Relay driving circuit and control method thereof

Abstract

The invention provides a relay driving circuit and a control method thereof, the relay driving circuit comprises a filtering module, a relay module, a transistor switch module and a PFC control module, the relay module comprises a coil and an armature switch, the transistor switch module comprises a switch transistor and a second diode DF2, and the PFC control module comprises a PFC control module. The input end of the first diode DF2 is connected to the input end of the coil, the input end of the second diode DF2 is connected to the output end of the coil, the output end of the second diode DF2 is connected to the input end of the coil, the drain electrode of the switch transistor is connected to the output end of the coil, and the PFC control module comprises a load current detection unit and a transistor control unit. The output end of the load current detection unit is connected to the input end of the transistor control unit, and the output end of the transistor control unit is connected to the grid electrode of the switching transistor, so that unnecessary electric energy loss when the circuit is in a no-load state can be effectively reduced, and meanwhile, the safety and reliability of the circuit are improved.

Description

Technical Field

[0001] This invention relates to the field of electronic technology, and in particular to a relay driving circuit and its control method. Background Technology

[0002] A traditional auxiliary power supply circuit is a circuit structure that directly drives switching elements such as relays to supply power to the load using only the main power supply voltage, without the need for external auxiliary control signals. It is commonly found in embedded devices, industrial automation, and simple power management modules. In a traditional auxiliary power supply circuit, when the main power supply voltage first rises to a certain threshold, the relay is immediately energized, closing the power supply circuit and thus powering the downstream device.

[0003] Because a relay coil is an inductive element, a continuous current flows through it when it is energized. Even without a downstream load, it maintains a magnetic field, keeping the contacts closed and consuming electrical energy. This energy consumption mainly comes from core losses and leakage flux losses, typically ranging from several hundred milliwatts to several watts. Therefore, even when the circuit is unloaded, the main power supply continues, and the relay coil remains "always closed" due to continuous energization, causing a surge in power consumption during no-load operation. This high no-load power consumption not only increases standby power consumption but also accelerates the temperature rise of the heat sink and circuit board, leading to circuit aging, decreased reliability, and increased costs. Summary of the Invention

[0004] Based on the above-mentioned problems, this invention proposes a relay driving circuit and its control method, which can effectively reduce unnecessary power loss when the circuit is unloaded, while improving the safety and reliability of the circuit.

[0005] In view of this, a first aspect of the present invention provides a relay driving circuit, comprising: The filtering module includes a rectifier unit and a voltage divider unit, which are used to rectify and divide the input voltage; The relay module includes a coil and an armature switch. The input end of the coil is connected to the output end of the filter module, and the armature switch is connected to the load circuit. The armature switch is used to attract the armature to make the load circuit conduct when the coil is energized and generates a magnetic field, or to release the armature to make the load circuit disconnect when the coil is de-energized and loses its magnetic field. Transistor switching module, including switching transistors The second diode DF2, whose input terminal is connected to the output terminal of the coil, and whose output terminal is connected to the input terminal of the coil, is the switching transistor. The drain of the switching crystal is connected to the output terminal of the coil. The source is grounded; The PFC control module includes a load current detection unit for detecting the magnitude of the current in the load circuit, and a control unit for controlling the switching transistor. A transistor control unit for switching on and off, wherein the output terminal of the load current detection unit is connected to the input terminal of the transistor control unit, and the output terminal of the transistor control unit is connected to the gate of the switching transistor.

[0006] Optionally, the transistor control unit includes a third diode DF3 and a third voltage divider resistor. First current-limiting resistor First capacitor Second capacitor The input terminal of the third diode DF3 is connected to the output terminal of the load current detection unit, and the output terminal of the third diode DF3 is connected to the third voltage divider resistor. The first terminal, the third voltage divider resistor The second terminal is connected to the switching transistor The gate; the first current-limiting resistor The first capacitor and the second capacitor The circuit is connected in parallel, with the first terminal of the parallel circuit connected to the third voltage divider resistor. and the switching transistor Between the gates, the second terminal is grounded.

[0007] Optionally, the load current detection unit includes a sampling amplification circuit, an optocoupler isolation circuit, and a logic signal output circuit. The sampling amplification circuit is connected to the load circuit to sample the current from the load circuit and linearly amplify the sampled current to obtain a linear gain voltage. The input terminal of the optocoupler isolation circuit is connected to the output terminal of the sampling amplification circuit to convert the linear gain voltage into an optocoupler output voltage. The input terminal of the logic signal output circuit is connected to the output terminal of the optocoupler isolation circuit to convert the optocoupler output voltage into a pulse voltage with a corresponding duty cycle.

