# Patent

## Title
Apparatuses for bleeding current from a transformer of a solid-state light emitting diode

## Abstract

A system configured to provide current to power a solid-state light emitting diode in accordance with a dimming level, wherein the dimming level corresponds to an amount of light provided from the solid-state light emitting diode. The system includes a transformer and a switch. The transformer includes a coil. The transformer is configured to receive a first current. The coil is configured to, based on the first current, output a second current to power the solid-state light emitting diode. The switch is configured to, based on a dimming level that corresponds to the amount of light provided from the solid-state light emitting diode of the system, bleed a portion of the second current out of the coil to a ground reference in order to divert the portion of the second current from being supplied to the solid-state light emitting diode.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
The present disclosure is a continuation of U.S. patent application Ser. No. 13/525,711 (now U.S. Pat. No. 8,847,517), filed on Jun. 18, 2012. This application claims the benefit of U.S. Provisional Application No. 61/498,376 filed on Jun. 17, 2011. The entire disclosures of the applications referenced above are incorporated herein by reference


FIELD
The present disclosure relates to triode for alternating current (TRIAC) dimmers.
BACKGROUND
The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
A dimmer for an incandescent lamp may include an input circuit with a thyristor. The thyristor switches ON at an adjustable time (or phase angle) subsequent to a start of each alternating current (AC) half-cycle of a power signal received from an AC power source. Switching ON and OFF of the thyristor affects a voltage waveform received at the incandescent lamp. The input circuit controls current supplied to the incandescent lamp based on a control input. The control input may be changed to adjust a dimming level of the incandescent lamp.
A thyristor operates as a bistable switch conducting when a current trigger is received and continuing to conduct while in a forward biased state. Since the thyristor switches ON and OFF instead of absorbing a portion of the power supplied from the AC power source, the amount of wasted power due to the thyristor is minimal. This is unlike traditional variable resistors, which absorb (or convert) a portion of the AC power provided to thermal energy.
As an alternative to using a single thyristor, a dimmer may include a TRIAC. A TRIAC includes two thyristors, operates as a bidirectional switch, and has specific latching properties. In order to latch a TRIAC in an ON state, a trigger voltage is applied across terminals of the TRIAC. The trigger voltage is greater than a predetermined voltage level to enable a minimum current (or latch-up current) to flow through and latch the TRIAC in the ON state. The latch-up current may be, for example, several milli-amps (mA) to tens of mA. The latch-up current must flow for a certain period of time to completely latch the TRIAC in the ON state. Subsequent to latching the TRIAC, a predetermined level of current (or hold-up current) is supplied to maintain the TRIAC in the ON state. The hold-up current may be less than the latch-up current. Different TRIACs have different latch-up and hold-up current levels.
Solid-state lighting refers to providing light from solid-state lamps, such as light from light emitting diodes (LEDs). A solid-state lamp can provide the same level of luminous intensity as an incandescent lamp while consuming less power. As an example, a LED may consume 6 watts of power for a given luminous intensity, whereas an incandescent light may consume 60 watts of power for the same luminous intensity. The luminous intensity per power usage rating (e.g., luminance/watt rating) of solid-state lamps continues to increase with technology improvements in solid-state lamps. As a result, solid-state lamps can provide a high level of luminous intensity (at least the same as an incandescent lamp) while operating based on a low level of power and/or current (less than that used by an incandescent lamp).
Due to the low power operation and corresponding operating current levels of solid-state lamps, it can be difficult to maintain a hold-up current using traditional TRIAC dimmers. The smaller the current level, the more difficult it is to maintain a sustainable hold-up current. A traditional TRIAC dimmer may be configured for an incandescent lamp having a full power rating of, for example, 60 W. Since a solid-state lamp may have a full power rating of, for example, 6 W during deep dimming (or low luminous intensity output) conditions, operating power may be less than 1 W. As a result, the current through a TRIAC of a traditional dimmer may decrease to a level less than a hold-up current and the TRIAC may shut OFF. Thus, load applications and dimming performance is limited for traditional TRIAC dimmers.
SUMMARY
A system is provided. The system is configured to provide current to power a solid-state light emitting diode in accordance with a dimming level. The dimming level corresponds to an amount of light provided from the solid-state light emitting diode. The system includes a transformer and a switch. The transformer includes a coil. The transformer is configured to receive a first current. The coil is configured to, based on the first current, output a second current to power the solid-state light emitting diode. The switch is configured to, based on the dimming level that corresponds to the amount of light provided from the solid-state light emitting diode, bleed a portion of the second current out of the coil to a ground reference in order to divert the portion of the second current from being supplied to the solid-state light emitting diode.
In other features, a system is provided. The system is configured to provide current to power a solid-state light emitting diode in accordance with a dimming level. The dimming level corresponds to an amount of light provided from the solid-state light emitting diode. The system includes a transformer and a switch. The transformer includes a coil. The transformer is configured to receive a first current and, based on the first current, output a second current to power the solid-state light emitting diode. The coil is configured to output a third current based on the first current. The switch is configured to, based on the dimming level that corresponds to the amount of light provided from the solid-state light emitting diode, bleed a portion of the third current out of the coil to a ground reference.
In other features, a system is provided. The system is configured to provide current to power a solid-state light emitting diode in accordance with a dimming level. The dimming level corresponds to an amount of light provided from the solid-state light emitting diode. The system includes a transformer, a resistance, a switch and a capacitance. The transformer includes a first coil, a second coil, and a third coil, where the first coil is configured to receive a first current or a voltage, where the second coil is configured to, based on the first current or the voltage, output a second current to power the solid-state light emitting diode, and where the third coil is configured to output a third current based on the first current or the voltage. The switch is connected in series with the resistance, where the switch is configured to, based on the first current or the voltage, bleed a portion of the third current out of the third coil to a ground reference via the resistance. The capacitance is connected in parallel with a combination of the resistance and the switch.
In other features, a system is provided. The system is configured to provide current to power a solid-state light emitting diode in accordance with a dimming level, where the dimming level corresponds to an amount of light provided from the solid-state light emitting diode. The system includes a transformer, a switch and a module. The transformer is configured to receive a voltage, where the voltage is based on a state of a dimmer, where the transformer includes a coil, and where the coil is configured to, based on the voltage, output a first current to the solid-state light emitting diode. The switch is connected in series with the coil. The module is configured to, based on the voltage, change a state of the switch to bleed to a reference terminal a portion of the first current.
In other features, a system is provided. The system is configured to provide current to power a solid-state light emitting diode in accordance with a dimming level, where the dimming level corresponds to an amount of light provided from the solid-state light emitting diode. The system includes a transformer, a switch and a module. The transformer is configured to receive a voltage, where the voltage is based on a state of a dimmer, where based on the voltage, the transformer is configured to output a first current to the solid-state light emitting diode, where the transformer includes a secondary coil, and where the secondary coil is configured to, based on the voltage, output a second current. The switch is connected in series with the secondary coil. The module is configured to, based on the voltage, change a state of the switch to bleed to a reference terminal a portion of the second current.
In other features, a system is provided and includes a transformer. The transformer includes a first coil and a second coil. The first coil is configured to receive a first voltage based on an output of a switching circuit. The second coil is configured to generate a first current based on the first voltage to power a solid-state load. The system also includes a third coil. The third coil is configured to generate a second voltage based on the first voltage.
In other features, the system further includes a first module configured to generate a first control signal to change a state of the first switch based on the dimming level of the system.
In yet other features, a method is provided. The method includes receiving a first voltage at a first coil of a transformer based on an output of a switching circuit. A first current is generated via a second coil based on the first voltage to power a solid-state load. A second voltage is generated via a third coil based on the first voltage. Current is bled from one of the second coil and the third coil to a ground reference via a first switch based on a dimming level.
In still other features, the method further includes generating a first control signal to change a state of the first switch based on the dimming level.
Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.



