Protection device of PFC (Power Factor Correction) circuit and electric equipment

Abstract

The invention relates to a protection device of a PFC (Power Factor Correction) circuit and electric equipment. The protection device comprises a temperature detection circuit, a first temperature protection circuit and an output voltage detection and protection circuit, the temperature detection circuit can detect the temperature of a heating device and generate a temperature signal, and when the temperature signal is larger than a safe temperature threshold value, the first temperature protection circuit is switched on. When a voltage sampling signal is larger than an output voltage threshold value, a temperature protection signal formed by the first temperature protection circuit enables the PFC circuit to stop working, the output voltage detection and protection circuit can sample the output voltage output by the PFC circuit, and when the voltage sampling signal is larger than the output voltage threshold value, the formed voltage protection signal enables the PFC circuit to stop working. Visibly, by utilizing the protection device, the adverse effects of overhigh temperature and overhigh output voltage on the PFC circuit can be avoided at the same time, and the protection reliability of the PFC circuit and the safety of the PFC circuit are greatly improved, so that the normal work of the PFC circuit is ensured. The electric equipment comprises the protection device.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and particularly to a protection device for a PFC circuit and an electrical equipment. Background Art

[0002] Power Factor Correction (PFC) is becoming increasingly important for the drive of motors (such as permanent magnet synchronous motors). If power factor correction is not performed, the current generated by the control circuit will contain significant harmonic components, which is prone to current distortion, polluting the power grid. Moreover, due to the highly inductive nature of the motor load, the distorted current will add a large amount of reactive power loss to the input system, thereby reducing the efficiency of the entire system. Through power factor correction, the output voltage can be better regulated and the harmonic content in the current can be reduced.

[0003] Power factor correction is generally divided into active power factor correction (APFC) and passive power factor correction (PPFC) in terms of implementation methods. With the development of power electronics technology, active power factor correction has gradually become the mainstream. Conventional PFC circuits include devices such as power switches and fast recovery diodes. By controlling the on and off of the power switch, sinusoidal current variation can be achieved, which has the advantages of small volume, light weight, and high power factor.

[0004] Devices such as power switches and fast recovery diodes in the PFC circuit are easily damaged or even fail due to overvoltage or overcurrent. Usually, a protection device for the PFC circuit is set up, and with this protection device, corresponding control is carried out when the PFC circuit is overvoltage or overcurrent. However, the prior art does not consider the influence of temperature and lacks protection for the overvoltage output of the PFC circuit, resulting in insufficient safety of the current PFC circuit. Summary of the Invention

[0005] In order to improve the reliability of the PFC circuit protection and then improve the safety of the PFC circuit, the present invention provides a protection device for an active power factor correction circuit. The present invention also provides an electrical equipment.

[0006] On the one hand, the present invention provides a protection device for a PFC circuit. The PFC circuit converts the rectified signal output by the power supply module into a corresponding output voltage. The protection device includes:

[0007] A temperature detection circuit configured to detect the temperature of the heating device and output a temperature signal;

[0008] A first temperature protection circuit configured to compare the temperature signal with a safety temperature threshold to form a temperature protection signal, and when the temperature signal is greater than the safety temperature threshold, the temperature protection signal causes the PFC circuit to stop working; and

[0009] An output voltage detection and protection circuit configured to sample the output voltage to obtain a voltage sampling signal, and compare the voltage sampling signal with an output voltage threshold to form a voltage protection signal, and when the voltage sampling signal is greater than the output voltage threshold, the voltage protection signal causes the PFC circuit to stop working.

[0010] Optionally, the temperature detection circuit includes:

[0011] A Wheatstone bridge including a first bridge arm and a second bridge arm coupled between a power supply voltage and ground, the first bridge arm including a first resistor and a third resistor connected in series, and the second bridge arm including a second resistor and a thermistor unit connected in series; and

[0012] An operational amplifier configured to be coupled to the first bridge arm and the second bridge arm of the Wheatstone bridge and generate the temperature signal, wherein a connection point of the first resistor and the third resistor is coupled to a non-inverting input terminal of the operational amplifier, and a connection point of the second resistor and the thermistor unit is coupled to an inverting input terminal of the operational amplifier.

[0013] Optionally, the thermistor unit includes an NTC thermistor and a fourth resistor connected in parallel.

[0014] Optionally, the PFC circuit includes a power switch that turns on and off in response to a PFC control signal; the first temperature protection circuit and the output voltage detection and protection circuit stop the PFC circuit from working by turning off the power switch.

