Plural phase pulsed power supply

A method and apparatus for supplying electrical power to plural phased loads from a single power source at staggered times, whereby the maximum energy demand upon the power source is reduced. A phase-divider creates synchronizing pulses defining the start of each power pulse. Plural pulse-width modulators are provided with analog information as to the amount of power to be supplied to each phase load and the width of the power pulse to that load is adjusted accordingly.

BACKGROUND OF THE INVENTION 
The simple pulse type power supply is known. It is a single phase device in 
which full power or no power is supplied to a load depending upon the part 
of a cycle of operation that is being instantaneously considered. 
Plural phase power has been supplied to a pair of fluorescent lamps that 
illuminate a common area for the purpose of reducing visual flicker. 
Usually, an all-alternating-current apparatus has been used and 
transformer means has been employed to split the phase of a single-phase 
alternating-current source, or of a three-phase alternating-current 
source, to convert it to two-phase for supplying the two fluorescent 
lamps. 
SUMMARY OF THE INVENTION 
The requirement that plural phase electrical loads be supplied with 
electric power that is regulated in amplitude by circumstances peculiar to 
each load is accomplished herein by the method of forming control pulses 
at unique times and individually altering the duration of power-supplying 
pulses. Each of the power-supplying pulses start at the time of the start 
of the corresponding control pulses, but the power-supplying pulses are of 
brief duration where a small magnitude of power is to be supplied to the 
load, and are of long duration where a large magnitude of power is to be 
supplied to the load. 
An oscillator, typically of the square-wave type, energizes a 
phase-divider, which latter provides plural series of synchronizing pulses 
at mutually unique times. Individual pulse-width modulators have 
synchronized leading edges. Individual control integrated circuit charge 
devices determine the desired pulse width for each phase load to give the 
amplitude of power required by that load according to selected criteria 
A single, typically direct-current, source of power provides the basic 
power to energize the several loads. The staggered phase of the power 
pulses reduces the peak power required inversely according to the 
plurality of loads that are powered. 
A feedback circuit may be employed to sense the energization of each phase 
load and to accordingly alter the performance of the pulse-width modulator 
according to any selected regimen.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In FIG. 1 numeral 1 identifies an electrical oscillator, or electric 
oscillatory means, that provides a continuous series of timing pulses to 
actuate the remainder of the power supply device. The example shown in 
FIG. 1 provides four phase power. Four differently timed series of pulses 
thus emanate from phase-divider means 2 of the oscillator entity. 
These separately enter inverter 3, where the polarity of each series of 
pulses is inverted. The inverted series of pulses are then separately 
entered into decoder 4. From the decoder four series of pulses emerge, 
each series having only half as many pulses as originally produced; there 
being one pulse skipped between each pulse transmitted. 
Each of these species passes into a separate pulse-width modulator means, 
as 5, 6, 7 and 8. An analog level of control potential also enters each of 
these modulators, the level being pertinent to the level of power that is 
to be supplied to each phase load. 
In FIG. 1 the loads are shown as separate lamps 9, 10, 11 and 12 in a 
lamphouse, such as is disclosed in copending U.S. patent applications 
entitled, "Additive Color Printing Method and Apparatus", Gyori and 
Tullio, Ser. No. 703,735, filed July 9, 1976; and "Additive Color Printer 
Control", Gyori, Ser. No. 715,610, filed Aug. 18, 1976 and No. 4,068,943, 
issued Jan. 17, 1978, respectively. 
However, the phase loads may operate only one device, such as a four-phase 
motor, rotary or stepping or any number of pluralphase loads, particularly 
where control of the power supplied to any one phase is to be separately 
controlled, an unusual aspect. 
In the application of this power supply to the device of the recited patent 
applications, the luminous outputs of the lamps are monitored by 
photo-electric transducers 14, 15 and 16; also to be characterized as 
control means. There is one transducer for each of the colors red, green 
and blue, this being arranged by suitable filters for the lamps and the 
transducers. 
The monitored values may be compared electrically with a set of selected 
values and the differences passed on to the pulse-width modulators, as set 
forth in the patent applications. Alternately, a transducer may be 
separately provided for each lamp, there then being four transducers. 
Further, equivalent sensors may be provided for other types of phase loads 
and the sensor outputs fed back for power control. 
Lamp driver means 17, 18, 19 and 20 of FIG. 1 receive the individually 
adjusted pulse widths from corresponding modulators 5, 6, 7 and 8, 
respectively; also power at a uniform voltage from power supply 22. The 
latter may be the known a.c. to d.c. power supply, with smoothing filter. 
The lamp drivers are essentially power transistors with auxiliary 
transistors to effect required control of the power transistors. 
The electrical output from each lamp driver is connected to the 
corresponding lamp for the controlled energization of each. 
FIG. 2 shows the essential details of the plural phase power supply shown 
in block diagram form in FIG. 1. 