BRIEF DESCRIPTION OF DRAWINGS
The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:
FIG. 1 is a functional block schematic diagram of a TRIAC-based dimmer circuit;
FIG. 2 is a functional block schematic diagram of a TRIAC dimming system in accordance with the present disclosure;
FIG. 3 is a functional block schematic diagram of another TRIAC dimming system illustrating elements of a bias module and a bleeder module in accordance with the present disclosure;
FIG. 4 is a functional block diagram of a control module in accordance with the present disclosure;
FIG. 5 is a signal diagram for the TRIAC dimming system of FIG. 3;
FIG. 6 is a signal diagram for the TRIAC dimming system of FIG. 3 operating in a leading edge mode with low-frequency bleeder switching;
FIG. 7 is a signal diagram for the TRIAC dimming system of FIG. 3 operating in a trailing edge mode with low-frequency bleeder switching;
FIG. 8 is a signal diagram for the TRIAC dimming system of FIG. 3 operating in a leading edge mode with high-frequency bleeder switching;
FIG. 9 is a signal diagram for the TRIAC dimming system of FIG. 3 operating in a trailing edge mode with high-frequency bleeder switching;
FIG. 10 is a functional block schematic diagram of another TRIAC dimming system with secondary side bleeder current operation in accordance with the present disclosure;
FIG. 11 is a functional block schematic diagram of another TRIAC dimming system incorporating a bleed coil in accordance with the present disclosure; and
FIG. 12 illustrates a method of operating a TRIAC dimming system in accordance with the present disclosure.



