869results about "Conversion without intermediate conversion to dc" patented technology

The invention relates to the field of transformer control, and discloses a solid-state distribution transformer control system and method for improving access of a distributed power supply, which are used for solving the problem that original controller parameters are not representative due to access change of the distributed power supply when the solid-state distribution transformer is controlled. The method comprises the following steps: constructing a solid-state distribution transformer with a multi-port power regulation capability, setting initial control parameters, obtaining equivalent impedance influenced data, evaluating according to the equivalent impedance influenced data to obtain an equivalent impedance change index, judging whether the equivalent impedance is changed according to the equivalent impedance change index, and if the equivalent impedance is judged to be changed, judging whether the equivalent impedance is changed or not. If yes, dynamically correcting the initial control parameter according to the equivalent impedance change index to obtain an actual control parameter, and adjusting the output of the solid-state transformer according to the actual control parameter, thereby effectively improving the accuracy of transformer control and the reliability of energy supply.

The present disclosure relates to circuits for connecting components of a hydrogen plant to a power grid to power the components in an efficient manner. In one implementation, power-side alternate current (AC) to direct current (DC) converters may be connected to a source power grid without the need for an isolation transformer by providing separate buses between the power-side AC-DC converters and load-side DC-DC converters instead of a shared DC bus between the converters. Other implementations for connecting components of a hydrogen plant to a power grid may include an adjustable transformer, such as a tappable transformer or an autotransformer, to connect any number of auxiliary loads of the plant to the power grid. The adjustable transformer may provide for various types of auxiliary load devices to connect to the power provided by the transformer at the same time, including both three-phase devices and one-phase devices.

The invention discloses a 10kV distribution transformer on-load voltage regulation control method and system, and relates to the technical field of transformer on-load voltage regulation, and the method comprises the steps: collecting the three-phase voltage and current of a low-voltage side of a distribution transformer and a tap switch gear signal, and loading a preset voltage regulation control mode and an oscillation region parameter; based on the acquired three-phase voltage and current of the low-voltage side of the distribution transformer and the tap switch gear signal, calculating a feeder comprehensive impedance parameter and a load reactive power parameter, and outputting a transformer operation state index; according to the transformer operation state index, the voltage regulation control mode and the oscillation area rule, current voltage out-of-limit and reactive power deviation are judged, and a voltage regulation strategy triggering instruction is generated according to the judgment result; and calculating upper and lower limit values of feed line correction voltage based on the voltage regulation strategy trigger instruction, and controlling the tap switch to execute voltage regulation action. According to the method, a combined calculation scheme of feeder comprehensive impedance and load reactive power is fused, and dynamic optimization of the triggering condition of the voltage regulation strategy is achieved.

A power receiving device performs a power supply control including repeatedly performing: first rectification mode in which in response to detection of an energization of a first bridge circuit, a first high-side and a second low-side switches are turned on and a first low-side and a second high-side switches are turned off; and second rectification mode in which in response to detection of an energization of a second bridge circuit, the first low-side and the second high-side switches are turned on and the first high-side and the second low-side switches are turned off, and a power adjustment control including: first commutation mode in which the first high-side switch is turned off and the first low-side switch is turned on during the first rectification mode; and second commutation mode in which the second high-side switch is turned off and the second low-side switch is turned on during the second rectification mode.

The invention discloses a wide-voltage bidirectional charging and discharging device and a control method thereof, the wide-voltage bidirectional charging and discharging device comprises a first bidirectional inversion module, a first transformer, a second bidirectional inversion module, a first voltage conversion module and a control module, the first voltage conversion module is controlled to be switched to a boost conversion state or a buck conversion state according to the charging and discharging state, the voltage of the first direct current port, the voltage of the fourth direct current port and the turn ratio of the first transformer; according to the technical scheme, the voltage is monitored in real time, the step-up state or the step-down state is intelligently switched according to the turn ratio of the first transformer, bidirectional charging and discharging control in a wide voltage range is achieved, the problems that an existing device is single in function and limited in adaptation range are solved, and the service life of the device is prolonged. And moreover, the compatibility of batteries and loads with different voltage levels is greatly improved, the efficient and flexible charging and discharging requirements in multiple scenes are met, and good applicability and popularization value are achieved.

