Operation protection device of power switch tube, PFC (Power Factor Correction) circuit and air conditioner

Abstract

The invention discloses an operation protection device of a power switch tube, a PFC (Power Factor Correction) circuit and an air conditioner, and the device comprises a voltage detection unit which is configured to detect the tube voltage drop of the power switch tube under the switching-on condition; the current detection unit is configured to detect the turn-on current of the power switch tube; and the control unit is configured to protect the power switch tube according to the turn-on current and the tube voltage drop. The operation protection device protects the power switch tube according to the turn-on current and the tube voltage drop of the power switch tube, so that the power switch tube is comprehensively protected, and the reliability of the protection method of the power switch tube is improved.

Description

Technical Field

[0001] This application relates to the field of power switching transistor technology, and in particular to a power switching transistor operation protection device, a PFC circuit, and an air conditioner. Background Technology

[0002] In related technologies, IGBTs (Insulated-Gate Bipolar Transistors) rely solely on current sampling for protection. Therefore, these technologies can only provide protection from the perspective of IGBT overcurrent, resulting in a very one-sided application and protection approach for IGBTs. This can easily lead to wasted IGBT resources or improper IGBT protection, thus the reliability of IGBT protection methods in these technologies is relatively low. Summary of the Invention

[0003] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, the first objective of this invention is to provide an operational protection device for a power switch transistor, which protects the power switch transistor based on its turn-on current and voltage drop, achieving comprehensive protection and thus improving the reliability of the power switch transistor protection method.

[0004] The second objective of this invention is to provide a PFC circuit.

[0005] The third objective of this invention is to provide an air conditioner.

[0006] To achieve the above objectives, a power switch operation protection device is provided according to a first aspect embodiment of the present invention, comprising: a voltage detection unit configured to detect the voltage drop of the power switch when it is turned on; a current detection unit configured to detect the turn-on current of the power switch; and a control unit configured to protect the power switch based on the turn-on current and the voltage drop.

[0007] The power switch transistor operation protection device according to an embodiment of the present invention includes a voltage detection unit, a current detection unit, and a control unit. The voltage detection unit is configured to detect the transistor voltage drop when the power switch transistor is turned on, the current detection unit is configured to detect the turn-on current of the power switch transistor, and the control unit is configured to protect the power switch transistor based on the turn-on current and the transistor voltage drop. Therefore, the control unit protects the power switch transistor based on the turn-on current and the transistor voltage drop. Compared to related technologies that only protect the power switch transistor based on its current, the operation protection device of this embodiment achieves more comprehensive protection, thereby avoiding waste of power switch transistor resources or inadequate protection, and thus improving the reliability of the power switch transistor protection method.

[0008] According to one embodiment of the present invention, the control unit is further configured to determine the transistor voltage drop-junction temperature relationship curve based on the turn-on current, and to determine the temperature of the power switch transistor based on the transistor voltage drop and the transistor voltage drop-junction temperature relationship curve.

[0009] According to one embodiment of the present invention, the control unit is further configured to compare the detection value corresponding to the turn-on current with the tube voltage drop to provide overcurrent protection or overtemperature protection for the power switch tube.

[0010] According to one embodiment of the present invention, the control unit is further configured to delay after issuing an on-control signal to control the power switch to turn on, and to sample the voltage drop of the switch when the delay time reaches a first preset time.

[0011] According to one embodiment of the present invention, the voltage detection unit includes: a first resistor, one end of which is connected to the collector of a power switch transistor; a first Zener diode, the cathode of which is connected to the other end of the first resistor and has a first node, the anode of which is grounded; a second resistor, one end of which is connected to the first node and the other end of which is adapted to be connected to the sampling terminal of the control unit; and a first capacitor, one end of which is connected to the other end of the second resistor and the other end of which is grounded.

[0012] According to one embodiment of the present invention, the voltage detection unit includes: a first resistor, one end of which is connected to the collector of a power switch transistor; a plurality of first diodes, the anode of which is connected in series with the first diodes is connected to the other end of the first resistor and has a first node, and the cathode of which is connected in series with the first diodes is grounded; a second resistor, one end of which is connected to the first node and the other end of which is adapted to be connected to the sampling terminal of the control unit; and a first capacitor, one end of which is connected to the other end of the second resistor and the other end of which is grounded.

[0013] According to one embodiment of the present invention, the voltage detection unit includes: a second diode, the cathode of which is connected to the collector of a power switch; a second resistor, one end of which is connected to a reference power supply, the other end of which is connected to the anode of the second diode, and having a second node adapted to be connected to a first sampling terminal of a control unit; a third resistor, one end of which is connected to the reference power supply; and a third diode, the anode of which is connected to the other end of the third resistor, and having a third node, the cathode of which is grounded, and the third node adapted to be connected to a second sampling terminal of a control unit.

[0014] According to one embodiment of the present invention, the control unit is further configured to acquire a first voltage sample value based on a first sampling terminal when the power switch is turned on, acquire a second voltage sample value based on a second sampling terminal when the power switch is turned off, and determine a second sample value corresponding to the tube voltage drop based on the first voltage sample value and the second voltage sample value.

[0015] According to one embodiment of the present invention, the voltage detection unit further includes: a fourth resistor, one end of which is connected to a third node; a fifth resistor, one end of which is connected to a second node; a sixth resistor, one end of which is connected to the other end of the fifth resistor, and the other end of which is grounded; a first operational amplifier, the negative input terminal of which is connected to the other end of the fourth resistor, and the positive input terminal of which is connected to the other end of the fifth resistor; a seventh resistor, which is connected between the negative input terminal and the output terminal of the first operational amplifier; an eighth resistor, one end of which is connected to the output terminal of the first operational amplifier, and the other end of which is adapted to be connected to the sampling terminal of the control unit; and a second capacitor, one end of which is connected to the other end of the eighth resistor, and the other end of which is grounded.

