Dynamic Trigger Voltage Control for IGBT ESD Protection
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Solution Overview
Problem
Conventional ESD protection circuitry often triggers at voltages close to the breakdown voltage of high voltage devices, posing a risk of damage during assembly and operation, as the trigger voltage of IGBT ESD protection devices is not dynamically controllable to ensure protection below the failure voltage of the devices they are intended to protect.
Innovation Solution
The circuitry dynamically controls the trigger voltage of an IGBT ESD protection device between a low and high threshold by using a resistor and a switching element in parallel current paths, allowing the gate of the IGBT device to be selectively coupled to the supply rail, thereby lowering or raising the resistance and trigger voltage based on the device's operating state, ensuring protection below the normal operating voltage during unpowered conditions and above during powered conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the trigger voltage of the IGBT ESD protection device is set high to prevent false triggering during normal operation, then the device can operate reliably during powered conditions, but it fails to provide adequate protection during unpowered conditions when ESD events occur during assembly
Solution Approach 1:
The patent applies the dynamics principle by making the trigger voltage dynamic rather than static. A switching element (transistor) is introduced to change the resistance in the gate circuit based on the powered/unpowered state. When powered, the switch closes to provide a low-resistance path to ground, raising the trigger voltage. When unpowered, the switch opens, forcing current through a high-resistance path that lowers the trigger voltage, enabling ESD protection during assembly while preventing false triggering during operation.
Solution Approach 2:
The patent applies parameter changes by modifying the resistance value in the gate circuit depending on the operational state. Two different resistance values are used: a low resistance when powered (to raise trigger voltage) and a high resistance when unpowered (to lower trigger voltage). This is achieved through a switching element that selectively connects different resistance paths to the gate, thereby changing the trigger voltage parameter dynamically.
2Object-affected harmful factors
If the trigger voltage is set low to ensure protection during unpowered assembly conditions, then ESD events are safely shunted, but the device may trigger during normal powered operation causing unnecessary discharge
Solution Approach 1:
The switching element dynamically adjusts the gate resistance based on the powered state. During unpowered assembly, the switch is open, creating a high-resistance path that lowers the trigger voltage to ensure ESD protection. During powered operation, the switch closes, creating a low-resistance path to ground that raises the trigger voltage above the operating voltage, preventing unnecessary discharge while maintaining the ability to respond to actual ESD events.
Solution Approach 2:
The patent changes the resistance parameter in the gate circuit from high to low depending on the operational state. When powered, the resistance is reduced by closing the switch, which increases the trigger voltage to prevent false triggering. When unpowered, the resistance is increased by opening the switch, which decreases the trigger voltage to ensure ESD protection during assembly operations.
3Device complexity
If a fixed resistance is used in the gate circuit, then the circuit is simple, but the trigger voltage cannot be dynamically adjusted to match different operational states
Solution Approach 1:
The patent introduces a switching element (transistor) controlled by a power indicator signal to dynamically change the gate resistance. The switch is connected in parallel with a high-value resistor, allowing it to short the resistor when closed (powered state) and leave it connected when open (unpowered state). This simple dynamic configuration enables the circuit to adapt its trigger voltage to the operational state without adding significant complexity.
Solution Approach 2:
The switching element is controlled by a power indicator signal that automatically indicates whether the device is powered or unpowered. This self-service mechanism allows the circuit to automatically adjust its trigger voltage based on its own power state without external intervention, simplifying the control logic while maintaining adaptability.
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
This approach effectively reduces the risk of damage from ESD events by ensuring the IGBT ESD protection device triggers before the protected circuitry, preventing unnecessary discharge during normal operation, thus safeguarding high voltage circuitry from ESD events.
Implementation Method 1
lowering or raising the resistance and trigger voltage based on the device's operating state
Implementation Method 2
The occurrence of a positive ESD event 190 on signal pad 102 causes a corresponding rise in voltage of the drift region
Implementation Method 3
the drain-body diode of M1 will avalanche breakdown, thereby generating electron-hole pairs in the process
Data Source
AI summary
Circuit configurations and related methods are provided that may be implemented using insulated-gate bipolar transistor (IGBT) device circuitry to protect at risk circuitry (e.g., such as high voltage output buffer circuitry or any other circuitry subject to undesirable ESD events) from damage due to ESD events that may occur during system assembly. The magnitude of the trigger voltage VT1 threshold for an IGBT ESD protection device may be dynamically controlled between at least two different values so that trigger voltage VT1 threshold for an IGBT ESD protection device may be selectively reduced when needed to better enable ESD operation.