Load control device with wide output range

Abstract

The present disclosure relates to load control devices having a wide output range. A load control device (e.g., an LED driver) for controlling the intensity of a lighting load (e.g., an LED light source) can provide a wide output range and flicker-free adjustment of the intensity of the lighting load. The load control device can include a load regulation circuit, a control circuit, and a filter circuit (e.g., a rectangular window filter circuit) that operates differently depending on a target current. When the intensity of the lighting load is near a low-end intensity, the control circuit can adjust a frequency of operation of the load regulation circuit in response to the target current and can control the filter circuit to filter a current feedback signal during periodically repeating filter windows. When the intensity of the lighting load is near a high-end intensity, the control circuit can control the filter circuit to filter the current feedback signal continuously.

Description

[0001] This application is a divisional application of PCT application number PCT / US2018 / 019519, filed on February 23, 2018, which entered the Chinese national phase on April 23, 2020, with national application number 201880069115.2 and entitled "Load Control Device with Wide Output Range".

[0002] Cross-references to related applications

[0003] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 562,066, filed September 22, 2017, and U.S. Provisional Patent Application No. 62 / 580,707, filed November 2, 2017, the entire disclosure of which is incorporated herein by reference. Background Technology

[0004] Light-emitting diode (LED) light sources (e.g., LED light engines) are replacing traditional incandescent, fluorescent, and halogen lamps as the primary form of lighting equipment. An LED light source can comprise multiple light-emitting diodes mounted on a single structure and housed in a suitable enclosure. Compared to incandescent, fluorescent, and halogen lamps, LED light sources are likely to be more efficient and offer a longer operating life. LED driver control devices (e.g., LED drivers) can be coupled between a power source, such as an alternating current (AC) or direct current (DC) power supply, and the LED light source to regulate the power supplied to the LED light source. For example, an LED driver can regulate the voltage supplied to the LED light source, the current supplied to the LED light source, or both current and voltage.

[0005] Different control technologies can be used to drive LED light sources, including, for example, current load control technology and voltage load control technology. LED light sources driven by current load control technology are characterized by a rated current (e.g., approximately 350 mA), and the magnitude of the current flowing through the LED light source (e.g., peak or average magnitude) can be adjusted to this rated current to ensure the LED light source is illuminated with appropriate intensity and / or color. LED light sources driven by voltage load control technology are characterized by a rated voltage (e.g., approximately 15 volts), and the voltage across the LED light source can be adjusted to this rated voltage to ensure proper operation of the LED light source. If the LED light source rated for voltage load control technology comprises multiple LEDs connected in parallel strings, a current balancing element can be used to ensure that the parallel strings have the same impedance so that the same current is drawn in each parallel string.

[0006] The light output of an LED light source is dimmable. Methods for dimming an LED light source can include, for example, pulse width modulation (PWM) and constant current reduction (CCR) techniques. In pulse width modulation dimming, a pulse signal with a varying duty cycle can be supplied to the LED light source. For example, if current load control is used to control the LED light source, the peak current supplied to the LED light source can be kept constant during the on-time of the pulse signal's duty cycle. However, the duty cycle of the pulse signal can be changed to alter the average current supplied to the LED light source, thereby changing the intensity of the LED light output. As another example, if voltage load control is used to control the LED light source, the voltage supplied to the LED light source can be kept constant during the on-time of the pulse signal's duty cycle. However, the duty cycle of the load voltage can be changed to adjust the intensity of the light output. If current load control is used to control the LED light source, constant current reduction dimming can be used. In constant current reduction dimming, current can be continuously supplied to the LED light source. However, the DC magnitude of the current supplied to the LED light source can be changed to adjust the intensity of the light output.

[0007] Examples of LED drivers are described in U.S. Patent No. 8,492,987, published July 23, 2013, entitled "LOAD CONTROL DEVICE FOR A LIGHT-EMITTING DIODE LIGHT SOURCE"; U.S. Patent No. 9,655,177, published May 16, 2017, entitled "FORWARD CONVERTER HAVING A PRIMARY-SIDE CURRENTSENSE CIRCUIT"; and U.S. Patent No. 9,247,608, published January 26, 2016, entitled "LOAD CONTROL DEVICE FOR A LIGHT-EMITTING DIODELIGHT SOURCE"; all of which are incorporated herein by reference in their entirety. Summary of the Invention

[0008] As described herein, load control devices (e.g., LED drivers) for controlling the intensity of lighting loads (e.g., LED light sources) can provide a wide output range for the current conducted through the lighting load to achieve flicker-free adjustment of the lighting load intensity. Because load control devices are characterized by a wide output range, they can potentially control a variety of different lighting loads with varying ratings (e.g., different rated output currents and / or rated output voltages). This allows manufacturers of load control devices, manufacturers of light source fixtures (such as original equipment manufacturers (OEMs)), and / or distributors of load control devices and / or fixtures to maintain a smaller number of stock units (SKUs) in stock.

[0009] Load control devices may include load conditioning circuitry, control circuitry, and filter circuitry (e.g., a boxcar filter circuit) that operates differently depending on the intensity of the load control device (e.g., a target intensity) to provide a wide output range. The load conditioning circuitry can control the magnitude of the load current conducted through the lighting load to adjust the intensity of the lighting load between low-end and high-end intensities. The filter circuitry can receive a current feedback signal from the load conditioning circuitry and filter the current feedback signal to generate a filtered feedback signal. The control circuitry is operatively coupled to the load conditioning circuitry to control the magnitude of the load current in response to the filtered feedback signal toward the target current. When the intensity of the lighting load is close to the low-end intensity (e.g., when the target current is less than the transition current), the control circuitry can adjust the operating frequency of the load conditioning circuitry in response to the target current and can control the filter circuitry to filter the current feedback signal during periodically repeating filter windows. When the intensity of the lighting load is close to the high-end intensity (e.g., when the target current is greater than the transition current), the control circuitry can control the filter circuitry to continuously filter the current feedback signal. When the target current is less than the transition current, the control circuit can generate a filter control signal to control the filter circuit to filter the current feedback signal during the filter window, and control the filter control signal to have a maximum duty cycle (e.g., 100%) when the target current is greater than the transition current. Attached Figure Description

[0010] Figure 1 This is a simplified block diagram of an example light-emitting diode (LED) driver used to control the intensity of an LED light source.

[0011] Figure 2 This is a simplified schematic diagram of an example LED driver.

[0012] Figure 3A yes Figure 2An example diagram showing the relationship between the operating frequency of an LED driver and the target current.

[0013] Figure 3B yes Figure 2 An example diagram showing the relationship between the magnitude of the target current control signal and the target current for an LED driver.

[0014] Figure 4A and Figure 4B The illustration is shown. Figure 2 Example waveforms of the operation of the LED driver.

[0015] Figure 5A The diagram illustrates the process when the LED driver is learning the load voltage. Figure 2 Example waveforms of the operation of the LED driver.

[0016] Figure 5B The illustration shows the LED light source being turned on by the LED driver using a learned load voltage. Figure 2 Example waveforms of the operation of the LED driver.

