阅读说明：本技术 发光二极管光源的驱动电路 (Driving circuit of light emitting diode light source ) 是由 斯图尔特·W·德扬 小罗伯特·C·纽曼 于 2019-08-30 设计创作，主要内容包括：可控照明设备可以利用可控阻抗电路来传导通过LED光源的负载电流。可控阻抗电路可以与第一开关设备串联耦合,可以经由脉宽调制信号使第一开关设备导通和不导通以调节负载电流的平均大小。可控照明设备可以进一步包括控制回路,该控制回路包括第二开关设备。可以协同第一开关设备,使第二开关设备导通和不导通,以控制何时将反馈信号提供给控制回路并用于控制LED光源。控制回路的特征在于时间常数,该时间常数明显大于负载电流的工作周期。(The controllable lighting device may utilize a controllable impedance circuit to conduct a load current through the LED light source. The controllable impedance circuit may be coupled in series with the first switching device, which may be rendered conductive and non-conductive via a pulse width modulated signal to adjust the average magnitude of the load current. The controllable lighting device may further comprise a control loop comprising the second switching device. The second switching device may be rendered conductive and non-conductive in conjunction with the first switching device to control when the feedback signal is provided to the control loop and used to control the LED light source. The control loop is characterized by a time constant that is significantly greater than the duty cycle of the load current.)

1. A controllable lighting device, comprising:

a Light Emitting Diode (LED) light source;

a controllable impedance circuit coupled in series with an LED light source and configured to conduct a load current through the LED light source;

a first switching device connected in series with the controllable impedance circuit;

a feedback circuit configured to generate a feedback signal indicative of a magnitude of the load current conducted through the LED light source;

a control loop coupled to the feedback circuit and configured to generate a drive signal for controlling the controllable impedance circuit based on the feedback signal, the control loop including a second switching device capable of being rendered conductive and non-conductive to control when the feedback signal is used to generate the drive signal; and

a digital control circuit configured to control the control loop to adjust a peak magnitude of the load current conducted through the LED light source toward a target magnitude, the digital control circuit further configured to render the first switching device conductive and non-conductive via a Pulse Width Modulation (PWM) signal and to adjust a duty cycle of the PWM signal to adjust an average magnitude of the load current, the digital control circuit further configured to render the second switching device conductive and non-conductive in coordination with the PWM signal.

2. The controllable lighting device of claim 1, wherein the digital control circuit is configured to render the second switching device conductive at an end of a first time period after the digital control circuit renders the first switching device conductive, the digital control circuit further configured to render the second switching device non-conductive at a beginning of a second time period before the digital control circuit renders the first switching device non-conductive.

3. The controllable lighting device of claim 1, wherein the digital control circuit is configured to render the second switching device conductive at a first time offset after the digital control circuit renders the first switching device conductive, the digital control circuit further configured to render the second switching device non-conductive at a second time offset before the digital control circuit renders the first switching device non-conductive.

4. A controllable lighting device according to claim 1, wherein the control loop further comprises a filter circuit configured to filter the feedback signal, and the second switching device is rendered conductive and non-conductive to control when the feedback signal is provided to the filter circuit.

5. The controllable lighting device of claim 4, wherein the filtering circuit comprises a resistor-capacitor (RC) filter coupled to the second switching device and configured to generate a signal representative of a peak magnitude of the feedback signal when the second switching device is rendered conductive.

6. The controllable lighting device of claim 1, wherein the control loop further comprises an integrator circuit, the control loop configured to receive a target current control signal from the digital control circuit and to generate the at least one drive signal by integrating a difference between the target current control signal and the feedback signal via the integrator circuit.

7. The controllable lighting device of claim 6, wherein the control loop is characterized by a time constant, the load current conducted by the controllable impedance circuit is characterized by a load current period, and the time constant of the control loop is greater than the load current period.

8. The controllable lighting device according to claim 1, wherein, when the target magnitude is less than a transition value, the digital control circuit is configured to maintain a peak magnitude of the load current conducted by the controllable impedance circuit at a constant magnitude and adjust the duty cycle of the PWM signal to adjust the average magnitude of the load current towards the target magnitude.

9. The controllable lighting device of claim 8, wherein when the target magnitude is greater than or equal to the transition value, the digital control circuit is configured to maintain the duty cycle of the PWM signal at about 99% and adjust the peak magnitude of the load current conducted by the controllable impedance circuit to adjust the average magnitude of the load current toward the target magnitude.

10. The controllable lighting device of claim 8, wherein when the target magnitude is greater than or equal to the transition value, the digital control circuit is configured to maintain the duty cycle of the PWM signal at about 100% and adjust the peak magnitude of the load current conducted by the controllable impedance circuit to adjust the average magnitude of the load current toward the target magnitude.

11. A controllable lighting device according to claim 1, wherein the first switching device is electrically coupled between the controllable impedance circuit and circuit common.

12. A controllable lighting device according to claim 1, wherein the controllable impedance circuit comprises a regulating transistor configured to operate in a linear region.

13. The controllable lighting device of claim 1, further comprising a bus adjustment circuit coupled to the controllable impedance circuit and configured to maintain a voltage developed across the controllable impedance circuit below a threshold.

14. The controllable lighting device of claim 1, further comprising a wireless communication circuit, wherein the digital control circuit is configured to control the controllable impedance circuit and the first switching device in response to a control message received via the wireless communication circuit.

15. A load control device comprising:

a controllable impedance circuit configured to conduct a load current through a Light Emitting Diode (LED) light source;

a first switching device connected in series with the controllable impedance circuit;

a feedback circuit configured to generate a feedback signal indicative of a magnitude of the load current conducted through the LED light source;

a control loop coupled to the feedback circuit and configured to generate a drive signal for controlling the controllable impedance circuit based on the feedback signal, the control loop including a second switching device capable of being rendered conductive and non-conductive to control when the feedback signal is used to generate the drive signal; and

a digital control circuit configured to control the control loop to adjust a peak magnitude of the load current conducted through the LED light source toward a target magnitude, the digital control circuit configured to render the first switching device conductive and non-conductive via a Pulse Width Modulation (PWM) signal and adjust a duty cycle of the PWM signal to adjust an average magnitude of the load current, the digital control circuit further configured to render the second switching device conductive and non-conductive in coordination with the PWM signal.

16. The load control device of claim 15, wherein the digital control circuit is configured to render the second switching device conductive at the end of a first time period after the digital control circuit renders the first switching device conductive, the digital control circuit further configured to render the second switching device non-conductive at the beginning of a second time period before the digital control circuit renders the first switching device non-conductive.

17. The load control device of claim 15, wherein the digital control circuit is configured to render the second switching device conductive at a first time offset after the digital control circuit renders the first switching device conductive, the digital control circuit further configured to render the second switching device non-conductive at a second time offset before the digital control circuit renders the first switching device non-conductive.

18. The load control device of claim 15, wherein the control loop further comprises a filter circuit configured to filter the feedback signal, and the second switching device is rendered conductive and non-conductive to control when the feedback signal is provided to the filter circuit.

19. The load control device of claim 18, wherein the filtering circuit comprises a resistor-capacitor (RC) filter coupled to the second switching device and configured to generate a signal representative of a peak magnitude of the feedback signal when the second switching device is rendered conductive.

20. The load control device of claim 15, wherein the control loop further comprises an integrator circuit, the control loop configured to receive a target current control signal from the digital control circuit and to generate the at least one drive signal via the integrator circuit by integrating a difference between the target current control signal and the feedback signal.

