Current transformer energy taking circuit and circuit breaker
By adjusting the switching on and off of the switching devices using PWM pulse signals controlled by software, the problems of unstable power supply and core saturation in the current transformer power extraction circuit under low current were solved, achieving stable power supply and reducing the cost and size of the circuit breaker.
Patent Information
- Application Number
- CN202511331904.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-18
- Publication Date
- 2025-12-02
AI Technical Summary
The existing current transformer power supply circuit is unstable under low current and the voltage is too high under high current, and the magnetic core is prone to saturation, which leads to increased measurement error. Existing improvement solutions are costly and not conducive to reducing the size of the circuit breaker.
By adopting a software control method, the switching devices are classified and controlled by the PWM pulse signal generated by the control unit circuit. The on and off of the switching devices are adjusted according to the magnitude of the main circuit current. The hysteresis comparator circuit is eliminated, so as to achieve stable power supply and reduce the cost and size of the circuit breaker.
It improves the power supply stability at low currents, enhances the output waveform quality of current transformers, avoids core saturation, and reduces the cost and size of circuit breakers.
Smart Images
Figure CN121055752A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a current transformer energy extraction circuit, belonging to the field of low-voltage electrical appliance technology. Background Technology
[0002] Current transformers are fundamental components in intelligent circuit breakers. They provide current detection signals for the main circuit and extract energy from the main circuit for components such as electronic trip units and communication circuits. In current mainstream molded case circuit breakers, current transformers are typically used to simultaneously perform measurement and power supply. This requires the current transformer to provide sufficient energy for the normal operation of components such as electronic trip units and communication circuits while ensuring current measurement accuracy. However, due to the inherent nonlinearity and magnetic saturation characteristics of current transformers, as well as their special application in circuit breakers, there are still some issues that need improvement: the power supply of current transformers itself suffers from unstable power supply under small currents and excessively high voltage under large currents, requiring specific energy extraction control circuits to obtain a stable operating voltage. Moreover, when the equivalent impedance of the load on the secondary side of the current transformer is large, its core requires a larger excitation current, which can easily lead to core saturation and potentially severe distortion of the secondary side current.
[0003] The structure of the existing current transformer power extraction circuit is as follows: Figure 1As shown, the circuit includes a rectifier circuit, an energy storage voltage limiting circuit, and a hysteresis comparator circuit. Its working principle and process are as follows: After the bridge rectifier circuit rectifies the secondary current of the current transformer, the output terminal forms a loop with the load of the control unit circuit (including working units such as voltage regulator circuit, microprocessor, signal processing circuit, and execution circuit) and the current sampling resistor. An energy storage capacitor is connected in parallel across the load of the control unit circuit to obtain a relatively stable DC voltage. In order to ensure that the output voltage of the bridge rectifier circuit does not exceed the working withstand voltage range of the control unit circuit load when the current is large, a MOSFET is used to bypass and discharge the excess current transformer energy before the energy storage capacitor and the load. In addition, an anti-reverse diode is used in the middle to prevent the energy storage capacitor from discharging through the MOSFET. The hysteresis comparator circuit controls the conduction and turn-off of the MOSFET by comparing the voltage of the energy storage capacitor with the voltage threshold. When the voltage of the energy storage capacitor exceeds the upper voltage threshold, the comparator outputs a high level, the MOSFET turns on, and the energy of the current transformer bypasses the MOSFET, stopping power supply to the load. At this time, the energy storage capacitor supplies power to the load. When the voltage of the energy storage capacitor falls below the lower voltage threshold, the comparator outputs a low level, the MOSFET turns off, and the current transformer resumes power supply to the load and the energy storage capacitor. This technical solution enables the load of the electronic trip unit control circuit to operate within a stable and controllable voltage range. However, due to the limitations of the hysteresis comparator circuit control, when the primary current of the current transformer is small, the MOSFET turn-off time triggered by the energy storage capacitor voltage falling below the lower voltage threshold will be long. During this period, the secondary side of the current transformer operates continuously in a high impedance state for a long time, which may lead to distortion of the secondary current. Especially when there are harmonics in the primary current, the transformer core may enter a saturation state, at which time its secondary current is severely distorted, resulting in a significant increase in measurement error and affecting the reliability of the circuit breaker operation. On the other hand, the conduction time of the MOSFET triggered by the energy storage capacitor voltage exceeding the upper voltage threshold is relatively fixed, and the energy of the secondary side of the current transformer is not fully utilized during this period.
