EP2498579A2 - Steuerungen, Systeme und Verfahren zur Steuerung der Dämpfung einer Lichtquelle - Google Patents

Steuerungen, Systeme und Verfahren zur Steuerung der Dämpfung einer Lichtquelle Download PDF

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Publication number
EP2498579A2
EP2498579A2 EP12156751A EP12156751A EP2498579A2 EP 2498579 A2 EP2498579 A2 EP 2498579A2 EP 12156751 A EP12156751 A EP 12156751A EP 12156751 A EP12156751 A EP 12156751A EP 2498579 A2 EP2498579 A2 EP 2498579A2
Authority
EP
European Patent Office
Prior art keywords
signal
dimming
light source
power
switch
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP12156751A
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English (en)
French (fr)
Other versions
EP2498579A3 (de
Inventor
Yung Lin Lin
Ching-Chuan Kuo
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
O2Micro Inc
Original Assignee
O2Micro Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US13/042,349 external-priority patent/US8508150B2/en
Application filed by O2Micro Inc filed Critical O2Micro Inc
Publication of EP2498579A2 publication Critical patent/EP2498579A2/de
Publication of EP2498579A3 publication Critical patent/EP2498579A3/de
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/10—Controlling the intensity of the light
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
    • H05B47/10—Controlling the light source
    • H05B47/175—Controlling the light source by remote control
    • H05B47/185—Controlling the light source by remote control via power line carrier transmission

Definitions

  • LEDs light emitting diodes
  • LED possesses relatively high efficiency, long life, vivid colors and can be used in a variety of industries including the automotive, computer, telecom, military and consumer goods, etc.
  • LED lamp which uses LEDs to replace traditional light sources such as electrical filament.
  • FIG. 1 shows a schematic diagram of a conventional LED driving circuit 100.
  • the LED driving circuit 100 utilizes an LED string 106 as a light source.
  • the LED string 106 includes a group of LEDs connected in series.
  • a power converter 102 converts an input voltage Vin to a desired output DC voltage Vout for powering the LED string 106.
  • a switch 104 coupled to the power converter 102 can enable or disable the input voltage Vin to the LED string 106, and therefore can turn on or turn off the LED lamp.
  • the power converter 102 receives a feedback signal from a current sensing resistor Rsen and adjusts the output voltage Vout to make the LED string 106 generate a desired light output.
  • a desired light output is predetermined. In operation, the light output of the LED string 106 is set to a predetermined level and may not be adjusted by users.
  • FIG. 2 illustrates a schematic diagram of another conventional LED driving circuit 200.
  • a power converter 102 converts an input voltage Vin to a desired output DC voltage Vout for powering the LED string 106.
  • a switch 104 coupled to the power converter 102 can enable or disable the input voltage Vin to the LED string 106, and therefore can turn on or turn off the LED lamp.
  • the LED string 106 is coupled to a linear LED current regulator 208.
  • Operational amplifiers 210 in the linear LED current regulator 208 compares a reference signal REF and a current monitoring signal from current sensing resistor Rsen, and generates a control signal to adjust the resistance of transistor Q1 in a linear mode. Therefore, the LED current flowing through the LED string 106 can be adjusted accordingly.
  • a dedicated apparatus such as a specially designed switch with adjusting buttons or a switch that can receive a remote control signal, to adjust the reference signal REF.
  • a controller for controlling dimming of an LED light source includes a control terminal and dimming control circuitry coupled to the control terminal.
  • the control terminal provides a driving signal to control a control switch coupled to the LED light source, thereby controlling the dimming of the LED light source.
  • the dimming control circuitry generates the driving signal according to a set of operations of a power switch that transfers an AC signal.
  • the dimming control circuitry further adjusts the driving signal by counting multiple waves of the AC signal to control the dimming of the LED light source.
  • FIG. 1 shows a schematic diagram of a conventional LED driving circuit.
  • FIG. 2 shows a schematic diagram of another conventional LED driving circuit.
  • FIG. 3 shows a block diagram of a light source driving circuit, in accordance with one embodiment of the present invention.
  • FIG. 4 shows a schematic diagram of a light source driving circuit, in accordance with one embodiment of the present invention.
  • FIG. 5 shows a structure of a dimming controller in FIG. 4 , in accordance with one embodiment of the present invention.
  • FIG. 6 illustrates signal waveforms in the analog dimming mode, in accordance with one embodiment of the present invention.
  • FIG. 7 illustrates signal waveforms in the burst dimming mode, in accordance with one embodiment of the present invention.
  • FIG. 8 illustrates a diagram illustrating an operation of a light source driving circuit which includes the dimming controller in FIG. 5 , in accordance with one embodiment of the present invention.
  • FIG. 9 shows a flowchart of a method for adjusting power of a light source, in accordance with one embodiment of the present invention.
  • FIG. 10 shows a schematic diagram of a light source driving circuit, in accordance with one embodiment of the present invention.
  • FIG. 11 shows a structure of a dimming controller in FIG. 10 , in accordance with one embodiment of the present invention.
  • FIG. 12 illustrates a diagram illustrating an operation of a light source driving circuit which includes the dimming controller in FIG. 11 , in accordance with one embodiment of the present invention.
  • FIG. 13 shows a flowchart of a method for adjusting power of a light source, in accordance with one embodiment of the present invention.
  • FIG. 14A shows a schematic diagram of an example of an LED light source driving system, in accordance with one embodiment of the present invention.
  • FIG. 14B shows an example of a power switch in FIG. 14A , in accordance with one embodiment of the present invention.
  • FIG. 15 shows a structure diagram of an example of a dimming controller in FIG. 14A , in accordance with one embodiment of the present invention.
  • FIG. 16 shows a structure diagram of an example of a dimmer in FIG. 15 , in accordance with one embodiment of the present invention.
  • FIG. 17 illustrates an example of a diagram illustrating an operation of an LED light source driving system, in accordance with one embodiment of the present invention.
  • FIG. 18 illustrates an example of a diagram illustrating an operation of an LED light source driving system, in accordance with one embodiment of the present invention.
  • FIG. 19 shows a schematic diagram of an example of an LED light source driving system, in accordance with one embodiment of the present invention.
  • FIG. 20 shows a structure diagram of an example of a dimming controller in FIG. 19 , in accordance with one embodiment of the present invention.
  • FIG. 21 shows a block diagram of an example of an LED light source driving system, in accordance with one embodiment of the present invention.
  • FIG. 22 shows a flowchart of an example of a method for controlling dimming of an LED light source, in accordance with one embodiment of the present invention.
  • FIG. 3 shows an example of a block diagram of a light source driving circuit 300, in accordance with one embodiment of the present invention.
  • the light source driving circuit 300 includes an AC/DC converter 306 for converting an AC input voltage V IN from a power source to a DC voltage V OUT , a power switch 304 coupled between the power source and the AC/DC converter 306 for selectively coupling the power source to the light source driving circuit 300, a power converter 310 coupled to the AC/DC converter 306 for providing an LED string 312 with a regulated power, a dimming controller 308 coupled to the power converter 310 for receiving a switch monitoring signal indicative of an operation of the power switch 304 and for adjusting the regulated power from the power converter 310 according to the switch monitoring signal, and a current sensor 314 for sensing an LED current flowing through the LED string 312.
  • the power switch 304 can be an on/off switch mounted on the wall.
  • the AC/DC converter 306 converts the input AC voltage V IN to the output DC voltage V OUT .
  • the power converter 310 receives the DC voltage V OUT and provides the LED string 312 with a regulated power.
  • the current sensor 314 generates a current monitoring signal indicating a level of an LED current flowing through the LED string 312.
  • the dimming controller 308 monitors the operation of the power switch 304, receives the current monitoring signal from the current sensor 314, and is operable for controlling the power converter 310 to adjust power of the LED string 312 in response to the operation of the power switch 304.
  • the dimming controller 308 operates in an analog dimming mode and adjusts the power of the LED string 312 by adjusting a reference signal indicating a peak value of the LED current. In another embodiment, the dimming controller 308 operates in a burst dimming mode and adjusts the power of the LED string 312 by adjusting a duty cycle of a pulse width modulation (PWM) signal. By adjusting the power of the LED string 312, the light output of the LED string 312 can be adjusted accordingly.
  • PWM pulse width modulation
  • FIG. 4 shows an example of a schematic diagram of a light source driving circuit 400, in accordance with one embodiment of the present invention.
  • FIG. 4 is described in combination with FIG. 3 .
  • Elements labeled the same as in FIG. 3 have similar functions and will not be detailed described herein.
