CN220821407U - Relay driving circuit and power control device - Google Patents

Abstract

The application relates to the technical field of power control, and discloses a relay driving circuit and a power control device, wherein the relay driving circuit comprises: the control unit, the switch unit, the step-down unit and the relay; the control unit is connected with the switch unit and is used for sending PWM control signals to the switch unit; the switch unit comprises a first input end, a first output end and a grounding end, wherein the first input end is electrically connected with the control unit, and the first output end is electrically connected with the voltage reducing unit and used for controlling the on-off of the voltage reducing unit and an external power supply; the step-down unit comprises a second input end, a second output end and a step-down control end, wherein the second input end is connected with an external power supply, the step-down control end is electrically connected with the first output end of the switch unit and is connected with the ground through the grounding end of the switch unit, and the second output end is electrically connected with the relay and is used for controlling the relay.

Description

Relay driving circuit and power control device

Technical Field

The embodiment of the application relates to the technical field of power control, in particular to a relay driving circuit and a power control device.

Background

Relays are widely used in power control devices for controlling electrical equipment, and when the relay needs to be closed, a rated current is required to be provided for magnetizing a coil to provide a magnetic attraction force for closing, so that the relay is closed; when the relay needs to be disconnected, the power supply needs to be disconnected, so that the magnetizing coil is demagnetized, and the relay is in a disconnected state.

The current relay driving circuit adopts constant voltage to drive, and the relay is always in a closed state by applying constant voltage to the coil of the relay, but the loss of the coil of the relay is high due to the mode, the temperature of the relay is possibly increased, and the service life of the relay is further reduced.

Disclosure of utility model

In view of the above, the present application provides a relay driving circuit and a power control device for solving the above technical problems in the prior art.

According to an aspect of the present application, there is provided a relay driving circuit including: the control unit, the switch unit, the step-down unit and the relay; the control unit is connected with the switch unit and is used for sending PWM control signals to the switch unit; the switch unit comprises a first input end, a first output end and a grounding end; the first input end is electrically connected with the control unit; the first output end is electrically connected with the voltage reducing unit and used for controlling the on-off of the voltage reducing unit and an external power supply; the voltage reducing unit comprises a second input end, a second output end and a voltage reducing control end; the second input end is connected with an external power supply; the voltage reduction control end is electrically connected with the first output end of the switch unit and is connected with the ground through the grounding end of the switch unit; the second output end is electrically connected with the relay and used for controlling the relay; when the control unit sends a first PWM control signal to the switch unit, the switch unit is conducted to enable the external power supply to provide power for the voltage reduction unit, and the voltage reduction unit provides a first voltage for the relay to enable the relay to be in a closed state; when the control unit sends a second PWM control signal to the switch unit, the switch unit is periodically conducted under the control of the second PWM control signal, so that the external power supply periodically supplies power to the voltage reduction unit, the voltage reduction unit performs voltage reduction processing on the power supplied by the external power supply and supplies a second voltage to the relay, and the relay is in a closed state, wherein the second voltage is smaller than the first voltage.

According to the application, different PWM control signals are sent to the switch unit through the control unit, so that the voltage reduction unit firstly provides high voltage for the relay to close the relay, and then provides low voltage for the relay to keep the relay closed, the loss of the relay coil is reduced, and the service life of the relay is prolonged. In addition, the switch unit is used for controlling the connection state of the voltage reducing unit and the ground, so that whether the external power supply can provide power for the voltage reducing unit or not is controlled, and the auxiliary power supply which is used for controlling the switch unit to be conducted or closed and the external power supply which provides power for the voltage reducing unit are grounded together, so that the auxiliary power supply and the external power supply do not need to be isolated.

In an alternative, the control unit comprises a DSP controller; the DSP controller is connected with the first input end of the switch unit through a GPIO interface on the DSP controller. Because the GPIO interfaces of the DSP controller are more than the PWM interfaces, and only one path of GPIO interfaces is needed to simulate and generate PWM control signals with different duty ratios, on one hand, the PWM control signals are simulated and realized by adopting the GPIO interfaces of the DSP controller, and PWM interface resources of the DSP controller can be saved; on the other hand, PWM control signals with different duty ratios are realized by adopting the output of one path of GPIO interface, so that software resources and hardware resources of a DSP controller can be saved, and convenience is provided for the interface output of other functional applications of the power control device.

In an alternative manner, the switching unit includes an N-channel type field effect transistor; the grid electrode of the N channel field effect transistor is electrically connected with a GPIO interface of the DSP controller; the source electrode of the N-channel field effect transistor is connected with the ground; the drain electrode of the N-channel field effect transistor is electrically connected with the voltage reduction control end of the voltage reduction unit; when the DSP controller outputs a high-level signal, the N-channel field effect transistor is in a conducting state, so that the voltage reducing unit is conducted with an external power supply; when the DSP controller outputs a low-level signal, the N-channel field effect transistor is in a cut-off state, so that the voltage reducing unit is disconnected from an external power supply. The switching unit can directly control the connection or disconnection of the first output end of the switching unit and the grounding end of the switching unit through a control signal by using the N-channel field effect transistor, and control whether the voltage reduction control end of the voltage reduction unit is connected with the ground or not, so as to control whether an external power supply supplies power to the voltage reduction unit or not. Meanwhile, by using only the N-channel field effect transistor as a switching unit, the circuit is simple and efficient.

In an alternative manner, the switch unit further includes a first voltage dividing resistor and a second voltage dividing resistor; one end of the first voltage dividing resistor is electrically connected with a GPIO interface of the DSP controller, the other end of the first voltage dividing resistor is electrically connected with a grid electrode of the N-channel field effect transistor, and the other end of the first voltage dividing resistor is also electrically connected with one end of the second voltage dividing resistor; the other end of the second voltage dividing resistor is connected with the ground. On one hand, after the voltage output by the DSP controller to the grid electrode of the N-channel type field effect transistor is reduced, the voltage is provided to the grid electrode of the N-channel type field effect transistor, so that the damage to the N-channel type field effect transistor caused by the fact that the voltage output by the DSP controller is larger is avoided; on the other hand, due to the existence of the second voltage dividing resistor, when the DSP controller does not output any control signal, the voltage of the grid electrode of the N-channel type field effect transistor can be ensured to be in a low level, so that the N-channel type field effect transistor is in a cut-off state, and the contact of the relay is kept in a cut-off state when the power control device is not in use.

