Power tube driving method, driving circuit and switching circuit

Abstract

The present invention discloses a power tube driving method, a driving circuit, and a switching circuit. When the power tube is turned off, the drain-source voltage of the power tube is detected. When the power tube is an N-type device, when the rate of change of the drain-source voltage of the power tube over time is less than a first slope threshold, the power tube is pulled down with a first current; then, when the rate of change of the drain-source voltage of the power tube over time is greater than the first slope threshold, the driving electrode of the power tube is pulled down with a second current; then, when the rate of change of the drain-source voltage of the power tube over time is again less than the first slope threshold, the pull-down switch is turned on or the driving electrode of the power tube is pulled down with a third current.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a power tube driving method, a driving circuit and a switching circuit. Background Art

[0002] Controlling the shutdown process of power devices in a switching power supply directly impacts its reliability. Improper shutdown of power devices can not only lead to low system efficiency but also damage the devices, compromising system reliability. Therefore, reliably shutting down switching devices is a crucial issue in power device driving. Summary of the Invention

[0003] In view of this, an object of the present invention is to provide a power tube driving method, a driving circuit and a switching circuit to solve the problem in the prior art that the power device shutdown process cannot achieve high reliability.

[0004] The technical solution of the present invention is to provide a power tube driving method, wherein when the power tube is turned off, the drain-source voltage of the power tube is detected. When the power tube is an N-type device, when the rate of change of the drain-source voltage of the power tube over time is less than a first slope threshold, the power tube is pulled down with a first current; then, when the rate of change of the drain-source voltage of the power tube over time is greater than the first slope threshold, the driving electrode of the power tube is pulled down with a second current; then, when the rate of change of the drain-source voltage of the power tube over time is again less than the first slope threshold, the pull-down switch is turned on or the driving electrode of the power tube is pulled down with a third current;

[0005] When the power tube is a P-type device, when the rate of change of the absolute value of the drain-source voltage of the power tube over time is less than a first slope threshold, the driving electrode of the power tube is pulled up with a first current; then, when the rate of change of the absolute value of the drain-source voltage of the power tube over time is greater than the first slope threshold, the driving electrode of the power tube is pulled up with a second current; then, when the rate of change of the absolute value of the drain-source voltage of the power tube over time is again less than the first slope threshold, the pull-up switch is turned on or the driving electrode of the power tube is pulled up with a third current;

[0006] The third current is greater than the second current.

[0007] Another technical solution of the present invention is to provide a power tube drive circuit. When the power tube is turned off, the power tube drive circuit detects the drain-source voltage of the power tube. When the power tube is an N-type device, when the rate of change of the drain-source voltage of the power tube over time is less than a first slope threshold, the power tube drive circuit pulls down the power tube with a first current. Then, when the rate of change of the drain-source voltage of the power tube over time is greater than the first slope threshold, the power tube drive circuit pulls down the driving electrode of the power tube with a second current. Then, when the rate of change of the drain-source voltage of the power tube over time is again less than the first slope threshold, the pull-down switch of the power tube drive circuit is turned on or the driving electrode of the power tube is pulled down with a third current.

[0008] When the power tube is a P-type device, when the rate of change of the absolute value of the drain-source voltage of the power tube over time is less than a first slope threshold, the power tube driving circuit pulls up the driving electrode of the power tube with a first current; then, when the rate of change of the absolute value of the drain-source voltage of the power tube over time is greater than the first slope threshold, the power tube driving circuit pulls up the driving electrode of the power tube with a second current; then, when the rate of change of the absolute value of the drain-source voltage of the power tube over time is again less than the first slope threshold, the pull-up switch of the power tube driving circuit is turned on or the driving electrode of the power tube is pulled up with a third current;

[0009] The third current is greater than the second current.

[0010] Optionally, a slope detection circuit is included to detect the rate of change of the drain-source voltage of the power tube over time.

