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Claims  |
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What is claimed is:
1. A corded/cordless system for power-operated apparatus, comprising:
an electrically power-operated device operable in a preselected voltage
range;
means defining an interface for electrically and mechanically mating said
device with one of a plurality of electric-power supply devices, said
interface means defining a pre-determined physical envelop configuration
for mechanically mating with the power supply devices;
first supply means defining a cordless electric-power supply device for
electrically and mechanically mating with said power-operated device
through said interface, said cordless electric-power supply device
containing cells capable of providing 50 or more watts of power in the
selected voltage range to said power-operated device;
second supply means defining a corded electric-power supply device for
electrically and mechanically mating with said power-operated device, said
corded electric-power supply device having a power cord for connection to
a source of electrical energy therethrough and containing an electrical
power converter for converting the source electrical energy to 50 or more
watts of power in the selected voltage range; and
wherein said second supply means comprises voltage converter means for
converting the source electrical energy into an alternating voltage of a
selected frequency and converting the alternating voltage to a lower
rectified voltage in the selected voltage range.
2. The system of claim 1, wherein the power-operated device includes a
motor.
3. The system of claim 1, wherein said interface means further comprises
means defining a cavity having the pre-determined physical envelop
configuration for accepting either of said first supply means and said
second supply means.
4. The system of claim 3, wherein said interface means further comprises
means defining electrical contacts positioned within said cavity for
effecting electrical connection with complementary contacts on either of
said first supply means and said second supply means.
5. The system of claim 1, wherein said interface means further comprises
means for releasably securing either of said first supply means and said
second supply means.
6. The system of claim 1, wherein said voltage converter means comprises:
means for converting a first-frequency alternating source voltage of the
source electrical energy into a second-frequency alternating voltage at
the selected frequency and for converting the second-frequency alternating
voltage to the lower rectified voltage in the secreted voltage range.
7. The system of claim 1, wherein said voltage converter means comprises:
means for converting a first-frequency alternating source voltage of the
source electrical energy to a DC voltage, for converting the DC voltage to
a second-frequency alternating voltage at the selected frequency, and for
converting the second-frequency alternating voltage to the lower rectified
voltage in the selected voltage range.
8. The system of claim 4, wherein said voltage converter means further
comprises:
a step-down transformer for stepping down the voltage of the
second-frequency alternating voltage.
9. The system of claim 6, wherein the frequency of the second-frequency
alternating voltage is between 350 and 600 times the frequency of the
first-frequency alternating source voltage.
10. The system of claim 9, wherein the second frequency is approximately 25
KHz.
11. The system of claim 6, wherein the first frequency is between 50 and 60
Hz.
12. The system of claim 6, wherein said voltage converter means further
comprises:
means for rectifying the stepped down second-frequency alternating voltage
of said step-down transformer.
13. The system of claim 6, wherein said voltage converter means further
comprises:
means for rectifying the stepped down second-frequency alternating voltage
of said step-down transformer to provide a rectified voltage of between
3.6 and 48 volts.
14. A power-operated device, comprising:
a housing having a device therein operable in a preselected voltage range;
means defining an interface for electrically and mechanically mating said
housing with any one of a plurality of electric-power supply devices, the
interface means defining a pre-determined physical envelope configuration
for mechanically mating with the power supply devices;
supply means defining a corded electric-power supply device for
electrically and mechanically mating with said housing through said
interface means, said corded electric-power supply having a power cord for
connection to a source of electrical energy therethrough and containing an
electrical voltage converter for converting current of the source of
electrical energy to 50 or more watts of power in the preselected voltage
range; and
wherein said voltage converter includes means for converting a
first-frequency alternating source voltage of the source of electrical
energy into a second-frequency alternating voltage and for converting the
second-frequency alternating voltage to a lower rectified voltage in the
preselected voltage range.
15. The power-operated device of claim 14 wherein said device within said
housing is a motor.
16. The power-operated device of claim 14, wherein said interface means
further comprises means defining a chamber having the pre-determined
physical envelop configuration for accepting said supply means.
17. The power-operated device of claim 16, wherein said interface means
further comprises means defining electrical contacts positioned within
said chamber for effecting electrical connection with complementary
contacts on said supply means.
18. The power-operated device of claim 16, wherein said interface means
further comprises means for releasably securing said supply means in its
mated position.