DESCRIPTION
In FIG. 1, a TRIAC-based dimmer circuit 10 is shown. The TRIAC-based dimmer circuit 10 includes an AC power source 12, a TRIAC module 14, a bridge 16, a DC-to-DC converter 18 and a solid-state load (SSL) circuit 20. The TRIAC module 14 receives a power signal from the AC power source 12. The TRIAC module 14 may include an input module 22 with a control input and one or more TRIAC(s) 24. The control input may be adjusted to adjust a dimming level of the SSL circuit 20.
The bridge 16 rectifies an AC output voltage received from the TRIAC module 14 to provide a first direct current (DC) voltage (e.g., 200-700 volts (V)) on a DC voltage bus 26. The DC-to-DC converter 18 converts the first DC voltage to a second DC voltage (e.g., voltage less than or equal to 30 V). The second DC voltage is provided to the SSL circuit 20.
The TRIAC-based dimmer circuit 10 may also include a bleeder resistance R1, a switch S1, and a control module 28. The bleeder resistance R1 and the switch S1 are connected in series between the DC voltage bus 26 and a ground reference 30. The bleeder resistance R1 is provided to increase current out of the TRIAC module 14 during, for example, low dimming conditions (e.g., when current supplied to the SSL circuit 20 is less than a predetermined level). The SSL circuit 20 may detect the first DC voltage of the DC voltage bus 26 via a line 32. The control module 28 controls state of the switch S1 based on the first DC voltage.
In operation, the first DC voltage (or bus voltage) across the bleeder resistance R1 provides a bleed current from the DC voltage bus 26 to the ground reference 30 when the switch S1 is closed. The bleed current is determined based on the first DC voltage and the bleeder resistance R1. The bleeder resistance R1 aids in maintaining a hold up current out of the TRIAC module 14. The control module 28 controls state of the switch S1 according to current supplied to the SSL circuit 20. As an example, if the SSL circuit 20 is receiving a current level greater than or equal to a load current associated with drawing the hold up current from the TRIAC module 14, then the control module 28 transitions the switch S1 to an OFF (or open) state. If the SSL circuit 20 is receiving a current level less than the load current associated with drawing the hold up current from the TRIAC module 14, then the control module 28 transitions the switch S1 to an ON (or closed) state. Bleed current loss is eliminated when the switch S1 is turned OFF. This increases operating efficiency during high load conditions.
The TRIAC-based dimmer circuit 10 provides the bleed current from the DC voltage bus 26 to the ground reference 30 on a high-voltage (or primary) side of the DC-to-DC converter 18. The DC voltage bus 26 is a high voltage (e.g., 200-700 V) bus. For this reason, the switch S1 is constructed to handle the high voltages and corresponding current levels experienced during operation.
In FIG. 2, a TRIAC dimming system 50 is shown. The TRIAC dimming system 50 includes a power train 52, which includes an AC power source 54, a TRIAC module 56 (referred to as a TRIAC dimmer), a bridge 58, a DC-to-DC converter 60 and a SSL circuit 62. The TRIAC module 56 receives a power signal from the AC power source 54. The TRIAC module 56 may include an input module 64 with a control input and one or more TRIAC(s) 66 (referred to as a bidirectional switching circuit). The TRIAC(s) 66 may be configured for incandescent light and/or solid-state light operation and have corresponding latch up and hold up current levels. The control input may be provided via, for example, a variable resistor or other suitable component(s) to adjust turn ON time of the TRIAC(s) and as a result a dimming level of the SSL circuit 62.
The bridge 58 rectifies an AC output voltage received from the TRIAC module 56 to provide a first DC voltage (e.g., 200-700 volts (V)) on a DC voltage bus 68. The DC-to-DC converter 60 converts the first DC voltage to a second DC voltage (e.g., voltage less than or equal to 30 V). The second DC voltage is provided to the SSL circuit 62. The DC-to-DC converter 60 may be in a flyback, boost, buck, buck-boost, or other suitable configuration. Examples of flyback configurations are shown in FIGS. 3, 10 and 11. The SSL circuit 62 may include, for example, one or more solid-state lamps, such as light emitting diodes (LEDs).
The TRIAC dimming system 10 may also include a first capacitance C1, a first switch Q1, and a sensor 70. The first capacitance C1 is connected between the DC voltage bus 68 and a ground reference 72. The first capacitance C1 aids in maintaining the first DC voltage on the DC voltage bus 68. The first switch Q1 and the sensor 70 are connected in series between the DC-to-DC converter 60 and the ground reference 72. The first switch Q1 and the sensor 70 are connected on a primary (high-voltage) side of the DC-to-DC converter 60. The first switch Q1 may be a metal-oxide-semiconductor field-effect transistor (MOSFET) and be controlled by a control module 74. The sensor 70 may be used to detect current through and/or voltage across the first switch Q1, which may be converted to a current level of the SSL circuit 62 via the control module 74. The sensor 70 may include, for example, a first resistance R1 or other suitable components for detecting voltage and/or current at a drain of the first switch Q1. The first resistance R1 may be connected in series with the first switch Q1 and connected between the first switch Q1 and the ground reference 72.
The control module 74 generates a first control signal PWM1 to control operation of the first switch Q1 based on the first DC voltage, the voltage VR1 across the first resistance R1, the current Ids passing through the first resistance R1, and/or the current IL passing through the SSL circuit 62. The first control signal PWM1 is provided to a control terminal of the first switch Q1. The control module 74 may be connected to the DC voltage bus 68 to detect the first DC voltage via a third resistance R3. The third resistance R3 is connected between the DC voltage bus 68 and the control module 74. The control module 74 may also be connected to a node between the first switch Q1 and the first resistance R1 to detect the voltage VR1 across the first resistance R1, and/or the current Ids passing through the first resistance R1. The control module 74 may determine the current IL based on the first DC voltage, the voltage VR1, and/or the current Ids. The control module 74 may be programmable to provide different luminance, bleed current, and dimming level relationships.
The TRIAC dimming system 10 further includes a bias module 80 and a bleeder module 82. The bias module 80 operates as a power supply and supplies power to the control module 74. The bias module 80 may supply power to the control module 74 based on power received from the DC-to-DC converter 60. The bleeder module 82 diverts current from the bias module 80 to the ground reference 72. The bleeder module 82 diverts current from the bias module 80 to the ground reference 72 based on a second control signal PWM2 received from the control module 74. The control module 74 generates the second control signal PWM2 based on the voltage VR1, the current Ids, and/or the current IL passing through the SSL circuit 62. This increases current passing through the TRIAC module 56, which aids in maintaining a hold up current through the TRIAC module 56.
In FIG. 3, another TRIAC dimming system 100 is shown. The TRIAC dimming system 100 includes a power train 102, which includes the AC power source 54, the TRIAC module 56 including the input module 64 and the TRIAC(s) 66, the bridge 58, a DC-to-DC converter 60 and the SSL circuit 62. Although the DC-to-DC converter 60 is shown in a flyback configuration, the DC-to-DC converter 60 may be in a boost, buck, buck-boost or other suitable converter configuration. The DC-to-DC converter 60 includes a transformer T1, first diode D1, and a second capacitance C2. The transformer T1 includes a primary coil 104 on a primary side and a secondary coil 106 on a secondary side. The transformer T1 may also include a bias coil 108, which receives secondary power from the primary coil 104.
The secondary coil 106, the first diode D1 and the second capacitance C2 operate as a power supply for the SSL circuit 62. The first diode D1, the second capacitance C2, and the SSL circuit 62 are connected on the secondary (or low-voltage) side of the transformer T1. The first diode D1 is connected in series with the bias coil 108 and prevents reverse current through the secondary coil 106. Current through the first diode D1 is designated Id1. The second capacitance C2 is connected between an output of the first diode D1 and a first ground reference 110 and is connected across the SSL circuit 62. The second capacitance C2 is connected in parallel with the bias coil 108 and aids in maintaining a second DC voltage across the SSL circuit 62. Current through the second capacitance C2 is designated IC2. The SSL circuit 62 may include, for example, LEDs connected in series between terminals of the second capacitance C2. Load current through the SSL circuit 62 is designated IL.
The TRIAC dimming system 100 also includes the first capacitance C1, the first switch Q1, the sensor 70 with the first resistance R1, and the control module 74. The first capacitance C1 is connected between the DC voltage bus 68 and a second ground reference 112. The second ground reference 112 may be different and isolated from the first ground reference 110. The first switch Q1 and the sensor 70 are connected in series between the primary coil 104 and the second ground reference 112. The first switch Q1 and the sensor 70 are connected on a primary (high-voltage) side of the transformer T1. The first switch Q1 may be controlled by the control module 74 via the first control signal PWM1. The first resistance R1 may be connected in series with the first switch Q1 and between the first switch Q1 and the second ground reference 112.
The TRIAC dimming system 100 further includes a bias module 114 and a bleeder module 116. The bias module 114 is on a load side (or low-voltage side) of the transformer T1, as the bias module 114 receives power through the transformer T1 and is not on the supply side (or high-voltage side) of the transformer T1. The bleeder module 116 is also on the load side of the transformer T1, as the bleeder module 116 receives current from the bias module 114. Although the bleeder module 116 is shown as being connected to and receiving current from the bias module 114, the bleeder module 116 may alternatively or additionally receive current from the secondary coil 106. An example of a bleeder module receiving current from a secondary coil of a transformer is shown in FIG. 10. The bleeder module 116 is connected on the load (or secondary side) of the transformer T1 regardless of whether the bleeder module 116 receives current from the secondary coil 106, the bias coil 108, or both the secondary coil 106 and the bias coil 108.
The bias module 114 operates as a power supply and supplies power to the control module 74. The bias module 114 includes the bias coil 108, a third diode D3 and a third capacitance C3. The bias coil 108 receives power from the primary coil 104 and supplies current to the control module 74 while supplying current to the bleeder module 116. The third diode D3 prevents reverse current through the bias coil 108. The third capacitance C3 aids in maintaining a bias voltage VBIAS (e.g., less than or equal to 30 V) across the bias coil 108, which is supplied to the control module 74. The control module 74 operates based on the bias voltage.
The bleeder module 116 diverts current from the bias coil 108 to the second ground reference 112. The bleeder module 116 diverts current from the bias module 114 to the second ground reference 112 based on the second control signal PWM2 received from the control module 74. The control module 74 generates the second control signal PWM2 based on the voltage VR1 across the first resistance R1, the current Ids passing through the first resistance R1, and/or the current IL passing through the SSL circuit 62.
The bleeder module 116 includes a second diode D2, a second resistance (or bleeder resistance) R2, and a second switch Q2. The second diode D2, the second resistance (or bleeder resistance) R2, and the second switch Q2 are connected in series between (i) the third diode D3 and the bias coil 108, and (ii) the second ground reference 112. The second diode D2 prevents reverse current through the bias coil 108. The bleeder resistance R2 is used to bleed current from the transformer T1 via the bias coil 108 to the second ground reference 112. The second switch Q2 may be a MOSFET and is used to control the bleed current through the second resistance R2 based on the second control signal PWM2.
Since the second switch Q2 receives current from the bias module 114 and shares the same ground reference 112 as the control module 74, the switch Q2 may be incorporated in the control module 74. The switch Q2 may be controlled based on the current supplied to the SSL circuit 62, which is based on a dimming level of the TRIAC module 56. The dimming level of the TRIAC module 56 may be determined based on the first DC voltage of the DC voltage bus 68. The second switch Q2 may be turned ON during deep dimming conditions, such as when a conduction angle of the TRIAC module 56 is low (less than a predetermined angle). A deep dimming condition may refer to a condition when a dimming level is less than a predetermined dimming level and/or when a luminous intensity output of the SSL circuit 62 is less than a predetermined luminous intensity output level. In order to effectively bleed power to hold up the TRIAC module 56, the bleed current Id2 through the second diode D2 and the second resistance R2 may be as high as, for example, multiple amps (A). As a first example, the bleed current Id2 may be provided when, for example, the current IL is less than the current Ids. As another example, the bleed current Id2 may be provided when, for example, the current ID1 is less than the current Ids.
Referring also to FIG. 4, the control module 74 is shown. The control module 74 may include, for example, a power switch over module 150, a load current module 152, a primary switch control module 154, and a bleed control module 156. The power switch over module 150 controls whether the control module 74 receives power from the DC voltage bus 68 or from the bias module 114. During initial startup of the TRIAC dimming system 100, the first switch Q1 is OFF. The control module 74 receives power including a first DC voltage VDC from the DC voltage bus 68. The control module 74 then generates the first control signal PWM1 to switch ON the first switch Q1. The control module 74 may then receive power including a bias voltage VBIAS from the bias module 114. The power switch over module 150 switches power from the DC voltage bus 68 to the bias module 114 when the control module 74 is active. The control module 74 then operates based on power from the bias module 114 instead of power from the DC voltage bus 28. While operating based on power from the bias module 114, the control module 74 may monitor the first voltage of the DC voltage bus 68.
The load current module 152 determines the load current IL of the SSL circuit 62. The load current module 152 may indirectly determine the load current IL based on a detection and/or determination of the first DC voltage VDC, the voltage VR1, and/or the current IDS. The first DC voltage VDC, the voltage VR1, and/or the current IDS may be directly and/or indirectly determined via, for example, the sensor 70 and the third resistance R3. As an example, the load current IL may be determined based on equations 1-5, where: Id3 is current supplied to the control module 74 from the bias coil 108; VL is the second DC voltage or voltage across the SSL circuit 62; RTOTAL1 is a parallel combined resistance of the second capacitance C2 and the SSL circuit 62; RL is the resistance of the SSL circuit 62; NS is a number of windings in the secondary coil 106; and NP is a number of windings in the primary coil 104. Impedance of the first diode D1 may be negligible and/or ignored.




