A blocking type surge protector with temperature compensation

Abstract

The present invention provides a blocking type surge protector with temperature compensation, which relates to the technical field of circuit protection and includes: a bidirectional surge protection circuit is connected in series between two protected devices; the temperature compensation unit adjusts the collected voltage signal according to the temperature change to match the threshold voltage of the enhancement type NMOS transistor when a transient voltage is generated, so as to achieve conduction, and then controls the depletion type NMOS transistor connected to the protected device to turn off to achieve surge blocking protection. The beneficial effect is that by introducing the temperature compensation unit, the surge protector of the present invention can adjust the voltage signal according to the temperature change to match the threshold voltage of the enhancement type NMOS transistor, so as to maintain the stability of the trigger current. Even at extreme temperatures, the trigger current can be maintained near the normal temperature reference current, and a stable trigger current can be maintained at different temperatures, greatly reducing the fluctuation caused by temperature change, thereby ensuring the reliability and consistency of the surge protection effect.

Description

Technical Field

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

[0002] With the popularization of new energy vehicles and the development of vehicle intelligence, electronic devices are widely used in automotive internal control systems, auxiliary and comfort systems, safety systems, etc. In the changing driving environment of vehicles, these electronic devices are prone to being affected by surge impacts. For example, the instantaneous increase in battery voltage when starting the vehicle engine may cause high-power surges. To effectively protect against these surge impacts, a blocking type surge protector (Block Surge Protector, abbreviated as BSP) has emerged.

[0003] The BSP is connected in series to the protected unit. When a transient voltage arrives, it can enter the blocking state in an extremely short time, completely blocking the influence of overvoltage on the protected unit, thereby greatly enhancing the safety of automotive transient voltage protection. Currently, there are various design schemes for BSP circuits in the market. These schemes usually use semiconductor devices such as depletion-type NMOS, current-feedback field-effect transistors, or enhancement-type NMOS to construct the basic framework of the blocking type circuit, and achieve surge blocking protection by controlling the switching states of these devices.

[0004] However, the existing BSP circuit technology has obvious defects, mainly reflected in the temperature stability of the trigger current. Specifically:

[0005] 1. The trigger current fluctuates with temperature:

[0006] In the prior art, the trigger current of the BSP circuit is often affected by temperature. Due to the specific temperature characteristics of the semiconductor devices (such as current-feedback field-effect transistors, enhancement-type NMOS, etc.) used in the circuit, when the ambient temperature changes, the electrical parameters (such as on-resistance, threshold voltage, etc.) of these devices will also change accordingly, resulting in fluctuations in the trigger current. Specifically, when the temperature rises, the on-resistance of some devices may increase, or the threshold voltage may decrease, resulting in a decrease in the trigger current; conversely, when the temperature drops, 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.

[0007] 2. Affects the reliability and consistency of surge protection:

[0008] Fluctuations in the trigger current lead to inconsistent surge protection effects of the BSP circuit at different temperatures. In high or low temperature environments, the trigger current may deviate from the designed value, causing the BSP circuit to malfunction or significantly reducing its protection effect. This problem of poor temperature stability not only affects the reliability of the BSP circuit but also reduces its applicability in application scenarios such as automobiles where the ambient temperature changes greatly.

[0009] 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 surge protection of automotive electronic devices. Therefore, developing a BSP circuit technology with better temperature stability is of great significance for improving the surge protection ability of automotive electronic devices. Summary of the Invention

[0010] In view of the problems existing in the prior art, the present invention provides a blocking type surge protector with temperature compensation, including: a bidirectional surge protection circuit, 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, the signal acquisition end of the temperature compensation unit is connected in parallel between 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 transistor in the bidirectional surge protection circuit, and is used to adjust the collected voltage signal to match the threshold voltage of the enhancement type NMOS transistor according to the temperature change when a transient voltage is generated to achieve conduction, and then control the depletion type NMOS transistor connected to the protected device to turn off to achieve surge blocking protection.

[0011] 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 transistor, and the other end of the negative temperature coefficient device is sequentially connected in series with a pull-up resistor and a voltage dividing resistor; the other end of the current feedback field effect transistor is connected to the voltage dividing resistor, and the gate of the enhancement type NMOS transistor is connected to the connection point between the voltage dividing resistor and the pull-up resistor.

