Coil driving circuit, control system of release and circuit breaker

Abstract

The utility model provides a coil driving circuit, a control system of a release and a circuit breaker. The coil driving circuit comprises a first operational amplifier, a first switching device, a first feedback regulation module and a second feedback regulation module. A first operational amplifier serves as a core, a first feedback regulation module and a second feedback regulation module respectively regulate first voltage output to a first input end of the first operational amplifier and second voltage output to a second input end of the first operational amplifier according to output of the first operational amplifier, and finally the first operational amplifier outputs PWM voltage to a first switching device. Therefore, the driving of the release is realized in a PWM driving mode. Firstly, the electrifying condition of the release can be influenced, the release is prevented from working for a long time, the heat productivity is reduced, the release is not easy to burn down, and the potential safety hazard is reduced; and secondly, the tripper with few turns and small equivalent resistance can be used for working, so that the cost of the tripper is reduced.

Description

Technical Field

[0001] This utility model relates to the field of circuit breaker technology, specifically to a coil drive circuit, a trip unit control system, and a circuit breaker. Background Technology

[0002] Circuit breakers, with the trip unit as their core, implement various electrical protection functions. Currently, most trip units on the market use a high-voltage direct-drive method, meaning the input voltage is directly connected to the trip unit after rectification. However, most existing undervoltage trip units have an input voltage of AC230V or AC380V, which is relatively high. Using the direct-drive method places stringent requirements on the trip unit, such as a high number of turns and a large equivalent resistance. Only under these conditions can it operate normally under prolonged high-voltage direct-drive conditions.

[0003] However, the existing solution has many drawbacks. First, there is the issue of heat generation. Since the trip unit needs to work for a long time, heat generation is inevitable. This long-term high-voltage operation generates a lot of heat. If there is no good heat dissipation method, the trip unit is prone to burnout, which poses a certain safety hazard. Second, there is the issue of cost. The trip unit has a large number of turns, which relatively increases the consumption of coil materials in the trip unit, resulting in increased costs. Utility Model Content

[0004] To address the shortcomings of existing technologies, this utility model provides a coil drive circuit, a trip unit control system, and a circuit breaker.

[0005] In one embodiment, the present invention provides a coil driving circuit, which includes a first operational amplifier, a first switching device, a first feedback adjustment module, and a second feedback adjustment module.

[0006] The first feedback regulation module includes a power supply terminal for connecting to a first operating voltage, a feedback terminal electrically connected to the output terminal of the first operational amplifier and the controlled terminal of the first switching device respectively, and an output terminal electrically connected to the first input terminal of the first operational amplifier.

[0007] The first and second access terminals of the first switching device are connected in series with the trip coil to control the current of the trip coil.

[0008] The second feedback adjustment module includes a feedback terminal electrically connected to the output terminal of the first operational amplifier and an output terminal electrically connected to the second input terminal of the first operational amplifier.

[0009] The first operational amplifier is used to output a PWM voltage to the first switching device through its output terminal based on the first voltage at its first input terminal and the second voltage at its second input terminal.

[0010] In one embodiment, the first feedback adjustment module includes a first voltage divider resistor, a second voltage divider resistor, and a third voltage divider resistor;

[0011] The first end of the first voltage divider resistor is used to connect to the first operating voltage. The second end of the first voltage divider resistor is electrically connected to the first end of the second voltage divider resistor, the first end of the third voltage divider resistor, and the non-inverting input terminal of the first operational amplifier. The second end of the second voltage divider resistor is used to ground. The second end of the third voltage divider resistor is electrically connected to the output terminal of the first operational amplifier and the controlled terminal of the first switching device.

[0012] In one embodiment, the first feedback adjustment module includes a first voltage divider resistor, a second voltage divider resistor, a third voltage divider resistor, and a second switching device.

[0013] The first end of the first voltage divider resistor and the first end of the third voltage divider resistor are respectively used to connect to the first working voltage. The second end of the first voltage divider resistor is electrically connected to the first end of the second voltage divider resistor, the first input terminal of the second switching device, and the non-inverting input terminal of the first operational amplifier. The second end of the second voltage divider resistor is used to ground. The second end of the third voltage divider resistor is electrically connected to the second input terminal of the second switching device. The controlled terminal of the second switching device is electrically connected to the output terminal of the first operational amplifier and the controlled terminal of the first switching device.

[0014] In one embodiment, the second feedback adjustment module includes a capacitor, a first charge-discharge resistor, and a second charge-discharge resistor;

[0015] The first end of the capacitor is electrically connected to the inverting input terminal of the first operational amplifier and the first end of the first charging and discharging resistor, respectively. The second end of the first charging and discharging resistor is electrically connected to the output terminal of the first operational amplifier, the controlled terminal of the first switching device, and the first end of the second charging and discharging resistor, respectively. The second end of the capacitor and the second end of the second charging and discharging resistor are respectively used for grounding.

[0016] In one embodiment, the second feedback regulation module further includes an isolation diode;

[0017] The cathode of the isolation diode is electrically connected to the second end of the first charge-discharge resistor and the first end of the second charge-discharge resistor, respectively, and the anode of the isolation diode is electrically connected to the output terminal of the first operational amplifier and the controlled terminal of the first switching device, respectively.

[0018] In one embodiment, the second feedback adjustment module includes a capacitor, a first charge-discharge resistor, and a second charge-discharge resistor;

[0019] The first end of the capacitor is electrically connected to the inverting input terminal of the first operational amplifier and the first end of the first charge-discharge resistor, respectively. The second end of the first charge-discharge resistor is electrically connected to the first input terminal of the first switching device and the first end of the second charge-discharge resistor, respectively. The second end of the capacitor and the second end of the second charge-discharge resistor are respectively used for grounding.

