U.S. patent number 3,753,076 [Application Number 05/248,035] was granted by the patent office on 1973-08-14 for inverter circuit and switching means.
Invention is credited to William B. Zelina.
United States Patent |
3,753,076 |
Zelina |
August 14, 1973 |
INVERTER CIRCUIT AND SWITCHING MEANS
Abstract
An inverter suitable for use as a fluorescent light ballast is
disclosed. The inverter has a constant output regardless of load.
Good efficiency at high frequency is provided by minimizing the
transistor switching losses by means of a resonant storage means
and a unique feedback and magnetic structure.
Inventors: |
Zelina; William B. (Edinboro,
PA) |
Family
ID: |
22937382 |
Appl.
No.: |
05/248,035 |
Filed: |
April 27, 1972 |
Current U.S.
Class: |
363/133;
200/11DA; 315/DIG.1; 315/219; 363/97 |
Current CPC
Class: |
H05B
41/295 (20130101); H02M 7/53835 (20130101); Y02B
70/10 (20130101); Y02B 70/1441 (20130101); Y10S
315/01 (20130101) |
Current International
Class: |
H02M
7/5383 (20060101); H05B 41/295 (20060101); H05B
41/28 (20060101); H02m 007/52 () |
Field of
Search: |
;200/11DA ;321/45R
;323/48 ;315/DIG.2,DIG.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Shoop, Jr.; William M.
Claims
I claim:
1. An inverter circuit comprising
magnetic load means,
electrical load means,
first excitation means,
second excitation means,
feedback means,
electrical valve means,
resonant energy storage capacitor means,
a source of direct current voltage,
first electrical means connecting said source of direct current
voltage through said electrical valve means to said first
excitation means,
a magnetic member having first magnetic means, second magnetic
means, and third magnetic means,
said first magnetic means connecting said first excitation means to
said magnetic load means,
second electrical means connecting said magnetic load means to said
electrical load means,
said second magnetic coupling means having an air gap coupling said
first excitation means to said second excitation means,
third electrical means connecting said second exitation means to
said resonant energy storage capacitor means,
fourth electrical means connecting said resonant energy storage
capacitor to said magnetic load means,
fifth electrical means connecting said feedback means to said
electrical valve means,
said third magnetic means connecting said second excitation means
to said feedback means,
fourth magnetic means having an air gap connecting said second
excitation means to said magnetic load means,
said feedback means being so coupled to said energy storage means
that said resonant frequency will be maintained for all values of
said electrical load means.
2. The circuit recited in claim 1 wherein said first, said second,
said third, and said fourth magnetic means comprise a transformer
having a first leg, a second leg, and a third leg,
magnetic means connecting said second leg and said third leg
together,
said first leg having a first end and a second end,
said first end of said first leg being connected to said magnetic
means,
said second end of said first leg being separated from said
magnetic means by an air gap,
said second excitation means and said feedback means comprising
windings wound on said first leg,
said first excitation means and said load means comprising windings
wound on said second leg and said third leg respectively.
3. The circuit recited in claim 1 wherein said first leg is
disposed between said second leg and said third leg.
4. The circuit recited in claim 1 wherein said magnetic load means
includes a single winding around said third leg.
5. An inverter comprising,
a source of direct current voltage,
a transformer,
said transformer having a plurality of windings comprising a
magnetic load winding, a first excitation winding, a second
excitation winding, and a feedback winding,
an electric valve having a control element,
said source of direct current voltage being connected to said first
excitation winding through said valve,
said feedback winding being connected to said control element on
said valve for controlling said valve whereby the energy to said
first excitation winding is controlled,
said transformer having a continuous magnetic path,
a first leg having a first end and a second end,
said first end of said first leg being connected to said continuous
magnetic path and an air gap between the said second end of said
first leg and said magnetic path,
said first excitation winding and said magnetic load winding being
wound around said continuous magnetic path,
said secound excitation winding and said feedback winding being
wound on said first leg.