[0012] Preferably, 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 transistor, and the cathode side of the diode is connected to the pull-up resistor.

[0013] Preferably, the number of diodes is 1 - 3.

[0014] Preferably, the negative temperature coefficient device is a diode, or the BE junction of a triode, or the BC junction of a triode, or a negative temperature coefficient thermistor.

[0015] 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 transistor, and the other end of the positive temperature coefficient device is sequentially connected in series with a voltage dividing resistor and a pull-up resistor; the other end of the current feedback field effect transistor is connected to the pull-up resistor, and the gate of the enhancement type NMOS transistor is connected to the connection point between the voltage dividing resistor and the pull-up resistor.

[0016] 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.

[0017] Preferably, the temperature compensation unit includes: a positive temperature coefficient thermistor, both ends of the positive temperature coefficient device are respectively connected to a voltage dividing resistor and a pull-up resistor; one end of the current feedback field effect transistor is connected to the pull-up resistor, the other end of the current feedback field effect transistor is connected to the voltage dividing resistor, and the gate of the enhancement type NMOS transistor is connected to the connection point between the positive temperature coefficient thermistor and the pull-up resistor.

[0018] Preferably, the depletion type NMOS transistors in the bidirectional surge protection circuit include a first depletion type NMOS transistor and a second depletion type NMOS transistor; the drain and source of the current feedback field effect transistor are respectively connected to the sources of the first depletion type NMOS transistor and the second depletion type NMOS transistor, the gate of the current feedback field effect transistor is connected to the cathodes of a first diode and a 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 transistor, and a second resistor is connected in series between the anode of the second diode and the drain of the second depletion type NMOS transistor; the drains of the first depletion type NMOS transistor and the second depletion type NMOS transistor are respectively connected to a device to be protected.

[0019] Preferably, the enhancement-mode NMOS transistors in the bidirectional surge protection circuit include a first enhancement-mode NMOS transistor and a second enhancement-mode NMOS transistor, and the temperature compensation unit includes a first temperature compensation unit and a second temperature compensation unit; the source electrodes of the first enhancement-mode NMOS transistor and the second enhancement-mode NMOS transistor are respectively connected to the drain electrode and the source electrode of the current feedback field-effect transistor, the gate electrode of the first enhancement-mode NMOS transistor is connected to the conduction control end of the first temperature compensation unit, and the gate electrode of the second enhancement-mode NMOS transistor is connected to the conduction control end of the second temperature compensation unit; the drain electrode of the first enhancement-mode NMOS transistor is connected to the gate electrode of the first depletion-mode NMOS transistor and one end of a third resistor, and the other end of the third resistor is connected to the source electrode of the current feedback field-effect transistor; the drain electrode of the second enhancement-mode NMOS transistor is connected to the gate electrode of the second depletion-mode NMOS transistor and one end of a fourth resistor, and the other end of the fourth resistor is connected to the drain electrode of the current feedback field-effect transistor.

[0020] 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 the temperature change to match the threshold voltage of the enhancement-mode NMOS transistor, thereby maintaining the stability of the trigger current. Even under extreme temperatures, the trigger current can remain near the normal temperature reference current, and a stable trigger current can be maintained at different temperatures, greatly reducing the fluctuations caused by temperature changes, thereby ensuring the reliability and consistency of the surge protection effect. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of the existing first BSP circuit;

[0022] Figure 2 It is a schematic structural diagram of the existing second BSP circuit;

[0023] Figure 3 It is a trigger current-temperature characteristic diagram of the existing first BSP circuit and the existing second BSP circuit;

[0024] Figure 4 It is a schematic structural diagram of the blocking-type surge protector with temperature compensation in the preferred embodiment of the present invention;

[0025] Figure 5 It is a comparison diagram of the trigger current-temperature characteristics of the present invention and the existing circuit;

[0026] Figure 6 It is a schematic structural diagram of the blocking-type surge protector in the second embodiment of the present invention;

[0027] Figure 7 It is a schematic structural diagram of the blocking-type surge protector in the third embodiment of the present invention;

[0028] Figure 8 Schematic diagram of the blocking type surge protector in Embodiment 4 of the present invention;

[0029] Figure 9 Schematic diagram of the blocking type surge protector in Embodiment 5 of the present invention;

[0030] Figure 10 Schematic diagram of the blocking type surge protector in Embodiment 6 of the present invention. Detailed implementation manners

[0031] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The present invention is not limited to this embodiment, and other embodiments also belong to the scope of the present invention as long as they conform to the gist of the present invention.

