U.S. patent application number 13/973475 was filed with the patent office on 2015-02-26 for system and method of providing isolated power to gate driving circuits in solid state fault current limiters.
This patent application is currently assigned to Varian Semiconductor Equipment Associates, Inc.. The applicant listed for this patent is Varian Semiconductor Equipment Associates, Inc.. Invention is credited to Piotr R. Lubicki, Kasegn Tekletsadik.
Application Number | 20150055261 13/973475 |
Document ID | / |
Family ID | 52480173 |
Filed Date | 2015-02-26 |
United States Patent
Application |
20150055261 |
Kind Code |
A1 |
Lubicki; Piotr R. ; et
al. |
February 26, 2015 |
SYSTEM AND METHOD OF PROVIDING ISOLATED POWER TO GATE DRIVING
CIRCUITS IN SOLID STATE FAULT CURRENT LIMITERS
Abstract
A system and method for providing isolated power to the gate
driving circuits used in solid state switching devices is
disclosed. Rather than using expensive isolated AC/DC power
supplies, an isolation transformer is used to provide isolated AC
voltage. In one embodiment, the primary winding of the isolation
transformer is disposed across an independent AC source. In another
embodiment, the primary winding of the isolation transformer is
disposed across two phases of the AC power line. Isolated AC
voltage is then generated across the secondary winding of the
isolation transformer. This isolated AC voltage is then used by a
non-isolated DC power supply, which generates the power for the
gate driving circuit.
Inventors: |
Lubicki; Piotr R.; (Peabody,
MA) ; Tekletsadik; Kasegn; (Middleton, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Varian Semiconductor Equipment Associates, Inc. |
Gloucester |
MA |
US |
|
|
Assignee: |
Varian Semiconductor Equipment
Associates, Inc.
Gloucester
MA
|
Family ID: |
52480173 |
Appl. No.: |
13/973475 |
Filed: |
August 22, 2013 |
Current U.S.
Class: |
361/91.1 ;
361/93.9 |
Current CPC
Class: |
H02H 9/04 20130101; H02H
9/025 20130101; H02H 1/06 20130101 |
Class at
Publication: |
361/91.1 ;
361/93.9 |
International
Class: |
H02H 9/02 20060101
H02H009/02; H02H 9/04 20060101 H02H009/04 |
Claims
1. A solid state fault current limiting device for use with an AC
power line, comprising: a solid state switching device, disposed in
series in said AC power line, said solid state switching device
having an input, an output and a gate, where a voltage applied to
said gate determines whether current flows between said input and
said output; a gate driving circuit in communication with said
gate, to apply a gate voltage to said gate, said voltage referenced
to either a voltage at said input or at said output; a current
monitor in communication with said AC power line and said gate
driving circuit, wherein said gate voltage is determined based on
an output from said current monitor; an isolation transformer,
having a primary winding and a secondary winding; and a
non-isolated AC-to-DC power supply, powered by said secondary
winding and referenced to said voltage at said input or at said
output, to supply DC power to said gate driving circuit.
2. The solid state fault current limiting device of claim 1,
wherein said primary winding is disposed between two phases of said
AC power line.
3. The solid state fault current limiting device of claim 1,
further comprising an independent AC source, where said primary
winding is disposed across said independent AC source.
4. The solid state fault current limiting device of claim 1,
further comprising an overvoltage protection circuit disposed
between said secondary winding and said non-isolated power
supply.
5. The solid state fault current limiting device of claim 1,
wherein said primary winding and said secondary winding are
physically separated so as to provide a voltage isolation rating
equal to at least a voltage of said AC power line.
6. A method of limiting fault current in an AC power line,
comprising: monitoring current through said AC power line; and
applying a voltage to a gate of a solid state switching device to
allow or inhibit the flow of current through said solid state
switching device, wherein said voltage is generated by: using an
isolation transformer to create an isolated AC voltage; using a
non-isolated AC-to-DC power supply referenced to said AC power line
to convert said isolated AC voltage to an isolated DC voltage; and
using said isolated DC voltage to power a gate driving circuit in
communication with said gate of said solid state switching
device.