6. An inverter comprising
an electrical load,
a source of direct current,
a transformer having a closed magnetic circuit and a leg connected
to said magnetic circuit at one end, and its other end spaced from
said closed magnetic circuit forming an air gap between the second
end of said leg and said closed magnetic circuit,
means for connecting said electrical load to said transformer,
valve means for connecting said source of direct current to said
transformer,
feedback means comprising said leg for controlling the flow of said
current through said valve,
said feedback means adapted to switch said valve means when current
through said valve means reaches substantially a minimum value,
and resonant means connected to said transformer for controlling
the output of said transformer to said electrical load.
7. An inverter comprising
an electrical load,
a source of direct current,
a transformer having a closed magnetic circuit and a leg connected
to said magnetic circuit at one end, and its other end spaced from
said closed magnetic circuit forming an air gap between the second
end of said leg and said closed magnetic circuit,
means for connecting said electrical load to said transformer,
valve means for connecting said source of direct current to said
transformer,
feedback means comprising said leg for controlling the flow of said
current through said valve,
said feedback means adapted to switch said valve means when current
through said valve means reaches substantially a minimum value,
and resonant means connected to said transformer for controlling
the output of said transformer to said electrical load,
said transformer has a first, a second, and a third leg comprising
a continuous magnetic path, and a primary winding on said
continuous path,
said primary winding being connected to said electrical valve,
said means connecting said electrical load to said t-ansformer
comprising a winding on said third leg.
8. The inverter recited in claim 7 wherein said magnetic load
comprises a plurality of load winding on said magnetic circuit.
9. The inverter recited in claim 8 wherein said electrical load
comprises fluorescent lamps having heaters,
and said load windings are connected in series with said
heaters.
10. The inverter recited in claim 5 wherein a second valve is
provided in said circuit,
and a second feedback means controls said second valve, controlling
the flow of current through said lamps.
11. The inverter recited in claim 5 wherein a second valve is
provided in said circuit,
and a second transformer winding connected in series with said
valve for controlling current through said circuit on half-cycles
other than those controlled by said first mentioned valve
means.
12. In combination, a switch and an electrical circuit
comprising
a chassis having a flat surface having a printed circuit board,
a switch body having a relatively flat surface,
a plurality of conductor elements,
said conductor elements being supported on a first side of said
board,
a plurality of circuit members supported on said board on a second
side of said board,
means movably supporting said switch body on said first side of
said board,
brushes on the side of said switch body adjacent said chassis and
adapted to engage said circuit members to selectively connect
predetermined members together at predetermined positions of said
switch body whereby predetermined circuits are established among
said circuit members when said switch body is moved to a
predetermined position,
said means movably supporting said switch body on said chassis
comprises a hole formed in said chassis,
a boss on said switch body extending into said hole,
at least one elongated wire spring means having a first end and a
second end fixed to said chassis at said first end and selectively
engaging notches in said switch body at its said second end whereby
said body is stopped at said predetermined positions relative to
said conductor members.
13. The combination recited in claim 12 wherein said circuit
members are arranged in concentric patterns around said hole in
said chassis.
14. An inverter circuit for lamps having filaments and requiring
starting voltage and running voltage comprising,
a magnetic means comprising a magnetic circuit having a plurality
of magnetic paths therein,
one of said paths including an air gap,
feedback winding means on said magnetic path having said air
gap,
said magnetic means having a first load winding means and a second
load winding means,
a lamp having a filament,
said second load winding means being connected to said filaments
for supplying heating voltage thereto,
said first load winding means being connected to said lamp to
supply starting and running voltage thereto,
said running voltage being lower than said starting voltage,
said circuit having means adapted to control said voltages so that
said filament voltage is reduced when said load winding is
supplying running voltage.
15. An inverter circuit for lamps having filaments and requiring
starting voltage and running voltage comprising,
a magnetic means,
said magnetic means having a first magnetic load winding means and
a second magnetic load winding means,
a lamp having a filament,
said second magnetic load winding means being connected to said
filaments for supplying heating voltage thereto,
said first magnetic load winding means being connected to said lamp
to supply starting and running voltage thereto,
said running voltage being lower than said starting voltage,
said circuit having means adapted to control said voltages so that
said filament voltage is reduced when said load winding is
supplying running voltage,
said filament voltage is reduced by the ratio of said starting
voltage to said running voltage.