[0032] In a preferred embodiment of the present invention, in view of the above problems existing in the prior art, a blocking type surge protector with temperature compensation is provided.

[0033] Embodiment 1:

[0034] In the blocking type surge protector with temperature compensation, as Figure 4 shown, it includes: a bidirectional surge protection circuit 1, the bidirectional connection terminals of the bidirectional surge protection circuit 1 are connected in series between two protected devices 100; a temperature compensation unit 2, the signal acquisition terminal of the temperature compensation unit 2 is connected in parallel between the source and drain of the current feedback field effect transistor Q3 of the bidirectional surge protection circuit 1, and the conduction control terminal of the temperature compensation unit 2 is connected to the gates of the enhancement type NMOS transistors 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 transistor according to the temperature change when a transient voltage is generated to achieve conduction, and then control the depletion type NMOS transistor connected to the protected device to turn off to achieve surge blocking protection.

[0035] More specifically, the depletion type NMOS transistors in the bidirectional surge protection circuit 1 include a first depletion type NMOS transistor Q1 and a second depletion type NMOS transistor Q2; the drain and source of the current feedback field effect transistor Q3 are respectively connected to the sources of the first depletion type NMOS transistor Q1 and the second depletion type NMOS transistor Q2, the gate of the current feedback field effect transistor Q3 is connected to the cathodes of the first diode D1 and 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 transistor 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 transistor Q2; the drains of the first depletion type NMOS transistor Q1 and the second depletion type NMOS transistor Q2 are respectively connected to a protected device 100.

[0036] More specifically, the enhancement-mode NMOS transistors in the bidirectional surge protection circuit include a first enhancement-mode NMOS transistor Q4 and a second enhancement-mode 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 electrodes of the first enhancement-mode NMOS transistor Q4 and the second enhancement-mode NMOS transistor Q5 are respectively connected to the drain electrode and the source electrode of the current feedback field-effect transistor Q3 (since it is a bidirectional surge protection circuit, it can also be connected by reversing the connection directions of the drain electrode and the source electrode of the current feedback field-effect transistor Q3), the gate electrode of the first enhancement-mode NMOS transistor Q4 is connected to the conduction control terminal of the first temperature compensation unit 21, and the gate electrode of the second enhancement-mode NMOS transistor Q5 is connected to the conduction control terminal of the second temperature compensation unit 22; the drain electrode of the first enhancement-mode NMOS transistor Q4 is connected to the gate electrode of the first depletion-mode NMOS transistor Q1 and one end of the third resistor R3, and the other end of the third resistor R3 is connected to the source electrode of the current feedback field-effect transistor Q3; the drain electrode of the second enhancement-mode NMOS transistor Q5 is connected to the gate electrode of the second depletion-mode NMOS transistor Q2 and one end of the fourth resistor R4, and the other end of the fourth resistor R4 is connected to the drain electrode of the current feedback field-effect transistor Q3.

[0037] 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-mode NMOS and current feedback field-effect transistors. Through the control of the gate electrode of the depletion-mode NMOS by the current feedback field-effect transistor, when the line current reaches the trigger current, the BSP circuit changes from conduction to cutoff, thereby realizing the blocking protection of the surge. The circuit is as Figure 1 shown.

[0038] There is also a BSP circuit containing enhancement-mode NMOS devices in the prior art. The main content is to utilize the characteristic that the threshold voltage of the enhancement-mode NMOS is relatively stable, and control the switching state of the gate circuit of the depletion-mode NMOS through it, so as to solve the problem of discrete trigger circuits of the BSP circuit caused by the unstable threshold voltage due to the inherent characteristics of the depletion-mode NMOS process manufacturing. The circuit is as Figure 2 shown.

