Method for detecting soft switching of a switching transistor and edge detection circuit

Abstract

This invention provides a method and edge detection circuit for detecting the soft switching of a switching transistor. The method, applied to the edge detection circuit, includes: driving the edge detection circuit based on a pulse width modulation (PWM) signal; detecting the soft switching pulse of the switching transistor based on the edge detection circuit; wherein the soft switching pulse characterizes the relationship between soft switching and switching current; obtaining soft switching information of the switching transistor by detecting the soft switching pulse through a microcontroller; and adjusting the switching current of the switching transistor based on the soft switching information. In this method, the soft switching status of the switching transistor can be detected by the edge detection circuit and closed-loop feedback can be achieved, ensuring that the MOSFET always operates under optimal soft switching conditions.

Description

Technical Field

[0001] This invention relates to the field of electronic circuit technology, and in particular to a method for detecting soft switching of a switching transistor and an edge detection circuit. Background Technology

[0002] Currently, there are no existing technologies to detect the soft-switching behavior of transistors. For example, in LLC devices (a resonant circuit network consisting of an inductor L, a capacitor C, and a resonant transformer), parameter design is used to ensure soft switching of the transistor. In BUCK (switch-mode buck converter), half-bridge, or full-bridge topologies, soft switching is ensured by the negative current of the inductor. The switching current of the transistor changes with operating conditions, and without guaranteeing the quality of soft switching, transistor failure is easily caused. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a method and an edge detection circuit for detecting the soft switching of a switching transistor, so as to detect the soft switching status of the switching transistor through the edge detection circuit and realize closed-loop feedback to ensure that the MOS (Metal-Oxide-Semiconductor Field-Effect Transistor) transistor always operates under the optimal soft switching conditions.

[0004] In a first aspect, embodiments of the present invention provide a method for detecting the soft switching of a switching transistor, applied to an edge detection circuit. The method includes: driving an edge detection circuit based on a pulse width modulation (PWM) signal; detecting a soft switching pulse of the switching transistor based on the edge detection circuit; wherein the soft switching pulse characterizes the relationship between soft switching and switching current; obtaining soft switching information of the switching transistor by detecting the soft switching pulse through a microcontroller; and adjusting the switching current of the switching transistor based on the soft switching information.

[0005] In an optional embodiment of this application, the step of driving the edge detection circuit based on the PWM signal includes: delaying the PWM signal through a dead time of a preset duration to obtain a driving signal; and driving the edge detection circuit based on the driving signal.

[0006] In an optional embodiment of this application, after the above-described step of adjusting the switching current of the switching transistor based on soft-switching information, the method further includes: controlling the edge of the output capacitor of the switching transistor to be 0 at the end of the dead zone based on the switching current of the switching transistor.

[0007] In an optional embodiment of this application, the edge detection circuit includes: a pulse width modulation source, a first capacitor R1, and a device group D1; wherein, the device group D1 includes: a diode and a resistor connected in parallel, and the pulse width modulation source, the first capacitor R1, and the device group D1 are connected in series.

[0008] In an optional embodiment of this application, the step of driving the edge detection circuit based on the pulse width modulation (PWM) signal includes: inverting the PWM signal using a logic inverting device; and the pulse width modulation source providing the edge detection circuit with an input power supply voltage of the same logic based on the inverted PWM signal.

[0009] In an optional embodiment of this application, the aforementioned switching transistor includes: the lower bridge arm of a switch-mode buck converter BUCK; the step of detecting the soft-switching pulse of the switching transistor based on an edge detection circuit includes: detecting the soft-switching pulse of the lower bridge arm M2 of BUCK based on a first capacitor R1 and a device group D1; wherein the soft-switching pulse characterizes the edge change of the lower bridge arm M2.

[0010] In an optional embodiment of this application, the step of detecting the soft-switching pulse of the lower bridge arm M2 of BUCK based on the first capacitor R1 and the device group D1 includes: when the lower bridge arm M2 of BUCK is open and the bridge arm M1 of BUCK is on, the output voltage of the lower bridge arm M2 is greater than the input power supply voltage, the device group D1 is off, and the voltage of the first capacitor C1 in the edge detection circuit is the input power supply voltage; when the lower bridge arm M2 of BUCK is on, the voltage of the first capacitor C1 is the on-state voltage drop of the device group D1; wherein, the on-state voltage drop of the device group D1 is less than the input power supply voltage; and the soft-switching pulse of the lower bridge arm M2 of BUCK is detected based on the voltage of the first capacitor C1.

