US2404624A - Voltage regulator for electron discharge devices - Google Patents

Description

July 23, 1946. R. B. DOME VOLTAGE'REGULATOR FOR ELECTRON DISCHARGE DEVICES Filed Jan. 23, 1943 Inventor Robert B. Dome,

is Attorney.

Patented July 23, 1946 VOLTAGE REGULATOR FOR ELECTRON v DISCHARGE DEVICES Robert B. Dome, Bridgeport, Conni, assignor to General Electric Company, a corporation of New York Application January 23, 1943, Serial No. 473,362

My invention relates to apparatus for the regulation of voltages applied to electron discharge devices, and particularly to apparatus for regulating the voltage applied between the anode and cathode of electron discharge devices of the cathode ray type.

In circuits employing electron discharge devices, such as cathode ray tubes, a relatively high voltage is applied between the anode and cathode of the device, and it is desirable to maintain this voltage constant. In apparatus such'as-oscilloscopes and television camera and reproducing devices, voltages derived from a common source are frequently applied to the deflection plates as well as to the anode-cathode circuit so that variations in the deflection voltage are proportional to variations in the anode cathode voltage. The intensity of the electron beam in a cathode ray tube may be controlled by a voltage applied to a grid or control element. For example, this voltage may represent changes in intensity of light in a picture or scene which is being reproduced, and changes in voltage between the anode and cathode circuit may result from resulting changes in the load on the cathode ray tube. It is, therefore, desirable to provide some arrangement for preventing variations in the anode voltage caused by changes in the anode current. In many cases it may be desirable to compensate for changes in voltage due to changes in load current, but not to regulate the anode voltage to prevent changes due to variations in th voltage of the common source from which the anode voltage and deflection voltages are derived.

It is an object of my invention to provide an tions in the current flowing in the anode-cathode circuit.

The features of my invention which I believe to be novel are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing, in which Fig. 1 is a circuit diagram illustrating schematically a portion of a television receiving appa- 6Claims. ((1315-14) 7 ratus embodying my invention, and Fig. 2 is a cir-'- cuit diagram illustrating a modification ofa. part of the circuit of Fig. l. 1

Referring now to Fig. 1, the apparatus includes an electron discharge device III of the cathode ray type, which includes an anode II, a cathode 12, a control electrode l3 and horizontal and ver-' tical deflection plates or members I4 and i5,-re:--

spectively. The device I 0 as illustrated is the picture tube or the television receiver, a voltage corresponding tothe picture or-video signalbeing applied to the grid l3 across a resistor Hi from a suitable source, not shown, coupled" to the re sistor through a condenser l1. Direct current voltages for supplying the anode voltage and de-'- flection voltages of the devic I 0 are derived from a suitable alternating current supply, not shown,

coupled to a primary 20 of a transformer 2L A 7 high direct current voltage is applied between the anode II and the cathode l2 and is derived from a secondary winding 22 of the transformer 2! through a half-wave rectifier comprising a two-electrode electron discharge device 23, and the usual smoothing condenser 24 connected be tween the cathode 25 of the device 23 and ground, the device 23 having an anode 26 connected to the secondary 22 One of'each pair of deflection plates I4 and I5 is also connected to'the cathode 25 in accordance with the usual practice. The deflection voltages for the vertical and horizontal plates l4 and I5 are derived from a full-wave rectifier 21. This rectifier includes a secondary winding 28 of the transformer 2 i, and an electron discharge deViceZB having anodes or plates 30 and 3i connected to opposite ends of the secondary 28, the center point of the secondary being connected to ground. The device 29 is provided with a cathode 32, which comprises a filamentor heater connected across a secondary 33 ofthe transformer 2|, and the rectifier 21 also comprises a smoothing filter including condensers 34 and 35 connected between ground and either end of a choke coil 36, and the direct current voltage pro duced by the rectifier is applied to vertical and horizontal deflection voltage generators and 4|, respectively, the rectifier being coupled to the generators through a resistor 43 and a condenser 44. The vertical deflection voltage'generator 40 across terminals 41. The generator 40 is coupled to the plates I through a condenser 48, and the generator 4| is coupled to the plates 1 4 through a condenser 49.

