US3826989A

US3826989A - Tube filament power supply

Info

Publication number: US3826989A
Application number: US00346543A
Authority: US
Inventors: E Keith
Original assignee: Magnavox Co
Current assignee: Philips North America LLC
Priority date: 1973-03-30
Filing date: 1973-03-30
Publication date: 1974-07-30
Anticipated expiration: 1991-07-30

Abstract

A power supply circuit for supplying power to a circuit having therein vacuum tubes which require a heater filament to heat the cathode to emission temperature. The power supply circuit has a bridge rectifier having four arms; each arm containing a rectifying element. As in conventional bridge rectifier circuits, two opposite ports of the bridge are connected to the a.c. power source and the remaining two ports are connected respectively to the ground and to the vacuum tube circuitry to supply B+ voltage to the circuitry. This invention places the heater filament circuit between the grounded port of the bridge rectifier and one of the a.c. power leads to provide half wave rectified power to the tube filaments, using a rectifying element of the bridge circuit to obtain the half wave rectified tube filament power, from the a.c. power source independently of B+ voltage circuit operation.

Description

TUBE FILAMENT POWER SUPPLY [111 3,826,989 1451 July 311, 1974 I Primary Examiner-John Zazworsky Attorney, Agent, or FirmT. A. Briody; W. W. Hollo- F W [75] Inventor grater-alt! Eugene Keith, on ayne y; R. T. Seeger [73] Ass1gnee: 'lvaiaeylg'iaglrrlliciivox Company, Fort [57] ABSTRACT A power supply circuit for supplying power to a cir- [22] 1973 cuit having therein vacuum tubes which require a [21] Appl. No.: 346,543 heater filament toheat the cathode to emission temperature. The power supply circuit has a bridge rectifier having four arms; each arm containing a rectifying [52] US. Cl 328/270, 315/96, 332285220588, element AS in conventional bridge rectifier circuits [51] Int Cl Hosk 19/82 two. opposite ports of the bridge are connected to the 58 Field of Search 328/208, 258,270; 315/96, W and emammg PM are 315/99 105 connected respectively to the ground and to the vacuum tube'circuitry to supply B+ voltage to the circuitry. This invention places the heater filament cir- [56] References cued cuit between the grounded port of the bridge rectifier UNITED STATES PATENTS and one of the a.c. power leads to provide half wave 2,872,573 2/1959 Wilson 328/270 rectified power to the tube filaments, using a rectify- 3J71-084 2/ 1965 Szlklah 328/270 ing element of the bridge circuit to obtain the half 313391105 M967 328/270 x wave rectified tube filament power, from the a.c. 3.6] 1,012 10/1971 Lemrnon 323/270 x power source independently of 3+ vohage Circuit 1 operation.

.2 s. .3 El ine 1,.Preuins, Fi ure. 2,

TV RECEIVER v 22 1 R 1 1RY so i INPUT TUBE HEATERS TUBE FILAMENT POWER SUPPLY BACKGROUND OF INVENTION As is well known, vacuum tubes have heater filaments which require a power supply to bring the filaments to operating temperature. The function of these filaments is to heat the cathodes of the vacuum tubes to emission temperature. The time required to bring the filaments to temperature is the time delay that is experienced in vacuum tube circuits before they become operative. This time delay is particularly annoying when experienced in radio, television and other electronic consumer entertainment devices and has lead to the provision in many such devices of a supplementary power circuit for the filaments which is so connected that it supplies continuous power to the filaments even when the receiver or other device was in an inoperative state.

These supplementary circuits have sometimes been in parallel with the B+ power circuit to the receiver so that the supplementary circuit would remain energized even though the B+ power circuit was de-energized, or

a separate circuit having a diode therein was used to supply half wave rectified power to the filament circuit. In some previous circuits, a switch has been placedin the bridge rectifier which opened an arm of the bridge upon opening of the B-lpower circuit. This would place a half wave rectified power supply to the filaments during inoperative periods of the receiver and full wave rectified power to the filament circuit during operative periods of the receiver.

This invention overcomes the need for placing a switch in the bridge rectifier circuit or providing a separate diode circuit for the filaments while at the same time providing a continuous half wave rectified power to the filament circuit, both during periods the receiver is in operation and when it is inoperative.

BRIEF SUMMARY OF INVENTION The above objects and advantages are accomplished by using a power supply having a bridge rectifier wherein each arm of the bridge has a rectifying element and wherein two opposite portsof the rectifier are connected to the ac. power leads and the remaining ports are connected respectively to the receivercircuitry to provide B+ power and to ground; this invention provides for placing the filament circuit between the ground port of the rectifier bridge and one of the ac. leads of the ac. power supply thereby using one of the diodes of the bridge circuit to supply the half wave rectified power to the filaments. In this way, half wave rectified power is supplied continuously to the heater filaments as long as the a.c. power is furnished and regardless of whether or not the B+ power circuit is open or closed.

