Transistorized Surge Protection Circuit with Segmented Crowbar
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Solution Overview
Problem
Existing surge protection circuits are bulky and prone to destruction during sustained voltage surges, leaving equipment vulnerable to damage, as they are not effective in handling surges lasting longer than 1-msec, such as those caused by power supply malfunctions.
Innovation Solution
An electrical surge protection apparatus featuring current paths with transistorised surge protection devices that assume an isolating state upon over-current and a voltage-triggered protective circuit that short-circuits surges to a low impedance, then isolates output nodes, using a crowbar-type device and voltage limiting elements like zener diodes to manage surges effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a diac and zener diode circuit is used for surge protection, then the response speed is quick and gas discharge tube problems are overcome, but the circuit is destroyed during sustained surges lasting longer than 1-msec
Solution Approach 1:
The surge protection function is divided into two independent stages: a voltage-triggered crowbar circuit for rapid initial response, and a current-triggered transistorised device for sustained surge handling. This segmentation allows each component to be optimized for its specific function, resolving the contradiction between quick response and sustained durability.
Solution Approach 2:
The voltage-triggered crowbar circuit acts as an intermediary that triggers the current-triggered transistorised surge protection device. This intermediary mechanism transfers the surge current to the more durable transistorised device, protecting the original diac-zener circuit from destruction during sustained surges.
2Reliability
If gas discharge tubes are used for surge protection, then surge protection is provided, but the circuits are bulky and have large associated capacitances
Solution Approach 1:
The patent replaces bulky gas discharge tubes with solid-state transistorised surge protection devices and integrated crowbar circuits. This substitution eliminates the need for large physical components while maintaining surge protection capability, significantly reducing circuit size and associated capacitances.
3Area of moving object
If the diac is made small with chip area of 4 mm2 for 1-msec surge protection, then the component size is reduced, but the circuit cannot handle surges lasting longer than 1-msec
Solution Approach 1:
The protection function is segmented into rapid-response voltage triggering and sustained-duration current handling. The small chip area diac crowbar provides instant response, while the transistorised device handles the sustained surge current, enabling protection against multi-second surges without increasing chip area.
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 rapidly isolates the circuit from surges, preventing damage by exposing the protective components to the surge for a minimal duration, allowing for smaller, high-capacity components and effective protection against both differential and common mode surges, even in high-speed communication applications.
Implementation Method 1
the voltage-triggered circuit assuming the low-impedance a surge current is passed through one or more of the transistorised surge protection devices to said surge sinking nodes
Implementation Method 2
one or more current paths each between corresponding one or more input nodes and one or more output nodes, each current path including a corresponding transistorised surge protection device configured to assume an isolating state in response to an over-current therethrough
Implementation Method 3
Zener diode 6 has a breakdown voltage VB slightly higher than power supply voltage Vps on signal line 10
Data Source
AI summary
An electrical surge protection device (12) confers protection to an output node (13) from electrical surges on a data or power line (10) incident on an input node (11). A transistorized surge protection device (18) is located in a current path between the input node (11) and the output node (13) and is configured to assume an isolating state in response to an over-current therethrough. A voltage-triggered protective circuit comprising a diac (16) in series with a bi-directional zener diode (14) is connected between the output side of the transistorized surge protection device (18) and a surge sinking node (15). The voltage-triggered circuit assumes a low-impedance state in response to an electrical surge at output terminal 13. Consequently a surge current is passed through zener diode (14) and surge diac (16) to the surge sinking node. In response to the surge current the transistorized surge protection device (18) assumes a high impedance configuration thereby isolating output node (13) from input node (11). Since neither the zener diode and diac combination, nor the transistorized surge protection device (18) are subject to sustained surge associated currents, embodiments of the invention can be compactly packaged.