Over-temperature protection circuit

Abstract

The invention relates to the technical field of intelligent power grid characteristic current communication, and discloses an over-temperature protection circuit, which is connected with a characteristic current generation circuit and a controller, and comprises a temperature acquisition module which is arranged in a preset range of a field effect transistor and generates structural change according to the temperature change of the field effect transistor, a detection voltage signal is output based on a voltage drop signal formed by the structure change; the voltage comparison module is connected with the temperature acquisition module, receives the detection voltage signal, and outputs a turn-off control signal when detecting that the detection voltage signal is smaller than a preset voltage signal; and the switch control module is respectively connected with the voltage comparison module and the controller, and is closed after receiving the turn-off control signal so as to stop transmitting the pulse width modulation signal sent by the controller to the characteristic current generation circuit, so that the field effect transistor stops working. The problem that the detection cost is high through a thermistor is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of smart grid characteristic current communication, and in particular to an over-temperature protection circuit. Background Art

[0002] The characteristic current generating circuit will accumulate a lot of heat on the MOSFET during operation. Long-term operation in a high temperature environment will cause damage to the MOSFET. Especially for the characteristic current generating circuit that works in a high temperature area for a long time, it is not conducive to the heat dissipation of components and aggravates the damage of the MOSFET. Therefore, it is particularly important to monitor the ambient temperature of the MOSFET in the characteristic current generating circuit and to issue an alarm and protection in the event of overtemperature.

[0003] However, conventional over-temperature monitoring circuits are generally implemented by combining a thermistor with a variety of components, which results in relatively high circuit costs. Summary of the invention

[0004] In view of this, the present invention provides an over-temperature protection circuit to solve the problem of high cost of over-temperature detection by thermistors in the prior art.

[0005] In a first aspect, the present invention provides an over-temperature protection circuit, wherein the over-temperature protection circuit is connected to a characteristic current generating circuit and a controller respectively, wherein the characteristic current generating circuit includes a field effect transistor, and the over-temperature protection circuit includes:

[0006] A temperature acquisition module, which is arranged within a preset range of the field effect tube and is used to generate a structural change according to a temperature change of the field effect tube and output a detection voltage signal based on a voltage drop signal formed by the structural change;

[0007] A voltage comparison module, the voltage comparison module is connected to the temperature acquisition module, and is used to receive the detection voltage signal, and output a shutdown control signal when it is detected that the detection voltage signal is less than a preset voltage signal;

[0008] A switch control module, the switch control module is connected to the voltage comparison module and the controller respectively, and is used to close after receiving the shutdown control signal to stop transmitting the pulse width modulation signal sent by the controller to the characteristic current generating circuit, so that the field effect tube stops working.

[0009] The over-temperature protection circuit provided by the present invention sets the temperature acquisition module within the preset range of the field effect tube, and outputs a detection voltage signal to the voltage comparison module by changing the structure according to the temperature in the temperature acquisition module and based on the characteristics of the voltage drop signal formed by the structural change. When the voltage comparison module detects that the detection voltage signal is less than the preset voltage signal, it outputs a shutdown control signal to the switch control module. After receiving the shutdown control signal, the switch control module stops sending the pulse width modulation signal to the characteristic current generating circuit, so that the field effect tube stops working. Thus, when the temperature of the field effect tube is high, the field effect tube stops working, thereby protecting the field effect tube. Compared with the traditional thermistor method of changing resistance based on temperature, the present application generates different voltage drop signals through temperature changes, thereby, no practical thermistor is required, and the cost is saved to a great extent.

[0010] In some feasible implementations, the temperature acquisition module includes:

[0011] A structural change unit, the structural change unit is arranged in a preset range of a field effect transistor in a characteristic current generating circuit, and is used to generate a structural change according to a temperature change of the field effect transistor, and output a voltage signal based on a voltage drop signal formed by the structural change;

[0012] an amplifying unit, wherein the amplifying unit is connected to the structure changing unit and the voltage comparing module respectively, and is used for receiving the voltage signal, amplifying the voltage signal to obtain an amplified voltage signal, and outputting the amplified voltage signal as a detection voltage signal.