  • the light source driving circuit 400 includes a power converter 310 (shown in FIG. 3 ) coupled to a power source and coupled to an LED string 312 for receiving power from the power source and for providing a regulated power to the LED string 312.
  • the power converter 310 can be a buck converter including an inductor L1, a diode D4 and a control switch Q16.
  • the control switch Q16 is implemented outside the dimming controller 308. In another embodiment, the control switch Q16 can be integrated in the dimming controller 308.
  • a dimming controller 308 is operable for receiving a switch monitoring signal indicative of an operation of a power switch, e.g., a power switch 304 coupled between the power source and the light source driving circuit, and for adjusting the regulated power from the power converter 310 (including the inductor L1, the diode D4 and the control switch Q16) by controlling the control switch Q16 coupled in series with the LED string 312 according to the switch monitoring signal.
  • the light source driving circuit 400 can further include an AC/DC converter 306 for converting an AC input voltage V IN to a DC output voltage V OUT , and a current sensor 314 for sensing an LED current flowing through the LED string 312.
  • the AC/DC converter 306 can be a bridge rectifier including diodes D1, D2, D7, D8, D10, and a capacitor C9.
  • the current sensor 314 can include a current sensing resistor R5.
  • terminals of the dimming controller 308 can include HV_GATE, SEL, CLK, RT, VDD, CTRL, MON and GND.
  • the terminal HV_GATE is coupled to a switch Q27 through a resistor R3 for controlling a conductance status, e.g., ON/OFF status, of the switch Q27 coupled to the LED string 312.
  • a capacitor C11 is coupled between the terminal HV_GATE and ground for regulating a gate voltage of the switch Q27.
  • a user can select a dimming mode, e.g., an analog dimming mode or a burst dimming mode, by coupling the terminal SEL to ground through a resistor R4 (as shown in FIG. 4 ), or coupling the terminal SEL to ground directly.
  • a dimming mode e.g., an analog dimming mode or a burst dimming mode
  • the terminal CLK is coupled to the AC/DC converter 306 through a resistor R3, and is coupled to ground through a resistor R6.
  • the terminal CLK can receive a switch monitoring signal indicating an operation of the power switch 304.
  • the switch monitoring signal can be generated at a common node between the resistor R3 and the resistor R6.
  • a capacitor C12 is coupled to the resistor R6 in parallel for filtering undesired noises.
  • the terminal RT is coupled to ground through a resistor R7 for determining a frequency of a pulse signal generated by the dimming controller 308.
  • the terminal VDD is coupled to the switch Q27 through a diode D9 for supplying power to the dimming controller 308.
  • an energy storage unit e.g., a capacitor C10, coupled between the terminal VDD and ground can power the dimming controller 308 when the power switch 304 is turned off.
  • the energy storage unit can be integrated in the dimming controller 308.
  • the terminal GND is coupled to ground.
  • the terminal CTRL is coupled to the control switch Q16.
  • the control switch Q16 is coupled in series with the LED string 312 and the switch Q27, and is coupled to ground through the current sensing resistor R5.
  • the dimming controller 308 is operable for adjusting the regulated power from the power converter 310 by controlling a conductance status, e.g., ON and OFF status, of the control switch Q16 using a control signal via the terminal CTRL.
  • the terminal MON is coupled to the current sensing resistor R5 for receiving a current monitoring signal indicating an LED current flowing through the LED string 312. When the switch Q27 is turned on, the dimming controller 308 can adjust the LED current flowing through the LED string 312 to ground by controlling the control switch Q16.
  • the AC/DC converter 306 converts an input AC voltage V IN to a DC voltage V OUT .
  • a predetermined voltage at the terminal HV_GATE is supplied to the switch Q27 through the resistor R3 so that the switch Q27 is turned on.
  • the dimming controller 308 If the dimming controller 308 turns on the control switch Q16, the DC voltage V OUT powers the LED string 312 and charges the inductor L1. An LED current flows through the inductor L1, the LED string 312, the switch Q27, the control switch Q16, the current sensing resistor R5 to ground. If the dimming controller 308 turns off the control switch Q16, an LED current flows through the inductor L1, the LED string 312 and the diode D4. The inductor L1 is discharged to power the LED string 312. As such, the dimming controller 308 can adjust the regulated power from the power converter 310 by controlling the control switch Q16.
  • the capacitor C10 is discharged to power the dimming controller 308.
  • a voltage across the resistor R6 drops to zero, therefore a switch monitoring signal indicating a turn-off operation of the power switch 304 can be detected by the dimming controller 308 through the terminal CLK.
  • the power switch 304 is turned on, the voltage across the resistor R6 rises to a predetermined voltage, therefore a switch monitoring signal indicating a turn-on operation of the power switch 304 can be detected by the dimming controller 308 through the terminal CLK.
  • the dimming controller 308 can turn off the switch Q27 by pulling the voltage at the terminal HV_GATE to zero such that the LED string 312 can be turned off after the inductor L1 completes discharging.
  • the dimming controller 308 can adjust a reference signal indicating a target light output of the LED string 312. Therefore, when the power switch 304 is turned on next time, the LED string 312 can generate a light output according to the adjusted target light output. In other words, the light output of the LED string 312 can be adjusted by the dimming controller 308 in response to the turn-off operation of the power switch 304.
  • FIG. 5 shows an example of a structure of the dimming controller 308 in FIG. 4 , in accordance with one embodiment of the present invention.
  • FIG. 5 is described in combination with FIG. 4 .
  • Elements labeled the same as in FIG. 4 have similar functions and will not be detailed described herein.
  • the dimming controller 308 includes a trigger monitoring unit 506, a dimmer 502 and a pulse signal generator 504.
  • the trigger monitoring unit 506 is coupled to ground through a Zener diode ZD1.
  • the trigger monitoring unit 506 can receive a switch monitoring signal indicating an operation of the external power switch 304 through the terminal CLK and can generate a driving signal for driving a counter 526 when an operation of the external power switch 304 is detected at the terminal CLK.
  • the trigger monitoring unit 506 is further operable for controlling a conductance status of the switch Q27.
  • the dimmer 502 is operable for generating a reference signal REF to adjust power of the LED string 312 in an analog dimming mode, or generating a control signal 538 for adjusting a duty cycle of a PWM signal PWM1 to adjust the power of the LED string 312.
  • the pulse signal generator 504 is operable for generating a pulse signal which can turn on a control switch Q16.
  • the dimming controller 308 can further include a start up and under voltage lockout (UVL) circuit 508 coupled to the terminal VDD for selectively turning on one or more components of the dimming controller 308 according to different power condition.
  • UVL start up and under voltage lockout
  • the start up and under voltage lockout circuit 508 is operable for turning on all the components of the dimming controller 308 when the voltage at the terminal VDD is greater than a first predetermined voltage.
  • the start up and under voltage lockout circuit 508 is operable for turning off other components of the dimming controller 308 except the trigger monitoring unit 506 and the dimmer 502 when the voltage at the terminal VDD is less than a second predetermined voltage, in order to save energy.
  • the start up and under voltage lockout circuit 508 is further operable for turning off the trigger monitoring unit 506 and the dimmer 502 when the voltage at the terminal VDD is less than a third predetermined voltage.
  • the first predetermined voltage is greater than the second predetermined voltage and the second predetermined voltage is greater than the third predetermined voltage. Because the dimming controller 308 can be powered by the capacitor C10 through the terminal VDD, the trigger monitoring unit 506 and the dimmer 502 can still operate for a time period after the power switch 304 is turned off.
  • the terminal SEL is coupled to a current source 532. Users can choose a dimming mode by configuring the terminal SEL, e.g., by coupling the terminal SEL directly to ground or coupling the terminal SEL to ground via a resistor. In one embodiment, the dimming mode can be determined by measuring a voltage at the terminal SEL. If the terminal SEL is directly coupled to ground, the voltage at the terminal SEL is approximately equal to zero. A control circuit can in turn switch on a switch 540, switch off a switch 541 and switch off a switch 542. Therefore, the dimming controller 308 can work in an analog dimming mode and can adjust the power of the LED string 312 (shown in FIG.
  • the dimming controller 308 can work in a burst dimming mode and can adjust the power of the LED string 312 (shown in FIG. 4 ) by adjusting a duty cycle of a PWM signal PWM1.
  • different dimming modes can be selected by controlling the ON/OFF status of the switch 540, switch 541 and switch 542.
  • the ON/OFF status of the switch 540, switch 541 and switch 542 can be determined by the voltage at the terminal SEL.
