Slewing power supply for programmable phase shifter drive

A programmable slewing power supply is used to drive microwave phase shifters according to a command signal from a system controller using: a Milberger converter; a power source; a rectifying circuit; two differential amplifier circuits; and two comparator amplifier circuits. The Milberger converter outputs a combined square wave which it produces by combining two independent square waves which add or cancel. The power source receives the combined square wave and outputs: a reference voltage, a positive voltage signal; and a negative voltage signal. The rectifying circuit produces a rectified command signal by rectifying the command signal from the system controller. The two differential amplifier circuits respectively measure the positive and negative voltage signals with respect to the reference voltage to produce a measured positive voltage signal, and a measured negative voltage signal. The comparator operational amplifiers produce complementary outputs to drive the phase shifters by respectively comparing the measured positive and negative voltage signals with the rectified command signal.

CROSS-REFERENCE TO RELATED APPLICATIONS 
The subject matter of this application is related to the subject matter 
contained in the following U.S. patent applications: Ser. No. 893,831, 
filed Aug. 6, 1986, entitled Self Generated Converter Filter by C. S. 
Kerfoot et al; Ser. No. 910,113, filed Jan. 28, 1986, entitled "Energy 
Recoverable Choke Feed" by W. E. Milberger et al; and Ser. No. 891,821, 
filed Aug. 1, 1986, entitled "High-Voltage Milberger Slip Slide Power 
Conditioner" by F. B. Jones et al. 
BACKGROUND OF THE INVENTION 
The present invention relates generally to electric power supply systems, 
and more specifically to a programmable slewing power supply to drive 
microwave phase shifters. 
Phased array radar and communications systems steer emitted electromagnetic 
radio frequency (RF) signals electronically by shifting the phase of these 
signals with respect to a matrix of transmitter elements housed in the 
array. Some of these systems use microwave phase shifters to adjust the 
phase of signals received from a high-power signal source. However, just 
as the phase of these signals needs to be adjusted to produce different 
waveforms, the voltage levels also need to be adjustable. 
The task of providing a programmable high-efficiency power supply for 
microwave phase shifters is alleviated, to some extent, by the systems 
disclosed in the following U.S. Patents, the disclosures of which are 
incorporated herein by reference: U.S. Pat. No. 3,237,088 issued to Karp; 
U.S. Pat. No. 3,448,372 issued to Goff; and U.S. Pat. No. 4,513,360 issued 
to Ikenoue. 
The above-cited references all disclose power supply systems. Typical prior 
art systems also include supply systems which provide supply voltages 
using a fixed power supply with a series linear amplifier. Such supply 
voltages are variable but the supply systems are characterized as being 
low in efficiency, excessive in terms of power dissipation, and as having 
poor reliability in the linear amplifier due to the wide variation 
required for output currents and voltages. The reasons for such 
performance problems are discussed below. 
Magnetic coils used in phase shifters present large inductive loads with a 
series resistance. Linear drive is typically implemented using a fixed 
voltage power supply and a transconductance amplifier. Current is 
commanded as a voltage to be developed across the sense resistor. The 
voltage provided by the power supplies can be divided into three portions. 
First, part of the available voltage is used to drive the load as required 
(V=I*R; V=L*dI/dt), with the load power being the product of this voltage 
and the drive current. 
A second portion of the voltage is required by the linear amplifier to stay 
in its active region of operation, free of saturation effects. The third 
portion, consisting of the voltage provided in excess of the preceding two 
portions, must also be used by the linear amplifier. This voltage serves 
no useful purpose, being dissipated as waste heat in the amplifier, but 
must be available to accommodate changing load requirements. 
The third portion of the voltage is dissipated by the linear amplifier as 
follows. For a resistive load, it can be shown that the maximum power 
dissipated by the linear amplifier with a fixed voltage power supply is at 
one half maximum current, Pdiss=1/2Imax * V. For an inductive load the 
current voltage waveforms are out of phase, so that the maximum amplifier 
dissipation is Pdiss=Imax * V. 
