Relay energy-saving control circuit suitable for wide-range voltage power supply

Abstract

The invention discloses a relay energy-saving control circuit suitable for wide-range voltage power supply, which relates to the field of relay energy conservation and comprises an oscillator circuit consisting of a voltage comparator U2 and other peripheral circuits, a voltage stabilizing circuit, a starting delay circuit, a driving amplification circuit and a driven load relay RL1, a voltage comparator U2 is used for controlling a driving transistor Q1 in a driving amplifying circuit, stable driving of relay driving in a wide voltage range can be achieved, sufficient driving energy can be provided in the relay starting stage to ensure reliable pull-in, the mode can be automatically switched to a low-duty-ratio PWM mode in the maintaining stage, energy consumption is remarkably reduced, and the service life of the relay is prolonged. And meanwhile, the voltage stabilizing circuit guarantees the stability of the reference voltage, the anti-interference capability of the system and the reliability of the switch are improved through a fly-wheel diode and a positive feedback design, and finally, dual optimization of efficient energy conservation and stable driving is achieved while occupation of control pins of the system is reduced.

Description

Technical Field

[0001] This invention relates to the field of relay energy saving, specifically to a relay energy-saving control circuit suitable for a wide range of voltage power supply. Background Technology

[0002] As we all know, the voltage required for a relay to close is greater than 80% of the rated voltage. Usually, the rated voltage is used to drive the closing action in order to allow for a certain design margin. The voltage that maintains the closed state of the relay is called the holding voltage. The holding voltage is generally relatively low to effectively maintain the closed state of the relay. Usually, more than 30% of the rated voltage is sufficient. Since the relay exhibits resistive characteristics in the holding state, the power consumption required to maintain the relay's closure is related to the square of the holding voltage.

[0003] For example, if the relay can be driven to close with 12V, and then maintained at 7-8V, this is an ideal control method. This will help reduce the power consumption of our relay drive by 60%. Usually, two sets of voltages are used to switch between them, which not only increases the complexity of the power supply design, but also consumes two control pins. It is also unsuitable for situations where the supply voltage changes, thus requiring an additional regulated power supply for the relay drive. Summary of the Invention

[0004] The purpose of this invention is to provide a relay energy-saving control circuit suitable for a wide range of voltage power supply, which can reliably power and drive the relay at a voltage higher than the rated driving voltage range of the relay, and the voltage applied to the relay can automatically adjust the closing voltage and the holding voltage to achieve the purpose of automatic energy saving of the relay, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a relay energy-saving control circuit suitable for wide-range voltage supply, comprising an oscillator circuit, a voltage regulator circuit, a start-up delay circuit, and a drive amplifier circuit.

[0006] The voltage regulator circuit is used to generate a stable reference voltage from a wide range of varying power supply bus voltages.

[0007] The oscillator circuit includes a voltage comparator U2. The positive input terminal of the voltage comparator U2 is connected to the output terminal of the voltage regulator circuit to receive the output stable reference voltage. The inverting input terminal of the voltage comparator U2 is connected to a charging / discharging circuit unit and a voltage divider circuit unit.

[0008] The startup delay circuit is connected between the inverting input terminal of the voltage comparator U2 and the voltage divider circuit unit. It is used to provide a startup reference voltage at the initial stage of circuit power-on and switch to a sustaining reference voltage after the delay. The startup reference voltage is higher than the sustaining reference voltage.

[0009] The input terminal of the drive amplifier circuit is connected to the output terminal of the voltage comparator U2, and the output terminal of the drive amplifier circuit is used to drive the load relay RL1.

[0010] The oscillator circuit generates a PWM signal by forming positive feedback oscillation with the output state of the voltage comparator U2 through the charging and discharging circuit unit. The average voltage applied to the load relay RL1 is controlled by the drive amplifier circuit. The start-up delay circuit automatically controls the duty cycle of the PWM signal to achieve automatic energy-saving control of high-voltage start-up and low-voltage maintenance of the relay.

[0011] Preferably, the charging and discharging circuit unit includes a capacitor C3, a resistor R4 and a positive feedback resistor R10. One end of the resistor R4 is connected to the capacitor C3 and the other end is connected to the positive feedback resistor R10. The other end of the capacitor C3 is grounded. The other end of the positive feedback resistor R10 is connected to the inverting input of the voltage comparator U2 to provide hysteresis voltage for the oscillator and ensure the stability of the oscillation waveform.

