WO2014035630A1 - Power conversion with controlled capacitance charging including attach state control - Google Patents
Power conversion with controlled capacitance charging including attach state control Download PDFInfo
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- WO2014035630A1 WO2014035630A1 PCT/US2013/054177 US2013054177W WO2014035630A1 WO 2014035630 A1 WO2014035630 A1 WO 2014035630A1 US 2013054177 W US2013054177 W US 2013054177W WO 2014035630 A1 WO2014035630 A1 WO 2014035630A1
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
- H05B45/37—Converter circuits
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
- H05B45/37—Converter circuits
- H05B45/3725—Switched mode power supply [SMPS]
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
- H05B45/37—Converter circuits
- H05B45/3725—Switched mode power supply [SMPS]
- H05B45/385—Switched mode power supply [SMPS] using flyback topology
Definitions
- the present invention relates in general to the field of electronics, and more specifically to power conversion with controlled capacitance charging that includes a dimmer attach state control.
- Many electronic systems utilize switching power converters to convert power from one source into power useable by a load. Additionally, many electronic systems also utilize dimmers that cause a controller of the switching power converter to modify output power delivered to the load depending on a dimming level. For example, in a lighting system, dimmers provide an input signal to a lighting system, and the load includes one or more light sources such as one or more light emitting diodes (LEDs) or one or more fluorescent light sources. The dimming level from the dimmer causes the lighting system to adjust power delivered to a lamp, and, thus, depending on the dimming level, increase or decrease the brightness of the lamp. Many different types of dimmers exist.
- Triac alternating current
- AC alternating current
- Modemating the phase angle of the supply voltage is also commonly referred to as “chopping” or “phase cutting” the supply voltage.
- Phase cutting the supply voltage causes the voltage supplied to a lighting system to rapidly turn “ON” and “OFF” thereby controlling the average power delivered to the lighting system.
- Figure 1 depicts a lighting system 100 that includes a phase cut dimmer 102.
- the phase-cut dimmer 102 can be any type of dimmer, such as a leading edge, trailing edge, or center-cut dimmer.
- a triac -based leading edge dimmer is described in the Background section of U.S. Patent Application No. 12/858, 164, entitled Dimmer Output Emulation, filed on August 17, 2010, and inventor John L. Melanson.
- the lighting system 100 receives an AC supply voltage VSUPPLY from voltage supply 104.
- the supply voltage VSUPPLY is, for example, a nominally 60 Hz/ 120 V line voltage in the United States of America or a nominally 50 Hz/230 V line voltage in Europe.
- the phase-cut dimmer 102 phase cuts the input voltage VIN to generate the phase-cut input voltage VOJN, and a full-bridge diode rectifier 106 rectifies the phase-cut input voltage V ⁇ DJN to generate the phase-cut, rectified, line input voltage Vo DIM-
- the lighting system 100 also includes a controller 1 12 that generates a control signal CSo to control the voltage Vo DIM into an output voltage VLED by a switching power converter 108.
- the switching power converter 108 can be any type of switching power converter. Many types of switching power converters exist. In general, switching power converters include a capacitor 1 14 or multiple additional capacitors (not shown) at the input of the switching power converter, a capacitor 1 16 within the switching power converter, and/or a capacitor 1 18 at the output of the switching power converter.
- a first stage of a two stage switching power converter is typically a boost switching power converter but can also be a buck or transformer coupled stage.
- the second stage is, for example, a flyback, buck, or other topology, such as a resonant topology.
- Two stage switching power converters generally include a high frequency, electromagnetic interference capacitor at an input of the switching power converter and a link capacitor after the first stage. The capacitors store energy to smooth out the transfer of power to the load 1 10, and the amount of smoothing generally depends upon the capacitor size and switching power converter topology.
- Two stage switching power converters are flexible but generally include more components than single stage switching power converters. Thus, two stage switching power converters are generally more expensive. [006]
- a single stage switching power converter converts power directly from the phase- cut, rectified voltage Vo DIM into a direct current (DC) voltage for the LED(s) 1 10.
- Single stage switching power converters are, for example, flyback, buck, or boost-buck type switching power converters.
- the single stage switching power converters generally include one large, energy storage capacitor at location 1 18, and the size of the capacitor generally increases as efficiency of the LED(s) 110 increases due to the dynamic impedance of a high efficiency LED(s) 110.
- Peak-rectified type switching power converters include a large capacitor at the input of the switching power converter that stores energy for each cycle of the rectified voltage Vo DIM- Peak rectified switching power converters are generally relatively inexpensive.
- the power factor of a peak-rectified switching power converter is generally worse than other single stage and two stage switching power converters, and ripple stress on the energy storage capacitor tends to be relatively high. Additionally, compatibility between the switching power converter 108 and/or efficiency is also compromised when using conventional peak-rectified switching power converters.
- a method in one embodiment, includes actively controlling a rate of charging of a capacitor circuit in a switching power converter to a first voltage level across the capacitor circuit. The method also includes allowing the capacitor to discharge to obtain a second voltage level across the capacitor circuit, wherein the second voltage level is sufficient to draw a current through a phase-cut dimmer to prevent the dimmer from prematurely resetting, and the first voltage is sufficient to allow the capacitor to discharge to the second voltage level during each cycle of the line voltage.
- an apparatus in another embodiment, includes a controller, and the controller is configured to actively control a rate of charging of a capacitor circuit in a switching power converter to a first voltage level across the capacitor circuit.
- the controller is also configured to allow the capacitor to discharge to obtain a second voltage level across the capacitor circuit, wherein the second voltage level is sufficient to draw a current through a phase-cut dimmer to prevent the dimmer from prematurely resetting, and the first voltage is sufficient to allow the capacitor to discharge to the second voltage level during each cycle of the line voltage.
- an apparatus includes a switching power converter having a switch and conductivity of the switch controls power conversion by the switching power converter.
- the apparatus also includes a load coupled to the switching power converter, a capacitor circuit coupled to the switching power converter, and a controller, coupled to the switch of the switching power converter and to the capacitor circuit.
- the controller is configured to actively control a rate of charging of a capacitor circuit in a switching power converter to a first voltage level across the capacitor circuit.
- the controller is also configured to allow the capacitor to discharge to obtain a second voltage level across the capacitor circuit, wherein the second voltage level is sufficient to draw a current through a phase-cut dimmer to prevent the dimmer from prematurely resetting, and the first voltage is sufficient to allow the capacitor to discharge to the second voltage level during each cycle of the line voltage.
- Figure 1 (labeled prior art) depicts a lighting system having a single or multi-stage switching power converter.
- Figure 2 depicts an electronic system that includes a controller that actively controls charging and discharging of an energy storage capacitor circuit.
