CN212849822U

CN212849822U - Control protection circuit

Info

Publication number: CN212849822U
Application number: CN202021399877.XU
Authority: CN
Inventors: 余灵先; 齐虎; 苏长记
Original assignee: Etekcity Corp
Current assignee: Etekcity Corp
Priority date: 2020-07-15
Filing date: 2020-07-15
Publication date: 2021-03-30
Anticipated expiration: 2030-07-15

Abstract

The utility model provides a control protection circuit, which comprises a control circuit, a load circuit, a first drive circuit and a second drive circuit, wherein the first drive circuit and the second drive circuit are electrically connected with the control circuit and the load circuit; the load circuit comprises a load and a first relay and a second relay which are connected with the load in series; the first driving circuit is electrically connected with the first relay and is configured to control the first relay to be switched on or switched off; the second driving circuit is electrically connected with the second relay and is configured to control the second relay to be switched on after the first relay is switched on and control the second relay to be switched off before the first relay is switched off, so that the first relay is always switched on or switched off under the condition that a load does not work, and further the first relay is switched on or switched off under the condition of zero current and voltage, therefore, the first relay does not have the condition of melting and adhering contacts, and the reliability of the control protection circuit is improved.

Description

Control protection circuit

Technical Field

The application belongs to the technical field of circuit control, and particularly relates to a control protection circuit.

Background

At present, among the control protection circuit of traditional electronic electric heat class product, can set up the switch that the relay controlled the product usually, and the relay often opens and shuts down in the control protection circuit of heavy current and high voltage, the easy situation that appears the contact and melt the adhesion, the product is uncontrolled and can work always this moment to use the product can take place danger.

Therefore, the problem that the contact of the relay is melted and adhered in the traditional technical scheme, so that the control protection circuit is uncontrollable is caused.

SUMMERY OF THE UTILITY MODEL

An object of the application is to provide a control protection circuit, aims at solving the relay contact that traditional control protection circuit exists and melts the adhesion, leads to the uncontrollable problem of control protection circuit.

The embodiment of the application provides a control protection circuit, includes: the circuit comprises a control circuit, a load circuit, a first driving circuit and a second driving circuit, wherein the first driving circuit and the second driving circuit are electrically connected with the control circuit and the load circuit;

the load circuit comprises a load and a first relay and a second relay connected in series with the load;

the first driving circuit is electrically connected with the first relay and is configured to control the first relay to be switched on or switched off;

the second drive circuit is electrically connected with the second relay, and is configured to control the second relay to be turned on after the first relay is turned on, and to control the second relay to be turned off before the first relay is turned off.

Compared with the prior art, the embodiment of the utility model beneficial effect who exists is: the control protection circuit comprises: the circuit comprises a control circuit, a load circuit, a first driving circuit and a second driving circuit, wherein the first driving circuit and the second driving circuit are electrically connected with the control circuit and the load circuit; the load circuit includes a load and first and second relays connected in series with the load. Through first drive circuit and first relay electricity connection, control first relay switch-on or turn-off, be connected with the second relay electricity through second drive circuit, control second relay switches on after first relay switches on, and control second relay switches off before first relay switches off, realize that first relay switches on earlier and then switches off, switch on earlier behind the second relay switches off, make first relay carry out the operation of switch-on or turn-off under the circumstances that the load did not work all the time, thereby make first relay switch on or turn-off under the circumstances of zero current voltage, consequently the contact melting adhesion condition can not appear in first relay, improve control protection circuit's reliability.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed for the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a control protection circuit of the present application;

FIG. 2 is a circuit diagram of a first embodiment of a control protection circuit of the present application;

FIG. 3 is a circuit diagram of a second embodiment of the control and protection circuit of the present application;

FIG. 4 is a circuit diagram of a third embodiment of the control and protection circuit of the present application;

FIG. 5a is a circuit diagram of a fourth embodiment of the control and protection circuit of the present application;

FIG. 5b is a circuit diagram of a fifth embodiment of the control and protection circuit of the present application;

fig. 6 is a circuit diagram of a sixth embodiment of the control protection circuit of the present application;

fig. 7 is a circuit diagram of a seventh embodiment of a control protection circuit of the present application;

fig. 8 is a circuit diagram of an eighth embodiment of the control protection circuit of the present application.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present application clearer, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

It should be noted that the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more unless specifically limited otherwise.

The utility model provides a control protection circuit can be applied to electronic electric heat class product, for example, fry the pot, the oven, the water heater, products such as motor, the first relay of the control protection circuit of this application carries out the operation of switch-on or turn-off under the circumstances that the load did not work all the time, thereby make first relay switch-on or turn-off under the circumstances of zero current voltage, consequently, the contact melting adhesion condition can not appear in first relay, the turn-off that can effectual control electronic electric heat class product, control protection circuit reliability is high, the uncontrolled condition of working always can not appear in electronic electric heat class product, the reliability of product is improved.

Fig. 1 shows a schematic structural diagram of a control protection circuit provided in the present application, where the control protection circuit includes: a control circuit 10, a load circuit 20, and a first drive circuit 30 and a second drive circuit 40 electrically connected to both the control circuit 10 and the load circuit 20;

the load circuit 20 includes a load F and a first relay K1 and a second relay K2 connected in series with the load F;

the first drive circuit 30 is electrically connected with the first relay K1 and is configured to control the first relay K1 to be switched on or off;

the second drive circuit 40 is electrically connected to the second relay K2, and is configured to control the second relay K2 to be turned on after the first relay K1 is turned on, and to control the second relay K2 to be turned off before the first relay K1 is turned off.

It should be noted that, the first drive circuit 30 is electrically connected to the first relay K1 to control the first relay K1 to turn on or off, the second drive circuit 40 is electrically connected to the second relay K2 to control the second relay K2 to turn on after the first relay K1 is turned on, and the second relay K2 is turned off before the first relay K1 is turned off, so that the first relay K1 is turned on first and then turned off, and the second relay K2 is turned on first and then turned off first (that is, in a time sequence from the operation of the load F to the stop operation, the first relay K1 is turned on, the second relay K2 is turned on, the second relay K2 is turned off, and the first relay K1 is turned off in turn, so that the first relay K1 is always turned on or off under the condition of zero current voltage, and therefore the first relay K1 is not turned on or off under the condition of zero current voltage, and the condition that the first relay K1 is not melted and stuck contacts is not generated, the reliability of the control protection circuit is improved.

