AC-DC Power Converter Current Detection via Virtual Reference
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Solution Overview
Problem
Existing power conversion systems face challenges in efficiently detecting circuit currents at non-ground potential, leading to signal insulation issues and noise-related malfunctions, especially when handling a wide range of frequencies like 50 Hz and 50 kHz, which increases the size and cost of current transformers.
Innovation Solution
The proposed power conversion apparatus includes a circuit structure with semiconductor switches and diodes or synchronous rectification switches, allowing current detection at a point nearest to control GND, reducing noise mixing by using the potential difference across capacitors and ON resistance voltages for current detection, eliminating the need for insulation current transformers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insulation current transformer is used to detect circuit current at non-GND potential, then signal insulation is achieved, but the device size and cost increase
Solution Approach 1:
The patent introduces an intermediary potential reference point (Vref) that is electrically connected to the non-GND potential through a high-impedance path. This Vref serves as a mediator that allows the detection circuit to reference the current at non-GND potential without requiring direct galvanic isolation. The intermediary reference potential enables signal detection while avoiding the need for bulky and expensive insulation current transformers.
Solution Approach 2:
The patent replaces the mechanical/physical isolation approach (insulation current transformer with magnetic core) with an electrical approach using high-impedance buffering and virtual reference potential. Instead of using electromagnetic induction and magnetic fields for isolation, the system uses electronic buffering circuits and impedance matching to achieve the same isolation effect, resulting in a more compact and cost-effective solution.
2Measurement precision
If a current transformer detects both 50 Hz and 50 kHz components, then complete current detection is achieved, but the core size and cost increase
Solution Approach 1:
The patent segments the current detection function into two separate detection paths: one for low-frequency (50 Hz) components and another for high-frequency (50 kHz) components. Each detection path is optimized for its specific frequency range, allowing the use of smaller, more cost-effective detection elements for each band rather than requiring a single large core to handle the entire frequency spectrum.
Solution Approach 2:
The patent changes the detection parameters by using different detection methods for different frequency ranges. For low-frequency detection, it uses one approach (e.g., voltage sampling across known impedance), while for high-frequency detection, it employs another approach (e.g., different sampling method or filtering). This parameter-based differentiation allows accurate detection across the full spectrum without requiring a single oversized component.
3Ease of operation
If current detection is performed at non-GND potential, then circuit functionality is maintained, but noise interference increases
Solution Approach 1:
The patent creates a virtual equipotential reference (Vref) that tracks the potential of the non-GND point while maintaining a stable reference for measurement. By establishing this equipotential relationship through high-impedance buffering, the system allows current detection at non-GND potential without introducing significant noise, as the reference potential moves with the circuit potential rather than being fixed at GND.
Solution Approach 2:
The patent creates a copied or virtual version of the GND reference at the non-GND potential point through the Vref node. This copied reference potential provides the same stabilizing effect as a true GND reference would, but without the noise issues associated with long trace connections or ground loops. The virtual copy allows accurate noise-free measurement while maintaining circuit functionality.
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 enables efficient detection of sine wave currents synchronized with alternating voltage, reducing power loss and noise, while maintaining compact size and low cost, thus improving the stability and efficiency of power conversion.
Implementation Method 1
a current detection section which detects a current flowing to the diodes
Implementation Method 2
a first inductor connecting with alternating voltage power supply in series
Data Source
AI summary
A power conversion apparatus comprises a circuit, a detection section and a control section. The control section supplies a pulse signal for enabling the first switch and the second switch to be opened and closed alternately according to a polarity of the alternating voltage power supply so that a sine wave current synchronized with a voltage phase of the alternating voltage power supply flows to the alternating voltage power supply on the basis of the voltages and current obtained from the detection section.