[0008] Optionally, the sampling amplification circuit includes a sampling resistor. Input resistance Feedback resistor and operational amplifiers The sampling resistor The input resistor is connected to the load circuit for current sampling; One end is connected to the sampling resistor The other end is connected to the operational amplifier between the armature switch and the armature switch. The inverting input terminal, the feedback resistor The two ends are respectively connected to the operational amplifier The inverting input terminal and the operational amplifier The operational amplifier at the output terminal The non-inverting input terminal of the operational amplifier is grounded. The negative power supply terminal is grounded, and the sampling operational amplifier is... The positive power supply terminal is connected to the power supply; the optocoupler isolation circuit includes a second current-limiting resistor. Optocoupler, output resistor The optocoupler internally includes a light-emitting diode and a phototransistor, and the second current-limiting resistor The first end is connected to the operational amplifier. The output terminal, the second current-limiting resistor The second terminal is connected to the positive terminal of the light-emitting diode, the negative terminal of the light-emitting diode is grounded, and the collector of the phototransistor is connected to the output resistor. At the first terminal, the emitter of the phototransistor is grounded, and the output resistor... The second terminal is connected to the input terminal of the logic signal output circuit.

[0009] Optionally, the logic signal output circuit includes a fourth voltage divider resistor. Fifth voltage divider resistor And comparator, the fourth voltage divider resistor The first terminal is connected to the power supply, and the fourth voltage divider resistor The second terminal is connected to the first input terminal of the comparator, and the fifth voltage divider resistor The first end is connected to the fourth voltage divider resistor. The fifth voltage divider resistor is located between the first input terminal of the comparator and the first input terminal of the comparator. The second terminal is grounded, and the fourth voltage divider resistor and the fifth voltage divider resistor The voltage divider network is used to provide a reference voltage to the comparator, and the output resistance of the optocoupler isolation circuit is... The second terminal is connected to the second input terminal of the comparator, and the output terminal of the comparator is connected to the input terminal of the transistor control unit.

[0010] A second aspect of the present invention provides a control method for a relay drive circuit, comprising: The current of the load circuit is sampled using a sampling amplifier circuit to obtain the sampled current. To sample the current Convert and amplify into a linear gain voltage ; The linear gain voltage is transmitted via an optocoupler. Convert to optocoupler output voltage ; Generates the output voltage of the optocoupler The size of the corresponding logic control signal The logic control signal It is a pulse voltage signal consisting of continuous high-level voltage and low-level voltage; The logic control signal Input transistor control unit to control the switching transistor To connect or disconnect.

[0011] Optionally, the sampling current Converted to linear gain voltage The specific steps include: Calculate the voltage at the sampling node: ; Convert the sampling node voltage into the linear gain voltage: ; in operational amplifier The sampling amplification factor, and satisfy: .

[0012] Optionally, the linear gain voltage can be converted via an optocoupler. Convert to optocoupler output voltage The specific steps include: The linear gain voltage The input current of the optocoupler is obtained by applying it to the input terminal of the optocoupler: , in The forward voltage drop of the light-emitting diode within the optocoupler; Calculate the output current of the optocoupler: , in The current transfer ratio of the optocoupler; The output current of the optocoupler Converted to the output voltage of the optocoupler: .

[0013] Optionally, generate the output voltage of the optocoupler. The size of the corresponding logic control signal The specific steps include: The power supply voltage is The DC source is converted into a reference voltage through a voltage divider network: ; The reference voltage The first input terminal of the input comparator converts the output voltage of the optocoupler. The second input terminal of the input comparator is used to compare the reference voltage. and the output voltage of the optocoupler Compare their sizes; The comparator is based on the reference voltage and the output voltage of the optocoupler The size generates the logic control signal: , in The high logic voltage of the comparator. This is the low logic voltage of the comparator.

[0014] Optionally, the logic control signal Input transistor control unit to control the switching transistor The specific steps for turning on or off include: The logic control signal is transmitted through the transistor control unit. Converted to the switching transistor Gate input voltage: ; The gate input voltage is input to the switching transistor. The gate; when At that time, the switching transistor Entering the conduction state; when At that time, the switching transistor It is currently disconnected.

