CN108736877B

CN108736877B - Driving circuit

Info

Publication number: CN108736877B
Application number: CN201810358350.3A
Authority: CN
Inventors: 陈启仁; 林俊孝; 杜圣旗
Original assignee: Qisda Optronics Suzhou Co Ltd; Qisda Corp
Current assignee: Qisda Optronics Suzhou Co Ltd; Qisda Corp
Priority date: 2018-04-20
Filing date: 2018-04-20
Publication date: 2021-10-01
Anticipated expiration: 2038-04-20
Also published as: CN108736877A

Abstract

The invention discloses a driving circuit for driving an electric element, comprising: the circuit comprises an input unit with an input end and a first node, an integrated driving chip with an over-power protection port, a switching unit with a first resistor and a first switch, a monitoring resistor and a second resistor. When the first signal is a first high-level signal, the first resistor is conducted, a first voltage is provided at two ends of the first resistor, and the voltage of the over-power protection port is the first voltage; when the first signal is a first low level signal, the first resistor is not conducted, a second monitoring voltage is provided at two ends of the monitoring resistor, and the voltage of the over-power protection port is the second monitoring voltage. According to the invention, by arranging the switching unit, when the driving circuit is in the standby mode, the current flowing into the electric element is small, so that the phenomenon that the electric element is over-temperature or even burnt due to the inflow of large current is prevented.

Description

Driving circuit

Technical Field

The present invention relates to a driving circuit, and more particularly, to a driving circuit capable of preventing an over-temperature phenomenon of an electric element in a standby mode.

Background

In the standby mode, the Over Power Protection (OPP) operating point of the current projector is almost the same as that of the normal operating mode. Since the cooling fan in the projector does not rotate in the standby mode and the driving circuit is the same as the circuit in the normal operation mode, the current flowing through the electric elements (such as the transformer) is the same as that in the normal operation mode, and since the cooling fan does not rotate, the temperature of the electric elements in the standby mode is too high and even the electric elements are burnt.

Disclosure of Invention

The present invention is directed to a driving circuit, so as to solve the problem in the prior art that the current flowing through the power consumption device in the standby mode is the same as that in the normal operation mode, which causes the power consumption device to have an excessively high temperature or even to be burned out in the standby mode.

In order to achieve the above object, the present invention provides a driving circuit for driving an electric element, the driving circuit including:

an input unit having an input terminal for receiving a first signal and a first node;

the integrated driving chip is provided with an over-power protection port, and the electric element is coupled with the integrated driving chip;

a switching unit having a first resistor and a first switch, the first resistor having a first end and a second end opposite to each other, the first switch being coupled to the first end of the first resistor and the first node, the second end of the first resistor being coupled to the over-power protection port;

the monitoring resistor is provided with a third end and a fourth end which are opposite, and the fourth end is grounded; and

a second resistor having a fifth end and a sixth end opposite to each other, the fifth end being coupled to the second end of the first resistor, the sixth end being coupled to the third end of the monitoring resistor;

when the first signal is a first high-level signal, the first node has a voltage, the first switch is opened to enable the first resistor to be conducted, a first voltage is arranged at two ends of the first resistor, a second voltage is arranged at two ends of the second resistor, a first monitoring voltage is arranged at two ends of the monitoring resistor, the first monitoring voltage is equal to the sum of the first voltage and the second voltage, and the voltage of the over-power protection port is the first voltage;

when the first signal is a first low level signal, the first node has no voltage, the first switch is turned off, the first resistor is not conducted, the two ends of the monitoring resistor are provided with a second monitoring voltage, and the voltage of the over-power protection port is the second monitoring voltage.

As an optional technical solution, the integrated driving chip further has an output port, and the driving circuit further includes a second switch, where the second switch has a control end, a seventh end and an eighth end, the control end is coupled to the output port, the seventh end is coupled to the third end of the monitoring resistor, and the eighth end is coupled to the power consumption element.

As an optional technical solution, the second switch is a first transistor, the control terminal is a gate of the first transistor, a current flowing through the monitoring resistor is defined as a first current, and when the output port of the integrated driving chip outputs a second high-level signal, the first current enters the electric element from the first transistor.

As an optional technical solution, the first resistor is defined to have a first resistance value, the second resistor is defined to have a second resistance value, and the monitoring resistor is defined to have a third resistance value, and a sum of the first resistance value and the second resistance value is much larger than the third resistance value.

As an optional technical solution, a resistance value of the first resistor is equal to a resistance value of the second resistor.

