MOSFET Regulator Rectifier Protection Against Reverse Voltage
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Solution Overview
Problem
Regulator rectifier devices are vulnerable to damage from reverse battery connections and short circuits, with existing protection methods like diodes and fuses either consuming power or being ineffective in automotive applications with bulk capacitors.
Innovation Solution
A protection system with a control unit that detects reverse voltage and short circuit conditions, switching a switching unit between ON and OFF states to break the circuit between the regulator rectifier device and the load section, using a combination of voltage detection units and a driver unit to manage the switching unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diode is connected in series with the battery to protect the regulator rectifier from reverse battery condition, then the regulator rectifier is protected from reverse voltage damage, but the diode drops approximately 0.6V during normal operation which could be a significant portion of supply voltage and reduces battery life due to power consumption
Solution Approach 1:
The patent uses MOSFETs that can dynamically switch between ON and OFF states based on voltage polarity detection. During normal operation, the MOSFET remains ON with minimal voltage drop, but when reverse voltage is detected, it quickly switches OFF to block reverse current. This dynamic switching capability resolves the contradiction by providing protection only when needed, eliminating continuous power consumption while maintaining reliability.
Solution Approach 2:
The invention changes the electrical parameters of the protection device by using MOSFETs with adjustable resistance characteristics. The MOSFET's on-resistance can be made very low (milliohms) compared to a diode's fixed forward voltage drop, and its off-state resistance becomes extremely high when reverse voltage is detected. This parameter change allows the system to achieve both low power consumption during normal operation and effective reverse voltage protection.
2Reliability
If a fuse is used in series with the battery to protect the regulator rectifier device, then the circuit is disconnected in reverse voltage condition, but the fuse may blow prematurely due to normal operating conditions and requires replacement rather than resetting
Solution Approach 1:
The MOSFET-based protection circuit dynamically responds to reverse voltage conditions by switching OFF only when needed. Unlike a fuse that permanently opens the circuit, the MOSFET can be turned back ON when normal conditions are restored, providing a resettable protection mechanism that maintains ease of repair while ensuring reliability.
Solution Approach 2:
The invention incorporates voltage detection circuits that continuously monitor the battery voltage polarity and provide feedback to the MOSFET gate control. When reverse voltage is detected, the feedback signal triggers the MOSFET to switch OFF. When normal voltage polarity is restored, the feedback signal allows the MOSFET to switch back ON. This feedback mechanism ensures the protection is both reliable and automatically resettable, eliminating the need for manual intervention.
3Reliability
If P-channel MOSFETs are used for protection from reverse current flow, then the regulator rectifier is protected, but P-channel MOSFETs are not commonly available in high current rating and are expensive as compared to N-channel MOSFETs
Solution Approach 1:
Instead of using the conventional approach of P-channel MOSFETs for high-side switching, the invention inverts the approach by using N-channel MOSFETs for low-side switching. The N-channel MOSFETs are connected between the battery negative terminal and ground, leveraging the abundance and low cost of N-channel devices while achieving the same reverse current protection function through complementary circuit configuration.
Solution Approach 2:
The invention uses multiple N-channel MOSFETs in a configuration that replicates the protection function of a single P-channel MOSFET. By using two or more N-channel MOSFETs connected in parallel or series-parallel arrangements, the circuit achieves equivalent or superior current handling capability at lower cost and higher availability, effectively copying the protective function with more accessible components.
4Reliability
If two N-channel power MOSFETs connected back to back are used for protection, then the regulator rectifier is protected from reverse current flow, but a MOSFET driver along with a charge pump is required which makes the solution expensive
Solution Approach 1:
The invention extracts and eliminates the complex charge pump and dedicated MOSFET driver components from the circuit. By using simple resistive gate control networks and leveraging the intrinsic body diode characteristics of the MOSFETs, the design achieves reverse current protection without requiring external driver ICs or charge pump circuits, significantly reducing device complexity while maintaining reliability.
Solution Approach 2:
The MOSFETs in the invention are designed to self-regulate their gate voltages through resistive dividers and body diode feedback mechanisms. The circuit automatically establishes the appropriate gate-source voltage to turn the MOSFETs ON or OFF based on the battery polarity, eliminating the need for external active driver components. This self-service approach reduces complexity while ensuring reliable protection.
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 protects the regulator rectifier device from reverse voltage and short circuit conditions without power consumption or premature failure, ensuring reliable operation and extended battery life.
Implementation Method 1
a switching unit (146) defined to switch between an ON state and an OFF state, wherein the switching unit completes a circuit between the positive terminal and the negative terminal of the regulator rectifier device in ON state and breaks the circuit in OFF state
Implementation Method 2
configured to detect at least one of a short circuit condition or a reverse battery condition based on an input received by the control unit in the circuit
Implementation Method 3
configured to detect at least one of a short circuit condition or a reverse battery condition based on an input received by the control unit in the circuit
Implementation Method 4
the control unit switches the switching unit from the ON state to the OFF state when the reverse battery condition is detected by the control unit, thereby breaking the circuit to protect the regulator rectifier device
Data Source
AI summary
The problem to be solved is to provide a system and a method to protect the regulator rectifiers from the reverse voltage condition and the short circuit condition, and the problem is solved in the present invention by a system and a method that use a protection device including a control unit that receives an input from the circuit based on the reverse voltage condition and the short circuit condition, and based on the existence of at least one of the condition or a combination thereof, the control unit switches a switching unit from an ON state to an OFF state, thereby breaking the circuit between the regulator rectifier device and the load section, thus protecting the regulator rectifier device.