Bidirectional DC/DC Converter No-Load Control and Overshoot Protection
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Solution Overview
Problem
Bi-directional DC-to-DC converters face challenges in voltage regulation at low load conditions and overshoot protection, particularly in boost mode, where excess energy storage in inductors leads to abnormal output voltage increases and destructive voltage spikes across switches.
Innovation Solution
The implementation of a control circuitry and capacitors C1 and C2 in an isolated bi-directional DC/DC converter, which allows for new boost mode drive waveforms to turn off switches S2 and S4 during no-load conditions, using only S1 and S3 for reverse energy flow, and provides soft switching for buck mode transistors, while capacitors C1 and C2 offer overshoot protection by managing leakage inductance during boost mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If switches S2 and S4 are operated to provide no-load operation in boost mode, then reverse energy flow is achieved, but overshoot protection for switches Q1 and Q2 is destroyed
Solution Approach 1:
The patent segments the switching operation by disabling switches S2 and S4 during boost mode no-load conditions, using only switches S1 and S3 for reverse energy flow. This segmentation isolates the problematic switching actions that cause overshoot while maintaining the essential reverse energy flow function.
Solution Approach 2:
The patent dynamically adjusts the switching configuration based on operating mode: in boost mode, only S1 and S3 are activated for reverse energy flow, while in buck mode, all four switches operate normally. This dynamic adaptation resolves the contradiction by changing the active switching elements according to the operational context.
2Manufacturing precision
If duty cycle is decreased to regulate output voltage at low load, then voltage regulation range is extended, but abnormal voltage increases occur due to excess energy storage in inductors
Solution Approach 1:
The patent implements a control mechanism that monitors output voltage and inductor current to detect no-load or light-load conditions. When excess energy storage is detected, the system activates reverse energy flow through the transformer, creating a feedback loop that prevents abnormal voltage increases by dynamically adjusting energy transfer based on actual load requirements.
Solution Approach 2:
The patent changes the operational parameters by switching from forward energy flow only to bidirectional energy flow. By enabling reverse energy flow through the transformer when load is minimal, the system adjusts the energy balance parameter, preventing the accumulation of excess energy in inductors that would otherwise cause voltage overshoot.
3Stability of the object's composition
If auxiliary transformer is added to magnetically couple inductor current paths, then current equality is ensured and output voltage stability is improved, but device complexity increases
Solution Approach 1:
The patent makes the existing isolation transformer multi-functional by utilizing it for both isolation and magnetic coupling of inductor current paths. By operating the transformer in bidirectional mode, it simultaneously provides galvanic isolation and ensures current equality between inductors, eliminating the need for a separate auxiliary transformer and reducing overall device 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 solution enables voltage regulation over a wide range at no-load conditions and provides effective overshoot protection for switches Q1 and Q2, maintaining stable operation across varying loads and preventing destructive voltage spikes.
Implementation Method 1
capacitors C1 and C2 provide overshoot protection for Q1 and Q2
Implementation Method 2
overshoot protection provided by C1 and C2 for Q1 and Q2 is destroyed by the switching action of S2 and S4
Implementation Method 3
an isolated two-inductor boost converter with one transformer. This component has two inductor windings intrinsically coupled
Data Source
AI summary
A method of operating an isolated bi-directional dc/dc converter to provide voltage regulation at a no-load condition over a wide voltage range and also provide overshoot protection for the boost mode main switching transistors uses new boost mode drive waveforms. The new waveforms drive switches S2 and S4 to be turned off during boost mode and only S1 and S3 are switched to provide reverse energy flow at no-load. In boost mode, C1 and C2 provide overshoot protection caused by leakage inductance of the isolation transformer when boost mode drive transistors turn off during forward energy flow and provide stored energy for reverse energy flow during reverse energy flow periods used for voltage regulation in the boost mode. In buck mode, C1 and C2 provide soft switching for buck mode main switching transistors S2 and S4.