Burst Mode Controller for SMPS Efficiency and Noise Reduction
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Solution Overview
Problem
Switched mode power supplies face challenges in maintaining high efficiency at low power levels and preventing audio noise during burst mode operation, while also ensuring rapid response to load steps and accurate control of ripple voltage and burst frequency.
Innovation Solution
A method and controller for controlling burst mode operation in switched mode power supplies, where the burst period is adjusted based on the duration of preceding bursts, allowing independent setting of burst frequency and ripple voltage, and enabling instantaneous reaction to load steps by calculating the desired duration of the current burst period from previous burst data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If burst mode operation is used to increase efficiency at low power levels, then efficiency is improved, but audio noise is generated due to vibrations in power components
Solution Approach 1:
The patent implements dynamic adjustment of burst frequency and burst on-time based on load conditions. The controller adapts the burst mode parameters in real-time, varying the frequency and duration of switching bursts to maintain efficiency while avoiding the 1-10 kHz range where human ears are most sensitive, thereby reducing audible noise.
Solution Approach 2:
The patent changes the operational parameters of burst mode by independently controlling burst frequency and burst on-time. By adjusting these parameters dynamically according to load requirements, the system optimizes efficiency while suppressing audio noise through frequency modulation that avoids sensitive human hearing ranges.
2Ease of operation
If fixed burst length is used to simplify control, then ease of operation is improved, but ripple voltage becomes unacceptably high at low loads
Solution Approach 1:
The patent implements dynamic control where the burst on-time is adjusted based on the error signal from the output voltage regulation loop. This allows the system to maintain simple burst mode operation while adaptively controlling the burst duration to keep ripple voltage within acceptable limits across different load conditions.
Solution Approach 2:
The patent uses feedback from the output voltage regulation loop to control the burst on-time. The error signal dynamically adjusts the duration of each burst, ensuring that ripple voltage remains acceptable at low loads while maintaining simple overall control architecture.
3Object-affected harmful factors
If fixed burst frequency is used to reduce audio noise, then audio noise is reduced, but response time to load steps becomes too slow
Solution Approach 1:
The patent implements dynamic burst frequency adjustment that responds to load conditions. The controller can operate at lower frequencies to reduce audio noise during steady-state low-load conditions, while rapidly increasing frequency and reducing burst duration in response to load steps, achieving both noise reduction and fast response.
Solution Approach 2:
The patent uses periodic burst mode operation with dynamically adjusted parameters. By controlling the timing and duration of switching bursts adaptively, the system achieves low audio noise during normal operation while maintaining rapid response capability when load changes occur.
4Manufacturing precision
If larger capacitors are used to reduce ripple voltage, then ripple voltage is reduced, but device complexity and cost increase
Solution Approach 1:
The patent applies preliminary control action by adjusting burst on-time based on predicted load requirements and error signals before ripple becomes excessive. This proactive control allows the use of smaller capacitors while maintaining acceptable ripple voltage levels.
Solution Approach 2:
The patent changes the operational parameters of the power supply by dynamically adjusting burst frequency and on-time, which controls ripple voltage through modulation rather than through larger filtering capacitors, thereby reducing device complexity and cost.
Data Source
AI summary
Consistent with an example embodiment, there is method and a controller for controlling burst mode operation of a switched mode power supply (SMPS). It also relates to switched mode power supplies comprising such a controller. One way to increase the efficiency of a switched mode power supply is to operate it at a power level close to the optimum efficiency point for a brief period, followed by a period where the power supply is not switching during which no energy is wasted. This type of operation is known as “burst mode” and results in high efficiency at low power levels.