Dual-Loop PWM Control for Light-Load Power Converter Efficiency
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Solution Overview
Problem
Existing PWM control circuits require high-frequency clock signals for digital operations, leading to significant power consumption, especially in multi-phase applications, and necessitate multiple ADCs for each phase, increasing both power consumption and cost.
Innovation Solution
A dual-loop PWM control circuit that combines digital and analog domains, reducing clock frequency and utilizing synthesized current signals to achieve low power consumption. The circuit includes a main loop control circuit for sensing phase currents and generating PWM signals, and a light-load loop control circuit that generates synthesized current signals based on input voltage, output voltage target, and inductance value to control duty ratios and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fully digital PWM control circuit with high-frequency clock signal is used, then time resolution and control precision are improved, but power consumption increases significantly
Solution Approach 1:
The patent implements dynamic switching between digital and analog control modes based on load conditions. In heavy-load mode, the fully digital control circuit operates with high-frequency clock signals to provide precise time resolution. In light-load mode, the system switches to an analog control mode using a light-load loop control circuit that generates synthesized current signals, significantly reducing clock frequency and power consumption while maintaining adequate control precision
Solution Approach 2:
The patent changes the operating parameters (clock frequency, control mode) based on load conditions. The main loop control circuit operates at high frequency for heavy loads, while the light-load loop control circuit operates at low frequency for light loads. This parameter adaptation resolves the contradiction by matching the control precision to the actual load requirements rather than maintaining maximum precision continuously
2Measurement precision
If multiple ADCs are used for multi-phase applications, then current sensing precision for each phase is improved, but power consumption and cost increase
Solution Approach 1:
The patent merges the current sensing function across multiple phases by using a single ADC to sense the total current (sum of all phase currents) rather than using separate ADCs for each phase. The light-load loop control circuit then generates synthesized current signals that represent the individual phase currents based on this total current sensing and known inductance values, achieving adequate current sensing precision with reduced power consumption and component count
Solution Approach 2:
The patent creates synthesized current signals that are mathematical representations (copies) of the actual phase currents. Instead of directly sensing each phase current with separate ADCs, the system senses the total current and generates synthesized copies of individual phase currents through calculation based on inductance values and switching patterns, reducing the number of physical sensing components needed
Data Source
AI summary
A pulse width modulation control circuit for controlling a power converter circuit includes: a main loop control circuit; and a light-load loop control circuit. The light-load loop control circuit includes a current synthesis circuit configured to generate a synthesized current signal according to an input voltage and a target value of an output voltage and an inductance value of an inductor in a power stage circuit of the power converter circuit. The light-load loop control circuit generates a pulse modulation signal in light-load mode according to the synthesized current signal, to control a duty ratio of the power stage circuit. In the light-load mode, the main loop control circuit enters a power-saving state to reduce the power consumption of the pulse width modulation control circuit. The power-saving state includes: reducing the power consumption of the current sense circuit or stopping the operation of the current sense circuit.