Bidirectional DC-DC Converter Wide Voltage Control
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Solution Overview
Problem
Existing bidirectional DC/DC converters face challenges in controlling output voltage to low values during light load or no load conditions, especially when the input/output voltage range is wide, due to the need for complex circuit configurations and limitations in pulse frequency modulation control.
Innovation Solution
A bidirectional DC/DC converter design that eliminates the need for a circuit to regulate the LC resonant circuit constants, using pulse frequency modulation control at a frequency equal to or lower than the resonance frequency for power flow from one direct current voltage supply to another, and fixed frequency control for power flow in the opposite direction, allowing for a wide input/output voltage range without a regulating circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If pulse frequency modulation control is used to control output voltage to low values during light load or no load conditions, then output voltage control range is improved, but the circuit configuration becomes complex and requires additional regulating circuits
Solution Approach 1:
The patent extracts and eliminates the LC resonant circuit regulating circuit from the system. By using fixed frequency control of the bridge circuit, the invention removes the need for additional regulating components while maintaining wide output voltage control capability through the inherent characteristics of the bridge circuit and transformer configuration.
Solution Approach 2:
The bridge circuit is designed to perform multiple functions: it provides both power conversion and voltage control across a wide range without requiring separate regulating circuits. The fixed frequency control mechanism enables the bridge circuit to universally handle both heavy load and light load conditions, as well as both charging and discharging modes, eliminating the need for mode-specific regulating components.
2Reliability
If a circuit to regulate LC resonant circuit constants is added to optimize resonance operation, then resonance operation is improved, but the converter size increases
Solution Approach 1:
The patent removes the LC resonant circuit regulating circuit that would otherwise be required to optimize resonance operation. By采用 fixed frequency control instead of resonance-based control, the invention eliminates the need for additional regulating components, thereby reducing converter size while maintaining reliable operation across wide input/output voltage ranges.
3Adaptability or versatility
If the input/output voltage range is made wide to suit applications like battery chargers, then adaptability is improved, but control of output voltage to low values becomes difficult during light load conditions
Solution Approach 1:
The bridge circuit is designed to universally handle wide input/output voltage ranges while maintaining ease of output voltage control through fixed frequency control. The system can operate in both charging and discharging modes, and can control output voltage to low values during light load conditions without requiring complex regulating circuits, as the fixed frequency control mechanism inherently provides wide voltage control capability.
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 design results in a smaller-sized bidirectional DC/DC converter capable of controlling output voltage across a wide range, reducing the size of the isolating transformer and eliminating the need for a circuit to regulate the resonant circuit constants, while maintaining high conversion efficiency.
Implementation Method 1
A so-called resonant bidirectional DC/DC converter that utilizes the resonance phenomenon of an LC resonant circuit configured of a reactor and capacitor
Implementation Method 2
an isolating transformer, and in particular, relates to a bidirectional DC/DC converter suited to an application wherein the input/output voltage range is wide
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3(a)~3(b)
AI summary
Included are a second control circuit 52A, which carries out fixed frequency control of a second bridge circuit 23 based on the voltage and current of a first direct current voltage supply 11, and a first control circuit 51, which carries out PFM control of a first bridge circuit 13 based on the voltage and current of a second direct current voltage supply 21. The first control circuit 51 carries out PFM control of the first bridge circuit 13 at a frequency equal to or lower than the resonance frequency of an LC resonant circuit 14 in accordance with a control amount based on the voltage and current of the second direct current voltage supply 21 when power is supplied from the first direct current voltage supply 11 to the second direct current voltage supply 21, and the second control circuit 52A carries out fixed frequency control of the second bridge circuit 23, using phase shift control or the like, in accordance with a control amount based on the voltage and current of the first direct current voltage supply 11 when power is supplied from the second direct current voltage supply 21 to the first direct current voltage supply 11.