MOSFET Reverse Current Protection Circuit for Low-Voltage Power Supply
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Solution Overview
Problem
Existing power supply systems using diode-OR circuits for reverse current protection are not suited for low-voltage operations, requiring expensive step-up and step-down power supply circuits to maintain voltage, which is not cost-effective.
Innovation Solution
A power supply system utilizing a MOSFET-based reverse current protection circuit with an on/off controller to manage power flow between main and sub power supply lines, ensuring the main power supply voltage is maintained high even at low input voltage, and limiting current through the sub power supply line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diode-OR circuit is used for reverse current protection, then reverse current flow is prevented, but voltage drop increases and low-voltage operation becomes difficult
Solution Approach 1:
The patent changes the electrical parameters of the protection circuit by replacing diodes with MOSFETs. The MOSFETs have much lower on-resistance compared to diode forward voltage, reducing voltage drop from typically 0.7V to millivolt range. This parameter change enables low-voltage operation while maintaining reverse current protection functionality.
Solution Approach 2:
The patent substitutes the passive diode-based protection mechanism with an active MOSFET-based system controlled by voltage signals. The on/off controller dynamically manages MOSFET switching based on power supply voltage levels, replacing the static diode conduction mechanism with a controllable electronic switch system.
2Reliability
If step-up and step-down power supply circuits are used to maintain voltage, then low-voltage operation is enabled, but system cost and complexity increase
Solution Approach 1:
The patent extracts and removes the complex step-up and step-down power supply circuits from the system. By using MOSFETs with low on-resistance, the system directly handles low-voltage input without requiring additional voltage conversion stages, eliminating unnecessary circuit complexity while maintaining voltage stability.
Solution Approach 2:
The MOSFET-based reverse current protection circuit serves multiple functions: it provides reverse current protection, enables low-voltage operation, and maintains voltage stability simultaneously. This multi-functional approach replaces the need for separate voltage conversion circuits, reducing overall system complexity.
3Reliability
If both main and sub power supply lines are configured to accommodate total supply current, then power supply reliability is ensured, but sub power supply circuit size increases unnecessarily
Solution Approach 1:
The patent introduces dynamic control through the on/off controller that monitors power supply voltage and selectively activates or deactivates the MOSFET. This dynamic switching capability allows the system to adapt current paths based on operating conditions, enabling the sub power supply line to remain compact while maintaining reliability through controlled current distribution.
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
This solution allows for reliable power supply from both main and sub power supply lines while minimizing unnecessary circuit complexity and cost, maintaining high main power supply voltage and reducing current through the sub power supply line.
Implementation Method 1
When the on/off controller applies an on-state control voltage to a gate of the MOSFET, the power from the main power supply input from the main power supply line is output to the common connection node via the MOSFET
Implementation Method 2
The diode is connected such that a forward current flows from the sub power supply line to the common connection node and does not flow reversely
Data Source
AI summary
A reverse current protection circuit includes a MOSFET and an on/off controller. When the on/off controller applies an on-state control voltage to a gate of the MOSFET, a main power supply input through a main power supply line is output to a common connection node via the MOSFET; and when an off-state control voltage is applied to the gate of the MOSFET, the electrical connection between the main power supply line and the common connection node is interrupted to prevent a reverse current. A diode is connected to enable a forward current flowing from a sub power supply line to the common connection node and the reverse current is prevented. The voltage drop of the main power supply, when the on-off controller applies the on-state control to the gate of the MOSFET, is lower than the voltage drop of the sub power supply through the diode.