Blocking type surge protector with temperature compensation

Abstract

The invention provides a blocking type surge protector with temperature compensation, and relates to the technical field of circuit protection, comprising a bidirectional surge protection circuit connected in series between two protected devices; the temperature compensation unit adjusts a collected voltage signal to be matched with a threshold voltage of the enhanced NMOS tube according to temperature change when generating a transient voltage so as to realize conduction, and further controls the depletion type NMOS tube connected with a protected device to be turned off so as to realize surge blocking protection. The beneficial effects are that by introducing the temperature compensation unit, the protector can adjust the voltage signal according to the temperature change, so that the voltage signal is matched with the threshold voltage of the enhanced NMOS tube, and the stability of the trigger current is maintained. Even at extreme temperature, the trigger current can be kept close to normal temperature reference current, stable trigger current can be kept at different temperatures, fluctuation caused by temperature change is greatly reduced, and reliability and consistency of surge protection effect are guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit protection, and in particular to a blocking type surge protector with temperature compensation. Background Art

[0002] With the popularization of new energy vehicles and the development of automobile intelligence, electronic devices are widely used in automobile internal control systems, auxiliary and comfort systems, safety systems, etc. These electronic devices are easily affected by surge shocks in the changing driving environment of the car. For example, the instantaneous increase in battery voltage when the car starts the engine may cause a high-power surge. In order to effectively protect against these surge shocks, the Block Surge Protector (BSP) came into being.

[0003] BSP is connected in series to the protected unit. When a transient voltage arrives, it can enter the blocking state in a very short time, completely blocking the impact of overvoltage on the protected unit, thereby greatly improving the safety of automotive transient voltage protection. At present, there are many BSP circuit design solutions on the market. These solutions usually use semiconductor devices such as depletion-type NMOS, current feedback field effect transistors or enhancement-type NMOS to build the basic framework of blocking circuits, and achieve surge blocking protection by controlling the switching state of these devices.

[0004] However, the existing BSP circuit technology has obvious defects, mainly in the temperature stability of the trigger current. Specifically: 1. The trigger current fluctuates with temperature: In the prior art, the trigger current of the BSP circuit is often affected by temperature. Since the semiconductor devices used in the circuit (such as current feedback field effect transistors, enhanced NMOS, etc.) have specific temperature characteristics, when the ambient temperature changes, the electrical parameters of these devices (such as on-resistance, threshold voltage, etc.) will also change accordingly, resulting in fluctuations in the trigger current. Specifically, when the temperature rises, the on-resistance of certain devices may increase, or the threshold voltage may decrease, resulting in a decrease in the trigger current; conversely, when the temperature decreases, the trigger current may increase. This phenomenon of the trigger current changing with temperature seriously affects the surge protection effect of the BSP circuit at different temperatures.

[0005] 2. Factors that affect the reliability and consistency of surge protection: The fluctuation of trigger current causes the surge protection effect of BSP circuit to be inconsistent at different temperatures. In high or low temperature environment, the trigger current may deviate from the design value, making the BSP circuit unable to work properly or greatly reducing the protection effect. This problem of poor temperature stability not only affects the reliability of BSP circuit, but also reduces its applicability in application scenarios with large changes in ambient temperature such as automobiles.

[0006] In summary, the existing BSP circuit technology has the defect that the trigger current fluctuates with temperature, which seriously affects its reliability and consistency in the surge protection of automotive electronic equipment. Therefore, developing a BSP circuit technology with better temperature stability is of great significance to improving the surge protection capability of automotive electronic equipment. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides a blocking surge protector with temperature compensation, comprising: a bidirectional surge protection circuit, wherein the input end and the output end of the bidirectional surge protection circuit are connected in series between the protected units; a temperature compensation unit, wherein the signal collection end of the temperature compensation unit is connected in parallel to the source and the drain of the current feedback field effect transistor of the bidirectional surge protection circuit, and the conduction control end of the temperature compensation unit is connected to the gate of the enhancement type NMOS tube in the bidirectional surge protection circuit, and is used for adjusting the collected voltage signal to match the threshold voltage of the enhancement type NMOS tube according to the temperature change when a transient voltage is generated to achieve conduction, thereby controlling the depletion type NMOS tube connected to the protected device to be turned off to achieve surge blocking protection.

[0008] Preferably, the temperature compensation unit includes: a negative temperature coefficient device, one end of the negative temperature coefficient device is connected to one end of the current feedback field effect tube, and the other end of the negative temperature coefficient device is connected in series with a pull-up resistor and a voltage divider resistor; the other end of the current feedback field effect tube is connected to the voltage divider resistor, and the gate of the enhanced NMOS tube is connected to the connection point between the voltage divider resistor and the pull-up resistor.