The peak voltage requirements can be much higher than the average voltage 
resulting in very high power levels. For a particular phase shifter drive, 
the maximum current of 7 amperes and peak linear voltage of 500 volts 
result in an amplifier dissipation of in excess of three kilowatts, which 
must be sustainable for an indefinite period. 
Clearly, it would be of great benefit to have power supplies which provide 
only the first two portions of voltage discussed, without the third. In 
general, this can be accomplished with any D.C.-D.C. converter which uses 
inductive filtering and is capable of providing efficient power conversion 
over a range of input and output voltages. 
Two important concerns arise, both related to the rate at which the output 
must change. The first is the bandwidth of the power supply regulation 
loop. For stability in switchmode power supplies, the unity gain crossover 
is limited to a theoretical maximum of one half of the switching 
frequency. In practice, the limit is lower because of the need to allow 
for variances. 
The second concern is the slew rate of the power supply under load. This is 
a function of the peak power output required and the rate of change of 
voltage needed. The supply must provide current at the proper voltage, 
while also providing current to charge the output capacitance to slew the 
voltage. This requires input line filtering to isolate surges from the 
prime power line. 
From the foregoing discussion it is apparent that there currently exists 
the need for a high frequency switchmode power supply with high peak power 
capabilities and wide output range to support systems including those with 
microwave phase shifters. The present invention is intended to satisfy 
that need. 
SUMMARY OF THE INVENTION 
The present invention is a slewing power supply which provides a variable 
voltage supply for microwave phase shifters using: a Milberger slip slide 
converter as a voltage power supply; and a regulation circuit. 
The Milberger slip slide power converter is best understood by referring to 
the above-cited disclosure of F. B. Jones et al, the disclosure of which 
is incorporated herein by reference. 
As described by F. B. Jones et al, the Milberger slip slide power converter 
is a high-voltage converter circuit which uses a slip slide power 
conditioner to reduce non-monotonic non-linearities in the converter 
output signal. The slip slide power conditioner includes: a choke feed 
D.C. circulator, two radio frequency (RF) power pumps; a phase detector; a 
phase controller; and combiner. The choke feed D.C. circulator receives 
the D.C. input signal and produces therefrom two voltage output signals 
which are each sent to one of the two RF power pumps. The two RF power 
pumps produce two out-of-phase square wave output signals which are 
algebraically combined in the combiner to form an output signal whose 
amplitude is a function of phase difference. The phase detector and phase 
controller sample this output signal and adjust the phase of the two power 
pumps to remove non-linearities due to secondary ringing (resonance) that 
beats with harmonics of their square wave signals. 
The regulation circuit of the present invention is a signal processing 
circuit which receives the output signals from the Milberger slip slide 
converter and command signals from a system controller and produces 
therefrom a complementary power supply for the microwave phase shifters. 
In one embodiment of the invention, this regulation circuit includes: two 
rectifying operational amplifier circuits; two differential operational 
amplifier circuits; and two comparator operation amplifier circuits which 
produce the complementary power supply for the phase shifters. In this 
embodiment, the invention uses the Milberger slip slide converter as a 
dynamic power supply with controlled amplitude. The voltage command signal 
is received by the two rectifying operational amplifier circuits which 
provide therefrom the absolute value of the command in the form of a 
rectified command voltage signal. 
The power supply output signals of the Milberger slip slide converter are 
sensed by the two differential amplifier circuits. These differential 
amplifier circuits respectively measure the positive and negative voltages 
of the Milberger slip slide converter with respect to the base voltage to 
produce a measured positive voltage signal and a measured negative voltage 
signal. 
The two comparator operational amplifier circuits respectively compare the 
measured positive voltage signal and the measured negative voltage signal, 
from the two differential amplifier circuits, with the rectified command 
voltage signal, from the rectifying operation amplifier circuits, to 
produce two command output control voltage signals. The higher of the two 
output control voltage signals dominates the output and is sent to the 
microwave phase shifters. By providing only the amount of voltage actually 
required under dynamic conditions, it greatly reduces power dissipation in 
series linear elements, easing design requirements and improving 
reliability. The supply is made possible by the Milberger slip slide 
converter, which provides efficient high frequency operation with high 
peak power capability. 