Alternatively, the load F may be a heating coil or a motor, but other loads may also be used, which is not limited herein.

Optionally, the load F, the two contacts of the first relay K1 and the two contacts of the second relay K2 form a closed loop and are connected to the live line L and the neutral line N, and when the two contacts of the first relay K1 and the two contacts of the second relay K2 are both closed, the load F starts to operate.

The embodiments of the control protection circuit of the present application are different in the first and

second driving circuits

30 and 40, and thus only the first and

second driving circuits

30 and 40 of the embodiments are described below.

Fig. 2 shows a circuit diagram of a first embodiment of the control protection circuit provided in the present application, which is detailed as follows:

the first driving circuit 30 includes a first resistor R1, a first capacitor C1, and a first switching unit Q1.

A first end of the first resistor R1 is electrically connected to the first output terminal of the control circuit 10, and a second end of the first resistor R1 is electrically connected to the first end of the first capacitor C1 and the control terminal of the first switch unit Q1.

A second terminal of the first capacitor C1 is connected to power ground.

A first terminal of the first switching unit Q1 is connected to ground, a second terminal of the first switching unit Q1 is electrically connected to a first control terminal of the first relay K1, and a second control terminal of the first relay K1 is connected to a first power source.

The second driving circuit 40 includes a third resistor R3, a fourth resistor R4, a second capacitor C2, and a second switching unit Q2.

The first end of the third resistor R3 is electrically connected to the first end of the first resistor R1, and the second end of the third resistor R3 is electrically connected to the first end of the fourth resistor R4 and the first end of the second capacitor C2.

The second terminal of the fourth resistor R4 and the second terminal of the second capacitor C2 are connected to ground.

The control end of the second switch unit Q2 is electrically connected to the second end of the third resistor R3, the first end of the second switch unit Q2 is connected to the ground, the second end of the second switch unit Q2 is electrically connected to the first control end of the second relay K2, and the second control end of the second relay K2 is connected to the second power supply.

The resistance value of the first resistor R1 is smaller than or equal to the resistance value of the third resistor R3.

The parallel resistance of the third resistor R3 and the fourth resistor R4 is smaller than the resistance of the first resistor R1.

Optionally, the resistance values of the first resistor R1, the third resistor R3, and the fourth resistor R4 are not limited, for example, the resistance values of the first resistor R1 and the third resistor R3 may be 1000 ohms, and the resistance value of the fourth resistor R4 may be 510 ohms.

Optionally, the capacitance values of the first capacitor C1 and the second capacitor C2 are not limited, for example, the capacitance value of the first capacitor C1 may be 1 μ F, and the capacitance value of the second capacitor C2 may be 1 μ F.

The description of fig. 2 is further described below in conjunction with the working principle:

when the load F needs to be powered on to operate, the first output end of the control circuit 10 outputs a high level, in the first driving circuit 30, the high level charges the first capacitor C1 through the first resistor R1, when the voltage of the first capacitor C1 reaches the turn-on voltage of the first switching unit Q1, the first switching unit Q1 is turned on, and the first relay K1 is turned on (that is, two contacts of the first relay K1 are closed); in the second driving circuit 40, after the high level passes through the third resistor R3, the current is shunted by the fourth resistor R4 and then charges the second capacitor C2, and when the voltage of the second capacitor C2 reaches the turn-on voltage of the second switching unit Q2, the second switching unit Q2 is turned on, and the second relay K2 is turned on. Since the resistance of the first resistor R1 is less than or equal to the resistance of the third resistor R3, the current charging the second capacitor C2 is shunted by the fourth resistor R4, the voltage rising speed of the second capacitor C2 is slower than the voltage rising speed of the first capacitor C1, so that the voltage of the second capacitor C2 reaches the turn-on voltage of the second switch unit Q2 later than the voltage of the first capacitor C1 reaches the turn-on voltage of the first switch unit Q1, the second switch unit Q2 is turned on after the first switch unit Q1 is turned on, and the second relay K2 is turned on after the first relay K1 is turned on (i.e., two contacts of the second relay K2 are closed).

When the load F needs to be powered off and stop working, the first output end of the control circuit 10 outputs a low level, in the first driving circuit 30, the first capacitor C1 discharges through the first resistor R1, and when the voltage of the first capacitor C1 is smaller than the on-voltage of the first switching unit Q1, the first switching unit Q1 is turned off, and the first relay K1 is turned off (that is, two contacts of the first relay K1 are turned off); in the second driving circuit 40, the second capacitor C2 is discharged in parallel through the third resistor R3 and the fourth resistor R4, and when the voltage of the second capacitor C2 is smaller than the on-voltage of the second switching unit Q2, the second switching unit Q2 is turned off, and the second relay K2 is turned off. Since the parallel resistance of the third resistor R3 and the fourth resistor R4 is smaller than the resistance of the first resistor R1, and the discharge speed of the second capacitor C2 is greater than the discharge speed of the first capacitor C1, the voltage of the second capacitor C2 is smaller than the turn-on voltage of the second switch unit Q2 and is faster than the turn-on voltage of the first capacitor C1 and is smaller than the turn-on voltage of the first switch unit Q1, the second switch unit Q2 is turned off before the first switch unit Q1 is turned off, and the second relay K2 is turned off before the first relay K1 is turned off (i.e. two contacts of the second relay K2 are turned off), so that the first relay K1 is turned on and then turned off, and the second relay K2 is turned on and then turned off.

Optionally, the first driving circuit 30 further includes a second resistor R2, a first end of the second resistor R2 is electrically connected to a second end of the first resistor R1, a second end of the second resistor R2 is electrically connected to a control end of the first switch unit Q1, and the second resistor R2 is arranged to protect the first switch unit Q1.

Optionally, the second driving circuit 40 further includes a fifth resistor R5, a first end of the fifth resistor R5 is electrically connected to a second end of the third resistor R3, a second end of the fifth resistor R5 is electrically connected to a control end of the second switch unit Q2, and the fifth resistor R5 is arranged to protect the first switch unit Q1.

