Isolated DC-DC Converter Feedback for Input Filter Oscillation Damping
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Solution Overview
Problem
Oscillations occur in DC-to-DC converters due to mismatched impedances between the input filter and power conversion circuit, leading to undesirable ripple voltages, which existing solutions either compromise performance or increase cost and size.
Innovation Solution
Utilize an auxiliary winding of the input filter's inductor to transfer feedback signals across the galvanic isolation barrier, allowing the voltage control loop to adjust the output voltage based on input filter output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional damping components are added at the output of the input filter to reduce output impedance at resonant frequency, then oscillations are prevented, but cost and size of the converter increase
Solution Approach 1:
The patent applies feedback by using the auxiliary winding to sense the output voltage of the input filter and feeding this signal back to the control circuit. The control circuit then adjusts the switching duty cycle to compensate for oscillations, effectively damping the resonant frequency without adding physical damping components. This resolves the contradiction by achieving oscillation prevention through control feedback rather than additional hardware.
Solution Approach 2:
The auxiliary winding acts as an intermediary element that enables signal transfer across the galvanic isolation barrier. By using this winding to sense the input filter output voltage and transmit the signal to the control circuit, the system can implement damping control without direct electrical connection, avoiding the need for additional damping components while maintaining isolation. This mediator approach prevents oscillations without increasing converter size or cost.
2Reliability
If input filter components are carefully selected and converter response is tuned to avoid impedance mismatch, then oscillations are avoided, but performance of the converter is compromised
Solution Approach 1:
The patent implements dynamic adjustment of the converter response through feedback control. Instead of statically tuning the converter to avoid impedance mismatch, the system dynamically adjusts the switching duty cycle based on real-time sensing of the input filter output voltage via the auxiliary winding. This allows the converter to adapt to varying operating conditions and maintain optimal performance while avoiding oscillations, resolving the contradiction between reliability and productivity.
Solution Approach 2:
The control circuit changes the switching parameters (duty cycle) dynamically based on the feedback signal from the auxiliary winding. When oscillations are detected, the control circuit adjusts the duty cycle to dampen the resonant frequency. This parameter adjustment allows the system to maintain high performance while avoiding the fixed compromises required by static impedance matching approaches.
3Reliability
If voltage at output of input filter is used as feedback term in voltage control loop, then converter is stabilized, but signal transfer across galvanic isolation barrier is required
Solution Approach 1:
The patent merges the feedback function with the existing auxiliary winding that is already part of the galvanically isolated architecture. Instead of adding a separate feedback mechanism that would complicate signal transfer, the solution combines the oscillation sensing function with the existing isolation transformer's auxiliary winding. This integrated approach achieves converter stabilization while utilizing the already-present isolation infrastructure, avoiding additional signal transfer 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
Stabilizes the converter by damping oscillations without increasing cost or size, maintaining performance by making the converter appear resistive at oscillation frequencies.
Implementation Method 1
uses an auxiliary winding of an inductor of the input filter to transfer the required signal across the galvanic isolation barrier
Implementation Method 2
uses the voltage at the output of the input filter as a feedback term in the converter's voltage control loop
Data Source
AI summary
In one embodiment, the present disclosure is directed to a DC-to-DC converter that includes an input filter. The inductor of the input filter has an auxiliary winding wound around the core element and not coupled to the input terminal. A voltage control circuit is configured to receive a first signal from the auxiliary winding of the inductor of the input filter, the first signal being indicative of an output voltage of the input filter. The voltage control circuit adjusts the desired output voltage level based on the first signal. An output terminal provides the adjusted desired output voltage level.