Analog Switch Overvoltage Protection Circuit
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Solution Overview
Problem
Existing overvoltage protection circuits for bidirectional data lines, such as 1-wire buses, are inadequate as they either fail to protect against both positive and negative overvoltages, or they compromise the low resistance and bidirectionality of the data line, especially in low-power modes or without a supply voltage.
Innovation Solution
A circuit featuring an analog switch and a voltage monitor that isolates the data line from the electronic functional unit upon detecting overvoltage, using a comparator and diodes to ensure reliable switching and maintain low resistance and bidirectionality, even in energy-saving modes or without supply voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a limiting or series resistor is used for overvoltage protection, then protection against overvoltage is provided, but voltage drop across the resistor prevents slave components from receiving enough supply voltage
Solution Approach 1:
The patent introduces an analog switch as an intermediary component between the data line and the electronic functional unit. This switch acts as a controllable mediator that can isolate the protected unit from overvoltage conditions while allowing normal operation when voltage levels are acceptable, thereby solving the contradiction between providing protection and maintaining adequate supply voltage.
2Reliability
If a zener diode is used for overvoltage protection, then protection against positive overvoltage is provided, but voltage drop occurs and protection against negative overvoltages is not offered
Solution Approach 1:
The patent employs a bidirectional suppressor diode that provides universal protection against both positive and negative overvoltages. This single component replaces the unidirectional zener diode, offering multi-functional protection capability that addresses the limitation of zener diodes which only protect against positive overvoltage and introduce voltage drops.
3Reliability
If a bidirectional suppressor diode is used, then protection against overvoltage transients is provided, but protection against overvoltages that lasted longer is not offered
Solution Approach 1:
The patent combines multiple protection mechanisms into a unified system: an analog switch for sustained overvoltage protection and a bidirectional suppressor diode for transient protection. This merging of components creates a comprehensive protection scheme that addresses both short-duration transients and long-duration overvoltage conditions.
4Reliability
If field effect transistors are used for protection, then protection against positive or negative voltage is provided, but bidirectionality is not possible or requires directional control which is unsuitable for 1-wire bus
Solution Approach 1:
The patent uses an analog switch as an intermediary component that maintains bidirectionality while providing protection. Unlike field effect transistors that require directional control, the analog switch can operate bidirectionally without compromising the 1-wire bus communication protocol, thus resolving the contradiction between protection capability and ease of bidirectional operation.
5Reliability
If varistor is used for protection, then overvoltage protection is provided, but voltage drop across the varistor occurs
Solution Approach 1:
The patent introduces an analog switch as a controllable intermediary that only activates during overvoltage conditions. Unlike a varistor that continuously presents a resistance path causing voltage drops, the analog switch remains open-circuit during normal operation, eliminating unnecessary voltage drops while providing protection when needed.
6Reliability
If protective circuit is added to protect against overvoltage, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent uses an analog switch controlled by a voltage monitor as a relatively simple intermediary protection mechanism. This approach adds minimal complexity compared to more elaborate protection schemes, as the analog switch and voltage monitor form a straightforward control system that can be integrated into existing 1-wire bus architectures with minimal additional components.
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 circuit effectively protects electronic functional units from both positive and negative overvoltages while ensuring continuous operation and maintaining data line properties, including low resistance and bidirectionality, across various power conditions.
Implementation Method 1
analog switch which can be closed by the voltage monitor if no overvoltage occurs and which can be opened by the voltage monitor if an overvoltage occurs
Implementation Method 2
voltage monitor which is set up to close the analog switch if no overvoltage occurs and to open the analog switch if an overvoltage occurs
Implementation Method 3
using a comparator and diodes to ensure reliable switching
Data Source
Figure 1
AI summary
The invention relates to a circuit for protecting an electronic functional unit (IC3) connected to a data line (Ltg. 1) against positive and negative overvoltages. The circuit has an analog switch (IC2) arranged in the data line (Ltg. 1) before the electronic functional unit (IC3). The circuit also comprises a voltage monitor, which is designed to control the analog switch (IC2), wherein the voltage monitor is designed to close the analog switch (IC2) if no overvoltage occurs and to open the analog switch (IC2) if an overvoltage occurs. The circuit also functions in an energy-saving mode and/or if no supply voltage is applied. A low resistance and a bidirectionality of the data line (Ltg. 1) are maintained.