[0004] An improved solution is to use one current transformer for energy extraction and another current transformer for measurement. This dual current transformer circuit breaker solution can effectively avoid the above problems, but the solution is more expensive and does not help to reduce the size of the circuit breaker. Summary of the Invention
[0005] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art and provide a current transformer energy extraction circuit that eliminates the traditional hysteresis comparator circuit. By using software control, different switching device on / off control schemes are adopted under different currents in the main circuit, thereby improving the energy supply stability and the output waveform quality of the current transformer at low currents, making full use of the energy on the secondary side of the current transformer, and effectively reducing the size of the circuit breaker and the implementation cost.
[0006] A current transformer power extraction circuit includes: A set of current transformers is used to draw energy from the main circuit; A set of rectifier circuits is used to rectify the secondary currents of the set of current transformers one by one; The current sampling circuit is used to sample the output current of each rectifier circuit. The energy storage voltage limiting circuit is used to limit the combined output current of all rectifier circuits to generate a system voltage Vcc to supply the load. It includes a switching device V1, a reverse protection diode D2, and an energy storage capacitor C1. The input terminal of the switching device V1 is connected to the positive output terminal of the rectifier circuit and the positive terminal of the reverse protection diode D2. The control terminal of the switching device V1 serves as the control signal input terminal of the energy storage voltage limiting circuit. The negative terminal of the reverse protection diode D2 is connected to the positive terminal of the energy storage capacitor C1 and serves as the output terminal of the system voltage Vcc. The output terminal of the switching device V1 and the negative terminal of the energy storage capacitor C1 are both grounded. The control unit circuit samples and calculates the output signal of the current sampling circuit and the system voltage Vcc to obtain the maximum value Imax of the primary current of each current transformer and the system voltage Vcc, and controls the conduction state of the switching device V1 according to the following control logic: If the current control cycle is in a low-current mode where Imax is less than the current threshold Im, first determine if there is a fixed PWM pulse sequence that is being executed but has not yet completed. If so, continue executing the fixed PWM pulse sequence to complete it; otherwise, then determine if Vcc is greater than the voltage threshold V. M When Vcc is greater than the voltage threshold V M When Vcc is less than or equal to the voltage threshold V, a fixed PWM pulse sequence is sent to the control signal input terminal of the energy storage voltage limiting circuit. The high and low levels of this fixed PWM pulse sequence can respectively turn on and off the switching device V1; when Vcc is less than or equal to the voltage threshold V M When this happens, the control switching device V1 remains continuously off; If the current control cycle is in high-current mode where Imax is greater than or equal to the current threshold Im, and Vcc is greater than the high-voltage threshold V... H If Vcc is less than the low voltage threshold V, then the control switching device V1 remains on; if Vcc is less than the low voltage threshold V L If V1 remains off, the control switching device V1 will remain off; if V L ≤Vcc≤V H Then, the switching device V1 is controlled according to the on / off state of the switching device V1 in the most recent control cycle; V L <V M <V H .
[0007] Preferably, the fixed PWM pulse sequence consists of multiple consecutive and identical pulse signals, the duration of the fixed PWM pulse sequence is 1ms to 5ms, and the duty cycle of the pulse signals is 70% to 90%.
[0008] Preferably, the control unit circuit uses the AD sampling port to sample the sampling signals of the current sampling circuit and the system voltage Vcc.