[0015] This invention proposes a relay driving circuit and its control method. The relay driving circuit includes a filtering module, a relay module, a transistor switching module, and a PFC control module. The relay module includes a coil and an armature switch, and the transistor switching module includes a switching transistor. The second diode DF2, whose input terminal is connected to the output terminal of the coil, and whose output terminal is connected to the input terminal of the coil, is the switching transistor. The drain of the circuit is connected to the output terminal of the coil. The PFC control module includes a load current detection unit and a transistor control unit. The output terminal of the load current detection unit is connected to the input terminal of the transistor control unit, and the output terminal of the transistor control unit is connected to the gate of the switching transistor. This can effectively reduce unnecessary power loss when the circuit is unloaded, while improving the safety and reliability of the circuit. Attached Figure Description

[0016] Figure 1 This is a schematic block diagram of a relay driving circuit provided in one embodiment of the present invention; Figure 2 This is a circuit diagram of a relay driving circuit provided in one embodiment of the present invention; Figure 3 This is a flowchart of a control method for a relay drive circuit provided in one embodiment of the present invention. Detailed Implementation

[0017] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0018] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0019] In the description of this invention, the term "multiple" refers to two or more. Unless otherwise explicitly defined, the terms "upper," "lower," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. The terms "connect," "install," "fix," etc., should be interpreted broadly. For example, "connect" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "multiple" means two or more.

[0020] In the description of this specification, the terms "one embodiment," "some implementations," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0021] A relay drive circuit and its control method according to some embodiments of the present invention will now be described with reference to the accompanying drawings.

[0022] like Figure 1 As shown, a first aspect of the present invention provides a relay driving circuit, comprising: The filtering module includes a rectifier unit and a voltage divider unit, which are used to rectify and divide the input voltage; The relay module includes a coil and an armature switch. The input end of the coil is connected to the output end of the filter module, and the armature switch is connected to the load circuit. The armature switch is used to attract the armature to make the load circuit conduct when the coil is energized and generates a magnetic field, or to release the armature to make the load circuit disconnect when the coil is de-energized and loses its magnetic field. Transistor switching module, including switching transistors The second diode DF2, whose input terminal is connected to the output terminal of the coil, and whose output terminal is connected to the input terminal of the coil, is the switching transistor. The drain of the switching crystal is connected to the output terminal of the coil. The source is grounded; The PFC (Power Factor Correction) control module includes a load current detection unit for detecting the magnitude of the current in the load circuit, and a control unit for controlling the switching transistor. A transistor control unit for switching on and off, wherein the output terminal of the load current detection unit is connected to the input terminal of the transistor control unit, and the output terminal of the transistor control unit is connected to the gate of the switching transistor.

[0023] Specifically, the filter module receives a voltage such as 5V, 12V, or 24V from a power source to supply power to the coil of the relay module. This causes the current flowing through the relay module's coil to generate a magnetic field, which in turn attracts the armature in the armature switch, thus connecting the load circuit. In some embodiments, the rectifier unit can use a bridge diode or a full-wave rectifier to convert the AC input into regulated DC. The voltage divider unit can use a voltage divider resistor network or a voltage regulator chip to reduce the rectified input voltage to the rated operating voltage of the relay module's coil.

[0024] Figure 2 A circuit diagram of a relay driving circuit according to some embodiments of the present invention is shown. For example... Figure 2 As shown, in some embodiments, the rectifier unit of the filter module includes a first diode DF1, and the voltage divider unit includes first voltage divider resistors connected in parallel. Second resistor The input terminal of the first diode DF1 is connected to the voltage output terminal, and the first voltage divider resistor is connected in parallel. and the second voltage divider resistor One end of the diode is connected to the output terminal of the first diode DF1. This embodiment allows for voltage adaptation for the relay and suppression of noise and ripple. Preferably, the first diode DF2 is a Schottky diode.

[0025] See also Figure 2 The relay module includes a coil and an armature switch. The input terminal of the coil is connected to the output of the filter module. The armature of the armature switch is set in the load circuit to control the on / off state of the load circuit. When the coil is energized and generates a magnetic field, the armature switch is attracted to make the load circuit conduct. When the coil is de-energized and loses its magnetic field, the armature switch is released to make the load circuit open.

[0026] The transistor switching module includes switching transistors. The second diode DF2, wherein the input terminal of the second diode DF2 is connected to the coil output terminal of the relay module, and the output terminal of the second diode DF2 is connected to the input terminal of the coil, is used to provide an electromagnetic reset path and to achieve reverse current suppression; the switching transistor The drain of the transistor is connected to the output terminal of the coil. The source is grounded, through the switching transistor The gate input control signal can realize the rapid closing and opening of the path between its source and drain, while the second diode DF2 is in the switching transistor. When turned off, a short-circuit path is formed, rapidly reducing the coil voltage to zero, thereby preventing the continuous generation of the magnetic field and avoiding high no-load power consumption. Preferably, the second diode DF2 is a Schottky diode. Preferably, the switching transistor is an N-channel enhancement-mode metal-oxide-semiconductor transistor.