7. A system for limiting fault current in an AC power line
comprising: an isolation transformer, having a primary winding and
a first secondary winding and a second secondary winding; an
independent AC source, wherein said primary winding is disposed
across said independent AC source; a first solid state fault
current limiting device, comprising: a first solid state switching
device, disposed in series in said AC power line, said first solid
state switching device having a first input, a first output and a
first gate, where a first gate voltage applied to said first gate
determines whether current flows between said first input and said
first output; a first gate driving circuit in communication with
said first gate, to apply said first gate voltage to said first
gate, said first gate voltage referenced to either a voltage at
said first input or at said first output; a first current monitor
in communication with said AC power line and said first gate
driving circuit, wherein said first gate voltage is determined
based on an output from said first current monitor; and a first
non-isolated AC-to-DC power supply, powered by said first secondary
winding and referenced to said voltage at said first input or at
said first output, to supply DC power to said first gate driving
circuit; and a second solid state fault current limiting device,
comprising: a second solid state switching device, disposed in
series in said AC power line, said second solid state switching
device having a second input in communication with said first
output, a second output and a second gate, where a second gate
voltage applied to said second gate determines whether current
flows between said second input and said second output; a second
gate driving circuit in communication with said second gate, to
apply said second gate voltage to said second gate, said second
gate voltage referenced to either a voltage at said second input or
at said second output; a second current monitor in communication
with said AC power line and said second gate driving circuit,
wherein said second gate voltage is determined based on an output
from said second current monitor; and a second non-isolated
AC-to-DC power supply, powered by said second secondary winding and
referenced to said voltage at said second input or at said second
output, to supply DC power to said second gate driving circuit.
8. The system of claim 7, further comprising a first overvoltage
protection circuit disposed between said first secondary winding
and said first non-isolated power supply and a second overvoltage
protection circuit disposed between said second secondary winding
and said second non-isolated power supply.
9. The system of claim 7, wherein said primary winding and said
first secondary winding are physically separated so as to provide a
voltage isolation rating equal to at least a voltage of said AC
power line.
10. The system of claim 7, wherein said first secondary winding and
said second secondary winding are physically separated so as to
provide a voltage isolation rating equal to at least a voltage of
said AC power line.
Description
[0001] Embodiments of the present invention relate to methods and
apparatus for providing isolated power to gate driving circuits of
semiconductor switches in solid state fault current limiters,
particularly when the semiconductor switches are disposed in
series.
BACKGROUND
[0002] Power line faults can be detected and remedied through the
use of solid state fault current limiters (SSFCL). These SSFCL
devices utilize solid state switching devices, such as IGBT, SCR,
IGCT or MOSFET transistors, to block or significantly increase the
impedance of the current path between the power source and the
load. However, these power lines typically carry voltages ranging
from 10 kV to over 230 kV. Since the typical switching device is
only rated to roughly 6 kV, often it is necessary to place a
plurality of these SSFCL devices in series. The total voltage of
the power line, also referred to as the power line voltage, is
divided across the total number of SSFCL devices in series, thereby
allowing each to operate within its rated range. When a fault is
detected, such as a surge in current through the power line, each
of the SSFCL devices disables its respective solid state switching
device, thereby increasing the resistance seen by the power source
and lowering the current.
[0003] FIG. 1 shows a SSFCL device 100 commonly used. The SSFCL
device 100 comprises a solid state switching device 110, which may
be any of the transistors described above. These solid state
switching devices 110 typically have at least three terminals, a
source or input side 111, a drain or output side 112, and a gate
113. The assertion of the gate 113 allows the passage of current
from the source 111 to the drain 112, while the deassertion of the
gate 113 disables the passage of current through the solid state
switching device 110.
