US2740902A - Power supply system - Google Patents

Description

April 1956 c. w. MILLER POWER SUPPLY SYSTEM Filed Jan. 14, 1952 ISnventor CZaf/es Zfl @Y/e'f United States Patent" POWER SUPPLY SYSTEM Charles W. Miller, Anderson, Ind., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application January 14, 1952, Serial No. 266,383

4 Claims. (Cl. 250-214) My invention relates to electrical power supplies, and, more particularly, to a regulated power supply system for electronic circuits that require a comparatively high operating voltage such, for example, as certain forms of automatic head lamp dimming circuits for motor vehicles.

For the purpose of securing the high sensitivity required for satisfactory operation of automatic head lamp dimmer circuits, the photo-multiplier type of photo-emissive photocell has been suggested for use as the light sensitive pick-up device therein. Such photocells require a high anode supply voltage of the order of 1,000 volts or more, and further require that the operating voltage supplied thereto be closely regulated in order to prevent undesirable fluctuations in the output of the photocell. The supply voltage for most forms of automatic dimmer circuits heretofore proposed is cutomarily obtained from 'a vibrator-type power pack which is energized from the vehicle battery, the output of which undergoes considerable variation with changes in engine speed and other electrical loads supplied thereby. Thus, although it is possible to obtain a high voltage output by employing a high voltage secondary winding on the output transformer associated with a vibrator-type power pack, this has been found unsatisfactory due to the expense and difficulty of providing adequate voltage regulation at the desired high voltage level.

In order to obtain a closely regulated high voltage supply from a high vibrator type power pack, it has been suggested to perform the voltage regulation at a lower voltage level at the output of the power pack and .to obtain the desired high output voltage by using a radio frequency oscillator. A system of this type is disclosed in copending U. S. patent application S. N. 165,- 392, filed June 1, 1950, in the names of George W. Onksen and Charles W. Miller, and of common ownership with this application.

, 2,740,902 Patented Apr. 3, 2

therefore, the operating etficiency thereof and which is stable in operation.

For the purpose of accurately setting the voltage supplied to the photo-multiplier tube, 1 have found it advantageous to be able to adjust the output of the power supply system over a range of output values. The present invention is an improvement over the system described in the above-mentioned application wherein such means as have been provided for adjusting the output voltage depend upon changing the tuning of the oscillator which results in operating the oscillator at offdesign conditions instead of at its peak efiiciency and also tends toward unstable operation thereof.

Accordingly, it is the general object of my invention to provide an improved high voltage power supply system which furnishes a closely regulated output voltage that may be varied over a wide range of output values. Another object is to provide an improved oscillator suitable for use in a high voltage power supply system. Still another object is to provide an improved oscillator the output of which may be readily adjusted over a wide range of output values without afiecting the tuning and,

- switch (not shown).

The preferred manner in which these and other objects are realized, together with the features and advantages attending my invention will appear more fully from the following detailed description and accompanying draw ing which represents a schematic circuit diagram of an automatic headlight dimmer system utilizing the embodiment of my invention.

The schematic circuit diagram shown in the drawing comprises, in general, a vibrator power pack 2 which supplies a rectified output voltage through a voltage regulator tube 4 to a high voltage high frequency oscillator section 6 enclosed in dashed outline. The output of the high voltage section of the power supply is rectified and supplied to a photo-multiplier tube 8 connected in the input of a dimming control circuit 10 which automatically controls the energizationof the high and low beam filaments of a pair 'of' vehicle head lamps (not shown) in accordance with the intensity of the illumination from 'an approaching vehicle impinging on the photocell.

The main source of power for operation of the above apparatus is obtained from the vehicle storage battery (not shown) which is connected to an incoming power line 12 through a conventional headlamp energizing Line 12 is connected to a selector switch 13 and 14, and also supplies power from the battery to' the vehicle head lamps (not shown) over a line 16 as explained hereinafter. The selector switch is manually operated and determines from its position whether the vehicle head light system shall be conditioned for standard foot switch operation or for automatic operation. When the selector switch-is closed, power is supplied therethrough from the battery to the input of the vibrator'power pack 2 over line 22.