[0020] In one embodiment, the second feedback adjustment module further includes a clamping diode;

[0021] The anode of the clamping diode is electrically connected to the second terminal of the first charge / discharge resistor, the first terminal of the second charge / discharge resistor, and the first access terminal of the first switching device, respectively, and the cathode of the clamping diode is used for grounding.

[0022] Secondly, in one embodiment, the present invention provides a control system for a trip unit, wherein the controller of the trip unit includes an undervoltage control circuit and a coil drive circuit as described in any of the above embodiments.

[0023] The power supply terminal of the undervoltage control circuit is used to connect to the second operating voltage, the input terminal of the undervoltage control circuit is used to connect to the sampling voltage of the power supply, and the output terminal of the undervoltage control circuit is electrically connected to the power supply terminal of the first feedback adjustment module.

[0024] The undervoltage control circuit is used to output a first operating voltage to the first feedback adjustment module when the sampled voltage is greater than the preset voltage.

[0025] In one embodiment, the undervoltage control circuit includes a first Zener diode, a second operational amplifier, a fourth voltage divider resistor, and a PNP transistor.

[0026] The cathode of the first Zener diode is electrically connected to the non-inverting input of the second operational amplifier and the first end of the fourth voltage divider resistor, respectively, and is used to input the second operating voltage. The anode of the first Zener diode is used to ground. The inverting input of the second operational amplifier is used to input the sampling voltage. The second end of the fourth voltage divider resistor is electrically connected to the output of the second operational amplifier and the base of the PNP transistor, respectively. The emitter of the PNP transistor is used to input the second operating voltage. The collector of the PNP transistor is electrically connected to the power supply terminal of the first feedback adjustment module.

[0027] In one embodiment, the control system of the trip unit further includes a power supply circuit and a sampling circuit;

[0028] The input terminals of the power supply circuit and the sampling circuit are used to connect to the power supply voltage. The output terminal of the power supply circuit is electrically connected to the power supply terminal of the undervoltage control circuit, and the output terminal of the sampling circuit is electrically connected to the input terminal of the undervoltage control circuit.

[0029] In one embodiment, the power supply circuit includes an NPN transistor and a second Zener diode;

[0030] The collector of the NPN transistor, the base of the NPN transistor, and the cathode of the second Zener diode are used to connect to the power supply voltage, respectively. The emitter of the NPN transistor is electrically connected to the power supply terminal of the undervoltage control circuit, and the anode of the second Zener diode is used to ground.

[0031] In one embodiment, the sampling circuit includes a fifth voltage divider resistor and a sixth voltage divider resistor;

[0032] The first end of the fifth voltage divider resistor is used to connect to the power supply voltage. The second end of the fifth voltage divider resistor is electrically connected to the first end of the sixth voltage divider resistor and the input terminal of the undervoltage control circuit. The second end of the sixth voltage divider resistor is used to ground.

[0033] Thirdly, in one embodiment, the present invention provides a circuit breaker including a trip unit and a control system for the trip unit in any of the above embodiments.

[0034] Through the aforementioned coil drive circuit, trip unit control system, and circuit breaker, a first operational amplifier, a first feedback adjustment module, and a second feedback adjustment module are configured. With the first operational amplifier as the core, the first and second feedback adjustment modules adjust the first voltage output to the first input terminal and the second voltage output to the second input terminal of the first operational amplifier, respectively, based on the output of the first operational amplifier. Ultimately, the first operational amplifier outputs a PWM voltage to the first switching device, thereby driving the trip unit through PWM drive. Firstly, this can affect the power supply of the trip unit, preventing it from working for a long time, reducing heat generation, and making it less likely to burn out, thus reducing safety hazards. Secondly, it allows the use of trip units with fewer turns and lower equivalent resistance, reducing the cost of the trip unit. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the coil driving circuit in one embodiment of the present invention;

[0037] Figure 2 This is a schematic diagram of the specific circuit implementation of the coil driving circuit in one embodiment of the present invention;

[0038] Figure 3 This is a schematic diagram of the specific circuit implementation of the first feedback adjustment module in another embodiment of the present invention;

[0039] Figure 4 This is a schematic diagram of the specific circuit implementation of the second feedback adjustment module in another embodiment of the present invention;

[0040] Figure 5 This is a schematic diagram of the control system of the trip unit in one embodiment of the present invention;

[0041] Figure 6 This is a schematic diagram of the specific circuit implementation of the undervoltage control circuit in one embodiment of the present invention;

[0042] Figure 7 This is a schematic diagram of the control system of the trip unit including a power supply circuit and a sampling circuit in one embodiment of the present invention;

[0043] Figure 8 This is a schematic diagram of the specific circuit implementation of the power supply circuit in one embodiment of the present invention;

[0044] Figure 9 This is a schematic diagram of the specific circuit implementation of the sampling circuit in one embodiment of the present invention;

[0045] Figure 10 This is a schematic diagram of the control system of a trip unit including a rectifier and filter circuit in one embodiment of the present invention;

[0046] Figure 11 This is a schematic diagram of the specific circuit implementation of the rectifier and filter circuit in one embodiment of the present invention. Detailed Implementation

[0047] 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, and 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.