[0016] According to one embodiment of the present invention, the voltage detection unit includes: a second diode, the cathode of which is connected to the collector of a power switch; a second resistor, one end of which is connected to a reference power supply, the other end of which is connected to the anode of the second diode, and having a second node adapted to be connected to a sampling terminal of a control unit; and a plurality of third diodes, the anode of which is connected to the second node after being connected in series, and the cathode of which is connected to ground.

[0017] According to one embodiment of the present invention, the operation protection device further includes a signal processing unit configured to process the turn-on current.

[0018] According to one embodiment of the present invention, the signal processing unit includes: a ninth resistor, one end of which is adapted to be connected to a first output terminal of a current detection unit; a tenth resistor, one end of which is adapted to be connected to a second output terminal of the current detection unit; a second operational amplifier, the positive input terminal of which is connected to the other end of the ninth resistor, the negative input terminal of which is connected to the other end of the tenth resistor, and the output terminal of which is adapted to be connected to a control unit; and an eleventh resistor, which is connected between the negative input terminal and the output terminal of the second operational amplifier.

[0019] According to one embodiment of the present invention, the control unit further includes: a comparator, the positive input terminal of the comparator being connected to the output terminal of the voltage detection unit, the negative input terminal of the comparator being connected to the output terminal of the second operational amplifier, and the output terminal of the comparator being adapted to be connected to the controller in the control unit.

[0020] To achieve the above objectives, a PFC circuit is provided according to a second aspect of the present invention, comprising: a power switching transistor; and an operation protection device of any of the foregoing embodiments.

[0021] According to the PFC circuit of the present invention, by employing the above-described operation protection device, the power switch is protected based on the turn-on current and voltage drop of the power switch, thereby achieving comprehensive protection of the power switch and improving the reliability of the power switch protection method.

[0022] According to one embodiment of the present invention, the control unit is further configured to determine the temperature of the power switch transistor at the zero-crossing point of the PFC circuit based on the transistor voltage drop and a preset transistor voltage drop-junction temperature relationship curve, and to control the PFC circuit according to the temperature of the power switch transistor.

[0023] To achieve the above objectives, an air conditioner is provided according to a third aspect of the present invention, including the PFC circuit of any of the foregoing embodiments.

[0024] According to the embodiments of the present invention, the air conditioner employs the above-described PFC circuit to protect the power switch transistor based on its turn-on current and voltage drop, thereby achieving comprehensive protection of the power switch transistor and improving the reliability of the power switch transistor protection method.

[0025] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the operation protection device for a power switch tube according to an embodiment of the present invention;

[0027] Figure 2 This is a curve showing the relationship between the junction temperature and current carrying capacity of a power switch transistor according to an embodiment of the present invention.

[0028] Figure 3 This is a curve showing the relationship between the tube voltage drop and junction temperature of a power switch transistor according to an embodiment of the present invention.

[0029] Figure 4 This is a curve showing the relationship between the voltage drop of a power switch transistor and its turn-on current according to an embodiment of the present invention.

[0030] Figure 5 The figures show the relationship curve between the transistor voltage drop and junction temperature of a power switch transistor and the voltage curve corresponding to the turn-on current, according to an embodiment of the present invention.

[0031] Figure 6This is a circuit diagram of an operation protection device according to an embodiment of the present invention;

[0032] Figure 7 This is a circuit diagram of a voltage detection unit according to an embodiment of the present invention;

[0033] Figure 8 This is a circuit diagram of a voltage detection unit according to another embodiment of the present invention;

[0034] Figure 9 This is a circuit diagram of a voltage detection unit according to another embodiment of the present invention;

[0035] Figure 10 This is a circuit diagram of a voltage detection unit according to another embodiment of the present invention;

[0036] Figure 11 This is a circuit diagram of a voltage detection unit according to another embodiment of the present invention;

[0037] Figure 12 is based on Figure 9 The diagram shown illustrates the process of a voltage detection unit determining the transistor voltage drop and the temperature of the power switch transistor.

[0038] Figure 13 is based on Figure 10 The diagram shown illustrates the process of a voltage detection unit determining the transistor voltage drop and the temperature of the power switch transistor.

[0039] Figure 14 is based on Figure 11 The diagram shown illustrates the process of a voltage detection unit determining the transistor voltage drop and the temperature of the power switch transistor.

[0040] Figure 15 This is a schematic diagram of current changes in a PFC circuit according to an embodiment of the present invention;

[0041] Figure 16 This is a schematic diagram of the structure of an air conditioner according to an embodiment of the present invention. Detailed Implementation

[0042] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0043] The following description, with reference to the accompanying drawings, describes an embodiment of the power switch tube operation protection device, a PFC circuit, and an air conditioner.

[0044] Figure 1This is a schematic diagram of the operation protection device for a power switching transistor according to an embodiment of the present invention. Figure 1 As shown, the operation protection device 100 for the power switch Q includes: a voltage detection unit 10, a current detection unit 20, and a control unit 30.

[0045] The voltage detection unit 10 is configured to detect the voltage drop Uce of the power switch Q when it is turned on; the current detection unit 20 is configured to detect the turn-on current Ic of the power switch Q; and the control unit 30 is configured to protect the power switch Q based on the turn-on current Ic and the voltage drop Uce.

