Flyback Converter CVCC Controller Using Auxiliary Winding Feedback
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Solution Overview
Problem
Conventional constant voltage constant current (CVCC) controllers for flyback converters face issues such as high power losses and high product costs due to feedback components, and complexity in control loops, leading to imprecise control and increased volume.
Innovation Solution
A CVCC controller that includes a current controller, voltage controller, selector, and PWM controller to operate in either constant voltage or constant current modes, using error signals and feedback circuits to precisely regulate output voltage and current, simplifying the circuit structure and improving transient response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If secondary-side feedback controller with optical coupler is used, then output voltage and current can be regulated, but power losses and product costs increase
Solution Approach 1:
The patent extracts and eliminates the optical coupler from the feedback system, transitioning from secondary-side to primary-side control. This removal of the optical coupler directly reduces power losses while maintaining regulation capability through alternative sensing and control mechanisms on the primary side.
Solution Approach 2:
The patent introduces an auxiliary winding as an intermediary element to obtain output voltage information without requiring direct secondary-side feedback. This auxiliary winding serves as a mediator that provides the necessary feedback signal on the primary side, eliminating the need for optical couplers and reducing power losses.
2Reliability
If secondary-side feedback controller with optical coupler is used, then output voltage and current can be regulated, but product costs increase
Solution Approach 1:
The patent removes the optical coupler and secondary-side feedback components, significantly reducing component count and manufacturing complexity. This extraction of unnecessary components directly lowers product costs while maintaining regulation functionality through primary-side control architecture.
Solution Approach 2:
The primary-side controller performs multiple functions including voltage regulation, current regulation, and feedback processing in a single integrated unit, eliminating the need for separate secondary-side controller and optical coupler. This multi-functionality reduces component count and manufacturing costs.
3Device complexity
If auxiliary winding is used to obtain output voltage information, then feedback signal can be generated, but control precision decreases when secondary current is reduced to zero
Solution Approach 1:
The patent applies preliminary action by detecting and holding the peak voltage value from the auxiliary winding before the secondary current reduces to zero. This preliminary detection and holding mechanism ensures accurate feedback information is captured and maintained throughout the switching cycle, preventing precision loss when current drops.
Solution Approach 2:
The patent introduces dynamic elements including a holding circuit that dynamically maintains the peak voltage value, and a compensating circuit that dynamically adjusts feedback signals based on switching state. These dynamic mechanisms ensure continuous precision feedback regardless of instantaneous current conditions.
4Reliability
If constant voltage control loop and constant current control loop with external compensating circuit are included, then CVCC control can be achieved, but circuit complexity increases
Solution Approach 1:
The patent merges the constant voltage control loop and constant current control loop into a unified primary-side control architecture. Both control functions share common components including the auxiliary winding for voltage sensing, the holding circuit for peak detection, and the PWM controller, significantly reducing overall circuit complexity while maintaining CVCC functionality.
Solution Approach 2:
The primary-side controller serves as a universal control unit that handles both constant voltage and constant current regulation through integrated control logic. The auxiliary winding and holding circuit provide multi-functional support for both control modes, eliminating the need for separate external compensating circuits and reducing overall system complexity.
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 proposed solution allows for precise control of output voltage and current, reduces power losses and costs, and enhances the transient response speed by setting the flyback converter to operate in specific modes, thereby improving overall performance and efficiency.
Implementation Method 1
Auxiliary winding NT can be used to obtain output voltage information
Implementation Method 2
a pulse-width modulation (PWM) controller configured to generate a PWM control signal to control a main switch
Data Source
AI summary
The present invention relates to a constant voltage constant current (CVCC) controller, and associated control methods. In one embodiment, a CVCC controller for a flyback converter can include: (i) a current controller configured to generate an error signal by comparing an output current feedback signal against a reference current; (ii) a voltage controller configured to receive an output voltage feedback signal and a reference voltage, and to generate a control signal; (iii) a selector configured to control the flyback converter to operate in a first or a second operation mode based on the control signal, and to further generate a constant voltage or a constant current control signal based on the error signal; and (iv) a pulse-width modulation (PWM) controller configured to generate a PWM control signal to control a main switch, and to maintain the output voltage and/or current of the flyback converter as substantially constant.