CA1191545A - Power source circuit - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A power source for an electronic system re-uses a cyclically re-curring event in the system as an on/off control for establishing a well regu-lated series of rectified DC pulses which recur at a predictable and high fre-quency. The cycle of the SCR is the regulating determinant of the system. In the preferred embodiment, the recurring event is a scan and retrace cycle of a CRT display. An SCR is switched off by the flyback transformer of the CRT
horizontal deflection circuit. Therefore, since this turn-off time is deter mined by the flyback, the resulting conduction period is the net controlling regulation characteristic of the system.

Description

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Th:is inventio~ relates to powe.r source systems and more pa-rticularly -. although not exclusively -- to power systems controlled ~y scanning systems for computer terminals, da-ta display monitors, arcade games, radar, and other CRT based systems.
Computer terminals, data display monitors a.nd the like are generally com~rised of sepa.rate modules ~such as keyboards, cathode ray tube (CRT) dis plays, floppy disc drives, and logic units)O ~ach of these e].ectronic compon-ents usually requires high quality, well regulated power supplies~ Therefore, the display unit or terminal also generally i.nclude a separate power supply chassis which powers the other modules.
Traditional compu~.er power supplies have been relatively design intensive, high-cost, and conlpletely separate units. As the cost and size of computers continues to drop, the cost and size of this traditional type of power supply stands out as an unwarranted proportion of the total system space requirements and cost. Hence, there is a substantial need to reduce cabinet si~e and power supply cost ~ithout, in any way, sacrificing the quality, high efficiency, broad dynamic range, load sensitive regulation, and good filter~ng that is demanded by sophisticated electronic devices.
Accordingly7 an object of the invention is -to provide new and im-2a proved power sourcesO Here, an object is to provide space efficient, lowercost power sources~ Another object is to reduce the cost of power sources by re-using existing components which are used elsew~ere in the systemO In parti-cular, an objec~ is to provide power source which ~e-usesthe flyback transform-er employed in a high voltage section o a CR~, as a major element in the power source regulator~
In keeping with an aspect o~ the invention, these and other objects ^,;.~

are accomplishecl by us.ing a part o~ a high voltage circui-t in a cathode ray-tube clisplay as part of a power source. More partic-ularly, during the CRT scan cycle, a high vol-tage flyback transfor-mer in the display unit prov.ides a syneh:ronous phase control that switches on a silicon con-trolled rectifier (SCR) to provide both the conventional high vol-tage supply for the CRT and an interrup-ted high current whichis of an easily rectified and filtered fre-quency, to provide a smooth, well regulated power source output.
At the end of the scan cycle and during -the retrace period, a negative pulse appears in the flyback transformer winding to switch off the SCR and terminate the high current. The power source out-put is well regulated and the scan cycle .Erequency is in the range of 10-35 KHz, with a preferred range o~ about 15-25 KHz. The speeifie frequencies: 15.750 KHz, 18.3 KHz, 19.2 KHz, 20.5 KHz, are those frequencies which are frequently being used commercially at the present time. These frequencies are easy to filter in order to meet the needs of an electronic circuit. The high vol-tage and power source may be constructed as a single integrated system, which reduces space requirements and component count.
More broadly, the presen-t invention provides a power source circuit eomprising eleetronic switching means for providing a rectified series of DC voltage pulses, means responsive -to the output of said electronic switching means for fil-tering and smooth-ing said rectified voltage to provide a steady, well regulated DC voltage, means responsive to said smoothed voltage for energiz-ing an opera-ting device having its own switch on and off cycle, control means responsive to said cyele for switehing on and off ~, ., ~S~

