Low-Voltage Reset Circuit for Transient Protection
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Solution Overview
Problem
Existing electronic devices are vulnerable to damage from high-voltage transients, such as load dump conditions, which can cause voltage spikes, and current solutions often require expensive or hard-to-find high-voltage devices for protection.
Innovation Solution
A circuit that includes a low-voltage reset circuit and an input transistor, where the gate and source are shorted together when a voltage transient occurs, using a voltage divider to provide a threshold voltage and a low-voltage reset circuit to manage the shorting, thereby protecting the transistor from breakdown and disabling the voltage regulator to prevent current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-voltage devices are used to protect against voltage transients, then device reliability is improved, but cost and availability worsen
Solution Approach 1:
A low-voltage reset circuit is introduced as an intermediary component that monitors the voltage at the gate of the input transistor and actively shorts the gate to source when over-voltage conditions are detected. This intermediary protection mechanism allows the use of lower-voltage transistors while maintaining system reliability during voltage transients.
Solution Approach 2:
The protection circuit uses the voltage divider network already present in the voltage regulator to generate the threshold voltage needed for detection. The input transistor itself becomes part of the protection mechanism, where the reset circuit controls its gate to create the protective shorting action, eliminating the need for separate high-voltage protection devices.
2Object-affected harmful factors
If high-voltage devices are used to withstand voltage spikes, then protection capability is improved, but device cost increases
Solution Approach 1:
The low-voltage reset circuit continuously monitors the gate voltage through the voltage divider and takes preliminary protective action by shorting the gate to source before the full voltage transient can damage the input transistor. This preemptive protection allows the use of cheaper, lower-voltage rated devices.
Solution Approach 2:
The circuit changes the operating parameters of the input transistor dynamically - under normal conditions the transistor operates with its gate at a specific voltage, but when over-voltage is detected, the reset circuit changes the gate voltage to zero (by shorting to source), fundamentally altering the transistor's state to protect it from damage.
3Reliability
If the gate and source are shorted during voltage transients, then transistor protection is improved, but circuit complexity increases
Solution Approach 1:
The voltage divider network serves multiple functions: it provides the reference voltage for the voltage regulator operation and simultaneously provides the threshold voltage for the over-voltage detection function. The input transistor also serves dual purposes as both the main switching element and the protected element. This multi-functionality reduces the need for additional separate components.
Solution Approach 2:
The protection function is merged with the existing voltage regulation circuitry. The voltage divider that is essential for regulator operation is combined with the detection function, and the reset circuit is integrated to control the input transistor's gate, creating a unified protection system rather than a separate add-on circuit.
Data Source
AI summary
A circuit for voltage transient protection is provided. The circuit includes a voltage divider, a low-voltage reset circuit, and an input transistor. The input transistor receives an input voltage at the source of the input transistor, and provides a protected input voltage at the drain of the input transistor. The voltage divider provides a threshold voltage from the input voltage. The low-voltage reset circuit receives the threshold voltage. The low-voltage reset circuit causes the gate and source of the input transistor to short together when the low-voltage reset circuit is not in a reset state.