[0011] Optionally, a third pull-down circuit and a first pull-up circuit are included, wherein the third pull-down circuit pulls down the driving electrode of the power tube with the first current;

[0012] The first pull-up circuit receives the output voltage of the slope detection circuit, and does not pull up the driving electrode of the power tube when the rate of change of the drain-source voltage of the power tube over time is less than a first slope threshold; and pulls up the driving electrode of the power tube when the rate of change of the drain-source voltage of the power tube over time is greater than the first slope threshold.

[0013] Optionally, the first pull-up circuit includes a fourth transistor and a fifth transistor, the sources of the fourth transistor and the fifth transistor are connected to the driving electrode of the power tube, the drain of the fourth transistor is connected to the driving electrode, and receives the output voltage of the slope detection circuit.

[0014] Optionally, the first pull-up circuit further includes a second conductive element and a first current limiting circuit, the first current limiting circuit is connected to the drain of the fifth transistor, the second conductive element is connected between the drain of the fourth transistor and the drain of the fifth transistor, and the second conductive element is a transistor or a diode whose drain is connected to the driving electrode.

[0015] Optionally, the slope detection circuit is a first capacitor, the third pull-down circuit is a fourth current source, the first current is equal to the third current, and the magnitude of the fourth current source is equal to the third current.

[0016] Optionally, the power tube driving circuit includes a sixth transistor, the driving electrode of the power tube is connected to the reference ground through the sixth transistor, and when the driving electrode voltage of the power tube is lower than a first voltage threshold, the sixth transistor is turned on.

[0017] Optionally, the device further includes a first pull-down circuit and a second pull-down circuit, wherein the first pull-down circuit pulls down the driving electrode of the power tube with the second current; and the second pull-down circuit includes the pull-down switch.

[0018] During the shutdown period of the power tube, when the rate of change of the drain-source voltage of the power tube with time is greater than the first slope threshold and then less than the first slope threshold, the pull-down switch of the second pull-down circuit is turned on.

[0019] Optionally, the second pull-down circuit includes a first transistor, a second transistor, a third transistor, a second current source, a first switch and a first resistor. The second current source and the first switch are connected in series to form a first series circuit. The drain of the first transistor is connected to the driving electrode of the power tube, the drain of the second transistor is connected to the driving electrode of the first transistor, the first series circuit is connected to the driving electrode of the first transistor, the driving electrode of the second transistor is connected to the reference ground through the first resistor, the sources of the first transistor and the second transistor are connected to the reference ground, the driving electrode of the second transistor receives the output voltage of the slope detection circuit, and the third The transistor is connected between the driving electrode of the first transistor and the reference ground. When the power tube is turned off, the rate of change of the drain-source voltage of the power tube over time is less than a first slope threshold, the first switch is turned off, the third transistor is turned on, the second pull-down circuit is disabled, and the first transistor does not pull down the driving electrode of the power tube; then, the rate of change of the drain-source voltage of the power tube over time is greater than the first slope threshold, the first switch is turned on, the third transistor is turned off, and the second pull-down circuit is enabled; then, the rate of change of the drain-source voltage of the power tube over time is again less than the first slope threshold, and the second pull-down circuit continues to be enabled; the first transistor serves as the pull-down switch.

[0020] Optionally, the second pull-down circuit further includes a first conductive element, which is connected between the driving electrode and the drain of the second transistor. The first conductive element is a transistor or a diode with the drain and the driving electrode connected.

[0021] Optionally, the slope detection circuit is a first capacitor, the first pull-down circuit is a first current source or a second resistor or a seventh transistor, and the magnitude of the first current source is the second current.

[0022] Optionally, the first capacitor is implemented by a power tube of the same type as the power tube, namely, a first power tube, the source of the first power tube is connected to the second pull-down circuit, and the drain of the first power tube is connected to the drain of the power tube.

[0023] Optionally, when the driving electrode voltage of the power tube is lower than a first voltage threshold, the first transistor is turned on.

[0024] Another technical solution of the present invention is to provide a switching circuit.