[0015] Optionally, the first temperature protection circuit includes:

[0016] A hysteresis comparator with an inverting input terminal coupled to the temperature signal, and the safety temperature threshold is coupled to the non-inverting input terminal and the output terminal of the hysteresis comparator through voltage dividing resistors, and the hysteresis comparator outputs the temperature protection signal; and

[0017] A first diode with a negative terminal coupled to the temperature protection signal and a positive terminal coupled to the PFC control signal.

[0018] Optionally, the protection device further includes a second temperature protection circuit configured to compare the temperature signal with a master control safety threshold and form a master control signal, wherein when the temperature signal is greater than the master control safety threshold, the master control signal causes the power supply module to stop power supply.

[0019] Optionally, the overall control safety threshold is greater than the safety temperature threshold.

[0020] Optionally, the second temperature protection circuit includes:

[0021] A first comparator, with its inverting input terminal coupled to the temperature signal and its non-inverting input terminal coupled to the overall control safety threshold; and

[0022] A second diode, with its negative terminal coupled to the output terminal of the first comparator and its positive terminal coupled to the overall control signal.

[0023] Optionally, the output voltage detection and protection circuit includes:

[0024] A second comparator, with its inverting input terminal coupled to the voltage sampling signal and its non-inverting input terminal coupled to the output voltage threshold; and

[0025] A third diode, with its negative terminal coupled to the output terminal of the second comparator and its positive terminal coupled to the PFC control signal.

[0026] Optionally, the protection device further includes:

[0027] A control module configured to output the PFC control signal and the safety temperature threshold, and collect at least one of the temperature signal, the temperature protection signal, the voltage sampling signal, and the voltage protection signal.

[0028] On the other hand, the present invention provides an electrical device, which includes a PFC circuit and the above protection device, and the PFC circuit converts the rectified signal output by the power supply module into a corresponding output voltage.

[0029] The protection device for the PFC circuit provided by the present invention includes a temperature detection circuit, a first temperature protection circuit, and an output voltage detection and protection circuit. Among them, the temperature detection circuit can detect the temperature of the heating device and generate a temperature signal. When the temperature signal is greater than the safety temperature threshold, the temperature protection signal generated by the first temperature protection circuit causes the protected PFC circuit to stop working. The output voltage detection and protection circuit can sample the output voltage output by the PFC circuit. When the voltage sampling signal is greater than the output voltage threshold, the generated voltage protection signal causes the protected PFC circuit to stop working. It can be seen that by using the protection device, the adverse effects of too high temperature and too high output voltage on the PFC circuit can be avoided simultaneously, greatly improving the reliability of the PFC circuit protection and the safety of the PFC circuit, thereby ensuring the normal operation of the PFC circuit.

[0030] The electrical equipment provided by the present invention includes a PFC circuit and the above protection device. The protection device can detect the temperature of the heating element and sample the output voltage of the PFC circuit, and compare it with the corresponding threshold. When the threshold is exceeded, the PFC circuit is stopped from working, which can avoid the adverse effects of excessive temperature and excessive output voltage on the PFC circuit at the same time, improve the reliability and safety of the PFC circuit and the electrical equipment, and thus ensure the normal operation of the PFC circuit and the electrical equipment. Description of the Drawings

[0031] Figure 1 FIG. is a schematic connection diagram of a power supply module, a PFC circuit, its protection device, and a load in an embodiment of the present invention.

[0032] Figure 2 FIG. is a schematic circuit diagram of a power supply module, a PFC circuit, and a load in an embodiment of the present invention.

[0033] Figure 3 FIG. is a schematic circuit diagram of a protection device for a PFC circuit in an embodiment of the present invention. Detailed Embodiment

[0034] The following further describes in detail the protection device for the PFC circuit and the electrical equipment of the present invention with reference to the drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the drawings are all in a very simplified form and use non-precise scales, only for the purpose of conveniently and clearly assisting in explaining the embodiments of the present invention.

[0035] The problems of device failure caused by overvoltage and overcurrent in the active PFC circuit account for a relatively large proportion in the after-sales failure rate of the applied electrical equipment (such as air conditioners). Temperature changes have an impact on the voltage withstand and current withstand performance of the PFC circuit. The maximum current withstand value of the PFC circuit often changes correspondingly at different temperatures, resulting in a reduction in the protection effect of the original current protection value when the temperature changes. Therefore, in the embodiments of the present invention, the protection device for the PFC circuit has a temperature protection function, and at the same time protects against output overvoltage, has better reliability, can improve the safety of the PFC circuit, and thus ensure the normal operation of the PFC circuit.

