Reverse Battery Protection Circuit With Isolated MOSFET Gate Control
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Solution Overview
Problem
Conventional reverse battery protection methods, such as back-to-back MOSFET configurations, are costly, dissipate excessive power, and slow in switching speed, making them inefficient for protecting electronic fuses and microcontrollers in automotive applications.
Innovation Solution
A circuit and method utilizing an isolation circuit with a P-channel MOSFET and BJT, coupled with a control circuit including a diode, to disconnect the E-fuse from external MOSFETs when reverse polarity is detected, reducing power dissipation and MOSFET count, and using N-channel and P-channel MOSFETs, along with Zener diodes to block reverse currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If back-to-back MOSFET configuration is used for reverse battery protection, then the E-fuse and microcontroller are protected from reverse polarity damage, but the power dissipation increases and switching speed decreases
Solution Approach 1:
The protection function is segmented between the isolation circuit (P-channel MOSFET) and the control circuit (N-channel MOSFET), allowing each to operate optimally for its specific function rather than relying on a single back-to-back configuration that compromises overall performance
Solution Approach 2:
The P-channel MOSFET in the isolation circuit acts as an intermediary that blocks reverse polarity before it reaches the E-fuse and microcontroller, while the N-channel MOSFET in the control circuit provides additional protection and control, together reducing power dissipation compared to direct back-to-back configuration
2Reliability
If back-to-back MOSFET configuration is used for reverse battery protection, then the E-fuse and microcontroller are protected from reverse polarity damage, but the switching speed becomes slow
Solution Approach 1:
The protection function is segmented between the isolation circuit (P-channel MOSFET) and the control circuit (N-channel MOSFET), allowing each to operate optimally for its specific function rather than relying on a single back-to-back configuration that compromises overall performance
Solution Approach 2:
The patent changes the electrical parameters by using different MOSFET types (P-channel for isolation, N-channel for control) with optimized characteristics for their respective functions, improving switching speed compared to uniform back-to-back MOSFET configuration
3Reliability
If conventional reverse battery protection methods are used, then basic protection is provided, but the component count and manufacturing cost increase
Solution Approach 1:
The P-channel MOSFET in the isolation circuit serves multiple functions: it blocks reverse polarity during normal operation and also provides a discharge path for capacitive energy storage during reverse battery conditions, reducing the need for additional protective components
Solution Approach 2:
The isolation circuit and control circuit are merged into a unified protection architecture where the P-channel and N-channel MOSFETs work together in coordinated fashion, reducing overall component count compared to separate protection stages
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 reduces power dissipation and MOSFET count, enhancing switching speed and efficiency in reverse battery protection, thereby safeguarding electronic components from damage while minimizing component and manufacturing costs.
Implementation Method 1
an isolation circuit coupled between a gate output of an electronic fuse (E-fuse) and at least one external metal-oxide-semiconductor field-effect transistor (MOSFET)... configured to disconnect the gate output from the at least one external MOSFET when a battery is installed with reverse polarity
Implementation Method 2
a N-channel MOSFET configured to block a reverse current flowing from the external ground pin to the ground pin of the E-fuse when the battery is installed with the reverse polarity
Implementation Method 3
a control circuit including a diode coupled between the external ground pin and the gate of the at least one external MOSFET... configured to turn on the at least one external MOSFET when the battery is installed with the reverse polarity
Implementation Method 4
a plurality of Zener diodes... each of the plurality of Zener diodes configured to block a reverse current flowing from the microcontroller to the corresponding SPI pin of the E-fuse when the battery is installed with the reverse polarity
Data Source
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AI summary
A circuit for reverse battery protection (216) includes an isolation circuit (218) and a control circuit (220). The isolation circuit (218) is coupled between a gate output of an electronic fuse, E-fuse (202) and at least one external metal-oxide-semiconductor field-effect transistor,MOSFET (210). The E-fuse (202) is coupled between a battery voltage pin and an external ground pin and further coupled to a microcontroller (206). The isolation circuit (218) is configured to disconnect the gate output from the at least one external MOSFET (210) when the battery is installed with reverse polarity. The control circuit (220) is coupled between the external ground pin and the at least one external MOSFET (210). The control circuit (220) is configured to turn on the at least one external MOSFET (210) when the battery is installed with the reverse polarity.