Auxiliary Power Supply Isolation for Interference Rejection
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Solution Overview
Problem
Existing auxiliary power supplies for switched-mode power supplies are sensitive to high-frequency interference, leading to inaccurate signal evaluation and increased costs due to the need for complex filtering or expensive measuring devices.
Innovation Solution
An auxiliary supply with a transformer-based design that uses a high-frequency generator on the primary side to generate AC voltage, transmitted via electrical isolation to the secondary side, where it is rectified and used to supply control electronics, with an impedance-based system to evaluate changes in secondary-side load conditions, reducing interference sensitivity and eliminating the need for additional filtering or complex devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If series resistors are used for signal transmission through galvanic isolation, then information can be transmitted from secondary side to primary side, but sensitivity to high-frequency interference and electromagnetic compatibility disturbances increases
Solution Approach 1:
The patent introduces a capacitor as an intermediary element for signal transmission across the galvanic isolation barrier. Instead of using resistive coupling, the capacitor serves as the mediating component that allows AC signal passage while blocking DC and providing inherent high-frequency filtering. This resolves the contradiction by enabling signal transmission (improving information loss) while the capacitor's reactive nature naturally attenuates high-frequency interference (reducing sensitivity to harmful factors).
Solution Approach 2:
The patent changes the transmission parameter from resistive coupling to capacitive coupling. By using a capacitor with specific capacitance value, the system transforms the signal transmission mechanism, allowing AC signals to pass while the capacitor's impedance characteristics naturally filter high-frequency disturbances. This parameter change enables simultaneous achievement of signal transmission and interference rejection.
2Measurement precision
If additional capacitors are used to filter signals and reduce interference sensitivity, then measurement accuracy improves, but device complexity and cost increase
Solution Approach 1:
The patent applies the self-service principle by using the capacitor that is already present in the galvanic isolation circuit to perform dual functions: signal transmission and high-frequency filtering. The capacitor inherently provides the filtering effect due to its reactive impedance characteristics, eliminating the need for additional filtering components. This resolves the contradiction by achieving measurement precision improvement without increasing device complexity.
Solution Approach 2:
The capacitor in the galvanic isolation circuit is made multi-functional, serving both as a signal transmission element and as a high-frequency filter. This universal application of the capacitor eliminates the need for separate filtering components, thereby improving measurement precision while maintaining simple device architecture and avoiding additional costs.
3Object-affected harmful factors
If fast-acting evaluation devices with high common-mode rejection are used, then interference sensitivity reduces, but manufacturing cost increases significantly
Solution Approach 1:
The patent converts the inherent reactive characteristic of the capacitor (which naturally impedes high-frequency signals) into a beneficial filtering function. By utilizing the capacitor's impedance properties at high frequencies, the system automatically rejects common-mode interference without requiring expensive specialized evaluation devices. This resolves the contradiction by reducing interference sensitivity through a low-cost passive component rather than expensive active filtering equipment.
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 solution significantly reduces interference sensitivity, allowing for simple and cost-effective implementation by using only potential isolation for signal transmission, enabling accurate evaluation of secondary-side supply voltage changes without complex filtering or expensive equipment.
Implementation Method 1
at least one frequency generator arranged on the primary side for generating an AC voltage with a predetermined frequency
Implementation Method 2
a rectifier unit arranged on the secondary side for a supply voltage on the secondary side
Data Source
AI summary
The invention relates to an auxiliary power supply for a power supply with at least one transformer having a primary side (P) and a secondary side (S). The auxiliary power supply (V) provides a voltage supply (Uv) on the secondary side (S) of the power supply that is independent of the operating state of the power supply. This auxiliary power supply consists of at least a frequency generator (FG) arranged on the primary side for generating an alternating voltage with a predetermined frequency, a rectifier unit (GL) arranged on the secondary side for a secondary-side supply voltage (Uv), and a first and a second galvanic isolation device (TC1, TC2) arranged between the primary side (P) and the secondary side (S). The first galvanic isolation device (TC1), through which the alternating voltage generated by the frequency generator (FG) can be transmitted, is connected to the frequency generator (FG) on the primary side via, for example, a high-impedance resistor (R1).The second galvanic isolation (TC2) is coupled at high frequency on the primary side (P) to a reference potential (Pp) assigned to the frequency generator and capacitively connects a secondary-side reference potential (Ps) to the primary side (P) with a low impedance. Furthermore, a voltage drop across the impedance (R1) can be used to evaluate the secondary-side supply voltage (Uv).