The vibrator power pack comprises a conventional synchronous type vibrator 24 and an output transformer 26 having primary and secondary windings 28 and 30 connected to the terminals 32 and 34, respectively, of the vibrator as shown. As is well known in the art, such an arrangement is self-rectifying and serves to provide a high D. C. output voltage from a low D. C. input voltage. The input to the vibrator is supplied over line 22 which is connected to the midpoint or center tap of the transformer primary Winding 28 through a filter 36. The filter 36 is formed by a radio frequency choke coil 38 connected in series with line 22 and a condenser 40 connected from one terminal of the choke coil to ground and serves to prevent high frequency disturbances occasioned by operation of the vibrator 16 from appearing on line 22 and affecting the main power source. A resistor 42 and buffer condenser 43 are connected in series 'across the outer terminals of the transformer secondary winding 30 and serve to prevent arcing of the vibrator contacts and the appearance of high frequency transients in the output of the power pack which is taken from the midpoint of the secondary winding 30 through an output lead 44. The output of the power pack ap pears between lead 44 and ground and is filtered by a condenser 46 connected therebetween.

The filtered output voltage of the power pack is supplied over lead 44 to a resistor 48 which is connected to the voltage regulator tube 4 which may be of the conventional cold cathode gas-filled variety. The regulator tube comprises an anode 49 connected to the resistor 48 and a cathode 50 connected to ground and functions to maintain the voltage between its anode and cathode substantially constant. The regulated voltage appearing across the electrodes of the regulator tube is further filtered by conductor 52 to the high voltage high frequency section 6 of'the power supply system.

The high voltage high frequency section 6 of the power supply system is constituted, by an oscillator 56- which comprises a vacuum tube 58 having aplate 59,; screen grid 60, control grid 61,-cathodev 62,. and-heater 63'; a tank circuit formed by a tuned parallel combination of a primary inductance coil 66 anda variable: condenser 68 shunted by a condenser. 78;. a grid. circuit. formed by an inductance coil 72, which. is, inductively coupled to the coil 66 of .the tank circuitand a parallel, combination of av resistor 74 and condenser 76; and a. load: circuit which,

comprises a secondary coil, 78, inductively coupled to the primary coil 66 and connected to, a high voltage'rectifier tube 88 having an anode 81, cathode 82,...and heater 8-3.

The plate 59 of the tube: 58 is; connected to one. side.

of thetuned resonant tankxcircuit, tthe other side of the tank, circuit being connected through line 86. and. resistor 88, to ground. Screen electrode. 60' is connected to an adjustable tap 90, on the resistor 88. The operatingvolt'age for the plate. 591 of the tube 58' is suppliedfrom thevoltageregulator tube 4 through line 52 and inductance coil 66. This voltage also appears across: the resistor 88 and a portion thereof is applied. to. the screen electrode 60.

through the adjustable tap 90 for the purpose of varying,

thev conductivity of the tube.

The inductance coils 66, 67 and 78v are wound on a common core so as to form an air core transformer. Cell 66 may be thoughtof as the primary and coil 78 the secondary of the transformer. nected to the. control grid 61 of the oscillator tube 58 with such polarity so as to aid the build up: of oscillations. Otherwise stated, the voltage induced in coil 72 by current flowing in coil 66 is applied to thecontrol grid 61 in phase with the voltage induced in coil 66. The parallel combination of the resistor 74- and condenser 76- connected between one terminal of the input coil 72 and ground is the conventional grid leak arrangement commonly used in oscillator circuits. to limit the amplitude of the generated oscillations. Thecathode 620E the tube 58 is connected to the grounded side of. the heater 63; the other side of which is connected through a conductor 92 and conductor 22 to themain power source.