In an alternative manner, the switching unit further includes a first filter capacitor; the first filter capacitor is connected with the second voltage dividing resistor in parallel, one end of the first filter capacitor is connected with the ground, and the other end of the first filter capacitor is electrically connected with the grid electrode of the N-channel field effect transistor. The high-frequency interference signals in the circuit are absorbed through the first filter capacitor, so that the situation that the N-channel type field effect transistor is turned on or off by mistake due to the interference signals is avoided, the reliability of the N-channel type field effect transistor in turn on and off is realized, and the stability of the relay driving circuit is further improved.

In an alternative manner, the step-down unit includes an inductor, a second filter capacitor, and a diode; one end of the inductor is connected with the cathode of the diode and is electrically connected with the external power supply, and the other end of the inductor is respectively connected with the first control end of the relay and one end of the second filter capacitor; the other end of the second filter capacitor is electrically connected with the second control end of the relay and the anode of the diode respectively; and the anode of the diode is electrically connected with the drain electrode of the N-channel field effect transistor. By arranging the inductor, the second filter capacitor and the diode, on one hand, when the GPIO interface of the DSP controller outputs a second PWM control signal to the N-channel field effect transistor, the voltage provided by the power supply can be reduced and then provided for the relay; on the other hand, the inductor and the second filter capacitor form a low-pass filter, which can filter high-frequency interference signals in the circuit, thereby improving the stability of the circuit.

In an alternative manner, the step-down unit further includes a third filter capacitor; the third filter capacitor is arranged in parallel with the second filter capacitor, one end of the third filter capacitor is electrically connected with the first control end of the relay, and the other end of the third filter capacitor is electrically connected with the second control end of the relay. By arranging the third filter capacitor, on one hand, the third filter capacitor and the second filter capacitor jointly filter high-frequency interference signals in the circuit, so that interference is further reduced; on the other hand, when the source electrode and the drain electrode of the N-channel field effect transistor are disconnected, the third filter capacitor can be used as a power supply to release energy, so that the stability of the circuit is further ensured.

In an alternative manner, the relay driving circuit further includes a fourth filter capacitor, one end of the fourth filter capacitor is electrically connected to the external power supply, and the other end of the fourth filter capacitor is connected to ground. Through setting up fourth filter capacitor, filter the input of external power source, reduce high frequency interference, and then improve the stability of circuit.

In an alternative manner, the high level duty cycle of the first PWM control signal is 100%; the high level duty cycle of the second PWM control signal is 40% -70%. Through setting up first PWM control signal and second PWM control signal, carry out accurate control to the voltage of appling on the relay, and then reduce relay coil's loss, prolonged the life of relay greatly.

According to another aspect of the present application, a power control apparatus includes: a relay driving circuit according to any one of the preceding claims.

According to the application, the control unit, the switch unit, the voltage reducing unit and the relay are arranged, and different PWM control signals can be sent to the switch unit through the control unit, so that the voltage reducing unit firstly provides high voltage for the relay to enable the relay to be closed, and then provides low voltage for the relay to enable the relay to be kept closed, thereby reducing the loss of a relay coil and further prolonging the service life of the relay. In addition, the switch unit is used for controlling the connection state of the voltage reducing unit and the ground, so that whether the external power supply can provide power for the voltage reducing unit or not is controlled, and the auxiliary power supply which is used for controlling the switch unit to be conducted or closed and the external power supply which provides power for the voltage reducing unit are grounded together, so that the auxiliary power supply and the external power supply do not need to be isolated.

The foregoing description is only an overview of the present application, and is intended to be implemented in accordance with the teachings of the present application in order that the same may be more clearly understood and to make the same and other objects, features and advantages of the present application more readily apparent.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the application. Also, like reference numerals are used to designate like parts throughout the figures. In the drawings:

Fig. 1 shows a schematic structural diagram of a relay according to an embodiment of the present application;

fig. 2 shows a structure diagram of a relay driving circuit provided by an embodiment of the present application;

FIG. 3 shows a relay control timing diagram provided by an embodiment of the present application;

fig. 4 shows a relay driving circuit diagram provided by an embodiment of the present application.

Reference numerals in the specific embodiments are as follows:

100-relay driving circuit;

11-control unit, 12-switch unit, 13-step-down unit, 14-relay;

121-first input terminal, 122-first output terminal, 123-ground terminal;

131-second input end, 132-second output end, 133-step-down control end;

141-coil, 142-spring, 143-armature, 144-contact;

VCC-external power supply, R1-first divider resistor, R2-second divider resistor, C1-first filter capacitor, C2-second filter capacitor, C3-third filter capacitor, C4-fourth filter capacitor, Q1-N channel type field effect transistor, D1-diode, L1-inductor, 1-first control end, 2-second control end.

Detailed Description

Embodiments of the technical scheme of the present application will be described in detail below with reference to the accompanying drawings. The following examples are only for more clearly illustrating the technical aspects of the present application, and thus are merely examples, and are not intended to limit the scope of the present application.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having" and any variations thereof in the description of the application and the claims and the description of the drawings above are intended to cover a non-exclusive inclusion.

In the description of embodiments of the present application, the technical terms "first," "second," and the like are used merely to distinguish between different objects and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated, a particular order or a primary or secondary relationship. In the description of the embodiments of the present application, the meaning of "plurality" is two or more unless explicitly defined otherwise.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those of skill in the art will explicitly and implicitly appreciate that the embodiments described herein may be combined with other embodiments.

In the description of the embodiments of the present application, the term "and/or" is merely an association relationship describing an association object, and indicates that three relationships may exist, for example, a and/or B may indicate: there are three cases, a, B, a and B simultaneously. In addition, the character "/" herein generally indicates that the front and rear associated objects are an "or" relationship.

In the description of the embodiments of the present application, the term "plurality" means two or more (including two), and similarly, "plural sets" means two or more (including two), and "plural sheets" means two or more (including two).

In the description of the embodiments of the present application, the orientation or positional relationship indicated by the technical terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are based on the orientation or positional relationship shown in the drawings, and are merely for convenience of description and simplification of the description, and do not indicate or imply that the apparatus or element referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the embodiments of the present application.

In the description of the embodiments of the present application, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured" and the like should be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally formed; or may be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. The specific meaning of the above terms in the embodiments of the present application will be understood by those of ordinary skill in the art according to specific circumstances.