[0013] In some feasible implementations, the structure change unit includes:

[0014] a first resistor, wherein a first end of the first resistor is connected to a preset reference voltage;

[0015] One or more first diodes, wherein the first diodes are connected in series, and a first end of the series connection is connected to the second end of the first resistor, and a second end of the series connection is grounded.

[0016] In some feasible implementations, the amplification unit includes:

[0017] an operational amplifier, wherein a first input terminal of the operational amplifier is connected to the second end of the first resistor, and an output terminal of the operational amplifier is connected to the voltage comparison module;

[0018] a second resistor, wherein a first end of the second resistor is connected to the second input end of the operational amplifier, and a second end of the second resistor is grounded;

[0019] a third resistor, wherein a first end of the third resistor is connected to the second input end of the operational amplifier, and a second end of the third resistor is connected to the output end of the operational amplifier;

[0020] A first capacitor, wherein a first end of the first capacitor is connected to the output end of the operational amplifier, and a second end of the first capacitor is grounded.

[0021] In some feasible implementations, the voltage comparison module includes:

[0022] A first switch tube, wherein a control end of the first switch tube is connected to the temperature acquisition module, a first end of the first switch tube is connected to the switch control module, and a second end of the first switch tube is grounded;

[0023] A fourth resistor, wherein a first end of the fourth resistor is connected to a preset reference voltage, and a second end of the fourth resistor is connected to a first end of the first switch tube.

[0024] In some feasible implementations, the voltage comparison module further includes:

[0025] a fifth resistor, wherein a first end of the fifth resistor is connected to the temperature acquisition module, and a second end of the fifth resistor is connected to the control end of the first switch tube;

[0026] a sixth resistor, wherein a first end of the sixth resistor is connected to a second end of the fifth resistor, and a second end of the sixth resistor is grounded;

[0027] A second capacitor, wherein a first end of the second capacitor is connected to a first end of the first switch tube, and a second end of the second capacitor is grounded.

[0028] In some feasible implementations, the switch control module includes:

[0029] A control unit, the control unit is connected to the voltage comparison module, and the control unit is used to receive the shutdown control signal and output a shutdown signal;

[0030] An output unit, wherein the output unit is respectively connected to the control unit, the characteristic current generating circuit and the controller, and is used to receive the shutdown signal and stop transmitting the pulse width modulation signal sent by the controller to the characteristic current generating circuit to shut down the field effect tube.

[0031] In some feasible implementations, the control unit includes:

[0032] a seventh resistor, a first end of the seventh resistor being connected to the voltage comparison module;

[0033] a second switch tube, wherein a control end of the second switch tube is connected to the second end of the seventh resistor, and a first end of the second switch tube is grounded;

[0034] an eighth resistor, a first end of the eighth resistor being connected to the second end of the second switch tube;

[0035] a third switch tube, wherein a control end of the third switch tube is connected to the second end of the eighth resistor, a first end of the third switch tube is connected to a preset reference voltage, and a second end of the third switch tube is connected to the output unit;

[0036] A ninth resistor, wherein a first end of the ninth resistor is connected to a preset reference voltage, and a second end of the ninth resistor is connected to the control end of the third switch tube.

[0037] In some feasible implementations, the output unit includes:

[0038] a tenth resistor, a first end of the tenth resistor being connected to the second end of the third switch tube;

[0039] a fourth switch tube, wherein a control end of the fourth switch tube is connected to the second end of the tenth resistor, a first end of the fourth switch tube is connected to the characteristic current generating circuit, and a second end of the fourth switch tube is connected to the controller;

[0040] An eleventh resistor, wherein a first end of the eleventh resistor is connected to the first end of the tenth resistor, and a second end of the eleventh resistor is grounded.

