DC-DC Converter Intermittent Capacitor Charging for Inrush Control
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Solution Overview
Problem
Conventional DC-DC converters experience excessive inrush current when switching from shut-off to energization control, which can lead to capacitor overcharging and potential circuit failures.
Innovation Solution
Incorporating a control unit that intermittently switches a shut-off switch between an ON and OFF state before energization, allowing controlled current flow from the external power source to the capacitor, thereby reducing inrush current and preventing capacitor overcharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shut-off switch is interposed between an external power source and a capacitor to protect against short-circuit failure, then circuit protection is improved, but excessive inrush current flows through the capacitor when the switch switches from OFF to ON
Solution Approach 1:
The control unit performs preliminary intermittent switching of the shut-off switch in a charging period before the converter operates, allowing the capacitor to charge gradually in stages rather than all at once. This preliminary action prevents the sudden inrush current that would occur if the switch were closed directly during normal operation, while still providing circuit protection when needed.
Solution Approach 2:
The control unit implements periodic intermittent switching of the shut-off switch during a charging period, where the switch alternates between ON and OFF states. This periodic action allows the capacitor to charge in multiple smaller current pulses rather than one large inrush current, reducing the harmful effects of inrush current while maintaining effective charging.
2Object-affected harmful factors
If the switch is kept in the OFF state to suppress inrush current, then inrush current is reduced, but the capacitor cannot be charged from the external power source
Solution Approach 1:
The control unit employs periodic intermittent switching of the shut-off switch, alternating between ON and OFF states during a charging period. This allows the capacitor to charge in multiple periodic cycles, accumulating energy over time while keeping individual current pulses manageable and avoiding excessive inrush current.
Solution Approach 2:
The control unit implements preliminary intermittent charging before the converter operates, where the switch is periodically closed to charge the capacitor in advance. This preliminary action ensures the capacitor is adequately charged for normal operation while using controlled periodic switching to prevent inrush current problems.
Data Source
AI summary
A DC-DC converter includes a first capacitor and a second capacitor provided between one of a first conductive path and a second conductive path and a reference conductive path, a first switch and a second switch interposed between a first external power source and the first capacitor and between a second external power source and the second capacitor, and a control unit configured to switch the first switch and the second switch between an ON state and an OFF state, whereby the control unit, in the case of switching from shut-off control in which the first switch and the second switch are kept in the OFF state to energization control in which the first switch and the second switch are kept in the ON state, performs intermittent control in which the first switch and the second switch are intermittently switched to the ON state prior to the energization control.