Relay driving circuit

Abstract

The utility model discloses a relay driving circuit. The driving circuit comprises a first voltage source, a second voltage source and a control assembly, the first voltage source is provided with a buffer switch circuit, the buffer switch circuit comprises a triode, a capacitor, a first resistor and a second resistor, and the voltage of the first voltage source is higher than that of the second voltage source; an emitter of the triode is connected with a first voltage source, a capacitor and a first resistor are connected in parallel between a base and a collector of the triode, a second resistor is connected between the emitter and the base, and the collector of the triode is connected with one end of the relay; the second voltage source is connected with one end of the relay through the switching device, and the other end of the relay is grounded and connected with the control assembly. The problem that in the prior art, when a relay drive circuit performs state switching between closing and opening, long-time delay can be formed, so that closing and opening actions cannot be quickly performed for multiple times is solved.

Description

Technical Field

[0001] The present application relates to the field of relay control technology, and in particular to a relay drive circuit. Background Art

[0002] In existing photovoltaic inverters, the relay drive circuit consumes different power when the relay is energized than when it is in the closed state. The power consumed when the relay is energized is greater than the power consumed when the relay is in the closed state. To minimize the power consumed in the closed state, a step-down holding drive circuit is generally used.

[0003] The traditional step-down holding circuit has two voltage sources. The high-voltage voltage source and the low-voltage voltage source are connected in parallel on the relay. An RC circuit is set between the high-voltage voltage source and the relay, that is, a resistor is connected in series between the high-voltage voltage source and the relay, and a capacitor is connected in parallel with the ground terminal.

[0004] When the relay is in the disconnected state, the capacitor is charged by the high-voltage voltage source, so that the capacitor voltage is equal to the high-voltage source voltage. When the relay is switched from disconnected to closed, the capacitor, which has been increased to a high voltage, supplies power to the relay. The resistance makes the current used by the high-voltage voltage source to charge the capacitor smaller than the current used by the capacitor to supply power to the relay, so the capacitor voltage gradually decreases. When the capacitor voltage is lower than the low-voltage voltage source, the low-voltage voltage source charges the capacitor, and the current is not restricted, so that the capacitor voltage will not continue to decrease.

[0005] Thus, the voltage source gradually switches from high voltage to low voltage and maintains it. However, it takes a certain amount of time for the relay to switch from opening to closing. During this period, the capacitor needs to be maintained above a certain voltage, which requires the capacitor capacity to reach a certain value.

[0006] When the relay switches from open to closed, the current used by the high-voltage source to charge the capacitor must be less than the relay's holding current. Otherwise, the relay's drive voltage will increase, the relay coil power will increase, and it will heat up severely, or even burn out. This means that after the relay is disconnected, it takes a long time for the capacitor voltage to rise close to the high-voltage source voltage. If the capacitor voltage is still relatively low before the next closure, it will be lower than the relay's pull-in voltage, and the relay may not close or close slowly. Therefore, the disadvantage of this circuit is that it cannot achieve fast contact closing and closing operations. In addition, the large capacitor value will be relatively expensive.

[0007] It can be seen from this that when the relay driving circuit in the related art switches between the states of energizing and disconnecting, a long delay will be generated, resulting in the problem that the energizing and disconnecting actions cannot be performed quickly and multiple times. Utility Model Content

[0008] The main purpose of this application is to provide a relay drive circuit to solve the problem in the related art that when the relay drive circuit switches between the states of attraction and disconnection, a long delay is generated, resulting in the inability to quickly and repeatedly perform the attraction and disconnection actions.

[0009] According to one aspect of the present application, a relay drive circuit is provided, comprising a first voltage source, a second voltage source, and a control component; a buffer switch circuit is provided on the first voltage source, the buffer switch circuit comprising a transistor, a capacitor, a first resistor, and a second resistor, wherein the voltage of the first voltage source is higher than the voltage of the second voltage source; the emitter of the transistor is connected to the first voltage source, the capacitor and the first resistor are connected in parallel between the base and the collector of the transistor, the second resistor is connected between the emitter and the base, and the collector of the transistor is connected to one end of the relay; the second voltage source is connected to one end of the relay via a switching device, the other end of the relay is grounded and connected to the control component.

