AC-AC Converter Synchronization via High-Frequency Segmentation
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Solution Overview
Problem
Existing AC-AC converters face issues with harmonic generation and flicker, leading to bulky filter components and electric losses, and are unable to provide a regulated, isolated output voltage synchronized with utility mains in terms of phase and frequency, especially for loads like printers.
Innovation Solution
An AC-AC converter design that includes a regulator with a fast reaction circuit and current regulation circuit, along with an opto-coupler for galvanic isolation, a resonant half bridge, and a step down converter, which allows for feedback of output voltage and current information to the primary side, enabling efficient regulation and synchronization with utility mains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase angle control is used to regulate output voltage, then voltage regulation is achieved, but harmonics are generated in the utility mains current
Solution Approach 1:
The patent divides the AC-AC conversion process into two independent stages: a high-frequency switching stage that performs voltage transformation and isolation, and a low-frequency output stage that reconstructs the sinusoidal waveform. This segmentation prevents harmonic generation by avoiding direct phase angle control on the utility mains, instead using pulse-width modulation at high frequency followed by filtering and sinusoidal synthesis at the output.
Solution Approach 2:
The patent replaces traditional mechanical/analogue phase angle control with a digital control system that uses microprocessor-based PWM modulation. This substitution allows for precise control of the switching elements while maintaining sinusoidal current draw from the utility mains, thereby eliminating harmonic distortion while achieving accurate output voltage regulation.
2Measurement precision
If integral cycle control is used to regulate output voltage, then voltage regulation is achieved, but periodic loading creates flicker in the utility mains voltage
Solution Approach 1:
The patent ensures continuous power draw from the utility mains by operating the high-frequency switching converter in a continuous mode rather than periodic packet control. The converter continuously processes power through the high-frequency switching stage, maintaining a steady load on the utility mains and eliminating the periodic interruptions that cause flicker in integral cycle control methods.
3Object-generated harmful factors
If harmonics are filtered using large filter circuit components, then harmonic reduction is achieved, but the overall solution becomes bulky and causes more electric losses
Solution Approach 1:
The patent extracts the harmonic filtering function from the main power conversion path by using a separate high-frequency switching stage that inherently produces minimal harmonics due to its continuous operation and high switching frequency. The filtering requirements are minimized and handled by small components in the high-frequency path rather than large filters in the low-frequency power path, reducing overall filter size and losses.
4Reliability
If isolated power source is used for printer loads, then safety standards are met, but regulation during fast changing loads is difficult
Solution Approach 1:
The patent implements dynamic control through a microprocessor-based control system that continuously monitors the output voltage and load conditions. The controller dynamically adjusts the PWM duty cycle of the high-frequency switching elements in real-time, enabling rapid response to fast-changing printer loads while maintaining galvanic isolation through the transformer. This dynamic adjustment capability allows the isolated converter to quickly regulate output voltage during transient load changes.
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 effectively reduces harmonic generation and flicker, minimizes filter size and losses, and ensures a regulated output voltage synchronized with utility mains, providing efficient and compact AC-AC conversion.
Implementation Method 1
a) an opto-coupler circuit configured to transfer an electrical signal from the primary side to the secondary side or vice versa or both, wherein the opto-coupler circuit maintains a galvanic isolation between the primary side and the secondary side
Implementation Method 2
b) a transformer having a primary winding and a secondary winding, wherein the primary winding is connected to the primary side and the secondary winding is connected to the secondary side
Data Source
Figure 1
Figure 2
AI summary
In an AC-AC converter comprising a primary side, a secondary side and a regulator, wherein the regulator comprises a voltage regulation circuit configured to determine an error voltage based on an at least partially alternating feedback voltage fed into the regulator from the secondary side of the AC-AC converter and to supply this error voltage and/or an information about this error voltage to the primary side of the AC-AC converter, the regulator comprises an averaging circuit configured to determine an average DC voltage based on the feedback voltage.