Isolated DC/DC Converter Regulation Circuit for Voltage Stress Reduction
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Solution Overview
Problem
Isolated DC/DC converters face challenges in maintaining efficiency due to significant voltage stress on rectifier diodes and varying output current ripples, especially when the duty cycle approaches 0% or 100%, which limits their use in vehicles with varying energy sources.
Innovation Solution
A regulation circuit that maintains a constant duty cycle for the isolated DC/DC converter, allowing operation across a range of input voltages by adjusting the voltage applied to the converter, thereby reducing voltage stress and ripple currents, and ensuring maximum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the duty cycle of the isolated DC/DC converter is varied to regulate output voltage when input voltage varies, then the output voltage can be maintained at a desired value, but the voltage stress on rectifier diodes becomes significant and efficiency decreases
Solution Approach 1:
A regulation circuit is introduced as an intermediary component between the input voltage source and the isolated DC/DC converter. This regulation circuit adjusts its duty cycle to maintain a fixed input voltage to the isolated DC/DC converter, thereby preventing excessive voltage stress on rectifier diodes and reducing switching losses while still achieving output voltage regulation
Solution Approach 2:
The voltage regulation function is segmented into two independent stages: (1) a regulation circuit that handles input voltage variations by adjusting its own duty cycle to provide a stable fixed voltage to the isolated DC/DC converter, and (2) the isolated DC/DC converter that operates at a fixed duty cycle optimized for maximum efficiency. This segmentation resolves the contradiction by separating the regulation burden from the main converter
2Loss of energy
If the duty cycle is kept constant to maintain maximum efficiency, then switching losses are reduced, but the converter cannot adapt to varying input voltages to maintain desired output voltage
Solution Approach 1:
The regulation circuit serves as a mediator that absorbs the adaptability requirement. It varies its duty cycle in response to input voltage changes, thereby protecting the isolated DC/DC converter from having to adapt. The converter itself operates at a fixed duty cycle, maintaining constant efficiency while the regulation circuit handles all the adaptability requirements
Solution Approach 2:
The system implements dynamic behavior at the regulation circuit level while maintaining static (fixed) operation at the isolated DC/DC converter level. The regulation circuit dynamically adjusts its duty cycle based on input voltage variations, while the isolated DC/DC converter operates statically at an optimized fixed duty cycle, creating a hybrid dynamic-static architecture that achieves both adaptability and efficiency
3Object-affected harmful factors
If different transformation ratios are used for the two transformers to limit rectifier diode voltage stress, then diode stress is reduced, but the design complexity increases and current discontinuities occur
Solution Approach 1:
The regulation circuit acts as a mediator that prevents excessive voltage stress on rectifier diodes by maintaining a fixed input voltage to the isolated DC/DC converter. This eliminates the need to use different transformation ratios for the two transformers, allowing both transformers to be identical and simplifying the design while still protecting the diodes from excessive stress
Solution Approach 2:
By using identical transformers with the same transformation ratio, the system achieves homogeneity in the transformer design. The regulation circuit ensures that both transformers operate under balanced conditions, eliminating current discontinuities and simplifying the overall design while still limiting diode voltage stress through fixed-duty-cycle operation
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 enables the isolated DC/DC converter to maintain a desired output voltage with minimal duty cycle variation, reducing voltage stress and ripple currents, thus enhancing efficiency and usability in vehicles with fluctuating energy sources.
Implementation Method 1
The converter comprises two switches, arranged as a half-bridge, which are connected at their midpoint to a branch which comprises two transformers in series. The switches control the transmission of energy through the transformers to obtain a conversion from an input voltage of the converter to an output voltage.
Implementation Method 2
Diodes connected to the secondaries of the transformers make it possible to rectify the output signal.
Data Source
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AI summary
The invention relates to a voltage converter (1) comprising: an isolated DC/DC converter circuit (3) having at least one first isolation transformer (T1) and switches (M31, M32) whose opening and closing successions with at least one duty ratio (α) make it possible to transmit energy through the isolated DC/DC converter (3) by way of said first transformer (T1); a circuit (2) for regulating the input voltage of the isolated DC/DC converter circuit (3); the regulating circuit (2) being configured to control the output voltage (Vout) of the isolated DC/DC converter circuit (3) by modifying the voltage delivered to the isolated DC/DC converter circuit (3), the duty ratio (α) of the isolated DC/DC converter circuit (3) remaining constant, and in said converter (1), the output of the regulating circuit is connected to a branch of the isolated DC/DC converter circuit comprising said first transformer (T1).