[0041] In some feasible implementations, the over-temperature protection circuit further includes: a power supply module, the power supply module being used to supply power to the temperature acquisition module, the voltage comparison module and the switch control module respectively;

[0042] The power supply module comprises:

[0043] A rectifier bridge, the input end of the rectifier bridge is connected to the power input end, and the rectifier bridge is used to convert the input alternating current into direct current and transmit it to the temperature acquisition module, the voltage comparison module and the switch control module respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1is a structural diagram of an over-temperature protection circuit according to an embodiment of the present invention;

[0046] Figure 2 is a characteristic current generating circuit according to an embodiment of the present invention;

[0047] Figure 3 is a structural diagram of a temperature acquisition module of an over-temperature protection circuit according to an embodiment of the present invention;

[0048] Figure 4 is a structural diagram of a temperature acquisition module of another over-temperature protection circuit according to an embodiment of the present invention;

[0049] Figure 5 is a structural diagram of a switch control module of an over-temperature protection circuit according to an embodiment of the present invention;

[0050] Figure 6 is a structural diagram of a power supply module of a temperature acquisition module of an over-temperature protection circuit according to an embodiment of the present invention;

[0051] Figure 7 Detailed structural diagram of a power supply module of an over-temperature protection circuit according to an embodiment of the present invention.

[0052] Description of Figure Numbers:

[0053] 10-temperature acquisition module; 20-voltage comparison module; 30-switch control module; 40-power supply module; K1-field effect tube; 11-structure change unit; 12-amplification unit; 31-control unit; 32-output unit; R1-first resistor; R2-second resistor; R3-third resistor; R4-fourth resistor; R5-fifth resistor; R6-sixth resistor; R7-seventh resistor; R8-eighth resistor; R9-ninth resistor; R10-tenth resistor; R11-eleventh resistor; R12-twelfth resistor; R13-thirteenth resistor; R14-fourteenth resistor; R15-fifteenth resistor; R16-sixteenth resistor; R17-seventeenth resistor; R18-eighteenth resistor; R19-nineteenth resistor; R20-twentieth resistor; D1-first diode; D2-second diode; D3-first voltage regulator diode; D4-Schottky diode; D5-second voltage regulator diode; G1-rectifier bridge. DETAILED DESCRIPTION

[0054] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the 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 cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0056] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0057] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0058] The characteristic current generating circuit will accumulate a lot of heat on the MOSFET during operation. Long-term operation in a high-temperature environment will cause damage to the MOSFET. Especially for the characteristic current generating circuit that works in a high-temperature area for a long time, it is not conducive to the heat dissipation of components and aggravates the damage of the MOSFET. Therefore, it is particularly important to monitor the ambient temperature of the MOSFET in the characteristic current generating circuit and to issue an alarm and protection in the event of overtemperature. However, the traditional over-temperature monitoring circuit is generally implemented by combining thermistors with a variety of components, which results in a relatively high circuit cost.

[0059] In this regard, an over-temperature protection circuit is provided in this embodiment. Figure 1 and Figure 2 As shown, the over-temperature protection circuit is connected to the characteristic current generating circuit and the controller respectively, the characteristic current generating circuit includes a field effect transistor K1, and the over-temperature protection circuit includes:

[0060] Specifically, refer to Figure 2In the conventional technology, the controller directly sends a PWM_OUT signal to the characteristic current generating circuit. When the PWM_OUT signal is at a high level, the fifth switch tube Q5 is controlled to be turned on, and the sixth switch tube Q6 is controlled to be turned off. When the PWM_OUT signal is at a low level, the fifth switch tube Q5 is controlled to be turned off, and the sixth switch tube Q6 is controlled to be turned on. Thus, the field effect tube K1 is controlled to work and the characteristic current signal VCC_LINE is output. Figure 7 , the output characteristic current signal VCC_LINE is transmitted to the power lines L and N, thereby generating current on the power lines according to the preset frequency requirements. In addition, the characteristic current generating circuit also includes a fifteenth resistor R15, a sixteenth resistor R16, a seventeenth resistor R17, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, a Schottky diode D4, a second voltage stabilizing diode D5 and a third capacitor C3.

[0061] A temperature acquisition module 10, which is arranged within a preset range of the field effect tube K1, and is used to generate a voltage drop signal according to a temperature change of the field effect tube K1, and output a detection voltage signal based on the voltage drop signal;

[0062] Specifically, refer to Figure 1 The temperature acquisition module 10 is set at a position close to the field effect tube K1. The preset range refers to a position that does not affect the normal operation of the field effect tube K1 and is sensitive to the temperature change of the field effect tube K1. Compared with the traditional method of using thermistors, the temperature acquisition module 10 of the present application can produce structural changes of internal materials according to changes in temperature. The structural changes of the internal materials produce a voltage drop signal, thereby reflecting the temperature change according to the change in the voltage drop signal. Therefore, a detection voltage signal is output based on the voltage drop signal, and the size of the detection voltage signal ultimately reflects the temperature of the field effect tube K1. Optionally, the temperature acquisition module 10 can specifically be a device that changes the material structure according to changes in temperature.