As an optional technical solution, the resistance values of the first resistor and the second resistor are 510 Ω, and the resistance value of the monitoring resistor is 0.6 Ω.

As an optional technical solution, the first switch is a first NPN type triode, a base of the first NPN type triode is coupled to the first node, a collector of the first NPN type triode is coupled to the first end of the first resistor, and an emitter of the first NPN type triode is grounded.

As an optional technical solution, the switching unit further includes a first voltage regulator diode, a positive terminal of the first voltage regulator diode is coupled to the first node, and a negative terminal of the first voltage regulator diode is coupled to the base of the first NPN type triode.

As an optional technical solution, the switching unit further includes a third resistor, one end of the third resistor is coupled to the positive terminal of the first zener diode, and the other end of the third resistor is coupled to the first node.

As an optional technical solution, the input circuit includes a second NPN type triode, a photoelectric coupling element, a third PNP type triode, and a fourth NPN type triode, a base of the second NPN type triode is coupled to the input terminal, the photoelectric coupling diode is coupled to a collector of the second NPN type triode and a gate of the third PNP type triode, a collector of the third PNP type triode is coupled to a collector of the fourth NPN type triode, and an emitter of the fourth NPN type triode is coupled to the first node.

Compared with the prior art, the driving circuit has the advantages that by arranging the switching unit, when the driving circuit is in a normal working mode, the voltage of the over-power protection port of the integrated driving chip is actually partial voltage of the voltage at two ends of the monitoring resistor by conducting the first resistor in the switching unit, so that the current flowing into the electric element is larger, and the electric element can normally work; when the driving circuit is in a standby mode, the first resistor in the switching unit is not conducted, so that the voltage of the over-power protection port of the integrated driving chip is the voltage at two ends of the monitoring resistor, the current flowing into the electric element is small, and the phenomenon that the electric element is over-temperature or even burnt due to the inflow of large current is prevented.

The invention is described in detail below with reference to the drawings and specific examples, but the invention is not limited thereto.

Drawings

FIG. 1 is a schematic diagram of a driving circuit according to the present invention;

FIG. 2 is a diagram of a driving circuit according to an embodiment of the present invention;

fig. 3 is a schematic diagram of the input unit in fig. 2.

Detailed Description

The following description of the embodiments refers to the accompanying drawings for illustrating the specific embodiments in which the invention may be practiced. The directional terms used in the present invention, such as "up", "down", "front", "back", "left", "right", "side", etc., refer to the directions of the attached drawings. Accordingly, the directional terms used are used for explanation and understanding of the present invention, and are not used for limiting the present invention.

In the following embodiments, the same portions are denoted by the same reference numerals in different drawings.

Referring to fig. 1, fig. 1 is a schematic diagram of a driving circuit according to the present invention. The driving circuit 1000 of the present invention is used for driving the electric element 2000. The driving circuit 1000 includes an input unit 100, an integrated driving chip IC603, a switching unit 200, a monitoring resistor R623, and a second resistor R647. The input unit 100 has an input terminal In for receiving a first signal and a first node Q. The integrated driver IC603 has an over-power protection port cs, and is coupled to the integrated driver IC603 by a power-consuming element 2000. In actual operation, when the voltage of the over-power protection port cs reaches the first preset voltage, the integrated driving chip IC603 performs over-power protection on the power consuming element 2000. The first predetermined voltage may be set according to actual circuit requirements. The switching unit 200 has a first resistor R669 and a first switch Q655, the first resistor R669 has a first end 01 and a second end 02 opposite to each other, the first switch Q655 is coupled to the first end 01 and the first node Q of the first resistor R669, and the second end 02 of the first resistor R669 is coupled to the over-power protection port cs of the integrated driver IC 603. The monitor resistor R623 has a third terminal 03 and a fourth terminal 04 opposite to each other, and the fourth terminal 04 is grounded. The second resistor R647 has a fifth terminal 05 and a sixth terminal 06 opposite to each other, the fifth terminal 05 is coupled to the second terminal 02 of the first resistor R669, and the sixth terminal 06 is coupled to the third terminal 03 of the monitoring resistor R623.

As shown in fig. 1, in the present embodiment, the first switch Q655 is a first NPN transistor Q655, a base of the first NPN transistor Q655 is coupled to the first node Q, a collector c of the first NPN transistor Q655 is coupled to the first end 01 of the first resistor R669, and an emitter e of the first NPN transistor Q655 is grounded. Thus, when the first signal received by the input terminal In of the input unit 100 is the first high level signal, the first node Q has a voltage, the first NPN transistor Q655 is turned on to turn on the first resistor R669, and the first terminal 01 of the first resistor R669 is equivalent to ground.