The primary or tank coil 66 of the oscillator is inductively coupled to the secondary load coil 78 aud=produces a-highvoltage which is rectified by the high-voltagerectifier tube 88. The anode 81 of the rectifier tube is. connected to one terminal of the coil 78'and"its-cathode 82 connected to the grounded side of the heater 83, the ungrounded side of which isconnected through line- 93 and conductor 92 to the main power source. The rectified output of the high voltage high frequency section-60f the power supply system appears between ground andcontuctor 94 connected to one side of the secondary: load coil 78 and a filter condenser 95 as-s h-own.

Conductor 94 is connected to a resistance terminal block 96, which is enclosed in dashed outline and com prises a plurality of resistors 100-109, inclusive, connected in series between conductor 94 and ground, the number of resistances corresponding to the number of stages in the photo-multiplier tube 8. The photo-mul tiplier tube is of conventional design and comprises an anode 112, cathode 11 6, and'anumber ofdynodes 128- 128, inclusive. Line 84, which is of negative polarity, is connected through a protective resistor 130 to the cathode 116 of the photo-multiplier tube 8. The intermediate points between the resistors 100-189, inclusive, are-connected through similar protective resistors 131-139, inclusive, to the dynodes 128-128 of the photo-multiplier tube. The protective resistors are providedto protect-the phototube from damage due to daylight illuininative impinging thereon.

The output electrode 112 of the photo rnultiplier tube 8 is connected through line 142 to the input'of an automatic dimmer circuit which may include anam- Inductance coil 72 isconsa ience plifier tube 144 having a plate 14-5, control grid 146, cathode 147' and heater 1'48. The cathode 147 is connected to the ungrounded side of the heater which is energized from the main power source through conductor 22. The control grid 146 is connected to receive the output of the photo-multiplier tube and is further connected to a resistor 150 which isconnected in series with a resistor 151 and a potentiometer 152, the adjustable arm 153 of the latter being connected to line 22.

Operating voltage for the plate of the amplifier tube 144 is supplied thereto from the regulated output of the vibrator power pack 2, through line 156 which is connected between the anode 49 of the voltage regulator tube 4 and a relay coil 158 in the plate circuit of the tube 144. A condenser 160 is shunted across the relay coil 158.

Relay 158 comprises an armature 162 which is associated with a pair of stationary contacts 163 and 16 4, the armature. being normally closed against contact 163. A resistor in series with a condenser 171 is shunted across armature 162 and. contact 164 of the relay to prevent arcing the'rebetween. The armature 162' is connected through conductor 173 and line 22 to the main power source. Stationary contact 163 is connected through line 174 to the junction between resistors 150 and 15 1 in the grid circuit of the amplifier, while stationarycontact 164 is connected through line 176 to the upper contact 179 of a manually operable switch 178, 179'. and 186, which may be the standard beam changing. foot switch customarily provided in motor vehicles.

Switch arm-.178 of the foot switch is connected in circuit with a relay coil 182 having an armature 183 and a pair of stationary contacts 184 and 185 which are associated with the high and low beam head lamp filament circuits through conductors 188 and 198, respectively. Armature 183 is normally closed against stationary contact 184 when the relay coil 182 is de-energized, in which condition the high beam filaments of the vehicle head lampsare energized through a circuit from the main power source, line. 16, armature 183, contact 184, and line 188 to the high beam filaments. With switch arm 1.78-of the foot switch depressed against lower contact 188, the relay coil182 is held energized and the low beam filaments of the vehicle headlamps are thus energized. For automatic control over the vehicle head lamps, switch arm 178 of the foot switch is closed on contact 179 thereof.

The operation of the automatic dimmer circuit is as follows. In the absence of illumination incident on the photomultiplier tube, the amplifier tube 144 conducts sutficient current to energize relay 158 to maintain its armature closed against contact 163 thereof, tie-energizing relay 182, and the high beam filaments of the vehicle headlamps are energized'from the main power source throughline 16, armature 183 and contact 184 of relay 182, and line 188. 7

Upon encountering a distantly approaching vehicle, the output of the photo-multiplier tube increases negatively so as to afiect'the conductivity of amplifier tube 144 and decrease the current therethrough. When the approaching vehicle has approached reasonably close so that the illumination therefrom is. sufiicient to de-energize relay 158; the-armature 162 thereof isreleased to engage contact 164- to energize the relay coil 182 from line 22 through ar'mature-162 and contact 164 of relay 158, line 176, contact 179 and switch arm 178 of the foot switch, and line 192. With relay 182 thus energized, the head lamps are switched from high to low beam position. Manual control over thehead lamp beam condition may be had under these conditions by virtue of the overriding action of the foot-switch.

