Circuit capable of preventing control failure during starting of relay

Abstract

The utility model discloses a circuit capable of preventing control failure when a relay is opened, which comprises an RC charging and discharging circuit, a threshold driving circuit, a driving return difference locking circuit, a controlled switching circuit, a relay enabling and coil discharging circuit and an enabling turn-off circuit before the relay is not closed, the RC charging and discharging circuit is respectively connected with the threshold value driving circuit and the driving return difference locking circuit, and the controlled switching circuit is respectively connected with the threshold value driving circuit, the driving return difference locking circuit, the relay enabling and coil discharging circuit and the enabling turn-off circuit before the relay is not closed. According to the circuit capable of preventing the control failure when the relay is started, a driving return difference locking circuit is added to a controlled switch circuit, so that the problem of frequent switching actions of the controlled switch is solved, the service life of the relay is prolonged, the reliability of a product is improved, and a power circuit is prevented from being started repeatedly. And meanwhile, the use experience of the user is improved.

Description

Technical Field

[0001] The utility model specifically relates to a circuit which can prevent control failure when a relay is turned on. Background Art

[0002] Relays are widely used in various weak current control strong current isolation application environments. The existing technology uses RC circuits for design. Due to the large time constant, C is mostly an electrolytic capacitor. Moreover, the capacity is large, the volume of the capacitor is relatively large, and it takes up more space; at the same time, due to the inherent characteristics of the electrolytic capacitor at high and low temperatures, the time constant will change greatly. It is bound to eventually affect the control action time, and there is even a risk of changing the timing logic.

[0003] In addition, because the influence of hysteresis is not fully considered in conventional circuit design, the working current of the relay coil is relatively large. It will absorb a large current at the moment of conduction, which will inevitably cause the voltage fluctuation of the power supply Vcc. This will affect the stable charging process of the RC charging circuit, resulting in the process of repeated opening and closing of the controlled transistor at the moment of relay opening. The external characteristic is that the relay is repeatedly opened and closed during the initial operation, and a "clicking" sound can be heard. After several cycles, the relay control system can enter a stable working link. Utility Model Content

[0004] In view of the defects in the prior art, the utility model provides a circuit which can prevent control failure when a relay is turned on, thereby solving the problems existing in the prior art.

[0005] The utility model provides a circuit capable of preventing control failure when a relay is turned on, comprising: an RC charging and discharging circuit, a threshold driving circuit, a driving hysteresis locking circuit, a controlled switching circuit, a relay enabling and coil discharging circuit, and a relay enabling and shutting-off circuit before the relay is attracted, wherein the RC charging and discharging circuit is respectively connected to the threshold driving circuit and the driving hysteresis locking circuit, and the controlled switching circuit is respectively connected to the threshold driving circuit, the driving hysteresis locking circuit, the relay enabling and coil discharging circuit, and the relay enabling and shutting-off circuit before the relay is attracted.

[0006] Furthermore, the RC charge and discharge circuit includes a first diode, a third resistor and a first capacitor, one end of the third resistor is connected to the cathode of the first diode and to a power supply, the other end of the third resistor is respectively connected to one end of the first capacitor and the anode of the first diode, and the other end of the first capacitor is grounded.

[0007] Furthermore, the first capacitor is a ceramic capacitor.

[0008] Furthermore, the threshold driving circuit includes a first voltage regulator tube, a sixth resistor and a second capacitor, the cathode of the first voltage regulator tube is connected to the anode of the first diode, the anode of the first voltage regulator tube is respectively connected to one end of the sixth resistor and the second capacitor, and the sixth resistor and the second capacitor are connected in parallel and grounded.

[0009] Further, the driving hysteresis locking circuit includes a first resistor, a second resistor, a first transistor, a third diode and a fifth resistor, the first transistor is a PNP transistor, one end of the first resistor is respectively connected to a power supply and an emitter of the first transistor, the base of the first transistor is respectively connected to the other end of the first resistor and one end of the second resistor, the collector of the first transistor is connected to the positive electrode of the third diode, the negative electrode of the third diode is connected to one end of the fifth resistor, and the other end of the fifth resistor is connected to the threshold driving circuit.

[0010] Furthermore, the controlled switching circuit includes a second transistor, which is an NPN transistor, a base of the second transistor is connected to the other end of the fifth resistor, a collector of the second transistor is connected to the other end of the second resistor, and an emitter of the second transistor is grounded.

