Control circuit and method for a relay

Abstract

The application discloses a control circuit and method of a relay, and relates to the technical field of electronic control. A specific state switching module is configured to receive and analyze the level state of a control signal and output corresponding internal control instructions accordingly; a self-terminating pulse generation module is triggered by the state switching module and is configured to generate only one self-terminating driving pulse with a predetermined duration at each triggering time through the transient characteristics of capacitor charging, so as to avoid burning the relay coil due to the continuous validity of the control signal; a power amplification module is electrically connected to the self-terminating pulse generation module and is used for amplifying the self-terminating driving pulse into a power pulse sufficient to drive the magnetic latching relay coil; and a polarity commutation module is controlled by the internal control instructions of the state switching module and applies the power pulse to the magnetic latching relay coil in a forward or reverse polarity. The application aims to adopt a novel control circuit with single power supply and less MCU resources.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic control, in particular to a control circuit and method of a relay. BACKGROUND

[0002] Magnetic Latching Relay, especially the double-coil or single-coil bidirectional pulse-controlled magnetic latching relay, is widely used in various occasions requiring state memory and energy saving, such as smart home, power automation, industrial control system, and remote device management, due to its unique self-holding characteristics. Unlike traditional relays that require continuous power supply to maintain their state, magnetic latching relays only need a short pulse current drive at the moment of state switching. After switching is completed, even if all power is removed, the armature can be reliably held in the current position by the magnetic force of the permanent magnet in the attracted or released state. This "pulse drive, no power consumption" feature has significant advantages in energy saving, reducing heat rise.

[0003] In order to drive the bidirectional pulse magnetic latching relay to realize reliable state flipping, the following two mainstream control schemes are usually adopted in the prior art:

[0004] The first is the driving scheme using positive and negative bipolar power supply. In this scheme, the control circuit usually needs a set of symmetrical positive and negative power supply, such as +12V and -12V or +24V and -24V. When the relay needs to be attracted, the control unit such as a single-chip microcomputer MCU will drive the power switch to conduct and apply a positive voltage pulse to both ends of the relay coil. When it needs to be released, a negative voltage pulse with opposite polarity is applied. The advantage of this scheme is that the circuit structure is relatively simple and intuitive. However, its defects are also very prominent. In most electronic systems that only provide a single DC power supply such as +5V or +12V, in order to obtain a negative power supply, a DC-DC negative voltage conversion chip and its supporting inductors, capacitors and other components must be additionally added. This not only significantly increases the bill of materials cost, but more seriously, according to industry practice statistics, this part of the negative power supply circuit usually occupies up to 40% or even more of the printed circuit board PCB area. This goes against the development trend of modern electronic products pursuing miniaturization and high integration, and is particularly unacceptable in space-limited applications.

[0005] The second is an H-bridge driving scheme to overcome the dual power supply problem. This scheme uses a single positive power supply to control the current direction through the relay coil by an H-bridge circuit composed of four power switches. By controlling the switch tube combination on the diagonal of the H-bridge to be turned on, the current can be made to flow forward or backward through the coil, thereby realizing the control of attraction and release. This scheme ingeniously avoids the dependence on negative power supply. However, the cost is the increase of control complexity. Driving an H-bridge requires at least 2, even up to 4 independent control signals. This means that a large number of GPIO port resources of the MCU will be occupied. In a complex embedded system, the I / O port of the MCU is often a tight resource. Occupying multiple I / O ports to drive a relay will limit the ability of the MCU to connect other peripherals such as sensors and communication modules, or force the designer to choose a MCU with more pins and higher cost.

[0006] The existing bidirectional pulse magnetic latching relay control technology has the technical problems of increasing PCB area and cost due to the dependence on dual power supply, or consuming a lot of MCU resources and being complex in control due to the use of H-bridge, and generally facing the problems of strict driving pulse window and risk of coil burning in abnormal conditions.

[0007] Therefore, there is an urgent need in the industry for a new control circuit that can use single power supply, occupy less MCU resources, simplify timing control, and fundamentally avoid coil burning due to accidental continuous power supply from the hardware level to realize the control of the magnetic latching relay. SUMMARY

[0008] The main purpose of the present application is to provide a relay control circuit and method, which can use single power supply, occupy less MCU resources, simplify timing control, and fundamentally avoid coil burning due to accidental continuous power supply from the hardware level to realize the control of the magnetic latching relay.

[0009] In order to achieve the above purpose, the present application provides a relay control circuit, which is powered by a single positive power supply and comprises:

[0010] A state switching module configured to receive and analyze the level state of a single control signal and output corresponding internal control instructions accordingly;

[0011] A self-terminating pulse generation module triggered by the state switching module and configured to generate only one self-terminating driving pulse with a predetermined duration at each trigger through the transient characteristics of capacitor charging, thereby avoiding the burning of the relay coil due to the continuous validity of the control signal;

[0012] a power amplification module electrically connected to the self-terminating pulse generation module, for amplifying the self-terminating driving pulse into a power pulse sufficient to drive the magnetic latching relay coil;

[0013] a polarity commutation module controlled by internal control instructions of the state switching module, for receiving the power pulse and applying the power pulse to the magnetic latching relay coil in positive or reverse polarity by switching the current path.