[0009] Preferably, the negative temperature coefficient device includes a plurality of diodes whose anodes and cathodes are connected in series in sequence; the cathode side of the diode is connected to one end of the current feedback field effect tube, and the cathode side of the diode is connected to the pull-up resistor.

[0010] Preferably, the number of diodes is 1-3.

[0011] Preferably, the negative temperature coefficient device is a diode, or a transistor BE junction, or a transistor BC junction, or a negative temperature coefficient thermistor.

[0012] Preferably, the temperature compensation unit includes: a positive temperature coefficient device, one end of the positive temperature coefficient device is connected to one end of the current feedback field effect tube, and the other end of the positive temperature coefficient device is connected in series with a voltage divider resistor and a pull-up resistor; the other end of the current feedback field effect tube is connected to the pull-up resistor, and the gate of the enhanced NMOS tube is connected to the connection point between the voltage divider resistor and the pull-up resistor.

[0013] Preferably, the positive temperature coefficient device is a positive temperature coefficient thermistor, or a field effect transistor on-resistance, or a metal film resistor, or a polysilicon resistor.

[0014] Preferably, the temperature compensation unit includes: a positive temperature coefficient thermistor, wherein two ends of the positive temperature coefficient device are respectively connected to a voltage divider resistor and a pull-up resistor; one end of the current feedback field effect transistor is connected to the pull-up resistor, and the other end of the current feedback field effect transistor is connected to the voltage divider resistor, and the gate of the enhanced NMOS tube is connected to the connection point between the positive temperature coefficient thermistor and the pull-up resistor.

[0015] Preferably, the depletion-type NMOS tube in the bidirectional surge protection circuit includes a first depletion-type NMOS tube and a second depletion-type NMOS tube; the drain and source of the current feedback field effect tube are respectively connected to the source of the first depletion-type NMOS tube and the source of the second depletion-type NMOS tube, the gate of the current feedback field effect tube is connected to the cathode of the first diode and the cathode of the second diode, a first resistor is connected in series between the anode of the first diode and the drain of the first depletion-type NMOS tube, and a second resistor is connected in series between the anode of the second diode and the drain of the second depletion-type NMOS tube; the drains of the first depletion-type NMOS tube and the second depletion-type NMOS tube are respectively connected to a protected device.

[0016] Preferably, the enhanced NMOS tube in the bidirectional surge protection circuit includes a first enhanced NMOS tube and a second enhanced NMOS tube, and the temperature compensation unit includes a first temperature compensation unit and a second temperature compensation unit; the source of the first enhanced NMOS tube and the source of the second enhanced NMOS tube are respectively connected to the drain and source of the current feedback field effect tube, the gate of the first enhanced NMOS tube is connected to the conduction control end of the first temperature compensation unit, and the gate of the second enhanced NMOS tube is connected to the conduction control end of the second temperature compensation unit; the drain of the first enhancement NMOS tube is connected to the gate of the first depletion NMOS tube and one end of the third resistor, and the other end of the third resistor is connected to the source of the current feedback field effect tube; the drain of the second enhancement NMOS tube is connected to the gate of the second depletion NMOS tube and one end of the fourth resistor, and the other end of the fourth resistor is connected to the drain of the current feedback field effect tube.

[0017] The above technical solution has the following advantages or beneficial effects: by introducing a temperature compensation unit, the protector of the present invention can adjust the voltage signal according to temperature changes to match the threshold voltage of the enhanced NMOS tube, thereby maintaining the stability of the trigger current. Even at extreme temperatures, the trigger current can be kept near the normal temperature reference current, and a stable trigger current can be maintained at different temperatures, greatly reducing the fluctuation caused by temperature changes, thereby ensuring the reliability and consistency of the surge protection effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of the first existing BSP circuit; Figure 2 It is a structural schematic diagram of the second existing BSP circuit; Figure 3 The trigger current-temperature characteristic diagram of the existing first BSP circuit and the existing second BSP circuit; Figure 4 It is a structural schematic diagram of a blocking type surge protector with temperature compensation in a preferred embodiment of the present invention; Figure 5 A comparison diagram of trigger current-temperature characteristics of the present invention and the prior art circuit; Figure 6 It is a structural schematic diagram of a blocking type surge protector in the second embodiment of the present invention; Figure 7 It is a schematic structural diagram of a blocking type surge protector in Embodiment 3 of the present invention; Figure 8 It is a structural schematic diagram of a blocking type surge protector in Embodiment 4 of the present invention; Fig. 9It is a structural schematic diagram of a blocking type surge protector in Embodiment 5 of the present invention; Fig.10 Schematic diagram of the structure of a blocking surge protector in Embodiment 6 of the present invention. DETAILED DESCRIPTION

[0019] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The present invention is not limited to this embodiment, and other embodiments may also fall within the scope of the present invention as long as they conform to the gist of the present invention.

[0020] In a preferred embodiment of the present invention, based on the above problems existing in the prior art, a blocking type surge protector with temperature compensation is provided.

