Through circuit
Half bridge, full bridge switching power supply commonly used topology, "straight" have great threat to its, through is the same bridge arm of the two transistors in the same time and guide through the phenomenon. During the commutation period, the switching power supply is easy to be disturbed and the direct current can be damaged. Once the direct phenomenon shall be to detect as soon as possible and immediately turn off the drive, in order to avoid switching devices in the PN junction accumulated too much heat and burn.
Over current circuit
When the load short circuit, overload or control circuit failure accidents, caused by excessive current through the switch tube and power tubes increases, the fever, if there is no too current protection device, high power switch tube may be damaged; regulating circuit failure may also led to the damage of over current. Over current protection is generally detected and compared by sampling resistors or Holzer sensors to achieve protection, but they have the disadvantages of large size and high cost.
Overshoot circuit
Stabilized current switching power supply in the startup and shutdown is easy to cause the current overshoot, such as an LED load to the MS level current overshoot is not allowed, instantaneous large current impact may damage the LED device.
Overvoltage circuit
Stabilized current power if the load circuit breaker, across the current sense resistor voltage drop to zero, once a given value is zero, the regulator will make voltage output soared to a maximum value, which of load is connected to the poor contact is very dangerous. For LED, semiconductor refrigeration and other load, the overvoltage occurs, the first task is to protect the load, and the second is to protect the switch power tube.
In order to solve the above problems, there are two kinds of protection methods used simultaneously, one is to place the bidirectional TVS to realize the protection of the instant impulse voltage.