Power Converter Minimum Off-Time Control for Overcurrent Protection
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Solution Overview
Problem
Conventional power converters face instability and reduced frequency when minimum off time is set high, and potential damage from overcurrent events when set low, due to insufficient time for overcurrent detection.
Innovation Solution
A power converter with a dynamically controlled minimum off time mechanism, incorporating a high-side and low-side switch, driver circuit, high-side overcurrent protecting circuit, and off time adjusting circuit, which adjusts the minimum off time based on current thresholds to ensure sufficient detection time for overcurrent events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the minimum off time is set to a large value, then the system stability is improved, but the system frequency is reduced
Solution Approach 1:
The patent applies dynamics by making the minimum off time adjustable rather than fixed. The off-time adjusting circuit dynamically changes the minimum off time based on operating conditions, allowing the system to optimize between stability and frequency requirements under different load conditions. This resolves the contradiction by enabling the minimum off time to adapt rather than being constrained to a single fixed value.
Solution Approach 2:
The patent changes the parameter of minimum off time from a constant value to a variable parameter controlled by the off-time adjusting circuit. By modifying this parameter dynamically based on system state, the patent achieves both adequate stability (when longer off time is needed) and higher frequency (when shorter off time suffices), resolving the trade-off between these two parameters.
2Speed
If the minimum off time is set to a small value, then the system frequency is improved, but the overcurrent detection capability is insufficient
Solution Approach 1:
The patent uses dynamics to adjust the minimum off time based on system conditions. When overcurrent protection is needed, the system extends the minimum off time to allow adequate detection time. When normal operation occurs, the system reduces the minimum off time to maintain high frequency. This dynamic adjustment resolves the contradiction between frequency and detection capability.
Solution Approach 2:
The patent changes the minimum off time parameter dynamically through the off-time adjusting circuit. By modifying this parameter based on whether overcurrent detection is required, the system achieves both high frequency operation (when detection isn't needed) and adequate detection capability (when overcurrent risk exists), resolving the contradiction.
3Speed
If the minimum off time is set to a very small value, then the system frequency is improved, but the circuit components are vulnerable to damage from overcurrent
Solution Approach 1:
The patent applies preliminary anti-action by proactively extending the minimum off time when overcurrent conditions are detected. This prevents overcurrent damage by ensuring adequate time for detection and response before the low-side switch can be turned on again. The system takes preventive action rather than reacting after damage occurs, resolving the contradiction between frequency and component protection.
Solution Approach 2:
The patent provides beforehand cushioning by using the off-time adjusting circuit to extend the minimum off time as a protective measure. This creates a time buffer that allows overcurrent detection and prevents rapid switching that could cause damage. The cushioning time ensures safe operation while allowing high frequency during normal conditions, resolving the contradiction.
4Reliability
If the minimum off time is set to a large value, then the overcurrent detection time is sufficient, but the system stability is compromised
Solution Approach 1:
The patent applies dynamics by making the minimum off time variable rather than fixed at a large value. The off-time adjusting circuit dynamically reduces the minimum off time when overcurrent detection is not required, maintaining system stability. When overcurrent protection is needed, it extends the time to ensure adequate detection. This dynamic behavior resolves the contradiction between detection time and stability.
Solution Approach 2:
The patent changes the minimum off time parameter from a constantly large value to a dynamically adjusted parameter. By modifying this parameter based on system state, the system achieves adequate overcurrent detection time (when extended) while maintaining stability (when reduced), resolving the contradiction between these two requirements.
Data Source
AI summary
A power converter having a mechanism of dynamically controlling a minimum off time is provided. A high-side overcurrent protecting circuit determines whether or not a current flows from a high-side switch through a node between a second terminal of the high-side switch and a first terminal of a low-side switch toward an inductor, and determines whether or not the current is larger than a threshold to output a high-side overcurrent detected signal and a high-side overcurrent protecting signal. An off time adjusting circuit outputs a minimum off time signal to a driver circuit according to the high-side overcurrent protecting signal. The driver circuit determines that an overcurrent event occurs when the high-side switch is turned on according to the high-side overcurrent detected signal, and accordingly the driver circuit at least continually turns on the low-side switch during a longer minimum off time of the minimum off time signal.