[0010] As an optional embodiment, the control component includes a control transistor; the base of the control transistor is connected to the drive control signal end, the emitter of the control transistor is grounded, and the collector of the control transistor is connected to the other end of the relay.

[0011] As an optional embodiment, the control transistor is a transistor or a field effect MOS transistor.

[0012] As an optional embodiment, the control component also includes an anti-parallel diode; the input end of the anti-parallel diode is connected to the negative pole of the relay, and the output end of the anti-parallel diode is connected to the positive pole of the relay; the input end of the anti-parallel diode is connected to the collector of the control transistor.

[0013] As an optional embodiment, the control component also includes a driving current limiting resistor; the driving current limiting resistor is arranged between the base of the control transistor and the driving control signal; one end of the driving current limiting resistor is connected to the base of the control transistor, and the other end of the driving current limiting resistor is connected to the input end of the driving control signal.

[0014] As an optional embodiment, the switching device is a switching diode; the input end of the switching diode is connected to the second voltage source, and the output end of the switching diode is connected to the relay.

[0015] As an optional embodiment, the output end of the switching diode is connected to the collector of the transistor and to the output end of the anti-parallel diode of the control component.

[0016] As an optional embodiment, the transistor is a PNP transistor.

[0017] As an optional embodiment, when the relay changes from open to closed, the transistor is turned on and the first voltage source supplies power to the relay; after the relay is closed, the transistor is cut off, so that the voltage of the collector of the transistor is lower than the voltage of the second voltage source, and the relay is powered by the second voltage source.

[0018] As an optional embodiment, when the relay changes from closed to open, the transistor is cut off, and the first voltage source provides a corresponding voltage to the output end of the collector of the transistor.

[0019] In the present application, when the first voltage source is passed through the collector of the transistor to power on the relay through the buffer switching circuit, a capacitor is used to achieve slow conduction and power-on, and based on the fact that the working state of the relay is a low-resistance state, after the relay is powered on, the voltage of the collector of the transistor will be automatically lowered to a value lower than the second voltage source, and the second voltage source will be automatically switched to power the relay, thereby achieving energy saving. Moreover, the capacitor is used as a transistor driver, and its capacity is very small. The resistance of the first capacitor and the second capacitor is very large, and the overall energy consumption of the circuit is very small.

[0020] Furthermore, when the relay is disconnected after closing, the second resistor and the first resistor can be used to quickly pull up the collector of the transistor, achieving rapid shutdown of the relay without buffering or delay. This not only meets the needs of rapid shutdown or continuous multiple state changes of the relay during passive shutdown, but also provides greater energy savings. This solves the problem in related arts that relay drive circuits incur delays when switching between the closed and open states, preventing rapid and multiple close and open actions. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0022] Figure 1 Schematic diagram of a relay drive circuit of a photovoltaic inverter in the related art;

[0023] Figure 2 A schematic diagram of a relay drive circuit disclosed in this application;

[0024] Figure 3 This is a schematic diagram of the relay drive circuit simulation test curve disclosed in this application. DETAILED DESCRIPTION

[0025] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0026] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0027] Unless otherwise specifically stated, the relative arrangement of the parts and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to actual proportional relationships. The techniques, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the techniques, methods and equipment should be considered as part of the authorization specification. In all examples shown and discussed here, any specific values should be interpreted as being merely exemplary, not as limitations. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following figures, and therefore, once an item is defined in one figure, it does not need to be further discussed in subsequent figures.

[0028] In the related art, the conventional step-down holding circuit is as follows Figure 1 As shown, the high voltage source +12V forms an RC circuit through R4 and C4. This step-down holding drive circuit first charges the capacitor C4 to 12V through the resistor R4. When the relay is closed, the relay is driven, and the voltage 12V on the capacitor C4 is discharged through the relay RY1, making the relay RY1 work.

[0029] When the voltage of capacitor C4 is discharged below 7V, diode D4 is turned on, and the coil voltage of relay RY1 is kept at 7V, thus achieving the purpose of maintaining the relay.

[0030] This circuit uses capacitor C4 to provide the voltage required to close the relay. To ensure reliable relay closure, C4's capacitance must be sufficiently large. Furthermore, to ensure the relay can quickly meet the next closure conditions after disconnection, R4's resistance must be small enough to quickly raise C4's voltage to 12V. This results in a higher power across R2 after the voltage across C4 drops to 7V when the relay closes, effectively increasing the power required to maintain the drive circuit. However, R4's resistance must be moderate, as this will cause the voltage across C4 to fall below 7V or take an unduly long time to reach 7V, resulting in a higher power requirement for the relay.

