AC/DC Converter Analog Correction Circuit for Waveform Distortion
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Solution Overview
Problem
Existing AC/DC converters with galvanic isolation, such as those used in aircraft electrical systems, face inefficiencies and compatibility issues with PWM-PFC regulators due to trapezoidal primary current shapes at medium to high voltages, which are detrimental to optimal operation according to the DO-160 standard.
Innovation Solution
An AC/DC converter design featuring a rectifier circuit connected in series with a primary winding of an isolation transformer and a cutting switch controlled by a PWM control circuit, along with an analog correction circuit that transforms the trapezoidal primary current signal into a triangular signal, ensuring optimal operation by mimicking a single conversion stage with galvanic isolation and PFC functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a dual-secondary-winding transformer structure is used to achieve galvanic isolation and PFC functions, then power transmission capability is improved, but primary current waveform distortion occurs
Solution Approach 1:
An analog correction circuit is introduced as an intermediary between the dual-secondary-winding transformer structure and the PWM-PFC regulator. This correction circuit processes the primary current signal to compensate for waveform distortion, transforming the distorted trapezoidal current into a sinusoidal waveform that is compatible with PWM-PFC regulation requirements.
Solution Approach 2:
The invention changes the parameters of the primary current waveform through the analog correction circuit. By adjusting the circuit components (resistors, capacitors, operational amplifiers), the distorted current parameters are modified to achieve the desired sinusoidal shape, enabling optimal operation of the PWM-PFC regulator.
2Measurement precision
If PWM-PFC regulation is applied to a dual-secondary-winding transformer, then control precision is improved, but compatibility with DO-160 standard deteriorates
Solution Approach 1:
The analog correction circuit serves as a mediator that adapts the primary current waveform to meet DO-160 standard requirements. It transforms the distorted trapezoidal current into a sinusoidal waveform, enabling the system to maintain both PWM-PFC control precision and compatibility with aviation standards.
Solution Approach 2:
The correction circuit performs preliminary correction of the primary current waveform before it reaches the PWM-PFC regulator. By pre-compensating for the distortion caused by the dual-secondary-winding structure, the system prevents waveform issues that would otherwise violate DO-160 standards.
3Device complexity
If trapezoidal primary current is allowed to pass through the PWM-PFC regulator, then circuit simplicity is maintained, but regulator operation efficiency deteriorates
Solution Approach 1:
The analog correction circuit is a relatively simple intermediary structure that efficiently converts the trapezoidal current waveform into a sinusoidal one. This modest addition significantly improves regulator operation efficiency without substantially increasing overall system complexity.
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
The converter achieves precise output voltage and sinusoidal current consumption, enhancing efficiency and compatibility with PWM-PFC regulators by converting the trapezoidal signal to a triangular signal, thus optimizing the control circuit's operation.
Implementation Method 1
an isolation transformer having a primary winding connected to a chopping switch... a first secondary winding which has the same direction as the primary winding... and a second secondary winding which has an opposite direction to the primary winding
Implementation Method 2
a chopping switch controlled by a width modulation control circuit by pulse or PWM
Implementation Method 3
a first secondary winding which has the same direction as the primary winding and which is connected to an output line of the converter via a diode... a second secondary winding which has an opposite direction to the primary winding and which is directly connected to the output line via a diode
Implementation Method 4
a first secondary winding which has the same direction as the primary winding and which is connected to an output line of the converter via a diode and a filter coil
Implementation Method 5
The second secondary winding therefore makes it possible to evacuate the energy stored in the magnetic core towards the output and avoids a waste of energy. It also ensures energy consumption, used by the output, for low voltages
Data Source
Figure 1~2
AI summary
The invention relates to an AC/DC converter comprising, at the inlet thereof, a rectifier circuit connected in series to a primary winding (5) of an isolating transformer (6) and to a splitting switch (T1) controlled by a control circuit (10) by pulse-width modulation of a signal representing a primary current, the isolating transformer comprising a first secondary winding (7) in the same direction as the primary winding and connected to an output line (8) of the converter via a diode (D4) and a filter coil (L1), and a secondary winding (9) in the opposite direction to the primary winding and directly connected to the output line via a diode (D2), the output line being connected to an output capacitor (Cout). The converter comprises an analog circuit for correction of the primary current, which is connected to the control circuit and to a measuring element (30) that supplies a signal representing the primary current and is arranged so as to transform said signal into a triangular signal able to control the control circuit.