SOLID STATE LIGHTING CONTROL

• US 20150035450A1
• Filed: 07/24/2014
• Published: 02/05/2015
• Est. Priority Date: 08/01/2013
• Status: Active Grant

• Current Assignee: Power Integrations Incorporated
• Original Assignee: Cambridge Semiconductor Limited (Power Integrations Incorporated)
• Inventors: Werner, Antonius Jacobus Johannes
• Granted Patent: US 10,149,362 B2
• Time in Patent Office: Days
• US Class Current: 315/291
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/385 using flyback topology
• CPC Class Codes: H05B 47/17 Operational modes, e.g. switching from manual to automatic mode or prohibiting specific operations
• 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: Y10S 362/80 Light emitting diode

Abstract

This invention generally relates to solid state lighting control, and more particularly to a dimmer interface circuit and a method for reducing ringing on a drive signal to a solid state lighting device. An embodiment is a dimmer interface circuit for controlling brightness of a solid state light emission device, the interface circuit having an input to receive a brightness control voltage from a dimmer circuit and comprising: a voltage converter to provide a converter output voltage and having an inductive component and a charge store, the charge store controllably coupled to receive charge from the inductive component to thereby convert the brightness control voltage to the converter output voltage; and control circuitry comprising: an input to receive a voltage level indication of the brightness control voltage; an input to receive a voltage level indication of the converter output voltage; a comparison circuit to compare a said received brightness control voltage level indication and a said received converter output voltage level indication; and a transition detector to detect a transition of the brightness control voltage, said transition for turning a said solid state light emission device on, wherein the control circuitry is configured to control the voltage converter dependent on a said comparison of said level indications received at a time of a said transition in a first cycle of the brightness control voltage, such that a difference between the brightness control voltage and the converter output voltage at a time of a said transition in a second, later said cycle is closer to a target voltage difference or target voltage difference range than a said difference at the time of the transition in the first cycle.

Claims

1. Dimmer interface circuit for controlling brightness of a solid state light emission device, the interface circuit having an input to receive a brightness control voltage from a dimmer circuit and comprising:

a voltage converter to provide a converter output voltage and having an inductive component and a charge store, the charge store controllably coupled to receive charge from the inductive component to thereby convert the brightness control voltage to the converter output voltage; and

control circuitry comprising;

an input to receive a voltage level indication of the brightness control voltage;

an input to receive a voltage level indication of the converter output voltage;

a comparison circuit to compare a said received brightness control voltage level indication and a said received converter output voltage level indication; and

a transition detector to detect a transition of the brightness control voltage, said transition for turning a said solid state light emission device on,

wherein the control circuitry is configured to control the voltage converter dependent on a said comparison of said level indications received at a time of a said transition in a first cycle of the brightness control voltage, such that a difference between the brightness control voltage and the converter output voltage at a time of a said transition in a second, later said cycle is closer to a target voltage difference than a said difference at the time of the transition in the first cycle.

2. Dimmer interface circuit of claim 1, comprising voltage clamp circuitry to clamp the brightness control voltage relative to the converter output voltage and to conduct to the charge store current received from the input to receive the brightness control voltage.

3. Dimmer interface circuit of claim 1, wherein the comparison circuit is configured to perform a said comparison to indicate a difference between the level indications received at the time of the transition in the first cycle, and the control circuitry is configured to perform the converter control dependent on the indicated difference.

4. Dimmer interface circuit of claim 1, the control circuitry configured to control an amount of charge delivered to the charge store from the inductive component during a said cycle of the brightness control voltage, to thereby perform said converter output voltage control.

5. Dimmer interface circuit of claim 4, comprising a switch to provide said controllable coupling, the control circuitry configured to control at least one switching cycle of the switch to thereby control the amount of charge.

6. Dimmer interface circuit of claim 5, the control circuit configured to control a plurality of switching cycles of the switch to control an average current received by the charge store from the inductive component, to thereby control said amount of charge.

7. Dimmer interface circuit of claim 4, the transition detector configured to trigger the charge delivery to the charge store.

