U.S. patent number 3,764,849 [Application Number 05/237,806] was granted by the patent office on 1973-10-09 for electronic flash charging and triggering circuitry.
Invention is credited to Yoshiharu Ohta.
United States Patent |
3,764,849 |
Ohta |
October 9, 1973 |
ELECTRONIC FLASH CHARGING AND TRIGGERING CIRCUITRY
Abstract
A charging and triggering circuit for an electronic flash device
of the type in which a voltage for triggering the flash is stored
by a condenser comprises structure for generating a feedback signal
in response to the triggering of the flash tube to actuate an
oscillating circuit for charging the condenser with the rectified
oscillatory output. A circuit disables the oscillator when the
condenser has reached a voltage sufficient to actuate the flash
tube thereby reducing the power consumed from a battery which
energizes the circuitry.
Inventors: |
Ohta; Yoshiharu (Hyogo-ken,
Kawanishi, JA) |
Family
ID: |
22895269 |
Appl.
No.: |
05/237,806 |
Filed: |
March 24, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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30828 |
Apr 22, 1970 |
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Current U.S.
Class: |
315/241P;
315/241R; 331/173; 331/112 |
Current CPC
Class: |
H05B
41/32 (20130101) |
Current International
Class: |
H05B
41/32 (20060101); H05B 41/30 (20060101); H05b
037/00 () |
Field of
Search: |
;315/241P,241R
;331/113A |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lake; Roy
Assistant Examiner: Dahl; Lawrence J.
Parent Case Text
This is a continuation of application Serial No. 30,828, filed Apr.
22, 1970, now abandoned.
Claims
I claim:
1. A charging and triggering circuit for an electronic flash device
comprising:
an electric power source;
a transformer connected to said power source and including a
winding for generating an oscillatory output;
means for rectifying said oscillatory output;
a flash circuit including means for storing the rectified output of
said rectifying means, a flash tube, said transformer including
primary and secondary windings for triggering said flash tube, and
said transformer further including an additional winding for
generating a feedback signal in response to the triggering of said
flash tube; and
means for controlling said oscillating means including an SCR
having its gate connected to said additional winding to be made
conductive by said feedback signal to oscillate said oscillating
means, and said SCR is made non-conductive with said means for
storing at a voltage sufficient to actuate said flash tube whereby
said oscillating means are de-actuated.
2. A circuit as in claim 1 further comprising means for initiating
the operation of said transformer for generating an oscillatory
output.
3. A circuit as in claim 2 further comprising means for maintaining
said SCR conductive at all operating frequencies of said
transformer during charging of said means for storing.
4. A circuit as in claim 2 wherein said flash circuit further
includes means for indicating the condition of said means for
storing and means interconnecting said indicating means with said
SCR, whereby said SCR is inoperative to actuate said transformer
with the actuation of said means for indicating and are operative
with said means for indicating non-conductive to actuate said
transformer.
5. A circuit as in claim 3 wherein said means for maintaining
conduction of said SCR at all frequencies is a capacitor connected
across said SCR.
6. A circuit as in claim 1 further comprising means for indicating
that said means for storing is at a voltage sufficient to actuate
said flash tube.
7. A circuit as in claim 4 wherein said means for indicating is
parallelly connected with said transformer, said means for
initiating operation of said transformer comprising a manually
operated switch interconnecting the gate of said SCR to said power
source, and further comprising a circuit interconnecting said gate
with said means for indicating.
Description
BACKGROUND OF THE INVENTION
In flash discharge equipment wherein a battery is used as a power
source, in order to miniaturize and lighten the equipment battery
of a small volume and capacity is generally used, so that if for
example the power switch is left closed, the battery is wasted on
account of the leakage current running through the condenser for
lighting the flash discharge tube in the secondary high voltage
circuit and the current running through the oscillator in the
primary circuit.
SUMMARY OF THE INVENTION
The present invention relates to electronic flash equipment of the
type using an oscillator operated by a battery and a circuit for
charging a condenser for lighting a flash discharge tube by
boosting and rectifying the output from the oscillator. A power
switch connected between a power source and the oscillator
initially actuates a SCR to energize the oscillator and charge the
condenser. The current running through the SCR is eventually
reduced below its holding current when the condenser for lighting
the flash discharge tube is charged.
The first object of the present invention is to provide electronic
flash circuitry wherein the power source battery consumption is
considerably reduced, by opening automatically a power switch when
the charging condenser for lighting a flash discharge tube is
substantially completed.
The second object of the present invention is to provide electronic
flash circuitry for recharging a condenser for lighting a flash
discharge tube by closing automatically a power switch when the
condenser is discharged after energizing the flash discharge
tube.
The third object of the present invention is to provide electronic
flash circuitry wherein a power switch is opened and closed
automatically so as to charge a condenser for lighting a flash
discharge tube within the limit of a constant voltage at all
times.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a circuit diagram of a first embodiment of the present
invention.