[0039] However, when considering application scenarios where the ambient temperature, such as in automobiles, will change significantly, the above-mentioned existing circuits have the problem that the trigger current fluctuates with temperature changes.

[0040] 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 transistor, its on-resistance gradually increases, resulting in a decrease in the trigger current of the overall BSP circuit; conversely, when the temperature gradually decreases, the trigger current increases; the trigger current of this BSP circuit exhibits a negative temperature characteristic.

[0041] For the second type of existing circuit, when the temperature gradually increases from room temperature (25°C), since the threshold voltage of the enhancement-mode NMOS responsible for controlling the gate state of the depletion-mode NMOS has a negative temperature characteristic, its threshold voltage decreases as the temperature increases. As a result, when the BSP passes through a small trigger current, the enhancement-mode NMOS turns on, causing the gate of the depletion-mode NMOS to receive a potential signal and change to the blocking state. Eventually, it is manifested that the trigger current of the overall BSP circuit decreases rapidly as the temperature increases. Conversely, when the temperature gradually decreases, the threshold voltage of the enhancement-mode NMOS increases accordingly, and the trigger current increases rapidly. The trigger current of this BSP circuit exhibits a more obvious negative temperature characteristic.

[0042] Figure 3 It is the percentage change of the trigger current of the above existing circuit within the temperature range of -50°C to 100°C compared to that at room temperature of 25°C. The change range of the trigger current of the first type of existing circuit is 78% - 133%. The change range of the trigger current of the second type of existing circuit is 67% - 152%. It can be seen that due to the added enhancement-mode NMOS circuit in the second type of existing circuit, the temperature stability of its trigger current deteriorates further compared to the first type of existing circuit.

[0043] In this embodiment of the present invention, a blocking type surge protector with temperature compensation is designed. The schematic diagram is as Figure 4 shown. A temperature compensation unit 2 is added to the BSP circuit. The temperature compensation unit 2 is connected in parallel across the drain and source of the current feedback field effect transistor Q3 (using a P-type JFET), and is used to capture the potential signal and transmit the processed potential signal from within itself to the gates of the enhancement-mode NMOS transistors Q4 / Q5 to control the switching state of the gates of the enhancement-mode NMOS transistors Q4 / Q5.

[0044] The potential transmitted by the temperature compensation unit 2 to the gates of the enhancement-mode NMOS transistors Q4 / Q5 has a negative temperature characteristic, which is matched with the negative temperature characteristic of the threshold voltage of the gates of the enhancement-mode NMOS transistors 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:

[0045] Case 1: At room temperature (25°C), the temperature compensation unit 2 collects the voltage signal from both ends of the drain and source of the current feedback field effect transistor Q3 and transmits it to the gates of the enhancement-mode NMOS transistors Q4 / Q5. When the BSP current reaches the trigger current, the voltage transmitted by the temperature compensation unit 2 to the gates of the enhancement-mode NMOS transistors Q4 / Q5 reaches its threshold voltage, and the enhancement-mode NMOS transistors Q4 / Q5 turn on and control the depletion-mode NMOS transistors Q1 / Q2 to turn off, achieving the blocking characteristic. The trigger current at this temperature is the reference current.

[0046] Case 2: When the temperature rises, the on-resistance of the current feedback FET Q3 increases accordingly (positive temperature characteristic), and the threshold voltages of the enhancement-mode NMOS transistors Q4 / Q5 decrease accordingly (negative temperature characteristic). At this time, although the voltage signal collected by the temperature compensation unit 2 from both ends of the drain and source of the current feedback FET Q3 increases, due to its own negative temperature characteristic, the voltage signal transmitted by the temperature compensation unit 2 to the gates of the enhancement-mode NMOS transistors Q4 / Q5 decreases instead as the temperature rises, and the decreasing amplitude matches the decreasing amplitude of the threshold voltages of the enhancement-mode NMOS transistors Q4 / Q5. Therefore, only when the BSP current still reaches the normal temperature reference current will the temperature compensation unit 2 turn on the enhancement-mode NMOS transistors Q4 / Q5 and then control the depletion-mode NMOS transistors Q1 / Q2 to turn off, achieving the blocking characteristic. Therefore, although the temperature rises, the trigger current of the BSP circuit still remains the same as at normal temperature.

