Switching Power Supply Control Circuit Light Load Efficiency
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Solution Overview
Problem
Switching power supplies designed for high efficiency in heavy loads experience reduced efficiency in light loads due to the trade-off between switching element size and gate capacitance, leading to increased gate driving current in light load states.
Innovation Solution
A control circuit for boost, buck, or buck-boost switching power supplies that includes two switching transistors of different sizes, with independent control terminals, and a pulse signal generating mechanism that adjusts the number of pulses in the driving signal based on load conditions, switching the larger transistor in heavy loads and the smaller transistor in light loads to minimize gate driving current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switching frequency is reduced in light load state to improve efficiency, then the gate driving current loss is reduced, but the control complexity increases
Solution Approach 1:
The control circuit is segmented into multiple functional modules including a pulse signal generating portion, a determination portion, and driver circuits. This modular segmentation organizes the control complexity into manageable components, making the system easier to design, implement, and maintain while achieving the desired light load efficiency improvements.
2Loss of energy
If two switching transistors with independent control terminals are used to optimize both heavy load and light load efficiency, then the device complexity increases
Solution Approach 1:
Both the first and second switching transistors are designed to perform the same fundamental switching function, but with different size optimizations for different load conditions. This multi-functionality approach allows a single switching element structure to serve multiple operating conditions, reducing the need for entirely separate circuits and minimizing the actual increase in device complexity.
Data Source
AI summary
The present invention improves the efficiency of a switching power supply in a light load. A control circuit is configured to repeat a driving duration enabling the switching element to be switched and a stop duration stopping the switching in a light load state. A pulse signal generating portion generates a driving pulse signal, in which the driving pulse signal at least includes a pulse in the driving duration, and the lighter a load is, the less the number of pulses in the driving duration is. A first driver drives a first switching transistor according to the at least one pulse in the driving pulse signal other than predetermined K pulses (K is a natural number). The K pulses are in the driving pulse signal when the number of the pulses is reduced to K.