  • the pulse signal generator 504 is coupled to ground through the terminal RT and the resistor R7 for generating a pulse signal 536 which can turn on the control switch Q16.
  • the pulse signal generator 504 can have different configurations and is not limited to the configuration as shown in the example of FIG. 5 .
  • the non-inverting input of an operational amplifier 510 receives a predetermined voltage V1.
  • V1 the voltage of the inverting input of the operational amplifier 510 can be forced to V1.
  • a current IRT flows through the terminal RT and the resistor R7 to ground.
  • a current I1 flowing through a MOSFET 514 and a MOSFET 515 is equal to IRT.
  • a current I2 flowing through the MOSFET 512 is also substantially equal to IRT.
  • the output of a comparator 516 and the output of a comparator 51 8 are respectively coupled to the S input and the R input of an SR flip-flop 520.
  • the inverting input of the comparator 516 receives a predetermined voltage V2.
  • the non-inverting input of the comparator 518 receives a predetermined voltage V3.
  • V2 is greater than V3, and V3 is greater than zero, in one embodiment.
  • a capacitor C4 is coupled between the MOSFET 512 and ground, and has one end coupled to a common node between the non-inverting input of the comparator 516 and the inverting input of the comparator 518.
  • the Q output of the SR flip-flop 520 is coupled to the switch Q15 and the S input of an SR flip-flop 522.
  • the switch Q15 is coupled in parallel with the capacitor C4.
  • a conductance status, e.g., ON/OFF status, of the switch Q15 can be determined by the Q output of the SR flip-flop 520.
  • the voltage across the capacitor C4 is approximately equal to zero which is less than V3. Therefore, the R input of the SR flip-flop 520 receives a digital 1 from the output of the comparator 518.
  • the Q output of the SR flip-flop 520 is set to digital 0, which turns off the switch Q15.
  • the switch Q15 is turned off, the voltage across the capacitor C4 increases as the capacitor C4 is charged by I2.
  • the S input of the SR flip-flop 520 receives a digital 1 from the output of the comparator 516.
  • the Q output of the SR flip-flop 520 is set to digital 1, which turns on the switch Q15.
  • the pulse signal generator 504 can generate a pulse signal 536 which includes a series of pulses at the Q output of the SR flip-flop 520.
  • the pulse signal 536 is sent to the S input of the SR flip-flop 522.
  • the trigger monitoring unit 506 is operable for monitoring an operation of the power switch 304 through the terminal CLK, and is operable for generating a driving signal for driving the counter 526 when an operation of the power switch 304 is detected at the terminal CLK.
  • the voltage at the terminal CLK rises to a level that is equal to a voltage across the resistor R6 (shown in FIG. 4 ).
  • the trigger monitoring unit 506 generates a driving signal when a turn-off operation is detected at the terminal CLK.
  • the trigger monitoring unit 506 is further operable for controlling a conductance status of the switch Q27 through the terminal HV_GATE.
  • a breakdown voltage across the Zener diode ZD1 is applied to the switch Q27 through the resistor R3. Therefore, the switch Q27 can be turned on.
  • the trigger monitoring unit 506 can turn off the switch Q27 by pulling the voltage at the terminal HV_GATE to zero.
  • the trigger monitoring unit 506 turns off the switch Q27 when a turn-off operation of the power switch 304 is detected at the terminal CLK and turns on the switch Q27 when a turn-on operation of the power switch 304 is detected at the terminal CLK.
  • the dimmer 502 includes a counter 526 coupled to the trigger monitoring unit 506 for counting operations of the power switch 304, a digital-to-analog converter (D/A converter) 528 coupled to the counter 526.
  • the dimmer 502 can further include a PWM generator 530 coupled to the D/A converter 528.
  • the counter 526 can be driven by the driving signal generated by the trigger monitoring unit 506. More specifically, when the power switch 304 is turned off, the trigger monitoring unit 506 detects a negative edge of the voltage at the terminal CLK and generates a driving signal, in one embodiment.
  • the counter value of the counter 526 can be increased, e.g., by 1, in response to the driving signal.
  • the D/A converter 528 reads the counter value from the counter 526 and generates a dimming signal (e.g., control signal 538 or reference signal REF) based on the counter value.
  • the dimming signal can be used to adjust a target power level of the power converter 310, which can in turn adjust the light output of the LED string 312.
  • the switch 540 In the burst dimming mode, the switch 540 is off, the switch 541 and the switch 542 are on.
  • the inverting input of the comparator 534 receives a reference signal REF1 which can be a DC signal having a predetermined substantially constant voltage.
  • REF1 can determine a peak value of the LED current, which can in turn determine the maximum light output of the LED string 312.
  • the dimming signal can be a control signal 538 which is applied to the PWM generator 530 for adjusting a duty cycle of the PWM signal PWM1.
  • the light output of the LED string 312 can be adjusted no greater than the maximum light output determined by REF1. For example, if PWM1 has a duty cycle of 100%, the LED string 312 can have the maximum light output. If the duty cycle of PWM1 is less than 100%, the LED string 312 can have a light output that is lower than the maximum light output.
  • the switch 540 In the analog dimming mode, the switch 540 is on, the switch 541 and the switch 542 are off, and the dimming signal can be an analog reference signal REF having an adjustable voltage.
  • the D/A converter 528 can adjust the voltage of the reference signal REF according to the counter value of the counter 526.
  • the voltage of REF can determine a peak value of the LED current, which can in turn determine an average value of the LED current. As such, the light output of the LED string 312 can be adjusted by adjusting the reference signal REF.
  • the D/A converter 528 can decrease the voltage of REF in response to an increase of the counter value. For example, if the counter value is 0, the D/A converter 528 adjusts the reference signal REF to have a voltage V4. If the counter value is increased to 1 when a turn-off operation of the power switch 304 is detected at the terminal CLK by the trigger monitoring unit 506, the D/A converter 528 adjusts the reference signal REF to have a voltage V5 that is less than V4. Yet in another embodiment, the D/A converter 528 can increase the voltage of REF in response to an increase of the counter value.
  • the counter value will be reset to zero after the counter 526 reaches its maximum counter value.
  • the counter value will increase from 0 to 1, 2, 3 and then return to zero after four turn-off operations have been detected. Accordingly, the light output of the LED string 312 can be adjusted from a first level to a second level, then to a third level, then to a fourth level, and then back to the first level.
  • the inverting input of a comparator 534 can selectively receive the reference signal REF and the reference signal REF1.
  • the inverting input of the comparator 534 receives the reference signal REF through the switch 540 in the analog dimming mode, and receives the reference signal REF1 through the switch 541 in the burst dimming mode.
  • the non-inverting input of the comparator 534 is coupled to the resistor R5 through the terminal MON for receiving a current monitoring signal SEN from the current sensing resistor R5.
  • the voltage of the current monitoring signal SEN can indicate an LED current flowing through the LED string 312 when the switch Q27 and the control switch Q16 are turned on.
  • the output of the comparator 534 is coupled to the R input of the SR flip-flop 522.
  • the Q output of the SR flip-flop 522 is coupled to an AND gate 524.
  • the PWM signal PWM1 generated by the PWM generator 530 is applied to the AND gate 524.
  • the AND gate 524 outputs a control signal to control the control switch Q16 through the terminal CTRL.
  • the switch 540 is turned on and the switches 541 and 542 are turned off.
  • the control switch Q16 is controlled by the SR flip-flop 522.
  • the SR flip-flop 522 In operation, when the power switch 304 is turned on, the breakdown voltage across the Zener diode ZD1 turns on the switch Q27.
  • the SR flip-flop 522 generates a digital 1 at the Q output to turn on the control switch Q16 in response to the pulse signal 536 generated by the pulse generator 504.
  • the voltage across the current sensing resistor R5, that is, the voltage of the current monitoring signal SEN can be increased.
  • the comparator 534 When the voltage of SEN is greater than that of the reference signal REF, the comparator 534 generates a digital 1 at the R input of the SR flip-flop 522 so that the SR flip-flop 522 generates a digital 0 to turn off the control switch Q16.
  • the inductor L1 After the control switch Q16 is turned off, the inductor L1 is discharged to power the LED string 312. An LED current which flows through the inductor L1, the LED string 312 and the diode D4 gradually decreases.
  • the control switch Q16 is turned on when the SR flip-flop 522 receives a pulse at the S input again, and then the LED current flows through the current sensing resistor R5 to ground again.
  • the control switch Q16 is turned off by the SR flip-flop 522.