The relay is an electric control device, and is an electric appliance which can make the controlled quantity generate preset step change in the electric output circuit when the change of the input quantity reaches the rule requirement, and is generally applied to the electric control circuit, and plays roles of automatic regulation, safety protection, conversion circuit and the like in the circuit.

In order to operate the relay, a method of driving the relay to operate by constant voltage is generally used, but the method can cause great loss of a coil of the relay, and also can cause temperature rise of the relay, thereby reducing service life of the relay, the loss of the relay mainly comprises coil loss and contact loss, and the contact loss is determined by the selected relay, so that the efficiency of the equipment can be improved by reducing the coil loss. The relay generally needs rated current to magnetize the coil when in actuation, and provides actuation energy; when the actuation is completed, the coil has completed magnetizing and only a small current is required to maintain the relay in the actuated state.

In order to solve the problem of large loss of the relay coil, the present inventors have noted that the relay may be driven by a dual power driving method, the relay may be powered by a high voltage power supply to close the relay, and then the relay may be continuously powered by a low voltage power supply, so that the coil voltage is maintained in a state of being greater than the holding voltage, thereby reducing the loss of the relay coil. However, the method requires the auxiliary power supply of the system to have multiple power supply outputs, and the driving circuit has complex design and more components.

In order to solve the problems of large loss and complex circuit structure of the relay, the inventor of the application provides a relay driving circuit, which comprises a control unit, a switch unit, a voltage reduction unit and a relay, wherein the relay driving circuit can firstly provide high voltage to enable the relay to be magnetized and closed in a magnetizing stage of a coil, then provide low voltage to maintain the closing of the relay, and the control unit can send PWM (Pulse width modulation ) control signals to the switch unit in a simulation manner for controlling the on or off of the switch unit so as to enable the voltage reduction unit to be connected with an external power supply and further control the relay; when the control unit sends a first PWN control signal to the switch unit, the switch unit is conducted so that the voltage reduction unit provides high voltage for the relay, and the relay is in a closed state; when the control unit sends a second PWM control signal to the switch unit, the switch unit is periodically conducted under the control of the second PWM control signal, so that the voltage reduction unit provides a lower voltage for the relay, and the relay is kept in a closed state.

The control unit, the switch unit and the voltage reduction unit are arranged, and different PWM control signals are sent to the switch unit through the control unit, so that the voltage reduction unit provides high level to enable the relay to be closed, and low voltage is provided to enable the relay to be kept in a closed state; the relay driving circuit reduces the loss of the relay coil on the premise of not increasing the design complexity of the circuit and the number of components, and further prolongs the service life of the relay.

The relay driving circuit disclosed by the embodiment of the application can be used for driving a relay, but is not limited to the relay, and can also be applied to driving of power equipment which needs to operate in a high-voltage state and then maintain operation in a low-voltage state.

The relay according to the embodiment of the application is an electric control device, which can give a prescribed input amount and keep the prescribed input amount for a long enough time, and a controlled amount is subjected to a preset step change in an electric control circuit, and when the input amount is reduced to a certain degree and kept for a long enough time, the relay is restored to an initial state. The relay is of various types and can be classified into an electromagnetic relay, an induction relay, an electric relay, an electronic relay and the like. As shown in fig. 1, fig. 1 is a schematic structural diagram of a relay according to an embodiment of the present application. The coil 141 is arranged in the relay 14, two ends of the coil 141 are respectively a first control end and a second control end of the relay 14, voltage is added to or current is introduced into the first control end and the second control end, so that the coil 141 can generate magnetic force, when the electromagnetic force is larger than the spring counter force generated by the spring 142, the armature 143 approaches the coil 141 under the action of the electromagnetic force, and then the contact 144 is closed, even if the relay 14 is closed; when the voltage or current of the coil 141 drops or disappears, the electromagnetic force applied to the armature 143 is smaller than the spring reaction force generated by the spring 142. Armature 143 moves away from coil 141 and opens contact 144, i.e., the relay. Electromagnetic relays are of many kinds, such as current relays, voltage relays, intermediate relays, etc. In the embodiment of the present application, a voltage relay is merely described as an example.

The control voltage of the voltage relay comprises an operating voltage and a holding voltage, wherein the holding voltage is smaller than the operating voltage. The working voltage is the minimum voltage for controlling the relay to be closed, when the voltage added to the first control end and the second control end of the relay is larger than the working voltage, the electromagnetic force generated by the coil of the relay is larger than the spring counter force generated by the spring, and the contact of the relay is closed, namely the relay is closed. The holding voltage is the minimum voltage which can control the relay to keep the relay in a closed state after the relay is closed, and after the relay is closed, the coil of the relay is magnetized, and the relay can be kept in the closed state only by enabling the voltage added by the first control end and the second control end of the relay to be larger than the holding voltage.

Fig. 2 shows a structure diagram of a relay driving circuit provided in an embodiment of the present application, and the relay driving circuit 100 includes a control unit 11, a switching unit 12, a step-down unit 13, and a relay 14.

The control unit 11 is connected to the switching unit 12 for sending PWM control signals to the switching unit 12.

The switch unit 12 includes a first input terminal 121, a first output terminal 122, and a ground terminal 123, where the first input terminal 121 is electrically connected to the control unit 11, and the first output terminal 122 is electrically connected to the step-down unit 13, for controlling on/off of the step-down unit 13 and the external power VCC.

The step-down unit 13 includes a second input terminal 131, a second output terminal 132, and a step-down control terminal 133, the second input terminal 131 being connected to the external power VCC, the step-down control terminal 133 being electrically connected to the first output terminal 122 of the switching unit 12 and to the ground GND through the ground terminal 123 of the switching unit 12, the second output terminal 132 being electrically connected to the relay 14 for controlling the relay 14.

When the control unit 11 transmits the first PWM control signal to the switching unit 12, the switching unit 12 is turned on to cause the external power VCC to supply power to the step-down unit 13, and the step-down unit 13 supplies the first voltage to the relay 14 to cause the relay 14 to be in a closed state.

When the control unit 11 sends the second PWM control signal to the switching unit 12, the switching unit 12 is periodically turned on under the control of the second PWM control signal, so that the external power VCC periodically supplies power to the step-down unit 13, and the step-down unit 13 steps down the power supplied from the external power VCC and supplies the second voltage to the relay 14, so that the relay 14 is in a closed state, wherein the second voltage is smaller than the first voltage.