[0017] Figure 6 This is a simplified flowchart of an example control process used to control an LED driver to control the magnitude of the load current conducted through the lighting load. Detailed Implementation

[0018] Figure 1 This is a simplified block diagram of a load control device such as a light-emitting diode (LED) driver 100, which is used to control the intensity of an LED light source 102 (e.g., an LED light engine). The LED light source 102 is... Figure 1 The LED light source 102 is shown as multiple LEDs connected in series, but depending on the specific lighting system, it may include a single LED or multiple LEDs connected in parallel, or a suitable combination thereof. Alternatively, the LED light source 102 may include one or more organic light-emitting diodes (OLEDs). The LED driver 100 may be adapted to work with multiple different LED light sources, which may be rated at different levels of load current and voltage.

[0019] LED driver 100 may include a means for receiving AC voltage V from an AC power source (not shown). AC The LED driver 100 includes a hot terminal H and a neutral terminal N. The LED driver 100 may include a radio frequency (RFI) filter and a rectifier circuit 110, which can receive an AC voltage V. AC The RFI filter and rectifier circuit 110 can operate to minimize the noise supplied to the AC power supply and generate a rectified voltage V. RECTThe LED driver 100 may include a power converter circuit 120 that can receive a rectified voltage V. RECT And in the bus capacitor C BUS A variable DC bus voltage V is generated at both ends. BUS The power converter circuit 120 may include any suitable power converter circuit for generating a suitable bus voltage, such as, for example, a boost converter, buck converter, buck-boost converter, flyback converter, single-ended primary inductor converter (SEPIC), Cuk converter, or other suitable power converter circuit. The power converter circuit 120 may also provide electrical isolation between the AC power supply and the LED light source 102 and serve as a power factor correction (PFC) circuit to adjust the power factor of the LED driver 100 toward a power factor of 1.

[0020] LED driver 100 may include load regulation circuitry, such as LED driver circuitry 130, which can receive bus voltage V. BUS The LED driver circuit 130 controls the amount of power supplied to the LED light source 102, thereby controlling the intensity of the LED light source 102. For example, the LED driver circuit 130 may include a buck converter, as will be described in more detail below. To control the amount of power supplied to the LED light source 102, the LED driver circuit 130 may be configured to control the load current I conducted through the LED light source 102. LOAD The average size.

[0021] LED driver 100 may include control circuitry 140 for controlling the operation of power converter circuitry 120 and LED driver circuitry 130. Control circuitry 140 may include, for example, a controller or any other suitable processing device, such as, for example, a microcontroller, programmable logic device (PLD), microprocessor, application-specific integrated circuit (ASIC), or field-programmable gate array (FPGA). Control circuitry 140 may be configured to control LED driver circuitry 130 to control the load current I conducted through the LED light source. LOAD The average size is used to control the amount of power supplied to the LED light source. The control circuit 140 can be configured to control the LED driver circuit 130 to turn the LED light source 102 on and off and direct it toward the target intensity L. TRGT Adjust (e.g., dim) the current intensity L of light source 102 PRES The target intensity L TRGT It can cover the dimming range of LED light sources, for example, at the low-intensity L... LE (e.g., approximately 0.1%-1.0%) and high-end strength L HE (For example, between approximately 100%).

[0022] The control circuit can be configured to increase the target intensity L of the LED light source 102. TRGT (and therefore the current intensity L) PRES Gradual change (e.g., gradual adjustment over a period of time). Control circuitry 140 can be configured to control the intensity L, which can be less than the low-end intensity. LE (For example, the minimum gradient intensity L such as approximately 0.02%) FADE -MIN to target intensity L TRGT Slowly increase the current intensity L of the LED light source PRES This causes the LED light source 102 to gradually change from off to on. The control circuit 140 can be configured to gradually turn the LED light source 102 on by switching it from an intensity greater than or equal to the low end L. LE The initial intensity is reduced to the minimum gradual intensity L at which the control circuit 140 can turn off the LED light source. FADE -MIN slowly decreases the current intensity of the LED light source L PRES This causes the LED light source 102 to gradually change from being on to being off.

[0023] Control circuitry 140 can be coupled to a configuration for storing operating characteristics of LED driver 100 (e.g., target intensity L). TRGT Low-end strength L LE High-end strength L HE The LED driver 100 may include a memory 112, which can be implemented as an external integrated circuit (IC) or internal circuitry of the control circuitry 140. The LED driver 100 may also include a communication circuitry 114, which can be coupled to, for example, a wired or wireless communication link, such as a radio frequency (RF) or infrared (IR) communication link. The control circuitry 140 may be configured to determine the target intensity L of the LED light source 102 in response to a digital message received via the communication circuitry 114. TRGT The operating characteristics may be stored in memory 112. In response to receiving a command to turn on LED light source 102, control circuitry 140 can be configured to execute an on-time routine. LED driver 100 may further include power supply 116, which can receive rectified voltage V. RECT It also generates a DC power supply voltage V for powering the low-voltage circuitry of the LED driver. CC (For example, approximately 5 volts). Additionally, power supply 116 can generate one or more additional power supply voltages, for example, to power the control circuitry of power converter circuitry 120 and / or LED driver circuitry 130.

[0024] Control circuitry 140 may include digital control circuitry, such as processor 142, which may be, for example, a microprocessor, programmable logic device (PLD), microcontroller, application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), or other suitable processing device or controller. Control circuitry 140 may also include analog control loop 150. Processor 142 and analog control loop 150 can work together to control LED driver circuitry 130 to transfer load current I... LOAD The average size of the target current I TRTT Adjustment. Target current I TRTT It can depend on the target intensity L TRGT (For example, target intensity L) TRGT (The function). Processor 142 can generate the target current control signal V. I-TRGT It can have an indicator that can show the target current I. TRTT The DC value or duty cycle. The processor 142 can be based on the target intensity L of the LED light source 102. TRGT To control the target current control signal V I-TRGT DC size or duty cycle.

[0025] The control circuit 140 may further include a latch circuit 160, which generates a drive signal V for controlling the operation of the LED driver circuit 130. DR (For example, the switching transistors of the LED driver circuit 130 are used to conduct and deconduct to drive the load current I) LOAD The average size of the target current I TRGT (Adjustment). Processor 142 can generate frequency control signal V. FREQ The frequency control signal V FREQ The operating frequency f of the LED driver circuit 130 can be set. OP In response to the frequency control signal V FREQ The latch circuit 160 can control the drive signal V DR To enable the switching transistor of the LED driver circuit 130 to conduct and start the cycle of the LED driver circuit, the LED driver circuit can then begin to conduct the inductor current I conducted through the inductor (not shown) of the LED driver circuit 130. L In response to sensor current I L The size of the analog control loop 150 can generate the peak current threshold V. TH-PK The latch circuit 160 can use this peak current threshold V TH-PK This makes the switching transistor of the LED driver circuit 130 non-conductive.

[0026] LED driver 100 may include amplifier circuit 170, which can receive current feedback signal V from LED driver circuit 130.I-FB Amplifier circuit 170 can amplify the current feedback signal V. I-FB To generate instantaneous current feedback signal V I-INST It can indicate the inductor current I flowing through the inductor of the LED driver circuit 130. L The instantaneous size.

