Desaturation detection circuit, motor control device and power system

Abstract

The utility model relates to the technical field of circuit detection, and discloses a desaturation detection circuit, a motor control device and a power system.The circuit comprises a driving circuit, a detection circuit and a decoupling circuit, the output end of the driving circuit is connected with the control end of a switching device, and the driving circuit is used for outputting a switching signal to control on-off of the switching device; the detection circuit is arranged between the input end of the driving circuit and the switching device and is used for outputting a desaturation detection signal to the driving circuit when detecting that the switching device is in a saturation state; the decoupling circuit is arranged between a detection wire of the detection circuit and a phase line of the motor or arranged on the detection wire side of the detection circuit and used for cutting off an electric field coupling path between the detection wire and the phase line, and the detection wire is a wire connected with a collector in the detection circuit. The problem that when an existing desaturation detection circuit detects the desaturation state of a power tube, electric field coupling is likely to happen, and false detection is caused is solved.

Description

Technical Field

[0001] This application relates to the field of circuit detection technology, and in particular, to a desaturation detection circuit, a motor control device, and a power system. Background Art

[0002] In the drive control of a motor, a common drive control method is to use a power transistor, such as an Insulated Gate Bipolar Transistor (IGBT), a MOS transistor, a bipolar transistor, etc. To achieve low-power utilization of the power transistor to drive the motor, a desaturation detection circuit is provided on the collector of the power transistor.

[0003] However, as the working current of the power transistor in the on state continues to increase, electric field coupling will occur between the desaturation detection circuit and the power line, resulting in false detection of the desaturation detection circuit. Summary of the Utility Model

[0004] In view of this, this application proposes a desaturation detection circuit, a motor control device, and a power system to solve the problem that the existing desaturation detection circuit is prone to electric field coupling and causes false detection when detecting the desaturation state of the power transistor.

[0005] The first aspect of this application provides a desaturation detection circuit, including: a drive circuit, whose output terminal is connected to the control terminal of the switching device, for outputting a switching signal to control the on and off of the switching device; a detection circuit, which is connected to the input terminal of the drive circuit and the switching device, for outputting a desaturation detection signal to the drive circuit when detecting that the switching device is in a saturated state; a decoupling circuit, which is arranged between the detection trace of the detection circuit and the phase line of the motor or on the side of the detection trace of the detection circuit, for cutting off the electric field coupling path between the detection trace and the phase line, where the detection trace is the trace in the detection circuit connected to the collector.

[0006] In a feasible implementation manner, the detection circuit includes: a sampling circuit and a comparison circuit; the input terminal of the sampling circuit is connected to the collector of the switching device, for sampling the voltage difference between the collector and the emitter of the switching device; the first input terminal of the comparison circuit is connected to the output terminal of the sampling circuit, and the second input terminal of the comparison circuit is connected to a preset voltage source, for comparing the magnitude relationship between the threshold voltage output by the preset voltage source and the voltage difference, and outputting a desaturation detection signal to the drive circuit when the voltage difference is greater than the threshold voltage.

[0007] In a feasible implementation manner, the acquisition circuit includes a resistor, a first diode, and a first capacitor; a first connection end of the first capacitor is connected to a reference ground, and a second connection end of the first capacitor is respectively connected to a first connection end of the resistor and a first input end of the comparison circuit; a second connection end of the resistor is connected to an anode of the first diode, a cathode of the first diode is connected to the collector, and the decoupling circuit is disposed between a trace of the anode of the first diode and a phase line of the motor.

[0008] In a feasible implementation manner, the decoupling circuit includes an electric field shielding circuit, the electric field shielding circuit is connected to the reference ground, and is disposed on a side of the trace of the anode of the first diode close to the phase line of the motor.

[0009] In a feasible implementation manner, the electric field shielding circuit is a metal layer of the reference ground, the metal layer, the trace of the anode of the first diode, and the phase line of the motor are disposed on different layers of the PCB board, and a PCB board layer corresponding to the metal layer is located between PCB board layers corresponding to the trace of the anode of the first diode and the phase line of the motor.