- Figure 3 depicts an electronic system that represents one embodiment of the electronic system of Figure 2.
- Figure 4 depicts exemplary waveforms associated with the electronic system of Figure 2.
- Figure 5 depicts an exemplary capacitor circuit.
- a system and method include an electronic system having a controller that actively controls a rate of charging and discharging of an energy storage capacitor to maintain compatibility with a dimmer and, in at least one embodiment, provides a better power factor than a conventional peak-rectified type switching power converter.
- the controller actively controls charging of a capacitor circuit in a switching power converter to a first voltage level across the capacitor circuit.
- the switching power converter is a modified peak-rectified design with the first voltage level across the capacitor circuit having a value that is less than a peak value of an input line voltage supplied to the switching power converter.
- the controller further allows the capacitor to discharge to obtain a second voltage level across the capacitor circuit.
- the second voltage level is sufficient to draw a current at the firing transition of a leading-edge dimmer. In at least one embodiment, this current is sufficient to prevent a triac of the dimmer from prematurely resetting.
- the first voltage is sufficient to allow the capacitor to discharge to the second voltage level during each cycle of the line voltage.
- FIG. 2 depicts an electronic system 200 that includes a controller 202 that actively controls charging and discharging of an energy storage capacitor circuit 204.
- the particular configuration of the energy storage capacitor circuit 204 is a matter of design choice.
- the energy storage capacitor circuit 204 includes at least one capacitor that is connected to the switch 206 and, in at least one embodiment, includes one or more additional capacitors that connected either to the switch 206 or to the reference voltage VREF via conductive path 208.
- Controller 202 generates the switch control signal CSi to control conductivity of the switch 206.
- the switch 206 can be any type of switch and is, for example, a field effect transistor (FET) or a bipolar junction transistor (BJT).
- FET field effect transistor
- BJT bipolar junction transistor
- the switch 206 and resistor 218 together control the charging of the capacitor circuit 204.
- the particular circuit and device implementation of the switch 206, resistor 218, and capacitor circuit 204 is a matter of design choice.
- the switch 206 as controlled by controller 202, resistor 218, and capacitor circuit 204 combine to allow a controlled charging current on the leading edge of the voltage Vo DIM and allow for the subsequent disconnect of the capacitor circuit 204 at a later time to provide energy to the switching power converter 210.
- phase-cut dimmer 102 includes a triac 212 and the phase-cut dimmer 102 initially turns ON, i.e. conducts, during a cycle of the supply voltage VIN
- an inductor and capacitor in the triac -based dimmer together form a resonant circuit 214 as, for example, explained in more detail in U.S. Patent Application No. 13/217, 174, entitled “Multi- Mode Dimmer Interfacing Including Attach State Control", filed August 24, 2011 , and inventors Eric J. King and John L. Melanson, which is incorporated by reference.
- the resonant circuit 214 can cause abrupt voltage and current changes at the input to the switching power converter 210 when the triac 212 initially conducts.
- a current i DIM through the triac 212 will decrease below a "hold current” value.
- the "hold current” value is a threshold value associated with the triac 212. If the current IDIM, which flows through the triac, decreases below the hold current value, the triac 212 will prematurely reset, i.e. become non-conductive, during a cycle of the supply voltage VIN.
- the triac 212 prematurely resets, the input voltage Vo IN to the power converter system 216 is disrupted, which can cause errors and disruptions to output power provided by the switching power converter 210.
- An exemplary error in the output power occurs when the output power does not accurately correlate with a dimming level of the phase-cut dimmer 102.
- the controller 202 actively controls a decreasing transition of the current ⁇ R , which controls the dimmer current I D IM, to prevent the triac 212 from prematurely resetting.
- the process of actively controlling the decreasing transition of the current ⁇ R to prevent the triac 212 from prematurely resetting is referred to herein as "attaching the dimmer”.
- the controller 202 actively controls the decreasing transition of the current IDIM by actively controlling charging of the capacitor circuit 204 so that the voltage Vc across the capacitor circuit 204 reaches a predetermined, first voltage value Vc j value, as for example shown and subsequently discussed in more detail with reference to Figures 3 and 4.
- the controller 202 in addition to actively controlling charging the capacitor circuit 204 to the first voltage level Vc j at a rate sufficient to attach the dimmer 102, the controller 202 also actively determines the value of the first voltage level Vc j .
- the controller 202 determines the value of the first voltage level Vc j so that the capacitor circuit 204 provides sufficient energy to the switching power converter 210 during a portion of the cycle of the rectified, line input voltage Vo DIM and so that the voltage Vc across the capacitor circuit 204 decays to a specific second voltage level Vc 2 (as for example subsequently explained in more detail with reference to Figures 3 and 4).
- the second voltage level Vc 2 allows the controller 202 to repeat attaching the dimmer to the power converter 216 and supplying sufficient energy to the switching power converter 210.
- the controller 202 attaches the phase- cut dimmer 102, provides energy to the switching power converter 210 during a portion of a cycle of the input voltage Vo DIM, and establishes a second voltage level Vc_ 2 that allows the controller 202 to repeat attaching the dimmer and supplying sufficient energy to the switching power converter 210.
- the controller 202 actively controls charging of the capacitor circuit 204 by generating the switch control signal CSi to turn the switch 206 ON, i.e. conduct, when the controller 202 detects a leading edge of the voltage Vo DIM-
- the switch 206 is ON, current ic flows through the switch 206 and resistor 218 and charges capacitor circuit 204.
- the resistance of resistor 218 and the capacitance of capacitor circuit 204 provide a time constant that together with the conductivity of switch 206 controls a rate of charging and, thus, current ⁇ R draw to charge the capacitor circuit 204.
- the controller 202 keeps switch 206 ON until the capacitor circuit voltage Vc reaches the first voltage value Vc i and then turns the switch 206 OFF.
- the diode 220 allows the energy in the capacitor circuit 204 to be used during the periods of low input voltage levels of the voltage Vo DIM, which partially discharges the capacitor circuit 204 to provide energy to the load 222.
- the capacitor circuit 204 provides energy via current ic E to the switching power converter 210 until the next leading edge of the Vo DIM occurs.
- the switching power converter 210 provides power to the load 222 via an output voltage VOUT and an output current ⁇ 0 ⁇
- the switching power converter 210 can be any type of switching power converter such as a flyback, buck, boost-buck, boost, or Cuk type switching power converter.
- the load 222 can be any type of load, such as one or more LEDs.
- the controller selection of the first voltage level Vc j and the second voltage level Vc 2 are made to optimize power factor or efficiency of the electronic system 200.
- the particular values of the first voltage level Vc_i and the second voltage level Vc_ 2 when no leading edge of the voltage Vo DIM is sensed are matters of design choice and, in at least one embodiment, depend on, for example, the output voltage VOUT for the load 222, the power requirements of the load 222.