[0025] Compared with the prior art, the circuit structure and method of the present invention have the following advantages: fast shutdown process, high reliability and good electromagnetic compatibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The voltage waveforms of the driving electrode relative to the source and the drain relative to the source when the N-type power tube is turned off;

[0027] Figure 2 The voltage waveforms of the driver electrode relative to the source electrode and the drain electrode relative to the source electrode when the P-type power tube is turned off;

[0028] Figure 3 This is a circuit diagram of a power tube driving circuit according to an embodiment of the present invention;

[0029] Figure 4 is a circuit diagram of a second pull-down circuit according to an embodiment of the present invention;

[0030] FIG5( a ) is a schematic circuit diagram of a first pull-down circuit according to an embodiment of the present invention;

[0031] FIG5( b ) is a circuit diagram of a first pull-down circuit according to another embodiment of the present invention;

[0032] Figure 6 This is a circuit diagram of a power tube driving circuit according to another embodiment of the present invention;

[0033] Figure 7 FIG. 4 is a circuit diagram of a power tube driving circuit according to another embodiment of the present invention. DETAILED DESCRIPTION

[0034] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention is not limited to these embodiments and covers any substitution, modification, equivalent method and solution made within the spirit and scope of the present invention.

[0035] In order to make the public have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, but those skilled in the art can also fully understand the present invention without description of these details.

[0036] The present invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. It should be noted that the drawings are simplified and not to exact proportions, and are only used for the purpose of conveniently and clearly illustrating the embodiments of the present invention.

[0037] The present invention provides a power tube driving method, please refer to Figure 1 Figure 2 shows the voltage waveforms of the driver relative to the source Vgs and the drain relative to the source Vds when an N-type power tube is turned off. When the power tube is turned off, the drain-source voltage Vds of the power tube is detected. If the power tube is an N-type device, during the interval t01-t02, when the rate of change of the drain-source voltage Vds of the power tube over time is less than a first slope threshold, the power tube is pulled down with a first current. Then, during the interval t02-t03, when the rate of change of the drain-source voltage Vds of the power tube over time is greater than the first slope threshold, the driver of the power tube is pulled down with a second current. Then, after t03, when the rate of change of the drain-source voltage Vds of the power tube over time is again less than the first slope threshold, the pull-down switch is turned on or the driver of the power tube is pulled down with a third current.

[0038] Please refer to Figure 2 As shown, when the power tube is a P-type device, in the interval t11-t12, when the rate of change of the absolute value of the drain-source voltage of the power tube over time is less than a first slope threshold, the driving electrode of the power tube is pulled up with a first current; then, in the interval t12-t13, when the rate of change of the absolute value of the drain-source voltage of the power tube over time is greater than the first slope threshold, the driving electrode of the power tube is pulled up with a second current; then, after t13, when the rate of change of the absolute value of the drain-source voltage of the power tube over time is again less than the first slope threshold, the pull-up switch is turned on or the driving electrode of the power tube is pulled up with a third current;

[0039] When the power tube is of N-type or P-type, the third current is greater than the second current. The first current can be equal to the second current or can be any fixed current value.

[0040] By detecting the slope of the drain-source voltage of the power tube and using different currents to drive the power tube according to the different stages of the power tube, the power tube shutdown process is reliable and fast, and the electromagnetic compatibility of the system is excellent.

[0041] Another technical solution of the present invention is to provide a power tube driving circuit, please refer to Figure 1 As shown, when the power tube is turned off, the power tube driving circuit detects the drain-source voltage Vds of the power tube. When the power tube is an N-type device, in the interval t01-t02, when the rate of change of the drain-source voltage Vds of the power tube over time is less than a first slope threshold, the power tube driving circuit pulls down the power tube with a first current; then, in the interval t02-t03, when the rate of change of the drain-source voltage of the power tube over time is greater than the first slope threshold, the power tube driving circuit pulls down the driving electrode of the power tube with a second current; then, after t03, when the rate of change of the drain-source voltage of the power tube over time is again less than the first slope threshold, the pull-down switch of the power tube driving circuit is turned on or the driving electrode of the power tube is pulled down with a third current.

