US3916288A - Momentary power supply shutdown system - Google Patents

Momentary power supply shutdown system Download PDF

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Publication number
US3916288A
US3916288A US447819A US44781974A US3916288A US 3916288 A US3916288 A US 3916288A US 447819 A US447819 A US 447819A US 44781974 A US44781974 A US 44781974A US 3916288 A US3916288 A US 3916288A
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United States
Prior art keywords
power supply
circuit
capacitor
shutdown
voltage
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Expired - Lifetime
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US447819A
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English (en)
Inventor
James E Hicks
Hugh C Willard
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Lockheed Martin Tactical Systems Inc
Maxar Space LLC
Original Assignee
Aeronutronic Ford Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Aeronutronic Ford Corp filed Critical Aeronutronic Ford Corp
Priority to US447819A priority Critical patent/US3916288A/en
Priority to CA219,057A priority patent/CA1040706A/en
Priority to BR1100/75A priority patent/BR7501100A/pt
Priority to JP2571775A priority patent/JPS546442B2/ja
Application granted granted Critical
Publication of US3916288A publication Critical patent/US3916288A/en
Assigned to LORAL AEROSPACE CORP. A CORPORATION OF DE reassignment LORAL AEROSPACE CORP. A CORPORATION OF DE ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: FORD AEROSPACE CORPORATION, A DE CORPORATION
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N3/00—Scanning details of television systems; Combination thereof with generation of supply voltages
    • H04N3/10—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical
    • H04N3/16—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical by deflecting electron beam in cathode-ray tube, e.g. scanning corrections
    • H04N3/20—Prevention of damage to cathode-ray tubes in the event of failure of scanning
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of AC power input into DC power output; Conversion of DC power input into AC power output
    • H02M7/02—Conversion of AC power input into DC power output without possibility of reversal
    • H02M7/04—Conversion of AC power input into DC power output without possibility of reversal by static converters
    • H02M7/12—Conversion of AC power input into DC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/145—Conversion of AC power input into DC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
    • H02M7/155—Conversion of AC power input into DC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
    • H02M7/1555—Conversion of AC power input into DC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only with control circuit
    • H02M7/1557—Conversion of AC power input into DC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only with control circuit with automatic control of the output voltage or current