[0046] Specifically, Figure 2 The curve showing the relationship between the temperature and current carrying capacity of the power switch Q is presented. Figure 2 As can be seen, the higher the temperature of the power switch Q, the smaller the collector current Ic and the worse its current-carrying capacity. This is because the higher the temperature of the power switch Q, the closer its core junction temperature Tj is to the temperature limit (150℃, and the temperature limit of some power switches Q can reach 175℃), where the gate-emitter voltage Vge ≥ 15V. When the power switch Q is turned on, it has a voltage drop Uce, at which point the power switch Q will have certain losses, causing the junction temperature Tj of the power switch Q to rise and approach the temperature limit. Therefore, the higher the temperature of the power switch Q, the lower its current-carrying capacity. Figure 3 The curve showing the relationship between the transistor voltage drop Uce of the power switch Q and the junction temperature Tj is shown, as follows: Figure 3 As shown, the voltage drop Uce of the power switch Q decreases as the junction temperature Tj increases (it exhibits a linear change after exceeding 100℃), and the voltage drop Uce of the power switch Q increases as the flux increases. Figure 4 The curve showing the relationship between the voltage drop Uce of the power switch Q and the turn-on current Ic is presented. Figure 4 As can be seen, the voltage drop Uce of the power switch Q increases with the increase of the turn-on current Ic, and then becomes linear after 1 / 6 of the rated current. When the power switch Q experiences overcurrent, it may cause the junction temperature Tj of the power switch Q to be higher, and from... Figures 2 to 4 As can be seen, the junction temperature Tj of the power switch Q is correlated with the turn-on current Ic and the voltage drop Uce. Therefore, over-temperature and over-current protection can be provided for the power switch Q based on its turn-on current Ic and voltage drop Uce. In this embodiment, the operation protection device 100 detects the voltage drop Uce of the power switch Q under turn-on conditions through the voltage detection unit 10 and detects the turn-on current Ic of the power switch Q through the current detection unit 20. The control unit 30 can provide over-temperature and over-current protection for the power switch Q based on the voltage drop Uce and the turn-on current Ic.

[0047] It should be noted that the power switch Q in this embodiment can be an IGBT, but it is not limited to an IGBT. It can also be a MOS (Metal-Oxide-Semiconductor Field-Effect Transistor). No specific limitation is made here.

[0048] In the above embodiments, based on the voltage drop and turn-on current of the power switch under turn-on conditions, overcurrent protection or overtemperature protection can be performed on the power switch, achieving comprehensive protection of the power switch and thus improving the reliability of the protection method for the power switch.

[0049] In some embodiments, the control unit 30 is further configured to determine the voltage drop-junction temperature relationship curve based on the turn-on current Ic, and to determine the temperature of the power switch Q based on the voltage drop Uce and the voltage drop-junction temperature relationship curve.

[0050] Specifically, such as Figure 3 As shown, the voltage drop-junction temperature relationship curves corresponding to different turn-on currents Ic are different. Therefore, it is necessary to first determine the voltage drop-junction temperature relationship curve corresponding to the turn-on current Ic, and then find the temperature of the power switch transistor Q corresponding to the voltage drop Uce from the voltage drop-junction temperature relationship curve.

[0051] For example, with Figure 5 For example, if a current of 6A is supplied to the power switch transistor Q, the turn-on current Ic is 6A. Therefore, the voltage drop-junction temperature curve is the voltage drop-junction temperature curve when the current is 6A. When the voltage drop Uce is 1.35V, the temperature of the power switch transistor Q is 125℃.

[0052] Furthermore, since the temperature of the power switch Q is obtained based on the voltage drop Uce, compared to detecting the temperature of the power switch Q through a temperature sensor installed next to the power switch Q, there is no temperature acquisition delay. Therefore, the power switch Q can be protected against temperature changes in a timely manner based on the voltage drop Uce, and no additional sensor is required, reducing the cost of the protection device.

[0053] In some embodiments, the control unit 30 is further configured to compare the detection value corresponding to the turn-on current Ic with the tube voltage drop Uce to provide overcurrent protection or overtemperature protection for the power switch tube Q.

[0054] It is understandable that, in adopting such Figure 6 When the circuit diagram shown detects the turn-on current Ic, the detected value corresponding to the turn-on current Ic is also a voltage signal. Figure 5For example, the detection value corresponding to the turn-on current Ic is 1.35V. Figure 5 (The dashed line in the diagram) Therefore, the detection value corresponding to the turn-on current Ic can be directly compared with the tube voltage drop Uce to determine whether the power switch tube Q has experienced overcurrent or overtemperature, thereby providing overcurrent or overtemperature protection for the power switch tube Q.

[0055] In an optional implementation, the control unit 30 is further configured to determine the tube voltage drop-junction temperature relationship curve based on the turn-on current Ic, determine the voltage threshold based on the intersection of the detection value corresponding to the turn-on current Ic and the tube voltage drop-junction temperature relationship curve, and perform over-temperature protection on the power switch tube Q when the tube voltage drop Uce is less than the voltage threshold.

[0056] Specifically, the voltage drop-junction temperature relationship curve corresponding to the turn-on current Ic is determined based on the turn-on current Ic, so as to... Figure 5 As shown, the diode voltage drop-junction temperature curve is the diode voltage drop-junction temperature curve when the current is 6A. The detection value corresponding to the turn-on current Ic is 1.35V, which intersects with the diode voltage drop-junction temperature curve. Therefore, the voltage threshold is 1.35V. When the diode voltage drop Uce is less than 1.35V, the temperature of the power switch Q is greater than 125℃. Therefore, over-temperature protection is required for the power switch Q. It should be noted that the temperature threshold can also be determined based on the intersection point. When the temperature of the power switch Q, determined by the diode voltage drop Uce and the diode voltage drop-junction temperature curve, is greater than the temperature threshold, over-temperature protection is implemented for the power switch Q. For example, the horizontal axis of the intersection point is 125℃. When the temperature of the power switch Q, determined by the diode voltage drop Uce and the diode voltage drop-junction temperature curve, is greater than 125℃, over-temperature protection is implemented for the power switch Q.

