Solid-state lighting with a driver controllable by a power-line dimmer
An LED luminaire comprises LED arrays, a full-wave rectifier, an LED driving circuit, and electric current bypass circuit(s). The full-wave rectifier is coupled to an external power-line dimmer which is coupled to the AC mains and configured to convert a phase-cut line voltage into a first DC voltage. With the electric current bypass circuit(s) to partially provide a holding current path to cause the external power-line dimmer to sustain a dimming function, the LED driving circuit can provide a second DC voltage with various driving currents according to various input power levels to drive LED arrays without flickering. By adapting switching frequencies and a duty cycle, the LED driving circuit can regulate the second DC voltage to reach a voltage level equal to or greater than a forward voltage of the LED arrays no matter whether the first DC voltage is higher or lower than the second DC voltage.
1. A light-emitting diode (LED) luminaire, comprising:
one or more LED arrays comprising a positive potential terminal and a negative potential terminal with a forward voltage across thereon;
at least one full-wave rectifier comprising a ground reference, the at least one full-wave rectifier configured to couple to an external power-line dimmer which is coupled to alternate-current (AC) mains and to convert a phase-cut line voltage from the external power-line dimmer into a first direct-current (DC) voltage;
at least one input filter coupled to the at least one full-wave rectifier and configured to suppress an electromagnetic interference (EMI) noise;
an LED driving circuit comprising a control device with a DC voltage input port, an electronic switch with on-time and off-time controlled by the control device, an output inductor with current charging and discharging controlled by the electronic switch, an output capacitor coupled to the output inductor, a diode coupled between the electronic switch and the output capacitor, and at least one current sensing resistor, wherein the LED driving circuit is coupled to the at least one full-wave rectifier via the at least one input filter and configured to convert the first DC voltage into a second DC voltage with an LED driving current to drive the one or more LED arrays; and
at least one electric current bypass circuit comprising a first resistor and a first capacitor connected in series with the first resistor, the at least one electric current bypass circuit coupled to the at least one input filter and configured to provide a first holding current path to cause the external power-line dimmer to sustain a dimming function when controlling the LED driving current,
wherein:
the electronic switch is configured to modulate the first DC voltage at a switching frequency controlled by the control device;
the second DC voltage has a reverse polarity relative to the first DC voltage; and
the LED driving circuit is further configured to provide various LED driving currents to drive the one or more LED arrays according to various input power levels of the phase-cut line voltage.
2. The LED luminaire of claim 1 , wherein the at least one input filter comprises an input capacitor and a filter assembly, the filter assembly comprising one or more combinations of an input inductor and a second capacitor, the filter assembly configured to reduce an initial current surge and to improve compatibility between the external power-line dimmer and the LED driving circuit.
3. The LED luminaire of claim 1 , wherein the LED driving circuit further comprises a second resistor and a third capacitor connected in series with the second resistor, the second resistor and the third capacitor configured to provide a second holding current path to cause the external power-line dimmer to sustain the dimming function when controlling the LED driving current.
4. The LED luminaire of claim 3 , wherein the second resistor is configured to couple to the positive potential terminal, wherein the third capacitor is configured to couple to the DC voltage input port with respect to the ground reference, and wherein the LED driving circuit is enabled when a voltage across the third capacitor reaches an operating voltage of the control device.
5. The LED luminaire of claim 3 , wherein the LED driving circuit further comprises an output resistor coupled in parallel with the output capacitor, the output resistor and the output capacitor configured to build up the second DC voltage, and wherein the output resistor is configured to supply the first DC voltage to the control device via the second resistor and to start up the control device.
6. The LED luminaire of claim 1 , wherein the LED driving circuit further comprises a transistor circuit coupled to the positive potential terminal and configured to draw partial energy from the second DC voltage to operate the control device.
7. The LED luminaire of claim 6 , wherein the transistor circuit comprises a transistor and a voltage regulator coupled to the transistor, and wherein the transistor is turned on when the second DC voltage reaches a predetermined level set by the voltage regulator.
8. The LED luminaire of claim 7 , wherein the transistor circuit further comprises one or more resistors connected in series, wherein the one or more resistors are configured to create a voltage bias to operate the transistor and to set up a voltage for the transistor to launch into the DC voltage input port, and wherein the transistor circuit is further configured to provide a third holding current path to cause the external power-line dimmer to sustain the dimming function when controlling the LED driving current to operate the one or more LED arrays.
9. The LED luminaire of claim 1 , wherein the output inductor is further configured to be charged over the on-time and discharged over the off-time, and wherein a part of an average current from the output inductor yields to the LED driving current to drive the one or more LED arrays.
