Flyback Converter Primary-Side Control via Auxiliary Winding
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Solution Overview
Problem
In power supply systems, accurately estimating the output power from the secondary winding is challenging without direct feedback from the secondary side to the primary side, leading to potential improper regulation of the output voltage.
Innovation Solution
A power supply control circuit that utilizes an auxiliary winding to estimate the secondary current by forming signals representative of the timing and peak values of the secondary current, allowing for improved regulation of the output voltage without the need for optical couplers or direct secondary-side feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct feedback from secondary side to primary side is used, then output power estimation accuracy is improved, but device complexity increases due to need for optical couplers and direct feedback circuits
Solution Approach 1:
The patent extracts the feedback function from the secondary side and implements it on the primary side using an auxiliary winding. This eliminates the need for optical couplers and direct secondary-side feedback circuits, reducing device complexity while maintaining output power estimation accuracy through primary-side current sensing and timing measurements.
Solution Approach 2:
The patent introduces an auxiliary winding as an intermediary element that couples the transformer to the primary side controller. This auxiliary winding enables indirect sensing of secondary current information through primary-side measurements, avoiding the need for direct secondary-side feedback while achieving accurate output power estimation.
2Device complexity
If primary side control is used without secondary feedback, then device complexity is reduced, but output voltage regulation becomes improper
Solution Approach 1:
The patent implements a primary-side feedback mechanism using an auxiliary winding that provides timing information about secondary current flow. By measuring the duration and characteristics of the auxiliary winding current, the controller can infer secondary load conditions and adjust primary switching parameters to maintain proper output voltage regulation without direct secondary feedback.
Solution Approach 2:
The patent enables the primary side controller to self-determine secondary load conditions through measurements taken on the primary side itself. The auxiliary winding current characteristics serve as a proxy for secondary current, allowing the controller to autonomously regulate output voltage without external feedback from the secondary side.
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
Enables accurate estimation and regulation of the output power, ensuring proper voltage regulation across the transformer, even when direct feedback is not available, thereby enhancing the efficiency and reliability of the power supply system.
Implementation Method 1
A flyback converter includes a transformer with a primary winding, a secondary winding, and an auxiliary winding. The primary winding is configured to be coupled to a primary side power switch. The secondary winding is configured to be coupled to a synchronous rectifier. The auxiliary winding is configured to form an auxiliary current signal that is representative of a timing and a peak value of the secondary current.
Data Source
AI summary
In one embodiment, a power supply controller, or alternately a semiconductor device having a power supply controller, may have a circuit configured configuring the PWM circuit to form a first signal having a value formed to be representative of a peak value of a primary current through the power switch and having a duration that is representative of a time interval that a secondary current is flowing through a secondary winding wherein the peak value is the peak value during an on-time of the power switch, and configured to form a current having a value that is representative of an average value of the secondary current.