[0057] Therefore, when the heat dissipation of the power switch Q is poor or the ambient temperature is high, the current carrying capacity of the power switch Q will decrease significantly (e.g., Figure 5 As shown, it can only carry a current of 6A. However, when the heat dissipation of the power switch Q is very good or the ambient temperature is very low, the junction temperature Tj of the power switch Q is low, which can achieve a greater current carrying capacity.

[0058] In another alternative implementation, the control unit 30 is further configured to determine the temperature of the power switch Q based on the tube voltage drop Uce when the turn-on current Ic is greater than a preset current threshold, and to perform over-temperature protection on the power switch Q based on the temperature of the power switch Q.

[0059] Specifically, when the turn-on current Ic is greater than the preset current threshold, the power switch Q is overcurrent. If the power switch Q is overcurrent at the moment of turn-on, the temperature of the power switch Q can also be determined according to the voltage drop Uce, and the power switch Q can be over-temperature protected according to the temperature of the power switch Q. This realizes real-time protection of the power switch Q, thereby enhancing the stable operation capability of the protection device.

[0060] In some embodiments, the control unit 30 is further configured to delay after issuing an on-control signal to control the power switch Q to turn on, and to sample the tube voltage drop Uce when the delay time reaches a first preset time.

[0061] Specifically, the control unit 30 sends an on-control signal to close the power switch Q. During the on-process of the power switch Q, oscillations will occur, which will cause the sampled tube voltage drop Uce to be inaccurate. Therefore, it is necessary to delay the acquisition of the tube voltage drop Uce. When the delay time reaches the first preset time, the tube voltage drop Uce stabilizes, so the tube voltage drop Uce is sampled.

[0062] In the above embodiments, after the power switch is turned on and the delay time reaches the first preset time, the voltage drop of the switch is sampled. This avoids the inaccuracy of the voltage drop caused by the oscillation generated during the turn-on process of the power switch, improves the accuracy of the voltage drop, and further enhances the reliability of the protection method.

[0063] In some embodiments, as Figure 7 As shown, the voltage detection unit 10 includes: a first resistor R1, a first Zener diode DZ1, a second resistor R2, and a first capacitor C1. One end of the first resistor R1 is connected to the collector of the power switch Q; the cathode of the first Zener diode DZ1 is connected to the other end of the first resistor R1 and has a first node J1, and the anode of the first Zener diode DZ1 is grounded; one end of the second resistor R2 is connected to the first node J1, and the other end of the second resistor R2 is adapted to be connected to the sampling terminal of the control unit 30; one end of the first capacitor C1 is connected to the other end of the second resistor R2, and the other end of the first capacitor C1 is grounded.

[0064] Specifically, one end of the first resistor R1 is connected to the collector of the power switch Q to acquire the collector voltage of the power switch Q. Since the emitter of the power switch Q is grounded, the collector voltage of the power switch Q is the transistor voltage drop Uce. The first Zener diode DZ1 is used to clamp the voltage at the first node J1 to prevent the collector voltage of the power switch Q from being too high and causing damage to subsequent circuits. The first capacitor C1 can filter out noise in the voltage signal input to the sampling terminal of the control unit 30, thereby further improving the accuracy of the transistor voltage drop Uce.

[0065] In some embodiments, such as Figure 8 As shown, the voltage detection unit 10 includes: a first resistor R1, a plurality of first diodes D1, a second resistor R2, and a first capacitor C1. One end of the first resistor R1 is connected to the collector of the power switch Q; the anode of the plurality of first diodes D1 connected in series is connected to the other end of the first resistor R1 and has a first node J1; the cathode of the plurality of first diodes D1 connected in series is grounded; one end of the second resistor R2 is connected to the first node J1, and the other end of the second resistor R2 is adapted to be connected to the sampling terminal of the control unit 30; one end of the first capacitor C1 is connected to the other end of the second resistor R2, and the other end of the first capacitor C1 is grounded.

[0066] In other words, multiple first diodes D1 can be used to replace... Figure 7 The first Zener diode DZ1 and multiple first diodes D1 can also clamp the voltage of the first node J1, thereby preventing the collector voltage of the power switch Q from being too high and causing damage to the subsequent circuit. The other components in the circuit remain unchanged.

[0067] It should be noted that, Figure 8 The two first diodes D1 in the example are exemplary, and the number of first diodes D1 is not limited to two, and can be set according to the actual situation.

[0068] In some embodiments, such as Figure 9 As shown, the voltage detection unit 10 includes: a second diode D2, a second resistor R2, a third resistor R3, and a third diode D3. The cathode of the second diode D2 is connected to the collector of the power switch Q. One end of the second resistor R2 is connected to the reference power supply VCC, and the other end of the second resistor R2 is connected to the anode of the second diode D2, and has a second node J2, which is adapted to be connected to the first sampling terminal of the control unit 30. One end of the third resistor R3 is connected to the reference power supply VCC. The anode of the third diode D3 is connected to the other end of the third resistor R3, and has a third node J3. The cathode of the third diode D3 is grounded, and the third node J3 is adapted to be connected to the second sampling terminal of the control unit 30.

