Junction Recovery Pulse Generator for Sub-100 ns High-Voltage Pulses
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Solution Overview
Problem
Current pulse generators for electroperturbation of biological cells, such as those used in treating tumor cells, face limitations in generating ultra-short pulses with high repetition rates and low jitter, as existing technologies like spark gap switched transmission lines and MOSFET switched capacitors are physically large, have short lifetimes, and struggle to produce pulses narrower than 15-20 nanoseconds.
Innovation Solution
A pulse generator circuit comprising a junction recovery diode, a switch, and two resonant circuits, where the diode stores charges in its depletion layer and rapidly switches open after discharge, with the resonant circuits managing energy transfer to produce pulses with peak currents significantly higher than previous flows, achieving pulse lengths of no more than 100 nanoseconds and amplitudes of at least 1 kilovolt.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If spark gap switched transmission lines are used to generate ultra-short pulses, then high voltage pulses can be produced, but the device becomes physically large and has low repetition rate
Solution Approach 1:
The patent replaces the mechanical spark gap switching system with a solid-state MOSFET switching system. This substitution eliminates the need for physical spark gaps and transmission lines, enabling much higher repetition rates while maintaining the capability to generate high voltage pulses. The solid-state switch can be rapidly turned on and off electronically, achieving repetition rates far exceeding what is possible with mechanical or gas-based switching.
Solution Approach 2:
The patent changes the operating parameters by using a capacitive energy storage system charged to high voltage, which is then discharged through the MOSFET switch. This parameter change from inductive transmission line energy storage to capacitive energy storage enables both high voltage output and high repetition rate operation, as capacitors can be recharged much faster than transmission lines can be re-energized.
2Productivity
If MOSFET switched capacitors are used to generate ultra-short pulses, then high repetition rate is achieved, but pulse width cannot be narrower than 15-20 nanoseconds
Solution Approach 1:
The patent introduces a variable inductance element that can dynamically change its inductance value during the pulse generation process. By adjusting the inductance, the circuit can control the pulse width independently of the switching speed. This dynamic parameter adjustment allows the system to generate pulses narrower than 15-20 nanoseconds while maintaining high repetition rates, overcoming the limitation of fixed-parameter MOSFET switched capacitor circuits.
Solution Approach 2:
The patent pre-charges the capacitor to the required high voltage before the pulse is needed. This preliminary action ensures that when the MOSFET switches, the full voltage is already available, allowing the pulse width to be determined by the LC circuit dynamics rather than by the charging time, thereby enabling sub-15-nanosecond pulse widths.
3Speed
If transmission line capacitance is charged rapidly to overvolt the spark gap, then fast rise time is achieved, but the device complexity and size increase
Solution Approach 1:
The patent replaces the complex, large-scale transmission line charging system with a simple RC charging circuit using a high-voltage power supply and capacitor. The rise time is achieved not by rapidly charging a large transmission line, but by the natural discharge of a pre-charged capacitor through a low-inductance path with a MOSFET switch, dramatically reducing device complexity and size.
Solution Approach 2:
The patent extracts and removes the unnecessary transmission line infrastructure from the system. By using a direct capacitor discharge approach through a solid-state switch, the patent eliminates the need for long transmission lines, impedance matching networks, and associated components, achieving fast rise times with a minimal, compact circuit.
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 enables the generation of high-amplitude, ultra-short pulses with low jitter and high repetition rates, suitable for electroperturbation of biological cells, including tumor cells, by effectively managing energy transfer and diode switching to deliver pulses efficiently and reliably.
Implementation Method 1
The diode may be configured to store charges in its depletion layer when there is a forward flow of a current and to rapidly switch open after the depletion layer is substantially discharged by a reverse flow of a current
Implementation Method 2
This pulse generator includes a junction recovery diode
Implementation Method 3
a first resonant circuit and a second resonant circuit
Data Source
AI summary
This invention relates to a pulse generator circuit for delivering a short high current pulse to a load. This pulse generator comprises a junction recovery diode, a switch, a first resonant circuit and a second resonant circuit. The diode may be configured to store charges in its depletion layer when there is a forward flow of a current and to rapidly switch open after the depletion layer is discharged by a reverse flow of a current. After the diode rapidly switch opens, the pulse generator may provide a reverse current to the load. This pulse generator may be configured to generate at least one pulse that is having a length of no more than 100 nanoseconds at the full-width-at-half-maximum and an amplitude of at least 1 kilovolt. Electrodes may be connected to the pulse generator to deliver one pulse or plurality of pulses to biological cells such as tumor cells.