Modular constant current power supply

Claim 2

A power supply for converting an unregulated D.C. voltage level to a desired constant current output comprising: transforming means having input means for converting an A.C. signal supplied to said input means to a D.C. level; power switching means for modulating said unregulated D.C. voltage level to produce an A.C. current waveform exhibiting successive ramps and connected to supply said A.C. current waveform to said input means of said transforming means; means for developing a control voltage waveform comprising successive ramps proportional to those of said A.C. current waveform; means for producing a reference voltage level and for setting said level such that each said control voltage ramp proportional to said A.C. current waveform normally crosses said reference level when said desired current output is produced; and means for actuating said power switching means only for those intervals during which a said control voltage ramp does not exceed said reference level to control said A.C. current waveform such that a deviation from said desired constant current output level is corrected.

Claim 3

The power supply of claim 1 wherein said A.C. current waveform and said control voltage waveform comprise trapezoidal pulse trains.

Claim 4

The power supply of claim 1 wherein said power switching means includes first and second power switching elements and wherein said means for actuating said power switching means comprises: means for comparing said control voltage waveform to said reference voltage level and developing a control pulse each time a said control voltage ramp exceeds said reference level; and means for actuating said first power switching element for a period bounded by the beginning of a first control voltage ramp and production of a first said control pulse and said second power switching element for a period bounded by the beginning of a second control voltage ramp and production of a second control pulse.

Claim 5

The power supply of claim 1 wherein said control voltage waveform developing means includes: a current transformer means having a primary circuit means for transmitting said A.C. current waveform from said power switching means to said transforming means and a secondary circuit means for developing a current feedback signal proportional to said A.C. current waveform.

Claim 6

The power supply of claim 1 wherein said transforming means comprises: a power transformer having first, second and third secondary output terminals and first, second and third primary input terminals, said second primary input terminal being connected to said unregulated D.C. level; a choke coil having first and second terminals, said first terminal of said choke coil connected to said first secondary output terminal; capacitor means having first and second terminals, said first terminal of said capacitor means connected to the second terminal of said choke coil; a first rectifier means connected between said second secondary output terminal and the second terminal of said capacitor means; and a second rectifier means connected to said third secondary output terminal and to the connection point of said first rectifier means and said capacitor means.

Claim 7

The power supply of claim 5 wherein said control voltage waveform developing means includes: a current transformer having first and second primary output terminals connected respectively to the first and third primary input terminals of said power transformer, said current transformer further having first and second primary input terminals and first and second secondary terminals.

Claim 8

The power supply of claim 6 wherein said A.C. current waveform comprises periodic alternating trapezoidal pulses and said power switching means comprises: a first electronic switch having a first power control electrode, a first electrode connected to said first primary input terminal of said current transformer and a second electrode connected to a common point; and a second electronic switch having a second power control electrode, a first electrode connected to said second primary input terminal of said current transformer, and a second electrode connected to a common point.

Claim 9

The power supply of claim 7 wherein said power switching means further includes: a first driver switching means having a first driver control electrode for actuating said first power control electrode; and a second driver switching means having a second driver control electrode for actuating said second power control electrode.

Claim 10

The power supply of claim 7 wherein said control voltage developing means further includes: rectification means for producing a rectified trapezoidal pulse train from the output appearing across said first and second secondary terminals of said current transformer means; and means for producing a control voltage signal comprising trapezoidal pulses proportional in magnitude to said rectified trapezoidal pulse train.

Claim 11

The power supply of claim 9 wherein said means for actuating said power switching means comprises: means for comparing said trapezoidal pulses to said reference level and developing a control pulse each time a said trapezoidal pulse exceeds said reference level; means for producing a first rectangular pulse train for driving said first power control electrode and a second rectangular pulse train identical to said first rectangular pulse train and 180 degrees out of phase therewith for driving said second power control electrode, thereby resulting in production of a said trapezoidal control voltage pulse in synchronization with each pulse of both said first and second rectangular pulse trains; and means for terminating each said first and second rectangular pulse for the duration succeeding production of a corresponding control pulse by said comparing means.

