Switching output circuit, circuit board assembly and electronic device

Abstract

The embodiments of the present application relate to the technical field of circuits, and propose a switching output circuit, a circuit board assembly, and an electronic device. The circuit includes a control circuit, a contact switch, a coil, a first overvoltage protection device, and a second overvoltage protection device, wherein a first side of the control circuit is connected to a first side of the coil, a second side of the control circuit is connected to a second side of the coil, a distributed capacitance exists between the contact switch and the coil, the control circuit controls the on / off of the contact switch by adjusting the magnetic field of the coil, the first side of the first overvoltage protection device is connected between the first side of the control circuit and the first side of the coil, the second side of the first overvoltage protection device is connected between the second side of the control circuit and the second side of the coil, the first side of the second overvoltage protection device is connected between the second side of the control circuit and the second side of the coil, and the second side of the second overvoltage protection device is connected to a protection ground.

Description

[Technical field]

[0001] This application is filed based on a Chinese patent application bearing application number "202011340211.1" and filed on November 25, 2020, and claims priority to that Chinese patent application, the entire text of which is incorporated herein by reference.

[0002] TECHNICAL FIELD The embodiments of the present application relate to the technical field of circuits, and more particularly to switching output circuits, circuit board assemblies, and electronic devices. [Background technology]

[0003] Conventionally, in the fields of communication, industrial control, power automation and the like, a switching quantity output interface is an electrical interface that realizes the interconnection, communication and control operation of equipment. However, in practice, since the switching quantity output interface operates in a complex electromagnetic environment, the switching quantity output interface may be impacted by a surge voltage caused by lightning strikes, operating overvoltage, etc. If no overvoltage protection device is added to the switching quantity output circuit connected to the switching quantity output interface and only the insulation performance of the device of the switching quantity output circuit itself is relied upon, the large surge voltage cannot be withstood, which may result in damage to the device of the switching quantity output circuit, loss of information, reset or malfunction. In order to respond to the impact of the surge voltage on the switching quantity output interface, an overvoltage protection device is added to each switching quantity output interface, so that the switching quantity output circuit has good surge protection capability.

[0004] However, the insulation of the switching output circuit is destroyed by the overvoltage protection device added to protect against the impact of the surge voltage, making it difficult for the switching output circuit to pass the withstand voltage test. That is, in the withstand voltage test, a high commercial power frequency or DC voltage is applied to the switching output circuit, and the commercial power frequency overvoltage that enters from the outside through the switching output cable causes damage due to overpowering of the overvoltage protection device, leading to failure of the withstand voltage test of the switching output circuit. In addition, for multi-circuit relays, an overvoltage protection device needs to be added for each contact, which increases the area occupied on the circuit board and increases the cost. Summary of the Invention [Means for solving the problem]

[0005] According to an embodiment of the present application, there is provided a switching quantity output circuit, the switching quantity output circuit including a control circuit, a contact switch, a coil, a first overvoltage protection device, and a second overvoltage protection device, a first side of the control circuit is connected to a first side of the coil, a second side of the control circuit is connected to a second side of the coil, a distributed capacitance exists between the contact switch and the coil, the control circuit controls the on / off of the contact switch by adjusting the magnetic field of the coil, one end of the contact switch is connected to a first terminal of a switching quantity output interface to which an external device is connected, and the other end is connected to a second terminal of the switching quantity output interface, the first side of the first overvoltage protection device is connected between the first side of the control circuit and the first side of the coil, the second side of the first overvoltage protection device is connected between the second side of the control circuit and the second side of the coil, the first side of the second overvoltage protection device is connected between the second side of the control circuit and the second side of the coil, and the second side of the second overvoltage protection device is connected to a protection ground. The rated voltage of the first overvoltage protection device is greater than the operating voltage of the switching quantity output circuit, and the rated voltage of the second overvoltage protection device is greater than the operating voltage of the switching quantity output circuit. In addition, a switching quantity output circuit according to another embodiment of the present application includes a control circuit, a contact switch, a coil, a first overvoltage protection device, and a second overvoltage protection device, a first side of the control circuit is connected to a first side of the coil, a second side of the control circuit is connected to a second side of the coil, a distributed capacitance exists between the contact switch and the coil, the control circuit controls the on / off of the contact switch by adjusting a magnetic field of the coil, one end of the contact switch is connected to a first terminal of a switching quantity output interface to which an external device is connected, and the other end of the contact switch is connected to a second terminal of the switching quantity output interface. a first side of the first overvoltage protection device connected between a first side of the control circuit and a first side of the coil, a second side of the first overvoltage protection device connected between a second side of the control circuit and a second side of the coil, a first side of the second overvoltage protection device connected between the second side of the control circuit and a second side of the coil, and a second side of the second overvoltage protection device connected to a protection ground, a rated voltage of the first overvoltage protection device is 1.2 times an operating voltage of the switching quantity output circuit, and a rated voltage of the second overvoltage protection device is 1.2 times an operating voltage of the switching quantity output circuit.

