Inductor Short Detection Circuit for DC-DC Converter Protection
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Solution Overview
Problem
Existing DC-DC converters, particularly inverting buck-boost converters, face significant risks from short circuits across the inductor, leading to potential damage to the integrated circuit, battery degradation, and safety hazards due to excessive heat generation.
Innovation Solution
An inductor short detection circuit is implemented, comprising a decoupling circuit, logic circuit, and control circuitry to generate a detection voltage, assert or deassert a detection signal based on voltage proximity to input or ground, and control the conduction phases of the DC-DC converter to prevent further damage upon detection of a short circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a short circuit detection mechanism is implemented, then the reliability of the DC-DC converter is improved, but the device complexity increases
Solution Approach 1:
The patent introduces an intermediary detection circuit that includes a decoupling circuit, logic circuit, and control circuitry. This intermediary system monitors the voltage at the inductor terminal and generates detection signals without requiring direct intervention in the main power conversion path, thus improving reliability while adding minimal complexity.
Solution Approach 2:
The detection circuit utilizes the existing voltage signals already present in the DC-DC converter circuitry. The logic circuit automatically compares the detected voltage against reference levels and generates appropriate detection signals, enabling the system to self-diagnose short circuit conditions without external monitoring equipment.
2Speed
If detection is performed on a cycle-by-cycle basis, then the speed of detection is improved, but the loss of time for control response increases
Solution Approach 1:
The detection circuit is designed to monitor voltage conditions continuously during each switching cycle and prepare detection signals in advance. The control circuitry receives these pre-prepared signals and can immediately respond by halting converter operation, eliminating delays between detection and protective action.
Solution Approach 2:
The patent implements immediate response logic that skips unnecessary intermediate steps. When a short circuit is detected during a switching cycle, the control circuitry instantly halts the converter operation without waiting for the end of the current cycle or performing additional verification steps, thus minimizing response time.
Data Source
AI summary
Circuitry for detecting a short across an inductor of a DC-DC converter includes a decoupling-circuit coupled between an inductor-terminal and an intermediate-node that, when activated, generates a detection-voltage (representative of voltage at the inductor-terminal) at the intermediate-node. A logic-circuit has an input coupled to the intermediate-node and an output generating a detection-signal. The detection-signal is asserted when the detection-voltage is closer to an input-voltage to the DC-DC converter than ground but is deasserted when the detection-voltage is closer to ground. Control-circuitry, at the beginning of a high-side conduction-phase, activates the decoupling-circuit and delays for a delay-period. After expiration of the delay-period and in response to the detection-signal being asserted, the control-circuitry completes the high-side conduction-phase. After expiration of the delay period and when the detection-signal is deasserted, the control-circuitry ceases the high-side conduction-phase of the DC-DC converter without completing the high-side conduction-phase and prevent beginning of a low-side conduction-phase.