[0048] In the description of this utility model, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified. In this application, the term "exemplary" is used to mean "used as an example, illustration, or description." Any embodiment described as "exemplary" in this application is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is provided to enable any person skilled in the art to implement and use this utility model. In the following description, details are set forth for illustrative purposes. It should be understood that those skilled in the art will recognize that this utility model can be implemented without using these specific details. In other instances, well-known structures and processes will not be described in detail to avoid unnecessary detail that would obscure the description of this utility model. Therefore, this utility model is not intended to be limited to the embodiments shown, but is consistent with the broadest scope of the principles and features disclosed in this application.

[0049] Firstly, such as Figure 1 As shown, in one embodiment, the present invention provides a coil driving circuit, the coil driving circuit including a first operational amplifier U501, a first switching device (such as...) Figure 1 The MOS transistor Q501, the first feedback regulation module, and the second feedback regulation module are included.

[0050] In other embodiments, other switches besides MOSFETs can be used as the first switching device, such as transistors, IGBTs, etc.

[0051] exist Figure 1 In the first feedback adjustment module, the power supply terminal is used to connect to the first operating voltage VCC_2. The feedback terminal of the first feedback adjustment module is electrically connected to the output terminal of the first operational amplifier U501 and the gate of the MOS transistor Q501, respectively, so as to connect to the target voltage UoB output by the first operational amplifier U501. The output terminal of the first feedback adjustment module is electrically connected to the first input terminal of the first operational amplifier U501, so as to output the first voltage UpB to the first operational amplifier U501.

[0052] The first feedback adjustment module can adjust the first voltage UpB output to the first operational amplifier U501 according to the target voltage UoB output by the first operational amplifier U501.

[0053] exist Figure 1 In this circuit, the drain and source of MOSFET Q501 are connected in series with the trip coil connected to terminal P2 to control the current of the trip coil.

[0054] In this circuit, the first terminal of P2 is used to connect the power supply voltage DC+, and the second terminal of P2 is used to connect to the drain of MOSFET Q501. The source of MOSFET Q501 is grounded. When MOSFET Q501 is in the ON state, the connected power supply voltage DC+ can pass through the trip coil connected to terminal P2 and MOSFET Q501 to ground, forming a current loop, and the trip coil is energized and works normally. Similarly, when MOSFET Q501 is in the OFF state, the connected power supply voltage DC+ cannot pass through the trip coil connected to terminal P2 and MOSFET Q501 to ground, and a current loop cannot be formed, and the trip coil is de-energized and stops working.

[0055] exist Figure 1 In the second feedback adjustment module, the feedback terminal is electrically connected to the output terminal of the first operational amplifier U501 to receive the target voltage UoB output by the first operational amplifier U501. The output terminal of the second feedback adjustment module is electrically connected to the second input terminal of the first operational amplifier U501 to output the second voltage UnB to the first operational amplifier U501.

[0056] The second feedback adjustment module can adjust the second voltage UnB output to the first operational amplifier U501 according to the target voltage UoB output by the first operational amplifier U501.

[0057] The first operational amplifier U501 is used to output a PWM voltage, such as the target voltage UoB, to the MOSFET Q501 through its output terminal based on the first voltage UpB at its first input terminal and the second voltage UnB at its second input terminal.

[0058] The target voltage UoB output by the first operational amplifier U501 can cause the first feedback adjustment module and the second feedback adjustment module to perform corresponding voltage adjustments, thereby changing the relationship between the first voltage UpB and the second voltage UnB after adjustment. This, in turn, changes the target voltage UoB output by the first operational amplifier U501, thus achieving a cycle and making the target voltage UoB output by the first operational amplifier U501 in the form of a PWM wave.

[0059] Specifically, when the target voltage UoB is high, the relationship between the first voltage UpB and the second voltage UnB changes from the first voltage UpB being greater than the second voltage UnB to the second voltage UnB being greater than the first voltage UpB, thus causing the target voltage UoB to switch to a low level; when the target voltage UoB is low, the relationship between the first voltage UpB and the second voltage UnB changes from the second voltage UnB being greater than the first voltage UpB to the first voltage UpB being greater than the second voltage UnB, thus causing the target voltage UoB to switch to a high level; this cycle repeats until the output target voltage UoB is a PWM wave.

[0060] When the target voltage UoB used to drive the MOSFET Q501 is a PWM wave, it can be turned on and off according to the corresponding duty cycle, thereby controlling the current on the trip coil in a PWM manner.

[0061] The above-described coil drive circuit includes a first operational amplifier, a first feedback adjustment module, and a second feedback adjustment module. With the first operational amplifier as the core, the first and second feedback adjustment modules adjust the first voltage output to the first input terminal and the second voltage output to the second input terminal of the first operational amplifier, respectively, based on the output of the first operational amplifier. This ultimately causes the first operational amplifier to output a PWM voltage to the first switching device, thereby driving the trip unit through PWM. Firstly, this affects the power supply of the trip unit, preventing it from operating for extended periods, reducing heat generation, and minimizing the risk of burnout, thus reducing safety hazards. Secondly, it allows the use of trip units with fewer turns and lower equivalent resistance, reducing the cost of the trip unit.

[0062] like Figure 2As shown, in one embodiment, the first feedback adjustment module includes a first voltage divider resistor R501, a second voltage divider resistor R502, and a third voltage divider resistor R503; the second feedback adjustment module includes a capacitor C502, a first charge-discharge resistor R504, and a second charge-discharge resistor R505.

