Drive Circuit for Power Transistor Negative Voltage Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing E-fuse switches struggle to effectively protect loads against large negative voltage transients and reverse polarity events, which can cause reverse current and damage during power surges and lightning strikes.
Innovation Solution
A circuit design incorporating NMOS transistors and a drive circuit that rapidly detects negative input voltages, turning off a solid-state switch to prevent damage by limiting current and avoiding shoot-through current paths, even during high slew rates and without active input voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing E-fuse switches are used to protect against over-voltage and over-current events, then basic protection is provided, but they fail to effectively protect against large negative voltage transients and reverse polarity events
Solution Approach 1:
The drive circuit proactively detects negative voltage transients and reverse polarity conditions before they can cause damage. By using a comparator to continuously monitor the input voltage and activate protective transistors in advance, the system prevents reverse current flow and shoot-through conditions from occurring, rather than merely reacting after damage begins
Solution Approach 2:
The patent introduces an intermediary drive circuit between the power source and load that acts as a protective barrier. This drive circuit includes control transistors that can rapidly block reverse current flow, preventing harmful effects from reaching the load during negative voltage transients and reverse polarity events
2Speed
If transistors are turned off rapidly during negative voltage transients, then protection against high-rate voltage changes is improved, but complex drive circuitry is required
Solution Approach 1:
The patent replaces complex active control mechanisms with a simpler voltage-threshold-based comparator system. The comparator automatically triggers protective transistors when voltage conditions are met, eliminating the need for complex microcontroller-based detection and control logic while achieving rapid response to negative voltage transients
Solution Approach 2:
The drive circuit is designed to automatically detect and respond to fault conditions without external intervention. The comparator continuously monitors voltage conditions and self-activates the protective transistors when negative voltage or reverse polarity is detected, providing autonomous protection that reduces overall system complexity
3Reliability
If protection is provided during power surges and lightning strikes, then load safety is improved, but the circuit must operate without active input voltage during transients
Solution Approach 1:
The protective transistors and comparator are designed to remain in a ready state with minimal power consumption, pre-configured to immediately activate when negative voltage conditions occur. The circuit maintains protection capability during power surges and lightning strikes without requiring active supply voltage, as the protective mechanism is already in place and can respond instantaneously
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 loads by rapidly turning off transistors during negative voltage transients, preventing damage from high-rate voltage changes and ensuring continuous current path interruption, even in the absence of positive supply voltage.
Implementation Method 1
A comparator has first and second comparator inputs. The first comparator input is coupled to the output voltage node. The second comparator input is coupled to a bias voltage node configured to be biased at a voltage greater than an input voltage on the input voltage node. The comparator has an output configured to control a power state of the third transistor.
Implementation Method 2
A first transistor having a first control input and first and second current terminals. The first current terminal is coupled to an input voltage node. A second transistor has a second control input and third and fourth current terminals. The third current terminal is coupled to the second current terminal at a first node.
Data Source
AI summary
A system includes a first transistor having a first control input and first and second current terminals. The first current terminal couples to an input voltage node. A second transistor has a second control input and third and fourth current terminals. The third current terminal couples to the second current terminal at a first node. The fourth current terminal couples to an output voltage node. A drive circuit is configured to charge a capacitor maintain the first transistor in an off state responsive to a negative voltage on the input voltage node, and, responsive to a negative voltage on the input voltage node, to cause the charge from the capacitor to be used to turn off the first transistor. The system provides a voltage to a load coupled to the output voltage node.