阅读说明：本技术 一种保护电路及电路保护装置 (Protection circuit and circuit protection device ) 是由 蔡锦波 沈能文 于 2021-08-27 设计创作，主要内容包括：本发明实施例公开了一种保护电路及电路保护装置。一种保护电路,包括：控制单元、过压保护单元和过流保护单元；控制单元为第一MOS管,第一MOS管的源极连接低电平,第一MOS管的栅极连接第一电阻后接入高电平,第一MOS管的漏极连接被保护的用电负载,用于控制用电负载的接通与关断；过压保护单元由第一稳压二极管与第二电阻串联后连接至三极管的基极构成；过流保护单元由可控硅、第三电阻和第四电阻组成分流电路。解决保险丝功能单一、响应慢、响应不精确和不可恢复的问题,实现过压、过流过温及短路保护功能,提高响应速度和精确度的效果。(The embodiment of the invention discloses a protection circuit and a circuit protection device. A protection circuit, comprising: the overvoltage protection device comprises a control unit, an overvoltage protection unit and an overcurrent protection unit; the control unit is a first MOS tube, the source electrode of the first MOS tube is connected with a low level, the grid electrode of the first MOS tube is connected with a first resistor and then is connected with a high level, and the drain electrode of the first MOS tube is connected with a protected electric load and is used for controlling the connection and disconnection of the electric load; the overvoltage protection unit is formed by connecting a first voltage-stabilizing diode and a second resistor in series and then connecting the first voltage-stabilizing diode and the second resistor to the base of the triode; the overcurrent protection unit consists of a thyristor, a third resistor and a fourth resistor to form a shunt circuit. The fuse solves the problems of single function, slow response, inaccurate response and unrecoverability of the fuse, realizes the functions of overvoltage, overcurrent, overtemperature and short-circuit protection, and improves the response speed and the accuracy.)

1. A protection circuit, comprising: the overvoltage protection device comprises a control unit, an overvoltage protection unit and an overcurrent protection unit;

the control unit is a first MOS tube, the source electrode of the first MOS tube is connected with a low level, the grid electrode of the first MOS tube is connected with a first resistor and then is connected with a high level, and the drain electrode of the first MOS tube is connected with a protected electric load and is used for controlling the connection and disconnection of the electric load;

the overvoltage protection unit is formed by connecting a first voltage-stabilizing diode and a second resistor in series and then connecting the first voltage-stabilizing diode and the second resistor to the base electrode of the triode, and is used for short-circuiting the first MOS tube to protect the power load when the voltage of the protection circuit is greater than the sum of the saturation voltages of the first voltage-stabilizing diode and the triode;

the overcurrent protection unit is composed of a thyristor, a third resistor and a fourth resistor to form a shunt circuit and is used for triggering the thyristor to be conducted when the current of the third resistor is larger than the threshold current of the thyristor, so that the first MOS tube is short-circuited to protect the power load.

2. The protection circuit according to claim 1, wherein an emitter of the transistor is connected to a source of the first MOS transistor, and a collector of the transistor is connected to a gate of the first MOS transistor.

3. The protection circuit according to claim 1, wherein a cathode of the thyristor is connected to an input terminal of a fourth resistor, a control electrode of the thyristor is commonly connected to the source electrode of the first MOS transistor through output terminals of a third resistor and the fourth resistor, an anode of the thyristor is connected to a power supply input terminal through the first resistor, and the third resistor serves as a sampling resistor.

4. The protection circuit of claim 3, wherein the third resistor is a negative temperature sensitive resistor, and when the temperature of the protection circuit exceeds a predetermined temperature, the resistance of the third resistor decreases, and the current flowing through the third resistor increases as the resistance decreases.

5. The protection circuit of claim 1, wherein the first MOS transistor is an NMOS transistor.

6. The protection circuit of claim 1, wherein the transistor is an NPN transistor.

7. The protection circuit of claim 1, further comprising a first bi-directional transient suppression diode, wherein one end of the first bi-directional transient suppression diode is connected to the source of the first MOS transistor, and the other end of the first bi-directional transient suppression diode is connected to the gate of the first MOS transistor.

8. The protection circuit of claim 1, further comprising a second bidirectional transient suppression diode connected between two poles of the power supply system.

9. A circuit protection device comprising a protection circuit according to any one of claims 1 to 8, wherein the circuit protection device is connected between the negative pole of an electrical load and the negative pole of a power supply.

Technical Field

The present invention relates to circuit technologies, and in particular, to a protection circuit and a circuit protection device.

Background

Fuses (fuses), also known as current fuses, are defined by the IEC127 standard as "fuse-links" and are placed primarily in the circuit to limit the current carried in the individual circuit loops to a safe range. When the circuit is in fault or abnormal, the fuse can be fused to cut off the current when the current is abnormally increased to a certain height and heat, so that the circuit and the electric equipment are protected.

At present, the fuses which are commonly used are fuse tubes, temperature fuses, PPTC and the like, and the fuse-type fuses have the defects of single function, slow response, inaccurate response and unrecoverability.