[0010] In a feasible implementation manner, the decoupling circuit includes a diode circuit, an anode of the diode circuit is connected to a second connection end of the resistor, and a cathode of the diode circuit is connected to an anode of the first diode.

[0011] In a feasible implementation manner, the diode circuit includes at least one second diode.

[0012] In a feasible implementation manner, the diode circuit further includes at least one second capacitor, and each second diode is connected in parallel with a second capacitor.

[0013] A second aspect of the present application provides a motor control device, including: at least one switching device and at least one desaturation detection circuit in any of the implementation manners in the first aspect above.

[0014] A third aspect of the present application provides a power system, including: at least three desaturation detection circuits in any of the implementation manners in the first aspect above, at least three switching devices, and a three-phase motor, wherein each desaturation detection circuit corresponds to one switching device, each switching device is connected to a phase line of the three-phase motor; when the detection circuit in the desaturation detection circuit detects that the switching device is in a saturated state, a desaturation detection signal is output to control the drive circuit to output a switching signal to the corresponding switching device.

[0015] In the technical solution provided by this application, the circuit includes a drive circuit, a detection circuit, and a decoupling circuit. The output terminal of the drive circuit is connected to the control terminal of the switching device, and is used to output a switching signal to control the on / off of the switching device; the detection circuit is disposed at the input terminal and the collector of the drive circuit, and when the voltage difference between the collector and the emitter is greater than the threshold voltage, it outputs a desaturation detection signal to the drive circuit; the decoupling circuit is disposed between the detection trace of the detection circuit and the phase line of the motor or on the side of the detection trace of the detection circuit, and is used to cut off the electric field coupling path between the detection trace and the phase line, where the detection trace is the trace in the detection circuit connected to the collector. In this application, a decoupling circuit is provided between the detection trace of the detection circuit and the phase line of the motor to cut off the electric field coupling path between the detection trace on the PCB board of the detection terminal in the desaturation detection circuit and the phase line of the motor, thereby reducing the influence of the desaturation detection circuit being affected by the electric field coupling between the lines and eliminating the problem of false detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 FIG. is a schematic diagram of a desaturation detection circuit provided by an embodiment of this application;

[0017] Figure 2 is Figure 1 a schematic diagram of the structure of the PCB board corresponding to the provided desaturation detection circuit;

[0018] Figure 3 FIG. is another schematic diagram of a desaturation detection circuit provided by an embodiment of this application;

[0019] Figure 4 FIG. is still another schematic diagram of a desaturation detection circuit provided by an embodiment of this application;

[0020] Figure 5 FIG. is a schematic circuit diagram of the detection circuit and the decoupling circuit provided by an embodiment of this application;

[0021] Figure 6 FIG. is a schematic diagram of a motor control device provided by an embodiment of this application;

[0022] Figure 7 FIG. is a schematic diagram of a power system provided by an embodiment of this application;

[0023] Figure 8 FIG. is a schematic circuit diagram of the power system provided by an embodiment of this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The present application provides a desaturation detection circuit, a motor control device, and a power system. Specifically, by adding a decoupling circuit, the electric field coupling path between the detection trace of the detection circuit in the desaturation detection circuit and the phase line in the motor is cut off, so as to eliminate or weaken the mutual electric field coupling between the detection trace and the phase line, thereby avoiding the problem that the peak voltage exceeding the threshold voltage of the detection circuit is generated at the collector of the switching device due to electric field coupling, which interferes with the desaturation detection result.

[0025] Specifically, the decoupling circuit is set in two ways to cut off the electric field coupling path. The first is a physical method, that is, the decoupling circuit is set as an electric field shielding circuit and then set at the spatial position between the detection trace and the phase line.

[0026] The other is a circuit method, that is, circuit devices are added to the detection trace in the detection circuit to increase the impedance and divide the voltage, thereby reducing the peak voltage and attenuating the interference of electric field coupling.