Claim 12

The power supply of claim 10 wherein said first and second rectangular pulse producing means comprises: a clock signal source; a first flip-flop means driven by said clock and having a first output terminal and a second output terminal whose output is the inverse of said first output terminal; a first NOR gate receiving an input of said clock signal and of the said first output terminal of said first flip-flop and having output means for driving said first power control electrode; and a second NOR gate receiving an input of said clock signal and of the said second output terminal of said first flip-flop and having output means for driving said second power control electrode.

Claim 13

The power supply of claim 11 wherein said rectangular pulse terminating means comprises: a second flip-flop means for producing a control level in response to a said control pulse and removing said control level in response to the next said clock signal occurring after said control pulse; and means for supplying said control level as a third input to both said first NOR gate and said second NOR gate.

Claim 14

In a constant current D.C. power source supplied by an unregulated D.C. power level and having current switching devices and transformers for converting the unregulated D.C. level to an A.C. signal which is then converted to a constant current D.C. output level to a load, the improvement comprising: (a) means for developing fixed frequency clock pulses; (b) logic means for controlling said clock pulses to cause said switching devices to have a controlled duration of a switch-on pulse; (c) means for generating a control signal derived from comparison of a settable voltage reference signal against a voltage feedback signal derived from a current feedback line from said A.C. signal, said control signal being used to determine the duration of said switch-on pulse; (d) means for sensing said A.C. signal and feeding back a current which is converted to a proportional voltage usable to compare to said reference voltage; (e) isolation means for separating said current switching devices from said A.C. signal sensing means, from said control signal generating means and from said logic means.

Claim 15

In a constant current D.C. power source supplied by an unregulated D.C. power level and having current switching devices and transformers for converting the unregulated D.C. level to an A.C. signal which is then converted to a constant current D.C. output level to a load, the improvement comprising: (a) means for developing fixed frequency clock pulses; (b) logic means for controlling said clock pulses to cause said switching devices to have a controlled duration of a switch-on pulse; (c) means for generating a control signal derived from comparison of a settable voltage reference signal against a voltage feedback signal derived from a current feedback line from said A.C. signal, said control signal being used to determine the duration of said switch-on pulse; (d) means for sensing said A.C. signal and feeding back a current which is converted to a proportional voltage usable to compare to said reference voltage; (e) isolation means for separating said current switching devices from said A.C. signal sensing means, from said control signal generating means and from said logic means.

Claim 16

A constant current D.C. power source comprising: (a) converter means including a power transformer and current switching means for converting an unregulated D.C. input level into a balanced A.C. current signal within said power transformer; (b) generation means for providing clock signals to drive said power switching means; (c) logic means to regulate the duration of said clock signals; (d) means for supplying a ramp voltage signal, said ramp voltage signal being derived from the balanced A.C. current developed in said transformer by said power switching means, said ramp signal being a voltage representation of the current existing in the windings of the said power transformer of said converter; (e) a settable reference voltage; (f) a trigger pulse output means to generate a shut-off pulse alternately to individual ones of said switching means, said trigger pulse being initiated at any time when said ramp voltage signal becomes equal to said reference voltage.

Claim 17

A constant current D.C. power source comprising: (a) converter means including a power transformer and current switching means for converting an unregulated D.C. input level into a balanced A.C. current signal within said power transformer; (b) generation means for providing clock signals to drive said power switching means; (c) logic means to regulate the duration of said clock signals; (d) means for supplying a ramp voltage signal, said ramp voltage signal being derived from the balanced A.C. current developed in said transformer by said power switching means, said ramp signal being a voltage representation of the current existing in the windings of the said power transformer of said converter; (e) a settable reference voltage; (f) a trigger pulse output means to generate a shut-off pulse alternately to individual ones of said switching means, said trigger pulse being initiated at any time when said ramp voltage signal becomes equal to said reference voltage.

