Control circuit for reducing working loss of relay
By controlling the voltage switching of the relay coil using voltage divider resistors and MOSFETs, the problems of high relay coil loss and large space occupation of the control circuit are solved, achieving low loss and reliable engagement of the relay in high power density applications.
Patent Information
- Application Number
- CN202422915406.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-27
- Publication Date
- 2025-10-28
- Estimated Expiration
- 2034-11-27
AI Technical Summary
In existing technologies, relay coil losses are high, control circuits occupy a large space and consume controller resources, making it difficult to effectively reduce the temperature rise and losses of relays in high power density applications.
A voltage divider resistor and a MOSFET are used to connect the relay coil. The MOSFET is turned on and turned off with a delay by a control signal. Combined with the delay reduction of the relay coil voltage by the charging capacitor, the rated voltage and holding voltage of the relay are switched when it is energized.
Without increasing power supply and controller resources, this method reduces relay coil losses, ensures reliable relay activation, reduces temperature rise, and improves power density utilization efficiency.
Smart Images
Figure CN223486953U_ABST
Abstract
Description
Technical Field
[0001] This utility model generally relates to the field of relays. More specifically, this utility model relates to a control circuit for reducing the operating losses of a relay. Background Art
[0002] A relay is an electrical control device that causes a predetermined step change in the controlled variable in the electrical output circuit when the change in the input quantity (excitation quantity) reaches a specified requirement. It has an interactive relationship between the control system (also known as the input circuit) and the controlled system (also known as the output circuit). It is commonly used in automated control circuits, and is essentially an "automatic switch" that uses a small current to control a large current. It plays a role in automatic adjustment, safety protection, and circuit switching in circuits. The working principle of a relay is based on electromagnetic effects. A relay consists of an iron core, a coil, and contacts. When the coil is energized, the iron core becomes magnetic, attracting the armature and causing the contacts to actuate, thereby changing the state of the circuit. When the coil is de-energized, the magnetism disappears, the armature resets under the action of the spring, and the contacts return to their original state.
[0003] In power electronics applications, relays are essential components in pre-charge circuits, significantly reducing losses caused by pre-charge resistance to achieve high efficiency and high power density. Relay contacts have two states: open and closed. By setting up a relay control circuit to control the operation of the relay contacts, the operating state of the circuit can be controlled. It is clear from the specifications of commercially available relays that as the switching current increases, the relay coil power increases. In power electronic systems, the heating of the relay is not only caused by the contact resistance of the springs, but the power loss of the coil also becomes significant. Currently, relay control typically employs three methods.
[0004] like Figure 1 As shown, the first method involves directly connecting the input terminal of the relay K1 coil to the power supply voltage VDD, which is the rated voltage required by the relay specifications. The output terminal of the relay coil is grounded through the switching transistor Q5. The controlled terminal of the switching transistor Q5 is used to receive the control signal from the controller. The controller controls the switching transistor Q5 to energize or de-energize the relay coil, thereby controlling the relay contacts. However, with this control circuit, the relay coil will experience a temperature rise during normal operation due to the long-term flow of the voltage during the energization.
[0005] like Figure 2As shown, the second method involves connecting the input terminal of the relay K1 coil to the supply voltage VDD through a voltage divider resistor R1, and grounding the output terminal of the relay coil through a switching transistor Q5. The controlled terminal of the switching transistor Q5 is used to receive control signals from the controller. The series resistor R1 and the relay K1 coil form a series voltage divider circuit. The voltage of the relay is low both at the moment of closing and during the holding phase, which reduces the coil loss to a certain extent and thus reduces the temperature rise of the relay. However, to ensure reliable engagement of the relay K1, this resistor R1 should not be too large, otherwise the relay loss will not be optimal.
[0006] like Figure 3 As shown, the third method involves connecting the input terminal of the relay K1 coil to the first power supply voltage VDD1 via the fifth control switch S1 and to the second power supply voltage VDD2 via the sixth control switch S2. The output terminal of the relay K1 coil is grounded. The fifth control switch S1 is turned on or off under the drive of the controller control signal 1, and the sixth control switch S2 is turned on or off under the drive of the controller control signal 2. This method uses dual power supply. The voltage of VDD1 is the reliable operating voltage of the relay, i.e., the rated voltage of the relay, and the voltage of VDD2 is the holding voltage after the relay operates. Both require two control signals to control, which can minimize the loss of the relay coil. However, in high power density applications, dual power supply takes up a lot of space and is generally difficult to implement. At the same time, dual control signals also consume more controller resources. Utility Model Content
[0007] To address the technical problems of high relay coil losses, large space occupation of relay control circuits, and occupation of controller resources in the prior art, this utility model provides solutions in the following aspects.
