Controlled Power Dissipation in a Switch Path in a Lighting System

Abstract

A lighting system includes one or more methods and systems to control dissipation of excess power in the lighting system when the power into a switching power converter from a leading edge, phase-cut dimmer is greater than the power out of the switching power converter. In at least one embodiment, the lighting system includes a controller that controls dissipation of excess energy in the lighting system to prevent a premature disconnection of the phase-cut dimmer. In at least one embodiment, the controller actively controls power dissipation by generating one or more signals to actively and selectively control power dissipation in the lighting system. By actively and selectively controlling power dissipation in the lighting system, the controller intentionally dissipates power when the power into the lighting system should be greater than the power out to a lamp of the lighting system. In at least one embodiment, the controller creates one or more intermixed and/or interspersed power dissipation phases with one or more switching power converter charging and/or flyback phases.

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         16 . An apparatus comprising:
 a controller configured to control a boost switch in a switching power converter of a phase cut compatible, dimmable lighting system, wherein the controller is configured to control the boost switch in an efficient mode and a power dissipation mode, wherein in the efficient mode, the controller is configured to operate the boost switch to minimize power dissipation in the boost switch and in the power dissipation mode the controller is configured to operate the boost switch to increase dissipation of energy in the boost switch relative to any power dissipation in the boost switch during operation in the efficient mode.   
     
     
         17 . The apparatus of  claim 16  wherein the controller is configured to generate a control signal to control conductivity of the boost switch and in the efficient mode, the controller is further configured to generate the control signal using two states in the efficient mode and is further configured to generate the control signal using at least three states in the power dissipation mode. 
     
     
         18 . The apparatus of  claim 16  wherein in the efficient mode the controller is configured to generate a control signal to cause a charging current to flow through the boost switch during a charging phase of the switching power converter and cut-off current through the boost switch during a flyback phase during the efficient mode and is further configured to limit current through the boost switch to an intermediate value between the charging current and zero during the power dissipation mode. 
     
     
         19 . The apparatus of  claim 16  wherein in the power dissipation mode the controller is configured to control dissipation of excess energy by at least the boost switch during a controlled power dissipation phase, and the controlled power dissipation phase occurs after a charging phase begins and before an end of a subsequent flyback phase of the switching power converter. 
     
     
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         35 . A method comprising:
 controlling a boost switch in a switching power converter of a phase cut compatible, dimmable lighting system in an efficient mode and in a power dissipation mode, wherein controlling the boost switch in the efficient mode comprises:
 operating the boost switch to minimize power dissipation in the boost switch; and 
 wherein controlling the boost switch in the power dissipation mode comprises:
 operating the boost switch to increase dissipation of energy in the boost switch relative to any power dissipation in the boost switch during operation in the efficient mode. 
 
   
     
     
         36 . The method of  claim 35  further comprising:
 generating a control signal to control conductivity of the boost switch and in the efficient mode, the controller is further configured to generate the control signal using two states in the efficient mode; and 
 generating the control signal using at least three states in the power dissipation mode. 
 
     
     
         37 . The method of  claim 35  wherein in the efficient mode the method further comprises:
 generating a control signal to cause a charging current to flow through the boost switch during a charging phase of the switching power converter and cut-off current through the boost switch during a flyback phase during the efficient mode; and 
 limiting current through the boost switch to an intermediate value between the charging current and zero during the power dissipation mode. 
 
     
     
         38 . The method of  claim 35  wherein in the power dissipation mode the method further comprises:
 controlling dissipation of excess energy by at least the boost switch during a controlled power dissipation phase, and the controlled power dissipation phase occurs after a charging phase begins and before an end of a subsequent flyback phase of the switching power converter. 
 
     
     
         39 . The apparatus of  claim 16  wherein the controller is further configured to control a current source to sink a constant current through the boost switch when controlling the boost switch in the power dissipation mode. 
     
     
         40 . The apparatus of  claim 16  wherein the controller is further configured to operate the boost switch in an approximately constant current mode when controlling the boost switch in the power dissipation mode. 
     
     
         41 . The apparatus of  claim 16  wherein the controller is further configured to control a duration of controlling the boost switch in the power dissipation mode to control an amount of energy dissipated through the boost switch. 
     
     
         42 . The apparatus of  claim 16  wherein the controller is configured to operate the boost switch in the power dissipation mode using intermixed phases to spread the dissipation of power over multiple charging phases. 
     
     
         43 . The apparatus of  claim 42  wherein the multiple charging phases occur during a single time frame, wherein the time frame occurs between when a first charging phase of the switching power converter following an immediately preceding flyback phase of the switching power converter begins and a flyback phase of the switching power converter immediately preceding a next charging phase ends. 
     
     
         44 . The apparatus of  claim 42  wherein the multiple controlled power dissipation phases occur during consecutive time frames, wherein each time frame occurs between when a first charging phase of the switching power converter following an immediately preceding flyback phase of the switching power converter begins and a flyback phase of the switching power converter immediately preceding a next charging phase ends. 
     
     
         45 . The apparatus of  claim 42  wherein the multiple controlled power dissipation phases are interspersed among non-consecutive time frames, wherein each time frame occurs between when a first charging phase of the switching power converter following an immediately preceding flyback phase of the switching power converter begins and a flyback phase of the switching power converter immediately preceding a next charging phase ends. 
     
     
         46 . The method of  claim 35  the method further comprises:
 controlling a current source coupled to the boost switch to control current through the boost switch when controlling the boost switch in the power dissipation mode. 
 
     
     
         47 . The method of  claim 35  the method further comprising:
 operating the boost switch in an approximately constant current mode when controlling the boost switch in the power dissipation mode. 
 
     
     
         48 . The method of  claim 35  the method further comprising:
 controlling a duration of controlling the boost switch in the power dissipation mode to control an amount of energy dissipated through the boost switch. 
 
     
     
         49 . The method of  claim 35  the method further comprising:
 controlling a boost switch in a switching power converter to dissipate excess energy through the boost switch using intermixed phases to spread the dissipation of excess energy over multiple charging phases. 
 
     
     
         50 . The method of  claim 49  wherein the multiple controlled power dissipation phases occur during a single time frame, wherein the time frame occurs between when a first charging phase of the switching power converter following an immediately preceding flyback phase of the switching power converter begins and a flyback phase of the switching power converter immediately preceding a next charging phase ends. 
     
     
         51 . The method of  claim 49  wherein the multiple controlled power dissipation phases occur during consecutive time frames, wherein each time frame occurs between when a first charging phase of the switching power converter following an immediately preceding flyback phase of the switching power converter begins and a flyback phase of the switching power converter immediately preceding a next charging phase ends. 
     
     
         52 . The method of  claim 49  wherein the multiple controlled power dissipation phases are interspersed among non-consecutive time frames, wherein each time frame occurs between when a first charging phase of the switching power converter following an immediately preceding flyback phase of the switching power converter begins and a flyback phase of the switching power converter immediately preceding a next charging phase ends. 
     
     
         53 . An apparatus comprising:
 means for controlling a boost switch in a switching power converter of a phase cut compatible, dimmable lighting system in an efficient mode and in a power dissipation mode, wherein the means for controlling the boost switch comprises:
 means for operating the boost switch to minimize power dissipation in the boost switch in the efficient mode; and 
 means for operating the boost switch in the power dissipation mode to increase dissipation of energy in the boost switch relative to any power dissipation in the boost switch during operation in the efficient mode.