Two-wire appliance power controller

Details Two-wire appliance power controller Two-wire appliance power controller

2000-10-19

2004-03-02

Wong, Don (Department: 2821)

Electric lamp and discharge devices: systems

Current and/or voltage regulation

C307S041000, C307S115000

Reexamination Certificate

active

06700333

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a low cost, compact electronic circuit that may be built into the electrical cord of a two wire AC electrical appliance and that implements different levels and schedules of power application based upon control signals provided from either a switch that is remotely located in the appliance and/or a switch that is remotely located at a location on the source side of the electric cord. An alternative implementation is built into a plug-in adapter that connects between a conventional wall outlet and into which a lamp or other appliance may be attached, thereby implementing power level control as determined by the number and timing of on/off switch closures from a remote switch. The invention also encompasses the use of internal electrostatic protection diodes in a CMOS based integrated circuit to power that circuit, thereby producing a minimal-parts-count circuit.
2. Background of the Invention
For AC electrical appliances such as curling irons, heaters, or electric blankets, that incorporate heating elements, a simple two position, ON/OFF switch is commonly used for power control. Such a switch is also common in incandescent lamps, where in the ON position, electrical current is allowed to pass to the lamp, thereby creating full brightness and in the OFF position, no electrical current is allowed to flow to the lamp, thereby turning off the light. A two position, ON/OFF switch, is also used in many electrical loads that incorporate motors. An example is electric fans. If the switch is ON, the fan operates at full speed. If the switch is OFF, no power is delivered to the fan motor and the fan is off.
In many applications, it is desirable to have more than just ON/OFF control. For example, in an electric blanket, it is desirable to have multiple levels of heating in order to adjust for the external air temperature and user preference. In a light, a low lighting level might be desirable to save energy or to set a mood while higher levels would be preferable for reading. For a fan, different fan speeds might be desirable depending upon room size and room temperature.
Different levels of appliance control may often be obtained by modifying the appliance. Many of these alternatives involve a more complicated switch, additional wiring, and/or modifications to the appliance. For example, in the U.S., many lamps are sold that have a so-called three-way socket. Such a lamp socket has three contacts designed to connect to an incandescent light bulb. The outer contact is neutral. There are two inner “hot” contacts. A three-way switch is provided on the socket. In the first position it supplies power to one of the hot contacts, in the second position it supplies power to the second of the hot contacts. In the third position it supplies power to both hot contacts. In a fourth position it is off and no power is applied to the bulb. A special “three way” bulb that is commercially available may then be used with the three-way socket to achieve multiple levels of lighting. A three-way bulb has two hot contacts with filaments connecting between each of these hot contacts to a third contact, the “neutral”, which is typically connected to the outer ring on the incandescent bulb. Depending upon which hot contacts are energized, either, both or neither of the filaments within the three-way bulb may be energized, consequently providing differing levels of lighting. The problem with this approach to multi-level lighting is that only three levels of brightness are typically provided, the socket is special and must be built into the lamp, and special three way bulbs must be purchased and these are expensive relative to conventional incandescent bulbs.
In a fan, speed control may be obtained by having multiple windings on the fan motor coils and by a multiple position switch, switching between different windings to vary the motor field and thereby vary the fan speed. A multiple position switch is more complicated than a two position switch and a motor that has multiple windings to implement multiple speeds is more complicated than a simple motor having a single set of magnetic field windings or an internally connected field.
There are commercially available lamp dimmers that provide a variable appliance control and that can be installed as a retrofit. These are often sold as a plug-in wall module, into which the consumer plugs an incandescent lamp or other appliance. A potentiometer (which is a type of switch that gives a range of resistance values depending upon its mechanical position) in the dimmer module allows the user to control the power level over a wide range. Power control is then achieved by the phase control of a thyristor, a type of solid state electronic AC switch that turns on in response to a voltage applied at the so-called gate terminal.
Thyristors have the advantage that they are latching. That is, once turned on or fired, even in the absence of additional gate excitation, a thyristor will continue to conduct electrical current until the current flow through the device reduces to zero. A type of thyristor called a triac may be used for a bidirectional AC switch and has three terminals: MT
1
, MT
2
and gate. The MT
1
and MT
2
terminals act as the two terminals of an AC switch. The voltage signal applied to the gate of a triac, the so-called gate pulse, may be classified according to one of four possible operating modes: quadrant I, II, III, or IV. When the gate pulse is in-phase with the AC line, then the triac is said to use quadrant I operation for positive going current flow (gate pulse is positive and current flows from MT
2
to MT
1
) and quadrant III operation for negative going current flow (gate pulse is negative and current flows from MT
1
to MT
2
). In quadrant II operation, the gate pulse is negative for positive current flow and in quadrant IV, the gate pulse is positive for negative current flow. Although any of the four quadrant operations may be used to fire a thyristor, quadrant I,II and III operation is much preferred because it takes substantially less electrical current to obtain a reliable triggering. Quadrant IV operation requires much higher gate currents to trigger the thyristor.
The disadvantage to potentiometer based dimmers is that they are often not convenient to control because a potentiometer that is mounted in the module at the wall outlet may not be easily accessible. Other products are designed to attach midway in the electrical cord, allowing the consumer to more easily control power levels but also requiring the user to make a more extensive (and permanent) modification to the cord. By contrast, the present invention does not require the introduction of additional switches into the lighting control but uses the existing switches. Furthermore, it can be built into a cordset at the manufacturing point, or it can be added at a later date as a module type of device that is portable among multiple appliances.
U.S. Pat. No. 3,979,601 to Franklin discloses a combination dimmer and timer switch mechanism which connects to the AC line and which implements appliance dimming in accordance with a predetermined timing sequence. A phase-controlled thyrister is used to regulate the appliance power. This system is fundamentally designed to be an open loop system without requiring user feedback for control and utilizes a complicated mechanical switch.
U.S. Pat. No. 4,276,486 to Ahuja et al. discloses a two terminal power controller whereby momentary interruptions of the AC supply are used to signal building lights to change state (if on, to turn off, if off, to turn on). The intent is to allow both a distributed control where each light may be individually turned on, or a global control where all lights may be turned on or off.
U.S. Pat. No. 4,504,778 to Evans discloses a self-powered electronic control system wherein the control circuitry is powered directly off the AC line and wherein momentary power loss events are sensed and are used as inputs to the control scheme. In this sys

Affiliated with

Also associated with

Rating

Two-wire appliance power controller does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Two-wire appliance power controller, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Two-wire appliance power controller will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3241245