  
    
      
        
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The primary switch control module 154 generates the first control signal PWM1 based on the first DC voltage VDC. As an example, the first control signal PWM1 may be a pulse-width modulated signal. The frequency of the first control signal PWM1 when provided as a pulse-width modulated signal may be determined based on the first DC voltage VDC. As another example, the first control signal PWM1 may be a constant (non-oscillating) voltage and/or current signal that is switched to either an ON state or an OFF state depending on the first DC voltage VDC. If the first DC voltage VDC is greater than a predetermined voltage, the first control signal PWM1 may be switched to and remain in the ON state. If the first DC voltage VDC is less than or equal to the predetermined voltage, the first control signal PWM1 may be switched to and remain in the OFF state.
The bleed control module 156 controls the bleed current Id2 drawn from the bias coil 108. The bleed control module 156 may set and/or adjust the bleed current Id2 based on the first DC voltage VDC, the voltage VR1, the current IDS, and/or the load current IL. The bleed control module 156 may set and/or adjust the bleed current Id2 based on characteristics of the TRIAC(s) 66. The characteristics of the TRIAC(s) 66 may include, for example, latch up and/or hold up current levels of the TRIAC(s) 66. The bleed current Id2 may be adjusted to maintain the TRIAC(s) 66 in a latched or ON state. The bleed current Id2 may be determined, for example, based on equations 1-7, where: VBIAS is the voltage across the bias coil 108; NBIAS is a number of windings in the bias coil 108; RTOTAL2 is a parallel combined resistance of the third capacitance C3, the resistance R2, and an input resistance RINPUT of the control module 74. Impedances of the diodes D2, D3 and the second switch Q2 may be negligible and/or ignored.




  
    
      
        