Claim 18

A constant current D.C. power source for supplying a constant current to loads of varying values comprising: (a) a first switching transistor having base, emitter, and collector terminals; (b) a second switching transistor having base, emitter and collector terminals; (c) a power output transformer having current through its primary winding supplied from an unregulated D.C. supply through the alternative switch-on of said first and second switching transistors, and having a secondary winding; (d) a current transformer having a pair of primary windings in series with the primary windings of said power transformer, and said current transformer having a secondary winding to provide A.C. current feedback along a feedback line; (e) a first rectification circuit means connected to the said secondary winding of said power output transformer for rectifying said current output; (f) second rectification circuit means connected to the secondary coil of said current transformer and to the said feedback line for rectifying the output of said current transformer to produce a rectified control signal; (g) resistor means connected to said second rectification circuit means for developing a control voltage from said rectified control signal and said current feedback line; (h) a settable reference level voltage set such that it is normally exceeded by said control voltage at some point in the existence of said control voltage cycle; (i) comparator means for comparing said reference level voltage and said control voltage from said resistor means, such that said comparator means will produce an output trigger pulse upon the voltage equality of the compared voltages; (j) isolating transformer means to isolate said transistor switching means from the feedback control means, from the output rectification means and from the control voltage and the trigger pulse means; (k) a clock pulse generator; (l) a first flip-flop means toggled by said clock pulse generator for producing first and second pulse trains of alternate phase and polarity; (m) second flip-flop means connected to said clock generator and said trigger pulse from said comparator for producing a modulation control signal in synchronization with said first and second pulse trains; (n) a first NOR gate receiving its inputs from said first pulse train, from said clock signal and from said modulation control signal, said first gate having an output; (o) a second NOR gate for receiving the second pulse train and for receiving said clock signal and said modulation control signal, said second gate having an output; (p) means for activating the base terminal of said first switching transistor by means of the output of said first NOR gate; and (q) means for activating the base terminal of said second switching transistor from the output of said second NOR gate.

Claim 19

A constant current D.C. power source for supplying a constant current to loads of varying values comprising: (a) a first switching transistor having base, emitter, and collector terminals; (b) a second switching transistor having base, emitter and collector terminals; (c) a power output transformer having current through its primary winding supplied from an unregulated D.C. supply through the alternative switch-on of said first and second switching transistors, and having a secondary winding; (d) a current transformer having a pair of primary windings in series with the primary windings of said power transformer, and said current transformer having a secondary winding to provide A.C. current feedback along a feedback line; (e) a first rectification circuit means connected to the said secondary winding of said power output transformer for rectifying said current output; (f) second rectification circuit means connected to the secondary coil of said current transformer and to the said feedback line for rectifying the output of said current transformer to produce a rectified control signal; (g) resistor means connected to said second rectification circuit means for developing a control voltage from said rectified control signal and said current feedback line; (h) a settable reference level voltage set such that it is normally exceeded by said control voltage at some point in the existence of said control voltage cycle; (i) comparator means for comparing said reference level voltage and said control voltage from said resistor means, such that said comparator means will produce an output trigger pulse upon the voltage equality of the compared voltages; (j) isolating transformer means to isolate said transistor switching means from the feedback control means, from the output rectification means and from the control voltage and the trigger pulse means; (k) a clock pulse generator; (l) a first flip-flop means toggled by said clock pulse generator for producing first and second pulse trains of alternate phase and polarity; (m) second flip-flop means connected to said clock generator and said trigger pulse from said comparator for producing a modulation control signal in synchronization with said first and second pulse trains; (n) a first NOR gate receiving its inputs from said first pulse train, from said clock signal and from said modulation control signal, said first gate having an output; (o) a second NOR gate for receiving the second pulse train and for receiving said clock signal and said modulation control signal, said second gate having an output; (p) means for activating the base terminal of said first switching transistor by means of the output of said first NOR gate; and (q) means for activating the base terminal of said second switching transistor from the output of said second NOR gate.