Switching Converter Light Load Regulation via Reverse Current
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Solution Overview
Problem
Conventional switching converters face inefficiencies in light load conditions due to the need for pulse skipping or excessive reverse current usage to regulate output voltage, particularly when operating at fixed switching frequencies.
Innovation Solution
A switching converter system that includes an inductor coupled with a first and second power switch, a signal generator producing a modulated signal with variable pulse width, and a controller that increases reverse current through the second power switch when the pulse width reaches a minimum value to prevent output voltage from exceeding a target value, ensuring efficient regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the predetermined value for inductor current is set to zero to deliver positive current to the load, then the converter can operate in light load conditions, but the output voltage increases at every cycle and regulation is lost
Solution Approach 1:
The patent changes the parameter of inductor current threshold from zero to a negative value, enabling the synchronous rectifier switch to conduct reverse current. This parameter change allows the converter to maintain output voltage regulation in light load conditions while operating at fixed switching frequency, resolving the contradiction between light load operation capability and output voltage regulation.
2Reliability
If the predetermined value is set to a negative value to guarantee regulation of output voltage, then output voltage regulation is maintained, but the efficiency of the system is lowered
Solution Approach 1:
The patent implements dynamic control of the synchronous rectifier switch by adjusting the inductor current threshold based on load conditions. The controller dynamically sets the current threshold to a negative value only when needed for regulation, and adjusts the amount of reverse current accordingly. This dynamic approach maintains output voltage regulation while minimizing energy loss compared to fixed negative threshold approaches.
3Reliability
If pulse skipping technique is implemented to prevent output voltage from increasing, then output voltage regulation is maintained, but fixed switching frequency operation is not suitable
Solution Approach 1:
The patent changes the control parameter from pulse skipping (variable frequency) to adjusting the inductor current threshold (negative value) at fixed switching frequency. By modifying the current threshold parameter, the system achieves output voltage regulation while maintaining constant switching frequency operation, thereby resolving the contradiction between voltage regulation and fixed frequency operation adaptability.
4Loss of energy
If the synchronous rectifier switch is turned off when inductor current decreases to zero, then the converter operates efficiently, but the output voltage increases above target value in light load conditions
Solution Approach 1:
The patent changes the turn-off current threshold of the synchronous rectifier switch from zero to a negative value. This parameter change enables the switch to remain conductive during light load conditions, allowing reverse current flow that prevents output voltage from rising above the target value. The switch is turned off when inductor current reaches this negative threshold, maintaining both efficiency and voltage regulation.
Data Source
AI summary
A switching converter and a method for providing an output voltage is presented. The switching converter includes an inductor coupled to a pair of power switches, a signal generator and a controller. The first power switch is used to magnetize the inductor, while the second power switch is used to de-magnetize it. The signal generator is adapted to generate a modulated signal having a pulse width variable between a minimum value and a maximum value and to drive the first and second power switches based on the modulated signal. Upon identifying that the modulated signal has the minimum pulse width value, the controller increases a reverse current flowing from the inductor through the second power switch to prevent the output voltage from increasing above a target value.