[0012] Preferably, the voltage regulator circuit includes a current-limiting resistor R1, a Zener diode ZD1, and a filter capacitor C2. The cathode of the Zener diode ZD1 is connected to the power supply bus through the current-limiting resistor R1, and the anode of the Zener diode ZD1 is grounded. The two ends of the filter capacitor C2 are respectively connected to the cathode and anode of the Zener diode ZD1, and its stable voltage serves as the reference voltage for the positive input terminal of the voltage comparator U2.

[0013] Preferably, the voltage divider circuit unit includes resistors R7 and R8, which are connected in series, and the other end of resistor R8 is grounded.

[0014] Preferably, the start-up delay circuit includes a capacitor C1 and a resistor R5, wherein the capacitor C1 and the resistor R5 are connected in series, the other end of the capacitor C1 is connected between the resistor R7 and the resistor R8, and the other end of the resistor R5 is connected between the resistor R7 and the resistor R8.

[0015] Preferably, the driving amplifier circuit includes a base current limiting resistor R2, a resistor R6, and a driving transistor Q1. The resistor R6 is connected in series with the base current limiting resistor R2. The other end of the resistor R6 is connected to the output terminal of the voltage comparator U2. The other end of the base current limiting resistor R2 is connected to the power supply bus. The base of the driving transistor Q1 is connected between the resistor R6 and the base current limiting resistor R2. The emitter of the driving transistor Q1 is connected to the load relay RL1. The other end of the load relay RL1 is grounded.

[0016] Preferably, the drive amplifier circuit further includes a freewheeling diode D1, which is connected in parallel with the load relay RL1 and provides an energy release circuit for the coil inductance when the drive transistor Q1 is turned off.

[0017] Preferably, the oscillator circuit further includes a bias resistor R3 and an optocoupler U1. One end of the bias resistor R3 is connected to the resistor R4, and the other end is connected to the collector of the optocoupler U1. The emitter of the optocoupler U1 is connected to the resistor R7.

[0018] Preferably, the time constant formed by the capacitor C1 and the resistor R5 is between 20 milliseconds and 100 milliseconds to ensure that the relay has enough time to complete the closing action.

[0019] Preferably, the frequency of the PWM signal generated by the oscillator circuit is between 10kHz and 50kHz.

[0020] In summary, the beneficial effects of this invention are:

[0021] This invention achieves adaptive drive control over a wide voltage range by coordinating a PWM oscillator composed of a voltage comparator with a start-up delay circuit. It not only provides sufficient drive energy to ensure reliable engagement during the relay startup phase, but also automatically switches to a low duty cycle PWM mode during the maintenance phase to significantly reduce energy consumption. At the same time, the voltage regulator circuit ensures the stability of the reference voltage, while the freewheeling diode and positive feedback design improve the system's anti-interference capability and switching reliability. Ultimately, it achieves a dual optimization of high efficiency and energy saving and stable drive while reducing the occupation of system control pins. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the overall structure of a relay energy-saving control circuit suitable for wide-range voltage power supply according to the present invention;

[0024] Figure 2 This is a schematic diagram of the operating voltage of an embodiment of a relay energy-saving control circuit applicable to a wide range of voltage power supply according to the present invention. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. These drawings are simplified schematic diagrams, which are only used to illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0026] To facilitate understanding of the present invention, a more complete description of the invention will be given below with reference to the accompanying drawings, which illustrate several embodiments of the invention. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the invention will be more thorough and complete.

[0027] All features disclosed in this specification, or all steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps.

[0028] Any feature disclosed in this specification (including any appended claims, abstract, and drawings) may be replaced by other equivalent or similar features, unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is merely one example of a series of equivalent or similar features.

[0029] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; they can refer to the internal communication of at least two elements or the interaction relationship of at least two elements, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0030] Please see Figure 1 - Figure 2This invention provides an embodiment of a relay energy-saving control circuit suitable for wide-range voltage supply. It employs automatic switching control and adaptive adjustment to drive the relay, effectively reducing the occupation of system control pins and saving relay drive energy. Specifically, it includes an oscillator circuit composed of a voltage comparator U2 and other peripheral circuits, a voltage regulator circuit, a start-up delay circuit, a drive amplifier circuit, and the driven load relay RL1. The voltage comparator U2 controls the drive transistor Q1 in the drive amplifier circuit, enabling stable drive of the relay across a wide voltage range. The relay control coil can be equivalently represented as a circuit of a resistor and an inductor in series. Since relay control involves the conversion of electrical energy into magnetic field energy, the magnitude of the relay drive coil current indicates the magnitude of the magnetic field energy. This invention utilizes the characteristics of the relay and the PWM signal generated by the voltage comparator U2 (PWM signal is a pulse width modulation signal). Combined with the start-up delay circuit, which effectively and cleverly modulates the duty cycle of the oscillator circuit, the energy of the driven relay is automatically controlled to achieve energy saving. A simple voltage regulator circuit provides a reference voltage to the comparator, which can adapt to changing supply voltages while ensuring the average value of the relay drive voltage remains stable.