21. The load control device of claim 20, wherein the control loop is characterized by a time constant, wherein the load current conducted by the controllable-impedance circuit is characterized by a load current period, and wherein the time constant of the integrator circuit is greater than the load current period.

22. The load control device of claim 15, wherein, when the target magnitude is less than a transition value, the digital control circuit is configured to maintain a peak magnitude of the load current conducted by the controllable impedance circuit at a constant magnitude and adjust the duty cycle of the PWM signal to adjust the average magnitude of the load current toward the target magnitude.

23. The load control device of claim 22, wherein, when the target magnitude is greater than or equal to the transition value, the digital control circuit is configured to maintain the duty cycle of the PWM signal at about 99% and adjust the peak magnitude of the load current conducted by the controllable impedance circuit to adjust the average magnitude of the load current toward the target magnitude.

24. The load control device of claim 23, wherein, when the target magnitude is greater than or equal to the transition value, the digital control circuit is configured to maintain the duty cycle of the PWM signal at about 100% and adjust the peak magnitude of the load current conducted by the controllable impedance circuit to adjust the average magnitude of the load current toward the target magnitude.

25. The load control device of claim 15, wherein the first switching device is electrically coupled between the controllable-impedance circuit and circuit common.

26. The load control device of claim 15, wherein the controllable-impedance circuit comprises a regulating transistor configured to operate in a linear region.

27. The load control device of claim 15, further comprising a bus regulation circuit coupled to the controllable impedance circuit and configured to maintain a voltage developed across the controllable impedance circuit below a threshold.

28. The load control device of claim 15, further comprising a wireless communication circuit, wherein the digital control circuit is configured to control the controllable impedance circuit and the first switching device in response to a control message received via the wireless communication circuit.

29. A load control device comprising:

a controllable impedance circuit configured to conduct a load current through a Light Emitting Diode (LED) light source;

a switching device connected in series with the controllable impedance circuit;

a feedback circuit configured to generate a feedback signal indicative of a magnitude of the load current conducted through the LED light source; and

a control circuit coupled to the feedback circuit and configured to generate a drive signal for controlling the controllable impedance circuit based on the feedback signal and to control the switching device to adjust a peak magnitude of the load current conducted through the LED light source toward a target magnitude, the control circuit further configured to render the switching device conductive and non-conductive via a Pulse Width Modulation (PWM) signal and to adjust a duty cycle of the PWM signal to adjust an average magnitude of the load current, the control circuit further configured to control when the feedback signal is sampled in coordination with the PWM signal.

30. The load control device of claim 29, wherein the control circuit is configured to sample the feedback signal during a time window beginning at or after the control circuit renders the switching device conductive in each duty cycle of the PWM signal, the time window ending at or before the control circuit renders the switching device non-conductive in the duty cycle of the PWM signal.

31. The load control device of claim 30, wherein the time window begins at an end of a first offset period after the control circuit renders the switching device conductive, and wherein the time window ends at a beginning of a second offset period before the control circuit renders the switching device non-conductive.

32. The load control device of claim 29, wherein the control circuit is further configured to filter the feedback signal via a low-pass filter, and wherein the drive signal is generated based on the filtered feedback signal.

33. A drive circuit for a Light Emitting Diode (LED) light source, comprising:

a controllable impedance circuit configured to conduct a load current through the LED light source;

a first switching device connected in series with the controllable impedance circuit and responsive to a Pulse Width Modulation (PWM) signal;

a feedback circuit configured to generate a feedback signal indicative of a magnitude of the load current conducted through the LED light source;

a control loop coupled to the feedback circuit and configured to generate a drive signal for controlling the controllable impedance circuit in response to a target current control signal and the feedback signal, the control loop including a second switching device that is rendered conductive and non-conductive in response to a switching control signal to control when the feedback signal is used to generate the drive signal, the control loop configured to adjust a peak magnitude of the load current conducted through the LED light source toward a target magnitude based on the target current control signal;

wherein the first switching device is rendered conductive and non-conductive in response to the PWM signal and a duty cycle of the PWM signal is adjusted to adjust an average magnitude of the load current, and wherein the second switching device is rendered conductive and non-conductive in cooperation with the PWM signal in response to the switching control signal.

34. The drive circuit of claim 33 in which the control loop further comprises a filter circuit configured to filter the feedback signal, and the second switching device is rendered conductive and non-conductive to control when the feedback signal is provided to the filter circuit.

35. The drive circuit of claim 34, wherein the filtering circuit comprises a resistor-capacitor (RC) filter coupled to the second switching device and configured to generate a signal representative of a peak magnitude of the feedback signal when the second switching device is rendered conductive.

36. The drive circuit of claim 33, wherein the control loop further comprises an integrator circuit, the control loop configured to receive a target current control signal from the control circuit and to generate the at least one drive signal via the integrator circuit by integrating a difference between the target current control signal and the feedback signal.

37. The drive circuit of claim 36 in which the control loop is characterized by a time constant, in which the load current conducted by the controllable impedance circuit is characterized by a load current period, and in which the time constant of the integrator circuit is greater than the load current period.

38. A drive circuit according to claim 33, wherein the first switching device is electrically coupled between the controllable impedance circuit and circuit common.

39. The driver circuit of claim 33, wherein the controllable impedance circuit comprises a regulating transistor configured to operate in a linear region.

Background

Light Emitting Diode (LED) light sources (e.g., LED light engines) are replacing traditional incandescent, fluorescent, and halogen lamps as the primary forms of lighting devices. The LED light source may comprise a plurality of light emitting diodes mounted on a single structure and disposed in a suitable housing. Compared with incandescent lamps, fluorescent lamps and halogen lamps, the LED light source has higher efficiency and longer service life. An LED driver control device (e.g., an LED driver) may be coupled between a power source, such as an Alternating Current (AC) power source or a Direct Current (DC) power source, and the LED light sources for regulating the power supplied to the LED light sources. For example, the LED driver may regulate a voltage provided to the LED light source, a current provided to the LED light source, or both the current and the voltage.

Different control techniques may be employed to drive the LED light sources, including, for example, current load control techniques and voltage load control techniques. LED light sources driven by current load control techniques may be characterized by a rated current (e.g., about 350 milliamps) to which the magnitude (e.g., peak or average magnitude) of the current through the LED light source may be adjusted to ensure that the LED light source is illuminated to the proper intensity and/or color. LED light sources driven by voltage load control techniques may be characterized by a nominal voltage (e.g., about 15 volts) to which the voltage across the LED light source may be adjusted to ensure proper operation of the LED light source. If the LED light source of the rated voltage load control technique comprises a plurality of parallel LED strings, a current balance adjustment element may be used to ensure that the parallel strings have the same impedance so that the same current is drawn in each parallel string.

The light output of the LED light source may be dimmed (dim). Methods for dimming LED light sources may include, for example, Pulse Width Modulation (PWM) techniques and Constant Current Reduction (CCR) techniques. In pulse width modulation dimming, a pulse signal with a varying duty cycle may be provided to the LED light source. For example, if a current load control technique is used to control the LED light source, the peak current supplied to the LED light source may be kept constant during the on-time of the duty cycle of the pulse signal. However, the duty cycle of the pulsed signal may be varied to vary the average current provided to the LED light source, thereby varying the intensity of the light output of the LED light source. As another example, if a voltage load control technique is used to control the LED light source, the voltage supplied to the LED light source may be kept constant during the on-time of the duty cycle of the pulse signal. However, the duty cycle of the load voltage may be varied to adjust the intensity of the light output. Constant current reduction dimming may be used if the LED light source is controlled using current load control techniques. In constant current reduction dimming, current may be continuously supplied to the LED light source. However, the DC magnitude of the current provided to the LED light source may be varied to adjust the intensity of the light output.