[0009] Preferably, the current sampling circuit includes a set of current sampling resistors that correspond one-to-one with the rectifier circuit, and are respectively connected in series between the positive and negative output terminals of the corresponding rectifier circuit.
[0010] Preferably, it further includes a voltage sampling circuit, which is a resistor divider sampling circuit connected in series between the two output terminals of the energy storage voltage limiting circuit.
[0011] Preferably, the energy storage voltage limiting circuit further includes a TVS diode FV1 and a pull-down resistor R4. The negative terminal of the TVS diode FV1 is connected to the positive output terminal of the rectifier circuit, the input terminal of the switching device V1, and the positive terminal of the anti-reverse diode D4. One end of the pull-down resistor R4 is connected to the control terminal of the switching device V1. The positive terminal of the TVS diode FV1 and the other end of the pull-down resistor R4 are both grounded.
[0012] Preferably, the switching device V1 is a power switching device, such as a MOSFET or IGBT.
[0013] Based on the same inventive concept, the following technical solutions can also be obtained: A circuit breaker includes a current transformer power extraction circuit as described in any of the above technical solutions.
[0014] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: This invention abandons the traditional hysteresis comparator circuit. Based on the magnitude of the main circuit current, it uses PWM pulse signals generated by the control unit circuit to classify and control the on / off state of the switching devices. When the main circuit current is small, a series of high-frequency PWM pulses are used to control the conduction of the switching devices. The duty cycle and duration of the PWM pulse sequence are precisely designed to ensure that there is enough energy to replenish the load side in each power frequency cycle to maintain voltage stability. By breaking down the originally "long" conduction time into many "short" PWM pulses, the current transformer carries a low impedance (sampling resistor) for most of the time. It only carries a high impedance when the PWM pulse is low. This greatly shortens the continuous high impedance time, effectively suppresses core saturation, and thus improves the quality of the current waveform on the secondary side of the current transformer. Compared to the traditional single current transformer scheme that uses a hysteresis comparator circuit to control based solely on a voltage threshold, this invention alleviates the core saturation caused by the secondary side needing to operate continuously at high impedance for extended periods to obtain sufficient energy when the primary current of the current transformer is small or even contains harmonics. This avoids the problem of increased measurement errors due to severe distortion of the secondary current caused by current transformer core saturation, and reduces circuit breaker costs by eliminating the hysteresis comparator circuit. Compared to a circuit breaker scheme that uses one current transformer for energy extraction and another for measurement, this invention uses a single current transformer to simultaneously achieve both energy extraction and measurement, effectively reducing circuit breaker costs and size. Attached Figure Description
[0015] Figure 1 This is a circuit diagram of a traditional current transformer power extraction circuit that uses a hysteresis comparator circuit. Figure 2 This is a circuit diagram of the current transformer energy extraction circuit of the present invention; Figure 3 This is a schematic diagram of the control circuit flow of the control unit in the technical solution of the present invention; Figure 4 This is a comparison diagram of the output waveforms of the present invention and the prior art at low current. Detailed Implementation
[0016] To address the shortcomings of existing technologies, the present invention eliminates the hysteresis comparator circuit in traditional solutions. Instead, it uses PWM pulse signals generated by the control unit circuit to classify and control the switching devices based on the magnitude of the main circuit current. This improves the power supply stability and the output waveform quality of the current transformer at low currents, fully utilizes the energy on the secondary side of the current transformer, and effectively reduces the size and cost of the circuit breaker.