Optionally, the resistances of the second resistor R2 and the fifth resistor R5 are not limited, for example, the resistances of the second resistor R2 and the fifth resistor R5 may be 1000 ohms.

Fig. 3 shows a circuit diagram of a second embodiment of the control protection circuit provided in the present application, which is detailed as follows:

the first driving circuit 30 includes a first switching unit Q1; the second driving circuit 40 includes a second switching unit Q2;

the control end of the first switch unit Q1 is electrically connected with the first output end of the control circuit 10, the first end of the first switch unit Q1 is connected with the ground of a power supply, the second end of the first switch unit Q1 is electrically connected with the first control end of the first relay K1, and the second control end of the first relay K1 is connected with the first power supply;

a control terminal of the second switch unit Q2 is electrically connected to a second output terminal of the control circuit 10, a first terminal of the second switch unit Q2 is connected to a ground, a second terminal of the second switch unit Q2 is electrically connected to a first control terminal of the second relay K2, and a second control terminal of the second relay K2 is connected to a second power supply;

the level output by the control circuit 10 at the first output terminal controls the conduction and non-conduction of the first switching unit Q1; the level output by the control circuit 10 at the second output terminal controls the conduction and non-conduction of the second switching unit Q2; when the first switching unit Q1 is turned on, the first relay K1 is turned on; when the first switching unit Q1 is not conductive, the first relay K1 is turned off; when the second switching unit Q2 is turned on, the second relay K2 is turned on; when the second switching unit Q2 is not conductive, the second relay K2 is turned off;

the control circuit 10 controls the first switching unit Q1 to be turned on earlier than the second switching unit Q2;

the control circuit 10 controls the first switching unit Q1 to be non-conductive at a timing later than the timing at which the second switching unit Q2 is controlled to be non-conductive.

The description of fig. 3 is further described below in conjunction with the working principle:

when the load F needs to be powered on to work, firstly, the first output end of the control circuit 10 outputs a high level, the first switch unit Q1 is turned on, and the first relay K1 is turned on; after the first relay K1 is turned on, the second output terminal of the control circuit 10 outputs a high level (for example, a timer may be provided in the control circuit 10 so that the second output terminal outputs a high level after the first relay K1 is turned on), the second switching unit Q2 is turned on, and the second relay K2 is turned on.

When the load F needs to be powered off and stop working, firstly, the second output end of the control circuit 10 outputs a low level, the second switch unit Q2 is turned off, and the second relay K2 is turned off; after the second relay K2 is turned off, the first output terminal of the control circuit 10 outputs a low level (for example, a timer may be provided in the control circuit 10 to realize that the first output terminal outputs a low level after the second relay K2 is turned off), the first switching unit Q1 is turned off, and the first relay K1 is turned off. In the second embodiment of the control protection circuit of the application, the time of controlling the first switch unit Q1 to be switched on by the control circuit 10 is earlier than the time of controlling the second switch unit Q2 to be switched on, and the time of controlling the first switch unit Q1 to be not switched on is later than the time of controlling the second switch unit Q2 to be not switched on, so that the first relay K1 is switched on and then switched off, and the second relay K2 is switched on and then switched off. Therefore, the circuit structures of the first driving circuit 30 and the second driving circuit 40 can be completely consistent, so as to save the development cost.

Optionally, the first driving circuit 30 further includes a first resistor R1, a second resistor R2, and a first capacitor C1.

A first end of the first resistor R1 is electrically connected to the first output terminal of the control circuit 10, and a second end of the first resistor R1 is electrically connected to the first end of the first capacitor C1, the first end of the second resistor R2, and the control terminal of the first switch unit Q1.

The second end of the first capacitor C1 and the second end of the second resistor R2 are both connected to power ground.

Optionally, the second driving circuit 40 further includes a third resistor R3, a fourth resistor R4, and a second capacitor C2.

A first end of the third resistor R3 is electrically connected to the second output terminal of the control circuit 10, and a second end of the third resistor R3 is electrically connected to the first end of the fourth resistor R4, the first end of the second capacitor C2, and the control end of the second switch unit Q2.

The second terminal of the fourth resistor R4 and the second terminal of the second capacitor C2 are both connected to ground.

A first terminal of the second switching unit Q2 is connected to a ground, a second terminal of the second switching unit Q2 is electrically connected to a first control terminal of the second relay K2, and a second control terminal of the second relay K2 is connected to a second power source.

Optionally, the resistance values of the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 are not limited, for example, the resistance value of the first resistor R1 may be 1000 ohms, the resistance value of the second resistor R2 may be 10000 ohms, the resistance value of the third resistor R3 may be 1000 ohms, and the resistance value of the fourth resistor R4 may be 10000 ohms.

Optionally, the capacitance values of the first capacitor C1 and the second capacitor C2 are not limited, for example, the capacitance value of the first capacitor C1 may be 100pF, and the capacitance value of the second capacitor C2 may be 100 pF.

Fig. 4 shows a circuit diagram of a third embodiment of the control protection circuit provided in the present application, which is detailed as follows:

the first driving circuit 30 includes a first resistor R1, a second resistor R2, a first diode D1, a first capacitor C1, and a first switching unit Q1.

The anode of the first diode D1 is electrically connected to the first output terminal of the control circuit 10, and the cathode of the first diode D1 is electrically connected to the first terminal of the first resistor R1.

The second end of the first resistor R1 is electrically connected to the first end of the first capacitor C1, the first end of the second resistor R2 and the control end of the first switch unit Q1.

A first end of the third resistor R3 is electrically connected to the anode of the first diode D1, and a second end of the third resistor R3 is electrically connected to a first end of the fourth resistor R4, a first end of the second capacitor C2, and a control end of the second switch unit Q2.

The resistance value of the first resistor R1 is smaller than that of the third resistor R3.

The parallel resistance of the third resistor R3 and the fourth resistor R4 is smaller than the resistance of the second resistor R2.

Optionally, the resistance values of the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 are not limited, for example, the resistance value of the first resistor R1 may be 100 ohms, the resistance value of the second resistor R2 may be 10000 ohms, the resistance value of the third resistor R3 may be 1000 ohms, and the resistance value of the fourth resistor R4 may be 5000 ohms.