[0014] In an embodiment of the present application, the state switching module specifically comprises:

[0015] a first NPN transistor Q2, a first relay K1, and a first resistor R2;

[0016] wherein the emitter of the first NPN transistor Q2 is directly grounded, the base thereof is electrically connected to the input end of the single control signal through the first resistor R2; the first coil end 1 of the first relay K1 is electrically connected to the collector of the first NPN transistor Q2; the first normally open contact 2 of the first relay K1 is grounded; the first normally closed contact 3 of the first relay K1 is connected to the polarity commutation module; the first common end 4, the second common end 5, the second normally open contact 7, and the second coil end 8 of the first relay K1 are all connected to the power supply VCC; and the second normally closed contact 6 of the first relay K1 is electrically connected to the self-terminating pulse generation module.

[0017] In an embodiment of the present application, the state switching module further comprises:

[0018] a freewheeling diode D2;

[0019] wherein the anode of the freewheeling diode D2 is electrically connected to the collector of the first NPN transistor Q2, and the cathode thereof is connected to the power supply VCC, for protecting the first NPN transistor Q2.

[0020] In an embodiment of the present application, the polarity commutation module specifically comprises:

[0021] a second NPN transistor Q1, a second relay K2, and a second resistor R3;

[0022] The first normally closed contact 3 of the first relay K1 in the state switching module is electrically connected to the base of the second NPN transistor Q1 through the second resistor R3; the emitter of the second NPN transistor Q1 is grounded, and the collector thereof is electrically connected to the first coil end 1 of the second relay K2; the second coil end 8 of the second relay K2 is connected to the power supply VCC; the contacts of the second relay K2 are configured in an H-bridge structure, and are used to apply the power supply VCC and the power amplification module output signal received by the common end thereof to the coil of the magnetic latching relay KM1A in different polarities.

[0023] In an embodiment of the present application, the polarity commutation module further comprises:

[0024] A freewheeling diode D1; wherein the anode of the freewiling diode D1 is electrically connected to the collector of the second NPN transistor Q1, and the cathode thereof is connected to the power supply VCC, for protecting the second NPN transistor Q1.

[0025] In an embodiment of the present application, the self-terminating pulse generation module specifically comprises:

[0026] An opto-coupler N1, a third resistor R1, and a first capacitor C1;

[0027] The second normally closed contact 6 of the first relay K1 in the state switching module is electrically connected to the first end of the third resistor R1, the second end of the third resistor R1 is connected to the first end of the first capacitor C1, and the second end of the first capacitor C1 is connected to the input anode of the opto-coupler N1; the input cathode of the opto-coupler N1 is grounded.

[0028] In an embodiment of the present application, the power amplification module specifically comprises:

[0029] An N-channel MOS transistor Q3 and a fourth resistor R4;

[0030] The source of the N-channel MOS transistor Q3 is grounded, and the drain thereof is connected to the polarity commutation module as a power output end; the fourth resistor R4 is connected across the gate of the N-channel MOS transistor Q3 and the ground; and the gate of the N-channel MOS transistor Q3 is further electrically connected to the output emitter of the opto-coupler N1 in the self-terminating pulse generation module.

[0031] In an embodiment of the present application, the circuit further provides a voltage stabilizing circuit for the drive stage of the power amplification module, which specifically comprises:

[0032] A fifth resistor R5, a voltage stabilizing diode D3, and a second capacitor C2;

[0033] The fifth resistor R5 is connected in series between the power supply VCC and the output collector of the photoelectric coupler N1; the voltage stabilizing diode D3 and the second capacitor C2 are connected in parallel and are connected in common across the output collector of the photoelectric coupler N1 and the ground.

[0034] In an embodiment of the present application, the power amplification module further comprises:

[0035] A third capacitor C3;

[0036] The third capacitor C3 is connected across the drain of the N-channel MOS transistor Q3 and the ground, for output buffering or energy storage.

[0037] The present application also discloses a control method of a relay, comprising the following steps:

[0038] Monitoring the change of the level state of the single control signal from a first state to a second state;

[0039] In response to the change of the level state, automatically and synchronously performing the following operations:

[0040] Based on the changed second level state, automatically selecting a current driving path corresponding to the forward or reverse direction from the hardware level;

[0041] Generating a driving pulse with a predetermined duration and self-terminating at the end of the pulse by a hardware timing circuit, wherein the generation and termination of the pulse are independent of whether the single control signal continuously remains in the second state, thereby fundamentally preventing the relay coil from being damaged due to accidental continuous energization;

[0042] Applying the self-terminating driving pulse to the configured current driving path to drive the magnetic latching relay to complete the attraction or release action corresponding to the second state.

[0043] With the above technical solution, first, the circuit only needs a single positive power supply, compared with the traditional scheme which needs positive and negative dual power supplies, greatly simplifying the power supply design and reducing the material cost and the circuit board area. Second, through the analysis of the single control signal by the state switching module, the bidirectional control of the magnetic latching relay is realized only by using one ordinary IO port of an MCU or PLC, saving valuable control resources. Third, the core self-terminating pulse generation module guarantees the accurate width and automatic stop of the driving pulse at the hardware level, completely eliminating the risk of burning out the relay coil due to inaccurate control signal timing or continuous validity, and significantly improving the stability and reliability of the circuit. BRIEF DESCRIPTION OF DRAWINGS

[0044] The present application will be described in detail below with reference to specific embodiments and drawings, in which:

[0045] Figure 1 The circuit structure diagram of the first embodiment of the present application is shown in the figure.