[0027] The LED driver 100 may further include a filter circuit 180, such as a rectangular window filter circuit. The filter circuit 180 can receive a transient current feedback signal V. I-INST And it generates a filtered feedback signal, such as the average current feedback signal V. I-AVE It can indicate (e.g., within a specific time window) the inductor current I flowing through the inductor of the LED driver circuit 130. L The average size. Processor 142 can generate filter control signals V for controlling the operation of filter circuit 180. FILTER (For example, a filter control signal), for instance, to control when the filter circuit 180 responds to the instantaneous current feedback signal V. I-INST Filtering is performed. For example, processor 142 can control the filter control signal V. FILTER To allow the filter circuit 180 to operate within the filter window time T during each cycle of the LED driver circuit 130. FILTER Upper instantaneous current feedback signal V I-INST Filtering is performed. Processor 142 can operate in conjunction with the frequency control signal V. FREQ Synchronous control of filter control signal V FILTER For example, in the filter window time T FILTER The LED driver circuit 130 is started in a loop at the beginning. For example, the filter window period T FILTER The LED driver circuit 130 can have the same length during each cycle, while the frequency control signal V... FREQ The frequency is independent. Average current feedback signal V I-AVE The size can indicate the time period T in the filter window. FILTER During (e.g., when filter circuit 180 is processing the instantaneous current feedback signal V) I-INST The inductor current I during filtering L The average size.

[0028] The analog control loop 150 of the control circuit 140 can receive the average current feedback signal V. I-AVE Furthermore, the latch circuit 160 can receive the instantaneous current feedback signal V. I-INST The analog control loop 150 can respond to the target current control signal V. I-TRGT and average current feedback signal V I-AVETo adjust the peak current threshold V TH-PK The size of the latch circuit 160. The latch circuit 160 can (e.g., at the beginning of a cycle in the LED driver circuit 130) respond to the frequency control signal V. FREQ To control the drive signal V DR This allows the switching transistor of the LED driver circuit 130 to conduct. The latch circuit 160 can respond to the peak current threshold V. TH-PK and instantaneous current feedback signal V I-INST To control the drive signal V DR This makes the switching transistor non-conductive. After the switching transistor of the LED driver circuit 130 is made non-conductive, the latching circuit 160 can remain in the latched state and keep the switching transistor non-conductive until the start of the next cycle of the LED driver circuit 130.

[0029] Control circuit 140 can be configured to determine or learn one or more operating characteristics of LED light source 102 (e.g., learned load characteristics) (e.g., measuring one or more operating characteristics of LED light source 102 or receiving indications of one or more operating characteristics of LED light source 102). For example, control circuit 140 can be configured to determine an indication of load voltage V. LOAD The voltage of the magnitude. The load voltage V generated across the LED light source 102. LOAD The magnitude can depend on the load current I LOAD (For example, control circuit 140 is adjusting the load current I towards it) LOAD Target load current I TRTG The size of the LED and the internal circuitry of the LED light source. The control circuit 140 can be configured to determine (e.g., measure) the load voltage V. LOAD The magnitude and / or the measurement result as the learned load voltage V LEARNED The signal is stored in memory 112. Control circuit 140 can be configured to use the load voltage feedback signal V received from LED driver circuit 130. V-LOAD To determine (e.g., measure) the load voltage V LOAD The size of the LED. For example, the LED driver circuit 130 may include a resistive voltage divider circuit (not shown) connected across the LED light source 102 to generate a load voltage feedback signal V. V-LOAD As a scaled load voltage. Load voltage feedback signal V V-LOAD The load voltage V can be received by the analog-to-digital converter (ADC) of processor 142 to learn the load voltage V. LOAD Size.

[0030] The control circuit 140 can be configured to, when the target intensity L TRGT Low-end strength L LEDetermine (e.g., measure) the load voltage V at or near it. LOAD The size. For example, the control circuit 140 can be configured such that when the control circuit 140 is gradually switching the LED light source 102 from on to off, for example, when the load current I... LOAD The average size is within its range and can be obtained from the maximum learning threshold I. LEARN-MAX To the minimum learning threshold I LEARN-MIN When within the measurement window, determine (e.g., measure) the load voltage V. LOAD The size of the maximum learning threshold I. LEARN-MAX and minimum learning threshold I LEARN-MIN It can be the rated (or maximum) current I of the LED light source 102. RATED The function, for example, 0.0020-I. RATED and 0.0002-I RATED .

[0031] The control circuit 140 can be configured to use the learned load voltage V LEARNED To control the LED driver circuit 130. For example, the control circuit 140 can be configured to respond to a learned load voltage V when the LED light source 102 is turned on. LEARNED The control circuit 140 is configured to charge (e.g., "pre-charge") the output capacitor (not shown) of the LED driver circuit 130 before attempting to turn on the LED light source 102. In response to receiving a command to turn on the LED light source 102 and / or in response to power applied to the LED driver to turn on the LED light source, the control circuit 140 can pre-charge the output capacitor until the load voltage V... LOAD The size reaches or exceeds the pre-charge voltage threshold V TH-PC Up to, for example, the pre-charge voltage threshold V TH-PC It can be the load voltage V being studied. LEARNED The function (e.g., as will be described in more detail below). Pre-charging of the output capacitor allows the LED driver 100 to, for example, fade into the low-end intensity L. LE The LED light source 102 is turned on quickly and consistently.

[0032] Control circuit 140 can be configured to determine the load voltage V as the learning voltage. LEARNED The operating parameters of the function (e.g., preload parameters) are used to control the LED driver circuit 130 to precharge the output capacitor of the LED driver circuit 130 before turning on the LED light source 102 (e.g., as will be described in more detail below). For example, the control circuit 140 may be configured to determine the load voltage V as a learned value. LEARNEDThe target current control signal V used by the function to precharge the output capacitor of the LED driver circuit 130 is... I-TRGT The DC magnitude or duty cycle. Additionally, processor 142 can generate a start control signal V for controlling the analog control loop 150. START-UP At the same time, the output capacitor of the LED driver circuit 130 is precharged to maintain the output of the analog control loop 150 at a predetermined voltage.

[0033] At load voltage V LOAD The size reaches or exceeds the pre-charge voltage threshold V TH-PC Then, the processor 142 can control the start control signal V START-UP To allow the analog control loop 150 to respond to the current feedback signal V I-FB Closed-loop control is used to control the LED driver circuit 130 to drive it toward the target current I. TRGT Adjusting the load current I LOAD Size.

[0034] Figure 2 This is a simplified schematic diagram of a load regulating device, such as an LED driver 200 (e.g., for controlling the intensity of an LED light source 202). Figure 1 LED driver 100). LED driver 200 may include a device for storing bus voltage V. BUS bus capacitor C BUS This can be generated by a power converter circuit (e.g., power converter circuit 120 of LED driver 100). LED driver 200 may include LED driver circuit 230, which can be configured to control the load current I conducted through LED light source 202. LOAD The size of the LED driver 200. The LED driver 200 may further include control circuitry 240, which may be a mixed-signal control circuit (e.g., control circuitry 140 of the LED driver 100). Control circuitry 240 may include processor 242, low-pass filter circuitry 244, analog control loop (e.g., which may include integrator circuitry 250), and latch circuitry 260. Latch circuitry 260 may generate a drive signal V that can be provided to LED driver circuitry 230. DR The LED driver 200 may further include components for generating instantaneous current feedback signals V. I-INST and average current feedback signal V I-AVE Amplifier circuit 270 and filter circuit 280 (e.g., rectangular window filter circuit).

