Dimming circuit for controlling electrical power

Abstract

A dimming circuit includes an isolated DC voltage source that is selectively coupled to a switch through which power is supplied from a source to a load. In a disclosed example, the switch comprises two MOSFETs. The isolated DC voltage source is selectively coupled directly to the gate and source of the MOSFETs to set them into an operative state for providing power to the load. A controller controls another switch that is operative to selectively control when the isolated DC voltage source is coupled to the switch.

1 . A dimmer circuit comprising:
 at least one switch configured to be placed between a power source and a load; and   an isolated DC voltage source that is distinct from the power source and that is selectively coupled to the at least one switch for controlling the switch to provide power from the source directly to the load.   
   
   
       2 . The dimmer circuit as set forth in  claim 1 , wherein the at least one switch comprises two MOSFETs and the isolated DC voltage source is selectively coupled with the gate and the source of the MOSFETs. 
   
   
       3 . The dimmer circuit as set forth in  claim 1 , comprising
 a second switch between the isolated DC voltage source and the at least one switch, the second switch having a first operative state in which the isolated DC voltage source is coupled to the at least one switch and a second operative state where the isolated DC voltage source is disconnected from the at least one switch.   
   
   
       4 . The dimmer circuit as set forth in  claim 3 , wherein the second switch comprises an opto-coupler. 
   
   
       5 . The dimmer circuit as set forth in  claim 3 , comprising
 a controller that provides a timing control signal that controls the operative state of the second switch for selectively coupling the isolated DC voltage source to the at least one switch.   
   
   
       6 . The dimmer circuit as set forth in  claim 5 , wherein the timing control signal comprises a pulse width modulation signal configured to achieve a desired amount of power delivery through the at least one switch to the load. 
   
   
       7 . The dimmer circuit as set forth in  claim 1 , comprising at least one voltage controlling component between the isolated DC voltage source and the at least one switch for limiting a voltage applied to the at least one switch. 
   
   
       8 . The dimmer circuit as set forth in  claim 7 , wherein the at least one voltage controlling component comprises a zener diode. 
   
   
       9 . The dimmer circuit as set forth in  claim 7 , wherein the at least one voltage controlling component comprises a first resistor that is operative to control a turn on time of the at least one switch and a second resistor that is operative to control a turn off time of the at least one switch. 
   
   
       10 . A method of controlling a dimmer circuit comprising:
 selectively coupling an isolated DC voltage source to at least one switch through which power is provided from a power source directly to a load, wherein the power source is distinct from the DC voltage source.   
   
   
       11 . The method of  claim 10 , comprising
 selectively controlling a second switch between the isolated DC voltage source and the at least one switch such that the second switch controls when the isolated DC voltage source is coupled to the at least one switch.   
   
   
       12 . The method of  claim 10 , comprising
 limiting the voltage provided by the isolated DC voltage source to the at least one switch to keep the provided voltage at or below a selected value.   
   
   
       13 . The method of  claim 10 , wherein the at least one switch comprises two MOSFETs. 
   
   
       14 . The method of  claim 13 , comprising using the two MOSFETs for reverse phase control. 
   
   
       15 . A dimmer circuit comprising:
 at least one switch configured to selectively allow power from a power source to be provided to a load; and   an isolated voltage source that is distinct from the power source, and that is channeled to the at least one switch for controlling the switch to provide power from the power source directly to the load.   
   
   
       16 . The dimmer circuit of  claim 15 , comprising:
 an opto-coupler that selectively couples the isolated voltage source to the at least one switch.   
   
   
       17 . The dimmer circuit as set forth in  claim 16 , wherein the at least one switch comprises two MOSFETs and the isolated voltage source is selectively coupled with the gate and the source of the MOSFETs.