News Column

Patent Issued for Systems, Methods, and Apparatus for Voltage Clamp Circuits

July 30, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- A patent by the inventors Wagoner, Robert Gregory (Roanoke, VA); Tian, Geng (Roanoke, VA), filed on May 8, 2012, was published online on July 15, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8780516 is assigned to General Electric Conpany (Schenectady, NY).

The following quote was obtained by the news editors from the background information supplied by the inventors: "Power semiconductor devices, such as, insulated gate bipolar transistors (IGBTs) are used in a variety of applications that require high frequency switching of electrical power. For instance, IGBTs may be used to generate pulse-width modulation (PWM) signals for industrial and traction applications. In such applications, the IGBTs are turned on and off at a high frequency. During operation, when inductive loads are switched off, the IGBTs become non-conducting, and a transition to a high voltage state is executed in a very short period of time.

"For instance, when a control signal is fed to the gate (G) of the IGBT, the IGBT may be turned on and the voltage between the collector (C) and the emitter (E) of the IGBT is approximately zero volts. During this period of time load current will flow between the collector (C) and the emitter (E) of the IGBT. When the control signal is switched off, the IGBT may become non-conducting between the collector C and the emitter E, and the voltage between the collector C and the emitter E of the IGBT rapidly increases at the initial period of the switch off period. As a result of the inductance in the wiring to the IGBT terminals, a voltage spike may occur, which can, in certain cases, result in damage to the IGBT and a power loss imbalance. To reduce the overvoltage of the IGBT during the turn off period, a voltage clamp circuit was developed.

"As shown in FIG. 2, a conventional voltage clamp circuit 110 may include at least one resistor R.sub.G and one or more zener diodes, ZD.sub.1, ZD.sub.2. The zener diodes, ZD.sub.1, ZD.sub.2, may be connected in series between the collector C and the gate G of the IGBT Q.sub.1, and the at least one resistor R.sub.G may be connected to the gate G of the IGBT Q.sub.1. During operation, when the voltage output between the collector C and the emitter E of the IGBT Q.sub.1 reaches the zener voltage, a current flows to the gate G and turns on the IGBT Q.sub.1 in order to limit the output voltage of the IGBT Q.sub.1 to the value of the zener voltage.

"While the prior art voltage clamp circuit 110 of FIG. 2 limits the output voltage of the IGBT, the zener protection is known to retard the time profile of the high voltage transition during the switching off period due to a time delay, due to parasitic inductances and capacitances in the wiring loop comprising the components in the conventional voltage clamp circuit. As shown in FIG. 3, when the load is switched off, at time 122, the voltage output V.sub.CE between the collector C and the emitter E of the IGBT increases rapidly and may overshoot above the zener voltage. Thereafter, the cut-in of limiting the output voltage V.sub.CE to the zener voltage is time delayed as represented at time point 120. This may result in a voltage overshoot of the IGBT at the start of the turn off cycle, which may cause damage to the IGBT."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "Some or all of the needs may be addressed by certain embodiments of the disclosure. Certain embodiments of the disclosure may include systems, methods, and apparatus for voltage clamp circuits. In one embodiment, a voltage clamp circuit may include a first circuit portion electrically coupled to the output of at least one power source. The first circuit portion comprises a power semiconductor device having a first, second and third node and one or more zener diodes electrically coupled to the first or the second node of the power semiconductor device. The voltage clamp circuit may further include a second circuit portion in electrical communication with the first circuit portion, where the second circuit portion comprises a resistor, a capacitor and a directional device, and where the second circuit portion connects to the one or more zener diodes to reduce peak voltage output between the second and the third node of the power semiconductor device.

"In another embodiment, a method may be provided. The method may include providing at least one power semiconductor device having a first node, a second node and a third node. The method may further include providing at least one directional electrical element between the first node and the second node of the at least one power semiconductor device. The method may also include providing a circuit segment comprising at least one resistor and a capacitor, where the circuit segment is associated with the at least one directional electrical element. Further, the method may include selectively providing power to the at least one power semiconductor device to reduce peak voltage output between the second node and the third node of the at least one power semiconductor device.

"In yet another embodiment, an alternative energy power system may be provided. The alternative energy power system may provide electrical power at an output voltage. The alternative energy power system may include a first circuit portion electrically connected to the output of at least one power source, where the first circuit portion comprises a power semiconductor device having a first, second and third node and one or more zener diodes. The alternative energy power system may further include a second circuit portion comprising a resistor, a capacitor and a directional device, where the second circuit portion is electrically connected to at least one of the zener diodes of the first circuit portion in order to reduce peak voltage output between the second and third nodes of the power semiconductor device.

"Other embodiments, features, and aspects of the disclosure are described in detail herein and are considered a part of the claims. Other embodiments, features, and aspects can be understood with reference to the following detailed description, accompanying drawings, and claims."

URL and more information on this patent, see: Wagoner, Robert Gregory; Tian, Geng. Systems, Methods, and Apparatus for Voltage Clamp Circuits. U.S. Patent Number 8780516, filed May 8, 2012, and published online on July 15, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8780516.PN.&OS=PN/8780516RS=PN/8780516

Keywords for this news article include: Electronics, General Electric Conpany, High Voltage, Semiconductor.

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Source: Electronics Newsweekly


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