[0046] Figure 2 The flow structure diagram of the present application is shown in the figure. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be described in detail below in combination with the figures and embodiments. It should be understood that the following specific embodiments are only used to explain the present application, and do not constitute limitation to the present application.

[0048] As shown in the figure, Figure 1 In order to achieve the above-mentioned purpose, the present application proposes a control circuit of a relay, which is powered by a single positive power supply and includes:

[0049] a state switching module, which is configured to receive and analyze the level state of a single control signal, and output corresponding internal control instructions accordingly;

[0050] a self-terminating pulse generation module, which is triggered by the state switching module, and through the transient characteristics of capacitor charging, is configured to generate only one self-terminating driving pulse with a predetermined duration at each trigger, so as to avoid burning the relay coil due to the continuous validity of the control signal;

[0051] a power amplification module, which is electrically connected to the self-terminating pulse generation module, for amplifying the self-terminating driving pulse into a power pulse sufficient to drive the magnetic latching relay coil;

[0052] a polarity commutation module, which is controlled by the internal control instructions of the state switching module, for receiving the power pulse and applying the power pulse to the magnetic latching relay coil with forward or reverse polarity by switching the current path.

[0053] Specifically, a control circuit of a relay is powered by a single positive power supply, and the overall circuit framework includes a state switching module, a self-terminating pulse generation module, a power amplification module, and a polarity commutation module. The state switching module serves as the control core, responsible for receiving an external single control signal and outputting internal control instructions to the self-terminating pulse generation module and the polarity commutation module according to the level state of the single control signal. After receiving the trigger instruction from the state switching module, the self-terminating pulse generation module generates a hardware-level self-terminating drive pulse with a predetermined duration and outputs the drive pulse to the power amplification module. The power amplification module amplifies the received drive pulse and outputs a power pulse sufficient to drive the final load to the polarity commutation module. The polarity commutation module determines whether to apply the power pulse to the magnetic latching relay coil in the forward or reverse direction according to the instructions from the state switching module, thereby completing the attraction or release operation of the magnetic latching relay.

[0054] In one embodiment, the state switching module can be composed of discrete components, such as an NPN transistor and a small electromagnetic relay. The single control signal is connected to the base of the NPN transistor through a current-limiting resistor, the emitter of the NPN transistor is grounded, and the collector of the NPN transistor is connected to the single positive power supply after being connected in series with the coil of the electromagnetic relay. The multiple sets of contacts of the electromagnetic relay are used as internal control instructions output to other modules.

[0055] In another embodiment, the state switching module can also be implemented using integrated logic circuits, such as an integrated circuit chip containing D flip-flops and logic gates (such as AND gates and NOT gates). The rising or falling edge change of the single control signal is detected using the D flip-flop, and the trigger signal and direction control signal are resolved as internal control instructions using the logic gate circuit.

[0056] The self-terminating pulse generation module, which is the core function of the module, generates a fixed-width pulse that is not affected by the duration of the input signal by using the transient characteristics of a capacitor. In one embodiment, the self-terminating pulse generation module can be composed of a resistor-capacitor differential circuit and a Schmitt trigger. The trigger command output by the state switching module is coupled to the input of the Schmitt trigger through a capacitor. A sharp pulse is generated at the input of the Schmitt trigger by using the transient charging and discharging characteristics of the capacitor. The Schmitt trigger then shapes the sharp pulse into a square wave drive pulse with steep edges and a predetermined width. The pulse width is determined by the time constant of the resistor-capacitor.

[0057] The power amplification module is used to enhance the driving capability. In one embodiment, the power amplification module can be composed of an N-channel enhancement-mode metal-oxide-semiconductor field-effect transistor (MOSFET). The drive pulse output by the self-terminating pulse generation module is connected to the gate of the N-channel enhancement-mode MOSFET. The source of the N-channel enhancement-mode MOSFET is connected to ground. The drain of the N-channel enhancement-mode MOSFET, which serves as the power output terminal, is connected to the polarity commutation module.

[0058] The polarity commutation module is responsible for switching the direction of the current applied to the coil of the latching relay. In one embodiment, the polarity commutation module can employ an H-bridge circuit composed of four power transistors. The coil of the latching relay is connected across the two output terminals of the H-bridge. The internal control command output by the state switching module is used to control the two pairs of transistors on the opposite corners of the H-bridge to alternate conduction, thereby achieving forward or reverse current flow. In another embodiment, the polarity commutation module can employ a double-pole double-throw (DPDT) power relay. The power pulse output by the power amplification module is connected to the two common terminals of the DPDT relay. The coil of the latching relay is connected between the two sets of normally open and normally closed contacts and forms a cross connection. The internal control command output by the state switching module is used to drive the coil of the DPDT relay, thereby changing the direction of the current flowing through the coil of the latching relay by switching the contact position of the DPDT relay.