[0042] Please refer to Figure 2 As shown, when the power tube is a P-type device, in the interval t11-t12, when the rate of change of the absolute value of the drain-source voltage of the power tube over time is less than the first slope threshold, the power tube driving circuit pulls up the driving electrode of the power tube with a first current; then, in the interval t12-t13, when the rate of change of the absolute value of the drain-source voltage of the power tube over time is greater than the first slope threshold, the power tube driving circuit pulls up the driving electrode of the power tube with a second current; then, after t13, when the rate of change of the absolute value of the drain-source voltage of the power tube over time is again less than the first slope threshold, the pull-up switch of the power tube driving circuit is turned on or the driving electrode of the power tube is pulled up with a third current.

[0043] When the power tube is of N-type or P-type, the third current is greater than the second current. The first current can be equal to the second current or can be any fixed current value.

[0044] It should be noted that in N-type devices, the source is generally connected to the reference ground or to the reference ground through a resistor. Therefore, the drain-source voltage of the power tube can be characterized by detecting the drain voltage of the power tube. In P-type devices, the source is generally connected to the power supply end or to the power supply end through a resistor. The drain-source voltage of the power tube can also be characterized by detecting the drain voltage of the power tube.

[0045] In one embodiment, the power tube driving circuit includes a slope detection circuit for detecting the rate of change of the drain-source voltage of the power tube over time. The slope detection circuit is a first capacitor.

[0046] In one embodiment, for an N-type power transistor, the power transistor driver circuit further includes a first pull-down circuit and a second pull-down circuit. The first pull-down circuit pulls down the driver electrode of the power transistor with the second current. The second pull-down circuit includes the pull-down switch. During the off-state of the power transistor, when the rate of change of the drain-source voltage of the power transistor with time exceeds a first slope threshold and then falls below the first slope threshold, the pull-down switch of the second pull-down circuit turns on. That is, when the power transistor is off and the rate of change of the drain-source voltage of the power transistor with time falls below the first slope threshold, the second pull-down circuit does not pull down the driver electrode of the power transistor. Subsequently, when the rate of change of the drain-source voltage of the power transistor with time exceeds the first slope threshold, the second pull-down circuit still does not pull down the driver electrode of the power transistor. Subsequently, when the rate of change of the drain-source voltage of the power transistor with time falls below the first slope threshold, the pull-down switch of the second pull-down circuit turns on. The first pull-down circuit is a first current source, the magnitude of which is equal to the second current. In another embodiment, the first pull-down circuit is a second resistor or a seventh transistor.

[0047] Please refer to Figure 3 As shown, in one embodiment, the second pull-down circuit includes a first transistor M11, a second transistor M12, a third transistor M13, a second current source I12, a first switch K11 and a first resistor R11. The second current source I12 and the first switch K11 are connected in series to form a first series circuit. The drain of the first transistor M11 is connected to the driving electrode of the power transistor, the drain of the second transistor M12 is connected to the driving electrode of the first transistor M11, the first series circuit is connected to the driving electrode of the first transistor M11, the driving electrode of the second transistor M12 is connected to the reference ground through the first resistor R11, the sources of the first transistor M11 and the second transistor M12 are connected to the reference ground, the driving electrode of the second transistor M12 receives the output voltage of the slope detection circuit, and the third transistor M13 is connected between the driving electrode of the first transistor and the reference ground. When the power transistor is turned off, Figure 1In the interval t01-t02, when the rate of change of the drain-source voltage of the power tube over time is less than the first slope threshold, the first switch K11 is turned off, the third transistor M13 is turned on, the second pull-down circuit is disabled, and the first transistor M11 does not pull down the driving electrode of the power tube; the first pull-down circuit pulls down the driving electrode of the power tube M01 with the first current. Then, in the interval t02-t03, the rate of change of the drain-source voltage Vds of the power tube over time is greater than the first slope threshold, the first switch K11 is turned on, the third transistor M13 is turned off, and the second pull-down circuit is enabled; however, because the rate of change of the drain-source voltage Vds of the power tube over time is greater than the first slope threshold, the slope detection circuit pulls up the second pull-down circuit, pulling up the driving electrode of the second transistor M12, turning on the second transistor, and turning off the first transistor M11. The second pull-down circuit still does not pull down the driving electrode of the power tube M01, and only the first pull-down circuit pulls down the driving electrode of the power tube M01 with the second current. Preferably, the first current is equal to the second current. Then, after t03, the rate of change of the drain-source voltage of the power transistor over time is less than the first slope threshold, and the second pull-down circuit continues to be enabled. The slope detection circuit does not pull up the second pull-down circuit, the driving electrode of the second transistor M12 is pulled down by the first resistor R11, the second transistor M12 is turned off, the second current source I12 pulls up the driving electrode of the first transistor M11, the first transistor M11 is turned on, and the driving electrode of the power transistor M01 is quickly pulled down through the first transistor M11. The first transistor M11 serves as the pull-down switch.