Definitions

  • ABSTRACT A power supply contains a circuit, including a switch [52] Cl 321/14; 178/75 R; rig/DIG- ll? device, which responds to a sudden increase in load 317/33 SC current and turns the power supply off for a short pre- [51] Ill!- Cl. H02m 7/00 determined time interval.
  • a switch [52] Cl 321/14; 178/75 R; rig/DIG- ll? device, which responds to a sudden increase in load 317/33 SC current and turns the power supply off for a short pre- [51] Ill!- Cl. H02m 7/00 determined time interval.
  • Such an arrangement is [58] Fleld 0f Search. 321/11-14, f l i a color television display wherein a cathode ray 321/2 178/75 11; 315/27 R; tube subject to arcing is used.
  • Such arcing can be de- 317/27 33 SC structive, particularly where a well
  • Patent application Ser. No. 384,116 which was filed July 30, 1973, and assigned to the present assignee, discloses a regulated power supply using an SCR as a combined rectifier and control device.
  • the present invention is useful in such a power supply, particularly where protection against load device arcing is desired.
  • CTR cathode ray tube
  • a conventional SCR is connected as a rectifier between the a-c line and a capacitor-input filter.
  • the SCR is triggered by means of a pulse generator that produces a trigger pulse delayed with respect to the zero crossing of the a-c input.
  • the delay is made a function of the d-c output voltage so that the SCR fires at a time that will vary to produce a constant d-c output voltage. This action produces a circuit that is regulated against load changes as well as a-c line in-put variations.
  • a switching circuit is connected to the power supply so that in the presence of a sudden load increase, such as would be encountered in a CRT display device when a CRT arc occurs, the switching device is actuated thereby shutting off the pulse generator and hence the SCR.
  • a time constant circuit is incorporated so that after a suitable off interval, the power supply operation is automatically restored.
  • FIG. 1 is a schematic diagram of a prior art circuit
  • FIG. 2 is a graph showing the operation of the circuit of FIG. 1;
  • FIG. 3 is a schematic diagram of a circuit employing the invention.
  • FIG. 4 is a schematic diagram showing in greater detail a power supply employing the invention.
  • SCR 1 is connected as a half wave'rectifier to the a-c input line.
  • This input can be the secondary of a transformer, but in the interests of economy, and if no voltage transformation is required, it is convenient to connect-the SCR directly to the volt a-c line.
  • the half-wave rectified output is applied to a conventional filter 2 which smooths the rectifier output to provide a steady d-c output voltage. If the circuit used a simple diode, or if the SCR gate electrode were returned through a suitable resistor to the anode, a conventional half-wave rectifier would result.
  • the rectifier would turn on during the rise of the positive excursion of the a-c input voltage and would charge filter capacitor 4 to the peak a-c line voltage.
  • the rectifier would turn off when the a-c input voltage drops to the cathode voltage level.
  • the filter capacitor would discharge until the next positive a-c input excursion whereupon the cycle repeats.
  • the d-c output voltage would be a function of the peak input voltage.
  • the SCR can be fired when desired by a controlled gate pulse.
  • the SCR is fired somewhere near the a-c input peak, the firing angle being designated 4) will be located in the range extending from shortly ahead of the 90 point to shortly ahead of the point on the input waveform. This is because the maximum power supply energy capability will occur when the SCR is fired slightly ahead of the 90 point on the input wave, and to have any output at all the SCR must be fired ahead of the 180 point.
  • the dashed line shows the voltage waveform across the input filter capacitor 4.
  • the capacitor will quickly charge along an exponential rise to whatever voltage is present at the SCR anode. Then the capacitor will discharge between positive input alternations until the next firing interval. It can be seen that the capacitor charge is no longer related to peak line voltage.
  • the magnitude of charge can easily be controlled or varied by changing the firing angle qb.
  • the pulse generator is synchronized by connecting it to the a-c input.
  • the generator supplies a pulse, delayed with respect to the a-c input, that will turn the SCR on in the range of less than 90 to less than 180.
  • the delay is made variable in response to the difference between the d-c output voltage and a separate fixed d-c reference voltage applied between the indicated terminals. If the d-c output voltage is too low, the delay is reduced so that the SCR fires sooner; this will locate the firing point closer to the a-c input peak. If the do output voltage is too high, the delay is increased so that the SCR fires later and, therefore, lower down on the a-c input waveform.
  • the firing angle d a strong function of d-c output, close control of the output voltage is obtained.
  • the circuit will compensate for input or power line variations as well as load variations.
  • FIG. 3 shows the components that are added to the circuit of FIG. 1 to practice the invention and how the power supply is connected to a CRT display.
  • Capacitor 7 charges through resistor 8 to the difference between the d-c output voltage and the d-c reference voltage.
  • the cathode of diode 9 will be at the positive potential of the d-c reference voltage.
  • the anode of diode 9 is at a substantially lower potential (as will be apparent from the more detailed description of the circuit of FIG. 4), diode 9 will be reverse biased and in its open switch state. For these conditions the circuit will function normally as a regulated power supply.
  • the power supply operates the CRT display circuits 30 which include a high voltage supply 31.
  • the display circuits and high voltage output are connected to CRT 32.
