AC-DC Converter Rectified Voltage Estimation
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Solution Overview
Problem
Conventional AC-DC converters with power factor correction (PFC) circuits require voltage-dividing resistors for detecting rectified voltage, leading to resistive losses and increased noise distortion during PWM operations, especially when the carrier signal amplitude is small.
Innovation Solution
An AC-DC converter design that eliminates the need for voltage-dividing resistors by using a rectified voltage estimation unit to derive an estimated value of the rectified voltage without detection, allowing for PWM control of the semiconductor switching device using an output voltage command, thereby reducing resistive losses and maintaining high power factor accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage-dividing resistors are used to detect rectified voltage, then voltage detection is achieved, but resistive losses occur and noise distortion increases
Solution Approach 1:
The patent replaces the physical voltage-dividing resistor network with an estimation algorithm that calculates rectified voltage based on switching device states and circuit parameters. This substitution eliminates the need for physical resistors, thereby removing resistive losses while maintaining voltage detection capability through computational estimation.
Solution Approach 2:
The patent introduces an estimation unit as an intermediary component that derives rectified voltage information indirectly through mathematical relationships rather than direct electrical measurement. This intermediary approach uses switching signals and circuit model parameters to compute the rectified voltage, avoiding the energy dissipation inherent in direct resistive voltage division.
2Measurement precision
If voltage-dividing resistors are used for rectified voltage detection, then voltage measurement is obtained, but noise distortion during PWM operations increases
Solution Approach 1:
The patent replaces the analog voltage-dividing resistor circuit with a digital estimation algorithm that processes switching device state information. This substitution eliminates the analog signal path that is susceptible to noise during PWM operations, providing a cleaner measurement free from switching noise distortion.
Solution Approach 2:
The patent creates a computational model that replicates the rectified voltage characteristics without requiring physical electrical connection to the rectified voltage node. By copying the voltage information through mathematical relationships and switching state analysis, the system obtains accurate voltage data without the noise inherent in direct electrical measurement during PWM switching.
3Measurement precision
If carrier signal amplitude is reduced, then power factor correction accuracy is maintained, but waveform distortion increases due to noise effects
Solution Approach 1:
The patent replaces the carrier signal amplitude modulation approach with a fixed-amplitude carrier and adaptive duty cycle control. The estimation algorithm allows the system to maintain accurate power factor correction with a stable carrier signal, eliminating the need to vary carrier amplitude which can amplify noise effects and cause waveform distortion.
Solution Approach 2:
The patent changes the control parameter from carrier signal amplitude to duty cycle ratio. By maintaining a constant carrier amplitude and adjusting only the duty cycle based on the estimated rectified voltage and load conditions, the system achieves accurate power factor correction without the waveform distortion that occurs when carrier amplitude is reduced and becomes susceptible to noise.
Data Source
AI summary
An AC-DC converter that converts an AC power supply voltage to a DC output voltage of a prescribed magnitude with power factor regulation includes a voltage regulation unit; an instantaneous value command calculator; a current regulation unit; an output voltage command calculator; a drive signal generator that generates a drive signal for a semiconductor switching device from the output voltage command and a carrier signal, the driving signal being provided to the semiconductor switching device so as to switch the semiconductor switching device ON and OFF; and a rectified voltage estimation unit that that derives an estimated value of a rectified voltage obtained by rectifying the AC power supply voltage from the output voltage command without actually detecting a rectified voltage, for providing to the instantaneous value command calculator and the output voltage command calculator.