[0063] In this configuration, the first terminal of the first voltage divider resistor R501 is connected to the first operating voltage VCC_2. The second terminal of the first voltage divider resistor R501 is electrically connected to the first terminals of the second voltage divider resistor R502, the third voltage divider resistor R503, and the non-inverting input terminal of the first operational amplifier U501. The second terminal of the second voltage divider resistor R502 is grounded. The second terminal of the third voltage divider resistor R503 is electrically connected to the output terminal of the first operational amplifier U501 and the gate of the MOSFET Q501. Similarly, the first terminal of the capacitor C502 is electrically connected to the inverting input terminal of the first operational amplifier U501 and the first terminal of the first charge / discharge resistor R504. The second terminal of the first charge / discharge resistor R504 is electrically connected to the output terminal of the first operational amplifier U501, the gate of the MOSFET Q501, and the first terminal of the second charge / discharge resistor R505. The second terminals of the capacitor C502 and the second terminals of the second charge / discharge resistor R505 are grounded.

[0064] It should be noted that the "first input terminal of the first operational amplifier U501" and "second input terminal of the first operational amplifier U501" mentioned in the above embodiments are general descriptions, while the "non-inverting input terminal of the first operational amplifier U501" and "inverting input terminal of the first operational amplifier U501" in this embodiment are specific descriptions under specific limiting scenarios.

[0065] Before the circuit is powered on, the target voltage UoB is at a low level (e.g., Figure 2 The first voltage UpB is higher than the second voltage UnB, so the target voltage UoB output by the first op-amp U501 is switched to a high level (e.g., GND in the circuit). Therefore, the second voltage UnB is low. When the circuit is powered on, the first voltage UpB increases, and since UpB is greater than UnB, the target voltage UoB output by the first op-amp U501 switches to a high level (e.g., GND in the circuit). Figure 2 The first operating voltage VCC_2 is used to charge capacitor C502 through isolation diode D502 and first charging / discharging resistor R504, causing the second voltage UnB to slowly increase. When the second voltage UnB is greater than the first voltage UpB, the target voltage UoB output by the first operational amplifier U501 switches to a low level, and the first voltage UpB suddenly decreases. The capacitor C502 is then discharged through the first charging / discharging resistor R504 and the second charging / discharging resistor R505, causing the second voltage UnB to gradually decrease. When the second voltage UnB is less than the first voltage UpB, the target voltage UoB output by the first operational amplifier U501 switches to a high level, and the first voltage UpB suddenly increases. The capacitor C502 begins to charge, and the entire circuit starts a new cycle. This process repeats to generate the PWM wave.

[0066] Without the isolation diode D502, during the discharge of capacitor C502, a portion of the current will flow to the first operational amplifier U501. This causes the output voltage of the first operational amplifier U501 to gradually decrease from a high level to a low level instead of abruptly changing from high to low, thus affecting the voltage at the non-inverting input of the first operational amplifier U501, and resulting in an output that does not meet expectations. With the isolation diode D502 installed, current is prevented from flowing into the first operational amplifier U501 during the discharge of capacitor C502, while the charging process of capacitor C502 is not affected, ensuring the integrity of the output signal.

[0067] The first voltage UpB depends on the applied first operating voltage VCC_2, the target voltage UoB, the first voltage divider resistor R501, the second voltage divider resistor R502, and the third voltage divider resistor R503. Since only the target voltage UoB is variable, a change in the target voltage UoB will cause a change in the first voltage UpB. The relationship between the first voltage UpB and the target voltage UoB can be expressed as follows:

[0068]

[0069] The target voltage UoB can control the capacitor C502 to be in a charging or discharging state, thereby controlling the change of the second voltage UnB.

[0070] From the above analysis, it can be seen that to achieve the target voltage UoB as a PWM wave, the following two points need to be controlled:

[0071] (1) The change of the target voltage UoB output by the first operational amplifier U501 can cause the change of the first voltage UpB, and the first voltage UpB when the target voltage UoB is the first working voltage VCC_2 needs to be greater than the first voltage UpB when the target voltage UoB is GND.

[0072] (2) The change of the target voltage UoB output by the first operational amplifier U501 can cause the change of the second voltage UnB. Specifically, the change of the target voltage UoB output by the first operational amplifier U501 can cause the change of the charging and discharging state of the capacitor C502. When the target voltage UoB is the first working voltage VCC_2, the capacitor C502 is in the charging state, and when the target voltage UoB is GND, the capacitor C502 is in the discharging state.

[0073] Regarding the first point above, besides using the specific circuit structure of the first feedback adjustment module mentioned in the above embodiments, other specific circuit structures can also be used. For example... Figure 3 As shown, in one embodiment, the first feedback adjustment module includes a first voltage divider resistor R501, a second voltage divider resistor R502, a third voltage divider resistor R503, and a second switching device (such as...). Figure 3(MOSFET Q502 in the middle).

[0074] Specifically, the first end of the first voltage divider resistor R501 and the first end of the third voltage divider resistor R503 are used to connect to the first working voltage VCC_2. The second end of the first voltage divider resistor R501 is electrically connected to the first end of the second voltage divider resistor R502, the source of the MOSFET Q502, and the non-inverting input of the first operational amplifier U501. The second end of the second voltage divider resistor R502 is used to ground. The second end of the third voltage divider resistor R503 is electrically connected to the drain of the MOSFET Q502. The gate of the MOSFET Q502 is electrically connected to the output of the first operational amplifier U501 and the gate of the MOSFET Q501.