  • capacitor 7 Once the d-c output voltage has dropped to some low value and capacitor 7 has discharged through resistor 8 to a value that will no longer hold diode 9 in its on switch state, the diode will cease to conduct and the pulse generator will resume its functioning. This will again turn SCR 1 on periodically and filter 2 will again become charged and the system will resume normal functioning.
  • the time constant of capacitor 7 and resistor 8 is established to give the circuit an off interval of about 2 seconds. This period will be long enough to make sure that any are will be completely interrupted but is short enough to have only a small efiect on TV viewing. Clearly this interval can be selected within wide limits to achieve the desired action.
  • FIG. 4 is a complete power supply schematic showing how the pulse generator of FIG. 3 can be implemented using a combined pulse generator-variable delay circuit.
  • SCR 1 is connected directly to the a-c input and provides rectified d-c output by way of filter 2 which is composed of input filter capacitor 4, output filter capacitor 5, and series filter inductor 6. Under typical conditions, the d-c output voltage may be of the order of volts.
  • Complementary transistors 10 and 11 are connected into a well known bistable latching complementary pair configuration. Transistor 10, in addition to being part of a latching pair, also acts as a Miller effect delay device. When transistor 10 is turned on from its off state, it will come on slowly due to the Miller effect. After a delay period, its output will become sufficient to turn transistor 11 on and the complementary pair will then rapidly switch on to saturation.
  • This latter turn on action provides a pulse that is coupled by way of couplingcapacitor 25, to the SCR so as to fire it. Since the turn on of transistor 10 is synchronized to the a-c input by way of the network consisting of resistors 13 and 18 and diode 12, the SCR firing angle is then controlled by the duration of the Miller effect delay. The delay is in turn controlled by applying (by way of resistance 17, 19, 20, 21, 22 and 23) a fraction of the d-c output voltage to the base of transistor 11 to act as a bias or threshold control. As the d-c output voltage varies, the threshold at which the complementary pair switches on will be varied. This action varies the duration of the Miller efiect delay. The sense of this feedback loop is such that the do output voltage will tend to remain nearly constant as will be discussed hereinafter.
  • a 20-volt reference supply is shown operating the delay and switching circuits.
  • a suitable regulated voltage is available it would be used. If no such regulated voltage. is available, the reference can be obtained from any convenient unregulated source that supplies more than the required value at the lowest a-c line voltage condition.
  • a dropping resistor and zener diode having the required voltage rating are connected in series across the unregulated source. The voltage present across the zener diode is then used as the reference. If no such unregulated source is available an additional rectifier diode and filter capacitor combination can be connected to the a-c input line and the above mentioned resistor-zener diode combination connected across the filter capacitor.
  • diode 12 In the quiescent state when the a-c input is near zero, diode 12 is forward biased by electron flow due to the 20-volt reference supply. Electrons will flow from ground through resistor 13, from the cathode of diode 12 to its anode, and then up through resistor 14 to the positive supply terminal. Resistor 13 is made quite small, about 0.1% of the value of resistor 14, so that the drop across it is negligible. Diode 12 being forward biased will develop about 0.6 volt at the base of transistor 10. Resistors l5 and 16 are proportioned to apply a positive voltage of about 2 volts to the emitter of transistor 10. Thus, transistor will not conduct until its base is more than about 2.7 volts positive. For these quiescent conditions transistor 10 will be cut off and its collector will rest at almost 20 volts. This will apply a high positive potential to the base of transistor 11 through resistor 17 and transistor 11 will be held in its off state. This is a stable state for both transistors.
  • Resistors l3 and 18 form a voltage divider across the a-c input and are proportioned to apply about 2% of the input to the cathode of diode 12. This will be about 3.4 peak volts for a l20-volt line condition.
  • diode 12 will be cut off or reverse biased. When this occurs, the base voltage on transistor 10 will rise toward the positive 20-volt supply because of resistor 14. When this rise exceeds about 2.7 volts, transistor 10 will start to conduct and its collector will start to fall toward ground potential. However, as soon as the collector starts to fall, capacitor 29 will couple the fall back into the base and oppose the change.
  • This circuit configuration is called a Millereflect circuit.
  • the circuit behaves as if a large capacitor were connected between base and ground.
  • This effective capacitor has a value approximately equal to the value of capacitor 29 multiplied by the circuit gain of transistor 10.
  • a relatively small capacitor 29 will act in conjunction with resistor 14 to form a relatively long time constant integrator.
  • a 0.02 microfarad capacitor can be made to act as if it were a 0.4 microfarad capacitor if the transistor circuit gain is only 20, an easily achieved value.
  • transistor 11 is returned to the 20-volt reference. Thus, when its base drops to about 19.3 volts it will begin to conduct. Resistors 17, 19, and 20 are selected, along with the valves of voltage divider resistors 21, 22, and 23 so that transistor 11 will be well below cutoff when transistor 10 is cut off. As the collector voltage of transistor 10 falls, at some point the base of transistor 11 will reach the 19.3-volt level. When this occurs and transistor 11 starts to conduct, collector conduction will tend to drive the base of transistor 10 positive. This in turn lowers the collector voltage of transistor 10 so as to turn transistor 11 on even harder. This regenerative action terminates the Miller-effect ramp and both transistors are quickly driven into saturation.
