A power transistor driving method, driving circuit and switching circuit

Abstract

The present invention discloses a power transistor driving method, a driving circuit and a switching circuit. When the power transistor is turned off, or the rate of change of the drain-source voltage of the power transistor with respect to time is greater than a first slope, or the drain-source voltage of the power transistor is greater than a first voltage, timing starts. When the power transistor is an N-type device, the driving pole of the power transistor is pulled down with a first current. When the timing reaches a first time, a pull-down switch is turned on or the driving pole of the power transistor is pulled down with a second current. If it is detected that the rate of change of the drain-source voltage of the power transistor with respect to time is greater than a second slope, the first time of the next switching period is increased; otherwise, the first time of the next switching period is decreased; the pull-down switch pulls down the driving pole of the power transistor; when timing starts from the turn-off of the power transistor, the first time is greater than the time from the turn-off of the switching transistor to the rate of change of the drain-source voltage of the power transistor with respect to time being greater than the first slope.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and particularly to a power transistor driving method, a driving circuit and a switching circuit. Background Art

[0002] In the control of the turn-off process of power devices in a switching power supply, it directly affects the reliability of the switching power supply. When the turn-off process of the power device is not properly handled, it not only causes low system efficiency, but also damages the power device and affects the reliability of the system. Therefore, how to reliably turn off the switching device is an important issue in the driving of power devices. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a power transistor driving method, a driving circuit and a switching circuit, so as to solve the problem that the turn-off process of power devices in the prior art cannot achieve high reliability.

[0004] The technical solution of the present invention is to provide a power transistor driving method. When the power transistor is turned off, or the rate of change of the drain-source voltage of the power transistor with respect to time is greater than a first slope, or the drain-source voltage of the power transistor is greater than a first voltage, timing starts. When the power transistor is an N-type device, the driving pole of the power transistor is pulled down with a first current. When the timing reaches a first time, the pull-down switch is turned on or the driving pole of the power transistor is pulled down with a second current. If it is detected that the rate of change of the drain-source voltage of the power transistor with respect to time is greater than a second slope, the first time of the next switching cycle is increased; otherwise, the first time of the next switching cycle is decreased; the pull-down switch pulls down the driving pole of the power transistor; when timing starts from the turn-off of the power transistor, the first time is greater than the time from the turn-off of the switch transistor to the rate of change of the drain-source voltage of the power transistor with respect to time being greater than the first slope.

[0005] The second current is greater than the first current.

[0006] Another technical solution of the present invention is to provide a power transistor driving circuit. When the power transistor is turned off, or the rate of change of the drain-source voltage of the power transistor with respect to time is greater than a first slope, or the drain-source voltage of the power transistor is greater than a first voltage, timing starts. When the power transistor is an N-type device, the power transistor driving circuit pulls down the driving pole of the power transistor with a first current. When the timing reaches a first time, the power transistor driving circuit turns on the pull-down switch or pulls down the driving pole of the power transistor with a second current. If it is detected that the rate of change of the drain-source voltage of the power transistor with respect to time is greater than a second slope, the first time of the next switching cycle is increased; otherwise, the first time of the next switching cycle is decreased; the pull-down switch pulls down the driving pole of the power transistor.

[0007] The second current is greater than the first current.

[0008] Optionally, it includes a time detection circuit and a pull-down circuit. The time detection circuit receives the drain-source voltage of the power transistor and outputs a voltage to indicate whether there is a change rate of the drain-source voltage of the power transistor over time greater than a second slope. The pull-down circuit receives the output voltage of the time detection circuit and adjusts the first time according to the output voltage of the time detection circuit.

[0009] Optionally, the time detection circuit includes a first capacitor, a first switch, and a first resistor, which are sequentially connected in series. The first capacitor receives the drain-source voltage of the power transistor. When pulling down the gate of the power transistor with a second current, the first switch is turned on, otherwise it is turned off. The voltage across the first resistor indicates whether there is a change rate of the drain-source voltage of the power transistor over time greater than the second slope.

[0010] Another technical solution of the present invention is to provide a switching circuit.

[0011] Adopting the circuit structure and method of the present invention, compared with the prior art, it has the following advantages: fast turn-off process, high reliability, and good electromagnetic compatibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is the voltage waveforms of the gate with respect to the source and the drain with respect to the source when the power transistor is turned off;

[0013] Figure 2 It is the circuit schematic diagram of the power transistor drive circuit according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0014] The following describes the preferred embodiments of the present invention in detail with reference to the accompanying drawings, but the present invention is not limited to these embodiments. The present invention covers any alternatives, modifications, equivalent methods, and solutions within the spirit and scope of the present invention.

[0015] In order to enable the public to have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, and those skilled in the art can fully understand the present invention without the description of these details.

[0016] In the following paragraphs, the present invention is described more specifically by way of example with reference to the accompanying drawings. It should be noted that the accompanying drawings are all in a relatively simplified form and use non-precise scales, only for the purpose of facilitating and clearly assisting in explaining the objectives of the embodiments of the present invention.