As shown in fig. 2, in the embodiment of the present application, the control unit 11 is configured to send a PWM control signal to the switching unit 12, so that the switching unit 12 is turned on or off under the control of the PWM control signal. PWM is a method of digitally encoding the level of an analog signal, which is capable of encoding the level of a specific analog signal; the PWM control signal is a periodic digital signal, that is, if the process of returning the signal from the high level to the low level to the high level is a period, the PWM control signal can cycle from the high level to the low level to the high level multiple times; in addition, the change of the signal, energy, etc. can also be adjusted by adjusting the change of the duty cycle of the PWM control signal, which is the percentage of the time the signal is at a high level in one period, which occupies the whole signal period. When the PWM control signal sent from the control unit 11 to the switching unit 12 is at a high level, the switching unit 12 is turned on, and the relay driving circuit is energized; when the PWM control signal transmitted from the control unit 11 to the switching unit 12 is at a low level, the switching unit 12 is turned off, and the relay driving circuit is powered off. The control unit 11 periodically turns on the switching unit 12 by sending PWM control signals of different duty ratios to the switching unit 12 to periodically energize the relay driving circuit, thereby causing the step-down unit 13 to supply different voltages to the relay 14. The control unit 11 may be a plurality of types of controllers, such as: MCU (Microcontroller Unit, single-chip microprocessor), DSP (DIGITAL SIGNAL Processing, digital signal processor) etc., as long as it has a function of sending PWM control signals, in the embodiment of the application, it is not limited.

The switch unit 12 is configured to control on-off of the step-down unit 13 and the external power VCC, and specifically, the first input end 121 of the switch unit 12 is electrically connected to the control unit and configured to receive the control information sent by the control unit, and as described above, the first input end 121 of the switch unit 12 receives the PWM control signal sent by the control unit, and controls on-off of the switch unit according to the PWM control signal. The ground 123 of the switching unit 12 may be directly or indirectly connected to ground, and the first output 122 of the switching unit 12 is connected to the step-down unit 13. Under the control of the control unit, when the ground terminal 123 of the switching unit 12 and the first output terminal 122 of the switching unit 12 are turned on, the voltage reducing unit 13 may be connected to ground through the switching unit 12; when the ground 123 of the switching unit 12 and the first output 122 of the switching unit 12 are disconnected, the step-down unit 13 cannot be connected to ground through the switching unit 12. The switch unit 12 may be a variety of types of switches, such as: the N-channel depletion type field effect transistor, the N-channel enhancement type field effect transistor, the P-channel depletion type field effect transistor, the P-channel enhancement type field effect transistor and the like are only required to have a control function and can be automatically turned on and off under control, and the embodiment of the application is not limited.

The step-down unit 13 is configured to control the relay 14, the second input end 131 of the step-down unit 13 may be directly or indirectly connected to the external power VCC, the second output end 132 of the step-down unit 13 is electrically connected to the relay 14, and the step-down control end 133 of the step-down unit 13 is electrically connected to the first output end 122 of the switch unit 12 and is connected to ground through the ground end 123 of the switch unit 12. In the embodiment of the present application, by providing the ground terminal 123 in the switching unit 12, the first input terminal 121 and the first output terminal 122 are respectively connected to the control unit 11 and the voltage reducing unit 13, so that the auxiliary power supply for supplying power to the control unit 11 and the external power supply VCC for supplying power to the voltage reducing unit 13 are grounded, that is, the auxiliary power supply for supplying control voltage to the first input terminal 121 of the switching unit 12 and the external power supply VCC for supplying power to the voltage reducing unit 13 are grounded, therefore, the external power supply VCC can be directly used as the auxiliary power supply for supplying power to the control unit 11, the auxiliary power supply of the control unit 11 and the external power supply VCC for supplying power to the voltage reducing unit 13 do not need to be isolated, the circuit structure is simplified, and the control cost is reduced.

When the switching unit 12 is turned on, the step-down control terminal 133 of the step-down unit 13 is connected to the ground through the switching unit 12, and the external power VCC supplies power to the step-down unit 13 so that the step-down unit 13 supplies the first voltage to the relay 14; when the switch unit 12 is periodically turned on, the voltage-reducing control terminal 133 of the voltage-reducing unit 13 is periodically connected to ground through the switch unit 12, the external power supply VCC periodically supplies power to the voltage-reducing unit 13, and the voltage-reducing unit 13 performs voltage-reducing processing on the power supplied from the external power supply VCC and supplies a second voltage to the relay 14; when the switching unit 12 is turned off, the voltage decreasing unit 13 cannot be connected to the ground through the switching unit 12, the external power source VCC cannot supply power to the voltage decreasing unit 13, and the voltage decreasing unit 13 cannot supply voltage to the relay 14. The voltage-reducing control terminal 133 of the voltage-reducing unit 13 is electrically connected to the first output terminal 122 of the switching unit 12, and can control the voltage provided by the relay 14 by the voltage-reducing unit 13 by controlling the conduction condition of the switching unit 12. The depressurization unit 13 may have various forms of structures such as: the step-down circuit and the like are not limited in the embodiment of the present application as long as they have an effect of performing a step-down process on the voltage supplied from the external power supply under the control of the switching unit.

When the control unit sends a first PWM control signal to the switch unit, the switch unit is turned on, the voltage reduction unit is connected with the ground through the switch unit, an external power supply supplies power to the voltage reduction unit, the voltage reduction unit supplies a first voltage to the relay, and when the first voltage supplied by the voltage reduction unit is higher than the working voltage of the relay, the relay is closed; when the control unit sends a second PWM control signal to the switch unit, the switch unit is periodically conducted, the voltage reduction unit is periodically connected with the ground through the switch unit, an external power supply periodically supplies power to the voltage reduction unit, the voltage reduction unit carries out voltage reduction treatment on the voltage of the external power supply and then supplies a second voltage to the relay, and when the second voltage supplied by the voltage reduction unit is larger than the holding voltage of the relay, the relay is kept in a closed state.