said electronic swltch means to cont.rol the frequency of said DC pulse series, whereby saicl cycle is re-used as a voltage regula-ting device for controlling said elec-tronic switch, and means responsive to the output of said electronic switch means for powering devices.
According to another broad aspect, there is provided a process for powering moclules o.F an el.ectronic system comprising the steps of: (a) driving an electronic switch through an on and off cycle responsive to a cyclically recurring event in one of said modules; (b) filtering and smoothing the output of said switch-ing means to provide a smooth and well regulated DC voltage; and (e) applying said DC voltage to power other of said modules;
whereby a naturally occurring cycle in said one module of s-tep (a) is re-used -to provide a control for establishing and maintain-ing a stable frequency Dc voltage pulse signal which is filtered and smoothed in step (c).
The invention will now be described in greater detail with reference to the accompanying drawings, in which:
Figure 1 is a block diagram of a first and preferred embodiment of the inventive power source, using a flyback transformer and an SCR, as a switching device; Figure 2 is a block diagram of a second embodiment of -the invention using a pulse transformer and an SCR; Figure 3 is a block diagram of a third embodiment of the invention using a transformer and a transistor switch;
Figure 4 is a schematic circuit diagram of an exemplary power source circuit using a flyback transEormer to control an SCR;
Figure 5 is a schematic circuit d.agram of an alterna-tive embodi-~, -2a-ment o:E this invention uslng an op-t.ical coupler; Figure 6 shows an alterna-tive embodiment o:E the invent:ion using a specially de-signed fly--~b-, .~,.
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back transforme:r; Pi.gure 7 shows another embodiment o:t the inven~i.on wherein the electronic switch is logically controlled; and ~:igure 8 are -voltage cu.rves on a time scale for explaining the operation of the circuit of ~igure 7.
In Figure 17 a line filter lO (including a rectifier a.nd fi.lter capacitors) maintains a rectified inpu-t voltage at terminal 12, responsive to a conventional AC commercial power (o:r -the equivalent) applicd to input terminals 13. The flyback transformer (already provided in the CRT display unit) has a commutating winding 1~7 a primary winding 16, a.nd one or more secondary windings 18~ The flyback transformer is used as a high speed switch for turning off an electronic switchO The synchronization with the flyback transformer may be taken from any convenient component such as a horizontal oscillator, horizontal drive transformer, a separa~e winding of the flyback transformer, a capacitor in series with the yoke or the like.
The terminal 12 is connected to the primary winding 16 by way of the commutating winding l~ and an electronic switch in the form of a thyristor7 or any memher of the thyris~or family7 here an SCR 200 The gate of the SCR is connec~ed through a pulse transformer 22 to a hori~on-tal scan regulator 2~.
Thus7 the SCR switches on at the cyclic rate of the horizontal scan system set by regulator 28. The SCR switches off when a negative pulse is induced in

2~ commutating winding l~ during the retrace period.
As the SCR 20 conducts, the primary winding 16 of the flyback trans-former is energized to induce a voltage in the secondary winding 180 The pulse induced in the secondary winding 18 is fed back through a diode 26 to a regula-tor 28 which provides a reference voltage that maintains the desired power source characteristics. The voltage at the bo-ttom (as viewed in ~igure 1) of primary winding 16 is a principal useful output, which powers a horizontal

- 3 -deflection drive output circu:it 30 ancl a deflection yoke 32. The secondary winding 18 po~iers any other suitable load or loads 36 of the comput.cr system.
Instead of or in addition to hori~ontal scan regulator 24, a pro-grammable unijunction transistor may be used -to cyclically swi-tch on the SCR 20 The SCR 20 switches on a-t or near the ~ero crossing of the regulator ~4 output7 to s~lpply a rect.ified nc voltage, whi.ch i.s a well regulated switch on frequencyO A rectifier 26 then feeds back a pulse induced in seeondary winding 18 during horizontal scan -~ the feedback being to a regulator 2~ which controls :regulator 24; that gates the SCRo A sMoothing capacitor 34 maintains a s-teady DC reference voltage responsive to the rectified vol~age derived from the voltage induced in secondary winding 1~. Alternatively, capacitor 34 could be replaced by a rechargeable battery (such as nickel cadmium battery~
which maintains a steady voltage~ For switching off the SCR, the circuit de-pends upon the commutating effects o a high negative pulse in winding 14 on the flyback transformer~ the negative pulse appearing during the retrace period.
The cycle for the flyback transformer controlled diode 26 is about S5% "on" during the horizontal scan and about 15% "off" during retrace, which leads to an efficient output that is easy to filter. The design and capacity of the flyback transformer are adJusted to supply both the conventional high voltage for the CRT and the rectified DC power supply~ This reduces both the number of components and the total space requirements.
The embodiment of Figure 2 has a pulse transformer 3~ which switches on and off an electronic switch, in the form of SCR 40. The output of the SCR 40 is filtered at 42 and fed as the B-~ supply to the horizontal deflec-tion circuit 44. The output of the horizontal deflection circuit 44 is applied to a timer circuit 46. This timer cyclically and alternately operates a trig-~ 4 --S