16. The circuit recited in claim 15 wherein said first winding is
connected to a resonant energy storage circuit.
17. The circuit recited in claim 15 wherein said magnetic means
comprises a transformer having a closed magnetic circuit and a
first leg connected to said closed magnetic circuit through an air
gap.
18. The circuit recited in claim 16 wherein said closed magnetic
circuit has a second leg and a third leg
said first leg being disposed between said second leg and said
third leg,
said first magnetic load winding and said second magnetic load
winding are supported on said third leg.
19. The circuit recited in claim 1 wherein said circuit has means
to control the output of said circuit to a substantially constant
value independent of the load connected to said circuit.
20. In combination, a printed circuit, a switch, and an inverter
circuit for a lamp,
a support means having a flat surface,
said printed circuit comprising a plurality of spaced conductor
members on said flat surface,
an electrical load comprising said lamp,
said inverter comprising a source of direct current,
a transformer,
means for connecting said electrical load to said transformer,
valve means for connecting said source of direct current to said
transformer,
feedback means connected to said transformer for controlling the
flow of said current through said valve,
said feedback means adapted to switch said valve means when current
through said valve means reaches substantially a minimum value,
and resonant means connected to said transformer for controlling
the output of said transformer to said electrical load,
said printed circuit spaced conductor members each being connected
to a part of said inverter circuit,
means movably supporting said switch on said flat surface,
brushes on the side of said switch adjacent said flat surface and
adapted to engage said circuit members to selectively connect
predetermined members together at predetermined positions of said
switch whereby predetermined circuits are established among said
circuit members when said switch is moved to a predetermined
position,
said movable member being supported on said flat surface and
adapted to connect predetermined said conductors together to
connect and disconnect said load from said source of power.
21. The combination recited in claim 20 wherein said movable means
is adapted to be moved to an on position and off position and a
charge position,
said movable member disconnecting said inverter circuit from said
source of power and connecting said source of power to a charging
source when said movable member is moved to said charge
position.
22. The combination recited in claim 20 wherein said movable member
is movable to an on position and an off position,
said movable member being adapted to connect predetermined of said
conductor members together in said on position and connecting said
source of power to said inverter circuit.
23. The combination recited in claim 20 wherein said movable member
is adapted to connect predetermined of said conductors together to
short-out said magnetic load means and to connect heaters on said
lamp in series with each other when said switch is in said start
position.
Description
BACKGROUND OF INVENTION
Almost since the invention of the transistor, those skilled in the
art have used it as a switching means in inverter systems to effect
AC power from a DC source. It is well recognized by those skilled
in the art that the switching loss of the transistor becomes a
critical limiting factor, particularly as the operating frequency
is raised. The ideal solution to the switching loss problem is well
recognized as some circuit means to reduce the level of current
that must be switched to as low a value as possible prior to the
time that actual switching occurs. This is true since switching
loss is represented by the instantaneous product of the voltage
across the switch and the current through it. Therefore, minimum
switching loss will be realized when zero current switching can be
made practical. Further, the high instantaneous power represented
by the product of voltage and current during switching can cause
the transistor to lose its voltage blocking capability (secondary
breakdown) and, thereby, be destroyed. So, in addition to operating
efficiency, zero current switching makes possible higher system
reliability through the elimination of the secondary breakdown
phenomena.
High frequency power has many applications, one of which is the
operation of fluorescent lamps. Here the high frequency provides
about 10 to 15 percent more lumens per lamp watt as compared to 60
HZ operation. Also, by setting the operating frequency higher than
20,000 HZ, the audible noise common to lower frequency is
eliminated. Also, in application where size and weight is important
such as transportation vehicle lighting, the high frequency makes
possible impressive gains. For the above described advantages of
high frequency operation to be realized, the solution of the
transistor switching loss must be effected.
Also, the fluorescent lamp, being of a gas ionization type,
requires a high voltage to start the lamp and a much lower
operating voltage. The lamp current must be limited to the safe
design value for good lamp life and to prevent over loading of the
inverter. Combining this current limiting characteristic into the
inverter would make possible an inverter ballast suitable for the
direct operation of fluorescent lamps from DC voltage sources. The
fluorescent lamp life is sensitive to the form factor of the
current through the lamp. For this reason, a suitable inverter
ballast should have a minimum of harmonic content in its
output.
