Flyback Power Supply Overvoltage Protection via Feedback Rate
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Solution Overview
Problem
Conventional flyback power supply circuits inadequately protect against overvoltage conditions, often resulting in circuit damage due to increasing output voltage during overvoltage events, and existing solutions increase cost and complexity without sufficient improvement.
Innovation Solution
A flyback power supply circuit with a programmable function that includes a primary winding, secondary winding, and a tertiary winding for generating a feedback signal, a power switch circuit, a primary side control circuit that determines overvoltage conditions based on the rate of increase and control level of the feedback signal and target control signal, and a secondary side control circuit that adjusts the target control signal to prevent overvoltage, using a comparison circuit and digital-to-analog converter for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional overvoltage protection methods are used, then circuit damage is prevented to some extent, but the output voltage continues to increase during overvoltage events causing insufficient protection
Solution Approach 1:
The patent implements preliminary detection of overvoltage conditions by monitoring the feedback signal rate of change before the output voltage reaches dangerous levels. The control circuit detects when dVout/dt exceeds a threshold and proactively adjusts the target control signal to prevent further voltage increase, rather than reacting after damage occurs.
Solution Approach 2:
The patent enhances feedback control by using the rate of change of the feedback signal (dVfb/dt) as an additional control parameter. The primary side control circuit compares both the feedback signal level and its rate of change against thresholds, enabling more precise detection and response to overvoltage conditions, preventing the output voltage from continuing to rise during faults.
2Reliability
If existing overvoltage protection solutions are implemented, then some protection is provided, but circuit complexity and cost increase without sufficient improvement
Solution Approach 1:
The patent makes the existing feedback control circuit perform multiple functions: normal voltage regulation and overvoltage detection. The same feedback signal used for regulation is also monitored for rate of change to detect overvoltage conditions, eliminating the need for separate protection circuits and reducing overall system complexity.
Solution Approach 2:
The control circuit uses its own feedback signal and existing comparison resources to detect overvoltage conditions. The primary side control circuit leverages the feedback signal it already processes for regulation, adding rate-of-change detection using existing circuit elements, making the protection mechanism self-contained without external components.
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
Effectively prevents overvoltage damage by accurately determining and responding to overvoltage conditions, maintaining output voltage within safe limits while reducing circuit complexity and cost compared to prior art solutions.
Implementation Method 1
A transformer circuit 102 of the flyback power supply circuit 100 receives the input voltage Vin, and converts it to the output voltage Vout. The transformer circuit 102 includes a primary winding W1 and a secondary winding W2.
Implementation Method 2
an opto-coupler circuit 104, for generating the target control signal according to the programmable output voltage and a programming signal
Data Source
AI summary
The present invention discloses a flyback power supply circuit with a programmable function and a control method thereof. The flyback power supply circuit includes: a transformer circuit, a power switch circuit, a primary side control circuit, an opto-coupler circuit, and a secondary side control circuit. The primary side control circuit determines whether an over voltage condition occurs, and further determines whether to generate an over voltage protection signal to turn OFF a power switch of the power switch circuit according to a rate of increase of a feedback signal and a control level, or according to the rate of increase of the feedback signal and a rate of change of a target control signal.