WO2019148632A1

WO2019148632A1 - Relay driving circuit and air conditioner

Info

Publication number: WO2019148632A1
Application number: PCT/CN2018/081476
Authority: WO
Inventors: 霍兆镜; 李洪涛
Original assignee: 广东美的制冷设备有限公司; 美的集团股份有限公司
Priority date: 2018-02-05
Filing date: 2018-03-31
Publication date: 2019-08-08
Also published as: CN207883612U

Abstract

Disclosed by the present application are a relay driving circuit and an air conditioner. The relay driving circuit comprises a control circuit, a power supply terminal, and a power supply regulating circuit. The power supply terminal and the relay coil form a power supply loop; the power supply regulating circuit is connected in series in the power supply loop, and the power supply regulating circuit is under control of the control circuit; after the relay is controlled to be closed for a preset duration, the control circuit controls the on/off of the power supply loop at a preset frequency and/or a preset duty cycle. Under the premise of ensuring the normal operation of the relay, the scheme effectively reduces the power consumption and heat generation of the relay, thereby improving the overall stability of the circuit in which the relay is located.

Description

Relay drive circuit and air conditioner

Technical field

The present application relates to the field of air conditioners, and in particular, to a relay driving circuit and an air conditioner.

Background technique

In the existing air conditioner relay driving technology, the relay is started with the rated voltage of the relay, and after the relay is closed, the rated voltage is still used to maintain the closed state of the relay; since the relay is closed, it does not need a large Maintaining power, the existing relay drive method not only wastes energy, but also causes the relay to heat up, increasing the total amount of heat generated by the circuit, thereby affecting the service life of other devices in the circuit.

Summary of the invention

The main purpose of the present application is to propose a relay driving circuit and an air conditioner, which are intended to reduce the power consumption of the relay.

To achieve the above object, a relay driving circuit is provided in the present application, the relay coil has a first end and a second end; and the relay driving circuit includes:

Control circuit;

a power supply end, comprising electrically connecting to the first end and the second end of the relay coil to form a high voltage side and a low voltage side of the power supply circuit;

a power supply adjustment circuit connected in series to the power supply end and the power supply circuit of the relay coil, and the power supply adjustment circuit is electrically connected to the control circuit to control the relay to be closed under the control of the control circuit Or disconnected; wherein, after the control relay is closed and reaches a preset duration, the power supply adjusting circuit controls on/off of the power supply circuit at a preset frequency and/or a preset duty ratio.

Preferably, the power supply regulation loop outputs a triangular wave, a rectangular pulse, and a sawtooth pulse for controlling the power supply circuit to supply power to the relay.

Preferably, the high voltage side is electrically connected to the first end of the relay coil, and the power supply regulating circuit comprises an input end, an output end and a controlled end;

An input end of the power supply adjusting circuit is connected to the low voltage side, and an output end of the power supply adjusting circuit is electrically connected to a second end of the relay coil; a controlled end of the power supply adjusting circuit is electrically connected to the control circuit connection.

Preferably, the low voltage side is electrically connected to the second end of the relay coil, and the power supply regulating circuit comprises an input end, an output end and a controlled end;

An input end of the power supply adjusting circuit is connected to the high voltage side, and an output end of the power supply adjusting circuit is electrically connected to a first end of the relay coil; a controlled end of the power supply adjusting circuit is electrically connected to the control circuit connection.

Preferably, the power supply regulation circuit includes a switch tube and a protection resistor, an input end of the switch tube is an input end of the power supply regulation loop, and an output end of the switch tube is an output end of the power supply regulation loop. The controlled end of the switch tube is connected to one end of the protection resistor, and the other end of the protection resistor is a controlled end of the power supply regulation loop.

Preferably, the switching transistor is a triode, a MOS transistor, a GTO, an IGBT or a driving chip.

Preferably, the relay driving circuit further includes a diode, an anode of the diode is connected to an output end of the switching tube, and a cathode of the diode is connected to the high voltage side.

Preferably, the control circuit controls a frequency of a power supply voltage of the power supply circuit to the relay according to an inductance of the relay coil; and the power supply circuit provides a power supply voltage pulse for the relay;

The relationship between the frequency of the supply voltage pulse and the inductance of the relay coil is: f ≥ Ue / (L * I);

f is the frequency of the supply voltage pulse, L is the inductance of the relay coil, I is the amount of current passing through the relay coil when the relay is in a steady state state, and Ue is the voltage value when the supply voltage pulse is at a high level.