- Particular values of the first voltage level Vc_i and the second voltage level Vc 2 to optimize power factor or efficiency of the electronic system 200 can be determined empirically.
- FIG. 3 depicts an electronic system 300, which represents one embodiment of the electronic system 200.
- Figure 4 depicts exemplary waveforms associated with the electronic system 300.
- the voltage Vo DIM is at a zero crossing, and, in at least one embodiment, the controller 302 draws a glue current IQLUE via path 304 to allow the triac 212 to fire, i.e. conduct, at the appropriate time indicated by an internal timing mechanism of the phase-cut dimmer 102.
- U.S. Patent Application No. 12/858, 164 entitled “Dimmer Output Emulation", filed August 17, 2010, and inventor John L. Melanson and U.S. Patent Application No.
- Capacitor 306 represents one embodiment of the capacitor circuit 204. The value of capacitor 306 is typically 0.5-20 uF, depending on the output voltage VOUT for the load 222, power, ripple requirements, and design choice. With the switch 206 conducting, at time ti the voltage Vc across the capacitor 306 rises from the second voltage level Vc 2 to the first voltage level Vc j .
- the current ic flowing through switch 206 and causing the capacitor 306 to charge to the first voltage level Vc 1 is sufficient to attach the dimmer.
- the voltage Vc across the capacitor 306 reaches the first voltage level Vc j , and the controller 302 generates the control signal CSi to turn the switch 206 OFF.
- the voltage Vc rises to the first voltage level Vc j during the initial portion of the voltage Vo DIM after the leading edge 402 occurs.
- the rate of the rise of the voltage Vc is actively controlled by the controller 202 using the switch 206 and the resistor 218, and the voltage Vc rises to a first voltage level Vc j, which, in at least one embodiment, is less than the peak value Vo DIM PEAK of the line input voltage Vo DIM-
- the voltage Vc across the capacitor 306 remains at the first voltage level Vc ⁇ until, at time t 4 , the line input voltage Vo DIM falls below the first voltage level Vc j . At time t 5 , the next leading edge 406 of the voltage Vo DIM occurs. Between times t 4 and t 5 , which is in the trough of the line input voltage Vo DIM, the voltage Vc is higher than the line input voltage Vo DIM, and the capacitor 306 provides energy via the current i c E to the flyback-type, switching power converter 308. As the capacitor 306 provides energy to the switching power converter 308, the voltage across the capacitor 306 decreases, and at time t 2 reaches the second voltage level Vc 2.
- Equation 1 represents the amount of energy E c TRANFERRED transferred from the capacitor 306 to the switching power converter 308 during the period T
- Vc j is the first level voltage value across the capacitor 306
- Vc 2 is the second level voltage value across the capacitor 306.
- the particular value of the voltage Vc 2 correlates with the phase angle of the line input voltage Vo DIM and can be empirically determined for each phase angle for a particular load, such as the LED(s) 310.
- Equation 2 represents the amount energy E S pc to be provided to the switching power converter 308 for a given phase angle of the line input voltage Vo DIM:
- Ti is the period of time between times t 4 and is, which represents the amount of time that the capacitor 306 is providing energy to the switching power converter 308.
- the controller 302 determines the value of Ti by determining the time between when the controller 302 causes the switch 206 to stop conducting and when the controller 302 detects the next leading edge of the voltage Vo DIM.
- P is the amount of power provided to the switching power converter 308 for conversion and provision to the LED(s) 310.
- the value of the amount of power P is predetermined for each phase angle since the amount of power to be provided to the LED(s) 310 directly correlates to the phase angle of the voltage Vo DIM and the corresponding power utilization by the LED(s) 310.
- U.S. Patent No. 7,852,017 entitled “Ballast for Light Emitting Diode Light Sources", filed March 12, 2008, assignee Cirrus Logic, Inc., which is herein incorporated by reference, describes exemplary systems and methods for detecting voltage phase angles.
- the controller 302 determines the values of the first level voltage Vc_i and the time Ti so that Equation 1 equals Equation 2 for the known values of the capacitance C of the capacitor 306, the second level voltage value Vc_ 2 , and the amount of power P provided to the switching power converter 308. In at least one embodiment, the controller 302 iterates over consecutive cycles of the voltage Vo DIM to obtain the values of the first level voltage Vc_i and the time Ti so that Equation 1 equals Equation 2. In at least one embodiment, the values of the variables in Equation 1 and Equation 2 are initialized using empirically obtained data, and controller 302 iterates the values if during operation of the electronic system 300, Equation 1 does not equal Equation 2 using the initialized values.
- this iterative process maximizes efficiency of the electronic system 200 and compatibility between the power converter 216 and the phase-cut dimmer 102.
- the controller 302 utilizes the flyback-type switching power converter 308 to convert the voltage Vo DIM into an LED drive current ILED and load voltage VLED on the side of the secondary-winding 314 of the transformer 316.
- the controller 302 provides source control to the source of the FET 312 to control the flyback-type, switching power converter 308 and, thus, control the current i c _E, the LED drive current I L ED, and the load voltage VLED-
- the values of the current i c _E, the LED drive current I L ED, and the load voltage VLED correlate with the phase angle of the voltage Vo DIM-
- the brightness of the LED(s) 310 directly correlates with the value of the LED drive current I L ED.
- the brightness of the LED(s) 310 directly conforms to the phase angle of the voltage Vo DIM-
- the controller 302 controls the conductivity of the FET 312 to control the current ic E to meet the power demands of LED(s) 310.
- the FET 312 is biased with a fixed gate voltage VG and conducts (i.e. ON) when the source voltage VSOURCE is less than the gate voltage VG minus a threshold voltage of the FET 606 and is nonconductive (i.e. OFF) when the source voltage VSOURCE is greater than the gate voltage VG minus the inherent threshold voltage of the FET 3 12.
- the current ic _E ramps up through the primary winding 320 of transformer 3 16.
- transformer 3 16 and the diode 322 prevent flow of the LED current ILED from the secondary-winding 3 14 when FET 3 12 conducts and the current ic E is flowing into the primary winding 320.
- the controller 302 turns the FET 3 12 OFF, the current ic E falls to 0, and the voltage across the primary winding 320 reverses for a period of time, referred to as the "flyback time".
- the flyback time the secondary current is quickly rises and charges capacitor 324.
- Capacitor 324 provides an output voltage VLED and current I L ED to the LED(s) 3 10.
- a diode and resistor-capacitor filter circuit 326 provides a path for voltage perturbations.
- controller 302 is hereby incorporated by reference and describe exemplary systems and methods for controlling the source of a FET.