[0006] According to an embodiment of the present application, there is further provided a circuit board assembly including the switching quantity output circuit described above.

[0007] According to an embodiment of the present application, there is further provided an electronic device including the above-described circuit board assembly. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic diagram of a circuit configuration of a switching amount output circuit according to a first embodiment of the present application; [Diagram 2] FIG. 4 is a voltage waveform diagram on the contact switch side of the switching amount output circuit according to the first embodiment of the present application. [Diagram 3] FIG. 4 is a voltage waveform diagram on the coil side of the switching amount output circuit according to the first embodiment of the present application. [Figure 4] FIG. 4 is a voltage waveform diagram in a control circuit of the switching amount output circuit according to the first embodiment of the present application. [Diagram 5] FIG. 11 is a schematic diagram of a circuit configuration of a switching amount output circuit according to a second embodiment of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A main objective of the embodiments of the present application is to propose a switching quantity output circuit, a circuit board assembly, and an electronic device that reduce a surge voltage received by an overvoltage protection device in the switching quantity output circuit while improving the voltage withstand capability of the switching quantity output circuit.

[0010] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the embodiments of the present application will be described in detail below in combination with the accompanying drawings. However, those skilled in the art can understand that many technical details are presented in the embodiments of the present application to allow the reader to better understand the present application. However, the technical solution sought to be protected by the present application can be realized without these technical details and various changes and modifications based on the following embodiments. The division of the following embodiments is made for the convenience of explanation and should not be construed as any limitation on the specific embodiment of the present application, and the embodiments can be combined or referenced with each other as long as they are not inconsistent.

[0011] The first embodiment of the present application relates to a switching quantity output circuit. The switching quantity output circuit in this embodiment includes a control circuit 101, a contact switch S, a coil L, a first overvoltage protection device 102, and a second overvoltage protection device 103, as shown in FIG.

[0012] Specifically, the first side a of the control circuit 101 is connected to the first side g of the coil L, the second side b of the control circuit 101 is connected to the second side h of the coil L, there is a distributed capacitance between the contact switch S and the coil L, the control circuit 101 controls the on / off of the contact switch S by adjusting the magnetic field of the coil L, the first side c of the first overvoltage protection device 102 is connected between the first side a of the control circuit 101 and the first side g of the coil L, i.e., SW, the second side d of the first overvoltage protection device 102 is connected between the second side b of the control circuit 101 and the second side h of the coil L, i.e., the ground side GND of the switching quantity output circuit, the first side e of the second overvoltage protection device 103 is connected between the second side b of the control circuit 101 and the second side h of the coil L, the second side f of the second overvoltage protection device 103 is connected to the protection ground PGND, and both ends of the contact switch are respectively the switching quantity output interfaces out+, out- of the switching quantity output circuit.

[0013] In practical applications, the configuration consisting of the contact switch S and the coil L may be provided by a single relay, or may be provided by another device having the contact switch S and the coil L if the contact switch S and the coil L exist.

[0014] In one example, the control circuit 101 is a digital control circuit.

[0015] FIG. 2 shows a voltage waveform diagram at the switching quantity output interfaces out+, out- when a surge exists at the switching quantity output interfaces out+, out-, and FIG. 3 shows a voltage waveform diagram on the coil L side when a surge exists at the switching quantity output interfaces out+, out-. The surges existing at the switching quantity output interfaces out+, out- in FIG. 2 and FIG. 3 are the same.

[0016] From Fig. 2, we can see that the voltage at the switching output interfaces out+ and out- can reach up to 4KV. From Fig. 3, we can see that when the same surge exists at the switching output interfaces out+ and out-, the voltage at the coil L side is only up to 200V. That is, when the switching output interfaces out+ and out- are subjected to a surge, the surge voltage at the contact switch S side is large and the surge voltage at the coil L side is small.

