Ideal Diode MOSFET Circuit for Negative Transient Protection
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Solution Overview
Problem
Current circuitry fails to effectively protect vehicle ECUs from negative transient pulses, allowing high current to flow through MOSFETs and reducing the charge stored in load side bulk capacitors, thereby compromising protection efficacy.
Innovation Solution
Incorporating an inductor in series with a MOSFET, a transistor, and a diode to detect voltage differences, turning off the MOSFET and providing an additional response time through the inductor's energy storage, ensuring the capacitor supplies current during negative transients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current circuitry is used without additional protection components, then the circuit is simpler, but it fails to protect against negative transient pulses and allows high current to flow through the MOSFET
Solution Approach 1:
The patent introduces an inductor as an intermediary component between the MOSFET and the load. This inductor acts as a mediator that slows down the negative transient pulse, providing additional response time for the protection circuit to activate. The inductor's inherent property of opposing changes in current flow allows it to buffer the transient pulse, preventing it from immediately affecting the MOSFET and load capacitor.
Solution Approach 2:
The protection circuit is designed to activate before the negative transient pulse can cause damage. The inductor is positioned to preemptively slow down any incoming transient pulse, and the circuit is configured to detect voltage differences and turn off the MOSFET in advance, preventing high current flow before it can occur.
2Reliability
If the MOSFET response time is faster, then protection is more effective, but the inductor adds additional response time that delays the protection
Solution Approach 1:
The patent converts the inductor's inherent property of slowing down current changes, which initially appears to be a disadvantage (delayed response), into a benefit. By deliberately introducing this delay, the circuit gains sufficient time to detect the negative transient pulse and activate the protection mechanism before damage occurs. The inductor's time constant becomes an ally rather than an obstacle, allowing the protection circuit to respond effectively.
3Object-affected harmful factors
If a diode is placed on the VBAT line for protection, then reverse voltage protection is provided, but it does not effectively protect against negative transient pulses
Solution Approach 1:
The patent segments the protection function into multiple components working together: the diode handles reverse voltage protection, while the inductor-transistor-capacitor combination specifically addresses negative transient pulse protection. This segmentation allows each component to specialize in protecting against its respective threat, with the inductor providing the time-delay mechanism needed to protect against transients that a simple diode cannot handle.
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
Prevents high current flow and maintains positive voltage and current levels during negative transients, enhancing protection against reverse voltage and transient pulses.
Implementation Method 1
in response to the MOSFET turning off, the inductor is configured to generate an additional response time to the circuit
Implementation Method 2
a capacitor on a load side is configured to supply current to the load side during a negative transient duration
Implementation Method 3
a diode connected to a source channel of the MOSFET and the base of the transistor, in response to the transistor and diode detecting a difference in voltage
Data Source
AI summary
A circuit includes a battery configured to supply voltage to the circuit, a metal-oxide-semiconductor field effect transistor (MOSFET) located within the circuit, an inductor in series with a drain channel of the MOSFET, a transistor in series with the inductor, wherein an emitter channel of the transistor is connected with the inductor and a base of the transistor is connected to a ground channel of the MOSFET, a diode connected to a source channel and the base of the transistor, in response to the transistor and diode detecting a difference in voltage, the transistor is configured to turn off the MOSFET utilizing a gate terminal, in response to the MOSFET turning off, the inductor is configured to generate an additional response time to the circuit, and in response to a voltage drop, a capacitor on a load side is configured to supply current to the load side.