ger circuit 48 and a commut.ltor circu:lt 50 whicll control the voltage pulses in~duced in tr~msformer 38, to switch the SCR ~0 on and of:f w:ith any desired duty cycle.
The embodiment of ~igure 3 has a choke coil 52 in ser:ies with the collector-emitter circuit of an electronic switch, transistor 54O The output of the transistor is applied to a hori~ontal deflection circuit 56. Capacitor 5~ fllters and smoothes tile output voltageO A feedhack circuit 60 applies the output voltage to a pulse width modulator 62 which provides cyclically recur-ring pulses of any desired pulse width, thereby setting the duty cycle of the 10 transistorO
In each of these systems, it is contemplated that the cyclic switch-ing will be in sychronization with the horizontal scan period. However, the invention also contemplates a power switching operation of any convenient, independent time baseO Each embodiment contemplates a feedback control oper-ating off a secondary winding of a transformer; however, it is also possible to operate the feedback off the primary windingO
A broad and dynamic operating range of voltages and currents is achieved because high frequency switching devices are used, such as: an SCR, a PUT, and a flyback transformer which has inherent design quality~ This use of high fre~uency devices enables the system to respon~ quickly and accurately to finite changes in the feed back controlO
A schematic circuit diagram (Figure ~) shows one practical embadiment of the inventionO An AC commercial power line is connected to input terminals 6~ leading through a fuse 65, a choke coil 68 and a current limiting resistor 79, to a rectifier diode 72, An electrolytic capacitor 74 smoothes and filters the rectified voltage~

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The rectit`ie~ voltage is applied from diode 72 through a voltage divider 76, 78 to ground via a parallel fil~er 80 and a zener diode 82. This combination maintains a stable and well regula~ed reference voltage at the cen-ter of the voltage divider (point Pl) -that provides a differential voltage through resistors 112, 114~ 118 and 116 such that variations impressed at AC
input 64 can be corrected in a simple matrix of feedback voltages.
I`he majority of -the current from ~he rectifying diode 72 is applied through commutating winding 14 to the anode of a silicon controlled rec-tifier CSCR) 84. The commutating winding 14 is part of a flyback transformer having lQ ~rimar~ ~inding 16 and secondary winding 18. Therefore~ whenever SCR 84 switch-es on to dra~ a heavy current, a voltage is induced in the primary and secondary windings. ~s those skilled in the art know, a negative voltage is induced in commutating winding 14 during ~he retrace period, rhe voltage induced in primary ~inding 16 energizes the horizontal d~flections drive circuit 30, which is a conventional part of the CRT display unit. This horizontal deflection circuit 30 includes a driver transistor 86~ an output transistor 88, and a damper diode ~O Since the contruction and opera-tion of a horizontal deflection circuit, such as this, is well ~nown~ it will not be described furtherO One point of the invention is that this circuit 30 is 2Q po~ered from the primary winding 16 of the fly~ack transformer.
The regulation of the current through the SCR 84 ~which in turn is a regulation of the current through primary winding 16) depends upon a cycle con-trolled by pulses applied to the SCR gate, the start of which is controlled by a triggering device 92~ The device ~2 is a progra~nable unijunction transistor~
sometimes called a ~PUT~o The end of the conductive segment of the cycle is set by the commutating winding 14, which induces a negative pulse to switch the SCR

s into an off condition.
The cyclic switching of the PUT 92 is controlled by current in the primary winding 160 ~ore particularly> at the start of each CRT scan cycle, the rectified current begins to flow from rectifying diode 72 through winding 1~, suppressing capacitor 94, and resistor 96, and a decoupling filter capaci-tor 98 to ground, and a voltage ls induced in primary winding 16. Responsive thereto, a current flow ~rom primary winding 16 through a resistor 100, capaci-tor 102, resistor 104 and isolating diode 106 to the gate of PUT 92. In this circuit~ a pair of parallel capacitors 108, 110 are connected between opposite sides of isolatio~ diode 106 and ground. The charging and discharging times of these two capacitors control the -turn of timing of PUT 920 The operation depends upon the ~C level applied to the anode of PUT
92~ That DC level is set by the regulated voltage appearing at point Pl, and applied through a voltage divider comprising resistor 112, potentiometer 114, and resistor 118 to groundO The midpoint of this voltage divider is connected through resistor 116 to the anode of PUT 920 The turn of timing of PUT 92 may be adjusted by potentiometer 1140 A pair of decoupling capacitors 120, 122 maintain a steady voltage at the anode.
To provide synchroni~ation and maintain regulation, resistor 100 and capacitor 102 provide a positive pulse from flyback winding 16. The pulse is adjusted in amplitude by zener diode 124 and added to the gate voltage of PUT
92 through resistor 104 and diode 106~ making the trigger point completely synchronous with the horizontal output stage.
The PUT 92 conducts a predetermined time period after current appears in commutating winding 14 of the flybac~ transformer, that time period being adjusted at potentiometer 1140 When the PUT 92 turns on, the charges 5~