[0027] Terms such as "first", "second", "third", "fourth", etc. (if any) in the specification, claims, and the above-mentioned drawings of the present application are used to distinguish similar objects and do not necessarily need to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so that the embodiments of the present application described herein, for example, can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0028] As Figure 1 shown, a desaturation detection circuit provided by an embodiment of the present application includes: a drive circuit 110, a detection circuit 120, and a decoupling circuit 130. Among them, the drive circuit 110 and the detection circuit 120 are electrically connected, and the decoupling circuit 130 is electrically connected or physically connected to the detection circuit 120.

[0029] It should be noted that the output end of the drive circuit 110 is connected to the switching device, which can be any switching device in the bridge circuit, such as a power transistor (IGBT, MOS transistor). The input end of the drive circuit 110 is connected to the output end of the detection circuit 120 for receiving the desaturation detection signal output by the detection circuit 120. The input end of the detection circuit 120 (i.e., the detection end) is connected to the collector of the switching device, and at the same time, the desaturation detection circuit and the emitter of the switching device are connected to the common ground (i.e., connected to the power ground or the signal reference ground).

[0030] In practical applications, when designing the PCB board of the desaturation detection circuit, the trace of the detection end in the detection circuit 120 corresponds to the phase line of the motor or the connection components are closely arranged, which will cause electric field coupling between the trace of the detection end (i.e., the detection trace) and the corresponding line of the phase line or the connection components. This electric field coupling will affect the detection signal of the detection circuit 120.

[0031] Based on this, the decoupling circuit 130 in the desaturation detection circuit of the present application is arranged between the trace of the detection end and the corresponding line of the phase line or the connection components, or can be arranged on one side of the trace of the detection end (for example, embedded in the detection circuit 120 and connected in series with the electronic devices in the detection circuit 120), so as to cut off the electric field coupling path between the detection trace and the phase line.

[0032] It can be understood that the detection circuit 120 monitors and collects the working voltage on the collector of the switching device it is connected to in real time. This working circuit is actually the voltage difference between the collector and the emitter of the switching device after it is turned on, and then compares this voltage difference with a preset threshold voltage, and outputs the comparison result to the drive circuit 110. This comparison result is a level signal (0 or 1). The drive circuit 110 determines whether the switching device is in the desaturation state based on the comparison result. If so, it adjusts the output of its own switching signal of the drive circuit 110 to control the switching device to work in the saturation state.

[0033] Such as Figure 1 and 2 As shown, it is a schematic diagram of arranging the decoupling circuit 130 between the detection trace of the detection circuit and the phase line of the motor. The decoupling circuit 130 is set as an electric field shielding circuit. In space, this electric field shielding circuit is arranged between the detection trace and the phase line of the motor. When corresponding to the PCB board, it means that the detection trace and the phase line of the motor are arranged on the upper and lower layers, and the electric field shielding circuit is arranged on the middle layer.

[0034] In practical applications, the PCB board on which the desaturation detection circuit is set can be a single-layer board, a three-layer board, or even a multi-layer board. When the PCB board is set as a single-layer board, the detection trace and the phase line of the motor are arranged on the left and right sides of the electric field shielding circuit. As shown in Figure 2 (a), vias are provided on the PCB board, and the detection trace A1 and the phase line A2 of the motor are respectively arranged on the left and right sides of the via, so as to isolate the detection trace A1 and the phase line A2. Then, the electric field shielding circuit is also connected to the signal reference ground, and the signal reference ground can be the power ground in the desaturation detection circuit.

[0035] In another embodiment, the electric field shielding circuit can also be implemented by surrounding the detection trace A1 or surrounding the phase line A2.

[0036] When the PCB board is set as a double-layer board, the detection trace A1 and the phase line A2 of the motor should be arranged on the front and back of the PCB board, and the electric field shielding circuit is inserted into the PCB board at the positions corresponding to the detection trace A1 and the phase line A2 of the motor. As shown in Figure 2 (b), the electric field shielding circuit at this time should be set as a metal layer, such as an iron sheet, etc. Correspondingly, the insulating material on the PCB board at the positions corresponding to the detection trace A1 and the phase line A2 of the motor is hollowed out to fill in the iron sheet, so as to cut off the electric field coupling path.

