Power Supply Controller Mode Transition via Current Pulse Length
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Solution Overview
Problem
Power supply controllers face challenges in transitioning between PWM and PFM modes efficiently, leading to unpredictable load points and output ripple voltage variations, which affect the accuracy and efficiency of power conversion.
Innovation Solution
A power supply controller with a switching circuit and transition circuit that monitors current pulse lengths to transition from PWM to PFM mode based on load conditions, using a control-signal adjuster to maintain a stable output voltage and adjust the inductor current peak ratios, thereby minimizing transition-induced transients and output ripple voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power supply controller uses fixed threshold for mode transition, then the transition point is predictable, but the transition occurs at suboptimal load points with higher output ripple voltage
Solution Approach 1:
The patent dynamically adjusts the threshold parameter for mode transition based on operating conditions. Specifically, the threshold is modified as a function of the measured output ripple voltage or related parameters, allowing the transition point to adapt to changing load conditions and minimize output ripple voltage while maintaining predictable transition behavior.
2Loss of energy
If the power supply controller transitions to PFM mode at light load conditions, then efficiency is improved, but output ripple voltage increases due to discontinuous operation
Solution Approach 1:
The patent implements dynamic switching between PWM and PFM modes based on real-time monitoring of load conditions and output ripple voltage. The controller continuously adjusts its operating mode to optimize efficiency while maintaining acceptable ripple levels, transitioning to PFM only when efficiency benefits outweigh the ripple increase.
Solution Approach 2:
The threshold for transitioning to PFM mode is dynamically adjusted based on output ripple voltage measurements. When ripple voltage exceeds acceptable levels, the threshold is raised to prevent premature transition to PFM mode, thereby maintaining lower ripple operation even at light loads.
3Adaptability or versatility
If the power supply uses discontinuous PWM mode, then adaptability to light load conditions is improved, but transition to PFM mode occurs at unpredictable load points
Solution Approach 1:
The patent employs feedback mechanisms that monitor output ripple voltage and use this information to determine the optimal transition point from discontinuous PWM to PFM mode. The measured ripple voltage feeds back to the control logic, which adjusts the transition threshold accordingly, making the transition point predictable while maintaining adaptability to light load conditions.
Data Source
AI summary
An embodiment of a power-supply controller includes a switching circuit and a transition circuit. The switching circuit is configured to generate a regulated output voltage by generating first current pulses at an approximately fixed frequency during a first mode, and generating second current pulses at a variable frequency during a second mode. And the transition circuit is configured to transition the switching circuitry from the first mode to the second mode in response to a length of one of the first current pulses. For example, a power supply may include such a power-supply controller to transition the supply from a PWM mode to a PFM mode under light-load conditions. To cause this transition at a predictable load point, the controller may monitor the lengths of the current pulses during the PWM mode, and may transition the supply to a PFM mode in response to the lengths being below a threshold.