[0075] Before the circuit is powered on, the target voltage UoB output by the first operational amplifier U501 is GND, the MOSFET Q502 is off, and the first voltage UpB is low. At the instant the circuit is powered on, the first voltage UpB suddenly increases, becoming greater than the second voltage UnB. The target voltage UoB output by the first operational amplifier U501 then suddenly becomes the first operating voltage VCC_2. The MOSFET Q502 is turned on, the capacitor C502 charges, and the second voltage UnB gradually increases. Due to the conduction of the MOSFET Q502, the first voltage UpB increases slightly. When the second voltage UnB is greater than the first voltage UpB, the target voltage UoB output by the first operational amplifier U501 suddenly changes to GND, the MOSFET Q502 is in the off state, the capacitor C502 discharges, the second voltage UnB gradually decreases, and the first voltage UpB decreases by a portion. When the second voltage UnB is less than the first voltage UpB, the target voltage UoB output by the first operational amplifier U501 suddenly changes to the first operating voltage VCC_2, the capacitor C502 charges, and the entire circuit begins a new cycle, repeating in this way.

[0076] The relationship between the first voltage UpB and the target voltage UoB can be expressed as follows:

[0077]

[0078] Regarding the second point above, besides using the specific circuit structure of the second feedback adjustment module mentioned in the above embodiments, other specific circuit structures can also be used. For example... Figure 4 As shown, in one embodiment, the second feedback adjustment module includes a capacitor C502, a first charge / discharge resistor R504, and a second charge / discharge resistor R505.

[0079] The first end of capacitor C502 is electrically connected to the inverting input terminal of the first operational amplifier U501 and the first end of the first charge-discharge resistor R504, respectively. The second end of the first charge-discharge resistor R504 is electrically connected to the source of MOSFET Q501 and the first end of the second charge-discharge resistor R505, respectively. The second end of capacitor C502 and the second end of the second charge-discharge resistor R505 are respectively used for grounding.

[0080] Before the circuit is powered on, the target voltage UoB is GND, so the second voltage UnB is low. When the circuit is powered on, the first voltage UpB increases, and since UpB is greater than the second voltage UnB, the target voltage UoB output by the first operational amplifier U501 abruptly changes to the first operating voltage VCC_2. The MOSFET Q501 is in the conducting state, charging capacitor C502 through the connected power supply voltage DC+, the trip coil connected to terminal P2, the MOSFET Q501, and the first charging / discharging resistor R504. The second voltage UnB then slowly increases. When the voltage UnB is greater than the first voltage UpB, the target voltage UoB output by the first operational amplifier U501 is converted to GND, the first voltage UpB suddenly decreases, and capacitor C502 is discharged through the first charging and discharging resistor R504 and the second charging and discharging resistor R505. The second voltage UnB begins to gradually decrease. When the second voltage UnB is less than the first voltage UpB, the target voltage UoB output by the first operational amplifier U501 is converted to a high level, the first voltage UpB suddenly increases, capacitor C502 begins to charge, and the entire circuit begins a new cycle. This process repeats to complete the generation of the PWM wave.

[0081] In this embodiment, capacitor C502 is charged based on the power supply voltage DC+ and requires a trip coil to form a circuit. Therefore, when the trip coil is not connected or is disconnected due to a fault, capacitor 502 will not be able to charge, so the second voltage UnB will always be at a low level, and thus the first operational amplifier U501 will not be able to output the target voltage UoB in the form of a PWM wave.

[0082] like Figure 4 As shown, in one embodiment, the second feedback adjustment module further includes a clamping diode D503.

[0083] The anode of the clamping diode D503 is electrically connected to the second terminal of the first charge / discharge resistor R504, the first terminal of the second charge / discharge resistor R505, and the source of the MOSFET Q501, respectively, and the cathode of the clamping diode D503 is used for grounding.

[0084] Among them, due to Figure 4The circuit is charged by the DC+ power supply voltage and the trip coil. The current in this circuit is large, which can easily damage the second charge-discharge resistor R505. The added clamping diode D503 can clamp the voltage across the second charge-discharge resistor R505 to a smaller value, thereby protecting the second charge-discharge resistor R505.

[0085] It should be noted that the charging time of capacitor C502 is the duration of the high-level signal output of the PWM signal, and the discharging time of capacitor C502 is the duration of the low-level signal output of the PWM signal. Figure 4 Taking the specific circuit structure shown as an example, the time constant τ of capacitor C502 has different values ​​during the charging and discharging process, as shown below:

[0086] τ ′ =R504*C502 Charging process

[0087] τ ′′ =(R504+R505)*C502 Discharge process

[0088] Under normal circumstances, the charging and discharging formula for capacitor C502 is:

[0089] Charging process

[0090] Discharge process

[0091] Where Vt is the voltage value at any moment during the charging / discharging process, Vo is the initial voltage during the charging / discharging process, and Vu is the power supply voltage value for charging capacitor C502 during the charging process, represented by Uf in the schematic diagram, which is the forward voltage drop of clamping diode D503. Figure 4 It can be seen that when the voltage of capacitor C502 is charged to a value greater than Up′B, the output of the first operational amplifier U501 reverses, and capacitor C502 begins to discharge. When the voltage of capacitor C502 is discharged to a value less than Up″B, the output of the first operational amplifier U501 reverses, and capacitor C502 begins to charge. Therefore, the target values ​​of capacitor C502 during the charging and discharging process are Up′B and Up″B, respectively. The charging and discharging time of capacitor C502 can be calculated by the formula shown below:

[0092] Charging time

[0093] Discharge time

[0094] When the first op-amp U501 is working normally, the frequency and duty cycle of the output PWM wave can be expressed by the following formulas:

[0095] frequency

[0096] Duty cycle

[0097] From the formula for the charging and discharging time constant τ of capacitor C502, it can be seen that when the resistance of resistor R504 is much larger than the resistance of resistor R505, the time constant τ of the charging and discharging process of capacitor C502 is approximately equal, that is, τ ′ ≈τ ′′ Therefore, the formula for frequency and duty cycle can be adjusted as follows:

[0098] Frequency, where Duty cycle, of which

[0099] As the formula shows, theoretically, the duty cycle is unrelated to the time constant τ. Therefore, when adjusting the frequency and duty cycle of the PWM wave, the duty cycle should be determined first. Determining the duty cycle only requires adjusting the parameters of four components: clamping diode D503, first voltage divider resistor R501, second voltage divider resistor R502, and third voltage divider resistor R503. After determining the duty cycle, the time constant τ can then be adjusted, i.e., by adjusting the parameters of the first charge / discharge resistor R504 and capacitor C502, to determine the frequency.