[0063] A voltage comparison module 20, the voltage comparison module 20 is connected to the temperature acquisition module 10, and is used to receive the detection voltage signal, and output a shutdown control signal when it is detected that the detection voltage signal is less than a preset voltage signal;

[0064] Specifically, the voltage comparison module 20 compares the detection voltage signal with the preset voltage signal, and outputs a shutdown control signal when it is detected that the detection voltage signal is less than the preset voltage signal, and outputs a start control signal when it is detected that the detection voltage signal is greater than the preset voltage signal. It should be noted that the shutdown control signal and the start control signal are control signals for the field effect transistor K1. Optionally, the voltage comparison module 20 can be a comparison circuit, and a circuit that outputs a control signal according to the comparison result.

[0065] The switch control module 30 is connected to the voltage comparison module 20 and the controller respectively, and is used to close after receiving the shutdown control signal to stop transmitting the pulse width modulation signal sent by the controller to the characteristic current generating circuit to shut down the field effect tube.

[0066] Specifically, the switch control module 30 receives the pulse width modulation signal sent by the controller, and when transmitting the pulse width modulation signal to the characteristic current generating circuit, the field effect tube works. When the switch control module 30 receives the shutdown control signal, it stops transmitting the pulse width modulation signal sent by the controller to the characteristic current generating circuit, so that the field effect tube stops working. The pulse width modulation signal input by the controller to the switch control module 30 is PWM_IN, and the pulse width modulation signal output by the switch control module 30 to the characteristic current generating circuit is PWM_OUT.

[0067] The over-temperature protection circuit provided by the present invention sets the temperature acquisition module within the preset range of the field effect tube, and outputs a detection voltage signal to the voltage comparison module by changing the structure according to the temperature in the temperature acquisition module and based on the characteristics of the voltage drop signal formed by the structural change. When the voltage comparison module detects that the detection voltage signal is less than the preset voltage signal, the voltage comparison module outputs a shutdown control signal to the switch control module. After receiving the shutdown control signal, the switch control module stops sending a pulse width modulation signal to the characteristic current generating circuit, so that the field effect tube stops working. Thus, when the temperature of the field effect tube is high, the field effect tube stops working, thereby protecting the field effect tube. Compared with the traditional thermistor method of changing resistance based on temperature, the present application generates different voltage drop signals through temperature changes, thereby, no practical thermistor is required, and the cost is saved to a great extent. It is particularly suitable for high-temperature environment areas to avoid the risk of damage to key components in the characteristic current generating circuit when working in a high-temperature environment for a long time.

[0068] In some optional embodiments, Figure 3 As shown, the temperature acquisition module includes:

[0069] A structural change unit 11, which is arranged within a preset range of the field effect tube K1 in the characteristic current generating circuit, and is used to generate a structural change according to a temperature change of the field effect tube K1, and output a detection voltage signal based on a voltage drop signal formed by the structural change;

[0070] Specifically, the structural change unit 11 generates a structural change of the internal material according to the temperature change of the field effect tube K1, forms a voltage drop signal according to the structural change, and then outputs a voltage signal based on the magnitude of the voltage drop signal.

[0071] The amplifying unit 12 is connected to the structure changing unit 11 and the voltage comparing module 20 respectively, and is used for receiving the voltage signal, amplifying the voltage signal to obtain an amplified voltage signal, and outputting the amplified voltage signal as a detection voltage signal.

[0072] Specifically, the amplifying unit 12 amplifies the voltage signal and transmits the amplified voltage signal as a detection voltage signal to the voltage comparison module 20. Optionally, the amplifying unit 12 is a device such as an amplifier that can amplify a signal.

[0073] In some optional embodiments, Figure 4 As shown, the structure change unit includes:

[0074] A first resistor R1, wherein a first end of the first resistor R1 is connected to a preset reference voltage VCC;

[0075] One or more first diodes D1, wherein the first diodes D1 are connected in series, and a first end of the series connection is connected to the second end of the first resistor R1, and a second end of the series connection is grounded.