[0035] like Figure 2As shown, the LED driver circuit 230 may include a buck converter. The LED driver circuit 230 may include a switching transistor, such as a field-effect transistor (FET) Q232, which is responsive to a drive signal V. DR Controlled to control the load current I LOAD The average size. The LED driver circuit 230 may also include an inductor L234, a switching diode D235, an output capacitor C236, and a feedback resistor R238. Drive signal V DR It can be coupled to the gate of FET Q232 through gate drive circuit 239. When FET Q232 is conducting, inductor L234 can draw energy from bus capacitor C through the parallel combination of output capacitor C236 and LED light source 202. BUS Conducting inductor current I L When FET Q232 is not conducting, inductor L234 can conduct inductor current I through the parallel combination of switching diode D235, output capacitor C236, and LED light source 202. L LED light source 202 can conduct inductor current I. L The average component, and the output capacitor C236 can conduct the inductor current I. L The transient component of the load current I. LOAD The average size can be approximated by the inductor current I. L The average size.

[0036] Current feedback signal V I-FB It can be generated across the feedback resistor R238 of the LED driver circuit 230, and can be related to the inductor current I. L The magnitude is proportional. Current feedback signal V I-FB This can be received by amplifier circuit 270. Amplifier circuit 270 may include operational amplifier U272 and may be configured as a non-inverting amplifier circuit. Operational amplifier U272 may have the ability to receive current feedback signal V. I-FB The amplifier circuit 270 may further include a resistor R274 coupled between the inverting input terminal and the circuit common terminal of the operational amplifier U272, and a resistor R276 coupled between the inverting input terminal and the output terminal of the operational amplifier U272. The amplifier circuit 270 can be configured to generate a transient current feedback signal V. I-INST It can be a current feedback signal V I-FB An enlarged version that can indicate the inductor current I L The instantaneous size.

[0037] Filter circuit 280 can process instantaneous current feedback signal V I-INST Filtering is performed to generate the average load current signal VI-AVE The average load current signal V I-AVE It can indicate the inductor current I L The average size. Filter circuit 280 may include controllable switching circuit 282 and low-pass filter circuit (e.g., third-order low-pass filter circuit), which includes resistors R284, R286, R288 and capacitors C285, C287, C289. Processor 242 may generate filter control signal V. FILTER This allows the controllable switch circuit 282 to be conductive and non-conductive. When the controllable switch circuit 282 is conductive, the filter circuit 280 can be configured to respond to the instantaneous current feedback signal V. I-INST Filtering is performed to generate the average current feedback signal V I-AVE When the controllable switch circuit 282 is not conducting, capacitors C285, C287, and C289 of the filter circuit 280 can transmit the average current feedback signal V. I-AVE The magnitude is maintained at the inductor current I during the period when the controllable switching circuit 282 was previously conducting. L The average size value.

[0038] Processor 242 can generate pulse width modulation (PWM) signal V PWM This signal can be received by the low-pass filter circuit 244 of the control circuit 240. The filter circuit 244 can be configured to generate the target current control signal V. I-TRGT It can have an indication of the target current I. TRTT The DC value. For example, the low-pass filter circuit 244 may include a resistor-capacitor (RC) circuit with a resistor R246 and a capacitor C248. The processor 242 may be configured to control the pulse width modulation signal V. PWM The duty cycle is adjusted to control the target current V. I-TRGT Size.

[0039] The average current feedback signal V generated by filter circuit 280 I-AVE and the target current control signal V generated by the low-pass filter circuit 244 I-TRGT This can be received by integrator circuit 250. Integrator circuit 250 includes operational amplifier U252, which has a signal coupled to the target current control signal V. I-TRGT The non-inverting input and the average current feedback signal V coupled via resistor R254 I-AVE The inverting input. The integrator circuit 250 may include a capacitor C256 coupled between the inverting input and output of the operational amplifier U252, such that the integrator circuit 250 can be configured to provide feedback to the average current signal V. I-AVE and target current control signal VI-TRGT The error between them is integrated. The integrator circuit 250 can generate the peak current threshold V. TH-PK The peak current threshold V TH-PK It has a control signal V that can depend on the target current. I-TRGT Magnitude and average current feedback signal V I-AVE The DC value increases or decreases due to the error between the magnitudes. The integrator circuit 250 may include a controllable switching circuit 258 coupled in parallel with capacitor C256. In response to a startup control signal V received from processor 242 during the startup routine... START-UP The controllable switching circuit 258 can become conductive and non-conductive (e.g., as will be described in more detail below).

[0040] The latch circuit 260 can receive the peak current threshold V generated by the integrator circuit 250. TH-PK and the instantaneous current feedback signal V generated by amplifier circuit 270 I-INST The latch circuit 260 may include a comparator U262, which is configured to compare the instantaneous current feedback signal V. I-INST The magnitude of the peak current threshold V TH The size of the value. The comparator U262 can generate a latch control signal V at the output. LATCH When the instantaneous current feedback signal V I-INST The magnitude is less than the peak current threshold V TH When the value is large or small, comparator U262 can latch the control signal V. LATCH The drive is a high-level output (e.g., towards the supply voltage Vcc). When the instantaneous current feedback signal V... I-INST The magnitude exceeds the peak current threshold V TH-PK When the value is large or small, comparator U262 can latch the control signal V. LATCH The drive is a low output level (e.g., towards the circuit common terminal).

[0041] Processor 242 can generate frequency control signal V FREQ It can set the operating frequency f of the LED driver circuit 230. OP The latch circuit 260 may include a PWM control circuit 266, which can receive a latch control signal V from the comparator U262. LATCH and frequency control signal V from processor 242 FREQ The PWM control circuit 266 can generate the drive signal V. DR It can be received by the gate driving circuit 239 of the LED driving circuit 230. When the frequency control signal V FREQWhen the LED driver circuit 230 is driven high at the beginning of its cycle, the PWM control circuit 266 can drive the drive signal VDR high, which allows the FET Q232 of the LED driver circuit 230 to conduct. When the instantaneous current feedback signal V... I-INST The magnitude exceeds the peak current threshold signal V TH When the value is large enough, comparator U262 can drive the latch control signal VLATCH low, which allows the PWM control circuit 266 to control the driver signal V. DR The drive signal is low. The PWM control circuit 266 can control the drive signal V. DR The value remains low until the processor 242 resets the frequency control signal V again at the end of the current cycle and the beginning of the next cycle of the LED driver circuit 230. FREQ The size drive is high level.

[0042] Processor 242 can use open-loop control, depending on the target current I of LED light source 202. TRGT To control the frequency control signal V FREQ Frequency and pulse width modulation control signal V PWM The duty cycle (and therefore the target current control signal V) I-TRGT (size). Figure 3A It is the frequency control signal V FREQ The frequency (e.g., the operating frequency f of the LED driver circuit 230) OP ) and target current I TRGT Example diagram of the relationship between 300. Figure 3B It is the target current control signal V I-TRGT The magnitude of the target current I TRGT Example diagram of the relationship between 310. For example, target current I. TRGT The range can be found in high-end strength L HE High-side current I HE (e.g., approximately 150 mA) and low-end strength L LE Low-end current I LE (For example, it varies between approximately 150 μA).