The first signal may be a switching signal between a normal operation mode and a standby mode, when the first signal is a first high level signal, i.e. the driving circuit 1000 is in the normal operation mode, the first node Q has a voltage, the first switch Q655 is turned on to turn on the first resistor R669, at this time, the first resistor R669 is connected in series with the second resistor R647, and the monitoring resistor R623 is connected in parallel with the first resistor R669 and the second resistor R647. The first resistor R669 has a first voltage V1 across it, the second resistor R647 has a second voltage V2 across it, the monitor resistor R623 has a first monitor voltage VP1 across it, the first monitor voltage VP1 is equal to the sum of the first voltage V1 and the second voltage V2. Since the over-power protection port cs is coupled to the second end 02 of the first resistor R669, the voltage of the over-power protection port cs is equal to the voltage of the second end 02 of the first resistor R669, and the first end 01 of the first resistor R669 can be regarded as ground at this time, so the voltage of the over-power protection port cs is equal to the first voltage V1 across the first resistor R669. Therefore, when the driving circuit 1000 is in the normal operation mode, the voltage of the over-power protection port cs is not equal to the first monitor voltage VP1 across the monitor resistor R623, and is equivalent to a partial voltage division of the first monitor voltage VP1, and the resistors involved in the over-power protection include the monitor resistor R623, the second resistor R647, and the first resistor R669.

When the first signal is the first low level signal, that is, the driving circuit 1000 is in the standby mode, the first node Q has no voltage, the first switch Q655 is turned off, the first resistor R669 is not turned on, and the series circuit formed by the first resistor R669 and the second resistor R647 is turned off. The over-power protection port cs is coupled to the fifth terminal 05 of the second resistor R647, i.e., the over-power protection port cs is coupled to the third terminal 03 of the monitoring resistor R623, the voltage of the over-power protection port cs is equal to the voltage of the third terminal 03 of the monitoring resistor R623, and since the fourth terminal 04 of the monitoring resistor R623 is grounded, the voltage of the over-power protection port cs is equal to the second monitoring voltage VP2 at the two terminals of the monitoring resistor R623. Therefore, when the driving circuit 1000 is in the standby mode, the voltage of the over-power protection port cs is equal to the second monitor voltage VP2 across the monitor resistor R623, and the resistors involved in over-power protection include the monitor resistor R623 and the second resistor R647.

As shown in fig. 1, the integrated driving chip IC603 further has an output port out, and the driving circuit 1000 further includes a second switch Q608, where the second switch Q608 has a seventh terminal and an eighth terminal. The control terminal of the second switch Q608 is coupled to the output port out of the integrated driving chip IC603, the seventh terminal of the second switch Q608 is coupled to the third terminal 03 of the monitoring resistor R623, and the eighth terminal of the second switch Q608 is coupled to the electric element 2000. In practice, the second switch Q608 may be a first transistor Q608 (e.g., a MOSFET), and the control terminal is a gate of the first transistor Q608. The current flowing through the monitor resistor R623 is defined as the first current I1, and when the output port out of the integrated driver IC603 outputs the second high-level signal, the first current I1 enters the electric element 2000 from the first transistor Q608. Generally, when the integrated driver chip IC603 operates normally, the output port out thereof outputs a second high level signal.

The first resistor R669 is defined to have a first resistance R1, the second resistor R647 is defined to have a second resistance R2, and the monitor resistor R623 is defined to have a third resistance R3. Generally, the sum of the first resistance r1 and the second resistance r2 may be much larger than the third resistance r 3. And in practice, the first resistance r1 may be equal to the second resistance r 2.

The following description will be given with reference to specific examples.

Assuming that the first preset voltage is 0.6v, that is, the voltage of the over-power protection port cs of the integrated driver IC603 reaches 0.6v, the integrated driver IC603 performs over-power protection on the electric element 2000. The monitoring resistor R623 has a resistance value of 0.6 Ω. The resistance of the first resistor R669 is equal to the resistance of the second resistor R647, which is 510 Ω. Then:

when the first signal received by the input terminal In is the first high level signal, i.e. the driving circuit 1000 is In the normal operation mode, the first node Q has a voltage, and the first switch Q655 is turned on to turn on the first resistor R669. Assuming that the first current I1 flowing through the monitor resistor R623 is detected to be 2A, the first monitor voltage VP1 across the monitor resistor R623 is calculated to be equal to 0.6 × 2 — 1.2 v. At this time, the first resistor R669 is connected in series with the second resistor R647 and then connected in parallel with the monitoring resistor R623, and the resistance of the first resistor R669 is equal to the resistance of the second resistor R647, so the first voltage V1 at two ends of the first resistor R669 is equal to the second voltage V2 at two ends of the second resistor R647, and both are equal to half of the first monitoring voltage VP1, that is, the first voltage V1 is equal to 0.6V. Since the voltage of the over-power protection port cs of the integrated driver IC603 is equal to the first voltage V1, the voltage of the over-power protection port cs is equal to 0.6V, and the first preset voltage is reached, so that the integrated driver IC603 performs over-power protection on the electric element 2000. Meanwhile, the output port out of the integrated driver IC603 outputs a second high signal to the first transistor Q608, and the first transistor Q608 is turned on, so that the first current I1 flowing through the monitor resistor R623 passes through the first transistor Q608 and enters the electric element 2000. In this embodiment, in the normal operation mode, when the first current I1 flowing through the monitoring resistor R623 and entering the electric element 2000 is 2A, the voltage of the over-power protection port cs reaches the first preset voltage, and the integrated driving chip IC603 performs over-power protection on the electric element 2000.

In practical operation, since the seventh terminal 03 of the monitoring resistor R623 is coupled to the seventh terminal of the first transistor Q608, it is simultaneously coupled to the sixth terminal 06 of the second resistor R647, and it should be noted that the total output current of the parallel circuit formed by the first resistor R669 and the second resistor R647 connected in series and the monitoring resistor R623 passes through the first transistor Q608 and enters the electric element 2000, that is, the current entering the electric element 2000 through the first transistor Q608 is the sum of the first current I1 passing through the monitoring resistor R623 and the current passing through the first resistor R669. Only, since the sum of the first resistance R1 of the first resistor R669 and the second resistance R2 of the second resistor R647 is much larger than the third resistance R3 of the monitoring resistor R623, the current flowing through the circuit is negligible, and only the first current I1 is considered to pass through the first transistor Q608 and enter the active device. Taking this embodiment as an example, the first voltage V1 across the first resistor R669 is 0.6V, and the first resistance R1 of the first resistor R669 is 550 Ω, so the current flowing through the first resistor R669 is calculated to be 0.6/550 — 0.001A, compared to 2A for the first current I1, the current flowing through the first resistor R669 is negligible.

As can be seen from this embodiment, when the driving circuit 1000 is in the normal operation mode and the voltage at the over-power protection port cs is to reach the first preset voltage, the first voltage V1 is required to reach the first preset voltage, and the first voltage V1 can be regarded as partial voltage of the first monitor voltage VP1 at two ends of the monitor resistor R623, so that the first monitor voltage VP1 is required to reach a larger value, and the value of the first current I1 flowing through the monitor resistor R623 is larger at this time, so that the electric element 2000 can operate normally.

When the first signal received by the input terminal In is the first low level signal, i.e. the driving circuit 1000 is In the standby mode, the first node Q has no voltage, and the first switch Q655 is turned off, so that the first resistor R669 is not turned on. Assuming that the first current I1 flowing through the monitor resistor R623 is detected to be 1A, the second monitor voltage VP2 across the monitor resistor R623 is calculated to be equal to 0.6 × 1 — 0.6V. At this time, since the voltage of the over-power protection port cs of the integrated driver IC603 is equal to the second monitoring voltage VP2, the voltage of the over-power protection port cs is equal to 0.6V, and the first preset voltage is reached, so that the integrated driver IC603 performs over-power protection on the electric element 2000. Meanwhile, at this time, the output port out of the integrated driving chip IC603 also outputs a second high level signal to the first transistor Q608, and the first transistor Q608 is turned on, so that the first current I1 flowing through the monitoring resistor R623 passes through the first transistor Q608 and enters the electric element 2000. In this embodiment, in the standby mode, when the first current I1 flowing through the monitoring resistor R623 and entering the electric element 2000 is 1A, the voltage of the over-power protection port cs reaches the first preset voltage, and the integrated driving chip IC603 performs over-power protection on the electric element 2000.

