Resonant DC/DC Converter Control for Light Load Loss Reduction
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Solution Overview
Problem
Conventional resonance DC/DC converters face challenges in stabilizing output voltage at light load or non-load conditions, leading to high circuit losses and difficulty in optimizing magnetic devices due to the need for broad frequency ranges, which complicates feedback control and increases non-load losses.
Innovation Solution
A method that adjusts the turn-on frequency of input switch devices and duty ratio of the resonance circuit based on feedback signals, switching between pulse frequency modulation (PFM) and pulse width modulation (PWM) control modes to stabilize output voltage, allowing for combined PFM+PWM control at light or non-load states, thereby extending the output voltage range and reducing circuit losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pulse frequency modulation (PFM) control is used to stabilize output voltage, then the output voltage can be regulated by changing operating frequency, but the operating frequency range becomes excessively broad causing difficulty in optimizing magnetic devices and increasing circuit losses
Solution Approach 1:
The patent applies dynamics by making the control mode adjustable based on operating conditions. The controller dynamically switches between PFM mode and PWM mode depending on the load state, allowing the system to adapt its control strategy rather than being fixed in one mode. This resolves the contradiction by using PFM only when appropriate (avoiding excessive frequency range) while using PWM when light-load conditions would otherwise require problematic frequency adjustments.
Solution Approach 2:
The patent changes the control parameter from frequency-only modulation (PFM) to duty ratio modulation (PWM) under specific conditions. By switching the controlled parameter based on load state, the system avoids the need for excessively broad frequency ranges that cause magnetic device optimization difficulties and increased circuit losses, while maintaining output voltage stability.
2Reliability
If operating frequency is increased to stabilize output voltage at light load conditions, then voltage regulation is improved, but switching losses of the switch device increase significantly
Solution Approach 1:
The controller dynamically selects the appropriate control mode based on load conditions. At light load conditions, it switches to PWM mode which regulates voltage through duty ratio adjustment rather than frequency increase, thereby avoiding the switching losses that would result from operating at excessively high frequencies.
Solution Approach 2:
Instead of increasing frequency to stabilize voltage (the conventional PFM approach), the patent inverts the approach by using duty ratio modulation at fixed or reduced frequency. This reverse strategy achieves voltage stabilization without the penalty of increased switching losses.
3Reliability
If broad frequency range is used for voltage regulation, then light load and non-load voltage stability is improved, but magnetic device optimization becomes difficult
Solution Approach 1:
The system dynamically adapts its control strategy based on load conditions, switching from PFM (which requires broad frequency range) to PWM mode at light load conditions. This eliminates the need for magnetic devices optimized for excessively broad frequency ranges, making magnetic component design and manufacturing more straightforward.
Solution Approach 2:
The patent changes the controlled parameter from frequency to duty ratio under specific conditions, thereby eliminating the requirement for broad frequency ranges. This makes magnetic device optimization easier since the frequency range can be narrowed and optimized for specific operating conditions rather than covering an excessively broad spectrum.
4Device complexity
If simple frequency modulated control is used, then control circuit complexity is reduced, but the ability to stabilize voltage at light load or non-load conditions is insufficient
Solution Approach 1:
The controller dynamically selects between PFM and PWM modes based on load conditions, enhancing voltage stabilization capability at light load without requiring excessively complex control circuitry. The switching logic between modes adds minimal complexity while dramatically improving performance.
Solution Approach 2:
The control circuit is designed to perform multiple functions: it can operate in PFM mode for normal load conditions and switch to PWM mode for light load conditions. This multi-functionality allows a single control circuit to handle a wide range of operating conditions effectively, improving voltage stabilization without proportionally increasing complexity.
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 the regulation ability of the resonance circuit, expands the voltage output range, and reduces circuit losses by smoothly switching between control modes, improving reliability and dynamic characteristics, while being applicable to various resonance circuit topologies.
Implementation Method 1
the series resonance DC/DC converter adopts resonance converting technique. As the resonance element operates at the sine resonance state, the voltage across the switch device is naturally cross-zero
Data Source
AI summary
The present invention refers to a method for controlling a resonance DC/DC converter, which adjusts an output voltage by changing a turn-on frequency of input switch devices of a resonance circuit of the converter, and extends the range of the output voltage of the resonance circuit by adjusting the duty ratio of the switch devices based on the feedback signal of the load circuit. The present invention also provides the resonance DC/DC converter structure using the controlling method. The advantage of the present invention lies in the use of two modes of frequency modulation and frequency modulation plus pulse width modulation to control the resonance DC/DC converter; the use of the frequency modulation controlling mode when the operating frequency of the power supply is low, and introducing the frequency modulation plus pulse width modulation controlling mode when the operating frequency of the power supply is too high. As a result, the problem of the resonance converter, that is, the high operating frequency and the big loss of the circuit when the circuit operates at a light load and non-load, can be solved, and thus the regulation ability for the output voltage of the resonance circuit is enormously improved, and the output range of the voltage is effectively expanded.