US3527998A - Voltage regulator starting system - Google Patents

Description

Sept. 8, 1970 DE LOSS J. TANNER 3,

VOLTAGE REGULATOR STARTING SYSTEM Filed April 26, 1967 R. E OUTPUT VIDEO AM P MODULATOR VFIG; 1

BEAM REGU LATOR RE OSC.

HORIZONTAL OUTPUT HoRosc.

a AMP.

PER

BLANKING CIR.

VE RT DET.

SYSTEM FIG. 2

0 In venfor DE LOSS J TANNE R, deceased 7 U by Arfhur L. He'llyer, Adminisfrafor.

' U.S. Cl. 323-22 United States Patent 3,527,998 VOLTAGE REGULATOR STARTING SYSTEM De Loss J. Tanner, deceased, late of Bensenville, 111., by

Arthur L. Hellyer, administrator, Wheaton, 11]., assignor to Motorola, Inc., Franklin Park, 11]., a corporation of Illinois Filed Apr. 26, 1967, Ser. No. 635,644 Int. Cl. GOSf 1/56, J/64 6 Claims ABSTRACT OF THE DISCLOSURE A starting and sustaining system for a regulated supply including a diode which couples an unregulated voltage to a Zener diode for starting the regulator which then produces a regulated output voltage. This regulated output voltage is fed back to remove the unregulated voltage by reverse biasing the diode and provide bias for the Zener thereby improving the regulation of the output voltage.

A power supply regulator circuit converts an unregulated input voltage into one or more regulated DC voltages and in a camera television system, for example, it is particularly important that the biasing voltages and heater voltages for respective circuits therein be maintained constant independent of changes in the line voltage in order to provide proper picture production. A Zener diode may be used to developa relatively constant reference voltage to bias one or more of the amplifying devices in the regulator circuit. In the past, the regulator circuit has been started by coupling a portion of the unregulated input voltage through a relatively large resistor to the Zener diode which in turn causes the regulator circuit to be operable to develop DC output voltages for the television camera system. A signal is then coupled back from a circuit in the system such as the horizontal output circuit to the Zener diode to provide the operating voltage therefor. Most of the bias is supplied by the latter circuit but the unregulated input voltage continues to be applied. Although the Zener does absorb a large percentage of the changes in the unregulated voltage, it is not a perfect device so that some degradation in regulator performance may be noted.

It is, therefore, an object of this invention to overcome the above defect by providing an improved starting system which furnishes a starting voltage to render a circuit or device operable and to automatically remove the starting voltage thereafter.

Another object is to provide reliable starting of a regulator circuit without degrading its performance.

Another object is to provide an improved power supply with means to start a regulator circuit therein with an unregulated voltage and thereafter removing the same so that the regulator circuit furnishes DC voltages which are independent of changes in the line voltage.

In a specific embodiment, an unregulated voltage is used to forward bias a diode in order to develop a starting voltage for a Zener diode in a regulator circuit. In response thereto, the regulator provides a voltage to bias the horizontal deflection circuit in a camera television system so that horizontal pulses are developed and rectified into a DC control potential. This potential is in turn coupled back to the diode to reverse bias the same so that the unregulated voltage is isolated from the Zener. The DC control potential is applied to the Zener diode in order to provide a regulated voltage therefor. Thus, the DC voltages developed by the regulator circuit for supplying other circuits in the camera television system is independent of amplitude changes in the unregulated input voltage.

In the drawings:

FIG. 1 shows a television camera system partly schematic and partly in block which incorporates the invention; and

FIG. 2 is a representation of the signal developed by the horizontal deflection system which is useful in explaining the operation of the invention.

Referring now to FIG. 1, there is illustrated a television camera system incorporating the features of this invention. The vidicon tube 10 has a light sensitive target 12 the resistance of which varies inversely with the amount of light flowing on it. An electromagnetic type of tube is utilized so that a relatively high DC voltage must be developed and applied to focus electrode 34 in order to provide electrostatic focus while a current must be developed and translated through a focus coil 56 wound around vidicon 10 to provide magnetic electron beam focus. The target 12 is coupled to a video amplifier 14. Horizontal sweep signals are developed by horizontal oscillator and amplifier 15 and processed in horizontal output circuit 16. Vertical sweep signals developed by vertical deflection system 18 along with the horizontal signals are coupled to mixer 20 which inserts the horizontal and vertical blanking and synchronizing pulses in the video signal at the output of video amplifier 14. The composite video signal is then applied to modulator 22 which cooperates with RF oscillator 24 to develop an RF output at terminal 26. Horizontal and vertical sweep signals are applied from their respective systems to the horizontal and vertical yokes represented by block 28 in order to scan the electron beam generated by the cathode 30 across target 12. Further signals from deflection systems 16 and 18 are processed in the blanking circuits 29 and applied to control grid 32 for blanking the electron beam during retrace. Beam regulator 31 is coupled to cathode 30 and provides means for automatically controlling the electron beam current.