stored on capacltors 108 and 110 are discharged through PUT 92, choke co:il 132 and capacitor 13~ to the gate o~ SCI~ 84~ ~his discharge is a control pulse which switches on the SCR 840 Circuit 136 includes a parallel resistor and diode which together provide a one-way discharge path for choke coil 13~ and capacitor 134.
The SCR 84 remains on during the required portion of tha CRT scan period, while a positive voltage is in winding 14 of the flyback transformer.
However, when the horizontal deflection circuit 30 reaches the end of the scan and the beglnning of its retrace cycle, a high negative pulse appears in a commutating winding 14 which is connected to the anode of SCR 840 When its anode goes more negative than the cathode, the SCR switches off. During the next scan cycle~ the process repeats and PUT 92 switches on SCR 84 until the start of the retrace cycleO Therefore, the output of the SCR 84 is a cyclic series of pulses of one polarity.
Reslstor 1~0, diode 26~ load 36~ and capacitor 34 load the secondary winding 18 of the flyback transformer. Diode 2~ rectifies and capacitor 34 smoothes voltage induced in the secondary winding 180 Load 36 may oe any suit-a~le au~-iliar~ circult ~hich is po~ered by the circuit of Figure 4.
The voltage on line 27 is sensed through resistor 140, as the con-~rolling signal for maintaining load regulation during any changes which theload may present, in its normal operationO The signal sensed through resistor 14Q afects the anode voltage of the PUT 92 and adjusts the firing time of the PU~ during a scan period, to give a correction factor for variations of the load demandO If there is fluctuation in the AC input at terminals 64, the fluctuation is ~eflected at both point Pl and on line 27 so that together they control the anode voltage on PUT 92, to give a correctional factor.

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In operationJ the commercial ~C power :Erom the line 6~ is rectified at 72 and applied as a B~ battery to the commutatlng windi.ng 14. There is an initial current through winding 1~, capacitor ~, resis~or 96, and capacitor 98 to ground. The rectified output of diode 72 also energizes a voltage divider 76,78 to establish a voltage regulated by ~ener diodes 82, 124 at the gate and anode of PUT 92.
A voltage is induced in primary winding 16 and applied through resistor 1~0, capacitor 102, rcsistor 10~ and diode 106 to the gate of PUT 92.
The PUT 92 switches on and pulses the gate of SCR 84, which, ln turn~ switches on, wi~h a heavy current to power the horizontal deflection ci.rcuit 30 during the CRT scan period.
At the end of the scan period, the transistor 88 switches off and a ~osi~ive pulse appears in the primary winding 16 by normal and well known trans-former actionO A negative voltage is induced in commutating winding 14 to switch off the SCR 8~, during the CRT retrace period.
Hence, there is no need for a completely separate power source be-cause the primary winding 16 of the flyback transformer is energized and self-regulated by the SCR 840 The voltage induced in the secondary winding 18 forms an auxiliary power source to any suitable load or loads 36, during the horizon-tal scan interv.al, which is about 85% of the conducting period of rectifier 260~he horizontal scan fre~uency is 15 ~Iz or higher, which fre~uency is easy to filter and smooth. Thus, the flyback transformer which is already present in virtually all CRT control circuits is reused as a power source and control de-vice to produce an easily filtered and well regulated voltage Figure 5 is an alternative embodiment which is somewhat similar to the embodiment of Figure 1, where similar parts have similar reference numerals.

