DC/DC Converter Duty Control Optimization for Power Loss Reduction
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Solution Overview
Problem
Conventional power conversion apparatuses experience increased power loss due to varying duty ratios in switching circuits, limiting the reduction of power loss during battery charging, especially when the duty ratio is low.
Innovation Solution
The apparatus includes an AC/DC converter section with a smoothing capacitor and a DC/DC converter section using a semiconductor switching device, where a control apparatus adjusts the DC voltage target value to optimize duty control, allowing for soft switching and reducing power loss by controlling the duty ratio and switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If duty control is used for the switching circuit to obtain desired DC output, then the DC output can be controlled, but the variation width of the duty ratio increases and power loss increases when the duty ratio is low
Solution Approach 1:
The patent changes the control parameter from duty ratio to switching frequency. By controlling the switching frequency of the semiconductor switching device while maintaining a substantially constant duty ratio, the system achieves desired DC output control without the power loss associated with large duty ratio variations. This parameter transformation resolves the contradiction by decoupling output control from duty ratio variation.
2Loss of energy
If the duty ratio of the switching circuit is controlled to be constant, then power loss is reduced, but the ability to adjust DC output is limited
Solution Approach 1:
The patent transforms the control approach by changing from duty ratio control to switching frequency control. This allows the system to maintain a constant duty ratio (reducing power loss) while achieving DC output adjustment through frequency modulation. The switching frequency becomes the adjustable parameter that provides adaptability without sacrificing energy efficiency.
3Adaptability or versatility
If the duty ratios of switching circuits on both primary and secondary sides are controlled to be variable, then battery charging flexibility is improved, but power loss increases due to duty ratio variation
Solution Approach 1:
The patent applies parameter transformation by controlling switching frequency instead of duty ratio. This enables flexible battery charging (adaptability) while maintaining constant duty ratio operation (low power loss). The frequency-controlled approach provides the necessary charging flexibility without incurring the power loss penalties of variable duty ratio control.
Data Source
AI summary
A power conversion apparatus includes a high-power-factor converter section converting an AC voltage to a DC voltage, a smoothing capacitor, a DC/DC converter section, and a control circuit. The control circuit controls the high-power-factor converter section such that the power factor of AC is controlled and a DC voltage follows a target value, and performs duty control for semiconductor switching devices such that a DC voltage from the DC/DC converter section to a load follows an instruction value. In accordance with the DC voltage, the control circuit adjusts the DC voltage target value of the high-power-factor converter section such that the duty ratio of the semiconductor switching devices approaches a set value, thereby optimizing the duty ratio of the semiconductor switching devices and reducing power loss.