GENERAL DESCRIPTION OF THE INVENTION
A circuit arrangement has been demonstrated that uses feedback
means to always maintain the operating frequency at resonance. The
magnetic-semiconductor combination, more completely described
later, utilizes the energy stored in the system resonance to reduce
the input current through the switching elements to near zero
during switching. Since feedback is utilized to maintain the
resonant frequency, good operating stability results for all
conditions. Minor variations of component values with temperature
and time is automatically compensated for by a corresponding minor
change in the operating frequency. The use of ferrite core material
and the above low loss switching make practical very high operating
efficiency at frequencies in the 20 to 30 KHZ range. Efficiencies
of 88 percent have been demonstrated on units delivering 80 watts
of output power. The output current, at a given input operating
voltage, is set by the frequency of operation and the value of
capacitor used in the resonant circuit. Because of the resonant
operation, the harmonics in the output current are maintained at a
low value.
OBJECTS OF THE INVENTION
It is an object of the invention to provide an improved inverter
circuit.
Another object of the invention is to provide an improved inverter
circuit suitable for use as a fluorescent light ballast.
Another object of the invention is to provide an inverter circuit
that is simple in construction, economical to manufacture, and
simple and efficient to use.
With the above and other objects in view, the present invention
consists of the combination and arrangement of parts hereinafter
more fully described, illustrated in the accompanying drawings and
more particularly pointed out in the appended claims, it being
understood that changes may be made in the form, size, proportions,
and minor details of construction without departing from the spirit
or sacrificing any of the advantages of the invention.
GENERAL DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of one embodiment of the
invention.
FIG. 2A shows wave forms of the primary voltage which occurs when
the output load of the circuit is short-circuited.
FIG. 2B shows a wave form of the current into the inverter when the
output load is short-circuited.
FIG. 2C shows a wave form of the voltage and current into the
center leg of the circuit when the output load is
short-circuited.
FIG. 3A shows the primary voltage wave form for the operating
condition with the inverter ballast providing current to
fluorescent lamps.
FIG. 3B shows the primary current when the inverter ballast is
supplying two fluorescent lamps.
FIG. 3C shows a wave form of the voltage and current in the center
leg of the magnetic winding 13-14 when the inverter ballast is
supplying current to two fluorescent lamps.
FIG. 4 is the wave form which occurs with normal load as in FIG.
3A, in an actual test.
FIG. 5 is a wave form by the voltage 13-14 as in FIG. 3B during an
actual test.
FIG. 6 is an actual wave form of the voltage and current into the
center leg of the circuit.
FIG. 7 is an actual wave form similar to FIGS. 2B and 2C.
FIG. 8 is a schematic view of the magnetic member used in the
embodiment of FIG. 1.
FIG. 9A is a schematic diagram of another embodiment of the
invention.
FIG. 9B is a schematic view of the magnetic member used in the
embodiment of FIG. 9A.
FIG. 10 is a block diagram of the circuits according to the
invention.
FIG. 11 is an isometric bottom view of the chassis with the switch
parts exploded for better understanding.
FIG. 12 is a bottom view of the switch.
DETAILED DESCRIPTION OF THE DRAWINGS
A description of the system operation will be made with reference
to FIG. 1, which shows schematically one such system operating two
40 watt rapid start fluorescent lamps from a DC voltage source.
FIG. 8 shows the magnetic structure and the location and relative
directions of the windings shown schematically in FIG. 1. Rectifier
diode RD6 is simply used to prevent damage in the event that
reverse voltage is applied to the system. Capacitor C1 provides
input voltage filtering to prevent any damaging voltage transient
from affecting the system. Capacitor C2, which is a much smaller
value, provides an energy storage arrangement capable of accepting
energy returned from the system. This phenomenon will be more
completely described later.
Resistor R2 provides a small turn-on current for both transistor T1
and T2 to assure reliable starting of the inverter.