[0008] In a first aspect, the present invention provides a control circuit for reducing relay operating losses, comprising:
[0009] The relay has one end of its coil connected to the power supply voltage through a voltage divider resistor and a MOSFET, and the other end of its coil grounded through a first control switch.
[0010] A first control switch, whose controlled end is connected to the control signal output end of the controller, is used to energize the relay coil when the control signal is high, and to de-energize the relay coil when the control signal is low.
[0011] A first control circuit, connected to the gate of the MOS transistor, is used to control the MOS transistor to turn on when the control signal is low.
[0012] The second control circuit is connected to the MOS transistor and is used to delay turning off the MOS transistor when the control signal is high.
[0013] Preferably, the MOSFET is a P-type MOSFET, and the first control circuit includes a second control switch and a third control switch. One end of the second control switch is connected to the gate of the MOSFET and connected to the power supply voltage through a first pull-up resistor, and the other end of the second control switch is grounded. One end of the third control switch is connected to the controlled terminal of the second control switch and connected to the power supply voltage through a second pull-up resistor, and the other end is grounded. Its controlled terminal is connected to the control signal output terminal of the controller.
[0014] Preferably, the second control circuit includes a charging capacitor connected in series between the gate and source of the P-type MOS transistor.
[0015] Preferably, the P-type MOS transistor is a YJQ3407A P-type MOS transistor.
[0016] Preferably, the charging capacitor is a 2.2uF 25V capacitor.
[0017] Preferably, the first control switch, the second control switch, and the third control switch are all transistors.
[0018] Preferably, the transistor is an MMBT4401 transistor.
[0019] The technical effect of this utility model is as follows: By adopting the control circuit of this utility model that reduces the working loss of the relay, the power supply voltage of the relay is the rated power supply voltage when it is energized, and the power supply voltage is reduced to the minimum holding voltage after the relay is reliably energized, so as to ensure the reliable energization of the relay and minimize the coil loss.
[0020] Furthermore, by employing the first control circuit of this utility model, the MOS transistor Q1 can be effectively turned on when the controller's control signal is low. Moreover, the first control circuit and the first control switch of this utility model are controlled by the same controller's control signal, eliminating the need for setting an additional controller signal.
[0021] Furthermore, by employing the second control circuit of this utility model, when the control signal of the controller is at a high level, the MOS transistor Q1 can be effectively controlled to turn off after a delay, thereby maintaining the voltage across the coil of relay K1 at the rated voltage for a certain period of time before reducing it to the holding voltage. Attached Figure Description
[0022] The above and other objects, features, and advantages of the present invention will become readily understood by reading the following detailed description of exemplary embodiments with reference to the accompanying drawings. In the drawings, several embodiments of the present invention are shown by way of example and not limitation, and like or corresponding reference numerals denote like or corresponding parts, wherein:
[0023] Figure 1 It is the first relay control circuit in the prior art;
[0024] Figure 2 This is the second type of relay control circuit in the prior art;
[0025] Figure 3 This is the third type of relay control circuit in the prior art;
[0026] Figure 4 This invention relates to the control circuit principle for reducing relay operating losses. Figure 1 ;
[0027] Figure 5 This invention relates to the control circuit principle for reducing relay operating losses. Figure 2 . DETAILED DESCRIPTION
[0028] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.
[0029] The specific embodiments of this utility model will now be described in detail with reference to the accompanying drawings.
[0030] Example of a control circuit to reduce relay operating losses:
[0031] like Figure 4As shown, the control circuit for reducing relay operating losses according to this utility model includes: a relay K1, one end of which is connected to the power supply voltage VDD1 through a voltage divider resistor R1 and a MOSFET Q1, and the other end of which is grounded through a first control switch Q2; the first control switch Q2, whose controlled end is connected to the control signal output terminal of the controller, is used to control the relay coil to be energized when the control signal is high, and to control the relay coil to be de-energized when the control signal is low; a first control circuit, connected to the gate of the MOSFET Q1, is used to control the MOSFET to be turned on when the control signal is low; and a second control circuit, connected to the MOSFET Q1, is used to delay the MOSFET to be turned off when the control signal is high.
