Switched-Mode Power Supply Loop Gain Control for Smooth CC Transition
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Solution Overview
Problem
Switched-mode power supplies face difficulties in smoothly transitioning from constant voltage mode to constant current mode, especially when loads have noise constraints, using existing methods like pulling on a main compensation node or voltage follower.
Innovation Solution
An integrated circuit with a control circuit that detects output current exceeding a threshold, reducing loop gain by adjusting the transconductance and output impedance of an amplifier to transition from constant voltage to constant current mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing approaches (pulling on COMP pin or voltage follower) are used to transition from constant voltage mode to constant current mode, then current control is achieved, but the transition is not smooth and causes noise issues
Solution Approach 1:
The patent applies dynamics by making the loop gain adjustable rather than fixed. The loop gain is dynamically reduced when transitioning from constant voltage to constant current mode, allowing the system to adapt its control characteristics to achieve smooth transition while maintaining current control. This is implemented through a control circuit that detects the mode transition and adjusts the amplifier's loop gain accordingly.
2Measurement precision
If loop gain is maintained high during mode transition, then voltage control precision is preserved, but the transition to constant current mode becomes difficult and non-smooth
Solution Approach 1:
The patent makes the loop gain dynamic by reducing it during mode transition. The control circuit detects when the power supply transitions from constant voltage to constant current mode and automatically reduces the loop gain of the amplifier. This dynamic adjustment allows the system to maintain voltage control precision during normal operation while enabling smooth transition to current mode when needed.
Solution Approach 2:
The patent changes the loop gain parameter during mode transition. By reducing the loop gain when transitioning to constant current mode, the system achieves smoother transition characteristics. This parameter change is implemented through the control circuit that modifies the amplifier's operation to reduce its loop gain, thereby facilitating the mode transition while maintaining measurement precision.
Data Source
AI summary
An integrated circuit is described. This integrated circuit may include a control circuit. During operation, the control circuit may detect when an output current provided to a load exceeds a current threshold. Moreover, in response to the detection, the control circuit may reduce a loop gain associated with an amplifier in the control circuit. Note that the output current may be associated with a switched-mode power supply. For example, the reduced loop gain may transition the switched-mode power supply from a constant voltage mode to a constant current mode. In some embodiments, the output current may be associated with a power supply or a source. Notably, the reduced loop gain may transition the power supply or the source from a constant voltage mode to a constant current mode.