In this embodiment, when the driving circuit 1000 is in the standby mode and the voltage of the over-power protection port cs is to reach the first preset voltage, since the voltage of the over-power protection port cs is equal to the second monitor voltage VP2 at two ends of the monitor resistor R623, the second monitor voltage VP2 can reach the first preset voltage. At this time, the second monitor voltage VP2 no longer needs to be divided to be transmitted to the over-power protection port cs, so the value of the second monitor voltage VP2 is small, and the value of the first current I1 flowing through the monitor resistor R623 is also small, so that the value of the current entering the electric element 2000 is small, and the phenomenon that the electric element 2000 is over-heated or even burnt due to an over-large current can be prevented.

In this embodiment, when the driving circuit 1000 is in the normal operation mode, and the first current I1 flowing through the monitoring resistor R623 reaches 2A, the voltage of the over-power protection port cs of the integrated driving chip IC603 reaches a first preset voltage, and the integrated driving chip IC603 performs over-power protection on the electric element 2000. Meanwhile, the first current I1 with the value of 2A enters the electric element 2000 through the first transistor Q608, so as to provide enough current to the electric element 2000, thereby ensuring the normal operation of the electric element 2000. The driving circuit 1000 can be applied to a projector, and the heat dissipation device in the projector can perform timely and effective heat dissipation on the electric element 2000 to ensure that the electric element 2000 does not generate an over-temperature phenomenon. When the driving circuit 1000 is in the standby mode, when the first current I1 flowing through the monitoring resistor R623 reaches 1A, the voltage of the over-power protection port cs of the integrated driving chip IC603 reaches a first preset voltage, so that the integrated driving chip IC603 performs over-power protection on the electric element 2000. Meanwhile, the first current I1 with the value of 1A enters the electric element through the first transistor Q608. At this time, the first current I1 is smaller and is only half of that in the normal operation mode, so that the over-temperature phenomenon of the electric element 2000 is not caused even though the heat dissipation device in the projector does not operate.

According to the driving circuit 1000 of the present invention, by providing the switching unit 200, when the driving circuit 1000 is in the normal operation mode, the voltage of the over-power protection port cs of the integrated driving chip IC603 is actually a partial voltage division of the voltage at the two ends of the monitoring resistor R623 by turning on the first resistor R669 in the switching unit 200, so that the current flowing into the electric element 2000 is relatively large, and the electric element 2000 can normally operate; when the driving circuit 1000 is in the standby mode, the first resistor R669 in the switching unit 200 is not turned on, so that the voltage of the over-power protection port cs of the integrated driving chip IC603 is substantially equal to the voltage across the monitoring resistor R623, and thus the current flowing into the electric element 2000 is small, thereby preventing the electric element 2000 from being over-heated or even burnt due to the inflow of a large current.

Referring to fig. 2 and 3, fig. 2 is a schematic diagram of a driving circuit according to an embodiment of the invention; fig. 3 is a schematic diagram of the input unit in fig. 2. As shown in fig. 2, the switching unit 200 further includes a first zener diode ZD602, a positive terminal of the first zener diode ZD602 is coupled to the first node Q, and a negative terminal of the first zener diode ZD602 is coupled to the base of the first NPN transistor Q655. The first zener diode ZD602 is configured to prevent some interference signals from causing the first NPN transistor Q655 to malfunction, so as to ensure stability and accuracy of the driving circuit 1000. The rated voltage of the first zener diode ZD602 is, for example, 3.3V. As shown in fig. 2, the switching unit 200 further includes a third resistor R667, one end of the third resistor R667 is coupled to the positive terminal of the first zener diode ZD602, and the other end of the third resistor R667 is coupled to the first node Q. The third resistor R667 is provided to ensure stable operation of the first zener diode ZD 602. The third resistor R667 has a resistance of 4.7k, for example. As shown in fig. 2, in the present embodiment, the electric element 2000 includes a transformer T603 and a rectifying element D712. In some embodiments, the first transistor Q608 may also be regarded as a part of the power-consuming element 2000, so that in the standby mode, since the first current I1 flowing through the monitoring resistor R623 is small, the current flowing through the first transistor 608 is also small, thereby protecting the first transistor 608 from over-temperature.

Referring to fig. 3, fig. 3 is a schematic diagram of a driving circuit according to the present invention. The input unit 100 includes a second NPN transistor Q701, a photocoupling element IC653, a third NPN transistor Q603, and a fourth NPN transistor Q653. The base of the second NPN transistor Q701 is coupled to the input terminal In, and the photocoupling element IC603 is coupled to the collector of the second NPN transistor Q701 and the base of the third PNP transistor Q603. A collector of the third PNP transistor Q603 is coupled to a collector of the fourth NPN transistor Q653, and an emitter of the fourth NPN transistor Q653 is coupled to the first node Q. In this embodiment, the emitter of the third PNP transistor Q603 is coupled to the voltage source Vcc.