[0047] Case 3: When the temperature drops, the on-resistance of the current feedback FET Q3 decreases accordingly (positive temperature characteristic), and the threshold voltages of the enhancement-mode NMOS transistors Q4 / Q5 increase accordingly (negative temperature characteristic). At this time, although the voltage signal collected by the temperature compensation unit 2 from both ends of the drain and source of the current feedback FET Q3 decreases, due to its own negative temperature characteristic, the voltage signal transmitted by the temperature compensation unit 2 to the gates of the enhancement-mode NMOS transistors Q4 / Q5 increases instead as the temperature drops, and the increasing amplitude matches the increasing amplitude of the threshold voltages of the enhancement-mode NMOS transistors Q4 / Q5. Therefore, only when the BSP current still reaches the normal temperature reference current will the temperature compensation unit 2 turn on the enhancement-mode NMOS transistors Q4 / Q5 and control the depletion-mode NMOS transistors Q1 / Q2 to turn off, achieving the blocking characteristic. Therefore, although the temperature drops, the trigger current of the BSP circuit still remains the same as at normal temperature.

[0048] As Figure 5 shown, it is the percentage fluctuation of the trigger current relative to the normal temperature (25°C) reference trigger current for the first existing circuit, the second existing circuit, and the present invention at an ambient temperature of -50°C to 100°C. 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%, while the variation range of the trigger current of the circuit in the present invention is only 96% to 109%, and the size of its fluctuation range is reduced. It can be seen that the circuit of the present invention can achieve excellent temperature stability.

[0049] In summary, it can be seen that the blocking type surge protector with temperature compensation of the present invention has the following three advantages:

[0050] 1. Compared with the first existing circuit and the second existing circuit, the surge protection effect of maintaining the blocking characteristic remains unchanged;

[0051] 2. Compared with the second existing circuit, the enhanced NMOS circuit is retained to solve the problem that the trigger current of the BSP circuit is discrete due to the unstable threshold voltage of the depletion NMOS transistor.

[0052] 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.

[0053] Embodiment 2:

[0054] Based on Embodiment 1, this 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 transistor Q3, and the other end of the negative temperature coefficient device is sequentially connected in series with a pull-up resistor and a voltage dividing resistor; the other end of the current feedback field effect transistor is connected to the voltage dividing resistor, and the gate of the enhanced NMOS transistor is connected to the connection point between the voltage dividing resistor and the pull-up resistor.

[0055] Specifically, as Figure 6 shown, since the bidirectional surge protection circuit shown in the present invention has symmetric and identical circuit designs in both directions, only one temperature compensation unit will be introduced below.

[0056] Taking the first temperature compensation unit 21 as an example, the first temperature compensation unit 21 is composed of a resistor R5, a resistor R6, and a negative temperature coefficient device, and the gate of the enhanced NMOS transistor 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 for the gate of the enhanced NMOS transistor 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 for the gate of the second enhanced NMOS transistor Q5.

[0057] The specific temperature compensation principle is as follows:

[0058] Case 1: At room temperature (25°C), the temperature compensation unit 2 collects a voltage signal from both ends of the drain and source of the current feedback field effect transistor Q3 and transmits it to the gate of the enhanced NMOS transistor Q4 / Q5. When the BSP current reaches the trigger current, the voltage transmitted by the temperature compensation unit 2 to the gate of the enhanced NMOS transistor Q4 / Q5 reaches its threshold voltage, and the enhanced NMOS transistor Q4 / Q5 turns on and controls the depletion NMOS transistor Q1 / Q2 to turn off, realizing the blocking characteristic. The trigger current at this temperature is the reference current.