Oscillator 1 is comprised of an integrated circuit (IC), which may be a 
type 555 IC with two external resistors and one external capacitor to 
provide a square-wave oscillator having an oscillation frequency of the 
order of 6,000 hertz. 
This oscillation acts as a clock frequency for the phase divider means, or 
ring counter, 2. The output frequency of the ring counter is one-eighth of 
the oscillator frequency, or approximately 760 hertz, for the four 
flip-flop embodiment illustrated. Should a three-phase embodiment be 
desired, three flip-flops are employed and the clock frequency may be 
decreased by one-fourth. 
The four flip-flop embodiment may be formed using a type 9300 IC. Between 
the flip-flops A,B,C,D (FF.sub.1 thru FF.sub.4), each Q output is 
connected to the next J input, and each Q output is connected to the next 
K input. The last Q output is connected to the first K input, but also 
through inverter 27 to the J input. This gives the inverted connection 
that results in only eight combinations in the code. The oscillator clock 
is fed to each clock terminal of flip-flops FF.sub.1 through FF.sub.4. 
An output is taken from each Q terminal and is passed to separate inverters 
28 through 31 that are within generic inverter 3. In each instance the Q 
input becomes a Q output. For example, the Q.sub.A input becomes Q.sub.A 
output. These NAND gates may be a part of a type 964 IC. 
Decoder 4 is comprised of four two-input NAND gates 32 through 35. The 
cross-connections from the inverters to the decoders gives the code 
required. 
Specifically, decoder 32 receives a Q.sub.A and a Q.sub.B input; decoder 33 
receives a Q.sub.B and a Q.sub.A input; decoder 34 receives a Q.sub.C and 
a Q.sub.D input; and decoder 35 receives a Q.sub.D and a Q.sub.C input. 
The functioning of the decoder, thus connected, gives the following truth 
table: 
______________________________________ 
A B C D 
______________________________________ 
* 1 = --A --D 0 0 0 0 
2 = A --B 1 0 0 0 
* 3 = B --C 1 1 0 0 
4 = C --D 1 1 1 0 
* 5 = A D 1 1 1 1 
6 = --A B 0 1 1 1 
* 7 = --B C 0 0 1 1 
8 = --C D 0 0 0 1 
______________________________________ 
What is wanted for actuating the pulse width modulators 5 through 8 is a 
series of four time-interval spaced pulses. 
These are obtained from decoder 4 by providing a unique output for the 
combinations designated by * in the truth table; i.e., states 1, 3, 5 and 
7. 
The decoder is of the four two-input type. This simplification is possible 
because of the reversal of the output to input from FF.sub.4 to FF.sub.1 
and because of the use of inverter section 3. If the inverter was omitted 
proper logic could be supplied, but a decoder of the four four-input type 
would be required. 
Decoder 32 is connected to pulse-width modulator 5. In the example of the 
previously mentioned patent applications where the several loads are 
incandescent lamps provided with color filters to give component colors 
for illumination in an additive color printer, pulse-width modulator 5 is 
the "green" one. The decoder to modulator connection conveys what may be 
termed a synchronizing pulse; i.e., the timing for the start of the 
pulse-width pulse. 
Pulse-width modulator 5 may be a 555 IC with an external circuit comprised 
of one resistor and one capacitor. In a specific example the resistor is 
connected between terminals (8) and (7) of the I.C. and has a resistance 
of 22,000 ohms, and the capacitor is connected between terminal (7) and 
ground and has a capacitance of 0.02 microfarads. 
Should the synchronizing pulse frequency be changed for a different design 
both the resistor and capacitor values are changed in proportion to 
maintain the same relationship, since that relationship is significant in 
the over-all determination of the pulse duration. 
The resistor is 25 and the capacitor is 26 in FIG. 2. 
As schematically represented in FIG. 1, modulator 5 is also provided with 
an analog input that determines how long the pulse duration will be for a 
specific operating condition. When the operating condition changes, of 
course, the pulse duration also changes; typically, to bring the operating 
condition back to a predetermined norm. 
The value of the analog input is determined by the power required to 
operate the load involved. In the color printer application described in 
the patent applications previously mentioned, the spectral composition of 
the "white" light desired for a given printing is set into the control 
apparatus. The response of the photo-electric transducer monitoring a 
given color component lamp is compared electrically with the set value and 
the difference becomes the value of the analog input. 
The analog input normally has a voltage value in the range of from 0 to 5 
volts of positive polarity. This amplitude is determined for each 
operating condition in comparator 37 of FIG. 2, herein. Continuing the 
prior application, two inputs enter the comparator, an output from a 
digital to analog converter at input 38 and an output from a corresponding 
photo-electric transducer 15 at input 39. The former input is the 
pre-determined criterion, and the latter is the intensity of the green 
component of the white light. 