[0031] See also Figure 2 As shown, the present application provides a relay drive circuit, including a first voltage source of +12V, a second voltage source of +7V, and a control component. The first voltage source of +12V provides the voltage required to close the relay, and the second voltage source of +7V provides the voltage required to maintain the relay closed. The relay closing voltage is greater than the maintenance voltage, that is, the voltage of the first voltage source of +12V is higher than the voltage of the second voltage source of +7V.

[0032] A buffer switch circuit is provided on the first voltage source +12V, which includes a transistor Q2, a capacitor C1, a first resistor R3 and a second resistor R2; the emitter of the transistor Q2 is connected to the first voltage source +12V, the capacitor C1 and the first resistor R3 are connected in parallel between the base and collector of the transistor Q2, the second resistor R2 is connected between the emitter and the base, and the collector of the transistor Q2 is connected to one end of the relay RY1; the second voltage source +7V is connected to one end of the relay RY1 through a switching device, and the other end of the relay RY1 is grounded and connected to the control component.

[0033] When the first voltage source +12V is applied to the collector of transistor Q2 to power the relay, the buffer switch circuit uses capacitor C1 to achieve slow conduction and power-up. Because relay RY1 is in a low-resistance state, when the driver circuit of relay RY1 is activated, the collector voltage of transistor Q2 is automatically lowered. Due to the action of C1, the base voltage of transistor Q2 is also lowered, turning on transistor Q2 and supplying power to the relay. As the first voltage source +12V charges capacitor C1 through second resistor R2, the voltage across capacitor C1 gradually increases, increasing the base voltage of transistor Q2. When the voltage approaches 12V, transistor Q2 turns off. After transistor Q2 turns off, the relay is powered by the second power source +7V. Automatically switching the second voltage source +7V to power relay RY1 saves energy. Furthermore, capacitor C1, which drives transistor Q2, has a very small capacitance, while the resistance of first capacitor R3 and second capacitor R2 is very large, resulting in very low overall energy consumption for the circuit.

[0034] Furthermore, when relay RY1 is disconnected after closing, the second resistor R2 and the first resistor R3 can be used to quickly pull up the collector of transistor Q2, thereby quickly shutting off relay RY1. It should be noted that the shutdown of relay RY1 is controlled by the drive circuit. After relay RY1 is shut off, the first voltage source +12V charges capacitor C1 through the second resistor R2 and the first resistor R3, rapidly reducing the voltage difference across capacitor C1 and ensuring that transistor Q2 can be turned on the next time the relay is opened.

[0035] The aforementioned relay RY1 has a very short shutdown buffer and delay time, which not only meets the requirements for rapid shutdown or multiple consecutive state changes of relay RY1 during passive shutdown, but also provides greater energy savings. This solves the problem in related arts where relay drive circuits often experience a long delay when switching between the on and off states, preventing rapid and repeated on and off operations.

[0036] Relay RY1 is typically initially disconnected. At this point, the first voltage source (+12V) provides a voltage of 12V to point A, the base of transistor Q2, through second resistor R2. Transistor Q2 is cut off, and the voltages at points A and B are the same, meaning the voltage difference across capacitor C1 is 0V. Point A gradually pulls up the voltage at point B, the collector voltage of transistor Q2, through first resistor R3 and capacitor C1.

[0037] The voltage at point B remains at 7V when the relay is on. When relay RY1 is off, the voltage at point B gradually increases due to the action of first resistor R3 until it reaches the same voltage as point A, which means the voltage difference across capacitor C1 is 0V. When the voltage at point B exceeds the 7V of the second voltage source, the switching diode D2 of the second voltage source (+7V) is reverse-blocked, and the voltage at point B continues to rise until it reaches 12V. The impedance of transistor Q2 gradually decreases, and the first voltage source (+12V) supplies power to point B through transistor Q2, bringing the voltages at points A and B to 12V.