- controller 302 can be (i) implemented as an integrated circuit including, for example, a processor to execute software or firmware instructions stored in a memory, (ii) implemented using discrete components, or (iii) implemented using any combination of the foregoing.
- all of the components in electronic system 300, except the voltage supply 104 and the phase-cut dimmer 102 are included in a lamp.
- FIG. 5 depicts a capacitor circuit 500, which represents another embodiment of the capacitor circuit 204.
- nodes A and B correspond with the nodes A and B of Figure 2.
- the capacitor circuit 500 includes capacitor 502 that charges when the switch 206 is ON. When switch 206 is OFF, the capacitors 502 and 504 discharge through diodes 506, 508, and 510.
- the values of capacitors 502 and 504 are typically .5-20 uF, depending on the output voltage VOUT for the load 222, power utilized by the load 222, ripple requirements, and design choice.
- an electronic system includes a controller that actively controls a rate of charging and discharging of an energy storage capacitor to maintain compatibility with a dimmer.
- the controller actively controls charging of a capacitor circuit in a switching power converter to a first voltage level across the capacitor circuit.
- the controller further allows the capacitor to discharge to obtain a second voltage level across the capacitor circuit.
- the second voltage level is sufficient to provide a decreasing transition of a current through a triac -based dimmer to prevent a triac of the dimmer from prematurely resetting.
- the first voltage is sufficient to allow the capacitor to discharge to the second voltage level during each cycle of the line voltage.
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Abstract
An electronic system includes a controller that actively controls a rate of charging and discharging of an energy storage capacitor to maintain compatibility with a dimmer. The controller actively controls charging of a capacitor circuit in a switching power converter to a first voltage level across the capacitor circuit. The controller further allows the capacitor to discharge to obtain a second voltage level across the capacitor circuit. The second voltage level is sufficient to draw a current through a phase-cut dimmer to prevent the dimmer from prematurely resetting. The first voltage is sufficient to allow the capacitor to discharge to the second voltage level during each cycle of the line voltage.
Description
POWER CONVERSION WITH CONTROLLED CAPACITANCE CHARGING INCLUDING ATTACH STATE CONTROL
John L. Melanson
Eric J. King
CROSS-REFERENCE TO RELATED APPLICATION
[001] This application claims the benefit under 35 U.S.C. § 1 19(e) and 37 C.F.R. § 1.78 of U.S. Provisional Application No. 61/693,351, filed August 27, 2012, and entitled "Single Stage and Stage and a Half LED Lamp Controller", which is incorporated by reference in its entirety. This application also claims the benefit under 35 U.S.C. § 120 and 37 C.F.R. § 1.78 of U.S. Patent Application No. 13/836,423, filed March 15, 2013, which is incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
Field of the Invention
[002] The present invention relates in general to the field of electronics, and more specifically to power conversion with controlled capacitance charging that includes a dimmer attach state control.
DESCRIPTION OF THE RELATED ART
[003] Many electronic systems utilize switching power converters to convert power from one source into power useable by a load. Additionally, many electronic systems also utilize dimmers that cause a controller of the switching power converter to modify output power delivered to the load depending on a dimming level. For example, in a lighting system, dimmers provide an input signal to a lighting system, and the load includes one or more light sources such as one or more light emitting diodes (LEDs) or one or more fluorescent light sources. The dimming level from the dimmer causes the lighting system to adjust power delivered to a lamp, and, thus, depending on the dimming level, increase or decrease the brightness of the lamp. Many different types of dimmers exist. Many common analog based dimmers utilize a triode for alternating current ("triac") device to modulate a phase angle of each cycle of an alternating current ("AC") supply voltage. "Modulating the phase angle" of
the supply voltage is also commonly referred to as "chopping" or "phase cutting" the supply voltage. Phase cutting the supply voltage causes the voltage supplied to a lighting system to rapidly turn "ON" and "OFF" thereby controlling the average power delivered to the lighting system.
[004] Figure 1 depicts a lighting system 100 that includes a phase cut dimmer 102. The phase-cut dimmer 102 can be any type of dimmer, such as a leading edge, trailing edge, or center-cut dimmer. A triac -based leading edge dimmer is described in the Background section of U.S. Patent Application No. 12/858, 164, entitled Dimmer Output Emulation, filed on August 17, 2010, and inventor John L. Melanson. The lighting system 100 receives an AC supply voltage VSUPPLY from voltage supply 104. The supply voltage VSUPPLY, indicated by voltage waveform 202, is, for example, a nominally 60 Hz/ 120 V line voltage in the United States of America or a nominally 50 Hz/230 V line voltage in Europe. The phase-cut dimmer 102 phase cuts the input voltage VIN to generate the phase-cut input voltage VOJN, and a full-bridge diode rectifier 106 rectifies the phase-cut input voltage V<DJN to generate the phase-cut, rectified, line input voltage Vo DIM-
[005] The lighting system 100 also includes a controller 1 12 that generates a control signal CSo to control the voltage Vo DIM into an output voltage VLED by a switching power converter 108. The switching power converter 108 can be any type of switching power converter. Many types of switching power converters exist. In general, switching power converters include a capacitor 1 14 or multiple additional capacitors (not shown) at the input of the switching power converter, a capacitor 1 16 within the switching power converter, and/or a capacitor 1 18 at the output of the switching power converter. For example, a first stage of a two stage switching power converter is typically a boost switching power converter but can also be a buck or transformer coupled stage. The second stage is, for example, a flyback, buck, or other topology, such as a resonant topology. Two stage switching power converters generally include a high frequency, electromagnetic interference capacitor at an input of the switching power converter and a link capacitor after the first stage. The capacitors store energy to smooth out the transfer of power to the load 1 10, and the amount of smoothing generally depends upon the capacitor size and switching power converter topology. Two stage switching power converters are flexible but generally include more components than single stage switching power converters. Thus, two stage switching power converters are generally more expensive.
[006] A single stage switching power converter converts power directly from the phase- cut, rectified voltage Vo DIM into a direct current (DC) voltage for the LED(s) 1 10. Single stage switching power converters are, for example, flyback, buck, or boost-buck type switching power converters. The single stage switching power converters generally include one large, energy storage capacitor at location 1 18, and the size of the capacitor generally increases as efficiency of the LED(s) 110 increases due to the dynamic impedance of a high efficiency LED(s) 110. Peak-rectified type switching power converters include a large capacitor at the input of the switching power converter that stores energy for each cycle of the rectified voltage Vo DIM- Peak rectified switching power converters are generally relatively inexpensive. However, the power factor of a peak-rectified switching power converter is generally worse than other single stage and two stage switching power converters, and ripple stress on the energy storage capacitor tends to be relatively high. Additionally, compatibility between the switching power converter 108 and/or efficiency is also compromised when using conventional peak-rectified switching power converters.