[0004] This solid state switching device 110 may be in parallel
with one or more of the following components: a snubber 120, a
reactor 130 and a transient suppressor 140. The snubber 120 is
typically a resistor in series with a capacitor used to dissipate
the energy of the transient and to reduce the overvoltage by
filtering the transient frequency (i.e. slowing the "ringing"
frequency). The transient suppressor 140 is used to clamp the
overvoltage transient below the level of the ratings of the snubber
120 and solid state switching device 110. The snubber 120, the
reactor 130 and the transient suppressor 140 may be referred to as
parallel components 145, since these components 145, in some
embodiments, provide a parallel path for current for travel when
the solid state switching devices 110 are in the disabled or off
state. These parallel components 145 are used to provide an
alternative high impedance current path from the power source to
the load when the solid state switching device 110 is in the off
state and protect the solid state switching device 110 from
transient overvoltage during turn on and turn off.
[0005] The gate 113 of solid state switching device 110 is in
communication with a gate driving circuit 150. This gate driving
circuit 150 monitors the current being supplied by the power line
101 using a current sensor 160. The gate driving circuit 150 is
used to enable or block the passage of current through the solid
state switching device 110, based on information from the current
sensor 160.
[0006] The gate driving circuit 150 may be referenced to the
voltage seen by the solid state device 110. In other words, its
output voltage is related to the voltages presented on the source
111 or drain 112 of the solid state switching device 110.
Traditionally, this is achieved by using an isolated power supply
170. This DC power supply 170 may be a relatively low voltage, low
current power supply. For example, the gate driving circuit 150
typically utilizes low voltage, such as up to 48V, and dissipates
only a few watts.
[0007] However, the isolated power supply 170 of each SSFCL 100
must be electrically isolated from every other isolated power
supply 170. In some embodiments, the magnitude of the isolation
voltage must be at least the total line voltage divided by the
number of SSFCL devices 110. In other embodiments, the magnitude of
the isolation voltage must be at least the total line voltage.
[0008] This isolation is typically performed using an isolated DC
power source 170. These isolated DC power sources 170 may be
optically isolated, or isolated using another means. In these
embodiments, despite the low voltage and current requirements, the
isolated DC power supply 170 may be unreliable and very expensive,
potentially costing thousands of dollars each. These isolated power
supplies 170 have to deliver stable power over the isolation rated
at high voltage. The higher the isolation voltage, the more
difficult this task becomes, as the size of the supplies will grow,
the cost will grow, the reliability will decrease due to higher
probability of high voltage breakdown causing insulation puncture.
The lower reliability may also be due to the fact that the output
voltage regulation will be difficult to control from the high
voltage side (it would have to be controlled on the ground side)
and it may be difficult to maintain the voltage needed by the gate
of the switch to turn it on and off. Thus, the need to use this
specialized isolated power supply 170 greatly increases the total
cost of a state solid fault current limiter system.
[0009] Therefore, it would be beneficial if there were a system and
method for providing isolated power to the gate driving circuits
that was less expensive and more reliable than current
solutions.
SUMMARY
[0010] A system and method for providing isolated power to the gate
driving circuits used in solid state switching devices is
disclosed. Rather than using expensive isolated AC/DC power
supplies, an isolation transformer is used to provide isolated AC
voltage. In one embodiment, the primary winding of the isolation
transformer is disposed across an independent AC source. In another
embodiment, the primary winding of the isolation transformer is
disposed across two phases of the AC power line. Isolated AC
voltage is then generated across the secondary winding of the
isolation transformer. This isolated AC voltage is then used by a
non-isolated DC power supply, which generates the power for the
gate driving circuit.