[0059] Case 2: When the temperature rises, the on-resistance of the current feedback field-effect transistor Q3 increases accordingly (positive temperature characteristic), and the threshold voltages of the enhancement-mode NMOS transistors Q4 / Q5 decrease accordingly (negative temperature characteristic). At this time, although the voltage signal collected by the temperature compensation unit 2 from both ends of the drain and source of the current feedback field-effect transistor Q3 increases, due to the negative temperature characteristics of the negative temperature coefficient devices therein, the overall voltage division of the pull-up resistor R6 and the negative temperature coefficient devices decreases, and the voltage signal transmitted by the temperature compensation unit 2 to the gates of the enhancement-mode NMOS transistors Q4 / Q5 decreases instead as the temperature rises, and the decreasing amplitude matches the decreasing amplitude of the threshold voltages of the enhancement-mode NMOS transistors Q4 / Q5. Therefore, only when the BSP current still reaches the normal temperature reference current, will the temperature compensation unit 2 turn on the enhancement-mode NMOS transistors Q4 / Q5 and then control the depletion-mode NMOS transistors Q1 / Q2 to turn off, achieving the blocking characteristic. Therefore, although the temperature rises, the trigger current of the BSP circuit still remains the same as at normal temperature.

[0060] Case 3: When the temperature drops, the on-resistance of the current feedback field-effect transistor Q3 decreases accordingly (positive temperature characteristic), and the threshold voltages of the enhancement-mode NMOS transistors Q4 / Q5 increase accordingly (negative temperature characteristic). At this time, although the voltage signal collected by the temperature compensation unit 2 from both ends of the drain and source of the current feedback field-effect transistor Q3 decreases, due to the negative temperature characteristics of the negative temperature coefficient devices therein, the overall voltage division of the pull-up resistor R6 and the negative temperature coefficient devices increases, and the voltage signal transmitted by the temperature compensation unit 2 to the gates of the enhancement-mode NMOS transistors Q4 / Q5 increases instead as the temperature drops, and the increasing amplitude matches the increasing amplitude of the threshold voltages of the enhancement-mode NMOS transistors Q4 / Q5. Therefore, only when the BSP current still reaches the normal temperature reference current, will the temperature compensation unit 2 turn on the enhancement-mode NMOS transistors Q4 / Q5 and control the depletion-mode NMOS transistors Q1 / Q2 to turn off, achieving the blocking characteristic. Therefore, although the temperature drops, the trigger current of the BSP circuit still remains the same as at normal temperature.

[0061] Embodiment 3:

[0062] Based on Embodiment 2, this embodiment specifically describes the structure in the negative temperature coefficient device. The negative temperature coefficient device is preferably a diode, or the BE junction of a triode, or the BC junction of a triode, or a negative temperature coefficient thermistor.

[0063] In this embodiment, taking a diode as an example, as Figure 7 shown, in the negative temperature coefficient device of the first temperature compensation unit 21, it includes a plurality of diodes D3 and D4 with anodes and cathodes 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.

[0064] 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 diode here can be one or more in series, and preferably the number of diodes in series is 1 to 3. This embodiment utilizes the negative temperature characteristic of the forward conduction voltage of the diode, and adjusts the voltage signal transmitted to the gate of the first enhanced NMOS transistor Q4 at different temperatures through the voltage division relationship of the resistors R5, R6 and the forward voltage drops of the diode strings D3 and D4.

[0065] Specifically, when the temperature rises compared to normal temperature, the forward conduction voltage drops of the diodes D3 and D4 decrease, and the threshold voltage of the enhanced NMOS transistor 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 transistor Q4 decreases, and this part of the voltage decrease offsets the decrease in the threshold voltage of the enhanced NMOS transistor Q4. Therefore, for the overall BSP circuit, the trigger current at normal temperature still needs to be reached to enter the blocking state.

[0066] When the temperature drops compared to normal temperature, the forward conduction voltage drops of the diodes D3 and D4 increase, and the threshold voltage of the enhanced NMOS transistor Q4 increases. At this time, the overall voltage division of the resistor R6 and the diodes D3 and D4 increases, and the voltage transmitted to the gate of the enhanced NMOS transistor Q4 increases, and this part of the voltage increase offsets the increase in the threshold voltage of the enhanced NMOS transistor Q4. Therefore, for the overall BSP circuit, the trigger current at normal temperature still needs to be reached to enter the blocking state.

[0067] Therefore, the above embodiment can maintain the stability of the circuit trigger current when the temperature changes.

