LLC Charger Mode Switching to Prevent Uncontrollable Rectified Current
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Solution Overview
Problem
Existing chargers for electric vehicles face a risk of uncontrollable rectified current generation when the voltage on the alternating-current side is high but the battery voltage is low, leading to potential safety and stability issues.
Innovation Solution
A charger control method and apparatus that dynamically switches the working mode of the LLC circuit based on the battery voltage, between full-bridge and half-bridge modes, to prevent uncontrollable rectified current generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the isolated DCDC circuit uses complementary turning on of upper and lower bridge arms to supply power to the battery, then the charging function is achieved, but uncontrollable rectified current is generated when AC voltage is high and battery voltage is low, leading to safety risks
Solution Approach 1:
The patent applies dynamic working mode switching between full-bridge and half-bridge modes based on real-time detection of battery voltage and AC voltage conditions. The controller dynamically adjusts the bridge arm turning-on strategy: in full-bridge mode, all four bridge arms are controlled complementarily; in half-bridge mode, only two bridge arms are controlled. This dynamic adaptation prevents uncontrollable rectified current generation while maintaining effective charging power delivery across different voltage conditions.
2Ease of operation
If a fixed working mode is used in the LLC circuit, then the control is simple, but the charger cannot adapt to different voltage conditions and may generate uncontrollable rectified current
Solution Approach 1:
The patent implements dynamic working mode switching between full-bridge and half-bridge modes based on real-time voltage conditions. The controller detects AC voltage and battery voltage levels, then automatically selects the appropriate working mode to prevent uncontrollable rectified current while maintaining charging effectiveness.
Solution Approach 2:
The patent changes the working mode parameter of the LLC circuit based on voltage conditions. By switching between full-bridge mode (all four bridge arms controlled) and half-bridge mode (two bridge arms controlled), the system adapts to different voltage scenarios, preventing harmful rectified current generation while maintaining charging performance.
3Device complexity
If the LLC circuit operates without working mode switching, then the device complexity is low, but the charger cannot prevent uncontrollable rectified current under certain voltage conditions
Solution Approach 1:
The patent introduces dynamic working mode switching with two distinct control strategies: full-bridge mode for normal operation and half-bridge mode for preventing uncontrollable rectified current. The controller automatically selects the appropriate mode based on voltage conditions, adding minimal complexity while effectively eliminating the harmful current issue.
Solution Approach 2:
The patent uses the working mode selection as an intermediary mechanism between the voltage detection system and the bridge arm control system. By introducing this intermediate control layer, the system can prevent uncontrollable rectified current generation without requiring complex direct control modifications, maintaining relative simplicity while ensuring safety.
Data Source
AI summary
A method for controlling a charger is provided. The charger is an on-board charger or a charging pile charger, and includes an LLC circuit that is connected to a battery. The method includes: determining a target working mode of an LLC circuit according to a first voltage of a battery, the target working mode being a full-bridge mode or a half-bridge mode; and controlling the LLC circuit to work according to the target working mode.