Disclosure of Invention

The invention provides a protection circuit and a circuit protection device, which are used for realizing the functions of overvoltage, overcurrent, overtemperature and short-circuit protection and improving the response speed and accuracy.

In a first aspect, an embodiment of the present invention provides a protection circuit, including: the device comprises a control unit, an undervoltage protection unit, an overvoltage protection unit and an overcurrent protection unit;

the control unit is a first MOS tube, the source electrode of the first MOS tube is connected with a low level, the grid electrode of the first MOS tube is connected with a first resistor and then is connected with a high level, and the drain electrode of the first MOS tube is connected with a protected electric load and is used for controlling the connection and disconnection of the electric load;

the overvoltage protection unit is formed by connecting a first voltage-stabilizing diode and a second resistor in series and then connecting the first voltage-stabilizing diode and the second resistor to the base electrode of the triode, and is used for short-circuiting the first MOS tube to protect the power load when the voltage of the protection circuit is greater than the sum of the saturation voltages of the first voltage-stabilizing diode and the triode;

the overcurrent protection unit is composed of a thyristor, a third resistor and a fourth resistor to form a shunt circuit and is used for triggering the thyristor to be conducted when the current of the third resistor is larger than the threshold current of the thyristor, so that the first MOS tube is short-circuited to protect the power load.

Optionally, an emitter of the triode is connected with a source of the first MOS transistor, and a collector of the triode is connected to a gate of the first MOS transistor.

Optionally, the cathode of the thyristor is connected to the input end of the fourth resistor, the control electrode of the thyristor is connected to the source electrode of the first MOS transistor through the output ends of the third resistor and the fourth resistor, the anode of the thyristor is connected to the power input end through the first resistor, and the third resistor is used as the sampling resistor.

Optionally, the third resistor is a negative temperature sensitive resistor, when the temperature of the protection circuit exceeds a preset temperature, the resistance of the third resistor decreases, and the current flowing through the third resistor increases with the decrease of the resistance.

Optionally, the first MOS transistor is an NMOS transistor.

Optionally, the triode is an NPN triode.

Optionally, the device further includes a first bi-directional transient suppression diode, where one end of the first bi-directional transient suppression diode is connected to the source of the first MOS transistor, and the other end of the first bi-directional transient suppression diode is connected to the gate of the first MOS transistor.

Optionally, the power supply system further comprises a second bidirectional transient suppression diode, and the second bidirectional transient suppression diode is connected between two poles of the power supply system.

In a second aspect, an embodiment of the present invention further provides a circuit protection device, including the protection circuit described in any one of the first aspects, where the circuit protection device is connected between a negative electrode of an electric load and a negative electrode of a power supply.

The embodiment of the invention controls the loop of the protection circuit through the first MOS tube, the source electrode of the first MOS tube is connected with the current input end, the drain electrode of the first MOS tube is connected with the protected electric load, the undervoltage protection unit is connected to a grid electrode of a first MOS (metal oxide semiconductor) tube after being connected with a first voltage stabilizing diode in series, the overvoltage protection unit is connected to a base electrode of a triode after being connected with a second voltage stabilizing diode in series, the overcurrent protection unit is composed of a second MOS tube, a fourth resistor and a silicon controlled rectifier, the undervoltage protection unit, the overvoltage protection unit and the overcurrent protection unit respectively carry out undervoltage, overvoltage and overcurrent protection on the electric load, the problems of single fuse function, slow response, inaccurate response and unrecoverable are solved, the overvoltage, overcurrent, overtemperature and short-circuit protection functions are realized, and the response speed and accuracy are improved.

Drawings

Fig. 1 is a circuit schematic diagram of a protection circuit according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

Fig. 1 is a schematic circuit diagram of a protection circuit according to an embodiment of the present invention, and as shown in fig. 1, the protection circuit includes: the device comprises a control unit 1, an overvoltage protection unit 2 and an overcurrent protection unit 3;

the control unit 1 is a first MOS transistor Q1, the source S of the first MOS transistor Q1 is connected to a low level, the gate G of the first MOS transistor Q1 is connected to a first resistor R1 and then connected to a high level, and the drain D of the first MOS transistor Q1 is connected to the protected electric load 4 for controlling the on and off of the electric load 4.

The overvoltage protection unit 2 is formed by connecting a first voltage-regulator diode DW1 and a second resistor R2 in series and then connecting the first voltage-regulator diode DW1 and the second resistor R2 to the base B of the triode Q2, and is used for short-circuiting the first MOS transistor Q1 to protect the electric load 4 when the protection circuit voltage is greater than the sum of the saturation voltages of the first voltage-regulator diode DW1 and the triode Q2.

The overcurrent protection unit 3 is composed of a thyristor Q3, a third resistor R3 and a fourth resistor R4, and is configured to trigger the thyristor Q3 to be turned on when the voltage of the fourth resistor R4 is greater than the threshold voltage of the thyristor Q3, so as to short-circuit the first MOS transistor Q1 to protect the power load 4.

Optionally, the emitter of the transistor Q2 is connected to the source S of the first MOS transistor Q1, and the collector C of the transistor Q2 is connected to the gate G of the first MOS transistor Q1.