[0017] The current transformer energy extraction circuit proposed in this invention includes: A set of current transformers is used to draw energy from the main circuit; A set of rectifier circuits is used to rectify the secondary currents of the set of current transformers one by one; The current sampling circuit is used to sample the output current of each rectifier circuit. The energy storage voltage limiting circuit is used to limit the combined output current of all rectifier circuits to generate a system voltage Vcc to supply the load. It includes a switching device V1, a reverse protection diode D2, and an energy storage capacitor C1. The input terminal of the switching device V1 is connected to the positive output terminal of the rectifier circuit and the positive terminal of the reverse protection diode D2. The control terminal of the switching device V1 serves as the control signal input terminal of the energy storage voltage limiting circuit. The negative terminal of the reverse protection diode D2 is connected to the positive terminal of the energy storage capacitor C1 and serves as the output terminal of the system voltage Vcc. The output terminal of the switching device V1 and the negative terminal of the energy storage capacitor C1 are both grounded. The control unit circuit samples and calculates the output signal of the current sampling circuit and the system voltage Vcc to obtain the maximum value Imax of the primary current of each current transformer and the system voltage Vcc, and controls the conduction state of the switching device V1 according to the following control logic: If the current control cycle is in a low-current mode where Imax is less than the current threshold Im, first determine if there is a fixed PWM pulse sequence that is being executed but has not yet completed. If so, continue executing the fixed PWM pulse sequence to complete it; otherwise, then determine if Vcc is greater than the voltage threshold V. M When Vcc is greater than the voltage threshold V M When Vcc is less than or equal to the voltage threshold V, a fixed PWM pulse sequence is sent to the control signal input terminal of the energy storage voltage limiting circuit. The high and low levels of this fixed PWM pulse sequence can respectively turn on and off the switching device V1; when Vcc is less than or equal to the voltage threshold V M When this happens, the control switching device V1 remains continuously off; If the current control cycle is in high-current mode where Imax is greater than or equal to the current threshold Im, and Vcc is greater than the high-voltage threshold V... H If Vcc is less than the low voltage threshold V, then the control switching device V1 remains on; if Vcc is less than the low voltage threshold V L If V1 remains off, the control switching device V1 will remain off; if V L ≤Vcc≤V H Then, the switching device V1 is controlled according to the on / off state of the switching device V1 in the most recent control cycle; V L <V M <V H .
[0018] To facilitate public understanding, the technical solution of the present invention will be described in detail below through a specific embodiment and in conjunction with the accompanying drawings: The current transformer energy extraction circuit in this embodiment uses three current transformers: the first to the third current transformers, which extract electrical energy from the three-phase currents I1 to I3 of the main circuit A, B, and C, respectively. The switching device V1 in this embodiment is exemplified by a MOSFET. Figure 2 As shown, the current transformer energy extraction circuit also includes rectifier bridges D11~D1N (N is the total number of current transformers, N is 3 in this embodiment), a current sampling circuit composed of current sampling resistors R11~R1N, an energy storage voltage limiting circuit composed of MOSFET V1, TVS diode FV1, anti-reverse diode D2, energy storage capacitor C1, and pull-down resistor R4, a voltage sampling circuit composed of voltage divider resistors R2 and R3, and a control unit circuit (including voltage regulator circuit, microcontroller, current signal processing circuit and other circuits). Rectifier bridges D11, D12, and D13 respectively rectify the AC current output from the secondary side of the corresponding first to third current transformers into pulsating DC current. Current sampling resistors R11, R12, and R13 are connected in series in the loop between the positive and negative output terminals of the corresponding rectifier bridges D11, D12, and D13, converting the pulsating DC current signal into a pulsating voltage signal. This voltage signal V is then connected to the negative output terminal of rectifier bridges D11, D12, and D13. I1 V I2 V I3 The current sampling signals are fed into the current signal processing circuit for processing, and the other end