Power Conversion Device Control Circuit Modulation Strategy
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Solution Overview
Problem
In power conversion apparatuses, step-down control of output voltage by frequency control alone leads to increased frequency variation range, resulting in higher power loss and potential damage to semiconductor and magnetic components, reducing efficiency.
Innovation Solution
Implementing a control circuit that performs pulse width modulation, pulse frequency modulation, and phase shift modulation based on voltage conversion ratio thresholds to manage power conversion between AC and DC power, thereby reducing power loss in semiconductor and magnetic components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If step-down control of output voltage is performed only by frequency control, then voltage control is achieved, but frequency variation range has to be significantly increased leading to higher power loss
Solution Approach 1:
The patent changes the control parameter from frequency-only control to a combination of pulse width modulation (duty ratio control) and pulse frequency modulation. By controlling the ON duty of switch elements Q1 to Q4 in addition to switching frequency, the system achieves voltage control without requiring significant frequency variation, thus reducing power loss in semiconductor devices and magnetic components.
Solution Approach 2:
The patent introduces dynamic control through pulse width modulation where the ON duty of switch elements can be adjusted independently of frequency. This dynamic parameter adjustment allows flexible voltage control while maintaining frequency within a narrower, more efficient range, preventing the need for large frequency swings that cause excessive power loss.
2Adaptability or versatility
If frequency variation range is significantly increased for voltage control, then voltage control range is improved, but power conversion efficiency is reduced and component destruction may occur
Solution Approach 1:
The patent introduces a new control parameter (ON duty of switch elements) to expand the control dimension. By controlling both duty ratio and frequency, the system achieves wide voltage control range while keeping frequency variation within safe limits, preventing component overheating and destruction while maintaining high power conversion efficiency.
Solution Approach 2:
The patent implements feedback control where the output voltage is monitored and the ON duty of switch elements is adjusted accordingly. This feedback mechanism ensures that voltage control is achieved through duty ratio adjustment rather than excessive frequency variation, protecting components from damage while maintaining efficient operation across the full voltage control range.
3Ease of operation
If frequency control is used for voltage regulation, then voltage output is controlled, but voltage variation sensitivity deteriorates at higher frequencies requiring larger frequency changes
Solution Approach 1:
The patent changes the primary control parameter from frequency to duty ratio (ON time of switch elements). By controlling the conduction time of switch elements Q1 to Q4 rather than relying on frequency changes, the system maintains high voltage variation sensitivity even at higher frequencies, avoiding the need for large frequency swings that would increase power loss.
Data Source
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AI summary
A control circuit (14) performs at least pulse width modulation control on a first leg (500) and selects to perform pulse width modulation control and pulse frequency modulation control, to perform pulse width modulation control and phase shift modulation control, or to perform pulse width modulation control, pulse frequency modulation control, and phase shift modulation control on a second leg (600), based on comparison of a voltage conversion ratio between DC voltage of a DC capacitor (4) and output voltage to a load with at least one threshold.