Front-stage bidirectional AC-DC converter of vehicle-mounted charger

Abstract

The invention relates to the technical field of power electronic conversion, in particular to a front-stage bidirectional AC-DC converter of a vehicle-mounted charger, which comprises an input filter circuit, an interleaved parallel totem pole power stage, an energy storage circuit, a driving and control circuit and a sampling and protecting circuit. The totem pole power level adopts two groups of silicon carbide MOSFET high-frequency switch tubes and low-frequency synchronous rectifier tubes which alternately work in the positive and negative half cycles of the power frequency, and the two paths are staggered by 180 degrees to operate. The control circuit adopts a double-loop control strategy of a DC bus voltage outer loop and a proportional resonance current inner loop to realize power factor correction and bidirectional power flow. Through combination of the silicon carbide device and the optimized topology, the efficiency is improved by 5%-10%, the power density is improved by 30%-50%, the cost is reduced by 20%-30%, the multi-functional application of G2V, V2G and V2L is achieved, an all-around protection mechanism is integrated, and the multi-functional protection device is suitable for a complex vehicle-mounted environment. The problem that a power device of an existing converter is large in conduction loss and switching loss is solved.

Description

Technical Field

[0001] This invention relates to the field of power electronic conversion technology, and more particularly to a bidirectional AC-DC converter for the front stage of an on-board charger. Background Technology

[0002] Currently, most AC-DC converters used in on-board chargers on the market suffer from numerous problems. Traditional unidirectional AC-DC converters can only achieve unidirectional energy transfer from the grid to the electric vehicle, failing to meet the functional requirements of future vehicle-to-grid (V2G) interaction and electric vehicles acting as mobile power sources to supply other loads (V2L). While bidirectional AC-DC converters have seen some development, they generally suffer from low efficiency, low power density, high cost, and insufficient reliability.

[0003] In terms of efficiency, existing converters suffer from significant conduction and switching losses in their power devices, especially in high-power applications. A large amount of energy is lost as heat, reducing energy conversion efficiency and increasing charging time and energy costs. Low power density results in larger converter size and weight, occupying excessive vehicle space and hindering lightweight design and internal space optimization for electric vehicles. High costs stem primarily from complex circuit topologies and expensive power device selection, which limits the market competitiveness of electric vehicles to some extent. Insufficient reliability manifests in the converter's susceptibility to failure in complex on-board environments, such as those with temperature variations and electromagnetic interference, affecting the normal operation of electric vehicles. Summary of the Invention

[0004] The purpose of this invention is to provide a bidirectional AC-DC converter for the front stage of an on-board charger, which aims to solve the problems of high conduction and switching losses of power devices in existing converters.

[0005] To achieve the above objectives, the present invention provides a bidirectional AC-DC converter for the front stage of an on-board charger, including an input filter circuit, a totem-pole power stage, an energy storage circuit, a drive and control circuit, and a sampling and protection circuit;

[0006] The input filter circuit is used to suppress electromagnetic interference and power-on surge current;

[0007] The totem pole power stage employs two sets of interleaved parallel totem pole power units to achieve bidirectional power flow.

[0008] The energy storage circuit is used to stabilize the bus voltage and filter out high-frequency ripple.

[0009] The driving and control circuit is used to generate PWM control signals and drive power devices;

[0010] The sampling and protection circuit is used to collect voltage and current signals and to protect the system.

[0011] The input filter circuit consists of a common-mode inductor, a relay, an X / Y capacitor, and a surge suppression NTC thermistor, used to suppress electromagnetic interference (EMI) and power-on surge current.

[0012] The totem pole power stage employs two sets of interleaved parallel totem pole power units, each set containing a high-frequency switching transistor and a low-frequency synchronous rectifier transistor; the first totem pole unit operates during the positive half-cycle of the power frequency, and the second totem pole unit operates during the negative half-cycle of the power frequency.

[0013] The energy storage circuit is composed of a large-capacity electrolytic capacitor and a film capacitor connected in parallel, which is used to stabilize the 380-400V bus voltage and filter out high-frequency ripple.

[0014] The controller of the drive and control circuit adopts dual-loop control: the outer loop is the DC bus voltage loop, and the inner loop is the current loop using proportional resonant control to ensure that the input current is in phase with the grid voltage; the gate drive chip is a dual-path drive chip, which can simultaneously drive the upper and lower bridge arm MOSFETs and set a dead time to prevent shoot-through. A drive transformer is added for electrical isolation, which can effectively isolate high voltage and low voltage. An NSI88515AC-DSWR chip is added for current and voltage monitoring and provides efficient power factor correction (PFC).