[0027] The PFC control module includes a load current detection unit and a transistor control unit. The load current detection unit measures the current of the load circuit in real time and generates a corresponding pulse control signal based on the current magnitude, which is then input to the transistor control unit. The transistor control unit controls the switching transistor according to the pulse control signal. The pulse control signal controls the opening and closing of the path between the source and drain. It is a low-level signal when the current in the load circuit is below a set no-load threshold and a high-level signal when the current in the load circuit is above the set no-load threshold. This signal is used to control the switching transistor. When a low-level signal is input to the gate of the switching transistor, its source and drain are disconnected; When a high-level signal is input to the gate, its source and drain are turned on.

[0028] In practical applications, once the load current detection unit detects that the current in the load circuit is lower than the set no-load threshold, it will no longer send current to the switching transistor. A voltage is applied to the gate of the relay module, thereby de-energizing the coil, releasing the armature, and keeping the load disconnected. When an increase in current in the load circuit is detected, exceeding a set no-load threshold, the transistor control unit sends a signal to the switching transistor. A voltage is applied to the gate to make its source and drain conduct, and the coil in the relay module is energized to complete the closing operation of the armature switch, thereby realizing the automatic cut-off of the coil current when the load circuit is unloaded, significantly reducing power consumption, while maintaining a fast response and reliable connection to normal loads.

[0029] Optionally, the transistor control unit includes a third diode DF3 and a third voltage divider resistor. First current-limiting resistor First capacitor Second capacitor The input terminal of the third diode DF3 is connected to the output terminal of the load current detection unit, and the output terminal of the third diode DF3 is connected to the third voltage divider resistor. The first terminal, the third voltage divider resistor The second terminal is connected to the switching transistor The gate; the first current-limiting resistor The first capacitor and the second capacitor The circuit is connected in parallel, with the first terminal of the parallel circuit connected to the third voltage divider resistor. and the switching transistor Between the gates, the second terminal is grounded.

[0030] In the above embodiment, the third diode DF3 is used to rectify the pulse signal output by the load current detection unit, so as to convert the pulse signal into a DC bias and send it to the third voltage divider resistor. The third voltage divider resistor With the switching transistor The gate of the diode forms a voltage divider, such that when the load current detection unit detects that the current of the load circuit is lower than a set threshold, the third diode DF3 sends a voltage divider signal to the third voltage divider resistor. The third voltage divider resistor outputs a low voltage. The switching transistor is controlled by voltage division. The gate voltage is pulled to the turn-off voltage. Conversely, when the load current detection unit detects an increase in the current of the load circuit, the third diode DF3 pulls the gate voltage of the third voltage divider resistor to the turn-off voltage. The switching transistor outputs a higher voltage. The gate voltage is higher than the turn-on voltage, which turns the circuit on.

[0031] Furthermore, in order to suppress the switching transistor To reduce gate noise and improve its response speed, the above embodiment uses the third voltage divider resistor. With the switching transistor The gate is provided with the first current-limiting resistor. The first capacitor and the second capacitor The resistors are connected in parallel to form a low-pass filter network, and their input terminals are connected to the third voltage divider resistor. With the switching transistor The gate and output terminals are grounded. The first current-limiting resistor... The first capacitor provides a corresponding load for high-frequency suppression. and the second capacitor The capacitors, set to small values ​​(e.g., 10pF–100pF) and medium values ​​(e.g., 0.1µF–1µF) respectively, together form a double-layer RC filter, which can both smooth the pulse output of the third diode DF3 and prevent the switching transistor from... The gate is pulled high rapidly along a "spike," thereby reducing the switching transistor's speed. The switching current fluctuations and relay chattering.

[0032] Optionally, the load current detection unit includes a sampling amplification circuit, an optocoupler isolation circuit, and a logic signal output circuit. The sampling amplification circuit is connected to the load circuit to sample the current from the load circuit and linearly amplify the sampled current to obtain a linear gain voltage. The input terminal of the optocoupler isolation circuit is connected to the output terminal of the sampling amplification circuit to convert the linear gain voltage into an optocoupler output voltage. The input terminal of the logic signal output circuit is connected to the output terminal of the optocoupler isolation circuit to convert the optocoupler output voltage into a pulse voltage with a corresponding duty cycle.

[0033] In some embodiments of the present invention, the sampling amplification circuit can be a low dropout linear operational amplifier or a dedicated current detection chip. The sampling amplification circuit converts the sampling current obtained from the load circuit into a node voltage through a sampling resistor and then performs a gain to obtain a DC signal that is proportional to the actual current of the load circuit.

[0034] The optocoupler isolation circuit is a signal conversion circuit that isolates the load side and control side circuits through photoelectric conversion. Specifically, the DC signal is input into the optocoupler of the optocoupler isolation circuit, where a corresponding light pulse is generated to convert the DC signal into an isolated signal output, thereby preventing load side noise from directly entering the control side and ensuring circuit safety and reliability.

