US2764730A - Electric control circuits - Google Patents

Description

Sept. 25, 1956 c. E. s. RIDGERS 2,764,730

ELECTRIC CONTROL CIRCUITS Filed Nov. 7, 1955 0., E. S. Rummy B Z MM United States Patent 'ce 2,764,730 ELECTRIC CONTROL CIRCUITS Charles Edward Sydney Ridgers, London, England, assignor to The Decca Record Company Limited, London, England, a British company Application November 7, 1955, Serial No. 545,498

Claims priority, application Great Britain March 30, 1955 7 Claims. (Cl. 323-42) This invention relates to circuits for the control of a high direct voltage.

As an example of the application of the invention, in a microwave radar apparatus of the kind having a rotating antenna system with the radio frequency part of the apparatus rotatable with the antenna system, it may be required to adjust, from a fixed location, a high direct voltage such as the reflector voltage of a klystron in the rotating part of the apparatus. The transmission of high voltages through slip rings frequently causes difliculties due to arcing over to other parts of the structure and it is one of the objects of the present invention, inter alia, to provide a control circuit which enables a high direct voltage to be controlled through slip rings without the high voltage appearing at the slip rings.

According to this invention, a circuit for the control of a high direct voltage comprises a potentiometer including an adjustable resistor, a source of high voltage with respect to a datum voltage connected across said potentiometer, the adjustable resistor being remote from the high voltage end of the potentiometer, a grid-controlled tube having a plate, a grid and a cathode, a load resistor, a circuit in shunt across said potentiometer which shunt circuit includes a stabilised high voltage supply of voltage less than that of said source and the plate-tocathode path of said grid-controlled tube and said load resistor, the load resistor being arranged in series directly between the tube and the stabilised high voltage supply,

and circuit means connecting said grid to a point on said potentiometer whereby adjustment of said adjustable resistor varies the current passed by said tube and hence controls the high voltage across said stabilised supply and load resistor. With this arrangemenh the stabilised high voltage supply is connected atone end directly to the load resistor; hence the total voltage across the stabilised power supply and the load resistor may be varied within certain limits by adjusting the current flow through the tube. This current flow can be controlled by the aforementioned adjustable resistor in the potentiometer. Since the voltage variations required on the grid of the tube are small, the voltage across the adjustable potentiometer is quite small. It will be seen, therefore, that the total voltage across the stabilised supply and the load resistor may be adjusted by control of the adjustable resister and that no high voltages with respect to the datum are present on the adjustable resistor. The aforementioned datum voltage is conveniently ground potential and the adjustable resistor may then be arranged at or 2 ,764,730 Patented Sept. 25, 1956 near the ground end of the potentiometer. The leads to this adjustable resistor would then be at or near ground potential which greatly facilitates the provision of a remote control for a high voltage since the adjustable resistor may be located remotely from the rest of the apparatus without any need for high voltage leads to the resistor. Conveniently one end of the adjustable resistor is connected to ground and the other end may then be connected by a single lead to the rest of the apparatus which may be independently grounded. It will be seen that this arrangement enables a high direct voltage to be controlled by the use of an adjustable resistor, the potentials at the adjustable resistor being near ground potential and that this adjustable resistor need only be connected to the apparatus by a single lead.

If the adjustable high voltage is to be a voltage adjustable with respect to ground potential, the stabilised supply would be connected in the ground end of the aforementioned shunt circuit. In this case it will be appreciated that, for high voltage which is negative with respect to ground, an anode load resistor would be employed.

In an arrangement having an anode load resistor connected to the stabilised voltage source, the aforementioned shunt circuit may include a cathode load resistor for said grid-controlled tube and there may be provided a second grid-controlled tube with a separate anode load resistor, the second tube and load resistor being connected in shunt across the first tube and first load resistor, and the grid of the second tube being connected to a point on said cathode load resistor or on said potentiometer such that the load on the supply drawn by the two tubes remains constant. It will be seen that, in this arrangement, as the anode of one tube falls in potential, the anode of the other tube rises in potential. It is thus possible to obtain two separate ranges of control voltage by switching the connection to one or other of the two anodes.

The following is a description of one embodiment of the invention, reference being made to the accompanying drawing which is a circuit diagram of a circuit for the remote control of the reflector voltage of a klystron.

