US 6,111,230 A · Method and apparatus for supplying AC power while meeting the European flicker and harmonic requirements

Abstract

An improved control method is provided that combines conventional ON-OFF control and conventional phase-angle control to reduce the AC inrush current to an electrical load, such as a tungsten halogen lamp used as a heating element in a laser printer, so that the power control circuit can satisfy both the European flicker and European harmonic requirements. Phase-angle control is applied to the load for a very short time period when it is initially energized, then the control circuit quickly switches from phase-angle control to standard ON-OFF control to reduce the harmonics generated by conventional phase-angle control methodologies. The electrical load exhibits three possible states: power full OFF, power ramp-up, and power full ON. During the power ramp-up state, power supplied to the load is adjusted by delaying the phase angle of the firing pulse relative to the start of each AC half cycle. Depending upon whether or not the system demand has been satisfied, the load's state can be changed from either power ramp-up to power full ON, or from power ramp-up to power full OFF. The phase-angle control methodology used during the power ramp-up state must be of sufficient time duration to reduce the amount of flicker to pass the European flicker test. However, this power ramp-up time interval must also be as short as possible to keep the harmonics as small as possible to the load, without the requirement of adding a large AC current harmonic attenuation inductor, which would otherwise be needed to pass the European harmonic test.

Claims20

Dependent claims

A method for controlling alternating current (AC) provided to an electrical device, said method comprising:

A. providing a source of alternating current electrical power;
B. providing an alternating current zero crossing detector, a phase-angle control circuit, an electrical load, and a main controller;
C. entering a power ON mode for said electrical load, by:
(i) after detecting an initial zero crossing of said alternating current electrical power, applying, under the control of said main controller, a small amount of alternating current to said electrical load by way of said phase-angle control circuit by:
loading a counter with an initial numeric value, counting down from said initial numeric value until said counter reaches a value of zero, and turning on an alternating current switching device to switch said source of alternating current electrical power to said electrical load until the next zero crossing;
(ii) after subsequent zero crossings, gradually increasing said amount of alternating current to said electrical load in a manner to achieve full power by repeatedly loading said counter with a lesser numeric value, and after detecting each of said subsequent zero crossings:
counting down from said lesser numeric value until said counter reaches a value of zero, turning on said alternating current switching device to switch said source of alternating current electrical power to said electrical load until the next zero crossing, to thereby smoothly ramp-up said amount of alternating current being supplied per half-cycle of AC until full power is achieved;
(iii) once achieving full power, continuing to apply said full power to said electrical load until a power OFF command is generated by said main controller;
and
D. entering a power OFF state for said electrical load, by removing said alternating current to said electrical load.

7 more elements

An electrically-powered apparatus, comprising:

A. a memory circuit for storage of data, said memory circuit containing a first register and a down-counter;
B. an alternating current zero crossing detector;
C. a phase-angle control circuit;
D. an electrical load;
and
E. a processing circuit that is configured to control a mode of operation of said electrical load, including an OFF-mode, a partial-ON-mode, and a full-ON-mode, by:
(i) entering said partial-ON-mode for said electrical load, wherein:
a. after said alternating current zero crossing detector detects an initial zero crossing of said alternating current electrical power, applying a small amount of alternating current (AC) to said electrical load by way of said phase-angle control circuit, said amount of alternating current being proportional to a count value stored by said processing circuit into said first register;
wherein said count value of said first register is initially transferred into said down-counter by said processing circuit;
and after each zero crossing while in said partial-ON-mode, said down-counter counts down until reaching a value of zero, after which said phase-angle control circuit provides a firing pulse to an output triac that turns on and energizes said electrical load, and said output triac remains turned on until reaching the next zero crossing;
b. after subsequent zero crossings, gradually increasing said amount of said alternating current to said electrical load in a manner to achieve full power so as to satisfy a European flicker requirement and to satisfy a European harmonic requirement;
(ii) entering said full-ON-mode upon achieving full power, and continuing to apply said full power to said electrical load until said processing circuit determines it is time to go into a power OFF mode;
and
(iii) entering said power-OFF-mode, by removing said alternating current to said electrical load.

11 more elements

A method for controlling alternating current (AC) provided to a fuser electrical heating element of an image forming apparatus, said method comprising:

A. providing a source of alternating current electrical power;
B. providing a print engine having an alternating current zero crossing detector, a phase-angle control circuit, a fuser electrical heating element, and a main controller;
C. energizing said fuser electrical heating element upon entering a printing mode of operation, by:
(i) after detecting an initial zero crossing of said alternating current electrical power, applying a small amount of alternating current to said fuser electrical heating element by way of said phase-angle control circuit, said amount of alternating current being under the control of said main controller;
(ii) after subsequent zero crossings, gradually increasing said amount of alternating current to said fuser electrical heating element at a first relatively quick ramp-up rate, yet in a manner to achieve full power so as to satisfy a European flicker requirement and to satisfy a European harmonic requirement;
(iii) once achieving full power, continuing to apply said full power to said fuser electrical heating element until a power OFF command is generated by said main controller;
D. energizing said fuser electrical heating element upon entering a standby mode of operation, by:
(i) after detecting an initial zero crossing of said alternating current electrical power, applying a small amount of alternating current to said fuser electrical heating element by way of said phase-angle control circuit, said amount of alternating current being under the control of said main controller;
(ii) after subsequent zero crossings, gradually increasing said amount of alternating current to said fuser electrical heating element at a second relatively slow ramp-up rate, yet in a manner to achieve full power so as to satisfy a European flicker requirement and to satisfy a European harmonic requirement;
(iii) once achieving full power, continuing to apply said full power to said fuser electrical heating element until a power OFF command is generated by said main controller;
and
E. de-energizing said fuser electrical heating element, from either of said printing mode and said standby mode of operation, upon entering a power OFF mode of operation.

9 more elements

Dependencies are inferred from the claim text.

Method and apparatus for supplying AC power while meeting the European flicker and harmonic requirements

Life of this patent

Method and apparatus for supplying AC power while meeting the European flicker and harmonic requirements

Life of this patent

Abstract

Claims20