[0017] Specifically, according to this embodiment, the first overvoltage protection device 102 and the second overvoltage protection device 103 are installed on the coil L side, so that there is a distributed capacitance with a certain insulating ability between the contact switch S and the coil L, and therefore it is possible to prevent the transmission of most of the surge from the contact switch S side to the coil L side. As a result, the surge voltage on the coil L side is significantly reduced, and when the switching output interface receives the same surge voltage, the overvoltage protection device of the present application receives a smaller surge voltage. In view of the fact that the overvoltage protection device receives a large surge voltage in the technical solution in which one overvoltage protection device is connected to each of the switching output interfaces out+ and out-, the first overvoltage protection device 102 and the second overvoltage protection device 103 of the present application are both installed on the coil L side and receive a smaller surge voltage, so that when the switching output interface receives the same surge voltage, the overvoltage protection device of the present application receives a smaller surge voltage, and the probability of the overvoltage protection device being damaged is reduced.

[0018] In practical application, when a surge exists in the switching output interfaces out+ and out-, first, the distributed capacitance between the contact switch S and the coil L prevents most of the surge from being transmitted from the contact switch S to the coil L. Then, a part of the surge reaches the first overvoltage protection device 102 and the second overvoltage protection device 103. Since the first side of the first overvoltage protection device 102 is connected to SW and the second side of the first overvoltage protection device 102 is connected to GND, the differential mode surge and the back electromotive force in the switching output circuit can be absorbed, and the first side of the second overvoltage protection device 103 is connected to GND and the second side of the second overvoltage protection device 103 is connected to the protection ground PGND, the surge of GND can be discharged to the protection ground PGND. When the surge voltage at SW exceeds the surge voltage at GND, the first overvoltage protection device 102 transmits the surge voltage at SW to GND, and releases the surge to the protection ground PGND via the second overvoltage protection device 103.

[0019] FIG. 4 shows the voltage waveform diagram of the control circuit of the switching output circuit of this embodiment, and the voltage of the switching output interface out+, out- is the same as FIG. 2 and FIG. 3. As can be seen, according to this embodiment, when the voltage of the switching output interface out+, out- reaches a maximum of 4KV, the voltage of the control circuit can be reduced to about 30V. Meanwhile, referring to FIG. 3, it can be seen that the voltage on the coil L side in FIG. 3 is the voltage of the control circuit by using a technical solution in which there is no overvoltage protection device between the coil L and the control circuit. In this way, the voltage in the control circuit of the present application is greatly reduced, so that the shock and destruction of the control circuit caused by the surge entering from the switching output interface out+, out- is avoided.

[0020] It should be noted that in the actual production and processing process, the switching quantity output circuit is subjected to a withstand voltage test. That is, in the withstand voltage test, a high commercial power frequency or DC voltage is applied to the switching quantity output circuit. Considering the technical solution of directly installing the overvoltage protection device on the switching quantity output interfaces out+, out-, the commercial power frequency overvoltage that enters from the outside through the switching quantity output cable will cause overpowering and damage to the overvoltage protection device, leading to failure of the withstand voltage test of the switching quantity output circuit. On the other hand, in this embodiment, if the switching quantity output interface receives the same test voltage, when the withstand voltage test is performed on the switching quantity output circuit in this embodiment, there is a distributed capacitance between the contact switch S and the coil L, and this distributed capacitance can prevent the voltage of the withstand voltage test from being transmitted to the first overvoltage protection device 102 and the second overvoltage protection device 103, so that the first overvoltage protection device 102 and the second overvoltage protection device 103 do not need to receive the test voltage, and the withstand voltage capability of the switching quantity output circuit is strong, that is, the pass rate of the withstand voltage test of the switching quantity output circuit is high.

[0021] In addition, in the technical proposal in which an overvoltage protection device, such as a varistor, is connected to each switching output interface of each contact switch in consideration of the possibility that the switching output circuit may have multiple contact switches, the overvoltage protection device is installed in each switching output interface of each contact switch, which not only increases the complexity and cost of the circuit, but also increases the volume of the circuit board equipped with the circuit. On the other hand, in the present application, the first overvoltage protection device 102 and the second overvoltage protection device 103 are only installed on the coil side, which ensures that the switching output circuit still has good surge prevention capability, while reducing the complexity of the switching output circuit, and reducing the volume and cost of the switching output circuit.

[0022] In this embodiment, the first overvoltage protection device 102 and the second overvoltage protection device 103 are installed on the coil L side, so that there is a distributed capacitance between the contact switch S and the coil L to insulate a large amount of surge, so that the surge reaching the coil L side is small, and when the surge voltage received by the switching quantity output interface is the same, the surge voltage received by the overvoltage protection device of the present application is smaller. When the withstand voltage test is performed on the switching quantity output circuit, the distributed capacitance exists between the contact switch S and the coil L, so that the voltage of the withstand voltage test is prevented from being transmitted to the first overvoltage protection device 102 and the second overvoltage protection device 103, so that the first overvoltage protection device 102 and the second overvoltage protection device 103 do not need to receive the test voltage, and when the rated voltage of the overvoltage protection device is the same, the withstand voltage capability of the switching quantity output circuit of the present application is higher.