Examples of LED drivers are described in U.S. patent No.8,492,987 entitled "LOAD CONTROL DEVICE FOR LIGHT-EMITTING DIODE LIGHT SOURCE" published on 23.7.7.2013, U.S. patent No.9,655,177 entitled "FORWARD CONVERTER with primary SIDE CURRENT sensing CIRCUIT" published on 16.5.7.8.2016, and U.S. patent No.9,247,608 entitled "LOAD CONTROL DEVICE FOR LIGHT-EMITTING DIODE LIGHT SOURCE" published on 26.1.2016, the entire disclosures of which are incorporated herein by reference.

Disclosure of Invention

Methods and apparatus for controlling LED light sources are described herein. The controllable impedance circuit may be coupled in series with the LED light source and configured to conduct a load current through the LED light source. The first switching device may be connected in series with the controllable impedance circuit, while the feedback circuit is configured to generate a feedback signal indicative of a magnitude of a load current conducted through the LED light source. The feedback circuit may be coupled to a control loop configured to generate a drive signal for controlling the controllable impedance circuit based on the feedback signal. The control loop may comprise a second switching device and/or a filter circuit. The second switching device may be capable of being turned on and off to control when the feedback signal is used to generate the drive signal (e.g., after passing the feedback signal through the filtering circuit).

The digital control circuit may control the control loop to adjust a peak magnitude of the load current conducted through the LED light source toward a target magnitude. The digital control circuit may render the first switching device conductive and non-conductive via a Pulse Width Modulation (PWM) signal and adjust a duty cycle of the PWM signal to adjust an average magnitude of the load current. The digital control circuit may further render the second switching device conductive and non-conductive in cooperation with the PWM signal. For example, the digital control circuit may be configured to render the second switching device conductive at the end of a first time period after the digital control circuit renders the first switching device conductive, and the digital control circuit may be further configured to render the second switching device non-conductive at the beginning of a second time period before the digital control circuit renders the first switching device non-conductive.

The control loop described herein may include an integrator circuit. The control loop may receive the target current control signal from the digital control circuit and integrate a difference between the target current control signal and the feedback signal via an integrator circuit to generate the drive signal. The control loop is characterized by a time constant that is greater than a load current period of a load current conducted by the controllable impedance circuit.

One or more of the components and/or functions described herein may be implemented digitally. For example, the sampling of the feedback signal may be controlled by a digital control circuit, and the filtering operation may be performed using a digital low-pass filter.

Drawings

Fig. 1 is a simplified block diagram of a controllable electrical device, such as a controllable light source.

Fig. 2 is a simplified schematic diagram of a drive circuit, such as a Light Emitting Diode (LED) drive circuit, and a control loop of an electrical device, such as the controllable light source of fig. 1.

Fig. 3 is an exemplary diagram of the relationship between various operating parameters of the controllable light source of fig. 1 and a target intensity of the controllable light source.

Fig. 4A-4C are simplified waveform diagrams illustrating the operation of the drive circuit and control loop of fig. 2.

FIG. 5 is a simplified flow diagram of an exemplary control process for controlling the control loop of FIG. 2.

Fig. 6 is a simplified schematic diagram of circuitry that may be used to implement the functionality of the drive circuit and control loop shown in fig. 2.

FIG. 7 is a simplified flow diagram of an exemplary control process for controlling the circuit shown in FIG. 6.

Detailed Description

Fig. 1 is a simplified block diagram of a controllable electrical device, such as a controllable lighting device 100 (e.g., a controllable light source). For example, the controllable lighting device 100 may be a lamp comprising one or more light sources, such as Light Emitting Diode (LED) light sources 102, 104 (e.g. LED light engines). The LED light sources 102, 104 may be controlled to adjust the intensity and/or color (e.g., color temperature) of the cumulative light output of the controllable lighting device 100. Each LED light source 102, 104 is shown in fig. 1 as a plurality of LEDs connected in series, but may comprise a single LED or a plurality of LEDs connected in parallel or a suitable combination thereof, depending on the particular lighting system. Additionally, each LED light source 102, 104 may include one or more Organic Light Emitting Diodes (OLEDs). The controllable lighting device 100 may comprise a plurality of different LED light sources, which may be rated at different magnitudes of load current and voltage. Although not shown in fig. 1, the controllable lighting device 100 may comprise a housing (e.g., a translucent housing) in which the LED light sources are located and through which the LED light sources may emit light. For example, the controllable lighting device 100 may be capable of providing thermal dimming such that the color temperature of the cumulative light output shifts towards a warm white color temperature as the intensity of the cumulative light output decreases. For example, the first LED light source 102 may comprise a white LED light source, while the second LED light source 104 may comprise a warm white (e.g., red) LED light source, and the first LED light source 102 may have a higher power rating than the second LED light source 104.

The controllable lighting device 100 may be a screw-in LED lamp configured to be screwed into a standard edison socket. The controllable lighting device 100 may comprise a screw-in base comprising a thermal connection H and a neutral connection N for receiving an Alternating Current (AC) voltage V from an AC power source (not shown)_AC. The hot connection H and the neutral connection N may also be configured to receive a Direct Current (DC) voltage from a DC power source. The controllable lighting device 100 may comprise a Radio Frequency Interference (RFI) filter and rectifier circuit 110, which may receive an AC voltage V_AC. The RFI filter and rectifier circuit 110 may operate to minimize noise provided on the AC power source and generate a rectified voltage V_RECT。

The controllable lighting device 100 may comprise a power converter circuit 120, such as a flyback converter, which may receive a rectified voltage V_RECTAnd in the bus capacitor C_BUSGenerating a variable Direct Current (DC) bus voltage V across_BUS. Power converter circuit 120 may include other types of power converter circuits such as a boost converter, a buck-boost converter, a single-ended primary inductor converter (SEPIC), a Cuk converter, or any other suitable power converter circuit for generating a suitable bus voltage. The power converter circuit 120 may provide electrical isolation between the AC power source and the LED light sources 102, 104 and may operate as a Power Factor Correction (PFC) circuit to adjust the power factor of the controllable lighting device 100 towards a power factor of 1.

As shown in fig. 1, the flyback converter 120 may include a flyback transformer 122, a Field Effect Transistor (FET) Q123, a diode D124, a resistor R125, a resistor R126, a flyback control circuit 127, and/or a feedback resistor R128. The flyback transformer 122 may include a primary winding and a secondary winding. The primary winding may be coupled in series with the FET Q123. Although shown as FET Q123, any switching transistor or other suitable semiconductor switch may be coupled in series with the primary winding of flyback transformer 122. The secondary winding of the flyback transformer 122 may be coupled to the bus capacitor C via a diode D124_BUS. Bus voltage feedback signal V_BUS-FBMay for example be formed by including a capacitor C coupled to the bus_BUSA voltage divider of resistors R125, R126 across. The flyback control circuit 127 may receive the bus voltage feedback signal V_BUS-FBAnd receives a control signal representative of the current through FET Q123 from a feedback resistor R128, which feedback resistor R128 may be coupled in series with FET Q123. The flyback control circuit 127 may control the FET Q123 to selectively conduct current through the flyback transformer 122 to generate the bus voltage V_BUS. The flyback control circuit 127 may render the FET Q123 conductive and non-conductive, e.g., in response to the bus voltage feedback signal V_BUS-FBAnd the magnitude of the current flowing through the FET Q123 toward the target bus voltage V_BUS-TRGTControl bus voltage V_BUSThe size of (2).