[0038] When relay RY1 switches from open to closed, point B supplies power to the relay and the voltage at point B is pulled down. Due to the characteristic of capacitor C1 that keeps the voltage across both ends unchanged, point A is also pulled down. The base voltage of transistor Q2 is lower than the emitter voltage, transistor Q2 is turned on, and the relay is powered by the first voltage source +12V, providing energy for the relay to close.

[0039] After relay RY1 works, it presents a low-resistance state, and the voltage at point B is gradually pulled down. The voltage at point A is supplemented by the first voltage source +12V through transistor Q2 and the second resistor R2. Since the second resistor R2 charges point A, the voltage difference across capacitor C1 gradually increases, and the voltage at point A remains basically unchanged.

[0040] The voltage at point A gradually approaches 12V again, meaning that the base voltage of transistor Q2 gradually equals the emitter voltage, effectively shutting off transistor Q2. Simultaneously, the voltage at point B also gradually decreases. The on-resistance of transistor Q2 also gradually increases, pulling the voltage at point B even lower. When the voltage at point B falls below the 7V supply of the first voltage source, the +7V supply powers relay RY1, maintaining the voltage at point B at 7V. The voltage at point A approaches 12V. At this point, the voltage difference between points A and B is 4V, and the impedance of transistor Q2 is very large, effectively shutting off. At this point, the relay driver's holding current is provided by the +7V supply, achieving a step-down hold function.

[0041] When the relay switches from closed to open, relay RY1 stops working, and the voltage at point B is gradually pulled up by point A through the first resistor R3. When the voltage at point B is higher than 7V of the first voltage source, diode D2 is reversely turned off, and the path between the second voltage source +7V and relay RY1 is disconnected. The voltage at point B continues to rise, and the voltage across capacitor C1 gradually decreases. Transistor Q2 remains turned off, and the first voltage source +12V supplies power to point B through transistor Q2. The voltage at point A is equal to the voltage at point B, both of which are 12V, and the initial state is restored.

[0042] Because capacitor C1 serves solely as a driver for transistor Q2, its capacitance can be very small compared to the voltage used for energy storage and delay in related art. This allows for larger resistances for resistors R2 and R3, reducing energy consumption. Furthermore, when relay RY1 is maintained at 7V, transistor Q2 is in the off state and consumes no energy, minimizing excess circuit loss.

[0043] As an optional embodiment, the control component includes a control transistor Q1; the base of the control transistor Q1 is connected to the drive control signal terminal, the emitter of the control transistor Q1 is grounded, and the collector of the control transistor Q1 is connected to the other end of the relay RY1.

[0044] The control transistor Q1 serves as a control switch tube of the relay RY1 and is connected to the input terminal DRIVE_RY of the drive signal. It is used to be turned on and off according to different drive signals to control the closing or opening action of the relay RY1.

[0045] The base of the control transistor Q1 is connected to the drive control signal terminal, the emitter of the control transistor Q1 is grounded, and the collector of the control transistor Q1 is connected to the relay RY1. In the initial state, the relay drive signal DRIVE_RY is low, the control transistor Q1 is turned off, and the control relay RY1 is turned off.

[0046] When the drive signal DRIVE_RY becomes high, the control transistor Q1 is turned on through the resistor R1, the voltage at point A is equal to the voltage at point B, the transistor Q2 is turned on, and the relay RY1 is driven by the first voltage source +12V.

[0047] When the voltage at point B is lower than 7V after relay RY1 is operated, diode D2 is turned on, the voltage at point B is maintained at 7V, and Q2 is turned off. Relay RY1 is driven by the second voltage source +7V.

[0048] As an optional embodiment, the control transistor Q1 is a transistor or a field effect MOS transistor, which serves as a control switch of the relay RY1 and has better control performance and response capability, and is more energy-efficient.

[0049] As an optional embodiment, the control component also includes an anti-parallel diode D1; the input end of the anti-parallel diode D1 is connected to the cathode of the relay RY1, and the output end of the anti-parallel diode D1 is connected to the anode of the relay RY1; the input end of the anti-parallel diode D1 is connected to the collector of the control transistor Q1.

[0050] The anti-parallel diode D1 is connected in anti-parallel with the drive coil of relay RY1. That is, the input end of anti-parallel diode D1 is connected to the cathode of relay RY1, and the output end of anti-parallel diode D1 is connected to the anode of relay RY1. This effectively prevents the coil current of relay RY1 from generating high voltage and damaging control transistor Q1 when control transistor Q1 is turned off.