[0048] The second pull-down circuit further includes a first logic circuit. The first logic circuit receives the output voltage of the slope detection circuit and controls the on and off of the first switch K11 and the third transistor M13, thereby controlling the enabling of the second pull-down circuit.

[0049] In one embodiment, the first capacitor C11 is implemented using a power tube of the same type as the power tube, namely, a first power tube. The source of the first power tube is connected to the second pull-down circuit, and the drain of the first power tube is connected to the drain of the power tube. The driving electrode and source of the first power tube are short-circuited, or the source of the first power tube is connected to a reference ground.

[0050] Please continue to refer to Figure 3 As shown, the power tube driving circuit further includes a comparison circuit, which receives the driving pole voltage of the power tube M01. The first logic circuit receives the output voltage of the comparator. The comparison circuit compares the driving pole voltage of the power tube M01 with a first voltage threshold. When the driving pole voltage of the power tube is lower than the first voltage threshold, the output of the comparison circuit is flipped, and the first logic circuit controls the third transistor to turn off, controls the first switch K11 to turn on, and turns on the first transistor M11.

[0051] Please continue to refer to Figure 3 As shown, the second pull-down circuit also includes a first conduction element, which can be implemented by a transistor M14. The gate and drain of the transistor M14 are connected, the source of the transistor M14 is connected to the drain of the second transistor M12, and the drain of the transistor M14 is connected to the gate of the second transistor M12. The transistor M14 is connected in the form of a diode. In the interval t02 to t03, the transistor M14 acts as a diode, pulling the driving electrode of the first transistor M11 to near the conduction threshold voltage. Therefore, at time t03, the first transistor M11 can be turned on faster. Figure 4 As shown, the first conduction element may also be a diode D11 connected between the drain and the gate of the second transistor M12.

[0052] Referring to FIG. 5( a ) and FIG. 5 ( b ), in one embodiment, the first pull-down circuit is a second resistor R12 or a seventh transistor M17 .

[0053] Please refer to Figure 6 As shown, in one embodiment, it includes a third pull-down circuit and a first pull-up circuit, the third pull-down circuit pulls down the driving electrode of the power tube with the first current; the first pull-up circuit receives the output of the slope detection circuit, and when the rate of change of the drain-source voltage of the power tube M01 over time is less than the first slope threshold, the driving electrode of the power tube is not pulled up; when the rate of change of the drain-source voltage of the power tube M01 over time is greater than the first slope threshold, the driving electrode of the power tube is pulled up.

[0054] Please continue to refer to Figure 6 As shown, the slope detection circuit is a first capacitor, the third pull-down circuit is a fourth current source I21, the first current is equal to the third current, and the magnitude of the fourth current source I21 is equal to the third current.