[0069] Specifically, the collector of the power switch Q is adapted to be connected to one end of the load resistor Rload, the other end of the load resistor Rload is adapted to be connected to a preset power supply, and the emitter of the power switch Q is grounded. When the power switch Q is turned on, the reference power supply VCC, the second resistor R2, the second diode D2, and the power switch Q form a current loop, and the control unit 30 samples the voltage at the second node J2. When the power switch Q is turned off, due to the blocking effect of the second diode D2, the reference power supply VCC, the third resistor R3, and the third diode D3 form a current loop, and the control unit 30 samples the voltage at the third node J3.

[0070] In some embodiments, the control unit 30 is further configured to acquire a first voltage sample value AD1 based on a first sampling terminal when the power switch Q is turned on, acquire a second voltage sample value AD2 based on a second sampling terminal when the power switch Q is turned off, and determine a second sample value corresponding to the tube voltage drop Uce based on the first voltage sample value AD1 and the second voltage sample value AD2.

[0071] Specifically, when the power switch Q is turned on, the first voltage sample value AD1 includes the voltage drop across the power switch Q, Uce, and the voltage drop across the second diode D2; when the power switch Q is turned off, the second voltage sample value AD2 includes the voltage drop across the third diode D3. Therefore, the second sample value corresponding to the voltage drop Uce is the difference between the first voltage sample value AD1 and the second voltage sample value AD2.

[0072] It should be noted that when the sampling circuit of this embodiment obtains the tube voltage drop Uce, the second diode D2 and the third diode D3 are of the same model to ensure that the voltage drop of the second diode D2 and the voltage drop of the third diode D3 are the same. This allows the second sampling value corresponding to the tube voltage drop Uce to be determined based on the first voltage sampling value AD1 and the second voltage sampling value AD2. Furthermore, the second diode D2 and the third diode D3 are two diodes of the same model within the same package.

[0073] In some embodiments, as Figure 10 As shown, the voltage detection unit 10 further includes: a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a first operational amplifier OPA1, a seventh resistor R7, an eighth resistor R8, and a second capacitor C2. One end of the fourth resistor R4 is connected to the third node J3; one end of the fifth resistor R5 is connected to the second node J2; one end of the sixth resistor R6 is connected to the other end of the fifth resistor R5, and the other end of the sixth resistor R6 is grounded; the negative input terminal of the first operational amplifier OPA1 is connected to the other end of the fourth resistor R4, and the positive input terminal of the first operational amplifier OPA1 is connected to the other end of the fifth resistor R5; the seventh resistor R7 is connected between the negative input terminal and the output terminal of the first operational amplifier OPA1; one end of the eighth resistor R8 is connected to the output terminal of the first operational amplifier OPA1, and the other end of the eighth resistor R8 is adapted to be connected to the sampling terminal of the control unit 30; one end of the second capacitor C2 is connected to the other end of the eighth resistor R8, and the other end of the second capacitor C2 is grounded.

[0074] Specifically, the negative input terminal of the first operational amplifier OPA1 is connected to the third node J3 through the fourth resistor R4 to obtain the first voltage value U1 of the third node J3 when the power switch Q is turned off. The positive input terminal of the first operational amplifier OPA1 is connected to the second node J2 through the fifth resistor R5 to obtain the second voltage value U2 of the second node J2 when the power switch Q is turned on. The first voltage value U1 includes the voltage drop Uce of the power switch Q and the voltage drop of the second diode D2. The second voltage value U2 includes the voltage drop of the third diode D3. Therefore, the first operational amplifier OPA1 can output the detection value Uo corresponding to the voltage drop Uce. When the resistance values ​​of the sixth resistor R6 and the seventh resistor R7 are the same, the voltage drop Uce is calculated according to formula (1):

[0075] Uce=n*Uo=R7 / R4*(U1-U2) (1)

[0076] Where n is the amplification factor, and Uo is the detected value corresponding to the tube voltage drop Uce (i.e., the output voltage of the first operational amplifier OPA1).

[0077] Furthermore, when the resistance values ​​of the fourth resistor R4, the fifth resistor R5, the sixth resistor R6, and the seventh resistor R7 are the same, the amplification factor n is 1, and formula (1) can be simplified to formula (2):

[0078] Uce=Uo=U1-U2 (2)

[0079] Therefore, the first operational amplifier OPA1 can directly output the tube voltage drop Uce.

[0080] In some embodiments, such as Figure 11 As shown, the voltage detection unit 10 includes: a second diode D2, a second resistor R2, and a plurality of third diodes D3. The cathode of the second diode D2 is connected to the collector of the power switch Q. One end of the second resistor R2 is connected to the reference power supply VCC, and the other end of the second resistor R2 is connected to the anode of the second diode D2. The second resistor R2 has a second node J2, which is adapted to be connected to the sampling terminal of the control unit 30. The anode of the plurality of third diodes D3 connected in series is connected to the second node J2, and the cathode of the plurality of third diodes D3 connected in series is grounded.

[0081] Specifically, when the power switch Q is turned on, the reference power supply VCC, the second resistor R2, the second diode D2, and the power switch Q form a current loop. At this time, the third voltage value U3 at the sampling terminal of the control unit 30 includes the voltage drop of the second diode D2 and the tube voltage drop Uce of the power switch Q. When the power switch Q is turned off, due to the blocking effect of the second diode D2, the reference power supply VCC, the second resistor R2, and multiple third diodes D3 form a current loop. At this time, the fourth voltage value U4 at the sampling terminal of the control unit 30 includes the voltage drops of multiple third diodes D3. The second diode D2 and the third diode D3 are of the same type, therefore, the voltage drop of the second diode D2 and the voltage drop of the third diode D3 are the same. When the power switch Q is turned off, the voltage drop of each third diode D3 can be obtained according to formula (3):

[0082] Ud=U4 / m (3)

[0083] Where m is the number of third diodes D3.

