Adaptive dimmer detection and control for LED lamp

• US 8,970,135 B2
• Filed: 12/19/2013
• Issued: 03/03/2015
• Est. Priority Date: 07/14/2009
• Status: Active Grant

• Current Assignee: Dialog Semiconductor Incorporated (Renesas Electronics Corporation)
• Original Assignee: Dialog Semiconductor Incorporated (Renesas Electronics Corporation)
• Inventors: Zheng, Junjie, Kesterson, John W., Myers, Richard M., Chen, Baorong, Chen, Gordon
• Primary Examiner(s): VU, JIMMY T
• Application Number:
  US14/135,039
• Publication Number:
  US 20140103838A1
• Time in Patent Office: 439 Days
• Field of Search: 315/185.R, 315/209.R, 315/224, 315/225, 315/291, 315/307, 315/308, 315/312
• US Class Current: 315/308
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/4225 using a non-isolated boost converter
• CPC Class Codes: H02M 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/385 using flyback topology
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

An LED lamp is provided in which the output light intensity of the LEDs in the LED lamp is adjusted based on the input voltage to the LED lamp. A dimmer control unit detects a type of dimmer switch during a configuration process. Using the detected dimmer type, the dimmer control unit generates control signals appropriate for the detected dimmer type to provide regulated current to the LEDs and to achieve the desired dimming effect. The LED lamp can be a direct replacement of conventional incandescent lamps in typical wiring configurations found in residential and commercial building lighting applications that use conventional dimmer switches.

Claims

1. A light-emitting diode (LED) lamp controller for a switching power converter LED lamp comprising a transformer, a primary side switch coupled to a primary side of the transformer, and one or more LEDs coupled to a secondary side of the transformer, the LED lamp controller comprising:

a dimmer control unit to detect a dimming amount of an input voltage from a dimmer switch, and to generate a dimming control signal representative of the detected dimming amount;

a switch controller to receive the dimming control signal, a current sense signal representing a current through a primary side winding of the transformer, and a voltage sense signal sensed on the primary side of the transformer, the switch controller to determine a reset time of the transformer based on the voltage sense signal, and control switching of the primary side switch based on the dimming control signal, the current sense signal, and the reset time to regulate a current through the one or more LEDs such that the one or more LEDs achieve a dimming level corresponding to the detected dimming amount.

2. The LED lamp controller of claim 1, wherein the voltage sense signal is based on a voltage across an auxiliary winding on the primary side of the transformer.

3. The LED lamp controller of claim 1, wherein the reset time is based on a time between when the primary side switch turns off and a falling edge of the voltage sense signal.

4. The LED lamp controller of claim 1, wherein the switch controller is configured to turn the primary side switch off when the sensed current signal exceeds a threshold value, and to adjust the threshold value in inverse proportion to the reset time of a prior cycle of the primary side switch.

5. The LED lamp controller of claim 1, wherein the switch controller is configured to sample the voltage sense signal at an end of each switching cycle of the primary side switch.

6. The LED lamp controller of claim 1, wherein the switch controller comprises a constant current controller to maintain substantially constant current through the one or more LEDs when the detected dimming amount is constant.

7. The LED lamp controller of claim 1, wherein the dimming control signal is indicative of a duty cycle for switching between operating states of the switch controller including a first state and second state, wherein the switch controller controls switching of the primary side switch to turn the one or more LEDs on when operating in the first state, and wherein switch controller controls switching of the primary side switch to turn the one or more LEDs off when operating in the second state, such that an average output of the LEDs corresponds to the detected dimming amount.

8. The LED lamp controller of claim 1, wherein the dimming control signal is indicative of an amplitude dimming amount, wherein the switch controller controls switching of the primary side switch to control an amplitude of an output current through the one or more LEDs based on the amplitude dimming amount.