Preferably, the control circuit controls a duty ratio of the power supply circuit to the power supply voltage of the relay according to a release voltage of the relay coil; and the power supply circuit supplies a power supply voltage pulse to the relay;

The relationship between the duty ratio of the supply voltage pulse and the release voltage of the relay is: D>Usf/Ue;

D is the duty ratio of the supply voltage pulse, Usf is the release voltage of the relay coil, and Ue is the voltage value when the supply voltage pulse is at a high level.

The present application also provides an air conditioner including a controller, an indoor unit, an outdoor unit, and the relay drive circuit; the outdoor unit includes a compressor and a control for starting/closing the compressor Relay

The relay drive circuit is electrically coupled to the relay for powering the relay.

In the present scheme, based on the working principle of the electromagnetic relay, the control function of the power supply regulating circuit is controlled by the control circuit, and after the relay is normally started, the power supply circuit of the relay coil is controlled with a preset frequency and/or a preset duty ratio. Turning on/off to realize pulsed power supply to the relay coil by the power supply loop, effectively reducing the power consumption and heat generation of the relay under the premise of ensuring normal operation of the relay, thereby improving the location of the relay The overall stability of the circuit. Further, the circuit structure of the solution is compact and utilizes fewer components, which can achieve better technical effects and effectively reduce production costs.

DRAWINGS

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings to be used in the embodiments or the prior art description will be briefly described below. Obviously, the drawings in the following description are only It is a certain embodiment of the present application, and other drawings can be obtained according to the structures shown in the drawings without any creative work for those skilled in the art.

1 is a schematic structural view of an embodiment of a relay driving circuit of the present application;

2 is a waveform diagram of a power supply voltage of the power supply loop of FIG. 1 to the relay coil.

Description of the reference numerals:

标号Label	名称name	标号Label	名称name
100 100	控制电路Control circuit	D1D1	二极管diode
200 200	供电调节电路Power supply regulation circuit	RYRY	继电器Relay
VCC1 VCC1	高压侧High pressure side	10 10	继电器线圈Relay coil
Q1 Q1	开关管turning tube	20 20	触点Contact
R1 R1	保护电阻Protection resistor

The implementation, functional features and advantages of the present application will be further described with reference to the accompanying drawings.

Detailed ways

The technical solutions in the embodiments of the present application are clearly and completely described in the following with reference to the drawings in the embodiments of the present application. It is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present application without departing from the inventive scope are the scope of the present application.

It should be noted that, if there is a directional indication (such as up, down, left, right, front, back, ...) in the embodiment of the present application, the directional indication is only used to explain in a certain posture (as shown in the drawing) The relative positional relationship between the components, the motion situation, and the like, if the specific posture changes, the directional indication also changes accordingly.

In addition, if there is a description relating to "first", "second", etc. in the embodiments of the present application, the description of "first", "second", etc. is used for descriptive purposes only, and is not to be construed as an Its relative importance or implicit indication of the number of technical features indicated. Thus, features defining "first" or "second" may include at least one of the features, either explicitly or implicitly. In addition, the technical solutions between the various embodiments may be combined with each other, but must be based on the realization of those skilled in the art, and when the combination of the technical solutions is contradictory or impossible to implement, it should be considered that the combination of the technical solutions does not exist. Nor is it within the scope of protection required by this application.

The application proposes a relay driving circuit for driving the relay RY. The relay RY is applied to a home appliance, which may be an air conditioner, a refrigerator, a washing machine, or the like. Here, taking an air conditioner as an example, the air conditioner includes a controller, an indoor unit, and an outdoor unit; when the controller controls the start or stop of the outdoor unit, the compressor of the outdoor unit is controlled by a relay. Working status. Of course, it is to be understood that the use of the relay RY in an air conditioner is not limited thereto. The relay RY is an electrical control device with an isolation function, and its structure and specifications are various. The structure of the relay RY is not specifically limited in this solution, but those skilled in the art can understand that the relay RY generally has a certain input variable (such as current, voltage, power, impedance, frequency, temperature, pressure, speed, Inductive mechanism (input part) of light, etc.; there is an actuator (output part) capable of "on" and "off" control of the controlled circuit; in the present scheme, the relay is an electromagnetic relay, and the sensing part thereof is The coil of the relay has an execution structure as a contact, and the contact may be a normally open type or a normally closed type; when the relay coil is energized, the suction force generated between the electromagnet core and the armature inside the relay is utilized, The state of the contact is changed to cause the relay to function as an on/off circuit.