[0043] Processor 242 can depend on the target current I TRGT Is it less than or greater than approximately the transition current I? TRAN (For example, approximately 16.8 mA) to operate in both the first and second operating modes. At the low-end intensity L LE Nearby (e.g., when the target current I) TRGT Less than approximately the transition current I TRAN(At that time), the processor 242 can operate in the first operating mode, during which the processor 242 can control the target current V. I-TRGT The magnitude remains constant (e.g., at the minimum voltage V). MIN At the same time, relative to the target current I TRGT At the minimum operating frequency f MIN and maximum operating frequency f MAX The frequency control signal V is adjusted (e.g., linearly) between these parameters. FREQ The frequency. At high-strength L... HE Nearby (e.g., when the target current I) TRGT Greater than or equal to approximately the transition current I TRAN (At this time), the processor 242 can operate in a second operating mode, during which the processor 242 can control the frequency control signal V. FREQ Keep constant (e.g., at the maximum operating frequency f) MAX At the same time, relative to the target current I TRGT At minimum voltage V MIN and maximum voltage V MAX Adjust the target current control signal V between (e.g., linearly) I-TRGT For example, the maximum operating frequency f MAX It can be approximately 140kHz, and the minimum operating frequency f MIN It can be approximately 1250Hz. For example, the maximum voltage V MAX It can be approximately 3.3V, and the minimum voltage V MIN It can be approximately 44mV.

[0044] Figure 4A and Figure 4B The illustration is shown. Figure 2 The example waveforms shown represent the operation of the LED driver 200. Figure 4A The diagram illustrates the situation when the target current I... TRGT Less than the transition current I TRAN Example waveforms of the operation of LED driver 200. Processor 242 can generate frequency control signal V. FREQ To set the operating frequency f of the LED driver circuit 230 OP For example, the duty cycle T of the LED driver circuit 230 OP It can be equal to the frequency control signal V FREQ The cycle time. Processor 242 can depend on the target current I. TRGT (For example, such as) Figure 3A (As shown) to set the operating frequency f OP (and therefore the work cycle T) OP The processor 242 can generate a frequency control signal V. FREQWith a predetermined conduction time T FREQ-ON It can have the same length in each cycle of the LED driver circuit 130 (e.g., with the frequency control signal V). FREQ Frequency or target current I TRGT (Irrelevant).

[0045] Processor 242 can be relative to frequency control signal V FREQ Generate filter control signal V in a synchronous manner FILTER For example, processor 242 can simultaneously process the filter control signal V FILTER and frequency control signal V FREQ Both are driven high to initiate the cycle of LED driver circuit 230 (e.g., in...). Figure 4A (at time t1). At time t1, the PWM control circuit 266 of the latch circuit 260 can control the drive signal V. DR The size drive is high (e.g., towards the power supply voltage V). CC This makes FET Q232 of the LED driver circuit 230 conductive. At this time, inductor L234 of the LED driver circuit 230 can begin to conduct inductor current II. When the instantaneous current feedback signal V... I-INST (It may be related to the inductor current I) L The magnitude is proportional to the peak current threshold signal V. TH When the magnitude is large, the PWM control circuit 266 can control the drive voltage V DR The size drive is low (e.g., towards the circuit common terminal), such as Figure 4A As shown in time t2, this may cause FET Q232 of the LED driver circuit 230 to become non-conductive. Figure 4A As shown, the driving signal V DR It can be determined by the conduction time T ON The sum can be equal to the working period T. OP The period is used to characterize it. The PWM control circuit 266 can make the FET Q232 operate at the drive signal V during each working cycle of the LED driver circuit 230. DR On-time T ON Conducting electricity within its length. Inductor current I L It can have peak amplitude I PK ,like Figure 4A As shown. Inductor current I L The magnitude can begin to decrease at time t2 until the inductor current I... L The magnitude of amperes decreases to zero amperes at time t3.

[0046] Processor 242 can be turned on for a predetermined time T FREQ-ON At the end (e.g., at) Figure 4AThe time t4) will control the frequency signal V FREQ The drive is low. Processor 242 can operate within the filter window period T. FILTER At the end (e.g., at) Figure 4A The filter control signal V will be applied at time t5. FILTER The drive is low. Processor 242 can control the filter signal V. FILTER and frequency control signal V FREQ Both are driven high to be active during the duty cycle T. OP At the end (e.g., at) Figure 4A At time t6, another cycle of the LED driver circuit 230 is started.

[0047] When the target current I TRGT Less than the transition current I TRAN At that time, the processor 242 can control the target current signal V I-TRGT The magnitude remains constant at the minimum voltage V MIN And as the target current I TRGT The function to be used at the minimum frequency f MIN and maximum frequency f MAX The frequency control signal V is linearly adjusted between them. FREQ The frequency (e.g., such as) Figure 3A and 3B (As shown). The filter circuit 280 can be configured to filter the LED driver circuit 230 during the filter window period T in each cycle. FILTER During this period, the instantaneous current feedback signal V I-INST Filtering is performed. When the target current I... TRGT Less than the transition current I TRAN At that time, the filter control signal V FILTER It can be a periodic signal characterized by an operating frequency fop. Processor 242 can control the filter signal V. FILTER The filter window period T FILTER The length of the LED driver circuit 230 remains constant from one cycle to the next, while the frequency control signal V... FREQ The frequency is independent. The filter control signal V FILTER The duty cycle can be controlled by the frequency control signal V. FREQ The frequency is adjusted and changed.

[0048] Due to the target current control signal V I-TRGT and filter window period T FILTER It remains constant, so even if the drive signal V DR The frequency can depend on the target current I TRGT The change drives the signal V. DR On-time TON (For example, work cycle T) OP It can also be approximately the same as each cycle of the LED driver circuit 230. As a result, when the target current I... TRGT Less than the transition current I TRAN During the period from one cycle of the LED driver circuit 230 to the next, the filtering window time T FILTER Inductor current I during the period L The peak and average values ​​can be approximately the same, while the target current I... TRGT Irrelevant. Filter window duration T FILTER The length can be determined to ensure that when the target current I... TRGT Less than the transition current I TRAN At that time, the inductor current I L During the filter window period T FILTER The current drops to zero amperes before ending. This occurs when the target current is less than the transition current I. TRAN At this time, the LED driver circuit 230 can be configured to operate in a discontinuous working mode.

[0049] Figure 4B The diagram illustrates the situation when the target current I... TRGT Greater than the transition current I TRAN Example waveforms of the operation of LED driver 200. When the target current I... TRGT Greater than the transition current I TRAN At that time, processor 242 can serve as the target current I TRGT The function at minimum voltage V MIN and maximum voltage V MAX The target current control signal V is linearly adjusted between these parameters. I-TRGT Size (e.g., such as) Figure 3A and 3B (As shown in the diagram). Additionally, the processor 242 can control the frequency signal V. FREQ The frequency is kept constant at the maximum operating frequency f MAX (For example, make the work cycle T) OP Constantly maintained at the minimum working cycle T MIN When the target current I TRGT Greater than the transition current I TRAN At that time, the processor 242 can control the filter signal V FILTER The duty cycle is controlled to the maximum filter duty cycle (e.g., 100%). For example, when the target current I... TRGT Greater than the transition current I TRAN During the work cycle T OP It can be equal to the filter window time T. FILTER The length. The result, as... Figure 4B As shown, processor 242 can target current ITRGT Greater than the transition current I TRAN At the same time, the filter control signal V is always kept in place. FILTER The drive is high (e.g., the filter control signal V). FILTER (For a constant signal). When the target current I TRGT Greater than the transition current I TRAN At that time, the average current feedback signal V I-AVE It can indicate the inductor current I L The average size. Additionally or alternatively, the processor 242 can, at all times (e.g., almost all times), for example, at a large duty cycle (e.g., approximately 90% or greater), control the filter signal V. FILTER The drive level is high.