9. The LED lamp controller of claim 1, wherein the dimmer control unit comprises:

a phase detector to receive the input voltage and determine a detected phase angle modulation of the input voltage representative of the detected dimming amount by comparing the input voltage to one or more threshold voltages; and

a dimming controller configured to generate the dimming control signal using the detected amount of phase angle modulation.

10. The LED lamp controller of claim 1, wherein the phase detector comprises:

a comparator for comparing the input voltage to a leading threshold to determine a start of a detected on-time, and for comparing the input voltage to a trailing threshold to determine an end of the detected on-time, wherein the amount of phase angle modulation is determined from the detected on-time.

11. A method for controlling dimming of one or more light-emitting diodes (LEDs) in a switching power converter comprising a transformer and a primary side switch coupled to a primary side of the transformer, the method comprising:

receiving an input voltage from a dimmer switch;

detecting a dimming amount of the input voltage;

generating a dimming control signal representative of the detected dimming amount;

determine a reset time of the transformer based on a voltage sense signal sensed on the primary side of the transformer;

controlling, by a switch controller, switching of the primary side switch based on the dimming control signal, the reset time, and a current sense signal representing a current through a primary side winding of the transformer, the switching to regulate current through the one or more LEDs such that the one or more LEDs achieve a dimming level corresponding to the detected dimming amount.

12. The method of claim 11, further comprising:

sensing the voltage sense signal based on a voltage across an auxiliary winding on the primary side of the transformer.

13. The method of claim 11, wherein

the reset time is based on a time between when the primary side switch turns off and a falling edge of the voltage sense signal.

14. The method of claim 11, wherein controlling switching of the primary side switch based on the dimming control signal, the reset time, and the current sense signal comprises:

turning the primary side switch off when the current sense signal exceeds a threshold value; and

adjusting the threshold value in inverse proportion to the reset time of a prior cycle of the primary side switch.

15. The method of claim 11, further comprising:

sampling the voltage sense signal at an end of each switching cycle of the primary side switch.

16. The method of claim 11, wherein the dimming control signal is indicative of a duty cycle for switching between operating states of the switch controller including a first state and second state such that an average output of the LEDs corresponds to the detected dimming amount, and wherein controlling switching of the primary side switch comprises:

controlling switching of the primary side switch to turn the one or more LEDs on when the switch controller is operating in the first state; and

controlling switching of the primary side switch to turn the one or more LEDs off when the switch controller is operating in the second state.

17. The method of claim 11, wherein the dimming control signal is indicative of an amplitude dimming amount, and wherein controlling switching of the primary side switch comprises:

controlling switching of the primary side switch to control an amplitude of output current through the one or more LEDs based on the amplitude dimming amount.

18. The method of claim 11, wherein generating the dimming control signal representative of the detected dimming amount comprises:

determining a detected phase angle modulation of the input voltage representative of the detected dimming amount by comparing the input voltage to one or more threshold voltages; and

generating the dimming control signal using the detected amount of phase angle modulation.

19. A light-emitting diode (LED) lamp comprising:

a transformer;

a primary side switch coupled to a primary side of the transformer;

one or more LEDs coupled to a secondary side of the transformer;

a dimmer control unit to detect a dimming amount of an input voltage from a dimmer switch, and to generate a dimming control signal representative of the detected dimming amount;

a switch controller to receive the dimming control signal, a current sense signal representing a current through a primary side winding of the transformer, and a voltage sense signal sensed on the primary side of the transformer, the switch controller to determine a reset time of the transformer based on the voltage sense signal, and control switching of the primary side switch based on the dimming control signal, the current sense signal, and the reset time to control a regulated current through the one or more LEDs such that the one or more LEDs achieve a dimming level corresponding to the detected dimming amount.

20. The LED lamp of claim 19, wherein the dimmer control unit comprises:

a phase detector to receive the input voltage and determine a detected phase angle modulation of the input voltage representative of the detected dimming amount by comparing the input voltage to one or more threshold voltages; and

a dimming controller configured to generate the dimming control signal using the detected amount of phase angle modulation.