[0011] According to one embodiment, a solid state fault current
limiting device for use with an AC power line is disclosed. This
fault current limiting device comprises a solid state switching
device, disposed in series in the AC power line, the solid state
switching device having an input, an output and a gate, where a
voltage applied to the gate determines whether current flows
between the input and the output; a gate driving circuit in
communication with the gate, to apply a gate voltage to the gate,
the voltage referenced to either a voltage at the input or at the
output; a current monitor in communication with the AC power line
and the gate driving circuit, wherein the gate voltage is
determined based on an output from the current monitor; an
isolation transformer, having a primary winding and a secondary
winding; and a non-isolated AC-to-DC power supply, powered by the
secondary winding and referenced to the voltage at the input or at
the output, to supply DC power to the gate driving circuit.
[0012] According to a second embodiment, a method of limiting fault
current in an AC power line is disclosed. This method comprises
monitoring current through the AC power line; and applying a
voltage to a gate of a solid state switching device to allow or
inhibit the flow of current through the solid state switching
device, wherein the voltage applied to the gate is generated by
using an isolation transformer to create an isolated AC voltage;
using a non-isolated AC-to-DC power supply referenced to the AC
power line to convert the isolated AC voltage to an isolated DC
voltage; and using the isolated DC voltage to power a gate driving
circuit in communication with the gate of the solid state switching
device.
[0013] According to a third embodiment, a system for limiting fault
current in an AC power line is disclosed. This system comprises an
isolation transformer, having a primary winding and a first
secondary winding and a second secondary winding; an independent AC
source, wherein the primary winding is disposed across the
independent AC source; a first solid state fault current limiting
device, comprising a first solid state switching device, disposed
in series in the AC power line, the first solid state switching
device having a first input, a first output and a first gate, where
a first gate voltage applied to the first gate determines whether
current flows between the first input and the first output; a first
gate driving circuit in communication with the first gate, to apply
the first gate voltage to the first gate, the first gate voltage
referenced to either a voltage at the first input or at the first
output; a first current monitor in communication with the AC power
line and the first gate driving circuit, wherein the first gate
voltage is determined based on an output from the first current
monitor; and a first non-isolated AC-to-DC power supply, powered by
the first secondary winding and referenced to the voltage at the
first input or at the first output, to supply DC power to the first
gate driving circuit; and a second solid state fault current
limiting device, comprising a second solid state switching device,
disposed in series in the AC power line, the second solid state
switching device having a second input in communication with the
first output, a second output and a second gate, where a second
gate voltage applied to the second gate determines whether current
flows between the second input and the second output; a second gate
driving circuit in communication with the second gate, to apply the
second gate voltage to the second gate, the second gate voltage
referenced to either a voltage at the second input or at the second
output; a second current monitor in communication with the AC power
line and the second gate driving circuit, wherein the second gate
voltage is determined based on an output from the second current
monitor; and a second non-isolated AC-to-DC power supply, powered
by the second secondary winding and referenced to the voltage at
the second input or at the second output, to supply DC power to the
second gate driving circuit.
BRIEF DESCRIPTION OF THE FIGURES
[0014] For a better understanding of the present disclosure,
reference is made to the accompanying drawings, which are
incorporated herein by reference and in which:
[0015] FIG. 1 is a schematic of a SSFCL device in accordance with
the prior art;
[0016] FIG. 2 shows a SSFCL device according to a first
embodiment;
[0017] FIGS. 3A-3B show example configurations using multiple SSFCL
devices arranged in series; and
[0018] FIG. 4 shows a SSFCL device according to a second
embodiment.
DETAILED DESCRIPTION
[0019] As described above, SSFCL devices can be arranged in series
in order to allow each solid state switching device to operate
within its rated range. However, the power supplies used to power
the gate driving circuits must be adequately isolated from one
another.
[0020] FIG. 2 shows a plurality of SSFCL devices 200 in accordance
with a first embodiment. In this embodiment, each of the SSFCL
devices 200 has many of the same components as that shown in FIG.