[0015] In the sampling and protection circuit, the AC input voltage is sampled through a voltage transformer and a voltage divider resistor, the input current is sampled through a Hall effect isolated current sensor, and the bus voltage is fed back to the controller through a voltage divider network. The protection mechanism includes an overcurrent fault signal output to notify the controller to shut down when the limit is exceeded, protection is provided by fuses and relays, and the drive control chip used has a monitoring function that can shut down immediately in case of abnormality. The sampling is also physically isolated.

[0016] This invention discloses a bidirectional AC-DC converter for the front-end of an on-board charger, comprising an input filter circuit, an interleaved parallel totem-pole power stage, an energy storage circuit, a drive and control circuit, and a sampling and protection circuit. The totem-pole power stage employs two sets of silicon carbide MOSFET high-frequency switches and low-frequency synchronous rectifiers, operating alternately in the positive and negative half-cycles of the power frequency and with the two paths interleaved by 180°. The control circuit adopts a dual-loop control strategy with an outer loop of DC bus voltage and an inner loop of proportional resonant current to achieve power factor correction and bidirectional power flow. This invention, through the combination of silicon carbide devices and optimized topology, improves efficiency by 5%-10%, increases power density by 30%-50%, and reduces cost by 20%-30%. It supports multi-functional applications such as G2V, V2G, and V2L, integrates a comprehensive protection mechanism, and is suitable for complex on-board environments. It solves the problem of high conduction and switching losses in the power devices of existing converters. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the bidirectional AC-DC converter for the front stage of the on-board charger provided by the present invention.

[0019] Figure 2 It is an input filter circuit.

[0020] Figure 3 It is the upper bridge arm circuit of the totem pole PFC power stage.

[0021] Figure 4 It is the lower bridge arm circuit of the totem pole PFC power stage.

[0022] Figure 5 It is an energy storage circuit.

[0023] Figure 6 It is a high-frequency bridge arm drive circuit.

[0024] Figure 7 It is a low-frequency bridge arm drive circuit.

[0025] Figure 8 It is an interleaved bidirectional PFC gate drive circuit.

[0026] Figure 9 It is a driver transformer circuit.

[0027] Figure 10 It is an AC input current sampling circuit.

[0028] Figure 11 It is an alternating current signal conditioning circuit.

[0029] Figure 12 It is an AC / DC voltage sampling circuit.

[0030] Figure 13 It is the TMS320F280049c control circuit.

[0031] In the diagram: 1-Input filter circuit, 2-Totem pole power stage, 3-Energy storage circuit, 4-Drive and control circuit, 5-Sampling and protection circuit. Detailed Implementation

[0032] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0033] Please see Figures 1 to 13 The present invention provides a bidirectional AC-DC converter for the front stage of an on-board charger, including an input filter circuit 1, a totem pole power stage 2, an energy storage circuit 3, a drive and control circuit 4, and a sampling and protection circuit 5;

[0034] The input filter circuit 1 is used to suppress electromagnetic interference and power-on surge current;

[0035] The totem pole power stage 2 employs two sets of interleaved parallel totem pole power units to achieve bidirectional power flow;

[0036] The energy storage circuit 3 is used to stabilize the bus voltage and filter out high-frequency ripple;

[0037] The drive and control circuit 4 is used to generate PWM control signals and drive power devices;

[0038] The sampling and protection circuit 5 is used to collect voltage and current signals and realize system protection.

[0039] This embodiment includes an input filter circuit 1, an interleaved parallel totem-pole power stage 2, an energy storage circuit 3, a drive and control circuit 4, and a sampling and protection circuit 5. The totem-pole power stage 2 employs two sets of silicon carbide MOSFET high-frequency switches and low-frequency synchronous rectifiers, operating alternately in the positive and negative half-cycles of the power frequency and running in a 180° interleaved manner. The control circuit adopts a dual-loop control strategy with an outer loop of DC bus voltage and an inner loop of proportional resonant current to achieve power factor correction and bidirectional power flow. This invention, through the combination of silicon carbide devices and optimized topology, improves efficiency by 5%-10%, increases power density by 30%-50%, and reduces costs by 20%-30%. It features multi-functional applications including G2V, V2G, and V2L, integrates a comprehensive protection mechanism, and is suitable for complex automotive environments. It solves the problem of high conduction and switching losses in existing converters' power devices.