[0011] Furthermore, the relay is enabled to shut down before it is energized, comprising a fourth resistor, a seventh resistor, a third capacitor, a fourth diode and a MOS tube, one end of the fourth resistor being respectively connected to one end of the seventh resistor, the positive electrode of the fourth diode, one end of the third capacitor and the gate of the MOS tube, the other end of the seventh resistor, the other end of the third capacitor and the source of the MOS tube being connected and then grounded, the cathode of the fourth diode being connected to the collector of the second triode, the drain of the MOS tube being connected to the controlled enable end of the integrated circuit chip, and the other end of the fourth resistor being connected to the power supply.

[0012] Furthermore, the relay enabling and coil discharging circuit includes a second diode and a relay, the anode of the second diode is respectively connected to the other end of the second resistor, the cathode of the fourth diode, the collector of the second transistor and the relay, and the cathode of the second diode is respectively connected to the other end of the fourth resistor and the power supply.

[0013] Beneficial effects of the utility model:

[0014] The utility model provides a circuit that can prevent control failure when the relay is turned on. Under the condition that the RC charging time constant remains unchanged, the solution of reducing capacitance and increasing resistance is adopted to ensure that the timing of the product will not change in the full operating temperature range. A driving hysteresis locking circuit is added to the controlled switch circuit to solve the frequent switching action of the controlled switch, increase the service life of the relay, improve the reliability of the product, and prevent the power circuit from being repeatedly started. At the same time, it improves the user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the specific implementation of the utility model or the technical solution in the prior art, the following is a brief introduction to the drawings required for the specific implementation or the prior art description. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, each element or part is not necessarily drawn according to the actual scale.

[0016] Figure 1 A principle block diagram of a circuit for preventing control failure when a relay is turned on, provided in the first embodiment of the utility model;

[0017] Figure 2 A circuit diagram of a circuit that can prevent control failure when a relay is turned on, provided in the first embodiment of the utility model. DETAILED DESCRIPTION

[0018] The following embodiments of the technical solution of the utility model are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the utility model, and are therefore only used as examples, and cannot be used to limit the protection scope of the utility model.

[0019] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by technicians in the field to which the utility model belongs.

[0020] Please refer to Figure 1-2 A first embodiment of the utility model provides a circuit that can prevent control failure when a relay is turned on, comprising: an RC charging and discharging circuit, a threshold driving circuit, a driving hysteresis locking circuit, a controlled switching circuit, a relay enabling and coil discharging circuit, and a relay enabling and shutting down circuit before the relay is energized. The RC charging and discharging circuit is respectively connected to the threshold driving circuit and the driving hysteresis locking circuit, and the controlled switching circuit is respectively connected to the threshold driving circuit, the driving hysteresis locking circuit, the relay enabling and coil discharging circuit, and the relay enabling and shutting down circuit before the relay is energized.

[0021] Among them, Vcc is the positive auxiliary power supply; GND is the negative auxiliary power supply; IC enable is the chip controlled enable terminal; NETA, NETB are the relay pull-in terminal interfaces. The RC charge and discharge circuit includes a diode VD1, a resistor R3 and a capacitor C1. One end of the resistor R3 is connected to the negative electrode of the diode VD1 and to the power supply Vcc, and the other end of the resistor R3 is connected to one end of the capacitor C1 and the positive electrode of the diode VD1 respectively, and the other end of the capacitor C1 is grounded. The resistor R3 and the capacitor determine the time constant, and the diode VD1 is used to discharge and reset the capacitor C1. When the RC charging time constant remains unchanged, we adopt the solution of reducing C and increasing R. And the capacitor C1 is changed to a smaller chip ceramic capacitor. In this way, its time constant will not change at high and low temperatures, ensuring that its timing will not change when the product is in the full operating temperature range. C2 is a bypass energy storage capacitor, R6 is a current limiting resistor, and VZ1 is a voltage regulator. Its voltage regulator value plus 0.7V is the threshold turn-on voltage.

[0022] The threshold driving circuit includes a voltage regulator tube VZ1, a resistor R6 and a capacitor C2. The cathode of the voltage regulator tube VZ1 is connected to the anode of the diode VD1. The anode of the voltage regulator tube VZ1 is connected to one end of the resistor R6 and the capacitor C2 respectively. The resistor R6 and the capacitor C2 are connected in parallel and then grounded.

