Electrical transmission or interconnection systems – Switching systems – Condition responsive
Reexamination Certificate
2000-04-13
2002-08-27
Nguyen, Matthew (Department: 2836)
Electrical transmission or interconnection systems
Switching systems
Condition responsive
Reexamination Certificate
active
06441513
ABSTRACT:
RELATED APPLICATION
The following application is related to the present application: U.S. patent application Ser. No. 09/549,422 entitled “METHOD AND APPARATUS FOR ASYMMETRICALLY INDUCING VOLTAGES IN TRANSFORMER SECONDARY WINDINGS WHILE AVOIDING SUTARATION OF THE TRANSFORMER CORE,” naming Daniel F. Mulhauser, as the inventor, assigned to the assignee of the present invention, and filed concurrently herewith.
FIELD OF THE INVENTION
The present invention relates generally to switching circuits and, more particularly, to circuits that may be used for switching transistors at high frequencies and high voltages.
BACKGROUND
Switching circuits have been designed for applications in which switching devices must stand off and supply high voltages, and in which rapid switching (e.g, in the range of microseconds or faster) is required. One of these applications, connecting a traveling wave tube to its high voltage cathode supply, is described in U.S. Pat. No. 4,754,176 to Jones, et al. As noted in Jones, switching transistors are preferred in these applications, as compared, for example, to mechanical relays, due to the requirements for rapid switching. In addition, it may be desirable to employ a number of switching transistors in series in order to overcome limitations on the amount of voltage that a single device can handle. Connecting the switching transistors in series typically imposes the additional requirements that the driving circuits of the transistors be electrically isolated from each other, and that the switching be synchronous. Jones accomplishes the isolation and synchronous switching of series-connected transistors by employing one transformer for turning the switches on (labeled
200
in
FIG. 2
, driven by transistor Q
1
), and another transformer for turning the switches off (unlabeled, driven by transistor Q
2
).
Another application in which high voltages must be rapidly switched is in the use of external heart defibrillators. These devices supply controlled electrical pulses that are applied to the chests of patients in cardiac arrest. Defibrillators may also be implanted, in which case the electrical pulses are applied directly to the heart and the voltages to be switched naturally are much smaller. Older external defibrillators typically used mechanical relays as the switching devices. Defibrillators that are more modern typically use solid state switching circuits having power transistors to switch the high voltages. These power transistors may be metal-oxide semiconducting, field-effect transistors (MOSFET's), insulated gate bipolar transistors (IGBT's), or similar known devices.
SUMMARY OF THE INVENTION
In one aspect of the present invention, a switching circuit is disclosed that includes one or more switching devices, one or more detector and driver circuits, and at least one control and driving signal provider (hereafter, simply “signal provider”). The signal provider provides one or more control and driving signals at one or more output ports. The signal provider may also have one or more input ports for accepting one or more primary control signals. The control and driving signals are based at least in part on the primary control signals. In some implementations, a first output port of a first signal provider is electrically isolated from a second output port of the first signal provider. Also, a first in put port of a first signal provider may be electrically isolated from a first output port of the first signal provider.
The detector and driver circuits each have an input coupled to an output port of the signal provider. The detector and driver circuits each also have an output coupled to at least one of the switching devices. Each detector and driver circuit detects when a control and driving signal at its input is in an on state and, responsive thereto, drives at least one of the switching devices on by applying to it the control and driving signal. In addition, each detector and driver circuit detects when the control and driving signal is in an off state and, responsive thereto, drives at least one of the switching devices off by applying to it the control and driving signal.
Thus, for each detector and driver circuit of this aspect of the invention, the same signal (the control and driving signal) performs both the function of controlling the turning on and off of the switching devices and the function of driving the switching devices on and off in response to the controlling function. In contrast, conventional circuits typically employ separate signals for controlling and driving, and/or they employ one signal for controlling and driving the switching device on and another signal for controlling and driving the switching device off. For example, in the circuit described in Jones (referred to above), the pulses generated by the three gates U
3
associated with Q
1
on the primary sides of the two single-turn transformers provide the turning on (through Q
1
) control function. The driving signal magnetically induced on the secondary side of transformer
200
turns the switching transistors Q
3
-Q
10
on. The pulses generated by the three gates U
3
associated with Q
2
on the primary sides of the two single-turn transformers provide the turning off (through Q
2
) control function. The driving signal magnetically induced on the secondary side of, the unlabelled transformer turns the switching transistors Q
3
-Q
10
off. Thus, separate circuits and signals are used to drive the switching transistors on and off.
In some aspects of the present invention, the signal provider may be a transformer. In these aspects, the input ports of the signal provider are primary windings on the primary side of the transformer, and the output ports of the signal provider are secondary windings on the secondary side of the transformer.
In some implementations, the signal provider consists of a single signal provider. The word “single” in this context means only one signal provider, as contrasted with two or more. In particular, in an implementation in which the signal provider is a transformer, a single transformer may be used to turn the switching devices on and off, rather than the two transformers used, for example, by Jones. In this single-transformer implementation of the present invention, advantages are therefore gained in terms of expense, weight, and volume as compared to the two-transformer circuit described in Jones.
Conventional switching circuits are known that employ single transformers. In particular,
FIGS. 1 and 2
of U.S. Pat. No. 5,939,927 to Myers show switching circuits having only one transformer. However, in these conventional circuits, the same signal is not used both to control the off state and to drive the switching device off. Rather, as described in Myers, the switching device is turned off when current in the secondary winding of the transformer is reversed, thereby turning on a depletion mode transistor that causes the gate of the switching transistor to discharge and thus cause the switching transistor to turn off. The switching transistor therefore is not driven off (either by the control signal or, another signal), but, rather, is enabled to discharge into an off state. Also, the circuit in Myers requires that an “on” state be followed by an “off” state, and that the period of the “on” state be within particular time constraints as established by the design values. The range of possible “on” time is determined by the magnetizing inductance of the transformer, the level at which its core saturates, and the voltage applied to its primary. An “off” state must follow an “on” state in this conventional circuit because when the primary ceases to be driven the field collapses. This collapsing field drives the secondary in the reverse direction, thereby allowing the depletion mode transistor to turn on, thus turning off the switching device.
The conventional circuits described in Myers generally require a transformer having a large magnetizing inductance that acts to slow the rate of increase of primary current. The current may thus be
LandOfFree
Method and apparatus for rapid, synchronized, and isolated... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for rapid, synchronized, and isolated..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for rapid, synchronized, and isolated... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2960725