The controllable lighting device 100 may comprise one or more load regulating circuits, such as LED driving circuits 130, 140, for controlling the power delivered to the LED light sources 102, 104 (e.g. their intensity), respectively. The LED driver circuits 130, 140 may each receive a bus voltage V_BUSAnd may adjust the respective load currents I conducted through the LED light sources 102, 104_LOAD1、I_LOAD2And/or the respective load voltage V generated across the LED light source_LOAD1、V_LOAD2The size of (2). As described herein, one or more of the LED driver circuits 130, 140 may include a controllable impedance circuit, such as a linear regulator. One or more of the LED driver circuits 130, 140 may include a switching regulator, such as a buck converter. Examples of various embodiments of LED driver circuits are described in U.S. patent No.8,492,987 filed on 7/23 in 2013 and U.S. patent No.9,253,829 published on 2/2016, both entitled "LOAD CONTROL DEVICE FOR LIGHT-EMITTING DIODE LIGHT source," the entire disclosures of which are incorporated herein by reference.

The controllable lighting device 100 may comprise a control circuit 150, the control circuit 150 being configured to control the LED driving circuits 130, 140 to control the respective load currents I conducted through the LED light sources 102, 104_LOAD1、I_LOAD2To adjust the size of the LED light sourceThe corresponding strength of. The control circuit 150 may be configured to switch the two LED light sources 102, 104 on and off to switch the controllable lighting device 100 on and off, respectively. The control circuit 150 may be configured to control the respective intensities of the LED light sources 102, 104 to control the intensity and/or color (e.g., color temperature) of the cumulative light emitted by the controllable lighting device 100. The control circuit 150 may be configured to face the target intensity L_TRGTAdjusting (e.g. dimming) the current intensity L of the accumulated light emitted by the controllable lighting device 100_PRESThe target intensity L_TRGTCan be in the dimming range of the controllable light source, e.g. at the low end intensity L_LE(e.g., a minimum intensity, such as about 0.1% to 1.0%) and a high-end intensity L_HE(e.g., maximum intensity, such as about 100%). The control circuit 150 may be configured to face the target color temperature T_TRGTAdjusting the current color temperature T of the accumulated light emitted by the controllable lighting device 100_PRESThe target color temperature T_TRGTMay be between a cold white color temperature (e.g., approximately 3100-.

The control circuitry 150 may include digital control circuitry 152, such as a microprocessor, microcontroller, Programmable Logic Device (PLD), Application Specific Integrated Circuit (ASIC), Field Programmable Gate Array (FPGA), or any other suitable processing device or controller. The control circuit 150 may comprise a memory (not shown) configured to store an operating characteristic (e.g. the target intensity L) of the controllable lighting device 100_TRGTTarget color temperature T_TRGTLow end intensity L_LEHigh end strength L_HEEtc.). The memory may be implemented as an external Integrated Circuit (IC) or as internal circuitry of the digital control circuit 152. The controllable lighting device 100 may include a power supply 160, the power supply 160 may be coupled to a winding 162 of the flyback transformer 122 of the power converter circuit 120 and may be configured to generate a supply voltage Vcc for powering the digital control circuit 152 and other low voltage circuits of the controllable lighting device.

The control circuit 150 may also include control loops (e.g., analog control loops) 154, 156 for controlling the LED driver circuits 130, 140, respectively. LED drive circuit130. 140 may include respective regulation devices (e.g., regulating Field Effect Transistors (FETs) Q132, Q142) coupled (e.g., in series) with the LED light sources 102, 104, respectively, for conducting the load current I_LOAD1、I_LOAD2. Each regulating FET Q132, Q142 may include any type of suitable power semiconductor switch, such as a Bipolar Junction Transistor (BJT) and/or an Insulated Gate Bipolar Transistor (IGBT). The control loops 154, 156 may generate respective drive signals V_DR1、V_DR2Which may be received by the gates of the regulating FETs Q132, Q142 for controlling the regulating FETs in the linear region to provide controllable impedances in series with the LED light sources 102, 104, respectively (e.g., to operate the regulating FETs Q132, Q142 as linear regulators). When the regulating FETs Q132, Q142 conduct the corresponding load current I_LOAD1、I_LOAD2Respective regulator voltages V may be generated across the regulator FETs Q132, Q142_R1、V_R2。

The regulating FETs Q132, Q142 may be coupled (e.g., in series) with respective feedback circuits (e.g., Current Feedback (CFB) circuits) 134, 144. The current feedback circuits 134, 144 may be coupled to the control loops 154, 156 of the control circuit 150 and may generate respective current feedback signals V that may be received by the control loops 154, 156_FB1、V_FB2. The control loops 154, 156 may be configured to be responsive to the current feedback signals V, respectively_FB1、V_FB2Adjusts the drive signal V provided to the gates of the regulating FETs Q132, Q142_DR1，V_DR2A size (e.g., DC size). The digital control circuit 152 may generate a corresponding target current control signal V_TRGT1、V_TRGT2Which may also be received by the control loops 154, 156. The control loops 154, 156 may be configured to regulate the drive signal V provided to the gates of the regulating FETs Q132, Q142_DR1、V_DR2Towards the target current control signal V_TRGT1、V_TRGT2Set corresponding target current I_TRGT1、I_TRGT2Controlling the load current I_LOAD1，I_LOAD2The size of (2).

The LED driver circuits 130, 140 may further compriseIncluding a dimming device (e.g., dimming FETs Q136, Q146 or another type of semiconductor switch) coupled (e.g., in series) with the regulating FETs Q132, Q142 and the current feedback circuits 134, 144. The digital control circuit 152 may generate respective dimming control signals V that may be received by the gates of the respective dimming FETs Q136, Q146_DIM1、V_DIM2To render the dimming FET conductive and non-conductive to respectively regulate the load current I_LOAD1、I_LOAD2Average size of (d). For example, the digital control circuit 152 may be configured to control the dimming frequency f by controlling the dimming frequency f_DIMWill adjust the light control signal V_DIM1、V_DIM2Generating as a Pulse Width Modulation (PWM) signal to control the load current I_LOAD1、I_LOAD2Pulse Width Modulation (PWM) is performed. The digital control circuit 152 may be configured to adjust the dimming control signal V_DIM1、V_DIM2Corresponding duty cycle DC of₁、DC₂To adjust the load current I respectively_LOAD1、I_LOAD2Average size of (d). When the digital control circuit 152 is pulse width modulating the dimming control signal V_DIM1、V_DIM2Time, load current I_LOAD1、I_LOAD2Can be determined by the load current frequency f_LOAD(e.g., it is approximately equal to the dimming control signal V_DIM1、V_DIM2Of the dimming frequency f_DIM) And corresponding load current period T_LOADAnd (5) characterizing. Frequency f of load current_LOADMay be high enough to prevent flicker visible to the human eye.

