Induction-Adder Pulse Modulator for Fast High-Power Switching
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Solution Overview
Problem
Existing pulse modulators face limitations in generating high-power pulses with short rise times and high repetition rates while maintaining compact size and flexibility, particularly for applications requiring high voltage and current.
Innovation Solution
A pulse modulator design utilizing a plurality of stages with solid-state power switches, including MOSFETs, IGBTs, and BJTs, connected as an induction adder with magnetic cores and baluns for isolated gate drives, enabling fast switching and high power output in a compact form.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If solid state switches are arranged in stacked cells to provide combined output for higher power requirements, then power output is improved, but device volume increases
Solution Approach 1:
The modulator is divided into multiple stages, each stage containing multiple cells with solid state switches. The stages are connected as an induction adder with magnetic cores, allowing power to be segmented across multiple smaller units that combine their output inductively, achieving high power without proportional volume increase.
Solution Approach 2:
The patent uses magnetic induction coupling between stages to combine power outputs. By utilizing the magnetic field dimension and inductive addition, multiple cell outputs are combined without simply stacking them in physical space, reducing the volume penalty associated with high power output.
2Device complexity
If conventional gate drive arrangements are used, then device complexity is reduced, but switching time increases
Solution Approach 1:
A balun (balanced-to-unbalanced transformer) is introduced as an intermediary component between the gate drive circuit and the solid state switch gate. The balun provides isolated gate drive with differential signaling, which reduces the voltage across source inductance during switching transitions, thereby reducing switching time despite adding a component.
Solution Approach 2:
The gate drive arrangement changes the electrical parameters during switching by using differential signaling through the balun. This changes the voltage distribution across parasitic inductances, reducing the effective voltage that drives current into the gate during transitions, thereby reducing switching time.
3Productivity
If pulse modulator operates at high repetition rates, then productivity is improved, but heat dissipation increases
Solution Approach 1:
The modulator is designed to operate with periodic pulse trains at high repetition rates. By optimizing the switching devices and gate drive for periodic operation, the system efficiently handles the thermal load through the repetitive nature of the pulses, allowing high productivity with controlled heat dissipation.
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 achieves pulse rise times of less than 5 nanoseconds, pulse lengths of 15-20 nanoseconds, and peak powers of tens of megawatts with high repetition rates, offering flexibility and compactness suitable for diverse applications like high-frequency transmitters and induction heating.
Implementation Method 1
During the switch transition, a voltage is induced across the source inductance due to the rate of change of current through it. This voltage opposes the gate voltage and reduces the voltage driving the current into the gate.
Implementation Method 2
The induction adder enables high voltages and high currents to be obtained by inductively adding voltages from the plurality of cells. Each stage includes a magnetic induction core, a single turn primary winding and a single turn secondary winding and the secondary windings are connected in series.
Data Source
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AI summary
A pulse modulator comprises a solid state power switch (13) having a source, a drain, a gate and a separate gate drive connected to ground. One pulse modulator comprises a plurality of stages connected as an induction adder. Each stage includes a plurality of cells (6) and at least some of the cells each include a solid state power switch (3) having a source, a drain, a gate and a separate gate drive connected to ground to control the discharge of a capacitor (11). In one embodiment the solid state power switch is a power MOSFET.