Power supply 44 comprises a power transformer 50 to which an AC line voltage is applied, a bridge rectifier circuit 46 which develops a pair of DC voltages from the AC signal across the secondary winding of transformer 50, and a regulator circuit 48 which generates three regulated DC voltages on terminals 80, 92 and 102 for various circuits in the television camera system.

It will be noted that several of the DC voltages in the circuit of FIG. 1 have numerical values labeled on the drawing. It will be appreciated that these values are merely for illustration purposes and voltages of different magnitudes may be employed and still come within the scope of this invention. Circuit 46 comprising four diodes and two filter capacitors is known and therefore further explanation is believed to be unnecessary. The rectifier circuit 46 develops DC voltages of 20 volts and 10 volts on leads 52 and 54 respectively which are utilized in regulator circuit 48.

In regulator circuit 48, emitter 66 of PNP transistor 60 is connected to a point of reference potential such as ground through resistor 68 and variable resistor 70. In order to derive 6.5 volts DC on emitter 66 of transistor 60 and at terminal 80, it is necessary to provide 6.7 volts on base 64 due to the .2 volt drop across the base-toemitter junction of a PNP transistor. It is further desirable that this 6.7 volt source be constant with changes in line voltage. This may be done by employing a 6.7 volt Zener diode from base 64 to ground and supplying the anode thereof with a minus voltage. However, Zeners are commercially available only in fixed values such as a 5.6 volt type. Since a 6.7 volt Zener is not a commercial item and thus available only at an increase in cost, a 5.6 volt Zener is connected from base 64 of transistor 60 to the movable arm of variable resistor 76. The -6.5 volts on emitter 66 is applied to a voltage divider network com- 3 prising variable resistor 76 and resistor 78 to ground. The movable arm is set so that approximately 1.1 volts is present on the Zener cathode. A 12 volts from terminal 102, the development of which will be explained subsequently, supplies current for the Zener 74 through a resistor 72 connected to the Zener anode to cause 6.7 volts to be developed at base 64 (5.61.1=6.7). Thus, since the base is clamped at 6.7, the emitter 66 is clamped at .2 volt more positive or at 6.5 volts.

The focus coil 56 provides means to supply 20 volts from lead 52 to collector 62 of transistor 60. Capacitor 58 coupled thereacross is used to limit high frequency oscillations which may occur. By merely adjusting variable resistor 70, any desired current may be allowed to flow through the collector-to-emitter junction of transistor 60 thereby determining the magnitude of current flowing through focus coil 56. Since resistor 70 alone determines the amount of focus coil current, if, for example, the line voltage drops so that there is a proportional voltage decrease on lead 52, the current will remain unaffected due to the corresponding drop on collector 62 of transistor 60.

Emitter 66 of PNP transistor 60 is DC coupled to base 88 of transistor 82 and lead 54 is connected to collector 84 to supply volts DC thereto. Since transistor 82 is a PNP type, there is a .2 volt drop across the base-toemitter junction and 6.3 volts is available on emitter 86 and at terminal 92. If the voltage on lead 54 changes, the voltage at terminal 92 would remain at 6.3 because the voltage on base 88 is at a constant 6.5 volts and the base-to-emitter drop of .2 is also constant. Bias for amplifying devices in horizontal output circuit 16 is coupled from terminal 92 to input terminal 106. Voltage for focus electrode 34 is developed by coupling horizontal pulses to a high voltage circuit comprising the primary winding 36 of a transformer 37, a diode 40 to rectify the pulses and capacitor 42 for filter purposes in order to provide a relatively ripple-free DC voltage.

Referring now more particularly to the operation of starting system 96, as was explained previously, -12 volts must be applied to resistor 72 to reverse bias Zener diode 74. The 12 volts at terminal 102 is used for this purpose and additionally may supply other circuits in the television camera system. The cathode of diode 98 is connected to lead 54 and its anode is connected to terminal 102. When plug 108 is inserted in a wall outlet, -10 volts is developed on lead 54 so that diode 98 becomes forward biased and -10 volts is available at terminal 102 (minus the small drop across diode 98). These 10 volts are applied to resistor 72 to reverse bias Zener diode 74 so that 6.5 volts is available on emitter 66 and 6.3 volts is available on emitter 86.

The biasing voltage on terminal 92 is connected to terminal 106 of horizontal output circuit 16 which causes it to develop horizontal pulses across primary winding 36 to be coupled to secondary winding 38 with the bottom connected to 6.3 volts. A tap 110 on the secondary winding is connected to the cathode of diode 100 the anode of which is connected to terminal 102. Reference is made to FIG. 2 which illustrates the waveform at tap 110. Since an inductance is essentially a short circuit to DC, the 6.3 volts at the top of secondary winding 38 appears at tap 110 so that the pulses thereat have a reference equal to 6.3 volts, indicated by level 112.