19. The power-operated device of claim 14, wherein said voltage converter
comprises:
means for converting the first-frequency alternating source voltage to a DC
voltage and for converting the DC voltage to the second-frequency
alternating voltage.
20. The power-operated device of claim 14, further comprising:
a step-down transformer for stepping down the voltage of the
second-frequency alternating voltage.
21. The power-operated device of claim 14, wherein the frequency of the
second-frequency alternating voltage is between 350 and 600 times the
frequency of the first-frequency alternating source voltage.
22. The power-operated device of claim 21, wherein the second frequency is
approximately 25 KHz.
23. The power-operated device of claim 14, wherein the first frequency is
between 50 and 60 Hz.
24. The power-operated device of claim 20, further comprising:
means for rectifying the stepped down second-frequency alternating voltage
of said step-down transformer.
25. The power-operated device of claim 22, further comprising:
means for rectifying the stepped down second-frequency alternating voltage
of said step-down transformer to provide a rectified voltage of between
3.6 and 48 volts.
26. A corded power-supply device for mechanical and electrical connection
with a power-operated device operated in a selected voltage range and an
interface that defines a physical envelop configuration for accepting
electric power-supply devices, comprising:
voltage converter means for converting the source electrical energy
provided from an electrical energy source by a power cord into an
alternating voltage of a selected frequency and converting the alternating
voltage to a lower rectified voltage in the selected voltage range at a
power of 50 or more watts;
means defining a housing for containing said voltage converter means and
having a physical envelop configuration that complements that of the
interface of the power-operated device to effect electrical and mechanical
connection therewith; and
wherein said voltage converter means comprises means for converting a
first-frequency alternating source voltage of the electrical energy source
into a second-frequency alternating voltage at the selected frequency and
for converting the second-frequency alternating voltage to the lower
rectified voltage in the selected voltage range.
27. The corded power-supply device of claim 26, wherein said voltage
converter means comprises means for converting the first-frequency
alternating source voltage to a DC voltage and for converting the DC
voltage to the second-frequency alternating voltage.
28. The corded power-supply device of claim 26, wherein said voltage
converter means further comprises:
a step-down transformer for stepping down the voltage of the
second-frequency alternating voltage.
29. The corded power-supply device of claim 26, wherein the frequency of
the second-frequency alternating voltage is between 350 and 600 times the
frequency of the first-frequency alternating source voltage.
30. The corded power-supply device of claim 28, wherein the second
frequency is approximately 25 KHz.
31. The corded power-supply device of claim 26, wherein the first frequency
is between 50 and 60 Hz.
32. The corded power-supply device of claim 25, further comprising:
means for rectifying the stepped down second-frequency alternating voltage
of said step-down transformer.
33. The corded power-supply device of claim 27, further comprising:
means for rectifying the stepped down second-frequency alternating voltage
of said step-down transformer to provide a rectified voltage of between
3.6 and 48 volts.
34. The corded power-supply device of claim 26 wherein the power operated
device includes a motor. |
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Claims |
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Description |
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CROSS REFERENCE TO RELATED APPLICATION
The subject matter of the present application is related to that disclosed
in co-pending and commonly assigned U.S. patent application Ser. No.
161,122, filed on even date herewith and entitled "Voltage Converter" and
U.S. patent application Ser. No. 160,912 filed on even date herewith and
entitled "Corded/Cordless Dual-Mode Power-Operated Device".
BACKGROUND OF THE INVENTION
The present invention relates to electrically operated devices and
appliances and, more particularly, to a power-operated device which can
operate in a cordless mode from a self-contained power source or in a
corded mode from a conventional AC or DC power source.
Electrically-operated devices that function in a cordless mode typically
include a housing having a chamber for receiving and retaining a
removable, enclosed battery pack. The battery pack completely encloses one
or more cells contained within the pack and provides the necessary DC
power for operation of the device. Historically, cordless electrically
powered devices have included relatively low-power devices such as
shavers, hand-held calculators, entertainment devices, typewriters and the
like, these representative devices generally having a relatively small
power consumption under constant load condition.