[0068] Embodiment 4:

[0069] This embodiment is another embodiment proposed on the basis of Embodiment 2, as Figure 8 shown; specifically, in this embodiment, the negative temperature coefficient device of the temperature compensation unit 2 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 gates of the enhanced NMOS transistors Q4 / Q5 at different temperatures through the voltage division relationship of the resistors R5, R6 and the NTC thermistor. Its working process is similar to that of Embodiment 3 and will not be elaborated here.

[0070] Embodiment 5:

[0071] Embodiment In this embodiment, 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 sequentially connected in series with a voltage dividing 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 type NMOS transistor is connected to the connection point between the voltage dividing resistor and the pull-up resistor.

[0072] 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.

[0073] Specifically, as Figure 9 shown, since the bidirectional surge protection circuit shown in the present invention has symmetric and identical circuit designs in both directions, only one temperature compensation unit will be introduced below.

[0074] Taking the first temperature compensation unit 21 as an example, the first temperature compensation unit 21 is composed of a resistor R5, a resistor R6, and a positive temperature coefficient device, and the gate of the enhancement type NMOS transistor 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 for the gate of the enhancement type NMOS transistor 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 for the gate of the second enhancement type NMOS transistor Q5. The positive temperature coefficient device can be a PTC thermistor, a field effect transistor on-resistance, a metal film resistor, a polysilicon resistor, etc.

[0075] The specific temperature compensation principle is as follows:

[0076] Case 1: At room temperature (25°C), the temperature compensation unit 2 collects a voltage signal from both ends of the drain and source of the current feedback field effect transistor Q3 and transmits it to the gates of the enhancement type NMOS transistors Q4 / Q5. When the BSP current reaches the trigger current, the voltage transmitted by the temperature compensation unit 2 to the gates of the enhancement type NMOS transistors Q4 / Q5 reaches their threshold voltages, and the enhancement type NMOS transistors Q4 / Q5 are turned on and control the depletion type NMOS transistors Q1 / Q2 to turn off, achieving the blocking characteristic. The trigger current at this temperature is the reference current.

[0077] Case 2: When the temperature rises, the on-resistance of the current feedback FET Q3 increases accordingly (positive temperature characteristic), and the threshold voltages of the enhancement-mode NMOS transistors Q4 / Q5 decrease accordingly (negative temperature characteristic). At this time, although the voltage signal collected by the temperature compensation unit 2 from both ends of the drain and source of the current feedback FET Q3 increases, due to the positive temperature characteristic of the positive temperature coefficient device therein, the overall voltage division of the voltage dividing resistor R5 and the positive temperature coefficient device increases, and the voltage division of the pull-up resistor R6 decreases. Instead, the voltage signal transmitted by the temperature compensation unit 2 to the gates of the enhancement-mode NMOS transistors Q4 / Q5 decreases with the increase in temperature, and the decrease amplitude matches the decrease amplitude of the threshold voltages of the enhancement-mode NMOS transistors Q4 / Q5. Therefore, only when the BSP current still reaches the normal temperature reference current, the temperature compensation unit 2 will turn on the enhancement-mode NMOS transistors Q4 / Q5 and then control the depletion-mode NMOS transistors Q1 / Q2 to turn off, achieving the blocking characteristic. Therefore, although the temperature rises, the BSP circuit trigger current still remains the same as that at normal temperature.

[0078] Case 3: When the temperature drops, the on-resistance of the current feedback FET Q3 decreases accordingly (positive temperature characteristic), and the threshold voltages of the enhancement-mode NMOS transistors Q4 / Q5 increase accordingly (negative temperature characteristic). At this time, although the voltage signal collected by the temperature compensation unit 2 from both ends of the drain and source of the current feedback FET Q3 decreases, due to the positive temperature characteristic of the positive temperature coefficient device therein, the overall voltage division of the voltage dividing resistor R5 and the positive temperature coefficient device decreases, and the voltage division of the pull-up resistor R6 increases. Instead, the voltage signal transmitted by the temperature compensation unit 2 to the gates of the enhancement-mode NMOS transistors Q4 / Q5 increases with the decrease in temperature, and the increase amplitude matches the increase amplitude of the threshold voltages of the enhancement-mode NMOS transistors Q4 / Q5. Therefore, only when the BSP current still reaches the normal temperature reference current, the temperature compensation unit 2 will turn on the enhancement-mode NMOS transistors Q4 / Q5 and control the depletion-mode NMOS transistors Q1 / Q2 to turn off, achieving the blocking characteristic. Therefore, although the temperature drops, the BSP circuit trigger current still remains the same as that at normal temperature.

