DC/DC Converter Undervoltage Circuit With Mode-Switched Thresholds
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Solution Overview
Problem
Existing undervoltage protection mechanisms for DC/DC converters in electrified vehicles face challenges in efficiently preventing large currents from flowing due to voltage dips, while also avoiding premature triggering that can disrupt the precharge stages.
Innovation Solution
An undervoltage protection circuit with a threshold value switching unit that adjusts undervoltage protection thresholds based on the operational mode of the DC/DC converter, allowing for real-time protection and preventing large currents from flowing during voltage dips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single undervoltage protection threshold is used, then the protection mechanism is simple, but it cannot prevent large currents during voltage dips in buck mode while avoiding premature triggering during precharge stages
Solution Approach 1:
The patent applies dynamics by making the undervoltage protection threshold adjustable based on operational mode. The controller dynamically switches between a first threshold value during precharge stages and a second threshold value during buck mode, allowing the system to adapt to different voltage conditions in each mode and prevent both premature triggering and insufficient protection
Solution Approach 2:
The patent changes the parameter of the undervoltage threshold value based on the operational mode of the DC/DC converter. By switching between different threshold values (first threshold during precharge, second threshold during buck mode), the system optimizes protection effectiveness for each specific operational condition
2Reliability
If the threshold is raised above 12V battery voltage to prevent large currents, then protection against current damage is improved, but the second precharge stage cannot be completed due to premature UVP triggering
Solution Approach 1:
The system dynamically adjusts the protection threshold based on the operational stage. During the second precharge stage, a higher first threshold value is used that allows voltage to rise adequately without premature triggering. When transitioning to buck mode, the system switches to a lower second threshold value that provides adequate protection against large currents, thus resolving the contradiction between protection and precharge completion
3Productivity
If the threshold is lowered to 5.5V to allow precharge completion, then precharge stage operation is maintained, but large currents can damage MOSFETs during buck mode voltage dips
Solution Approach 1:
The patent implements dynamic threshold adjustment where the controller switches between a first threshold value (higher, allowing precharge completion) and a second threshold value (lower, providing MOSFET protection during buck mode). This temporal and mode-based switching resolves the contradiction by applying the appropriate threshold for each operational phase
Solution Approach 2:
The system performs preliminary action by setting an appropriate threshold for each operational mode in advance. Before entering buck mode, the controller configures the second threshold value that will prevent large current damage, while during precharge stages, the first threshold value is configured to allow proper voltage buildup, thus preparing the protection mechanism in advance for each mode's specific requirements
Data Source
AI summary
The present disclosure relates to an undervoltage protection circuit for a DC/DC converter of an electrified vehicle. The DC/DC converter generally operates in a first precharge stage, a second precharge stage and a buck mode. The undervoltage protection circuit comprises a threshold value switching unit which is connected with a controller and configured for receiving a control signal from the controller and switching among at least two predetermined undervoltage protection threshold values based on the control signal as received. The undervoltage protection circuit also comprises an undervoltage protection unit configured for outputting a signal indicating whether to activate an undervoltage protection based on a comparison between the switched undervoltage protection threshold value and a sampled voltage value from a high voltage side of the DC/DC converter. In the circumstance that the DC/DC converter operates in the buck mode, the undervoltage protection unit will activate the undervoltage protection such as to prevent a large current flowing from a low side voltage side to the high voltage side if the sampled voltage value is less than or equal to the switched undervoltage protection threshold value, and the DC/DC converter will continuously operate in the buck mode if the sampled voltage value is greater than the switched undervoltage protection threshold value. The present disclosure also relates to a method of undervoltage protection for a DC/DC converter of an electrified vehicle.