Voltage Limiter for Electromagnetic Transponder
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Solution Overview
Problem
Existing electromagnetic transponders face challenges in protecting electronic circuits from overvoltages and high power levels, particularly in near field communication systems, where voltage limiting techniques often require high-voltage rectifier bridges and can compromise modulation quality.
Innovation Solution
A voltage limiting circuit is introduced that detects peak voltages and adjusts impedance between the rectifier bridge's input terminals, using a filter circuit with a longer time constant for voltage decrease than increase to preserve modulation and reduce component stress, eliminating the need for high-voltage rectifier bridges and modifying data interpretation circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage limiting circuits are provided to protect electronic circuits from overvoltages, then circuit protection is improved, but the modulation quality deteriorates due to clipping of the radio frequency signal
Solution Approach 1:
A limiting device is introduced as an intermediary component between the resonant circuit and the rectifier bridge. This device includes a detection circuit that monitors the voltage across the resonant circuit terminals and controls an adjustable impedance element to limit voltage without directly clipping the RF signal, thereby protecting downstream circuits while preserving modulation quality.
Solution Approach 2:
The voltage limiting action is performed preliminarily, before the signal reaches the rectifier bridge and electronic circuits. The detection circuit continuously monitors voltage levels and preemptively adjusts the impedance to prevent overvoltage conditions from developing, rather than reacting after damage occurs.
2Strength
If high voltage rectifier bridges are used to handle overvoltages, then voltage handling capability is improved, but device complexity and component stress increase
Solution Approach 1:
The voltage is limited in advance before it reaches the rectifier bridge, preventing overvoltage conditions from occurring at the bridge stage. This eliminates the need for the rectifier bridge to be designed with high voltage handling capability, allowing the use of standard, simpler components.
Solution Approach 2:
The adjustable impedance element acts as a cushioning mechanism that absorbs and limits voltage excursions before they can propagate to the rectifier bridge and subsequent circuits. This protective action is prepared and activated in advance, shielding downstream components from voltage stress.
3Reliability
If voltage limiting is implemented downstream of the rectifier bridge, then circuit protection is improved, but power loss increases due to heat generation in limiting components
Solution Approach 1:
Voltage limiting is performed upstream of the rectifier bridge, intercepting and limiting overvoltage conditions before they can be converted to high power dissipation in downstream components. This positioning reduces the energy that would otherwise be wasted as heat in limiting components located after rectification.
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 effectively limits power absorption, reduces heating, and maintains modulation quality by filtering voltage upstream of the rectifier bridge, allowing components downstream to operate within safe voltage ranges without needing to withstand overvoltages, thus enhancing the reliability and efficiency of electromagnetic transponders.
Implementation Method 1
These systems use the energy produced by a radiofrequency field from a terminal to communicate with, and most often power, an electromagnetic transponder
Implementation Method 2
a bridge rectifier whose input terminals are connected to the terminals of the resonant circuit and whose rectified output terminals provide a supply voltage for electronic circuits
Implementation Method 3
said circuit controlling an element of adjustable impedance, connected between the terminals of input of the rectifier bridge
Implementation Method 4
a filter circuit is inserted between the peak voltage detection circuit and the impedance. The filter has a time constant when the detected voltage decreases which is greater, in a ratio of at least 10, than its time constant when the detected voltage increases
Data Source
Figure 1~3
Figure 4~5
Figure 6
AI summary
The invention relates to an electromagnetic transponder comprising a resonant circuit (20); a rectifier bridge (23) whose input terminals (33, 34) are connected to the terminals of the resonant circuit and whose rectified output terminals (31, 32) provide a supply voltage (Vdd) for electronic circuits (25); and a device (4) for limiting the voltage (Vrf) across the terminals of the resonant circuit, connected between the input terminals of the rectifier bridge.