Driving circuit for light emitting diode light source

Abstract

A controllable lighting device can include a drive circuit characterized by one or more cycles and a control circuit configured to control the drive circuit to conduct a load current through a light source of the lighting device. The control circuit can be configured to determine one or more operating parameters of the lighting device based on a feedback signal indicative of a peak amplitude of the load current conducted through the light source during a current cycle of the drive circuit. The control circuit can be capable of adjusting an average amplitude of the load current conducted through the light source in order to adjust an intensity of the light source toward a target intensity based on the operating parameters.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 968,566, filed on January 31, 2020, the disclosure of which is incorporated herein by reference in its entirety. Background Art

[0003] Light emitting diode (LED) light sources (e.g., LED light engines) are replacing conventional incandescent, fluorescent, and halogen lamps as the primary form of lighting. An LED light source may include a plurality of light emitting diodes mounted on a single structure and disposed in a suitable housing. Compared to incandescent, fluorescent, and halogen lamps, LED light sources may be more efficient and have a longer lifespan. 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 source to regulate the power supplied to the LED light source. For example, the LED driver may regulate the voltage supplied to the LED light source, the current supplied to the LED light source, or both the current and the voltage.

[0004] Different control techniques can be used to drive LED light sources, including, for example, current load control techniques and voltage load control techniques. An LED light source driven by current load control techniques can be characterized by a rated current (e.g., approximately 350 milliamperes), to which the amplitude (e.g., peak or average amplitude) of the current through the LED light source can be adjusted to ensure that the LED light source illuminates with appropriate intensity and / or color. An LED light source driven by voltage load control techniques can be characterized by a rated voltage (e.g., approximately 15 volts), to which the voltage across the LED light source can be adjusted to ensure proper operation of the LED light source. If the LED light source rated for voltage load control techniques includes multiple parallel LED strings, current balancing adjustment elements can be used to ensure that the parallel strings have the same impedance so that the same current is drawn in each parallel string.

[0005] The light output of an LED light source can be dimmed. Methods for dimming an LED light source include, for example, pulse width modulation (PWM) and constant current reduction (CCR) techniques. In PWM dimming, pulse signals with varying duty cycles can be supplied 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 can remain constant during the on-time of the pulse signal's duty cycle. However, the duty cycle of the pulse signal can be varied to change the average current supplied to the LED light source, thereby varying the intensity of the light output from 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 can remain constant during the on-time of the pulse signal's duty cycle. However, the duty cycle of the load voltage can be varied to adjust the intensity of the light output. If a current load control technique is used to control the LED light source, constant current reduction dimming can be used. In constant current reduction dimming, current is supplied to the LED light source continuously. However, the DC amplitude of the current supplied to the LED light source can be varied to adjust the intensity of the light output.

[0006] Examples of LED drivers are described in U.S. Patent No. 8,492,987, issued on July 23, 2013, and entitled LOAD CONTROL DEVICE FOR A LIGHT-EMITTING DIODE LIGHT SOURCE; U.S. Patent No. 9,655,177, issued on May 16, 2017, and entitled FORWARD CONVERTER HAVING A PRIMARY-SIDE CURRENT SENSE CIRCUIT; and U.S. Patent No. 9,247,608, issued on January 26, 2016, and entitled LOAD CONTROL DEVICE FOR A LIGHT-EMITTING DIODE LIGHT SOURCE; the entire disclosures of which are incorporated herein by reference. Summary of the Invention

[0007] As described herein, a controllable lighting device includes a light emitting diode (LED) light source, an LED driver circuit, a feedback circuit, and a control circuit. The LED driver circuit may include a controllable conductive device configured to conduct a load current through the LED light source, and the feedback circuit may be configured to generate a feedback signal indicating a peak amplitude of the load current conducted through the LED light source. The control circuit is operable to cause the controllable conductive device of the LED driver circuit to conduct and not conduct to adjust the average amplitude of the load current conducted through the LED light source, thereby adjusting the intensity of the LED light source toward a target intensity. For example, the control circuit may cause the controllable conductive device to conduct during an on-time during a current cycle of the LED driver circuit, so that the controllable conductive device conducts the load current at the peak amplitude during the on-time. The control circuit may receive the feedback signal during the on-time of the current cycle of the LED driver circuit and determine an operating period for the current cycle based on the amplitude of the feedback signal and the target intensity.

[0008] The controllable lighting device may further include a power converter circuit configured to generate a bus voltage received by the LED driver circuit. The peak amplitude of the load current during the on-time of the current cycle of the LED driver circuit may depend on the amplitude of the bus voltage, and the control circuit may be coupled to the power converter circuit and configured to generate a bus control signal for adjusting the amplitude of the bus voltage to maintain the corresponding operating period of one or more cycles of the LED driver circuit between a maximum value and a minimum value. For example, the control circuit may control the bus control signal to decrease the bus voltage in response to determining that the operating period of the current cycle of the LED driver circuit is above the maximum value, and to increase the bus voltage in response to determining that the operating period of the current cycle of the LED driver circuit is below the minimum value. When the target intensity is between the maximum intensity and the transition intensity, the maximum value of the operating period may be set to a first value, and when the target intensity is below the transition intensity, the maximum value may be increased from the first value. The minimum value of the operating period may be set to a value independent of the target intensity of the LED light source. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a simplified block diagram of a controllable electrical device, such as a controllable light source.

[0010] Figure 2A and Figure 2B is a simplified schematic diagram of an exemplary driver circuit for a controllable light source, such as a light emitting diode (LED) driver circuit.

[0011] Figure 3An example plot showing the relationship between various operating parameters of the controllable light source of FIG. 2 and the target intensity.

[0012] Figure 4 An example waveform showing the load current illustrating the operation of the controllable lighting device at various target intensities.

[0013] Figure 5 is a simplified flowchart of an example control process for controlling a controllable light source.

[0014] Figures 6A to 6C is an example waveform showing the operation of the controllable lighting device during execution of the control process of Figure 5 . DETAILED DESCRIPTION

[0015] Figure 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 can be a lamp including one or more light sources, such as light emitting diode (LED) light sources 102, 104 (e.g., LED light engines). The controllable LED light sources 102, 104 are 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 Figure 1 as a plurality of series-connected LEDs, but can include a single LED or a plurality of parallel-connected LEDs or appropriate combinations thereof, depending on the particular lighting system. Moreover, each LED light source 102, 104 can include one or more organic light emitting diodes (OLEDs). The controllable lighting device 100 can include a plurality of different LED light sources, which can be rated at different magnitudes of load current and voltage. Although not shown in Figure 1 , the controllable lighting device 100 can include a housing (e.g., a translucent housing) in which the LED light sources are located and through which the LED light sources can emit light. For example, the controllable lighting device 100 can be capable of providing warm dimming such that as the intensity of the cumulative light output is reduced, the color temperature of the cumulative light output shifts toward a warm white color temperature. For example, the first LED light source 102 can include a white LED light source and the second LED light source 104 can include a warm white (e.g., red) LED light source, and the first LED light source 102 can have a higher rated power than the second LED light source 104.

[0016] The controllable lighting device 100 can be a screw-in LED light configured to be screwed into a standard Edison socket. The controllable lighting device 100 can include a screw-in base including a hot connection H and a neutral connection N for receiving an alternating current (AC) voltage V ACThe 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 include a radio frequency interference (RFI) filter and a rectifier circuit 110 that may receive an AC voltage V AC The RFI filter and rectifier circuit 110 is operable to minimize noise provided on the AC power source and to generate a rectified voltage V RECT .

[0017] The controllable lighting device 100 may include a power converter circuit 120, such as a flyback converter, which may receive a rectified voltage V RECT And the bus capacitor C BUS A variable DC bus voltage V is generated across the two ends BUS The power converter circuit 120 may include other types of power converter circuits, such as, for example, a boost converter, a buck converter, a buck-boost converter, a single-ended primary inductor converter (SEPIC), A converter or any other suitable power converter circuit is used to generate an appropriate bus voltage. The power converter circuit 120 can provide electrical isolation between the AC power source and the LED light sources 102, 104 and can operate as a power factor correction (PFC) circuit to adjust the power factor of the controllable lighting device 100 toward a power factor of 1.

