Switched Capacitor Converter Startup Fault Detection for Short Protection
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Solution Overview
Problem
Conventional fault detection techniques for DC-to-DC converters in devices like smartphones are complicated and impractical due to increased power consumption and bidirectional charging requirements, which can lead to electrical shorts in switched capacitor converters, potentially damaging the converters.
Innovation Solution
A fault detection system for switched capacitor converters that monitors second terminal voltages of flying capacitors during a startup sequence, using threshold comparisons to detect pin shorts and capacitor plate shorts, and disables the converter if faults are detected, employing analog-to-digital converters and finite state machines to manage the detection process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fault detection techniques are applied to bidirectional DC-to-DC converters, then fault detection capability is provided, but the system complexity and impracticality increase due to bidirectional charging requirements
Solution Approach 1:
The fault detection is segmented into specific startup sequence phases (first time period and second time period) with distinct detection methods for each phase. This segmentation simplifies the overall detection system by breaking down the complex bidirectional converter fault detection into manageable temporal segments with different detection strategies.
Solution Approach 2:
The fault detection system performs preliminary voltage monitoring during the startup sequence before full bidirectional operation begins. By detecting faults early in the startup phase when the converter is in known states, the system avoids the complexity of detecting faults during dynamic bidirectional operation.
2Reliability
If voltage monitoring is performed during startup sequence, then electrical shorts are detected early, but additional circuitry and power consumption are required
Solution Approach 1:
The fault detection system utilizes the existing startup sequence voltage conditions and built-in ADC resources to perform self-diagnosis without requiring separate dedicated monitoring hardware. The system services its own fault detection needs using existing operational phases, minimizing additional power consumption.
3Measurement precision
If second terminal voltages are monitored with threshold comparisons, then pin shorts and capacitor plate shorts are detected, but false positives may occur without proper timing
Solution Approach 1:
The system performs preliminary voltage sampling and threshold comparison during specifically defined time periods in the startup sequence. By establishing expected voltage ranges before full operation begins, the system creates a baseline for accurate fault detection that minimizes false positives.
Solution Approach 2:
The fault detection system continuously monitors second terminal voltages and provides feedback through fault signals that trigger converter shutdown. This feedback mechanism allows the system to adjust and confirm fault conditions, reducing false positives by requiring sustained threshold violations rather than transient anomalies.
Data Source
AI summary
System and methods of fault detection for switched capacitor converters are provided. A system includes a switched capacitor converter and fault detection circuitry. The switched capacitor converter is configured to perform direct current (DC)-to-DC conversion at a predefined conversion ratio and includes a first power stage having first switches and includes first capacitors having first terminals and second terminals. The fault detection circuitry is coupled to second terminals of the first capacitors and is configured to monitor second terminal voltages of the first capacitors and to assert at least one fault signal in response to determining that any of the second terminal voltages indicates a fault during a startup sequence of the switched capacitor converter.