The dimming FETs Q136, Q146 may be coupled between the respective current feedback circuits 134, 144 and circuit common. The digital control circuit 152 may be configured to control when the control loops 154, 156 are responsive to respective current feedback signals V_FB1、V_FB2To adjust the driving signal V_DR1、V_DR2The size of (2). The digital control circuit 152 may be configured to cooperate with a corresponding dimming control signal V_DIM1、V_DIM2Having control loops 154, 156 responsive and non-responsive to respective current feedback signals V_FB1And VFB 2. For example, the digital control circuit 152 may be configured to operate within a feedback window T_WINDuring which the control loops 154, 156 are enabled to respond to respectiveCurrent feedback signal V_FB1、V_FB2The feedback window T_WINMay be as long as or slightly shorter than the time period when the dimming FETs Q136, Q146 are turned on. The digital control circuit 152 may be configured to cause the control loops 154, 156 to respond to the respective current feedback signals V at about the same time or shortly after causing the dimming FETs Q136, Q146 to turn on_FB1、V_FB2. The digital control circuit 152 may be configured to cause the control loops 154, 156 to feed back the signal V to the respective currents at the same time or shortly before causing the dimming FETs Q136, Q146 to be non-conductive_FB1、V_FB2No response is made. To control the operation of the respective control loops 154, 156, the digital control circuit 152 may generate respective feedback window control signals V_WIN1、V_WIN2The feedback window control signal V_WIN1、V_WIN2Can be received by the control loop to enable and disable when the control loop is responsive to the respective current feedback signal V_FB1、V_FB2. As a result, each control loop 154, 156 may be responsive to a respective current feedback signal V_FB1、V_FB2Is detected (e.g., when the dimming FETs Q136, Q146 are on).

The techniques described herein may help prevent erroneous operation of the controllable lighting device 100 in various situations. For example, since the dimming FETs Q136, Q146 may be coupled between the respective current feedback circuits 134, 144 and circuit common, the current feedback signal V is made to be non-conductive when the dimming FETs Q136, Q146 are made to be non-conductive_FB1、V_FB2May be pulled towards the bus voltage V_BUSThis may cause the control loops 154, 156 to erroneously drive the regulating FETs Q132, Q142. By configuring the digital control circuit 152 to control (e.g., at least with respect to timing) when the control loops 154, 156 respond to the respective current feedback signals V_FB1、V_FB2To adjust the driving signal V_DR1、V_DR2Can avoid generating the driving signal V by mistake_DR1、V_DR2。

The controllable lighting device 100 may comprise means for controlling the bus voltage V_BUSE.g., to ensure that adjusting the FETs Q132, Q142 does not consume too muchPower) bus conditioning circuit 170. For example, the bus regulation circuit 170 may be coupled to the junction of the first regulation FET Q132 and the first LED light source 102, and may be responsive to a first regulator voltage V across the first regulation FET Q132_R1. The bus conditioning circuit 170 may be coupled to the junction of the resistors R125, R126 for conditioning the bus voltage feedback signal V_BUS-FBTo enable the flyback control circuit 127 to regulate the bus voltage V_BUSThe size of (2). For example, bus regulation circuit 170 may regulate bus voltage V_BUSTo control the first regulator voltage V_R1Is less than the maximum regulator voltage threshold V_R-MAX(e.g., about 0.6 volts), for example, to prevent excessive power dissipation from being dissipated in the regulating FETs Q132, Q142. In an example (e.g., as shown in fig. 1), the bus conditioning circuit 170 may be coupled to only the first conditioning transistor Q132. Since the first LED light source 102 may have a higher power rating than the second LED light source 104 (as previously described), it is responsive to the first regulator voltage V_R1To adjust the bus voltage V_BUSTo ensure that the first regulating FET Q132 does not consume too much power and to ensure that the second regulating FET Q142 does not consume too much power.

The controllable lighting device 100 may comprise a communication circuit 180 coupled to the digital control circuit 152. Communications circuitry 180 may include wireless communications circuitry, such as a Radio Frequency (RF) transceiver coupled to antenna 182, for transmitting and/or receiving RF signals. The wireless communication circuitry may be an RF transmitter for transmitting RF signals, an RF receiver for receiving RF signals, or an Infrared (IR) transmitter and/or receiver for transmitting and/or receiving IR signals. The communication circuit 180 may be coupled to the hot connection H and the neutral connection N of the controllable lighting device 100 for transmitting the control signal via a wire using, for example, a Power Line Carrier (PLC) communication technology. The digital control circuit 152 may be configured to determine the target intensity L of the controllable lighting device 100 in response to a message (e.g. a digital message) received via the communication circuit 180_TRGT. The digital control circuit 152 may be configured to respond to the determined target intensity L for the controllable lighting device 100_TRGTDetermine the respective purpose for the LED light sources 102, 104Mark strength L_TRGT1、L_TRGT2。

When the target intensity L of at least one of the LED light sources 102, 104_TRGT1、L_TRGT2Greater than or equal to the transition intensity L_TRANWhen desired, the digital control circuit 152 may be configured to render the respective dimming FETs Q136, Q146 conductive (e.g., always on) and to adjust the intensity of the respective LED light sources using a Constant Current Reduction (CCR) dimming technique. Using CCR dimming techniques, the digital control circuit 152 may adjust the corresponding target current control signal V_TRGT1、V_TRGT2To direct the respective control loops 154, 156 toward the respective target currents I_TRGT1、I_TRTG2Regulating the load current I_LOAD1、I_LOAD2Average size of (d). Target current I_TRGT1、I_TRGT2Can be respectively at the maximum current I_MAX(e.g., at high end intensity L_HELower) and minimum current I_MIN(e.g. at transition intensity L_TRANAbove).

When the target intensity L of at least one of the LED light sources 102, 104_TRGT1、L_TRGT2Less than the transition intensity L_TRANWhen desired, the digital control circuit 152 may be configured to control the respective dimming FETs Q136, Q146 to adjust the intensity of the respective LED light sources using a Pulse Width Modulation (PWM) dimming technique. For example, the digital control circuit 152 may be configured to control the respective target current control signal V_TRGT1、V_TRGT2To maintain the corresponding target current I_TRGT1、I_TRGT2Is constant. Using PWM dimming techniques, the digital control circuit 152 may adjust the corresponding dimming control signal V_DIM1、V_DIM2Duty cycle of DC₁、DC₂To control the load current I_LOAD1、I_LOAD2Is adjusted to the minimum current I_MINThe following. For example, the digital control circuit 152 may be based on the corresponding target intensity L_TRGT1、L_TRGT2To adjust each dimming control signal V_DIM1、V_DIM2Duty cycle of DC₁、DC₂. For example, with corresponding target intensity L_TRGT1、L_TRGT2To reduce, the digital control circuit 152 mayReducing duty cycle DC in a linear manner₁、DC₂And vice versa. When the respective dimming FETs Q136, Q146 are turned on, each control loop 154, 156 may continue toward the target current I_TRGT1、I_TRGT2Regulating the load current I_LOAD1、I_LOAD2Peak size of (I)_PK. Each control loop 154, 156 is characterized by a time constant that is, for example, greater than the corresponding load current I_LOAD1、I_LOAD2Load current period T of_LOADIs much larger to help avoid the corresponding drive signal V when the dimming FETs Q136, Q146 are non-conductive_DR1、V_DR2The size of (2) is changed. The time constant may be associated with, for example, one or more integrator circuits and/or RC filter circuits included in the control loops 154, 156. The value of the time constant may be determined by an electrical characteristic (e.g., capacitance and/or resistance) of one or more components included in the control loop 154, 156.