When the first signal received by the input terminal In of the input unit 100 is the first high level signal, that is, the driving circuit 1000 is In the normal operation mode, the second NPN transistor Q701 is turned on, so that the photoelectric coupling element IC653 is turned on, the third PNP transistor Q603 is turned on, the fourth NPN transistor Q653 is turned on, the first node Q has a voltage, and the first switch Q655 is turned on to turn on the first resistor R669.

When the first signal received by the input terminal In of the input unit 100 is the first low level signal, that is, the driving circuit 1000 is In the standby mode, the second NPN transistor Q701 is turned off, so that the photoelectric coupling element IC653 is turned off, the third PNP transistor Q603 is turned off, the fourth NPN transistor Q655 is turned off, the first node Q has no voltage, and the first switch Q655 is turned off, so that the first resistor R669 is not turned on.

In summary, in the driving circuit of the present invention, by providing the switching unit, when the driving circuit is in the normal operating mode, the voltage of the over-power protection port of the integrated driving chip is actually a partial voltage division of the voltage at the two ends of the monitoring resistor by turning on the first resistor in the switching unit, so that the current flowing into the power consumption element is relatively large, and the power consumption element can operate normally; when the driving circuit is in a standby mode, the first resistor in the switching unit is not conducted, so that the voltage of the over-power protection port of the integrated driving chip is actually equal to the voltage at two ends of the monitoring resistor, the current flowing into the electric element is small, and the phenomenon that the electric element is over-temperature or even burnt due to the inflow of large current can be prevented.

The above detailed description of the preferred embodiments is intended to more clearly illustrate the features and spirit of the present invention, and is not intended to limit the scope of the present invention by the preferred embodiments disclosed above. On the contrary, it is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims. The scope of the claims to be accorded the invention is therefore to be accorded the broadest interpretation so as to encompass all such modifications and equivalent arrangements as is known in the art.

Claims

1. A drive circuit for driving an electric element, the drive circuit comprising:

2. The drive circuit according to claim 1, wherein: the integrated driving chip further has an output port, and the driving circuit further includes a second switch having a control terminal, a seventh terminal and an eighth terminal, wherein the control terminal is coupled to the output port, the seventh terminal is coupled to the third terminal of the monitoring resistor, and the eighth terminal is coupled to the power consumption element.

3. The drive circuit according to claim 2, wherein: the second switch is a first transistor, the control terminal is a grid electrode of the first transistor, the current flowing through the monitoring resistor is defined as a first current, and when the output port of the integrated driving chip outputs a second high-level signal, the first current enters the electric element from the first transistor.

4. The drive circuit according to claim 1, wherein: the first resistor is defined to have a first resistance value, the second resistor is defined to have a second resistance value, and the monitoring resistor is defined to have a third resistance value, wherein the sum of the first resistance value and the second resistance value is far larger than the third resistance value.

5. The drive circuit according to claim 4, wherein: the resistance value of the first resistor is equal to the resistance value of the second resistor.

6. The drive circuit according to claim 4 or 5, wherein: the resistance values of the first resistor and the second resistor are 510 Ω, and the resistance value of the monitoring resistor is 0.6 Ω.

7. The drive circuit according to claim 1, wherein: the first switch is a first NPN type triode, a base of the first NPN type triode is coupled to the first node, a collector of the first NPN type triode is coupled to the first end of the first resistor, and an emitter of the first NPN type triode is grounded.

8. The drive circuit according to claim 7, wherein: the switching unit further comprises a first voltage stabilizing diode, wherein the positive electrode end of the first voltage stabilizing diode is coupled with the first node, and the negative electrode end of the first voltage stabilizing diode is coupled with the base electrode of the first NPN type triode.

9. The drive circuit according to claim 8, wherein: the switching unit further comprises a third resistor, one end of the third resistor is coupled to the positive terminal of the first zener diode, and the other end of the third resistor is coupled to the first node.

10. The drive circuit according to claim 1, wherein: the input unit comprises a second NPN type triode, a photoelectric coupling element, a third PNP type triode and a fourth NPN type triode, wherein the base electrode of the second NPN type triode is coupled with the input end, the photoelectric coupling element is coupled with the collector electrode of the second NPN type triode and the grid electrode of the third PNP type triode, the collector electrode of the third PNP type triode is coupled with the collector electrode of the fourth NPN type triode, and the emitter electrode of the fourth NPN type triode is coupled with the first node.