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Referring now also to FIG. 5, a signal diagram for the TRIAC dimming system 100 is shown. The signal diagram includes examples of the first control signal PWM1, the current IDS through the first switch Q1, the bias voltage VBIAS, a conduction time of the second switch Q2, the current Id1 and the current Id2. Although the first control signal PWM1 is shown as a pulse-width modulated signal, the first control signal PWM1 may be a constant (non-oscillating) voltage and/or current signal having corresponding ON and OFF states.
The current IDS through the primary coil 104 increases when the first control signal PWM1 is in an ON (or HIGH) state, shown by pulse 160. The current IDS decreases a propagation delay PD after the first control signal PWM1 transitions to on OFF (or LOW) state. The bias voltage VBIAS transitions from a NULL or zero voltage state to a LOW state (designated at 162) when the current IDS is greater than, for example, zero. The bias voltage VBIAS transitions from the LOW state to a HIGH state (designated at 164) subsequent to the propagation delay PD. The conduction ON time of the second switch Q2 (designated by pulse 166) may occur when the bias voltage VBIAS transitions from the LOW state to the HIGH state.
The first and second diode currents Id1, Id2 are shown for when a dimming level of the TRIAC module 56 is less than a predetermined threshold. If the dimming level is less than a predetermined threshold, bleed current Id2 is increased and may follow the current Id1, as shown. The bleed current Id2 may be less than the current Id1. Increasing the bleed current Id2 allows the current through the primary coil 104 to be maintained above a predetermined level. This prevents the TRIAC(s) 66 from transitioning to an OFF state and allows the SSL circuit 62 to provide low levels of illumination during deep dimming conditions. The first and second diode currents Id1, Id2 may increase when the bias voltage VBIAS transitions to the HIGH state and the second switch Q2 is in an ON state.
In FIG. 6, a signal diagram for the TRIAC dimming system 100 of FIG. 3 operating in a leading edge mode with low-frequency bleeder switching is shown. The signal diagram includes a TRIAC output voltage signal OUT and the second control signal PWM2. The TRIAC output voltage signal OUT refers to an alternating current (AC) voltage at an output of the TRIAC(s) 66 or an AC voltage at a point between the TRIAC(s) and the bridge 58. The TRIAC output voltage signal OUT increases when the second control signal PWM2 transitions to a HIGH state and then gradually decreases while and subsequent to when the second control signal PWM2 is in the ON state.
In FIG. 7, a signal diagram for the TRIAC dimming system 100 of FIG. 3 operating in a trailing edge mode with low-frequency bleeder switching is shown. The signal diagram includes a TRIAC output voltage signal OUT and the second control signal PWM2. The TRIAC output voltage signal OUT refers to an AC voltage at an output of the TRIAC(s) 66 or an AC voltage at a point between the TRIAC(s) and the bridge 58. The TRIAC output voltage signal OUT gradually increases prior to when the second control signal PWM2 transitions to a HIGH state, gradually increases to a maximum while the second control signal PWM2 is in the HIGH state, and then decreases while and subsequent to when the second control signal PWM2 is in the ON state. Increase and decrease rates of the TRIAC output voltage signal OUT depend upon the duty cycle or amount of time the second control signal is in the ON state. The TRIAC output voltage signal OUT remains in a LOW state for a predetermined period of time subsequent to when the second control signal PWM2 is transitioned to a LOW state.
TRIAC output voltages may increase when the second control signal PWM2 transitions to and remains in an ON state for a period of time, as shown in FIGS. 6 and 7 or may increase when the second control signal PWM2 transitions between OFF and ON states at a high frequency (a frequency greater than a predetermined frequency), as shown in FIGS. 8 and 9.
In FIG. 8, a signal diagram for the TRIAC dimming system of FIG. 3 operating in a leading edge mode with high-frequency bleeder switching is shown. The signal diagram includes a TRIAC output voltage signal OUT and the second control signal PWM2. The TRIAC output voltage signal OUT refers to an AC voltage at an output of the TRIAC(s) 66 or an AC voltage at a point between the TRIAC(s) and the bridge 58. The TRIAC output voltage signal OUT increases when the second control signal PWM2 transitions to a HIGH state and then gradually decreases while and subsequent to when the second control signal PWM2 continues to be transitioned between OFF and ON states at a high frequency.
In FIG. 9, a signal diagram for the TRIAC dimming system of FIG. 3 operating in a trailing edge mode with high-frequency bleeder switching is shown. The signal diagram includes a TRIAC output voltage signal OUT and the second control signal PWM2. The TRIAC output voltage signal OUT refers to an AC voltage at an output of the TRIAC(s) 66 or an AC voltage at a point between the TRIAC(s) and the bridge 58. The TRIAC output voltage signal OUT gradually increases prior to when the second control signal PWM2 transitions to a HIGH state, gradually increases to a maximum while the second control signal PWM2 continues to be transitioned between OFF and ON states at a high frequency, and then decreases while and subsequent to when the second control signal PWM2 is transitioning between the OFF and ON states at a high frequency. The TRIAC output voltage signal OUT remains in a LOW state for a predetermined period of time when the second control signal PWM2 is transitioning between the OFF and ON states at a high frequency.
In FIG. 10, a TRIAC dimming system 200 with secondary side bleeder current operation is shown. The TRIAC dimming system 200 includes the power train 102 with the AC power source 54, the TRIAC module 56 including the input module 64 and the TRIAC(s) 66, the bridge 58, a DC-to-DC converter 60 and the SSL circuit 62. Although the DC-to-DC converter 60 is shown in a flyback configuration, the DC-to-DC converter 60 may be in a boost, buck, buck-boost or other suitable converter configuration. The DC-to-DC converter 60 includes the transformer T1, the first diode D1, and the second capacitance C2. The transformer T1 includes the primary coil 104 and the secondary coil 106. The transformer T1 may also include the bias coil 108, which receives secondary power from the primary coil 104. Current through the first diode D1 is designated Id1. Current through the second capacitance C2 is designated IC2. Load current through the SSL circuit 62 is designated IL.
The TRIAC dimming system 200 also includes the first capacitance C1, the first switch Q1, the sensor 70 with the first resistance R1, and the control module 74. The first capacitance C1 is connected between the DC voltage bus 68 and a second ground reference 112. The second ground reference 112 may be different and isolated from the first ground reference 110. The first switch Q1 and the sensor 70 are connected in series between the primary coil 104 and the second ground reference 112. The first switch Q1 may be controlled by a control module 202 via the first control signal PWM1. The control module 202 may include the modules of and operate similar to the control module 74, but may be configured to control bleed current drawn from the secondary coil 106 instead of the bias coil 108.
The TRIAC dimming system 200 further includes a bias module 204 and a bleeder module 206. The bias module 204 is on a load side (or low-voltage side) of the transformer T1, as the bias module 204 receives power through the transformer T1 and is not on the supply side (or high-voltage side) of the transformer T1. The bleeder module 206 is also on the load side of the transformer T1, as the bleeder module 206 receives current from the secondary coil 106.
The bias module 204 operates as a power supply and supplies power to the control module 202. The bias module 204 includes the bias coil 108, the third diode D3 and the third capacitance C3. The bias coil 108 receives power from the primary coil 104 and supplies current to the control module 202 while supplying current to the bleeder module 206. The third diode D3 prevents reverse current through the bias coil 108. The third capacitance C3 aids in maintaining a bias voltage VBIAS across the bias coil 108, which is supplied to the control module 202. The control module 202 operates based on the bias voltage VBIAS.
The bleeder module 206 diverts current from the secondary coil 106 to the first ground reference 110. The bleeder module 206 diverts current from the secondary coil 106 to the first ground reference 110 based on the second control signal PWM2 received from the control module 202. The control module 202 generates the second control signal PWM2 based on the voltage VR1 across the first resistance R1, the current Ids passing through the first resistance R1, and/or the current IL passing through the SSL circuit 62.
The bleeder module 206 includes the second diode D2, the second resistance (or bleeder resistance) R2, and the second switch Q2. The second diode D2, the second resistance (or bleeder resistance) R2, and the second switch Q2 are connected in series between (i) an output of the secondary coil 106 and the first diode D1, and (ii) the first ground reference 110. The second diode D2 prevents reverse current through the secondary coil 106. The bleeder resistance R2 is used to bleed current from the transformer T1 via the secondary coil 106 to the first ground reference 110. The second switch Q2 is used to control the bleed current through the second resistance R2 based on the second control signal PWM2.
Since the second switch Q2 receives current from the secondary coil 106 and does not share the same ground reference as the control module 74, the switch Q2 may be isolated from the control module 202 via an optocoupler 210. The optocoupler 210 may be connected between the control module 202 and the second switch Q2. The optocoupler 210 may receive a second control signal PWM2 and generate a third control signal PWM3. The second control signal PWM2 may be generated based on the current supplied to the SSL circuit 62, which is based on a dimming level of the TRIAC module 56. The dimming level of the TRIAC module 56 may be determined based on the first DC voltage of the DC voltage bus 68.
The second switch Q2 may be turned ON during deep dimming conditions, such as when a conduction angle of the TRIAC module 56 is low (less than a predetermined angle). In order to effectively bleed power to hold up the TRIAC module 56, the bleed current Id2 through the second diode D2 and the second resistance R2 may be as high as, for example, multiple amps (A). As a first example, the bleed current Id2 may be provided when, for example, the current IL is less than the current Ids. As another example, the bleed current Id2 may be provided when, for example, the current ID1 is less than the current Ids.
In FIG. 11, a TRIAC dimming system 250 incorporating a bleed coil 252 is shown. The TRIAC dimming system 250 includes the power train 102, which includes the AC power source 54, the TRIAC module 56 including the input module 64 and the TRIAC(s) 66, the bridge 58, a DC-to-DC converter 60 and the SSL circuit 62. Although the DC-to-DC converter 60 is shown in a flyback configuration, the DC-to-DC converter 60 may be in a boost, buck, buck-boost or other suitable converter configuration. The DC-to-DC converter 60 includes the transformer T1, the first diode D1, and the second capacitance C2. The transformer T1 includes the primary coil 104 and the secondary coil 106. The transformer T1 may also include the bias coil 108 and a bleed coil, which receive secondary power from the primary coil 104. Current through the first diode D1 is designated Id1. Current through the second capacitance C2 is designated IC2. Load current through the SSL circuit 62 is designated IL.