[0035] The logic signal output circuit generates the switching transistor. The signal generation circuit for the gate control signal generates a pulse signal corresponding to the comparison result between the output signal of the optocoupler isolation circuit and a preset reference signal. In a specific implementation, the logic signal output circuit can be any one of a comparator, a counter / duty cycle generator, or a microcontroller.

[0036] Optionally, the sampling amplification circuit includes a sampling resistor. Input resistance Feedback resistor and operational amplifiers The sampling resistor The input resistor is connected to the load circuit for current sampling; One end is connected to the sampling resistor The other end is connected to the operational amplifier between the armature switch and the armature switch. The inverting input terminal, the feedback resistor The two ends are respectively connected to the operational amplifier The inverting input terminal and the operational amplifier The operational amplifier at the output terminal The non-inverting input terminal of the operational amplifier is grounded. The negative power supply terminal is grounded, and the sampling operational amplifier is... The positive power supply terminal is connected to the power supply; the optocoupler isolation circuit includes a second current-limiting resistor. Optocoupler, output resistor The optocoupler internally includes a light-emitting diode and a phototransistor, and the second current-limiting resistor The first end is connected to the operational amplifier. The output terminal, the second current-limiting resistor The second terminal is connected to the positive terminal of the light-emitting diode, the negative terminal of the light-emitting diode is grounded, and the collector of the phototransistor is connected to the output resistor. At the first terminal, the emitter of the phototransistor is grounded, and the output resistor... The second terminal is connected to the input terminal of the logic signal output circuit.

[0037] In the technical solution of the above embodiments, the sampling resistor The sampling resistor is a low-resistance resistor. Connected directly in parallel or series on the load side to generate a small voltage drop proportional to the current flowing through it; the input resistor and the feedback resistor Together they constitute the operational amplifier The input network, the input resistor The sampling resistor The linear gain voltage signal is sent to the operational amplifier. The inverting input terminal, the feedback resistor Used to form the operational amplifier The feedback loop, the input resistor and the feedback resistor The resistance value determines the operational amplifier. The gain magnitude. Using the technical solution described above, an amplified output proportional to the original linear gain voltage can be obtained. This amplified output is further converted into a digital signal via optocoupler for comparison with a reference signal, ultimately generating a signal to control the switching transistor. The gate control signal that controls whether the source and drain are turned on or off.

[0038] Furthermore, the sampling resistor The resistance value needs to account for a sufficient voltage drop to drive the operational amplifier. At the same time, it maintains low power consumption. For example, the sampling resistor... The resistance value can be configured to be between 0.01Ω and 0.1Ω.

[0039] In the technical solution of the above embodiments, the second current-limiting resistor This is used to limit the current flowing through the light-emitting diode (LED) in the optocoupler, protecting the LED and preventing it from burning out; the LED inside the optocoupler receives signals from the operational amplifier. The analog signal is converted into an optical signal, and the phototransistor inside the optocoupler converts the optical signal into a current signal; the output resistor This is used to convert the collector current of the phototransistor into a voltage signal, providing a stable output voltage to the logic signal output circuit.

[0040] Optionally, the logic signal output circuit includes a fourth voltage divider resistor. Fifth voltage divider resistor And comparator, the fourth voltage divider resistor The first terminal is connected to the power supply, and the fourth voltage divider resistor The second terminal is connected to the first input terminal of the comparator, and the fifth voltage divider resistor The first end is connected to the fourth voltage divider resistor. The fifth voltage divider resistor is located between the first input terminal of the comparator and the first input terminal of the comparator. The second terminal is grounded, and the fourth voltage divider resistor and the fifth voltage divider resistor The voltage divider network is used to provide a reference voltage to the comparator, and the output resistance of the optocoupler isolation circuit is... The second terminal is connected to the second input terminal of the comparator, and the output terminal of the comparator is connected to the input terminal of the transistor control unit.

[0041] In the above-described embodiment, the logic signal output circuit utilizes the fourth voltage divider resistor. and the fifth voltage divider resistor The voltage divider network is connected to a power supply such as 5V, 12V, or 24V, and passes through the fourth voltage divider resistor. and the fifth voltage divider resistor After voltage division, the voltage divider network generates a fixed reference voltage, which is provided to the comparator as one comparison signal. The collector of the optocoupler provides an output signal corresponding to the sampling current, serving as the other comparison signal for the comparator. The comparator compares the voltages of the two comparison signals in real time. When the output voltage of the optocoupler's collector is lower than the reference voltage, the logic control signal output by the logic signal output circuit is a low-level signal; conversely, when the output voltage of the optocoupler's collector is higher than the reference voltage, the logic control signal output by the logic signal output circuit is a high-level signal. The logic control signal is input to the switching transistor through the transistor control unit. The gate of the transistor is used to determine the switching transistor. Whether the gate is driven.