[0018] like Figure 1 As shown, 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 FET Q123 is shown, any switching transistor or other suitable semiconductor switch may be coupled in series with the primary winding of the 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-FB It can be generated, for example, by a voltage divider comprising a bus capacitor C coupled to the BUS The flyback control circuit 127 can receive the bus voltage feedback signal V from the feedback resistor R128. BUS-FB And / or a control signal representing the current through FET Q123, the feedback resistor can be coupled in series with FET Q123. The flyback control circuit 127 can control FET Q123 to selectively conduct current through the flyback transformer 122 to generate the bus voltage V BUSThe flyback control circuit 127 can make the FET Q123 conductive and non-conductive, for example, in response to the bus voltage feedback signal V BUS-FB The DC magnitude and / or magnitude of the current through FET Q123 will affect the bus voltage V BUS The amplitude is controlled towards the target bus voltage V BUS-TRGT .

[0019] The controllable lighting device 100 may include one or more load regulation circuits, such as LED driver circuits 130 and 140, for controlling the power (eg, intensity) delivered to the LED light sources 102 and 104, respectively. The LED driver circuits 130 and 140 may each receive a bus voltage V BUS and the corresponding load current I conducted by the LED light sources 102 and 104 can be adjusted LOAD1 , I LOAD2 The magnitude and / or the corresponding load voltage V generated across the LED light source LOAD1 、V LOAD2 Examples of various implementations of LED driver circuits are described in U.S. Patent No. 8,492,987, filed on July 23, 2013, and U.S. Patent No. 9,253,829, issued on February 2, 2016, both entitled LOAD CONTROL DEVICE FOR A LIGHT-EMITTING DIODE LIGHT SOURCE, the entire disclosures of which are incorporated herein by reference.

[0020] The controllable lighting device 100 may include a control circuit 150 for controlling the LED driving circuits 130 and 140 to control the corresponding load current I conducted through the LED light sources 102 and 104. LOAD1 , I LOAD2 , thereby adjusting the corresponding intensity of the LED light source. For example, the control circuit 150 may include digital control circuitry, such as a microprocessor, a microcontroller, a programmable logic device (PLD), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or any other suitable processing device or controller. The control circuit 150 can be configured to turn on one or both of the LED light sources 102, 104 to turn on the controllable lighting device 100, and to turn off both of the LED light sources 102, 104 to turn off the controllable lighting device 100. The control circuit 150 can 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 can be configured to convert the current intensity L of the cumulative light emitted by the controllable lighting device 100 to the current intensity L of the cumulative light emitted by the controllable lighting device 100. PRES Towards target strength L TRGTAdjust (eg, dim), the target intensity range may be within the dimming range of the controllable light source, for example, at the low end intensity L LE (eg, minimum intensity, such as about 0.1% to 1.0%) and a high end intensity L HE (eg, maximum intensity, such as approximately 100%). The control circuit 150 may be configured to set the current color temperature T of the accumulated light emitted by the controllable lighting device 100 to PRES Towards the target color temperature T TRGT The target color temperature may be adjusted to a range between a cool white temperature (e.g., approximately 3100K to 4500K) and a warm white temperature (e.g., approximately 2000K to 3000K). For example, the control circuit may be configured to respond to the target intensity L of the controllable lighting device 100. TRGT and / or target color temperature T TRGT Determine the corresponding target intensity L for each LED light source 102, 104 TRGT1 , L TRGT2 .

[0021] The control circuit 150 may include a memory (not shown) configured to store operating characteristics of the controllable lighting device 100 (eg, target intensity L TRGT , target color temperature T TRGT , low-end strength L LE , high-end strength L HE The memory may be implemented as an external integrated circuit (IC) or as an internal circuit of the control circuit 150. The controllable lighting device 100 may include a power supply 160 that 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 V for powering the control circuit 150 and other low-voltage circuits of the controllable lighting device. CC .

[0022] The controllable lighting device 100 may include a communication circuit 170 coupled to the control circuit 150. The communication circuit 170 may include wireless communication circuitry, such as, for example, a radio frequency (RF) transceiver coupled to an antenna 172 to transmit and / or receive 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 170 may be coupled to the hot connection H and the neutral connection N of the controllable lighting device 100 to transmit control signals via the electrical wiring using, for example, power line carrier (PLC) communication technology. The control circuit 150 may be configured to determine a target intensity L for the controllable lighting device 100 in response to a message (e.g., a digital message) received via the communication circuit 170. TRGT and / or target color temperature T TRGT .

[0023] The LED driving circuits 130 and 140 may include respective controllable conductive devices (e.g., switching devices such as field effect transistors (FETs) Q132 and Q142) coupled (e.g., in series) to the LED light sources 102 and 104, respectively, for conducting the load current I LOAD1 , I LOAD2 FETs Q132, Q142 may each include any type of suitable power semiconductor switch, such as, for example, a bipolar junction transistor (BJT) and / or an insulated gate bipolar transistor (IGBT). Control circuit 150 may be configured to generate one or more drive signals, such as a drive signal V DR1 、V DR2 These drive signals can be received by the gates of the corresponding FETs Q132, Q142 to turn the FETs on and off. The control circuit 150 can be configured to control the drive signal V DR1 、V DR2 Perform pulse width modulation (PWM) to adjust the load current I LOAD1 , I LOAD2 For example, the control circuit 150 can be configured to adjust the drive signal V DR1 、V DR2 The corresponding duty cycle is used to adjust the load current I LOAD1 , I LOAD2 The control circuit 150 may be configured to generate a target intensity L based on the target intensity L of the LED light sources 102, 104. TRGT1 , L TRGT2 Determine the driving signal V DR1 、V DR2 The on-time T of each current cycle ON (e.g., as described in more detail below).

[0024] FETs Q132 and Q142 may be coupled (eg, in series) to respective feedback circuits (eg, current feedback (CFB) circuits 134 and 144). The current feedback circuits 134 and 144 may generate respective current feedback signals V FB1 、V FB2 , these current feedback signals can be received by the control circuit 150. The control circuit 150 can generate a feedback window control signal V WIN1 、V WIN2 These feedback window control signals can be received by the corresponding current feedback circuits 134 and 144 to control the operation of the current feedback circuits so that the current feedback signal V FB1 、V FB2 The magnitude of the corresponding load current I LOAD1 , I LOAD2 The peak amplitude I PK1 , IPK2 The control circuit 150 can be configured to drive the signal V DR1 、V DR2 The current feedback signal V FB1 、V FB2 is sampled and responds to the load current I LOAD1 , I LOAD2 The corresponding peak amplitude I PK1 , I PK2 Determine the drive signal V DR1 、V DR2 The corresponding operating period T of each current cycle OP (e.g., as described in more detail below).

[0025] Corresponding load current I LOAD1 , I LOAD2 The peak amplitude I PK1 , I PK2 can depend on the bus voltage V BUS The control circuit 150 can be configured to respond to the corresponding load current I LOAD1 , I LOAD2 The peak amplitude I PK1 , I PK2 To control the operation of the power converter circuit 120. The control circuit 150 can generate a bus control signal V BUS-CNTL The bus control signal can be received by the flyback control circuit 127 to adjust the target bus voltage V of the power converter circuit 120. BUS-TRGT The control circuit 150 can be configured to drive the signal V DR1 、V DR2 The corresponding operation cycle T OP Limited to the minimum operating period T OP-MIN and the maximum operating cycle T OP-MAX For example, the control circuit 150 can be configured to DR1 、V DR2 The operation period T of at least one of OP Less than the minimum operating cycle T OP-MIN When increasing the bus voltage V BUS The control circuit 150 can be configured to DR1 、V DR2 The operation period T of at least one of OP Greater than the maximum operating cycle T OP-MAX When the bus voltage V BUS The amplitude.

[0026] Figure 2AFIG1 is a simplified schematic diagram of an example of an LED driver circuit 210 (e.g., one of the LED driver circuits 130 and 140 ) of an electrical device 200 such as a load control device, an LED driver, or a controllable light source (e.g., the controllable lighting device 100 ). The LED driver circuit 210 can be coupled in series with an LED light source 202 (e.g., one of the LED light sources 102 and 104 ) to conduct a load current I through the LED light source. LOAD The LED light source 202 may be configured to receive a bus voltage V from a power converter circuit (eg, power converter circuit 120 ). BUS .