This particular inverter ballast was designed to operate under a
voltage range of 25 volts to 45 volts and for that reason,
transistor T3, Resistor R1, rectifying diode RD1 and RD7, and
resistor R3 comprise a constant current regulating means to assure
an adequate feedback signal for transistor T1 and T2 at the 25 volt
operating point, while preventing an excessive feedback current for
the 45 volt operating point. If the inverter ballast design were to
operate at a single nominal voltage, then this regulating circuit
could be replaced by a single limiting resistor. Capacitor C4
provides a lead function in the feedback, thereby compensating for
the delay and storage times that are inherent in all transistors.
Feedback current is provided alternately by winding 5-6 for
transistor T1 and then winding 7-8 for transistor T2. Capacitor C3
and the very small inductor L1 serve to limit induced voltage
transients in the primary winding due to the leakage reactance of
the primary windings.
Winding 11-12 is connected in series aiding to winding 13-14 and
these windings are closed through a capacitor C6 to form a loop
circuit. It is this loop circuit that is maintained in resonance
and provides the desirable low-loss switching previously described.
Note that the primary windings 1-2 and 3-4 are wound on the outer
leg P of the E-Core in FIG. 8. Also, that winding 13-14 and the
feedback windings 5-6 and 7-8 are wound on the center leg (C) while
the winding 11-12 is wound on the other outer leg (S). Further,
that an air gap G is provided in series with the center leg.
Windings A-A, B-B, and C-C are filament heater windings to heat the
fluorescent lamp filaments. These windings are also wound on the
secondary leg S. Certain inherent advantages of having these
filament heater windings located as shown will be later
described.
Capacitor C5 is selected relatively large for the operating
frequency being used so that it will present negligible A-C
impedance. Its function, however, is very important when the
fluorescent lamps comprise the inverter load. The reason for this
is as follows:
The fluorescent lamp conducts current by the emission of electrons
from the respective cathodes at the lamp ends. If for some reason
the active material becomes depleted on one of the lamp ends, the
lamp will continue to conduct current in one direction, but will
not conduct in the other; and, in effect, will impose a half-wave
rectified load on the inverter. The inverter operation is adversely
affected by such operation and hence, capacitor C5 prevents such
operation by preventing any DC component of current from flowing
through the inverter load. Capacitor C8 provides a limit of output
voltage which otherwise could reach a damaging value when either
the lamp loads are disconnected or the lamps are so damaged as to
present an open circuit to the inverter.
Consider a single half-cycle of inverter operation as the inverter
is operating. Certain early-cycle transients occur during inverter
start-up that are not important to the system operation; and, for
that reason, the explanation will assume that the inverter is
already operating.
Transistor T1 is turned on by the feedback voltage on winding 5-6
causing current to flow through the base of transistor T1 out of
its emitter through the previously described current limiting
circuit through rectifier diode RD3 and back to the feedback
winding. The transistor T1 is now completely turned-on and current
flow is from the voltage source through rectifying diode RD6 and
into the primary winding 1-2 through the collector to emitter of
transistor T1 and back to the negative of the voltage source. The
winding convention utilized is such that all of the dotted winding
ends will experience a positive induced voltage at the same
instant. Therefore, the terminal 13 of winding 13-14 will be
positive and the terminal 11 of winding 11-12 will be positive and
a current will flow to charge capacitor C6 around the loop
comprising winding 13-14, 11-12 and the capacitor C6 and current
will also flow to charge capacitor C8 and to provide the load
current through lamp No. 2, lamp No. 1 and capacitor C5. Note that
the feedback windings 5-6 and 7-8, being wound on the center leg,
experience the same rate of change of flux or induced voltage per
turn that is experienced by winding 13-14. Then, that by circuit
design, transistor T1 will be switched off and T2 will be switched
on when a reversal in the induced voltage of winding 13-14 is
experienced. The induced voltage in winding 13-14 will be zero when
the rate of change of flux through the center leg is zero and that
occurs when the flux density in the center leg is at its maximum
value and when the current through winding 13-14 reaches a peak
value. Current flowing in winding 13-14 leads the voltage induced
in 13-14 by 90.degree. and reaches a peak value when the
transistors T1 and T2 are switched. If the previously described
desirable operation of transistor switching at minimum or zero
current are to be realized, the primary windings must be rendered
as non-current receptive at this time due to the operation of some
energy storing means in the system. Referring to the wave shapes of
FIGS. 2A, 2B and 2C, which occur for the special case of a
short-circuit on the output load, the primary voltage is shown in
FIG. 2A, the current supplied to the inverter in FIG. 2B, and the
wave shapes of the center leg winding 13-14 and its associated
capacitor C6 are shown in FIG. 2C. For the time period A-B of FIG.