is connected to the reference ground. The drain of MOSFET V1 is connected to the positive output of rectifier bridges D11, D12, and D13, the source is connected to the reference ground, and the gate is connected to the PWM output port of the microcontroller and connected to the reference ground through pull-down resistor R4. When the PWM output port of the microcontroller is in a high-impedance state or outputs a low level, the MOSFET is turned off; when the PWM output port of the microcontroller outputs a high level, the MOSFET is turned on. The cathode and anode of TVS transistor FV1 are connected to the drain of MOSFET V1, respectively. The source and electrode are connected to absorb instantaneous overvoltage energy for protection. The anode of the anti-reverse diode D2 is connected to the positive output terminal of rectifier bridges D11, D12, and D13, and the cathode is connected to the positive terminal of energy storage capacitor C1, preventing energy storage capacitor C1 from discharging through MOSFET V1. The negative terminal of energy storage capacitor C1 is connected to reference ground, and its two ends are connected in parallel to the load of the control unit circuit to provide a relatively stable DC system voltage Vcc for the load. Voltage divider resistors R2 and R3 divide the system voltage Vcc on energy storage capacitor C1 to obtain a voltage signal V suitable for sampling. Vcc The signal is then sent to the microcontroller's A / D port to calculate the system voltage Vcc across the energy storage capacitor C1. The control unit circuit acts as the load, including the microcontroller, current signal processing circuit, and voltage regulator circuit. The voltage regulator circuit converts Vcc into a power supply voltage suitable for the microcontroller's operation, and the current signal processing circuit processes the current sampling signal V from sampling resistors R11, R12, and R13. I1 VI2 and V I3 After processing, the data is sent to the microcontroller's A / D port to calculate the primary currents I1, I2, and I3 of the first, second, and third current transformers, respectively, and to obtain the maximum value among I1, I2, and I3, Imax = (I1, I2, I3)max. The microcontroller then uses the calculated system voltage Vcc and Imax to determine the on / off state of the MOSFETs and outputs a fixed PWM pulse sequence or a fixed-level signal Vpwm through the PWM output port. In this embodiment, three current transformers are used to draw power from phases A, B, and C of the main circuit, respectively. However, depending on the actual situation, one or two current transformers can be used to draw power from one or two phases of the main circuit.
[0019] like Figure 3 As shown, the control logic executed by the control unit circuit of the present invention is as follows: Step 1: The microcontroller acquires the system voltage measurement value Vcc on the energy storage capacitor C1, and simultaneously acquires the primary current measurement values I1, I2, and I3 of each current transformer on the first to third protection lines in the circuit breaker, and obtains the maximum value (I1, I2, I3) max among I1, I2, and I3. It then compares (I1, I2, I3) max with the set large current judgment threshold Im. When (I1, I2, I3) max < Im, it executes Step 2 (small current control mode); when (I1, I2, I3) max ≥ Im, it executes Step 3 (large current control mode). Taking a rated current of 32A as an example, the high current judgment threshold Im can be set to 32A. In actual operation, the system voltage on the energy storage capacitor C1 and the current sampling signals of the first, second, and third current transformers are sampled respectively. After sampling, the instantaneous value of Vcc and the measured values (RMS values) of I1, I2, and I3 are calculated, and the maximum value (I1,I2,I3)max among I1, I2, and I3 is obtained. The magnitude of (I1,I2,I3)max and Im are compared. When (I1,I2,I3)max < 32A, the primary current of all current transformers is considered to be a small current, and step 2 (small current control mode) is then executed. When (I1,I2,I3)max < 32A, the current of all current transformers is considered to be a small current. When max≥32A, it is considered that the primary current of a certain current transformer is a large current, and step 3 (large current control mode) is executed next. The small current control mode uses a fine PWM pulse sequence to control the MOSFET, ensuring normal power extraction while taking into account waveform quality. When the current is large, the secondary side of the current transformer outputs sufficient energy, and waveform distortion is no longer the main problem. At this time, in order to reduce the microcontroller overhead and deal with more urgent overcurrent scenarios, a simpler and more direct large current control mode is adopted.