The description of fig. 4 is further described below in conjunction with the working principle:

when the load F needs to be powered on to work, the first output end of the control circuit 10 outputs a high level, in the first driving circuit 30, after the high level passes through the first diode D1 and passes through the first resistor R1, the current is shunted by the second resistor R2 and then charges the first capacitor C1, when the voltage of the first capacitor C1 reaches the turn-on voltage of the first switching unit Q1, the first switching unit Q1 is turned on, and the first relay K1 is turned on; in the second driving circuit 40, after the high level passes through the third resistor R3, the current is shunted by the fourth resistor R4 and then charges the second capacitor C2, and when the voltage of the second capacitor C2 reaches the turn-on voltage of the second switching unit Q2, the second switching unit Q2 is turned on, and the second relay K2 is turned on. Since the resistance value of the third resistor R3 is greater than that of the first resistor R1, the charging current of the first capacitor C1 is greater than that of the second capacitor C2, and the voltage rising speed of the second capacitor C2 is slower than that of the first capacitor C1, the voltage of the second capacitor C2 reaches the turn-on voltage of the second switch unit Q2 later than the voltage of the first capacitor C1 reaches the turn-on voltage of the first switch unit Q1, the second switch unit Q2 is turned on after the first switch unit Q1 is turned on, and the second relay K2 is turned on after the first relay K1 is turned on.

When the load F needs to be powered off and stop working, the first output end of the control circuit 10 outputs a low level, in the first driving circuit 30, because the first diode D1 is reversely cut off, the first capacitor C1 can only discharge through the second resistor R2, and when the voltage of the first capacitor C1 is smaller than the on-state voltage of the first switching unit Q1, the first switching unit Q1 is cut off, and the first relay K1 is turned off; in the second driving circuit 40, the second capacitor C2 is discharged in parallel through the third resistor R3 and the fourth resistor R4, and when the voltage of the second capacitor C2 is smaller than the on-voltage of the second switching unit Q2, the second switching unit Q2 is turned off, and the second relay K2 is turned off. Because the parallel resistance of the third resistor R3 and the fourth resistor R4 is smaller than the resistance of the second resistor R2, the discharging speed of the second capacitor C2 is greater than the discharging speed of the first capacitor C1, the voltage of the second capacitor C2 is smaller than the turn-on voltage of the second switch unit Q2 and is faster than the turn-on voltage of the first capacitor C1 and is smaller than the turn-on voltage of the first switch unit Q1, the second switch unit Q2 is turned off before the first switch unit Q1 is turned off, and the second relay K2 is turned off before the first relay K1 is turned off, so that the first relay K1 is turned on first and then turned off, and the second relay K2 is turned on then turned off first.

Fig. 5a shows a circuit diagram of a fourth embodiment of the control protection circuit provided in the present application, which is detailed as follows:

A second terminal of the first capacitor C1 is connected to power ground.

The second driving circuit 40 includes a third resistor R3, a second capacitor C2, a zener diode ZD, a second switching unit Q2, and a third switching unit Q3.

A first end of the third resistor R3 is electrically connected to a first end of the first resistor R1, and a second end of the third resistor R3 is electrically connected to a cathode of the zener diode ZD.

A control end of the second switch unit Q2 is electrically connected to an anode of the zener diode ZD, a first end of the second switch unit Q2 is electrically connected to a second end of the second capacitor C2, a second end of the second switch unit Q2 is electrically connected to a first control end of the second relay K2, and a second control end of the second relay K2 is connected to the second power supply.

A control terminal of the third switching unit Q3 is electrically connected to a first terminal of the third resistor R3, a first terminal of the third switching unit Q3 is electrically connected to a cathode of the zener diode ZD, and a second terminal of the third switching unit Q3 is electrically connected to a second terminal of the second capacitor C2.

A first end of the second capacitor C2 is electrically connected to the cathode of the zener diode ZD.

The resistance value of the third resistor R3 is greater than the resistance value of the first resistor R1.

Optionally, the resistance of the first resistor R1 and the third resistor R3 are not limited, for example, the resistance of the first resistor R1 may be 1000 ohms, and the resistance of the third resistor R3 may be 3300 ohms.

Optionally, the capacitance values of the first capacitor C1 and the second capacitor C2 are not limited, for example, the capacitance value of the first capacitor C1 may be 1 μ F, and the capacitance value of the second capacitor C2 may be 3.3 μ F.

The description of fig. 5a is further described below in connection with the working principle:

when the load F needs to be powered on to work, the first output end of the control circuit 10 outputs a high level, in the first driving circuit 30, the high level charges the first capacitor C1 after passing through the first resistor R1, and when the voltage of the first capacitor C1 reaches the turn-on voltage of the first switching unit Q1, the first switching unit Q1 is turned on, and the first relay K1 is turned on; in the second driving circuit 40, the third switching unit Q3 is turned off, the high level charges the second capacitor C2 through the third resistor R3, and when the voltage of the second capacitor C2 reaches the turn-on voltage of the second switching unit Q2 and the voltage of the second capacitor C2 exceeds the regulated voltage value of the zener diode ZD, the second switching unit Q2 is turned on, and the second relay K2 is turned on. Since the resistance value of the third resistor R3 is greater than that of the first resistor R1, the charging current of the first capacitor C1 is greater than that of the second capacitor C2, and the voltage rising speed of the second capacitor C2 is slower than that of the first capacitor C1, the voltage of the second capacitor C2 reaches the turn-on voltage of the second switch unit Q2 later than the voltage of the first capacitor C1 reaches the turn-on voltage of the first switch unit Q1, the second switch unit Q2 is turned on after the first switch unit Q1 is turned on, and the first relay K2 is turned on after the first relay K1 is turned on.

When the load F needs to be powered off and stop working, the first output end of the control circuit 10 outputs a low level, in the first driving circuit 30, the first capacitor C1 discharges through the first resistor R1, and when the voltage of the first capacitor C1 is smaller than the on-state voltage of the first switching unit Q1, the first switching unit Q1 is turned off, and the first relay K1 is turned off; in the second driving circuit 40, the third switching unit Q3 is turned on, the second capacitor C2 is short-circuited by the third switching unit Q3 to be rapidly discharged, and when the voltage of the second capacitor C2 is less than the turn-on voltage of the second switching unit Q2, the second switching unit Q2 is turned off, and the first relay K1 is turned off. Since the second capacitor C2 is directly and rapidly discharged through the short circuit of the third switching unit Q3, and the discharging speed of the second capacitor C2 is greater than that of the first capacitor C1, the second switching unit Q2 is turned off before the first switching unit Q1 is turned off, and the first relay K2 is turned off before the first relay K1 is turned off, so that the first relay K1 is turned on first and then turned off, and the second relay K2 is turned on second and then turned off first.

