Electric power conversion systems – Current conversion – Including automatic or integral protection means
Reexamination Certificate
2000-08-02
2001-06-12
Nguyen, Matthew (Department: 2838)
Electric power conversion systems
Current conversion
Including automatic or integral protection means
C323S282000
Reexamination Certificate
active
06246598
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to high-power, high-voltage modulators.
BACKGROUND
A broad range of applications require high-voltage, high-power, variable-voltage sources with pulse-switching capabilities. Such applications include radar transmitters, X-ray machines, and semiconductor wafer manufacturing equipment. These machines and equipment employ such high-power amplifiers as cross-field amplifiers, traveling-wave tubes, magnetrons, and klystron amplifiers (collectively referred to as vacuum-electron devices). A number of high-power modulators are adapted to deliver pulsed power to these types of high-power amplifiers.
Conventional high-power modulators can be implemented using high-power vacuum tubes, but the technology is moving toward solid-state high-power switches, which are generally smaller and more robust. Insulated-gate bipolar transistors (IGBTs) are a common solid-state switch used in high-voltage applications. For a more detailed discussion of one type of conventional high-power modulator that employs IGBTs, see U.S. Pat. Nos. 5,444,610 and 5,646,833, both to Gaudreau et al., issued Aug. 22, 1995, and Jul. 8, 1997, respectively. Both of these documents are incorporated herein by reference.
IGBT-based high-power modulators provide excellent high-power, high-speed switching performance. There is always room for improvement, however, as competitive technology markets are ever watchful for cost-competitive systems that offer improved efficiency, reliability, speed performance, or a combination of these.
SUMMARY
The present invention is directed to an improved high-power modulation system. The system includes novel drive circuitry connected between a signal source and a conventional high-power switch. The drive circuitry receives input signals from the signal source via a series of transformers. The drive circuitry then amplifies the input signals and provides the resulting amplified signals to the high-power switch. A storage capacitor within the drive circuitry stores energy derived from the input signals, and the stored energy is used to power the drive circuitry.
Using energy derived from the input signal to power the driver circuitry eliminates the need to connect the driver circuitry to a separate power supply. This simplification allows the driver circuitry to be manufactured using fewer components, advantageously reducing size, cost, and power consumption. Also advantageous, reducing the number of components increases the mean time between failures.
In one embodiment, the high-power switch includes a series of power-switching devices that together switch current. The drive circuitry includes a number of drivers, one for each power-switching device. Each driver, in turn, includes a pair of series-connected drive transistors that alternately turn on and off the corresponding power-switching device via a pair of driver output lines. One of the driver output lines connects to a control terminal of the power-switching device; the other driver output line connects to a current-handling terminal of the power-switching device. In an embodiment in which the power-switching device is an IGBT, the driver output lines connect to the gate and emitter of the IGBT.
In one embodiment, the driver takes advantage of inductive ringing present on the output lines to more rapidly turn off the power-switching device. A diode connected in series between two drive transistors rectifies the ringing signals, pulling the control signal to the control terminal of the corresponding power-switching device negative relative to the respective current-handling terminal. Pulling the control signal to the power-switching device negative advantageously shuts the device off quickly, improving speed performance.
This summary does not limit the invention, which is instead defined by the appended claims.
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Goins Lawrence W.
Tarter Ralph E.
Behiel Arthur J.
Nguyen Matthew
Polarity, Inc.
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