  • resistor 24 is made much smaller than resistor 14 which, in conjunction with the Miller-effect capacitance, established the ramp rate.
  • the value of resistor 24 is made as about equal to the value of resistor 15.
  • the circuit will act to maintain nearly a constant d-c output voltage value. It will, in fact, act to maintain a nearly fixed difference between the d-c output voltage and the reference voltage. Thus, it is responsive to variations of a-c input as well as load variations.
  • resistor 23 is made variable. As this resistor is varied, a variable fraction of the d-c output voltage is supplied to the base of transistor 11. This will vary the length of the ramp needed to drive transistor 11 into conduction and will, therefore, vary the SCR 1 firing angle. For a given set of input conditions resistor 23 can vary the cl-c output voltage over a substantial range. The circuit will then act to maintain the d-c output voltage constant at nearly the set value.
  • Capacitor 7 will charge through resistor 8 to the difference in potential between the 20-volt reference supply and the d-c output voltage. Thus if the power supply were to be set at 100 volts, capacitor 7 would charge to 80 volts. This would place the cathode of diode 9 at a positive 20 volts. Since the anode of diode 12 is connected to the base of transistor which operates at a positive potential of only a few volts, the diode will be biased in its off switching state. Thus for normal operating conditions the circuit behaves as if components 7, 8, and 9 were not present.
  • capacitor 7 will not have time to discharge and the voltage change is coupled directly to the cathode of diode 9. If the drop in power supply voltage is sufficient to drive diode 9 into its on switch state the base of transistor 10 will suddenly become connected to capacitor 7. This will drive the base of transistor to negative -with respect to its emitter thereby cutting it off. This will halt the pulsing of SCR 1. The elements of filter 2 will then start to discharge and the output voltage will continue to fall. This falling output will keep diode 9 turned on by way of action of capacitor 7. Thus the filter section 2 will discharge, the power supply output will be terminated, and the causal arc extinguished.
  • capacitor! will start to discharge through resistor 8.
  • the cathode of diode 9 will be driven to a potential with respect to its anode that will turn it off.
  • the values of resistor 8 and capacitor 7 are selected to have a time constant that will establish a suitable power supply off interval. A value found to be useful is 2 seconds.
  • a suitable set of component values for the circuit of FIG. 4 is as follows:
  • Capacitor 25 .047 Microfarad This circuit of FIG. 4 with the above component values functioned with good regulation. With the inception of a sudden load increase such as would be occasioned by a CRT arc, the output voltage was interrupted for a period of about 2 seconds.
  • resistor 8 could be returned to a source of potential other than the 20-volt reference or even a fraction thereof. The lower the potential to which resistor 8 is returned, the more sensitive the circuit will be to a drop in d-c output potential. For the conditions given a drop in d-c output of slightly less than 20 volts will initiate momentary shutoff.
  • a momentary shutdown circuit for a regulated power supply said power supply including at least one SCR connected as a rectifier between an a-c input source and a smoothing filter, a pulse generator synchronized by said a-c input source and connected to fire said SCR, a reference supply source connected for comparison with said power supply output, a variable pulse delay circuit connected into said pulse generator so as to vary the timing of firing said SCR, said pulse delay connected to sense the difference between the potentials of said power supply and said reference supply and to reduce said delay as said difference decreases, said shutdown circuit comprising:
  • a storage capacitor having two terminals, one terminal of said capacitor being connected to the output of said power supply and the second terminal being connected through a series resistor to a shutdown source of potential independent from said power supply and having a potential value substantially lower than the nominal potential of said power supply, and unidirectional switch connected between said second terminal of said capacitor and a control element of said pulse generator, said switch being connected in a polarity such that said shutdown source biases said switch to be normally nonconductive but conductive when a sudden drop in power supply voltage is coupled by way of said capacitor to said switch, said switch when conductive acting upon said control element to render said pulse generator inactive thereby shutting down the operation of said power supply for a period of time determined by the time constant of said resistorcapacitor conbination.
  • a circuit of claim 2 wherein the time constant of said capacitor and said resistor is adjusted to produce a shutdown duration of about 2 seconds.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Rectifiers (AREA)
  • Television Receiver Circuits (AREA)
  • Details Of Television Scanning (AREA)
  • Emergency Protection Circuit Devices (AREA)
  • Protection Of Static Devices (AREA)
  • Control Of Voltage And Current In General (AREA)
US447819A 1974-03-04 1974-03-04 Momentary power supply shutdown system Expired - Lifetime US3916288A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US447819A US3916288A (en) 1974-03-04 1974-03-04 Momentary power supply shutdown system
CA219,057A CA1040706A (en) 1974-03-04 1975-01-30 Momentary power supply shutdown system
BR1100/75A BR7501100A (pt) 1974-03-04 1975-02-24 Circuito de parada momentanea
JP2571775A JPS546442B2 (en, 2012) 1974-03-04 1975-03-04