[0021] Embodiment 1: In a blocking type surge protector with temperature compensation, Figure 4 As shown, it includes: a bidirectional surge protection circuit 1, wherein the bidirectional connection terminal of the bidirectional surge protection circuit 1 is connected in series between two protected devices 100; a temperature compensation unit 2, wherein the signal collection end of the temperature compensation unit 2 is connected in parallel to the source and drain of the current feedback field effect transistor Q3 of the bidirectional surge protection circuit 1, and the conduction control end of the temperature compensation unit 2 is connected to the gate of the enhancement type NMOS tube Q4 / Q5 in the bidirectional surge protection circuit 1, and is used to adjust the collected voltage signal to match the threshold voltage of the enhancement type NMOS tube according to the temperature change when a transient voltage is generated to achieve conduction, thereby controlling the depletion type NMOS tube connected to the protected device to be turned off to achieve surge blocking protection.

[0022] To be more specific, the depletion-type NMOS tube in the bidirectional surge protection circuit 1 includes a first depletion-type NMOS tube Q1 and a second depletion-type NMOS tube Q2; the drain and source of the current feedback field effect tube Q3 are respectively connected to the source of the first depletion-type NMOS tube Q1 and the source of the second depletion-type NMOS tube Q2, the gate of the current feedback field effect tube Q3 is connected to the cathode of the first diode D1 and the cathode of the second diode D2, a first resistor R1 is connected in series between the anode of the first diode D1 and the drain of the first depletion-type NMOS tube Q1, and a second resistor R2 is connected in series between the anode of the second diode D2 and the drain of the second depletion-type NMOS tube Q2; the drains of the first depletion-type NMOS tube Q1 and the second depletion-type NMOS tube Q2 are respectively connected to a protected device 100.

[0023] More specifically, the enhanced NMOS transistor in the bidirectional surge protection circuit includes a first enhanced NMOS transistor Q4 and a second enhanced NMOS transistor Q5, and the temperature compensation unit 2 includes a first temperature compensation unit 21 and a second temperature compensation unit 22; the source of the first enhanced NMOS transistor Q4 and the source of the second enhanced NMOS transistor Q5 are respectively connected to the drain and source of the current feedback field effect transistor Q3 (because it is a bidirectional surge protection circuit, the drain and source of the current feedback field effect transistor Q3 can also be connected in the reverse direction), and the gate of the first enhanced NMOS transistor Q4 is connected to the drain and source of the current feedback field effect transistor Q3. The gate of the second enhancement mode NMOS tube Q5 is connected to the conduction control end of the second temperature compensation unit 22; the drain of the first enhancement mode NMOS tube Q4 is connected to the gate of the first depletion mode NMOS tube Q1 and one end of the third resistor R3, and the other end of the third resistor R3 is connected to the source of the current feedback field effect tube Q3; the drain of the second enhancement mode NMOS tube Q5 is connected to the gate of the second depletion mode NMOS tube Q2 and one end of the fourth resistor R4, and the other end of the fourth resistor R4 is connected to the drain of the current feedback field effect tube Q3.

[0024] Specifically, there is a BSP circuit in the prior art, in which the basic framework of a blocking circuit is constructed by using common semiconductor devices such as depletion-type NMOS and current feedback field effect transistors. The current feedback field effect transistor controls the gate of the depletion-type NMOS. When the line current reaches the trigger current, the BSP circuit changes from on to off, thereby achieving surge blocking protection. Figure 1 shown.

[0025] In the prior art, there is also a BSP circuit containing an enhancement-type NMOS device, which mainly utilizes the relatively stable threshold voltage characteristic of the enhancement-type NMOS to control the switching state of the depletion-type NMOS gate circuit, thereby solving the problem of the BSP circuit triggering circuit discreteness caused by the threshold voltage instability caused by the inherent characteristics of the depletion-type NMOS process manufacturing. Figure 2 shown.

[0026] However, when considering application scenarios such as automobiles where the ambient temperature may vary greatly, the above-mentioned existing circuits have the problem that the trigger current fluctuates with temperature changes.

[0027] For the first existing circuit, when the temperature gradually rises from room temperature (25°C), due to the positive temperature characteristic of the on-resistance of the current feedback field effect tube, its on-resistance gradually increases, causing the trigger current of the overall BSP circuit to decrease accordingly; conversely, when the temperature gradually decreases, the trigger current increases accordingly; the trigger current of this BSP circuit presents a negative temperature characteristic.

[0028] For the second existing circuit, when the temperature gradually rises from room temperature (25°C), since the threshold voltage of the enhancement NMOS responsible for controlling the gate state of the depletion-type NMOS has a negative temperature characteristic, its threshold voltage decreases as the temperature rises, resulting in the enhancement NMOS being turned on when a small trigger current passes through the BSP, thereby causing the depletion-type NMOS gate to receive a potential signal and turn into a blocking state, which is ultimately reflected in the rapid decrease in the trigger current of the overall BSP circuit as the temperature rises; conversely, when the temperature gradually decreases, the threshold voltage of the enhancement NMOS increases accordingly, and the trigger current increases rapidly accordingly; the trigger current of this BSP circuit presents a more obvious negative temperature characteristic.