The output of modulator 5 passes to output terminal 40, and thence to lamp 
driver 17 of FIG. 1 in the use for the power supply that has been 
postulated. 
The detailed schematic circuit of driver 17 is given in FIG. 3. 
The electrical output of modulator 5 is a series of pulses, and width of 
each which depends upon the amount of power that is to be supplied to that 
phase load. When only a small amount of power is to be supplied the pulse 
is of short duration, with a long dwell time at zero axis thereafter until 
the next pulse. When a large amount of power is to be supplied the pulse 
is of long duration, ceasing only shortly before the start of the next 
pulse. 
The circuits for the remaining phases are duplicates of that described 
above. Decoder 33 is connected to pulse-width modulator 6 to determine the 
start of the pulse-width pulse for that element; which start is delayed in 
time with respect to the pulse for modulator 5. Comparator 41 is also 
provided with inputs from the digital to analog converter that represents 
the desired pre-set value of power for this phase and from the feed-back 
response of the red 2 transducer 14. Comparator 41 is connected to 
modulator 6. 
In the present example two red light emitting lamps are used to obtain a 
desired illumination response level for this color. 
Similarly, decoder 34 is connected to pulse-width modulator 7. Comparator 
43 is similarly provided with two inputs and is connected to modulator 7 
to determine the pulse duration thereof. 
Further, decoder 35 is connected to pulse-width modulator 8. The "red" 
comparator 41 is also connected to modulator 8, having previously been 
described as connected to modulator 6. These embrace the two red lamps 10 
and 12 of FIG. 1. The timing of the power pulse is different for the two 
modulators, but the level of power is the same, being sensed by transducer 
14. 
In another application of this invention, should there be a requirement 
that the fourth phase be independently controlled, this can be 
accomplished by the addition of one more comparator that is provided with 
independent inputs and gives an output only to the fourth phase modulator 
8. 
It will be understood that should a three phase power supply be desired, 
the same can be embodied by reducing various elements by one; i.e., ring 
counter 2 would have only three flip-flops, inverter 3 would have only 
three elements, and decoder 4 would have only three NAND gates. Similarly, 
only three pulse-width modulators would be required. 
Further, a two phase embodiment is realized by eliminating still one more 
of each of the recited elements. A five phase embodiment is realized by 
adding one element each to the entities of the four phase embodiment, and 
a six phase embodiment by adding two elements. 
It is required that the control pulse width available at each of the output 
terminals, such as 40, be combined with a source of electric power so that 
such power at a level commensurate with the requirements of the plural 
phase loads will be supplied to each. 
This requirement is met by the lamp drivers designated as 17-20 in FIG. 1; 
one of which is detailed in FIG. 3. 
In FIG. 3, input terminal 40' is illustrative of the output from a 
pulse-width modulator, such as from terminal 40 in FIG. 2. This terminal 
is connected to a phase-inverting buffer amplifier 46, which may be of the 
MC946 type. This moderately increases the power level. The output 
therefrom passes through isolation resistor 47, having a resistance of 
approximately 5,000 ohms, and then to the base of transistor 48, which may 
be a 2N3053. This transistor increases the current level in the circuit. 
It is fed from power supply 22 through resistor 49, of approximately 1,000 
ohms, which resistor is connected to the collector. The emitter is 
connected to ground. 
The peak d.c. voltage allowable on the several lamps, as 9 in FIG. 1, is 28 
volts. 
Accordingly, the d.c. voltage output of power supply 22 is 30 volts. The 
power supply is typically the known full-wave semiconductor rectifier type 
employing a transformer that is connected to a 115 v. a.c. input and 
having an output capacitor filter of several microfarads capacitance. 
The output of transistor 48, from the collector, passes through variable 
resistor 50, having a maximum resistance of the order of 1,000 ohms, and 
also, in series therewith, fixed resistor 51, having about 750 ohms 
resistance. The latter resistor is connected to the base of transistor 52, 
which is one of a Darlington pair. It may be the 2N3055 type. In the known 
manner the emitter of transistor 52 is connected to the base of the second 
Darlington transistor 53, a 2N3771, and the collectors of both transistors 
are connected to the output terminal of power supply 22. The base and 
emitter of transistor 53 are connected by resistor 54, having a resistance 
of 1,000 ohms. 
Transistor 53, as specified, is capable of carrying a current of the order 
of 25 amperes maximum and the lamp load 9 is typically rated at about 
one-third of this current. Transistor 52 increases the effective beta of 
transistor 53, and so the signal power to drive the pair is minimal. 
Essentially, the power supplied to load 9 by transistor 53 is in pulsed 
form, following the pulse duration set by the pulse-width modulator 
involved. If it is desired that the current through the load should be 
more nearly a direct current, capacitor 56 may be added in shunt to 
accomplish this. A capacitance of the order of 6,000 microfarads is 
suitable.