[0100] Secondly, such as Figure 5 As shown, in one embodiment, the present invention provides a control system for a trip unit, the controller of which includes an undervoltage control circuit and a coil drive circuit as described in any of the above embodiments.

[0101] The power supply terminal of the undervoltage control circuit is used to connect to the second working voltage VCC, the input terminal of the undervoltage control circuit is used to connect to the sampling voltage UnA of the power supply, and the output terminal of the undervoltage control circuit is electrically connected to the power supply terminal of the first feedback adjustment module to output the first working voltage VCC_2.

[0102] The undervoltage control circuit is used to output the first operating voltage VCC_2 to the first feedback adjustment module when the sampled voltage UnA is greater than the preset voltage.

[0103] Undervoltage protection is an important protection mechanism in circuit breakers. When undervoltage occurs, the power supply to the trip coil must be cut off, thereby disconnecting the power supply to the downstream load. In this embodiment, when the sampled voltage is greater than the preset voltage, it can be determined that the power supply is not undervoltage, and thus the first operating voltage VCC_2 can be output to the first feedback adjustment module in the coil drive circuit; conversely, when the sampled voltage is less than the preset voltage, it can be determined that the power supply is undervoltage, and thus the first operating voltage VCC_2 cannot be output to the first feedback adjustment module in the coil drive circuit.

[0104] The control system of the aforementioned trip unit includes a first operational amplifier, a first feedback adjustment module, and a second feedback adjustment module. With the first operational amplifier as the core, the first and second feedback adjustment modules adjust the first voltage output to the first input terminal and the second voltage output to the second input terminal of the first operational amplifier, respectively, based on the output of the first operational amplifier. Ultimately, this causes the first operational amplifier to output a PWM voltage to the first switching device, thereby driving the trip unit through PWM. Firstly, this affects the power supply of the trip unit, preventing it from operating for extended periods, reducing heat generation, and minimizing the risk of burnout, thus reducing safety hazards. Secondly, it allows the use of trip units with fewer turns and lower equivalent resistance, reducing the cost of the trip unit.

[0105] like Figure 6 As shown, in one embodiment, the undervoltage control circuit includes a first Zener diode ZD401, a second operational amplifier U401, a fourth voltage divider resistor R403, and a PNP transistor Q401.

[0106] In this configuration, the cathode of the first Zener diode is electrically connected to the non-inverting input of the second operational amplifier and the first end of the fourth voltage divider resistor via resistor R402, and is also used to connect to the second operating voltage VCC via resistor R401. The anode of the first Zener diode ZD401 is grounded. The inverting input of the second operational amplifier U401 is used to connect to the sampling voltage UnA. The second end of the fourth voltage divider resistor R403 is electrically connected to the output of the second operational amplifier U401 and the base of the PNP transistor Q401. The emitter of the PNP transistor Q401 is used to connect to the second operating voltage VCC. The collector of the PNP transistor Q401 is electrically connected to the power supply terminal of the first feedback adjustment module to output the first operating voltage VCC_2.

[0107] Specifically, when the sampling voltage UnA gradually increases to a level greater than the reference voltage UpA connected to the non-inverting input of the second operational amplifier U401, the output state of the second operational amplifier U401 reverses. That is, the output voltage UoA of the second operational amplifier U401 changes abruptly from the second operating voltage VCC to GND, causing the reference voltage UpA to decrease. Only when the sampling voltage UnA is lower than the reference voltage UpA at this time will the output of the second operational amplifier U401 reverse again. After the reversal, the reference voltage UpA will increase with the sudden change in the output voltage UoA. Only when the sampling voltage UnA is higher than the reference voltage UpA at this time will the second operational amplifier U401 reverse again. A PNP transistor Q401 is connected to the output of the second operational amplifier U401. When the output voltage UoA of the second operational amplifier U401 is the second operating voltage VCC, the PNP transistor Q401 is in the off state, and the first operating voltage VCC_2 is de-energized. When the output voltage UoA of the second operational amplifier U401 is GND, the PNP transistor Q401 is in the on state, and the first operating voltage VCC_2 is energized. The first operating voltage VCC_2 is the power supply for the subsequent coil drive circuit. If it is de-energized, the subsequent coil drive circuit cannot work. Therefore, the coil drive circuit can only work and drive the trip unit to operate when the sampling voltage UnA is greater than the reference voltage UpA, that is, when the input voltage of the power supply is within a certain range of the rated voltage.

[0108] The undervoltage control circuit is powered by the second operating voltage VCC. Throughout the undervoltage control circuit, the cathode voltage Ur of the first Zener diode ZD401 remains constant, being its reverse breakdown voltage. The reference voltage UpA changes with the output voltage UoA of the second operational amplifier U401, as follows:

[0109]

[0110] From the equation, we can see that Up ′ A > Up″A, meaning that when the second operational amplifier U401 outputs the second operating voltage VCC, the reference voltage UpA is higher. By selecting appropriate values ​​for the fourth voltage divider resistors R403 and R402, the requirement of Up... ′ A is the sampling voltage UnA when it is less than the rated voltage, and Up″A is the sampling voltage UnA when it is greater than 0.5 times the rated voltage. Up″A can be adjusted according to the actual situation.