[0023] In one example, the first overvoltage protection device 102 includes one of a transient diode, a rectifier diode, and an RC circuit.

[0024] In one example, the second overvoltage protection device 103 is one of a transient diode and a clamp diode.

[0025] In one example, the rated voltage of the first overvoltage protection device is higher than the operating voltage of the switching quantity output circuit, for example, 1.2 times, 1.3 times, 1.4 times. The rated voltage of the second overvoltage protection device is higher than the operating voltage of the switching quantity output circuit, for example, 1.2 times, 1.3 times, 1.4 times. By setting the rated voltage of the overvoltage protected device higher than the operating voltage of the switching quantity output circuit, the voltage at which the switching quantity output circuit normally operates in the absence of an overvoltage shock will not operate the overvoltage protection device, and the overvoltage protection device will not affect the operation of the switching quantity output circuit when the switching quantity output circuit is operating normally. In the event of a surge shock, when the voltage of the overvoltage protection device rises to the start-up voltage of the overvoltage protection device (this start-up voltage is a little higher than the rated voltage of the overvoltage protection device), the overvoltage protection device will turn on and operate to absorb the surge voltage, thereby achieving the purpose of protecting the control circuit. Therefore, in order to ensure that the overvoltage protection device operates only when a surge shock occurs, it is necessary to set the rated voltage of the overvoltage protection device higher than the voltage at which the switching quantity output circuit operates normally, and to ensure that the overvoltage protection device does not operate when the switching quantity output circuit is operating normally.

[0026] The second embodiment of the present application relates to a switching quantity output circuit. The second embodiment is almost the same as the first embodiment, but the main difference is that in the second embodiment of the present application, the first overvoltage protection device is a unidirectional transient diode, and the second overvoltage protection device is a bidirectional transient diode. Note that the details of each implementation of the first embodiment are also valid in this embodiment, so they will not be described here to reduce duplication.

[0027] The second embodiment of the present application relates to a switching quantity output circuit. As shown in Fig. 5, the switching quantity output circuit includes a control circuit 201, a contact switch S, a coil L, a unidirectional transient diode VD1, and a bidirectional transient diode VD2.

[0028] Specifically, the first side a of the control circuit 201 is connected to the first side g of the coil L, the second side b of the control circuit 201 is connected to the second side h of the coil L, there is a distributed capacitance between the contact switch S and the coil L, the control circuit 201 controls the on / off of the contact switch S by adjusting the magnetic field of the coil L, the first side c of the unidirectional transient diode VD1 is a cathode, which is connected between the first side a of the control circuit 201 and the first side g of the coil L, i.e., SW, the second side d of the unidirectional transient diode VD1 is an anode, which is connected between the second side b of the control circuit 101 and the second side h of the coil L, i.e., the ground side GND of the switching quantity output circuit, the first side e of the bidirectional transient diode VD2 is connected between the second side b of the control circuit 201 and the second side h of the coil L, the second side f of the bidirectional transient diode VD2 is connected to the protection ground PGND, and both ends of the contact switch are respectively the switching quantity output interfaces out+, out- of the switching quantity output circuit.

[0029] Specifically, when a surge at the switching output interfaces out+, out- is transmitted to the coil L side via the distributed capacitance between the contact switch S and the coil L, if the surge voltage at SW exceeds the surge voltage at GND, the unidirectional transient diode VD1 is destroyed by the surge, and the surge voltage at SW is transmitted to GND and discharged to the protection ground PGND via the second overvoltage protection device 103, and if the surge voltage at GND exceeds the surge voltage of SW, the bidirectional transient diode VD2 discharges the surge at GND to the protection ground PGND.

[0030] According to this embodiment, by installing a unidirectional transient diode as the first overvoltage protection device, not only is the speed of absorbing the back electromotive force and the differential mode improved, but also the cost of the unidirectional transient diode is lower than that of the bidirectional transient diode, so the cost of the switching output circuit can be saved. According to this embodiment, by installing a bidirectional transient diode as the second overvoltage protection device, the speed of absorbing the ground side surge voltage by the second overvoltage protection device is improved.

