CROSS-REFERENCE TO RELATED APPLICATIONS

The present disclosure claims priority of Chinese Patent Application No. 201911119090.5, filed to China Patent Office on Nov. 15, 2019. Contents of the present disclosure are hereby incorporated by reference in entirety of the Chinese Patent Application.

TECHNICAL FIELD

The present disclosure relates to the field of power electronic technologies, and in particular to a power transistor driving method, a driving circuit and a switching circuit.

BACKGROUND

The control of a turn-off process of a power component in a switching power supply directly affects the reliability of the switching power supply. When the turn-off process of the power component is not handled properly, not only low system efficiency is caused, but also the power component is damaged, and a reliability of a system is affected. Therefore, how to reliably turn off a switching component is an important problem in power component driving.

SUMMARY

At least some embodiments of the present disclosure provide a power transistor driving method, a driving circuit and a switching circuit, so as at least to partially solve a problem in related art that a power component may not be turned off with high reliability.

In one embodiment of the present disclosure, a power transistor driving method is provided, when a power transistor is turned off or a change rate of a drain-source voltage of the power transistor along with time is higher than a first slope or the drain-source voltage of the power transistor is higher than a first voltage, a timer is started, and when the power transistor is an N-type component, a driving pole of the power transistor is pulled down in a first current, and when a time period recorded by the timer reaches a first time period, a pull-down switch of a power transistor driving circuit is turned on or the driving pole of the power transistor is pulled down in a second current, when detecting that the change rate of the drain-source voltage of the power transistor along with the time is higher than a second slope, the first time period corresponding to a next switching period is increased; when detecting that the change rate of the drain-source voltage of the power transistor along with the time is lower than or equal to the second slope, the first time period corresponding to the next switching period is decreased; the driving pole of the power transistor is pulled down by the pull-down switch; when the a timer is started from a moment at which the power transistor is turned off, the first time period is higher than a time period from a moment at which a switching tube is turned off to a moment at which the change rate of the drain-source voltage of the power transistor along with the time is higher than the first slope; and the second current is higher than the first current.

In one embodiment of the present disclosure, a power transistor driving circuit is further provided, when a power transistor is turned off or a change rate of a drain-source voltage of the power transistor along with time is higher than a first slope or the drain-source voltage of the power transistor is higher than a first voltage, a timer is started, and when the power transistor is an N-type component, a driving pole of the power transistor is pulled down in a first current by the power transistor driving circuit, and when a time period recorded by the timer reaches a first time period, a pull-down switch of the power transistor driving circuit is turned on or the driving pole of the power transistor is pulled down in a second current, when detecting that the change rate of the drain-source voltage of the power transistor along with the time is higher than a second slope, the first time period corresponding to a next switching period is increased; when detecting that the change rate of the drain-source voltage of the power transistor along with the time is lower than or equal to the second slope, the first time period corresponding to the next switching period is decreased; the driving pole of the power transistor is pulled down by the pull-down switch; and the second current is higher than the first current.

In one optional embodiment, the power transistor driving circuit includes a time detection circuit and a pull-down circuit, the time detection circuit is configured to receive the drain-source voltage of the power transistor, and output a voltage to represent whether the change rate of the drain-source voltage of the power transistor along with the time is higher than the second slope, the pull-down circuit is configured to receive an output voltage of the time detection circuit, and regulate the first time period according to the output voltage of the time detection circuit.

In one optional embodiment, the time detection circuit includes a first capacitance, a first switch and a first resistance, the first capacitance, the first switch and the first resistance are serially connected in turn; the first capacitance is configured to receive the drain-source voltage of the power transistor, when the driving pole of the power transistor is pulled down in the second current, the first switch is turned on, and when the driving pole of the power transistor is not pulled down in the second current, the first switch is turned off; and a voltage of the first resistance represents whether the change rate of the drain-source voltage of the power transistor along with the time is higher than the second slope.

In one optional embodiment, when the voltage of the first resistance is higher than a first voltage threshold, the change rate of the drain-source voltage of the power transistor along with the time is higher than the second slope.

In one embodiment of the present disclosure, a switching circuit is further provided.

Through adopting the circuit structure and method of the present disclosure, compared with the related art, it has the following advantages: a rapid turn-off process, high reliability and good electromagnetic compatibility.