[0029] Figure 3 It is the percentage change of the trigger current of the above-mentioned existing circuits in the temperature range of -50℃~100℃ compared with the normal temperature of 25℃. The change range of the trigger current of the first existing circuit is 78%~133%. The change range of the trigger current of the second existing circuit is 67%~152%. It can be seen that due to the addition of the enhanced NMOS circuit, the temperature stability of the trigger current of the second existing circuit is further deteriorated compared with the first existing circuit.

[0030] In this embodiment of the present invention, a blocking type surge protector with temperature compensation is designed, and the principle diagram is as follows: Figure 4 As shown, a temperature compensation unit 2 is added to the BSP circuit. The temperature compensation unit 2 is connected in parallel to the drain and source of the current feedback field effect tube Q3 (using a P-type JFET) to capture the potential signal and transmit the processed potential signal from its own interior to the gate of the enhancement NMOS tube Q4 / Q5 to control the switching state of the gate of the enhancement NMOS tube Q4 / Q5.

[0031] The potential transmitted by the temperature compensation unit 2 to the gate of the enhancement type NMOS transistor Q4 / Q5 has a negative temperature characteristic, which matches the negative temperature characteristic of the threshold voltage of the gate of the enhancement type NMOS transistor Q4 / Q5 and the positive temperature characteristic of the on-resistance of the current feedback field effect transistor. The specific temperature compensation principle is as follows: Case 1: At room temperature (25°C), the temperature compensation unit 2 collects voltage signals from the drain and source of the current feedback field effect tube Q3 and transmits them to the gate of the enhancement type NMOS tube Q4 / Q5. When the BSP current reaches the trigger current, the voltage transmitted by the temperature compensation unit 2 to the gate of the enhancement type NMOS tube Q4 / Q5 reaches its threshold voltage, and the enhancement type NMOS tube Q4 / Q5 turns on and controls the depletion type NMOS tube Q1 / Q2 to turn off, realizing the blocking characteristic. The trigger current at this temperature is the reference current.

[0032] Case 2: When the temperature rises, the on-resistance of the current feedback field effect tube Q3 increases (positive temperature characteristics), and the threshold voltage of the enhanced NMOS tube Q4 / Q5 decreases (negative temperature characteristics). At this time, although the voltage signal collected by the temperature compensation unit 2 from the drain and source of the current feedback field effect tube Q3 increases, due to its own negative temperature characteristics, the voltage signal transmitted by the temperature compensation unit 2 to the gate of the enhanced NMOS tube Q4 / Q5 decreases with the increase of temperature, and the decrease amplitude matches the decrease amplitude of the threshold voltage of the enhanced NMOS tube Q4 / Q5. Therefore, only when the BSP current still reaches the normal temperature reference current, the temperature compensation unit 2 will turn on the enhanced NMOS tube Q4 / Q5 and then control the depletion NMOS tube Q1 / Q2 to turn off, realizing the blocking characteristic. Therefore, although the temperature rises, the trigger current of the BSP circuit remains the same as that at normal temperature.

[0033] Case 3: When the temperature decreases, the on-resistance of the current feedback field effect tube Q3 decreases (positive temperature characteristics), and the threshold voltage of the enhanced NMOS tube Q4 / Q5 increases (negative temperature characteristics). At this time, although the voltage signal collected by the temperature compensation unit 2 from the drain and source of the current feedback field effect tube Q3 decreases, due to its own negative temperature characteristics, the voltage signal transmitted by the temperature compensation unit 2 to the gate of the enhanced NMOS tube Q4 / Q5 increases as the temperature decreases, and the increase amplitude matches the increase amplitude of the threshold voltage of the enhanced NMOS tube Q4 / Q5. Therefore, only when the BSP current still reaches the normal temperature reference current, the temperature compensation unit 2 will turn on the enhanced NMOS tube Q4 / Q5 and control the depletion NMOS tube Q1 / Q2 to turn off, realizing the blocking characteristic. Therefore, although the temperature decreases, the trigger current of the BSP circuit remains the same as that at normal temperature.

[0034] like Figure 5 As shown, the fluctuation percentage of the trigger current relative to the reference trigger current at room temperature (25°C) for the first existing circuit, the second existing circuit and the present invention at an ambient temperature of -50°C to 100°C is shown. The variation range of the trigger current of the first existing circuit is 78% to 133%, the variation range of the trigger current of the second existing circuit is 67% to 152%, and the variation range of the trigger current of the circuit in the present invention is only 96% to 109%, and the fluctuation range is reduced. It can be seen that the circuit of the present invention can achieve excellent temperature stability.