The particular circuit shown in the drawing is required to control a high direct voltage which is negative with respect to ground. A negative power supply of -2.4 kv. with respect to ground is applied across a potentiometer which potentiometer comprises in series (considered from the negative potential end) a fixed resistor 10, a second fixed resistor 11, a pre-set adjustable resistor 12 and a circuit having two parallel arms, one arm of which comprises a fixed resistor 13 and a pre-set adjustable resistor 14 and the other arm of which comprises a fixed resistor 15 and an adjustable resistor 16. A shown in the drawing this circuit with two parallel arms is at the ground end of the potentiometer. A stabilised power supply of -2 kv. with respect to ground is also provided, the negative terminal of this stabilised supply being connected to one end of a plate load resistor 17 of a triode tube 18, the other end of this load resistor being connected to the plate of the tube. The cathode of the tube is connected to the 2.4 kv. negative supply line through a cathode resistor 19 and the grid of the tube 18 is connected to the junction between the resistors 10 and 11 on the aforementioned potentiometer. A second triode tube has its cathode connected to the cathode of tube 18 and has its plate connected through a plate load resistor formed by two series resistors 21, 22, this load resistor being connected to the 2 kv. stabilised power supply. The two resistors 21, 22 together are made approximately equal in value to the load resistor 17 for tube 18. The grid of tube 20 is connected to a point on a potentiometer circuit formed by a high resistance 23 and a low resistance 24, this potentiometer circuit being connected between the junctions of the aforementioned resistors 21, 22 and the -2.4 kv. supply. The resistance 24 is so small that the grid of tube 2.0 can be considered efiectively as being connected to the 2.4 lcv. line with a substantially constant bias potential across resistance 24. By means of a switch 25, an output lead 26 may be connected to the anode of either tube 18 or tube 20.

The operation of the above described circuit is as follows: Assuming in the first place that the switch is set as shown in the drawings except that the output end 26 is connected to the plate of tube 18, when an alteration is made to the setting of the adjustable resistor 16 the voltage across the resistor 14) will be altered and hence the grid-to-cathode voltage on the tube 18 will change. This will alter the current flow through the plate load resistor 17 and hence will vary the potential on the output lead 26. The pre-set adjustable resistor 14 enables the maximum voltage to be applied to the grid of tube 13 to be pre-set and hence enables the minimum range of the voltage control provided by resistor 16 to be pre-set. The pre-set adjustable resistor 12 enables the minimum voltage on the grid of tube 18 to be pre-set and hence enables the maximum voltage at the plate of tube 18 to be pre-set. When the current drawn by tube 18 decreases, the voltage across the cathode rcsistor 19 decreases and hence the grid potential of tube 20 rises so that the current drawn by this tube increases. This will increase the bias developed by the cathode resistor and the circuit tends to maintain a constant total current through the two tubes. Thus as the plate potenti-al of tube 18 falls, the plate potential of tube 20 rises and the switch 25 thus enables two separate ranges of control voltage to be obtained by switching the lead 26 to one or other of the two anodes.

It will be particularly noted that the resistor 15 and series connected adjustable resistor 16 need only have a relatively small potential across them and that the resistor 16 is connected to ground at one end. The resistors 15 and 16, that is the part of the circuit to the left of the chain line AA may readily be located remotely from the rest of the circuit and no high voltage connections would be required. Furthermore, the resistor 16 and the rest of the circuit may be independently connected to ground so that only one connection, lead 30, would be required between the two parts of the circuit on either side of the line AA.

1 claim:

1. A circuit for the control of a high direct voltage comprising a potentiometer including an adjustable resistor, a source of high voltage with respect to a datum voltage connected across said potentiometer, the adjustable resistor being remote from the high voltage end of the potentiometer, a gridcontrolled tube having a plate, a grid and a cathode, a load resistor, a circuit in shunt across said potentiometer, which shunt circuit includes a stabilised high voltage supply of voltage less than that of said source and the plate-to-cathode path of said gridcontrolled tube and said load resistor, the load resistor being arranged in series directly between the tube and the stabilised high voltage supply, and circuit means connecting said grid to a point on said potentiometer whereby adjustment of said adjustable resistor varies the current passed by said tube and hence controls the high voltage across said stabilised supply and load resistor.

