SMPS Demagnetization Detection Circuit Using Winding Voltage Differentiation
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Solution Overview
Problem
Existing switched mode power supply (SMPS) technologies face challenges in accurately determining the end of the demagnetization stroke, leading to imprecise control and output level regulation due to ringing oscillations and the need for complex or expensive feedback mechanisms.
Innovation Solution
A circuit comprising a differentiation element, a steady state detector, and a logic arrangement that differentiates the winding voltage, sets a zero derivative signal when the derivative signal remains below a threshold for a predetermined period, and identifies the end of the demagnetization stroke by crossing the threshold value, providing adaptive and flexible operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional feedback mechanisms are used to determine the end of demagnetization stroke, then output level regulation can be achieved, but the device complexity and cost increase due to expensive opto-couplers and complex circuits
Solution Approach 1:
The patent extracts the essential detection function from complex feedback mechanisms. By using a simple differentiator circuit that processes the auxiliary winding voltage to detect the demagnetization stroke end, the invention removes the need for expensive opto-couplers and complex feedback circuits while maintaining determination accuracy.
Solution Approach 2:
The circuit uses the auxiliary winding voltage itself and its derivative to determine the demagnetization stroke end, without requiring external feedback signals. The differentiator circuit self-generates the detection signal from the available winding voltage, eliminating the need for separate feedback pathways and reducing overall system complexity.
2Measurement precision
If traditional feedback mechanisms are used to determine the end of demagnetization stroke, then output level regulation can be achieved, but the cost increases due to expensive opto-couplers
Solution Approach 1:
The patent replaces expensive, long-lived components like opto-couplers with inexpensive, simple electronic components such as resistors, capacitors, and operational amplifiers configured as a differentiator. These cheaper components achieve the same functional goal of accurate demagnetization stroke detection without the high cost associated with opto-coupler-based feedback mechanisms.
3Speed
If the end of demagnetization stroke is determined during ringing oscillations, then faster detection is achieved, but measurement precision deteriorates due to incorrect identification
Solution Approach 1:
The differentiator circuit is designed to anticipate the demagnetization stroke end by detecting the derivative of the auxiliary winding voltage. The circuit prepares the detection signal in advance, allowing the zero-crossing detection to occur at the precise moment of demagnetization end rather than during the oscillating ring phase, thus achieving both speed and accuracy.
Solution Approach 2:
The patent skips the problematic ringing oscillation period by using derivative-based detection. Instead of waiting for the oscillations to settle or trying to detect during the ring phase, the differentiator circuit rushes through the detection process by identifying the characteristic voltage derivative pattern that signifies the true demagnetization end, bypassing the ambiguous oscillation period entirely.
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
This solution enables precise determination of the demagnetization period, improving SMPS control and output current accuracy, reducing the impact of ringing oscillations, and eliminating the need for expensive opto-couplers, thus achieving accurate output regulation with simplified implementation.
Implementation Method 1
a differentiation element configured to differentiate the winding voltage with respect to time in order to determine a derivative signal
Data Source
Figure 1
Figure 2a~2b
Figure 3
AI summary
A circuit (500) for a switched mode power supply (200) having a winding (206). The circuit (500) comprising: an input configured to receive a winding voltage (503), derived from the winding (206); a differentiation element (501) configured to differentiate the winding voltage (503) with respect to time in order to determine a derivative signal (509) and compare the derivative signal (509) with a threshold value (554); a steady state detector (502) configured to set a zero derivative signal (507) when the derivative signal (509) has not exceeded the threshold value (554) for a predetermined period of time, and a logic arrangement (513) configured to identify an end of a demagnetization stroke of the switched mode power supply when the derivative signal (509) crosses a final threshold value (554) after the zero derivative signal (507) has been set.