FIG. 2 is a graph showing the change in the charging current of a
condenser for lighting a flash discharge tube in the embodiment
shown in FIG. 1.
FIG. 3 is a circuit diagram of a second embodiment of the present
invention.
FIG. 4 is a graph showing the oscillating voltage characteristic of
the oscillator in the embodiment shown in FIG. 3.
FIG. 5 is a circuit diagram of the primary side oscillation circuit
of a modified embodiment provided with a circuit for holding the
conduction of the SCR in the second embodiment of the present
invention.
FIG. 6 is a circuit diagram of a third embodiment of the present
invention.
FIG. 7 is a circuit diagram of a fourth embodiment of the present
invention, which is arranged to maintain the charging voltage of a
condenser for lighting a flash discharge tube within the limit of a
constant voltage.
FIG. 8 is a graph showing the voltage of the trigger condenser
caused by the relaxation oscillation circuit in the embodiment
shown in FIG. 4.
FIG. 9 is a graph showing the charging voltage of the condenser for
lighting a flash discharge tube in the embodiment shown in FIG.
8.
FIG. 10 is a circuit diagram of a fifth embodiment of the present
invention .
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 is a circuit diagram of the first embodiment of the
electronic flash circuitry in accordance with the present
invention, wherein lighting circuit b is formed as follows. Flush
discharge tube 13, on which the voltage of condenser 8 for lighting
is impressed, is provided with trigger electrode 12 and when the
charging voltage of trigger condenser 9 is discharged to the
primary side of trigger transformer 11 by closing synchro switch 10
the secondary side voltage of trigger transformer 11 is impressed
on trigger electrode 12 to discharge condenser 8 for lighting flash
discharge tube 13, and accordingly lighting circuit b is
momentarily lit.
The charging of condenser 8 is effected by oscillator a wherein
transistor 3 is connected to the primary circuit of transformer 4,
and the secondary current of transformer 4 is rectified by diode 7.
And, to the base of transistor 3 there is connected the oscillation
circuit composed of resistance 5 and condenser 6 and the negative
side of power source battery 1 is connected to the collector of
transistor 3. The positive side of power source battery 1 is
connected to the emitter of transistor 3 through SCR 2.
A trigger circuit for the gate of SCR 2 is formed through
resistance 21. One part of the SCR trigger circuit is a series
circuit composed of battery 18 and normally open starting switch 19
and the other part is provided with rectifier 23 and one winding 20
coupled magnetically with trigger transformer 11.
In lighting circuit b, condenser 8 is connected in parallel with
indicating neon tube 17 connected in series to protective
resistance 16, and to both sides of trigger condenser 9 in parallel
with condenser 8 adjusting resistances 14, 15 are connected in
series with each other.
The gate of SCR 2 is connected to battery 18 by closing starting
switch 19 and thereby made conductive, and accordingly condenser 8
and trigger condenser 9 are charged through transistor 3,
transformer 4, and diode 7. As shown by curve m in FIG. 2, the
charging current decreases during the time required for increasing
of the charging voltage of conenser 8, and when the charging
voltage is sufficient to flash discharge tube 13, neon tube 17 for
indicating the conclusion of charging lights.
Meanwhile, when the charging current gets below a fixed value the
current running through the base of transistor 3 also decreases
gradually and at last drops down below the current value necessary
to hold SCR 2 in the conductive state, and accordingly SCR 2 is
turned off and the operation of the oscillator is automatically
stopped. That is, with condenser 8 and trigger condenser 9 charged
above the constant voltage necessary to light the flash discharge
tube, the circuits prevents power source battery 1 from wasting
current, and thus, even without opening manually the power
switch.
Next, when synchro switch 10 is closed, the high voltage is
impressed on trigger electrode 12, flash discharge tube 13 is lit,
and condenser 8 is discharged. However, in this case AC voltage is
induced in coil 20 which is one winding for trigger transformer 11
so that SCR 2 is turned on, oscillator a is connected to power
source 1, and condenser 8 is charged again. When condenser 8 is
charged to the constant voltage SCR 2 is shut off again as
described above.
Therefore, every time the flash is ignited condenser 8 is also
charged automatically and even when used repeatedly there is no
need for the manual opening and closing of the power switch.
With reference to FIG. 3, in order to initially effect the
conduction of SCR 2, while in the first embodiment battery 18 is
provided, in the second embodiment shown in FIG. 3 the positive
side of power source battery 1 is connected to the gate of SCR 2
through starting switch 19 and resistance 21 In all other respects
the second embodiment is essentially the same as the first
embodiment.
In the first and second embodiments, the time for the SCR to be
shut off from a conductive state is generally from 10 to 20
.mu.sec. Therefore, when the half period of oscillation frequency
shown by curve n in FIG. 4 is longer than that turn off time, the
SCR is shut off and the circuit does not operate as described
above. In order to make the half period shorter than the turn off
time, the oscillation frequency must be made above 25 KC, however,
in view of the conversion efficiency of a transistor oscillator the
suitable oscillation frequency should be below 5 KC.