[0035] In summary, it can be seen that the blocking type surge protector with temperature compensation of the present invention has the following three advantages: 1. Compared with the first existing circuit and the second existing circuit, the surge protection effect of the blocking characteristic is maintained unchanged; 2. Compared with the second existing circuit, the enhanced NMOS circuit is retained to solve the problem of the BSP circuit triggering current discreteness caused by the unstable threshold voltage of the depletion NMOS tube; 3. Greatly improve the temperature stability of the trigger current of the overall BSP circuit and reduce the amplitude of the trigger current changing with temperature.

[0036] Embodiment 2: Based on the first embodiment, the present embodiment specifically describes the structure in the temperature compensation unit 2, including: a negative temperature coefficient device, one end of the negative temperature coefficient device is connected to one end of the current feedback field effect tube Q3, and the other end of the negative temperature coefficient device is connected in series with a pull-up resistor and a voltage divider resistor in sequence; the other end of the current feedback field effect tube is connected to the voltage divider resistor, and the gate of the enhanced NMOS tube is connected to the connection point between the voltage divider resistor and the pull-up resistor.

[0037] Specifically, Figure 6 As shown, since the present invention shows a bidirectional surge protection circuit, the circuit designs in two directions are symmetrical and the same, so only one temperature compensation unit is introduced below.

[0038] Taking the first temperature compensation unit 21 as an example, a resistor R5, a resistor R6, and a negative temperature coefficient device are used to form the first temperature compensation unit 21, and the gate of the enhanced NMOS tube Q4 directly receives a voltage signal from the resistor R5 and the resistor R6. Among them, the resistor R5 is a voltage-dividing resistor, and the resistor R6 is a pull-up resistor of the gate of the enhanced NMOS tube Q4. Similarly, in the second temperature compensation unit 22, the resistor R7 is a voltage-dividing resistor, and the resistor R8 is a pull-up resistor of the gate of the second enhanced NMOS tube Q5.

[0039] The specific temperature compensation principle is as follows: Case 1: At room temperature (25°C), the temperature compensation unit 2 collects voltage signals from the drain and source of the current feedback field effect tube Q3 and transmits them to the gate of the enhancement type NMOS tube Q4 / Q5. When the BSP current reaches the trigger current, the voltage transmitted by the temperature compensation unit 2 to the gate of the enhancement type NMOS tube Q4 / Q5 reaches its threshold voltage, and the enhancement type NMOS tube Q4 / Q5 turns on and controls the depletion type NMOS tube Q1 / Q2 to turn off, realizing the blocking characteristic. The trigger current at this temperature is the reference current.

[0040] Case 2: When the temperature rises, the on-resistance of the current feedback field effect tube Q3 increases (positive temperature characteristics), and the threshold voltage of the enhanced NMOS tube Q4 / Q5 decreases (negative temperature characteristics). At this time, although the voltage signal collected by the temperature compensation unit 2 from the drain and source of the current feedback field effect tube Q3 increases, due to the negative temperature characteristics of the negative temperature coefficient device, the overall voltage division of the pull-up resistor R6 and the negative temperature coefficient device decreases, and the voltage signal transmitted by the temperature compensation unit 2 to the gate of the enhanced NMOS tube Q4 / Q5 decreases with the increase of temperature, and the reduction amplitude matches the reduction amplitude of the threshold voltage of the enhanced NMOS tube Q4 / Q5. Therefore, only when the BSP current still reaches the normal temperature reference current, the temperature compensation unit 2 will turn on the enhanced NMOS tube Q4 / Q5 and then control the depletion NMOS tube Q1 / Q2 to turn off, realizing the blocking characteristic. Therefore, although the temperature rises, the trigger current of the BSP circuit remains the same as that at normal temperature.

[0041] Case 3: When the temperature decreases, the on-resistance of the current feedback field effect tube Q3 decreases (positive temperature characteristics), and the threshold voltage of the enhanced NMOS tube Q4 / Q5 increases (negative temperature characteristics). At this time, although the voltage signal collected by the temperature compensation unit 2 from the drain and source of the current feedback field effect tube Q3 decreases, due to the negative temperature characteristics of the negative temperature coefficient device, the pull-up resistor R6 and the overall voltage division of the negative temperature coefficient device increase, and the voltage signal transmitted by the temperature compensation unit 2 to the gate of the enhanced NMOS tube Q4 / Q5 increases as the temperature decreases, and the increase amplitude matches the increase amplitude of the threshold voltage of the enhanced NMOS tube Q4 / Q5. Therefore, only when the BSP current still reaches the normal temperature reference current, the temperature compensation unit 2 will turn on the enhanced NMOS tube Q4 / Q5 and control the depletion NMOS tube Q1 / Q2 to turn off, realizing the blocking characteristic. Therefore, although the temperature decreases, the trigger current of the BSP circuit remains the same as that at normal temperature.