According to the embodiment of the application, the control unit, the switch unit, the voltage reduction unit and the relay are arranged, the control unit can send different PWM control signals to the switch unit, and the switch unit is controlled to be turned on or turned off so as to control whether the voltage reduction unit can be connected with the ground through the switch unit or not, further control whether an external power supply can provide power for the voltage reduction unit or not, and finally control the voltage reduction unit to provide different voltages for the relay. As shown in fig. 3, fig. 3 is a timing chart of relay control provided in the embodiment of the present application, when the control unit sends a first PWM control signal to the switch unit, that is, in a period from t0 to t1, the control unit sends a PWM control signal with a duty ratio of 100% to the switch unit, so that the switch unit is turned on, and the external power supply provides power to the step-down unit, so that the step-down unit provides a first voltage to the relay, and the relay is turned on; when the control unit sends a second PWM control signal to the switch unit, namely in the time period of t 1-t 2, the control unit sends a PWM control signal with a certain duty ratio to the switch unit, so that the switch unit is periodically conducted, the external power supply periodically supplies power to the voltage reducing unit, so that the voltage reducing unit reduces the voltage of the external power supply, and then the second voltage is supplied to the relay, and the relay is kept closed. The time length of t 0-t 1 is determined by the selected relay, and the time length of t 1-t 2 is determined by the working time length of the relay.

In the embodiment of the application, different PWM control signals are sent to the switch unit through the control unit, so that the voltage reduction unit firstly provides high voltage for the relay to close the relay, and then provides low voltage for the relay to keep the relay closed, thereby not only reducing the loss of the relay coil, prolonging the service life of the relay, but also avoiding the need of additionally adding an auxiliary power supply, and leading the relay driving circuit to be simple and efficient. In addition, the switch unit is used for controlling the connection state of the voltage reducing unit and the ground, so that whether the external power supply can provide power for the voltage reducing unit or not is controlled, and the auxiliary power supply which is used for controlling the switch unit to be conducted or closed and the external power supply which provides power for the voltage reducing unit are grounded together, so that the auxiliary power supply and the external power supply do not need to be isolated.

In order to better utilize the pin resources of the control unit, referring to fig. 4, fig. 4 shows a relay driving circuit diagram provided by another embodiment of the present application, and the embodiment of the present application provides a control unit 11, where the control unit 11 is a DSP controller, and the DSP controller is connected to a first Input terminal 121 of the switch unit 12 through a GPIO (General-Purpose Input/Output) interface on the DSP controller.

In the embodiment of the present application, the DSP controller uses the GPIO interface to realize the output of the high-level signal, the low-level signal and the PWM control signals with different high-level duty ratios, and the GPIO interface may be directly or indirectly connected to the first input terminal 121 of the switch unit 12. When the DSP controller outputs a high-level signal to the switch unit 12 through the GPIO interface, that is, when the DSP controller outputs a PWM control signal with a high-level duty ratio of 100% to the switch unit 12 through the GPIO interface, the switch unit 12 is turned on, the external power VCC supplies power to the step-down unit 13, and the step-down unit 13 supplies a first voltage to the relay to close the relay; when the DSP controller outputs a low-level signal to the switching unit 12 through the GPIO interface, that is, when the DSP controller outputs a PWM control signal with a high-level duty ratio of 0% to the switching unit 12 through the GPIO interface, the switching unit 12 is turned off, the external power VCC cannot provide power to the step-down unit 13, and the step-down unit 13 cannot provide voltage to the relay to turn off the relay; when the DSP controller outputs other PWM control signals with high level duty ratio to the switch unit 12 through the GPIO interface, the switch unit 12 is periodically turned on, the external power VCC periodically supplies power to the step-down unit 13, the step-down unit 13 steps down the power supplied from the external power, and supplies the processed voltage to the relay, and when the stepped-down voltage is greater than the holding voltage of the relay, the relay is kept in a closed state.

Because the GPIO interfaces of the DSP controller are more than the PWM interfaces, and only one path of GPIO interfaces is needed to simulate and generate PWM control signals with different duty ratios, on one hand, the PWM control signals are simulated and realized by adopting the GPIO interfaces of the DSP controller, and PWM interface resources of the DSP controller can be saved; on the other hand, PWM control signals with different duty ratios are realized by adopting the output of one path of GPIO interface, so that software resources and hardware resources of a DSP controller can be saved, and convenience is provided for the interface output of other functional applications of the power control device.

In order to make the circuit of the switch unit simpler and more efficient, please continue to refer to fig. 4, the embodiment of the application proposes a switch unit 12, wherein the switch unit 12 is an N-channel field effect transistor Q1, the gate of the N-channel field effect transistor Q1 is electrically connected to the GPIO interface of the DSP controller, the source of the N-channel field effect transistor Q1 is connected to the ground, and the drain of the N-channel field effect transistor Q1 is electrically connected to the step-down control terminal 133 of the step-down unit 13; when the DSP controller outputs a high-level signal, the N-channel field effect transistor Q1 is in a conducting state, so that the voltage reducing unit is conducted with an external power supply; when the DSP controller outputs a low-level signal, the N-channel field effect transistor Q1 is in a cut-off state, so that the voltage reducing unit is disconnected from an external power supply.

The structure of the N-channel field effect transistor Q1 includes a source, a drain, and a gate. The conductive path between the source and drain is formed of an n-type semiconductor material, and the gate is formed of metal or polysilicon. When the voltage of the grid electrode is smaller than the starting voltage of the N-channel type field effect transistor Q1, the N-channel type field effect transistor Q1 is in a cut-off state, the source electrode and the drain electrode of the N-channel type field effect transistor Q1 are disconnected, and an external power supply VCC cannot provide power for the voltage reducing unit 13, so that the voltage reducing unit 13 cannot provide voltage to the relay; when the voltage of the gate is greater than the turn-on voltage of the N-channel fet Q1, the N-channel fet Q1 is in a conductive state, and the source and the drain of the N-channel fet Q1 are conductive, and the external power VCC supplies power to the step-down unit 13, so that the step-down unit 13 supplies voltage to the relay. The turn-on voltage is also referred to as a gate threshold voltage, and a certain voltage needs to be applied to the gate of the N-channel fet Q1 to turn on the source and the drain of the N-channel fet Q1, and the minimum value of the voltage is referred to as the turn-on voltage.

