AC/DC Converter with Segmented Isolation Transformer
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Solution Overview
Problem
Existing AC/DC converters for aircraft electrical distribution networks face inefficiencies due to high distortion in current consumption, leading to transformer overheating, electromagnetic interference, and increased mass and size requirements, particularly when dealing with variable frequency alternators.
Innovation Solution
An AC/DC converter design with a primary winding divided into two parts by an intermediate point, controlled by pulse-width modulation switches, utilizing a first secondary winding for 'Forward' operation and a second secondary winding for 'Flyback' operation, optimizing transformer sizing and energy transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transformer with primary winding connected to alternator and secondary winding connected to rectifier bridge is used, then galvanic isolation is achieved, but current distortion causes transformer overheating and reduced efficiency
Solution Approach 1:
The primary winding is divided into two separate windings: a first primary winding connected to the alternator and a second primary winding connected to the rectifier bridge. This segmentation allows independent optimization of each winding's function, reducing current distortion in the first winding and improving overall transformer efficiency while maintaining galvanic isolation.
2Loss of energy
If series filtering is applied on the primary circuit of the transformer, then current distortion is reduced, but the solution is not suitable for variable frequency alternators
Solution Approach 1:
The invention uses two separate primary windings that can dynamically adapt to different operating conditions. The first primary winding handles the alternator connection with optimized parameters for reduced distortion, while the second primary winding handles the rectifier bridge connection. This dynamic configuration allows the transformer to effectively handle variable frequency inputs without requiring series filtering.
3Loss of energy
If a BOOST type PFC circuit is used, then current waveform is improved, but galvanic isolation is lost requiring additional DC/DC converter
Solution Approach 1:
The invention merges the PFC function and galvanic isolation function into a single transformer structure. The first primary winding connected to the alternator performs power factor correction by drawing sinusoidal current, while the transformer itself provides galvanic isolation between the alternator and the rectifier bridge. This eliminates the need for a separate DC/DC converter that would be required in a BOOST type PFC circuit.
4Reliability
If a FLYBACK type PFC circuit is used, then galvanic isolation is achieved, but large energy storage in magnetic core increases transformer size and mass
Solution Approach 1:
The transformer is segmented into two separate primary windings with different functions. The first primary winding is optimized for continuous operation with the alternator and requires minimal energy storage, while the second primary winding handles the rectifier bridge connection. This segmentation eliminates the need for large energy storage in the magnetic core that would be required in a traditional FLYBACK type circuit, thereby reducing transformer mass and size.
5Reliability
If a FORWARD type PFC circuit is used, then galvanic isolation is achieved, but current cannot be exploited over entire sinusoid reducing efficiency
Solution Approach 1:
The invention uses two primary windings that can dynamically operate in different modes. The first primary winding can operate throughout the entire sinusoidal cycle to maximize energy exploitation, while the second primary winding provides galvanic isolation. This dynamic configuration overcomes the FORWARD type limitation where current cannot be exploited over the entire sinusoid, thereby improving energy consumption efficiency.
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 design achieves efficient galvanic isolation and power factor correction with reduced switching losses and energy waste, minimizing overvoltages and maintaining high efficiency across varying input voltages.
Implementation Method 1
an isolation transformer (6) whose primary winding (5) is connected in series to a rectifier circuit output
Implementation Method 2
a first chopping switch (T1) connected to a control circuit (10) by pulse width modulation
Implementation Method 3
a first secondary winding (7) which is of identical direction to the primary winding (5) and which is connected to an output line (8) of the converter via a diode (D3)
Implementation Method 4
the output line (8) being connected to an output capacitor (Cout)
Data Source
AI summary
The invention relates to an AC/DC converter comprising a primary winding (5) belonging to an isolation transformer (6), and a first secondary winding (7) and a second secondary winding (9) which are disposed in the same direction as, and the opposite direction to the primary winding respectively and which are connected to an output line connected in turn to an output capacitor (Cout), said first secondary winding being connected to the output line (8) via a filter choke (L1) and said primary winding being connected to a first splitting switch (T1) connected in turn to a control circuit (10). The invention is characterised in that the primary winding comprises an intermediate point connected to a second splitting switch that is connected to the control circuit, dividing the primary winding into a first part and a second part, such as to optimise the transfer of energy between the primary winding and the secondary windings according to the conduction of the switches which are controlled as a function of the presence of current at the output of the first secondary winding.