Semiconductor Switch Overvoltage Protection Circuit
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Solution Overview
Problem
Current overvoltage protection methods, such as those using varistors and inductive chokes, face challenges in managing slow-front transient overvoltages and low-frequency overvoltages, leading to potential damage of protection components due to increased energy absorption and power losses.
Innovation Solution
A fast electronic protection circuit that disconnects the device from the voltage source using a semiconductor switch when an overvoltage or overcurrent is detected, reconnecting only when the voltage is zero and the conditions are safe, with additional components like capacitors and voltage limiters to manage energy and prevent interference currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If overvoltage is limited by loading it through protection components like varistors, then overvoltage protection is achieved, but the protection components may be damaged due to increased energy absorption and power losses
Solution Approach 1:
The harmful function of energy dissipation is extracted from the protection circuit by removing the varistor component. The patent replaces the traditional varistor-based overvoltage protection with a semiconductor switch that disconnects the load from the voltage source during overvoltage conditions, eliminating the need for energy-dissipating protection components.
Solution Approach 2:
The patent replaces the passive mechanical/electrical varistor system with an active semiconductor switching system. Instead of using a varistor that passively limits voltage through resistance changes and energy dissipation, the invention uses a semiconductor switch controlled by a control circuit to actively disconnect the load, thereby avoiding energy loss in protection components.
2Speed
If a semiconductor switch is used for fast breaking of the circuit, then the protection speed is improved, but additional components are required to manage voltage and current conditions
Solution Approach 1:
The control circuit performs multiple functions: it monitors voltage and current conditions, controls the semiconductor switch operation, detects zero-crossing points, and manages the reconnection logic. By consolidating these functions into a single control circuit, the patent avoids the need for separate complex circuits for each function, thereby managing device complexity while achieving fast protection.
Solution Approach 2:
The control circuit continuously monitors the electrical conditions (voltage and current) and provides feedback control to the semiconductor switch. This feedback mechanism enables the circuit to automatically detect overvoltage/overcurrent conditions, trigger the switch at appropriate moments (zero-crossing points), and manage reconnection, thereby achieving fast protection with a manageable number of components.
3Loss of time
If the switch is reopened quickly after overvoltage subsides, then the influence on device operation is minimized, but interference currents may be generated
Solution Approach 1:
The control circuit preliminarily detects the zero-crossing point of the voltage or current waveform before actually reopening the semiconductor switch. By anticipating the optimal moment for switch operation (when voltage/current is near zero), the circuit minimizes the generation of interference currents while ensuring rapid reconnection. This preliminary detection and timing strategy allows the switch to be reopened quickly without generating harmful interference currents.
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 significantly reduces the risk of damage to protection components by avoiding energy dissipation and ensuring quick, safe reconnection, thus enhancing the reliability of overvoltage protection.
Implementation Method 1
a series-connected switch element of the electric circuit, which is implemented by a semiconductor switch member
Implementation Method 2
a capacitor member connected in parallel with the semiconductor switch member
Implementation Method 3
a voltage limiter member connected after the semiconductor switch member in order to limit the output voltage
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An overvoltage protector disconnects a device (31) to be protected from a voltage source (V1) by breaking an electric circuit by a semiconductor switch (S1) connected in series with the electric circuit when an overvoltage or overcurrent is detected (B1, B3). The electric circuit may again be quickly closed when the overvoltage or overcurrent has subsided, so that the breaking does not influence the operation of the device to be protected. The voltage across the semiconductor switch is monitored by a zero voltage detector, the switch is closed again and the device to be protected is reconnected to the supplying voltage source when the voltage across the switch (S1), according to measurement (B2), is zero.