An inverter is an apparatus that uses a power tube component to convert a direct current into an alternating current, which is used by an alternating current load. In recent years, with rapid development of electronics and electrical technologies, an inverter power supply has been widely applied to fields such as daily life, in-vehicle systems, and posts and telecommunications.
An inverter mainly includes an inverter bridge, control logic, and a filter circuit. In an instant that a load circuit is connected to an inverter circuit by using the filter circuit, especially when a serious reverse sag in an output voltage is caused when the load circuit is a capacitive load, a relatively high surge current is generated in the inverter circuit, and a current increases in a relatively short time. A power tube component in the inverter is usually damaged because of overcurrent. Therefore, each existing inverter apparatus is provided with an overcurrent protection circuit. An inductor current detection circuit of the inverter obtains an inductor current by means of sampling. A comparator circuit is used to compare an inductor current sampled value with a fixed current limit threshold. When the inductor current sampled value is greater than the current limit threshold, a power tube is turned off according to a specific time sequence, so that the power tube is prevented from being burnt because of overcurrent.
However, during the foregoing process, a specific transmission delay Δt (mainly including an inherent latency of a component in a signal transmission line and a dejittering delay of a signal) exists between a time point when the inductor current sampled value is greater than the current limit threshold and a time point when the power tube is successfully turned off; therefore, Δt*di/dt causes quite large Δi. Assuming that the current limit threshold is I0, an actual current of the power tube during current limiting is I0+Δi. Especially, in an inverter circuit with a smaller inductor value, the power tube bears larger current stress, resulting in damage to the power tube. A present current limiting method has an undesirable overcurrent protection effect for an inverter, and has low reliability