[0042] like Figure 3 As shown, a second aspect of the present invention provides a control method for a relay drive circuit, comprising: The current of the load circuit is sampled using a sampling amplifier circuit to obtain the sampled current. To sample the current Convert and amplify into a linear gain voltage ; The linear gain voltage is transmitted via an optocoupler. Convert to optocoupler output voltage ; Generates the output voltage of the optocoupler The size of the corresponding logic control signal The logic control signal It is a pulse voltage signal consisting of continuous high-level voltage and low-level voltage; The logic control signal Input transistor control unit to control the switching transistor To connect or disconnect.

[0043] In some implementation solutions, the sampling current is located on the load side. Through a low-resistance resistor, i.e., the sampling resistor The linear gain voltage is generated. For the operational amplifier The sampling current The corresponding node voltage and the operational amplifier The DC voltage signal obtained by multiplying by the amplification factor, the linear gain voltage This is the analog drive source at the input terminal of the optocoupler. On the control side, the optocoupler output voltage... It is the voltage generated at the output terminal of the optocoupler, i.e., the collector of the phototransistor inside it; the logic control signal The output voltage of the optocoupler is converted by a comparator. The pulse voltage signal obtained after comparing with the reference voltage will be used to generate the logic control signal. Input to the transistor control unit, so that the transistor control unit sends a signal to the switching transistor. A voltage of a corresponding magnitude is applied to the gate to control the switching transistor. The circuit is switched on or off, thereby causing the armature switch of the relay module to engage or disengage.

[0044] The technical solution described above can output a lower linear gain voltage when the load circuit is unloaded. This makes the optocoupler output voltage When the voltage drops below the set reference voltage, the logic signal output circuit outputs a low-level logic control signal. , so that the switching transistor By keeping it off, the problem of high power consumption under no-load conditions is avoided.

[0045] Optionally, the sampling current Converted to linear gain voltage The specific steps include: Calculate the voltage at the sampling node: ; Convert the sampling node voltage into the linear gain voltage: ; in operational amplifier The sampling amplification factor, and satisfy: .

[0046] In the above-described embodiment, the sampling amplification factor is the voltage gain coefficient of the sampling amplification circuit, and its gain can be determined during design by selecting the input resistor. and the feedback resistor The resistance value is used for configuration.

[0047] For example, the sampling resistor It can be a high-precision, low-temperature-drift, low-resistance shunt resistor. Using the technical solution of the above embodiment, the linear gain voltage... It is the node voltage The linear gain is obtained by ensuring that the amplified signal remains linear throughout the entire operating range, thus making the comparator error predictable.

[0048] Optionally, the linear gain voltage can be converted via an optocoupler. Convert to optocoupler output voltage The specific steps include: The linear gain voltage The input current of the optocoupler is obtained by applying it to the input terminal of the optocoupler: , in The forward voltage drop of the light-emitting diode within the optocoupler; Calculate the output current of the optocoupler: , in The current transfer ratio of the optocoupler; The output current of the optocoupler Converted to the output voltage of the optocoupler: .

[0049] In the technical solution of the above embodiment, the linear gain voltage of the sampling amplification circuit is first... When applied to the input terminal of the optocoupler, the light-emitting diode of the optocoupler will generate a certain voltage drop when operating in the forward direction, i.e., the forward emission voltage drop. The forward voltage drop of a light-emitting diode The voltage is typically in the range of 1.2 volts to 1.4 volts, depending on the color and model of the light-emitting diode used in the optocoupler.

[0050] The second current-limiting resistor A line is connected between the light-emitting diode (LED) of the optocoupler and ground to prevent the operating current of the LED from exceeding its maximum forward current limit, thereby ensuring that the optocoupler can operate normally and stably.

[0051] It should be understood that the linear gain voltage It should be greater than the forward voltage drop of the light-emitting diode. When the linear gain voltage When this occurs, the LED cannot be lit. Therefore, a suitable sampling amplification factor needs to be configured. This ensures that the optocoupler can function properly.

[0052] In the linear operating region of the optocoupler, its input current Its output current There is a fixed proportional relationship between them, that is, in the linear operating region, the optocoupler has a fixed current transfer ratio. It is defined as the ratio between the output current and the input current of the optocoupler, and is determined by the pre-measured current transfer ratio of the optocoupler. The magnitude of the output current can be calculated based on the magnitude of the input current.

