US2570175A - Alternating-current-direct-cur-rent rectifier circuit - Google Patents

Description

Oct. 2, 1951 P. R. WEILER ALTERNATING CURRENT-DIRECT CURRENT RECTIFIER CIRCUIT Filed Jan. 5, 1949 r12 D Tr4?) r-|4 l5 I6 Intermediate 9 8C r Ourpur O Frequency f g Audio I s o o C Y Amplifier Amplifier Amplifier PETER R. WEILER zzvmvrox.

HIS AGENT Patented Oct. 2, 1951 ALTERNATING-CURRENT-DIRECT-CUR- RENT RECTIFIER CIRCUIT Peter R. Weiler, Aurora, 111., assignor to Zenith Radio Corporation, a corporation of Illinois Application January 3, 1949, Serial No. 68,821

7 Claims. (01. 250-273) This invention relates to a novel power supply and more particularly to such a power supply adapted to be employed to supply the total space current and filament current for the several electron discharge devices of a radio receiver or other signalling system from an alternating current or direct current line.

In order to comply with the requirements set out in the fire hazard clause of the Underwriters Code, without providing a completely enclosed chassis for an A. C.-D. C. radio receiver, it is necessary to fuse the B current circuit. This is normally done by passing at least a portion of the B current through a fusible section of the filament of a rectifier tube. In prior arrangements, the power supply circuit utilizes a conventional rectifier tube having both a primary heater filament section and a secondary fusible heater filament section, as for example a, 3525. The filament current for the primary section and the B current must pass, at least in part, through the fusible section. Since the current rating for this section is usually less than these combined currents, a form of fusible shunt, such as a pilot light, must be connected across the fusible filament section to bypass a portion of the combined currents. When a short circuit occurs in the B circuit it over-loads and burns out the fusible filament section and the pilot light. The required current protection is thus provided. As used throughout the specification the term fusible section refers to that section of a heater filament of a rectifier tube, or of another electron discharge device, which is designed to operate in a manner similar to a fuse as well as to perform the function of a heater.

It has been found desirable to construct an A. C.-D. C. radio receiver wherein no pilot light is employed and which utilizes aminimum of component elements, as an economy measure. This receiver must also conform to the fusing requirements of the Underwriters Code to preclude the need for a completely enclosed chassis.

Therefore, it is an object of this invention to provide a novel power supply fusing system which avoids the use of a pilot light or any other fusible element in addition to a fusible filament section of a rectifying device, or other electron discharge device. 7

It is a further object of this invention to provide a novel power supply for an A. C.-D. C. radio receiver which is economical to construct and yet conforms to the specifications, as to fire hazards, recited in the Underwriters Code.

In accordance with the invention the power supply for a signalling system including a plurality of unidirectionally conductive devices comprises a heater filament included in the envelope of one of the devices. The filament has a fusible section and one other section. There is provided a pair of input terminals adapted to be coupled to a source of energizing potential. A primary heater circuit for the one device is connected to the input terminals and includes the other filament section but excludes the fusible filament section. A rectifying circuit also is connected to the input terminals and includes the fusible filament section connected in series circuit relation with one of said devices.

The features of the present invention, which are believed to be novel, are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages thereof, may best be understood, however, by reference to the following description taken in connection with the accompanying drawing in which Fig. 1 illustrates, partially in block form and partially in schematic form, the circuit of a complete superheterodyne receiver including a power supply system embodying the present invention, and Fig. 2 shows a circuit diagram of a modification of the arrangement of Fig. 1.

Referring to Fig. 1 of the drawing the receiver comprises, in cascade, a signal collector it which forms a source of radio-frequency signals, coupled either directly or through radio-frequency amplifier stages to a mixer-oscillator ll. of mixer-oscillator II is amplified in an intermediate-frequency amplifier [2 which may comprise one or more stages of amplification. Detection, AVC voltage generation and primary audio amplification are performed in a stage It. The audio signals from stage 13 are further amplified in an output amplifier l4 and the resulting signals are impressed on an output transformer l5 and consequently on a reproducer it. Appropriate anode and screen operating potentials for the over-all receiver are supplied by a power supply system 18 which is connected to a conventional source of line voltage through a connector I1.