[0032] A MOSFET, short for Metal-Oxide-Semiconductor Field-Effect Transistor, is a semiconductor device with special functions. It is a voltage-controlled device where current is controlled by changing the voltage. Its structure mainly consists of three electrodes: gate (G), drain (D), and source (S). The gate and source are insulated from each other; due to the presence of the SiO2 insulating layer, a capacitor exists between them. When the gate voltage VGS generates an electric field, it leads to the generation of a source-drain current. The MOSFET operates by utilizing the different conductivity characteristics of the diffusion current and electric field between the P-type region under the insulated gate and the source / drain in the vertical direction. The drain and source can only conduct when the voltage between the gate and source exceeds a certain value (called the threshold voltage). At this point, the gate voltage VGS determines the magnitude of the drain current; by controlling the magnitude of the gate voltage VGS, the magnitude of the drain current ID can be controlled.
[0033] There are two types of MOSFETs: P-type MOSFETs and N-type MOSFETs. The conduction condition for an N-type MOSFET is that the gate potential is higher than the source potential, and the difference between the two is greater than the turn-on voltage. The conduction condition for a P-type MOSFET is that the gate potential is lower than the source potential, and the difference between the two is greater than the turn-on voltage.
[0034] The working principle of the control circuit for reducing relay operating losses in this utility model is as follows: When the control signal of the controller is low, the first control circuit controls the MOS transistor Q1 to conduct. At this time, the power supply voltage VDD1 is directly applied to one pin of the K1 coil. Since the first control switch Q2 is in the off state, the coil of the relay K1 is in the de-energized state and will not be energized.
[0035] When the controller signal is high, the first control switch Q2 is turned on. At this time, the MOSFET Q1 is still in the on state. The supply voltage VDD1 is applied to the input terminal of the relay K1 coil through the MOSFET Q1. The output terminal of the relay K1 coil is grounded through the second control switch. The voltage across the relay K1 coil is VDD1, and the normally open contact of the relay K1 is effectively energized. Under the action of the second control circuit, after a certain delay, the MOSFET Q1 is turned off. The supply voltage VDD1 can only be applied to the input terminal of the relay K1 coil through the resistor R1. Since the resistor R1 has the effect of voltage division, the voltage at the input terminal of the relay K1 coil is less than VDD1. By selecting a resistor R1 with an appropriate resistance value, the voltage across the relay K1 coil can be reduced to the minimum holding voltage, thereby reducing the winding loss and achieving the purpose of reducing the temperature rise of the relay. Because after the first control switch Q2 is turned on, the voltage across the relay K1 coil is kept at the supply voltage VDD1 for a period of time before the voltage across the relay K1 coil is adjusted to the holding voltage, the reliable engagement of the relay is ensured and the engagement delay of the relay is avoided.
[0036] The control circuit of this utility model, which reduces the working loss of the relay, can achieve the following without adding an extra power supply or occupying the control resources of the controller: when the relay is energized, its power supply voltage is the rated power supply voltage, and after the relay is reliably energized, its power supply voltage is reduced to the minimum holding voltage. This ensures the reliable energization of the relay and minimizes the coil loss.
[0037] like Figure 5 As shown, in one embodiment, the MOSFET is a P-type MOSFET. The first control circuit includes a second control switch Q3 and a third control switch Q4. One end of the second control switch is connected to the gate of the MOSFET and connected to the power supply voltage VDD1 through a first pull-up resistor R2. The other end of the second control switch is grounded. One end of the third control switch Q4 is connected to the controlled terminal of the second control switch Q3 and connected to the power supply voltage through a second pull-up resistor R3. The other end of the third control switch Q4 is grounded. The controlled terminal of the third control switch Q4 is connected to the control signal output terminal of the controller.
[0038] The working principle of the first control circuit is as follows: When the control signal of the controller is low, the third control switch Q4 is turned off. The controlled terminal of the second control switch Q3 is connected to the power supply voltage VDD1 through the second pull-up resistor R3, which is at a high potential. The second control switch Q3 is turned on, thereby grounding the gate of the MOS transistor Q1. The source of the MOS transistor Q1 is connected to the power supply voltage VDD1 through the resistor R1, which is at a high potential. The gate-source voltage of the MOS transistor Q1 is negative, and the MOS transistor Q1 is turned on.
