P-channel MOSFET Reverse Battery Protection Circuit
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Solution Overview
Problem
High Side power outputs struggle to handle high energy inductive loads without adequate protection, particularly from reverse battery conditions and high current events, leading to user dissatisfaction with existing solutions.
Innovation Solution
A circuit protection system utilizing a P-channel MOSFET, freewheeling diode, and charge pump that clamps high energy transients without power dissipation in normal modes, providing reverse battery protection and sharing the MOSFET among multiple outputs to reduce costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple freewheeling diodes are used for each output, then individual load protection is improved, but system cost and part count increase
Solution Approach 1:
The patent merges multiple protection functions into a single integrated circuit that can protect multiple outputs. One P-channel MOSFET can be shared among multiple outputs, reducing the total part count while maintaining individual load protection capability through the circuit's ability to handle multiple freewheeling diodes.
Solution Approach 2:
The protection circuit is designed as a universal module that can protect multiple outputs simultaneously. The circuit architecture allows a single protection unit to serve multiple loads, reducing redundancy and lowering overall system cost while maintaining comprehensive protection.
2Reliability
If robust protection circuits are implemented, then reliability against high energy events is improved, but power dissipation and cost increase
Solution Approach 1:
The protection circuit uses dynamic switching elements (MOSFETs) that can rapidly transition between on and off states. The P-channel MOSFET remains off during normal operation to minimize power dissipation, and only activates when fault conditions are detected. The charge pump dynamically enables protection only when needed, reducing continuous power consumption.
Solution Approach 2:
The circuit uses low-cost MOSFETs and diodes that can handle high energy events temporarily but are designed to be replaced rather than protected. The protection circuit allows these components to dissipate energy during fault conditions without requiring expensive heat sinks or continuous active cooling.
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 effectively protects against high current and inductive events while preventing damage from reverse battery conditions, maintaining low costs and part count, and ensuring reliable operation across various loads.
Implementation Method 1
the charge pump receives a voltage from a voltage regulator, and is configured to multiply and reverses the polarity of the voltage to supply to the gate of the MOSFET
Implementation Method 2
when a driver switch to a load opens, the MOSFET and freewheeling diode cooperate to recirculate current in the load
Data Source
AI summary
An apparatus for providing protection to an electric circuit includes a P-channel MOSFET; a freewheeling diode coupled to a drain of the P-channel MOSFET and coupled to a load; and a charge pump coupled to a gate of the P-channel MOSEFT. In a normal operating mode, the charge pump receives a voltage from a voltage regulator, and is configured to multiply and reverses the polarity of the voltage to supply to the gate of the MOSFET. In a reverse battery operating mode, the charge pump receives no voltage from the voltage regulator to supply to the gate of the MOSFET causing the MOSFET to deactivate such that when the MOSFET deactivates, current is prevented from flowing through the freewheeling diode to protect the freewheeling diode.