[0055] Please continue to refer to Figure 6 As shown, the first pull-up circuit includes a fourth transistor M21 and a fifth transistor M22, the fourth transistor M21 and the fifth transistor M22 forming a mirror current mirror, the source of the fourth transistor M21 and the fifth transistor M22 are connected to the driving electrode of the power tube M01, the drain of the fourth transistor M21 is connected to the driving electrode and receives the output voltage of the slope detection circuit. When the power tube M01 is turned off, Figure 1 In the interval t01-t02, the slope detection circuit does not pull up the drain of the fourth transistor M21, no current flows through the fourth transistor M21 and the fifth transistor M22, the first pull-up circuit does not pull up the driving electrode of the power tube, and the third pull-down current pulls down the driving electrode of the power tube with the first current; Figure 1In the interval t02-t03, when the rate of change of the drain-source voltage of the power tube M01 over time is greater than the first slope threshold, the slope detection circuit pulls up the drain of the fourth transistor M21, the first pull-up circuit pulls up the driving electrode of the power tube M01, and the third pull-down circuit pulls down the driving electrode of the power tube M01. The difference between the pull-down current of the third pull-down circuit and the pull-up current of the first pull-up circuit is the second current; Figure 1 After the interval t03, since the rate of change of the drain-source voltage of the power tube M01 over time is less than the first slope threshold, the slope detection circuit does not pull up the drain of the fourth transistor M21, no current flows through the fourth transistor M21 and the fifth transistor M22, the first pull-up circuit does not pull up the driving electrode of the power tube, and the third pull-down current pulls down the driving electrode of the power tube with the third current, and the third current is equal to the first current.

[0056] Please continue to refer to Figure 6 As shown, to accelerate the shutdown speed in the interval after t03 and when the power tube driving electrode voltage is lower than the first voltage threshold, the power tube driving circuit further includes a sixth transistor M24. The driving electrode of the power tube is connected to the reference ground through the sixth transistor M24. When the driving electrode voltage of the power tube is lower than the first voltage threshold, the sixth transistor is turned on. The power tube driving circuit further includes a comparison circuit that receives the driving electrode voltage of the power tube M01 and compares the driving electrode voltage of the power tube M01 with the first voltage threshold. When the driving electrode voltage of the power tube is lower than the first voltage threshold, the output of the comparison circuit controls the sixth transistor to be turned on, thereby significantly accelerating the pull-down speed of the driving electrode of the power tube M01.

[0057] Please continue to refer to Figure 6 As shown, the first pull-up circuit also includes a second conductive element and a first current-limiting circuit. The first current-limiting circuit is connected to the drain of the fifth transistor M22. The second conductive element can be implemented as a transistor M23. The gate and drain of transistor M23 are connected, the source of transistor M23 is connected to the drain of transistor M22, and the drain of transistor M23 is connected to the drain of transistor M21. Transistor M23 is connected as a diode to prevent the gate terminal of the current mirror from being raised too high. This allows the pull-up current to be turned off more quickly when the output current of the slope detection circuit disappears. The second conductive element can also be implemented as a diode, connected between the drain of transistor M22 and the drain of transistor M21. The first current-limiting circuit can be a current source, a resistor, or a transistor.

[0058] Please refer to Figure 7FIG2 shows another embodiment of a power transistor driver circuit. The power transistor driver circuit includes a first pull-down circuit, a second pull-down circuit, and a slope detection circuit. The slope detection circuit receives the drain voltage of the power transistor M01, and the first pull-down circuit receives the output voltage of the slope detection circuit. Both the first and second pull-down circuits are connected to the drive electrode and source electrode of the power transistor M01. The first pull-down circuit includes a current source I31, and the second pull-down circuit includes a transistor M31. The output of the slope detection circuit is connected to the gate electrode of transistor M31, the source electrode of M31 is connected to the source electrode of the power transistor M01, and the drain electrode of M31 is connected to the drive electrode of the power transistor M01.

[0059] When the power tube M01 is turned off, Figure 1 In the interval t01-t02, the slope detection circuit output is low, the transistor M31 is turned off, the first pull-down circuit pulls down the driving electrode of the power tube, and the second pull-down circuit does not pull down the driving electrode of the power tube M01; Figure 1 In the interval t02-t03, when the rate of change of the drain-source voltage of the power tube M01 over time is greater than the first slope threshold, the output of the slope detection circuit is low, the second pull-down circuit does not pull down the driving electrode of the power tube M01, and the first pull-down circuit pulls down the driving electrode of the power tube, and the pull-down current is the second current; Figure 1 After the t03 interval, since the rate of change of the drain-source voltage of the power tube M01 over time is less than the first slope threshold, the slope detection circuit output is high, and the second pull-down circuit and the first pull-down circuit both pull down the driving electrode of the power tube. Figure 1 During the t01-t02 interval and after the t03 interval, the rate of change of the drain-source voltage of power tube M01 over time is less than the first slope threshold. However, during the t01-t02 interval, the slope detection circuit outputs a low value; after the t03 interval, the slope detection circuit outputs a high value. In other words, the slope detection circuit adjusts its output not only based on the drain-source voltage of power tube M01 but also based on the timing. For example, the slope detection circuit will only output a high value after the rate of change of the drain-source voltage of power tube M01 over time is greater than the first slope threshold and then less than the first slope threshold.