The invention relates to the technical field of power electronics, and discloses a dielectric barrier discharge high-voltage series resonance system and a control method thereof. The system comprises a high-voltage series resonance circuit, an upper computer and a hardware circuit. The upper computer is electrically connected with the hardware circuit, and the hardware circuit is electrically connected with the high-voltage series resonance circuit; wherein the high-voltage series resonance circuit comprises a PFC circuit, a Buck circuit, an LC series resonance circuit, a high-voltage pulse transformer and a dielectric barrier discharge load which are connected in sequence, the high-voltage series resonance circuit converts alternating current into high-frequency high-voltage pulse voltage and provides the high-frequency high-voltage pulse voltage for the dielectric barrier discharge load, and stable dielectric barrier discharge is generated; the upper computer is used for setting parameters, the hardware circuit controls the on-off state of the Buck circuit and the LC series resonance circuit according to the parameters set by the upper computer, accurate generation and control of high-voltage pulse voltage in the dielectric barrier discharge process are achieved, and the response speed and the control precision of the system are also improved.

The invention discloses a parallel discharge circuit and an electric flame stove. The parallel discharge circuit comprises a transformer and at least two groups of discharge branches, and the two groups of discharge branches comprise a first discharge branch and a second discharge branch. The scheme that a single transformer replaces multiple transformers is adopted, multi-time conversion loss of electric energy-magnetic energy-electric energy is reduced, electromagnetic interference is reduced, meanwhile, a stove body does not need to be provided with a large number of transformers, the size is more compact, and the parallel connection requirement of hundreds of discharging devices of the high-power electric flame stove is met; according to the invention, continuous control of asynchronous breakdown and independent charging and discharging of multiple discharging branches is realized, the method is adaptive to the breakdown threshold value difference of discharging devices among the discharging branches and the charging speed deviation of voltage-multiplying capacitors, extra voltage-sharing control is not needed, and it is ensured that all the discharging branches can stably complete charging and discharging closed loop, discharging failure is avoided, and mutual interference is avoided; the wide-voltage input circuit is suitable for various voltage inputs, and wide-voltage input is achieved.

The invention relates to the technical field of air purification, and discloses a negative oxygen ion generator and a method thereof.The negative oxygen ion generator comprises an external shell used for providing installation positions for related parts; the power supply input module is mounted in the external shell, is internally provided with a filtering unit, and is used for receiving external direct current; the direct current and alternating current inversion module is electrically connected with the output end of the power supply input module, is internally provided with a switch assembly and is used for converting the direct current into high-frequency alternating current; a primary winding, a secondary winding and a feedback winding are arranged in the boosting transformer. A boosting transformer is arranged between a direct current and alternating current inversion module and a high-voltage double-voltage rectification module, so that the voltage is effectively boosted, more importantly, the magnetic field coupling characteristics of a primary winding and a secondary winding are utilized, reliable electrical isolation is constructed, and a physical path from a high-voltage side circuit to a low-voltage side circuit is blocked.

The invention discloses an efficient new energy transformer and an electric energy control system, and relates to the technical field of transformers, an input power conversion module is used for converting a direct current or alternating current variable voltage source into high-frequency alternating current for output, and a high-frequency isolation transformer module adopts a nanocrystalline-amorphous alloy mixed magnetic core. The windings are arranged in a three-layer staggered mode and provided with an oil dual-cooling system, and the output rectification inversion module is used for converting high-frequency alternating current into needed direct current or alternating current to be output and integrates the multi-phase synchronous rectification function and the active filtering function. By designing the nanocrystalline-amorphous alloy mixed magnetic core and the three-layer staggered winding, leakage inductance is reduced, the coupling coefficient is increased, the problems of leakage inductance and nonuniform magnetic flux caused by serious iron loss, large leakage inductance and unreasonable coil arrangement of a traditional single-material low-frequency iron core at medium and high frequencies are solved, hysteresis and eddy-current loss are effectively inhibited, and the service life of the low-frequency iron core is prolonged. The leakage inductance is minimized, the high-frequency transformation efficiency is improved, and the size and the weight are reduced.

