US3348134A - Saturated phase shift circuit - Google Patents

Description

Oct. 17, 1967 H. H. HOGE SATURATED PHASE SHIFT CIRCUIT Filed March 25, 1965 FIG. 2

IN VENTOR HE/VR/ H065 BY (Zaxa/ W FIG. 3

ATTORNEY United States Patent 3,348,134 SATURATED PHASE SHIFT CIRCUIT Henri H. Hoge, Baltimore, Md., assignor, by mesne assignments, to the United States of America as represented by the ecretary of the Navy Filed Mar. 25, 1965, Ser. No. 442,834 4 Claims. (Cl. 323-126) The present invention relates generally to a phase shift circuit and more particularly to a phase shift circuit utilizing saturable reactors.

When utilizing multi-phase power supplies, it is necessary that one or more of the outputs be adjusted in phase with respect to a standard. Generally, with the increased use of solid state switching devices following such a power supply, a square wave is utilized for switching in such an operation. Particularly when silicon controlled rectifiers are utilized, it is required that the signal drive to such elements be continuous throughout the half cycle that such elements are in their on condition.

Conventional phase shifters do not lend themselves to the type of operation described above. This is especially true with the conventional R-C type phase shift network due to losses associated therewith and the variable reactive loads to which the signal from the phase shift circuit is applied.

Further, prior art devices have been contemplated utilizing a square loop magnetic core to delay or phase shift an input waveform by employing the blocking characteristic of a core. These devices, however, also fall short of a complete solution to the problem mentioned hereinabove in that they do not provide drive for a complete detected half cycle of operation, without utilization of additional elements providing feedback to complete the drive cycle.

The present invention provides an inexpensive and uncomplicated solution to this problem, utilizing a low impedance square loop core in a novel arrangement to obtain a complete half cycle phase shifted drive signal without the use of auxiliary feedback circuitry.

An object of the present invention is the provision of a reliable phase shifter.

Yet another object of the present invention is the provision of a phase shifter which provides a complete half cycle drive signal.

Still another object of the invention is to provide a phase shifted complete half cycle drive signal without the use of complicated feedback circuitry.

Other objects and features of the present invention will become apparent upon consideration of the following description when considered in conjunction with the appended claims and accompanying figures of drawing, wherein:

FIG. 1 illustrates a schematic drawing of an embodiment of the invention;

FIG. 2 depicts waveforms at various points on the embodiment of FIG. 1 when a square Wave input is applied thereto; and

FIG. 3 depicts waveforms at various points on the embodiment of FIG. 1 when a sinusoidal waveform input is applied thereto.

Turning now to FIG. 1, there is shown an input transformer 11, the secondary Winding 12 of which is connected on either end to coils 13 and 14, respectively, which coils are wound about a square loop magnetic core 15. Coils or windings 13 and 14 are wound about the core in such a direction that a positive current from the transformer to either coil will induce a clockwise flux pattern in the core 15. The other end of coils 13 and 14 are connected to the anode of diodes 16 and 17, respectively, both of the cathodes of these diodes are tied to a junction point 18. Between the connection of coil 13 and diode 16, one end of a resistor 19 is connected, the other end of which is connected to the junction formed by the secondary 12 and coil 14. A further resistor 21 is connected on one end to the junction 18 and on the other end to the junction formed by the secondary 12 and coil 14.

FIG. 2, waveform a, illustrates the waveform appearing at point a of the secondary 12 of transformer 11 when a square wave input signal is applied to the transformer. Waveforms b and c are the waveforms at the output of coils 13 and 14, respectively, induced by waveform a. Assuming the core to be in negative saturation at the time t waveform a instantaneously changes to a positive value. Due to the volt-second characteristics of the core, no signal appears at point b until the core flips from negative to positive saturation. This occurs at time t At time t the square wave a again changes instantaneously to a negative value causing the core to flip to the region of negative saturation at time t, which in turn causes the negative waveform shown in FIG. 2b, between times t and t At time t the cycle commences again.