Advances in battery technologies and systems have led to the development of
physically compact and electrically efficient batteries that store a
relatively large amount of electrical energy. These higher energy
batteries have permitted the development of higher power cordless devices
that operate at power levels above 50 watts, including power levels that
extend to 500 watts or so. These higher power devices include, for
example, portable hand-held power tools and appliances such as drills,
screwdrivers, screwdriver-drills, hammer-drills, jig saws, circular saws,
shears, hedge trimmers, and various household products and appliances. In
addition to operating at much higher power levels than prior devices,
these devices typically encounter widely varying load conditions during
normal use. For example, an electrically driven drill bit typically
encounters a lighter load condition when the workpiece is wood or plastic,
in contrast to steel, and, for any particular material, the drill bit may
be subjected to widely varying loads, such as those conditions which tend
to bind the drill bit in the workpiece. These varying loads cause
corresponding variations in the current drawn by the drive motor from the
power source and subject the power source to high-current demands not
typically encountered with the low-power devices.
The current state of battery pack technology is such that battery packs are
available to meet both the total power requirements for the higher powered
devices as well as accommodate the range of electrical current variations
consequent to operation under varying load conditions.
Electrically-operated power devices of the cordless type described above
permit work operations to be performed in areas where a conventional AC
power source is not available, although the use of such cordless devices
is limited to the effective charge life of the cells within the battery
pack. When the battery pack is discharged, the battery pack must be
recharged or replaced with a fully charged pack.
When the operator of a cordless-mode power-operated device, as described
above, is in an area in which an external power source is available, such
as a continuous AC power source or a high level DC voltage source, it is
oftentimes more efficient to connect the device to the external power
source by a power cord to conserve the battery charge for subsequent use
in areas where the AC source or high level DC source is not available. In
general, those cordless-mode devices that use a low-voltage DC motor
cannot be directly driven from an AC source or from a high level DC
source.
Certain design criteria are presented when attempting to drive the higher
power (e.g., 50 watts or higher), low-voltage DC motors of a cordless
device using a corded converter for adapting or converting the AC source
or high-level DC source for the motor. The cordless battery pack
represents a physical envelop that can limit the ultimate current and
power providing capacity of the corded converter, since the internal
electrical components and circuitry of the converter must conform to the
overall physical envelop constraints. As current and power demands are
increased to provide adequate energy for the higher power tools discussed
above, the physical size of the electrical components required for the
converter increases proportionately and tend to define a practical power
and current limit for a corded converter that is designed to be
interchanged with the cordless battery pack.
One low-power device, i.e., having a power consumption of between one and
five watts, and which can operate in a cordless mode using a primary or
secondary battery or in a corded mode using a transformer/rectifier
combination is an electrical shaver of the type described in U.S. Pat. No.
3,079,510 to Hartwig. The low-power electric shaver employs a DC motor
that drives the shaving head and which can be operated in a cordless mode
by use of either a primary battery or a rechargeable secondary battery.
The battery is mounted in an open, cup-shaped cap, is provided with a pair
of U-shaped terminals on opposite sides thereof, and is positioned in the
open end of the cap and partially exposed outwardly from the open end. The
battery is installed by manipulating the cap to first insert the exposed
portion of the battery into an opening of the shaver housing with the
battery terminals effecting contact with complementary spring contacts
within the housing to effect electrical connection to the DC motor within
in the shaver housing. As the battery enters the housing, the
spring-contacts mechanically guide the battery into its assembled
position, and tongues formed within the cap snap into grooves formed in
the housing to retain the cap and its battery in place.
In addition to battery operation, the shaver can be operated by a corded
power adapter in the form of another open, cup-shaped cap that contains a
terminal block to which one end of power cord is assembled with a
conventional male plug connected at the other end of the power cord. A
transformer is mounted in the open cap in a position similar to the
battery mounting with portions of the transformer being exposed. The
transformer is capable of transforming 110 volts or 220 volts of a
low-frequency AC source current to a lower level AC voltage which is
rectified to the voltage level of the DC motor. A pair of terminals are
mounted on opposite sides of the transformer in position to engage the
spring contacts of the housing as the cap is assembled with the housing.
The primary of the transformer is connected through the terminal block to
the AC source while the secondary of the transformer is connected to a
rectifier mounted in the base of the cap. The output of the rectifier
provides a low-voltage DC voltage at a low-power level that is sufficient
to operate the electric shaver. Thus, the corded transformer-rectifier
assembly within the open cap can be inserted into the housing in place of
the battery-containing cap to facilitate operation of the electric shaver
in a corded mode from an AC power source. The transformer-rectifier
combination is designed to provide only low power in a narrow current
range required to operate the electric shaver and represents a reasonable
design solution. Since the shaver does not experience a wide range of
loads, the transformer-rectifier combination does not have to accommodate
operating loads that develop high current conditions and attendant
electrical stressing of the transformer or rectifier.
