Limiter Circuit Attenuates Common Mode Surge Oscillations
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Solution Overview
Problem
Existing connection circuitries for electrical devices fail to effectively prevent high voltage oscillations caused by common mode surges, leading to potential device damage and operational failures, especially when subjected to high surge voltages like 2 kV, as they can cause saturation of common mode chokes and voltage breakthroughs.
Innovation Solution
A limiter circuit is introduced, comprising a voltage dependent element, such as a voltage dependent resistor, connected in series with diodes, which bypasses the common mode choke and attenuates high voltage oscillations, ensuring the circuitry's capacitance is low enough not to compromise interference filtering during normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a common mode choke and Y-capacitor form a series resonance circuit to filter common mode interference, then common mode interference is filtered, but high voltage oscillations arise that can cause saturation and damage
Solution Approach 1:
A voltage dependent element (varistor) is introduced as an intermediary component connected in parallel with the series resonance circuit. This varistor acts as a mediator that becomes conductive when voltage exceeds a threshold, providing a safe discharge path for surge energy and preventing voltage breakdown without interfering with normal filtering operation.
Solution Approach 2:
The voltage dependent element's resistivity changes dynamically based on voltage levels. During normal operation, it maintains high resistance and does not affect the resonance circuit. During surge conditions, its resistance decreases dramatically, allowing it to clamp the voltage and protect the circuit from damaging oscillations.
2Reliability
If the capacitance of the limiter circuit is increased to improve surge protection, then surge protection is enhanced, but interference filtering during normal operation is compromised
Solution Approach 1:
The voltage dependent element provides dynamic protection that adapts to operating conditions. During normal operation, it remains non-conductive and transparent to the circuit, preserving the resonance circuit's filtering characteristics. During surge events, it activates dynamically to provide protection, thus maintaining both filtering performance and surge protection.
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 limiter circuit effectively limits high voltage values, preventing damage and operational errors by attenuating surge-induced oscillations while maintaining the circuit's interference filtering capabilities, thus ensuring safe operating conditions for electrical devices at reasonable costs.
Implementation Method 1
a voltage dependent element for decreasing resistivity of said element according to an increase in voltage in said element
Implementation Method 2
the common mode choke and the Y-capacitor form a series resonance circuit as shown in figure 2. Due to the common mode surge voltage, the voltage of the Y-capacitor may be up to twice the peak value of the surge voltage. A voltage oscillation arises in the resonance frequency of the common mode choke LEMI and the Y-capacitor.
Implementation Method 3
a diode bridge for rectifying alternating voltage from the power source to rectified voltage in the second circuit
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The object of the invention is a limiter circuit for a connection circuitry making a connection from a power source (100) to a load (102), said connection circuitry comprising a common mode choke (104), a first circuit (106) connecting the power source (100) and the common mode choke (104), and a second circuit (108) connecting the common mode choke (104) and the load (102). The limiter circuit (110) comprises a voltage dependent element (112) for decreasing resistivity of said element (112) according to an increase of voltage in said element (112), said voltage dependent element comprising at least two terminals (114, 116), the first terminal (114) being connected to the first circuit (106) and the second terminal (116) being connected to the second circuit (108) bypassing the common mode choke (104), a serial connection of at least two diodes (D1,D2) being connected to the second circuit (108), and the second terminal (116) of the voltage dependent element (112) being connected in between said at least two diodes (D1, D2) for limiting substantially high voltage values from arising in the connection circuitry.