[0020] Step 2: First, determine if there is a fixed PWM pulse sequence that is being executed but has not yet completed. If so, continue executing the fixed PWM pulse sequence to complete it; otherwise, compare the system voltage measurement value Vcc with the set control voltage threshold V. M The size, when Vcc > V M First, a fixed PWM pulse sequence is output through the PWM output port of the microcontroller to control the conduction and cutoff of the MOSFET, and then step 1 is executed; when Vcc≤V M When the MOSFET is turned off, the PWM output port is used to output a continuous low level or cancel the high level output to control the MOSFET to turn off, and then step 1 is executed. The setting of the fixed PWM pulse sequence needs to take into account the quality of the current waveform on the secondary side of the current transformer under the minimum operating starting current of the circuit breaker, and that the system voltage measurement value Vcc after the execution of a PWM pulse sequence cannot deviate from the threshold V. M The current is too large, while also taking into account the setting of the large current judgment threshold Im. This ensures that when the primary current of the current transformer approaches Im, the measured system voltage Vcc after the execution of a PWM pulse sequence is not too large. Generally, the preferred duration of a single PWM pulse sequence is 1ms to 5ms, and the preferred duty cycle of a single pulse is 70% to 90%. The fixed PWM pulse sequence described in this embodiment consists of three consecutive pulses with a period of 1ms and a duty cycle of 90%, i.e., the high level and low level times of a single pulse are 0.9ms and 0.1ms, respectively. The PWM pulse sequence controls the MOSFET to turn on and off multiple times within a certain period of time, preventing the system voltage Vcc on the energy storage capacitor C1 from dropping too quickly, thus ensuring normal energy extraction. At the same time, it also slows down the rise of the core magnetic induction intensity, avoiding saturation.
[0021] Step 3: Compare the system voltage measurement value Vcc with the set high voltage threshold V. H Low voltage threshold V L Size (V) L <V M <V H When Vcc > V H First, the MOSFET is turned on by outputting a continuous high level through the PWM output port, and then step 1 is executed; when Vcc < V L When V is in operation, first control the MOSFET to turn off by outputting a continuous low level or canceling the high level output through the PWM output port, and then execute step 1; when V L ≤Vcc≤V H Then, control MOSFET V1 according to the on / off state of MOSFET V1 in the most recent control cycle; and execute step 1. This step is a high-current control mode, which is similar to the traditional control method using a hysteresis comparator circuit, in order to set a high voltage threshold V. H The voltage is 14.5V, and the low voltage threshold is V. L Taking a voltage of 13.5V as an example, the microcontroller compares the system voltage measurement value Vcc with V... H The voltage level varies depending on the voltage level. When Vcc > 14.5V, the microcontroller outputs a continuous high level through the PWM output port to control the MOSFET to turn on until the next control change. When Vcc < 13.5V, the microcontroller outputs a continuous low level through the PWM output port or sets the output port to a high-impedance state to control the MOSFET to turn off until the next control change. When 13.5V ≤ Vcc ≤ 14.5V, the microcontroller's PWM output port controls the MOSFET V1 according to the on / off state of the MOSFET V1 in the most recent control cycle and executes step 1.
[0022] In this embodiment, the microcontroller monitors the system voltage Vcc in real time during the ADC interrupt. Once the measured system voltage Vcc reaches or exceeds a threshold set under a specific current control mode, a fixed PWM pulse sequence or a fixed-level signal output is immediately triggered. The specific current control mode is determined by the microcontroller through a status flag after processing the A / D sampling data. The ADC interrupt executes the corresponding control mode operation based on this status flag. The fixed PWM pulse sequence triggered under low-current control mode is implemented by the microcontroller's internal PWM module, using an independent timer to precisely control the duration of the entire pulse sequence (e.g., 3ms). Once the timer expires, an interrupt is generated, immediately shutting down the PWM output. This ensures the accuracy and predictability of the PWM pulse sequence control. The fixed-level signal triggered under high-current control mode is implemented through the microcontroller's general-purpose I / O port output function. This output shares the same microcontroller function pin as the PWM module output under low-current control mode.
[0023] Figure 4 The diagram shows a comparison between the signal waveform obtained by the present invention under low current conditions and the traditional control method using a hysteresis comparator. The comparison shows that the current sampling signal waveform obtained by the traditional control method using a hysteresis comparator exhibits obvious distortion, while the current sampling signal waveform obtained by the present invention has significantly improved quality.