[0031] Here, voltage comparator U2 converts the sampled analog voltage into the duty cycle corresponding to the PWM to control the inductor current of the relay.

[0032] Specifically, in this embodiment, the oscillator circuit includes a voltage comparator U2, a bias resistor R3, a resistor R4, a capacitor C3, a positive feedback resistor R10, a resistor R7, a resistor R8, and an optocoupler U1. One end of the bias resistor R3 is connected to the resistor R4, and the other end is connected to the collector of the optocoupler U1. The emitter of the optocoupler U1 is connected to the resistor R7. One end of the resistor R4 is connected to the capacitor C3, and the other end is connected to the positive feedback resistor R10. The other end of the capacitor C3 is grounded. The other end of the positive feedback resistor R10 is connected to the inverting input of the voltage comparator U2 to provide hysteresis voltage for the oscillator, ensuring the stability of the oscillation waveform. The resistors R7 and R8 are connected in series, and the other end of the resistor R8 is grounded.

[0033] First, the logic control signal outputs a high level, turning on optocoupler U1. At this time, since the voltage across capacitor C3 is low, the bias resistor R3 provides a static bias voltage, ensuring the reliable turn-off of voltage comparator U2. Therefore, the voltage at the inverting input port of voltage comparator U2 is essentially composed of the voltage divider formed by resistors R7 and R8. The voltage designed here, after voltage division, needs to be higher than the voltage at the non-inverting input pin of voltage comparator U2. At this point, voltage comparator U2 outputs a low level, driving transistor Q1 to conduct, powering the relay.

[0034] Secondly, because the relay receives power and reverses its output, the positive feedback resistor R10 generates a hysteresis voltage difference for the voltage comparator U2. Simultaneously, resistor R4 charges capacitor C3, causing the voltage to gradually increase. When the voltage of capacitor C3 exceeds the inverting input of voltage comparator U2, the comparator outputs a high level, driving transistor Q1 to turn off. The relay continues operation using the energy stored in its coil inductance through the freewheeling diode D1 circuit. Similarly, the positive feedback resistor R10 generates a hysteresis voltage difference, and resistor R4 begins discharging capacitor C3. When the voltage of capacitor C3 falls below the inverting input of voltage comparator U2, the comparator outputs a low level, driving transistor Q1 to turn on and begin storing energy in the relay coil. The charging and discharging speeds of resistor R4 and capacitor C3, along with the hysteresis voltage difference from the positive feedback resistor R10, control the PWM frequency. The voltage division between resistors R7 and R8 controls the PWM pulse width. Typically, the control frequency is between 10kHz and 50kHz, or the frequency can be determined based on the relay characteristics.

[0035] It is worth mentioning that, since it needs to adapt to an unstable voltage range, and the average value of the PWM output voltage is proportional to the average value of the inverting input voltage of the voltage comparator U2, a stable voltage needs to be provided to the inverting input of the voltage comparator U2 as a reference. In this embodiment, the voltage regulator circuit includes a current-limiting resistor R1, a Zener diode ZD1, and a filter capacitor C2. The cathode of the Zener diode ZD1 is connected to the power supply bus through the current-limiting resistor R1, and the anode of the Zener diode ZD1 is grounded. The two ends of the filter capacitor C2 are connected to the cathode and anode of the Zener diode ZD1, respectively, and its stable voltage serves as the reference voltage for the positive input of the voltage comparator U2. The optocoupler U1 acts as a switch for transmitting control logic signals to control whether the comparator current works, regardless of how the bus voltage changes.

[0036] It should be noted that since the relay requires a relatively high voltage to open and can maintain a lower voltage operation after closing, it is necessary to increase the voltage of the inverting input port of the voltage comparator U2. In this embodiment, this is achieved through the start-up delay circuit, which includes the capacitor C1 and the resistor R5. The capacitor C1 and the resistor R5 are connected in series. The other end of the capacitor C1 is connected between the resistor R7 and the resistor R8. The other end of the resistor R5 is connected to the resistor R7.