SUMMARY OF THE INVENTION
[007] In one embodiment of the present invention, a method includes actively controlling a rate of charging of a capacitor circuit in a switching power converter to a first voltage level across the capacitor circuit. The method also includes allowing the capacitor to discharge to obtain a second voltage level across the capacitor circuit, wherein the second voltage level is sufficient to draw a current through a phase-cut dimmer to prevent the dimmer from prematurely resetting, and the first voltage is sufficient to allow the capacitor to discharge to the second voltage level during each cycle of the line voltage.
[008] In another embodiment of the present invention, an apparatus includes a controller, and the controller is configured to actively control a rate of charging of a capacitor circuit in a switching power converter to a first voltage level across the capacitor circuit. The controller is also configured to allow the capacitor to discharge to obtain a second voltage level across the capacitor circuit, wherein the second voltage level is sufficient to draw a current through a phase-cut dimmer to prevent the dimmer from prematurely resetting, and the first voltage is sufficient to allow the capacitor to discharge to the second voltage level during each cycle of the line voltage.
[009] In a further embodiment of the present invention, an apparatus includes a switching power converter having a switch and conductivity of the switch controls power conversion by the switching power converter. The apparatus also includes a load coupled to the switching power converter, a capacitor circuit coupled to the switching power converter, and a controller, coupled to the switch of the switching power converter and to the capacitor circuit. The controller is configured to actively control a rate of charging of a capacitor circuit in a switching power converter to a first voltage level across the capacitor circuit. The controller is also configured to allow the capacitor to discharge to obtain a second voltage level across the capacitor circuit, wherein the second voltage level is sufficient to draw a current through a phase-cut dimmer to prevent the dimmer from prematurely resetting, and the first voltage is sufficient to allow the capacitor to discharge to the second voltage level during each cycle of the line voltage.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The present invention may be better understood, and its numerous objects, features and advantages made apparent to those skilled in the art by referencing the accompanying drawings. The use of the same reference number throughout the several figures designates a like or similar element.
[0011] Figure 1 (labeled prior art) depicts a lighting system having a single or multi-stage switching power converter.
[0012] Figure 2 depicts an electronic system that includes a controller that actively controls charging and discharging of an energy storage capacitor circuit.
[0013] Figure 3 depicts an electronic system that represents one embodiment of the electronic system of Figure 2.
[0014] Figure 4 depicts exemplary waveforms associated with the electronic system of Figure 2.
[0015] Figure 5 depicts an exemplary capacitor circuit. DETAILED DESCRIPTION
[0016] In at least one embodiment, a system and method include an electronic system having a controller that actively controls a rate of charging and discharging of an energy storage capacitor to maintain compatibility with a dimmer and, in at least one embodiment,
provides a better power factor than a conventional peak-rectified type switching power converter. In at least one embodiment, the controller actively controls charging of a capacitor circuit in a switching power converter to a first voltage level across the capacitor circuit. In at least one embodiment, the switching power converter is a modified peak-rectified design with the first voltage level across the capacitor circuit having a value that is less than a peak value of an input line voltage supplied to the switching power converter. In at least one embodiment, the controller further allows the capacitor to discharge to obtain a second voltage level across the capacitor circuit. The second voltage level is sufficient to draw a current at the firing transition of a leading-edge dimmer. In at least one embodiment, this current is sufficient to prevent a triac of the dimmer from prematurely resetting. The first voltage is sufficient to allow the capacitor to discharge to the second voltage level during each cycle of the line voltage.
[0017] Figure 2 depicts an electronic system 200 that includes a controller 202 that actively controls charging and discharging of an energy storage capacitor circuit 204. The particular configuration of the energy storage capacitor circuit 204 is a matter of design choice. In at least one embodiment, the energy storage capacitor circuit 204 includes at least one capacitor that is connected to the switch 206 and, in at least one embodiment, includes one or more additional capacitors that connected either to the switch 206 or to the reference voltage VREF via conductive path 208. Controller 202 generates the switch control signal CSi to control conductivity of the switch 206. The switch 206 can be any type of switch and is, for example, a field effect transistor (FET) or a bipolar junction transistor (BJT). The switch 206 and resistor 218 together control the charging of the capacitor circuit 204. The particular circuit and device implementation of the switch 206, resistor 218, and capacitor circuit 204 is a matter of design choice. In at least one embodiment, the switch 206 as controlled by controller 202, resistor 218, and capacitor circuit 204 combine to allow a controlled charging current on the leading edge of the voltage Vo DIM and allow for the subsequent disconnect of the capacitor circuit 204 at a later time to provide energy to the switching power converter 210.
[0018] When the phase-cut dimmer 102 includes a triac 212 and the phase-cut dimmer 102 initially turns ON, i.e. conducts, during a cycle of the supply voltage VIN, an inductor and capacitor in the triac -based dimmer (not shown) together form a resonant circuit 214 as, for example, explained in more detail in U.S. Patent Application No. 13/217, 174, entitled "Multi-
Mode Dimmer Interfacing Including Attach State Control", filed August 24, 2011 , and inventors Eric J. King and John L. Melanson, which is incorporated by reference. The resonant circuit 214 can cause abrupt voltage and current changes at the input to the switching power converter 210 when the triac 212 initially conducts. In at least one embodiment, if an input impedance presented to the triac-based, phase-cut dimmer 104 by the power converter system 216 is sufficiently high to prevent adequate damping of the resonant circuit 214, a current iDIM through the triac 212 will decrease below a "hold current" value. The "hold current" value is a threshold value associated with the triac 212. If the current IDIM, which flows through the triac, decreases below the hold current value, the triac 212 will prematurely reset, i.e. become non-conductive, during a cycle of the supply voltage VIN. If the triac 212 prematurely resets, the input voltage Vo IN to the power converter system 216 is disrupted, which can cause errors and disruptions to output power provided by the switching power converter 210. An exemplary error in the output power occurs when the output power does not accurately correlate with a dimming level of the phase-cut dimmer 102.
[0019] In at least one embodiment, to prevent the phase-cut dimmer 102 from prematurely resetting, after sensing a leading edge of the input voltage Vo DIM, the controller 202 actively controls a decreasing transition of the current ίφ R, which controls the dimmer current IDIM, to prevent the triac 212 from prematurely resetting. The process of actively controlling the decreasing transition of the current ίφ R to prevent the triac 212 from prematurely resetting is referred to herein as "attaching the dimmer". In at least one embodiment, the controller 202 actively controls the decreasing transition of the current IDIM by actively controlling charging of the capacitor circuit 204 so that the voltage Vc across the capacitor circuit 204 reaches a predetermined, first voltage value Vc j value, as for example shown and subsequently discussed in more detail with reference to Figures 3 and 4.