[0027] The electrical device 200 may include a control circuit 230 (eg, the control circuit 150). The control circuit 230 may also generate a drive signal V DR , used to control the LED driving circuit 210 to adjust the load current I LOAD The control circuit 230 may be configured to adjust the intensity of the LED light source 202 toward the target intensity L TRGT Adjust the target intensity to the minimum intensity L MIN (e.g., about 0.1% to 1.0%) and a maximum intensity L MAX (e.g., about 100%). Minimum intensity L MIN It can be approximately that the control circuit 230 can be operated under steady-state conditions (eg, when the target intensity L TRGT The control circuit 230 can be configured to control the minimum intensity of the LED light source 202 according to the target intensity L TRGT Determine the target current I TRGT (For example, the load current I LOAD The control circuit 230 can be configured to adjust the target intensity L of the LED light source 202 to the target average current. TRGT The control circuit 230 may be configured to gradually adjust the intensity of the LED light source (and thus the current intensity) by turning on the LED light source to a minimum gradually changing intensity L FADE-MIN Then slowly increase the current intensity L of the LED light source. PRES From the minimum gradient intensity L FADE-MIN Increase to target strength L TRGT To gradually change the LED light source 202 from off to on. For example, the minimum gradient intensity L FADE-MIN May be less than the minimum strength L MIN (For example, such as about 0.02%).

[0028] The LED driver circuit 210 may include a controllable conductive device (e.g., a switching device, such as a FET Q212) coupled in series with the LED light source 202. The FET Q212 may include any type of suitable power semiconductor switch, such as, for example, a bipolar junction transistor (BJT) and / or an insulated gate bipolar transistor (IGBT). The drive signal V generated by the control circuit 230 is DR It can be received by the gate of FET Q212. FET Q212 can be turned on and off to adjust the load current I LOAD The control circuit 230 can be configured to control the FET Q212 as a switching device by driving the FET Q212 into a saturation region when the FET Q212 is turned on. When the FET Q212 is controlled in the saturation region, the FET Q212 can be characterized by a drain-source on-resistance R DS-ON The control circuit 230 may be configured to control the LED driving circuit 210 on a periodic (eg, cyclic) basis. For example, the control circuit 230 may be configured to control the driving signal V DR Pulse width modulation (PWM) is performed to control the load current I LOAD Each control cycle of the LED driver circuit 210 can be controlled by the operation cycle T OP (e.g., the length of the cycle) is associated with (e.g., characterized by) the operating period.

[0029] The LED driving circuit 210 may include a current feedback circuit 214 coupled in series with the FET Q212 to generate a current feedback signal V FB , the current feedback signal may have a value representing the load current I LOAD The amplitude (e.g., peak amplitude I PK ) of the DC amplitude. Figure 2A As shown, the current feedback circuit 214 can be coupled to the source of the FET Q212. The current feedback circuit 214 can include a resistor R SENSE The sensing resistor R220 can be coupled in series between the FET Q212 and the circuit common terminal to generate a sensing voltage V across the sensing resistor R220. SENSE The current feedback circuit 214 may include a circuit that receives a sensing voltage V SENSE The first controllable switch 222 is responsive to the feedback window control signal V generated by the control circuit 230. WIN (eg, a switch control signal) can make the first controllable switch 222 conductive and non-conductive. The first controllable switch 222 can be coupled to a filter circuit, which can include a capacitor C224 and a resistor R226. The feedback signal V FBmay be generated across capacitor C224. Current feedback circuit 214 can also include a second controllable switch 228 coupled in parallel with capacitor C224. Second controllable switch 228 can be rendered conductive and non-conductive in response to a reset control signal V RST . may be rendered conductive and non-conductive by control circuit 230.

[0030] Control circuit 230 can be configured to control first controllable switch 222 of current feedback circuit 214 to be conductive during an on-time T DR of drive signal V ON ( e.g., when FET Q212 is conductive). After rendering first controllable switch 222 conductive at the beginning of on-time T ON , capacitor C224 can be charged through resistor R226 to a peak amplitude V SENSE of sense voltage V PK such that an amplitude of current feedback signal V FB may be indicative of a peak amplitude I LOAD of load current I PK . Control circuit 230 can receive current feedback signal V FB generated by current feedback circuit 214 and can sample current feedback signal V DR during on-time T ON of drive signal V ON ( e.g., throughout on-time T ON or during a portion of on-time T FB ) to determine peak amplitude I LOAD of load current I PK . For example, control circuit 230 can use a sampled amplitude of current feedback signal V FB and a resistance R SENSE of sense resistor R220 to calculate peak amplitude I LOAD of load current I PK , e.g., I PK = V FB / R SENSE . For example, control circuit 230 can store resistance R SENSE of sense resistor R220 in memory and can retrieve resistance R SENSE from memory in order to calculate peak amplitude I LOAD of load current I PK . Control circuit 230 can render first controllable switch 222 non-conductive at or before the end of on-time T ON . After the end of on-time T ON , control circuit 230 can render second controllable switch 228 conductive for a reset period T RSTthe second controllable switch 228 is turned on for a duration of the reset pulse to discharge the capacitor C224 so that the current feedback circuit 214 can control the amplitude of the current feedback signal V FB during a subsequent cycle (e.g., the next cycle) of the LED driving circuit 210 to indicate a peak amplitude I LOAD of the load current I PK .

[0031] During each control cycle of the LED driving circuit 210, the control circuit 230 can be configured to turn on the FET Q212 for a first portion (e.g., the on-time T ON ) of the cycle and not turn on for a second portion (e.g., the off-time T OFF ) of the cycle. For example, the control circuit 230 can be configured to adjust the average amplitude of the load current I LOAD by adjusting the duty cycle DC of the drive signal V DR , e.g., DC = T ON / T OP = T ON / (T ON + T OFF ). The control circuit 230 can be configured to determine the on-time T ON of the drive signal V DR (e.g., for the current cycle of the LED driving circuit 210) based on the target intensity L TRGT of the LED light source 202 (e.g., using open loop control). Since the FET Q212 is controlled as a switching device and turned on during the on-time T ON of the drive signal V DR (e.g., controlled in the saturation region), the load current I LOAD may be characterized by an on-time of the same length as the on-time T ON of the drive signal V DR . The FET Q212 can conduct the load current I LOAD at a peak amplitude I PK during the on-time. The control circuit 230 can be configured to determine the length of the operating period T OP of the drive signal V DR for the current cycle of the LED driving circuit 210 in response to the peak amplitude I PK of the load current I LOAD determined (e.g., using closed loop control) from the current feedback signal V FB . The control circuit 230 can not use closed loop control to control the peak amplitude I PK of the load current I LOAD during the on-time (e.g., by clamping the peak current I PKCompare with the threshold and adjust the peak amplitude I to the target peak current PK ).

[0032] The control circuit 230 can also be configured to generate a bus control signal V BUS-CNTL , the bus control signal can be received by the power converter circuit to adjust the bus voltage V BUS The control circuit 230 may be configured to maintain the bus control signal V during each cycle of the LED drive circuit 210. BUS-CNTL Constant (eg, substantially constant). The control circuit 230 may be configured to control the bus control signal V BUS-CNTL to adjust the amplitude from one cycle to the next (e.g., as will be referred to below). Figure 6B and Figure 6C ). Since FET Q212 is on during the on time T ON is driven into the saturation region during the on-time T ON During the load current I LOAD The peak amplitude I PK may depend on the bus voltage V BUS The magnitude of the drain-source on-resistance R DS-ON , the resistance R of the sensing resistor R220 SENSE and the characteristics of the LED light source 202 (eg, the equivalent resistance of the LED light source). Since the control circuit 230 cannot adjust the drain-source on-resistance R DS-ON , the resistance R of the sensing resistor R220 SENSE and the characteristics of the LED light source 202, and the bus voltage V BUS The magnitude of remains constant within each cycle of the LED driver circuit 210, so the control circuit 230 may not be able to control the load current I during the current cycle. LOAD The peak amplitude I PK . Load current I LOAD The peak amplitude I PK For different LED light sources that can be controlled by the LED driver circuit 210, the peak amplitude I PK may not be deterministic). Therefore, the load current I LOAD The peak amplitude I PK can be considered as an uncontrolled or unregulated magnitude (eg, an uncontrolled or unregulated current). Since the control circuit 230 does not use closed-loop control to control the load current I during the on-time LOAD The peak amplitude I PK (For example, adjust the peak amplitude I toward the target peak current PK ), so the load current I LOAD The peak amplitude I PKMay not depend on the operation of the control circuit 230 during the current cycle (eg, during the on-time). If the control circuit 230 uses closed-loop control to control the peak amplitude I during the on-time PK , then the peak amplitude I PK The current will be the same (eg, controlled to a target peak current) regardless of the particular LED light source controlled by the LED driver circuit 210 .