Optionally, the second driving circuit 40 further includes a fourth resistor R4, a first end of the fourth resistor R4 is electrically connected to the control end of the second switch unit Q2, a second end of the fourth resistor R4 is electrically connected to the first end of the second switch unit Q2, and the fourth resistor R4 is arranged to protect the second switch unit Q2.

Optionally, the second driving circuit 40 further includes a fifth resistor R5, a first end of the fifth resistor R5 is electrically connected to the control end of the third switching unit Q3, a second end of the fifth resistor R5 is electrically connected to the second end of the third switching unit Q3, and the fifth resistor R5 is disposed to protect the third switching unit Q3.

Optionally, the resistance values of the fourth resistor R4 and the fifth resistor R5 are not limited, for example, the resistance values of the fourth resistor R4 and the fifth resistor R5 may be 1000 ohms.

Fig. 5b shows a circuit diagram of a fifth embodiment of the control protection circuit provided in the present application, which is detailed as follows:

the first driving circuit 30 includes a first resistor R1, a second resistor R2, a first capacitor C1, and a first switch unit Q1.

Optionally, the resistance values of the first resistor R1, the second resistor R2, and the third resistor R3 are not limited, for example, the resistance value of the first resistor R1 may be 1000 ohms, the resistance value of the second resistor R2 may be 10000 ohms, and the resistance value of the third resistor R3 may be 3300 ohms.

The description of fig. 5b is further described below in conjunction with the working principle:

when the load F needs to be powered on to work, the first output end of the control circuit 10 outputs a high level, in the first driving circuit 30, the high level passes through the first resistor R1, is shunted by the second resistor R2, and then charges the first capacitor C1, when the voltage of the first capacitor C1 reaches the turn-on voltage of the first switching unit Q1, the first switching unit Q1 is turned on, and the first relay K1 is turned on; in the second driving circuit 40, the third switching unit Q3 is turned off, the high level charges the second capacitor C2 through the third resistor R3, and when the voltage of the second capacitor C2 reaches the turn-on voltage of the second switching unit Q2 and the voltage of the second capacitor C2 exceeds the regulated voltage value of the zener diode ZD, the second switching unit Q2 is turned on, and the second relay K2 is turned on. Since the resistance value of the third resistor R3 is greater than that of the first resistor R1, the charging current of the first capacitor C1 is greater than that of the second capacitor C2, and the voltage rising speed of the second capacitor C2 is slower than that of the first capacitor C1, the voltage of the second capacitor C2 reaches the turn-on voltage of the second switch unit Q2 later than the voltage of the first capacitor C1 reaches the turn-on voltage of the first switch unit Q1, the second switch unit Q2 is turned on after the first switch unit Q1 is turned on, and the first relay K2 is turned on after the first relay K1 is turned on.

When the load F needs to be powered off and stops working, the first output end of the control circuit 10 outputs a low level, in the first driving circuit 30, the first capacitor C1 is discharged in parallel through the first resistor R1 and the second resistor R2, and when the voltage of the first capacitor C1 is smaller than the on-state voltage of the first switching unit Q1, the first switching unit Q1 is turned off, and the first relay K1 is turned off; in the second driving circuit 40, the third switching unit Q3 is turned on, the second capacitor C2 is short-circuited by the third switching unit Q3 to be rapidly discharged, and when the voltage of the second capacitor C2 is less than the turn-on voltage of the second switching unit Q2, the second switching unit Q2 is turned off, and the first relay K1 is turned off. Since the second capacitor C2 is directly and rapidly discharged through the short circuit of the third switching unit Q3, and the discharging speed of the second capacitor C2 is greater than that of the first capacitor C1, the second switching unit Q2 is turned off before the first switching unit Q1 is turned off, and the first relay K2 is turned off before the first relay K1 is turned off, so that the first relay K1 is turned on first and then turned off, and the second relay K2 is turned on second and then turned off first.

Fig. 6 shows a circuit diagram of a sixth embodiment of the control protection circuit provided in the present application, which is detailed as follows:

A second terminal of the first capacitor C1 is connected to power ground.

The second driving circuit 40 includes a third resistor R3, a second capacitor C2, a second diode D2, a second switching unit Q2, and a third switching unit Q3.

The anode of the second diode D2 is electrically connected to the first terminal of the first resistor R1, and the cathode of the second diode D2 is electrically connected to the first terminal of the third resistor R3.

A second terminal of the third resistor R3 is electrically connected to a first terminal of the third switching unit Q3.

A first terminal of the second capacitor C2 is electrically connected to a first terminal of the third switching unit Q3, and a second terminal of the second capacitor C2 is connected to the power ground.

A control terminal of the third switching unit Q3 is electrically connected to the anode of the second diode D2, and a second terminal of the third switching unit Q3 is connected to the power ground.

The resistance of the third resistor R3 is greater than the resistance of the first resistor R1.

Optionally, the resistance of the first resistor R1 and the third resistor R3 are not limited, for example, the resistance of the first resistor R1 may be 1000 ohms, and the resistance of the third resistor R3 may be 3000 ohms.

The description of fig. 6 is further described below in conjunction with the working principle:

when the load F needs to be powered on to work, the first output end of the control circuit 10 outputs a high level, in the first driving circuit 30, the high level charges the first capacitor C1 through the first resistor R1, when the voltage of the first capacitor C1 reaches the turn-on voltage of the first switching unit Q1, the first switching unit Q1 is turned on, and the first relay K1 is turned on; in the second driving circuit 40, the third switching unit Q3 is turned off, a high level passes through the second diode D2, and then the second capacitor C2 is charged through the third resistor R3, and when the voltage of the second capacitor C2 reaches the turn-on voltage of the second switching unit Q2, the second switching unit Q2 is turned on, and the second relay K2 is turned on. Since the resistance value of the third resistor R3 is greater than that of the first resistor R1, the charging current of the first capacitor C1 is greater than that of the second capacitor C2, and the voltage rising speed of the second capacitor C2 is slower than that of the first capacitor C1, the voltage of the second capacitor C2 reaches the turn-on voltage of the second switch unit Q2 later than the voltage of the first capacitor C1 reaches the turn-on voltage of the first switch unit Q1, the second switch unit Q2 is turned on after the first switch unit Q1 is turned on, and the second relay K2 is turned on after the first relay K1 is turned on.