[0011] In an optional embodiment of this application, the step of detecting the soft-switching pulse of the lower bridge arm M2 of BUCK based on the voltage of the first capacitor C1 includes: taking the pulse signal between the first moment and the second moment as the soft-switching pulse of the lower bridge arm M2 of BUCK based on the voltage of the first capacitor C1; wherein, the first moment is the moment when the logic inverting device is greater than a preset first threshold, and the second moment is the moment when the drive signal obtained after the dead time delay of the lower bridge arm M2 is greater than a preset second threshold.

[0012] In an optional embodiment of this application, the step of obtaining the soft-switching information of the switching transistor by detecting the soft-switching pulse through a microcontroller includes: detecting the pulse width of the soft-switching pulse through a microcontroller as the soft-switching information of the switching transistor; if the pulse width of the soft-switching pulse is within a preset range, determining that the switching transistor is qualified.

[0013] Secondly, embodiments of the present invention also provide an edge detection circuit, which is used to perform the above-described method for soft-switching the detection switch transistor.

[0014] The embodiments of the present invention bring the following beneficial effects: This invention provides a method and edge detection circuit for detecting the soft switching of a switching transistor. The edge detection circuit is driven by a pulse width modulation (PWM) signal, and detects the soft switching pulse of the switching transistor. The soft switching pulse characterizes the relationship between soft switching and the switching current. A microcontroller detects the soft switching pulse to obtain the soft switching information of the switching transistor. The switching current of the switching transistor is adjusted based on this information. This method allows for the detection of the soft switching status of the switching transistor through the edge detection circuit and achieves closed-loop feedback, ensuring that the MOSFET always operates under optimal soft switching conditions.

[0015] Other features and advantages of this disclosure will be set forth in the following description, or some features and advantages may be inferred from the description or determined without doubt, or may be learned by practicing the techniques described above.

[0016] To make the above-mentioned objects, features and advantages of this disclosure more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 A flowchart of a method for detecting soft switching of a switching transistor provided in an embodiment of the present invention; Figure 2 A schematic diagram of a signal waveform provided for an embodiment of the present invention; Figure 3 A schematic diagram of another signal waveform provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of an edge detection circuit provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of another method for detecting soft switching of a switching transistor provided in an embodiment of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Currently, there are no existing technologies to detect the soft-switching behavior of transistors. For example, in LLC devices, parameter design is used to ensure soft switching, while in BUCK, half-bridge, or full-bridge topologies, the negative current of the inductor is used to ensure soft switching. The switching current of a transistor changes with operating conditions, and without guaranteeing the quality of soft switching, transistor failure is easily caused.

[0021] Based on this, the present invention provides a method and edge detection circuit for detecting the soft switching of a switching transistor. The edge detection circuit can detect the soft switching status of the switching transistor and realize closed-loop feedback to ensure that the MOSFET always operates under the optimal soft switching conditions.

[0022] To facilitate understanding of this embodiment, a method for detecting soft switching of a switching transistor disclosed in this embodiment of the invention will first be described in detail.

[0023] Example 1: This invention provides a method for detecting the soft switching of a switching transistor, applied to an edge detection circuit. See [link to relevant documentation]. Figure 1 The flowchart shown illustrates a method for detecting the soft switching of a switching transistor, which includes the following steps: Step S102: Drive the edge detection circuit based on the pulse width modulation (PWM) signal, and detect the soft switching pulse of the switching transistor based on the edge detection circuit; wherein, the soft switching pulse characterizes the relationship between soft switching and switching current.

[0024] In this embodiment, a PWM (Pulse Width Modulation) signal can be used to drive an edge detection circuit, which detects the soft-switching pulse soft_plus of the switching transistor.

[0025] In some embodiments, the PWM signal can be delayed by a preset dead time to obtain a drive signal; the edge detection circuit is driven based on the drive signal.

