Switching Regulator Phase-Node Capacitance for Fixed-Frequency Efficiency
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Solution Overview
Problem
Existing switching regulators face challenges in maintaining stable light-load efficiency due to varying switching losses at different phase node voltages, and zero voltage switching methods exceed the operating frequency range required by certain load devices.
Innovation Solution
A switching regulator with a control method that adjusts equivalent capacitance at the phase node based on the phase node voltage, using a control circuit to determine and sustain an enable state, and adjust capacitance to reduce voltage across the power switch, ensuring operation at a fixed frequency while enhancing light-load efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If zero voltage switching is used to adjust the timing of the low-side switch turn-on to achieve zero voltage switching, then light-load efficiency is improved, but the operating frequency range is exceeded which is not suitable for load devices requiring fixed switching frequency
Solution Approach 1:
The patent changes the parameter of equivalent capacitance at the phase node to reduce the voltage across the power switch. By adjusting the capacitance value dynamically, the voltage waveform is modified to achieve lower switching losses without changing the switching frequency, thus resolving the contradiction between efficiency improvement and frequency stability.
2Loss of energy
If a single fixed switching frequency is used, then the operating frequency range is maintained for load devices, but light-load efficiency becomes unstable due to varying switching losses at different phase node voltages
Solution Approach 1:
The patent introduces dynamic adjustment of the equivalent capacitance at the phase node, transforming the static fixed-frequency system into a dynamic one. The capacitance value is adjusted in real-time based on operating conditions, enabling the system to maintain stable light-load efficiency while preserving the fixed switching frequency requirement for load devices.
3Speed
If the phase node voltage is higher (near the peak of resonant signal), then the operating frequency is maintained, but switching losses increase resulting in lower light-load efficiency
Solution Approach 1:
The patent performs preliminary action by adjusting the equivalent capacitance before the switching event occurs. By proactively modifying the capacitance value in advance, the voltage across the power switch is reduced before switching, thereby minimizing switching losses while maintaining the required switching frequency.
Data Source
AI summary
A switching regulator includes: a power stage circuit configured to operably control a power switch therein according to a pulse width modulation signal to switch an inductor coupled to a phase node, so as to convert an input voltage to an output voltage; and a control circuit configured to operably determine an equivalent capacitance adjustment procedure to enter or sustain an enabled state according to a phase node voltage at the phase node at an inductor magnetization start time point in a discontinuous conduction mode (DCM) to adjust an equivalent capacitance at the phase node, so as to reduce a voltage across the power switch at another inductor magnetization start time point after the equivalent capacitance adjustment procedure.