The grid electrode of the N-channel field effect transistor Q1 can be directly or indirectly electrically connected with a GPIO interface of the DSP controller, and PWM control signals output by the DSP controller control whether the voltage reduction unit 13 is connected with the ground or not by controlling the on or off of the N-channel field effect transistor Q1, so as to control whether an external power supply VCC provides power for the voltage reduction unit 13 or not. When the DSP controller outputs a high-level signal, the voltage of the grid electrode of the N-channel type field effect transistor Q1 is larger than the starting voltage, the drain electrode and the source electrode of the N-channel type field effect transistor Q1 are conducted, the voltage reducing unit 13 is connected with the ground through the switch unit 12, and an external power supply supplies power to the voltage reducing unit; when the DSP controller outputs a low-level signal, the voltage of the gate of the N-channel field effect transistor Q1 is smaller than the on voltage, the N-channel field effect transistor Q1 is in an off state, the step-down unit 13 cannot be connected to ground through the switch unit 12, and the external power supply cannot supply power to the step-down unit. The N-channel type field effect transistor Q1 may be various types, for example, an N-channel type MOS transistor, an N-channel type insulated gate field effect transistor, an N-channel type junction field effect transistor, etc., which are not limited in the embodiment of the present application.

According to the embodiment of the application, the first output end of the switch unit and the grounding end of the switch unit can be directly controlled to be conducted or disconnected through the control signal by using the N-channel field effect transistor, so that whether the voltage reduction control end of the voltage reduction unit is connected with the ground or not is controlled, and whether an external power supply supplies power to the voltage reduction unit or not is further controlled. Meanwhile, by using only the N-channel field effect transistor as a switching unit, the circuit is simple and efficient. In addition, if the N-channel type field effect transistor is an N-channel type MOS transistor, on one hand, the low on-resistance characteristic of the N-channel type MOS transistor can reduce the power loss in the switching-on process of the switch unit, and further reduce the driving loss; on the other hand, the switching frequency of the N-channel MOS tube can reach hundreds of kHz, and the power density can be improved.

In order to improve stability of the switch unit and avoid damage to the switch unit when the voltage output by the DSP controller is relatively large, referring to fig. 4, in the embodiment of the present application, the switch unit 12 further includes a first voltage dividing resistor R1 and a second voltage dividing resistor R2, one end of the first voltage dividing resistor R1 is electrically connected with the GPIO interface of the DSP controller, the other end of the first voltage dividing resistor R1 is electrically connected with the gate of the N-channel field effect transistor, the other end of the first voltage dividing resistor R1 is also electrically connected with one end of the second voltage dividing resistor R2, and the other end of the second voltage dividing resistor R2 is connected with ground.

In the embodiment of the application, one end of a first voltage dividing resistor R1 is electrically connected with a GPIO interface of a DSP controller, the other end of the first voltage dividing resistor R1 is electrically connected with a grid electrode of an N-channel field effect transistor, the other end of the first voltage dividing resistor R1 is also electrically connected with one end of a second voltage dividing resistor R2, and the other end of the second voltage dividing resistor R2 is connected with the ground. When the GPIO interface of the DSP controller outputs a PWM control signal to the grid electrode of the N-channel field effect transistor Q1, as the first voltage dividing resistor R1 and the second voltage dividing resistor R2 are arranged in series, the currents on the first voltage dividing resistor R1 and the second voltage dividing resistor R2 are the same, the sum of the voltages at the two ends of the first voltage dividing resistor R1 and the voltages at the two ends of the second voltage dividing resistor R2 is equal to the voltage output by the DSP controller, namely the voltage output by the DSP controller can be reduced through the first voltage dividing resistor R1, and then the voltage is provided for the second voltage dividing resistor R2; the second voltage dividing resistor R2 and the N-channel field effect transistor Q1 are arranged in parallel, and the voltage of the gate electrode of the N-channel field effect transistor Q1 is the same as the voltage of the second voltage dividing resistor R2, so that the voltage output by the DSP controller can be reduced by the first voltage dividing resistor R1, and then the voltage is supplied to the gate electrode of the N-channel field effect transistor Q1.

By setting the first voltage dividing resistor and the second voltage dividing resistor, on one hand, after the voltage output by the DSP controller to the grid electrode of the N-channel type field effect transistor is reduced, the voltage is provided for the grid electrode of the N-channel type field effect transistor, so that the N-channel type field effect transistor is prevented from being damaged when the voltage output by the DSP controller is larger; on the other hand, the voltage of the second voltage dividing resistor is related to the resistance value of the first voltage dividing resistor and the resistance value of the second voltage dividing resistor, and the voltage of the second voltage dividing resistor can be controlled by setting the first voltage dividing resistor and the second voltage dividing resistor with different resistance values, namely, the voltage of the grid electrode of the N-channel field effect transistor can be controlled by setting the first voltage dividing resistor and the second voltage dividing resistor with different resistance values. In addition, due to the existence of the second voltage dividing resistor, when the DSP controller does not output any control signal, the voltage of the grid electrode of the N-channel type field effect transistor can be ensured to be in a low level, so that the N-channel type field effect transistor is in a cut-off state, and the contact of the relay is kept in a cut-off state when the power control device is not in use.

In order to further improve the stability of the relay driving circuit, referring to fig. 4, in the embodiment of the present application, the switch unit 12 further includes a first filter capacitor C1, where the first filter capacitor C1 is parallel connected to the second voltage dividing resistor R2, one end of the first filter capacitor C1 is connected to ground, and the other end of the first filter capacitor C1 is electrically connected to the gate of the N-channel field effect transistor.

In the embodiment of the application, one end of the first filter capacitor C1 is connected with the ground, the other end of the first filter capacitor C1 is electrically connected with the grid electrode of the N-channel field effect transistor Q1, so that the first divider resistor R1 and the first filter capacitor C1 form a low-pass filter, the principle that the first filter capacitor C1 passes high-frequency and low-frequency resistance is utilized, the high-frequency signals needing to be cut off are blocked from passing through by utilizing a capacitor absorption method, and the low-frequency signals needing to be low-frequency signals are enabled to pass through by utilizing the characteristic of high resistance of the capacitor.

The high-frequency interference signals in the circuit are absorbed through the first filter capacitor, so that the situation that the N-channel type field effect transistor is turned on or off by mistake due to the interference signals is avoided, the reliability of the N-channel type field effect transistor in turn on and off is realized, and the stability of the relay driving circuit is further improved.