[0026] See Figure 2 The diagram shown is a schematic representation of a signal waveform. Figure 2 The diagram shows the PWM signal, the DR signal after a 200ns dead-time delay of the PWM signal, and the output capacitor signal of the switching transistor (i.e., the VDS signal). In this embodiment, the edge detection circuit can be driven by the soft-switching drive signal of the PWM signal after a 200ns dead-time delay.

[0027] Step S104: The soft switching pulse is detected by the microcontroller to obtain the soft switching information of the switching transistor.

[0028] In this embodiment, the soft-switching information of the switching transistor can be obtained by detecting the soft-switching pulse soft_plus using a microcontroller.

[0029] Step S106: Adjust the switching current of the switching transistor based on the soft-switching information.

[0030] In this embodiment, the switching current can be adjusted based on the soft-switching information of the switching transistor.

[0031] In some embodiments, the edge of the output capacitance of the switching transistor can be controlled to be 0 at the end of the dead zone based on the switching current of the switching transistor.

[0032] See Figure 3 The diagram shows another signal waveform. Figure 3 The image shows the soft-switching pulse signal soft_plus, which characterizes the relationship between soft switching and switching current, detected by an edge detection circuit.

[0033] like Figure 2 and Figure 3 As shown, in this embodiment, the switching current of the switching transistor can be controlled so that the edge signal of the output capacitor (i.e., VDS capacitor CO2) of the switching transistor reaches zero just at the end of the dead zone, thereby achieving the theoretically best ZVS (Zero Voltage Switching) soft switching effect.

[0034] This invention provides a method for detecting the soft switching of a switching transistor. It utilizes a pulse width modulation (PWM) signal to drive an edge detection circuit, which detects the soft switching pulse of the transistor. The soft switching pulse characterizes the relationship between soft switching and the switching current. A microcontroller detects the soft switching pulse to obtain the soft switching information of the transistor. The switching current of the transistor is then adjusted based on this information. This method allows for the detection of the soft switching status of the transistor through an edge detection circuit, achieving closed-loop feedback and ensuring that the MOSFET always operates under optimal soft switching conditions.

[0035] Example 2: This embodiment provides another method for detecting the soft switching of a switching transistor. This method is implemented based on the above embodiment, focusing on the specific implementation of the edge detection circuit. (See also...) Figure 4 The diagram shows a schematic of an edge detection circuit. Figure 4 As shown, the edge detection circuit includes: a pulse width modulation source (pwm_source), a first capacitor (R1), and a device group (D1); wherein, the device group (D1) includes: a diode and a resistor connected in parallel, and the pulse width modulation source (pwm_source), the first capacitor (R1), and the device group (D1) are connected in series.

[0036] like Figure 4As shown, the pulse source Pulse is used to output the PWM signal; NOT is a logic inverting device; t(2e-07s) refers to the dead time of the upper and lower transistors of the BUCK (switch-mode buck converter), which is used to prevent the upper and lower transistors from shoot-through; M1 is the upper transistor bridge arm of the BUCK; M2 is the lower transistor bridge arm of the BUCK. In this embodiment, the switching transistor can be the lower transistor bridge arm M2. switch_current is a constant current source. In this embodiment, the inductor can be abstracted as the constant current source switch_current, that is, the current of the upper and lower transistors can be considered to be 4.5A.

[0037] Based on the above description, please refer to Figure 5 The diagram shows another method for detecting soft switching of a switching transistor.

[0038] In step S502, the PWM signal is inverted by the logic inverting device NOT; the pulse width modulation source provides the same logic input power supply voltage to the edge detection circuit based on the inverted PWM signal.

[0039] like Figure 4 As shown, in this embodiment, the pulse width modulation source pwm_source can provide the edge detection circuit with the same logic 3.3V input power supply voltage according to the output of the logic inverting device NOT.

[0040] Step S504: Based on the first capacitor R1 and the device group D1, detect the soft switching pulse of the lower bridge arm M2 of BUCK to obtain the soft switching information of the switching transistor; wherein, the soft switching pulse characterizes the edge change of the lower bridge arm M2.

[0041] like Figure 4 As shown, in this embodiment, the edge change of the lower bridge arm M2 of BUCK can be detected by the first capacitor R1 and the device group D1.