[0036] Figure 1 FIG. shows the connection relationship of a power supply module, a PFC circuit, its protection device, and a load, where the solid line represents the circuit connection and the dashed line represents the controlled object. Refer to Figure 1 , the protection device 100 is coupled to the PFC circuit 20; the PFC circuit 20 is respectively coupled to the power supply module 10 and the load 30 to perform power factor correction (PFC) on the rectified signal output by the power supply module 10. After correction, the output voltage is supplied to the load 30.

[0037] Reference Figure 2 , for example, the power supply module 10 includes a relay K1 and a rectifier VC1. One input terminal of the relay K1 is coupled to the live wire of the AC power supply, and the other input terminal is coupled to a power supply voltage VCC1. One input terminal of the rectifier VC1 is coupled to the output terminal of the relay K1, and the other input terminal is coupled to the neutral wire of the AC power supply. In this embodiment, the power supply module 10 further includes a relay control circuit configured to control the conduction and cut-off of the relay K1. Reference Figure 2 , the relay control circuit includes, for example, a switching device Q1 and a resistor R0. The switching device Q1 is coupled between the control terminal of the relay K1 and the ground. One end of the resistor R0 is coupled to the control terminal of the switching device Q1, and the other end is coupled to a master control signal. Thus, through the master control signal, the conduction and cut-off of the switching device Q1 and the relay K1 can be controlled, and further the purpose of controlling whether the AC power supply supplies power to the circuit can be achieved. The switching device Q1 is, for example, an NPN-type triode.

[0038] As Figure 2 shown, the PFC circuit 20 is coupled to the output terminal of the rectifier VC1 and performs power factor correction on the voltage signal output by the rectifier VC1 to form an output voltage. The PFC circuit 20 can adopt a boost topology, a buck topology, a buck-boost topology, a forward topology, or a flyback topology, which can be specifically set according to needs. In the following embodiments, the PFC circuit 20 is, for example, a boost topology (boost).

[0039] For example, the PFC circuit 20 includes an inductor L1, a power switch VT1, a fast recovery diode D, a sampling resistor R, and an energy storage capacitor E1. Among them, the power switch VT1 is, for example, an NMOS transistor. Specifically, one end of the inductor L1 is coupled to the positive output terminal of the rectifier VC1, and the other end is coupled to the positive extreme of the fast recovery diode D and the drain extreme of the power switch VT1. The control terminal of the power switch VT1 is coupled to a PFC control signal; the sampling resistor R is respectively coupled to the negative output terminal of the rectifier VC1 and the source extreme of the power switch VT1; the upper plate of the energy storage capacitor E1 is coupled to the negative extreme of the fast recovery diode D, and the lower plate is coupled to the source extreme of the power switch VT1 and grounded. When the PFC circuit 20 is operating, the power switch VT1 is alternately turned on and off through the PFC control signal, so that the inductor L alternately stores and releases energy to form an output voltage. The PFC control signal can be formed by a hardware circuit and / or by a software program. As Figure 1 shown, optionally, in the protection device 100 of the PFC circuit 20, the control module outputs the PFC control signal to the PFC circuit, and the control module includes, for example, an MCU.

[0040] As Figure 1 andFigure 2 As shown, the load 30 is coupled to the output terminal of the PFC circuit 20, specifically coupled between the upper and lower plates of the energy storage capacitor E1. The load 30 has a load resistor R load , and the load resistor R load The voltage value across both ends is the output voltage value of the PFC circuit 20.

[0041] To protect the above-mentioned PFC circuit 20, especially to avoid the influence of the overheating of the heating device and the too high output voltage on the safe operation of the PFC circuit 20, such as Figure 1 As shown, in the embodiment of the present invention, the protection device 100 of the PFC circuit 20 includes a temperature detection and protection circuit 40 and an output voltage detection and protection circuit 50. The protection device 100 may further include a control module. The following will combine Figures 1 to 3 to make a specific description of the protection device 100.