The invention discloses an anti-countercurrent control method and system for an energy storage transformer driven by bidirectional power regulation, and relates to the technical field of anti-countercurrent control of transformers, and the method comprises the steps: collecting the active power of a gateway ammeter, the active power of a load, the capacity of a transformer and a power factor of a power grid power supply grid-connected point in real time, and constructing a real-time operation data set; energy storage discharge countercurrent risk identification is carried out, segmented discharge is triggered to reduce protection, and segmented power adjustment is carried out in the discharge direction; according to the real-time operation data set, overload risk identification of the energy storage charging transformer is carried out, segmented charging demand reduction protection is triggered, and segmented power adjustment is executed in the charging direction. The technical problems that in the prior art, countercurrent is likely to happen during discharging of the energy storage transformer, overload is likely to happen during charging, and consequently equipment operation is not safe and a power grid is not stable are solved, and the technical effect that the operation safety of the energy storage transformer and the stability of the power grid are improved through the segmented power adjustment and power slow rising strategy is achieved.

The invention relates to a flexible loop closing device and a flexible loop closing method. The flexible loop closing device is arranged between a first power distribution network and a second power distribution network, and comprises a three-phase full-bridge inverter and a three-phase transformer, the three-phase output end of the three-phase full-bridge inverter is connected with the primary side of the three-phase transformer. The secondary side of the three-phase transformer is connected with a control switch, and each control switch is connected in series between the first power distribution network and the second power distribution network; and the flexible loop closing device controls the control switch to be closed under the condition that the actual output voltage of the flexible loop closing device meets a preset condition, so that flexible loop closing of the first power distribution network and the second power distribution network is realized. By adopting the device, the switch can be controlled to be switched on under the condition that the actual output voltage of the flexible loop closing device meets the preset condition, at the moment, flexible loop closing of the first power distribution network and the second power distribution network is achieved, and large impact current generated by direct loop closing is restrained.

The invention provides an AC-AC converter control parameter setting method, and belongs to the field of power electronic control. In order to solve the problems that traditional PID control parameters are lagged in adjustment and large in overshoot under the dynamic working condition, an AC-AC converter small-signal model of a single-tube reverse series bidirectional electronic switch topology is established, and the control parameters are optimized in combination with frequency domain characteristics. The method specifically comprises the following steps: establishing a state-space equation by adopting a switching period averaging method, performing linearization processing, and deducing a system dynamic transfer function; introducing duty ratio disturbance based on a steady-state working point to construct a small-signal model, and forming a three-order open-loop system through a serial PI controller; and according to a closed-loop pole configuration matching characteristic equation coefficient, analyzing and solving proportion and integral parameters. By dynamically optimizing the phase margin and the gain margin, the response speed and stability of the converter under input fluctuation and load abrupt change are remarkably improved, and the method has high engineering application value.

A method of generating a timing control signal for controlling the timing of a change of a transformer tap of a transformer is provided. The transformer includes an on-load tap changer including plural respective transformer taps. The method includes monitoring a voltage on a primary side and / or on a secondary side of the transformer to obtain a monitoring signal and deriving, from the monitoring signal, an intermediate signal that is indicative of at least one zero crossing of a tap voltage at the transformer tap. Deriving the intermediate signal includes estimating, based on the monitoring signal, a phase of the monitored voltage to obtain a phase signal and applying to the phase signal a phase correction for a phase shift between the monitoring signal or a signal derived therefrom and the tap voltage at the transformer tap. The timing control signal is derived from the intermediate signal.

The invention discloses a magnetic flux coupling regulation type hybrid transformer and a control method thereof, and relates to the technical field of power distribution network voltage regulation equipment. The magnetic flux coupling regulation and control type hybrid transformer is composed of three three-column four-winding transformers and a voltage source type back-to-back converter. The three three-column four-winding transformers are the same in structure, and four windings are respectively an input winding, an output winding, an energy taking winding and a voltage regulating winding. The back-to-back converter is composed of a rectification unit, an inversion unit and a direct current capacitor. The rectification unit realizes stable control of DC voltage through controlling port current, and carries out reactive power and harmonic compensation on an input port of the hybrid transformer. And the inversion unit realizes flexible adjustment of the voltage of the output winding port of the hybrid transformer by controlling the output voltage of the inversion side. The method has the characteristic that the line fault current does not directly flow through the converter, and can reduce the voltage and current resistance level of a converter power device and the equipment protection difficulty, thereby reducing the cost of the hybrid transformer.