[0040] Furthermore, the input filter circuit 1 consists of a common-mode inductor, a relay, an X / Y capacitor, and a surge suppression NTC thermistor, used to suppress electromagnetic interference (EMI) and power-on surge current.

[0041] In this embodiment, Figure 2The circuit shown is the AC input module of the PFC front end, mainly responsible for EMI filtering, surge suppression, soft start, and input voltage sampling. First, the AC input and protection section: J1, J2, and J3 are AC input interfaces, each equipped with a 250V 30A fuse to prevent short circuits or overcurrent damage to subsequent circuits. The other end connects to a thermistor RT1 (20D30K), which limits surge current upon power-up and decreases resistance as temperature rises, reducing losses. Next is the EMI filtering network, mainly composed of the following parts: L1 (common-mode inductor 5mH / 30A): suppresses common-mode electromagnetic interference. C34, C5, C13, C35 (472M 1kV safety capacitors): Y / X capacitors, suppressing differential-mode and common-mode noise. C17, C18 (2.2µF MKP capacitors): connected in parallel across the inductor to further filter high-frequency interference. This is a typical EMI filter, preventing circuit interference to the power grid and suppressing power grid interference to the circuit. To avoid power-on anomalies, this circuit employs a PFC front-end soft-start scheme. During power-on, RT1 (a 20D30K thermistor) is connected in series at the input to further limit inrush current. Once the bus voltage is fully charged, the relay closes, bypassing the NTC / RT1 to reduce operating losses. At the moment of power-on, current is limited by the NTC. The relay closure reduces voltage drop and heat generation, ensuring stable system operation. The AC voltage sampling section uses an SGM8554 operational amplifier and a resistor divider network for sampling. The voltage signal is processed through voltage divider resistors (such as R4 and R5), and after passing through the operational amplifier, a suitable signal is obtained and sent to the controller for further analysis.

[0042] Furthermore, the totem pole power stage 2 adopts two sets of interleaved parallel totem pole power units, each set including a high-frequency switching transistor and a low-frequency synchronous rectifier transistor; the first totem pole unit operates during the positive half-cycle of the power frequency, and the second totem pole unit operates during the negative half-cycle of the power frequency.

[0043] In this embodiment, the figure shows two key circuits of the totem-pole PFC power stage. In the interleaved parallel totem-pole PFC circuit of this invention, the power stage mainly consists of two parts. Q1 to Q4 use SiC MOSFETs to form a high-frequency interleaved bridge arm. The two power units work alternately with a 180° phase shift to achieve current shaping and power factor correction. To suppress the peak voltage and dv / dt interference generated during switching, absorption capacitors and anti-parallel diodes are configured at both ends of the bridge arm. At the same time, electrolytic capacitors and film capacitors are connected in parallel on the bus side to stabilize the DC bus voltage and filter out high-frequency ripple. Q5 to Q8 form a low-frequency bridge arm, which operates at the power frequency and replaces the traditional diode rectifier with synchronous rectification, avoiding the losses caused by diode reverse recovery, thereby further improving efficiency. By coordinating the operation of the high-frequency interleaved bridge arm and the low-frequency synchronous rectifier bridge arm, this topology achieves high-efficiency, low-loss DC bus energy conversion while ensuring that the input current is close to a sine wave and in phase with the grid voltage, providing a stable 380-400V DC voltage support for subsequent power conversion.

[0044] Furthermore, the energy storage circuit 3 is composed of a large-capacity electrolytic capacitor and a film capacitor connected in parallel, which is used to stabilize the 380-400V bus voltage and filter out high-frequency ripple.

[0045] Furthermore, the controller of the drive and control circuit 4 adopts dual-loop control: the outer loop is the DC bus voltage loop, and the inner loop is the current loop using proportional resonant control to ensure that the input current is in phase with the grid voltage; the gate drive chip is a dual-path drive chip, which can simultaneously drive the upper and lower bridge arm MOSFETs and set a dead time to prevent shoot-through, and a drive transformer is added for electrical isolation, which can effectively isolate high voltage and low voltage, ensuring that the control signal can be safely and effectively transmitted to the power switching element. An NSI88515AC-DSWR chip is added for current and voltage monitoring and provides efficient power factor correction (PFC), which optimizes the input current waveform and ensures that the circuit operates at the optimal power factor.