In order to hold'the head lamps in dim position after the headlamps of the approaching vehicle have been dimmedin response thereto, the dimmer control circuit iscausedto operate at an increased threshold of sensitivity so as to prevent the amplifier tube 144 from returning to its original conductivity in view of the decreased illumination now received from the dimmed head lamps of the approaching vehicle. This function is accomplished by automatically inserting resistor 151 and potentiometer 152 in the grid circuit of the amplifier tube, these elements having been previously shorted out of the grid circuit when relay 158 was energized. The output of the photo-multiplier tube then flows through the series combination of resistors 150, 151 and potentiometer 152 and develops a negative grid bias voltage thereacross that is suificient to maintain the amplifier tube 144 in substantially non-conducting condition. Upon removal of the external illumination incident on the photocell, the amplifier is returned to its original dark actuated condition, and the head lamps are switched from dim back to high beam.

A manually operated auxiliary foot switch 196, 197, which is connected from ground through a resistor 198, conductor 199, and relay coil 158 to the regulated output of the vibrator power pack, is provided to enable the operator to return his head lamps, which have been dimmed by the bright lights of an approaching vehicle, to brightened condition upon failure of the operator of the latter vehicle to dim his bright lights. When the dimmer control circuit is in dim condition, relay 158 is de-energized while relay 182 is energized through a circuit rom the main power source, lines 22 and 173, armature 162 and contact 164 of relay 158, line 176, contact 179 and switch arm 178 of the standard foot switch, line 192 to the relay coil 182 and to ground. The standard foot switch is maintained in this position when automatic control over the vehicle head lamps is to be effected. Under these conditions, the dimmed head lamps of the vehicle cannot be automatically returned to brightened condition to flash the operator of the approaching vehicle. However, by closing the auxiliary foot switch, the relay 158 may be energized through a circuit from the regulated output of the power pack, lines 156 and 199, resistance 198 to ground, thereby de-energizing relay 182 and returning the headlamps to brightened condition.

In order to operate the dimmer circuit under twilight conditions at dawn or dusk, a manually operated switch 201, 202 is provided to short the potentiometer 152 out of the grid circuit of the amplifier tube 144. This switch functions to change the ratio of the sensitivity level of the dimmer system between the hold and dim positions sufiiciently to prevent natural twilight illumination from holding the head lamps in their automatically dimmed condition after the vehicles have passed. By decreasing the resistance in the grid circuit of the amplifier control tube the grid bias, which is furnished by the voltage drop developed across the total grid circuit resistance, for a given output from the photo-multiplier tube is reduced which decreases the sensitivity of the system. Otherwise stated, the system requires a greater amount of illumination on the photo-multiplier tube to hold the head lamps in dimmed condition. It will be noted that the sensitivity of the system when the control system is in bright position is unaffected.

Referring now more particularly to the power supply system of my invention, its operation is as follows. D. C. power is supplied from the vehicle battery to the input of the vibrator power pack 2. Due to changes in engine speed and in other electrical loads supplied by the battery, the voltage supplied thereby may vary from, say 5.5 to 7.0 volts which represents a variation of the order of 25%. Since the self-rectified output voltage appearing between the center tap and ground of the transformer secondary winding 30 of the power pack is subject to approximately the same percentage variation, the secondary winding thereof is designed to deliver a normal output voltage of the order of 300 volts instead of the full 1100 volts, for example, required to operate the photo-multiplier tube 8. This is done to provide for 6 regulating the output of the power pack at a voltage level that is relatively low in comparison to the high voltage for the photo-multiplier tube in view of the dilficulty and expense of obtaining satisfactory voltage regulation at high voltage levels.