Fig. 2 is a simplified schematic diagram of an LED driver circuit 210 (e.g., one of LED driver circuits 130, 140) and a control loop 220 (e.g., one of control loops 154, 156) of an electrical device 200, such as an LED driver or a controllable light source (e.g., controllable lighting device 100). The LED drive circuit 210 may be coupled in series with the LED light source 202 (e.g., one of the LED light sources 102, 104) for conducting a load current I through the LED light source_LOAD. The control loop 220 may generate a driving signal V for controlling the LED driving circuit 210_DRTo adjust the load current I through the LED light source_LOADThe size of (2). The LED driver 100 may further include a digital control circuit 252 (e.g., the digital control circuit 152) for generating a PWM control signal (e.g., the target current control signal V) that may be received by the control loop 220_TRGT-PWM) For setting up a current I for the load_LOADTarget current I of_TRGT. The digital control circuit 252 may be configured to face the target intensity L_TRGTAdjusting the intensity of the LED light source 202, the target intensity L_TRGTCan be at a minimum intensity L_MIN(e.g., about 0.1% -1.0%) and a maximum intensity L_MAX(e.g., between about 100%). Minimum intensity L_MINCan be approximated as being stableIn the steady state (e.g. when the target intensity L is_TRGTWhen held constant), the digital control circuit 252 may control the minimum intensity of the LED light source 202.

The LED driver circuit 210 may include a regulation device, such as a regulation FET Q212 coupled in series with the LED light source 202. The regulating FET Q212 may include any type of suitable power semiconductor switch, such as a Bipolar Junction Transistor (BJT) and/or an Insulated Gate Bipolar Transistor (IGBT). When the regulating FET Q212 is turned on, a regulator voltage V can be generated across the regulating FET_R. The LED driver circuit 210 may include a current feedback circuit (e.g., a current feedback resistor R214) coupled in series with the regulating FET Q212 for generating a current feedback signal V_FBThe current feedback signal V_FBMay have a representative load current I_LOADDC size of the magnitude of (d). The LED driver circuit 210 may include a dimming device (e.g., such as a dimming FET Q216 or another type of semiconductor switch) coupled between the current feedback resistor R214 and circuit common. The digital control circuit 252 may generate a dimming control signal V that may be received by the gate of the dimming FET Q216_DIM. In response to dimming control signal V_DIMThe dimming FET Q216 may be rendered conductive and non-conductive for regulating the load current I_LOADAverage size of (d).

The control loop 220 may receive a current feedback signal V generated by a current feedback resistor R214_FBAnd/or the PWM target current control signal V generated by the digital control circuit 252_TRGT-PWM. Current feedback signal V_FBMay be received by a controllable switch 222 included in the control loop 220. Responsive to a feedback window control signal V generated by a digital control circuit 252_WIN(e.g., a switch control signal) that renders controllable switch 222 conductive and non-conductive. The controllable switch 222 may be coupled to a filter circuit, which may include a capacitor C224 and a resistor R225. When the controllable switch 222 is turned on, the capacitor C224 (e.g., having a capacitance of about 1.0 μ F) may be charged to about the current feedback signal V through the resistor R225 (e.g., having a resistance of about 100)_FBPeak size of (I)_PKFor generating a peak current feedback signal across the capacitorNumber V_FB-PK。

The control loop 220 may include an operational amplifier U226, the operational amplifier U226 including an inverting input coupled to receive the current feedback signal V through a resistor R228_FB. Control loop 220 may include a filter circuit (e.g., a low pass RC filter circuit) including a resistor R230 (e.g., having a resistance of about 1 kQ) and a capacitor C232 (e.g., having a capacitance of about 0.1 μ F). PWM target current control signal V_TRGT-PWMCan be received by the resistor R230 to generate a DC target current control signal V at the junction of the resistor R230 and the capacitor C232_TRGT-DCAnd has a representative for the load current I_LOADTarget current I of_TRGTThe DC magnitude of (c). DC target current control signal V_TRGT-DCMay be coupled to the non-inverting input of operational amplifier U226. For example, the digital control circuit 252 may control the PWM target current control signal V_TRGT-PWMGenerating as a pulse width modulated signal having a duty cycle DC_TRGTFor load current I_LOADTarget current I of_TRGT. In addition, the digital control circuit 252 may include a digital-to-analog converter (DAC) for generating the DC target current control signal V_TRGT-DCThe digital-to-analog converter (DAC) may be directly coupled to the non-inverting input of the operational amplifier U226 (e.g., without the resistor R230 and capacitor C232).

The control loop 220 may include a capacitor C234 coupled between the inverting input and the output of the operational amplifier U226 such that the control loop 220 may be configured to integrate the peak current feedback signal V_FB-PKAnd a DC target current control signal V_TRGT-DCThe error between. The control loop 220 may generate a drive signal V that may be received by the gate of the regulating FET Q212_DRFor controlling the regulating FET in the linear region to provide a controllable impedance in series with the LED light source 202 (e.g., the regulating FET may be operated as a linear regulator). The output of the operational amplifier EG226 may be coupled to the conditioning F by another filter circuit (e.g., a low pass RC filter circuit) including a resistor R236 (e.g., having a resistance of about 1 kQ) and a capacitor C238 (e.g., having a capacitance of about 0.1 μ F)ET Q212 gate.

The digital control circuit 252 can control the dimming control signal V_DIMTo render the dimming FET Q216 conductive and non-conductive to regulate the load current I_LOADAverage size of (d). For example, the digital control circuit 252 may be configured to control the dimming frequency f by controlling the dimming frequency f_DIMWill adjust luminance the control signal V_DIMGenerating as a Pulse Width Modulation (PWM) signal to a load current I_LOADPulse Width Modulation (PWM) is performed. The digital control circuit 252 may be configured to adjust the dimming control signal V_DIMDuty cycle of DC_DIMTo regulate the load current I_LOADAverage size of (d). When the digital control circuit 252 is positively pulsing the dimming control signal V_DIMTime, load current I_LOADIs characterized by a load current frequency f_LOADIs approximately equal to the dimming control signal V_DIMThe dimming frequency of (1). Frequency f of load current_LOADMay be high enough to prevent flicker visible to the human eye in the LED light sources 202.

The digital control circuit 252 may be configured to cooperate with the dimming control signal V_DIMRendering controllable switch 222 conductive and non-conductive. For example, the digital control circuit 252 may be configured to turn on the controllable switch 222 at about the same time or shortly after the digital control circuit turns on the dimming FET Q216. The digital control circuit 252 may be configured to render the controllable switch 222 nonconductive at about the same time or shortly before the digital control circuit renders the dimming FET Q216 nonconductive. Thus, the peak current feedback signal V_FB-PKCan represent the load current I_LOADPeak size of (I)_PKThis can prevent erroneous operation of the control circuit in various situations. For example, since the dimming FET Q216 may be coupled between the current feedback resistor R214 and circuit common, the current feedback signal V is not conductive when the dimming FET Q216 is non-conductive_FBCan be pulled towards the bus voltage V_BUS. This may cause the control loop 220 to erroneously drive the regulating FET Q212. By configuring the digital control circuit 252 to control when the controllable switch 222 is turned on, erroneous generation of the driving signal V can be avoided_DR。

The digital control circuit 252 may be based on the target intensity L_TRGTControl signal V for controlling PWM target current_TRGT-PWMDuty cycle of DC_TRGTDimming control signal V_DIMDuty cycle of DC_DIMAnd/or dimming control signal V_DIMOf the dimming frequency f_DIM. FIG. 3 shows the load current I_LOADPeak current I of_PKWith target intensity L_TRGTRelation between, dimming control signal V_DIMDuty cycle of DC_DIMWith target intensity L_TRGTAnd the dimming control signal V_DIMOf the dimming frequency f_DIMAnd target intensity L_TRGTExamples of relationships between.