[0042] The temperature detection and protection circuit 40 includes a temperature detection circuit 41, and the temperature detection circuit 41 is configured to detect the temperature of the heating device and output a temperature signal. The heating device is, for example, a component in the PFC circuit 20 whose performance is greatly affected by overheating, such as the power switch VT1, and can be specifically set according to needs. Before temperature measurement, the temperature detection and protection circuit 40 can be placed near the heating device to be measured. For example, the thermistor in the temperature detection and protection circuit 40 is tightly fixed to the heating device to be measured. In this embodiment, in order to improve the accuracy and sensitivity of temperature detection and meet the temperature protection requirements of the PFC circuit 20, the temperature detection circuit 41 adopts a Wheatstone bridge.

[0043] Figure 3 shows the circuit of the protection device 100 in an embodiment. Refer to Figure 3, in the temperature detection circuit 41, the Wheatstone bridge includes a first bridge arm and a second bridge arm coupled between the power supply voltage VCC and the ground. The first bridge arm includes a first resistor R1 and a third resistor R3 connected in series, and the second bridge arm includes a second resistor R2 and a thermistor unit RT connected in series. When the temperature of the heating device changes, the resistance value of the thermistor unit RT changes accordingly, and the voltage difference between the connection point of the first resistor R1 and the third resistor R3 on the first bridge arm and the connection point of the second resistor R2 and the thermistor unit RT on the second bridge arm changes, so that the temperature change is converted into a high-precision voltage change. This voltage change is compared and amplified by the operational amplifier U1 to generate a corresponding temperature signal containing the temperature information of the heating device. Specifically, the operational amplifier U1 is configured to be coupled to the first bridge arm and the second bridge arm of the Wheatstone bridge and generate a corresponding temperature signal. Among them, the connection point of the first resistor R1 and the third resistor R3 is coupled to the non-inverting input terminal of the operational amplifier U1, and the connection point of the second resistor R2 and the thermistor unit RT is coupled to the inverting input terminal of the operational amplifier U1. In this embodiment, a fifth resistor R5 is coupled between the connection point of the first resistor R1 and the third resistor R3 and the non-inverting input terminal of the operational amplifier U1, a sixth resistor R6 is coupled between the thermistor unit RT and the inverting input terminal of the operational amplifier U1, a seventh resistor R7 is coupled between the inverting input terminal and the output terminal of the operational amplifier U1, and an eighth resistor R8 is coupled between the non-inverting input terminal of the operational amplifier U1 and the ground.

[0044] In this embodiment, an NTC thermistor (i.e., a negative temperature coefficient thermistor, Negative Temperature Coefficient Thermistor) is used to detect the temperature change of the heating device. Considering that the resistance value of the NTC thermistor and the temperature are non-linear, in order to reduce the influence of measurement error on the system, the thermistor unit RT includes an NTC thermistor RT1 and a fourth resistor R4 connected in parallel to perform hardware compensation using the fourth resistor R4. Thus, when the temperature of the heating device changes, the change in the resistance value of the parallel resistor composed of the NTC thermistor RT1 and the fourth resistor R4 is smaller than the change in the resistance value of the NTC thermistor when only the NTC thermistor is used, which can reduce the influence of the non-linear relationship. The present invention is not limited to this. In another embodiment, after generating the temperature signal, the influence of the above non-linear relationship can be reduced by calculation and fitting (i.e., software compensation), and more accurate temperature information can also be obtained.

[0045] The temperature signal generated by the temperature detection circuit 41 can be collected by the control module to obtain the current temperature value of the heating device. In order to avoid the influence of excessive temperature, a corresponding threshold can be set to perform software protection when collecting the temperature signal.

[0046] Referring to Figure 3 , the temperature detection and protection circuit 40 at least includes a first temperature protection circuit 42. The first temperature protection circuit 42 is configured to compare the temperature signal generated by the temperature detection circuit 41 with a safety temperature threshold to form a temperature protection signal. When the temperature signal is greater than the safety temperature threshold, the temperature protection signal causes the PFC circuit 20 to stop working. In this embodiment, the temperature protection signal stops the PFC circuit 20 by adjusting the above-mentioned PFC control signal for controlling the power switch VT1. In some other embodiments, the temperature protection signal can also be used to adjust other input signals of the PFC circuit 20 to stop it. The safety temperature threshold can be set and output by the control module, so that the safety temperature threshold is a controllable threshold, which can improve the flexibility of the protection device 100.