The TRIAC dimming system 250 also includes the first capacitance C1, the first switch Q1, the sensor 70 with the first resistance R1, and a control module 254. The control module 254 may include the modules of and operate similar to the control module 74, but may be configured to account for the bleed coil 252. The first capacitance C1 is connected between the DC voltage bus 68 and a second ground reference 112. The second ground reference 112 may be different and isolated from the first ground reference 110. The first switch Q1 and the sensor 70 are connected in series between the primary coil 104 and the second ground reference 112. The first switch Q1 may be controlled by the control module 74 via the first control signal PWM1.
The TRIAC dimming system 250 further includes a bias module 258 and the bleeder module 116. The bias module 258 is on a load side (or low-voltage side) of the transformer T1, as the bias module 258 receives power through the transformer T1 and is not on the supply side (or high-voltage side) of the transformer T1. The bleeder module 116 is also on the load side of the transformer T1 and receives current from the bias module. Although the bleeder module 116 is shown as being connected to and receiving current from the bias module 114, the bleeder module 116 may alternatively or additionally receive current from the secondary coil 106. An example of a bleeder module receiving current from a secondary coil of a transformer is shown in FIG. 10.
The bias module 258 operates as a power supply and supplies power to the control module 254. The bias module 258 includes the bias coil 108, the bleed coil 252, the third diode D3 and the third capacitance C3. The bias coil 108 receives power from the primary coil 104 and supplies current to the control module 254. The bleed coil 252 is in series with the bias coil 108 and receives power from the primary coil 104 while supplying current to the bleeder module 116. The bleed coil 252 may be incorporated to increase a voltage provided to the bleeder module 116 and/or to decrease current in the bias coil 108.
The bleed coil 252 may also be provided to prevent a voltage collapse at the bias coil 108. In the implementation of FIG. 10, if a sum of the current consumed by the control module 202 and the bleed current is greater than a predetermined current, then a voltage collapse may occur. By incorporating the bleed coil 252, a voltage collapse is prevented, as the control module 254 primarily receives current from the bias coil 108 and the bleeder module 116 primarily receives current from the bleed coil 252.
The third diode D3 prevents reverse current through the bias coil 108. The third capacitance C3 aids in maintaining a bias voltage across the bias coil 108, which is supplied to the control module 254. The control module 254 operates based on the bias voltage VBIAS.
The bleeder module 116 diverts current from the bias coil 108 and the bleed coil 252 to the second ground reference 112. The bleeder module 116 diverts current from the bias module 258 to the second ground reference 112 based on the second control signal PWM2 received from the control module 74. The control module 74 generates the second control signal PWM2 based on the voltage VR1 across the first resistance R1, the current Ids passing through the first resistance R1, and/or the current IL passing through the SSL circuit 62. The bleeder module 116 includes the second diode D2, the second resistance (or bleeder resistance) R2, and the second switch Q2. The second diode D2, a second resistance (or bleeder resistance) R2, and a second switch Q2 are connected in series between (i) the third diode D3 and the bias coil 108, and (ii) the second ground reference 112.
The TRIAC dimming systems disclosed herein may be operated using numerous methods, an example method is provided by the method of FIG. 12. In FIG. 12, a method of operating a TRIAC dimming system is shown. Although the following tasks are primarily described with respect to the implementations of FIGS. 2-4 and 10-11, the tasks may be easily modified to apply to other implementations of the present disclosure. The tasks may be iteratively performed. The method may begin at 300.
At 302, an AC power signal is received from a power source (e.g., the power source 54) at a TRIAC module. At 304, the TRIAC module sets a DC bus voltage VDC (e.g., voltage on DC bus 68) based a dimming level or TRIAC conduction angle of the TRIAC module. The dimming level may be adjusted, as described above. At 306, a bridge (e.g., the bridge 58) rectifies an output signal received from the TRIAC module to generate the DC bus voltage VDC.
At 308, a control module (e.g., one of the control modules 74, 202, 254) receives power from the DC bus. At 310, a transformer (e.g., the transformer T1) converts the DC bus voltage VDC to a secondary voltage via primary and secondary coils.
At 312, the control module generates the first control signal PWM1 based on the power including current and voltage received from the DC bus to transition a first switch (e.g., the first switch Q1) to an ON state. The control module transitions the first switch and the first control signal PWM1 to the ON state and/or adjusts a frequency of the first control signal PWM1 based on the DC bus voltage VDC. This provides current to the secondary coil, which provides current to a SSL circuit (e.g., the SSL circuit 62). The SSL circuit is operated based on the current and/or voltage provide via the secondary coil.
At 314, the DC bus voltage VDC may be converted to a bias voltage via a bias coil (e.g., the bias coil 108). The bias voltage is provided to the control module. At 316, a power switch over module (e.g., the power switch over module 150) switches over power for the control module from the DC bus to the bias coil. The control module then receives and operates based on power received from the bias coil instead of power received from the DC bus.
At 318, the control module may detect the DC bus voltage VDC via a resistance (e.g., the third resistance R3) connected to the DC bus. At 320, the control module generates the first control signal PWM1 to change the state and/or frequency of the first switch based on the DC bus voltage VDC and/or the dimming level. The dimming level is directly related to the DC bus voltage VDC. The control module may determine the dimming level based on the DC bus voltage VDC. The control module may change the state and/or frequency of the first switch based on conduction level requirements of lamps or LEDs of the SSL circuit.
At 322, the control module determines whether the dimming level is less than a predetermined threshold. The dimming level may be determined based on the DC bus voltage VDC. If the dimming level is less than the predetermined threshold, task 324 may be performed, otherwise task 318 may be performed.
At 324, the control module determines at least one of current passing through the primary coil (e.g., the current Ids), voltage across a first resistance or detected by a sensor (e.g., the first resistance R1 and the sensor 70), and/or a load current (e.g., the current IL). The control module may determine the current passing through the primary coil based on the dimming level, which is directly related to the voltage across the first resistance (e.g., the voltage VR1).
At 326, the control module adjusts bleed current based on at least one of the primary coil, voltage across the first resistance or detected by the sensor, and/or the load current. At 326A, the control module generates a second control signal (e.g., the control signal PWM2) to change state of a second switch (e.g., the second switch Q2). At 32681, current is bled from the primary coil via the bias coil based on the second control signal (e.g., PWM2). The control module adjusts the bleed current as drawn from the bias coil. Task 326B1 is associated with the implementation of FIG. 3. At 326B2, current is bled from the secondary coil based on the second control signal. The control module adjusts the bleed current as drawn from the secondary coil. Task 326B2 is associated with the implementation of FIG. 10. At 326B3, current is bled from the primary coil via a bleed coil (e.g., the bleed coil 252) based on the second control signal. The control module adjusts the bleed current as drawn from the bleed coil and bias coil. Task 326B3 is associated with the implementation of FIG. 11.
At 328, the control module may determine whether TRIAC(s) of the TRIAC module are in an ON state. This may be determined based on the DC bus voltage VDC. If the TRIAC(s) are ON, task 318 may be performed, otherwise the method may end at 330.
The above-described tasks are meant to be illustrative examples; the tasks may be performed sequentially, synchronously, simultaneously, continuously, during overlapping time periods or in a different order depending upon the application. Also, any of the tasks may not be performed or skipped depending on the implementation and/or sequence of events.
The above-disclosed implementations provide bleeder modules with low-voltage operation. Current is bled on the load side under deep dimming conditions. This current is reflected from the load side or secondary side of a transformer back to the primary side of the transformer, which maintains TRIAC(s) of a TRIAC dimmer in an ON state. As a result, a TRIAC dimmer for SSL applications is maintained in a state of conduction under deep dimming conditions. The TRIAC diming systems disclosed herein are compatible with existing TRIAC dimmers and aid in maintaining TRIACs of the TRIAC dimmers in an ON state during deep dimming conditions. Since the TRIAC dimming systems disclosed herein aid in maintaining a TRIAC(s) in ON states during deep dimming conditions, the TRIAC dimming systems may be implemented in SSL applications where TRIAC dimmers currently exist. For example, the TRIAC dimming systems may be implemented in a circuit of a lamp that has solid-state LEDs. The lamp may then be plugged into a circuit that has a TRIAC dimmer. The TRIAC dimming system may then be used to maintain TRIAC(s) in the TRIAC dimmer in an ON state.
The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical OR. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure.
As used herein, the term module may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC); an electronic circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor (shared, dedicated, or group) that executes code; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip. The term module may include memory (shared, dedicated, or group) that stores code executed by the processor.
The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, and/or objects. The term shared, as used above, means that some or all code from multiple modules may be executed using a single (shared) processor. In addition, some or all code from multiple modules may be stored by a single (shared) memory. The term group, as used above, means that some or all code from a single module may be executed using a group of processors. In addition, some or all code from a single module may be stored using a group of memories.
In the following description, various terms are used to describe the physical relationship between components. When a first element is referred to as being “on”, “engaged to”, “connected to”, or “coupled to” a second element, the first element may be directly on, engaged, connected, disposed, applied, or coupled to the second element, or intervening elements may be present. In contrast, when an element is referred to as being “directly on”, “directly engaged to”, “directly connected to”, or “directly coupled to” another element, there may be no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between”, “adjacent” versus “directly adjacent”, etc.).
Although the terms first, second, third, etc. may be used herein to describe various voltages, currents, coils, resistances, capacitances, signals, elements, and/or components, these items should not be limited by these terms. These terms may be only used to distinguish one item from another item. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first item discussed below could be termed a second item without departing from the teachings of the example implementations.
The apparatuses and methods described herein may be implemented by one or more computer programs executed by one or more processors. The computer programs include processor-executable instructions that are stored on a non-transitory tangible computer readable medium. The computer programs may also include stored data. Non-limiting examples of the non-transitory tangible computer readable medium are nonvolatile memory, magnetic storage, and optical storage.

