Junction Recovery Diode Pulse Circuit for Compact Nanosecond Output
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Solution Overview
Problem
Current pulse generators for electroperturbation of biological cells, such as those used in treating tumor cells, face challenges in generating ultra-short, high-field strength electric pulses with low repetition rates, high jitter, and limited scalability, as well as difficulties in achieving precise control over pulse length and amplitude.
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, allowing energy transfer between the circuits to produce pulses with peak currents significantly higher than previous flows, enabling pulses of up to 100 nanoseconds in length and 1 kilovolt in amplitude, suitable for electroperturbation of biological cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If spark gap switched transmission lines are used to generate ultra-short pulses, then pulse length can be reduced to nanosecond range, but device size becomes physically large and repetition rate becomes low
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 large transmission lines and spark gaps, enabling compact nanosecond pulse generation with high repetition rates. The MOSFETs can switch at nanosecond speeds while occupying minimal space, directly resolving the contradiction between short pulse duration and small device size.
2Duration of action of moving object
If spark gap switched transmission lines are used, then ultra-short pulses can be generated, but pulse timing becomes erratic with large jitter and device lifetime is short
Solution Approach 1:
The patent replaces the unreliable mechanical spark gap system with solid-state MOSFETs that provide precise, repeatable switching. The MOSFETs offer controlled turn-on and turn-off characteristics, eliminating the erratic timing and large jitter inherent in spark gap systems. This solid-state approach significantly improves pulse timing stability and extends device lifetime.
3Volume of moving object
If MOSFET switched capacitors are used to generate ultra-short pulses, then device size is reduced, but pulse length cannot be narrower than 15-20 nanoseconds
Solution Approach 1:
The patent employs dynamic control of MOSFET switching timing and duration to achieve pulse widths narrower than 15-20 nanoseconds. By precisely controlling the gate drive signals and utilizing the inherent fast switching characteristics of modern MOSFETs, the system can generate sub-15 nanosecond pulses. The dynamic adjustment of switching parameters enables pulse durations that were previously unachievable with MOSFET-based systems.
4Stress or pressure
If diode opening switches are used in nanosecond pulse generators, then high voltage pulses can be generated, but circuit damage occurs due to high peak currents
Solution Approach 1:
The patent introduces an inductor as an intermediary energy storage element between the power source and the diode opening switch. The inductor limits the rate of current rise (di/dt) and absorbs excess energy, preventing damaging peak currents from reaching the diode and other circuit components. This intermediary element enables high voltage pulse generation while protecting the circuit from current-induced damage.
Solution Approach 2:
The patent implements protective circuitry including clamping diodes and voltage limiting networks that act as beforehand cushioning against potential damage. These protective elements are pre-positioned in the circuit to clamp voltage spikes and limit current peaks before they can cause damage to sensitive components, thereby extending circuit durability while maintaining high voltage pulse capability.
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 minimal jitter and scalability, effectively targeting biological cells like basal cell carcinoma and melanoma, with the ability to deliver repetitive pulses while minimizing damage to the circuit.
Implementation Method 1
The diode is 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
A pulse generator circuit for delivering a short high current pulse to a load may include a junction recovery diode
Implementation Method 3
A pulse generator circuit comprising a junction recovery diode, a switch, and two resonant circuits
Implementation Method 4
allowing energy transfer between the circuits to produce pulses with peak currents significantly higher than previous flows
Implementation Method 5
The switch is configured to allow storage of energy from a source when it is opened and to allow the forward current flow after it is closed
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.