[0039] The first control circuit of this invention can effectively control the MOS transistor Q1 to turn on when the controller's control signal is low. Furthermore, the first control circuit and the first control switch of this invention are controlled by the same controller's control signal, eliminating the need for an additional controller signal.
[0040] In one embodiment, the second control circuit includes a charging capacitor C1 connected in series between the gate and source of the P-type MOS transistor.
[0041] The working principle of the second control circuit is as follows: when the control signal of the controller is high, the third control switch Q4 is turned on, the controlled terminal of the second control switch Q3 is grounded, the second control switch Q3 is turned off, the connection between the gate of MOS transistor Q1 and ground is broken, the supply voltage VDD1 charges the charging capacitor C1 through the first pull-up resistor R2, the gate potential of MOS transistor Q1 gradually increases, and when the voltage across the charging capacitor C1 is close to the supply voltage VDD1, the MOS transistor is turned off.
[0042] The second control circuit of this invention can effectively control the MOS transistor Q1 to turn off after a delay when the controller signal is high, so that the voltage across the coil of relay K1 is maintained at the rated voltage for a certain period of time before decreasing to the holding voltage.
[0043] In one embodiment, the P-type MOS transistor is a YJQ3407A P-type MOS transistor.
[0044] In one embodiment, the charging capacitor is a 2.2uF 25V capacitor.
[0045] In one embodiment, the first control switch, the second control switch, and the third control switch are all transistors.
[0046] In one embodiment, the transistor is a transistor of model MMBT4401.
[0047] In the foregoing description of this specification, unless otherwise expressly specified and limited, the terms "connected" or "linked" should be interpreted broadly. For example, the term "linked" can refer to a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; or it can refer to the internal communication of two components or the interaction between two components. Therefore, unless otherwise expressly limited in this specification, those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.
[0048] Furthermore, the terms "first" or "second," etc., used in this specification to refer to numbers or ordinal numbers are for descriptive purposes only and should not be construed as indicating, explicitly or implicitly, relative importance or specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this specification, "a plurality of" means at least two, such as two, three, or more, unless otherwise explicitly specified.
[0049] While this specification has shown and described various embodiments of the present invention, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Many modifications, alterations, and alternatives will occur to those skilled in the art without departing from the spirit and essence of the present invention. It should be understood that various alternatives to the embodiments of the present invention described herein may be employed in the practice of the present invention.
Claims
1. A control circuit for reducing relay operating losses, characterized in that, include: The relay has one end of its coil connected to the power supply voltage through a voltage divider resistor and a MOSFET, and the other end of its coil grounded through a first control switch. A first control switch, whose controlled end is connected to the control signal output end of the controller, is used to energize the relay coil when the control signal is high, and to de-energize the relay coil when the control signal is low. A first control circuit, connected to the gate of the MOS transistor, is used to control the MOS transistor to turn on when the control signal is low. The second control circuit is connected to the MOS transistor and is used to delay turning off the MOS transistor when the control signal is high.
2. The control circuit for reducing relay operating losses as described in claim 1, characterized in that, The MOSFET is a P-type MOSFET. The first control circuit includes a second control switch and a third control switch. One end of the second control switch is connected to the gate of the MOSFET and connected to the power supply voltage through a first pull-up resistor. The other end of the second control switch is grounded. One end of the third control switch is connected to the controlled terminal of the second control switch and connected to the power supply voltage through a second pull-up resistor. The other end of the third control switch is grounded. The controlled terminal of the third control switch is connected to the control signal output terminal of the controller.
3. The control circuit for reducing relay operating losses as described in claim 2, characterized in that, The second control circuit includes a charging capacitor connected in series between the gate and source of the P-type MOS transistor.
4. The control circuit for reducing relay operating losses as described in claim 2, characterized in that, The P-type MOSFET used is a YJQ3407A P-type MOSFET.
5. The control circuit for reducing relay operating losses as described in claim 3, characterized in that, The charging capacitor is a 2.2uF 25V capacitor.
6. The control circuit for reducing relay operating losses as described in any one of claims 2 to 5, characterized in that, The first control switch, the second control switch, and the third control switch all use transistors.
7. The control circuit for reducing relay operating losses as described in claim 6, characterized in that, The transistor used is a MMBT4401 transistor.