Other commercially available lower power systems also employ a similar
principle of substituting a converter unit within the battery compartment
of a device which operates on a low DC voltage. For example, one
commercially available video camera recorder operates at DC voltage levels
of 8.5 volts with a power consumption of 20 watts. Another commercially
available video camera recorder operates at a DC voltage level of 12 volts
with a power consumption of 22 watts. Typically, each of the available
camera recorders includes a facility for supporting a battery pack to
provide the operating DC voltage and power. As an alternative, a corded AC
pack or adaptor, which is contained in a housing with essentially the same
exterior shape and terminal location as the housing of the battery pack,
can be substituted for the battery pack in the camera recorder. The AC
pack will then provide the operating DC voltage and power when the pack is
connected to a conventional AC power source such as, for example, a 120
volts, 60 Hz wall source. These commercially available camera recorder
systems also include a battery charger unit which is separate from and
operates independently of the camera recorder. When using the battery
charger unit, both the battery pack and the AC pack are inserted into the
unit. The AC pack is then connected to a conventional AC source whereby
the AC pack provides the DC voltage and power necessary to charge the
batteries.
Even on those rare occasions when an overload condition occurs, the video
camera recorder, as well as the shaver described above, operate at such
low power levels that it is unlikely that catastrophic reactions will
occur within the converters used with these types of devices. In contrast,
if converters are used at higher power levels, e.g., such as 50 watts and
higher, an overload condition can result in severe over-stressing of the
components and attendant increased operating temperature within the
converters which could destroy one or more components of the converters.
In the context of a low-power device, the transformer-rectifier combination
of the shaver and the corded AC pack of the video camera recorders
represent a relatively simple and appropriate solution. The physical size
of low current electronic devices, including step-down transformers,
rectifiers, and similar power-supply components, is such that the
converter can be fabricated with a continuous power rating that is
suitable for the powered device and which readily fits within the physical
envelop prescribed by the battery pack. However, such a solution does not
lend itself to higher power devices of the type described, especially
where a wide current variation is drawn because of widely varying load
conditions. For example, if the power and current demand were increased an
order of magnitude or more, viz., for a power demand of 50 watts or more,
a contemporary battery pack can be provided to meet both the power and
current demands, even where the current varies over a wide range because
of different load conditions experienced by the device. However, a higher
power corded converter that follows the design approach presented in U.S.
Pat. No. 3,079,510 would require disproportionately larger and heavier
components, particularly the step-down transformer, with higher current
carrying capacities to supply the needed power and to also accommodate the
variation in current caused by the varying loads experienced by such
devices. Thus in high-power devices, a practical design constraint exists
with regard to the fabrication of corded AC/DC converters having the
requisite power and current providing capacity in a corded converter
housing that is commensurate in size with the envelop prescribed by the
battery pack and which does not compromise or diminish the utility of the
device. Thus, the feasibility of providing a practical corded converter
that provides the power and current requirements in a physical envelope
prescribed by the cordless battery pack diminishes as the power levels
increase. If corded AC/DC converters using above-described design approach
were applied to high-power drills, screwdrivers, screwdriver-drills,
hammer-drills, jig saws, circular saws, shears, hedge trimmers, related
household products and the like, the size and weight of the corded AC/DC
converters, as well as the cost of such devices, would comprise the
utility of the devices.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the present invention, among
others, to provide a system by which high power devices can be operated by
a cordless battery pack or a corded converter that can provide the
necessary power and current requirements of the high power device.
It is another object of the present invention to provide a system by which
high power devices can be operated by a cordless battery pack or a corded
converter that can provide the necessary power and current in a physical
envelop commensurate with that of the cordless battery pack.
It is still another object of the present invention to provide a system by
which high power devices can be operated by a cordless battery pack or a
corded converter that can respond in a corrective sense to overload
conditions caused by different load conditions placed on the device.
It is a further object of the present invention to provide a system by
which high power devices can be operated by a cordless battery pack or a
corded converter in which the weight, portability, and utility of the
device is not compromised by operation in a corded mode.