2B current is flowing into the inverter and for the period B-C is
is flowing out of the inverter. The difference in these two values
of current is simply the short circuit loss of the inverter. That
is, since the load is short-circuited, it cannot absorb any power;
hence, during each half cycle, energy accepted by the inverter
during the beginning of the half cycle will be returned to the
source during the end of the half cycle less any system loss.
Referring to FIG. 2C, for the time period A-B, current is flowing
out of winding 13-14 and for the period B-C current is actually
flowing in the opposite direction or into winding 13-14. By
transformer action, the current into winding 13-14 makes the
induced voltage in the primary winding 1-2 go 1 positive, with
respect to 2 transferring this energy back into the source.
Previously the function of C2 was described. It is the type of
circuit operation which requires C2 so that the current flowing out
of the inverter will experience a receptive source. Similar
operation is repeated in the following half-cycle, except with the
complimentary portions of the circuit. The reason for studying the
special case of the shorted output condition now becomes clear. We
have shown that this system arrangement makes possible energy
storage during the first portion of each half cycle which can then
be either returned to the source if the load is non-receptive or
used to satisfy load and system loss requirements during normal
operation (output not shorted, hence, receptive load) during the
latter or switching portion of the cycle, thus rendering the
current to be switched to a low or zero or negative value.
With reference to the schematic circuit of FIG. 1, the wave shapes
shown in FIGS. 3A, 3B, and 3C illustrate the operating condition
where the inverter ballast is working into the two fluorescent
lamps as shown. The primary voltage wave form is shown in FIG. 3A.
It looks much like the case where the inverter was operating into a
short circuit. Notice, however, that the input current into the
inverter shown in FIG. 3B changes from the large value negative of
3A to very near zero at the time that the inverter switches. It is
this desirable near zero current switching that makes the high
frequency and efficiency operation possible. To further develop a
physical picture of this operating phenomena, refer to FIG. 3C
which shows the voltage induced in winding 13-14, the voltage
experienced by capacitor C6 and the current through the combination
of winding 13-14 and C6. Again we see that the current is leading
the voltage of winding 13-14 and in that portion of the cycle just
prior to switching this current reverse polarity, and in effect is
flowing into winding terminal 13 of schematic FIG. 1. Unlike the
short circuit operation previously described and demonstrated in
FIG. 2A, 2B and 2C, a load voltage is actually impressed on winding
11-12. The instantaneous polarity of the 11-12 winding and 13-14
winding as shown in FIG. 1A is such that when current is flowing
into the dotted winding terminal 13 it is also flowing into the
dotted winding terminal 11, thereby reflecting by transformer
action an increase in the induced voltage of primary 1-2 in such a
manner that it becomes less receptive for current from the source
thereby causing the input current to reduce toward zero. Compare
the input current wave shapes shown in FIGS. 2B and 3B. Remember
that the input current wave shape of FIG. 2B was for the case when
the output was shorted, thereby no power was transmitted to the
load, hence all input power not consumed in inverter losses had
been transformed back to the source during the latter portion of
each cycle. For the wave shape of FIG. 3B on the other hand, where
the load now constitutes 80 watts of fluorescent lamp, now that no
current is being transformed back to the source. One should
intuitively deduct, then, that for every design the ideal of zero
current switching will occur at a given output load and for all
load less than this value, current will be transformed back to the
source and conversely for all loads greater than this value the
actual switching will occur at a positive value of current. This,
in fact, is the demonstrated characteristic of the inverter
circuitry.