DRAWINGS These and other advantages will become more apparent when the operation of a preferred embodiment is considered in connection with the drawing which is a schematic-block drawing of a receiver utilizing the power supply in this invention.

DESCRIPTION OF A PREFERRED EMBODIMENT In the drawing. a.c. connection 20 is provided for removable power connection to an ac. power supply such as the conventional home power voltage. A bridge rectifier 21 is utilized to full wave rectify the a.c. power from connection 20 and has in the arms thereof rectifying elements D1, D2, D3 and D4. Lines 22 and 23'from the ac. connection 20 are connected respectively to

opposite ports

24, 25 of bridge 21.

Connected to port 26 of bridge 21 is a switch 29, shown in the open position, and a filter circuit 27 having capacitances C1, C2 and resistance R2 for suppressing the full wave rectified ripple from the B+ voltage fumished to television receiver circuitry 28.

Receiver circuitry 28 has a plurality of vacuum tube devices 30 each of which has a cathode which when heated to operating temperature will emit electrons. The television receiver circuitry 28 receives and demodulates a television signal and provides video information which is displayed on the face of cathode ray tube (CRT) 31 which likewise has a cathode for emitting electrons when heated to emission temperature. Circuitry 28 is well known in'the art and it also provides for demodulation of the accompanying sound for the television receiver.

Each of the cathodes in the television receiver circuitry 28 and the cathode in CRT 31 requires a heater filament to bring the cathode to operating temperatures. These filaments appear in close proximity to the cathodes which they heat as shown diagramatically in the circuit 28 and CRT 31. The filaments F1, F2, F3, F4 and F5, are also shown as connected between line 22 and port 32 of bridge rectifier 21. Also connected in the filament circuit is resistor R1 which is selected to obtain voltage to filaments F1, F2, F3, F4, and F5 as desired.

By placing the filaments F1, F2, F3, F4 and F5 between one of the ac. power leads and the grounded port 32 of bridge rectifier 21, there will be half wave rectified power to the filaments at all times that the ac. connection 20 receives ac. power regardless of the positionof switch 29 which determines whether television circuitry 28 is on or off. Diode D1 of the bridge rectifier 21 is also utilized as a rectifier in the tube filament circuit.

A vacation switch 33 is shown in the filament circuit which may be opened in order to conserve power, when the receiver is going to be inoperative for rela tively long periods of time. This invention thus effectively simplifies prior methods and apparatus for accomplishing a continuous power to the filament heater circuitry with conservation in power and circuit component expense.

Modifications of the closed preferred embodiment may be made and still be within the teaching of this invention which is defined by the following claims.

I claim:

1. Apparatus comprising means for supplying alternating current power supply over two leads,

a full wave bridge rectifier having four ports and four arms each having a rectifying element, with each of said arms being connected at each end through a port to another arm,

said power supply leads being connected to two opposing ports of said full wave bridge rectifier,

a tube circuit having at least one vacuum tube therein with each vacuum tube having a heater filament therein,

said circuit being connected to one of the remaining ports of said rectifier,

3 4 switch means to switch said tube circuit between optus of said tube circuit.

erative and inoperative status 2. The apparatus of claim 1 with said vacuum tube a heater filament circuit being connected at one end comprising a cathode ray tube.

to the other of said remaining ports and at the other 3. The apparatus of claim 1 with second switch end to one of said a.c. leads, to provide half wave 5 means being in said a.c. leads to disconnect the ac. rectified power to said heater filament circuit power to said heater filament circuit,

whereby a rectifying element'of said bridge rectisaid second switch means being independent in operfier is used to establish half wave rectified power to ation from said first mentioned switch means. said filament circuit regardless of the operative sta- I

Claims

1. Apparatus comprising means for supplying alternating current power supply over two leads, a full wave bridge rectifier having four ports and four arms each having a rectifying element, with each of said arms being connected at each end through a port to another arm, said power supply leads being connected to two opposing ports of said full wave bridge rectifier, a tube circuit having at least one vacuum tube therein with each vacuum tube having a heater filament therein, said circuit being connected to one of the remaining ports of said rectifier, switch means to switch said tube circuit between operative and inoperative status a heater filament circuit being connected at one end to the other of said remaining ports And at the other end to one of said a.c. leads, to provide half wave rectified power to said heater filament circuit whereby a rectifying element of said bridge rectifier is used to establish half wave rectified power to said filament circuit regardless of the operative status of said tube circuit.

2. The apparatus of claim 1 with said vacuum tube comprising a cathode ray tube.

3. The apparatus of claim 1 with second switch means being in said a.c. leads to disconnect the a.c. power to said heater filament circuit, said second switch means being independent in operation from said first mentioned switch means.