[0033] The control circuit 230 can be configured to adjust the driving signal V DR The operating period of the current cycle is T OP To control the load current I LOAD The control circuit can be configured to respond to the current feedback signal V FB Determine the load current I LOAD The peak amplitude I (e.g., uncontrolled current) PK To determine the driving signal V DR The operating period of the current cycle is T OP For example, the control circuit 230 can be configured to calculate the load current I LOAD The current on-time T ON and the current peak amplitude I PK (For example, according to the current feedback signal V FB Determine) to achieve the target current I TRGT (For example, the load current I LOAD The average amplitude) required operating cycle T OP , for example, T OP =(I PK ·T ON ) / I TRGT The off time of the driving signal T OFF The operating period T can be determined based on OP , for example, T OFF =T OP –T ON The control circuit can operate in the operating cycle T OP End (for example, the current off time T OFF At the end of the cycle, the FET is turned on to start the next cycle.

[0034] Figure 2B FIG1 is a simplified schematic diagram of another example of an LED driver circuit 260 (e.g., one of the LED driver circuits 130, 140) of an electrical device 250, such as a load control device, an LED driver, or a controllable light source (e.g., the controllable lighting device 100). The LED driver circuit 260 can be coupled in series with an LED light source 252 (e.g., one of the LED light sources 102, 104) to conduct a load current I through the LED light source.LOAD The LED light source 252 may be configured to receive a bus voltage V from a power converter circuit (eg, power converter circuit 120 ). BUS .

[0035] The electrical device 250 may include a control circuit 280 (eg, the control circuit 150). The control circuit 280 may also generate a drive signal V DR , used to control the LED driving circuit 260 to adjust the load current I through the LED light source LOAD The control circuit 280 can be configured to adjust the intensity of the LED light source 252 toward the target intensity L TRGT Adjust the target intensity to the minimum intensity L MIN (e.g., about 0.1% to 1.0%) and a maximum intensity L MAX (e.g., about 100%). Minimum intensity L MIN It can be approximately that the control circuit 280 can be in a steady state condition (eg, when the target intensity L TRGT The control circuit 280 can be configured to control the minimum intensity of the LED light source 252 according to the target intensity L TRGT Determine the target current I TRGT (For example, the load current I LOAD The control circuit 280 can be configured to adjust the target intensity L of the LED light source 252 to the target average current. TRGT The control circuit 280 may be configured to gradually adjust the intensity of the LED light source (and thus the current intensity) by turning on the LED light source to a minimum gradually changing intensity L FADE-MIN , then slowly increase the current intensity L of the LED light source PRES From the minimum gradient intensity L FADE-MIN Increase to target strength L TRGT To gradually change the LED light source 252 from off to on. For example, the minimum gradient intensity L FADE-MIN May be less than the minimum strength L MIN (For example, such as about 0.02%).

[0036] The LED driver circuit 260 may include a controllable conductive device (e.g., a switching device such as a FET Q262) coupled in series with the LED light source 252. Figure 2B As shown, the drain of FET Q262 can be coupled to the bus voltage V BUS, and the source of FET Q262 can be coupled to the circuit common. FET Q262 can include any type of suitable power semiconductor switch, such as, for example, a bipolar junction transistor (BJT) and / or an insulated gate bipolar transistor (IGBT). The drive signal V generated by the control circuit 280 DR It can be received by the gate of FET Q262. FET Q262 can be turned on and off to adjust the load current I LOAD The control circuit 280 can be configured to control the FET Q262 as a switching device by driving the FET Q262 into a saturation region when the FET Q262 is turned on. When the FET Q262 is controlled in the saturation region, the FET Q262 can be characterized by a drain-source on-resistance R DS-ON The control circuit 280 may be configured to control the LED driving circuit 260 on a periodic (eg, cyclic) basis. For example, the control circuit 280 may be configured to control the driving signal V DR Pulse width modulation (PWM) is performed to control the load current I LOAD Each control cycle of the LED driver circuit 260 can be controlled by the operation period T OP (e.g., the length of the cycle) is associated with (e.g., characterized by) the operating period.

[0037] The LED driving circuit 260 may include a current feedback circuit 264, which may be configured to generate a current feedback signal V FB , the current feedback signal may have a value representing the load current I LOAD The amplitude (e.g., peak amplitude I PK ) of the DC amplitude. The current feedback circuit 264 can be coupled to the drain of the FET Q262 and can respond to the sense voltage V generated across the FET Q262. SENSE (For example, the current feedback circuit 264 may not include a sense resistor, such as Figure 2A The sensing resistor R220 is shown). The sensing voltage V SENSE The magnitude may depend on the load current I LOAD The peak amplitude I PK and the drain-source on-resistance R of FET Q262 DS-ON The current feedback circuit 264 may include a circuit that receives a sensing voltage V SENSE The first controllable switch 272 is responsive to the feedback window control signal V generated by the control circuit 280. WIN (eg, a switch control signal) can make the first controllable switch 272 conductive and non-conductive. The first controllable switch 272 can be coupled to a filter circuit, which can include a capacitor C274 and a resistor R276. The feedback signal VFB The current feedback circuit 264 may further include a second controllable switch 278 coupled in parallel with the capacitor C274. In response to the reset control signal V generated by the control circuit 280, RST , which can make the second controllable switch 278 conductive and non-conductive.

[0038] The control circuit 280 may be configured to control the first controllable switch 272 of the current feedback circuit 264 to drive ... DR The on-time T ON During the on-time T ON After the first controllable switch 272 is turned on at the beginning, the capacitor C274 can be charged to a voltage close to the sensing voltage V through the resistor R276. SENSE The peak amplitude V PK , so that the current feedback signal V FB The magnitude of the load current I LOAD The peak amplitude I PK The control circuit 280 can receive the current feedback signal V generated by the current feedback circuit 264. FB and can be driven by a signal V DR The on-time T ON During (for example, during the entire on-time T ON During the on-time T ON During part of the period) the current feedback signal V FB Sampling is performed to determine the load current I LOAD The peak amplitude I PK .

[0039] The control circuit 280 can use the current feedback signal V FB The sampling amplitude and the drain-source on-resistance R of FET Q262 DS-ON To calculate the load current I LOAD The peak amplitude I PK , for example, I PK =V FB / R DS-ON For example, the control circuit 280 can set the drain-source on-resistance R of the FET Q262 to DS-ON The drain-source on-resistance R is stored in memory and can be retrieved from memory DS-ON , in order to calculate the load current I LOAD The peak amplitude I PK (For example, the drain-source on-resistance R DS-ON It can be a fixed value or a constant value). In addition, the drain-source on-resistance R DS-ONMay depend on the current temperature T of FET Q212 PRES For example, the control circuit 280 can be configured to use a temperature measurement circuit to determine the current temperature T of the FET Q212. PRES and / or a temperature sensing device located near the FET Q212. The control circuit 280 may also be configured to control the output of the electrical device 250 based on one or more operating parameters of the electrical device 250 (such as the load current I LOAD The peak amplitude I PK and / or the sense voltage V generated across FET Q262 SENSE ) to estimate the current temperature T of FET Q212 PRES The control circuit 280 can be configured to use the drain-source on-resistance R of the FET Q212 DS-ON and the current temperature T PRES The predetermined relationship between the current temperature T of the FET Q212 is determined based on the current temperature T of the FET Q212. PRES To determine the drain-source on-resistance R of FET Q262 DS-ON For example, the drain-source on-resistance R of FET Q212 can be DS-ON and the current temperature T PRES The predetermined relationship between is stored in memory as a lookup table and / or function (eg, an equation). The control circuit 280 may use the determined drain-source on-resistance R of the FET Q262. DS-ON To calculate the load current I LOAD The peak amplitude I PK For example, the drain-source on-resistance R DS-ON and the current temperature T PRES and / or the drain-source on-resistance R DS-ON The initial value of may be calibrated during the manufacturing process of the electronic device 250 .

[0040] The control circuit 280 can be turned on during the conduction time T ON At the end of the on time T, the first controllable switch 272 is turned off. ON After the reset period T RST (eg, a reset pulse) turns on the second controllable switch 278 to discharge the capacitor C274 so that the current feedback circuit 264 can control the current feedback signal V FB , indicating the magnitude of the load current I during a subsequent cycle (eg, the next cycle) of the LED driver circuit 260. LOAD The peak amplitude I PK .