[0042] like Figure 4 As shown, when the lower bridge arm M2 of BUCK is disconnected and the bridge arm M1 of BUCK is turned on, the output voltage Vds_M2 of the lower bridge arm M2 is greater than the input power supply voltage Vdc (i.e., 3.3V), the device group D1 is cut off, and the voltage of the first capacitor C1 in the edge detection circuit is the input power supply voltage c (i.e., 3.3V, which is pulled up to 3.3V by resistor R1 when the drive signal is high before passing through the dead zone module); when the lower bridge arm M2 of BUCK is turned on, the voltage of the first capacitor C1 is the on-state voltage drop of the device group D1, and the voltage of the first capacitor C1 is clamped to about 0.5V (i.e., the on-state voltage drop of the device group D1 is 0.5V); where the on-state voltage drop of the device group D1 is less than the input power supply voltage; the soft switching pulse of the lower bridge arm M2 of BUCK is detected based on the voltage of the first capacitor C1.

[0043] In some embodiments, the pulse signal between the first moment and the second moment can be used as the soft switching pulse of the lower bridge arm M2 of BUCK based on the voltage of the first capacitor C1; wherein, the first moment is the moment when the logic inverting device is greater than a preset first threshold, and the second moment is the moment when the drive signal obtained after the dead time delay of the lower bridge arm M2 is greater than a preset second threshold.

[0044] In this embodiment, the on / off state of M2 can be detected by the voltage of the first capacitor C1. For example... Figure 4 As shown, since 3.3V is the same logic voltage as the driving voltage of the lower bridge arm M2, which differs from the driving voltage of the lower bridge arm M2 by one dead time, the voltage of the first capacitor C1 can be used to determine the pulse signal within 200ns between the output signal of the logic inverting device being high (i.e., the first moment when the logic inverting device is greater than the preset first threshold) and the driving signal after the dead time delay of the lower bridge arm M2 being high (i.e., the second moment when the driving signal after the dead time delay of the lower bridge arm M2 is greater than the second threshold, at which time the MOS transistor is driven to conduct). Finally, a 3.3V pulse signal with a duration of no more than 200ns is output.

[0045] In some embodiments, the pulse width of the soft-switching pulse can be detected by a microcontroller as the soft-switching information of the switching transistor; if the pulse width of the soft-switching pulse is within a preset range, the switching transistor is determined to be qualified.

[0046] In this embodiment, the pulse signal width represents the time it takes for the lower bridge arm M2 to go low before the drive signal arrives, which can then determine whether the soft switch is qualified (a qualified soft switch should make the pulse width within the preset range of 150ns-180ns).

[0047] Step S506: Adjust the switching current of the switching transistor based on the soft-switching information.

[0048] like Figure 4 As shown, if the pulse signal is 100ns, it indicates that the lower bridge arm M2 becomes 0V in 100ns, which means that the constant current source switch_current is too large, i.e., the capacitor CO3 is discharging too quickly. In this case, the current needs to be reduced. If the pulse signal is within the 200ns dead zone, it means that the lower bridge arm M2 is not fully turned on, which means that the current is too small to achieve 0-voltage turn-on, and the switching current needs to be increased.

[0049] Currently, the switching current of a switching transistor varies with operating conditions, and without ensuring the quality of soft switching, the transistor is prone to failure. The method provided in this invention can detect the soft switching status of a MOSFET using a simple edge detection circuit and achieve closed-loop feedback, ensuring that the MOSFET always operates under optimal soft-switching conditions.

[0050] like Figure 4 As shown, in this embodiment, the BUCK inductor is abstracted as a constant current source switch_current, which can represent the switching current. CO3 is the drain-source (DS) capacitor of the switching transistor. The switching current needs to be controlled to draw the CO3 capacitor to 0V during the 200ns dead time before driving the lower bridge arm M2 to turn on, thus achieving ZVS turn-on of the lower bridge arm M2. To ensure that the lower bridge arm M2 achieves soft switching in the optimal state (if the current is too small, the CO3 capacitor voltage will not be drawn to 0V; if the current is too large, it will cause excessive operating current and additional losses), the pulse width of the soft switching needs to be detected to control the constant current source switch_current, thereby achieving optimal soft switching.

