US2089039A - Relaxation circuit - Google Patents

Description

Aug. 3, 1937- F. SCHRGTER RELAXATION CIRCUIT Filed Aug. 4, 1954 INVENTOB' y R0752? BY WM.

F/P/TZ SC ATTORNEY Patented Aug. 3, 1937 :l-TED STATES.

RELAXATION CIRCUIT Fritz Schriiter, Berlin, Germany,

assignor to Telelunken Gesellschaft fiir Drahtlose Telegraphic in. b. H., Berlin, Germany, a. corporation of Germany Application August 4, 1934, Serial No. 738,431 In Germany August 5, 1933 4 Claims.

As is known, in cathode ray tubes for television purposes, the deviation of the electron ray can be accomplished by means of so called relaxation circuits. These consist of a condenser of con- 5 siderable capacity periodically charged by a source of sufficiently high voltage across a high resistance, and an electron tube operating in the region of the anode current saturation or the like, said condenser being discharged at the ignition 10 of a relaxation tube (ion tube, Thyratron, glow relay), placed in parallel thereto. To the capacity (5) as shown in the figure, the respective pair of deviation plates 8 of the cathode ray tube 8 is placed in parallel.

15 In the television tubes of today having a large and bright picture field, i. e. a high plate potential, the desired large deviation angle of the oathode ray requires the application of considerable maximum voltages at the deviation condensers.

20 The controlled ion tube connected in parallel to these condensers therefore must be strongly blocked if a premature breakdown of the high voltage of the condenser between anode and cathode is to be avoided, i. e. the control grid 5 must be maintained upon a high negative potential with respect to the cathode. Hereby it is unavoidable that a certain distinct discharge current flows from the anode I in the drawing tothe grid 2 and across the parallel resistance 4 30 between grid 2 and cathode 3. This lost current leakage current causes a continuous deficiency of the charge of the deviation condenser 5. Its amperage depends upon the momentary voltage at 5 in the manner known in gas discharges. The

35 leakage current thus causes a distortion of the charging curve which highly increases with the condenser voltage, and which in view of a true reproduction of the picture should always represent a linear function of time.

40 In order to avoid this distorting influence or the leakage current upon the charging curve of condenser 5, an ohmic resistance 1 is connected in parallel to the said condenser in accordance with the invention. Its size is so dimensioned 45 that at each instantaneous value of the condenser voltage it permits passage of a current between I and 2 which is a multiple of the leakage current. The charging resistance 6 must then obviously be correspondingly lower in order 50 to compensate the increased deficiency of the charge of condenser 5 caused by the resistance 1. On the other hand, the capacity of 5 is to be chosen from the outset as high as possible, so as to maintain the distorting influence of the vari- 55 able leakage current as small as possible.

It will thus be apparent that this invention is concerned with eliminating the distortion of the wave shape produced by relaxation oscillator due to non-linear leakage currents, resulting from the flow of ionization current from the anode to the grid of a gaseous discharge device. This nonlinear leakage current results from the application of potential to the anode which is positive with respect to the grid 2 in the discharge tube. Since the tube is gas filled, increasing potential 10 between the anode and the grid 2 causes ionization of the gas and consequently an ionization current flows from the anode to the grid through the resistor 4 back to the negative side of the voltage supply. As is well known, this ionization current is not linear with respect tovoltage. See for example, Crowthers Ions, Electrons & Ionizing Radiotrons, Fourth Edition page 56 et seq. In fact, an ion tube requires the flow of current from grid to plate before the discharge may be initiated. This is well known in the art.

In order, therefore, to overcome this non-linear leakage current, this invention provides a linear leakage path in which the leakage current is greater than that occurring through the gaseous discharge tube. This serves to make the nonlinear leakage component small in comparison with the linear leakage component and consequently serves to eliminate distortion of the wave shape of the relaxation oscillation.

I claim:

1. In a relaxation oscillation generator wherein distortion is present due to leakage current between two points which is not directly proportional to voltage applied therebetween, the steps in the method of reducing said distortion which comprise causing current to flow between said two points which is directly proportional to said voltage, and regulating said second mentioned current to be large compared to said first mentioned current.

2. The steps in the method of operating a relaxation oscillation generator, having a path through which current flows proportional to the potential difference of the path, and another path wherein the current is not proportional to the potential difference of said second path and also having a storage device which include storing electrical energy in said storage device, discharging a minor portion of the stored energy through the non-proportional path thereby causing distortion, and simultaneously discharging through the proportional path a greater portion of the stored energy thereby reducing distortion.

3. In a relaxation oscillator, the combination of 2 a voltage source, a condenser in series with said voltage source, a charging impedance in series with said condenser and voltage source, a grid controlled gaseous discharge device having a cathode, a control element, and an anode, said cathode and anode being connected across said condenser, a circuit connected across the grid and cathode, and a current path wherein the current is proportional to the voltage applied thereto 10 connected across said condenser and said discharge device.

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