Reverse Voltage Protection Circuit for Power Switches
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Solution Overview
Problem
Power supply systems face damage from reverse voltage conditions, where the input voltage becomes negative, causing current to flow backward and potentially discharging batteries, due to the breakdown of internal parasitic diodes in power switches.
Innovation Solution
A power system with a reverse voltage control circuit that passively couples the input voltage to the control terminal or bulk connection of a power switch, using a pair of transistors oppositely connected in series, to deactivate the power switch and prevent reverse current flow, along with an output shutoff circuit that couples the output voltage to a neutral-voltage rail to prevent floating voltage potentials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional reverse voltage protection circuits are used, then the power switch is protected from reverse voltage damage, but the circuit occupies larger silicon area and has longer reaction time
Solution Approach 1:
The patent combines the reverse voltage detection function and power switch control function into a single integrated circuit structure. The reverse voltage control circuit is merged with the power switch device, eliminating the need for separate protection circuits and reducing overall silicon area while maintaining protection functionality.
Solution Approach 2:
The patent implements preliminary protection by proactively detecting reverse voltage conditions before they can cause damage to the power switch. The control circuit monitors the voltage condition and preemptively adjusts the power switch state to prevent harmful reverse current flow, rather than reacting after damage occurs.
2Reliability
If traditional reverse voltage protection circuits are used, then the power switch is protected from reverse voltage damage, but the reaction time is longer
Solution Approach 1:
The control circuit continuously monitors voltage conditions and maintains readiness to respond to reverse voltage events. By keeping the control logic integrated and ready-state, the system can react immediately when reverse voltage occurs, minimizing the time between fault occurrence and protective action.
Solution Approach 2:
The patent divides the protection function into discrete control stages: voltage detection, condition evaluation, and switch control. This segmented approach allows each function to be optimized independently, with the detection and control stages operating in rapid succession to minimize overall reaction time.
3Productivity
If the power switch remains active during reverse voltage condition, then the circuit operates normally, but current flows backward damaging the power switch and discharging the battery
Solution Approach 1:
The control circuit implements feedback by continuously monitoring the voltage condition at the input of the power switch and using this information to control the switch state. When reverse voltage is detected, the feedback loop automatically adjusts the switch to block reverse current, preventing damage while maintaining system functionality during normal operation.
Solution Approach 2:
The patent makes the power switch state dynamic rather than static, allowing it to transition between on and off states based on real-time voltage conditions. The switch operates in a normal on-state during proper operation for continuous power flow, and automatically transitions to an off-state when reverse voltage is detected to prevent damage.
Data Source
AI summary
One embodiment includes a power system. The system includes a power switch device that is activated to provide an output voltage to a load in response to an input voltage. The power switch device includes a control terminal and a bulk connection. The system also includes a reverse voltage control circuit configured to passively couple the input voltage to one of the control terminal and the bulk connection in response to a reverse voltage condition in which an amplitude of the input voltage becomes negative. The system further includes an output shutoff circuit configured to passively couple the output voltage to a neutral-voltage rail during the reverse voltage condition.