[0059] The working principle of the whole circuit is as follows: when the single control signal changes from low level to high level, the state switching module analyzes the change, on the one hand, outputs an internal control instruction set as forward driving to the polarity commutation module, and on the other hand, outputs a trigger instruction to the self-terminating pulse generation module at the same time; after the self-terminating pulse generation module is triggered, a self-terminating driving pulse with a predetermined width is immediately generated and sent to the power amplification module; the power amplification module amplifies the driving pulse into a power pulse and transmits it to the polarity commutation module; under the set forward driving path, the polarity commutation module applies the power pulse to the magnetic latching relay coil, so that the magnetic latching relay is attracted. After the pulse ends, due to the characteristics of the magnetic latching relay, the state is maintained. When the single control signal changes from high level to low level, the state switching module analyzes the change, outputs an internal control instruction set as reverse driving to the polarity commutation module, and triggers the self-terminating pulse generation module again to generate the same pulse. After power amplification and reverse polarity application, the magnetic latching relay is released.

[0060] By adopting the technical scheme, firstly, the circuit only needs a single positive power supply, compared with the traditional scheme needing positive and negative dual power supplies, the power supply design is greatly simplified, and the material cost and the circuit board area are reduced. Secondly, through the analysis of the single control signal by the state switching module, the bidirectional control of the magnetic latching relay is realized only by using one ordinary IO port of an MCU or a PLC, and the valuable control resource is saved. Thirdly, the core self-terminating pulse generation module guarantees the accurate width and automatic stop of the driving pulse at the hardware level, completely eliminates the risk of burning the relay coil due to the timing inaccuracy or continuous validity of the control signal, and significantly improves the stability and reliability of the circuit.

[0061] The IO port represents an input and output port.

[0062] In an embodiment of the present application, the state switching module specifically comprises:

[0063] The first NPN transistor Q2, the first relay K1, and the first resistor R2.

[0064] The emitter of the first NPN transistor Q2 is directly grounded, the base thereof is electrically connected to the input end of the single control signal through the first resistor R2; the first coil end 1 of the first relay K1 is electrically connected to the collector of the first NPN transistor Q2; the first normally open contact 2 of the first relay K1 is grounded; the first common end 4, the second common end 5, the second normally open contact 7, and the second coil end 8 of the first relay K1 are connected to the power supply VCC; and the second normally closed contact 6 of the first relay K1 is electrically connected to the self-terminating pulse generation module.

[0065] Specifically, the state switching module specifically comprises a first NPN transistor Q2, a first relay K1, and a first resistor R2. In terms of circuit connection, the emitter of the first NPN transistor Q2 is directly grounded, and the base of the first NPN transistor Q2 is electrically connected to the input end of the single control signal through the first resistor R2. The first coil end 1 of the first relay K1 is electrically connected to the collector of the first NPN transistor Q2. In order to supply power to the relay and its contacts, the first common end 4, the second common end 5, the second normally open contact 7, and the second coil end 8 of the first relay K1 are all connected to the power supply VCC. The first normally open contact 2 of the first relay K1 is directly grounded. The first relay K1 is used to output internal control instructions, wherein the first normally closed contact 3 of the first relay K1 is connected to the polarity commutation module, and the second normally closed contact 6 of the first relay K1 is electrically connected to the self-terminating pulse generation module.

[0066] The working principle of the circuit is as follows: when the single control signal is high, current flows into the base of the first NPN transistor Q2 through the first resistor R2, so that the first NPN transistor Q2 is turned on. After being turned on, the collector potential of the first NPN transistor Q2 is pulled low, thereby forming a current path through the coil of the first relay K1 between the power supply VCC and the ground, and thus exciting the first relay K1 to act. After acting, the internal contacts of the first relay K1 are switched, the first common end 4 connected to the power supply VCC is disconnected from the first normally closed contact 3, and instead connected to the first normally open contact 2 grounded; at the same time, the second common end 5 connected to the power supply VCC is disconnected from the second normally closed contact 6, and instead connected to the second normally open contact 7 also connected to the power supply VCC. When the single control signal is low, the first NPN transistor Q2 is turned off, the coil of the first relay K1 loses power, and its internal contacts return to the normal state. In this normal state, the first common end 4 connected to the power supply VCC is connected to the first normally closed contact 3, outputting a high-level signal to the polarity commutation module; at the same time, the second common end 5 connected to the power supply VCC is connected to the second normally closed contact 6, outputting a high-level signal to the self-terminating pulse generation module.

[0067] By using the above technical solution, the first NPN transistor Q2 is used to drive the first relay K1, which can use a weak control signal to control the switching of the relay, realizing power amplification and electrical isolation of the control end. At the same time, by using the double-pole double-throw contact structure of the first relay K1, the change of the single control signal is ingeniously converted into two independent internal control instructions that can act in coordination in logic, and the circuit structure is simple and reliable in operation.

[0068] In an embodiment of the present application, the state switching module further comprises:

[0069] a freewheeling diode D2;

[0070] The anode of the freewheeling diode D2 is electrically connected to the collector of the first NPN transistor Q2, and the cathode is connected to the power supply VCC, for protecting the first NPN transistor Q2.