The operation of those portions of the radio receiver just described, excluding the power supply system I8, is that of a conventional superheterodyne. is Well known and will not be dwelt upon in any further detail here, the invention covered The output The operation of such a receiver by the present application residing in the power supply system. The electron discharge devices employed in the several stages of the receiver are of conventional types and can be considered as being unilaterally conductive devices, since such a characteristic is generally inherent in an electron discharge device. 7

Referring now more particularly to that portion of the circuit shown in Fig. 1 embodying the present invention, rectifying device IS includes a filament section 2!] which constitutes a portion of a primary heater circuit. The primary heater circuit is connected to power plug 11 and comprises, a lead 21, filament section 20, a lead 22, a dropping resistor 23, the several filaments 24 of the vacuum tubes (not shown) utilized in the circuits of stages ll, I2, [Sand lAof'the radio receiver, and a current return conductor 25. A secondary heater circuit includes a fusible filament section 26 of; rectifying device 19. This circuitis also connected to power plug H and comprises lead 2], filament. section 26, a lead 21 and an anode 28 of rectifying device 19. The secondary heater circuit is completed from a cathode 29 of rectifying device l9, through resistors 30 and 3! of a filter circuit including condensers 32 and 33, through the load circuit consisting of the radio receiver to ground connections 3G, to current return conductor 25 and thence to power plug 11.

When connector or power plug I! is connected to a 117 volt A. C. or DC. power line, filament section 20 is heated by the current flowing therethrough as a result of the series voltage drop across leads 2! and 22. The total resistance of resistor 23 and thefilaments 24 is so adjusted that the voltage drop appearing across filament section 20 produces the normal operating current therein. Considering for a moment that filament section 26 is but a normal connection between lead 21 and anode 28, it is apparent that a voltage will appear between cathode 29 and current return conductor 25 by reason of the space current fiowing through rectifying'device l9 and the associated circuit. Current thus fiows in a path including lead 2!, filament section 20, lead 21, anode 28, cathode 29, resistors 30 and 3|, the load andcurrent return conductor 25. Since filament section 26 is operable as a heater, this current, if of proper magnitude, produces a voltage drop between leads 2! and 2'! such that filament section 26 is heated to its normal operating temperature. Thus, it is seen that both filament sections 20 and 26 operate to heat indirectly heated cathode 29 for normal tube operation. 7

Rectifying device I!) is of a conventional type having a fusible filament section and normally operative at a total filament'supply voltage between leads 22 and 21 of approximately 35 volts. It is apparent that any other similar rectifying device operable at any filament voltage, such as 25 volts for example, and having a fusible filament section can beemployed within the meaning of this invention. Filament, section 20 is designed to operate at a current of approximately 150 milliamperes. Fusiblefilament, section 26 is designed to operate at a current of approximately 60 milliamperes and is so constructed that a current of approximately 600 milliamperes or morecauses this section to burn out, in much the same manner as a conventional fuse. As opposed to a conventional fuse, filament section 26 can withstand instantaneous surges of up to two amperes.

The receiver utilized in one application of the invention draws a load current through filament section 26, of approximately 60 milliamperes, which is the normal operating current for this filament section. It is apparent that any short circuit in the B supply circuit, or between cathode 29 and current return conductor 25 causes an excessive current to flow through filament section 26 which burns out as a result.

The following circuit constants were used ina particular application of one embodiment of the invention:

Tube l type 35Z5 or 35W4 Resistor 25, 39 ohms A modification of the power supply system 'of- Figure l and embodying this invention is shown in Figure 2 and may readily be employed in the receiver of Figure 1. A modified form of power supply 18 is similar to that of Figure 1 and corresponding circuit elements are indicated by identical reference numerals. vIn Figure 2, a barrier layer rectifier 35, selenium for example, is utilized to perform the rectifying function performed by rectifying device 19 shown in Figure 1. An electron discharge device 36 is utilized as the output audio amplifier in that portion of the circuit shown in Figure-1 which is designated as it. This device 35 includes a fusible filament section 2 and a filament section 20 constituting a portion of a primary heater circuit. The primary heater circuit is connected in the same manner as the primary heater circuit shownand described in connection with Figure 1 and a secondary heater circuit includes fusible filament section 26 and barrier layer rectifier 35 connected in series circuit relationship.

The operation of the circuit of Figure 2 will be readily understood from the aforedescribed operation of the circuit of Figure 1. -t is apparent that the fusible filament section may be included within the envelope of any of the electron discharge devices employed in stages H, H2 or E3, as well as stage M of the receiver illustrated in Figure 1.