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The principle of Figu:re 5 is that the secondary winding 18, and its associated components and loads are electrically isolated from the AC line 13. Ilere, an optical coupler 2ao (usually ~ LED and photosensltive transis~or or the like) is connected into the circuit to provide isolation between the AC line 12 and the load 360 Thus, load 36 may be any remotely powered equipment which may be plugged into a coupler at contacts Cl~ C2, without any danger that the user mig~t touch a point energized di~ectly from line 13. There could be a plurality of such secondary ~indings 18 which could jointly provide a plurality of iso-lated power sources. Since the optical coupler effectively isolates the secon-dary windings from each other, separate loads may be connected to individualsecondar~ windings so that one load is unaffected by the other load.
Figure 6 shows, by way o sxa~ple, a pair o-f secondary windings 18A, 18B These windings may be complctely independent and totally separate from each other. Each may be controlled by its own feedback circuitO Or, alterna-tively, by a use of various winding techniques, several independent secondary windings may be ormed within a single transformerO In this multiply wound transformer, one winding senses the current in all windings and supplies ~he resulting signals for eadback regwlation.
Figure 7 sho~s a circuit which is similar to the circuits of Figures 2Q 1 and 4. Those parts which have alread~ been explained have the same reference numerals and will not be explained again~
The load 36 is powered by the inventive system, wherein the power source output voltage appears across conductors 300, 302. This output voltage is subject to analog change responsive to fluctuations at either ~he power input~
to terminals 64 or the load 36. The purpose of the circuit is to supply correc-tive control signals or immediately counteracting the analog changes and re-turning the voltage to stability~

rhe~ analog to clig:ital converter 30~1 is a voltage controlled oscilla-tor (~C0) which generates a continuous train of pulses having a frequency which is a function of the level input of the voltage. If the analog voltage across lines 3qO, 302 goes up, the frequency slows; if t}le analog voltage goes down, the frequency increasesO These pulses are counted by a count down counter 306 which is preprogrammed to count a number of pulses and then -to give an outputO
The frequency of the VC0 and the preprogrammed count depend upon the resolution that is desired.
Simultaneously with the count down in counter 306, a resettable mas-ter oscillator 308 is operated to detect the beginning and ending of each hori-zontal scan cycle. At the end of each cycle the master oscillator 30~ produces a ~r~llse which resets and returns all of the circuits to normal, A gate 310 i5 essentially an AND gate which produces a pulse when the count down counter 306 reaches it5 preprogrammed countO
The operation of the circuit of Figure 7 i5 explained by the voltage diagram of Figure 80 In three horizontal scan pulses 312, 314~ 316 define two horizontal scan cyclesO The voltage out curve described the voltage impressed bet~een conductors 300, 3020 Arbi~rarily, it could be assumed that the level during period Vl is~ say 90 volts~ In the period V2, the load begins to draw ~0 a heavy curren~ and the voltage falls to, say, 89 volts. During period V39 the voltage i5 once again 90 volts. In the period V4, the load stops drawing a heavy current and the voltage rises to, say, 91 volts.
During time period Vl, the output of the VC0 of converter 304 has a sta~le frequency flo When the voltage across conductors 300, 302 begins to fall during time V2, the frequency of the VCO increases to f2O ~hus, the counter 306 quickly reaches its preprogrammed coun~ "N" to send a trigger pulse 318 through gate 31Q to switch on the S~R 8~-l. At the end of the hori70nkal period the master oscillator 308 gives a reset pulse 320 -to switch off the SCR
~0 Thus~ ~he SCR conducts for the relatively long periocl of time ~etween pulses ~1~, 32~ to return the output voltàge to the original level of 90 volts.
In the next cycle, the VCO 304 again operates at the frequency fl.
This time~ however, the voltage impressed across conductors 30~, 302 rises and t~e VCO frequency slo~Ys to f30 rhis Ineans tlla-t it takes longer for counter 306 to reach its preprogrammed count "N", and generate a trigger pulse 322 for switching on the SCR 84. The master oscillator 308 generates pulse 324 to suitch off the SCR at the end of the hori~ontal scan cycle, This time9 the SCR 84 was on for the relatively short period between pulses 322, 324. Hence, the voltage output returns to 90 volts during time period V40 One advantage of the inventive power source system is that it oper-ates at an efficiency which is much greater than the efficiency normally ex-pected from comparable presently used power supplies. This efficiency occurs because the existing components are re-used. Thus, any losses, heat dissipa-tion or other power consuming functions are already in the system and therefore are not duplicated in a power source. Also~ the preferred system normally provides for the total power neads of the CRT and associated systems, including slave monitors~ logic systems and othex peripheral systems.
Those who are skilled in the art will readily perceive how to modify the in~ention Therefore9 the appended claims are to be constrwed to cover all equivalent structures which fall within the true scope and spirit of the invention.

Claims (23)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE.
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A power source circuit comprising electronic switching means for providing a rectified series of DC voltage pulses, means responsive to the out-put of said electronic switching means for filtering and smoothing said recti-fied voltage to provide a steady, well regulated DC voltage, means responsive to said smoothed voltage for energizing an operating device having its own switch on and off cycle, control means responsive to said cycle for switching on and off said electronic switch means to control the frequency of said DC pulse series, whereby said cycle is reused as a voltage regulating device for con-trolling said electronic switch, and means responsive to the output of said electronic switch means for powering devices.