In the present system, the voltage regulation is obtained by the gaseous voltage regulator 4 which is connected through its resistor 48 to the output of the power pack. Variations in the output of the power pack are absorbed in the voltage drop across resistor 48 and the voltage appearing across the electrodes of the regulator tube is stabilized at approximately 150 volts within plus or minus 2 volts.

The stabilized voltage appearing across the voltage regulator tube is then supplied to the high voltage high frequency section 6 of the power supply system which functions to generate a highly stable radio frequency output voltage which is rectified and supplied to the photo-multiplier tube 8 at the desired high voltage level. The oscillator section 56 of the high frequency section of the power supply system is of the tuned plate variety and is tuned to generate a radio frequency in the neighborhood of 350 kc., for example, which is intermediate the 455 kc. and 260 kc. intermediate frequencies employed in broadcast superheterodyne receivers. If desired an audio frequency oscillator could be employed, but for reasons of economy and efiiciency a radio frequency oscillator is preferred. Tuning of the tank circuit of the oscillator is accomplished by varying the adjustable condenser 68 therein until the voltage between line 94 and ground is at a maximum. The oscillator is then operating at maximum output and peak efiiciency.

In order to accurately set the operating voltage supplied to the electrodes of the photo-multiplier tube for the most efficient operation thereof, it is desired that the output of the high voltage section of the power supply be adjustable over a range of output values. This is accomplished in my invention by adjusting the position of the variable tap on resistor 88 so as to change the voltage applied to the screen grid 60 of the tube 58, thereby changing the conductivity thereof. Since the tuning of the oscillator tank circuit is not afliected, the oscillator continues to operate at its peak efficiency and to deliver a highly stable output voltage, the magnitude of which may be adjusted over a wide range of values in accordance with the voltage applied to the screen grid circuit thereof.

Further stability of the oscillator is afforded by the action of the condenser 78 which is connected across the variable condenser 68 in the oscillator tank circuit. Condenser 70 is a conventional temperature compensated condenser, the capacitance of which changes in a negative direction and oppositely to the change in capacitance of condenser 68 with temperature changes. Thus, the frequency of the oscillator tank circuit remains unaffected, with the result that the oscillator operates at its maximum efficiency and delivers a highly stable output therefrom for substantially all operating conditions.

Although my invention has been shown and described in connection with a particular form of automatic dimmer circuit, it may be employed equally well with different types of dimmer circuits and still other forms of electronic circuits that require a closely regulated high voltage power supply. it is to be understood that the above described arrangement is but illustrative of the application of the principles of the invention and that other arrangements may be devised by those skilled in the art without departing from the spirit and scope thereof.

I claim:

1. A high-voltage power supply system comprising, in combination, a source of low-voltage D. C., means connected to said source to change the low voltage D. C. to a higher voltage D. C., a voltage regulator tube connected to said voltage changing means to regulate the said higher D. C. voltage therefrom, a resistance connected across.

said voltage-regulator tube, means'for generating.an A.- C.-

voltage several timcs'higher than said higher D C. voltago, said generating means includinga vacuum tubeoscillatorhavin'g a-plate, a cathodeand apair of grid electrodes, a resonant tank circuit connected to said plate electrodeand a connection from the high potential side of said resistance across said voltage regulator tube to supply a-regulated D. C. operating voltage through said resonant tank circuit to the said plate electrode of said oscillator tube,- an input circuit connected to one of said grid electrodes and regenerativelycoupled to said tank circuit, an adjustabletap on said resistance connected to the other of said grid electrodes, an output circuit inductively coupledto said tank circuit and high-voltage rectifying means connected in said output circuit for converting-the A. C. output voltage therefrom to D. C.