[0037] For a three-layer board or a multi-layer board, one layer or any layer in the middle of the PCB board is selected to be set as a complete copper layer and grounded, or any layer in the middle of the PCB board is selected and a complete copper layer is set and grounded at the positions corresponding to the detection trace A1 and the phase line A2 of the motor in this layer, while the detection trace A1 and the phase line A2 of the motor are arranged on the upper and lower layers of this copper layer. As shown in Figure 2 (c), in this way, the electric field coupling path between the detection trace A1 and the phase line A2 of the motor is cut off by the copper layer serving as the electric field shielding circuit.

[0038] In a feasible embodiment, the detection circuit 120 includes: an acquisition circuit 121 and a comparison circuit 122;

[0039] The input end 121a of the acquisition circuit 121 is connected to the collector of the switching device, and is used for acquiring the voltage difference between the collector and the emitter of the switching device;

[0040] The first input terminal 122a of the comparison circuit 122 is connected to the output terminal 121b of the acquisition circuit 121. The second input terminal 122b of the comparison circuit 122 is connected to a preset voltage source, which is used to compare the magnitude relationship between the threshold voltage output by the preset voltage source and the voltage difference, and when the voltage difference is greater than the threshold voltage, an oversaturation detection signal is output to the drive circuit 110.

[0041] It should be noted that the comparison circuit 122 is a circuit designed by a comparator, which has a positive input terminal, a negative input terminal and an output terminal. The positive input terminal corresponds to the first input terminal 122a, the negative input terminal corresponds to the second input terminal 122b, and the output terminal 122c is connected to the input terminal of the drive circuit 110. After the acquisition circuit 120 acquires the voltage of the collector of the switching device, it outputs it to the drive circuit 110. The drive circuit 110 compares the voltage received by the positive input terminal with the threshold voltage input by the negative input terminal. When the threshold voltage is greater than the voltage received by the positive input terminal, the output level is inverted, so as to realize the detection of the oversaturation state of the switching device.

[0042] In a feasible implementation manner, the acquisition circuit 121 includes a resistor 1211, a first diode 1212 and a first capacitor 1213;

[0043] The first connection terminal of the first capacitor 1213 is connected to the reference ground, and the second connection terminal of the first capacitor 1213 is respectively connected to the first connection terminal of the resistor 1211 and the first input terminal 122a of the comparison circuit 122;

[0044] The second connection terminal of the resistor 1211 is connected to the anode of the first diode 1212, the cathode of the first diode 1212 is connected to the collector of the switching device, and the decoupling circuit 130 is arranged between the trace of the anode of the first diode 1212 and the phase line of the motor.

[0045] For example, as Figure 3 shown, the dashed box in the figure is the decoupling circuit 130, which is arranged below the acquisition circuit 121 on the PCB board, and the phase line of the motor is arranged below the decoupling circuit 130, so as to increase the electric field coupling between the decoupling circuit 130 and the detection trace.

[0046] It can be understood that for the setting method of arranging the decoupling circuit 130 below the acquisition circuit 121, it is required that the acquisition circuit 121 adopts PCB wiring, the phase line of the motor adopts a power copper bar setting, or the oversaturation detection circuit adopts a multi-layer PCB board and the acquisition circuit 121 and the phase line of the motor are arranged on different layers of the PCB board.

[0047] When adding the decoupling circuit 130 in the manner of Figure 3 Figure 3 , the decoupling circuit 130 can be implemented by an electric field shielding circuit. The electric field shielding circuit is connected to the reference ground and serves as the shield for the detection trace of the acquisition circuit 121, and is arranged in the trace on the anode side of the first diode 1212 close to the phase line of the motor. That is, it is understood to be arranged below the trace between the anode of the first diode 1212 and the second connection end of the resistor 1211.

[0048] In practical applications, the electric field shielding circuit is a metal layer of the reference ground. The metal layer, the trace of the anode of the first diode 1212, and the phase line of the motor are arranged on different layers of the PCB board, and the PCB board layer corresponding to the metal layer is located between the PCB board layers corresponding to the trace of the anode of the first diode 1212 and the phase line of the motor.