[0017] The present invention provides a power transistor drive method. When the power transistor is turned off, or the change rate of the drain-source voltage of the power transistor over time is greater than a first slope, or the drain-source voltage of the power transistor is greater than a first voltage, start timing. Please refer to Figure 1As shown, if the rate of change of the drain-source voltage of the power transistor with respect to time is greater than the first slope or the drain-source voltage of the power transistor is greater than the first voltage, that is, starting from time t01 or near time t01, when the power transistor is an N-type device, the driving pole of the power transistor is pulled down with a first current, that is, in the interval t01 - t02, it is pulled down with a first current; when the timing reaches the first time, at time t02, the pull-down switch is turned on or the driving pole of the power transistor is pulled down with a second current. If it is detected that the rate of change of the drain-source voltage of the power transistor with respect to time is greater than the second slope, the first time of the next switching period is increased; otherwise, the first time of the next switching period is decreased; the pull-down switch pulls down the driving pole of the power transistor; when starting to time from the turn-off of the power transistor, the first time is greater than the time from the turn-off of the switching transistor to the rate of change of the drain-source voltage of the power transistor with respect to time being greater than the first slope; that is to say, it must be after the Figure 1 time t01 in

[0018] that the first-time timing ends. Before time t01, the first-time timing cannot end. The second current is greater than the first current.

[0019] Please refer to Figure 2 As shown, the power transistor driving circuit includes a time detection circuit and a pull-down circuit. The time detection circuit receives the drain-source voltage of the power transistor and outputs a voltage to indicate whether there is a rate of change of the drain-source voltage of the power transistor with respect to time greater than the second slope. The pull-down circuit receives the output voltage of the time detection circuit and adjusts the first time according to the output voltage of the time detection circuit.

[0020] Please continue to refer to Figure 2As shown, the time detection circuit includes a first capacitor C31, a first switch K31, and a first resistor R31. The first capacitor C31, the first switch K31, and the first resistor R31 are connected in series in sequence. The first capacitor C31 receives the drain voltage of the power transistor M01. When pulling down the gate of the power transistor with a second current, the first switch K31 is turned on; otherwise, it is turned off. The voltage across the first resistor characterizes whether there is a change rate of the drain-source voltage of the power transistor with respect to time greater than a second slope. If the voltage of the first resistor is greater than a first voltage threshold, that is, it is detected that the change rate of the drain-source voltage of the power transistor with respect to time is greater than the second slope, then increase the first time of the next switching cycle; otherwise, decrease the first time of the next switching cycle.

[0021] Another technical solution of the present invention is to provide a switching circuit including the driving circuit of the above-mentioned power transistor.

[0022] Although the embodiments are described and illustrated separately above, for some common technologies, in the view of those of ordinary skill in the art, replacements and integrations can be made between the embodiments. For the content not explicitly recorded in one of the embodiments, reference can be made to the other embodiment with relevant records.

[0023] The above-described embodiments do not constitute a limitation on the protection scope of the technical solution. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the above embodiments shall be included in the protection scope of the technical solution.

Claims

1. A power transistor driving method, when the power transistor is turned off, or the rate of change of the drain-source voltage of the power transistor with respect to time is greater than a first slope, or the drain-source voltage of the power transistor is greater than a first voltage, timing starts. When the power transistor is an N-type device, the driving pole of the power transistor is pulled down with a first current. When the timing reaches a first time, the pull-down switch is turned on or the driving pole of the power transistor is pulled down with a second current. If it is detected that the rate of change of the drain-source voltage of the power transistor with respect to time is greater than a second slope, the first time of the next switching cycle is increased. ； Otherwise, the first time of the next switching cycle is decreased; The pull-down switch pulls down the driving pole of the power transistor; When timing starts from the turn-off of the power transistor, the first time is greater than the time from the turn-off of the switching transistor to the rate of change of the drain-source voltage of the power transistor with respect to time being greater than the first slope; The second current is greater than the first current.

2. A power transistor driving circuit, when the power transistor is turned off, or the rate of change of the drain-source voltage of the power transistor with respect to time is greater than a first slope, or the drain-source voltage of the power transistor is greater than a first voltage, timing starts. When the power transistor is an N-type device, the power transistor driving circuit pulls down the driving pole of the power transistor with a first current. When the timing reaches a first time, the power transistor driving circuit pull-down switch is turned on or the driving pole of the power transistor is pulled down with a second current. If it is detected that the rate of change of the drain-source voltage of the power transistor with respect to time is greater than a second slope, the first time of the next switching cycle is increased. ； Otherwise, the first time of the next switching cycle is decreased; The pull-down switch pulls down the driving pole of the power transistor; the second current is greater than the first current.

3. The power transistor driving circuit according to claim 2, characterized in that: It includes a time detection circuit and a pull-down circuit. The time detection circuit receives the drain-source voltage of the power transistor and outputs a voltage to indicate whether there is a rate of change of the drain-source voltage of the power transistor with respect to time greater than the second slope. The pull-down circuit receives the output voltage of the time detection circuit and adjusts the first time according to the output voltage of the time detection circuit.

4. The power transistor driving circuit according to claim 3, characterized in that: The time detection circuit includes a first capacitor, a first switch and a first resistor. The first capacitor, the first switch and the first resistor are connected in series in sequence. The first capacitor receives the drain-source voltage of the power transistor. When the driving pole of the power transistor is pulled down with a second current, the first switch is turned on, otherwise it is turned off. The voltage across the first resistor indicates whether there is a rate of change of the drain-source voltage of the power transistor with respect to time greater than the second slope.

5. A switching circuit, characterized in that: It includes the power transistor driving circuit according to any one of claims 2 to 4.

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