[0051] Example 3: This invention provides an edge detection circuit, implemented based on the above embodiments, which is used to execute the soft-switching method for the detection switch provided in the foregoing embodiments.

[0052] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the edge detection circuit described above can be referred to the corresponding process in the aforementioned method embodiment of soft switching of the switching transistor, and will not be repeated here.

[0053] Furthermore, in the description of the embodiments of the present invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances.

[0054] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0055] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for detecting soft switching of a switching transistor, characterized in that, Applied to an edge detection circuit, the method includes: The edge detection circuit is driven by a pulse width modulation (PWM) signal, and the soft switching pulse of the switching transistor is detected by the edge detection circuit; wherein, the soft switching pulse represents the relationship between soft switching and switching current. The soft-switching information of the switching transistor is obtained by detecting the soft-switching pulse using a microcontroller. The switching current of the switching transistor is adjusted based on the soft-switching information.

2. The method according to claim 1, characterized in that, The steps of driving the edge detection circuit based on the PWM signal include: The PWM signal is delayed by a preset dead time to obtain the drive signal; The edge detection circuit is driven based on the driving signal.

3. The method according to claim 2, characterized in that, After the step of adjusting the switching current of the switching transistor based on the soft-switching information, the method further includes: The edge of the output capacitor of the switching transistor is controlled to be 0 at the end of the dead zone based on the switching current of the switching transistor.

4. The method according to claim 3, characterized in that, The edge detection circuit includes: a pulse width modulation source, a first capacitor R1, and a device group D1; wherein, the device group D1 includes: a diode and a resistor connected in parallel, and the pulse width modulation source, the first capacitor R1, and the device group D1 are connected in series.

5. The method according to claim 4, characterized in that, The steps of driving the edge detection circuit based on the pulse width modulation (PWM) signal include: The PWM signal is inverted using a logic inverting device; The pulse width modulation source provides the edge detection circuit with the same logic input power supply voltage based on the inverted PWM signal.

6. The method according to claim 5, characterized in that, The switching transistor includes: the lower bridge arm of a switch-mode buck converter; the step of detecting the soft-switching pulse of the switching transistor based on the edge detection circuit includes: The soft-switching pulse of the lower bridge arm M2 of the BUCK is detected based on the first capacitor R1 and the device group D1; wherein the soft-switching pulse characterizes the edge change of the lower bridge arm M2.

7. The method according to claim 6, characterized in that, The step of detecting the soft-switching pulse of the lower bridge arm M2 of the BUCK based on the first capacitor R1 and the device group D1 includes: When the lower bridge arm M2 of the BUCK is disconnected and the bridge arm M1 of the BUCK is turned on, the output voltage of the lower bridge arm M2 is greater than the input power supply voltage, the device group D1 is turned off, and the voltage of the first capacitor C1 in the edge detection circuit is the input power supply voltage. When the lower bridge arm M2 of the BUCK is turned on, the voltage of the first capacitor C1 is the on-state voltage drop of the device group D1; wherein, the on-state voltage drop of the device group D1 is less than the input power supply voltage. The soft-switching pulse of the lower bridge arm M2 of the BUCK is detected based on the voltage of the first capacitor C1.

8. The method according to claim 7, characterized in that, The step of detecting the soft-switching pulse of the lower bridge arm M2 of the BUCK based on the voltage of the first capacitor C1 includes: Based on the voltage of the first capacitor C1, the pulse signal between the first moment and the second moment is used as the soft switching pulse of the lower bridge arm M2 of the BUCK; wherein, the first moment is the moment when the logic inverting device is greater than a preset first threshold, and the second moment is the moment when the drive signal obtained after the dead time delay of the lower bridge arm M2 is greater than a preset second threshold.

9. The method according to claim 1, characterized in that, The step of obtaining the soft-switching information of the switching transistor by detecting the soft-switching pulse using a microcontroller includes: The pulse width of the soft-switching pulse is detected by a microcontroller and used as the soft-switching information of the switching transistor. If the pulse width of the soft switching pulse is within a preset range, the switching transistor is determined to be qualified.

10. An edge detection circuit, characterized in that, The edge detection circuit is used to perform the method for soft switching of the detection switch tube as described in any one of claims 1-9.

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