[0050] Because processor 242 is the target current I TRGT The function changes the target current control signal V I-TRGT The size, so even the drive signal V DR Frequency (e.g., duty cycle T) OP Keep the driving signal V constant. DR On-time T ON The length can also be used as the target current I TRGT It changes as a function of the target current I. TRGT Increase the peak current I of the inductor current. PK This can be increased to the point where the LED driver circuit 230 can begin operating in continuous mode. Due to the minimum duty cycle T... MIN (For example, when the target current I) TRGT Greater than the transition current I TRAN The working cycle T OP It can be equal to the filter window time T. FILTER The length of the LED driver 200 is such that the processor 242 can be configured to cause the LED driver 200 to operate when the target current I... TRGT Less than the transition current I TRAN The first operating mode and when the target current I TRGT Greater than the transition current I TRAN Smooth transition between the second and third working modes.

[0051] When the target current I TRGT Greater than the transition current I TRAN At that time, the frequency control signal T FREQ The scheduled conduction time T FREQ-ON The length is less than the working period T OP The length. The processor 242 can (e.g., in...) Figure 4B The time t7) will control the frequency signal T FREQThe LED is driven low and then driven high at the end of each cycle of the LED driver circuit 230 (e.g., at time t8). This causes the PWM control circuit 266 of the latch circuit 260 to stop driving the drive signal V. DR The magnitude remains low, and when the frequency control signal T... FREQ When driven high to initiate the next cycle of the LED driver circuit 230 (e.g., at time t9), the drive signal V is activated. DR The value becomes high again.

[0052] The processor 242 of the control circuit 240 can be configured to determine or learn the load voltage V. LOAD The magnitude (e.g., the measured load voltage V) LOAD Size or received load voltage V LOAD (indicating the magnitude), and / or using the measurement result as the learned load voltage V LEARNED Stored in memory (e.g., memory 112). The load voltage V generated across the LED light source 202. LOAD The magnitude can depend on the load current I LOAD The size (e.g., the control circuit 240 is directed toward regulating the load current I) LOAD Target load current I TRTG The processor 242 can be configured to receive a load voltage feedback signal (e.g., the load voltage feedback signal V of the LED driver 100) from the LED driver circuit 230, as well as the internal circuitry of the LED light source. V-LOAD This signal can be the load voltage V generated by the resistor divider circuit (not shown) of the LED driver circuit 230. LOAD A scaled-down version. Processor 242 can use an analog-to-digital converter (ADC) to sample the load voltage feedback signal to measure the load voltage V. LOAD Size.

[0053] Figure 5A The diagram illustrates the process when processor 242 is learning the load voltage V. LOAD The operation of the LED driver 200 at that time. The processor 242 can be configured to determine (e.g., measure) the load voltage V when the processor 242 causes the LED light source 202 to gradually change from on to off. LOAD Size. For example... Figure 5A As shown, when the LED light source 202 is gradually switched from on to off, the processor 242 can transfer the load current I at time t0. LOAD The average magnitude from the initial current I INIT The voltage begins to decrease, and the time t0 is the load voltage V. LOAD The magnitude can also be, for example, from the initial voltage V. INITThe time at which the decrease begins. Processor 242 can be configured to determine (e.g., measure) the load voltage V. LOAD The size of the load current I LOAD The average size is within the maximum learning threshold I. LEARN-MAX and minimum learning threshold I LEARN-MIN Within a measurement window that varies between (e.g., at time t) WIN-START and t WIN-END Between, such as Figure 5A (As shown). Maximum learning threshold I LEARN-MAX and minimum learning threshold I LEARN-MIN This can be the rated (or maximum) current of the LED light source 202. IRATED The function, for example, 0.0020T. RATED and 0.0002T RATED The processor 242 can be configured to periodically sample the load voltage feedback signal during the measurement window and process multiple samples to determine the learned load voltage V. LEARNED For example, processor 242 can be configured to process multiple samples of the load voltage feedback signal by calculating the average or median of multiple samples or by filtering the samples using a digital low-pass filter.

[0054] Processor 242 can be configured to measure the load voltage V when (e.g., each time) processor 242 turns off LED light source 202 (e.g., causes LED light source to gradually turn off). LOAD And determine the load voltage V to be learned. LEARNED Processor 242 can be configured to use the learned load voltage V determined at the most recent time when processor 242 turned off LED light source 202. LEARNED To cover the learned load voltage V stored in memory LEARNED Furthermore, the processor 242 can be configured to operate over a load voltage V that overwrites the learned data stored in memory. LEARNED The previous process obtained the learned load voltage V from multiple shutdown events. LEARNED (For example, calculating the average or median of multiple learned load voltages).

[0055] Processor 242 can be configured, for example, to use a learned load voltage V when LED light source 202 is turned on. LEARNED To control the LED driver circuit 230. Figure 5B The illustration shows when the processor 242 causes the LED light source 202 to gradually change (e.g., to match the target current I). TRGT Corresponding target intensity L TRGTExample waveforms of the operation of LED driver 200 during (gradual) transition. In response to receiving a command to turn on LED light source 202 and / or in response to applying power to LED driver 200 to turn on LED light source, processor 242 can be configured to perform a pre-charging period T before attempting to turn on LED light source 202. PRE-CHARGE During this period, the output capacitor C236 of the LED driver circuit is pre-charged. During the pre-charging period T... PRE-CHARGE In this context, the processor 242 can be configured as the load voltage V for learning. LEARNED The function is used to control the pulse width modulation signal V. PWM The duty cycle (and therefore the target current control signal V) I-TRGT The DC value is used to make the output capacitor C236 charge faster than normal (e.g., for example, ...). Figure 3B The processor 242 shown responds to the target current I TRGT Control target current control signal V I-TRGT (Fast case of DC size). Output capacitor C236 during the pre-charge period T PRE-CHARGE The faster charging speed during this period allows the processor 242 to, for example, gradually reduce the intensity of the LED light source to a lower end L. LE The LED light source 202 is turned on quickly and consistently.

[0056] Control circuit 240 can be configured to precharge the output capacitor C236 of LED driver circuit 230 until the load voltage V LOAD The size reaches or exceeds the pre-charge voltage threshold V TH-PC Precharge voltage threshold V TH-PC It can be used, for example, as the load voltage V for learning. LEARNED (For example, V) TH-PC =α·V LEARNED Where α is a function that can be determined, for example, a constant of approximately 0.90. Since the LED light source 202 has a cold load voltage V... LOAD The size can be larger than the load voltage V when the LED light source is warm. LOAD The value of the constant α can be set to be less than 1 to ensure that the LED driver circuit 230 does not exceed the learned load voltage V when pre-charging the output capacitor C236. LEARNED Additional or alternative ground can be, for example, using the learned load voltage V. LEARNED Different functions (e.g., V) TH-PC =V LEARNED -β, where β is a constant, for example, it could be approximately one volt, to determine the pre-charge voltage threshold V. TH-PC Additional or alternative ground, pre-charge voltage threshold V TH-PCThis can be a fixed threshold (e.g., a predetermined threshold). If the load voltage V LOAD The size does not exceed the pre-charge voltage threshold V during the timeout period. TH-PC Then, processor 242 can be configured to stop pre-charging the output capacitor C236. Processor 242 can be configured based on the learned load voltage V. LEARNED To select the pulse width modulation signal V PWM The duty cycle value makes the pre-charge period T of the LED driver 200... PRE-CHARGE Different LED light sources with different load voltages can be roughly the same.