While the waveforms at point b appear as described above, the coil 14 induces the waveforms at point c as shown in FIG. 20, since coil 14 is connected to the other side of the secondary winding 12 from that of coil 13. As the square wave a changes polarity, instantaneously, the waveforms appearing at point e are generated and appear at alternate time slots from those of FIG. 2b.

The diodes 16 and 17 only allow currents to flow therethrough that are positive. Thus, the detected and combined output appearing at d, or across resistor 21, is a combination of the positive portions of the waveforms b and c.

In practice, as seen in FIG. 2d, there is a slight switching notch in the waveshape. This is so slight that it may be neglected, and the output signal constitutes a phase shifted signal which is continuous for a half cycle for all practical applications.

The amount of delay or phase shift may be controlled by choosing a core with appropriate volt-second characteristics; that is, with an appropriate cross-section, and by the number of turns of coils 13 and 14. Obviously, other circuit parameters are carefully selected to obtain the correct output signal.

As shown in FIG. 3, a sinusoidal input signal applied to the transformer 11 results in the waveform of FIG. 3a as an input to the device. FIG. 3d illustrates that a phase shifted signal results.

The principle of operation is the same as that described above with respect to FIG. 2.

Thus, a device has been fully disclosed which provides a complete half cycle phase shifted output signal.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims in the invention may be practiced otherwise than as specifically described.

What is claimed is:

l. A half cycle phase shift circuit for shifting the positive portion only of an alternating Voltage and attenuating the negative portion thereof comprising:

a magnetic core characterized by binary stages of saturation;

a first and a second coil wound about said core wherein said first coil sets said magnetic core to one of its binary stages of saturation and said second coil resets said magnetic core to its other binary stage of saturation;

means for applying an alternating voltage to said coils;

and

first and second unidirectional current devices each having two terminals, said unidirectional current devices being connected to said first and second coils,

respectively, at one terminal and in common together at the other terminal; and an output resistor coupled to said common connection of said first and second unidirectional current devices.

2. The circuit of claim 1 wherein said first and second coils are at any one instant referred to voltages of opposite sense one relative to the other.

3. The device of claim 1 wherein said magnetic core is ofthe square hysteresis loop type.

4. The device of claim 2 wherein said unidirectional current devices are diodes.

References Cited 5 UNITED STATES PATENTS 3,026,504 3/1962 Aurand et a1 323-126 X 3,031,610 4/1962 Hamilton 323-8912 3,210,651 10/1965 Runyan 323l08 10 JOHN F. COUCH, Primary Examiner.

A. D. PELLINEN, Assistant Examiner.

Claims (1)

1. A HALF CYCLE PHASE SHIFT CIRCUIT FOR SHIFTING THE POSITIVE PORTION ONLY OF AN ALTERNATING VOLTAGE AND ATTENUATING THE NEGATIVE PORTION THEREOF COMPRISING: A MAGNETIC CORE CHARACTERIZED BY BINARY STAGES OF SATURATION; A FIRST AND A SECOND COIL WOUND ABOUT SAID CORE WHEREIN SAID FIRST COIL SETS SAID MAGNETIC CORE TO ONE OF ITS BINARY STAGES OF SATURATION AND SAID SECOND COIL RESETS SAID MAGNETIC CORE TO ITS OTHER BINARY STAGE OF SATURATION; MEANS FOR APPLYING AN ALTERNATING VOLTAGE TO SAID COILS; AND FIRST AND SECOND UNIDIRECTIONAL CURRENT DEVICES EACH HAVING TWO TERMINALS, SAID UNIDIRECTIONAL CURRENT DEVICES BEING CONNECTED TO SAID FIRST AND SECOND COILS, RESPECTIVELY, AT ONE TERMINAL AND IN COMMON TOGETHER AT THE OTHER TERMINAL AND AN OUTPUT RESISTOR COUPLED TO SAID COMMON CONNECTION OF SAID FIRST AND SECOND UNIDIRECTIONAL CURRENT DEVICES.

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