[0041] During each control cycle of the LED driver circuit 260, the control circuit 280 can be configured to cause the FET Q262 to be turned on for the first portion of the cycle (eg, the on-time T ON ) and in the second part of the cycle (e.g., the off time T OFF For example, the control circuit 250 can be configured to adjust the drive signal V DR The duty cycle DC is used to adjust the load current I LOAD The average amplitude, for example, DC = T ON / T OP =T ON / (T ON +T OFF The control circuit 280 may be configured to generate a target intensity L based on the target intensity L of the LED light source 252. TRGT The drive signal V is determined (e.g., using open-loop control) DR The on-time T ON (For example, within the current cycle of the LED driver circuit 260). Since the FET Q212 is controlled as a switching device and is driven by the drive signal V DR The on-time T ON During the conduction period (for example, it is controlled in the saturation region), so the load current I LOAD The characteristics can be with the driving signal V DR The on-time T ON FET Q262 can conduct at a peak amplitude I PK Conducting load current I LOAD The control circuit 280 may be configured to respond to the current feedback signal V FB Determine (e.g., using closed-loop control) the load current I LOAD The peak amplitude I PK To determine the current cycle of the driving signal V of the LED driving circuit 260 DR The operating cycle T OP The control circuit 280 may not use closed-loop control to control the load current I during the on-time. LOAD The peak amplitude I PK (For example, by measuring the peak current I PK Compare with the threshold and adjust the peak amplitude I to the target peak current PK ).

[0042] The control circuit 280 may also be configured to generate a bus control signal V BUS-CNTL , the bus control signal can be received by the power converter circuit to adjust the bus voltage V BUSThe control circuit 280 can be configured to maintain the bus control signal V during each cycle of the LED drive circuit 260 BUS-CNTL Constant (eg, substantially constant). The control circuit 280 may be configured to control the bus control signal V BUS-CNTL to adjust the amplitude from one cycle to the next (e.g., as will be referred to below). Figure 6B and Figure 6C ). Since FET Q262 is on during the on time T ON is driven into the saturation region during the on-time T ON During the load current I LOAD The peak amplitude I PK may depend on the bus voltage V BUS The magnitude of the drain-source on-resistance R DS-ON and the characteristics of the LED light source 252 (e.g., the equivalent resistance of the LED light source). Since the control circuit 280 cannot adjust the drain-source on-resistance R DS-ON and the characteristics of the LED light source 252, and the bus voltage V BUS The magnitude of remains constant during each cycle of the LED driver circuit 260, so the control circuit 280 may not be able to control the load current I during the current cycle. LOAD The peak amplitude I PK . Load current I LOAD The peak amplitude I PK For different LED light sources that can be controlled by the LED driver circuit 260, the peak amplitude I PK may not be deterministic). Therefore, the load current I LOAD The peak amplitude I PK can be considered as an uncontrolled or unregulated magnitude (eg, an uncontrolled or unregulated current). Since the control circuit 280 does not use closed-loop control to control the load current I during the on-time LOAD The peak amplitude I PK (For example, adjust the peak amplitude I toward the target peak current PK ), so the load current I LOAD The peak amplitude I PK May not depend on the operation of the control circuit 280 during the current cycle (e.g., during the on-time). If the control circuit 280 uses closed-loop control to control the peak amplitude I during the on-time PK , then the peak amplitude I PK The current will be the same (eg, controlled to a target peak current) regardless of the particular LED light source controlled by the LED driver circuit 260 .

[0043] The control circuit 280 can be configured to adjust the driving signal V DR The operating period of the current cycle is T OP To control the load current I LOAD The control circuit can be configured to respond to the current feedback signal V FB Determine the load current I LOAD The peak amplitude I PK (e.g., uncontrolled amplitude) to determine the drive signal V DR The operating period of the current cycle is T OP For example, the control circuit 280 can be configured to calculate the current on-time T ON and load current I LOAD The current peak amplitude I PK (For example, according to the current feedback signal V FB Determine) to achieve the target current I TRGT (For example, the load current I LOAD The average amplitude) required operating cycle T OP , for example, T OP =(I PK ·T ON ) / I TRGT The off time of the driving signal T OFF The operating period T can be determined based on OP , for example, T OFF =T OP –T ON The control circuit can operate in the operating cycle T OP End (for example, the current off time T OFF At the end of the cycle, the FET is turned on to start the next cycle.

[0044] Figure 3 The diagram shows an example of a circuit that can be used by a control circuit (eg, control circuit 150, 230, 280) to control an LED driver circuit (eg, Figure 1 LED drive circuit 13, 140, Figure 2A The LED driving circuit 210 and / or Figure 2B FIG. 2 is a diagram showing the control relationship of the LED driving circuit 260). Figure 3 shows the driving signal V DR The on-time T ON The target intensity L of the LED driver circuit TRGT When the target intensity L TRGT Greater than (eg, greater than or equal to) the transition strength L TRAN (For example, at the transition intensity L TRAN and maximum strength L MAX When the conduction time TON Can be set to the maximum on-time T ON-MAX When the target intensity L TRGT Less than (eg, less than or equal to) the minimum intensity L MIN (For example, at the minimum intensity L MIN and the minimum gradient strength L FADE-MIN When the conduction time T ON Can be set to the minimum on-time T ON-MIN When the target intensity L TRGT At minimum intensity L MIN and transition strength L TRAN When the target intensity L TRGT Adjust the on-time T ON (For example, at the minimum on-time T ON-MIN and maximum on-time T ON-MAX linear adjustment between Figure 3 shown).

[0045] The control circuit can be configured to respond to the target intensity L TRGT Determine the target current I of the LED light source TRGT (For example, the load current I LOAD target average amplitude). Figure 3 The target current I of the LED driver circuit is also shown. TRGT and target strength L TRGT A diagram showing an exemplary relationship between Figure 3 As shown, the target current I TRGT Can be linearly dependent on the target intensity L TRGT and can be at a minimum current I MIN (For example, at the minimum intensity L MIN ) and the maximum current I MAX (For example, at maximum intensity L MAX ). In addition, the target current I TRGT and target strength L TRGT The relationship between can be nonlinear.

[0046] The control circuit can be configured to adjust the drive signal V DR The operating period of the current cycle is T OP To control the load current I LOAD The control circuit can be configured to respond to the current feedback signal V FB Determine the load current I LOAD The peak amplitude I PK (e.g., uncontrolled amplitude) to determine the drive signal V DR The operating period of the current cycle is T OPFor example, the control circuit can be configured to calculate the load current I LOAD The current on-time T ON and the current peak amplitude I PK (For example, according to the current feedback signal V FB Determine) to achieve the target current I TRGT (e.g., average current) required operating period T OP , for example, T OP =(I PK ·T ON ) / I TRGT The off time of the driving signal T OFF The operating period T can be determined based on OP , for example, T OFF =T OP –T ON The control circuit can operate in the operating cycle T OP End (for example, the current off time T OFF At the end of the cycle, the FET is turned on to start the next cycle.

[0047] The control circuit can be configured to control the bus control signal V BUS-CNTL To adjust the bus voltage V BUS , thus trying to change the operating cycle T OP Keep the minimum operating cycle T OP-MIN and the maximum operating cycle T OP-MAX When the operation cycle T OP (For example, the control circuit is based on the load current I LOAD The peak amplitude I PK Determine) is less than the minimum operating cycle T OP-MIN , the control circuit can be configured to increase the bus voltage V BUS Increase the load current I LOAD The peak amplitude I PK The control circuit can increase the operating cycle T OP (For example, the operation period T OP May be greater than the minimum operating period T OP-MIN ). When the operation cycle T OP Greater than the maximum operating cycle T OP-MAX , the control circuit can be configured to reduce the bus voltage V BUS The magnitude (for example, reducing the load current I LOAD The peak amplitude I PK ). Reduce the load current I LOAD The peak amplitude I PK The control circuit can reduce the operating cycle T OP (For example, the operation period T OPMay be less than the maximum operating cycle T OP-MAX ).