2. A circuit as claimed in claim 1 wherein said datum voltage is ground potential and wherein. one end of said adjustable resistor is connected to ground.

3. A circuit for the control of a high direct voltage with respect to ground potential, comprising a potentiometer including an adjustable resistor, a source of high voltage with respect to ground connected across said potentiometer, the adjustable resistor being at the ground end of the potentiometer, a grid-controlled tube having a plate, a grid and a cathode, circuit means connecting said grid to a point on said potentiometer, a load resistor, a stabilised high voltage supply of voltage less than that of said source, and a circuit in shunt across said potentiometer, which shunt circuit includes in series said stabilised high voltage supply, the plate-to-cathode path of said grid-controlled tube and said load resistor, the stabilised supply being at the ground end of said shunt circuit and said load resistor being arranged in series between the tube andthe stabilised supply.

4. A circuit as claimed in claim 3 wherein said high direct voltage is a negative voltage with respect to ground and wherein said load resistor is connected between the plate of said. tube and the negative terminal of said stabilised supply.

5. A circuit for the control of a high direct voltage comprising a potentiometer including an adjustable resistor, a, source of high negative direct voltage with respect to a datum voltage connected across said potentiometer, said adjustable resistor being remote from the negative voltage end of said potentiometer, a grid-controlled tube having a plate, a grid, and a cathode, a load resistor one end of which is connected to the plate of said tube, a stabilised high voltage supply providing a negative voltage with respect to the datum less than the voltage of said source which stabilised supply is connected between the datum voltage end of said potentiometer and the end of said load resistor remote from said plate, a direct-current circuit from said cathode to the negative voltage end of said potentiometer and circuit means connecting said grid to a point on said potentiometer whereby adjustment of said adjustable resistor varies the current passed by said tube and hence controls the high voltage across said stabilised supply and load resistor.

6. A circuit for the control of a high direct voltage comprising a potentiometer including an adjustable resistor, a source of high negative direct voltage with respect. to a datum voltage connected across said potentiometer, said adjustable resistor being remote from the negative voltage end of said potentiometer, a pair of grid-controlled tubes each having a plate, a grid and a cathode, a single cathode load resistor connected at one end to the cathodes of both tubes and connected at the other end to the negative voltage end of said potentiometer, a pair of plate load resistors connected together at one end and with their other ends connected respectively to the plates of each of said tubes, a stabilised high voltage supply providing a negative voltage with respect to the datum less than the voltage of said source which stabilised supply is connected between the datum voltage end of said potentiometer and the junction of said plate load resistors, circuit means connecting the grid of one of said tubes to a point of said potentiometer whereby adjustment of said adjustable resistor varies the current passed by said one tube, further circuit means connecting the grid of the second tube to said cathode load resistor at a point thereon remote from the cathodes so that any tendency to change in the total cathode current of the two tubes cause corresponding variations in the grid-to-cathode voltage of said second tube such as to oppose this tendency, an output lead, and switch means for connecting either of said plates to said output lead.

7. A circuit for the control of a high direct voltage comprising a potentiometer including an adjustable resistor, a source of high negative direct voltage with respect to a datum voltage connected across said potentiometer, said adjustable resistor being remote from the negative voltage end of said potentiometer, a pair of grid-controlled tubes each having a plate, a grid and a cathode, a single cathode load resistor connected at one end to the cathodes of both tubes and connected at the other end to the negative voltage end of said potentiometer, a pair of plate load resistors connected together at one end and with their other ends connected respectively to the plates of each of said tubes, a stabilised high voltage supply providing a negative voltage with respect to the datum less than the voltage of said source which stabilised supply is connected between the datum voltage end of said potentiometer and the junction of said plate load resistors, circuit means connecting the grid of one of said tubes to a point of said potentiometer whereby adjustment of said adjustable resistor varies the current passed by said one tube, further circuit means connecting the grid of the second tube to said potentiometer near the negative voltage end thereof so that any tendency to change in the cathode current drawn by said one tube causes variations in the grid-to-cathode voltage of said second tube such as to oppose this tendency, an output lead, and switch means for connecting either of said plates to said output lead.

No references cited.

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