8. Dimmer interface circuit of claim 4, configured to control a duration of the charge delivery, to thereby perform the controlling the amount of charge.

9. Dimmer interface circuit of claim 8, comprising a timing circuit configured to end the charge delivery when the duration elapses, the timing circuit configured to indicate a zero crossing of a mains voltage based on the brightness control voltage and to time the duration from said zero crossing indication.

10. Dimmer interface circuit of claim 4, configured to control the charge delivery such that a said duration of the charge delivery extends through a peak of the brightness control voltage.

11. Dimmer interface circuit of claim 4, configured to deliver a first average current followed a second lower average current to the charge store to thereby deliver the amount of charge.

12. Dimmer interface circuit of claim 1, configured to control a peak voltage of the converter output voltage to thereby perform said converter output voltage control.

13. Dimmer interface circuit of claim 1, wherein the charge store comprises a non-electrolytic capacitor.

14. Dimmer interface circuit of claim 1, comprising a voltage indicator circuit to indicate a value of a mains voltage at a said transition, the control circuitry configured to control the target voltage difference based on the indicated value of the mains voltage.

15. A solid state lighting device driver comprising a dimmer circuit and a dimmer interface circuit of claim 1, the dimmer circuit comprising a triac and operable to control a phase angle of switching of the triac to thereby control the brightness control voltage.

16. A solid state lighting device driver comprising a dimmer interface circuit of claim 1 and an output stage for driving a solid state light emission device, the dimmer interface circuit coupled to provide the converter output voltage to the output stage, the output stage having a power controller configured to reduce a power consumption of the output stage in response to the converter output voltage falling below a threshold voltage.

17. A solid state lighting device driver comprising a dimmer interface circuit of claim 1 and an output stage for driving a solid state light emission device, the dimmer interface circuit coupled to provide the converter output voltage to the output stage, the output stage configured to shunt charge from the charge store dependent on a dimming angle indicated by the brightness control voltage, the shunting to reduce the converter output voltage.

18. Method for reducing ringing on a drive signal to a solid state lighting device, the method comprising:

controlling a phase angle of switching of a triac of an AC dimmer circuit to thereby provide a brightness control signal for determining brightness of the lighting device;

detecting a transition of the brightness control voltage in a first cycle of the brightness control signal, said transition for turning a said solid state light emission device on;

comparing a level of the brightness control signal and a level of the output voltage of the converter, the brightness control and output control voltages having the levels at a time of a said detected transition;

regulating a boost converter output voltage such that a difference between the brightness control and output control voltages at the time of a said transition occurring during a later cycle of the brightness control signal is closer to to a target voltage difference than a said difference detected in a earlier cycle comprising the detected transition;

using the converter output signal to drive the lighting device.

19. Method of claim 18, comprising determining the target voltage difference on the basis of at least one of:

an indication of a mains voltage at the time of a said detected transition;

a capacitance value of the charge store;

a rated power of an LED driver coupled to an output of the boost converter.

20. Method of claim 18, wherein the target voltage difference is between 30V and 80V, preferably at least 50V.

21. Dimmer interface circuit for controlling brightness of a solid state light emission device, the interface circuit having an input to receive a brightness control voltage from a dimmer circuit and comprising:

a voltage converter to provide a converter output voltage and having an inductive component and a charge store, the charge store controllably coupled to receive charge from the inductive component to thereby convert the brightness control voltage to the converter output voltage; and

control circuitry comprising;

an input to receive a voltage level indication of the brightness control voltage;

an input to receive a voltage level indication of the converter output voltage;

a comparison circuit to compare a said received brightness control voltage level indication and a said received converter output voltage level indication; and

a transition detector to detect a transition of the brightness control voltage, said transition for turning a said solid state light emission device on,

wherein the control circuitry is configured to control the voltage converter dependent on a said comparison of said level indications received at a time of a said transition in a first cycle of the brightness control voltage, to provide a difference between the brightness control voltage and the converter output voltage at a time of a said transition in a second, later said cycle within a target voltage difference range.