[0042] Embodiment three: This embodiment specifically describes the structure of the negative temperature coefficient device based on the second embodiment. The negative temperature coefficient device preferably adopts a diode, or a transistor BE junction, or a transistor BC junction, or a negative temperature coefficient thermistor.

[0043] In this embodiment, a diode is taken as an example. Figure 7 As shown, the negative temperature coefficient device of the first temperature compensation unit 21 includes a plurality of diodes D3 and D4 whose anodes and cathodes are connected in series in sequence; the cathode side of the diode D4 is connected to one end of the current feedback field effect transistor Q3, and the cathode side of the diode D3 is connected to the pull-up resistor R6.

[0044] Specifically, in this embodiment, the negative temperature coefficient devices of the first temperature compensation unit 21 and the second temperature compensation unit 22 are selected to be composed of diodes. The diodes here can be one or more connected in series, and the preferred number of diodes is 1 to 3 connected in series. This embodiment utilizes the negative temperature characteristics of the forward conduction voltage of the diode, and adjusts the voltage signal transmitted to the gate of the first enhancement mode NMOS tube Q4 at different temperatures through the voltage division relationship of the resistor R5, the resistor R6 and the forward voltage drop of the diode string D3 and D4.

[0045] Specifically, when the temperature rises from the normal temperature, the forward conduction voltage drop of the diodes D3 and D4 decreases, and the threshold voltage of the enhanced NMOS tube Q4 decreases. At this time, the overall voltage division of the resistor R6 and the diodes D3 and D4 decreases, and the voltage transmitted to the gate of the enhanced NMOS tube Q4 decreases, and this voltage reduction offsets the decrease in the threshold voltage of the enhanced NMOS tube Q4. Therefore, for the overall BSP circuit, the current still needs to reach the trigger current at normal temperature to enter the blocking state.

[0046] When the temperature drops from room temperature, the forward voltage drop of diodes D3 and D4 increases, and the threshold voltage of the enhanced NMOS tube Q4 increases. At this time, the overall voltage division of resistor R6 and diodes D3 and D4 increases, and the voltage transmitted to the gate of the enhanced NMOS tube Q4 increases, and this part of the voltage increase offsets the increase in the threshold voltage of the enhanced NMOS tube Q4. Therefore, for the overall BSP circuit, the current still needs to reach the trigger current at room temperature to enter the blocking state.

[0047] Therefore, the above embodiment can maintain the stability of the circuit trigger current when the temperature changes.

[0048] Embodiment 4: This embodiment is another embodiment proposed on the basis of the second embodiment. Figure 8 As shown; specifically, the negative temperature coefficient device of the temperature compensation unit 2 in this embodiment is selected to be composed of an NTC thermistor. This embodiment utilizes the negative temperature characteristic of the resistance value of the NTC thermistor, and adjusts the voltage signal transmitted to the gate of the enhancement type NMOS tube Q4 / Q5 at different temperatures through the voltage division relationship between the resistor R5, the resistor R6 and the NTC thermistor. Its working process is similar to that of the third embodiment and will not be repeated.

[0049] Embodiment five: Embodiment In this embodiment, also on the basis of Embodiment 2, the structure of the temperature compensation unit is specifically described, including: a positive temperature coefficient device, one end of the positive temperature coefficient device is connected to one end of the current feedback field effect transistor Q3, and the other end of the positive temperature coefficient device is connected in series with a voltage divider resistor and a pull-up resistor; the other end of the current feedback field effect transistor Q3 is connected to the pull-up resistor, and the gate of the enhancement NMOS tube is connected to the connection point between the voltage divider resistor and the pull-up resistor.

[0050] Preferably, the positive temperature coefficient device is a positive temperature coefficient thermistor, or a field effect transistor on-resistance, or a metal film resistor, or a polysilicon resistor.

[0051] Specifically, Fig. 9 As shown, since the present invention shows a bidirectional surge protection circuit, the circuit designs in two directions are symmetrical and the same, so only one temperature compensation unit is introduced below.

[0052] Taking the first temperature compensation unit 21 as an example, a resistor R5, a resistor R6, and a positive temperature coefficient device are used to form the first temperature compensation unit 21, and the gate of the enhanced NMOS tube Q4 also receives a voltage signal from between the resistor R5 and the resistor R6. Among them, the resistor R5 is a voltage-dividing resistor, and the resistor R6 is a pull-up resistor of the gate of the enhanced NMOS tube Q4. Similarly, in the second temperature compensation unit 22, the resistor R7 is a voltage-dividing resistor, and the resistor R8 is a pull-up resistor of the gate of the second enhanced NMOS tube Q5. The positive temperature coefficient device can be a PTC thermistor, a field effect tube on-resistance, a metal film resistor, a polysilicon resistor, etc.

