Power Converter Current Sensing via Auxiliary Transformer Winding
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Solution Overview
Problem
Conventional methods for detecting output current in LLC power converters face challenges such as high switching loss, large circuit size, and inaccurate current detection, especially under low-voltage and large-current conditions.
Innovation Solution
A power converter design incorporating a current detection circuit with an auxiliary winding, a switch, and an impedance device, which detects the voltage of the impedance device to derive the current of the secondary side winding, allowing for accurate output current detection with reduced component count and circuit volume, and enabling operation with either DC or AC terminal potentials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a resistor is disposed at the output terminal of the transformer for sampling the output current, then the output current can be detected, but large loss is caused by the output current flowing through the resistor and the volume of the resistor needs to increase as the output power increases
Solution Approach 1:
The patent introduces an auxiliary winding as an intermediary element that magnetically couples to the secondary winding. This auxiliary winding transforms the current measurement function from direct electrical contact (resistor) to magnetic coupling, allowing current detection without the output current flowing through a physical resistor, thereby eliminating the power loss issue while maintaining detection capability
Solution Approach 2:
The patent replaces the mechanical/electrical contact-based current sensing method (resistor with direct current flow) with a magnetic field-based sensing method (auxiliary winding through magnetic coupling). This substitution eliminates the need for current to physically flow through a resistive element, solving both the power loss and volume expansion problems
2Measurement precision
If a current transformer is electrically connected to the secondary side of the transformer for detecting the output current, then the output current can be detected, but additional magnetic components are required resulting in increment of the circuit size of the converter
Solution Approach 1:
The patent merges the auxiliary winding with the existing transformer structure, utilizing the same magnetic core and spatial arrangement. The auxiliary winding is wound on the same core as the primary and secondary windings, sharing the magnetic path and physical space, thereby eliminating the need for separate magnetic components and reducing overall circuit size
Solution Approach 2:
The auxiliary winding serves multiple functions: it provides current detection capability while sharing the transformer's magnetic core and structure. This multi-functional design allows the transformer to simultaneously perform power transfer and current sensing without requiring dedicated components for each function
3Measurement precision
If a series branch circuit including a resistor and an auxiliary winding is electrically connected to two terminals of the secondary side winding of the transformer, then the output current can be detected by measuring the voltage across the resistor, but one terminal of the secondary side winding must be a DC potential terminal
Solution Approach 1:
The patent uses the auxiliary winding as an intermediary that magnetically couples to the secondary winding without requiring direct electrical connection or a common reference potential. This magnetic coupling mechanism allows voltage induction and current detection regardless of whether the secondary terminals are at DC or AC potential, eliminating the DC potential terminal requirement
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 approach reduces the volume and loss of the power converter while improving its applicability by enabling accurate output current detection with fewer electronic components and accommodating various terminal potentials.
Implementation Method 1
The first auxiliary winding and the secondary side winding are coupled to each other and the number of turns of the first auxiliary winding is the same as that of the secondary side winding
Data Source
AI summary
The present disclosure provides a power converter including a transformer, a first current detection circuit and a rectifier circuit. The transformer includes a primary side winding and a secondary side winding coupled to each other. The first current detection circuit is electrically connected in parallel to the secondary side winding and includes a first auxiliary winding, a first switch and a first impedance device electrically connected in series. The first auxiliary winding is coupled to the secondary side winding. The rectifier circuit includes a first bridge arm and a second bridge arm electrically connected in parallel. The first bridge arm includes a second switch and a third switch electrically connected in series, and the second bridge arm includes a fourth switch and a fifth switch electrically connected in series.