[0084] Therefore, the voltage drop Uce of the power switch Q can be calculated using formula (4):

[0085] Uce=U3-Ud (4)

[0086] It should be noted that, Figure 11 The three third diodes D3 in the example are exemplary, and the number of third diodes D3 is not limited to three; it can be set according to the actual situation. The second diode D2 and multiple third diodes D3 can also be diodes within the same package.

[0087] In some embodiments, as Figure 6 As shown, the operation protection device 100 also includes a signal processing unit 40, configured to process the turn-on current Ic.

[0088] As mentioned above, the control unit 30 also compares the detection value corresponding to the turn-on current Ic with the tube voltage drop Uce, and the signal processing unit 40 processes the turn-on current Ic to generate the detection value corresponding to the turn-on current Ic.

[0089] In some embodiments, as Figure 6As shown, the signal processing unit 40 includes: a ninth resistor R9, a tenth resistor R10, a second operational amplifier OPA2, and an eleventh resistor R11. One end of the ninth resistor R9 is adapted to be connected to the first output terminal of the current detection unit 20; one end of the tenth resistor R10 is adapted to be connected to the second output terminal of the current detection unit 20; the positive input terminal of the second operational amplifier OPA2 is connected to the other end of the ninth resistor R9, the negative input terminal of the second operational amplifier OPA2 is connected to the other end of the tenth resistor R10, and the output terminal of the second operational amplifier OPA2 is adapted to be connected to the control unit 30; the eleventh resistor R11 is connected between the negative input terminal and the output terminal of the second operational amplifier OPA2.

[0090] Specifically, the current detection unit 20 generates a differential voltage signal based on the turn-on current Ic. The positive input terminal of the second operational amplifier OPA2 is connected to the positive terminal of the differential voltage signal through the ninth resistor R9, and the negative input terminal of the second operational amplifier OPA2 is connected to the negative terminal of the differential voltage signal through the tenth resistor R10. The second operational amplifier OPA2 generates the detection value corresponding to the turn-on current Ic based on the differential voltage signal.

[0091] In one alternative implementation, such as Figure 6 As shown, the current detection unit 20 includes a sampling resistor Rs, one end of which is adapted to be connected to the emitter of the power switch Q, and the other end of the sampling resistor Rs is grounded.

[0092] In some embodiments, as Figure 6 As shown, the control unit 30 also includes a comparator 31, the positive input terminal of which is connected to the output terminal of the voltage detection unit 10, the negative input terminal of which is connected to the output terminal of the second operational amplifier OPA2, and the output terminal of the comparator 31 is adapted to be connected to the controller 32 in the control unit 30.

[0093] Specifically, the positive input terminal of comparator 31 is connected to the output terminal of voltage detection unit 10 to receive the tube voltage drop Uce, and the negative input terminal of comparator 31 is connected to the output terminal of second operational amplifier OPA2 to receive the detection value corresponding to the turn-on current Ic. Comparator 31 compares the tube voltage drop Uce and the detection value corresponding to the turn-on current Ic, and outputs the comparison result to comparator 31 so that controller 32 can control power switch Q according to the comparison result.

[0094] The technical solution of this application will be further described in detail below with reference to specific implementation methods:

[0095] When adopting such Figure 9 When the circuit diagram shown is used to detect the voltage drop across the transistor, such as... Figure 12 As shown, determining the temperature of the power switch transistor based on the transistor voltage drop includes the following steps:

[0096] S101, obtain the second voltage sample value from the second sampling terminal.

[0097] S102 sends an on-control signal to the power switch transistor to turn it on.

[0098] S103 starts the delay timing after the power switch is turned on.

[0099] S104. Determine whether the delay time has reached the first preset time. If the delay time has reached the first preset time, proceed to step S105. If the delay time has not reached the first preset time, proceed to step S108.

[0100] S105, obtain the first voltage sample value from the first sampling terminal.

[0101] S106, determine the tube voltage drop as the difference between the first voltage sample value and the second voltage sample value.

[0102] S107, find the temperature of the power switch corresponding to the tube voltage drop on the predetermined tube voltage drop-junction temperature relationship curve.

[0103] S108, continue the delay timing, and then execute step S104.

[0104] In the above embodiment, the first voltage sampling value includes the diode voltage drop and the second diode voltage drop, and the second voltage sampling value includes the third diode voltage drop. The second and third diodes are of the same type, and their voltage drops are the same. Therefore, the diode voltage drop can be calculated based on the first and second voltage sampling values. The diode voltage drop-junction temperature relationship curve is predetermined based on the turn-on current. Thus, the temperature of the power switching transistor can be quickly determined based on the diode voltage drop-junction temperature relationship and the diode voltage drop.

[0105] When adopting such Figure 10 When the circuit diagram shown is used to detect the voltage drop across the transistor, such as... Figure 13 As shown, determining the temperature of the power switch transistor based on the transistor voltage drop includes the following steps:

[0106] S201 sends an on-control signal to the power switch transistor to turn it on.

[0107] S202 starts the delay timing after the power switch is turned on.

[0108] S203, determine whether the delay time has reached the first preset time. If the delay time has reached the first preset time, proceed to step S204. If the delay time has not reached the first preset time, proceed to step S207.