  • the reference signal REF determines a peak value of the LED current, which can in turn determine the light output of the LED string 312. By adjusting the reference signal REF, the light output of the LED string 312 can be adjusted.
  • the capacitor C10 (shown in FIG. 4 ) is discharged to power the dimming controller 308.
  • the counter value of the counter 526 can be increased by 1 when the trigger monitoring unit 506 detects a turn-off operation of the power switch 304 at the terminal CLK.
  • the trigger monitoring unit 506 can turn off the switch Q27 in response to the turn-off operation of the power switch 304.
  • the D/A converter 528 can adjust the voltage of the reference signal REF from a first level to a second level in response to the change of the counter value. Therefore, the light output of the LED string 312 can be adjusted in accordance with the adjusted reference signal REF when the power switch 304 is turned on.
  • the switch 540 is turned off and the switches 541 and 542 are turned on.
  • the inverting input of the comparator 534 receives a reference signal REF1 having a predetermined voltage.
  • the control switch Q16 is controlled by both of the SR flip-flop 522 and the PWM signal PWM1 through the AND gate 524.
  • the reference signal REF1 can determine a peak value of the LED current, which can in turn determine a maximum light output of the LED string 312.
  • the duty cycle of the PWM signal PWM1 can determine the on/off time of the control switch Q16. When the PWM signal PWM1 is logic 1, the conductance status of the control switch Q16 is determined by the Q output of the SR flip-flop 522.
  • the control switch Q16 is turned off.
  • the duty cycle of the PWM signal PWM1 the power of the LED string 312 can be adjusted accordingly.
  • the combination of the reference signal REF1 and the PWM signal PWM1 can determine the light output of the LED string 312.
  • a turn-off operation of the power switch 304 can be detected by the trigger monitoring unit 506 at the terminal CLK.
  • the trigger monitoring unit 506 turns off the switch Q27 and generates a driving signal.
  • the counter value of the counter 526 can be increased, e.g., by 1, in response of the driving signal.
  • the D/A converter 528 can generate the control signal 538 to adjust the duty cycle of the PWM signal PWM1 from a first level to a second level. Therefore, when the power switch 304 is turned on next time, the light output of the LED string 312 can be adjusted to follow a target light output which is determined by the reference signal REF1 and the PWM signal PWM1.
  • FIG. 6 illustrates examples of signal waveforms of an LED current 602 flowing through the LED string 312, the pulse signal 536, V522 which indicates the output of the SR flip-flop 522, V524 which indicates the output of the AND gate 524, and the ON/OFF status of the control switch Q16 in the analog dimming mode.
  • FIG. 6 is described in combination with FIG. 4 and FIG. 5 .
  • the pulse signal generator 504 generates pulse signal 536.
  • the SR flip-flop 522 generates a digital 1 at the Q output in response to each pulse of the pulse signal 536.
  • the control switch Q16 is turned on when the Q output of the SR flip-flop 522 is digital 1.
  • the control switch Q16 is turned on, the inductor L1 ramps up and the LED current 602 increases.
  • the comparator 534 generates a digital 1 at the R input of the SR flip-flop 522 so that the SR flip-flop 522 generates a digital 0 at the Q output.
  • the control switch Q16 is turned off when the Q output of the SR flip-flop 522 is digital 0.
  • the control switch Q16 is turned off, the inductor L1 is discharged to power the LED string 312 and the LED current 602 decreases.
  • the reference signal REF by adjusting the reference signal REF, the average LED current can be adjusted accordingly and therefore the light output of the LED string 312 can be adjusted.
  • FIG. 7 illustrates examples of signal waveforms of the LED current 602 flowing through the LED string 312, the pulse signal 536, V522 which indicates the output of the SR flip-flop 522, V524 which indicates the output of the AND gate 524, and the ON/OFF status of the control switch Q16, and the PMW signal PWM1 in the burst dimming mode.
  • FIG. 7 is described in combination with FIG. 4 and FIG. 5 .
  • PWM1 When PWM1 is digital 1, the relationship among the LED current 602, the pulse signal 536, V522, V524, and the ON/OFF status of the switch Q1 is similar to that is illustrated in FIG. 6 .
  • PWM1 When PWM1 is digital 0, the output of the AND gate 524 turns to digital 0. Therefore, the control switch Q16 is turned off and the LED current 602 decreases. If the PWM1 holds digital 0 long enough, the LED current 602 can falls to zero. In this burst dimming mode, by adjusting the duty cycle of PWM1, the average LED current can be adjusted accordingly and therefore the light output of the LED string 312 can be adjusted.
  • FIG. 8 shows an example of a diagram illustrating an operation of a light source driving circuit which includes the dimming controller in FIG. 5 , in accordance with one embodiment of the present invention.
  • FIG. 8 is described in combination with FIG. 5 .
  • the counter 526 can be a 2-bit counter which has a maximum counter value of 3.
  • the D/A converter 528 reads the counter value from the counter 526 and decreases the voltage of the reference signal REF in response to an increase of the counter value.
  • the voltage of REF can determine a peak value Imax of the LED current, which can in turn determine an average value of the LED current.
  • the D/A converter 528 reads the counter value from the counter 526 and decreases the duty cycle of the PWM signal PWM1 (e.g., decreases 25% each time) in response to an increase of the counter value.
  • the counter 526 is reset after it reaches its maximum counter value (e.g., 3).
  • FIG. 9 shows a flowchart 900 of a method for adjusting power of a light source, in accordance with one embodiment of the present invention.
  • FIG. 9 is described in combination with FIG. 4 and FIG. 5 .
  • a light source e.g., the LED string 312 is powered by a regulated power from a power converter, e.g., the power converter 310.
  • a switch monitoring signal can be received, e.g., by the dimming controller 308.
  • the switch monitoring signal can indicate an operation of a power switch, e.g., the power switch 304 coupled between a power source and the power converter.
  • a dimming signal is generated according to the switch monitoring signal.
  • a switch coupled in series with the light source e.g., the control switch Q16, is controlled according to the dimming signal so as to adjust the regulated power from the power converter.
  • the regulated power from the power converter in an analog dimming mode, can be adjusted by comparing the dimming signal with a feedback current monitoring signal which indicates a light source current of the light source. In another embodiment, in a burst dimming mode, the regulated power from the power converter can be adjusted by controlling a duty cycle of a PWM signal by the dimming signal.
  • embodiments in accordance with the present invention provide a light source driving circuit that can adjust power of a light source according to a switch monitoring signal indicative of an operation of a power switch, e.g., an on/off switch mounted on the wall.
  • the power of the light source which is provided by a power converter, can be adjusted by a dimming controller by controlling a switch coupled in series with the light source.
  • users can adjust the light output of the light source through an operation (e.g., a turn-off operation) of a common on/off power switch. Therefore, extra apparatus for dimming, such as an external dimmer or a specially designed switch with adjusting buttons, can be avoided and the cost can be reduced.
  • FIG. 10 shows an example of a schematic diagram of a light source driving circuit 1000, in accordance with one embodiment of the present invention.
  • FIG. 10 is described in combination with FIG. 3 .
  • Elements labeled the same as in FIG. 3 and FIG. 4 have similar functions.
  • the light source driving circuit 1000 includes a power converter 310 coupled to a power source and an LED string 312 for receiving power from the power source and for providing a regulated power to the LED string 312.
  • a dimming controller 1008 is operable for monitoring a power switch 304 coupled between the power source and the light source driving circuit 1000 by monitoring the voltage at a terminal CLK.
  • the dimming controller 1008 is operable for receiving a dimming request signal indicative of a first set of operations of the power switch 304 and for receiving a dimming termination signal indicative of a second set of operations of the power switch 304.
  • the dimming controller 1008 can receive the dimming request signal and the dimming termination signal via the terminal CLK.
  • the dimming controller 1008 is further operable for continuously adjusting the regulated power from the power converter 310 if the dimming request signal is received, and for stopping adjusting the regulated power from the power converter 310 if the dimming termination signal is received. In other words, the dimming controller 1008 can continuously adjust the power from the power converter 310 upon detection of the first set of operations of the power switch 304 until the second set of operations of the power switch 304 are detected. In one embodiment, the dimming controller 1008 can adjust the regulated power from the power converter 310 by controlling a control switch Q16 coupled in series with the LED string 312.
  • FIG. 11 shows an example of a structure of the dimming controller 1008 in FIG. 10 , in accordance with one embodiment of the present invention.
  • FIG. 11 is described in combination with FIG. 10 .
  • Elements labeled the same as in FIG. 4 , FIG. 5 and FIG. 10 have similar functions.
