DC-DC Converter Nonlinear Frequency Control
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Solution Overview
Problem
Existing DC-DC converters face issues with abnormal oscillations due to inter-winding stray capacitance, leading to increased switching frequency and the need for high photocoupler gain, which can result in efficiency loss and instability, especially under light load conditions.
Innovation Solution
Incorporating a nonlinear response unit within the controller to exponentially change the switching frequency based on feedback current, eliminating the need for increased photocoupler gain and avoiding the use of dummy loads, thereby stabilizing feedback control and maintaining efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the switching frequency is increased to prevent voltage increase under light load, then the output voltage regulation is improved, but the efficiency deteriorates due to increased switching losses
Solution Approach 1:
The patent applies dynamics by making the switching frequency variable rather than fixed. The frequency is dynamically adjusted based on load conditions - increased under light load to prevent voltage rise and abnormal oscillations, and optimized under heavy load to maintain regulation while minimizing switching losses. This dynamic adaptation resolves the contradiction between voltage regulation and efficiency.
Solution Approach 2:
The patent changes the switching frequency parameter according to load conditions. Under light load, the frequency is increased to suppress voltage increase and abnormal oscillations. Under heavy load, the frequency is optimized to balance regulation performance and switching losses. This parameter change strategy directly addresses the technical contradiction.
2Reliability
If the gain of the photocoupler is increased to suppress abnormal oscillation, then the stability is improved, but the device complexity increases and mass production becomes difficult
Solution Approach 1:
The patent uses feedback control where the switching frequency is automatically adjusted based on the output voltage feedback. The controller detects voltage deviations and abnormal oscillations and responds by modifying the switching frequency, eliminating the need for high-gain photocouplers and complex manual adjustments while maintaining stability.
Solution Approach 2:
The system performs self-service by automatically adjusting its own switching frequency in response to load changes and voltage deviations. This self-regulation mechanism eliminates the need for external gain adjustment components and simplifies the feedback control system, making it suitable for mass production.
3Reliability
If a dummy load is added to prevent abnormal oscillation under light load, then the stability is improved, but the loss of energy increases due to the additional load
Solution Approach 1:
Instead of using a static dummy load, the patent employs dynamic switching frequency adjustment that adapts to actual load conditions. Under light load, the frequency is increased to suppress oscillations without requiring additional power-consuming components. This dynamic approach eliminates dummy load losses while maintaining stability.
Solution Approach 2:
The patent converts the potentially harmful effect of light load (voltage increase and oscillation) into a beneficial control signal that triggers frequency adjustment. The controller detects the light load condition and responds by increasing frequency, turning a problematic operating condition into an opportunity for optimized performance without energy waste.
4Measurement precision
If the switching frequency is increased to maintain output voltage under varying loads, then the voltage regulation is improved, but the abnormal oscillation increases due to inter-winding stray capacitance
Solution Approach 1:
The patent uses feedback control to detect abnormal oscillations and voltage deviations caused by inter-winding stray capacitance. The controller responds by adjusting the switching frequency to suppress oscillations while maintaining voltage regulation. This closed-loop feedback mechanism resolves the contradiction between regulation precision and oscillation suppression.
Solution Approach 2:
The patent changes the switching frequency parameter in response to detected oscillations and load variations. When abnormal oscillation is detected, the frequency is adjusted to a value that suppresses the oscillation while maintaining adequate voltage regulation. This parameter adaptation resolves the contradiction between regulation and oscillation 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
The solution prevents abnormal oscillations and maintains stable feedback control without increasing photocoupler gain, ensuring efficient operation across varying loads without the need for dummy loads, thus enhancing mass production feasibility and reducing losses.
Implementation Method 1
The excitation current is a sinusoidal resonant current created by an inductive reactance of the reactor Lr and the excitation inductance Lp and a capacitive reactance of the current resonant capacitor Cri
Implementation Method 2
energy accumulated in the transformer T by the excitation current causes a quasi-voltage-resonance of the inductive reactance to the reactor Lr and the excitation inductance Lp and the capacitive reactance to the current resonant capacitor Cri and the voltage resonant capacitor Cry
Data Source
AI summary
A DC-DC converter includes a plurality of switch elements connected in series between both ends of a DC power source, a series circuit of a primary winding of a transformer and a capacitor, connected between a connection point of the plurality of switch elements and an end of the DC power source, a rectifying-smoothing circuit to rectify and smooth a voltage generated by a secondary winding of the transformer into a DC voltage, and a controller to change a switching frequency of the plurality of switch elements according to a feedback signal generated from the DC voltage and alternately turn on/off the plurality of switch elements. The controller includes a nonlinear response unit 11a to nonlinearly change the switching frequency according to a feedback amount represented by the feedback signal.