[0048] Minimum operating cycle T OP-MIN and the maximum operating cycle T OP-MAX Can be a constant value and / or depend on the target intensity L TRGT The variable value of . Figure 3 Also shown is the minimum operating period T OP-MIN and the maximum operating cycle T OP-MAX With target strength L TRGT A diagram showing an exemplary relationship between the minimum operating period T OP-MIN Can be the minimum value T MIN (For example, a constant value such as 10 microseconds, which can be consistent with the target intensity L TRGT When the target intensity L TRGT Greater than (eg, greater than or equal to) the transition strength L TRAN (For example, at the transition intensity L TRAN and maximum strength L MAX When the maximum operating cycle T OP-MAX Can be set to the first maximum value T MAX1 (For example, with the target intensity L TRGT When the target intensity L TRGT At minimum intensity L MIN and transition strength L TRAN When the maximum operating cycle T OP-MAX Can be dependent on the target intensity L TRGT For example, the maximum operating cycle T OP-MAX The first maximum value T MAX1 and the second maximum value T MAX2 Adjust between, and when the target intensity L TRGT At minimum intensity L MIN and transition strength L TRAN When the target intensity L TRGT Linear correlation. Figure 3 As shown, with the target intensity L TRGT From the transition intensity L TRAN Reduce to minimum intensity L MIN , maximum operating cycle T OP-MAX From the first maximum value T MAX1 Increase to the second maximum value T MAX2 When the target intensity L TRGT Less than (eg, less than or equal to) the minimum intensity L MIN (For example, at the minimum intensity L MIN and the minimum gradient strength L FADE-MIN When the maximum operating cycle T OP-MAXCan be dependent on the target intensity L TRGT For example, the maximum operating cycle T OP-MAX The second maximum value T MAX2 and the third maximum value T MAX3 Adjust between, and when the target intensity L TRGT Less than the minimum strength L MIN When the target intensity L TRGT Linear correlation. Figure 3 As shown, when the target intensity L TRGT From the minimum strength L MIN Reduce to minimum gradient strength L FADE-MIN When the maximum operating cycle T OP-MIN From the second maximum value T MAX2 Increase to the third maximum value T MAX3 . T MAX1 、T MAX2 and T MAX3 The value can be adjusted based on the target intensity L TRGT For example, in some cases, T MAX3 A value of 800 microseconds might be used.

[0049] When the target intensity L TRGT Greater than the transition strength L TRAN When the driving signal V DR The on-time T ON Can be set to a constant value (e.g. Figure 3 The maximum on-time T ON-MAX ). In addition, when the target intensity L TRGT Greater than the transition strength L TRAN (For example, close to the maximum intensity L MAX ), the driving signal V DR The operating cycle T OP Controlled to approximate minimum value T MIN (For example, Figure 3 When the target intensity L TRGT Adjusted to near maximum strength L MAX (For example, above the transition strength L TRAN ), the control circuit can adjust the bus voltage V BUS The magnitude (eg, and thereby adjust the load current I LOAD The peak amplitude I PK ) in an attempt to drive the signal V DR The operating cycle T OP Keep it greater than the minimum operating period T OP-MIN (For example, the minimum value T MIN ). As a result, when the target intensity L TRGT Greater than the transition strength LTRAN and close to the maximum intensity L MAX When the driving signal V DR The operating cycle T OP Relative to target intensity L TRGT Can be approximately constant (e.g., approximately equal to the minimum value T MIN ). In addition, when the target intensity L TRGT Greater than the transition strength L TRAN When the load current I LOAD The peak amplitude I PK Can be compared with the target current I TRGT Monotonically correlated (e.g., approximately linearly correlated). For example, as the target intensity L TRGT From the maximum intensity L MAX Transition strength L TRAN Reduce, load current I LOAD The peak amplitude I PK It may also decrease, and vice versa. TRGT Continue to transition intensity L TRAN Reduce the operating cycle T OP may increase above the minimum operating cycle T OP-MIN (For example, the minimum value T MIN ), but is still limited to less than the maximum operating cycle T OP-MAX (For example, the first maximum value T MAX1 ).

[0050] Figure 4 FIG. 1 shows a diagram illustrating controllable lighting devices (eg, lighting control device 100 and / or electrical devices 200, 250) at various target intensities L. T1 To L T6 The load current I LOAD When the target intensity L TRGT At the first target intensity L T1 (For example, at or near maximum intensity L MAX ), the control circuit (eg, the control circuit 150, 230, 280) may DR The on-time T ON Set to the first on-time T ON1 (For example, Figure 3 The maximum on-time T ON-MAX ), which may cause the on-time of the load current to be different from the first on-time T ON1 The load current I LOAD The feature can be that during the first on-time TON1 The first peak amplitude during the period I P1 The control circuit can control the driving signal VDR The operating cycle T OP , so that the load current I LOAD With a first operation period T OP1 (For example, depending on the first on-time T ON1 During the load current I LOAD The first peak amplitude I P1 ). For example, the first operation cycle T OP1 Can be the minimum operating period T OP-MIN (For example, the minimum value T MIN ).

[0051] When the target intensity L TRGT Reduce to the second target intensity L T2 (For example, less than the first target intensity L T1 and is greater than the transition strength L TRAN The load current I LOAD It may still have the first on-time T ON1 (For example, Figure 3 The maximum on-time T ON-MAX ). Load current I LOAD The characteristic may be that at the second target intensity L T2 The first on-time T ON1 The second peak amplitude during the period I P2 . Load current I LOAD The second target intensity L T2 With a second operation period T OP2 Since the target intensity L TRGT Greater than the transition strength L TRAN When the driving signal V DR The operating cycle T OP can be approximately constant, so the load current I LOAD At the second target intensity L T2 The second operation cycle T OP2 Can be compared with the load current I LOAD At the first target intensity L T1 The first operation cycle T OP1 For example, the second operation cycle T OP2 Can be the minimum operating period T OP-MIN (For example, the minimum value T MIN ). In addition, since the target intensity L TRGT Greater than the transition strength L TRAN When the load current I LOAD The peak amplitude I PK Possibly related to the target current I TRGT Monotonically related (e.g., approximately linearly related), so in response to the target intensity LTRGT From the first target intensity L T1 Reduce to the second target intensity L T2 , load current I LOAD The peak amplitude I PK From the first peak amplitude I P1 Reduced to the second peak amplitude I P2 .

[0052] When the target intensity L TRGT Reduce to the third target intensity L T3 (For example, approximately equal to the transition strength L TRAN ), the load current I LOAD It may still have the first on-time T ON1 (For example, Figure 3 The maximum on-time T ON-MAX ). At the third target intensity L T3 When the load current I LOAD The peak amplitude I PK During the first on-time T ON1 During the period, the peak amplitude is reduced to the third peak I P3 . Load current I LOAD The third target intensity L T3 With a third operation period T OP3 , which can be greater than the first target intensity L T1 The first operation cycle T OP1 and / or at a second target intensity L T2 (For example, it can be at the minimum value T MIN and the maximum value T MAX The second operation cycle T OP2 .

[0053] When the target intensity L TRGT Reduce to the fourth target intensity L T4 (For example, less than the transition strength L TRAN and is greater than the minimum strength L MIN ), the load current I LOAD It may have a second on-time T ON2 , which may be less than the first on-time T ON1 (e.g., linearly dependent on the target intensity L TRGT ,like Figure 3 Load current I LOAD The characteristic of the fourth peak amplitude I P4 (For example, it may be approximately equal to the third peak amplitude I PK3 ). As the target intensity L TRGT Reduced to below the transition strength L TRAN (For example,Figure 3 As shown), the maximum operating cycle T OP-MAX From the first maximum value T MAX1 Towards the second maximum value T MAX2 increases, so the load current I LOAD It may have a fourth operation period T OP4 , the fourth operation cycle can be greater than the third operation cycle T OP3 .

[0054] When the target intensity L TRGT Reduce to the fifth target intensity L T5 (For example, approximately equal to the minimum intensity L MIN ), the load current I LOAD Can be set to the third on-time T ON3 (For example, Figure 3 The minimum on-time T ON-MIN ). Load current LOAD The characteristic of the fifth peak amplitude I P5 (For example, it may be approximately equal to the third peak amplitude I PK3 and / or the fourth peak amplitude I P4 ). Load current I LOAD There may be a fifth operation period T OP5 , the fifth operation cycle can be greater than the fourth operation cycle T OP4 .

[0055] When the target intensity L TRGT Reduce to the sixth target intensity L T6 (For example, less than the minimum intensity L MIN and is greater than the minimum gradient strength L FADE-MIN ), the load current I LOAD It can still be set to the third on-time T ON3 (For example, Figure 3 The minimum on-time T ON-MIN ). Load current I LOAD The characteristic of the sixth peak amplitude I P6 (For example, it may be approximately equal to the third peak amplitude I PK3 , the fourth peak amplitude I P4 and / or the fifth peak amplitude I P5 ). Load current I LOAD There may be a sixth operation cycle T OP6 , the sixth operation cycle can be greater than the fifth operation cycle T OP5 .