[0047] Referring to Figure 3 , as an example, the first temperature protection circuit 42 includes a hysteresis comparator U3 and a first diode D1. The inverting input terminal of the hysteresis comparator U3 is coupled to the temperature signal output by the operational amplifier U1. The safety temperature threshold is coupled to the non-inverting input terminal and the output terminal of the hysteresis comparator U3 through voltage dividing resistors. Specifically, the safety temperature threshold is coupled to the non-inverting input terminal of the hysteresis comparator U3 through the voltage dividing resistor R13. In addition, the safety temperature threshold is coupled to the output terminal of the hysteresis comparator U3 through the series resistor of the voltage dividing resistor R13 and the voltage dividing resistor R14. The hysteresis comparator U3 outputs a temperature protection signal. The negative terminal of the first diode D1 is coupled to the temperature protection signal and the positive terminal is coupled to the PFC control signal. In addition, the first temperature protection circuit 42 may further include a pull-up resistor R18 coupled between the power supply voltage VCC and the output terminal of the hysteresis comparator U3 to ensure that the signal at the output terminal of the hysteresis comparator U3 does not appear abnormally.

[0048] The working principle of the first temperature protection circuit 42 is as follows: When the temperature signal output by the temperature detection circuit 41 does not exceed the safety temperature threshold, the temperature protection signal formed by the hysteresis comparator U3 is at a high level. At this time, due to the blocking of the first diode D1, the temperature protection signal does not affect the PFC control signal (the PFC control signal is output by the control module, for example), and the PFC circuit 20 operates normally; when the temperature signal exceeds the safety temperature threshold, the temperature protection signal formed by the hysteresis comparator U3 is at a low level, the first diode D1 conducts, and the PFC control signal is pulled low, so that the power switch VT1 is forced to turn off, and the PFC circuit 20 stops working. After that, when the temperature of the heating device gradually decreases until the temperature signal returns to the temperature lower limit value related to the corresponding hysteresis curve, the temperature protection signal returns to a high level. At this time, due to the blocking of the first diode D1, the temperature protection signal does not affect the PFC control signal, and the PFC circuit 20 resumes normal operation. It can be seen that by using the first temperature protection circuit 42, the PFC circuit 20 is allowed to work only after ensuring that the temperature is stably lower than the safety temperature threshold, so as to protect the PFC circuit 20 and reduce the impact of overheating of the heating device on the PFC circuit 20.

[0049] To further avoid the impact of overheating of the heating device on the PFC circuit 20 and improve the safety of the PFC circuit, as Figure 3 shown, the temperature detection and protection circuit 40 may further include a second temperature protection circuit 43. The second temperature protection circuit 43 is configured to compare the temperature signal output by the temperature detection circuit 41 with the total control safety threshold and form a total control signal. Among them, when the temperature signal is greater than the total control safety threshold, the total control signal controls the power supply module 10 to stop supplying power to the PFC circuit 20 (that is, to cut off the circuit). The total control safety threshold can be set as needed.

[0050] Specifically, referring to Figure 3, the second temperature protection circuit 43 includes a first comparator U2 and a second diode D2. The inverting input terminal of the first comparator U2 is coupled to the temperature signal output by the operational amplifier U1, while the non-inverting input terminal is coupled to the signal of the overall control safety threshold. The negative terminal of the second diode D2 is coupled to the output terminal of the first comparator U2, and the positive terminal is coupled to the overall control signal. The overall control safety threshold can be set and output by the control module or generated by a hardware circuit. Here, for example, it is the latter. As an example, the second temperature protection circuit 43 further includes a voltage-dividing resistor R15 and a voltage-dividing resistor R16 connected in series between the power supply voltage VCC and the ground. The voltage at the connection point of the voltage-dividing resistor R15 and the voltage-dividing resistor R16 is used as the overall control safety threshold. By adjusting the resistance values of the voltage-dividing resistor R15 and the voltage-dividing resistor R16, the overall control safety threshold can be adjusted. In addition, the second temperature protection circuit 43 may further include a pull-up resistor R19 coupled between the power supply voltage VCC and the output terminal of the first comparator U2 to ensure that the signal at the output terminal of the first comparator U2 does not show abnormalities.

[0051] The working principle of the second temperature protection circuit 43 is as follows: When the temperature signal output by the temperature detection circuit 41 does not exceed the overall control safety threshold, the signal at the output terminal of the first comparator U2 is high. At this time, blocked by the second diode D2, the output of the first comparator U2 does not affect the overall control signal, so as to refer to Figure 2 , at this time, the relay K1 and the power supply module 10 work normally; when the temperature signal exceeds the overall control safety threshold, the signal at the output terminal of the first comparator U2 is low, the second diode D2 conducts, and the overall control signal is pulled low, so that Figure 2 the switching device Q1 in is forced to turn off, causing the relay K1 to turn off and the power supply module 10 to stop power supply, and at the same time achieving the purpose of protecting the PFC circuit 20.

