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US 5,691,607 AGranted
Modular high power modulator
AssigneeNorthrop Grumman Corporation
InventorsRobert Matthew Zawislak, Kenneth John King, John Michael Rein, Jeffrey Coe Perkins
Life of this patent
Estimating the term…
Abstract
A single-stage modular modulator for pulsed illumination sources uses a full-range converter which converts unregulated DC to a 40-50 kHz carrier modulated at a frequency of a few hundred to a few thousand hertz. The modulated carrier is applied to the illumination source through a step-down transformer followed by a low-pass filter circuit which removes the carrier. The converter is controlled by a modulation control which uses an instantaneous load current signal feedback to follow a modulation commend signal, and a current mode signal representing the primary current of the transformer to compensate for converter output variations caused by input voltage variations.
Claims10
A modulator for pulsed illumination sources, comprising:
- a) a source of AC power;
- b) a rectifier for converting said AC power to unregulated DC power;
- c) a full-bridge converter arranged to receive said DC power and to convert it to substantially square-wave AC power at a carrier frequency, the duty cycle of said square wave being variable at a lower modulation frequency under current control;
- d) a load;
- e) a transformer connected between said converter and said load;
- f) a low-pass filter connected between said transformer and said load for removing said carrier-frequency AC from the output of said transformer;
- g) a modulation control circuit connected to said converter and having a modulation command input;
- h) a monitoring element arranged to provide to said modulation control circuit a signal indicative of the primary current of said transformer;
- and
- i) a current sensing element arranged to provide to said modulation control circuit a signal indicative of the instantaneous current through said load;
- j) said modulation control circuit being arranged to vary said modulation frequency in accordance with said modulation command input, said primary current signal, and said instantaneous current signal.
8 more elements
A modulator for pulsed illumination sources, comprising:
- a) a source of AC power;
- b) a rectifier for converting said AC power to unregulated DC power;
- c) a full-bridge converter arranged to receive said DC power and to convert it to substantially square-wave AC power at a carrier frequency, the duty cycle of said square wave being variable at a lower modulation frequency Under current control;
- d) a load;
- e) a transformer connected between said converter and said load;
- f) a low-pass filter connected between said transformer and said load for removing said carrier-frequency AC from the output of said transformer;
- g) a modulation control circuit connected to said converter and having a modulation command input;
- h) a monitoring element arranged to provide to said modulation control circuit a signal indicative of the primary current of said transformer;
- and
- i) a current sensing element arranged to provide to said modulation control circuit a signal indicative of the instantaneous current through said load;
- j) said modulation control circuit being arranged to vary said modulation frequency in accordance with said modulation command input, said primary current signal, and said instantaneous current signal;
- and
- k) said primary current monitoring element being a second transformer having its primary winding connected in series with the primary winding of said first-named transformer, the output of the secondary winding of said second transformer being said signal indicative of said primary current of said first-named transformer.
10 more elements
A modulator for pulsed arc lamps, comprising:
- a) a source of AC power;
- b) a rectifier for converting said AC power to unregulated DC power;
- c) a full-bridge converter arranged to receive said DC power and to convert it to substantially square-wave AC power at a carrier frequency, the duty cycle of said square wave being variable at a lower modulation frequency under current control;
- d) an arc lamp;
- e) a transformer connected between said converter and said load;
- f) a low-pass filter connected between said transformer and said load for removing said carrier-frequency AC from the output of said transformer;
- g) a modulation control circuit connected to said converter for switching said converter, said modulation control including:
- i) a source of modulation commands;
- ii) a simmer level reference representing a minimum current level for said arc lamp;
- iii) an adder for said modulation commands and reference;
- iv) a source of current signals indicative of the actual instantaneous current drawn by said arc lamp;
- v) a first comparator connected to produce an output representative of the difference between the instantaneous current commanded by said combined modulation command and said actual instantaneous current;
- vi) a source of current mode control signals representative of the current drawn by said transformer;
- vii) a second comparator connected to produce a pulse width output signal representative of said difference output modified as a function of said current mode control signals;
- and
- viii) a pulse width modulator responsive to said pulse width output signal and connected to cause said converter to be switched in accordance with said pulse width output signal.
13 more elements
A modulation system for arc lamps or the like, comprising:
- a) a source of unregulated DC power;
- b) an output transformer having first and second windings;
- c) a converter connected to said unregulated DC source and arranged to alternately supply pulses of opposite polarity to said first winding at a predetermined frequency;
- d) drive circuitry arranged to vary the width of said pulses in response to a modulation signal;
- e) an output circuit connected to said second winding and to a load, and arranged to produce a DC load current varying in accordance with said pulse width and with the level of said unregulated DC power;
- f) a current sensor in said output circuit arranged to produce a current feedback signal representative of said load current;
- and
- g) a modulator arranged to produce said modulation signal, said modulator including:
- i) a first input receiving a current mode signal representative of the current flowing in said first winding;
- ii) a second input receiving said current feedback signal;
- and
- iii) a third input receiving a modulation command signal representative of the desired load current;
- iv) said modulation combining said current mode, current feedback and signals modulation command to produce said modulation signal.
10 more elements
Dependencies are inferred from the claim text.