It is an object of the present invention to provide a dynamic supply of 
power to microwave phase shifters. 
It is another object of the present invention to reduce power dissipation 
and increase the efficiency of power supply systems. 
It is another object of the present invention to provide a regulator 
circuit for use with a Milberger slip slide converter to produce a slewing 
power supply.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The present invention is a slewing power supply which can be used to drive 
microwave phase shifters with high efficiency. 
The reader's attention is now directed towards FIG. 1 which is an 
electrical schematic of a typical prior art power supply system. The power 
supply system of FIG. 1 uses magnetic coils 10 to implement a linear 
drive. Magnetic coils used in phase shifters present large inductive loads 
with a series resistance. Linear drive is typically implemented using a 
fixed voltage power supply 11 and a transconductance amplifier 12. Current 
is commanded as a voltage to be developed across the sense resistor 13. 
FIG. 2 is a chart depicting the three portions of voltage usage in power 
supply systems. As mentioned above, the voltage provided by the power 
supplies can be divided into three portions. Part of the available voltage 
is used to drive the load as required (V=I*R; V=L*dI/dt), with the load 
power being the product of this voltage and the drive current. 
The second portion of the voltage is required by the linear amplifier to 
stay in its active region of operation, free of saturation effects. The 
third portion, consisting of the voltage provided in excess of the 
preceding two portions, must also be dropped by the linear amplifier. This 
voltage serves no useful purpose, being dissipated as waste heat in the 
amplifier, but must be available to accommodate changing load 
requirements. 
For a resistive load, it can be shown that the maximum power dissipated by 
the linear amplifier with a fixed voltage power supply is at one half the 
maximum current, Pdiss=1/2Imax * V. For an inductive load the current and 
voltage waveforms are out of phase, so that the maximum amplifier 
dissipation is Pdiss=Imax * V. 
FIG. 3 is a chart depicting drive current and voltage which indicates that 
the peak voltage requirements can be much higher than the average 
resulting in very high power levels. For one particular phase shifter 
drive, the maximum current of 7 amperes and peak linear voltage of 500 
volts result in an amplifier dissipation of in excess of 3 kilowatts, 
which must be sustainable for an indefinite period. 
To satisfy the foregoing considerations, which require a high frequency 
switchmode power supply with high peak power capability and a wide output 
range, a 150 KHz Milberger slip slide converter is used in the present 
invention as the means of D.C.-D.C. conversion in a power supply. In this 
converter two 150 KHz square waves, known as the "slip" and "slide" 
phases, are generated by MOSFET full bridge choppers. These phases are 
magnetically combined and integrated with the relative phase determining 
the output power. 
FIG. 4 is a schematic of a Milberger slip slide converter, as described in 
the above-cited reference of F. B. Jones et al, the disclosure of which is 
incorporated by reference. The high-voltage Milberger slip slide power 
conditioner operates as follows: The choke feed D.C. circulator receives 
the D.C. input signal and produces therefrom two voltage output signals 
which are each sent to one of the two RF power pumps 101 and 102. The 
purpose of the choke feed circulator 100 is to supply a current feed to 
both the power pumps with current limiting imposed on the D.C. input 
signal. This current limiting is intended to minimize transistor switch 
through losses and is also effective when short circuit and overload 
conditions appear at the load. The choke feed D.C. circulator 100 is 
intended to provide fail-safe protection to the circuit, enhance the full 
load efficiency, and divide the D.C. input signal into a first and second 
voltage reference signal which are sent to the two power pumps 101 and 
102. 
The two RF power pumps 101 and 102 are actually two phase control choppers 
that produce two out-of-phase square wave output signals which are 
algebraically combined in the combiner to form an output signal whose 
amplitude is a function of phase difference. The first of the two phase 
control choppers is a continuous phase pump which receives the first 
voltage reference signal from the choke feed D.C. circulator, and produces 
therefrom a continuous phase square wave signal. The second of the two 
phase control choppers is a reference phase pump which receives the second 
voltage reference signal from the choke feed D.C. circulator, and produces 
therefrom a phase square wave signal. 
