On-Board Charger Soft Start for Main Transistor Impulse Current
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Solution Overview
Problem
New energy vehicles' on-board chargers face safety risks due to high impulse currents during startup, particularly affecting the main power transistor in low-voltage direct-current converters.
Innovation Solution
An on-board charger system with a controller that employs a current soft start method by gradually increasing current through an inductor connected to the main power transistor, using a dual-loop control system where the current loop functions and the voltage loop does not, to minimize the impact on the main power transistor during startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the main power transistor is used in the low-voltage direct-current converter during startup, then the converter can operate, but the main power transistor experiences large impulse current that endangers its safety
Solution Approach 1:
The patent applies preliminary action by implementing a soft-start mechanism that gradually increases the current through the main power transistor during startup. A controllable switching transistor is introduced to initially bear the startup current, and the current is gradually transferred to the main power transistor over a predetermined time period, preventing impulse current damage before the main transistor is fully operational
Solution Approach 2:
The patent uses a controllable switching transistor as an intermediary element during the startup phase. This intermediary component initially handles the current flow and gradually transfers it to the main power transistor, acting as a buffer that protects the main transistor from direct exposure to impulse current during the critical startup period
Data Source
AI summary
An on-board charger, a DCDC converter and a control method are provided. The on-board charger includes a power factor corrector, a high-voltage direct-current converter, a low-voltage direct-current converter, and a controller. An input terminal of the high-voltage direct-current converter is connected to an output terminal of the power factor corrector. An input terminal of the low-voltage direct-current converter is connected to an output terminal of the high-voltage direct-current converter or the output terminal of the power factor corrector. An output terminal of the low-voltage direct-current converter is connected to a low-voltage battery and a low-voltage load. The low-voltage direct-current converter includes a main power transistor and a controllable switching transistor.