Power Source Circuit Topology for Reverse Flow Blocking
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Solution Overview
Problem
Existing power source circuits face issues with reverse flow and negative voltage application, which can damage internal circuitry and components like transistors and comparators.
Innovation Solution
A protection circuit using NMOS and PMOS transistors, resistors, diodes, and a comparator to control gate voltages and prevent reverse flow and negative voltage damage, incorporating an ESD element for electrostatic protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a switch circuit is inserted in a power source line to prevent internal circuitry from being destroyed when power source and ground are connected in reverse, then protection against reverse connection is improved, but a reverse flow may occur when output terminal voltage becomes higher than input terminal voltage during on-operation
Solution Approach 1:
A diode is introduced as an intermediary component between the switch circuit and the internal circuitry. The diode's unidirectional conduction property allows it to block reverse flow while permitting normal forward current flow, thus resolving the contradiction between providing reverse connection protection and preventing reverse flow during operation.
Solution Approach 2:
The diode is positioned to preemptively block reverse flow before it can reach and damage the internal circuitry. By placing the diode in the power source line upstream of the internal circuitry, the system prevents the harmful reverse flow effect before it can occur, rather than attempting to mitigate it after the fact.
2Reliability
If protection circuits are added to prevent reverse flow and negative voltage damage, then circuit reliability is improved, but device complexity increases
Solution Approach 1:
The diode serves multiple protective functions simultaneously: it blocks reverse flow during switch on-operation, prevents negative voltage from reaching the comparator and transistors, and protects against electrostatic discharge when combined with the ESD element. This multi-functionality reduces the need for separate protection components for each threat, thereby limiting the increase in device complexity.
Solution Approach 2:
The protection circuit combines multiple protective elements (diode, ESD element, and the existing switch circuit) into a unified protection architecture. Rather than implementing separate independent protection circuits for reverse flow, negative voltage, and electrostatic discharge, the design merges these functions into a coordinated system that shares common components and control mechanisms.
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
Effectively prevents reverse flow and negative voltage damage to transistors and comparators, ensuring circuit integrity and reliability.
Implementation Method 1
a diode connected between the first input terminal and the second input terminal of the comparator
Implementation Method 2
incorporating an ESD element for electrostatic protection
Data Source
AI summary
A power source circuit according to an embodiment includes: first and second transistors connected to a current path between an input terminal and an output terminal; a first node that supplies a first control voltage to a gate of the first transistor; a comparator with a first input terminal to which a voltage supplied to the input terminal is applied and a second input terminal to which a voltage appearing at a second node being a connecting point of respective drains of the first and second transistors is applied, the comparator being configured to compare voltages of the first input terminal and the second input terminal to each other and to control the first control voltage to be supplied to the first node based on a comparison result; and a diode connected between the first input terminal and the second input terminal of the comparator.