The Milberger computer works by the principal of having parts of two 
independent square waves either add or cancel. FIGS. 5A, 5B and 5C are 
charts that respectively depict the slip and slide square waves produced 
by the two square choppers of the Milberger converter and the combined 
output signal produced by the combiner. Note that the relative phase 
between the square waves of FIGS. 5A and 5B affects the amplitude of the 
combined output of FIG. 5C. 
FIG. 6 is a detailed circuit diagram of an embodiment of the regulator 
circuit of the present invention, which receives the output signals of the 
Milberger converter of FIG. 4, and command signals from a system 
controller to produce a complementary power supply for microwave phase 
shifters. The voltage command signal is received from the system 
controller 600 by two rectifying operational amplifier circuits 601 and 
602 to produce therefrom the absolute value of the command in the form of 
a rectified command voltage signal. 
The Milberger slip slide converter 611 is used as a part of the power 
source 610. The regulator circuit receives three inputs from the power 
source 610: a reference voltage V.sub.REF and the positive and negative 
components V+ and V- of the Milberger converter combined output signal 
depicted in FIG. 5C. These positive and negative components are available 
by rectifying the output of the square wave signal. All three inputs from 
the power source 610 are amplified by three input amplifiers in a booster 
circuit 620. 
The three amplified power supply signals from the booster circuit 620 are 
sensed by two differential amplifier circuits 621 and 622. These 
differential amplifier circuits respectively measure the positive and 
negative voltages (V+ and V-) of the Milberger slip slide converter, with 
respect to the base voltage V.sub.REF to produce a measured positive 
voltage signal and a measured negative voltage signal. 
Two comparator operational amplifier circuits 630 and 631 respectively 
compare the measured positive voltage signal and the measured negative 
voltage signal (from differential amplifier circuits 621 and 622) with the 
rectified command voltage signal to produce two command output control 
voltage signals which meet and a single output to the microwave phase 
shifters 650. The higher of the two command output control voltage signals 
produced by the comparator circuits 630 and 631 predominates and is sent 
to the microwave phase shifters 650. 
The embodiment of FIG. 6 also includes a slow start circuit 660 which 
controls power surges during initial operation of the slewing power 
supply. The slow start circuit 660 is electrically connected to the two 
comparator operational amplifier circuits 630 and 631 to receive the two 
command output control voltage signals received by them. The slow start 
circuit contains an operational amplifier which serves to control 
transient spikes which may occur during initial activation of the power 
supply. 
A significant feature of the slewing power supply system of FIG. 6 is the 
use of a dynamic output D.C.-to-D.C. conversion for the high efficiency 
linear drive of an inductive load. The outputs of the Milberger converter 
are complementary voltages, which allow balanced operation of operational 
amplifiers. These outputs can be centered on dynamic floating base voltage 
rather than ground to decrease the voltage standoff requirements of the 
linear amplifier. At any instant only one of the two outputs will be 
providing power to the load. The voltage is therefore regulated according 
to the more heavily loaded output at any instant, to assure that the 
minimum required voltage is available at all times. 
The power supply of FIG. 6 uses a 150 KHz Milberger slip slide converter to 
provide high efficiency and high frequency power conversion. The high 
switching frequency of 150 KHz allows a regulation loop, sufficiently fast 
to track the voltage requirements, to be closed. The use of MOSFETs 
instead of Bipolar transistors in the choppers allows high peak power 
output, as the MOSFET is limited by average than peak current. The slip 
slide's input circulator provides a current reserve for these peaks, while 
presenting a more uniform average load to the prime power line. 
The Milberger converter and regulator circuit uses complementary outputs as 
a voltage bracket for the operational amplifier circuits, and uses the 
superposition of output voltages on a base voltage to minimize the voltage 
standoff requirements on series linear elements. 
While the invention has been described in its presently preferred 
embodiment it is understood that the words which have been used are words 
of description rather than words of limitation and that changes within the 
purview of the appended claims may be made without departing from the 
scope and spirit of the invention in its broader aspects.