Inrush Current Suppression Module for On-Board Bidirectional Charger
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Solution Overview
Problem
Conventional circuits for suppressing inrush current in high-power on-board bidirectional chargers fail to provide effective protection against inrush currents in harsh AC power supply environments, leading to reliability issues and increased size and cost due to the use of mechanical relays and inflexible control methods.
Innovation Solution
A module for suppressing inrush current is integrated into the on-board bidirectional charger, comprising a controlled switch and a suppressor connected in parallel, with a MOSFET or SiC/GaN MOSFET as the controlled switch and a positive temperature coefficient resistor as the suppressor, connected in series with the bus capacitor, allowing for efficient control and protection against inrush currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical relay is used to suppress inrush current, then the circuit can provide inrush current protection, but the device volume increases and reliability decreases due to limited switch life
Solution Approach 1:
The patent replaces the mechanical relay with a controlled switch (such as MOSFET or IGBT) that is controlled by a control circuit. This substitution eliminates the mechanical moving parts, thereby improving reliability by removing the limited mechanical switch life while maintaining the inrush current protection function. The controlled switch can be rapidly turned on and off without mechanical wear, solving both the reliability and volume issues simultaneously.
2Reliability
If a relay is used for inrush current suppression, then protection function is provided, but the response speed is too slow to protect against secondary inrush current
Solution Approach 1:
The controlled switch replaces the slow-acting mechanical relay with an electronically controlled device that can respond in microseconds. The control circuit monitors the current and voltage conditions and rapidly activates the controlled switch when inrush current is detected, providing fast protection against both primary and secondary inrush currents. This electronic control system achieves rapid response without significantly increasing overall circuit complexity.
3Reliability
If controlled switches such as thyristors are used in the rectifier bridge, then inrush current protection is improved, but control flexibility is reduced making it hard to realize special protection function
Solution Approach 1:
The patent uses controllable switches such as MOSFETs or IGBTs instead of thyristors. These devices offer superior control flexibility because they can be turned on and off rapidly through gate control, allowing the control circuit to dynamically adjust the switching timing and duration. This enables sophisticated protection strategies including detection of both primary and secondary inrush currents, adaptive response to different fault conditions, and precise control of the protection activation, thereby achieving both excellent protection capability and high control flexibility.
4Adaptability or versatility
If separate charging and inverting circuits are used, then functional requirements are met, but cost and size increase
Solution Approach 1:
The patent integrates the charging circuit and inverting circuit into a single unified circuit system. The same power conversion circuitry, controlled switches, and control logic are used to perform both charging (AC to DC conversion) and inverting (DC to AC conversion) functions by simply changing the switching sequences and control modes. This merging eliminates the need for separate dedicated circuits, thereby reducing device volume, component count, and overall system cost while maintaining full bidirectional functionality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances power density, reliability, and cost-effectiveness by reducing electromagnetic interference, improving device performance, and providing protection against secondary inrush currents in complex power grid environments, while eliminating the need for mechanical relays and enhancing the multiplexing of charging and inverting circuits.
Implementation Method 1
a positive temperature coefficient resistor as the suppressor
Data Source
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AI summary
The present invention proposes a module (603, 702, 801) of suppressing inrush current, a method of controlling the module (603, 702, 801) of suppressing inrush current and an on-board bidirectional charger using the same. The on-board bidirectional charger includes a PFC-inverter module (602, 701) and the module (603, 702, 801) of suppressing inrush current, and the module (603, 702, 801) of suppressing inrush current includes a controlled switch (Q2) and a suppressor (R1) of suppressing inrush current connected in parallel with the controlled switch (Q2). The charging and inverting circuits of the present invention are fully multiplexed, which solves the problem that a high-power on-board charger under harsh AC power supply environment in bidirectional charging cannot provide special protection against inrush current, and can improve power density and circuit efficiency of charging and inversion, realize isolation function including reducing EMI electromagnetic interference and reducing switching interference signals, realize more convenient buck/boost functions, improve using life and performance of devices, reduce cost, and reduce the size of equipment.