[0071] Specifically, the state switching module further comprises a freewheeling diode D2. In terms of circuit connection, the anode of the freewheeling diode D2 is electrically connected to the collector of the first NPN transistor Q2, and the cathode is connected to the power supply VCC. The core function of the freewheeling diode D2 is to protect the first NPN transistor Q2.

[0072] With the above technical solution, by reversely connecting the freewheeling diode D2 in parallel across the first relay K1 coil, an effective discharge path is provided for the reverse electromotive force generated by the coil when the first NPN transistor Q2 is turned off, which significantly enhances the stability and reliability of the circuit and effectively prolongs the service life of the first NPN transistor Q2.

[0073] In an embodiment of the present application, the polarity commutation module specifically comprises:

[0074] a second NPN transistor Q1, a second relay K2, and a second resistor R3;

[0075] The first normally closed contact 3 of the first relay K1 in the state switching module is electrically connected to the base of the second NPN transistor Q1 through the second resistor R3; the emitter of the second NPN transistor Q1 is grounded, and the collector is electrically connected to the first coil end 1 of the second relay K2; the second coil end 8 of the second relay K2 is connected to the power supply VCC; the contacts of the second relay K2 are configured in an H-bridge structure, for applying the power supply VCC and the power amplification module output signal received by the common end to the coil of the magnetic latching relay KM1A with different polarities.

[0076] Specifically, the polarity commutation module specifically comprises a second NPN transistor Q1, a second relay K2, and a second resistor R3. A control input signal of the module is derived from a first normally closed contact 3 of a first relay K1 in the state switching module, and the first normally closed contact 3 of the first relay K1 is electrically connected to a base of the second NPN transistor Q1 through the second resistor R3. The second NPN transistor Q1 serves as a switching element, with an emitter directly grounded and a collector electrically connected to a first coil end 1 of the second relay K2 for controlling on-off of the second relay K2. A second coil end 8 of the second relay K2 is connected to a power supply VCC, and together with the second NPN transistor Q1, forms a complete driving circuit. The core function of the second relay K2 is to perform switching of current direction, and for this purpose, contacts of the second relay K2 are configured in an H-bridge structure, and by switching the contact state, the power supply VCC received at a common end and a power pulse signal output from the power amplification module can be applied to a coil of a magnetic latching relay KM1A in different polarities.

[0077] The working principle is as follows: when the first normally closed contact 3 of the first relay K1 outputs a high level, current flows into the base of the second NPN transistor Q1 through the second resistor R3, so that the second NPN transistor Q1 is turned on. The conduction of the second NPN transistor Q1 causes the coil of the second relay K2 to be energized, resulting in switching of the H-bridge contacts of the second relay K2 to a first working state. In this state, the power supply VCC and the output signal of the power amplification module are applied to the coil of the magnetic latching relay KM1A through the contacts configured in a current path, for example, in a forward direction. Conversely, when the first normally closed contact 3 of the first relay K1 outputs a low level or a high impedance state, the second NPN transistor Q1 is turned off, the coil of the second relay K2 loses power, and the H-bridge contacts of the second relay K2 return to a second working state (normal state). In this state, the power supply VCC and the output signal of the power amplification module are applied to the coil of the magnetic latching relay KM1A through the contacts configured in a current path opposite to the first working state, for example, in a reverse direction.

[0078] By using the second NPN transistor Q1 to drive the second relay K2, the logic level signal from the state switching module is used to control the on-off of a power relay.

[0079] In an embodiment of the present application, the polarity commutation module further comprises:

[0080] A freewheeling diode D1, wherein an anode of the freewheeling diode D1 is electrically connected to a collector of the second NPN transistor Q1, and a cathode of the freewheeling diode D1 is connected to the power supply VCC, for protecting the second NPN transistor Q1.

[0081] Specifically, the polarity commutation module further comprises a freewheeling diode D1. In terms of the connection relationship of the circuit, the anode of the freewheeling diode D1 is electrically connected to the collector of the second NPN transistor Q1, and the cathode of the freewheeling diode D1 is connected to the power supply VCC. The purpose of adding the freewheeling diode D1 is to protect the second NPN transistor Q1.

[0082] With the above technical solution, by connecting a freewheeling diode D1 in parallel with the switch transistor for driving the relay coil, a reliable discharge channel is provided for the reverse electromotive force generated by the inductive load when power is off, thereby greatly improving the working reliability and service life of the second NPN transistor Q1 and ensuring long-term stable operation of the entire polarity commutation module.

[0083] In an embodiment of the present application, the self-terminating pulse generation module specifically comprises:

[0084] a photoelectric coupler N1, a third resistor R1, and a first capacitor C1;

[0085] Among them, the second normally closed contact 6 of the first relay K1 in the state switching module is electrically connected to the first end of the third resistor R1, the second end of the third resistor R1 is connected to the first end of the first capacitor C1, and the second end of the first capacitor C1 is connected to the input anode of the photoelectric coupler N1; the input cathode of the photoelectric coupler N1 is grounded.

[0086] Specifically, the self-terminating pulse generation module specifically comprises a photoelectric coupler N1, a third resistor R1, and a first capacitor C1. The input signal of this module is provided by the state switching module, specifically, the second normally closed contact 6 of the first relay K1 in the state switching module is electrically connected to the first end of the third resistor R1. The second end of the third resistor R1 is then connected in series to the first end of the first capacitor C1, and then the second end of the first capacitor C1 is connected to the input anode of the photoelectric coupler N1, and the input cathode of the photoelectric coupler N1 is directly grounded. This connection mode constitutes an RC series charging circuit responding to voltage step change, for driving the light-emitting diode of the photoelectric coupler N1.