2. A stabilized high-voltage regulated power supply system comprising, in combination, a low voltage battery source ofD. C., vibrator power supply means connected to said battery forchangiug said low voltage D. C. to a higher D.'C., a voltage regulator tube connected to said vibrator power supply means to regulate the said higher D. C. voltage therefrom, a resistance connected across said-voltage regulator tube, means for generating an A. C. voltage several times higher than said higher D. C. voltage, said generating meansineluding a vacuum tube oscillator having a plate, a cathode and a pair of grid electrodes, a resonant'tank circuit connected to said plate electrode and having a negative temperature coefficient condenser therein, a connection from the high potential side of said resistance acrosssaid voltage regulator tube to supply a regulated D. C. operating voltage to the said plate electrode of said oscillator tube, an input circuit connected to one of said grid electrodes and regeneratively coupled to said tank circuit, an adjustable tap on said resistance connected to the other of said grid electrodes, an output circuit inductively coupled to' said tank circuit and high voltage rectifying means connected in said output circuit for converting the A. C. output voltage'therefrom to D. C.

3. in combination with an automatic headlight dimmer system having a photomultiplier light pick-up cell requiringa high level D. C. operating voltage and an amplifier tube controlled from said pick-up cell and requiring a considerably lower level operating voltage therefor, a low voltage batter-y source of D. C., vibrator power supply means connected to said battery changing said low voltage D. C. to a higher D. C. voltage approximately in the range of that required for said amplifier tube of said automatic headlight dimmer system, means including a voltage regulator tube connected to said vibrator power supply means to regulate the said higher D. C. voltage therefrom, a resistance connected across said'voltage regulator tube and a connection from the highpotential side of said resistance to supply a'regulated D. C/operating voltage to said amplifier tube of said automatic headlight dimmer system, means generating an A. C. voltage in the range of that required for said photomultiplier tube of said automatic headlight- .dimmer'system includinga vacuum,

tube oscillator-havingza plate, cathode and at least two grid electrodes,- a tuned tank circuit connected to' said plate electrode and a connection from the high potential side. of'said resistance across said voltage regulator tube to supply a regulated D. C. operating voltage to said plate electrode of said oscillator tube, an input circuit connected to one of said grid electrodes and regeneratively coupled to said tank circuit, an adjustable tap on said resistance acrosssaid voltageregulator tube connected to the other of said grid electrodes of said vacuum tube oscillator and supplying an adjustable portion of said regulated D. C. voltage thereto, an output circuit coupled to said tank circuit and high voltage rectifying means in said output circuit converting'the high A. C. output voltage therefrom to a high level D. C. voltage for operating said photomultiplier tube of said automatic headlight dimmer system.

4. In combination withan automatic headlamp dimmer system having. a light sensitive pick-up device requiring a high. level operating voltageandan amplifier tube con trolled from said pick-up device and requiring a lower level operating voltage, a power supply system including a battery, a vibrator connected tosaid battery and supplying an output voltage approximately in the'range of 'said amplifier tube operating voltage, voltage regulating means connected to said vibrator and maintaining the output voltage supplied therefrom substantially constant, a con-.

nection from said'voltage regulating means to said amplifier tube to supply a regulated operating'voltage thereto,

a vacuum tube oscillator havinga plate, a cathode and a pair of grid electrodes, a tuned tank circuit connected to said plate electrode and a connection from said voltage regulating means to said'tank circuit supplying a regulated operating voltageto'theplate' electrode of the oscillator tube through thesaid'tank circuit thereof, an oscillator input circuit connected to one of the said grid electrodes of said oscillator tube and regeneratively coupled to said tank circuit thereof, a potentiometer connected across said voltage regulating means and having an adjustable arm connected to the other of said grid electrodes of said oscillator tube,'and an output circuit coupled to the said tank circuit of said oscillator tube and connected to said light sensitive pick-updevice of said automatic headlamp dimmer system'for' supplying a'regulated high level opcrating voltage thereto.

References Cited in'the'file of this patent UNITED STATES PATENTS 2,162,520 Whitaker June 13, 1939 2,276,832 Dome Mar. 17, 1942 2,374,781 Schade May 1, 1945 2,535,651 Newman Dec. 26, 1950 2,543,902 Dye; Mar. 6, 1951 2,549,923 OBrien Apr. 24, 1951 2,565,621 olson Aug. 28, 1951 2,600,247 Huetten June 10, 1952

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