Firing Circuit for Complete Electro-Explosive Device Capacitor Discharge
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Solution Overview
Problem
Miniature electro-explosive devices (EEDs) often fail to fully discharge their storage capacitors due to the gate-to-source voltage across the Field Effect Transistor (FET) dropping below the turn-on threshold as the capacitor voltage decreases, limiting their reliability, especially in applications with limited space.
Innovation Solution
A firing circuit comprising a storage capacitor, an inductor, and a diode connected in series with the FET gate, which creates inductive-capacitive ringing to increase the gate voltage beyond the initial capacitor voltage and a diode to block discharge, ensuring complete capacitor discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a FET switch is used to discharge the storage capacitor, then the circuit can be simple and fast, but the capacitor cannot be fully discharged because the gate-to-source voltage drops below the turn-on threshold
Solution Approach 1:
The patent applies periodic action by creating an oscillating circuit with the inductor and capacitor that generates ringing voltage. This periodic oscillation maintains the gate-to-source voltage above the turn-on threshold throughout the entire discharge process, ensuring complete capacitor discharge while using only simple passive components added to the basic FET switch circuit.
2Productivity
If the capacitor voltage drops during discharge, then the discharge progresses, but the gate-to-source voltage drops below the turn-on threshold turning off the switch
Solution Approach 1:
The patent implements feedback by using the capacitor's own discharge voltage to drive the LC oscillation that feeds back to the FET gate. The oscillating circuit continuously regenerates the gate drive signal based on the capacitor voltage itself, ensuring the FET remains conductive throughout the entire discharge process without external control signals.
3Reliability
If additional components are added to ensure complete discharge, then discharge reliability improves, but the volume available for the firing circuit is reduced
Solution Approach 1:
The patent merges the discharge function with the gate drive function by combining the capacitor discharge path with the LC oscillating circuit. The same capacitor that needs to be discharged also provides the energy for the oscillation that drives the FET gate, eliminating the need for separate gate drive components and minimizing additional volume.
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 allows for complete discharge of the storage capacitor, maintaining a constant gate-to-source voltage and keeping the FET in a low resistance state, thereby enhancing the reliability of EED activation.
Implementation Method 1
the inductor and the capacitor being configured for inductor capacitor ringing, the inductive capacitive ringing creating upon initiation of the circuit a gate voltage at the gate having a greater magnitude than the initial capacitor voltage of the storage capacitor
Implementation Method 2
the diode blocking the discharge of the gate voltage ensuring that the capacitor can be fully discharged
Data Source
AI summary
A firing circuit configured for complete discharge of a storage capacitor is provided with a storage capacitor, an inductor, a diode, a transistor switch having a gate to which the inductor and the diode are connected in series, the inductor and the capacitor being configured for inductor capacitor ringing, the inductive capacitive ringing creating upon initiation of the circuit a gate voltage at the gate above an initial capacitor voltage of the storage capacitor; and the diode blocking the discharge of the gate voltage ensuring that the capacitor can be fully discharged.