[0020] However, in at least one embodiment, in addition to actively controlling charging the capacitor circuit 204 to the first voltage level Vc j at a rate sufficient to attach the dimmer 102, the controller 202 also actively determines the value of the first voltage level Vc j . The controller 202 determines the value of the first voltage level Vc j so that the capacitor circuit 204 provides sufficient energy to the switching power converter 210 during a portion of the cycle of the rectified, line input voltage Vo DIM and so that the voltage Vc across the capacitor circuit 204 decays to a specific second voltage level Vc 2 (as for example subsequently explained in more detail with reference to Figures 3 and 4). The second voltage
level Vc 2 allows the controller 202 to repeat attaching the dimmer to the power converter 216 and supplying sufficient energy to the switching power converter 210. Thus, by charging the capacitor circuit 204 to the first voltage value Vc j, the controller 202 attaches the phase- cut dimmer 102, provides energy to the switching power converter 210 during a portion of a cycle of the input voltage Vo DIM, and establishes a second voltage level Vc_2 that allows the controller 202 to repeat attaching the dimmer and supplying sufficient energy to the switching power converter 210.
[0021] The controller 202 actively controls charging of the capacitor circuit 204 by generating the switch control signal CSi to turn the switch 206 ON, i.e. conduct, when the controller 202 detects a leading edge of the voltage Vo DIM- When the switch 206 is ON, current ic flows through the switch 206 and resistor 218 and charges capacitor circuit 204. The resistance of resistor 218 and the capacitance of capacitor circuit 204 provide a time constant that together with the conductivity of switch 206 controls a rate of charging and, thus, current ίφ R draw to charge the capacitor circuit 204. The controller 202 keeps switch 206 ON until the capacitor circuit voltage Vc reaches the first voltage value Vc i and then turns the switch 206 OFF. The diode 220 allows the energy in the capacitor circuit 204 to be used during the periods of low input voltage levels of the voltage Vo DIM, which partially discharges the capacitor circuit 204 to provide energy to the load 222. When the voltage Vo DIM falls below the capacitor circuit voltage Vc, the capacitor circuit 204 provides energy via current ic E to the switching power converter 210 until the next leading edge of the Vo DIM occurs. The switching power converter 210 provides power to the load 222 via an output voltage VOUT and an output current ί0υτ· The switching power converter 210 can be any type of switching power converter such as a flyback, buck, boost-buck, boost, or Cuk type switching power converter. The load 222 can be any type of load, such as one or more LEDs. An exemplary system and method for detecting a leading edge of the voltage Vo DIM is described in U.S. Patent Application No. 13/077,483, entitled "Dimmer Detection", filing date March 31, 201 1, inventors Robert T. Grisamore, Firas S. Azrai, Mohit Sood, John L. Melanson, and Eric J. King, and assignee Cirrus Logic, Inc. and U.S. Patent No. 8,018, 171, entitled "Multi-function Duty Cycle Modifier", inventors John L. Melanson and John J. Paulos, and assignee Cirrus Logic, Inc., which are herein incorporated by reference in their entireties. If the controller 202 does not sense a leading edge of the voltage Vo DIM, the controller selection of the first voltage level Vc j and the second voltage level Vc 2 are made
to optimize power factor or efficiency of the electronic system 200. The particular values of the first voltage level Vc_i and the second voltage level Vc_2 when no leading edge of the voltage Vo DIM is sensed are matters of design choice and, in at least one embodiment, depend on, for example, the output voltage VOUT for the load 222, the power requirements of the load 222. Particular values of the first voltage level Vc_i and the second voltage level Vc 2 to optimize power factor or efficiency of the electronic system 200 can be determined empirically.
[0022] Figure 3 depicts an electronic system 300, which represents one embodiment of the electronic system 200. Figure 4 depicts exemplary waveforms associated with the electronic system 300. Referring to Figures 3 and 4, at time t0, the voltage Vo DIM is at a zero crossing, and, in at least one embodiment, the controller 302 draws a glue current IQLUE via path 304 to allow the triac 212 to fire, i.e. conduct, at the appropriate time indicated by an internal timing mechanism of the phase-cut dimmer 102. U.S. Patent Application No. 12/858, 164, entitled "Dimmer Output Emulation", filed August 17, 2010, and inventor John L. Melanson and U.S. Patent Application No. 13/290,032, entitled "Switching Power Converter Input Voltage Approximate Zero Crossing Determination", filed November 4, 201 1, and inventors Eric J. King and John L. Melanson, are herein incorporated by reference and describe exemplary embodiments of generating the glue current.
[0023] At time t the controller 302 detects the leading edge 402 of the voltage Vo DIM and generates a pulse 404 of the control signal CSi to turn the switch 206 ON. At the end of the previous cycle (not shown) of the voltage Vo DIM, the voltage Vc across the capacitor 306 was at the second voltage level Vc_2. Capacitor 306 represents one embodiment of the capacitor circuit 204. The value of capacitor 306 is typically 0.5-20 uF, depending on the output voltage VOUT for the load 222, power, ripple requirements, and design choice. With the switch 206 conducting, at time ti the voltage Vc across the capacitor 306 rises from the second voltage level Vc 2 to the first voltage level Vc j. Between times ti and t2, the current ic flowing through switch 206 and causing the capacitor 306 to charge to the first voltage level Vc 1 is sufficient to attach the dimmer. At time t2, the voltage Vc across the capacitor 306 reaches the first voltage level Vc j, and the controller 302 generates the control signal CSi to turn the switch 206 OFF. Thus, the voltage Vc rises to the first voltage level Vc j during the initial portion of the voltage Vo DIM after the leading edge 402 occurs. However, unlike a conventional peak-rectified system, the rate of the rise of the voltage Vc is actively
controlled by the controller 202 using the switch 206 and the resistor 218, and the voltage Vc rises to a first voltage level Vc j, which, in at least one embodiment, is less than the peak value Vo DIM PEAK of the line input voltage Vo DIM-
[0024] The voltage Vc across the capacitor 306 remains at the first voltage level Vc ι until, at time t4, the line input voltage Vo DIM falls below the first voltage level Vc j . At time t5, the next leading edge 406 of the voltage Vo DIM occurs. Between times t4 and t5, which is in the trough of the line input voltage Vo DIM, the voltage Vc is higher than the line input voltage Vo DIM, and the capacitor 306 provides energy via the current ic E to the flyback-type, switching power converter 308. As the capacitor 306 provides energy to the switching power converter 308, the voltage across the capacitor 306 decreases, and at time t2 reaches the second voltage level Vc 2.