When the target intensity L of the LED light source 202 is_TRGTGreater than or equal to the transition intensity L_TRANWhen desired, the digital control circuit 252 may be configured to turn on (e.g., almost always on) the dimming FET Q216 and regulate the load current I_LOADPeak size of (I)_PKTo adjust the intensity of the LED light source (e.g., using a Constant Current Reduction (CCR) dimming technique). For example, the digital control circuit 252 may adjust the PWM target current control signal V_TRGT-PWMDuty cycle of DC_TRGTTo drive the control loop 220 towards the target current I_TRGTRegulating the load current I_LOADPeak size of (I)_PKTarget current I_TRGTCan be at the maximum current I_MAXAnd minimum current I_MINIn the meantime. When the target intensity L of the LED light source 202 is_TRGTGreater than or equal to the transition intensity L_TRANTime, light modulation control signal V_DIMDuty cycle of DC_DIMCan be kept constant at the maximum duty cycle DC_MAX. Maximum duty cycle DC_MAXMay be less than 100% (e.g., as shown in fig. 3) such that the digital control circuit 252 may pulse-width modulate the load current I_LOAD. Maximum duty cycle DC_MAXMay be equal to 100% such that when LED light source 202 has a target intensity L_TRGTGreater than or equal to the transition intensity L_TRANWhen this occurs, the dimming FET Q216 may be always on.

When the target intensity L of the LED light source 202 is_TRGTLess than the transition intensity L_TRANWhen desired, the digital control circuit 252 may be configured to control the dimming FET Q216 (e.g., using pulse widthModulation (PWM) dimming technique) adjusts the intensity of the LED light source. When using PWM dimming techniques, the digital control circuit 252 may be configured to maintain the target current control signal V_TRGT-PWMDuty cycle of DC_TRGTIs constant to maintain the target current I_TRGTConstant and adjusting the dimming control signal V_DIMDuty cycle of DC_DIMTo regulate the load current I_LOADThe size of (2). For example, as shown in FIG. 3, the digital control circuit 252 may be based on the target intensity L_TRGT(e.g. linearly) to regulate duty cycle DC_DIM. When the dimming FET Q216 is turned on, the control loop 220 may continue toward the target current I_TRGTRegulating the load current I_LOADPeak size of (I)_PK. The control loop 220 is characterized by a time constant that is specific to the load current I_LOADLoad current period T of_LOADMuch larger, e.g., to help avoid the drive signal V when the dimming FET Q216 is non-conductive_DRThe size of (2) is changed.

The digital control circuit 252 may be configured to cause a target intensity L of the LED light source 202_TRGT(and thus the current intensity) fades down (e.g., adjusts gradually over a period of time). The digital control circuit 252 may be configured to control the current intensity L of the LED light source by comparing the current intensity L of the LED light source_PRESFrom minimum fading strength L_FADE-MINSlowly increasing to the target intensity L_TRGTTo fade LED light source 202 from off to on, the minimum fading intensity L_FADE-MINPossibly less than the minimum intensity L_MIN(e.g., such as about 0.02%). The digital control circuit 252 may be configured to control the current intensity L of the LED light source by comparing the current intensity L of the LED light source_PRESFrom greater than or equal to the minimum intensity L_MINSlowly decreases to a minimum fading strength L_FADE-MINTo gradually turn the LED light source 202 from on to off, at which time the digital control circuit 252 may turn the LED light source off. As shown in fig. 3, when the target intensity L is_TRGTLess than minimum intensity L_MINAt (e.g., while maintaining target current control signal V)_TRGT-PWMDuty cycle of DC_TRGTAnd a dimming control signal V_DIMDuty cycle of DC_DIMWhile constant) digital control circuit 252 may be relative to the target powerStream I_TRGTAdjusting dimming control signal V_DIMOf the dimming frequency f_DIM。

Fig. 4A-4C show waveforms illustrating the operation of the LED driver circuit 210 and the control loop 220 of fig. 2. In the example shown in FIG. 4A, the target intensity L_TRGTMay be equal to and/or close to the maximum intensity L_MAX. Load current I_LOADPeak current I of_PKCan be controlled to a maximum current I_MAX. Dimming control signal V_DIMDuty cycle of DC_DIMCan be controlled to a maximum duty cycle DC_MAX(e.g., 99%) resulting in an on-time T of the dimming control signal_ONAnd (5) prolonging. Slave dimming control signal V_DIMA first offset period T from being driven high_OFFSET1Thereafter, the digital control signal 252 may direct the window control signal V toward the supply voltage Vcc_WINDriven high. Make the dimming control signal V_DIMSecond offset period T before driving Low_OFFSET2The digital control signal 252 may drive the window control signal V towards circuit common_WINDriven low. Peak current feedback signal V_FB-PKMay have a current I dependent on (e.g. representative of) the load current_LOADPeak size of (I)_PK(e.g., maximum current I_MAX) The size of (2). Drive signal V provided to the gate of regulating transistor Q212_DRCan be in a first size V_DR1。

In the example shown in FIG. 4B, the target intensity L_TRGTMay be approximately equal to the transition intensity L_TRAN. Load current I_LOADPeak current I of_PKCan be controlled to about a minimum current I_MIN. Dimming control signal V_DIMDuty cycle of DC_DIMCan still be controlled to the maximum duty cycle DC_MAXResulting in a similar on-time T of the dimming control signal_ONAs shown in fig. 4A. At the slave dimming control signal V_DIMA first offset period T from being driven high_OFFSET1Thereafter, the digital control signal 252 may direct the window control signal V toward the supply voltage Vcc_WINDriven high. In dimming controlSignal V_DIMSecond offset period T before being driven to low level_OFFSET2In time, the digital control signal 252 may be common to the circuits, the window control signal V_WINDriven low. Peak current feedback signal V_FB-PKMay have a current I dependent on (e.g. representative of) the load current_LOADPeak size of (I)_PKIs (e.g. minimum current I)_MIN). Drive signal V provided to the gate of regulating transistor Q212_DRCan be in a second size V_DR2。

In the example shown in FIG. 4C, the target intensity L_TRGTMay be less than the transition intensity L_TRANAnd is greater than the minimum intensity L_MIN. As in FIG. 4B, the load current I may be adjusted_LOADPeak current I of_PKControlled to approximate minimum current I_MIN. Can adjust the light control signal V_DIMDuty cycle of DC_DIMControlled to less than maximum duty cycle DC_MAXResulting in the on-time T of the dimming control signal_ONSmaller than that shown in fig. 4A and 4B. At the slave dimming control signal V_DIMA first offset period T from being driven high_OFFSET1Thereafter, the digital control signal 252 may direct the window control signal V toward the supply voltage Vcc_WINDriven high. In the dimming control signal V_DIMSecond offset period T before being driven Low_OFFSET2In time, the digital control signal 252 may drive the window control signal V towards circuit common_WINDriven low. Peak current feedback signal V_FB-PKMay have a characteristic dependent on the load current I_LOADPeak size of (I)_PKIs (e.g. minimum current I)_MIN). Drive signal V provided to the gate of regulating transistor Q212_DRMay be at about a second size V_DR2(e.g., as in fig. 4B).