[0076] Specifically, refer to Figure 4 , the preset reference voltage VCC is transmitted to the ground terminal through the first resistor R1 and one or more first diodes D1. It is designed according to the input temperature characteristic of the first diode D1, which is shown as the forward volt-ampere characteristic curve of the first diode D1 will shift to the left when the temperature rises, and will shift to the right when the temperature drops. The forward voltage drop of the first diode D1 has a negative temperature coefficient characteristic. When the temperature changes by 1°C, the forward voltage drop of the diode changes by about 2 to 2.5mV, that is, when the working environment temperature increases by 1°C, the forward voltage drop of the first diode D1 decreases by about 2 to 2.5mV, and when the working environment temperature decreases by 1°C, the forward voltage drop of the diode increases by about 2 to 2.5mV. The diode maintains this characteristic well in the temperature range of 20 to 150°C, so the stability of the detection field effect tube K1 is very high.

[0077] It should be noted that if the working environment of K1 in the characteristic current generating module is within the safe working temperature range, the PN junction voltage of a first diode D1 is about 0.7V. If the structural change unit includes n first diodes D1, the voltage drop after series connection is n*0.7V, that is, Figure 4 V_TEST in is n*0.7V. Figure 4 , the second end of the first resistor R1 is output as a voltage signal V_TEST to the amplification unit. Optionally, the first resistor R1 may be composed of a plurality of resistors connected in series and / or in parallel.

[0078] In some optional embodiments, Figure 4 As shown, the amplification unit 12 includes:

[0079] An operational amplifier A1, wherein a first input terminal of the operational amplifier A1 is connected to the second terminal of the first resistor R1, and an output terminal of the operational amplifier A1 is connected to the voltage comparison module 20;

[0080] A second resistor R2, wherein a first end of the second resistor R2 is connected to the second input end of the operational amplifier A1, and a second end of the second resistor R2 is grounded;

[0081] A third resistor R3, wherein a first end of the third resistor R3 is connected to the second input end of the operational amplifier A1, and a second end of the third resistor R3 is connected to the output end of the operational amplifier A1;

[0082] A first capacitor C1 , wherein a first end of the first capacitor C1 is connected to the output end of the operational amplifier A1 , and a second end of the first capacitor C1 is grounded.

[0083] Specifically, the operational amplifier A1 can be an integrated operational amplifier, and the amplification factor can be changed by changing the resistance values ​​of the second resistor R2 and the third resistor R3. The voltage signal V_TEST is amplified and output as the detection voltage signal A1_VOUT. The first capacitor C1 plays the role of filtering the output detection voltage signal A1_VOUT.

[0084] In some optional embodiments, Figure 4 As shown, the voltage comparison module 20 includes:

[0085] A first switch tube Q1, wherein a control end of the first switch tube Q1 is connected to the temperature acquisition module 10, a first end of the first switch tube Q1 is connected to the switch control module 30, and a second end of the first switch tube Q1 is grounded;

[0086] A fourth resistor R4, wherein a first end of the fourth resistor R4 is connected to a preset reference voltage VCC, and a second end of the fourth resistor R4 is connected to a first end of the first switch tube Q1.

[0087] Specifically, when the working environment temperature of the field effect tube K1 rises, the detection voltage signal A1_VOUT is detected by the first switch tube Q1 to be less than the preset voltage signal, so that the first switch tube Q1 is turned on, the second end voltage of the fourth resistor R4 is pulled down, and then the shutdown control signal is output. When the working environment temperature of the field effect tube K1 is normal, the detection voltage signal A1_VOUT is detected by the first switch tube Q1 to be greater than the preset voltage signal, so that the first switch tube Q1 is turned off, and the preset reference voltage VCC is output after passing through the fourth resistor R4, and then the start control signal is output. Optionally, the first switch tube Q1 is a bipolar transistor. The first end of the first switch tube Q1 is the emitter, the second end of the first switch tube Q1 is the collector, and the control end of the first switch tube Q1 is the base.