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US447819A US3916288A (en) 1974-03-04 1974-03-04 Momentary power supply shutdown system

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US3916288A true US3916288A (en) 1975-10-28

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US447819A Expired - Lifetime US3916288A (en) 1974-03-04 1974-03-04 Momentary power supply shutdown system

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US (1) US3916288A (en, 2012)
JP (1) JPS546442B2 (en, 2012)
BR (1) BR7501100A (en, 2012)
CA (1) CA1040706A (en, 2012)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3980821A (en) * 1975-08-29 1976-09-14 Rca Corporation Power supply for a television receiver
US4024437A (en) * 1974-11-14 1977-05-17 Sony Corporation D.C. power supply circuit
FR2336016A1 (fr) * 1975-12-17 1977-07-15 Int Standard Electric Corp Circuit d'alimentation pour recepteur de television
FR2374802A1 (fr) * 1975-12-17 1978-07-13 Int Standard Electric Corp Circuit d'alimentation pour recepteur de television
US4163926A (en) * 1978-09-07 1979-08-07 Rca Corporation Switching regulator for a television apparatus
US4270157A (en) * 1977-11-07 1981-05-26 Rca Corporation Power supply protection circuit
WO1998000967A1 (en) * 1996-07-01 1998-01-08 Philips Electronics N.V. Over-current protection circuit in line deflection circuits
US20050110787A1 (en) * 2003-11-24 2005-05-26 Tony Lin Display apparatus with power saving capability

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3573598A (en) * 1969-05-16 1971-04-06 Bell Telephone Labor Inc Overload protected switching regulator-converter
US3590323A (en) * 1970-01-22 1971-06-29 Udylite Corp Peak current limiting system
US3743887A (en) * 1972-03-24 1973-07-03 Itt Power supply for an electronic pabx
US3813580A (en) * 1973-01-19 1974-05-28 Rca Corp High voltage protection circuit

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5232532B2 (en, 2012) * 1971-12-24 1977-08-22
JPS4883711U (en, 2012) * 1972-01-13 1973-10-12

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3573598A (en) * 1969-05-16 1971-04-06 Bell Telephone Labor Inc Overload protected switching regulator-converter
US3590323A (en) * 1970-01-22 1971-06-29 Udylite Corp Peak current limiting system
US3743887A (en) * 1972-03-24 1973-07-03 Itt Power supply for an electronic pabx
US3813580A (en) * 1973-01-19 1974-05-28 Rca Corp High voltage protection circuit

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4024437A (en) * 1974-11-14 1977-05-17 Sony Corporation D.C. power supply circuit
US3980821A (en) * 1975-08-29 1976-09-14 Rca Corporation Power supply for a television receiver
FR2336016A1 (fr) * 1975-12-17 1977-07-15 Int Standard Electric Corp Circuit d'alimentation pour recepteur de television
FR2374802A1 (fr) * 1975-12-17 1978-07-13 Int Standard Electric Corp Circuit d'alimentation pour recepteur de television
US4270157A (en) * 1977-11-07 1981-05-26 Rca Corporation Power supply protection circuit
US4163926A (en) * 1978-09-07 1979-08-07 Rca Corporation Switching regulator for a television apparatus
WO1998000967A1 (en) * 1996-07-01 1998-01-08 Philips Electronics N.V. Over-current protection circuit in line deflection circuits
US20050110787A1 (en) * 2003-11-24 2005-05-26 Tony Lin Display apparatus with power saving capability
US7193624B2 (en) * 2003-11-24 2007-03-20 Amtran Technology Co., Ltd. Display apparatus with power saving capability

Also Published As

Publication number Publication date
JPS50143056A (en, 2012) 1975-11-18
JPS546442B2 (en, 2012) 1979-03-28
BR7501100A (pt) 1975-12-02
CA1040706A (en) 1978-10-17

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Owner name: LORAL AEROSPACE CORP. A CORPORATION OF DE, NEW Y

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:FORD AEROSPACE CORPORATION, A DE CORPORATION;REEL/FRAME:005906/0022

Effective date: 19910215