[0109] S204, obtain the detection value corresponding to the pipe pressure drop from the sampling end.

[0110] S205, calculate the pipe pressure drop based on the detected value corresponding to the pipe pressure drop.

[0111] S206, find the temperature of the power switch corresponding to the tube voltage drop on the predetermined tube voltage drop-junction temperature relationship curve.

[0112] S207, continue the delay timing, and then execute step S203.

[0113] In the above embodiment, the detection value corresponding to the tube voltage drop can be directly obtained using the second operational amplifier, and the tube voltage drop can be calculated based on the amplification factor of the second operational amplifier. Then, the temperature of the power switching tube is quickly determined based on the tube voltage drop-junction temperature relationship and the tube voltage drop.

[0114] When adopting such Figure 11 When the circuit diagram shown is used to detect the voltage drop across the transistor, such as... Figure 14 As shown, determining the temperature of the power switch transistor based on the transistor voltage drop includes the following steps:

[0115] S301, obtains the fourth voltage value from the sampling terminal.

[0116] S302 calculates the voltage drop of each third diode based on the fourth voltage value.

[0117] S303 sends an on-control signal to the power switch transistor to turn it on.

[0118] S304 starts the delay timing after the power switch is turned on.

[0119] S305, determine whether the delay time has reached the first preset time. If the delay time has reached the first preset time, proceed to step S306. If the delay time has not reached the first preset time, proceed to step S309.

[0120] S306, obtains the third voltage value from the sampling terminal.

[0121] S307 determines the tube voltage drop as the difference between the third voltage value and the voltage drop of each third diode.

[0122] S308: Locate the temperature of the power switch corresponding to the voltage drop on the predetermined voltage drop-junction temperature curve.

[0123] S309, continue the delay timing, and then execute step S305.

[0124] The principle of tube pressure drop detection in this embodiment is the same as... Figure 9The detection principle shown is similar, but this embodiment uses only one sampling terminal to obtain the tube voltage drop, and then quickly determines the temperature of the power switch tube based on the tube voltage drop-junction temperature relationship and the tube voltage drop.

[0125] In summary, the power switch transistor operation protection device according to an embodiment of the present invention includes a voltage detection unit, a current detection unit, and a control unit. The voltage detection unit is configured to detect the transistor voltage drop when the power switch transistor is turned on, the current detection unit is configured to detect the turn-on current of the power switch transistor, and the control unit is configured to protect the power switch transistor based on the turn-on current and the transistor voltage drop. Therefore, the control unit protects the power switch transistor based on the turn-on current and the transistor voltage drop. Compared to related technologies that only protect the power switch transistor based on its current, the operation protection device of this embodiment achieves more comprehensive protection, thereby avoiding waste of power switch transistor resources or inadequate protection, and thus improving the reliability of the power switch transistor protection method.

[0126] Corresponding to the above embodiments, embodiments of the present invention also provide a PFC (Power Factor Correction) circuit. For example... Figure 1 As shown, the PFC circuit includes a power switch Q and an operation protection device 100 of any of the foregoing embodiments.

[0127] According to the PFC circuit of the present invention, by employing the above-described operation protection device, the power switch is protected based on the turn-on current and voltage drop of the power switch, thereby achieving comprehensive protection of the power switch and improving the reliability of the power switch protection method.

[0128] In some embodiments, the control unit 30 is further configured to determine the temperature of the power switch transistor at the zero-crossing point of the PFC circuit based on the transistor voltage drop and a preset transistor voltage drop-junction temperature relationship curve, and to control the PFC circuit according to the temperature of the power switch transistor.

[0129] In practical applications, the timing of voltage drop monitoring can be determined based on the current corresponding to a preset voltage drop-junction temperature curve. Assuming the current corresponding to the preset voltage drop-junction temperature curve is 1A, then... Figure 15 As shown, at the zero-crossing point of the PFC circuit, if the turn-on current is 1A, the voltage drop of the power switch is detected. Then, the temperature of the power switch corresponding to the voltage drop is found on the preset voltage drop-junction temperature relationship curve. The PFC circuit is controlled according to the temperature of the power switch, thus realizing simple, efficient and accurate temperature detection.

[0130] Corresponding to the above embodiments, embodiments of the present invention also provide an air conditioner. For example... Figure 16 As shown, the air conditioner 300 includes the PFC circuit 200 of any of the foregoing embodiments.

[0131] According to the embodiments of the present invention, the air conditioner employs the above-described PFC circuit to protect the power switch transistor based on its turn-on current and voltage drop, thereby achieving comprehensive protection of the power switch transistor and improving the reliability of the power switch transistor protection method.

[0132] It should be understood that various parts of the present invention can be implemented using hardware, software, firmware, or a combination thereof. In the above-described embodiments, multiple steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof can be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application-specific integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0133] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0134] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0135] Furthermore, the terms "first," "second," etc., used in the embodiments of this invention are for descriptive purposes only and should not be construed as indicating or implying relative importance, or implicitly specifying the number of technical features indicated in this embodiment. Therefore, features defined with terms such as "first" and "second" in the embodiments of this invention can explicitly or implicitly indicate that the embodiment includes at least one of those features. In the description of this invention, the word "multiple" means at least two or more, such as two, three, four, etc., unless otherwise explicitly specified in the embodiments.

[0136] In this invention, unless otherwise explicitly specified or limited in the embodiments, the terms "installation," "connection," "joining," and "fixing" appearing in the embodiments should be interpreted broadly. For example, a connection can be a fixed connection, a detachable connection, or an integral part; it can also be a mechanical connection, an electrical connection, etc. Of course, it can also be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components, or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific implementation.