[0111] like Figure 7 As shown, in one embodiment, the control system of the trip unit further includes a power supply circuit and a sampling circuit.

[0112] The input terminals of the power supply circuit and the sampling circuit are respectively connected to the power supply voltage DC+. The output terminal of the power supply circuit is electrically connected to the power supply terminal of the undervoltage control circuit to output the second working voltage VCC. The output terminal of the sampling circuit is electrically connected to the input terminal of the undervoltage control circuit to output the sampling voltage UnA.

[0113] like Figure 8 As shown, in one embodiment, the power supply circuit includes an NPN transistor Q202 and a second Zener diode ZD202.

[0114] The collector of NPN transistor Q202, the base of NPN transistor Q202, and the cathode of the second Zener diode ZD202 are respectively connected to the power supply voltage DC+. The emitter of NPN transistor Q202 is electrically connected to the power supply terminal of the undervoltage control circuit to output the second operating voltage VCC. The anode of the second Zener diode ZD202 is grounded.

[0115] The power supply voltage DC+ of about 300V is used to generate a second working voltage VCC of about 12V after passing through a series voltage regulator circuit composed of NPN transistor Q202 and second Zener diode ZD202.

[0116] like Figure 9 As shown, in one embodiment, the sampling circuit includes a fifth voltage divider resistor (such as...). Figure 9 The resistors R301 and R302 in the middle and the sixth voltage divider resistor R303.

[0117] Among them, the first end of resistor R301 is used to connect the power supply voltage DC+, the second end of resistor R301 is electrically connected to the first end of resistor R302, the second end of resistor R302 is electrically connected to the first end of the sixth voltage divider resistor R303 and the input end of the undervoltage control circuit to output the sampling voltage UnA, and the second end of the sixth voltage divider resistor R303 is used to ground.

[0118] The sampling circuit samples the power supply voltage DC+. After passing through three voltage divider resistors R301, R302, and the sixth voltage divider resistor R303, the sampling voltage UnA is approximately 10V when the power supply voltage DC+ is at its rated voltage. As the power supply voltage DC+ decreases slowly, the sampling voltage UnA also decreases. When the power supply voltage DC+ decreases to 0.5 times the rated voltage, the sampling voltage UnA is approximately 5V.

[0119] like Figure 10 As shown, in one embodiment, the control system of the trip unit further includes a rectifier filter circuit.

[0120] The output of the rectifier and filter circuit is electrically connected to the input of the sampling circuit and the input of the power supply circuit, respectively, to output the power supply voltage DC+.

[0121] Among them, such as Figure 11 As shown, the rectifier-filter circuit includes a varistor RV101, a rectifier diode D101, a rectifier diode D102, a rectifier diode D103, a rectifier diode D104, and a filter capacitor CE101.

[0122] The rectifier and filter circuit absorbs the AC power (L, N) connected to terminal P1 through the varistor RV101 and filters it through the full-wave rectifier unit composed of rectifier diodes D101, D102, D103, and D104, and can generate a power supply voltage of about 300V DC+.

[0123] Thirdly, in one embodiment, the present invention provides a circuit breaker including a trip unit and a control system for the trip unit in any of the above embodiments.

[0124] The circuit breaker described above is configured with a first operational amplifier, a first feedback adjustment module, and a second feedback adjustment module. With the first operational amplifier as the core, the first and second feedback adjustment modules adjust the first voltage output to the first input terminal and the second voltage output to the second input terminal of the first operational amplifier, respectively, based on the output of the first operational amplifier. Ultimately, this causes the first operational amplifier to output a PWM voltage to the first switching device, thereby driving the trip unit through PWM. Firstly, this affects the energization of the trip unit, preventing it from operating for extended periods, reducing heat generation, and minimizing the risk of burnout, thus reducing safety hazards. Secondly, it allows the use of trip units with fewer turns and lower equivalent resistance, reducing the cost of the trip unit.

[0125] The above provides a detailed description of the insulation detection circuit and circuit breaker system provided by this utility model. Specific examples have been used to illustrate the principle and implementation of this utility model. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​this utility model. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​this utility model. Therefore, the content of this specification should not be construed as a limitation of this utility model.

[0126] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A coil driving circuit, characterized in that, The coil driving circuit includes a first operational amplifier, a first switching device, a first feedback adjustment module, and a second feedback adjustment module; The first feedback regulation module includes a power supply terminal for connecting to a first operating voltage, a feedback terminal electrically connected to the output terminal of the first operational amplifier and the controlled terminal of the first switching device, and an output terminal electrically connected to the first input terminal of the first operational amplifier. The first and second access terminals of the first switching device are connected in series with the trip coil to control the current of the trip coil; The second feedback adjustment module includes a feedback terminal electrically connected to the output terminal of the first operational amplifier and an output terminal electrically connected to the second input terminal of the first operational amplifier; The first operational amplifier is used to output a PWM voltage to the first switching device through its output terminal based on the first voltage at its first input terminal and the second voltage at its second input terminal.