[0052] In this embodiment, the overall control safety threshold used in the second temperature protection circuit 43 is, for example, greater than the safety temperature threshold used in the first temperature protection circuit 42. The protection device 100 uses the first temperature protection circuit 42 and the second temperature protection circuit 43 to double-protect the PFC circuit 20. Specifically, when the temperature signal output by the temperature detection circuit 41 does not exceed the safety temperature threshold, at this time, the first temperature protection circuit 42 and the second temperature protection circuit 43 do not affect the operation of the PFC circuit 20 and the power supply module 10; when the temperature signal exceeds the safety temperature threshold but is less than the overall control safety threshold, the first temperature protection circuit 42 causes the PFC circuit 20 to stop working while the power supply module 10 still normally performs energy transfer. When the temperature drops to the lower temperature limit value, the first temperature protection circuit 42 no longer affects the PFC circuit 20, and the PFC circuit 20 automatically resumes operation; when the temperature signal exceeds the overall control safety threshold, at this time, due to the excessively high temperature, the first temperature protection circuit 42 causes the PFC circuit 20 to stop working, and moreover, the second temperature protection circuit 13 cuts off the power supply to the power supply module 10, that is, shuts down the entire circuit, so as to facilitate the staff to check the cause of overheating and make repairs. It can be seen that by using the first temperature protection circuit 42 and the second temperature protection circuit 43 to protect the PFC circuit 20 from the perspective of avoiding overheating. On the one hand, when the overheating amplitude of the heating device is small (the temperature signal exceeds the safety temperature threshold but is less than the overall control safety threshold), the PFC circuit 20 stops working when the temperature exceeds the safety temperature threshold and resumes operation after the temperature stably drops below the safety temperature threshold, which has a small impact on the system. On the other hand, when the overheating amplitude of the heating device is large (the temperature signal exceeds the safety temperature threshold and the overall control safety threshold), shutting down the entire circuit helps to avoid serious damage to circuit components caused by overheating. Compared with only using the first temperature protection circuit for temperature control, shutting down the entire circuit can avoid the adverse risks generated by repeatedly starting the PFC circuit 20, making the protection device 100 highly flexible and reliable.

[0053] Referring to Figure 1 and Figure 3 , the protection device 100 further includes an output voltage detection and protection circuit 50. The output voltage detection and protection circuit 50 is configured to sample the output voltage generated by the PFC circuit 20 to obtain a voltage sampling signal, and compare the voltage sampling signal with an output voltage threshold to form a voltage protection signal. When the voltage sampling signal is greater than the output voltage threshold, the voltage protection signal causes the PFC circuit 20 to stop working.

[0054] Referring to Figure 3, by way of example, the output voltage detection and protection circuit 50 includes a second comparator U4 and a third diode D3. The inverting input terminal of the second comparator U4 is coupled to the voltage sampling signal, and the non-inverting input terminal is coupled to the output voltage threshold. The negative terminal of the third diode D3 is coupled to the output terminal of the second comparator U4, and the positive terminal is coupled to the above-mentioned PFC control signal. The voltage sampling signal is, for example, a voltage division of the output voltage value of the PFC circuit 20 (such as the "PFC circuit output voltage value" shown in Figure 2 and Figure 3 ). Specifically, the output voltage detection and protection circuit 50 may include a voltage division resistor R11 and a voltage division resistor R12 connected in series between the output voltage value of the PFC circuit 20 and the ground. Among them, the voltage sampling signal is the voltage signal at the connection point of the voltage division resistor R11 and the voltage division resistor R12. The output voltage threshold can be output by the control module or generated by a hardware circuit. Here, for example, it is the latter. By way of example, as shown in Figure 3 , the output voltage detection and protection circuit 50 may include a voltage division resistor R9 and a voltage division resistor R10 connected in series between the power supply voltage VCC and the ground. The voltage at the connection point of the voltage division resistor R9 and the voltage division resistor R10 is used as the output voltage threshold, and the output voltage threshold can be adjusted by adjusting the resistance values of the voltage division resistor R9 and the voltage division resistor R10. In addition, the output voltage detection and protection circuit 50 may further include a pull-up resistor R17 coupled between the power supply voltage VCC and the output terminal of the second comparator U4 to ensure that the signal at the output terminal of the second comparator U4 does not appear abnormally.

