DC-DC Converter Burst Mode with Foldback Curves
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Solution Overview
Problem
Switched Mode Power Supply (SMPS) circuits face inefficiencies under light load conditions due to continuous operation, leading to increased switching losses and reduced efficiency, especially when operating with varying line voltages.
Innovation Solution
Implementing a burst mode operation with multiple foldback curves for different voltage ranges, where the DC-DC converter enters a burst mode when output power falls below predetermined thresholds, using a single minimum current threshold for controlling the on-time of the primary-side switch, regardless of the foldback curve, to optimize blanking intervals and reduce power transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If continuous operation mode is used under light load conditions, then the converter maintains stable output voltage, but switching losses increase and efficiency decreases
Solution Approach 1:
The patent implements burst mode operation where the converter operates in periodic cycles of on-time and off-time under light load conditions. During on-time, the converter transfers energy to maintain output voltage; during off-time, the converter remains inactive to reduce switching losses. This periodic operation allows the system to maintain output stability while significantly reducing energy waste from continuous switching.
2Loss of energy
If multiple foldback curves are implemented for different voltage ranges, then efficiency is improved across varying line voltages, but device complexity increases
Solution Approach 1:
The patent employs dynamic selection of foldback curves based on the detected line voltage range. The control circuit automatically switches between different foldback curves (first foldback curve for high line voltage, second foldback curve for low line voltage) to optimize the blanking interval and minimize switching losses under varying input conditions. This dynamic adaptation allows efficient operation across a wide voltage range without requiring manual configuration.
Solution Approach 2:
The patent changes the parameters of the foldback curve based on operating conditions. By selecting different foldback curves corresponding to different line voltage ranges, the system adjusts the relationship between feedback voltage and blanking interval frequency to match optimal efficiency points for each voltage condition, thereby reducing overall energy losses.
3Loss of energy
If burst mode is entered under light load, then switching losses are reduced, but audible noise may occur
Solution Approach 1:
The patent adjusts the blanking interval frequency parameter dynamically based on the selected foldback curve and operating conditions. By optimizing the blanking interval frequency within the burst mode operation, the system reduces switching losses while avoiding frequencies that would generate audible noise, thus balancing efficiency improvement with noise suppression.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances efficiency by reducing power transfer during light loads, balancing switching and conduction losses across different line voltage conditions, and preventing audible noise issues, thereby improving overall performance and energy utilization.
Implementation Method 1
After the energy stored in the transformer is dissipated (that is, when the discharge phase ends), the resonant circuit causes a node voltage of the switch element to ring.
Data Source
AI summary
In an embodiment, a circuit for a Direct Current to Direct Current (DC-DC) converter comprises an input voltage detection circuit, an oscillator circuit, and a burst entry detection circuit. The input voltage detection circuit produces, using a voltage sense signal, a first input voltage indicator. The first input voltage indicator indicates a voltage range selected from a plurality of voltage ranges. The oscillator circuit selects, using the first indicator, a foldback curve from a plurality of foldback curves. The foldback curve is used to determine a blanking time of a gate signal. The burst entry detection circuit determines, using an indicator of an output power of the DC-DC converter, whether to operate the circuit in a burst mode.