[0025] Equation 1 represents the amount of energy Ec TRANFERRED transferred from the capacitor 306 to the switching power converter 308 during the period T
Equation 1
£<C TRANFERRED ~ ½-C-(Vc_i - Vc /)
where C is the capacitance value of capacitor 306, Vc j is the first level voltage value across the capacitor 306, and Vc 2 is the second level voltage value across the capacitor 306. In at least one embodiment, the particular value of the voltage Vc 2 correlates with the phase angle of the line input voltage Vo DIM and can be empirically determined for each phase angle for a particular load, such as the LED(s) 310.
[0026] Equation 2 represents the amount energy ESpc to be provided to the switching power converter 308 for a given phase angle of the line input voltage Vo DIM:
where Ti is the period of time between times t4 and is, which represents the amount of time that the capacitor 306 is providing energy to the switching power converter 308. The controller 302 determines the value of Ti by determining the time between when the controller 302 causes the switch 206 to stop conducting and when the controller 302 detects the next leading edge of the voltage Vo DIM. P is the amount of power provided to the
switching power converter 308 for conversion and provision to the LED(s) 310. In at least one embodiment, the value of the amount of power P is predetermined for each phase angle since the amount of power to be provided to the LED(s) 310 directly correlates to the phase angle of the voltage Vo DIM and the corresponding power utilization by the LED(s) 310. U.S. Patent No. 7,852,017, entitled "Ballast for Light Emitting Diode Light Sources", filed March 12, 2008, assignee Cirrus Logic, Inc., which is herein incorporated by reference, describes exemplary systems and methods for detecting voltage phase angles.
[0027] In at least one embodiment, the controller 302 determines the values of the first level voltage Vc_i and the time Ti so that Equation 1 equals Equation 2 for the known values of the capacitance C of the capacitor 306, the second level voltage value Vc_2, and the amount of power P provided to the switching power converter 308. In at least one embodiment, the controller 302 iterates over consecutive cycles of the voltage Vo DIM to obtain the values of the first level voltage Vc_i and the time Ti so that Equation 1 equals Equation 2. In at least one embodiment, the values of the variables in Equation 1 and Equation 2 are initialized using empirically obtained data, and controller 302 iterates the values if during operation of the electronic system 300, Equation 1 does not equal Equation 2 using the initialized values. In other words, if the desired value of the second level voltage Vc 2 is n°t met on a cycle of the voltage Vo DIM, then the value of the first level voltage Vcj is adjusted for the next cycle. In at least one embodiment, this iterative process maximizes efficiency of the electronic system 200 and compatibility between the power converter 216 and the phase-cut dimmer 102.
[0028] The controller 302 utilizes the flyback-type switching power converter 308 to convert the voltage Vo DIM into an LED drive current ILED and load voltage VLED on the side of the secondary-winding 314 of the transformer 316. The controller 302 provides source control to the source of the FET 312 to control the flyback-type, switching power converter 308 and, thus, control the current ic _E, the LED drive current ILED, and the load voltage VLED- The values of the current ic _E, the LED drive current ILED, and the load voltage VLED correlate with the phase angle of the voltage Vo DIM- The brightness of the LED(s) 310 directly correlates with the value of the LED drive current ILED. Thus, the brightness of the LED(s) 310 directly conforms to the phase angle of the voltage Vo DIM-
[0029] The controller 302 controls the conductivity of the FET 312 to control the current ic E to meet the power demands of LED(s) 310. For an n-channel FET, the FET 312 is biased
with a fixed gate voltage VG and conducts (i.e. ON) when the source voltage VSOURCE is less than the gate voltage VG minus a threshold voltage of the FET 606 and is nonconductive (i.e. OFF) when the source voltage VSOURCE is greater than the gate voltage VG minus the inherent threshold voltage of the FET 3 12. When the FET 3 12 conducts, the current ic _E ramps up through the primary winding 320 of transformer 3 16. The dot convention of transformer 3 16 and the diode 322 prevent flow of the LED current ILED from the secondary-winding 3 14 when FET 3 12 conducts and the current ic E is flowing into the primary winding 320. When the controller 302 turns the FET 3 12 OFF, the current ic E falls to 0, and the voltage across the primary winding 320 reverses for a period of time, referred to as the "flyback time". During the flyback time, the secondary current is quickly rises and charges capacitor 324. Capacitor 324 provides an output voltage VLED and current ILED to the LED(s) 3 10. A diode and resistor-capacitor filter circuit 326 provides a path for voltage perturbations.
[0030] An exemplary flyback-type switching power converter and corresponding control and auxiliary power supply is described in U.S. Patent Application No. 13/715,45 1, entitled "Isolation of Secondary Transformer Winding Current During Auxiliary Power Supply Generation", inventors John L. Melanson, Prashanth Drakshapalli, and Siddharth Maru, filing date December 14, 2012, which is incorporated by reference in its entirety. U.S. Patent Application No. 12/289,845, entitled "Controlled Power Dissipation in a Switch Path in a Lighting System", filed November 4, 201 1, and inventors John L. Melanson and Eric J. King, and U.S. Patent Application No. 13/774,914, entitled "Mixed Load Current Compensation for LED Lighting", filed February 22, 2013, and inventors Eric J. King, John L. Melanson, and Daniel J. Baker, are hereby incorporated by reference and describe exemplary systems and methods for controlling the source of a FET. The particular implementation of controller 302 is a matter of design choice. For example, controller 302 can be (i) implemented as an integrated circuit including, for example, a processor to execute software or firmware instructions stored in a memory, (ii) implemented using discrete components, or (iii) implemented using any combination of the foregoing. Additionally, in at least one embodiment, all of the components in electronic system 300, except the voltage supply 104 and the phase-cut dimmer 102 are included in a lamp.
[003 1 ] Figure 5 depicts a capacitor circuit 500, which represents another embodiment of the capacitor circuit 204. For reference purposes, nodes A and B correspond with the nodes A and B of Figure 2. The capacitor circuit 500 includes capacitor 502 that charges when the
switch 206 is ON. When switch 206 is OFF, the capacitors 502 and 504 discharge through diodes 506, 508, and 510. By utilizing two capacitors 502 and 504, more current is drawn in phase with the voltage Vo DIM when the voltage Vo DIM has no phase cuts, which increases the power factor of the electronic system 200. The values of capacitors 502 and 504 are typically .5-20 uF, depending on the output voltage VOUT for the load 222, power utilized by the load 222, ripple requirements, and design choice. The two values of the capacitors 502 and 504 can be the same, or may differ, with capacitor 502 typically having a larger capacitance than capacitor 504. Thus, an electronic system includes a controller that actively controls a rate of charging and discharging of an energy storage capacitor to maintain compatibility with a dimmer. The controller actively controls charging of a capacitor circuit in a switching power converter to a first voltage level across the capacitor circuit. The controller further allows the capacitor to discharge to obtain a second voltage level across the capacitor circuit. The second voltage level is sufficient to provide a decreasing transition of a current through a triac -based dimmer to prevent a triac of the dimmer from prematurely resetting. The first voltage is sufficient to allow the capacitor to discharge to the second voltage level during each cycle of the line voltage.