[0055] The working principle of the output voltage detection and protection circuit 50 is as follows: When the voltage sampling signal does not exceed the output voltage threshold, the voltage protection signal output by the second comparator U4 is high level. At this time, due to the blocking of the third diode D3, the voltage protection signal does not affect the PFC control signal, and the PFC circuit 20 works normally. When the voltage sampling signal exceeds the output voltage threshold, the voltage protection signal is low level, the third diode D3 conducts, and the PFC control signal is pulled low, so that the power switch VT1 is forced to turn off, and the PFC circuit 20 stops working. It can be seen that by using the output voltage detection and protection circuit 50, the influence of too high output voltage on the PFC circuit 20 can be reduced.

[0056] The control module can collect at least one of the temperature signal generated by the temperature detection circuit 41, the temperature protection signal generated by the first temperature protection circuit 42, the voltage sampling signal and the voltage protection signal generated by the output voltage detection and protection circuit 50. By collecting the temperature signal, the control module can convert it into the corresponding temperature, so that the staff can timely know the temperature of the heating device. By collecting the voltage sampling signal, it is convenient for the staff to timely understand the output voltage situation. In order to avoid damage to the control module caused by too high output voltage, when collecting the voltage sampling signal, corresponding thresholds can be set for software protection. By collecting the temperature protection signal or the voltage protection signal, it is convenient for the staff to confirm whether the reason for the PFC circuit 20 to stop working is too high output voltage or too high temperature of the heating device when the PFC circuit 20 stops working, which is convenient for the staff to analyze and eliminate faults. In order to be able to judge the reason for the PFC circuit to stop working and save the pins of the MCU at the same time, the control module only needs to collect one of the temperature protection signal and the voltage protection signal. As an example, the control module collects the temperature protection signal. When the PFC circuit 20 stops working, if the temperature protection signal shows a high level, it means that the temperature protection signal does not affect the PFC control signal, and it can be judged that the PFC circuit 20 stops working due to too high output voltage by the voltage protection signal. If the temperature protection signal is at a low level, it means that the temperature protection signal will pull down the PFC control signal, and it can be judged that the PFC circuit 20 stops working due to over-temperature of the heating device by the temperature protection signal.

[0057] Optionally, the protection device 100 may include an over-temperature alarm and / or an over-voltage alarm. The over-temperature alarm is coupled to the temperature protection signal. Wherein, when the temperature signal is greater than the safety temperature threshold, the temperature protection signal controls the over-temperature alarm to emit warning light and / or warning sound. The over-voltage alarm is coupled to the voltage protection signal. Wherein, when the voltage sampling signal is greater than the output voltage threshold, the voltage protection signal controls the over-voltage alarm to emit warning light and / or warning sound. By using the over-temperature alarm and the over-voltage alarm, information on whether there is over-temperature and whether there is over-voltage can be obtained more intuitively.

[0058] In the protection device 100 of the PFC circuit 20 described in the above embodiments, the temperature detection circuit 41 can detect the temperature of the heat-generating device and generate a temperature signal. When the temperature signal is greater than the safety temperature threshold, the temperature protection signal generated by the first temperature protection circuit 42 causes the PFC circuit 20 to stop working. When the temperature signal is greater than the master control safety threshold, the master control signal generated by the second temperature protection circuit 43 causes the relay K1 to turn off, so that the power supply module 10 stops supplying power to the circuit. Moreover, the output voltage detection and protection circuit 50 can sample the output voltage output by the PFC circuit 20. And when the voltage sampling signal is greater than the output voltage threshold, the generated voltage protection signal causes the PFC circuit 20 to stop working. It can be seen that by using the protection device 100, the adverse effects of excessive temperature and excessive output voltage on the PFC circuit 20 can be avoided simultaneously, greatly improving the reliability of the protection of the PFC circuit 20 and the safety of the PFC circuit 20, thereby ensuring the normal operation of the PFC circuit 20.

[0059] An embodiment of the present invention further relates to an electrical device. Referring to Figures 1 to 3 , the electrical device includes a PFC circuit 20 and the protection device 100 of the PFC circuit 20 described in the above embodiments. The PFC circuit 20 converts the rectified signal output by the power supply module 10 into a corresponding output voltage. The electrical device can be various devices that use the PFC circuit 20 for power factor correction. For example, it can be a household appliance such as an air conditioner.