When the load F needs to be powered off and stop working, the first output end of the control circuit 10 outputs a low level, in the first driving circuit 30, the first capacitor C1 discharges through the first resistor R1, and when the voltage of the first capacitor C1 is smaller than the on-state voltage of the first switching unit Q1, the first switching unit Q1 is turned off, and the first relay K1 is turned off; in the second driving circuit 40, the third switching unit Q3 is turned on, the second capacitor C2 is rapidly discharged by short-circuiting the third switching unit Q3 due to the reverse turn-off of the second diode D2, and when the voltage of the second capacitor C2 is less than the turn-on voltage of the second switching unit Q2, the second switching unit Q2 is turned off, and the second relay K2 is turned off. Since the second capacitor C2 is directly and rapidly discharged through the short circuit of the third switch unit Q3, and the discharging speed of the second capacitor C2 is greater than that of the first capacitor C1, the voltage of the second capacitor C2 is smaller than the on voltage of the second switch unit Q2 and is smaller than the on voltage of the first capacitor C1 and is smaller than that of the first switch unit Q1, and then the second switch unit Q2 is turned off before the first switch unit Q1 is turned off, and the second relay K2 is turned off before the first relay K1 is turned off, so that the first relay K1 is turned on first and then turned off, and the second relay K2 is turned on after being turned on and then turned off first.

Optionally, the second driving circuit 40 further includes a fourth resistor R4, a first end of the fourth resistor R4 is electrically connected to a first end of the third switching unit Q3, a second end of the fourth resistor R4 is connected to a ground, and the second switching unit Q2 is protected by the fourth resistor R4.

Optionally, the resistance of the fourth resistor R4 and the resistance of the fifth resistor R5 are not limited, for example, the resistance of the fourth resistor R4 may be 10000 ohms, and the resistance of the fifth resistor R5 may be 1000 ohms.

Fig. 7 shows a circuit diagram of a seventh embodiment of the control protection circuit provided in the present application, which is detailed as follows:

A second terminal of the first capacitor C1 is connected to power ground.

The second driving circuit 40 includes a third resistor R3, a second capacitor C2, a second diode D2, and a second switching unit Q2.

The anode of the second diode D2 is electrically connected to the second terminal of the third resistor R3, and the cathode of the second diode D2 is electrically connected to the first terminal of the first resistor R1.

A first end of the third resistor R3 is electrically connected to the cathode of the second diode D2.

A first terminal of the second capacitor C2 is electrically connected to the anode of the second diode D2, and a second terminal of the second capacitor C2 is connected to ground.

A control terminal of the second switching unit Q2 is electrically connected to the positive electrode of the second diode D2, a first terminal of the second switching unit Q2 is connected to the ground, a second terminal of the second switching unit Q2 is electrically connected to a first control terminal of the second relay K2, and a second control terminal of the second relay K2 is connected to the second power supply.

Optionally, the resistances of the first resistor R1 and the third resistor R3 are not limited, for example, the resistance of the first resistor R1 may be 800 ohms, and the resistance of the third resistor R3 may be 1000 ohms.

The description of fig. 7 is further described below in conjunction with the working principle:

when the load F needs to be powered on to work, the first output end of the control circuit 10 outputs a high level, in the first driving circuit 30, the high level charges the first capacitor C1 through the first resistor R1, when the voltage of the first capacitor C1 reaches the turn-on voltage of the first switching unit Q1, the first switching unit Q1 is turned on, and the first relay K1 is turned on; in the second driving circuit 40, since the second diode D2 is turned off in the reverse direction, the high level charges the second capacitor C2 through the third resistor R3, and when the voltage of the second capacitor C2 reaches the on voltage of the second switching unit Q2, the second switching unit Q2 is turned on, and the second relay K2 is turned on. Since the resistance of the first resistor R1 is smaller than the resistance of the third resistor R3, the charging current of the first capacitor C1 is larger than the charging current of the second capacitor C2, the voltage rising speed of the second capacitor C2 is slower than the voltage rising speed of the first capacitor C1, the voltage of the second capacitor C2 reaches the turn-on voltage of the second switch unit Q2 later than the voltage of the first capacitor C1 reaches the turn-on voltage of the first switch unit Q1, the second switch unit Q2 is turned on after the first switch unit Q1 is turned on, and the second relay K2 is turned on after the first relay K1 is turned on.

When the load F needs to be powered off and stop working, the first output end of the control circuit 10 outputs a low level, in the first driving circuit 30, the first capacitor C1 discharges through the first resistor R1, and when the voltage of the first capacitor C1 is smaller than the on-state voltage of the first switching unit Q1, the first switching unit Q1 is turned off, and the first relay K1 is turned off; in the second driving circuit 40, the second diode D2 is turned on, the second capacitor C2 is rapidly discharged through the second diode D2, and when the voltage of the second capacitor C2 is smaller than the on voltage of the second switching unit Q2, the second switching unit Q2 is turned off, and the second relay K2 is turned off. Since the second capacitor C2 is directly and rapidly discharged through the second diode D2, and the discharging speed of the second capacitor C2 is greater than that of the first capacitor C1, the voltage of the second capacitor C2 is smaller than the turn-on voltage of the second switch unit Q2 and is smaller than the turn-on voltage of the first capacitor C1 and is smaller than the turn-on voltage of the first switch unit Q1, and then the second switch unit Q2 is turned off before the first switch unit Q1 is turned off, and the second relay K2 is turned off before the first relay K1 is turned off, so that the first relay K1 is turned on and then turned off, and the second relay K2 is turned on and then turned off.