[0087] The working principle is that when the output end of the second normally closed contact 6 of the first relay K1 jumps from low level to high level, because the voltage across the first capacitor C1 cannot jump, a transient charging current immediately flows through the third resistor R1, the first capacitor C1 and the input light-emitting diode of the optocoupler N1. This transient current makes the light-emitting diode inside the optocoupler N1 emit light, so that the light-sensitive transistor is turned on, generating a starting edge of a driving pulse. As the charging process proceeds, the voltage across the first capacitor C1 gradually rises, causing the charging current flowing through the entire series circuit to decay exponentially. When the current decays below the threshold value insufficient to maintain the light-emitting diode inside the optocoupler N1 emitting light, the light-emitting diode is extinguished, and the light-sensitive transistor is turned off, ending the driving pulse. The duration of the entire pulse is determined by the time constant determined by the values of the third resistor R1 and the first capacitor C1, thereby realizing automatic generation and automatic termination of the pulse at the hardware level, regardless of whether the second normally closed contact 6 of the first relay K1 remains high.

[0088] By adopting the technical scheme, a simple and reliable hardware pulse generator is constructed by connecting the resistor, the capacitor and the optocoupler in series and skillfully utilizing the transient characteristics of capacitor charging. The design can automatically generate a driving pulse with a determined width, eliminating the complex requirement for accurate timing control of the main controller, and realizes electrical isolation between the control signal and the power circuit in the rear stage through the optocoupler N1, effectively suppressing noise interference and improving the stability and anti-interference ability of the entire control circuit.

[0089] In an embodiment of the present application, the power amplification module specifically comprises:

[0090] an N-channel MOS transistor Q3 and a fourth resistor R4;

[0091] The source of the N-channel MOS transistor Q3 is connected to ground, and the drain thereof is connected to the polarity commutation module as a power output end. The fourth resistor R4 is connected across the gate of the N-channel MOS transistor Q3 and the ground. The gate of the N-channel MOS transistor Q3 is also electrically connected to the output emitter of the optocoupler N1 in the self-terminating pulse generation module.

[0092] Specifically, the power amplification module specifically comprises an N-channel MOS transistor Q3 and a fourth resistor R4. In the connection structure of the circuit, the N-channel MOS transistor Q3 serves as a main power switch element, and the source thereof is directly connected to the ground. The drain of the N-channel MOS transistor Q3 serves as a power output terminal of the entire module, and is electrically connected to the polarity commutation module, for delivering an amplified power pulse to a subsequent circuit. In order to ensure that the N-channel MOS transistor Q3 can be reliably turned off, the fourth resistor R4 is connected across the gate of the N-channel MOS transistor Q3 and the ground. The control input signal of the module is derived from the self-terminating pulse generation module of a previous stage, and specifically, the gate of the N-channel MOS transistor Q3 is also electrically connected to the output emitter of the optocoupler N1 in the self-terminating pulse generation module.

[0093] The working principle of the circuit is as follows: when the optocoupler N1 in the self-terminating pulse generation module is triggered to turn on, the output emitter thereof outputs a forward driving pulse signal to the gate of the N-channel MOS transistor Q3. When the gate voltage exceeds the threshold voltage of the N-channel MOS transistor Q3, the N-channel MOS transistor Q3 is rapidly turned on, and the drain and the source thereof present an extremely low on-resistance, so that the drain potential of the N-channel MOS transistor Q3 is pulled to a ground level, forming a large-current switch path. When the driving pulse output by the optocoupler N1 ends, the fourth resistor R4 provides a discharge path to the ground for the charge accumulated on the gate of the N-channel MOS transistor Q3, so that the gate voltage can be rapidly pulled down to zero, thereby ensuring that the N-channel MOS transistor Q3 can be quickly and reliably switched from the on state to the off state, and avoiding the mis-conduction caused by the suspended gate.

[0094] By using the N-channel MOS transistor Q3 as a switch and utilizing the voltage driving and low on-resistance characteristics thereof, the above technical solution realizes efficient power amplification of a weak driving signal from a previous-stage optocoupler, and can drive a larger load current. Meanwhile, the fourth resistor R4 is a pull-down resistor, which ensures that the power switch tube is in a determined off state when there is no driving signal, thereby enhancing the stability and anti-interference ability of the circuit and preventing the accidental turn-on of the power output terminal.

[0095] In an embodiment of the present application, the circuit further provides a voltage stabilizing circuit for the driving stage of the power amplification module, which specifically comprises:

[0096] a fifth resistor R5, a voltage stabilizing diode D3 and a second capacitor C2;

[0097] The fifth resistor R5 is connected in series between the power supply VCC and the output collector of the photoelectric coupler N1; and the voltage stabilizing diode D3 and the second capacitor C2 are connected in parallel and then are connected in common across the output collector of the photoelectric coupler N1 and the ground.

