Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
2001-11-13
2003-12-02
Sherry, Michael (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C307S039000, C323S237000
Reexamination Certificate
active
06657418
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to an improved system for providing power to a control device used to control application of electrical power to a load; and, more particularly, it relates to a parasitic control device powered by the electrical power to be applied to a load and arranged to provide regulated electrical power to a control device whether the load is actively powered or not.
2. Description of the Prior Art
Simple control systems for controlling application of electrical power to load devices are known. For example, environmental control systems such as heating, cooling, ventilating, humidifying, and air conditioning devices are known to be subject to activation and deactivation control by thermostats, timers, humidistats, and the like. In heating, cooling and air conditioning devices, simple bi-metal thermostatic switches have been utilized to directly control the application of electrical power to the device, and require no external power to the device and no external or auxiliary electrical power source to switch the load power.
Developments in electronics have resulted in the replacement of the bi-metal thermostatic switches and other control devices with electronic control devices to achieve expanded operational controls and to enhance performance. Such electronic control devices require power to operate, and typically require either battery power or an additional power circuit. It has been common to utilize an external transformer to provide this additional power, thereby adding to the component cost and necessitating installation of an additional power circuit.
It is known to utilize sensor and/or control devices to selectively control the application of electrical power to load devices in response to various sensed or controlled conditions. By way of example, thermostats are used to sense ambient temperatures of target atmospheres and function to turn on power to controlled furnaces when the sensed ambient temperatures are reduced below preset thresholds. Systems are also known to utilize timers to maintain heating or cooling cycles operational for predetermined timed cycles. In addition, such systems can include separate plenum temperature sensors to control the operation of associated blower fans to hold off activation until plenum temperatures are raised to predetermined levels. Such operation saves power until the systems are operative to move warmed air and minimizes movement of cool air and avoids feelings of cold drafts. Such plenum sensors are also often used to maintain power to blower fans after controlled furnaces have been shut off to thereby efficiently capture and make use of residual plenum heat.
It is also known to utilize sensor and/or control devices to selectively control application of electrical power to many other types of loads. Examples include utilizing control devices to selectively control application of electrical power to refrigeration equipment in response to sensed ambient temperatures or other controlled parameters; to lighting equipment in response to timers or sensed levels of light; to fan equipment in response to timed or sensed ambient temperatures; to humidity control apparatus to add or reduce humidity in response to sensed ambient humidity conditions; to timer controls to selectively activate various loads; and to valve systems in response to sensed or controlled conditions, to name a few.
Prior art systems of the type summarized characteristically utilize a separate sources of power for the sensors or control devices than that provided to power the controlled loads. In most arrangements, separate power sources, applied over separate wiring, are required. Often the separate power sources are required to be regulated, and are often at different voltage levels from that of the power source for the affected loads. As indicated, separate wiring installations for providing power to the sensors or control devices are required, such installations being separate from the electrical wiring utilized for providing power to the loads. In those installations where only load power electrical wiring is available, these requirements for separate wiring are unduly difficult and costly to provide. Prior art systems often require dc power, whereas many loads require ac power; and, as indicated, regulation of the dc power may be required; or alternatively, batteries may be required to provide power to the sensors or control devices.
A low voltage solution to some of the deficiencies in other prior art systems was provided in U.S. Pat. No. 5,903,139 (hereinafter '139), entitled Power Stealing Solid State Switch For Supplying Operating Power To An Electronic Control Device, assigned to the assignee of this invention. This prior art system recognized the advantages of eliminating the need for utilizing separate transformers, wiring, or batteries to power electronic control devices. It also recognized the desirability of utilizing power Field Effect Transistors (FETs) in a circuit that “steals” power from the load circuit during low power phase switching to provide the necessary power for the control device. To accomplish this advantageous capability, one or more timer circuits and associated switching logic circuit were utilized to control the timing of disabling the back-to-back power FETs to allow power stealing from the load circuit to maintain the low voltage power source for the control device and a higher voltage supply for controlling the gates of the FETs. These relatively complex circuits allow controlling various low levels of load voltages, for example up to about 24 volts ac or dc.
Another prior art power “stealing” circuit utilized a power transformer with a primary current winding to provide power to a control device when power is applied to the load, and a primary voltage winding to provide power to the control device when the load is not powered. This type of configuration has limited utility because it places severe limitations on the range of load currents that can be handled, and characteristically the power transformer can be quite large in size.
It is apparent, then, that prior art systems that require separate wiring installations for sensor or control systems that are used to control application of power to loads are unduly costly and/or difficult to install. Prior art systems require separate dc power sources to power the sensor or control circuits. Alternatively, battery supplies must be provided. These requirements cannot readily be satisfied in an installation where power to drive a load is only available on a single line with the power circuit to be terminated through the load.
SUMMARY OF THE INVENTION
To overcome the problems of the prior art, an improved parasitic control system and method has been developed that includes a means or method process for parasitically diverting enough power from a source of load power to provide power to a control device that is utilized to control switching of the load power to the load when a sensed or control condition is determined to exist. The power that is diverted is insufficient to negatively impact the power supplied to the load and is operative whether the power is being applied to the load or not. The parasitic diversion is accomplished through operation of a bias means or method process that controls the operation of a transconductance means that carries the load power. The bias means includes a capacitor that is charged continuously through interaction of the bias means and the transconductance means. The capacitor provides the source of voltage utilized by voltage regulator means to develop the regulated dc voltage that is supplied to provide power to the control device. In varying usages the voltage regulator can be directly powered to provide a non-isolated output voltage, or can be indirectly powered to provide an isolated output voltage.
The improved parasitic control system and method for parasitically developing a regulated dc voltage to power an associated control device directly from the ac load pow
Fredrick Kris T.
Laxton Gary L.
Sherry Michael
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