1, such as a solid state switching device 110, including a source
111, a drain 112 and a gate 113. Parallel components 145, such as a
snubber 120, a reactor 130, and a transient suppressor 140, may be
disposed in parallel with the solid state switching device 110. In
addition, a gate driving circuit 150 may be in communication with
the gate 113. A current sensor 160 is in communication with the
power line 101 to detect the flow of current through the power line
101. These components perform the same function as described with
respect to FIG. 1 and will not be described again.
[0021] In this embodiment, the isolated power supply 170 of the
prior art (see FIG. 1) has been replaced with a lower cost
non-isolated AC-to-DC power supply 210, which does not need to
include isolation protection. Rather, the isolation protection is
provided by an isolation transformer 220. This isolation
transformer 220 has a primary winding 222 and one or more secondary
windings 224. The primary winding 222 may be connected to AC power
line 101, such as across two phases of the AC power line 101, or to
an independent AC voltage source 250. The secondary winding is
connected to the lower cost non-isolated AC-to-DC power supply 210.
Optionally, an overvoltage protection circuit 230 may be disposed
between each secondary winding 224 and the respective non-isolated
AC-to-DC power supply 210. The isolation transformer 220 provides
the necessary isolation.
[0022] These SSFCL devices 200 may be arranged in at least two
different configurations. For example, FIG. 3A shows a reactor 130
in parallel with each SSFCL device 200 (as depicted in FIG. 2).
However, FIG. 3B shows a single reactor 130 in parallel with the
series connection of SSFCL devices 200 in FIG. 3B. It is noted that
when configured according to FIG. 3A, a respective set of these
parallel components 145 is connected in parallel with each solid
state switching device 110. In contrast, when configured as shown
in FIG. 3B, a single reactor 130 is connected in parallel with the
entire set of series connected solid state switching devices 110.
Thus, the reactor 130, shown in FIG. 2, is not present in this
embodiment. In addition, though not shown in FIG. 3A-3B, the
snubber 120 and transient suppressor 140 are preferably in parallel
with each solid state switching device 110.
[0023] As described above, the isolation transformer 220 provides
isolation between these SSFCL devices 200. For example, when
installed in accordance with the embodiment of FIG. 3A, the
secondary windings 224 must meet certain criteria. First, the
isolation voltage between any two secondary windings 224 may be
greater than the power line voltage divided by the number of SSFCL
devices 100. The isolation voltage between the secondary winding
224 to the primary winding 222 may be greater than the power line
voltage. Any secondary winding 224 to ground isolation voltage may
be greater than the power line voltage. In the case where the
primary winding is energized from the power line 101, the primary
winding 222 to ground isolation voltage may be greater than the
power line voltage.
[0024] Furthermore, the primary and secondary windings, and
adjacent secondary windings are all physically separated to
provide, by design, proper high voltage isolation rating, equal to
at least the line voltage of the system. In some embodiments, a
design margin of, for example, 25%, may be incorporated as well. Of
course, the distances between the winding assemblies depend on the
voltage and isolation material used. For example, the use of epoxy
and transformer oil can allow them to be relatively small. In the
isolation transformer 220, it is much easier to accomplish the task
of providing the power over isolation barrier than in the case of
an isolated power supply 170, as there is no additional electronics
in the isolation point. A non-isolated AC-to-DC power supply 210 is
connected to each respective secondary winding, and its input and
output are referenced to the same electrical common connection,
which serves to make the system more reliable as far as the power
supply is concerned.
[0025] When the SSFCL device 200 is installed in accordance with
the embodiment of FIG. 3B, the isolation voltage between any two
secondary windings 224 may be greater than the power line voltage.
Criteria for other isolation voltages may be as described
above.
[0026] It should be noted that FIG. 2 shows all of the gate driving
circuits 150 for the respective SSFCL devices 200 powered from
secondary windings 224 in communication with a single isolation
transformer 220. However, other configurations are possible. For
example, two or more isolation transformers 220 may be used, where
secondary windings from these isolation transformers 220 provide
power to all of the SSFCL devices 200.