FIG. 6 shows an actual curve that corresponds to FIG. 2C, and FIG.
7 shows an actual curve for FIGS. 2A and 2B with the voltage wave
forms V13-14 of FIG. 2B all superimposed. The curve of FIG. 4
corresponds to FIG. 3C, and the curve of FIG. 5 corresponds to
FIGS. 3A, 3B and the voltage wave form V13-14 of FIG. 3C all
super-imposed. The difference in these curves should be noted:
Where FIGS. 2B and 3B show the input current for the entire cycle,
the curves were taken from actual wave shapes and were taken with
the input current of only a half current, however, that current
simply repeats itself in the following half cycle.
A schematic diagram of another embodiment of the invention combined
with unique switching arrangements and dual function battery
chargers is shown in FIG. 9A. A storage battery is used to power an
inverter circuit used in a portable lighting means. FIG. 9A shows
transformer X1 with rectifying diodes RD1 and RD2 with suitable
switching means so that the storage battery can be charged when S1
is connected to S2. By alternately connecting a 12 volt DC source
between terminals marked 7 and 2, and disconnecting the AC supply
to transformer X1; the battery can be charged through an 8 ohm
ballast resistor, and the previously mentioned switch arrangement.
If desired, an AC supply external battery can be used rather than
consuming energy from the 8 volt internal battery made possible by
the following switching arrangements: S1 may be connected to S2, S2
may be connected to S3, and the appropriate either AC supply or
external battery connection may be made. Capacitor C3' corresponds
to capacitor C6 of FIG. 1 and can be paralleled by capacitor C4'
through switching arrangement S8 to S9. With S8 connected to S9 the
inverter ballast will deliver increased power to the fluorescent
tube. Therefore, this arrangement provides for a dim or bright
operation of the fluorescent lantern making possible two light
levels and also longer portable lighting for the dim position.
While the arrangement of FIG. 1 uses the rapid start lamp wherein
the filament windings are continuously energized, for battery power
conservation reasons the electric lantern uses only a momentary
pre-heat of the fluorescent tube filament. This is accomplished by
the connection of points S6 and S7 and points S4 and S5, therefore
the fluorescent lighting system schematic depicted in FIG. 9A
requires a multitude of switching function combined with both DC
and AC charging means to effect an efficient portable lighting
means capable of either external DC operation, external AC
operation, DC voltage source re-charging, AC voltage source
re-charging, dim operation, bright operation, and lamp pre-heat
capability. By suitable printed circuit structuring combined with a
rotary index switch all of the aforedescribed switching functions
are performed directly on the printed circuit board, therefore
allowing an economical solution of the problem. The peculiar
combination of the inverter ballast, the internal battery source,
the AC charging means, the DC charging means, and the integral
switching means constitute a novel solution to this problem.
In FIG. 10, a block diagram shows how the components of the circuit
cooperate. The source is indicated as a battery which is
electrically connected through the transistors T1 and T2 which are
referred to as electric valves. These vales are electrically
connected to the first excitation means, referred to as winding
1-2. The winding 1-2 is magnetically connected through the magnetic
core H, to the magnetic load means referred to as windings 11-12,
A-A, B-B and C-C.
The electric load means which is lamps L1 and L2 in FIG. 1, and
lamp FL in FIG. 9A, are electrically connected to the resonant
storage capacitor C2 in the embodiment of FIG. 1 and is capacitors
C3' and C4' in the embodiment of FIG. 9A.
The resonant energy storage capacitor is electrically connected to
the second excitation means which is the winding 13-14, as shown.
The second excitation means is magnetically connected through the
air gap G to the magnetic load means, winding 11-12. The feedback
means is made up of winding 5-6 and is electrically connected to
the transistors T1 and T2 and magnetically connected through the
magnetic member H to the winding 13-14.
It will be noted in FIG. 8 that the windings 1-2 and 3-4 are wound
in the same direction around the leg P. The windings 5-6, 7-8, and
13-14 are wound in the same direction around the central leg C of
the core H. The windings A-A, B-B, C-C and 11-12 are wound in the
same direction around the leg S. The air gap indicated at G is of a
critical magnitude and for purposes of this application, a proper
gap has been found to be approximately 0.020 inches.
