power supply a few V, in order to be completely on and off, P-MOS is the other way around. Not completely on and loss is too large resulting in output power dissipation, the equivalent circuit DC characteristic impedance is larger, the loss is expanded, so U * I is also expanded, depletion represents heat. This is also the most avoided incorrect design program control circuit.
2, the frequency is too high, mainly sometimes too much pursuit of perfect volume, resulting in frequency enhancement, MOSFET on the expansion of the consumption, so the heat also increased.
3, did not do sufficient heat exclusion design program, the current is too high, MOSFET tolerance current value, generally must maintain good heat exclusion can be done. Therefore, ID is lower than the higher current, it is also likely to heat more serious, must be sufficient to assist the heat sink.
4, MOSFET model selection is not correct, the output power is not correct, MOSFET resistance is not taken into account, resulting in the expansion of the switching characteristic impedance.
MOSFET small current heating is more serious how to solve?
1.get the MOSFET heat exclusion design program, assist a certain number of heat sinks.
2.Paste the heat exclusion glue.
Post time: Jul-11-2024