An AC-to-AC converter includes input terminals for connection to an AC source, output terminals for connection to a load, a transformer having a primary winding and a secondary winding, a primary-side switch, a pair of secondary-side switches, and a control circuit to control the switches. Closing the primary-side switch causes a primary current to be drawn from the AC source and through the primary winding to store energy in the transformer. Closing one of the secondary-side switches causes a secondary current to be output at the output terminals to transfer energy from the transformer to the load. The secondary current has the same polarity as the primary current when a first of the secondary-side switches is closed, and the opposite polarity when a second of the secondary-side switches is closed. The control circuit is operable to control the switches such that an alternating current is output at the output terminals.

The present application provides an on-board charger and a control method thereof. Since the transformer side of the AC / AC conversion circuit is connected to the AC side of the AC / DC conversion circuit via a transformer, the on-board charger has a single-stage structure. Furthermore, since the instantaneous sampling value of the grid-side current is equal to its instantaneous reference value when stable, and the instantaneous reference value of the grid-side current is determined by the phase of the instantaneous sampling value of the grid-side voltage and the reference peak value of the grid-side current, the on-board charger has a PFC function. Furthermore, since the battery-side charging power can be indirectly controlled by controlling the grid-side current, the on-board charger has a battery-side voltage and current control function. Furthermore, since phase shift control is performed on the two conversion circuits, and the phase shift control enables soft switching of the power devices in the two conversion circuits, and the single-stage structure reduces the current flowing through the devices, efficiency is improved. Therefore, the single-stage structure efficiently implements the PFC and battery-side voltage and current control functions of the two-stage isolated on-board charger.

Examples described herein provide a circuit that includes a power electronics converter disposed in a vehicle, the power electronics converter to receive alternating current (AC) electrical power from an AC grid source and to provide AC electrical power to an AC load external to the vehicle. The power electronics converter includes an AC-AC converter that includes a rectifier and an inverter, the rectifier being electrically connected to the inverter by a direct current (DC) link. The circuit further includes an on-board charging module electrically connected to the power electronics converter and a battery disposed in the vehicle. The power electronics converter provides vehicle-to-load functionality by providing, to the AC load, AC electric power as an output of at least one of a 120 Vac output or a 240 Vac output.

The invention belongs to the technical field of flexible networking of a power distribution network, and discloses a flexible loop closing device based on series-parallel cooperative adjustment, so as to solve the defects in the prior art. The device comprises a main loop, a bypass loop, data acquisition equipment and a control and protection system, wherein the main loop comprises a parallel transformer, a parallel power valve group, a series power valve group and a series transformer; the input end of the primary winding of the shunt transformer is connected with an inlet wire 1, and the output end forms a neutral point after star connection; the input of the series transformer power valve group is respectively connected with the taps of the secondary winding of the series transformer, and the output terminal is connected with the output of the three power valves in the parallel power valve group after being connected in series; a primary winding of the series transformer is connected in series between the inlet wire 1 and the inlet wire 2; the bypass loop is connected in parallel between the inlet wire 1 and the inlet wire 2; the data acquisition equipment is used for monitoring voltage and current parameters of the incoming line 1 and the incoming line 2; the control and protection system is used for collecting voltage, current and device state signals and controlling the working state of the power valve.

An AC-AC converter is provided. The AC-AC converter includes a primary circuit, a secondary circuit, a transformer, a resonant tank, and a controller. The primary circuit includes four bidirectional switches, each including upper and lower switches connected back-to-back and capable of operating in four quadrants in a voltage-current plane. The first and fourth bidirectional switches operate synchronously, and the second and third bidirectional switches operate synchronously. When the input voltage is greater than a predefined threshold voltage, the first and second lower switches are maintained in an on state, and the first and second upper switches operate with PWM signals and are complementary to each other. When the input voltage is smaller than an additive inverse of the predefined threshold voltage, the first and second upper switches are maintained in the on state, and the first and second lower switches operate with PWM signals and are complementary to each other.

