Switched Capacitor Converter Fault Isolation for Over-Voltage Stress
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Solution Overview
Problem
Switched capacitor power converters face challenges in protecting their switch elements from transient or fault conditions, such as over-voltage stress, which can lead to damage and faulty operation, especially when using low-voltage transistors for high-voltage conversion ratios.
Innovation Solution
The implementation of fault detection and control circuitry that measures internal voltages and currents associated with switching elements and phase nodes, allowing for the alteration of operation by disconnecting or limiting current flow through switch elements, and implementing over-voltage and under-voltage protection mechanisms to prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If low-voltage transistors are used for high-voltage conversion ratios, then device cost and switching power loss are reduced, but the transistors become vulnerable to over-voltage stress and transient fault conditions
Solution Approach 1:
A fault detection circuit is introduced as an intermediary between the low-voltage transistors and the high-voltage environment. This circuit monitors voltages and currents at strategic points (such as phase nodes and switch terminals) and detects transient fault conditions before they can damage the transistors, thereby protecting the energy-efficient low-voltage devices without requiring them to inherently withstand high voltages
Solution Approach 2:
The fault detection circuit performs preliminary monitoring of voltage and current parameters before transient faults can cause damage. By detecting abnormal conditions in advance (such as voltage spikes or current anomalies), the system can take preventive action (such as shutting down or isolating affected transistors) before the low-voltage devices suffer over-voltage stress, thus maintaining both energy efficiency and reliability
2Reliability
If fault detection and control circuitry is added, then protection against transient faults is improved, but device complexity increases
Solution Approach 1:
The fault detection circuit is designed to perform multiple functions: it monitors both voltage and current parameters, detects various types of faults (over-voltage, over-current, transient spikes), and can control multiple transistors or switch pairs. This multi-functionality allows comprehensive protection against transient faults while minimizing the addition of separate dedicated circuits for each protection function, thereby reducing overall device complexity relative to the level of protection provided
3Difficulty of detecting and measuring
If measurement circuitry is added to monitor switch element characteristics, then fault detection capability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The measurement circuitry is designed to utilize existing signals and parameters already present in the switched capacitor power converter operation. By monitoring voltages and currents that naturally occur during normal operation (such as phase node voltages and switch terminal currents), the fault detection system achieves high detection capability without requiring additional precision measurement components or external calibration, thereby avoiding increased manufacturing precision requirements
Data Source
AI summary
Transient or fault conditions for a switched capacitor power converter are detected by measuring one or more of internal voltages and/or currents associated with switching elements (e.g., transistors) or phase nodes, or voltages or currents at terminals of the converter, and based on these measurements detect that a condition has occurred when the measurements deviate from a predetermined range. Upon detection of the condition fault control circuitry alters operation of the converter, for example, by using a high voltage switch to electrically disconnect at least some of the switching elements from one or more terminals of the converter, or by altering timing characteristics of the phase signals.