Referring to FIG. 1, the relay driving circuit in the present scheme realizes driving the relay RY by controlling the energization state of the relay coil 10. Specifically, the relay coil 10 has a first end and a second end; the relay driving circuit includes a control circuit 100, a power supply end, and a power supply adjustment circuit 200. The power supply end includes a first end and a second end electrically connected to the relay coil 10 to form a high voltage side VCC1 and a low voltage side of the power supply circuit; the power supply regulating circuit 200 is connected in series to the power supply end and the a power supply circuit of the relay coil 10, and the power supply regulating circuit 200 is electrically connected to the control circuit 100 to control the relay RY to be closed or opened under the control of the control circuit 100; wherein, in the control relay After the RY is closed and reaches a preset duration, the control circuit 100 controls the on/off of the power supply loop at a preset frequency and/or a preset duty ratio. In an embodiment, the high voltage side VCC1 is a driving power source, and the low voltage side is a ground end. The control circuit 100 in the present solution may be an MCU or a main control board or controller of the air conditioner.

It can be understood that, in an embodiment, the first end of the relay coil 10 is electrically connected to the high voltage side VCC1, and the second end of the relay coil 10 passes through the power supply adjusting circuit 200 and the low voltage. a side connection; in another embodiment, the first end of the relay coil 10 is connected to the high voltage side VCC1 through the power supply adjustment circuit 200, and the second end of the relay coil 10 is electrically connected to the low voltage side . Since the power supply regulating circuit 200 is connected in series in the power supply circuit, the on/off state of the power supply circuit can be controlled by controlling the on/off state of the power supply adjusting circuit 200.

It should be explained here that since the relay coil 10 is an inductive component, when the power supply circuit is turned on, the relay coil 10 is energized, and after the relay coil 10 is energized, the relay RY contact 20 acts on the one hand. To switch the state of the relay RY contact 20; on the other hand, the relay coil 10 performs energy storage. When the power supply circuit is disconnected, since the relay coil 10 has a certain amount of energy, the relay coil 10 can still control the relay RY contact 20, thereby achieving even disconnection of the power supply circuit. At the time, the relay RY is still able to maintain a closed/open state between. Of course, under the action of the control circuit 100, the power supply adjustment circuit 200 must control the on and off times of the power supply circuit to be appropriate to avoid the power supply circuit being powered off for too long, resulting in the relay coil 10 The stored energy is exhausted, thereby losing control of the relay RY contact 20.

When the relay RY is powered on, since the relay coil 10 is excited, an instantaneous large current is required to establish the magnetic field so that the contact 20 of the relay RY is closed or opened; therefore, when the relay RY is powered on, power is required. The circuit maintains power supply to the relay coil 10 to provide greater power to the relay coil 10; the supply voltage of the relay coil 10 is generally not lower than the rated voltage of the relay RY, otherwise the relay RY closes too slowly, affecting the relay The service life of RY. When the relay RY is powered on, the relay coil 10 does not need a large holding current, and can maintain the control of the relay RY contact 20, so in this solution, the preset time is set after the relay RY is powered on. The power supply regulating circuit 200 controls the on/off of the power supply circuit to control the power supply circuit to supply the pulse of the relay coil 10 to reduce the power consumption of the relay RY under the premise of ensuring the normal operation of the relay RY. Loss and heat.

In the present solution, the power supply adjustment circuit 200 controls the on/off of the power supply circuit at a preset frequency, which means that the power supply adjustment circuit 200 controls the power supply circuit to be turned on/off within 1 second. The power supply adjustment circuit 200 controls the on/off of the power supply circuit with a preset duty ratio, which means that the on time is always turned on and off during a period of turn-on and turn-off. The ratio of the sum of the times; that is, the power supply adjusting circuit 200 controls the power supply circuit to be turned off once every time, wherein the conduction time accounts for the ratio of the on time and the off time. Referring to Figure 2, when the relay RY is turned on, the power supply circuit provides a supply voltage pulse of 0.5 seconds to 10 seconds. After the relay completes the closing action, it will be driven by the pulse drive. The duty cycle of the pulse can be 10% to 99%. In this embodiment, the relay is driven with a 35% duty cycle, 20 kHz supply pulse.