[0088] For example, if the temperature acquisition module 10 includes two diodes, the voltage drop of each diode is about 0.7V, A1_VOUT=1.4*(1+R3 / R2), and the voltage drop of the first switch tube Q1 is 0.7V. When VB_Q1>(VC_Q1-0.7), the first switch tube Q1 is turned off. When VB_Q1<(VC_Q1-0.7), the first switch tube Q1 is turned on.

[0089] In some optional embodiments, Figure 4 As shown, the voltage comparison module 20 also includes:

[0090] A fifth resistor R5, wherein a first end of the fifth resistor R5 is connected to the temperature acquisition module 10, and a second end of the fifth resistor R5 is connected to the control end of the first switch tube Q1;

[0091] a sixth resistor R6, wherein a first end of the sixth resistor R6 is connected to a second end of the fifth resistor R5, and a second end of the sixth resistor R6 is grounded;

[0092] A second capacitor C2, wherein a first end of the second capacitor C2 is connected to a first end of the first switch tube Q1, and a second end of the second capacitor C2 is grounded.

[0093] Specifically, the detection voltage signal A1_VOUT is connected to the base of the first switch tube Q1 after being divided by the fifth resistor R5 and the sixth resistor R6. At this time, the base voltage value of the first switch tube Q1 is VB_Q1=R6 / (R5+R6)*A1_VOUT. The second capacitor C2 is used to filter the outputted on control signal and off control signal.

[0094] In some optional embodiments, Figure 5 As shown, the switch control module 30 includes:

[0095] A control unit 31, wherein the control unit 31 is connected to the voltage comparison module 20, and the control unit 31 is used to receive the shutdown control signal and output a shutdown signal;

[0096] The output unit 32 is respectively connected to the control unit 31, the characteristic current generating circuit and the controller, and is used to receive the shutdown signal and stop transmitting the pulse width modulation signal sent by the controller to the characteristic current generating circuit to shut down the field effect tube K1.

[0097] Specifically, after receiving the shutdown control signal, the control unit 31 outputs a shutdown signal to the output unit 32, thereby controlling the output unit 32 to stop transmitting the pulse width modulation signal sent by the controller to the characteristic current generating circuit.

[0098] In some optional embodiments, Figure 4 As shown, the control unit 31 includes:

[0099] a seventh resistor R7, wherein a first end of the seventh resistor R7 is connected to the voltage comparison module 20;

[0100] A second switch tube Q2, wherein a control end of the second switch tube Q2 is connected to the second end of the seventh resistor R7, and a first end of the second switch tube Q2 is grounded;

[0101] an eighth resistor R8, a first end of the eighth resistor R8 being connected to a second end of the second switch tube Q2;

[0102] A third switch tube Q3, wherein a control end of the third switch tube Q3 is connected to the second end of the eighth resistor R8, a first end of the third switch tube Q3 is connected to a preset reference voltage VCC, and a second end of the third switch tube Q3 is connected to the output unit 32;

[0103] A ninth resistor R9, wherein a first end of the ninth resistor R9 is connected to a preset reference voltage VCC, and a second end of the ninth resistor R9 is connected to a control end of the third switch tube Q3.

[0104] Specifically, when the working environment temperature of the field effect tube K1 rises, the first switch tube Q1 outputs a shutdown control signal, at which time the second switch tube Q2 is turned off, and the third switch tube Q3 is turned off, and then the shutdown signal is output to the output unit 32. On the contrary, when the working environment temperature of the field effect tube K1 is normal, the first switch tube Q1 outputs a start control signal, at which time the second switch tube Q2 is turned on, and the third switch tube Q3 is turned on, and then the start signal is output to the output unit 32. Among them, the seventh resistor R7 is the driving resistor of the second switch tube Q2. The eighth resistor R8 and the ninth resistor R9 are the driving resistors of the third switch tube Q3. The first end of the second switch tube Q2 is the emitter, the second end of the second switch tube Q2 is the collector, and the control end of the second switch tube Q2 is the base. The first end of the third switch tube Q3 is the emitter, the second end of the third switch tube Q3 is the collector, and the control end of the third switch tube Q3 is the base.

