Hybrid DC-DC Converter Control for Light-Load Noise Reduction
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Solution Overview
Problem
Conventional DC-DC converting circuits experience high frequency noise, high frequency switching loss, and electromagnetic interference when operating in quasi-resonant mode under light or lighter loading conditions.
Innovation Solution
A multi-mode hybrid control DC-DC converting circuit that includes a switching power converter and a microcontroller, which sets multiple thresholds to determine the loading and adjusts the frequency of the driving signal between variable-frequency, constant-frequency, and pulse-skipping modes, maintaining a constant frequency even under lighter loads to mitigate noise and loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If quasi-resonant mode is used to improve power conversion efficiency, then efficiency is improved, but high frequency noise and electromagnetic interference increase under light loading
Solution Approach 1:
The patent implements dynamic frequency adjustment by switching between quasi-resonant mode and pulse-skipping mode based on loading conditions. The microcontroller monitors the load and dynamically changes the operating mode: using QR mode for heavy loads to maximize efficiency, and PSM for light loads to reduce noise and EMI while maintaining acceptable efficiency.
Solution Approach 2:
The patent changes the operating parameters (frequency and mode) of the switching power converter based on loading conditions. By adjusting the driving signal frequency and switching between different operating modes (QR and PSM), the system optimizes performance across different load scenarios, reducing high-frequency noise and EMI during light loading while maintaining efficiency during heavy loading.
2Use of energy by moving object
If driving signal frequency is increased under light loading to maintain efficiency, then power conversion efficiency is maintained, but switching loss increases
Solution Approach 1:
The system dynamically adjusts the driving signal frequency based on loading conditions. During light loading, instead of maintaining high frequency to preserve efficiency, the system switches to pulse-skipping mode which uses lower frequency operation, thereby reducing switching losses while still maintaining acceptable power conversion efficiency through intelligent mode selection.
Solution Approach 2:
The patent employs periodic action through pulse-skipping mode where the switching converter operates in intermittent pulses rather than continuous high-frequency switching. This periodic operation reduces the average switching frequency under light loading conditions, thereby decreasing switching losses while maintaining sufficient power delivery efficiency.
3Object-affected harmful factors
If multi-mode hybrid control is implemented to reduce noise and interference, then electromagnetic interference is reduced, but device complexity increases
Solution Approach 1:
The patent uses feedback control where the microcontroller monitors the loading conditions and automatically selects the appropriate operating mode (QR or PSM). This feedback mechanism simplifies the control complexity by using intelligent decision-making based on load detection, rather than requiring complex analog control circuits, thereby reducing EMI while keeping the control system manageable.
Solution Approach 2:
The microcontroller serves as an intermediary between the load conditions and the switching converter operation. It processes load information and generates appropriate control signals to switch between QR and PSM modes, thereby managing the complexity of multi-mode operation through a centralized intelligent controller rather than distributed complex circuitry, reducing EMI in the process.
Data Source
AI summary
A multi-mode hybrid control DC-DC converting circuit has a switching power converter and a microcontroller. The switching power converter has a transformer and a switching switch. The switching switch is connected to a primary-side winding of the transformer in series. The microcontroller is connected to the switching power converter and a control terminal of the switching switch. The microcontroller sets multiple thresholds according to an input voltage of the switching power converter, and determines whether a feedback voltage of the switching power converter is higher or lower than each one of the thresholds to perform a variable-frequency mode, a constant-frequency mode, or a pulse-skipping mode. The microcontroller outputs a driving signal to the switching switch and correspondingly adjusts a frequency of the driving signal according to the variable-frequency mode, the constant-frequency mode, or the pulse-skipping mode which is performed.