Flyback Converter Control Circuit With Pole Adjustment for Stability
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Solution Overview
Problem
Existing flyback converters face challenges in reducing current consumption of closed-loop control circuits while maintaining stability, as increasing efficiency often leads to instability due to the dominant pole moving to lower frequencies.
Innovation Solution
The proposed control circuit incorporates a feedback circuit with current mirrors, compensation resistors and capacitors, and pole adjusters to move the dominant pole to a high-frequency position, generating a new dominant pole, thereby stabilizing the circuit and reducing current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the current consumption of the closed-loop control circuit is reduced to increase conversion efficiency, then energy efficiency is improved, but the stability of the control circuit deteriorates due to the dominant pole moving to lower frequencies
Solution Approach 1:
The patent introduces a pole adjuster that dynamically adjusts the dominant pole frequency by changing the effective resistance value in the feedback network. This allows the system to maintain stability by keeping the dominant pole at an appropriate frequency even when operating currents are reduced, thus resolving the contradiction between low current consumption and control stability
Solution Approach 2:
The pole adjuster acts as an intermediary component between the feedback circuit and the power stage. It mediates the relationship between the feedback signal and the control output by adjusting the dominant pole position, enabling the system to achieve both low current consumption and stable control through this intermediate adjustment mechanism
Data Source
AI summary
A control circuit adapted to a flyback converter includes a feedback circuit, a first current mirror, a second current mirror, a compensation resistor, and a pole adjuster. The feedback circuit generates a feedback current based on the output voltage from the flyback converter. The first current mirror maps the feedback current to a first mapping current. The second current mirror maps the first mapping current to a second mapping current. The compensation resistor is coupled to an internal node. The second mapping current flows through the compensation resistor to generate an internal voltage at the internal node. The pole adjuster generates a compensation voltage based on the internal voltage. The flyback converter raises the output power of the output voltage as the compensation voltage increases.