[0051] As an optional embodiment, the control component also includes a driving current limiting resistor R1; the driving current limiting resistor R1 is arranged between the base of the control transistor Q1 and the driving control signal; one end of the driving current limiting resistor R1 is connected to the base of the control transistor Q1, and the other end of the driving current limiting resistor R1 is connected to the input end of the driving control signal DRIVE_RY.

[0052] The drive current-limiting resistor R1 is positioned between the base of the control transistor Q1 and the drive control signal to increase the voltage of the drive signal to effectively control the conduction of the control transistor Q1. Furthermore, the drive current-limiting resistor R1 limits the current entering the control transistor Q1, providing current-limiting protection for the control transistor Q1 and improving the safety and reliability of the control transistor Q1.

[0053] As an optional embodiment, the switching device is a switching diode D2; the input end of the switching diode D2 is connected to the second voltage source +7V, and the output end of the switching diode D2 is connected to the relay RY1.

[0054] The voltage across the switching diode D2 is used to control the conduction and dielectric properties of the switching diode, thereby achieving connection and disconnection of the second voltage source +7V.

[0055] The input end of the switching diode D2 is connected to the second voltage source +7V, and the output end of the switching diode D2 is connected to the relay RY1. When the voltage at the output end of the switching diode D2 is less than 7V, the switching diode D2 is turned on, and the second voltage source +7V is used to power the relay RY1. When the voltage at the output end of the switching diode D2 is greater than 7V, the switching diode D2 is turned off, shutting down the second voltage source +7V.

[0056] As an optional embodiment, the output end of the switching diode D2 is connected to the collector of the transistor Q2 and to the output end of the anti-parallel diode D1 of the control component.

[0057] The conduction and dielectric of the switching diode are controlled by utilizing the voltage of the switching diode D2, the second voltage source +7V and the collector of the transistor Q2, thereby realizing connection and disconnection of the second voltage source +7V.

[0058] The input of switching diode D2 is connected to a second voltage source of +7V, and the output of switching diode D2 is connected to relay RY1 and the collector of transistor Q2. When the voltage at the collector of transistor Q2, or the voltage at point B, gradually decreases below 7V, switching diode D2 turns on, supplying power to relay RY1 via the second voltage source of +7V. When the voltage at point B gradually rises above 7V, switching diode D2 turns off, shutting off the second voltage source of +7V.

[0059] As an optional embodiment, transistor Q2 is a PNP transistor. PNP transistors conduct at low voltage, further saving energy and reducing circuit power consumption. Furthermore, transistor Q2 in this embodiment is off most of the time, turning on only at the moment the relay closes, resulting in very low energy consumption.

[0060] As an optional embodiment, when the relay RY1 changes from open to closed, the transistor Q2 is turned on, and the first voltage source +12V supplies power to the relay RY1; when the relay RY1 is closed, the transistor Q2 is turned off, so that the voltage of the collector of the transistor Q2 is lower than the voltage of the second voltage source +7V, and the relay RY1 is powered by the second voltage source +7V.

[0061] That is, when relay RY1 switches from open to closed, point B provides power to the relay, and capacitor C1 maintains the voltage difference between points A and B constant or slowly changes. The voltage at point A can be considered equal to the voltage at point B. Transistor Q2 conducts, and relay RY1 is driven by the first voltage source, +12V.

[0062] After relay RY1 is closed, it is in a low-resistance state, and the voltage at point B is gradually pulled down. The voltage at point A is supplemented by the first voltage source +12V through transistor Q2 and the second resistor R2. Since the second resistor R2 charges point A, the voltage difference across capacitor C1 gradually increases, and the voltage at point A remains basically unchanged.

[0063] At this point, the voltage at point A gradually approaches 12V again, meaning that the base voltage of transistor Q2 gradually equals the emitter voltage, and transistor Q2 is turned off. Simultaneously, the voltage at point B gradually decreases, causing the voltage at point A to gradually exceed that at point B. The on-resistance of transistor Q2 also gradually increases, pulling the voltage at point B even lower. When the voltage at point B falls below the 7V of the first voltage source, the +7V first voltage source powers relay RY1, maintaining the voltage at point B at 7V. The voltage at point A approaches 12V, and the voltage difference between points A and B is now 4V. The impedance of transistor Q2 is very large, effectively turning it off.