  • the structure of the dimming controller 1008 in FIG. 11 is similar to the structure of the dimming controller 308 in FIG. 5 except for the configuration of the dimmer 1102 and the trigger monitoring unit 1106.
  • the trigger monitoring unit 1106 is operable for receiving the dimming request signal and the dimming termination signal via the terminal CLK, and for generating a signal EN to enable or disable a clock generator 1104.
  • the trigger monitoring unit 1106 is further operable for controlling a conductance status of the switch Q27 coupled to the LED string 312.
  • the dimmer 1102 is operable for generating a reference signal REF to adjust power of the LED string 312 in an analog dimming mode, or generating a control signal 538 for adjusting a duty cycle of a PWM signal PWM1 to adjust the power of the LED string 312 in a burst dimming mode.
  • the dimmer 1102 can include the clock generator 1104 coupled to the trigger monitoring unit 1106 for generating a clock signal, a counter 1126 driven by the clock signal, a digital-to-analog (D/A) converter 528 coupled to the counter 1126.
  • the dimmer 1102 can further include a PWM generator 530 coupled to the D/A converter 528.
  • the trigger monitoring unit 1106 can detect a positive edge or a negative edge of the voltage at the terminal CLK.
  • the capacitor C10 is discharged to power the dimming controller 1108.
  • a voltage across the resistor R6 drops to zero. Therefore, a negative edge of the voltage at the terminal CLK can be detected by the trigger monitoring unit 1106.
  • the power switch 304 is turned on, the voltage across the resistor R6 rises to a predetermined voltage. Therefore, a positive edge of the voltage at the terminal CLK can be detected by the trigger monitoring unit 1106.
  • operations, e.g., turn-on operations or turn-off operations, of the power switch 304 can be detected by the trigger monitoring unit 1106 by monitoring the voltage at the terminal CLK.
  • a dimming request signal can be received by the trigger monitoring unit 1106 via the terminal CLK when a first set of operations of the power switch 304 are detected.
  • a dimming termination signal can be received by the trigger monitoring unit 1106 via the terminal CLK when a second set of operations of the power switch 304 are detected.
  • the first set of operations of the power switch 304 includes a first turn-off operation followed by a first turn-on operation.
  • the second set of operations of the power switch 304 includes a second turn-off operation followed by a second turn-on operation.
  • the dimming controller 1108 begins to continuously adjust the regulated power from the power converter 310.
  • the dimming controller 1108 adjusts a voltage of a reference signal REF to adjust the regulated power from the power converter 310.
  • the dimming controller 1108 adjusts a duty cycle of a PWM signal PWM1 to adjust the regulated power from the power converter 310.
  • the dimming controller 1108 can stop adjusting the regulated power from the power converter 310.
  • FIG. 12 illustrates an example of a diagram illustrating an operation of a light source driving circuit which includes the dimming controller 1008 in FIG. 11 , in accordance with one embodiment of the present invention.
  • FIG. 12 is described in combination with FIG. 10 and FIG. 11 .
  • the initial light output can be determined by an initial voltage of the reference signal REF.
  • the initial light output can be determined by an initial duty cycle (e.g., 100%) of the PWM signal PWM1.
  • the reference signal REF and the PWM signal PWM1 can be generated by the D/A converter 528 according to a counter value of the counter 1126, in one embodiment. Therefore, the initial voltage of REF and the initial duty cycle of PWM1 can be determined by an initial counter value (e.g., zero) provided by the counter 1126.
  • the user can apply a first set of operations to the power switch 304.
  • a dimming request signal is generated upon detection of the first set of operations of the power switch 304.
  • the first set of operations can include a first turn-off operation followed by a first turn-on operation.
  • a dimming request signal including a negative edge 1204 followed by a positive edge 1206 of the voltage at the terminal CLK can be detected and received by the trigger monitoring unit 1106.
  • the trigger monitoring unit 1106 can generate a signal EN having a high level.
  • the clock generator 1104 is enabled to generate a clock signal.
  • the counter 1126 driven by the clock signal can change the counter value in response to each clock pulse of the clock signal.
  • the counter value increases in response to the clock signal.
  • the counter value can be reset to zero after the counter 1126 reaches its predetermined maximum counter value.
  • the counter value increases until the counter 1126 reaches its predetermined maximum counter value, and then decreases until the counter 1126 reaches its predetermined minimum counter value.
  • the D/A converter 528 reads the counter value from the counter 1126 and decreases the voltage of the reference signal REF in response to an increase of the counter value, in one embodiment.
  • the D/A converter 528 reads the counter value from the counter 1126 and decreases the duty cycle of the PWM signal PWM1 (e.g., decreases 10% each time) in response to an increase of the counter value, in one embodiment. Accordingly, the light output of the LED string 312 can be adjusted because the regulated power from the power converter 310 can be determined by the voltage of the reference signal REF (in the analog dimming mode) or by the duty cycle of the PWM signal PWM1 (in the burst dimming mode).
  • the user can terminate the adjustment process by applying a second set of operations to the power switch 304.
  • a dimming termination signal is generated upon detection of the second set of operations of the power switch 304.
  • the second set of operations can include a second turn-off operation followed by a second turn-on operation.
  • the dimming termination signal including a negative edge 1208 followed by a positive edge 1210 of the voltage at the terminal CLK can be detected and received by the trigger monitoring unit 1106.
  • the trigger monitoring unit 1106 can generate the signal EN having a low level.
  • the clock generator 1104 is disabled, such that the counter 1126 can hold its counter value.
  • the voltage of the reference signal REF can be held at a desired level.
  • the duty cycle of the PWM signal PWM1 can be held at a desired value. Therefore, the light output of the LED string 312 can be maintained at a desired light output.
  • FIG. 13 shows a flowchart 1300 of a method for adjusting power of a light source, in accordance with one embodiment of the present invention.
  • FIG. 13 is described in combination with FIG. 10 and FIG. 11 .
  • a light source e.g., the LED string 312 is powered by a regulated power from a power converter, e.g., the power converter 310.
  • a dimming request signal can be received, e.g., by the dimming controller 1108.
  • the dimming request signal can indicate a first set of operations of a power switch, e.g., the power switch 304 coupled between a power source and the power converter.
  • the first set of operations of the power switch includes a first turn-off operation followed by a first turn-on operation.
  • the regulated power from the power converter is continuously adjusted, e.g., by the dimming controller 1108.
  • a clock generator 1104 can be enabled to drive a counter 1126.
  • a dimming signal (e.g., control signal 538 or reference signal REF) can be generated according to the counter value of the counter 1126.
  • the regulated power from the power converter can be adjusted by comparing the reference signal REF with a feedback current monitoring signal which indicates a light source current of the light source. The voltage of REF can be determined by the counter value.
  • the regulated power from the power converter can be adjusted by varying a duty cycle of a PWM signal PWM1 by the control signal 538. The duty cycle of PWM1 can be also determined by the counter value.
  • a dimming termination signal can be received, e.g., by the dimming controller 1108.
  • the dimming termination signal can indicate a second set of operations of a power switch, e.g., the power switch 304 coupled between a power source and the power converter.
  • the second set of operations of the power switch includes a second turn-off operation followed by a second turn-on operation.
  • the adjustment of the regulated power from the power converter is terminated if the dimming termination signal is received.
  • the clock generator 1104 is disabled such that the counter 1126 can hold its counter value.
  • the voltage of REF can be held at a desired level.
  • the duty cycle of the PWM signal PWM1 can be held at a desired value. Consequently, the light source can maintain a desired light output.
  • embodiments in accordance with the present invention provide a light source driving circuit that can automatically and continuously adjust power of a light source if a dimming request signal is received.
  • the light source driving circuit can stop adjusting power of the light source if a dimming termination signal is received.
  • a user can enable a light/brightness adjustment by applying a first set of operations to a power switch, e.g., an on/off switch mounted on the wall.
  • a power switch e.g., an on/off switch mounted on the wall.
  • the light output of the light source gradually decreases or increases. If a desired light output has been achieved, the user can terminate the light adjustment by applying a second set of operations to the power switch. Therefore, extra apparatus for dimming, such as an external dimmer or a specially designed switch with adjusting buttons, can be avoided and the cost can be reduced.
  • FIG. 14A shows a schematic diagram of an example of an LED light source driving system 1400, in accordance with one embodiment of the present invention.
  • FIG. 14A is described in combination with FIG. 10 .
  • Elements labeled the same as in FIG. 10 have similar functions.