[0046] In this embodiment, the interleaved parallel totem pole PFC circuit of the present invention relates to a drive circuit for the PFC circuit, specifically designed to drive the power switching devices of the upper bridge arm. This drive circuit uses an NSI68515AC-DSWR chip as the core control unit, receiving PWM control signals and controlling the SiCMOSFET switching elements of the upper bridge arm by adjusting the output voltage. The circuit effectively suppresses high-frequency noise in the power supply and signals through an EMI filter network, utilizing capacitors and inductors to ensure stable operation of the power system and reduce electromagnetic interference. Simultaneously, a current and voltage feedback mechanism (FAULT pin) monitors the circuit status in real time, issuing fault signals in case of abnormalities and providing timely protection to prevent damage. The voltage clamping function limits the output voltage through the ANODEVCLAMP pin, preventing it from exceeding the safe operating range, thereby protecting the power switching devices from overvoltage. This drive circuit, when used in the upper bridge arm, achieves efficient and stable power conversion and possesses excellent protection, making it widely applicable in high-power power supply systems and power electronic equipment.

[0047] This invention also relates to a drive circuit for driving the lower bridge arm. The circuit uses an NSI8602B-DSWR driver chip, receives a PWM signal from the controller, and converts the low-voltage signal into a high-voltage signal suitable for driving the MOSFET. This signal is output through the OUTA and OUTB pins to directly control the switching state of the lower bridge arm MOSFET. The circuit includes current protection, using diodes D15 and D16 to prevent reverse current and ensure the safe operation of the power switching devices. Furthermore, a dead time (DT pin) is set to prevent simultaneous conduction of the upper and lower bridge arm switches, thus preventing turbulent current. A voltage clamping function protects the circuit from overvoltage through the VCLAMP pin. This drive circuit is suitable for low-frequency applications, providing stable and reliable power conversion, and is widely used in power electronic systems.

[0048] This invention also relates to a gate drive module for an interleaved bidirectional PFC circuit, specifically designed to drive MOSFETs in the upper and lower bridge arms. The drive module uses a DRM1 driver chip, receives PWM control signals, and provides high-voltage drive signals through the OUTA and OUTB pins to control the switching operation of the MOSFETs. The circuit optimizes the power factor and achieves bidirectional current regulation through interleaved control technology, improving energy efficiency. It includes a current feedback mechanism and dead-time control to avoid current turbulence caused by simultaneous conduction of the upper and lower bridge arm MOSFETs. Furthermore, fault protection, voltage clamping, and filter capacitors ensure stable system operation and efficient power conversion, making it widely applicable in high-power power supply systems.

[0049] This invention employs a drive transformer to achieve isolation, signal conversion, and voltage boosting for driving MOSFET switching devices. By providing electrical isolation, the drive transformer effectively protects the control circuit from high-voltage interference, while converting low-voltage control signals into high-voltage drive signals, ensuring stable MOSFET switching. Furthermore, the use of a drive transformer reduces switching noise, improves the system's anti-interference capability, and enhances the overall reliability and efficiency of the circuit.

[0050] Furthermore, in the sampling and protection circuit 5, the AC input voltage is sampled through a voltage transformer and a voltage divider resistor, the input current is sampled through a Hall effect isolated current sensor, and the bus voltage is fed back to the controller through a voltage divider network; the protection mechanism includes an overcurrent fault signal output, which notifies the controller to shut down when the limit is exceeded.

[0051] In this embodiment, the current sampling in this circuit uses a Hall effect isolated current sensor NSM2015-20B5F, which features a wide bandwidth and output-input isolation. The input current flows through IP+ / IP-, and the Hall sensor detects and outputs a corresponding voltage signal. The output voltage is proportional to the current. Electrical isolation is achieved through the Hall effect, completely isolating the high-voltage input side from the low-voltage controller side, improving system safety. The output voltage is filtered by a capacitor and divided by a resistor before being sent to the MCU / control card ADC pin for current loop control. The Fault pin can be used for overcurrent protection; when the limit is exceeded, the signal is pulled low to notify the controller to shut down. The function of this part of the circuit is to detect the input current through an isolated current sensor, filter and condition it, and then provide it to the controller for current loop control and protection.

[0052] Beneficial effects:

[0053] High-efficiency energy conversion: By combining silicon carbide (SiC) wide-bandgap semiconductor devices with optimized topology and dual closed-loop control, conduction and switching losses are significantly reduced, achieving a 5%-10% increase in energy conversion efficiency under full load conditions. This directly shortens the charging time of electric vehicles, while reducing energy waste and lowering the energy consumption costs for users.