[0056] Figure 5is a simplified flow chart of an example control process 500 that may be performed by control circuitry (e.g., control circuitry 150, 230, 280) of a controllable lighting device (e.g., lighting control device 100 and / or electrical device 200, 250) for controlling an LED light source (e.g., LED light sources 102, 104, 202, 252). Figures 6A to 6C 5 shows exemplary waveforms illustrating the operation of a controllable lighting device when the control circuit is executing the control process 500. The control circuit may generate a drive signal V DR The control circuit can make the FETs (e.g., FETs Q132, Q142, Q212) of the LED driver circuits (e.g., LED driver circuits 130, 140, 210, 260) conductive and non-conductive during each control cycle of the LED driver circuit. The control circuit can receive a current feedback signal V from a current feedback circuit (e.g., current feedback circuits 134, 144, 214, 264). FB , where the current feedback signal V FB The magnitude of the load current I conducted by the LED light source LOAD The control circuit can control the LED driving circuit to move the LED toward the target intensity L TRGT Controls the intensity of the LED light source. Figures 6A to 6C The waveform shows that when the target intensity L TRGT Operation of a constant time controllable lighting device.

[0057] The control process 500 may be executed by the control circuit at step 510, for example, at the beginning of each control cycle of the LED driver circuit (e.g., periodically). For example, the execution period of the control process 500 may be set during a previous (e.g., previous) execution of the control process 500. At 512, the control circuit may determine the target intensity L based on the target intensity L. TRGT (For example, Figure 3 As shown) determine the drive signal V DR The on-time T ON . On time T ON The target intensity L may be determined based on predetermined and / or stored values ​​or may be determined by the control circuit based on the target intensity L TRGT At 514, the control circuit may turn on the FET of the LED driver circuit at the beginning of the current control cycle of the LED driver circuit. For example, the control circuit may turn on the FET of the LED driver circuit at 514 by turning the supply voltage V CC The driving signal V DR Driven high (for example, Figure 6A After turning on the FET, the LED light source can conduct the load current I LOAD , and the load current I LOAD During the on-time TON The peak amplitude I PK (For example, Figure 6A The first peak amplitude I PK1 ).

[0058] At 516, the control circuit may also turn on the first controllable switch of the current feedback circuit (eg, controllable switches 222, 272) at the beginning of the current cycle or slightly after the beginning of the current cycle, so that the current feedback signal V FB The magnitude indicates the load current I during the current cycle LOAD The peak amplitude I PK (For example, the first peak amplitude I PK1 For example, the control circuit can be directed toward the supply voltage V CC The window control signal V WIN Driven high (for example, Figure 6A t0 in FIG), so that the first controllable switch is turned on at 516. After the first controllable switch is turned on, the capacitor of the current feedback circuit (eg, capacitors C224, C274) can be charged, and the current feedback signal V FB The amplitude can be increased to the first feedback level V I-PK1 , which can indicate the load current I LOAD The first peak amplitude I PK1 .

[0059] At 518, the control circuit may process the current feedback signal V FB The sample is then used to determine the load current I LOAD The peak amplitude I PK (For example, the first peak amplitude I PK1 For example, the control circuit can be close to the on-time T ON At the end (e.g., Figure 6A Before the time t1 shown) the current feedback signal V FB At 520, the control circuit can drive the signal V toward the circuit common terminal. DR Driven low to turn the FET off, causing the FET to stop conducting the load current I LOAD (For example, Figure 6A At 522, the control circuit may transmit the window control signal V to the circuit common terminal. WIN is driven low to render the first controllable switch of the current feedback circuit non-conductive (e.g., as Figure 6A At 524, the control circuit may be configured to turn on the second controllable switch (eg, controllable switches 228, 278) to discharge the capacitor of the current feedback circuit. For example, the control circuit may be configured to turn on the second controllable switch (eg, controllable switches 228, 278) during the reset period T RST(eg, to generate a reset pulse) toward the supply voltage V CC The reset control signal V RST Driven high, the second controllable switch is in the reset period T RST The length of the conduction (for example, Figure 6A time t2).

[0060] At 526 , the control circuit may be configured to generate a current signal based on the current feedback signal V FB The sample amplitude (eg, as determined at 518) is used to determine the load current I LOAD The peak amplitude I PK (For example, the first peak amplitude I PK1 ). For example, the control circuit can use the current feedback signal V FB The sampling amplitude and the resistance of the sense resistor (e.g., Figure 2A The resistance R of the sensing resistor R220 of the LED driving circuit 210 is shown as SENSE ) to calculate the load current I LOAD The peak amplitude I PK , which can be stored in memory. In addition, the control circuit can use the current feedback signal V FB The sampling amplitude and the drain-source on-resistance of the FET of the LED driver circuit (for example, Figure 2B The drain-source on-resistance R of the FET Q262 of the LED driver circuit 260 is shown as DS-ON )Calculate the load current I LOAD The peak amplitude I PK For example, the control circuit may retrieve the drain-source on-resistance (e.g., a constant value or fixed value) from memory. Additionally, the control circuit may determine the drain-source on-resistance based on the current temperature T of the FET. PRES Determine the drain-source on-resistance. For example, the control circuit can be configured to use a temperature measurement circuit and / or a temperature sensing device to determine the current temperature T of the FET. PRES , and / or may be configured to estimate the temperature of FET Q262 based on one or more operating parameters of the electrical device.

[0061] At 528, the control circuit can be configured to calculate the drive signal V DR The operating period of the current cycle is T OP (For example, Figure 6A The first operation cycle T shown in OP1 For example, the control circuit can be configured to LOAD The target current I TRGT , conduction time T ON (e.g., as determined at 512) and / or the current peak amplitude I PK(For example, the first peak amplitude I determined at 526 PK1 ) Calculate the operating cycle T OP , for example, T OP =(I PK ·T ON ) / I TRGT For example, at 528, the control circuit may determine the target intensity L TRGT (For example, Figure 3 As shown) determine the target current I TRGT At 530, the control circuit may be configured to have an operating period T OP (For example, the first operation cycle T OP1 ) timer to make the control circuit operate in the operation cycle T OP For example, the timer can start running at the beginning of the current cycle (for example, at Figure 6A time t0 and / or before determining the length of the current cycle), and when the timer indicates the operation period T OP At the end, the control circuit may execute the control process 500 again to start the next cycle. During a subsequent execution of the control process 500 (eg, at the beginning of the next cycle), the control circuit may turn on the FET at 514, and the load current I LOAD During the on-time T ON The second peak amplitude I PK2 (For example, Figure 6A In addition, the control circuit may turn on the first controllable switch of the current feedback circuit at 516, and the current feedback signal V FB The amplitude can be increased to the second feedback level V I-PK2 , which indicates the load current I LOAD The second peak amplitude I PK2 At 526, the control circuit may determine the load current I LOAD The target current I TRGT , conduction time T ON and / or the current peak amplitude I PK (For example, the second peak amplitude I PK2 ) Calculate the operation period T of the next cycle OP (For example, the second operation cycle T OP2 ).

[0062] The control circuit may control the power converter circuit (eg, power converter circuit 102 ) to adjust the magnitude of the bus voltage in an attempt to reduce the operating period T to OP Keep the minimum operating cycle T OP-MIN and the maximum operating cycle T OP-MAX At 532, the control circuit can be based on the target intensity LTRGT (For example, Figure 3 As shown) determine the minimum operating cycle T OP-MIN and the maximum operating cycle T OP-MAX When the operation cycle T OP (e.g., as calculated at 526) is less than the minimum operating period T at 534 OP-MIN , the control circuit may increase the bus voltage V at 536 before exiting the control process 500. BUS The control circuit can adjust the bus voltage V BUS The magnitude of the bus voltage V BUS For example, during the on-time T ON After the end (for example, Figure 6B Time t 1a As shown), the control circuit can determine the bus voltage V BUS The amplitude of the first bus is V B1a Increase to the second bus amplitude V B2a For example, the second bus amplitude V B2a can be compared with the first bus amplitude V B1a Proportional, for example, V B2a =V B1a / K, where K is a constant less than 1. The control circuit can adjust the bus voltage control signal V BUS-CTRL To set the target bus voltage V BUS-TRGT Set the second bus amplitude V B2a (For example, towards the operating period T OP The end, such as Figure 6B Time t 2a Since when the next cycle starts (for example, Figure 6B Time t 3a When the FET is turned on, the bus voltage V BUS The amplitude is equal to the second bus amplitude V B2a , so the load current I LOAD The peak amplitude I PK The first peak amplitude I during the previous cycle can be PK1a Increase to the second peak amplitude I during the next cycle PK2a .