  • the driving system 1400 receives AC power through the power switch 304 and generates regulated power to an LED light source.
  • the power switch 304 can be an on/off switch mounted on the wall.
  • An example of the power switch 304 is illustrated in FIG. 14B .
  • the driving system 1400 includes power conversion circuitry, e.g., the AC/DC converter 306 and a DC/DC converter 1410, and dimming control circuitry, e.g., a dimming controller 1408.
  • the power conversion circuitry receives an AC signal, e.g., the AC input voltage V IN provided by the AC power source, through the power switch 304 and provides the regulated power, e.g., a regulated current I REG , to an LED light source 1412.
  • the LED light source 1412 includes an LED string.
  • the AC/DC converter 306 of the conversion circuitry receives AC power (e.g., the AC input voltage V IN ) and converts the AC power to DC power (e.g., the DC output voltage V OUT ).
  • the DC/DC converter 1410 of the conversion circuitry converts the DC power (e.g., the DC output voltage V OUT ) to the regulated power (e.g., the regulated current I REG ) by controlling a control switch Q16, e.g., coupled in series with the LED light source via the DC/DC converter 1410, according to a dimming signal (not shown in FIG. 14A ).
  • the dimming controller 1408 generates the dimming signal and controls dimming of the LED light source 1412 according to the dimming signal.
  • the dimming controller 1408 generates the dimming signal according to a set of operations of the power switch 304 and adjusts the dimming signal by counting the waves, e.g., sinusoidal full-waves or sinusoidal half-waves, or periodic cycles of the AC signal V IN .
  • the AC signal V IN is a sinusoidal signal.
  • the invention is not limited to sinusoidal AC signals.
  • the full-bridge circuit of the AC/DC converter 306, e.g., including the diodes D1, D2, D7 and D8, receives the AC input voltage V IN from the AC power source and generates sinusoidal half-waves, e.g., having one polarity, to the filter capacitor C9.
  • the filter capacitor C9 can therefore provide the DC output voltage V OUT to the DC/DC converter 1410.
  • the resistor divider including the resistors R3 and R6 can provide a dimming request or dimming termination signal indicative of a set of operations of the power switch 304. Similar to the operations of the power switch 304 described in relation to FIG. 10 , the operations of the power switch 304 in FIG.
  • the 14A includes turning off the power switch 304 followed by turning on the power switch 304 within a predefined time interval ⁇ T, e.g., 2 seconds.
  • the diming controller 1408 can enable a dimming process of the LED light source 1412.
  • the resistor divider provides a periodic signal 1454 indicative of the sinusoidal half-waves of the AC signal V IN to the dimming controller 1408.
  • the power converter 1410 is a buck converter including the control switch Q16, a diode 1414, a current sensor 1428 (e.g., a resistor), coupled inductors L1 and L2, and a capacitor 1424.
  • the control switch Q16 may be integrated in the dimming controller 1408.
  • the inductors L1 and L2 are magnetically coupled and electrically coupled together, e.g., to a common node 1433.
  • the common node 1433 in FIG. 14A is between the resistor 1428 and the inductor L1, the common node 1433 can also locate between the control switch Q16 and the resistor 1428, in another embodiment.
  • the common node 1433 provides a reference ground for the dimming controller 1408.
  • the reference ground of the dimming controller 1408 is different from the ground of the driving system 1400, in one embodiment.
  • the regulated current I REG flowing through the inductor L1 can be adjusted, thereby adjusting the power provided to the LED light source 1412.
  • the capacitor 1424 absorbs the ripples of the regulated current I REG , such that the current flowing through the LED light source 1412 is smoothened and substantially equal to the average of the regulated current I REG .
  • the inductor L2 senses an electrical condition of the inductor L1, for example, whether the current flowing through the inductor L1 decreases to a predetermined minimum level.
  • the inductor L2 further generates a detection signal AUX indicative of the electrical condition of the inductor L1.
  • the resistor 1428 has one end coupled to a node between the switch Q16 and the cathode of the diode 1414, and the other end coupled to the reference ground.
  • the resistor 1428 provides a current monitoring signal SEN indicating the regulated current I REG flowing through the inductor L1.
  • the dimming controller 1408 has terminals CLK, ZCD, GND, CTRL, VDD, MON, COMP and FB.
  • the terminal ZCD is coupled to the inductor L2 and receives the detection signal AUX.
  • the terminal MON is coupled to the resistor 1428 and receives the monitoring signal SEN.
  • the terminal COMP is coupled to the reference ground of the dimming controller 1408 through a capacitor and provides a compensating voltage REF2 to the dimming controller 1408.
  • the terminal FB receives a monitoring signal AVG indicative of the average of the current I REG flowing through the inductor L1.
  • the terminal CLK monitors the power switch 304, e.g., whether the power switch 304 is on or off.
  • the terminal CLK When the power switch 304 is on, the terminal CLK, in the example of FIG. 14A , further receives the periodic signal 1454 indicative of sinusoidal waves of the AC signal V IN .
  • the dimming controller 1408 includes different terminals to respectively monitor the power switch 304 and receive the periodic signal 1454.
  • the control terminal CTRL is coupled to the control switch Q16 and generates a driving signal CTRL, e.g., a PWM signal, to control the control switch Q16, thereby controlling the dimming of the LED light source 1412.
  • the driving signal CTRL is generated based on the operations of the power switch 304, and based on the periodic signal 1454, the detection signal AUX, and the monitoring signals SEN and AVG.
  • the terminal VDD can receive power from the AC/DC converter 306 or the inductor L2.
  • the terminal GND is coupled to the reference ground of the dimming controller 1408.
  • the power switch 304 is turned on.
  • a current I REG flows through the switch Q16, the resistor 1428, the inductor L1, the LED light source 1412 to the ground of the driving system 1400, and the current I REC increases.
  • the switch Q16 is off, the current I REG continues to flow through the resistor 1428, the inductor L1, the LED light source 1412 and the diode 1414, and the current I REG decreases.
  • the monitoring signal SEN indicates that the current I RES increases to a maximum level I MAX
  • the dimming controller 1408 turns off the switch Q16 to decrease the current I REG .
  • the dimming controller 1408 turns on the switch Q16 to increase the current I REG .
  • the current I REC is adjusted in a range from the predetermined minimum level to the maximum level I MAX .
  • the maximum level I MAX is adjustable. For example, if the monitoring signal AVG indicates that the average of the current I REG is less than a preset level, the dimming controller 1408 increases the maximum level I MAX to increase the average of the current I REG .
  • the dimming controller 1408 decreases the maximum level I MAX to decrease the average of the current I REG . Therefore, the current flowing through the LED light source 1412 is adjusted to the preset level. In other words, the light output of the LED light source 1412 is adjusted to a corresponding preset level.
  • a user can control the power switch 304 to control the dimming of the LED light source 1412, e.g., to control the preset level for the light output. More specifically, a user can apply a set of operations on the power switch 304.
  • the dimming controller 1408 generates the driving signal CTRL according to the operations of the power switch 304.
  • the dimming controller 1408 when the user first turns on the power switch 304, the dimming controller 1408 generates the driving signal CTRL independent from a dimming signal, e.g., a reference REF or a PWM signal PWM1, and controls the light output of the LED light source 1412 to a predetermined level, e.g., a maximum level.
  • the dimming controller 1408 generates the dimming signal to control the driving signal CTRL.
  • the dimming controller 1408 further adjusts the dimming signal and the driving signal CTRL by counting the waves of the AC signal V IN to control the dimming of the LED light source 1412, e.g., to adjust the regulated current I REG .
  • the dimming controller 1408 counts the half-waves of the AC signal V IN by counting cycles of the periodic signal 1454.
  • the dimming controller 1408 can receive the AC signal V IN directly or indirectly, and count the half-waves or full-waves of the AC signal V IN .
  • FIG. 15 shows an example of a structure of the dimming control circuitry 1408 in FIG. 14A , in accordance with one embodiment of the present invention.
  • FIG. 15 is described in combination with FIG. 10 and FIG. 14A . Elements labeled the same as in FIG. 10 and FIG. 14A have similar functions.
  • the dimming control circuitry 1408 includes a trigger monitoring unit 1506, a dimmer 1502, and driving signal generator circuitry that includes an error amplifier 1550, the comparator 534, the SR flip-flop 522, the AND gate 524, and a trigger circuit 1504.
  • the trigger monitoring unit 1506 can monitor the operations of the power switch 304 via the terminal CLK and generate a pulse TRIG in response to a detection of a set of operations of the power switch 304.