[0032] Although embodiments have been described in detail, it should be understood that various changes, substitutions, and alterations can be made hereto without departing from the spirit and scope of the invention as defined by the appended claims.
Claims
WHAT IS CLAIMED IS; 1. A method comprising:
actively controlling a rate of charging of a capacitor circuit in a switching power converter to a first voltage level across the capacitor circuit; and allowing the capacitor to discharge to obtain a second voltage level across the
capacitor circuit, wherein the second voltage level is sufficient to draw a current through a phase-cut dimmer to prevent the dimmer from prematurely resetting, and the first voltage is sufficient to allow the capacitor to discharge to the second voltage level during each cycle of the line voltage.
2. The method of claim 1 wherein actively controlling charging of the capacitor comprises:
controlling current through the capacitor circuit at a rate that prevents a triac of the phase-cut dimmer from prematurely resetting and allows the voltage across the capacitor circuit to reach the first voltage level.
3. The method of claim 2 wherein controlling current through the capacitor circuit further comprises:
controlling conductivity of a switch coupled to the capacitor circuit.
4. The method of claim 3 wherein the switch is a member of a group consisting of: a bipolar junction transistor and a field effect transistor.
5. The method of claim 1 wherein actively controlling charging of the capacitor circuit further comprises:
setting the first voltage level and the second voltage level so that discharging a
capacitor network from the first voltage level to the second voltage level supplies an approximate amount of energy to a load, which is coupled to the switching power converter, wherein the amount of energy correlates with a phase angle of an input line voltage supplied to the switching power converter.
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6. The method of claim 1 wherein:
actively controlling charging of the capacitor circuit further comprises:
controlling one or more switches to regulate current from a terminal of the capacitor circuit that is coupled to a reference voltage node; and allowing the capacitor to discharge to obtain a second voltage level across the
capacitor circuit comprises:
controlling the one or more switches to cease current flow through the one or more switches.
7. The method of claim 1 wherein the capacitor circuit consists of a single capacitor.
8. The method of claim 1 wherein the capacitor circuit comprises multiple capacitors.
9. The method of claim 1 wherein the first voltage level across the capacitor circuit is less than a peak value of an input line voltage supplied to the switching power converter.
10. The method of claim 1 wherein the phase-cut dimmer is a triac based dimmer that includes a triac, and the second voltage level is sufficient to draw a current through the triac -based dimmer to prevent the triac of the dimmer from prematurely resetting, and the first voltage is sufficient to allow the capacitor to discharge to the second voltage level during each cycle of the line voltage.
1 1. An apparatus comprising:
a controller, wherein the controller is configured to:
actively control a rate of charging of a capacitor circuit in a switching power converter to a first voltage level across the capacitor circuit; and allow the capacitor to discharge to obtain a second voltage level across the capacitor circuit, wherein the second voltage level is sufficient to draw
a current through a phase-cut dimmer to prevent the dimmer from prematurely resetting, and the first voltage is sufficient to allow the capacitor to discharge to the second voltage level during each cycle of the line voltage.
12. The apparatus of claim 1 wherein to actively control charging of the capacitor the controller is further configured to:
control current through the capacitor circuit at a rate that prevents a triac of the phase- cut dimmer from prematurely resetting and allows the voltage across the capacitor circuit to reach the first voltage level.
13. The apparatus of claim 2 wherein to control current through the capacitor circuit the controller is further configured to:
control conductivity of a switch coupled to the capacitor circuit.
14. The apparatus of claim 3 wherein the switch is a member of a group consisting of: a bipolar junction transistor and a field effect transistor.
15. The apparatus of claim 1 wherein to actively control charging of the capacitor circuit the controller is further configured to:
sett the first voltage level and the second voltage level so that discharging a capacitor network from the first voltage level to the second voltage level supplies an approximate amount of energy to a load, which is coupled to the switching power converter, wherein the amount of energy correlates with a phase angle of an input line voltage supplied to the switching power converter.
16. The apparatus of claim 1 wherein:
to actively control charging of the capacitor circuit the controller is further configured to:
control one or more switches to regulate current from a terminal of the
capacitor circuit that is coupled to a reference voltage node; and
to allow the capacitor to discharge to obtain a second voltage level across the capacitor circuit the controller is further configured to:
control the one or more switches to cease current flow through the one or more switches.
17. The apparatus of claim 1 wherein the capacitor circuit consists of a single capacitor.
18. The apparatus of claim 1 wherein the capacitor circuit comprises multiple capacitors.
19. The apparatus of claim 1 wherein the first voltage level across the capacitor circuit is less than a peak value of an input line voltage supplied to the switching power converter.
20. The apparatus of claim 1 wherein the phase-cut dimmer is a triac based dimmer that includes a triac, and the second voltage level is sufficient to draw a current through the triac -based dimmer to prevent the triac of the dimmer from prematurely resetting, and the first voltage is sufficient to allow the capacitor to discharge to the second voltage level during each cycle of the line voltage.
21. The apparatus of claim 1 1 wherein the controller comprises an integrated circuit.
22. An apparatus comprising:
a switching power converter having a switch and conductivity of the switch controls power conversion by the switching power converter;
a load coupled to the switching power converter;
a capacitor circuit coupled to the switching power converter; and
a controller, coupled to the switch of the switching power converter and to the
capacitor circuit, wherein the controller is configured to:
actively control a rate of charging of the capacitor circuit in a switching power converter to a first voltage level across the capacitor circuit; and
allow the capacitor to discharge to obtain a second voltage level across the capacitor circuit, wherein the second voltage level is sufficient to draw a current through a phase-cut dimmer to prevent the dimmer from prematurely resetting, and the first voltage is sufficient to allow the capacitor to discharge to the second voltage level during each cycle of the line voltage.
23. The apparatus of claim 21 wherein the load comprises one or more lig emitting diodes.
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EP13753230.5A EP2888927A1 (en) | 2012-08-27 | 2013-08-08 | Power conversion with controlled capacitance charging including attach state control |
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US13/836,423 US9184661B2 (en) | 2012-08-27 | 2013-03-15 | Power conversion with controlled capacitance charging including attach state control |
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US9184661B2 (en) | 2015-11-10 |
EP2888927A1 (en) | 2015-07-01 |
US20140055055A1 (en) | 2014-02-27 |
CN104770064A (en) | 2015-07-08 |
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