[0049] For example, when adding an iron plate (i.e., the electric field shielding circuit) between the copper busbar corresponding to the acquisition circuit 121 and the phase line of the motor, in order to realize the connection with the reference ground, the iron plate can be arranged on the casing of the subsequent desaturation detection circuit and connected to the terminal connected to the ground wire in the casing, such as the casing itself; or the detection trace of the acquisition circuit 121 is routed on the top layer of the PCB board, and the second layer of the PCB board uses the corresponding reference ground as copper plating under the detection trace to cut off the electric field coupling path between the detection trace and the copper busbar or power trace corresponding to the phase line.

[0050] By implementing the above-provided desaturation detection circuit, in the case where safety regulations and the overall machine structure are restricted, generally, the phase line of the motor is arranged below the desaturation detection circuit. And for the desaturation detection circuit solution provided in this embodiment, only the layout spatial position between the detection trace and the phase line is changed, and a shielding layer is added between the detection trace and the phase line as a decoupling circuit to shield the interference of the electric field coupling to the desaturation detection signal of the switching device, which belongs to cutting off the coupling path at the interference source and eliminating the problem of false detection caused by electric field coupling interference.

[0051] In a feasible implementation manner, as Figure 4 shown, the decoupling circuit 130 can also be implemented by being embedded in the acquisition circuit 121, that is, by increasing the impedance in the acquisition circuit 121 to attenuate the spike voltage generated by electric field coupling, so as to improve the accuracy of desaturation detection.

[0052] The decoupling circuit 130 includes a diode circuit. The anode of the diode circuit is connected to the second connection end of the resistor 1211, and the cathode of the diode circuit is connected to the anode of the first diode 1212.

[0053] That is, a diode circuit is added after the detection trace (i.e., the anode of the first diode 1212) that forms an electric field coupling with the phase line of the motor, so as to attenuate the coupling interference caused by the copper bar or power trace corresponding to the phase line of the motor. The attenuation principle is that the newly added diode circuit forms a large impedance in the series circuit composed of the resistor 1211 and the first capacitor 1213, diverting most of the voltage, and can effectively attenuate the interference signal.

[0054] It should be noted that the diode circuit can be a single diode or a combined circuit composed of two or more diodes. When a single diode is used, the diode circuit should be connected in series in the same direction as the first diode 1212.

[0055] In a feasible implementation, as Figure 5 shown, the diode circuit includes at least one second diode 131 and at least one second capacitor 132. When there are more than two second diodes 131, the second diodes 131 are connected in series and then connected in series with the first diode 1212, and each second diode 131 is connected in parallel with a second capacitor 132. The series connection of the two diodes here should be understood as the cathode of the previous diode being connected to the anode of the next diode.

[0056] It should be noted that when the diode circuit is implemented by a single second diode 131, the cathode of the second diode 131 is connected to the anode of the first diode 1212, and the anode of the second diode 131 is connected to the second connection end of the resistor 1211.

[0057] As Figure 5 shown, the diode circuit is composed of two second diodes 131 connected in series, that is, after the cathode of the diode Ddesat2 and the anode of the diode Ddesat3 in the figure are connected, it is arranged between the second connection end of the resistor Rdesat 1211 and the anode of the first diode Ddesat1 1212. The first diode Ddesat1 1212 is connected to the collector of the switching device, and its installation position on the BCB board is usually close to the collector. That is, the connection line between the first diode Ddesat1 1212 and the switching device is short, and the connection line with the resistor Rdesat 1211 is long. Based on this, after the switching device is turned on, it will be affected by the generated electric field, and setting a diode circuit between the second connection end of the resistor Rdesat 1211 and the anode of the first diode Ddesat1 1212 can attenuate the influence of the electric field.