A capacitance electricity-taking circuit for a primary and secondary fusion pole-mounted circuit breaker comprises a first electricity-taking capacitor and a second electricity-taking capacitor which are connected in series, and a transformer which is connected with the second electricity-taking capacitor in parallel through a high-voltage side, and the low-voltage side of the transformer is connected with an output end. The first end, connected with the first electricity taking capacitor, of the second electricity taking capacitor is grounded and connected with a current discharging access, a discharging tube is arranged on the current discharging access, the control end of the discharging tube is connected with a discharging control circuit, and the discharging control circuit comprises a first protection diode. The second end of the second electricity taking capacitor is connected with the negative electrode of the first protection diode, and the positive electrode of the first protection diode is connected with the control end of the bleeder tube. According to the utility model, grounding protection and overvoltage protection of the input end can be realized at the same time by using the current discharge path, synchronous protection when the input end is abnormal can be realized by using the no-load protection circuit of the output end, and multiple protection functions are realized through circuit multiplexing.

The invention provides a medium-voltage alternating-current voltage regulating device and a control method, and relates to the technical field of circuits, and the medium-voltage alternating-current voltage regulating device comprises a transformer, at least one power conversion module, a main controller and at least one bypass module. The power conversion module comprises a first inverter bridge arm, a second inverter bridge arm, a third inverter bridge arm, a first inductor, a second inductor, a third inductor and a capacitor bank. When the voltage of the medium-voltage power grid is too high or too low, the power conversion module automatically compensates the voltage of the power grid, so that the voltage is recovered to a normal range. The medium-voltage alternating-current voltage regulating device is large in regulating range, can effectively stabilize the power supply voltage of a medium-voltage power grid, has the effects of high response speed, low cost, high reliability and convenience in maintenance, and can effectively improve the power transmission capacity of the medium-voltage power distribution network.

The invention discloses a two-stage multi-equipment participation power distribution system deduction simulation control strategy and device, and relates to the technical field of new energy photovoltaic power generation and power distribution system optimization operation. The strategy comprises the following steps of initializing a power flow model and collecting information, loading key data, building a power flow equation, regulating and controlling OLTC discrete actions in a first stage, optimizing by adopting a DQN algorithm, judging discrete control ending, and regulating reactive power of a photovoltaic inverter in a second stage. Modeling a PV agent, and adopting a multi-agent depth deterministic strategy gradient algorithm for cooperative control and overvoltage node judgment and ending; according to the invention, coordination and advantage complementation of various adjustable devices can be realized while the problems of aggravation of fluctuation risk and voltage out-of-limit of the power distribution system caused by distributed photovoltaic grid connection are solved, and the utilization efficiency of distributed energy is improved while safe and stable operation of the power distribution system is ensured.

The invention discloses a transient power flow type voltage out-of-limit treatment method, device and system, and belongs to the technical field of low-voltage and high-voltage out-of-limit treatment, and the technical scheme is characterized in that the method comprises the steps: obtaining a voltage signal and a current signal corresponding to a transformer at the current moment; according to the LSTM model, the voltage signal and the current signal, obtaining a voltage prediction value corresponding to the adjacent next moment; according to the voltage prediction value, executing iterative operation to obtain a first compensation gear; and obtaining the target compensation gear according to the first compensation gear and the Q learning algorithm. The voltage prediction value corresponding to the next moment is obtained through the LSTM model, the target compensation gear is determined in advance through the voltage prediction value and is adjusted, the voltage out-of-limit time is reduced, and when the target compensation gear is determined, iterative operation and the Q learning algorithm are combined, so that the compensation precision is improved. And the final target compensation gear can reduce the action times of the contactor on the premise of ensuring that the voltage is qualified.

A high-efficiency power electronic voltage regulating device with a reclosing function is connected in series with a low-voltage line and comprises a silicon controlled bypass switch, a series power unit, a parallel power unit, an input filtering unit, an output filtering unit, a controller, a topology change-over switch, a mechanical bypass switch, an input switch, an output switch and the like. Under a normal working condition, power is supplied to a user through the silicon controlled bypass switch; through an AI pre-judgment technology, a power grid voltage drop or increase trend is pre-judged, and a series power unit is conducted in advance; a topology change-over switch is connected to form a boost or buck topology, and when the voltage of a power grid is too low or too high, the normal voltage of a user is ensured through PR closed-loop control; when the rear-end line / load breaks down, reclosing control is carried out; and voltage upper and lower limits are adjusted remotely. The device utilizes the AI pre-judgment technology, has the characteristics of stable voltage, no need of input / output commutation and the like, solves the problems of over-high and over-low voltage and automatic reclosing in fault, and improves the high power supply quality and the power supply reliability of users.

