Dual-mode AC/DC Converter Current Control via Auxiliary Winding
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Solution Overview
Problem
Existing AC/DC power converters face inefficiencies and structural complexity in current monitoring circuits, particularly in isolation transformer systems, which require improved control mechanisms for high efficiency and low complexity.
Innovation Solution
The AC/DC converter employs a dual-mode circuit with a feedback system that adjusts the peak current limit based on a feedback voltage threshold, using a combination of transistors, operational amplifiers, and a subtraction functional unit to control the switching of the oscillator, allowing for efficient current regulation without complex secondary-side monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current monitoring circuit on the secondary-side is used for current control, then current control accuracy is improved, but device complexity and energy consumption increase
Solution Approach 1:
The patent extracts the current monitoring function from the secondary-side to the primary-side by using the auxiliary winding of the transformer. The monitoring circuit is implemented on the primary-side using simple voltage division and rectification circuits, eliminating the need for complex secondary-side monitoring while maintaining current control accuracy through the transformer's magnetic coupling.
Solution Approach 2:
The auxiliary winding of the transformer serves multiple functions: it provides both the isolation required for safety and the signal source for current monitoring. The same transformer structure that provides galvanic isolation also generates the monitoring signal through its auxiliary winding, reducing overall device complexity while maintaining measurement precision.
2Ease of operation
If complex models based on monitoring input voltage, output diode on duration, and peak current limit are used, then current control is achieved, but device complexity increases
Solution Approach 1:
The circuit uses the natural characteristics of the transformer's auxiliary winding to generate the monitoring signal. The auxiliary winding automatically provides a voltage proportional to the primary current through magnetic coupling, eliminating the need for external sensors or complex monitoring circuits. The circuit serves itself by using its own operating parameters (auxiliary winding voltage) for control.
Solution Approach 2:
The patent implements a feedback mechanism where the rectified voltage from the auxiliary winding is compared with a reference voltage, and the difference is used to adjust the switching duty cycle. This closed-loop feedback ensures accurate current control while keeping the circuit structure simple, as the feedback signal is derived directly from the transformer's own operation.
3Reliability
If galvanic isolation is implemented using an isolation transformer, then safety is improved, but device complexity and energy loss increase
Solution Approach 1:
The isolation transformer performs multiple functions simultaneously: it provides galvanic isolation for safety, steps down the voltage from primary to secondary side, and generates the monitoring signal through its auxiliary winding. By combining isolation, transformation, and signal generation in a single component, the patent reduces overall device complexity while maintaining safety.
Solution Approach 2:
The patent merges the isolation function, voltage transformation function, and current monitoring signal generation function into a single transformer structure. The primary winding provides isolation and voltage step-down, while the auxiliary winding on the same transformer core provides the monitoring signal, combining multiple functions that could otherwise require separate components.
Data Source
AI summary
Dual-mode AC/DC power converters and associated methods of operation are disclosed herein. In one embodiment, the AC/DC converter includes a primary winding, a switching transistor coupled to the primary winding, the switching transistor configured to carry a drain-source current, and a feedback voltage port configured to carry a feedback voltage. The feedback voltage port is coupled to the switching transistor to switch off the switching transistor when the drain-source current reaches a peak current limit. The peak current limit increases with increasing feedback voltage if and only if the feedback voltage satisfies an ordered relationship with a threshold.