During the operation of the cathode ray device ID the load current flowing between the anode H and cathode l2 varies and tends to produce changes in the voltage between the anode and cathode. In order to prevent changes in voltage due to the changes in the load current in the cathode ray device, an electron discharge device 52 is connected in parallel with the device I0 between the anode H and cathode l2. The device 52 includes an anode 53 connected to. the

anode II, a cathode 54 connected to groundthrough a resistance 55, and a control electrode 56 connected to an intermediate point of the resistance 55. The resistance 55 is connected between the output of the rectifier 21 and ground,- and the voltage drop in. the resistor 55 therefore varies with the voltage of the rectifier. Consequently,.the changes in drop across the resistor 55 follow change in the voltage of the source applied to the primary 20. The bias on the control electrode 56, therefore, change with changes in the voltage of the source and is proportional tov corresponding changes in the deflection voltages. and in the anode voltage of the device it. The bias voltage of the grid 56 is selected so that under the most severe load conditions, when the current flowing through the device I!) is at its highest value, a very low current in the vicinity of the cut-ofi value flows through the device 52. During the operation of the apparatus, when the device I0 draws less current than the maximum value, the device 52 draws more current and, as a result, the voltage across the parallel circuit including the anode l I and the cathode 12 of the device l0 does not rise appreciably. Since the bias voltage on the control electrode 56 varies with the direct current voltage applied to the anodes H and 53, as a result of line voltage changes at primary 20, the device 52 does not regulate for changes in the applied anode voltage because the cut-off point of the device 52 moves in direct proportion to the change in the applied voltage and but little increase in current through the device 52 results.

Should it be desired to regulate both for changes in load current in the cathode ray device and for changes in the applied voltage derived from the source connected to the primary 20, the circuit of Fig. 1 may be changed in accordance with Fig. 2 which illustrates the portion of the circuit of Fig. 1. including the device 52 and the filter condensers and inductance of the rectifier 21. Corresponding elements of Flg. 2 are designated by the same numerals as in Fig. 1. The resistance 55 of Fig. 1 is replaced in Fig. 2 by a resistance 58 connected between the cathode 54 and ground, but not connected to the direct current supply from the rectifier 21. A constant voltage device 59 is connected across resistance 58. The device 59 may, for example, be a neon tube which maintains substantially constant voltage over a wide range of current flowing therethrough. The point at which the control electrode 56 is connected to the resistance 58 is selected, so that, at the lowest voltage applied to the anode II and at the greatest load current, the device 52 is biased almost to cut-off and draws very low current. Then, as the voltage rises across the device 52, a larger current will be drawn thereby, and since the bias on the grid 56 is maintained substantially constant by 4 the device 59, the current drawn by the device 52 compensates for changes in voltage regardless of whether they are due to changes in load cur rent or in applied voltage, or both.

It will be evident that my invention provides a simple and effective arrangement for regulating the voltage applied across an electron discharge device, such as acathode ray tube so that the applied voltage is not varied by changes in load current. As an example, by way of illustration. only, and not by way of limitation, a satisfactory regulator embodying my invention, and which would be suitable for the circuit of Fig. 1, may be provided by employing a 6F5GT tube as the device 52 with a resistance 55 having a value of 10,000 ohms. This regulator was employed with aload circuit at a potential of 2500 volt and this voltage was maintained substantially constant over a wide range of load currents.