[0023] Due to the design of a smaller C, the smaller ceramic capacitor has no ability to resist the collection voltage fluctuation caused by the power supply Vcc fluctuation at the moment the relay is turned on. Therefore, we must introduce a drive hysteresis locking circuit to completely solve this problem. In other words, the RC circuit here has only evolved into a timing circuit. Due to the weak driving ability and being easily affected by the power supply Vcc voltage fluctuation. Once the controlled transistor is turned on, the drive hysteresis locking circuit takes over the drive of the controlled transistor, improving the stability and reliability of the circuit.

[0024] The driving hysteresis locking circuit includes a resistor R1, a resistor R2, a transistor VT1, a diode VD3 and a resistor R5. The transistor VT1 is a PNP transistor. One end of the resistor R1 is connected to the power supply Vcc and the emitter of the transistor VT1 respectively. The base of the transistor VT1 is connected to the other end of the resistor R1 and one end of the resistor R2 respectively. The collector of the transistor VT1 is connected to the positive electrode of the diode VD3. The negative electrode of the diode VD3 is connected to one end of the resistor R5. The other end of the resistor R5 is connected to the positive electrode of the voltage regulator tube VZ1, one end of the resistor R6 and one end of the capacitor C2 respectively. The controlled switch circuit includes a second transistor VT2. The transistor VT2 is an NPN transistor. The base of the transistor VT2 is connected to the other end of the resistor R5. The collector of the transistor VT2 is connected to the other end of the resistor R2. The emitter of the transistor VT2 is grounded.

[0025] The enabling shutdown circuit before the relay is not attracted includes a resistor R4, a resistor R7, a capacitor C3, a diode VD4 and a MOS tube VM1. One end of the resistor R4 is respectively connected to one end of the resistor R7, the positive electrode of the diode VD4, one end of the capacitor C3 and the gate of the MOS tube. The other end of the resistor R7, the other end of the capacitor C3 and the source of the MOS tube VM1 are connected and then grounded. The cathode of the diode VD4 is connected to the collector of the transistor VT2. The drain of the MOS tube VM1 is connected to the controlled enabling end of the integrated circuit chip. The other end of the resistor R4 is connected to the power supply Vcc. C3 is a bypass capacitor. VD4 is a discharge diode. VM1 is a small signal MOS tube.

[0026] The relay enabling and coil discharging circuit includes a diode VD2 and a relay K1. The anode of the diode VD2 is connected to the power supply Vcc through the relay K1. The anode of the diode VD2 is also connected to the other end of the resistor R2, the cathode of the diode VD4 and the collector of the transistor VT2. The cathode of the diode VD2 is respectively connected to the power supply Vcc and the other end of the resistor R4.

[0027] Working principle of this circuit:

[0028] When the voltage on capacitor C1 exceeds the threshold turn-on voltage, transistor VT2 turns on. When transistor VT2 turns on, R1 and R2 divide the power supply Vcc voltage. R1 is set to make the Vbe of transistor VT1 greater than 0.7V, and transistor VT1 turns on. The power supply Vcc provides a turn-on current and Vbe greater than 0.7V to the Vbe of transistor VT2 through diodes VD3 and R5. So far, the drive hysteresis lock circuit has been turned on, and is not controlled by whether the voltage division signal provided by resistor R3 and capacitor C1 exists. Transistor VT2 is controlled by whether the voltage on capacitor C2 reaches the turn-on voltage, and turns on when the turn-on voltage is reached. Otherwise, it is closed. When transistor VT2 is turned on, the coil of relay K1 adds the power supply Vcc voltage, thereby driving the reed of the isolation circuit part to attract. Diode VD2 is a discharge circuit. When the voltage on C1 does not reach the threshold turn-on voltage, the power supply Vcc divides the voltage through resistors R4 and R7 to provide the turn-on voltage Vth to the MOS tube VM1. The MOS tube VM1 is turned on to control the enable terminal of the integrated circuit IC, so that the chip does not work and is passively pulled down. After the power supply Vcc is established, the resistor R3 charges the capacitor C1. When the preset time is reached, the transistor VT2 is turned on, and the voltage on the capacitor C3 is quickly pulled down by the diode VD4 and the transistor VT2. The MOS tube VM1 is turned off, and the IC enable signal is not pulled down, thereby achieving the purpose of delayed startup.

[0029] The circuit provided by the utility model that can prevent control failure when the relay is turned on is applied to the actual rail power supply series products. From the experimental results and data and low temperature test conditions, all test data meet expectations. The delayed start time is consistent at high and low temperatures, and the relay pull-in action does not produce repeated clicking sounds. This solution perfectly solves the problem of repeated pull-in of the original relay control circuit at the initial power-on and the temperature drift problem of high and low temperature start-up delay.

