Group Pulse Mode Control for Switching Noise Concentration
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Solution Overview
Problem
Switching power converters, such as flyback converters, generate electromagnetic interference (EMI) that affects noise-sensitive components like touchscreens, as the noise frequency spreads across a wide band due to pulse frequency modulation (PFM) operation, making it difficult to find noise-free bands for operation.
Innovation Solution
Implementing a group pulse mode (GPM) control in switching power converters, where the controller transitions from PWM or PFM to GPM based on a control voltage threshold, concentrating noise at a specific frequency and its harmonics, allowing for efficient noise management across varying loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If pulse frequency modulation (PFM) operation is used to increase efficiency at light loads, then power conversion efficiency is improved, but switching noise spreads across a wide frequency band making it difficult to find noise-free bands for touchscreen operation
Solution Approach 1:
The patent applies periodic action by using pulse width modulation (PWM) during heavy load periods and pulse frequency modulation (PFM) during light load periods. This periodic switching strategy allows the system to maintain high efficiency during light loads while concentrating noise at specific frequencies during heavy loads when touchscreens are less sensitive, thereby resolving the contradiction between efficiency and noise interference
Solution Approach 2:
The patent changes the switching frequency parameter dynamically based on load conditions. During heavy loads, the switching frequency is maintained at a higher value where touchscreen sensitivity is lower. During light loads, PFM reduces the switching frequency to improve efficiency. This parameter change strategy allows the system to optimize both efficiency and noise management at different operating points
2Object-affected harmful factors
If pulse width modulation (PWM) operation is used during heavy loads, then switching noise is concentrated at a specific frequency, but it is not efficient to extend PWM operation across the full load range
Solution Approach 1:
The patent implements dynamic operation mode switching between PWM and PFM based on real-time load detection. The controller dynamically transitions from PWM during heavy loads (where noise concentration is acceptable) to PFM during light loads (where efficiency is prioritized). This dynamic adaptation resolves the contradiction by allowing PWM's noise concentration benefit during heavy loads while using PFM's efficiency benefit during light loads
Solution Approach 2:
The system periodically evaluates load conditions and switches between PWM and PFM modes accordingly. During heavy load periods, PWM is used to concentrate noise at frequencies less sensitive to touchscreen operation. During light load periods, PFM is used to maximize efficiency. This periodic mode switching resolves the contradiction between noise concentration and efficiency
Data Source
AI summary
A switching power converter is provided that cycles a power switch during a group pulse mode of operation to produce a train of pulses within a group period responsive to a control voltage being within a group mode control voltage range. Depending upon the control voltage, the number of pulses in each train of pulses is varied to provide a linear power delivery to the load.