Based on the circuit diagram of fig. 7, in an alternative implementation, the second driving circuit 40 further includes a fourth resistor R4, a first end of the fourth resistor R4 is electrically connected to a first end of the second switching unit Q2, and a second end of the fourth resistor R4 is connected to the power ground.

The resistance of the first resistor R1 may be equal to the resistance of the third resistor R3.

When the load F needs to be powered on to work, the first output end of the control circuit 10 outputs a high level, in the first driving circuit 30, the high level charges the first capacitor C1 through the first resistor R1, when the voltage of the first capacitor C1 reaches the turn-on voltage of the first switching unit Q1, the first switching unit Q1 is turned on, and the first relay K1 is turned on; in the second driving circuit 40, since the second diode D2 is turned off in the reverse direction, after the high level passes through the third resistor R3, the current is shunted by the fourth resistor R4 and then charges the second capacitor C2, and when the voltage of the second capacitor C2 reaches the on voltage of the second switching unit Q2, the second switching unit Q2 is turned on, and the second relay K2 is turned on. Since the resistance value of the first resistor R1 is equal to that of the third resistor R3, and the current for charging the second capacitor C2 is shunted by the fourth resistor R4, the charging current of the first capacitor C1 is greater than the charging current of the second capacitor C2, the voltage rising speed of the second capacitor C2 is slower than that of the first capacitor C1, the voltage of the second capacitor C2 reaches the turn-on voltage of the second switch unit Q2, which is later than the voltage of the first capacitor C1, and reaches the turn-on voltage of the first switch unit Q1, so that the second switch unit Q2 is turned on after the first switch unit Q1 is turned on, and the second relay K2 is turned on after the first relay K1 is turned on.

When the load F needs to be powered off and stops working, the resistance value of the first resistor R1 is equal to that of the third resistor R3, so that the second switch unit Q2 is cut off before the first switch unit Q1 is cut off, the second relay K2 is turned off before the first relay K1 is turned off, and therefore the first relay K1 is turned on first and then turned off, and the second relay K2 is turned on first and then turned off first.

Optionally, the resistance of the fourth resistor R4 is not limited, for example, the resistance of the fourth resistor R4 may be 1000 ohms.

Fig. 8 shows a circuit diagram of an eighth embodiment of the control protection circuit provided in the present application, which is detailed as follows:

The second terminal of the first capacitor C1 and the second terminal of the second resistor R2 are connected to power ground.

The second driving circuit 40 includes a third resistor R3, a fourth resistor R4, a second capacitor C2, a second diode D2, and a second switching unit Q2.

A first end of the fourth resistor R4 is electrically connected to the anode of the second diode D2, and a second end of the fourth resistor R4 is connected to the power ground.

The description of fig. 8 is further described below in conjunction with the working principle:

when the load F needs to be powered on to work, the first output end of the control circuit 10 outputs a high level, in the first driving circuit 30, after the high level passes through the first diode D1 and passes through the first resistor R1, the current is shunted by the second resistor R2 and then charges the first capacitor C1, when the voltage of the first capacitor C1 reaches the turn-on voltage of the first switching unit Q1, the first switching unit Q1 is turned on, and the first relay K1 is turned on; in the second driving circuit 40, since the second diode D2 is turned off in the reverse direction, after the high level passes through the third resistor R3, the current is shunted by the fourth resistor R4 and then charges the second capacitor C2, and when the voltage of the second capacitor C2 reaches the on voltage of the second switching unit Q2, the second switching unit Q2 is turned on, and the second relay K2 is turned on. Since the resistance value of the first resistor R1 is smaller than that of the third resistor R3, the charging current of the first capacitor C1 is larger than that of the second capacitor C2, and the voltage rising speed of the second capacitor C2 is slower than that of the first capacitor C1, the voltage of the second capacitor C2 reaches the turn-on voltage of the second switch unit Q2 later than that of the first capacitor C1 to the turn-on voltage of the first switch unit Q1, so that the second switch unit Q2 is turned on after the first switch unit Q1 is turned on, and the second relay K2 is turned on after the first relay K1 is turned on.

When the load F needs to be powered off and stop working, the first output end of the control circuit 10 outputs a low level, in the first driving circuit 30, because the first diode D1 is reversely cut off, the first capacitor C1 discharges through the second resistor R2, and when the voltage of the first capacitor C1 is smaller than the on-state voltage of the first switching unit Q1, the first switching unit Q1 is cut off, and the first relay K1 is turned off; in the second driving circuit 40, the second diode D2 is turned on, the second capacitor C2 is rapidly discharged through the second diode D2, and when the voltage of the second capacitor C2 is smaller than the on voltage of the second switching unit Q2, the second switching unit Q2 is turned off, and the second relay K2 is turned off. Since the second capacitor C2 is directly and rapidly discharged through the second diode D2, and the discharging speed of the second capacitor C2 is greater than that of the first capacitor C1, the voltage of the second capacitor C2 is smaller than the turn-on voltage of the second switch unit Q2 and is smaller than the turn-on voltage of the first capacitor C1 and is smaller than the turn-on voltage of the first switch unit Q1, and then the second switch unit Q2 is turned off before the first switch unit Q1 is turned off, and the second relay K2 is turned off before the first relay K1 is turned off, so that the first relay K1 is turned on and then turned off, and the second relay K2 is turned on and then turned off.

Optionally, the first switch unit Q1, the second switch unit Q2, and the third switch unit Q3 in the present application may be transistors or MOS transistors, and may also be other devices having a switching function. When the first switching unit Q1, the second switching unit Q2, and the third switching unit Q3 are all transistors, the control terminal refers to a base, the first terminal refers to an emitter, and the second terminal refers to a collector. When the first switch unit Q1, the second switch unit Q2 and the third switch unit Q3 are MOS transistors, the control terminal refers to a gate, the first terminal refers to a source, and the second terminal refers to a drain.

In the above embodiments, the descriptions of the respective embodiments have respective emphasis, and reference may be made to the related descriptions of other embodiments for parts that are not described or illustrated in a certain embodiment.

The above-mentioned embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present application and are intended to be included within the scope of the present application.