[0079] Embodiment 6:

[0080] Based on Embodiment 2, the temperature compensation unit adopted includes: a positive temperature coefficient thermistor, with a voltage dividing resistor and a pull-up resistor connected to both ends of the positive temperature coefficient device respectively; one end of the current feedback FET Q3 is connected to the pull-up resistor, the other end of the current feedback FET is connected to the voltage dividing resistor, and the gates of the enhancement-mode NMOS transistors Q4 / Q5 are connected to the connection point between the positive temperature coefficient thermistor and the pull-up resistor. Among them, the resistor R5 is the voltage dividing resistor, and the resistor R6 is the pull-up resistor for the gate of the enhancement-mode NMOS transistor Q4. Similarly, in the second temperature compensation unit 22, the resistor R7 is the voltage dividing resistor, and the resistor R8 is the pull-up resistor for the gate of the second enhancement-mode NMOS transistor Q5.

[0081] Specifically, in this embodiment, the positive temperature coefficient device of the temperature compensation unit 2 is selected to be composed of a PTC thermistor. Different from Embodiment Four, the gate of the enhanced NMOS transistor Q4 in this embodiment only collects the voltage of the pull-up resistor R6; this embodiment uses the PTC thermistor to adjust the voltage division of the pull-up resistor R6. Therefore, as Figure 10 shown, the PTC thermistor is placed on the left side of the connection point of the gate of the enhanced NMOS transistor Q4, rather than on the right side. This embodiment utilizes the positive temperature characteristic of the resistance value of the PTC thermistor, and through the voltage division relationship of the resistor R5, the resistor R6, and the PTC thermistor, adjusts the voltage signal transmitted to the gate of the enhanced NMOS Q4 at different temperatures. Its working process is similar to that of Embodiment Five and will not be elaborated here.

[0082] The above are only the preferred embodiments of the present invention, and do not limit the implementation manners and protection scope of the present invention. For those skilled in the art, it should be realized that all equivalent replacements and obvious changes made by using the content of this specification and the drawings 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 comprises: 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 dividing resistor, and the gate of the enhancement mode NMOS tube is connected to the connection point between the voltage dividing resistor and the pull-up resistor.

3. The blocking type surge protector according to claim 2, characterized in that: The negative temperature coefficient device comprises 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 comprises: A positive temperature coefficient device, one end of which is connected to one end of the current feedback field effect tube, and the other end of which 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 enhancement mode NMOS tube is connected to the connection point between the voltage dividing 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 thermistor are respectively connected to a voltage divider resistor and a pull-up resistor; One end of the current feedback field effect tube is connected to the pull-up 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 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 transistor are connected to the source of the first depletion-type NMOS transistor and the source of the second depletion-type NMOS transistor respectively, the gate of the current feedback field effect transistor 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 transistor, and a second resistor is connected in series between the anode of the second diode and the drain of the second depletion-type NMOS transistor; 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 9, characterized in that: The enhanced NMOS transistor in the bidirectional surge protection circuit includes a first enhanced NMOS transistor and a second enhanced NMOS transistor, and the temperature compensation unit includes a first temperature compensation unit and a second temperature compensation unit; The source of the first enhancement mode NMOS tube and the source of the second enhancement mode NMOS tube are respectively connected to the drain and source of the current feedback field effect tube, the gate of the first enhancement mode NMOS tube is connected to the conduction control terminal of the first temperature compensation unit, and the gate of the second enhancement mode NMOS tube is connected to the conduction control terminal of the second temperature compensation unit; The drain of the first enhancement-mode NMOS transistor is connected to the gate of the first depletion-mode NMOS transistor and one end of a third resistor, and the other end of the third resistor is connected to the source of the current feedback field effect transistor; 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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