In the present solution, the power supply adjusting circuit 200 can control the power supply of the relay RY by the power supply loop by outputting a triangular wave, a rectangular pulse, a sawtooth wave pulse, or the like. A specific circuit for outputting a triangular wave, a rectangular pulse, or a sawtooth pulse can utilize the prior art. Preferably, in the present solution, after the preset time of the relay RY is normally started, the power supply circuit supplies power to the relay RY in the form of a voltage pulse. In an embodiment, only the power supply voltage pulse can be controlled. Frequency, setting the supply voltage pulse with a fixed duty ratio; or setting the supply voltage pulse at a fixed frequency only by adjusting the duty ratio of the supply voltage pulse; preferably, simultaneously adjusting the supply voltage pulse The frequency and duty cycle are such that the supply voltage pulse can maintain the relay RY with minimal energy, thereby greatly reducing the power loss of the relay RY.

In the present scheme, based on the working principle of the electromagnetic relay RY, the control function of the power supply regulating circuit 200 is controlled by the control circuit 100, and after the relay RY is normally started, the power supply is controlled at a preset frequency and/or a preset duty ratio. Turning on/off the circuit to realize pulsed power supply to the relay coil 10 by the power supply loop, and effectively reducing the power consumption and heat generation of the relay RY under the premise of ensuring the normal operation of the relay RY; The overall stability of the circuit in which the relay RY is located. Further, the circuit structure of the solution is compact and utilizes fewer components, which can achieve better technical effects and effectively reduce production costs.

In this embodiment, in an embodiment, the high voltage side VCC1 is electrically connected to the first end of the relay coil 10, and the power supply regulating circuit 200 includes an input end, an output end, and a controlled end; the power supply adjusting circuit An input end of the battery 200 is connected to the low voltage side, and an output end of the power supply regulating circuit 200 is electrically connected to a second end of the relay coil 10; a controlled end of the power supply regulating circuit 200 is electrically connected to the control circuit 100 connection. In another embodiment, the low voltage side is electrically connected to the second end of the relay coil 10, the input end of the power supply regulating circuit 200 is connected to the high voltage side VCC1, and the output end of the power supply regulating circuit 200 The first end of the relay coil 10 is electrically connected; the controlled end of the power supply regulating circuit 200 is electrically connected to the control circuit 100. Since the power supply regulation loop is connected to the high voltage side VCC1, the components in the power supply regulation circuit 200 are subjected to a relatively high voltage. If the protection circuit is added, the production cost is increased. Therefore, the present scheme preferably adopts the latter one. An embodiment, that is, a power supply regulation loop is connected in series between the second end and the low voltage side of the relay coil 10.

Referring to FIG. 1 , the power supply adjustment circuit 200 includes a switch tube Q1 and a protection resistor R1 electrically connected to the controlled end of the switch tube Q1. The input end of the switch tube Q1 is an input end of the power supply adjustment circuit 200. The output end of the switch tube Q1 is the output end of the power supply adjustment circuit 200, the controlled end of the switch tube Q1 is connected to one end of the protection resistor R1, and the other end of the protection resistor R1 is The controlled end of the power supply regulation loop. The switch transistor Q1 is one of a triode, a MOS transistor, a GTO, an IGBT or a driver chip; when the switch transistor Q1 is a driver chip, the model of the driver chip is preferably ULN2003; ULN2003 is high withstand voltage and large Current composite transistor array integrated chip; of course, it can also be replaced by a driver chip with similar functions. When the switch tube Q1 is a triode, the emitter of the triode is extremely the input end of the switch tube Q1, the collector of the triode is the output end of the switch tube Q1, and the base of the triode corresponds to The controlled end of the switch Q1. The control circuit 100 controls the turn-on or turn-off of the triode by controlling the base voltage of the triode, thereby achieving the purpose of controlling the on/off of the power supply loop. It will be understood by those skilled in the art that by controlling the triode to operate at a preset frequency/duty ratio, that is, the power supply loop is controlled to supply power to the relay coil 10 at a preset frequency/duty ratio.