## Claims

1. A system configured to provide current to power a solid-state light emitting diode in accordance with a dimming level, wherein the dimming level corresponds to an amount of light provided from the solid-state light emitting diode, the system comprising:
a transformer comprising a coil, wherein the transformer is configured to receive a first current, and wherein the coil is configured to, based on the first current, output a second current to power the solid-state light emitting diode; and
a switch configured to, based on the dimming level that corresponds to the amount of light provided from the solid-state light emitting diode, bleed a portion of the second current out of the coil to a ground reference in order to divert the portion of the second current from being supplied to the solid-state light emitting diode.

2. The system of claim 1, wherein the transformer is configured to receive the first current based on an output of a switching circuit.

3. The system of claim 1, further comprising a triode,
wherein the switch is configured to bleed the portion of the second current out of the coil to the ground reference to maintain the triode in an ON state.

4. The system of claim 1, further comprising a control module configured to generate a control signal to change a state of the switch based on a voltage, wherein the voltage is indicative of the dimming level that corresponds to the amount of light provided from the solid-state light emitting diode.

5. The system of claim 4, wherein the control module is configured to generate the control signal based on the first current.

6. The system of claim 4, wherein the control module is configured to:
determine whether the dimming level that corresponds to the amount of light provided from the solid-state light emitting diode is less than a predetermined threshold; and
generate the control signal to change the state of the switch to an ON state when the dimming level that corresponds to the amount of light provided from the solid-state light emitting diode is less than the predetermined threshold.

7. The system of claim 4, wherein the control module is configured to adjust a frequency of the control signal based on the dimming level that corresponds to the amount of light provided from the solid-state light emitting diode.

8. The system of claim 4, further comprising a second switch configured to adjust the first current,
wherein the control module is configured to generate a second control signal to change a state of the second switch based on the first current.

9. The system of claim 4, further comprising:
a second coil;
a second diode connected in series with the second coil; and
a capacitance connected in parallel with the second coil,
wherein the second coil, the second diode and the capacitance are configured to power the control module.

10. The system of claim 1, wherein:
the coil is a first coil; and
the transformer comprises
a second coil configured to receive the first current based on an output of a switching circuit, and
a third coil configured to output a third current based on the first current.

11. The system of claim 10, further comprising:
a first module configured to, based on a voltage, generate a first control signal to change a state of the switch, wherein the voltage is indicative of the dimming level that corresponds to the amount of light provided from the solid-state light emitting diode; and
a second module, wherein the second module comprises
a second diode configured to receive the portion of the second current from the first coil, and
a resistance connected in series with the second diode and the switch, wherein the resistance is configured to receive the portion of the second current from the second diode.

12. The system of claim 1, further comprising a module configured to:
determine a load current of the solid-state light emitting diode based on the first current or a voltage received by the transformer; and
based on the load current, generate a control signal to change a state of the switch.

13. The system of claim 1, further comprising:
a second diode connected in series with the coil; and
a capacitance connected in parallel with the solid-state light emitting diode.