The number of turns on secondary winding 38 is selected so that the amplitude of the pulses provided at tap 110 will forward bias diode 100 which will rectify the same and cause approximately 12 volts to appear at terminal 102. Now diode 98 is reversed biased because there is 10 volts on its cathode and 12 volts on its anode. Thus the voltage on terminal 102 is supplied solely from the horizontal output circuit. This 12 volts is used to bias Zener diode 74 so that the 6.3 volts at terminal 92 is regulated and therefore the pulses applied to the cathode of diode 100 are also regulated which in turn causes the 12 volts at terminal 102 to be regulated. It

will be noted that initially resistor 72 was supplied from lead 54 the voltage on which is subject to variations according to line voltage changes. But, once the horizontal deflection system 16 becomes operable and the 12 volts at terminal 102 is developed, the unregulated voltage on lead 54 is isolated from the Zener diode. The circuit thus described provides voltage on terminal 102 not only to bias the Zener but also provides an additional regulated voltage for use in various circuits of the camera system of FIG. 1.

What has been described, therefore, is a starting system which utilizes an unregulated starting voltage to cause a regulator to become operable after which a regulated voltage is derived to maintain the regulator operable and to isolate the unregulated starting voltage. The invention has been explained with reference to a regulator circuit. However, the novel starting system described herein may be employed in any application requiring the turning on of a circuit or device where continued application of the starting voltage would be undesirable.

What is claimed is:

1. In a regulator circuit having an input circuit adapted to be coupled to an unregulated input voltage and an output circuit adapted to provide a regulated output voltage, the combination of; a 'bias circuit for controlling the regulator circuit, said bias circuit having a Zener diode to establish a reference voltage for said regulator circuit, means including a switching device coupled between said bias circuit and the input circuit and switched into conduction by the unregulated input voltage for translation thereof to said bias circuit to provide a starting voltage which varies with changes in said unregulated input voltage for said regulator circuit so that an unregulated output voltage is developed in the output circuit, first circuit means coupled to the output circuit and energized by the unregulated output voltage for developing a control signal, second circuit means coupling said first circuit means to said switching device for supplying said control signal thereto to render said switching device nonconductive, said second circuit means also coupled to said Zener diode for supplying said control signal thereto to establish a reference voltage which is relatively constant with changes in said unregulated input voltage.

2. The regulator circuit according to claim 1, said control signal being an AC signal, said second circuit means comprising a further switching device and capacitance means to rectify and filter said control signal to develop a DC control potential for rendering said first mentioned switching device non-conductive so that the unregulated input voltage is isolated from said bias circuit.

3. In a regulator circuit, for providing a regulated output, having an input terminal conected to a supply of unregulated voltage and an output circuit coupled to an output terminal, the combination of: bias circuit means for controlling the regulation of the regulator, first switching device connected in series between the supply of unregulated voltage and said bias circuit means, said first switching device being first switched into conduction by the unregulated input voltage to thereby apply an unregulated voltage to said bias circuit means which provides a starting voltage to said regulator circuit, said regulator circuit thereby developing a first output having a substantially greater degree of regulation than the unregulated voltage, first circuit means connected to the output circuit and responsive to said first output to develop a control signal, second switching device connected in series between said first circuit means and said bias circuit means, said second switching means being switched into conduction by said control signal to thereby apply the control signal to both said first switching means thus rendering it nonconductive and to said bias circuit means, said regulator developing a second output in response to said control voltage which has a greater degree of regulation than said first output.

4. The combination of claim 3 wherein said bias circuit means includes a Zener diode.

5. The combination of claim 3 wherein: the regulator circuit includes a transistor having emitter, base and collector electrodes; said bias circuit means comprises a Zener diode connected both to one end of a resistor and from said base electrode to ground for establishing a reference voltage for said transistor; said first switching device includes a first diode connected between the other end of said resistor and the supply of unregulated voltage, said first diode being poled to translate the unregulated voltage to said Zener diode to establish said starting voltage; said second switching device includes a second diode coupled from said first circuit means to said other end of said resistor; said second diode being poled to translate said control voltage, which has both a greater amplitude and a greater degree of regulation than said unregulated voltage, to both reverse bias said first diode, thereby isolating the unregulated voltage from said bias circuit means, and supply said control voltage through said resistor to energize said Zener diode; the regulator circuit being responsive to said control voltage to provide said second out- 6 put having a greater degree of regulation than said first output.

6. The regulator circuit according to claim 3 wherein said control signal is an alternating current signal, said second switching means includes a diode to rectify and a capacitor to filter said control signal to develop a direct current control potential for rendering said first switching device nonconductive so that the unregulated voltage is isolated from said bias circuit means.

References Cited UNITED STATES PATENTS 3,335,361 8/1967 Natale et a1 323-22 3,344,340 9/1967 Webb 323-22 3,403,320 9/1968 Whitman 3234 J D MILLER, Primary Examiner A. D. PELLINEN, Assistant Examiner US. Cl. X.R.

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