[0053] The specific temperature compensation principle is as follows: Case 1: At room temperature (25°C), the temperature compensation unit 2 collects voltage signals from the drain and source of the current feedback field effect tube Q3 and transmits them to the gate of the enhancement type NMOS tube Q4 / Q5. When the BSP current reaches the trigger current, the voltage transmitted by the temperature compensation unit 2 to the gate of the enhancement type NMOS tube Q4 / Q5 reaches its threshold voltage, and the enhancement type NMOS tube Q4 / Q5 turns on and controls the depletion type NMOS tube Q1 / Q2 to turn off, realizing the blocking characteristic. The trigger current at this temperature is the reference current.

[0054] Case 2: When the temperature rises, the on-resistance of the current feedback field effect tube Q3 increases (positive temperature characteristics), and the threshold voltage of the enhanced NMOS tube Q4 / Q5 decreases (negative temperature characteristics). At this time, although the voltage signal collected by the temperature compensation unit 2 from the drain and source of the current feedback field effect tube Q3 increases, due to the positive temperature characteristics of the positive temperature coefficient device, the voltage division of the voltage divider resistor R5 and the positive temperature coefficient device increases, and the voltage division of the pull-up resistor R6 decreases. The voltage signal transmitted by the temperature compensation unit 2 to the gate of the enhanced NMOS tube Q4 / Q5 decreases with the increase of temperature, and the decrease amplitude matches the decrease amplitude of the threshold voltage of the enhanced NMOS tube Q4 / Q5. Therefore, only when the BSP current still reaches the normal temperature reference current, the temperature compensation unit 2 will turn on the enhanced NMOS tube Q4 / Q5 and then control the depletion NMOS tube Q1 / Q2 to turn off, realizing the blocking characteristic. Therefore, although the temperature rises, the trigger current of the BSP circuit remains the same as that at normal temperature.

[0055] Case 3: When the temperature decreases, the on-resistance of the current feedback field effect tube Q3 decreases (positive temperature characteristics), and the threshold voltage of the enhanced NMOS tube Q4 / Q5 increases (negative temperature characteristics). At this time, although the voltage signal collected by the temperature compensation unit 2 from the drain and source of the current feedback field effect tube Q3 decreases, due to the positive temperature characteristics of the positive temperature coefficient device, the voltage division of the voltage divider resistor R5 and the positive temperature coefficient device as a whole decreases, and the voltage division of the pull-up resistor R6 increases. The voltage signal transmitted by the temperature compensation unit 2 to the gate of the enhanced NMOS tube Q4 / Q5 increases as the temperature decreases, and the increase amplitude matches the increase amplitude of the threshold voltage of the enhanced NMOS tube Q4 / Q5. Therefore, only when the BSP current still reaches the normal temperature reference current, the temperature compensation unit 2 will turn on the enhanced NMOS tube Q4 / Q5 and control the depletion NMOS tube Q1 / Q2 to turn off, realizing the blocking characteristic. Therefore, although the temperature decreases, the trigger current of the BSP circuit remains the same as that at normal temperature.

[0056] Embodiment six: On the basis of the second embodiment, the temperature compensation unit used includes: a positive temperature coefficient thermistor, and the two ends of the positive temperature coefficient device are respectively connected to a voltage divider resistor and a pull-up resistor; one end of the current feedback field effect tube Q3 is connected to the pull-up resistor, and the other end of the current feedback field effect tube is connected to the voltage divider resistor, and the gate of the enhanced NMOS tube Q4 / Q5 is connected to the connection point between the positive temperature coefficient thermistor and the pull-up resistor. Among them, the resistor R5 is a voltage divider resistor, and the resistor R6 is a pull-up resistor of the gate of the enhanced NMOS tube Q4. Similarly, in the second temperature compensation unit 22, the resistor R7 is a voltage divider resistor, and the resistor R8 is a pull-up resistor of the gate of the second enhanced NMOS tube Q5.

[0057] Specifically, the positive temperature coefficient device of the temperature compensation unit 2 in this embodiment is selected to be composed of a PTC thermistor. Different from the fourth embodiment, the gate of the enhanced NMOS tube Q4 in this embodiment only collects the voltage of the pull-up resistor R6; this embodiment uses a PTC thermistor to adjust the voltage division of the pull-up resistor R6, so Fig.10 As shown, the PTC thermistor is placed on the left side of the gate connection point of the enhanced NMOS tube Q4, rather than on the right side. This embodiment utilizes the positive temperature characteristic of the resistance value of the PTC thermistor, and adjusts the voltage signal transmitted to the gate of the enhanced NMOS Q4 at different temperatures through the voltage division relationship between the resistor R5, the resistor R6 and the PTC thermistor. Its working process is similar to that of the fifth embodiment and will not be repeated here.