2. The coil driving circuit according to claim 1, characterized in that, The first feedback adjustment module includes a first voltage divider resistor, a second voltage divider resistor, and a third voltage divider resistor; The first end of the first voltage divider resistor is used to connect to the first operating voltage. The second end of the first voltage divider resistor is electrically connected to the first end of the second voltage divider resistor, the first end of the third voltage divider resistor, and the non-inverting input terminal of the first operational amplifier. The second end of the second voltage divider resistor is used to ground. The second end of the third voltage divider resistor is electrically connected to the output terminal of the first operational amplifier and the controlled terminal of the first switching device.

3. The coil driving circuit according to claim 1, characterized in that, The first feedback adjustment module includes a first voltage divider resistor, a second voltage divider resistor, a third voltage divider resistor, and a second switching device; The first end of the first voltage divider resistor and the first end of the third voltage divider resistor are respectively used to connect to the first working voltage. The second end of the first voltage divider resistor is electrically connected to the first end of the second voltage divider resistor, the first input terminal of the second switching device, and the non-inverting input terminal of the first operational amplifier. The second end of the second voltage divider resistor is used to ground. The second end of the third voltage divider resistor is electrically connected to the second input terminal of the second switching device. The controlled terminal of the second switching device is electrically connected to the output terminal of the first operational amplifier and the controlled terminal of the first switching device.

4. The coil driving circuit according to claim 2 or 3, characterized in that, The second feedback adjustment module includes a capacitor, a first charge / discharge resistor, and a second charge / discharge resistor; The first end of the capacitor is electrically connected to the inverting input terminal of the first operational amplifier and the first end of the first charge-discharge resistor, respectively. The second end of the first charge-discharge resistor is electrically connected to the output terminal of the first operational amplifier, the controlled terminal of the first switching device, and the first end of the second charge-discharge resistor, respectively. The second end of the capacitor and the second end of the second charge-discharge resistor are respectively used for grounding.

5. The coil driving circuit according to claim 4, characterized in that, The second feedback regulation module also includes an isolation diode; The cathode of the isolation diode is electrically connected to the second end of the first charge-discharge resistor and the first end of the second charge-discharge resistor, respectively, and the anode of the isolation diode is electrically connected to the output terminal of the first operational amplifier and the controlled terminal of the first switching device, respectively.

6. The coil driving circuit according to claim 2 or 3, characterized in that, The second feedback adjustment module includes a capacitor, a first charge / discharge resistor, and a second charge / discharge resistor; The first end of the capacitor is electrically connected to the inverting input terminal of the first operational amplifier and the first end of the first charge-discharge resistor, respectively. The second end of the first charge-discharge resistor is electrically connected to the first input terminal of the first switching device and the first end of the second charge-discharge resistor, respectively. The second end of the capacitor and the second end of the second charge-discharge resistor are respectively used for grounding.

7. The coil driving circuit according to claim 6, characterized in that, The second feedback adjustment module also includes a clamping diode; The anode of the clamping diode is electrically connected to the second terminal of the first charge / discharge resistor, the first terminal of the second charge / discharge resistor, and the first access terminal of the first switching device, respectively, and the cathode of the clamping diode is used for grounding.

8. A control system for a trip unit, characterized in that, The controller of the trip unit includes an undervoltage control circuit and a coil drive circuit as described in any one of claims 1 to 7; The power supply terminal of the undervoltage control circuit is used to connect to the second operating voltage, the input terminal of the undervoltage control circuit is used to connect to the sampling voltage of the power supply, and the output terminal of the undervoltage control circuit is electrically connected to the power supply terminal of the first feedback adjustment module. The undervoltage control circuit is used to output the first operating voltage to the first feedback adjustment module when the sampled voltage is greater than the preset voltage.

9. The control system for the trip unit according to claim 8, characterized in that, The undervoltage control circuit includes a first Zener diode, a second operational amplifier, a fourth voltage divider resistor, and a PNP transistor. The cathode of the first Zener diode is electrically connected to the non-inverting input of the second operational amplifier and the first end of the fourth voltage divider resistor, and is used to connect to the second operating voltage. The anode of the first Zener diode is grounded. The inverting input of the second operational amplifier is used to connect to the sampling voltage. The second end of the fourth voltage divider resistor is electrically connected to the output of the second operational amplifier and the base of the PNP transistor. The emitter of the PNP transistor is used to connect to the second operating voltage. The collector of the PNP transistor is electrically connected to the power supply terminal of the first feedback adjustment module.

10. The control system for the trip unit according to claim 8, characterized in that, The control system of the trip unit also includes a power supply circuit and a sampling circuit; The input terminal of the power supply circuit and the input terminal of the sampling circuit are respectively used to connect to the power supply voltage. The output terminal of the power supply circuit is electrically connected to the power supply terminal of the undervoltage control circuit, and the output terminal of the sampling circuit is electrically connected to the input terminal of the undervoltage control circuit.

11. The control system for the trip unit according to claim 10, characterized in that, The power supply circuit includes an NPN transistor and a second Zener diode; The collector of the NPN transistor, the base of the NPN transistor, and the cathode of the second Zener diode are respectively used to connect to the power supply voltage. The emitter of the NPN transistor is electrically connected to the power supply terminal of the undervoltage control circuit, and the anode of the second Zener diode is used to ground.

12. The control system according to claim 10, characterized in that, The sampling circuit includes a fifth voltage divider resistor and a sixth voltage divider resistor; The first end of the fifth voltage divider resistor is used to connect to the power supply voltage. The second end of the fifth voltage divider resistor is electrically connected to the first end of the sixth voltage divider resistor and the input end of the undervoltage control circuit. The second end of the sixth voltage divider resistor is used to ground.

13. A circuit breaker, characterized in that, The system includes a trip unit and a control system for the trip unit as described in any one of claims 8 to 12.

Images