Fig. 5 is a simplified flow diagram of an exemplary control process 500 for controlling a control loop (e.g., control loop 220 of fig. 2), as described herein. At step 510, for example, periodically and/or in response to the target current I of the light source 202_TRGTCan be controlled by the digital control circuit 252Process 500. At 512, the digital control circuit may determine the dimming control signal V, e.g., based on the current duty cycle of the dimming control signal_DIMOn-time T of_ON. The timer may be started at 514 and at 516, for example, by asserting the dimming control signal V_DIMDriven high (e.g., at about the same time that a timer is started), turns on the dimming FET Q216. At 518, the value of the timer may be compared (e.g., periodically) to the first offset period of time T_OFFSET1And (6) comparing. Once the timer value reaches the first offset period of time T_OFFSET1At 520, the digital control circuit 252 may control the signal V, for example, by controlling a feedback window_WINDriven high, turning on the controllable switch 222. Then, at 522, the digital control circuit 252 may be calibrated for a time equal to the on-time T_ONAnd a second offset period T_OFFSET2Difference between (e.g. T)_ON-T_OFFSET2) Continues (e.g., periodically) checking the value of the timer. Once the timer value reaches the on-time T_ONAnd a second offset period of time T_OFFSET2The difference between, at 524, the digital control circuit 252 may control the signal V, for example, by feeding back a window_WINDriven to a level to render the controllable switch 222 non-conductive. Subsequently, at 526, the digital control circuit 252 may continue to monitor the value of the timer until the value reaches the on-time T_ON. At this point, at 528, the digital control circuit 252 may, for example, adjust the dimming control signal V_DIMDriven high to render the dimming FET Q216 non-conductive and the control process 500 may exit.

Some or all of the functionality of the control loop 220 may be implemented in a digital control circuit (e.g., the digital control circuit 252 of the control device 200 or another digital control circuit). Fig. 6 is a simplified schematic diagram of a circuit 600 that may be used to implement the functionality of the LED driver circuit 210 and/or the control loop 220 shown in fig. 2. The circuit 600 may include an LED driver circuit 610. May be implemented and configured in a similar manner as the LED driver circuit 210. For example, the LED driver circuit 610 may include a regulation device such as a regulation FET Q612 (e.g., similar to the regulation FET Q212). The LED driver circuit 610 may include a current feedback circuit (e.g., a LED driver circuit)E.g., current feedback resistor 614, which may be similar to current feedback resistor R214). The LED driver circuit 610 may further include a dimming device, such as a dimming FET Q616 (e.g., similar to dimming FET Q216), coupled between the current feedback resistor 614 and circuit common. The digital control circuit 652 may generate a dimming control signal V that may be received by the gate of the dimming FET Q616_DIM. In response to dimming control signal V_DIMThe dimming FET Q616 can be rendered conductive and non-conductive for regulating the load current I conducted through the LED light source 602_LOADAverage size of (d).

The digital control circuit 652 may provide a current feedback signal V generated via the current feedback resistor 614 during the time window_FBSampling is performed to derive a signal representative of the load current I_LOADPeak size of (I)_PKIs measured by the average value of the feedback signal of (1). The digital control circuit 652 may cooperate with the dimming control signal V_DIMThe time window is controlled. For example, the digital control circuit 652 may control the time window to begin at about the same time or later (e.g., after an offset period) when the digital control circuit turns on the dimming FET Q616. The digital control circuit 652 may control the time window to end at about the same time or slightly before (e.g., before the offset period of time) the digital control circuit renders the dimming FET Q616 non-conductive. The derived feedback signal may be filtered (e.g., via a digital low-pass filter) and used to generate the drive signal V_DRThe drive signal V_DRCan be received by the gate of the regulating FET Q612 to control the regulating FET in the linear region to provide a controllable impedance in series with the LED light source 602 (e.g., to operate the regulating FET as a linear regulator).

The digital control circuit 652 may control the dimming control signal V_DIMTo render the dimming FET Q616 conductive and non-conductive to regulate the load current I_LOADAverage size of (d). For example, the digital control circuit 652 may be configured to control the dimming frequency f by_DIMGenerating a dimming control signal V_DIMAs pulse width modulation signal for load current I_LOADPulse width modulation is performed. The digital control circuit 652 may be configured to adjust the dimming control signal V_DIMDuty cycle of DC_DIMTo regulate the load current I_LOADAverage size of (d). When the digital control circuit 652 is facing the dimming control signal V_DIMWhen pulse width modulation is performed, load current I_LOADIs characterized by a load current frequency f_LOADWhich is approximately equal to the dimming control signal V_DIMThe dimming frequency of (1). Frequency f of load current_LOADMay be high enough to prevent flicker visible to the human eye in the LED light source 602. The digital control circuit 652 may be configured to maintain the drive signal V when the dimming FET Q616 is non-conductive_DRThe size of (2).

Fig. 7 is a simplified flow diagram of an exemplary control process 700 for controlling the circuit 600 shown in fig. 6. At step 710, the target current I of the light source 602 is measured, for example, periodically and/or in response_TRGTThe control process 700 may be performed by the digital control circuit 652. At 712, the digital control circuit 652 may determine the dimming control signal V, e.g., based on the current duty cycle of the dimming control signal_DIMOn-time T of_ON. When the dimming FET Q616 is turned on at 716, a timer may be started at 714. The value of the timer may be compared to the first offset period T at 718_OFFSET1A comparison is made (e.g., periodically). Once the timer value reaches the first offset period of time T_OFFSET1But still specific on-time T_ONIs smaller by at least a second offset period T_OFFSET2(e.g., Timer)<T_ON-T_OFFSET2) At 720, digital control circuit 652 may repeatedly sample current feedback signal V_FBAnd at 722, an average of the samples is calculated. At 724, the digital control circuit 652 may determine that the timer value has reached T_ON-T_OFFSET2And then the current feedback signal V may be stopped at 726_FBSampling is performed. At 728, the digital control circuit 652 may further determine that the on-time T has been reached_ONTo this end, at 730, the digital control circuit 652 may render the dimming FET 616 non-conductive and may process the current feedback signal V at 732_FBTo determine the average value for the drive signal V_DRTo a suitable level. The determined drive signal V may be paired at 734_DRIs filtered by the level ofWaves (e.g., using a digital Low Pass Filter (LPF)). Based on the filtered levels, at 736, the digital control circuit 562 can generate a DC voltage (e.g., using a DAC or by generating a PWM signal that can be filtered with an external RC filter) to drive the regulating FET 612. The control routine 700 may then exit.

Although described with reference to controllable light sources and/or LED drivers, one or more embodiments described herein may be used with other load control devices. For example, one or more embodiments described herein may be performed by various load control devices configured to control various electrical load types, such as an LED driver for driving an LED light source (e.g., an LED light engine); a screw-in luminaire comprising a dimmer circuit and an incandescent or halogen lamp; a screw-in luminaire comprising a ballast and a compact fluorescent lamp; a screw-in luminaire comprising an LED driver and an LED light source; a dimming circuit for controlling the intensity of an incandescent lamp, a halogen lamp, an electronic low voltage lighting load, a magnetic low voltage lighting load, or other types of lighting loads; an electronic switch, controllable circuit breaker or other switching device for switching an electrical load or appliance on and off; plug-in load control devices, controllable electrical outlets or controllable power boards for controlling one or more plug-in electrical loads (e.g., coffee makers, space heaters, other household appliances, etc.); a motor control unit for controlling a motor load (e.g., a ceiling fan or an exhaust fan); a driving unit for controlling the motorized window treatment or the projection screen; an electrically powered interior or exterior shutter; a thermostat for a heating and/or cooling system; a temperature control device for controlling a heating, ventilation, and air conditioning (HVAC) system; an air conditioner; a compressor; an electric substrate heater controller; a controllable damper; a humidity control unit; a dehumidifier; a water heater; a swimming pool pump; a refrigerator; an ice chest; a television or computer monitor; a power source; an audio system or amplifier; a generator; a charger, such as an electric vehicle charger; and alternative energy controllers (e.g., solar, wind, or thermal controllers). A single control circuit may be coupled to and/or adapted to control multiple types of electrical loads in a load control system.