[0060] Another technical solution of the present invention is to provide a switching circuit including a driving circuit of the power tube.

[0061] Although the embodiments are described and explained separately above, some common technologies are involved. It is the opinion of ordinary technicians in this field that they can be replaced and integrated between the embodiments. If there is anything not clearly recorded in one of the embodiments, reference can be made to another recorded embodiment.

[0062] The above-described embodiments do not constitute a limitation on the scope of protection of this technical solution. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the above-described embodiments shall be included in the scope of protection of this technical solution.

Claims

1. A power tube driving method, comprising: detecting the drain-source voltage of the power tube when the power tube is turned off; and when the power tube is an N-type device, when the rate of change of the drain-source voltage of the power tube over time is less than a first slope threshold, pulling down a driving electrode of the power tube with a first current; then, when the rate of change of the drain-source voltage of the power tube over time is greater than the first slope threshold, pulling down the driving electrode of the power tube with a second current; and then, when the rate of change of the drain-source voltage of the power tube over time is again less than the first slope threshold, turning on a pull-down switch or pulling down the driving electrode of the power tube with a third current; When the power tube is a P-type device, when the rate of change of the absolute value of the drain-source voltage of the power tube over time is less than a first slope threshold, the driving electrode of the power tube is pulled up with a first current; then, when the rate of change of the absolute value of the drain-source voltage of the power tube over time is greater than the first slope threshold, the driving electrode of the power tube is pulled up with a second current; then, when the absolute value of the rate of change of the absolute value of the drain-source voltage of the power tube over time is less than the first slope threshold, the pull-up switch is turned on or the driving electrode of the power tube is pulled up with a third current; The third current is greater than the second current.

2. A power tube drive circuit, wherein when the power tube is turned off, the power tube drive circuit detects the drain-source voltage of the power tube. When the power tube is an N-type device, when the rate of change of the drain-source voltage of the power tube over time is less than a first slope threshold, the power tube drive circuit pulls down the drive electrode of the power tube with a first current. Then, when the rate of change of the drain-source voltage of the power tube over time is greater than the first slope threshold, the power tube drive circuit pulls down the drive electrode of the power tube with a second current. Then, when the rate of change of the drain-source voltage of the power tube over time is again less than the first slope threshold, the pull-down switch of the power tube drive circuit is turned on or the drive electrode of the power tube is pulled down with a third current. When the power tube is a P-type device, when the rate of change of the absolute value of the drain-source voltage of the power tube over time is less than a first slope threshold, the power tube driving circuit pulls up the driving electrode of the power tube with a first current; then, when the rate of change of the absolute value of the drain-source voltage of the power tube over time is greater than the first slope threshold, the power tube driving circuit pulls up the driving electrode of the power tube with a second current; then, when the rate of change of the absolute value of the drain-source voltage of the power tube over time is less than the first slope threshold, the pull-up switch of the power tube driving circuit is turned on or the driving electrode of the power tube is pulled up with a third current; The third current is greater than the second current.

3. The power tube driving circuit according to claim 2, wherein: A slope detection circuit is included to detect the time rate of change of the drain-source voltage of the power tube.

4. The power tube driving circuit according to claim 3, wherein: comprising a third pull-down circuit and a first pull-up circuit, wherein the third pull-down circuit pulls down the driving electrode of the power tube with the first current; The first pull-up circuit receives the output voltage of the slope detection circuit, and does not pull up the driving electrode of the power tube when the rate of change of the drain-source voltage of the power tube over time is less than a first slope threshold; and pulls up the driving electrode of the power tube when the rate of change of the drain-source voltage of the power tube over time is greater than the first slope threshold.