[0064] As an optional embodiment, when the relay RY1 switches from closed to open, the transistor Q2 is turned off, and the first voltage source +12V provides a corresponding voltage of 12V to the output terminal of the collector of the transistor Q2.

[0065] When the relay switches from closed to open, relay RY1 stops operating. The voltage at point B is gradually pulled up by point A through first resistor R3. When the voltage at point B exceeds the 7V of the first voltage source, diode D2 reverses and shuts off, disconnecting the second voltage source +7V from relay RY1. The voltage at point B continues to rise, gradually decreasing the impedance of transistor Q2 and the voltage across capacitor C1. Transistor Q2 remains off, and the first voltage source +12V supplies power to point B through transistor Q2. The voltage at point A equals the voltage at point B, both at 12V. This ensures that the next time relay RY1 closes, the first voltage source +12V can quickly supply power.

[0066] It should be noted that this embodiment also provides an optional implementation method, which is described in detail below.

[0067] like Figure 2 As shown, RY1 is the driven relay; the control transistor Q1 is an NPN transistor, which can also be an N-type field-effect MOS transistor, serving as the control switch tube of the relay RY1; D1 is the anti-parallel diode of the driving coil of the relay RY1, which prevents the relay coil current from generating high voltage and damaging the control transistor Q1 when the control transistor Q1 is turned off; DRIVE_RY is the driving signal of the control transistor Q1; and R1 is the driving current-limiting resistor of the control transistor Q1.

[0068] D2 is the switching diode of the +7V voltage source.

[0069] Transistor Q2 is a PNP transistor; capacitor C1 is Q2's drive capacitor; resistor R2 is the current-limiting resistor for charging C1; resistor R3 is the discharge resistor for C1. Point A is Q2's base voltage; point B is Q2's collector voltage. 12V is the voltage required for the relay to operate; 7V is the relay's hold voltage.

[0070] In this step-down holding drive circuit, in the initial state, the relay drive signal DRIVE_RY is at a low level, the transistor Q1 is controlled to be turned off, the voltages at points A and B across the capacitor C1 are both 12V, and the diode D2 is reversely cut off.

[0071] When the relay drive signal DRIVE_RY becomes high, the control transistor Q1 is turned on through the resistor R1. Since the voltage is maintained by the capacitor C1, the voltage at point A is equal to the voltage at point B, the transistor Q2 is turned on, and the relay RY1 is driven by the 12V voltage.

[0072] After relay RY1 operates, it assumes a low-resistance state, gradually pulling down the voltage at point B. The voltage at point A is supplemented by 12V through transistor Q2 and the second resistor R2. Since second resistor R2 charges point A, the voltage difference across capacitor C1 gradually increases, and the voltage at point A remains essentially unchanged. The voltage at point A gradually approaches 12V again, meaning that the base voltage of transistor Q2 gradually equals the emitter voltage, and transistor Q2 is turned off. Simultaneously, the voltage at point B also gradually decreases, eventually causing the voltage at point A to exceed that at point B. The on-resistance of transistor Q2 also gradually increases, pulling the voltage at point B even lower. When the voltage at point B falls below 7V, diode D2 conducts, maintaining the voltage at point B at 7V. At this point, the voltage difference between points A and B is 4V, and the impedance of transistor Q2 is very large, effectively turning it off.

[0073] The relay drive holding current is provided by a 7V voltage, implementing a step-down hold function. When the relay drive signal DRIVE_RY goes low, transistor Q1 is turned off, and relay RY1 stops operating. The voltage at point B is gradually pulled up by point A through R3. When the voltage at point B exceeds 7V, D2 is reversed and cut off, causing the voltage at point B to continue rising. The impedance of transistor Q2 gradually decreases, and the first voltage source +12V is supplied to point B through transistor Q2. The voltage at points A and B becomes equal, and the drive circuit returns to its initial state.

[0074] Because capacitor C1 serves only as a driver for transistor Q2, its capacitance can be very small, allowing for larger resistances for second resistor R2 and first resistor R3. When relay RY1 is maintained at 7V, transistor Q2 is cut off, minimizing excess circuit losses.

