Auxiliary Winding Primary-Side Load Current Sensing
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Solution Overview
Problem
Existing isolated power supply systems require additional components for secondary side sensing and feedback, increasing parts costs and complicating PCB layout, while direct primary-side load current sensing is challenging due to electrical isolation between circuit sides.
Innovation Solution
A DC-to-DC converter with a DC-to-AC inverter and an auxiliary winding generates a feedback signal responsive to the primary magnetizing current, combined with a sensed secondary current signal to isolate the primary magnetizing current component, allowing for accurate load current control without additional coupling components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If secondary side sensing and feedback components are added to achieve accurate load current control, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent uses the auxiliary winding as an intermediary element that magnetically couples the primary and secondary sides through the transformer core. This auxiliary winding senses the magnetizing current and provides a feedback signal that represents the load current, eliminating the need for direct secondary side sensing components while maintaining measurement accuracy through magnetic coupling.
Solution Approach 2:
The patent implements a feedback mechanism where the auxiliary winding generates a signal proportional to the magnetizing current, which is then combined with the reflected load current signal. This feedback loop allows the primary side controller to accurately determine the load current and adjust the power supply output accordingly, achieving precise control without additional secondary side components.
2Measurement precision
If additional coupling components are added for secondary side sensing, then measurement precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent merges the sensing function with the existing transformer structure by incorporating the auxiliary winding into the transformer core. This integration eliminates the need for separate coupling components and reduces PCB layout complexity, as the sensing is achieved through the magnetic coupling already present in the transformer design.
Solution Approach 2:
The auxiliary winding serves as an intermediary that provides the sensing function through magnetic coupling rather than requiring physical coupling components on the PCB. This approach simplifies manufacturing and PCB layout while maintaining accurate load current measurement capability.
3Device complexity
If direct primary-side load current sensing is implemented, then device complexity is reduced, but measurement precision deteriorates due to electrical isolation
Solution Approach 1:
The auxiliary winding acts as an intermediary that overcomes the electrical isolation barrier between primary and secondary sides. By sensing the magnetizing current through magnetic coupling and combining it with the reflected load current signal, the system achieves accurate load current measurement on the primary side without breaking the electrical isolation.
Solution Approach 2:
The feedback signal from the auxiliary winding provides the necessary information about the magnetizing current, which when combined with the reflected load current, enables accurate load current sensing on the primary side. This feedback mechanism resolves the measurement precision issue while maintaining device simplicity.
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 simplifies circuit design and PCB layout by enabling accurate primary-side sensing of secondary load current, reducing component count and costs while maintaining precise load current control.
Implementation Method 1
The auxiliary winding voltage is applied to an inductor to generate an auxiliary current proportional to the primary winding magnetizing current
Data Source
AI summary
A DC-to-AC inverter provides an AC voltage to the primary winding of an output isolation transformer having at least one secondary winding and having an auxiliary winding. The current supplied to a secondary load is reflected back into the primary winding as a reflected secondary current. A first feedback signal has a reflected secondary current component and has a primary magnetizing current component. An auxiliary winding voltage is applied to an inductor to generate an auxiliary current proportional to the primary winding magnetizing current. A second feedback signal is responsive to the auxiliary current. The second feedback signal is combined with the first feedback signal to produce a total feedback signal responsive only to the reflected secondary current. The DC-to-AC inverter responds to the total feedback signal and a reference signal to adjust the AC voltage to maintain the total feedback signal at a magnitude corresponding to the reference signal.