[0053] Because the input current and output current of the optocoupler have a specific proportional relationship, and the output voltage of the optocoupler also has a fixed proportional relationship with the output current of the optocoupler, the magnitude of the load current can still be retained after using the optocoupler to electrically isolate the load side and the control side. This information can then be used to generate corresponding logic control signals to control the switching transistor. To connect or disconnect.

[0054] Optionally, generate the output voltage of the optocoupler. The size of the corresponding logic control signal The specific steps include: The power supply voltage is The DC source is converted into a reference voltage through a voltage divider network: ; The reference voltage The first input terminal of the input comparator converts the output voltage of the optocoupler. The second input terminal of the input comparator is used to compare the reference voltage. and the output voltage of the optocoupler Compare their sizes; The comparator is based on the reference voltage and the output voltage of the optocoupler The size generates the logic control signal: , in The high logic voltage of the comparator. This is the low logic voltage of the comparator.

[0055] In the technical solutions of the above embodiments, The high logic voltage of the comparator. The low logic voltage of the comparator, wherein the high logic voltage Input voltage of DC power supply Approximately equal, the low logic voltage This is the ground voltage, which is close to 0 volts.

[0056] The above implementation uses a DC source and the fourth voltage divider resistor and the fifth voltage divider resistor The voltage divider network provides a reference voltage of a specific size to the comparator. In a specific implementation, the fourth voltage divider resistor can be configured according to the electrical parameters of the relay and the load characteristics of the load circuit. and the fifth voltage divider resistor The size of the switching transistor is determined to precisely configure the switching transistor. The trigger point for switching on or off.

[0057] The comparator generates the logic control signal based on the relationship between the voltages input to the two input terminals. The logic control signal For high logic voltage and low logic voltage The pulse voltage signal, composed of these signals, is processed by the transistor control unit to generate the logic control signal. Input to the switching transistor The gate, so that the logic control signal For high logic voltage At that time, the switching transistor In the ON state; the logic control signal For low logic voltage At that time, the switching transistor It is currently disconnected.

[0058] Optionally, the logic control signal Input transistor control unit to control the switching transistor The specific steps for turning on or off include: The logic control signal is transmitted through the transistor control unit. Converted to the switching transistor Gate input voltage: ; The gate input voltage is input to the switching transistor. The gate; when At that time, the switching transistor Entering the conduction state; when At that time, the switching transistor It is currently disconnected.

[0059] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0060] As described above, these embodiments of the present invention do not exhaustively cover all details, nor do they limit the invention to the specific embodiments described. Clearly, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to effectively utilize the invention and its modifications. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A relay drive circuit, characterized in that, include: The filtering module includes a rectifier unit and a voltage divider unit, which are used to rectify and divide the input voltage; The relay module includes a coil and an armature switch. The input end of the coil is connected to the output end of the filter module, and the armature switch is connected to the load circuit. The armature switch is used to attract the armature to make the load circuit conduct when the coil is energized and generates a magnetic field, or to release the armature to make the load circuit disconnect when the coil is de-energized and loses its magnetic field. Transistor switching module, including switching transistors The second diode DF2, whose input terminal is connected to the output terminal of the coil, and whose output terminal is connected to the input terminal of the coil, is the switching transistor. The drain of the switching crystal is connected to the output terminal of the coil. The source is grounded; The PFC control module includes a load current detection unit for detecting the magnitude of the current in the load circuit, and a control unit for controlling the switching transistor. A transistor control unit for switching on and off, wherein the output terminal of the load current detection unit is connected to the input terminal of the transistor control unit, and the output terminal of the transistor control unit is connected to the gate of the switching transistor.

2. The relay drive circuit according to claim 1, characterized in that, The transistor control unit includes a third diode DF3 and a third voltage divider resistor. First current-limiting resistor First capacitor Second capacitor The input terminal of the third diode DF3 is connected to the output terminal of the load current detection unit, and the output terminal of the third diode DF3 is connected to the third voltage divider resistor. The first terminal, the third voltage divider resistor The second terminal is connected to the switching transistor The gate; the first current-limiting resistor The first capacitor and the second capacitor The circuit is connected in parallel, with the first terminal of the parallel circuit connected to the third voltage divider resistor. and the switching transistor Between the gates, the second terminal is grounded.

3. The relay drive circuit according to claim 1, characterized in that, The load current detection unit includes a sampling amplification circuit, an optocoupler isolation circuit, and a logic signal output circuit. The sampling amplification circuit is connected to the load circuit to sample the current from the load circuit and linearly amplify the sampled current to obtain a linear gain voltage. The input terminal of the optocoupler isolation circuit is connected to the output terminal of the sampling amplification circuit to convert the linear gain voltage into an optocoupler output voltage. The input terminal of the logic signal output circuit is connected to the output terminal of the optocoupler isolation circuit to convert the optocoupler output voltage into a pulse voltage with a corresponding duty cycle.