[0057] Processor 242 can control the start control signal V START-UP So that the controllable switching circuit 258 of the integrator circuit 250 can operate during the pre-charging period T. PRE-CHARGE Conductive during the period. Under load voltage V LOAD The size reaches or exceeds the pre-charge voltage threshold V TH-PC Then, the processor 242 can control the start control signal V START-UP This prevents the controllable switching circuit 258 of the integrator circuit 250 from conducting. This allows the integrator circuit 250 and the latch circuit 260 to respond to the current feedback signal V. I-FB Closed-loop control is used to control the LED driver circuit 230 to drive it toward the target current I. TRGT Adjusting the load current I LOAD Size.

[0058] Figure 6 This is a simplified flowchart of an example control process 600 for controlling a load control device (e.g., LED driver 200) to control the magnitude of the load current conducted through a lighting load (e.g., LED light source 202). The control process 600 may, for example, be periodically controlled by the control circuitry of the load control device (e.g., control circuitry 240 of LED driver 200) in step 610 and / or in response to a target current I for the lighting load. TRGT The execution depends on the change. If at 612 (for example, when the target intensity L...), TRGT At low end strength L LE (When nearby) target current I TRGT Less than the transition current I TRAN Then the control circuit can transmit the target current control signal V at 614. I-TRGT The magnitude remains constant (e.g., remains at the minimum voltage V). MIN And it can respond to the target current I at 616. TRGT (For example, such as) Figure 3A (As shown) to adjust the frequency control signal V FREQThe frequency. The control circuit can then control the filter by the filter control signal V at 618. FILTER The control is periodic (e.g., with a frequency control signal V). FREQ (same frequency) and with frequency control signal V FREQ Synchronization (e.g., as Figure 4A (As shown) to control the filter circuit (e.g., filter circuit 280). Then, the control process 600 can exit.

[0059] If at 612 (for example, when the target intensity L) TRGT In high-strength L HE (When nearby) target current I TRGT Greater than the transition current I TRAN (For example, greater than or equal to the transition current I) TRAN Then the control circuit can set the frequency control signal V at 620. FREQ The frequency remains constant (e.g., maintained at the maximum operating frequency f). MAX And it can respond to the target current I at 622. TRGT To adjust the target current control signal V I-TRGT Size (e.g., such as) Figure 3B (As shown). Then, the control circuit can, at 624, before exiting the control process 600, set the filter control signal V... FILTER The control is essentially constant. For example, the control circuit could use a maximum duty cycle such as 100% at 624 (e.g., as...). Figure 4B As shown, by controlling the filter signal V FILTER The control signal V is driven by either a continuous high level or a very high duty cycle (e.g., equal to or greater than 90%). FILTER .

Claims

1. A load control device, comprising: A load regulating circuit is configured to control the magnitude of the load current conducted through the lighting load to regulate the intensity of the lighting load between a low-end intensity and a high-end intensity, the load regulating circuit being characterized by an operating frequency. A filter circuit is configured to receive a current feedback signal from the load regulation circuit and filter the current feedback signal to generate a filtered feedback signal. as well as A control circuit, operatively coupled to the load regulation circuit, is used to control the magnitude of the load current toward the target current in response to the filtered feedback signal; The control circuit is configured as follows: Receive the target intensity for the lighting load; The target current is determined based on the received target intensity; When the target current is less than the set transition current value, the operating frequency of the load regulation circuit is adjusted in response to the target current, and the filter circuit is controlled to filter the current feedback signal during the periodically repeated filter window. When the target current is greater than or equal to the set transition current value, the operating frequency of the load regulation circuit is kept constant, and the filter circuit is controlled to continuously filter the current feedback signal. The load regulating circuit includes a semiconductor switch, and the control circuit is configured to turn on the semiconductor switch for a certain on-time during each operating cycle of the load regulating circuit. Wherein, when the magnitude of the target current is greater than the transition current, the control circuit is further configured to adjust the on-time of the semiconductor switch of the load regulating circuit in response to the target current.

2. The load control device according to claim 1, wherein when the magnitude of the target current is greater than the transition current, the control circuit is configured to adjust the magnitude of the target current control signal to adjust the on-time of the semiconductor switch of the load regulation circuit.

3. The load control device according to claim 2, wherein when the magnitude of the target current is less than the transition current, the control circuit is configured to maintain the magnitude of the target current control signal constant, and to adjust the operating frequency of the load regulation circuit in response to the target current.

4. The load control device according to claim 1, wherein the control circuit comprises: The digital control circuit is configured to generate the target current control signal; and An analog control loop circuit is configured to control the semiconductor switch of the load regulation circuit in response to the target current control signal to control the magnitude of the load current.

5. The load control device of claim 4, wherein when the magnitude of the target current is less than the transition current, the control circuit is configured to maintain the magnitude of the target current control signal constant, and to adjust the operating frequency of the load regulation circuit in response to the target current.

6. The load control device according to claim 1, wherein the control circuit is configured to: control the filter circuit with a periodic signal when the magnitude of the target current is less than the transition current, and control the filter circuit with a constant signal when the magnitude of the target current is greater than the transition current.

7. The load control device of claim 6, wherein the control circuit is configured to generate a frequency control signal for controlling the operating frequency of the load regulating circuit.

8. The load control device according to claim 7, wherein the periodic signal for controlling the filter circuit has a constant on-time.

9. The load control device according to claim 8, wherein the periodic signal for controlling the filter circuit is synchronized with the frequency control signal.

10. The load control device according to claim 9, wherein the on-time of the periodic signal used to control the filter circuit is equal to the minimum period of the frequency control signal.

11. The load control device according to claim 6, wherein the filter circuit includes a rectangular window filter circuit.

12. A lighting system, comprising: A load regulation circuit is configured to control the magnitude of the load current conducted through the lighting load to regulate the intensity of the lighting load; A filter circuit is configured to receive a current feedback signal from the load regulation circuit and filter the current feedback signal to generate a filtered feedback signal. as well as A control circuit, operatively coupled to the load regulation circuit, is used to control the magnitude of the load current toward a target current in response to the filtered feedback signal. The control circuit is configured as follows: When the target current of the lighting load is less than the transition current, the operating frequency of the load regulation circuit is adjusted in response to the target current, and the filter circuit is controlled to filter the current feedback signal during the periodically repeated filter window. as well as When the target current of the lighting load is greater than the transition current, the operating frequency of the load regulation circuit is kept constant, and the filter circuit is controlled to continuously filter the current feedback signal.

13. The lighting system of claim 12, wherein the control circuit is configured to: When the target current is greater than the transition current, the operating frequency of the load regulation circuit is maintained constant, and the on-time of the semiconductor switches arranged in the load regulation circuit is adjusted in response to the target current; and When the target current is less than the transition current, the operating frequency of the load regulation circuit is adjusted in response to the target current.