[0030] The utility model provides a circuit that can prevent control failure when the relay is turned on. The capacitor in the RC timing circuit uses a ceramic capacitor with a small temperature drift, which can solve the temperature drift problem of the start delay circuit. A drive hysteresis locking circuit is added to the controlled switch to solve the frequent switching action of the controlled switch. Thus, the system instability problem caused by the mutual influence of the timing circuit and the drive circuit can be separated. The circuit increases the service life of the relay, improves the reliability of the product, prevents the power circuit from starting repeatedly, and improves the user experience.

[0031] Here, it should be noted that the functions, algorithms, methods, etc. involved in the present utility model are merely conventional adaptive applications of the prior art. Therefore, the improvement of the prior art by the present utility model is essentially the connection relationship between the hardware, rather than the functions, algorithms, and methods themselves. That is, although the present utility model involves some functions, algorithms, and methods, it does not include improvements to the functions, algorithms, and methods themselves. The description of the functions, algorithms, and methods in the present utility model is for the purpose of better explaining the present utility model so as to better understand the present utility model.

[0032] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some or all of the technical features can be replaced by equivalents. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A circuit that can prevent control failure when a relay is turned on, characterized in that: include: An RC charging and discharging circuit, a threshold driving circuit, a driving hysteresis locking circuit, a controlled switching circuit, a relay enabling and coil discharging circuit, and a relay enabling and shutting-off circuit before the relay is energized. The RC charging and discharging circuit is respectively connected to the threshold driving circuit and the driving hysteresis locking circuit, and the controlled switching circuit is respectively connected to the threshold driving circuit, the driving hysteresis locking circuit, the relay enabling and coil discharging circuit, and the relay enabling and shutting-off circuit before the relay is energized.

2. The circuit according to claim 1, characterized in that The RC charge and discharge circuit includes a first diode, a third resistor and a first capacitor, one end of the third resistor is connected to the cathode of the first diode and to a power supply, the other end of the third resistor is respectively connected to one end of the first capacitor and the anode of the first diode, and the other end of the first capacitor is grounded.

3. The circuit according to claim 2, characterized in that The first capacitor is a ceramic capacitor.

4. The circuit according to claim 2 or 3, characterized in that The threshold driving circuit includes a first voltage regulator tube, a sixth resistor and a second capacitor. The cathode of the first voltage regulator tube is connected to the anode of the first diode. The anode of the first voltage regulator tube is respectively connected to one end of the sixth resistor and the second capacitor. The sixth resistor and the second capacitor are connected in parallel and grounded.

5. The circuit according to claim 2 or 3, characterized in that The driving hysteresis locking circuit includes a first resistor, a second resistor, a first transistor, a third diode and a fifth resistor, the first transistor is a PNP transistor, one end of the first resistor is respectively connected to a power supply and an emitter of the first transistor, the base of the first transistor is respectively connected to the other end of the first resistor and one end of the second resistor, the collector of the first transistor is connected to the positive electrode of the third diode, the negative electrode of the third diode is connected to one end of the fifth resistor, and the other end of the fifth resistor is connected to the threshold driving circuit.

6. The circuit according to claim 5, characterized in that The controlled switch circuit includes a second transistor, which is an NPN transistor. The base of the second transistor is connected to the other end of the fifth resistor, the collector of the second transistor is connected to the other end of the second resistor, and the emitter of the second transistor is grounded.

7. The circuit according to claim 6, characterized in that The relay is enabled before being energized and turned off circuit comprises a fourth resistor, a seventh resistor, a third capacitor, a fourth diode and a MOS tube, one end of the fourth resistor is respectively connected to one end of the seventh resistor, the positive electrode of the fourth diode, one end of the third capacitor and the gate of the MOS tube, the other end of the seventh resistor, the other end of the third capacitor and the source of the MOS tube are connected and then grounded, the cathode of the fourth diode is connected to the collector of the second triode, the drain of the MOS tube is connected to the controlled enable end of the integrated circuit chip, and the other end of the fourth resistor is connected to the power supply.

8. The circuit according to claim 7, characterized in that The relay enabling and coil discharging circuit includes a second diode and a relay, wherein the anode of the second diode is respectively connected to the other end of the second resistor, the cathode of the fourth diode, the collector of the second transistor and the relay, and the cathode of the second diode is respectively connected to the other end of the fourth resistor and the power supply.

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