It is seen that the novel circuit which is the subject of this invention, provides a fuse arrangement for the B supply such that the circuit is amply protected and thus within the requirements as to fire hazards provided by the Underwriters Lode. utilizes a minimum of component elements, and therefore, is inexpensive to construct.

While particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects, and therefore, the aim in the appended claims is to cover such changes and modifications as fall within the true spirit and scope of this invention.

I claim:

l. A power supply for a signalling system including a plurality of unidirectionally conductive input terminals adapted to be coupled to a source of energizing potential; a primary heater" circuit Further, the arrangement.

for said one device connected to said terminals and including said other filament section but excluding said fusible filament section; and a rectifying circuit connected to said terminals and including said fusible filament section, connected in series circuit relation with one of said devices.

2. A power supply for a signalling system including a plurality of unidirectionally conductive devices comprising: a heater filament included in the envelope of one of said devices having a fusible section and one other section connected in series relationship with said fusible section; a pair of input terminals adapted to be coupled to a source of energizing potential; a primary heater circuit for said one device connected to said terminals and including said other filament section but excluding said fusible filament section; and a rectifying circuit connected to said terminals and including said fusible filament section, connected in series circuit relation with one of said devices.

3. A power supply for a signalling system including a plurality of electron discharge devices comprising: a rectifying device including an anode, an indirectly heated cathode, and a heater filament for said cathode having a fusible section and at least one other section; a pair of input terminals adapted to be coupled to a source of energizing potential; a primary heater circuit for said device, connected to said terminals, exclusive of said fusible filament section but including said other filament section; and a secondary heater circuit including said fusible filament section connected between one of said terminals and said anode, and said cathode connected to the other of said terminals.

4. A power supply for a signalling system including a plurality of electron discharge devices comprising: a rectifying device including an anode, an indirectly heated cathode and a heater filament for said cathode having a fusible section connected in series relationship with at least one other section; a pair of input terminals, adapted to be coupled to a source of energizing potential, one of which is directly connected to a point common to both said fusible filament section and said other filament section, and the other of which is connected to a current return conductor; a pair of output terminals, one of which is connected to said current return conductor, and the other of which is connected to said cathode; a connection extending from the free end of said other filament section to said current return conductor; and a connection extending from the free end of said fusible filament section to said anode.

5. A power supply for a signalling system including a plurality of electron discharge devices comprising: a rectifying device; one of said electron discharge devices having a fusible filament section and at least one other section; a pair of input terminals adapted to be coupled to a source 5o Riders Troubleshooters Manual,

of energizing potential; a primary heater circuit for said electron discharge device, connected to said terminals, exclusive of said fusible filament section but including said other filament section; and a secondary heater circuit connected to said terminals and including said fusible filament and said rectifying device arranged in series relationship.

6. A power supply for a signalling system including a plurality of electron discharge devices comprising: a barrier layer rectifying device; one of said electron discharge devices having a fusible filament section and at least one other section; a pair of input terminals adapted to be coupled to a source of energizing potential; a primary heater circuit for said electron discharge device, connected to said terminals, exclusive of said fusible filament section but including said other filament section; and a secondary heater circuit connected to said terminals and including said fusible filament and said rectifying device arranged in series relationship.

'7. A power supply for a signalling system including a plurality of electron discharge devices comprising: a rectifying device; one of said electron discharge devices having a fusible filament section and at least one other section connected in series relationship with said fusible section; a pair of input terminals, adapted to be coupled to a source of energizing potential, one of which is directly connected to a point common to both said fusible filament section and said other filament section, and the other of which is connected to a current return conductor; a pair of output terminals, one of which is connected to said current return conductor, and the other of which is connected to one side of said rectifying device; a connection extending from said current return conductor to the free end of said other filament section; and a connection extending from the free end of said fusible filament section to the other side of said rectifying device.

PETER R. WEILER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,303,184 Ehret May 6, 1919 1,318,855 Ehret Oct. 14, 1919 1,907,670 Roberts May 9, 1933 OTHER REFERENCES RCA Model 35X disclosed in Volume 13, pages 13-41 of Riders Troubleshooters Manual, Copyright 1942.

Phillips Model 3-5A, disclosed in Volume 17 of pages 17-1, Copyright 1948.

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