[0058] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of this specification and illustrations should be included in the protection scope of the present invention.

Claims

1. A blocking type surge protector with temperature compensation, characterized in that: include: A bidirectional surge protection circuit, wherein the bidirectional connection terminals of the bidirectional surge protection circuit are connected in series between two protected devices; A temperature compensation unit, wherein the signal collection end of the temperature compensation unit is connected in parallel to the source and drain of the current feedback field effect tube of the bidirectional surge protection circuit, and the conduction control end of the temperature compensation unit is connected to the gate of the enhancement NMOS tube in the bidirectional surge protection circuit, and is used to adjust the collected voltage signal to match the threshold voltage of the enhancement NMOS tube according to the temperature change when a transient voltage is generated to achieve conduction, thereby controlling the depletion NMOS tube connected to the protected device to be turned off to achieve surge blocking protection.

2. The blocking type surge protector according to claim 1, characterized in that: The temperature compensation unit includes: a negative temperature coefficient device, one end of the negative temperature coefficient device is connected to one end of the current feedback field effect tube, and the other end of the negative temperature coefficient device is connected in series with a pull-up resistor and a voltage divider resistor in sequence; the other end of the current feedback field effect tube is connected to the voltage divider resistor, and the gate of the enhanced NMOS tube is connected to the connection point between the voltage divider resistor and the pull-up resistor.

3. The blocking type surge protector according to claim 2, characterized in that: The negative temperature coefficient device includes a plurality of diodes with anodes and cathodes connected in series in sequence; the cathode side of the diode is connected to one end of the current feedback field effect tube, and the anode side of the diode is connected to the pull-up resistor.

4. The blocking type surge protector according to claim 3, characterized in that: The number of diodes is 1-3.

5. The blocking type surge protector according to claim 2, characterized in that: The negative temperature coefficient device is a diode, or a transistor BE junction, or a transistor BC junction, or a negative temperature coefficient thermistor.

6. The blocking type surge protector according to claim 1, characterized in that: The temperature compensation unit includes: a positive temperature coefficient device, one end of the positive temperature coefficient device is connected to one end of the current feedback field effect tube, and the other end of the positive temperature coefficient device is connected in series with a voltage divider resistor and a pull-up resistor in sequence; the other end of the current feedback field effect tube is connected to the pull-up resistor, and the gate of the enhanced NMOS tube is connected to the connection point between the voltage divider resistor and the pull-up resistor.

7. The blocking type surge protector according to claim 6, characterized in that: The positive temperature coefficient device is a positive temperature coefficient thermistor, or a field effect tube on-resistance, or a metal film resistor, or a polysilicon resistor.

8. The blocking type surge protector according to claim 1, characterized in that: The temperature compensation unit comprises: a positive temperature coefficient thermistor, wherein two ends of the positive temperature coefficient device are respectively connected to a voltage divider resistor and a pull-up resistor; one end of the current feedback field effect transistor is connected to the pull-up resistor, and the other end of the current feedback field effect transistor is connected to the voltage divider resistor, and the gate of the enhanced NMOS tube is connected to the connection point between the positive temperature coefficient thermistor and the pull-up resistor.

9. The blocking type surge protector according to claim 1, characterized in that: The depletion-type NMOS tube in the bidirectional surge protection circuit includes a first depletion-type NMOS tube and a second depletion-type NMOS tube; the drain and source of the current feedback field effect tube are respectively connected to the source of the first depletion-type NMOS tube and the source of the second depletion-type NMOS tube, the gate of the current feedback field effect tube is connected to the cathode of the first diode and the cathode of the second diode, a first resistor is connected in series between the anode of the first diode and the drain of the first depletion-type NMOS tube, and a second resistor is connected in series between the anode of the second diode and the drain of the second depletion-type NMOS tube; the drains of the first depletion-type NMOS tube and the second depletion-type NMOS tube are respectively connected to a protected device.

10. The blocking type surge protector according to claim 2, characterized in that: The enhanced NMOS tube in the bidirectional surge protection circuit includes a first enhanced NMOS tube and a second enhanced NMOS tube, and the temperature compensation unit includes a first temperature compensation unit and a second temperature compensation unit; the source of the first enhanced NMOS tube and the source of the second enhanced NMOS tube are respectively connected to the drain and source of the current feedback field effect tube, the gate of the first enhanced NMOS tube is connected to the conduction control end of the first temperature compensation unit, and the gate of the second enhanced NMOS tube is connected to the conduction control end of the second temperature compensation unit; the drain of the first enhanced NMOS tube is connected to the gate of the first depletion NMOS tube and one end of the third resistor, and the other end of the third resistor is connected to the source of the current feedback field effect tube; The drain of the second enhancement-mode NMOS tube is connected to the gate of the second depletion-mode NMOS tube and one end of a fourth resistor, and the other end of the fourth resistor is connected to the drain of the current feedback field effect tube.

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