[0058] Furthermore, since the junction capacitance of the first diode Ddesat1 1212 is only about 10 pf and the first capacitor Cdesat 1213 is generally 220 pf, according to the capacitive reactance formula 1 / (jwC), it can be calculated that after the two second diodes 131 (i.e., Ddesat2 and Ddesat3 in the figure) form a series circuit with the resistor Rdesat 1211 and the first capacitor Cdesat 1213, a relatively large impedance will be generated, thus diverting most of the voltage and effectively attenuating the interference signal. On the other hand, when the switching device (such as an IGBT) turns off by itself, there will also be a certain interference caused by the rising VCE voltage resulting in i = C*du / dt. The newly added two second diodes 131 can also reduce the series parasitic capacitance of the desat detection circuit desat loop and have a certain attenuation effect on the interference signal.

[0059] By setting the decoupling circuit in the acquisition circuit in this embodiment, only adding a diode to the existing acquisition circuit can avoid the influence of electric field coupling. The cost is relatively low, and it can also divide the reverse voltage of the diode, which is convenient for wiring during safety regulations limit and selecting a diode with a smaller reverse voltage. It belongs to adding an attenuation measure in the interference path to reduce the interference of the interference path on the detection signal.

[0060] This application also provides a motor control device, including: at least one switching device 610 and at least one desaturation detection circuit 620 provided in the above embodiment, as Figure 6 shown, the circuit structure of the desaturation detection circuit 720 here is as Figure 5 shown.

[0061] It should be noted that the switching device 610 is an IGBT. The collector C of the IGBT is connected to the input end of the desaturation detection circuit 620, the output end of the desaturation detection circuit 620 is connected to the base G of the IGBT, the decoupling circuit 130 in the desaturation detection circuit 620 is set as a diode, and the power ground of the desaturation detection circuit 620 is connected to the emitter E of the IGBT.

[0062] When the motor is working, the drive circuit 110 in the desaturation detection circuit 620 outputs a switching signal to control the switching device 610 to work in the saturation state, and the voltage of the collector C of the switching device 610 is detected in real time through the acquisition circuit 120. After the voltage is divided by the diode in the decoupling circuit 130, it is compared with a preset threshold voltage, and a desaturation detection signal is output to the drive circuit 110, so as to control the drive circuit 110 to adjust the switching signal to control the on-off of the IGBT, so that it exits the desaturation state.

[0063] Further, the present application also provides a power system, including at least three desaturation detection circuits 620 provided in the above embodiments, at least three switching devices 610, and a three-phase motor 630. Among them, each of the desaturation detection circuits 620 corresponds to one of the switching devices 610, and each of the switching devices 610 is connected to one phase line of the three-phase motor 630; when the detection circuit in the desaturation detection circuit 620 detects that the switching device 610 is in a saturated state (that is, the voltage difference between the collector and the emitter of the switching device 610 is greater than the threshold voltage), it outputs a desaturation detection signal to control the drive circuit 110 to output a switching signal to the corresponding switching device 610, such as Figure 7 and 8 shown.

[0064] It should be noted that each phase line in the three-phase circuit 630 is composed of two switching devices 610. For example, an upper and lower transistor switching circuit composed of two IGBTs. A desaturation detection circuit 620 is provided on each IGBT. One of the IGBTs is specifically expanded in the figure, and the other settings and principles are the same.

[0065] Such as Figure 8 shown, in the W phase of the three-phase motor 630, the W phase is respectively connected to the emitter E of IGBT1 and the collector C of IGBT2. For example, when the drive circuit 110 controls IGBT1 to work in a saturated state, that is, when it is turned on, its acquisition circuit and decoupling circuit real-time collect the voltage of the collector C of IGBT1, and make a comparison and judgment in the comparison circuit. Specifically, the voltage of the collector C of IGBT1 collected is compared with a preset threshold voltage. When the threshold voltage is greater than the voltage of the collector C of IGBT1, the output level is inverted, so as to realize the detection of the desaturation state of IGBT1. Further, the drive circuit outputs a new switching signal to control IGBT1 to turn off or adjust to work in a saturated state.