14. The system of claim 1, further comprising:
a second switch connected in series with a second coil,
wherein the transformer comprises the second coil; and
a control module configured to generate a control signal to change a state of the second switch.

15. The system of claim 1, further comprising:
a dimmer configured to receive an alternating current;
a bridge configured to rectify the alternating current;
a capacitance connected to an output of the bridge;
a resistance connected to an output of the bridge; and
a module configured to detect a voltage at the resistance and change a state of the switch based on the voltage.

16. A system configured to provide current to power a solid-state light emitting diode in accordance with a dimming level, wherein the dimming level corresponds to an amount of light provided from the solid-state light emitting diode, the system comprising:
a transformer comprising a coil, wherein the transformer is configured to receive a first current and, based on the first current, output a second current to power the solid-state light emitting diode, and wherein the coil is configured to output a third current based on the first current; and
a switch configured to, based on the dimming level that corresponds to the amount of light provided from the solid-state light emitting diode, bleed a portion of the third current out of the coil to a ground reference.

17. The system of claim 16, further comprising a triode,
wherein the switch is configured to bleed the portion of the third current out of the coil to the ground reference to maintain the triode in an ON state.

18. The system of claim 16, further comprising:
a first module configured to control a state of the switch; and
a second module comprising
a second diode connected in series with the coil, and
a capacitance connected in parallel with a combination of the second diode and the coil.

19. The system of claim 18, further comprising a third module comprising:
the switch; and
a resistance connected in series with the switch.

20. The system of claim 19, further comprising a third diode connected in series with the coil, the resistance and the switch.

21. The system of claim 16, further comprising:
a first module configured to control a state of the switch;
a second module comprising a capacitance connected in parallel with the coil; and
a third module comprising
a second diode connected in series with the coil,
a resistance connected in series with the second diode, and
the switch connected in series with the resistance.

22. The system of claim 16, further comprising:
a first module configured to control a state of the switch;
a second module comprising a capacitance connected in parallel with the coil; and
a third module comprising
a second coil configured to output a fourth current based on the first current,
a second diode connected in series with the second coil,
a resistance connected in series with the second diode, and
the switch connected in series with the resistance.

23. The system of claim 16, further comprising a module configured to:
determine whether the dimming level that corresponds to the amount of light provided from the solid-state light emitting diode is less than a predetermined threshold; and
generate a control signal to change the state of the switch to an ON state when the dimming level that corresponds to the amount of light provided from the solid-state light emitting diode is less than the predetermined threshold.

24. The system of claim 16, further comprising a control module configured to generate a control signal to change a state of the switch, wherein the control module is configured to adjust a frequency of the control signal based on the dimming level that corresponds to the amount of light provided from the solid-state light emitting diode.

25. The system of claim 16, further comprising a module configured to:
determine a load current of the solid-state light emitting diode based on the first current or a voltage received by the transformer; and
based on the load current, generate a control signal to change a state of the switch.

26. The system of claim 16, further comprising:
a second diode connected to the transformer; and
a capacitance connected in parallel with the solid-state light emitting diode.

27. The system of claim 16, further comprising:
a second switch connected in series with a second coil,
wherein the transformer comprises the second coil; and
a control module configured to generate a control signal to change a state of the second switch.

28. The system of claim 16, further comprising:
a dimmer configured to receive an alternating current;
a bridge configured to rectify the alternating current;
a capacitance connected to an output of the bridge;
a resistance connected to an output of the bridge; and
a module configured to detect a voltage at the resistance and change a state of the switch based on the voltage.

29. A system configured to provide current to power a solid-state light emitting diode in accordance with a dimming level, wherein the dimming level corresponds to an amount of light provided from the solid-state light emitting diode, the system comprising:
a transformer comprising a first coil, a second coil, and a third coil, wherein the first coil is configured to receive a first current or a voltage, wherein the second coil is configured to, based on the first current or the voltage, output a second current to power the solid-state light emitting diode, and wherein the third coil is configured to output a third current based on the first current or the voltage;
a resistance;
a switch connected in series with the resistance, wherein the switch is configured to, based on the first current or the voltage, bleed a portion of the third current out of the third coil to a ground reference via the resistance; and
a capacitance connected in parallel with a combination of the resistance and the switch.

30. The system of claim 29, further comprising a second diode connected between the third coil and the capacitance.

31. The system of claim 29, further comprising a second diode connected between the third coil and the resistance.

32. The system of claim 29, further comprising a control module configured to receive a second portion of the third current out of the third coil and control operation of the switch.

33. The system of claim 32, wherein:
the control module is configured to control operation of the switch based on the first current or a voltage; and
the voltage is generated based on the first current.

34. The system of claim 29, further comprising a second switch configured to adjust the first current.

35. The system of claim 34, further comprising a control module configured to control operation of the second switch.

36. A system configured to provide current to power a solid-state light emitting diode in accordance with a dimming level, wherein the dimming level corresponds to an amount of light provided from the solid-state light emitting diode, the system comprising:
a transformer configured to receive a voltage, wherein the voltage is based on a state of a dimmer, wherein the transformer comprises a primary coil and a secondary coil, wherein the secondary coil is configured to, based on the voltage, output a first current, and wherein a first portion of the first current is received by the solid-state light emitting diode;
a bleeder module comprising
a switch connected in series with the secondary coil,
a second diode connected to the secondary coil, and
a resistance connected in series with the second diode,
wherein the resistance is configured to forward a second portion of the first current from the second diode to the switch; and

a second module configured to, based on the voltage, change a state of the switch to bleed the second portion of the first current to a reference terminal.

37. The system of claim 36, further comprising a third coil,
wherein the second module is configured to receive power from the third coil.

38. The system of claim 37, wherein the module is configured to switch between receiving power from a direct current bus to receiving the power from the third coil.

39. The system of claim 36, wherein the secondary coil is in series with the solid-state light emitting diode.

40. The system of claim 36, further comprising:
a third coil configured to output a second current,
wherein the transformer comprises the third coil, and
wherein the secondary coil and the third coil are configured to receive power from the primary coil; and
a third diode configured to receive the second current from the third coil,
wherein the second module is configured to receive a portion of the second current from the third diode.

41. A system configured to provide current to power a solid-state light emitting diode in accordance with a dimming level, wherein the dimming level corresponds to an amount of light provided from the solid-state light emitting diode, the system comprising:
a transformer configured to receive a voltage, wherein the voltage is based on a state of a dimmer, wherein based on the voltage, the transformer is configured to output a first current to the solid-state light emitting diode, wherein the transformer comprises a secondary coil, and wherein the secondary coil is configured to, based on the voltage, output a second current;
a switch connected in series with the secondary coil; and
a module configured to, based on the voltage, change a state of the switch to bleed to a reference terminal a portion of the second current.

42. The system of claim 41, wherein the module is configured to switch between receiving power from a direct current bus to receiving the power from the secondary coil.