The magnetic core H has the bar B which closes the outer legs P, S
and forms a magnetic circuit through the bar B and through the
legs. Central leg C is integral with the core H and has the air gap
G between the central leg C and the bar B.
In the embodiment of the invention shown in FIG. 9B, the gap G' and
the E-frame H' is generally similar to the corresponding numbers in
FIG. 8. The windings have corresponding numbers as shown on both
the magnetic member and in the circuit.
The switches S2 and S3 in FIG. 9A are for the purpose of connecting
the battery to the lighting circuit. The switch S1 is for the
purpose of connecting the AC supply indicated at X1 to a suitable
power line through the terminals 1-3. The battery K is indicated as
an automobile battery or other auxiliary source of battery and it
may be used instead of the internal battery J in FIG. 9A. Thus
there may be three alternate sources of power for the embodiment
shown in FIGS. 9A-9B; namely, the internal battery J, the external
battery K, or the AC source X1.
The tube L-1' is started by closing switches 6-7 and 8-9 and switch
2-3 with the internal battery J connected. This will connect a
voltage through the heaters of tube L-1' and heat them. When the
switches 6-7 and 4-5 are opened, the power will flow through from
the battery J to the tube in the manner described above.
The following table shows the several parts of the block diagram
FIG. 10:
BLOCKS OF DIAGRAM
Embodiment of Embodiment of FIG. 1 & 8 FIG. 9A & 9B
Electrical load means L1-L2 L1' Magnetic load Windings 11-12,
11'-12' A--A, B--B, C--C First excitation means Winding 1-2 Winding
1'-2' Second excitation means Winding 13-14 Winding 13'-14'
Feedback means Winding 5-6 Winding 5'-6' Electric valve T1, T2 T1',
T2' Resonant energy storage C6 C3', C4' capacitor Source of power
Battery J Battery J Magnetic means Core H Core H' Magnetic means
with Gap G Gap G' air gap
FIG. 11 shows a printed circuit board with the circuit according to
the invention built on it, together with an integral switch. The
board 39 supports the circuit components; for example, transformer,
transistors, resistors, and capacitor, and the other electronic
components of the circuit. The end of the board remote from the
switch body 40 may have the terminals best shown in FIG. 11. The
switch body or disk 40 has a boss 41 which is received in the hole
42 in the board and the switch disk has the wiper brushes 31, 32
and 33 which are in the form of leaf springs having wiper contacts
on the ends which connect between the arcuate contacts that
surround the opening 42 and are connected to the various conductors
on the bottom of the board 39. A handle 50 is connected to the
switch to move the switch to its normal positions.
The outer periphery of the body disk 40 has notches 44 which
receive the curved ends of springs 45 and 46. The springs 45 and 46
stop the disk at any one of several selected positions so that the
switch brushes 31, 32 and 33 engage the proper conductors 47
thereby forming the connections at S1, S2, S3, S4, S5, S6, S7, S8,
and S9. When the members 51 and 52 on handle 50 engage in the slots
38, 43, and 48, the switch disk can be rotated to the proper
position to close circuits at the respective positions S1-S9; when
the switch handle is in the desired position, the ends 55 of
springs 45 and 46 are resiliently received in slots 57 in board
39.
The switch may be moved to the following positions to carry out the
several functions of the circuit: (1) charge, (2) off, (3) start,
(4) dim, (5) bright. The position of the contacts on the switch
when the switch is moved to positions 1 through 5, is as outlined
below:
1. "Charge" position; S1 to S2 & S2 to S3 are closed, S4
through S9 are open.
2. "Off" position; S1 through S9 are all open.
3. "Start" position; S2 to S3, S4 to S5 & S6 to S7 are closed;
S1, S8 and S9 are open.
4. "Dim" position; move S1 to S2 and S2 to S3 are closed, S4
through S9 are open.
5. "Bright" position; S1 to S2, S2 to S3 & S8 to S9 are closed;
S4 through S7 are open.
The above contact positions of the switches are accomplished by
simply rotating the switch disk 40 through the positions numbered 1
to 5 above.
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