Power Supply Controller Leakage Inductance Compensation
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Solution Overview
Problem
Existing methods for estimating output current in power supply systems, particularly in flyback power supply systems, often result in inaccurate readings due to the use of auxiliary voltage from an auxiliary winding, which is affected by parasitic leakage inductance.
Innovation Solution
A power supply controller circuit that includes a demag detect circuit to sense the demagnetization time of the transformer, a leakage detect circuit to sense the discharge time of the parasitic leakage inductance, and a compensation circuit to form a compensation control signal representing the difference between these times, allowing for more accurate control of the output current by adjusting the ON-time of the power switch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If auxiliary voltage from an auxiliary winding is used to estimate output current, then the power supply system can operate without additional sensing components, but the output current estimation accuracy deteriorates due to parasitic leakage inductance
Solution Approach 1:
The patent introduces an intermediary compensation signal that represents the parasitic leakage inductance effect. This compensation signal is generated by sensing the auxiliary winding voltage and processing it through a compensation circuit. The compensated output current signal is then obtained by combining the original auxiliary voltage signal with this compensation signal, thereby eliminating the measurement error caused by parasitic leakage inductance without adding complex external sensing components.
Solution Approach 2:
The patent changes the parameter of the auxiliary voltage signal by applying a compensation operation. The compensation circuit processes the auxiliary winding voltage to generate a corrected signal that accounts for the parasitic leakage inductance. This parameter transformation converts the inaccurate auxiliary voltage into an accurate representation of the output current, resolving the measurement precision issue while maintaining system simplicity.
2Measurement precision
If parasitic leakage inductance is compensated for accurate output current control, then output current control accuracy improves, but the control circuit complexity increases
Solution Approach 1:
The patent makes the existing auxiliary winding serve multiple functions: it originally provided only a voltage signal for basic operation, but now it also provides the basis for accurate output current measurement after compensation. The compensation circuit processes this same auxiliary voltage signal to extract both the operating voltage and the compensated current information, thereby achieving accurate current control without adding separate sensing windings or components.
Solution Approach 2:
The patent enables the power supply system to self-compensate for its own parasitic leakage inductance effects. The compensation circuit uses the auxiliary winding voltage itself as the input signal and processes it to generate the compensation effect. The system essentially uses its own operating signals to correct its own measurement errors, eliminating the need for external calibration or additional sensing infrastructure.
Data Source
AI summary
In one embodiment, a power supply controller is configured to adjust a peak value of a primary current through a power switch responsively to a difference between a demagnetization time and a discharge time of the parasitic leakage inductance of a transformer.