[0098] Specifically, the circuit further provides a voltage stabilizing circuit for the driving stage of the power amplification module, which specifically includes the fifth resistor R5, the voltage stabilizing diode D3 and the second capacitor C2. In the connection structure of the circuit, the fifth resistor R5 is connected in series between the power supply VCC and the output collector of the photoelectric coupler N1. The voltage stabilizing diode D3 and the second capacitor C2 are first connected in parallel with each other and then are connected in common across the output collector of the photoelectric coupler N1 and the ground. This circuit constitutes a typical parallel voltage stabilizing circuit.

[0099] By adopting the above technical solution, the voltage stabilizing circuit composed of the resistor, the voltage stabilizing diode and the capacitor is added to the output stage of the photoelectric coupler N1, so as to ensure that the voltage amplitude of the driving signal is not affected by the fluctuation of the main power supply VCC, thereby ensuring the stability and consistency of the gate driving voltage of the N-channel MOS transistor Q3.

[0100] In an embodiment of the present application, the power amplification module further includes:

[0101] a third capacitor C3;

[0102] The third capacitor C3 is connected across the drain of the N-channel MOS transistor Q3 and the ground, for output buffering or energy storage.

[0103] Specifically, the power amplification module further includes the third capacitor C3. In the connection structure of the circuit, the third capacitor C3 is connected across the drain of the N-channel MOS transistor Q3 and the ground. The third capacitor C3 mainly plays a role of output buffering or energy storage in the circuit.

[0104] By adopting the above technical solution, the third capacitor C3 is connected in parallel at the output end of the power amplification module, which can effectively suppress the noise and voltage spikes generated in the switching process, improve the quality of the output pulse signal and the electromagnetic compatibility of the circuit, and can also provide instantaneous large current support, enhance the driving capability and load response speed of the circuit, so that the performance of the entire power output stage is more stable and reliable.

[0105] As shown in Figure 2 The present application further discloses a control method of the relay, which includes the following steps:

[0106] monitoring the change of the level state of the single control signal from the first state to the second state;

[0107] in response to the change in the level state, the following operations are performed automatically and synchronously:

[0108] based on the changed second level state, a current driving path corresponding to the forward or reverse direction is automatically selected from the hardware level;

[0109] a driving pulse with a predetermined duration and self-terminating at the end of the pulse is automatically generated by a hardware timing circuit, wherein the generation and termination of the pulse is independent of whether the single control signal remains in the second state, thereby fundamentally preventing the relay coil from being damaged due to accidental continuous energization;

[0110] the self-terminating driving pulse is applied to the configured current driving path to drive the magnetic latching relay to complete the attraction or release action corresponding to the second state.

[0111] Specifically, the change in the level state of the single control signal from the first state to the second state is monitored. For example, when the voltage of the single control signal jumps from the low level representing the first state to the high level representing the second state, the circuit detects this change. In response to the change in the level state, the following operations are performed automatically and synchronously. The first operation is: based on the changed second level state, a current driving path corresponding to the forward or reverse direction is automatically selected from the hardware level. For example, when the signal becomes high (second state), the first relay K1 in the state switching module will act, and the change of its contact will control the second relay K2 in the polarity switching module to switch to a preset position, thereby configuring a forward current path that can attract the magnetic latching relay for the upcoming power pulse.

[0112] The second parallel operation is: a driving pulse with a predetermined duration and self-terminating at the end of the pulse is automatically generated by a hardware timing circuit. This operation is completed by the self-terminating pulse generation module, for example, the change of the contact of the first relay K1 in the state switching module will trigger an RC circuit (composed of the third resistor R1 and the first capacitor C1) to start charging, and this transient process of charging will generate a fixed-width pulse, and the width of the pulse is determined by the RC time constant. The generation and termination of the pulse is independent of whether the single control signal remains in the second state, thereby fundamentally preventing the relay coil from being damaged due to accidental continuous energization. Once the RC circuit completes charging, the pulse will automatically end, even if the single control signal remains at high level at this time.

[0113] The last step is to apply the self-terminating drive pulse to the configured current drive path to drive the magnetic latching relay to complete the attraction or release action corresponding to the second state. The hardware timing pulse generated in the previous step is amplified by the power amplifier module and applied to the positive current path selected by the polarity conversion module, thereby driving the coil of the magnetic latching relay KM1A to reliably attract. When the single control signal changes from high level (second state) to low level (first state), the above process is triggered again, but this time the polarity conversion module is configured to the reverse current path, finally driving the magnetic latching relay to release.

[0114] With the above technical solution, the method completely solidifies the complex timing control logic in hardware, and the controller only needs to change the level state of the output signal without needing to care about the width and timing of the pulse, greatly simplifying the control difficulty of the upper software. The self-terminating pulse generated by the hardware timing circuit fundamentally eliminates the risk of burning the expensive magnetic latching relay due to abnormal control signals, significantly improving the reliability and safety of the system.

[0115] The above only describes the preferred embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent structural transformation, direct / indirect application in other related technical fields, or direct / indirect application in other related technical fields within the inventive concept of the present application and the content of the specification and drawings are included in the patent protection scope of the present application.