  • the operations includes turning off the power switch 304 followed by turning on the power switch 304 within a predefined time interval ⁇ T. If such operations is performed, the trigger monitoring unit 1506 can detect a negative edge of the voltage at the terminal CLK followed by a positive edge.
  • the dimmer 1502 can count the waves of the AC signal V IN , e.g., by counting the periodic signal 1454, based on the pulse TRIG. For example, the trigger monitoring unit 1506 can generate a pulse TRIG to enable or disable the counting of the periodic signal 1454.
  • the dimmer 1502 includes the D/A converter 528 and the PWM generator 530, and further includes a dimming indicator 1526 and a clock generator 1504.
  • the clock generator 1504 receives the periodic signal 1454 and generates a clock signal 1544 indicative of the periodic signal 1454.
  • the clock generator 1504 can generate one pulse in each cycle of the periodic signal 1454.
  • the dimming indicator 1526 counts the waves of the AC signal V IN by counting the pulses of the clock signal 1544.
  • the dimming indicator 1526 further generates a digital output 1548 indicating a dimming value according to the result of the counting, in one embodiment.
  • the dimming indicator 1526 increases the dimming value of the digital output 1548 by one and restarts the counting.
  • the D/A converter 538 can increase the dimming signal, e.g., the reference signal REF or the duty cycle of the PWM signal PWM1, if the digital output 1548 increases, and decrease the dimming signal if the digital output 1548 decreases.
  • the dimmer 1502 can adjust the dimming signal by counting the waves of the AC signal V IN to adjust the driving signal CTRL.
  • the trigger circuit 1504 is coupled to the terminal ZCD of the dimming control circuitry 1408. In one embodiment, if the terminal ZCD detects that the regulated current I REG decreases to a predetermined minimum level, e.g., zero amperes, the trigger circuit 1504 generates a pulse signal 1536, e.g., a logic-high signal, to set the Q output of the flip-flop 522 to be logic high and to turn on the switch Q16.
  • a pulse signal 1536 e.g., a logic-high signal
  • the comparator 534 outputs a logic-high signal to reset the Q output of the flip-flop 522 to logic low to turn off the switch Q16.
  • the regulated current I REG can be adjusted in a range between the predetermined minimum level, e.g., zero amperes, and a maximum level determined by the compensating voltage REF2.
  • the dimming controller 1408 controls the dimming of the LED light source 1412 by comparing the reference signal REF with the monitoring signal AVG indicative of the current flowing through the LED light source 1412. More specifically, the error amplifier 1550 compares the reference signal REF with the monitoring signal AVG. The error amplifier 1550 further increases the compensating voltage REF2 if the monitoring signal AVG is less than the reference signal REF, or decreases the compensating voltage REF2 if the monitoring signal AVG is greater than the reference signal REF, in one embodiment. Thus, the current through the LED light source 1412 is adjusted to a level determined by the reference signal REF. Accordingly, the light output of the LED light source 1412 is adjusted by the reference signal REF.
  • the dimming controller 1408 controls the dimming of the LED light source 1412 according to the PWM signal PWM1 and the Q output, e.g., a PWM signal, of the flip-flop 522. More specifically, when the PWM signal PWM1 is logic high, the regulated current I REG is adjusted by the Q output and the average of the regulated current I REG is determined by the reference signal REF1. When the PWM signal PWM1 is logic low, the regulated current I REG is cut off. Thus, the light output of the LED light source 1412 can increase if the duty cycle of the PWM signal PWM1 increases, or decrease if the duty cycle of the PWM signal PWM1 decreases.
  • FIG. 16 An example of a structure of the dimmer 1502 in FIG. 15 is illustrated in FIG. 16 , in accordance with one embodiment of the present invention.
  • FIG. 16 is described in combination with FIG. 15 .
  • the clock generator 1504 includes a comparator and the dimming indicator 1526 includes a clock counter.
  • the PWM generator 530 includes a sawtooth signal generator and a comparator.
  • the clock generator 1504 compares the periodic signal 1454 indicative of the AC signal V IN with a voltage reference V REF to generator the clock signal 1544. Each pulse of the clock signal 1544 corresponds to a cycle of the periodic signal 1454, in one embodiment.
  • the dimming indicator 1526 increases the dimming value of the digital output 1548 by a predetermined number (e.g., by one) and restarts the counting.
  • the D/A converter 528 therefore can control the dimming signal, e.g., the reference signal REF or the duty cycle of the PWM signal PWM1, from a first preset level to a second preset level.
  • the dimming value can increase by one for each 1 second, and thus the light output of the LED light source 1412 can also increase by a predetermined amount for each 1 second.
  • the dimming indicator 1526 can set the digital output 1548 to a predetermined dimming value, e.g., a maximum dimming value.
  • a predetermined dimming value e.g., a maximum dimming value.
  • the reference signal REF is preset to a maximum level, e.g., equal to the reference signal REF1.
  • the duty cycle of the PWM signal PWM1 is preset to 100%. Accordingly, the LED light source 1412 in FIG. 14A can emit a maximum light intensity/brightness.
  • the trigger monitoring unit 1506 detects a negative edge of the voltage at the terminal CLK followed by a positive edge. Therefore, the trigger monitoring unit 1506 generates a first pulse based on the operations of the power switch 304.
  • the first pulse can enable the counting of the waves of the AC signal V IN to adjust the dimming signal, e.g., the reference signal REF or the PWM signal PWM1.
  • the dimming indicator 1526 increases the digital output 1548 from a minimum dimming value, and the light output of the LED light source 1412 increases from a corresponding minimum intensity/brightness.
  • the dimming signal When the dimming signal is adjusted to a desired level, e.g., the light output of the LED light source 1412 is adjusted to a desired intensity/brightness, the user can turn off the power switch 304 and then turn on the power switch 304 within the predefined time interval ⁇ T. Accordingly, the trigger monitoring unit 1506 generates a second pulse based on the operations of the power switch 304. The second pulse can disable the counting of the waves of the AC signal V IN . Therefore, the dimming indicator 1526 maintains the dimming signal at the desired level to maintain the light output of the LED light source 1412 at the desired intensity/brightness.
  • the dimming indicator 1526 can restart the counting of the clock signal 1544 and increase the digital output 1548 from the minimum dimming value again.
  • the dimming indicator 1526 can stop counting the clock signal 1544 and maintain the digital output 1548 to the maximum dimming value.
  • the light output of the LED light source 1412 remains at the maximum intensity/brightness.
  • the trigger monitoring unit 1506 can enable the dimming indicator 1526 to restart the counting of the clock signal 1544.
  • the dimming indicator 1526 can increase the digital signal 1548 from the minimum dimming value again.
  • FIG. 17 illustrates an example of a diagram illustrating an operation of the light source driving system 1400 in FIG. 14A , in accordance with one embodiment of the present invention.
  • FIG. 17 is described in combination with FIG. 14A , FIG. 15 and FIG. 16 .
  • the LED light source 1412 is powered by regulated power from the power converter 1410 to generate an initial light output, in one embodiment.
  • the initial light output can be determined by an initial voltage of the reference signal REF.
  • the initial light output can be determined by an initial duty cycle (e.g., 100%) of the PWM signal PWM1.
  • the reference signal REF and the PWM signal PWM1 can be generated according to the dimming value of the dimming indicator 1526. Therefore, the initial voltage of REF and the initial duty cycle of PWM1 can be determined by an initial dimming value (e.g., 10) provided by the dimming indicator 1526.
  • the user can apply a first set of operations to the power switch 304.
  • a dimming request signal is generated upon detection of a first turn-off operation followed by a first turn-on operation of the power switch 304 within a predefined time interval ⁇ T.
  • a dimming request signal including a negative edge 1704 followed by a positive edge 1706 of the voltage at the terminal CLK can be detected.
  • the trigger monitoring unit 1506 can generate a pulse TRIG.
  • the dimming indicator 1526 is enabled to count the clock signal 1544.
  • the dimming indicator 1526 increases the dimming value from a minimum value, e.g., 1, and increases the dimming value by one in response to three pulses of the clock signal 1544.
  • the dimming indicator 1526 can increase the dimming value by two, three, or other number, in response to a predetermined number of the pulses of the clock signal 1544.
  • the dimming indicator 1526 can decrease the dimming value from a predetermined value, e.g., 10, and decreases the dimming value by one, two, or other number, in response to a predetermined number of the pulses of the clock signal 1544.
  • the D/A converter 528 reads the dimming value from the dimming indicator 1526 and increases the voltage of the reference signal REF in response to an increase of the dimming value, in one embodiment.