[0054] Space adaptation optimization: Relying on a new hybrid topology structure, combined with miniaturized components such as flat wire wound inductors and low ESR film capacitors, the size and weight of the converter are significantly reduced while ensuring performance. The power density is increased by 30%-50% compared with traditional solutions of the same power. It can flexibly adapt to the on-board space layout of different vehicle models, and help the lightweight design of electric vehicles.

[0055] Precise cost control: Simplifying circuit topology reduces the amount of power devices used, and selecting high-performance domestic components reduces raw material costs; at the same time, due to improved energy conversion efficiency, the design complexity and investment cost of the heat dissipation system are reduced, which together reduce the manufacturing cost of the converter by 20%-30% compared with traditional products, thereby enhancing the market competitiveness of the whole vehicle products.

[0056] Diverse Functional Applications: It has bidirectional power flow capability, enabling efficient charging from the grid to the vehicle (G2V) and energy feedback from the vehicle to the grid (V2G), meeting the diverse needs of smart grid energy storage scheduling, outdoor power supply, emergency rescue and other scenarios, and expanding the boundaries of electric vehicle energy applications.

[0057] Stable Operation: It integrates a full-dimensional protection mechanism for overcurrent, overvoltage, undervoltage, and overheating. Under complex conditions such as fluctuating vehicle ambient temperature and electromagnetic interference, it can quickly respond to anomalies and cut off risks. At the same time, it optimizes circuit design to reduce component stress, extend converter life, reduce vehicle maintenance frequency and cost, and ensure the long-term stable operation of the on-board charger system.

[0058] The above-disclosed embodiments are merely preferred embodiments of the on-board charger front-end bidirectional AC-DC converter of the present invention, and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that all or part of the processes of the above embodiments can be implemented, and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A bidirectional AC-DC converter for the front stage of an on-board charger, characterized in that, This includes an input filter circuit, a totem pole power stage, an energy storage circuit, a drive and control circuit, and a sampling and protection circuit. The input filter circuit is used to suppress electromagnetic interference and power-on surge current; The totem pole power stage employs two sets of interleaved parallel totem pole power units to achieve bidirectional power flow. The energy storage circuit is used to stabilize the bus voltage and filter out high-frequency ripple. The driving and control circuit is used to generate PWM control signals and drive power devices; The sampling and protection circuit is used to collect voltage and current signals and to protect the system.

2. The on-board charger front-end bidirectional AC-DC converter as described in claim 1, characterized in that, The input filter circuit consists of a common-mode inductor, a relay, an X / Y capacitor, and a surge suppression NTC thermistor, used to suppress electromagnetic interference (EMI) and power-on surge current.

3. The on-board charger front-end bidirectional AC-DC converter as described in claim 1, characterized in that, The totem pole power stage employs two sets of interleaved parallel totem pole power units, each set containing a high-frequency switching transistor and a low-frequency synchronous rectifier transistor; the first totem pole unit operates during the positive half-cycle of the power frequency, and the second totem pole unit operates during the negative half-cycle of the power frequency.

4. The on-board charger front-end bidirectional AC-DC converter as described in claim 1, characterized in that, The energy storage circuit consists of a large-capacity electrolytic capacitor and a film capacitor connected in parallel, used to stabilize the 380-400V bus voltage and filter out high-frequency ripple.

5. The on-board charger front-end bidirectional AC-DC converter as described in claim 1, characterized in that, The controller of the drive and control circuit adopts dual-loop control: the outer loop is the DC bus voltage loop, and the inner loop is the current loop using proportional resonant control to ensure that the input current is in phase with the grid voltage; the gate drive chip is a dual-path drive chip, which can simultaneously drive the upper and lower bridge arm MOSFETs and set a dead time to prevent shoot-through, and a drive transformer is added for electrical isolation, which can effectively isolate high voltage and low voltage; an NSI88515AC-DSWR chip is added for current and voltage monitoring.

6. The on-board charger front-end bidirectional AC-DC converter as described in claim 1, characterized in that, In the sampling and protection circuit, the AC input voltage is sampled through a voltage transformer and a voltage divider resistor, the input current is sampled through a Hall effect isolated current sensor NSM2015, and the bus voltage is fed back to the controller through a voltage divider network. The protection mechanism includes an overcurrent fault signal output, which notifies the controller to shut down when the limit is exceeded. It includes protection with fuses and relays, and the drive control chip used has a monitoring function that can immediately shut down when an abnormality occurs. All sampling is also physically isolated.

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