Claims
1. A current transformer energy extraction circuit, characterized in that, include: A set of current transformers is used to draw energy from the main circuit; A set of rectifier circuits is used to rectify the secondary currents of the set of current transformers one by one; The current sampling circuit is used to sample the output current of each rectifier circuit. The energy storage voltage limiting circuit is used to limit the combined output current of all rectifier circuits to generate a system voltage Vcc to supply the load. It includes a switching device V1, a reverse protection diode D2, and an energy storage capacitor C1. The input terminal of the switching device V1 is connected to the positive output terminal of the rectifier circuit and the positive terminal of the reverse protection diode D2. The control terminal of the switching device V1 serves as the control signal input terminal of the energy storage voltage limiting circuit. The negative terminal of the reverse protection diode D2 is connected to the positive terminal of the energy storage capacitor C1 and serves as the output terminal of the system voltage Vcc. The output terminal of the switching device V1 and the negative terminal of the energy storage capacitor C1 are both grounded. The control unit circuit samples and calculates the output signal of the current sampling circuit and the system voltage Vcc to obtain the maximum value Imax of the primary current of each current transformer and the system voltage Vcc, and controls the conduction state of the switching device V1 according to the following control logic: If the current control cycle is in a low-current mode where Imax is less than the current threshold Im, first determine if there is a fixed PWM pulse sequence that is being executed but has not yet completed. If so, continue executing the fixed PWM pulse sequence to complete it; otherwise, then determine if Vcc is greater than the voltage threshold V. M When Vcc is greater than the voltage threshold V M When the time is right, a fixed PWM pulse sequence is sent to the control signal input terminal of the energy storage voltage limiting circuit. The high and low levels of the fixed PWM pulse sequence can turn the switching device V1 on and off, respectively. When Vcc is less than or equal to the voltage threshold V M When this happens, the control switching device V1 remains continuously off; If the current control cycle is in high-current mode where Imax is greater than or equal to the current threshold Im, and Vcc is greater than the high-voltage threshold V... H If Vcc is less than the low voltage threshold V, then the control switching device V1 remains on; if Vcc is less than the low voltage threshold V L If V1 remains off, the control switching device V1 will remain off; if V L ≤Vcc≤V H Then, the switching device V1 is controlled according to the on / off state of the switching device V1 in the most recent control cycle; V L <V M <V H .
2. The current transformer energy extraction circuit as described in claim 1, characterized in that, The fixed PWM pulse sequence consists of multiple consecutive and identical pulse signals. The duration of the fixed PWM pulse sequence is 1ms to 5ms, and the duty cycle of the pulse signal is 70% to 90%.
3. The current transformer energy extraction circuit as described in claim 1, characterized in that, The control unit circuit uses the AD sampling port to sample the current sampling circuit and the system voltage Vcc.
4. The current transformer energy extraction circuit as described in claim 1, characterized in that, The current sampling circuit includes a set of current sampling resistors that correspond one-to-one with the rectifier circuit, and are respectively connected in series between the positive and negative output terminals of the corresponding rectifier circuit.
5. The current transformer energy extraction circuit as described in claim 1, characterized in that, It also includes a voltage sampling circuit, which is a resistor voltage divider sampling circuit connected in series between the two output terminals of the energy storage voltage limiting circuit.
6. The current transformer energy extraction circuit as described in claim 1, characterized in that, The energy storage voltage limiting circuit also includes a TVS diode FV1 and a pull-down resistor R4. The negative terminal of the TVS diode FV1 is connected to the positive output terminal of the rectifier circuit, the input terminal of the switching device V1, and the positive terminal of the anti-reverse diode D4. One end of the pull-down resistor R4 is connected to the control terminal of the switching device V1. The positive terminal of the TVS diode FV1 and the other end of the pull-down resistor R4 are both grounded.
7. The current transformer energy extraction circuit as described in claim 1, characterized in that, The switching device V1 is a power switching device.
8. A circuit breaker, characterized in that, Includes the current transformer power extraction circuit as described in any one of claims 1 to 7.