[0027] As described above, the primary winding of the isolation
transformer 220 may be connected to an independent AC source 250.
This independent source 250 may be any single output AC source line
with its own breaker. If desired, filters can be added to the AC
source line to eliminate switching noise injected into the line. In
one embodiment, the primary winding is connected to a standard AC
line, having 120-240V AC, although other voltages are possible. In
this embodiment, the isolation transformer 220 may be a primary
winding to secondary winding ratio (referred to as the turns ratio)
of 0.5 to 2, so that the secondary AC voltage is in the range of
120 to 240 volts. This secondary AC voltage is the input voltage
required by the non-isolated AC-to-DC power supply 210. Therefore,
if a different input voltage is preferred, the turns ratio is
modified to achieve that input voltage in accordance with the
relationship: the input voltage to non-isolated AC-to-DC power
supply is equal to AC source voltage divided by the turns
ratio.
[0028] In another embodiment, the primary winding of the isolation
transformer 220 may be connected to the power line 101. In some
embodiments, the isolation transformer 220 may be inserted in the
power line 101 after the last reactor 130 (i.e. between the last
SSFCL device 200 and the load). Of course, the isolation
transformer 220 may be connected in other locations but the
overprotection circuit 230 may be more complex. In this embodiment,
the primary winding 222 may be disposed between two phases of the
AC power line 101. In this embodiment, the isolation transformer
220 may have a suitable turns ratio, so that the secondary AC
voltage is in the range of 120 to 240 volts. The overprotection
circuits 230 may be used to limit the voltage in cases where the
current through the power line 101 is higher than expected. In
addition, the secondary AC voltage may dip during faults. To
compensate for this, the non-isolated AC-to-DC power supply 210 may
be designed to have a suitable input voltage range to accommodate
this. For example, the input voltage range may be rated to a
voltage less than 120V.
[0029] Each non-isolated AC-to-DC power supply 210 is referenced to
the voltage of the power line 101 that is in communication with the
solid state switching device 110. For example, the solid state
switching device 110 is in communication with the power line 101 at
its source side 111 and passes that voltage (when enabled) to its
drain side 112. In one embodiment, the voltage at its source side
111 may be used as the common reference for the non-isolated
AC-to-DC power supply 210. In another embodiment, the voltage at
its drain side 112 may be used as the common reference for the
non-isolated AC-to-DC power supply 210.
[0030] In this way, the output of the gate driving circuit 150,
which is in communication with gate 113, for each SSFCL device 200
is referenced to a voltage at one of the terminals 111, 112 of the
solid state switching device 150.
[0031] As described above, the lower cost non-isolated AC-to-DC
power supply is greatly simplified by the inclusion of isolation
transformer 220. Thus, rather than including the complex circuitry
typically found in the isolated power supplies 170 of the prior
art, the lower cost non-isolated AC-to-DC power supply 210 has
fewer components. For example, a 45 kV DC isolated DC/DC, very low
power (such as 5 W) power supply may cost more than $2000 and may
require manufacturing lead times of 4-8 weeks. Furthermore, few
vendors are capable of making such a power supply. In contrast, a
non-isolated power supply having the same power requirements may
cost less than $100, are readily available, and are much more
reliable.
[0032] As described above, the SSFCL device 200 of FIG. 2 may be
used with the configuration shown in FIG. 3A, where a set of
parallel components 145 is associated with each solid state
switching device 110. In addition, the SSFCL device 200 of FIG. 2
may be used with the configuration shown in FIG. 3B, where one
reactor 130 is in parallel with all of the solid state switching
devices 110, with snubbers 120 and transient suppressors 140 is
parallel with each switching device 110.