Claims

1. A control circuit for a relay, characterized by The circuit is powered by a single positive power supply, comprising: a state switching module configured to receive and analyze the level state of a single control signal and output corresponding internal control instructions accordingly; a self-terminating pulse generation module triggered by the state switching module and configured to generate only one self-terminating driving pulse with a predetermined duration at each trigger through the transient characteristics of capacitor charging, thereby avoiding the burning of the relay coil due to the continuous effectiveness of the control signal; a power amplification module electrically connected to the self-terminating pulse generation module for amplifying the self-terminating driving pulse into a power pulse sufficient to drive the magnetic latching relay coil; a polarity commutation module controlled by the internal control instructions of the state switching module for receiving the power pulse and applying it to the magnetic latching relay coil with positive or negative polarity by switching the current path.

2. The control circuit of a relay according to claim 1, characterized in that, The state switching module specifically includes: a first NPN transistor Q2, a first relay K1, and a first resistor R2; wherein the emitter of the first NPN transistor Q2 is directly grounded, the base is electrically connected to the input of the single control signal through the first resistor R2; the first coil end 1 of the first relay K1 is electrically connected to the collector of the first NPN transistor Q2; the first normally open contact 2 of the first relay K1 is grounded; the first normally closed contact 3 of the first relay K1 is connected to the polarity commutation module; the first common end 4, the second common end 5, the second normally open contact 7, and the second coil end 8 of the first relay K1 are all connected to the power supply VCC; the second normally closed contact 6 of the first relay K1 is electrically connected to the self-terminating pulse generation module.

3. The control circuit of a relay according to claim 2, wherein The state switching module further includes: a freewheeling diode D2; wherein the anode of the freewheeling diode D2 is electrically connected to the collector of the first NPN transistor Q2, and the cathode is connected to the power supply VCC, for protecting the first NPN transistor Q2.

4. The control circuit of a relay according to claim 2, wherein The polarity commutation module specifically includes: a second NPN transistor Q1, a second relay K2, and a second resistor R3; wherein the first normally closed contact 3 of the first relay K1 in the state switching module is electrically connected to the base of the second NPN transistor Q1 through the second resistor R3; the emitter of the second NPN transistor Q1 is grounded, and the collector is electrically connected to the first coil end 1 of the second relay K2; the second coil end 8 of the second relay K2 is connected to the power supply VCC; the contacts of the second relay K2 are configured in an H-bridge structure for applying the power supply VCC and the power amplification module output signal received at its common end to the coil of the magnetic latching relay KM1A with different polarities.

5. The control circuit of a relay according to claim 4, characterized in that, The polarity commutation module further includes: a freewheeling diode D1; wherein the anode of the freewheeling diode D1 is electrically connected to the collector of the second NPN transistor Q1, and the cathode is connected to the power supply VCC, for protecting the second NPN transistor Q1.

6. The control circuit of a relay according to claim 2, wherein The self-terminating pulse generation module specifically includes: The optoelectronic coupler N1, the third resistor R1, and the first capacitor C1; The second normally closed contact 6 of the first relay K1 in the state switching module is electrically connected to the first end of the third resistor R1, the second end of the third resistor R1 is connected to the first end of the first capacitor C1, and the second end of the first capacitor C1 is connected to the input anode of the optoelectronic coupler N1; the input cathode of the optoelectronic coupler N1 is grounded.

7. The control circuit of a relay according to claim 6, characterized in that, The power amplification module specifically includes: An N-channel MOS transistor Q3 and a fourth resistor R4; The source of the N-channel MOS transistor Q3 is grounded, and the drain thereof is connected to the polarity commutation module as a power output end; the fourth resistor R4 is connected between the gate of the N-channel MOS transistor Q3 and the ground; the gate of the N-channel MOS transistor Q3 is also electrically connected to the output emitter of the optoelectronic coupler N1 in the self-terminating pulse generation module.

8. The control circuit of a relay according to claim 7, characterized in that, The circuit further provides a voltage stabilizing circuit for the drive stage of the power amplification module, which specifically includes: A fifth resistor R5, a voltage stabilizing diode D3, and a second capacitor C2; The fifth resistor R5 is connected in series between the power supply VCC and the output collector of the optoelectronic coupler N1; the voltage stabilizing diode D3 and the second capacitor C2 are connected in parallel and are commonly connected between the output collector of the optoelectronic coupler N1 and the ground.

9. The control circuit of a relay according to claim 7, wherein The power amplification module further includes: A third capacitor C3; The third capacitor C3 is connected between the drain of the N-channel MOS transistor Q3 and the ground, for output buffering or energy storage.

10. A control method of a relay for the control circuit of the relay according to any one of claims 1 to 9, characterized by, The method includes the following steps: Monitoring the change of the level state of a single control signal from a first state to a second state; In response to the change of the level state, automatically and synchronously performing the following operations: Based on the changed second level state, automatically selecting a current driving path corresponding to the forward or reverse direction from the hardware level; Generating a driving pulse with a predetermined duration and self-terminating at the end of the pulse through a hardware timing circuit, wherein the generation and termination of the pulse are independent of whether the single control signal continuously remains in the second state, thereby fundamentally preventing the relay coil from being damaged due to accidental continuous energization; Applying the self-terminating driving pulse to the configured current driving path to drive the magnetic latching relay to complete the attraction or release action corresponding to the second state.

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