In view of these objects, and others, the present invention provides a
system by which higher power electrically operated devices can be operated
in a corded or cordless mode. The device is provided with an interface for
accepting either a cordless battery pack that supplies the power and
current demands for the device in a cordless mode or a corded converter
that supplies the necessary power and current demands in a physical
envelop commensurate with that of the battery pack. The corded converter
is provided with a high efficiency power supply that allows the converter
to generate the power and current required by the driven device and
accommodate widely varying loads consequent to normal operation of the
device and do so in a physical envelop that is commensurate in size with
and interchangeable with the cordless battery pack.
In the preferred embodiment, the cordless battery pack is designed to be
removeably received with a pack receiving chamber formed in the device and
interconnect with control circuitry to allow controlled operation of the
device motor using power provided from the battery pack. Corded operation
is achieved by substituting a corded converter for the battery pack. The
corded converter includes a power conditioner that conditions input source
voltage, such as 120 or 240 volts AC or DC, to provide a relatively high
DC voltage that is chopped at a comparatively high frequency, e.g., 25
KHz, by switching devices. The high-frequency, high voltage current is
presented to a step-down transformer with the stepped-down output
rectified to provide a low-voltage DC current to the drive motor.
The present invention advantageously provides a dual-mode system for the
cordless or corded operation of a higher power device in which the corded
converter is provided with a high efficiency converter circuitry that
allows a corded converter that successfully meets the total power and
current demands of the device in a physical envelop commensurate in size
and interchangeable with the battery pack used during cordless operation.
Other objects and further scope of applicability of the present invention
will become apparent from the detailed description to follow, taken in
conjunction with the accompanying drawings, in which like parts are
designated by like reference characters.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a side elevational view of a cordless electric having a battery
pack received within a chamber of a handle portion of the drill;
FIG. 2 is a partial side elevational view showing the handle portion of the
electric drill of FIG. 1 with the battery pack removed from its receiving
chamber;
FIG. 3 is a partial side elevational view, similar to FIG. 2, showing the
handle portion of the electric drill of FIG. 1 with the battery pack
installed in its receiving chamber and latched into place;
FIG. 4 is a side elevation view partially showing the handle portion of the
electric drill of FIG. 1 with a container for housing a power converter in
which the container is positioned for insertion into the chamber of the
handle portion;
FIG. 5 is a rear elevational view partially showing the electric drill of
FIG. 1, with a portion broken away, to reveal the manner of electrically
connecting either the battery container of FIGS. 1-3 or the power
converter container of FIG. 4 to an electric motor contained within the
drill;
FIG. 6 is a top plan view, taken along line 5--5 of FIG. 2, showing the top
of the battery pack of FIGS. 2-3; and
FIG. 7 is a schematic of a voltage converter assembled and contained within
the container of FIG. 4 in accordance with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
A high-power corded/cordless system for power-operated devices in
accordance with the present invention is shown in FIGS. 1-7 in the form of
an electric drill, designated generally by the reference character 10. As
shown in FIG. 1, the drill 10 includes a chuck 12 secured to a rotatable
spindle 14 which is driven through a gear train (not shown) by an electric
motor 16 (shown in dotted line illustration) in the conventional manner.
The motor 16 is mounted in a motor casing 18 of a housing 20 that includes
a handle 22 depending therefrom. A trigger switch 24 is mounted in the
handle 22 immediately below the motor casing 18 and is actuated in the
usual manner to operate the drill 10. In FIG. 1, a battery pack, indicated
generally by the reference character 25, is installed within the handle 22
as explained below and provides electrical current to the motor 16 in
response to actuation of the trigger switch 24.
As illustrated in FIG. 2, the battery pack 25 includes a plurality of cells
26 (phantom line illustration) housed within a battery-pack container 28.
A first section 30 of the container 28 is shaped externally to fit within
a chamber 32 formed within handle 22. The chamber 32 is formed with an
open end 34 to facilitate insertion of the first section 30 of the
container 28 into the chamber 32. A latch member 36 is connected in a
hinged fashion to the handle 22 adjacent one side of the open end 34.
