Power Supply Circuit Gain Adjustment for Stability
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Solution Overview
Problem
Conventional power supply circuits face instability due to varying capacitance values of smoothing capacitors, leading to either slow load responsiveness or oscillation, necessitating a solution that maintains stable operation regardless of capacitance values.
Innovation Solution
A power supply circuit with a control loop and gain adjustment circuit that adjusts the gain of the error amplifier based on the charge current after capacitor charging starts, using threshold values to detect capacitance changes and adjust the control loop's bandwidth accordingly, ensuring stable operation across different capacitance values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the capacitance value of the smoothing capacitor is increased, then circuit operation stability is improved, but load responsiveness becomes slow
Solution Approach 1:
The patent applies dynamics by making the control loop gain adjustable based on operating conditions. The gain adjustment circuit dynamically changes the gain of the error amplifier according to the output current magnitude, allowing the system to adapt between stability and responsiveness requirements depending on the current operating state.
Solution Approach 2:
The patent changes the gain parameter of the control loop based on output current thresholds. When output current exceeds a threshold, the gain is reduced to improve stability; when current is below the threshold, normal gain is maintained for fast responsiveness. This parameter adjustment resolves the contradiction between stability and speed.
2Speed
If the capacitance value of the smoothing capacitor is decreased, then load responsiveness is improved, but oscillation occurs
Solution Approach 1:
The control loop gain is made dynamically adjustable based on output current conditions. When the output current is large (exceeding threshold), the gain is automatically reduced to prevent oscillation, while allowing small capacitance values to maintain fast responsiveness during low-current operation.
Solution Approach 2:
The gain parameter of the error amplifier is changed based on output current magnitude. By reducing gain when current exceeds a threshold, the system prevents oscillation that would otherwise occur with small capacitance values, while maintaining fast response capability during normal operation.
3Stability of the object's composition
If a configuration to avoid oscillation is added, then circuit stability is improved, but device complexity increases
Solution Approach 1:
The patent merges the oscillation prevention function with the existing control loop by adding a gain adjustment circuit that works together with the error amplifier. This integrated approach avoids the need for separate oscillation prevention configurations, reducing overall system complexity while maintaining stability.
Solution Approach 2:
The patent uses feedback by monitoring the output current and automatically adjusting the error amplifier gain accordingly. When output current exceeds a threshold, the feedback mechanism reduces the gain to prevent oscillation, providing stable operation without complex additional configurations.
Data Source
AI summary
According to one embodiment, a power supply circuit includes a smoothing capacitor that is charged with a charge current from an output transistor and outputs a voltage as an output voltage; a control loop that controls a conduction state of the output transistor depending on a difference value between the output voltage and a reference voltage; and a gain adjustment circuit that adjusts a gain of the control loop depending on magnitude of the charge current after the charge starts.