Although I have illustrated one embodiment of my invention in connection with a television receiver, other applications will readily be apparent to those skilled in the art.. Therefore, it will be appreciated that I do. not wish to be limited to the particular embodiment of my invention disclosed herein, and I contemplate by the appended claims to cover all-modifications-which fall within the spirit. and scope. of my invention;

What I claim as new and desire to secure by Letters Patent of the United' States is:

1. In combination, a first electron discharge device having an anode, a cathode and a control electrode, a source of voltage connectedbetween said anode and said cathode, and-means fonpreventing changes in the voltage between said. anode and said cathode due to changes in'the current flowing therebetween, said means including a second electron discharge device connectedin parallel with the anode to cathode path of. said first device and having an anode and acathode and a control electrode, said means alsov including means connected in the cathode circuit of said second device for providing a predetermined bias on said control electrode of said second device whereby current flows through said second device to'compensate for changes in current flowing between the anode and. cathode of said first device.

2. In combination, a first electron discharge device having an anode and a cathode and a control electrode, a source of voltage connected between said anode and said cathode, and means for preventing changes in the voltage between said anode and said cathode due to changes in the current flowing therebetween, said means including a second electron discharge device connected in parallel with the anode to cathode path of said first device and having an anode and a cathode and a control electrode, said means also including a constant voltage device connected in the cathode circuit of said second device for providing a predetermined substantially constant bias on said control electrode of said secondv device whereby current fiowsthrough said seconddevice to compensate for changes in current flowing between said anode and cathode of said first device and to maintain the voltage between said anode and cathode of said first device substantially constant regardless of variations in the voltage of said source.

3. In combination, afirst electron discharge devic having an anode and a-cathode and a control electrode, a source of voltage connected between said anode and said cathode; and means for preventing changes in the voltage between said anode and said cathode due to changes in the current flowing therebetween, said means including a second electron discharge device connected in parallel with the anode to cathode path of said first device and having an anod and a cathode and a control electrode, said means also including means connected in the cathode circuit of said second device to produce a voltage varying in accordance with the voltage of said source for providing a predetermined bias on said control electrode of said second device whereby th voltage across said second device varies with the voltage of said source but is independent of variations due to changes in current flowing through said first device.

4. In combination, a cathode ray device having a cathode and a control electrode and an anode and deflection members, a source of variable voltage, means energized from said source for supplying deflecting voltage to said deflection members and for supplying anode voltage between said cathode and said anode whereby said deflecting and anode voltages tend to be subject to variation in the voltage of said source, means for preventing changes in the voltage between said anode and said cathode due to changes in the current flowing therebetween, and means associated with said last mentioned means for effecting operation thereof to prevent changes of voltage at said deflecting members and at said anode due to variations in the voltage of said source.

5. In combination, a cathode ray device having a cathode and a control electrode and an anode and deflection members, a source of variable voltage, means energized from said source for supplying deflecting voltage to said deflection members and for supplying anode voltage between said cathode and said anode whereby said deflecting and anode voltages are subject to variations in the voltage of said source, and means for preventing changes in the voltage between said anode and said cathode due to changes in the current flowing therebetween, said last mentioned means including an electron discharge device having an anode and a cathode and a control electrode and connected between the anode and cathod of said cathode my device, said last mentioned means also including means connected in the cathode circuit of said electron discharge device for providing a predetermined bias on the control electrode thereof whereby current flows through said electron discharge device to compensate for changes in current flowing between the anode and cathode of said cathode ray device.

6. In combination, a cathode ray device having a cathode and an anode and a control electrode and vertical and horizontal deflection members, a source of variable voltage, means energized from said source for supplying deflecting voltages to said deflection members and for supplying anode voltage between said cathode and said anode whereby said deflecting and anode voltages are subject to variations in the voltage of said source, and means for preventing changes in the voltage between said anode and said cathode due to changes in the current flowing therebetween, said last mentioned means including an electron discharge device having an anode and a cathode and a control electrode and connected between the anode and cathode of said cathode ray device, said last mentioned means also including a voltage supply connected in the cathode circuit of said electron discharge device and subject to the variations in the voltage of said source for providing a bias on the control electrode thereof whereby current flows through said electron discharge device to compensate solely for changes in current flowing between the anode and cathode of said cathode ray device.

ROBERT B. DOME.

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