In another embodiment of the present solution, the power supply adjusting circuit 200 may have multiple switching tubes Q1 implemented in combination with a resistor. For example, the power supply adjusting circuit includes a first triode and a second triode, wherein the first three An emitter of the pole tube is connected to a base of the second transistor, and a collector and an emitter of the second transistor are connected in series to the power supply circuit, and a base of the first transistor is connected to the control circuit 100; This way can realize the working stability of the second triode, and those skilled in the art can understand that the switching tube Q1 can realize the amplification and impedance transformation of the control signal through different connection relationships, thereby realizing Matching different control circuits 100. The relay driving circuit further includes a diode D1; an anode of the diode D1 is connected to an output end of the switching transistor Q1, and a cathode of the diode D1 is connected to the high voltage side VCC1.

When the frequency of the power supply voltage pulse of the power supply circuit to the relay RY is too high, the loss of the switching transistor Q1 is increased; when the frequency is too low, the relay RY emits noise. In the R&D experiment, the R&D personnel of the solution finds that the frequency of the supply voltage pulse is related to the inductance of the relay RY, and further concludes that the frequency of the supply voltage pulse and the inductance of the relay RY are corresponding according to experimental data. The empirical formula of the relationship: f ≥ Ue / (L * I); where L is the inductance of the relay coil 10, I is the amount of current passing through the relay coil 10 when the relay RY is in a closed state, and Ue is when the power supply loop is turned on, The voltage value when the supply voltage pulse is high. When Ue is a fixed value, since I can be obtained according to the coil impedance provided by the manufacturer in combination with Ue, the frequency of the supply voltage pulse has a corresponding relationship with the inductance L of the relay RY. Table 1 shows the relevant experimental data. The data is supplied in the form of a rectangular pulse after the relay RY is turned on for 1.5 s. The frequency of the supply voltage pulse is gradually adjusted according to the inductance of the relay RY, and the relay RY is measured. In the case of closing, the maximum value of the power supply pulse frequency corresponds to the inductance of the relay RY. Where Ue takes the rated voltage value of the relay RY.

Table 1

继电器线圈电感量（mH）Relay coil inductance (mH)	供电电压脉冲频率(Hz)Supply voltage pulse frequency (Hz)
100100	15001500
150150	10001000
200200	750750
250250	600600
300300	500500
350350	429429

It can be seen that as the inductance of the relay coil 10 gradually increases, the minimum frequency of the power supply pulse decreases accordingly; and the experimenter also measures the frequency of the power supply pulse and the relay coil 10 when the voltage value of the power supply pulse is changed. The relationship between inductances also has the same correlation trend.

Further, in the R&D experiment, the R&D personnel of the solution found that the duty cycle of the power supply voltage pulse of the power supply circuit to the relay RY is related to the release voltage of the relay RY. Further, based on the experimental data, an empirical formula for the correspondence between the duty ratio of the supply voltage pulse and the release voltage of the relay RY is summarized: D>Usf/Ue. The average voltage of the supply voltage of the relay RY is Up=Ue*ton/T; where D is the duty ratio of the supply voltage pulse, Ue is the voltage value when the supply voltage pulse is high level, and ton is the power supply loop conduction time . The sum of the on-time and off-time of the power supply loop of one cycle. It has been found in the experiment that the closed state of the relay RY can be maintained as long as the average voltage Up of the supply voltage of the relay RY is greater than the release voltage of the relay RY. Table 2 is the relevant experimental data. After the relay RY is turned on, the data is supplied in the form of a rectangular pulse. The duty cycle of the power supply pulse is gradually adjusted according to the release voltage of the relay RY, and the measured value is kept closed. In the case, the correspondence between the minimum value of the power supply pulse duty ratio and the release voltage of the relay RY, wherein Ue takes the rated voltage value of the relay RY.

Table 2

继电器的释放电压（V）Relay release voltage (V)	占空比Duty cycle
7.37.3	6565
6.86.8	6060
6.26.2	5555
5.65.6	5050
5.15.1	4545
4.44.4	4040
3.93.9	3535
3.33.3	3030

It can be seen that as the voltage of the relay RY is gradually reduced, the duty cycle of the power supply pulse also decreases; and the experimenter also measures the duty cycle of the power supply pulse and the relay RY when changing the voltage value of the power supply pulse. The release voltage relationship also shows the same correlation trend.

