Battery Charging Circuit Mode Switching for High-Voltage Stability
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Solution Overview
Problem
Conventional battery chargers experience higher power losses, ripples in DC current, and instability in DC-to-DC converters when operating at higher battery voltage levels, particularly above a predefined threshold.
Innovation Solution
A battery charging circuit operates in two modes: a first mode where the AC-to-DC converter regulates the DC link voltage and the DC-to-DC converter outputs a voltage less than the threshold, and a second mode where the AC-to-DC converter outputs DC current while bypassing the DC-to-DC converter to equalize the voltage with the battery level, reducing power losses and ripples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the battery charging circuit operates at higher battery voltage levels, then the voltage output is improved, but power losses and ripples in DC current increase
Solution Approach 1:
The patent implements dynamic switching between two operating modes based on the battery voltage level. When battery voltage exceeds a predefined threshold, the system transitions from a first mode (with DC-to-DC converter regulating voltage) to a second mode (with DC-to-DC converter bypassed and AC-to-DC converter directly controlling output). This dynamic adaptation allows the system to optimize performance and minimize power losses at different voltage levels.
2Force
If the duty cycle of the DC-to-DC converter is increased to meet high voltage requirements, then the voltage output is improved, but stability of the DC-to-DC converter deteriorates
Solution Approach 1:
The patent extracts the DC-to-DC converter from the power conversion path when operating at high voltage levels by bypassing it. This eliminates the stability issues associated with high duty cycle operation of the DC-to-DC converter while maintaining the required high voltage output through direct control of the AC-to-DC converter.
3Force
If the DC-to-DC converter is used to output DC current at high voltage, then the voltage regulation is improved, but switching losses increase
Solution Approach 1:
The patent converts the harmful effect of high voltage operation into a beneficial control strategy by detecting when battery voltage exceeds a threshold and automatically switching to a bypass mode. This eliminates the switching losses in the DC-to-DC converter while maintaining proper voltage regulation through the AC-to-DC converter, effectively turning the high voltage condition into an opportunity to optimize efficiency.
Data Source
AI summary
A method of operating a battery charging circuit for charging a battery is described. The method includes controlling the battery charging circuit to operate in a first mode to output a direct current (DC) current at a first voltage less than or equal to a predefined threshold and controlling the battery charging circuit to operate in a second mode to output the DC current at a second voltage greater than the predefined threshold. In the first mode, the AC-to-DC converter is controlled to regulate a DC link voltage across a DC link capacitor and the DC-to-DC converter is configured to output the DC current at the first voltage. In the second mode, the AC-to-DC converter is controlled to output the DC current and the DC-to-DC converter is bypassed to equalize the DC link voltage with the second voltage.