After the first section 30 of the container 28 has been inserted fully
into the chamber 32, as shown in FIG. 1, the latch member 36 is pivoted
into a nest 38, as shown in the cross-section view of FIG. 3, of a second
section 40 of the container 28. The latch member 36 engages a latching
mechanism 41 that is part of the handle 22. In the preferred embodiment,
the latching function is achieved in accordance with that presented in
U.S. Pat. No. 3,999,110, issued to Ramstrom et al. on Dec. 21, 1976, the
disclosure of which is incorporated herein by reference.
The cells 26 are arranged and connected within the battery pack 25 to
provide a low-level DC voltage compatible with the operating DC voltage
supply level of the motor 16, for example, 12 volts. This voltage supply
level is normally associated with a cordless mode of operation for a
power-operated device, such as the drill 10, although the voltage supply
level could be in a range of 3.6 to 48 volts DC without departing from the
spirit and scope of the invention.
The cells 26 are connected internally within the battery pack 25 to a pair
of output contacts or terminals 42 and 44, as best shown in the top view
of FIG. 6, located on opposite sides of the section 30 at the proximate
end of the container 28. As shown in FIG. 5, input contacts in the form of
wire strap contacts 46 and 48 are mounted internally of the handle 22 and
are positioned to engage the terminals 42 and 44, respectively, as the
first section 30 of the container 28 is inserted into the chamber 32 of
the handle 22. The input contacts 46 and 48 are connected through internal
wiring to the switch 24 which, in turn, is connected through wiring to the
motor 16. When the switch 24 is closed by an operator, energy is applied
by the cells 26 to the motor 16 to operate the drill 10.
A cordless power-operated device, such as the drill 10, is lightweight, is
easily manipulated by the operator, and is designed for portable utility.
While such a device is useful in any work area, it has particular utility
in work areas where conventional power sources are not available. The
drill 10, for example, can be operated in such work areas by use of the
low-level DC voltage available from the cells 26 and will typically
operate in a power range of, for example, 50 watts and higher. While this
demonstrates the clear advantage of such cordless devices, the cells 26
have a limited charge life and must be periodically recharged.
Consequently, it is desirable to conserve the charge of the cells 26
whenever a conventional AC power source is available in the work area.
However, cordless devices, such as the drill 10, operate on a low-level DC
voltage such as, for example, 12 volts. Typically, the AC source provides
120 volts at 60 Hz. in the United States and other values outside the
United States, for example, 220/240 volts at 50 Hz, which values are
unsuitable for direct operation of the cordless device.
In the preferred embodiment of this invention, a corded converter 100, as
illustrated in circuit diagram form in FIG. 7, is housed within a
container 72 which, as illustrated in FIG. 4, is insertable into the
chamber 32 in a manner analogous to the battery pack 25. The container 72
has an exterior envelop that is substantially identical to the container
28 (FIG. 1) and is received within the chamber 32 of the handle 22 for
assembly with the drill 10. A power cord 74 and plug 76 extend from the
container 72 to facilitate connection of the power converter 100 to an
external power source. The power converter 100 includes a pair of output
terminals 78 and 80 (FIG. 4) that correspond in position and function to
the terminals 42 and 44 (FIGS. 2 and 6) of the container 28.
The power converter 100 is described in the afore-referenced U.S. patent
application Ser. No. (Black & Decker Case 4787), filed on even date
herewith and entitled "Voltage Converter," the disclosure of which is
incorporated herein by reference thereto. The converter 100 is designed to
convert either a high AC voltage, or a high level DC voltage, to a lower
level DC voltage. For example, the converter 100 can convert an input of
120 volts, 60 Hz AC to any low-level DC voltage required by the motor 16
such as, for example, 12 volts or 24 volts DC. In addition, the converter
100 can convert a high-level DC voltage to a low-level DC voltage, for
example, 150 volts DC to 12 volts DC.
As illustrated in FIG. 7, the voltage converter 100 includes a bridge
rectifier 102 formed by diodes 104, 106, 108, and 110. The plug 76 is
connected to the bridge rectifier 102 and is connectable to a conventional
AC source, which supplies, for example, 120 volts at 60 Hz. In this
instance, the AC source functions as a primary power source for the
voltage converter 100. The output of the rectifier 102 is applied between
a ground reference line 114 and a line 116. The rectified output is
filtered by a capacitor 118 to thereby provide 150 volts DC between the
lines 114 and 116. As an alternate to the AC power source, the lines 114
and 116 can be connected directly to a DC voltage source of 150 volts that
would then be converted to the low voltage required for the drill 10 | | |