2. The power source circuit of claim 1 wherein said DC voltage pulses are a series of horizontal deflection pulses.

3. The power source circuit of claim 1 wherein said control means com-prises a flyback transformer.

4. The power source circuit of claim 1 wherein said control means is a pulse transformer driven by a timer.

5. The power source circuit of claim 1 wherein said control means is a pulse width modulator.

6. The power source circuit of claim 1 wherein said control means has a logical circuit means for counting output pulses of a voltage sensitive oscilla-tor which generates pulses at a frequency which is responsive to the output of said power source.

7. The power source circuit of claim 1 wherein said electronic switch means is a thyristor device, means responsive to said control means at a con-trolled point during each on period of said cycles for applying a switch-on signal to said thyristor device, and means responsive to said control means at a start of each off period of said cycle for applying a switch-off signal to said thyristor device.

8. The power source circuit of claim 7 wherein said thyristor device is a silicon controlled rectifier.

9. The power source circuit of claim 8 wherein said operating device is a CRT display device and said on and off cycle is a CRT horizontal deflection scan and retrace cycle.

10. The power source circuit of claim 9 and a programmable unijunction transistor driven responsive to the start of each of said on periods for switching on said electronic switch a predetermined period after the start of said on cycle.

11. A process for powering modules of an electronic system comprising the steps of: (a) driving an electronic switch through an on and off cycle responsive to a cyclically recurring event in one of said modules; (b) filter-ing and smoothing the output of said switching means to provide a smooth and well regulated DC voltage; and (c) applying said DC voltage to power other of said modules; whereby a naturally occurring cycle in said one module of step (a) is re-used to provide a control for establishing and maintaining a stable frequency DC voltage pulse signal which is filtered and smoothed in step (c).

12. The process of claim 11 wherein said one module of step (a) includes a CRT horizontal deflection circuit and said recurring event is a scan and re-trace cycle in said deflection circuit.

13. The process of claim 12 wherein said deflection circuit includes a flyback transformer connected to control said on and off cycle of said electron-ic switch.

14. The process of claim 11 wherein said one module of step (a) in-cludes a pulse transformer driven by a timer having a voltage sensitive on/off cycle.

15. The process of claim 11 wherein said one module of step (a) includes a pulse width modulator having a synchronous on/off cycle,

16. The process of claim 11 wherein said electronic switch is an SCR.

17. The process of claim 16 and PUT means for switching on said SCR a predetermined period of time after the start of each cycle in said recurring event.

18. The invention of either claim 1 or claim 11 wherein said electronic switch provides a transformed output with a cycle which is approximately 85% on and 15% off.

19. A power source circuit comprising a flyback transformer having pri-mary, secondary, and commutating windings; line filter means including a recti-fier for connecting an AC power source to said commutating winding; means comprising a programmable unijunction transistor for generating a pulse res-ponsive to a rectifier voltage from said AC power source in said commutating winding and to a voltage in said primary and secondary windings; silicon con-trolled rectifier means having an anode connected to receive said rectified voltage via said commutating winding; means for applying said pulse from said unijunction transistor to a gate of said silicon controlled rectifier; circuit means. connected to a cathode of said silicon control led rectifier whereby said circuit means is energized by current from said AC power source applied through said line filter means; said commutating winding, and said silicon con-trolled rectifier to said circuit means during periods while said silicon con-trolled rectifier is conducting; and means responsive to said circuit means for establishing an on/off cycle in the winding of flyback transformer for switching said silicon controlled rectifier at a predetermined rate in the order of 15 to 25 KHz and with a predetermined output cycle of approximately 85% on and 15% off.

20. The power source circuit of claim 19 and means comprising said cir-cuit means for driving a cathode ray tube horizontal deflection circuit, said 85% being the scan period and said 15% being the retrace period.

21. The power source circuit of claim 20 and load means connected to said secondary winding.

22. The power source circuit of either of the claims 7 or 19, and isolat-ing means for coupling the outputs of a plurality of said power source circuits whereby each of said power source circuits may operate completely independently of each other to contribute to powering a common device.

23. The power source circuit of either claims 7 or 19 and a multiwinding transformer means for powering a plurality of separate circuits responsive to each of said winding.