[0137] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A power switching transistor operation protection device, characterized in that, include: A voltage detection unit is configured to detect the voltage drop across the power switch when it is turned on. A current detection unit is configured to detect the turn-on current of the power switch transistor; The control unit is configured to protect the power switch transistor based on the turn-on current and the transistor voltage drop.

2. The apparatus according to claim 1, characterized in that, The control unit is further configured to determine the transistor voltage drop-junction temperature relationship curve based on the turn-on current, and to determine the temperature of the power switch transistor based on the transistor voltage drop and the transistor voltage drop-junction temperature relationship curve.

3. The apparatus according to claim 1, characterized in that, The control unit is further configured to compare the detection value corresponding to the turn-on current with the tube voltage drop to provide overcurrent protection or overtemperature protection for the power switch tube.

4. The apparatus according to claim 1, characterized in that, The control unit is further configured to delay after issuing an on-control signal to control the power switch to turn on, and to sample the voltage drop of the switch when the delay time reaches a first preset time.

5. The apparatus according to any one of claims 1-4, characterized in that, The voltage detection unit includes: A first resistor, one end of which is connected to the collector of the power switch transistor; The first Zener diode has its cathode connected to the other end of the first resistor and has a first node, and its anode is grounded. A second resistor, one end of which is connected to the first node, and the other end of which is adapted to be connected to the sampling terminal of the control unit; A first capacitor, one end of which is connected to the other end of the second resistor, and the other end of the first capacitor is grounded.

6. The apparatus according to any one of claims 1-4, characterized in that, The voltage detection unit includes: A first resistor, one end of which is connected to the collector of the power switch transistor; A plurality of first diodes, wherein the anode of the plurality of first diodes connected in series is connected to the other end of the first resistor and has a first node, and the cathode of the plurality of first diodes connected in series is grounded; A second resistor, one end of which is connected to the first node, and the other end of which is adapted to be connected to the sampling terminal of the control unit; A first capacitor, one end of which is connected to the other end of the second resistor, and the other end of the first capacitor is grounded.

7. The apparatus according to any one of claims 1-4, characterized in that, The voltage detection unit includes: The cathode of the second diode is connected to the collector of the power switch. A second resistor, one end of which is connected to a reference power supply, and the other end of which is connected to the anode of the second diode, and has a second node adapted to be connected to the first sampling terminal of the control unit; A third resistor, one end of which is connected to the reference power supply; A third diode, the anode of which is connected to the other end of the third resistor and has a third node, the cathode of which is grounded, and the third node is adapted to be connected to the second sampling terminal of the control unit.

8. The apparatus according to claim 7, characterized in that, The control unit is further configured to acquire a first voltage sample value based on the first sampling terminal when the power switch is turned on, acquire a second voltage sample value based on the second sampling terminal when the power switch is turned off, and determine a second sample value corresponding to the tube voltage drop based on the first voltage sample value and the second voltage sample value.

9. The apparatus according to claim 7, characterized in that, The voltage detection unit further includes: A fourth resistor, one end of which is connected to the third node; The fifth resistor, one end of which is connected to the second node; A sixth resistor, one end of which is connected to the other end of the fifth resistor, and the other end of the sixth resistor is grounded; A first operational amplifier, the negative input terminal of which is connected to the other end of the fourth resistor, and the positive input terminal of which is connected to the other end of the fifth resistor; The seventh resistor is connected between the negative input terminal and the output terminal of the first operational amplifier; An eighth resistor, one end of which is connected to the output terminal of the first operational amplifier, and the other end of which is adapted to be connected to the sampling terminal of the control unit; The second capacitor has one end connected to the other end of the eighth resistor, and the other end of the second capacitor is grounded.

10. The apparatus according to any one of claims 1-4, characterized in that, The voltage detection unit includes: The cathode of the second diode is connected to the collector of the power switch. A second resistor, one end of which is connected to a reference power supply, and the other end of which is connected to the anode of the second diode, and has a second node adapted to be connected to the sampling terminal of the control unit; Multiple third diodes are connected in series, with the anode of the series-connected third diodes connected to the second node and the cathode of the series-connected third diodes grounded.

11. The apparatus according to claim 3, characterized in that, Also includes: The signal processing unit is configured to process the turn-on current.

12. The apparatus according to claim 11, characterized in that, The signal processing unit includes: A ninth resistor, one end of which is adapted to be connected to the first output terminal of the current detection unit; The tenth resistor, one end of which is adapted to be connected to the second output terminal of the current detection unit; The second operational amplifier has its positive input terminal connected to the other end of the ninth resistor, its negative input terminal connected to the other end of the tenth resistor, and its output terminal adapted to be connected to the control unit. The eleventh resistor is connected between the negative input terminal and the output terminal of the second operational amplifier.

13. The apparatus according to claim 12, characterized in that, The control unit further includes: The comparator has its positive input connected to the output of the voltage detection unit, its negative input connected to the output of the second operational amplifier, and its output adapted to be connected to the controller in the control unit.

14. A PFC circuit, characterized in that, include: Power switching transistors; The operation protection device according to any one of claims 1-13.

15. The PFC circuit according to claim 14, characterized in that, The control unit is further configured to determine the temperature of the power switch transistor at the zero-crossing point of the PFC circuit based on the transistor voltage drop and a preset transistor voltage drop-junction temperature relationship curve, and to control the PFC circuit according to the temperature of the power switch transistor.

16. An air conditioner, characterized in that, Includes the PFC circuit according to claim 14 or 15.

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