  • the D/A converter 528 reads the dimming value from the dimming indicator 1526 and increases the duty cycle of the PWM signal PWM1 (e.g., increases 10% each time) in response to an increase of the dimming value, in one embodiment. Accordingly, the light output of the LED light source 1412 is adjusted.
  • the user can terminate the adjustment process by applying a second set of operations to the power switch 304.
  • a dimming termination signal is generated upon detection of a second turn-off operation followed by a second turn-on operation of the power switch 304 within a predefined time interval ⁇ T.
  • the dimming termination signal including a negative edge 1708 followed by a positive edge 1710 of the voltage at the terminal CLK can be detected.
  • the trigger monitoring unit 1506 can generate a pulse TRIG.
  • the dimming indicator 1526 is disabled and holds its dimming value, Accordingly, in the analog dimming mode, the voltage of the reference signal REF can be held at a desired level. In the burst dimming mode, the duty cycle of the PWM signal PWM1 can be held to a desired value. Therefore, the light output of the LED light source 1412 can be maintained at a desired level.
  • the user can apply a third set of operations to the power switch 304.
  • a dimming request signal is generated upon detection of a third turn-off operation followed by a third turn-on operation of the power switch 304 within a predefined time interval ⁇ T.
  • a dimming request signal including a negative edge 1712 followed by a positive edge 1714 of the voltage at the terminal CLK can be detected.
  • the dimming control circuitry 1408 adjusts the light output of the LED light source 1412 through adjusting the dimming levels by counting the clock signal 1544.
  • FIG. 18 illustrates an example of a diagram illustrating an operation of the light source driving system 1400 in FIG. 14A , in accordance with one embodiment of the present invention.
  • FIG. 18 is described in combination with FIG. 14A , FIG. 15 , FIG. 16 and FIG. 17 .
  • the power switch 304 is off.
  • the LED light source 1412 is powered by regulated power from the power converter 1410 to generate an initial light output, in one embodiment.
  • the user can apply a first set of operations to the power switch 304.
  • a dimming request signal is generated upon detection of a first turn-off operation followed by a first turn-on operation within a predefined time interval ⁇ T.
  • a dimming request signal including a negative edge 1804 followed by a positive edge 1806 of the voltage at the terminal CLK can be detected.
  • the dimming control circuitry 1408 adjusts the regulated power to the LED light source 1412 through adjusting dimming levels by counting the clock signal 1544.
  • the dimming indicator 1526 can maintain the dimming value to its maximum value. In another embodiment, the dimming value decreases from its maximum value, e.g., 10. If the dimming value decreases to its minimum value, e.g., 1, the dimming indicator 1526 can maintain the dimming value to its minimum value.
  • the voltage of the reference signal REF remains at its maximum level or its minimum level
  • the duty cycle of the PWM signal PWM1 remains at its maximum duty cycle, e.g., 100%, or its minimum duty cycle, e.g., 10%.
  • the light output of the LED light source 1412 remains at its maximum level or its minimum level accordingly.
  • the user can restart the adjustment process by applying a second set of operations to the power switch 304.
  • a dimming request signal is generated upon detection of a second turn-off operation followed by a second turn-on operation within a predefined time interval ⁇ T.
  • the dimming request signal including a negative edge 1808 followed by a positive edge 1810 of the voltage at the terminal CLK can be detected, and the dimming control circuitry 1408 can adjust the regulated power to the LED light source 1412 through adjusting dimming levels by counting the clock signal 1544.
  • FIG. 19 shows an example of a schematic diagram of an LED light source driving system 1900, in accordance with one embodiment of the present invention.
  • FIG. 19 is described in combination with FIG. 10 and FIG. 14A . Elements labeled the same as in FIG. 10 and FIG. 14A have similar functions.
  • the driving system 1900 includes power conversion circuitry, e.g., the AC/DC converter 306 and a DC/DC converter 1910, and dimming control circuitry, e.g., a dimming controller 1908.
  • the DC/DC converter 1910 and the dimming controller 1908 have similar functions as the DC/DC converter 310 and the dimming controller 1008 described in relation to FIG. 10 .
  • the dimming controller 1908 receives the periodic signal 1454, e.g., via the terminal CLK, and counts the sinusoidal waves of the AC signal V IN by counting the cycles of the periodic signal 1454.
  • the dimming controller 1908 can adjust the regulated power I REG to the LED light source 1412 by counting the sinusoidal waves of the AC signal V IN .
  • the adjusting process of the regulated power I REG is similar to that described in relation to FIG. 14A .
  • the control switch Q16 may be integrated in the dimming controller 1908.
  • FIG. 20 shows an example of a structure of the dimming control circuitry 1908 in FIG. 19 , in accordance with one embodiment of the present invention.
  • FIG. 20 is described in combination with FIG. 11 , FIG. 15 and FIG. 19 . Elements labeled the same as in FIG. 11 , FIG. 15 and FIG. 19 have similar functions.
  • the structure of the dimming control circuitry 1908 is similar to the structure of the dimming controller 1008 in FIG. 11 except for the configuration of the trigger monitoring unit 1506 and the dimmer 1502.
  • the trigger monitoring unit 1506 and the dimmer 1502 have similar functions as in the dimming control circuitry 1408 in FIG. 15 .
  • FIG. 21 shows an example of a block diagram of an LED light source driving system 2100, in accordance with one embodiment of the present invention.
  • FIG. 21 is described in combination with FIG. 14A , FIG. 15 , FIG. 19 and FIG. 20 . Elements labeled the same as in FIG. 14A and FIG. 19 have similar functions.
  • the driving system 2100 includes multiple power converters 2110 to power multiple LED sources, e.g., LED strings 2112 and 2118.
  • the driving system 2100 further includes multiple dimming controllers 2108 to control regulated power, e.g., regulated currents I REG1 and I REG2 , provided to the LED sources by counting the waves of the AC signal V IN , e.g., counting the cycles of the periodic signal 1454.
  • the power converters 2110 can have similar functions and/or structures as the power converter 1410 in FIG. 14A or the power converter 1910 in FIG. 19 .
  • the dimming controllers 2108 can have similar functions and/or structures as the dimming controller 1408 (in FIG. 14A and FIG. 15 ) or the dimming controller 1908 (in FIG. 19 and FIG. 20 ).
  • the driving system 2100 can power other number of LEDs or LED strings. Accordingly, the driving system 2100 includes corresponding number of DC/DC converters and dimming controllers.
  • the adjusting process of the light outputs of the LED sources are synchronized with each other. In other words, variation of the light outputs of the LED sources can be substantially the same.
  • the LED sources can emit substantially the same light intensity/brightness.
  • internal oscillator circuits can be omitted in the dimming controllers 2108.
  • FIG. 22 shows a flowchart of an example of a method for controlling dimming of an LED light source, in accordance with one embodiment of the present invention.
  • FIG. 22 is described in combination with FIG. 14A , FIG. 15 , FIG. 16 , FIG. 17 , FIG. 18 , FIG. 19 , FIG. 20 and FIG. 21 .
  • an AC signal V IN is transferred through the power switch 304.
  • a dimming controller generates a driving signal CTRL according to a set of operations of the power switch 304.
  • the dimming controller adjusts the driving signal CTRL by counting the waves of the AC signal V IN to control the dimming of the LED light source 1412.
  • the driving signal CTRL controls the control switch Q16 coupled to the LED light source 1412.
  • a driving system can include multiple dimming controllers to adjust the light outputs of the LED light sources respectively.
  • Each dimming controller can count the waves, e.g., sinusoidal waves of the AC input voltage from an AC power source, and can increase or decrease the light output of a corresponding LED source by a predetermined amount in response to a predetermined number of the waves of the AC input voltage.
  • the dimming of the multiple LED sources can be synchronized to each other, and the multiple LED sources can emit substantially the same light intensity/brightness.

Landscapes

  • Circuit Arrangement For Electric Light Sources In General (AREA)
EP12156751.5A 2011-03-07 2012-02-23 Steuerungen, Systeme und Verfahren zur Steuerung der Dämpfung einer Lichtquelle Withdrawn EP2498579A3 (de)

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CN102685975A (zh) 2012-09-19
BR102012005134A2 (pt) 2016-07-19
EP2498579A3 (de) 2013-11-13
CN102685975B (zh) 2014-11-12
TWI483647B (zh) 2015-05-01
TW201238397A (en) 2012-09-16
IN2012DE00358A (de) 2015-04-10
JP6104511B2 (ja) 2017-03-29

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