[0033] FIG. 4 shows a second embodiment of the SSFCL device 300
that can be used to create a less expensive, more reliable power
system. In this embodiment, the SSFCL device 300 comprises the
parallel components 145, solid state switching device 110, current
monitor 160, gate switching circuit 150, low cost non-isolated
AC-to-DC power supply 210 and overvoltage protection circuit 230
described above with respect to FIG. 2. These components perform
the same function in this embodiment and will not be described
again here. This second embodiment of the SSFCL device 300 can also
be used in both embodiments shown in FIG. 3A and FIG. 3B,
configured in the manner described above.
[0034] However, in this embodiment, each SSFCL device 300 comprises
a respective isolation transformer 310. Each of these isolation
transformers 310 has their primary windings connected to the power
line 101. In one embodiment, the primary winding is disposed
between two phases of the AC power line 101. In this way, the line
voltage (V.sub.line) is across the primary winding. The primary
winding of the isolation transformer 310 may be disposed either
proximate the source 111 or the drain 112 of the solid state
switching device 110. In other words, the primary winding of the
isolation transformer 310 may be disposed on either side of the
solid state switching device 110. Consequently, it is necessary for
there to be current flow through the power line 101 even when the
switching device 110 is in the disabled state.
[0035] The secondary windings of the isolation transformers 310 are
in communication with the low cost non-isolated AC-to-DC power
supply 210. As described above, an overvoltage protection circuit
230 may be disposed between the secondary windings of the isolation
transformer 310 and the non-isolated AC-to-DC power supply 210.
[0036] Each isolation transformer 310 may have a suitable turns
ratio, such that the voltage created at the secondary windings 314
is between, for example, 120 and 240 volts, regardless of the state
of the switching device 110. For example, if the line voltage
(V.sub.line) is 10 kV and the desired input voltage for the
non-isolated AC-to-DC power supply 210 is 120V, the turns ratio may
be determined as V.sub.line/120V, or 83. Of course different line
voltages and input voltages may also be used and the turns ratio is
calculated accordingly.
[0037] In this way, the expensive and largely unreliable isolated
power supply 170 may be replaced by an isolation transformer 220,
310 and a non-isolated AC-to-DC power supply 210. This change
reduces the cost of the system and increases its reliability. The
system may include an isolation transformer 220 having multiple
secondary windings, as is shown in FIG. 2. In another embodiment, a
dedicated isolation transformer 310 may be used with each SSFCL
device 300, as is shown in FIG. 4.
[0038] Furthermore, a method of limiting fault current in an AC
power line is disclosed. First, the current in the AC power line is
monitored, such as by current monitor 160. Then, a voltage is
applied to the gate 113 of the solid state switching device 110 to
allow or inhibit the flow of current through the solid state
switching device. The voltage used to control the gate 113 is
generated by the gate driving circuit 150. Power is supplied to the
gate driving circuit 150 by a non-isolated AC-to-DC power supply
210. The non-isolated AC-to-DC power supply is powered by an
isolated AC voltage. This isolated AC voltage is created using an
isolation transformer 220, 310. As described above, the primary
winding of the isolation transformer 310 may be disposed across two
phases of the AC power line. In another embodiment, the primary
winding of the isolation transformer 220 is disposed across an
independent AC source 250.
[0039] The present disclosure is not to be limited in scope by the
specific embodiments described herein. Indeed, other various
embodiments of and modifications to the present disclosure, in
addition to those described herein, will be apparent to those of
ordinary skill in the art from the foregoing description and
accompanying drawings. Thus, such other embodiments and
modifications are intended to fall within the scope of the present
disclosure. Furthermore, although the present disclosure has been
described herein in the context of a particular implementation in a
particular environment for a particular purpose, those of ordinary
skill in the art will recognize that its usefulness is not limited
thereto and that the present disclosure may be beneficially
implemented in any number of environments for any number of
purposes. Accordingly, the claims set forth below should be
construed in view of the full breadth and spirit of the present
disclosure as described herein.
* * * * *