[0063] When the operation cycle T OP At 534, it is not less than the minimum operating period T OP-MIN But in 538 is greater than the maximum operating cycle T OP-MAX , the control circuit may reduce the bus voltage V at 540 before exiting the control process 500. BUSThe control circuit can adjust the bus voltage V BUS The magnitude of the bus voltage V BUS For example, during the on-time T ON After the end (for example, Figure 6C Time t 1b As shown), the control circuit can determine the bus voltage V BUS The amplitude of the first bus is V B1b Reduce to the second bus amplitude V B2b For example, the second bus amplitude V B2b can be compared with the first bus amplitude V B1b Proportional, for example, V B2b =K·V B1b , where K is a constant less than 1. The control circuit can adjust the bus voltage control signal V BUS-CTRL To set the target bus voltage V BUS-TRGT Set the second bus amplitude V B2b (For example, towards the operating period T OP The end, such as Figure 6C Time t 2b Since when the next cycle starts (for example, Figure 6C Time t 3b When the FET is turned on, the bus voltage V BUS The amplitude is equal to the second bus amplitude V B2b , so the load current I LOAD The peak amplitude I PK The first peak amplitude I during the previous cycle can be PK1 Decreases to the second peak amplitude I during the next cycle PK2 .

[0064] When the operation cycle T OP At 534, it is not less than the minimum operating period T OP-MIN , and not greater than the maximum operating cycle T at 538 OP-MAX When the control circuit does not adjust the bus voltage V BUS In the case of the magnitude of , the control process 500 exits. After the control process 500 exits, when the timer indicates the operation cycle T OP Upon completion (eg, as determined at 526 of the current loop), the control circuitry may again execute the control process 500 .

[0065] 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 implemented by various load control devices that are configured to control various electrical load types, such as, for example: an LED driver for driving an LED light source (e.g., an LED light engine); a screw-in lamp fixture comprising a dimmer circuit and an incandescent or halogen lamp; a screw-in lamp fixture comprising a ballast and a compact fluorescent lamp; a screw-in lamp fixture 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 type of lighting load; an electronic switch, a controllable circuit breaker, or other switching device for turning an electrical load or appliance on and off; a device for controlling one or more plug-in electrical loads (e.g., a coffee maker, a space heater, a microwave oven ... The present invention also includes plug-in load control devices, controllable electrical outlets, or controllable power strips for use with electrical loads (e.g., appliances, other household appliances, etc.); motor control units for controlling motor loads (e.g., ceiling fans or exhaust fans); drive units for controlling motorized window treatments or projection screens; motorized interior or exterior blinds; thermostats for heating and / or cooling systems; temperature control devices for controlling heating, ventilation, and air conditioning (HVAC) systems; air conditioners; compressors; electric baseboard heater controllers; controllable dampers; humidity control units; dehumidifiers; water heaters; pool pumps; refrigerators; freezers; televisions or computer monitors; power supplies; audio systems or amplifiers; generators; chargers such as electric vehicle chargers; and alternative energy controllers (e.g., solar, wind, or thermal). A single control circuit can be coupled to and / or adapted to control multiple electrical loads in a load control system.

Claims

1. A controllable lighting device, comprising: Light-emitting diode (LED) light sources; an LED driving circuit, the LED driving circuit comprising a controllable conductive device, the controllable conductive device being configured to conduct a load current through the LED light source; a feedback circuit configured to generate a feedback signal indicative of a peak magnitude of the load current conducted through the LED light source; and a control circuit configured to render the controllably conductive device of the LED driver circuit conductive and non-conductive to adjust an average magnitude of the load current conducted through the LED light source so as to adjust the intensity of the LED light source toward a target intensity; The control circuit is configured to cause the controllable conductive device to conduct during a conduction time during a current cycle of the LED driver circuit, so that the controllable conductive device conducts the load current at the peak amplitude during the conduction time, and the control circuit is configured to receive the feedback signal during the conduction time of the current cycle of the LED driver circuit, and determine the length of the operating period of the current cycle based on the amplitude of the feedback signal and the target intensity.

2. The controllable lighting device according to claim 1, further comprising: a power converter circuit configured to generate a bus voltage received by the LED driver circuit; The peak magnitude of the load current during the on-time of the current cycle of the LED driver circuit depends on the magnitude of the bus voltage.

3. The controllable lighting device of claim 2, wherein the control circuit is further configured to limit the length of the corresponding operation period of the one or more cycles of the LED driver circuit to between a maximum value and a minimum value.

4. The controllable lighting device of claim 3 , wherein the control circuit is further coupled to the power converter circuit and is configured to generate a bus control signal for adjusting the magnitude of the bus voltage to maintain a length of a corresponding operating period of one or more cycles of the LED driver circuit between the maximum value and the minimum value.

5. The controllable lighting device of claim 4 , wherein the control circuit is configured to control the bus control signal to decrease the bus voltage in response to determining that the length of the operation period of the current cycle of the LED driver circuit is higher than the maximum value, and to increase the bus voltage in response to determining that the length of the operation period of the current cycle of the LED driver circuit is lower than the minimum value.

6. A controllable lighting device as described in claim 3, wherein the control circuit is configured to set the maximum value of the length of the operating cycle to a first value when the target intensity is between the maximum intensity and the transition intensity, and to increase the maximum value of the length of the operating cycle from the first value when the target intensity is lower than the transition intensity.

7. The controllable lighting device of claim 3, wherein the minimum value of the length of the operating cycle is set to a value that is independent of the target intensity of the LED light source.

8. The controllable lighting device of claim 3 , wherein the control circuit is configured to generate a bus control signal for adjusting the amplitude of the bus voltage, and the control circuit is further configured to maintain the length of the corresponding operating period of the one or more cycles of the LED driver circuit between the maximum value and the minimum value by controlling the power converter circuit to adjust the amplitude of the bus voltage.

9. The controllable lighting device of claim 1 , wherein the control circuit is further configured to determine the on-time of the LED driver circuit based on the target intensity, and further determine the length of the operating period of the current cycle based on the on-time.

10. A controllable lighting device as described in claim 9, wherein the control circuit is configured to keep the on-time of the LED driver circuit constant when the target intensity of the LED light source is between the transition intensity and the maximum intensity or when the target intensity of the LED light source is lower than the minimum intensity, and the control circuit is further configured to linearly adjust the on-time of the LED driver circuit according to the target intensity of the LED light source when the target intensity is between the transition intensity and the minimum intensity.

11. The controllable lighting device of claim 9 , wherein the control circuit is configured to set the on-time of the LED driver circuit to a maximum on-time when the target intensity of the LED light source is between a transition intensity and a maximum intensity, and the control circuit is further configured to set the on-time of the LED driver circuit to a minimum on-time when the target intensity of the LED light source is lower than a minimum intensity. 12 . The controllable lighting device according to claim 9 , wherein the control circuit is configured to turn on the controllable conductive device during the on-time of the LED driving circuit. 13 . The controllable lighting device of claim 1 , wherein the control circuit is configured to sample the feedback signal during the on-time of the current cycle of the LED driver circuit.

14. The controllable lighting device of claim 13, wherein the feedback circuit of the LED driving circuit further comprises a first controllable switch device, and wherein the control circuit is further configured to turn on the first controllable switch device before sampling the feedback signal.

15. The controllable lighting device of claim 14, wherein the feedback circuit of the LED driving circuit further comprises a second controllable switch device, and wherein the control circuit is further configured to turn on the second controllable switch device during a reset period before sampling the feedback signal. 16 . The controllable lighting device of claim 1 , wherein the control circuit is configured to determine the peak amplitude of the load current in response to an amplitude of the feedback signal.

17. The controllable lighting device of claim 16 , wherein the feedback circuit of the LED driver circuit is configured to generate the feedback signal in response to a voltage generated across the controllable conductive device of the LED driver circuit, and the control circuit is configured to determine the peak amplitude of the load current in response to the amplitude of the feedback signal and the resistance of the controllable conductive device.

18. The controllable lighting device of claim 17, wherein the resistance of the controllably conductive device depends on a temperature of the controllably conductive device, and the control circuit is further configured to determine the peak amplitude of the load current in response to the temperature of the controllably conductive device.

19. The controllable lighting device of claim 16 , wherein the feedback circuit of the LED driver circuit is configured to generate the feedback signal in response to a sense voltage generated across a sense resistor, and the control circuit is configured to determine the peak amplitude of the load current in response to the amplitude of the feedback signal and the resistance of the sense resistor.

20. The controllable lighting device of claim 1, wherein the control circuit is configured to set a timer for determining when the operating period of the current cycle of the LED driver circuit ends.

21. The controllable lighting device of claim 1, further comprising a communication circuit, wherein the control circuit is configured to determine the target intensity of the LED light source based on a message received via the communication circuit.

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