Power Converter Current Limit Control for Peak Load Efficiency
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Solution Overview
Problem
Conventional switched mode power converters face inefficiencies due to constant design for peak power conditions, leading to reduced efficiency during normal operation, particularly in applications with varying power demands.
Innovation Solution
A controller with an adaptive current limit generator that adjusts the upper threshold of the current limit based on switching frequency, transitioning between 'normal' and 'peak' power modes to optimize efficiency across different load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the power converter is designed for peak power conditions, then high power delivery is achieved, but efficiency deteriorates during normal operation
Solution Approach 1:
The patent implements dynamic adjustment of the current limit threshold based on switching frequency. The controller transitions between normal power mode and peak power mode by varying the threshold, allowing the system to adapt its operating characteristics in real-time rather than being fixed for peak conditions. This dynamic behavior resolves the contradiction by enabling high power delivery when needed while maintaining efficiency during normal operation.
Solution Approach 2:
The patent changes the parameter of current limit threshold dynamically based on switching frequency measurements. When switching frequency exceeds a threshold, the system transitions to peak power mode with adjusted threshold values, enabling the converter to optimize between efficiency and power delivery by changing operational parameters rather than being designed for worst-case conditions only.
2Power
If the upper threshold of current limit is increased for peak power mode, then power delivery is improved, but conduction losses increase during normal operation
Solution Approach 1:
The system dynamically adjusts the upper threshold of the current limit based on detected switching frequency. During normal operation, the threshold remains at a lower value optimized for efficiency. When peak power demand is detected through switching frequency analysis, the threshold increases to enable higher power delivery. This dynamic adjustment resolves the contradiction by applying different threshold values appropriate to different operational states.
3Reliability
If switched mode power converter uses conventional control, then output regulation is achieved, but efficiency is reduced during varying load conditions
Solution Approach 1:
The patent employs feedback by monitoring switching frequency as an indicator of load conditions and power mode. The controller uses this feedback to determine whether to operate in normal power mode or peak power mode, adjusting the current limit threshold accordingly. This feedback mechanism enables the system to maintain output regulation while optimizing efficiency for varying load conditions, resolving the contradiction between reliable regulation and efficiency.
Data Source
AI summary
A controller for a power converter comprising a drive circuit and an adaptive current limit generator. The drive circuit is coupled to receive a request signal representative of a power demand of an output of the power converter. The drive circuit is configured to generate a drive signal to control switching of a power switch in response to the request signal. The adaptive current limit generator configured to generate a current limit signal and the drive circuit is configured to turn off the power switch when a current sense signal reaches the current limit signal. The adaptive current limit generator is configured to vary an upper threshold of the current limit signal to a first value when a switching frequency is less than a frequency threshold and vary the upper threshold to a second value when the switching frequency is greater than the frequency threshold.