[0060] In the electrical device, the protection device 100 of the PFC circuit 20 can detect the temperature of the heating element and sample the output voltage of the PFC circuit 20, and compare it with the corresponding threshold. When the corresponding threshold is exceeded, the PFC circuit 20 is caused to stop working. The adverse effects of excessive temperature and excessive output voltage on the PFC circuit 20 can be avoided simultaneously, and the reliability and safety of the PFC circuit 20 and the electrical device can be improved, thereby ensuring the normal operation of the PFC circuit 20 and the electrical device.

[0061] It should be noted that the embodiments in this specification are described in a progressive manner. Each part focuses on the differences from the previous part. The same and similar parts between each part can be understood by reference.

[0062] The above description is only a description of the preferred embodiments of the present invention, and does not limit the scope of the rights of the present invention in any way. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention without departing from the technical solutions of the present invention all belong to the protection scope of the technical solutions of the present invention.

Claims

1. A protection device for a PFC circuit, characterized in that, The PFC circuit converts the rectified signal output by the power supply module into a corresponding output voltage. The protection device includes: A temperature detection circuit configured to detect the temperature of a heat-generating device and output a temperature signal; A first temperature protection circuit configured to compare the temperature signal with a safety temperature threshold to form a temperature protection signal. When the temperature signal is greater than the safety temperature threshold, the temperature protection signal causes the PFC circuit to stop working; and An output voltage detection and protection circuit configured to sample the output voltage to obtain a voltage sampling signal, and compare the voltage sampling signal with an output voltage threshold to form a voltage protection signal. When the voltage sampling signal is greater than the output voltage threshold, the voltage protection signal causes the PFC circuit to stop working.

2. The protection device according to claim 1, characterized in that, The temperature detection circuit includes: A Wheatstone bridge including a first bridge arm and a second bridge arm coupled between a power supply voltage and ground. The first bridge arm includes a first resistor and a third resistor connected in series, and the second bridge arm includes a second resistor and a thermistor unit connected in series; and An operational amplifier configured to be coupled to the first bridge arm and the second bridge arm of the Wheatstone bridge and generate the temperature signal. Among them, the connection point of the first resistor and the third resistor is coupled to the non-inverting input terminal of the operational amplifier, and the connection point of the second resistor and the thermistor unit is coupled to the inverting input terminal of the operational amplifier.

3. The protection device according to claim 2, wherein The thermistor unit includes an NTC thermistor and a fourth resistor connected in parallel.

4. The protection device according to claim 1, characterized in that, The PFC circuit includes a power switch that conducts and turns off in response to a PFC control signal; the first temperature protection circuit and the output voltage detection and protection circuit cause the PFC circuit to stop working by turning off the power switch.

5. The protection device according to claim 4, characterized in that, The first temperature protection circuit includes: A hysteresis comparator with its inverting input terminal coupled to the temperature signal. The safety temperature threshold is coupled to the non-inverting input terminal and the output terminal of the hysteresis comparator through voltage-dividing resistors, and the hysteresis comparator outputs the temperature protection signal; and A first diode with its negative terminal coupled to the temperature protection signal and its positive terminal coupled to the PFC control signal.

6. The protection device according to claim 1, characterized in that, It further includes: A second temperature protection circuit configured to compare the temperature signal with a master control safety threshold and form a master control signal. When the temperature signal is greater than the master control safety threshold, the master control signal causes the power supply module to stop power supply.

7. The protection device according to claim 6, characterized in that, The master control safety threshold is greater than the safety temperature threshold.

8. The protection device according to claim 6, characterized in that, The second temperature protection circuit includes: A first comparator with its inverting input terminal coupled to the temperature signal and its non-inverting input terminal coupled to the master control safety threshold; and A second diode with its negative terminal coupled to the output terminal of the first comparator and its positive terminal coupled to the master control signal.

9. The protection device according to claim 4, wherein, The output voltage detection and protection circuit includes: A second comparator with its inverting input terminal coupled to the voltage sampling signal and its non-inverting input terminal coupled to the output voltage threshold; and A third diode with its negative terminal coupled to the output terminal of the second comparator and its positive terminal coupled to the PFC control signal.

10. The protection device according to claim 4, characterized in that, It further includes: A control module, configured to output the PFC control signal and the safety temperature threshold, and collect at least one of the temperature signal, the temperature protection signal, the voltage sampling signal, and the voltage protection signal.

11. An electrical device, characterized in that, Comprising: A PFC circuit, which converts the rectified signal output by the power supply module into a corresponding output voltage; And The protection device according to any one of claims 1 to 10.

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