A protection circuit is required to be arranged at a power supply inlet of the direct current equipment for protection of overvoltage, overcurrent, short circuit and the like, and the protection circuit is connected between a power supply and a load to protect the power load. When the voltage of the protection circuit exceeds the sum of the critical breakdown voltage of the first voltage-stabilizing diode DW1 and the breakdown critical voltage of the triode Q2, the overvoltage protection unit 2 of the protection circuit is triggered, the emitter E and the collector C of the triode Q2 are conducted, the first MOS transistor Q1 is short-circuited, and the current is connected to the low level through the first voltage-stabilizing diode DW1 and the second resistor R2 connected in series, so that overvoltage protection is realized on the electric load 4. The switching response speed of the triode Q2, namely the judging speed of the overvoltage protection of the circuit, is generally within 10uS, so that the judging speed of the overvoltage protection is improved, and the judging result is more accurate than that of a conventional resistance wire. When the current flowing through the fourth resistor R4 reaches the control current of the thyristor Q3, the thyristor Q3 is turned on, the overcurrent protection unit 3 is triggered, and the first MOS transistor Q1 is short-circuited to protect the electric load. The first MOS transistor Q1 is a PMOS transistor, and the transistor Q2 is an NPN transistor.

A third resistor R3 in the overcurrent protection unit 3 is a sampling resistor, a cathode K of a thyristor Q3 is connected to an input end of a fourth resistor R4, a control electrode G of the thyristor Q3 is commonly connected to a source S of the first MOS transistor Q1 through output ends of the third resistor R3 and the fourth resistor R4, and an anode a of the thyristor Q3 is connected to a power supply input end through the first resistor R1. The third resistor R3, the fourth resistor R4 and the internal resistance of the thyristor Q3 form a shunt circuit, the current flowing through the third resistor R3 is equal to the current flowing through the thyristor Q3, when the current of the protection circuit is increased, the current of the third resistor R3 is increased, and when the current of the third resistor R3 is larger than the threshold current of the thyristor Q3, the thyristor Q3 is triggered to be conducted, so that the first MOS transistor Q1 is short-circuited to protect the electric load 4.

The protection circuit of the embodiment has no process of heating and re-fusing the conventional resistance wire, the reaction is faster, and the control is more accurate.

Optionally, the third resistor R3 is a negative temperature sensitive resistor, when the temperature of the protection circuit exceeds a preset temperature, the resistance of the third resistor R3 decreases, and the current flowing through the third resistor R3 increases with the decrease of the resistance.

When the temperature of the protection circuit is too high, the resistance of the third resistor R3 is reduced, the voltage at the two ends of the third resistor R3 is unchanged, the current flowing through the third resistor R3 is gradually increased, the overcurrent protection unit 3 acts to cut off the power supply to the electric load 4, and the overcurrent protection effect is further achieved.

Optionally, the device further includes a first bidirectional transient suppression diode DW2, where one end of the first bidirectional transient suppression diode DW2 is connected to the source S of the first MOS transistor Q1, and the other end is connected to the gate G of the first MOS transistor Q1.

Optionally, a second bidirectional transient suppression diode DW3 is further included, and the second bidirectional transient suppression diode DW3 is connected between two poles of the power supply system.

The drain D of the first MOS transistor Q1 is connected to the electrical load 4, and when the first MOS transistor Q1 is impacted by transient high energy, the first bidirectional transient suppression diode DW2 changes the high impedance between the gate G and the drain D of the first MOS transistor Q1 to a low impedance, thereby effectively protecting the first MOS transistor Q1; when the protection circuit is subjected to transient high-energy impact, the second bidirectional transient suppression diode DW3 can change the high impedance between the two poles into low impedance at the speed of 10 in the order of minus 12 th power second, absorb the surge power of thousands of watts and clamp the voltage between the two poles at a preset value, thereby effectively protecting precise components in the electric load from being damaged by various surge pulses.

The embodiment of the invention controls the loop of the protection circuit through the first MOS tube, the source electrode of the first MOS tube is connected with the current input end, the drain electrode of the first MOS tube is connected with the protected electric load, the undervoltage protection unit is connected to a grid of a first MOS tube after being connected with a first voltage stabilizing diode in series, the overvoltage protection unit is connected to a base of a triode after being connected with a second voltage stabilizing diode in series, the overcurrent protection unit is composed of a second MOS tube, a fourth resistor and a silicon controlled rectifier, the undervoltage protection unit, the overvoltage protection unit and the overcurrent protection unit perform undervoltage, overvoltage and overcurrent protection on the electric load respectively, the problems of single fuse function, slow response, inaccurate response and unrecoverable are solved, the overvoltage, undervoltage, overcurrent, overtemperature and short-circuit protection functions are realized, and the response speed and accuracy are improved.

In addition to the above embodiments, another embodiment further includes a circuit protection device, including the protection circuit of any of the above embodiments, the circuit protection device being connected between the negative electrode of the electric load and the negative electrode of the power supply. Illustratively, the electric load can be the front end of an automobile audio-visual electronic device, a computer power supply inlet and the like.

It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.