[0037] When the power is first applied, the voltage across capacitor C1 is zero. Therefore, the voltage applied to the inverting input of voltage comparator U2 is the voltage obtained by dividing the voltage across resistors R5, R7, and R8. As resistor R5 charges capacitor C1, the voltage across bias resistor R3 gradually approaches 0. At this point, the voltage at the inverting input of the comparator is the voltage obtained by dividing the voltage across resistors R7 and R8. Therefore, the starting voltage is obtained by dividing the voltage across resistors R5, R7, and R8, and the voltage after stabilization is obtained by dividing the voltage across resistors R7 and R8. Here, the time constant of bias resistor R3 and capacitor C1 is set to 20~100ms to ensure that the relay has enough time to close.

[0038] It is also worth mentioning that, in this embodiment, the driving amplifier circuit further includes a base current limiting resistor R2, a resistor R6, and a freewheeling diode D1. The resistor R6 is connected in series with the base current limiting resistor R2. The other end of the resistor R6 is connected to the output terminal of the voltage comparator U2. The other end of the base current limiting resistor R2 is connected to the power supply bus. The base of the driving transistor Q1 is connected between the resistor R6 and the base current limiting resistor R2. The emitter of the driving transistor Q1 is connected to the load relay RL1. The other end of the load relay RL1 is grounded. The freewheeling diode D1 is connected in parallel with the load relay RL1, providing an energy release circuit for the coil inductor when the driving transistor Q1 is turned off, ensuring the safe and reliable operation of the driving transistor Q1.

[0039] For specific runtime instructions, please refer to... Figure 2 Green represents the input logic signal, and blue represents the average voltage applied to the relay. The drive voltage is applied at 50ms. Taking a 12V relay as an example, the relay closing voltage reaches 12V. After about 100ms, the average drive voltage drops to 7.5V and is unaffected by the supply voltage.

[0040] In the initial state (0-50ms)

[0041] When the control logic signal is low, optocoupler U1 is off, voltage comparator U2 is not working, drive transistor Q1 is off, relay RL1 is not energized and is in the released state.

[0042] Startup phase (50ms)

[0043] When the control logic signal goes high, optocoupler U1 turns on and a drive voltage is applied at 50ms. The voltage regulator circuit provides a stable 5V reference voltage to the positive input of voltage comparator U2. The initial voltage of capacitor C1 in the start-up delay circuit is 0V. The voltage at the inverting input of voltage comparator U2 is determined by the voltage divider of R5, R7, and R8, and is approximately 8.4V. Since the voltage at the inverting input (8.4V) is greater than the voltage at the positive input (5V), U2 outputs a low level, driving transistor Q1 to saturate and turn on, and the relay receives a full voltage drive close to 12V.

[0044] Oscillation setup phase (50-100ms)

[0045] The positive feedback resistor R10 generates a hysteresis voltage to ensure stable oscillation. Resistor R4 and capacitor C3 begin to charge and discharge, generating a PWM signal of about 25kHz. Capacitor C1 is slowly charged through resistor R5. The time constant is set to 50ms. The initial duty cycle of the PWM is high (about 85%) to ensure reliable relay engagement.

[0046] Stable operation phase (150ms interval)

[0047] With capacitor C1 charging nearly complete and its voltage stabilizing, the voltage at the inverting input of voltage comparator U2 drops to the voltage divider value of R7 and R8, approximately 6.2V. The PWM duty cycle automatically adjusts to approximately 62.5%. The average relay drive voltage is 12V × 62.5% = 7.5V. The relay remains engaged under the reduced drive voltage.

[0048] In summary, the energy-saving control circuit of this invention achieves adaptive drive control over a wide voltage range through the coordinated operation of a PWM oscillator composed of a voltage comparator and a start-up delay circuit. It not only provides sufficient drive energy to ensure reliable engagement during the relay start-up phase, but also automatically switches to a low duty cycle PWM mode during the maintenance phase to significantly reduce energy consumption. At the same time, the voltage regulator circuit ensures the stability of the reference voltage, while the freewheeling diode and positive feedback design improve the system's anti-interference capability and switching reliability. Ultimately, it achieves a dual optimization of high efficiency and stable drive while reducing the occupation of system control pins.

[0049] The above description is merely a specific embodiment of the invention, but the scope of protection of the invention is not limited thereto. Any variations or substitutions conceived without inventive effort should be included within the scope of protection of the invention. Therefore, the scope of protection of the invention should be determined by the scope defined in the claims.

