Power Converter Crossover Frequency Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing DC/DC power converters have a fixed crossover frequency, which limits the ability to achieve faster loop response times and stability when the user selects a switching frequency higher than the lowest allowed, preventing faster recovery from changes in input voltage or output load.
Innovation Solution
The gain of the error amplifier in a power converter is controlled responsive to the switching frequency, allowing the crossover frequency to change, thereby enabling a single terminal to control the switching frequency, error amplifier gain, and resultant crossover frequency within the feedback loop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the crossover frequency is fixed at 20-25% of the lowest switching frequency, then stability is ensured, but the loop response time cannot be faster and recovery from changes is slower
Solution Approach 1:
The error amplifier's transconductance is made dynamically adjustable through a current squarer circuit that processes a frequency-proportional current signal. This allows the crossover frequency to adapt to different switching frequencies, enabling faster loop response when operating above the minimum switching frequency while maintaining stability.
Solution Approach 2:
The patent changes the transconductance parameter of the error amplifier based on the switching frequency. By using a current squarer to process the frequency-proportional current, the system adjusts the error amplifier's gain characteristic to achieve optimal loop response time for each operating condition.
2Loss of time
If a higher crossover frequency is used, then faster loop response time is achieved, but stability cannot be ensured at lower switching frequencies
Solution Approach 1:
The system uses feedback through the current squarer circuit to automatically adjust the error amplifier's transconductance based on the actual switching frequency. This feedback mechanism ensures that the crossover frequency remains at the optimal 20-25% ratio regardless of the switching frequency setting, maintaining both stability and speed.
3Loss of time
If the crossover frequency is set for fastest response, then loop response time is minimized, but the converter cannot operate at lower switching frequencies with stability
Solution Approach 1:
The current squarer-based transconductance adjustment circuit provides universal operation across the entire switching frequency range. The circuit automatically adapts the error amplifier's characteristics to match any switching frequency from the minimum to maximum operating points, enabling the system to maintain optimal performance across all conditions.
Data Source
AI summary
A power converter constituted of: a reference source; a clock generator exhibiting a variable frequency output, the value of the frequency of the variable frequency output responsive to an external resistor value; and an error amplifier in communication with the reference source, the error amplifier exhibiting a gain whose value is responsive to the external resistor value. Preferably the error amplifier is a transconductance amplifier. In one embodiment the power converter further exhibits a current squarer, arranged to produce a squared value of a current whose value is responsive to the external resistor and provide the squared value to the transconductance amplifier.