Inductorless AC-to-DC Converter Synchronization
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Solution Overview
Problem
Inductorless AC-to-DC converters face challenges in achieving high efficiency, accuracy, and low EMI due to unsynchronized switching, leading to unsteady charging and high ripples in the output voltage, which requires additional regulation, compromising energy efficiency and manufacturing cost.
Innovation Solution
Implementing a control method that synchronizes switch control with zero-crossing detection of the AC supply voltage, using a sawtooth signal generator and comparator to set a controllable on-time inversely proportional to the output current or power, ensuring precise voltage or current regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If unsynchronized switching is used in inductorless AC-to-DC converters, then circuit simplicity is maintained, but output voltage ripples increase and regulation precision deteriorates
Solution Approach 1:
The patent applies preliminary action by detecting zero-crossing points of the AC supply voltage in advance and using this information to synchronize the switching timing. The controller pre-determines when to turn on and off the switch based on the zero-crossing detection, ensuring that switching occurs at optimal moments in the AC cycle. This preliminary synchronization action eliminates the need for complex feedback regulation while maintaining precise output voltage control and reducing ripples.
2Measurement precision
If additional voltage regulation is added to reduce ripples, then output voltage precision is improved, but energy efficiency decreases and manufacturing cost increases
Solution Approach 1:
The patent implements self-service by designing a system where the synchronized switching itself provides the voltage regulation function. The controller uses zero-crossing detection to automatically adjust switching timing, and the natural charging/discharging of the capacitor during synchronized switching cycles provides inherent ripple reduction. This self-regulating mechanism eliminates the need for separate voltage regulation components, maintaining energy efficiency and avoiding additional manufacturing costs while achieving precise output voltage control.
3Stability of the object's composition
If switch on-time is extended to reduce ripples, then output voltage smoothness is improved, but output voltage precision and response to load changes deteriorate
Solution Approach 1:
The patent applies dynamics by making the switch on-time variable rather than fixed. The controller dynamically adjusts the switch on-time based on real-time conditions including zero-crossing detection and output voltage feedback. During different phases of the AC cycle and under different load conditions, the on-time is optimized to maintain both voltage smoothness and precision. This dynamic adjustment allows the system to respond quickly to load changes while keeping ripples minimal.
Data Source
AI summary
A method of AC-to-DC conversion is disclosed, comprising steps of: rectifying an AC voltage to a pulsating DC voltage; coupling the pulsating DC voltage to a capacitor via a switch; coupling an output voltage of the capacitor to a load; monitoring a signal of the load; determining a voltage deviation of the signal of the load from a predetermined reference; in synchronization and in every cycle of the pulsating DC voltage, turning on the switch at a first time instant when the switch is not forward biased and turning off the switch in response to the voltage deviation at a second time instant; whereby the signal of the load is controlled.