Driving circuit with dimming controller for driving light sources

Patent metadata

Field	Value
Publication number	US-9253843-B2
Application number	US-201414509711-A
Country	US
Kind code	B2
Filing date	Oct 8, 2014
Priority date	Dec 12, 2008
Publication date	Feb 2, 2016
Grant date	Feb 2, 2016

Abstract

A driving circuit includes a power converter, a dimming controller and a current path coupled to the dimming controller. The power converter receives input power from a rectifier and provides output power to a light source. A power switch transfers power from an AC power source to the rectifier when the power switch is on. The dimming controller receives a switch monitoring signal indicative of the state of the power switch. An average current flowing through the light source has a first value if the power switch is on. The dimming controller is operable for adjusting the average current based on the switch monitoring signal. A current flows from the AC power source through the current path to ground when the power switch is off.

First claim

What is claimed is:

1. A dimming controller for a light source, said dimming controller comprising:
a monitoring terminal operable for receiving a switch monitoring signal indicative of an on/off state of a power switch, wherein said power switch transfers power from an AC power source to a rectifier and wherein a power converter receives input power from said rectifier and provides output power to said light source if said power switch is on, and wherein an average current flowing through said light source has a first value when said power switch is on;
a control terminal operable for providing a control signal to adjust said average current based on said switch monitoring signal and control dimming of said light source;
a power terminal operable for receiving power from said AC power source through said power switch when said power switch is on, and operable for receiving power from said AC power source through an illuminated indicator when said power switch is off;
a trigger monitoring unit operable for receiving said switch monitoring signal and for generating a driving signal in response to operation of said power switch;
a timer, coupled to said trigger monitoring unit and controlled by said driving signal, operable for measuring the period of time between when said power switch is turned off and when said power switch is next turned on; and
a reference signal generator coupled to said timer and operable for generating a reference signal based on an output of said timer.

2. The dimming controller of claim 1 , wherein said control terminal is operable for providing said control signal to adjust said average current from said first value to a second value if said switch monitoring signal indicates that said power switch is turned on within a predetermined time period after said power switch was turned off.

3. The dimming controller of claim 1 , wherein said control terminal is operable for providing said control signal to maintain said average current at said first value if said switch monitoring signal indicates that said power switch is turned on after expiration of a predetermined time period that began when said power switch was turned off.

4. The dimming controller of claim 1 , wherein said reference signal generator is operable for adjusting said reference signal from a first level to a second level if said period of time is less than a predetermined time period, and wherein said reference signal generator is operable for maintaining said reference signal at said first level if said period of time is greater than a predetermined time period.

5. The dimming controller of claim 1 , further comprising:
an amplifier operable for generating an error signal by comparing said reference signal and a sensing signal indicating said average current flowing through said light source,
wherein said control signal is determined based on said error signal.

6. The dimming controller of claim 5 , further comprising:
a current monitoring terminal operable for receiving a current monitoring signal indicating a current flowing through said light source; and
a filter coupled to said current monitoring terminal and operable for generating said sensing signal based on said current monitoring signal.

7. A driving circuit comprising:
a power converter operable for receiving input power from a rectifier and providing output power to a light source, wherein a power switch transfers power from an AC power source to said rectifier when said power switch is on;
a dimming controller, coupled to said power converter, and operable for receiving a switch monitoring signal indicative of an on/off state of said power switch, wherein an average current flowing through said light source has a first value if said power switch is on, and wherein said dimming controller is operable for adjusting said average current based on said switch monitoring signal and controlling dimming of said light source;
a current path coupled to said dimming controller, wherein a current flows from said AC power source through said current path to ground when said power switch is off;
a trigger monitoring unit operable for receiving said switch monitoring signal and for generating a driving signal in response to operation of said power switch;
a timer, coupled to said trigger monitoring unit and controlled by said driving signal, operable for measuring the period of time between when said power switch is turned off and when said power switch is next turned on; and
a reference signal generator coupled to said timer and operable for generating a reference signal based on an output of said timer.

8. The driving circuit of claim 7 , further comprising:
a control switch coupled to said light source,
wherein said dimming controller is operable for adjusting said average current flowing through said light source by controlling said control switch according to said switch monitoring signal, and wherein said dimming controller is operable for adjusting said average current from said first value to a second value if said switch monitoring signal indicates that said power switch is turned on within a predetermined time period after said power switch was turned off.

9. The driving circuit of claim 7 , further comprising:
a control switch coupled to said light source,
wherein said dimming controller is operable for adjusting said average current flowing through said light source by controlling said control switch according to said switch monitoring signal, and wherein said dimming controller is operable for maintaining said average current at said first value if said switch monitoring signal indicates that said power switch is turned on after expiration of a predetermined time period that began when said power switch was turned off.

10. The driving circuit of claim 7 , wherein said reference signal generator is operable for adjusting said reference signal from a first level to a second level if said period of time is less than a predetermined time period, and wherein said reference signal generator is operable for maintaining said reference signal at said first level if said period of time is greater than a predetermined time period.

11. The driving circuit of claim 7 , wherein said dimming controller further comprises:
an amplifier operable for generating an error signal by comparing said reference signal and a sensing signal indicating said average current flowing through said light source,
wherein said control signal is determined based on said error signal.

12. The driving circuit of claim 11 , further comprising:
a current sensor operable for providing a current monitoring signal indicating a current flowing through said light source; and
a filter coupled to said current sensor and operable for generating said sensing signal based on said current monitoring signal.

Assignees

• O2Micro Inc
• 02Micro Inc

Inventors

• Lee Sheng-Tai
• Kuo Ching-Chuan
• Lin Yung-Lin

Classifications

• H05B45/14

  using electrical feedback from LEDs or from LED modules · CPC title

• H05B45/395 Primary

  Linear regulators · CPC title

• H05B33/0812

  Electricity · mapped topic

• H05B33/0848

  Electricity · mapped topic

• H05B33/0818

  Electricity · mapped topic