Claims

1. A relay energy-saving control circuit suitable for wide-range voltage supply, comprising an oscillator circuit, a voltage regulator circuit, a start-up delay circuit, and a drive amplifier circuit, characterized in that: The voltage regulator circuit is used to generate a stable reference voltage from a wide range of varying power supply bus voltages. The oscillator circuit includes a voltage comparator (U2), the positive input terminal of which is connected to the output terminal of the voltage regulator circuit to receive the output stable reference voltage, and the inverting input terminal of which is connected to a charging / discharging circuit unit and a voltage divider circuit unit. The startup delay circuit is connected between the inverting input of the voltage comparator (U2) and the voltage divider circuit unit. It is used to provide a startup reference voltage at the initial stage of circuit power-on and switch to a sustaining reference voltage after the delay. The startup reference voltage is higher than the sustaining reference voltage. The input terminal of the drive amplifier circuit is connected to the output terminal of the voltage comparator (U2), and the output terminal of the drive amplifier circuit is used to drive the load relay (RL1). The oscillator circuit generates a PWM signal by forming positive feedback oscillation with the output state of the voltage comparator (U2) through the charging and discharging circuit unit. The average voltage applied to the load relay (RL1) is controlled by the drive amplifier circuit. The start-up delay circuit automatically controls the duty cycle of the PWM signal to achieve automatic energy-saving control of high-voltage start-up and low-voltage maintenance of the relay.

2. The relay energy-saving control circuit suitable for wide-range voltage supply according to claim 1, characterized in that: The charging and discharging circuit unit includes a capacitor (C3), a resistor (R4), and a positive feedback resistor (R10). One end of the resistor (R4) is connected to the capacitor (C3), and the other end is connected to the positive feedback resistor (R10). The other end of the capacitor (C3) is grounded. The other end of the positive feedback resistor (R10) is connected to the inverting input of the voltage comparator (U2) to provide hysteresis voltage to the oscillator and ensure the stability of the oscillation waveform.

3. The relay energy-saving control circuit suitable for wide-range voltage supply according to claim 1, characterized in that: The voltage regulator circuit includes a current-limiting resistor (R1), a Zener diode (ZD1), and a filter capacitor (C2). The cathode of the Zener diode (ZD1) is connected to the power supply bus through the current-limiting resistor (R1), and the anode of the Zener diode (ZD1) is grounded. The two ends of the filter capacitor (C2) are connected to the cathode and anode of the Zener diode (ZD1) respectively, and its stable voltage serves as the reference voltage for the positive input terminal of the voltage comparator (U2).

4. The relay energy-saving control circuit suitable for wide-range voltage supply according to claim 1, characterized in that: The voltage divider circuit unit includes a resistor (R7) and a resistor (R8), which are connected in series, and the other end of the resistor (R8) is grounded.

5. A relay energy-saving control circuit suitable for wide-range voltage supply according to claim 4, characterized in that: The start-up delay circuit includes a capacitor (C1) and a resistor (R5). The capacitor (C1) and the resistor (R5) are connected in series. The other end of the capacitor (C1) is connected between the resistor (R7) and the resistor (R8). The other end of the resistor (R5) is connected between the resistor (R7).

6. A relay energy-saving control circuit suitable for wide-range voltage supply according to claim 1, characterized in that: The driving amplifier circuit includes a base current limiting resistor (R2), a resistor (R6), and a driving transistor (Q1). The resistor (R6) is connected in series with the base current limiting resistor (R2). The other end of the resistor (R6) is connected to the output terminal of the voltage comparator (U2). The other end of the base current limiting resistor (R2) is connected to the power supply bus. The base of the driving transistor (Q1) is connected between the resistor (R6) and the base current limiting resistor (R2). The emitter of the driving transistor (Q1) is connected to the load relay (RL1). The other end of the load relay (RL1) is grounded.

7. A relay energy-saving control circuit suitable for wide-range voltage supply according to claim 6, characterized in that: The drive amplifier circuit also includes a freewheeling diode (D1), which is connected in parallel with the load relay (RL1) and provides an energy release circuit for the coil inductance when the drive transistor (Q1) is turned off.

8. A relay energy-saving control circuit suitable for wide-range voltage supply according to claim 4, characterized in that: The oscillator circuit also includes a bias resistor (R3) and an optocoupler (U1). One end of the bias resistor (R3) is connected to the resistor (R4), and the other end is connected to the collector of the optocoupler (U1). The emitter of the optocoupler (U1) is connected to the resistor (R7).

9. A relay energy-saving control circuit suitable for wide-range voltage supply according to claim 4, characterized in that: The time constant formed by the capacitor (C1) and the resistor (R5) is between 20 milliseconds and 100 milliseconds to ensure that the relay has enough time to complete the closing action.

10. A relay energy-saving control circuit suitable for wide-range voltage supply according to claim 1, characterized in that: The frequency of the PWM signal generated by the oscillator circuit is between 10kHz and 50kHz.

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