[0105] In some optional embodiments, Figure 4 As shown, the output unit 32 includes:

[0106] a tenth resistor R10, wherein a first end of the tenth resistor R10 is connected to a second end of the third switch tube Q3;

[0107] A fourth switch tube Q4, wherein a control end of the fourth switch tube Q4 is connected to the second end of the tenth resistor R10, a first end of the fourth switch tube Q4 is connected to a characteristic current generating circuit, and a second end of the fourth switch tube Q4 is connected to a controller;

[0108] An eleventh resistor R11, a first end of the eleventh resistor R11 is connected to the first end of the tenth resistor R10, and a second end of the eleventh resistor R11 is grounded.

[0109] Specifically, when the working environment temperature of the field effect tube K1 rises, the third switch tube Q3 outputs a shutdown signal to the output unit 32, at which time the fourth switch tube Q4 is turned off, and stops sending the pulse width modulation signal sent by the controller to the characteristic current generation module. On the contrary, when the working environment temperature of the field effect tube K1 is normal, the third switch tube Q3 outputs a start signal to the output unit 32, at which time the fourth switch tube Q4 is turned on, and sends the pulse width modulation signal sent by the controller to the characteristic current generation module. The first end of the fourth switch tube Q4 is the emitter, the second end of the fourth switch tube Q4 is the collector, and the control end of the fourth switch tube Q4 is the base.

[0110] In some optional embodiments, Figure 6 and Figure 7 As shown, the over-temperature protection circuit further includes: a power supply module 40, the power supply module 40 is used to supply power to the temperature acquisition module 10, the voltage comparison module 20 and the switch control module 30 respectively;

[0111] Specifically, refer to Figure 6 The power supply module 40 provides a preset reference voltage VCC to the over-temperature protection circuit, and at the same time, can also provide a preset reference voltage VCC to the characteristic current generating circuit. Therefore, there is no need to separately power the temperature acquisition module 10, the voltage comparison module 20 and the switch control module 30, which reduces power consumption and cost, is applicable to regions of any latitude, and reduces the requirements for temperature changes in the working environment.

[0112] The power supply module 40 includes:

[0113] The rectifier bridge G1 has an input end connected to a power input end, and is used to convert input alternating current into direct current, and transmit the direct current to the temperature acquisition module 10 , the voltage comparison module 20 , and the switch control module 30 .

[0114] It should be noted that the rectifier bridge G1 may be composed of four second diodes D2 connected in series and in parallel. Figure 7 The power input end is the power line L and N, which are respectively transmitted to the rectifier bridge G1 through the twelfth resistor R12 and the thirteenth resistor R13, and after the AC is converted into DC, the preset reference voltage VCC is output after passing through the fourteenth resistor R14. Among them, the first voltage stabilizing diode D3 plays a role in stabilizing the voltage. The third capacitor C3 and the fourth capacitor C4 play a filtering role. The twelfth resistor R12 and the thirteenth resistor R13 play a protective role.

[0115] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. An over-temperature protection circuit, characterized in that: The over-temperature protection circuit is connected to the characteristic current generating circuit and the controller respectively, the characteristic current generating circuit includes a field effect transistor, and the over-temperature protection circuit includes: A temperature acquisition module, which is arranged within a preset range of the field effect tube and is used to generate a structural change according to a temperature change of the field effect tube and output a detection voltage signal based on a voltage drop signal formed by the structural change; A voltage comparison module, the voltage comparison module is connected to the temperature acquisition module, and is used to receive the detection voltage signal, and output a shutdown control signal when it is detected that the detection voltage signal is less than a preset voltage signal; A switch control module, the switch control module is connected to the voltage comparison module and the controller respectively, and is used to close after receiving the shutdown control signal to stop transmitting the pulse width modulation signal sent by the controller to the characteristic current generating circuit, so that the field effect tube stops working.

2. The over-temperature protection circuit according to claim 1, characterized in that: The temperature acquisition module comprises: A structural change unit, the structural change unit is arranged in a preset range of a field effect transistor in a characteristic current generating circuit, and is used to generate a structural change according to a temperature change of the field effect transistor, and output a voltage signal based on a voltage drop signal formed by the structural change; an amplifying unit, wherein the amplifying unit is connected to the structure changing unit and the voltage comparing module respectively, and is used for receiving the voltage signal, amplifying the voltage signal to obtain an amplified voltage signal, and outputting the amplified voltage signal as a detection voltage signal.

