Protection circuit and method for a switching power supply

Abstract

The invention discloses a switching power supply protective circuit and method. The protective circuit comprises a sampling circuit, a judging circuit and an action circuit, wherein the sampling circuit is used for sampling at least one signal, needing to be protected, of a switching power supply to generate at least one sampling signal, the judging circuit is used for judging states of the switching power supply according to the at least one sampling signal to generate at least one state control signal, the action circuit is used for generating a final driving signal according to an initial driving signal and the at least one state control signal, the final driving signal is in a low level when the switching power supply is in a fault state, and the initial driving signal is treated as the final driving signal from a first falling edge of the initial driving signal after the fault ends when the state of the switching power supply is converted from the fault state to a normal state. Through the technical scheme, the problem of too high electrical stressing of a switching pipe is solved, and therefore running reliability of the whole switching power supply is improved.

Description

technical field [0001] The invention relates to the field of switching power supplies, in particular to a protection circuit and method for switching power supplies. Background technique [0002] With the development of power electronics technology and the improvement of various application requirements, switching power supplies are developing in the direction of miniaturization, diversification, high efficiency and high reliability. For high-power switching power supplies (greater than 3KW), the current switching power supply topology mostly uses Figure 1A The resonant topology shown in the full-bridge LLC (resonant circuit) or Figure 2A The resonant topology shown in the three-level LLC, Figure 1A The driving signal of the full-bridge LLC in resonant topology is as Figure 1B as shown, Figure 2A The drive signal for the resonant topology three-level LLC is shown as Figure 2B shown. However, no matter what switching topology is used, various protection circuits nee...

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Problems solved by technology

like Figure 3A , 3B As shown, there is an obvious shortcoming in this circuit, because: due to the randomness of fault recovery, it is easy to cause excessive electrical stress of the switching tube of the switching power supply

For example, when the fault ends at time t1, the drive signals GA1 and GB1 will be output to the corresponding switch tubes, and the drive signal GB1 will have a very small drive pulse width. If the drive signals GA1 and GB1 are used as the final drive signals, At this time, it will cause a large VDS (drain-source) voltage spike of the switch tubes Q2 and Q3, which will affect the safe and reliable operation of the switch tubes Q2 and Q3.

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