Power Converter Over-Current Protection with Dynamic Threshold
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Solution Overview
Problem
Conventional over-current protection systems in power converters are not effective in maintaining constant maximum current and power over a wide range of input voltages, leading to potential damage from excessive current and voltage stress, and they consume significant power due to external resistors.
Innovation Solution
A control system that includes a comparator and pulse-width-modulation generator to adjust the input current based on input voltage, using a threshold signal generated from both input current and voltage signals, allowing for constant maximum current and power delivery across varying input voltages while minimizing standby power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional OCP systems use external resistors for current sensing, then over-current protection is provided, but significant power is consumed during standby mode
Solution Approach 1:
The patent combines the OCP resistor function with the startup resistor function into a single shared resistor. During startup, the resistor provides the necessary startup current path, and during normal operation, it continues to provide current sensing for OCP. This eliminates the need for a separate standby power-consuming resistor while maintaining protection functionality.
Solution Approach 2:
The resistor is designed to serve multiple functions: startup current provision, over-current sensing, and over-power protection. By making the resistor multi-functional, the patent eliminates redundant components that would consume power during standby mode while maintaining all necessary protection capabilities.
2Reliability
If cycle-by-cycle control is used for OCP, then maximum current is limited, but maximum power delivery is restricted
Solution Approach 1:
The patent implements a dynamic OCP threshold that adjusts based on operating conditions rather than using a fixed cycle-by-cycle limit. The control system monitors multiple parameters and dynamically sets the current threshold to allow maximum power delivery when conditions permit while still providing protection when necessary.
Solution Approach 2:
The patent changes the OCP parameter from a fixed current threshold to a variable threshold that depends on operating conditions such as input voltage, output load, and temperature. This allows the system to deliver maximum power when conditions are favorable while maintaining safety limits when conditions require restriction.
3Adaptability or versatility
If adjustable OCP threshold based on line input voltage is used, then protection adapts to voltage variations, but actual limitation on maximum current is not constant over wide voltage range
Solution Approach 1:
The patent implements a feedback control system that continuously monitors input voltage, output current, and other operating parameters to maintain a constant maximum current limit. The system adjusts the OCP threshold in real-time based on feedback signals to compensate for voltage variations, ensuring consistent current limitation across the full input voltage range.
Data Source
AI summary
System and method for protecting a power converter. A system includes a threshold generator configured to generate a threshold signal, and a first comparator configured to receive the threshold signal and a first signal and to generate a comparison signal. The first signal is associated with an input current for a power converter. Additionally, the system includes a pulse-width-modulation generator configured to receive the comparison signal and generate a modulation signal in response to the comparison signal, and a switch configured to receive the modulation signal and adjust the input current for the power converter. The threshold signal is associated with a threshold magnitude as a function of time. The threshold magnitude increases with time at a first slope during a first period, and the threshold magnitude increases with time at a second slope during a second period. The first slope and the second slope are different.