In the embodiments mentioned above, therefore, it is necessary to
use a SCR having a long turn off time, or the oscillation frequency
must be increased.
In the modification of the second embodiment shown in FIG. 5 this
matter is solved, and between the base and emitter of transistor 3
of the oscillator, holding condenser 22 is connected in parallel
with SCR 2 so as to form a holding circuit. In this manner, even
though the oscillation frequency of oscillator a is low as compared
with the turn off time of SCR 2, in the conductive state condenser
22 is charged and the charging current is discharged during phase
to of the oscillator, so that SCR 2 is not shut off.
The third embodiment shown in FIG. 6 in accordance with the present
invention is an embodiment in which the base and collector of
transistor 3 are coupled with transformer 4. That is, the base of
transistor 3 is connected to a coil on the secondary side of
transformer 4, and the oscillation circuit composed of resistance 5
and condenser 6, and power source battery 1 are connected to the
emitter through SCR 2. And, the collector circuit of transistor 3
is connected to the negative side of power source battery 1 through
the coil on the primary side of transformer 4 and connected to one
electrode of condenser 8 from the coil on the secondary side of
transformer 4 through diode 7.
In every embodiment described above, when condenser 8 reaches a
substantially constant voltage SCR 2 shuts off the oscillation
circuit, so that in order to effect again the conduction of SCR 2
it is necessary to light flash discharge lamp 13 or close manually
starting switch 19.
However, after condenser 8 is charged once to the constant voltage,
even though flash discharge lamp 13 is not lit charging current is
discharged gradually through neon tube 17 for indicating the
charging condition, and on account of the internal leakage of
condenser 8 and trigger condenser 9 the charging voltage drops
gradually and at last gets below the voltage possible to light
flash discharge lamp 13. Therefore, as long as starting switch 19
is not closed flash discharge lamp 13 cannot be flashed.
The embodiments shown in FIGS. 7 and 10 remove such a drawback as
mentioned above, and when condenser 8 reaches a substantially
constant voltage, the SCR shuts off automatically the oscillator,
however, when the charging voltage drops below a certain voltage
the SCR is adapted to effect automatically the operation of the
oscillator so as to furnish charging current.
In the lighting circuit b shown in FIG. 7, there is connected in
parallel with condenser 8 trigger condenser 9 having on its both
sides respectively resistances 14 and 15, and in parallel with the
primary winding of trigger transformer 11 connected through the
synchro switch, there are series connected resistance 16' and neon
tube 17' for indicating the charging condition. The junction
between neon tube 17' and resistance 16' is connected to the gate
of SCR 2 together with the starting circuit, and relaxation
oscillator C is formed by condenser 8, trigger condenser 9, and
neon tube 17' and resistance 16'.
Therefore, after condenser 8 is charged, the appropriate charging
voltage is divided by resistances 14, 15 to charge trigger
condenser 9, however, the charging voltage of trigger condenser 9
is discharged gradually through neon tube 17' and resistance 16',
and the terminal voltage of trigger condenser 9 drops and neon tube
17' is extinguished. After that, condenser 9 is charged through
resistances 14, 15 by condenser 8 and neon tube 17' is lit
again.
In this manner, relaxation oscillation is repeated and while the
voltage of trigger condenser 9 is changing as shown by curve p in
FIG. 8 the charging voltage of condenser 8 also damps
gradually.
However, when neon tube 17' is lit the voltage drop in resistance
16' is fed to the gate of SCR 2, so that SCR 2 is turned on to
replenish charging to condenser 8. And thus, the charging voltage
of condenser 8 is shown by curve q in FIG. 9 and is maintained
between voltages V.sub.1 and V.sub.2, which is sufficient for
enabling flash discharge tube 13 to discharge by closing synchro
switch 10.
And thus, in this embodiment, when the excitation condenser reaches
the substantially constant voltage oscillator a and power source
battery 1 are shut off by the SCR, and when the charging voltage of
the excitation condenser drops to some extent the SCR is turned on
to replenish charging and maintain it within the limits of the
constant voltage.
Switch 24 is a manual power source switch and is normally opened,
however, even if it remains closed it the power source battery is
used only for replenishing a portion in which the charging voltage
of condenser 8 is low, so that it is possible to prevent
unnecessary consumption of the power source battery.
In the embodiment shown in FIG. 10, the charging voltage of
condenser 8 is maintained within the limits of the constant voltage
in the same manner as the previous embodiments, and the base and
the collector connections of transistor 3 in oscillator a are the
same as those coupled with transformer 4 in FIG. 6. The modified
embodiment of FIG. 5 may be used with any of the other
embodiments.
* * * * *