Claims

1. A control protection circuit, comprising: the circuit comprises a control circuit, a load circuit, a first driving circuit and a second driving circuit, wherein the first driving circuit and the second driving circuit are electrically connected with the control circuit and the load circuit;

2. The control protection circuit according to claim 1, wherein the first driving circuit includes a first resistor, a first capacitor, and a first switching unit;

a first end of the first resistor is electrically connected with a first output end of the control circuit, and a second end of the first resistor is electrically connected with a first end of the first capacitor and a control end of the first switch unit;

the second end of the first capacitor is connected with the power ground;

the first end of the first switch unit is connected with a power ground, the second end of the first switch unit is electrically connected with the first control end of the first relay, and the second control end of the first relay is connected with a first power supply.

3. The control protection circuit of claim 2, wherein said first driver circuit further comprises a second resistor;

the first end of the second resistor is electrically connected with the control end of the first switch unit, and the second end of the second resistor is connected with the power ground.

4. The control protection circuit of claim 3, wherein said first driver circuit further comprises a first diode;

the anode of the first diode is electrically connected with the first output end of the control circuit, and the cathode of the first diode is electrically connected with the first end of the first resistor.

5. The control protection circuit according to claim 2, wherein the second driving circuit comprises a third resistor, a fourth resistor, a second capacitor and a second switching unit;

the first end of the third resistor is electrically connected with the first end of the first resistor, and the second end of the third resistor is electrically connected with the first end of the fourth resistor and the first end of the second capacitor;

a second end of the fourth resistor and a second end of the second capacitor are both connected with a power ground;

the control end of the second switch unit is electrically connected with the second end of the third resistor, the first end of the second switch unit is connected with a power ground, the second end of the second switch unit is electrically connected with the first control end of the second relay, and the second control end of the second relay is connected with a second power supply;

the resistance value of the first resistor is smaller than or equal to the resistance value of the third resistor, and the parallel resistance value of the third resistor and the fourth resistor is smaller than the resistance value of the first resistor.

6. The control protection circuit according to claim 1, wherein the first drive circuit includes a first switching unit; the second driving circuit includes a second switching unit;

the control end of the first switch unit is electrically connected with the first output end of the control circuit, the first end of the first switch unit is connected with a power ground, the second end of the first switch unit is electrically connected with the first control end of the first relay, and the second control end of the first relay is connected with a first power supply;

the control end of the second switch unit is electrically connected with the second output end of the control circuit, the first end of the second switch unit is connected with a power ground, the second end of the second switch unit is electrically connected with the first control end of the second relay, and the second control end of the second relay is connected with a second power supply;

the level output by the control circuit at the first output end controls the conduction and the non-conduction of the first switch unit; the level output by the control circuit at the second output end controls the conduction and the non-conduction of the second switch unit; when the first switch unit is conducted, the first relay is switched on; when the first switch unit is not conducted, the first relay is turned off; when the second switch unit is conducted, the second relay is switched on; when the second switch unit is not conducted, the second relay is turned off;

the moment when the control circuit controls the first switch unit to be conducted is earlier than the moment when the control circuit controls the second switch unit to be conducted;

the time when the control circuit controls the first switch unit to be not conducted is later than the time when the control circuit controls the second switch unit to be not conducted.

7. The control protection circuit according to claim 4, wherein the second driving circuit comprises a third resistor, a fourth resistor, a second capacitor and a second switching unit;

a first end of the third resistor is electrically connected with the anode of the first diode, and a second end of the third resistor is electrically connected with a first end of the fourth resistor, a first end of the second capacitor and a control end of the second switch unit;

the first end of the second switch unit is connected with a power ground, the second end of the second switch unit is electrically connected with the first control end of the second relay, and the second control end of the second relay is connected with a second power supply;

the resistance value of the first resistor is smaller than that of the third resistor, and the parallel resistance value of the third resistor and the fourth resistor is smaller than that of the second resistor.

8. The control protection circuit according to claim 2 or 3, wherein the second driving circuit includes a third resistor, a second capacitor, a zener diode, a second switching unit, and a third switching unit;

the first end of the third resistor is electrically connected with the first end of the first resistor, and the second end of the third resistor is electrically connected with the cathode of the voltage stabilizing diode;

the control end of the second switch unit is electrically connected with the anode of the voltage stabilizing diode, the first end of the second switch unit is electrically connected with the second end of the second capacitor, the second end of the second switch unit is electrically connected with the first control end of the second relay, and the second control end of the second relay is connected with a second power supply;

the control end of the third switching unit is electrically connected with the first end of the third resistor, the first end of the third switching unit is electrically connected with the cathode of the voltage stabilizing diode, and the second end of the third switching unit is electrically connected with the second end of the second capacitor;

the first end of the second capacitor is electrically connected with the cathode of the voltage stabilizing diode;

the resistance value of the third resistor is larger than that of the first resistor.

9. The control protection circuit according to claim 2, wherein the second driving circuit includes a third resistor, a second capacitor, a second diode, a second switching unit, and a third switching unit;

the anode of the second diode is electrically connected with the first end of the first resistor, and the cathode of the second diode is electrically connected with the first end of the third resistor;

a second end of the third resistor is electrically connected with a first end of the third switching unit;

the first end of the second capacitor is electrically connected with the first end of the third switch unit, and the second end of the second capacitor is connected with the power ground;

the control end of the third switching unit is electrically connected with the anode of the second diode, and the second end of the third switching unit is connected with the power ground;

10. The control protection circuit according to claim 2, wherein the second driving circuit includes a third resistor, a second capacitor, a second diode, and a second switching unit;

the anode of the second diode is electrically connected with the second end of the third resistor, and the cathode of the second diode is electrically connected with the first end of the first resistor;

the first end of the third resistor is electrically connected with the cathode of the second diode;

the first end of the second capacitor is electrically connected with the anode of the second diode, and the second end of the second capacitor is connected with the power ground;

the control end of the second switch unit is electrically connected with the anode of the second diode, the first end of the second switch unit is connected with a power ground, the second end of the second switch unit is electrically connected with the first control end of the second relay, and the second control end of the second relay is connected with a second power supply;

the resistance value of the first resistor is smaller than that of the third resistor.

11. The control protection circuit according to claim 4, wherein the second driving circuit comprises a third resistor, a fourth resistor, a second capacitor, a second diode and a second switching unit;

a first end of the fourth resistor is electrically connected with the anode of the second diode, and a second end of the fourth resistor is connected with a power ground;