[0031] In one example, the rated voltage of the first overvoltage protection device is 1.2 times the operating voltage of the switching quantity output circuit, and the rated voltage of the second overvoltage protection device is 1.2 times the operating voltage of the switching quantity output circuit. Since the rated voltage parameter of the overvoltage protection device has a certain tolerance range, and the operating voltage of the switching quantity output circuit also has a fluctuation upper limit, in order to avoid the overvoltage protection device malfunctioning due to the fluctuation of its own tolerance range and the operating voltage of the switching quantity output circuit when there is no overvoltage shock caused by an external surge, the rated voltage of the overvoltage protection device must be higher than the operating voltage of the switching quantity output circuit. Therefore, considering the tolerance range of the rated voltage of the overvoltage protection device and the fact that the operating voltage of the switching quantity output circuit also has a fluctuation upper limit, in this embodiment, the rated voltage of the overvoltage protection device is set to 1.2 times the operating voltage of the switching quantity output circuit. By setting the rated voltage of the overvoltage protection device to this value, it is possible to avoid the malfunction problem of the overvoltage protection device when there is no overvoltage shock caused by an external surge.

[0032] A third embodiment of the present application relates to a circuit board assembly including the switching quantity output circuit of the first embodiment or the second embodiment described above.

[0033] According to this embodiment, by using the above-mentioned switching quantity output circuit, the surge voltage received by the overvoltage protection device in the circuit board assembly is reduced, while the voltage resistance of the circuit board assembly is improved.

[0034] A fourth embodiment of the present application relates to an electronic device including the circuit board assembly of the third embodiment described above.

[0035] According to this embodiment, by using the above-described circuit board assembly, the surge voltage received by the overvoltage protection device in the circuit board assembly of the electronic device is reduced, while the voltage withstand capability of the circuit board assembly of the electronic device is improved.

Claims

1. A switching amount output circuit, a control circuit, a contact switch, a coil, a first overvoltage protection device, and a second overvoltage protection device; a first side of the control circuit is connected to a first side of the coil, a second side of the control circuit is connected to a second side of the coil, a distributed capacitance exists between the contact switch and the coil, and the control circuit controls the on / off of the contact switch by adjusting a magnetic field of the coil; One end of the contact switch is connected to a first terminal of a switching output interface to which an external device is connected, and the other end is connected to a second terminal of the switching output interface; a first side of the first overvoltage protection device is connected between a first side of the control circuit and a first side of the coil, and a second side of the first overvoltage protection device is connected between a second side of the control circuit and a second side of the coil; a first side of the second overvoltage protection device is connected between a second side of the control circuit and a second side of the coil, and a second side of the second overvoltage protection device is connected to a protection ground; The rated voltage of the first overvoltage protection device is greater than the operating voltage of the switching quantity output circuit, and the rated voltage of the second overvoltage protection device is greater than the operating voltage of the switching quantity output circuit. Switching quantity output circuit.

2. A switching amount output circuit, a control circuit, a contact switch, a coil, a first overvoltage protection device, and a second overvoltage protection device; a first side of the control circuit is connected to a first side of the coil, a second side of the control circuit is connected to a second side of the coil, a distributed capacitance exists between the contact switch and the coil, and the control circuit controls the on / off of the contact switch by adjusting a magnetic field of the coil; One end of the contact switch is connected to a first terminal of a switching output interface to which an external device is connected, and the other end is connected to a second terminal of the switching output interface; a first side of the first overvoltage protection device is connected between a first side of the control circuit and a first side of the coil, and a second side of the first overvoltage protection device is connected between a second side of the control circuit and a second side of the coil; a first side of the second overvoltage protection device is connected between a second side of the control circuit and a second side of the coil, and a second side of the second overvoltage protection device is connected to a protection ground; The rated voltage of the first overvoltage protection device is 1.2 times the operating voltage of the switching output circuit, and the rated voltage of the second overvoltage protection device is 1.2 times the operating voltage of the switching output circuit. Switching quantity output circuit.

3. The first overvoltage protection device includes one of a transient diode, a clamp diode, a rectifier diode, and an RC circuit.

3. A switching amount output circuit according to claim 1 or 2.

4. The first overvoltage protection device is a unidirectional transient diode.

3. A switching amount output circuit according to claim 1 or 2.

5. The second overvoltage protection device is one of a transient diode and a clamp diode. A switching quantity output circuit according to any one of claims 1 to 4.

6. The second overvoltage protection device is a bidirectional transient diode. A switching quantity output circuit according to any one of claims 1 to 4.

7. The control circuit is a digital control circuit. A switching quantity output circuit according to any one of claims 1 to 6.

8. A switching amount output circuit according to any one of claims 1 to 7 is included. circuit board assembly.

9. The circuit board assembly according to claim 8 is included. electronic equipment.

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