In some embodiments of the present application, referring to fig. 4, a step-down unit 13 is provided, where the step-down unit 13 includes an inductor L1, a second filter capacitor C2 and a diode D1, one end of the inductor L1 is connected to a cathode of the diode D1 and electrically connected to an external power source VCC, the other end of the inductor L1 is connected to a first control end 1 of the relay 14 and one end of the second filter capacitor C2, and the other end of the second filter capacitor C2 is electrically connected to a second control end 2 of the relay 14 and an anode of the diode D1, and an anode of the diode D1 is electrically connected to a drain of the N-channel field effect transistor Q1.

In the embodiment of the application, one end of an inductor L1 is connected with a cathode of a diode D1 and is electrically connected with an external power supply VCC, the other end of the inductor L1 is respectively connected with a first control end 1 of a relay 14 and one end of a second filter capacitor C2, the other end of the second filter capacitor C2 is respectively electrically connected with a second control end 2 of the relay 14 and an anode of the diode D1, and the anode of the diode D1 is electrically connected with a drain electrode of an N-channel field effect transistor Q1. As shown in fig. 3, when the GPIO interface of the DSP controller outputs the first PWM control signal to the gate of the N-channel type field effect transistor Q1, that is, in the period of t0 to t1, the GPIO interface of the DSP controller outputs the PWM control signal with the duty ratio of 100% to the gate of the N-channel type field effect transistor Q1, the source and the drain of the N-channel type field effect transistor Q1 are conducted, the external power VCC inputs a current to the inductor L1, the diode D1 is not conducted, the external power VCC, the inductor L1, the first control terminal 1 of the relay 14, the second control terminal 2 of the relay 14, the N-channel type field effect transistor Q1 and the current loop are formed, and the voltages at both ends of the first control terminal 1 and the second control terminal 2 of the relay 14 are increased to be equal to the input voltage of the external power, which is greater than the operating voltage of the relay 14, so that the relay 14 is closed.

As shown in fig. 3, when the GPIO interface of the DSP controller outputs the second PWM control signal to the gate of the N-channel field effect transistor Q1, that is, in the period of t1 to t2, the GPIO interface of the DSP controller outputs the PWM control signal with a certain duty ratio to the gate of the N-channel field effect transistor Q1, and the source and the drain of the N-channel field effect transistor Q1 are periodically turned on. When the second PWM control signal output is at a high level, when the source and the drain of the N-channel field effect transistor Q1 are turned on, the external power supply VCC inputs a current to the inductor L1, the inductor L1 stores energy, the external power supply VCC further charges the second filter capacitor C2, and the external power supply VCC, the inductor L1, the first control terminal 1 of the relay 14, the second control terminal 2 of the relay 14, the N-channel field effect transistor Q1 and a current loop are formed; when the output of the second PWM control signal is at a low level, the source and the drain of the N-channel field effect transistor Q1 are turned off, the inductor L1 releases energy, the diode D1 is turned on, the inductor L1, the first control terminal 1 of the relay 14, the second control terminal 2 of the relay 14 and the diode form a current reflux, and when the release of energy from the inductor L1 is completed, the second filter capacitor C2 is used as a power source to start releasing energy, the second filter capacitor, the first control terminal 1 of the relay 14 and the second control terminal 2 of the relay 14 form a current loop, and voltage is continuously supplied to the relay 14, so that the relay 14 is in a closed state.

Under the control of the second PWM control signal, when the source and the drain of the N-channel field effect transistor Q1 are turned on, the inductor L1 senses an increase in current, so that the inductor L1 generates a reverse current to prevent the increase in current, so that the current in the relay driving circuit is gradually increased, and the voltages applied to the first control terminal 1 and the second control terminal 2 of the relay 14 are gradually increased, and the second filter capacitor C2 is charged. Since the source and the drain of the N-channel fet Q1 are periodically turned on under the control of the second PWM control signal, when the voltages applied to the first control terminal 1 and the second control terminal 2 of the relay 14 have not increased to the voltage provided by the power supply, the source and the drain of the N-channel fet Q1 are turned off, the second filter capacitor C2 gradually discharges to provide power to the relay 14 due to the inductance L1 and the second filter capacitor C2, and as the second filter capacitor C2 discharges, the current in the relay driving circuit will be in a gradually decreasing state, so that the voltages applied to the first control terminal 1 and the second control terminal 2 of the relay 14 start to gradually decrease, and when the voltages have not decreased below the holding voltage, the source and the drain of the N-channel fet Q1 will be turned back on, so that the voltages applied to the first control terminal 1 and the second control terminal 2 of the relay 14 are smaller than the voltage provided by the power supply.

According to the embodiment, the inductor, the second filter capacitor and the diode are arranged, so that on one hand, when the GPIO interface of the DSP controller outputs a second PWM control signal to the N-channel field effect transistor, the voltage provided by the power supply can be reduced and then provided for the relay; on the other hand, the inductor and the second filter capacitor form a low-pass filter, which can filter high-frequency interference signals in the circuit, thereby improving the stability of the circuit.

In order to further improve the stability of the step-down unit, in the embodiment of the present application, referring to fig. 4, the step-down unit 13 further includes a third filter capacitor C3, where the third filter capacitor C3 is disposed in parallel with the second filter capacitor C2, one end of the third filter capacitor C3 is electrically connected to the first control end 1 of the relay 14, and the other end of the third filter capacitor C3 is electrically connected to the second control end 2 of the relay 14.

In the above embodiment, one end of the third filter capacitor C3 is electrically connected to the first control terminal 1 of the relay 14, and the other end of the third filter capacitor C3 is electrically connected to the second control terminal 2 of the relay 14. When the source electrode and the drain electrode of the N-channel field effect transistor Q1 are conducted, the external power supply can charge the third filter capacitor C3 in addition to the second filter capacitor C2; when the source and the drain of the N-channel fet Q1 are disconnected, the third filter capacitor C3 may also be used as a power source to release energy.

By arranging the third filter capacitor, on one hand, the third filter capacitor and the second filter capacitor jointly filter high-frequency interference signals in the circuit, so that interference is further reduced; on the other hand, when the source electrode and the drain electrode of the N-channel field effect transistor are disconnected, the third filter capacitor can be used as a power supply to release energy, so that the stability of the circuit is further ensured.

In order to further reduce the high-frequency interference, referring to fig. 4, in the embodiment of the present application, the relay driving circuit further includes a fourth filter capacitor C4, one end of the fourth filter capacitor C4 is electrically connected to the external power VCC, and the other end of the fourth filter capacitor C4 is connected to the ground.