[0075] This embodiment also simulates this circuit, setting R1 = 1KΩ, R2 = 1KΩ, R3 = 10KΩ, C1 = 100nF, and the simulation results are as follows: Figure 3 As shown, when the drive signal DRIVE_RY is high, it drives the relay RY closed; when it is low, it drives the relay RY open. When the first low level changes to a high level, I_12V indicates that the first voltage source +12V quickly provides a large current when it jumps from a low level to a high level, then gradually decreases, and jumps to 0 when it intersects the current curve I_7V of the second voltage source +7V, and the second voltage source +7V is powering the relay.

[0076] I_RY1 represents the current in relay RY1, which is the sum of I_12V and I_7V. It can be seen that when the voltage level jumps from high to low, the current in relay RY1 quickly jumps to zero, meaning there is no delay. This avoids the problem of using an RC circuit in related technologies. After relay RY1 is turned off, the capacitor continues to discharge, causing the current in relay RY1 to gradually decay to zero, preventing rapid shutdown and, consequently, failing to meet the requirements of multiple continuous on and off state switching.

[0077] In addition, it can be seen that VA, that is, the voltage at point A, is basically constant at around 12V. VB, that is, the voltage at point B, quickly decays to around 6V (less than 7V) when it jumps from a low level to a high level, achieving a fast and automatic switch from the first voltage source +12V to the second voltage source +7V. And when it jumps from a high level to a low level, it slowly rises to 12V, which is more energy-efficient.

[0078] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used herein to describe the spatial positional relationship of a device or feature to other devices or features as shown in the figures. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figures. For example, if the device in the drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0079] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of this application.

[0080] The above are merely preferred embodiments of the present application and are not intended to limit the present application. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A relay drive circuit, characterized in that: comprising a first voltage source, a second voltage source, and a control component; The first voltage source is provided with a buffer switch circuit, the buffer switch circuit comprising a transistor, a capacitor, a first resistor and a second resistor, wherein the voltage of the first voltage source is higher than the voltage of the second voltage source; The emitter of the transistor is connected to the first voltage source, the capacitor and the first resistor are connected in parallel between the base and the collector of the transistor, the second resistor is connected between the emitter and the base, and the collector of the transistor is connected to one end of the relay; The second voltage source is connected to one end of the relay through a switch device, and the other end of the relay is grounded and connected to the control component.

2. The relay drive circuit according to claim 1, wherein: The control component includes a control transistor; The base of the control transistor is connected to the drive control signal terminal, the emitter of the control transistor is grounded, and the collector of the control transistor is connected to the other end of the relay.

3. The relay drive circuit according to claim 2, wherein: The control transistor is a transistor or a field effect MOS transistor.

4. The relay driving circuit according to claim 2, wherein: The control component also includes an anti-parallel diode; The input end of the anti-parallel diode is connected to the cathode of the relay, and the output end of the anti-parallel diode is connected to the anode of the relay; The input end of the anti-parallel diode is connected to the collector of the control transistor.

5. The relay driving circuit according to claim 2, wherein: The control component also includes a driving current limiting resistor; The driving current limiting resistor is arranged between the base of the control transistor and the driving control signal; One end of the driving current limiting resistor is connected to the base of the control transistor, and the other end of the driving current limiting resistor is connected to the input end of the driving control signal.

6. The relay drive circuit according to claim 1, wherein: The switching device is a switching diode; An input end of the switching diode is connected to the second voltage source, and an output end of the switching diode is connected to the relay.

7. The relay drive circuit according to claim 6, characterized in that: The output end of the switching diode is connected to the collector of the transistor and to the output end of the anti-parallel diode of the control component.

8. The relay driving circuit according to claim 1, wherein: The transistor is a PNP transistor.

9. The relay drive circuit according to any one of claims 1 to 8, characterized in that: When the relay changes from open to closed, the transistor is turned on and the first voltage source supplies power to the relay; after the relay is closed, the transistor is cut off, so that the voltage of the collector of the transistor is lower than the voltage of the second voltage source, and the relay is powered by the second voltage source.

10. The relay drive circuit according to any one of claims 1 to 8, characterized in that: When the relay switches from closed to open, the transistor is turned off, and the first voltage source provides a corresponding voltage to the output terminal of the collector of the transistor.

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