The invention relates to the technical field of electronic circuits, in particular to a differential transformer resonant bridge resonant frequency detection and adjustment device and method, a rapid tuning capacitor bridge is composed of a plurality of tuning capacitors, and the resonant frequency is changed by adjusting the capacitance values of the tuning capacitors connected into a circuit; in addition, an analog-to-digital conversion circuit is used for collecting voltage data, and the upper computer is used for directly observing the minimum value of an output voltage peak-to-peak value to judge the resonance state. According to the device and the method provided by the invention, the resonant frequency can be detected, the tuning range can be adjusted as required, the tuning capacitance stepping precision can be adjusted as required, the tuning precision is high, and the resonant frequency adjustment efficiency is improved; meanwhile, the rapid tuning capacitor bridge is used as an independent adjusting unit, so that repeated welding and dewelding of the front-end circuit during the tuning process when the tuning capacitor is changed are effectively avoided, the safety and the reliability of the front-end bridge are ensured, and the engineering application requirements are better met.

To provide a reactor which can easily adjust an inductance and a heat dissipation without increasing the size.SOLUTION: In a reactor, a coil of which the number of winding parts is one, and a magnetic core are provided, an outer peripheral surface of each winding part contains a part contacted to an installation object of the reactor, and the magnetic core includes an E-shape like first core part, a T-shaped like second core part, and a gap part. The first core part is constructed by a compact of a composite material, and the second core part is constructed by a dust compact. The gap part is arranged between a first middle core part of the first core part and a second middle core part of the second core part in an inner part of each winding part. A length from the second end surface of each winding part to the gap part is 0.2 times or more and 0.49 times or less of the length of each winding part. A total volume of a volume of the first core part, a volume of the second core part, and a volume of the gap part is 50 cm3 or more and 500 cm3 or less.SELECTED DRAWING: Figure 4

The invention relates to the technical field of transformers, and discloses an on-load voltage regulation method and device based on an existing transformer and a storage medium, according to the method, a transient overvoltage suppression device is arranged on a switch, one end of the transient overvoltage suppression device is connected with an action end, the other end of the transient overvoltage suppression device is connected with a contact end corresponding to middle gear voltage, and the break-over voltage of the transient overvoltage suppression device is larger than the maximum voltage difference value between the action end and the contact end. And the action end is connected with a phase correction capacitor and then is connected with a primary side sleeve through the capacitor. Each contact end is correspondingly connected with a current-limiting reactor and is connected to taps with different turns of a primary side winding of the transformer through the current-limiting reactor, and the other tap of the winding is connected with another primary side sleeve. Detecting the secondary side voltage value of the transformer, and driving the action end to be connected with the contact end which is positively correlated with the secondary voltage value according to the secondary side voltage value; according to the method, the existing transformer can realize on-load voltage regulation, and the power supply voltage stability is effectively improved.

Controller and method for a power converter. For example, a controller for a power converter includes: a first drive signal generator configured to generate a first drive signal and output the first drive signal to a first transistor configured to receive an input voltage and related to a primary winding coupled to an auxiliary winding and a secondary winding related to an output voltage; a second drive signal generator configured to generate a second drive signal and output the second drive signal to a second transistor coupled to the first transistor and related to the primary winding; a demagnetization detector configured to generate a demagnetization signal based at least in part on a first voltage related to the auxiliary winding, the demagnetization signal indicating an end of a demagnetization process; and a first controller configured to generate a first control signal.

The disclosed family of electrical power converters consists of two multiphase semiconductor conversion stages to accomplish variable voltage and variable frequency (VVVF) AC-AC power conversion. A middle filter network is positioned between the two conversion stages to absorb high-frequency harmonic currents produced by converter switching and to provide a freewheel path for inductive output currents. Additionally, an input filter network is placed at the input terminals of the first conversion stage to minimize input current distortion, while an output filter network is located at the output terminals of the second conversion stage to suppress high-frequency harmonics in the output currents. Moreover, the disclosed converter family is generalized for N-phase to M-phase power conversion, where N≥3 and M≥3.

Disclosed in the present application is a control method, the method comprising: (01) acquiring target operation state information of an output end circuit of a transformer, and determining the operation state of a power grid on the basis of the target operation state information; and (02) when it is determined that the power grid is in the preset operation state, controlling switch transistors in the output end circuit and an input end circuit of the transformer, so as to reduce the target current.