Output Current Estimation Using Snubber Voltage Compensation
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Solution Overview
Problem
Existing methods for estimating output current in power supply devices inaccurately account for the current flowing to snubber circuits, leading to errors between estimated and actual output currents.
Innovation Solution
A power supply device with a switch control circuit that generates an estimation voltage based on a detection sense voltage and a compensated discharge period, which includes determining the start and termination of the discharge period using delay voltage comparisons and snubber current detection, allowing for precise output current estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the output current is estimated using the equation (peak of current)*(discharge period)/(switching cycle), then the estimation is simple, but the accuracy deteriorates due to unaccounted snubber circuit current
Solution Approach 1:
The patent replaces direct measurement of discharge current with voltage-based detection. By detecting the voltage across the snubber resistor instead of directly measuring current, the system achieves accurate snubber current detection using voltage sensing circuits, which are simpler and more practical than direct current measurement methods
Solution Approach 2:
The patent introduces a snubber resistor as an intermediary element to detect snubber current. The resistor converts the difficult-to-measure snubber current into a measurable voltage signal, allowing the control circuit to accurately determine when snubber current flows and compensate the discharge period accordingly
2Ease of operation
If the discharge period is measured from turn-off instant to zero current, then the measurement is straightforward, but the accuracy deteriorates due to snubber circuit interference
Solution Approach 1:
The patent implements feedback by continuously monitoring the voltage across the snubber resistor and using this information to adjust the discharge period measurement. The control circuit uses the detected voltage signal to determine whether the discharge period should be compensated, creating a closed-loop system that improves measurement accuracy
Solution Approach 2:
The patent performs preliminary detection of snubber current by monitoring the voltage across the snubber resistor before finalizing the discharge period measurement. This allows the system to pre-determine whether compensation is needed and adjust the measurement boundaries accordingly
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 method enables accurate estimation of output current by accounting for the snubber circuit current, reducing estimation errors and improving the accuracy of power supply operations.
Implementation Method 1
an auxiliary winding coupled to the secondary winding in an insulated manner; and a delay voltage generator generating a delay voltage delaying an auxiliary voltage generated in the auxiliary winding
Implementation Method 2
a capacitor coupled to a first node to which the first resistor and the second resistor are coupled, and the delay voltage may be a voltage of the first node
Data Source
AI summary
A power supply device according to the invention includes: a power switch; a rectification diode generating an output current by rectifying a current supplied according to a switching operation of the power switch; and a switch control circuit generating an output current estimation voltage corresponding to the output current using a detection sense voltage corresponding to a sense voltage that depends on a switch current flowing to the power switch and a compensated discharge period. The compensated discharge period is a period from the peak of a discharge current flowing to the rectification diode to an instant at which the discharge current becomes zero current.