In the embodiment of the present application, one end of the fourth filter capacitor C4 is electrically connected to the external power VCC, and the other end of the fourth filter capacitor C4 is connected to the ground. The fourth filter capacitor C4 is a filter capacitor of the external power supply VCC, and when the source and the drain of the N-channel field effect transistor Q1 are turned on, the fourth filter capacitor C4 can filter the input of the external power supply VCC, thereby reducing high frequency interference. Through setting up fourth filter capacitor, filter the input of external power source, reduce high frequency interference, and then improve the stability of circuit.

In the embodiment of the application, the high-level duty ratio of the first PWM control signal is 100%, and the high-level duty ratio of the second PWM control signal is 40% -70%.

The first PWM control signal is used to make the voltage provided by the voltage reducing unit to the relay higher than the working voltage of the relay so as to close the relay, so that the high level duty ratio of the first PWM control signal is 100%, so that the voltage provided by the voltage reducing unit to the relay can be continuously increased to the voltage provided by the external power supply, so that the voltage provided by the voltage reducing unit to the relay is higher than the working voltage of the relay so as to close the relay. The second PWM control signal is used for enabling the voltage provided by the voltage reducing unit to the relay to be higher than the holding voltage of the relay and lower than the voltage provided by an external power supply, so that the high-level duty ratio of the second PWM control signal is 40% -70%; when the high-level duty ratio of the PWM control signal is smaller than 40%, the voltage obtained by the step-down processing of the external power supply through the step-down unit is smaller than the holding voltage of the relay, and the relay cannot be kept in a closed state; when the high-level duty ratio of the PWM control signal is larger than 70%, the voltage obtained by the step-down processing of the external power supply through the step-down unit is larger, so that the loss of the relay coil is overlarge, and the service life of the relay is further shortened.

Through setting up first PWM control signal and second PWM control signal, carry out accurate control to the voltage of appling on the relay, and then reduce relay coil's loss, prolonged the life of relay greatly.

According to some embodiments of the present application, the present application further provides a power control device, including a relay driving circuit according to any one of the above schemes.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the application, and are intended to be included within the scope of the appended claims and description. In particular, the technical features mentioned in the respective embodiments may be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions falling within the scope of the claims.

Claims (10)

1. A relay driving circuit, comprising: the control unit, the switch unit, the step-down unit and the relay;

The control unit is connected with the switch unit and is used for sending PWM control signals to the switch unit;

The switch unit comprises a first input end, a first output end and a grounding end; the first input end is electrically connected with the control unit; the first output end is electrically connected with the voltage reducing unit and used for controlling the on-off of the voltage reducing unit and an external power supply;

The voltage reducing unit comprises a second input end, a second output end and a voltage reducing control end; the second input end is connected with an external power supply; the voltage reduction control end is electrically connected with the first output end of the switch unit and is connected with the ground through the grounding end of the switch unit; the second output end is electrically connected with the relay and used for controlling the relay;

When the control unit sends a first PWM control signal to the switch unit, the switch unit is conducted to enable the external power supply to provide power for the voltage reduction unit, and the voltage reduction unit provides a first voltage for the relay to enable the relay to be in a closed state;

When the control unit sends a second PWM control signal to the switch unit, the switch unit is periodically conducted under the control of the second PWM control signal, so that the external power supply periodically supplies power to the voltage reduction unit, the voltage reduction unit performs voltage reduction processing on the power supplied by the external power supply and supplies a second voltage to the relay, and the relay is in a closed state, wherein the second voltage is smaller than the first voltage.

2. The relay driving circuit according to claim 1, wherein the control unit includes a DSP controller;

the DSP controller is connected with the first input end of the switch unit through a GPIO interface on the DSP controller.

3. The relay driving circuit according to claim 2, wherein the switching unit includes an N-channel field effect transistor;

The grid electrode of the N-channel field effect transistor is electrically connected with the GPIO interface of the DSP controller; the source electrode of the N-channel field effect transistor is connected with the ground; the drain electrode of the N-channel field effect transistor is electrically connected with the voltage reduction control end of the voltage reduction unit;

When the DSP controller outputs a high-level signal, the N-channel field effect transistor is in a conducting state, so that the voltage reducing unit is conducted with an external power supply;

When the DSP controller outputs a low-level signal, the N-channel field effect transistor is in a cut-off state, so that the voltage reducing unit is disconnected from an external power supply.

4. The relay driving circuit according to claim 3, wherein the switching unit further comprises a first voltage dividing resistor and a second voltage dividing resistor;

One end of the first voltage dividing resistor is electrically connected with a GPIO interface of the DSP controller, the other end of the first voltage dividing resistor is electrically connected with a grid electrode of the N-channel field effect transistor, and the other end of the first voltage dividing resistor is also electrically connected with one end of the second voltage dividing resistor;

the other end of the second voltage dividing resistor is connected with the ground.

5. The relay driving circuit according to claim 4, wherein the switching unit further comprises a first filter capacitor;

The first filter capacitor is connected with the second voltage dividing resistor in parallel, one end of the first filter capacitor is connected with the ground, and the other end of the first filter capacitor is electrically connected with the grid electrode of the N-channel field effect transistor.

6. The relay driving circuit according to claim 3, wherein the step-down unit includes an inductance, a second filter capacitance, and a diode;

one end of the inductor is connected with the cathode of the diode and is electrically connected with the external power supply, and the other end of the inductor is respectively connected with the first control end of the relay and one end of the second filter capacitor;

The other end of the second filter capacitor is electrically connected with the second control end of the relay and the anode of the diode respectively;

And the anode of the diode is electrically connected with the drain electrode of the N-channel field effect transistor.

7. The relay driving circuit according to claim 6, wherein the step-down unit further includes a third filter capacitor;

The third filter capacitor is arranged in parallel with the second filter capacitor, one end of the third filter capacitor is electrically connected with the first control end of the relay, and the other end of the third filter capacitor is electrically connected with the second control end of the relay.

8. The relay driving circuit according to any one of claims 2 to 7, further comprising a fourth filter capacitor, one end of the fourth filter capacitor being electrically connected to the external power supply, and the other end of the fourth filter capacitor being connected to ground.

9. The relay driving circuit according to any one of claims 2 to 7, wherein,

The high level duty ratio of the first PWM control signal is 100%;

The high level duty cycle of the second PWM control signal is 40% -70%.

10. An electric power control apparatus comprising the relay driving circuit according to any one of claims 1 to 9.