5. The power tube driving circuit according to claim 4, wherein: The first pull-up circuit includes a fourth transistor and a fifth transistor, the sources of the fourth transistor and the fifth transistor are connected to the driving electrode of the power tube, the drain of the fourth transistor is connected to the driving electrode, and receives the output voltage of the slope detection circuit.

6. The power tube driving circuit according to claim 5, wherein: The first pull-up circuit also includes a second conductive element and a first current limiting circuit, the first current limiting circuit is connected to the drain of the fifth transistor, the second conductive element is connected between the drain of the fourth transistor and the drain of the fifth transistor, and the second conductive element is a transistor or a diode whose drain is connected to the driving electrode.

7. The power tube driving circuit according to claim 6, wherein: The slope detection circuit is a first capacitor, the third pull-down circuit is a fourth current source, the first current is equal to the third current, and the magnitude of the fourth current source is equal to the third current.

8. The power tube driving circuit according to claim 5, wherein: The power tube driving circuit includes a sixth transistor, the driving electrode of the power tube is connected to the reference ground through the sixth transistor, and when the voltage of the driving electrode of the power tube is lower than a first voltage threshold, the sixth transistor is turned on.

9. The power tube driving circuit according to claim 3, wherein: The device further includes a first pull-down circuit and a second pull-down circuit, wherein the first pull-down circuit pulls down the driving electrode of the power tube with the second current; and the second pull-down circuit includes the pull-down switch. During the shutdown period of the power tube, when the rate of change of the drain-source voltage of the power tube with time is greater than the first slope threshold and then less than the first slope threshold, the pull-down switch of the second pull-down circuit is turned on.

10. The power tube driving circuit according to claim 9, wherein: The second pull-down circuit includes a first transistor, a second transistor, a third transistor, a second current source, a first switch and a first resistor. The second current source and the first switch are connected in series to form a first series circuit. The drain of the first transistor is connected to the driving electrode of the power tube, the drain of the second transistor is connected to the driving electrode of the first transistor, the first series circuit is connected to the driving electrode of the first transistor, the driving electrode of the second transistor is connected to the reference ground through the first resistor, the sources of the first transistor and the second transistor are connected to the reference ground, the driving electrode of the second transistor receives the output voltage of the slope detection circuit, and the third transistor The power tube is connected between the driving electrode of the first transistor and the reference ground. When the power tube is turned off, the rate of change of the drain-source voltage of the power tube over time is less than the first slope threshold, the first switch is turned off, the third transistor is turned on, the second pull-down circuit is disabled, and the first transistor does not pull down the driving electrode of the power tube; then, the rate of change of the drain-source voltage of the power tube over time is greater than the first slope threshold, the first switch is turned on, the third transistor is turned off, and the second pull-down circuit is enabled; then, the rate of change of the drain-source voltage of the power tube over time is again less than the first slope threshold, and the second pull-down circuit continues to be enabled; the first transistor serves as the pull-down switch.

11. The power tube driving circuit according to claim 10, wherein: The second pull-down circuit further includes a first conductive element connected between the driving electrode and the drain of the second transistor. The first conductive element is a transistor or a diode with the drain and the driving electrode connected.

12. The power tube driving circuit according to claim 10, wherein: The slope detection circuit is a first capacitor, the first pull-down circuit is a first current source or a second resistor or a seventh transistor, and the magnitude of the first current source is the second current.

13. The power tube driving circuit according to claim 12, wherein: The first capacitor is implemented by a power tube of the same type as the power tube, namely, a first power tube. The source of the first power tube is connected to the second pull-down circuit, and the drain of the first power tube is connected to the drain of the power tube.

14. The power tube driving circuit according to claim 10, wherein: When the driving voltage of the power tube is lower than a first voltage threshold, the first transistor is turned on.

15. A switching circuit, characterized in that: It comprises the power tube driving circuit as claimed in any one of claims 2 to 14.

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