4. The relay drive circuit according to claim 3, characterized in that, The sampling amplification circuit includes a sampling resistor. Input resistance Feedback resistor and operational amplifiers The sampling resistor The input resistor is connected to the load circuit for current sampling; One end is connected to the sampling resistor The other end is connected to the operational amplifier between the armature switch and the armature switch. The inverting input terminal, the feedback resistor The two ends are respectively connected to the operational amplifier The inverting input terminal and the operational amplifier The operational amplifier at the output terminal The non-inverting input terminal of the operational amplifier is grounded. The negative power supply terminal is grounded, and the sampling operational amplifier is... The positive power supply terminal is connected to the power supply; the optocoupler isolation circuit includes a second current-limiting resistor. Optocoupler, output resistor The optocoupler internally includes a light-emitting diode and a phototransistor, and the second current-limiting resistor The first end is connected to the operational amplifier. The output terminal, the second current-limiting resistor The second terminal is connected to the positive terminal of the light-emitting diode, the negative terminal of the light-emitting diode is grounded, and the collector of the phototransistor is connected to the output resistor. At the first terminal, the emitter of the phototransistor is grounded, and the output resistor... The second terminal is connected to the input terminal of the logic signal output circuit.

5. The relay drive circuit according to claim 4, characterized in that, The logic signal output circuit includes a fourth voltage divider resistor. Fifth voltage divider resistor And comparator, the fourth voltage divider resistor The first terminal is connected to the power supply, and the fourth voltage divider resistor The second terminal is connected to the first input terminal of the comparator, and the fifth voltage divider resistor The first end is connected to the fourth voltage divider resistor. The fifth voltage divider resistor is located between the first input terminal of the comparator and the first input terminal of the comparator. The second terminal is grounded, and the fourth voltage divider resistor and the fifth voltage divider resistor The voltage divider network is used to provide a reference voltage to the comparator, and the output resistance of the optocoupler isolation circuit is... The second terminal is connected to the second input terminal of the comparator, and the output terminal of the comparator is connected to the input terminal of the transistor control unit.

6. A control method applied to the relay drive circuit as described in claim 5, characterized in that, include: The current of the load circuit is sampled using a sampling amplifier circuit to obtain the sampled current. To sample the current Convert and amplify into a linear gain voltage ; The linear gain voltage is transmitted via an optocoupler. Convert to optocoupler output voltage ; Generates the output voltage of the optocoupler The size of the corresponding logic control signal The logic control signal It is a pulse voltage signal consisting of continuous high-level voltage and low-level voltage; The logic control signal Input transistor control unit to control the switching transistor To connect or disconnect.

7. The relay drive circuit according to claim 6, characterized in that, The sampling current Converted to linear gain voltage The specific steps include: Calculate the voltage at the sampling node: ； Convert the sampling node voltage into the linear gain voltage: ； in operational amplifier The sampling amplification factor, and satisfy: 。 8. The relay drive circuit according to claim 6, characterized in that, The linear gain voltage is transmitted via an optocoupler. Convert to optocoupler output voltage The specific steps include: The linear gain voltage The input current of the optocoupler is obtained by applying it to the input terminal of the optocoupler: ， in The forward voltage drop of the light-emitting diode within the optocoupler; Calculate the output current of the optocoupler: ， in The current transfer ratio of the optocoupler; The output current of the optocoupler Converted to the output voltage of the optocoupler: 。 9. The relay drive circuit according to claim 6, characterized in that, Generates the output voltage of the optocoupler The size of the corresponding logic control signal The specific steps include: The power supply voltage is The DC source is converted into a reference voltage through a voltage divider network: ； The reference voltage The first input terminal of the input comparator converts the output voltage of the optocoupler. The second input terminal of the input comparator is used to compare the reference voltage. and the output voltage of the optocoupler Compare their sizes; The comparator is based on the reference voltage and the output voltage of the optocoupler The size generates the logic control signal: ， in The high logic voltage of the comparator. This is the low logic voltage of the comparator.

10. The relay drive circuit according to claim 6, characterized in that, The logic control signal Input transistor control unit to control the switching transistor The specific steps for turning on or off include: The logic control signal is transmitted through the transistor control unit. Converted to the switching transistor Gate input voltage: ； The gate input voltage is input to the switching transistor. The gate; when At that time, the switching transistor Entering the conduction state; when At that time, the switching transistor It is currently disconnected.

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