3. The over-temperature protection circuit according to claim 2, characterized in that: The structural change unit comprises: a first resistor, wherein a first end of the first resistor is connected to a preset reference voltage; One or more first diodes, wherein the first diodes are connected in series, and a first end of the series connection is connected to the second end of the first resistor, and a second end of the series connection is grounded.

4. The over-temperature protection circuit according to claim 3, characterized in that: The amplification unit comprises: an operational amplifier, wherein a first input terminal of the operational amplifier is connected to the second end of the first resistor, and an output terminal of the operational amplifier is connected to the voltage comparison module; a second resistor, wherein a first end of the second resistor is connected to the second input end of the operational amplifier, and a second end of the second resistor is grounded; a third resistor, wherein a first end of the third resistor is connected to the second input end of the operational amplifier, and a second end of the third resistor is connected to the output end of the operational amplifier; A first capacitor, wherein a first end of the first capacitor is connected to the output end of the operational amplifier, and a second end of the first capacitor is grounded.

5. The over-temperature protection circuit according to claim 2, characterized in that: The voltage comparison module comprises: A first switch tube, wherein a control end of the first switch tube is connected to the temperature acquisition module, a first end of the first switch tube is connected to the switch control module, and a second end of the first switch tube is grounded; A fourth resistor, wherein a first end of the fourth resistor is connected to a preset reference voltage, and a second end of the fourth resistor is connected to a first end of the first switch tube.

6. The over-temperature protection circuit according to claim 5, characterized in that: The voltage comparison module also includes: a fifth resistor, wherein a first end of the fifth resistor is connected to the temperature acquisition module, and a second end of the fifth resistor is connected to the control end of the first switch tube; a sixth resistor, wherein a first end of the sixth resistor is connected to a second end of the fifth resistor, and a second end of the sixth resistor is grounded; A second capacitor, wherein a first end of the second capacitor is connected to a first end of the first switch tube, and a second end of the second capacitor is grounded.

7. The over-temperature protection circuit according to claim 1, characterized in that: The switch control module comprises: A control unit, the control unit is connected to the voltage comparison module, and the control unit is used to receive the shutdown control signal and output a shutdown signal; An output unit, wherein the output unit is respectively connected to the control unit, the characteristic current generating circuit and the controller, and is used to receive the shutdown signal and stop transmitting the pulse width modulation signal sent by the controller to the characteristic current generating circuit to shut down the field effect tube.

8. The over-temperature protection circuit according to claim 7, characterized in that: The control unit comprises: a seventh resistor, a first end of the seventh resistor being connected to the voltage comparison module; a second switch tube, wherein a control end of the second switch tube is connected to the second end of the seventh resistor, and a first end of the second switch tube is grounded; an eighth resistor, a first end of the eighth resistor being connected to the second end of the second switch tube; a third switch tube, wherein a control end of the third switch tube is connected to the second end of the eighth resistor, a first end of the third switch tube is connected to a preset reference voltage, and a second end of the third switch tube is connected to the output unit; A ninth resistor, wherein a first end of the ninth resistor is connected to a preset reference voltage, and a second end of the ninth resistor is connected to the control end of the third switch tube.

9. The over-temperature protection circuit according to claim 8, characterized in that: The output unit comprises: a tenth resistor, a first end of the tenth resistor being connected to the second end of the third switch tube; a fourth switch tube, wherein a control end of the fourth switch tube is connected to the second end of the tenth resistor, a first end of the fourth switch tube is connected to the characteristic current generating circuit, and a second end of the fourth switch tube is connected to the controller; An eleventh resistor, wherein a first end of the eleventh resistor is connected to the first end of the tenth resistor, and a second end of the eleventh resistor is grounded.

10. The over-temperature protection circuit according to claim 1, characterized in that: The over-temperature protection circuit further includes: a power supply module, which is used to supply power to the temperature acquisition module, the voltage comparison module and the switch control module respectively; The power supply module comprises: A rectifier bridge, the input end of the rectifier bridge is connected to the power input end, and the rectifier bridge is used to convert the input alternating current into direct current and transmit it to the temperature acquisition module, the voltage comparison module and the switch control module respectively.

Images