10. The LED luminaire of claim 9 , wherein, responsive to detecting zero current in the output inductor, the control device is configured to generate a zero current detection signal to control the electronic switch on and off with a duty cycle controlling the second DC voltage and the LED driving current to drive the one or more LED arrays.
11. The LED luminaire of claim 10 , wherein the duty cycle is configured to regulate the second DC voltage to reach a voltage level equal to or greater than the forward voltage no matter whether the first DC voltage is higher or lower than the second DC voltage.
12. The LED luminaire of claim 1 , further comprising the external power-line dimmer which comprises a triode for alternating current (TRIAC) dimmer or a silicon controlled rectifier (SCR) dimmer.
13. A light-emitting diode (LED) luminaire, comprising:
one or more LED arrays comprising a positive potential terminal and a negative potential terminal with a forward voltage across thereon;
at least one full-wave rectifier comprising a ground reference, the at least one full-wave rectifier configured to couple to an external power-line dimmer which is coupled to alternate-current (AC) mains and to convert a phase-cut line voltage from the external power-line dimmer into a first direct-current (DC) voltage;
at least one input filter coupled to the at least one full-wave rectifier and configured to suppress an electromagnetic interference (EMI) noise;
an LED driving circuit comprising a control device with a DC voltage input port, an electronic switch with on-time and off-time controlled by the control device, a transformer comprising a primary winding and a secondary winding, an output capacitor coupled to the secondary winding, a first diode coupled between the secondary winding and the output capacitor, and at least one current sensing resistor, wherein the LED driving circuit is coupled to the at least one full-wave rectifier via the at least one input filter and configured to convert the first DC voltage into a second DC voltage with an LED driving current to drive the one or more LED arrays, and wherein the primary winding is coupled to the electronic switch with current charging and discharging controlled by the electronic switch;
at least one electric current bypass circuit comprising a first resistor and a first capacitor connected in series with the first resistor, the at least one electric current bypass circuit coupled in parallel with the at least one input filter and configured to provide a first holding current path to cause the external power-line dimmer to sustain a dimming function when controlling the LED driving current,
wherein:
the electronic switch is configured to modulate the first DC voltage at a switching frequency controlled by the control device;
the second DC voltage has a reverse polarity relative to the first DC voltage; and
the LED driving circuit is further configured to provide various LED driving currents to drive the one or more LED arrays according to various input power levels of the phase-cut line voltage.
14. The LED luminaire of claim 13 , wherein the at least one input filter comprises an input capacitor and a filter assembly, the filter assembly comprising one or more combinations of an input inductor and a second capacitor, the filter assembly configured to reduce an initial current surge and to improve compatibility between the external power-line dimmer and the LED driving circuit.
15. The LED luminaire of claim 13 , wherein the LED driving circuit further comprises a second resistor and a third capacitor connected in series with the second resistor, the second resistor and the third capacitor configured to provide a second holding current path to cause the external power-line dimmer to sustain the dimming function when controlling the LED driving current.
16. The LED luminaire of claim 15 , wherein the second resistor is configured to couple to the first DC voltage, wherein the third capacitor is configured to couple to the DC voltage input port with respect to the ground reference, and wherein the LED driving circuit is enabled when a voltage across the third capacitor reaches an operating voltage of the control device.
17. The LED luminaire of claim 13 , wherein the primary winding is further configured to be charged over the on-time and discharged over the off-time, and wherein a part of an average current flowing through the primary winding yields to the LED driving current induced in the secondary winding to drive the one or more LED arrays.
18. The LED luminaire of claim 17 , wherein, responsive to detecting zero current in the primary winding, the control device is configured to generate a zero current detection signal to control the electronic switch on and off with a duty cycle controlling the second DC voltage and the LED driving current to drive the one or more LED arrays.
19. The LED luminaire of claim 18 , wherein the duty cycle is configured to regulate the second DC voltage to reach a voltage level equal to or greater than the forward voltage no matter whether the first DC voltage is higher or lower than the second DC voltage.
20. The LED luminaire of claim 13 , wherein the transformer further comprises an auxiliary winding, wherein the LED driving circuit further comprises a second diode and a third diode coupled to the second diode, and wherein the second diode is coupled to the auxiliary winding and configured to draw partial energy from the auxiliary winding and to deliver the partial energy to the control device via the third diode to operate the control device.
21. The LED luminaire of claim 13 , further comprising the external power-line dimmer which comprises a triode for alternating current (TRIAC) dimmer or a silicon controlled rectifier (SCR) dimmer.