[0066] In the present application, a desaturation detection circuit with an additional decoupling circuit is used to detect whether the switching device of the motor is in a desaturation state. The decoupling circuit can reduce the coupling between the electric field generated by the detection trace in the desaturation detection circuit and the electric field generated by the phase line of the motor, thereby avoiding the generation of spike voltage, avoiding false detection, and improving the accuracy of desaturation detection.

[0067] Finally, it should be noted that the above embodiments are only specific implementation manners of the present application, used to illustrate the technical solutions of the present application, rather than limiting it. The protection scope of the present application is not limited thereto. Although the present application 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 within the technical scope disclosed by the present application can still modify the technical solutions recorded in the foregoing embodiments, or can easily think of changes, or perform equivalent replacements on some of the technical features; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A desaturation detection circuit, characterized in that, Comprising: A drive circuit, whose output terminal is connected to the control terminal of the switching device, for outputting a switching signal to control the on / off of the switching device; A detection circuit, which is connected to the input terminal of the drive circuit and the switching device, for outputting a desaturation detection signal to the drive circuit when detecting that the switching device is in a saturation state; A decoupling circuit, which is provided between the detection trace of the detection circuit and the phase line of the motor or on the side of the detection trace of the detection circuit, for cutting off the electric field coupling path between the detection trace and the phase line, wherein the detection trace is the trace in the detection circuit connected to the switching device; 2. The desaturation detection circuit according to claim 1, wherein The detection circuit includes: a sampling circuit and a comparison circuit; The input terminal of the sampling circuit is connected to the collector of the switching device, for sampling the voltage difference between the collector and the emitter of the switching device; The first input terminal of the comparison circuit is connected to the output terminal of the sampling circuit, and the second input terminal of the comparison circuit is connected to a preset voltage source, for comparing the magnitude relationship between the threshold voltage output by the preset voltage source and the voltage difference, and outputting a desaturation detection signal to the drive circuit when the voltage difference is greater than the threshold voltage; 3. The desaturation detection circuit according to claim 2, wherein The sampling circuit includes a resistor, a first diode and a first capacitor; The first connection terminal of the first capacitor is connected to the reference ground, and the second connection terminal of the first capacitor is respectively connected to the first connection terminal of the resistor and the first input terminal of the comparison circuit; The second connection terminal of the resistor is connected to the anode of the first diode, the cathode of the first diode is connected to the collector, and the decoupling circuit is provided between the trace of the anode of the first diode and the phase line of the motor; 4. The desaturation detection circuit according to claim 3, wherein, The decoupling circuit includes an electric field shielding circuit, which is connected to the reference ground and is provided on the side of the trace of the anode of the first diode close to the phase line of the motor; 5. The desaturation detection circuit according to claim 4, wherein The electric field shielding circuit is a metal layer of the reference ground, and the metal layer, the trace of the anode of the first diode and the phase line of the motor are provided on different layers of the PCB board, and the PCB board layer corresponding to the metal layer is located between the PCB board layers corresponding to the trace of the anode of the first diode and the phase line of the motor; 6. The desaturation detection circuit according to claim 3, wherein The decoupling circuit includes a diode circuit, the anode of the diode circuit is connected to the second connection terminal of the resistor, and the cathode of the diode circuit is connected to the anode of the first diode; 7. The desaturation detection circuit according to claim 6, wherein The diode circuit includes at least one second diode; 8. The desaturation detection circuit according to claim 7, wherein The diode circuit further includes at least one second capacitor, and each second diode is connected in parallel with a second capacitor; 9. A motor control device, characterized in that, Comprising: At least one switching device and at least one desaturation detection circuit according to any one of claims 1-8; 10. A power system, characterized in that, Comprising: At least three desaturation detection circuits according to any one of claims 6-8, at least three switching devices and a three-phase motor, wherein each desaturation detection circuit corresponds to one switching device, and each switching device is connected to one phase line of the three-phase motor; When the detection circuit in the desaturation detection circuit detects that the switching device is in a saturated state, it outputs a desaturation detection signal to control the drive circuit to output a switching signal to the corresponding switching device.

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