The present application also provides an air conditioner including a controller, an indoor unit, an outdoor unit, and the relay drive circuit; the outdoor unit includes a compressor and a control for starting/closing the compressor a relay RY; the relay drive circuit is electrically connected to the relay RY for supplying power to the relay RY. The specific structure of the relay driving circuit is referred to the above embodiment. Since the air conditioner adopts all the technical solutions of all the above embodiments, at least all the beneficial effects brought by the technical solutions of the above embodiments are eliminated. Narration.

The above description is only a preferred embodiment of the present application, and is not intended to limit the scope of the patents of the present application, and the equivalent structural transformation, or direct/indirect use, of the present application and the contents of the drawings is used in the present invention. All other related technical fields are included in the patent protection scope of the present application.

Claims

A relay driving circuit, the relay coil having a first end and a second end; wherein the relay driving circuit comprises:

Control circuit;

a power supply end, comprising electrically connecting to the first end and the second end of the relay coil to form a high voltage side and a low voltage side of the power supply circuit;

a power supply adjustment circuit connected in series to the power supply end and the power supply circuit of the relay coil, and the power supply adjustment circuit is electrically connected to the control circuit to control the relay to be closed under the control of the control circuit Or disconnected; wherein, after the control relay is closed and reaches a preset duration, the power supply adjusting circuit controls on/off of the power supply circuit at a preset frequency and/or a preset duty ratio.
The relay drive circuit of claim 1, wherein the power supply regulation loop outputs a triangular wave, a rectangular pulse, and a sawtooth pulse for controlling the power supply circuit to supply power to the relay coil.
The relay driving circuit of claim 1 , wherein the high voltage side is electrically connected to the first end of the relay coil, and the power supply regulating circuit comprises an input end, an output end and a controlled end;

An input end of the power supply adjusting circuit is connected to the low voltage side, an output end of the power supply adjusting circuit is electrically connected to a second end of the relay coil, and a controlled end of the power supply adjusting circuit is electrically connected to the control circuit connection.
The relay driving circuit of claim 1 , wherein the low voltage side is electrically connected to the second end of the relay coil, and the power supply regulating circuit comprises an input end, an output end and a controlled end;

An input end of the power supply adjusting circuit is connected to the high voltage side, an output end of the power supply adjusting circuit is electrically connected to a first end of the relay coil, and a controlled end of the power supply adjusting circuit is electrically connected to the control circuit connection.
The relay drive circuit according to claim 3 or 4, wherein the power supply regulation circuit includes a switch tube and a protection resistor, and an input end of the switch tube is an input end of the power supply regulation loop, and an output of the switch tube The end is the output end of the power supply regulation loop, the controlled end of the switch tube is connected to one end of the protection resistor, and the other end of the protection resistor is the controlled end of the power supply regulation loop.
The relay driving circuit according to claim 5, wherein said switching transistor is one of a triode, a MOS transistor, a GTO, an IGBT, or a driving chip.
A relay driving circuit according to claim 5, wherein said relay driving circuit further comprises a diode, an anode of said diode is connected to an output end of said switching transistor, and a cathode of said diode is connected to said high voltage side.
The relay driving circuit according to claim 1, wherein said control circuit controls a frequency of said power supply circuit to said relay supply voltage according to an inductance of said relay coil; said power supply circuit supplies power to said relay Voltage pulse

The relationship between the frequency of the supply voltage pulse and the inductance of the relay coil is: f ≥ Ue / (L * I);

f is the frequency of the supply voltage pulse, L is the inductance of the relay coil, I is the amount of current passing through the relay coil when the relay is in a steady state state, and Ue is the voltage value when the supply voltage pulse is at a high level.
The relay driving circuit according to claim 1, wherein said control circuit controls a duty ratio of said power supply circuit to said relay supply voltage according to a release voltage of said relay coil; said power supply circuit is said relay Supplying a supply voltage pulse;

The relationship between the duty ratio of the supply voltage pulse and the release voltage of the relay is: D>Usf/Ue;

D is the duty ratio of the supply voltage pulse, Usf is the release voltage of the relay coil, and Ue is the voltage value when the supply voltage pulse is at a high level.
An air conditioner, wherein the air conditioner includes a controller, an indoor unit, an outdoor unit, and the relay drive circuit according to any one of claims 1 to 9; the outdoor unit includes a compressor and is for controlling the a relay that starts/turns off the compressor;

The relay drive circuit is electrically coupled to the relay for powering the relay.