14. The lighting system of claim 12, wherein the control circuit is configured to: When the target current is less than the transition current, the filter circuit is controlled by a periodic signal; and When the target current is greater than the transition current, the filter circuit is controlled by a constant signal.

15. A lighting system comprising: A load regulation circuit is configured to control the magnitude of the load current conducted through the lighting load to adjust the intensity of the lighting load between a low-end intensity and a high-end intensity. A filter circuit is configured to receive a current feedback signal from the load regulation circuit and filter the current feedback signal to generate a filtered feedback signal. as well as A control circuit, operatively coupled to the load regulation circuit, is used to control the magnitude of the load current toward a target current in response to the filtered feedback signal. The control circuit is configured as follows: When the target current is less than the transition current, the operating frequency of the load regulation circuit is adjusted in response to the target current, and a filter control signal is generated. This filter control signal controls the filter circuit to filter the current feedback signal during periodically repeating filter windows. When the target current is greater than the transition current, the operating frequency of the load regulation circuit is kept constant and the filter control signal is controlled to have the maximum duty cycle.

16. The lighting system of claim 15, wherein the filter control signal is a periodic signal when the target current is less than the transition current, and a constant signal when the target current is greater than the transition current.

17. The lighting system of claim 16, wherein the control circuit is configured to generate a frequency control signal for controlling the operating frequency of the load regulating circuit, the control circuit being configured to control the periodic signal to have a constant on-time and to be synchronized with the frequency control signal.

18. The lighting system of claim 17, wherein the maximum duty cycle is 100%.

19. The lighting system of claim 17, wherein the maximum duty cycle is greater than 90%.

20. An LED driver for controlling the intensity of a light-emitting diode (LED) light source, the LED driver comprising: An LED driving circuit is configured to control the magnitude of the load current conducted through the LED light source to adjust the intensity of the LED light source between a low-end intensity and a high-end intensity, the LED driving circuit being characterized by an operating frequency. A filter circuit is configured to receive a current feedback signal from the LED driver circuit and filter the current feedback signal to generate a filtered feedback signal. as well as A control circuit, operatively coupled to the LED driver circuit, is used to control the magnitude of the load current toward the target current in response to the filtered feedback signal. The control circuit is configured to adjust the operating frequency of the LED driver circuit in response to the target current when the target current is less than a set transition current value. The control circuit is configured to control the filter circuit to filter the current feedback signal during a periodically repeating filter window when the target current is less than the set transition current value. The control circuit is configured to control the filter circuit to continuously filter the current feedback signal when the target current is greater than or equal to the set transition current value.

21. The LED driver of claim 20, wherein the LED driving circuit includes a semiconductor switch, and the control circuit is configured to turn on the semiconductor switch for a conduction time during each operating cycle of the LED driving circuit.

22. The LED driver of claim 21, wherein when the magnitude of the target current is greater than the transition current, the control circuit is configured to maintain the operating frequency of the LED driving circuit constant, and to adjust the on-time of the semiconductor switch of the LED driving circuit in response to the target current.

23. The LED driver of claim 22, wherein the control circuit is configured to adjust the magnitude of the target current control signal to adjust the on-time of the semiconductor switch of the LED driving circuit when the magnitude of the target current is greater than the transition current.

24. The LED driver of claim 23, wherein when the magnitude of the target current is less than the transition current, the control circuit is configured to maintain the magnitude of the target current control signal constant and to adjust the operating frequency of the LED driving circuit in response to the target current.

25. The LED driver of claim 20, wherein the control circuit is configured to control the filter circuit with a periodic signal when the magnitude of the target current is less than the transition current, and to control the filter circuit with a constant signal when the magnitude of the target current is greater than the transition current.

26. The LED driver of claim 25, wherein the control circuit is configured to generate a frequency control signal for controlling the operating frequency of the LED driving circuit.

27. The LED driver of claim 26, wherein the periodic signal for controlling the filter circuit has a constant on-time.

28. The LED driver of claim 27, wherein the periodic signal for controlling the filter circuit is synchronized with the frequency control signal.

29. The LED driver of claim 28, wherein the on-time of the periodic signal for controlling the filter circuit is equal to the minimum period of the frequency control signal.

30. The LED driver of claim 25, wherein the filter circuit comprises a rectangular window filter circuit.

31. The LED driver according to claim 22, wherein the control circuit comprises: The digital control circuit is configured to generate the target current control signal; and An analog control loop circuit is configured to control the semiconductor switch of the LED driver circuit in response to the target current control signal to control the magnitude of the load current.

32. The LED driver of claim 31, wherein when the magnitude of the target current is less than the transition current, the control circuit is configured to maintain the magnitude of the target current control signal constant and to adjust the operating frequency of the LED driving circuit in response to the target current.

33. An LED driver for controlling the intensity of a light-emitting diode (LED) light source, the LED driver comprising: The LED driving circuit is configured to control the magnitude of the load current conducted through the LED light source to adjust the intensity of the LED light source; A filter circuit is configured to receive a current feedback signal from the LED driver circuit and filter the current feedback signal to generate a filtered feedback signal. as well as A control circuit, operatively coupled to the LED driver circuit, is used to control the magnitude of the load current toward the target current in response to the filtered feedback signal. The control circuit is configured to adjust the operating frequency of the LED driving circuit in response to the target current when the target current of the LED light source is less than the transition current. The control circuit is configured to control the filter circuit to filter the current feedback signal during a periodically repeating filter window when the magnitude of the target current of the LED light source is less than the transition current. The control circuit is configured to control the filter circuit to continuously filter the current feedback signal when the magnitude of the target current of the LED light source is greater than the transition current.

34. The LED driver of claim 33, wherein the control circuit is configured to: During each operating cycle of the LED driving circuit, for the on-time, the semiconductor switch of the LED driving circuit is turned on; When the target current is greater than the transition current, the operating frequency of the LED driving circuit is maintained constant, and the on-time of the semiconductor switch of the LED driving circuit is adjusted in response to the target current; and When the target current is less than the transition current, the operating frequency of the LED driving circuit is adjusted in response to the target current.

35. The LED driver of claim 33, wherein the control circuit is configured to control the filter circuit with a periodic signal when the magnitude of the target current is less than the transition current, and to control the filter circuit with a constant signal when the magnitude of the target current is greater than the transition current.

36. An LED driver for controlling the intensity of a light-emitting diode (LED) light source, the LED driver comprising: An LED driving circuit is configured to control the magnitude of the load current conducted through the LED light source in order to adjust the intensity of the LED light source between low-end and high-end intensities. A filter circuit is configured to receive a current feedback signal from the LED driver circuit and filter the current feedback signal to generate a filtered feedback signal. as well as A control circuit, operatively coupled to the LED driver circuit, is used to control the magnitude of the load current toward the target current in response to the filtered feedback signal. The control circuit is configured to adjust the operating frequency of the LED driver circuit in response to the target current when the target current is less than the transition current. The control circuit is configured to generate a filter control signal for controlling the filter circuit to filter the current feedback signal during a periodically repeating filter window when the magnitude of the target current is less than the transition current. The control circuit is configured to control the filter control signal to have a maximum duty cycle when the magnitude of the target current is greater than the transition current.

37. The LED driver of claim 36, wherein the filter control signal is a periodic signal when the target current is less than the transition current, and the filter control signal is a constant signal when the target current is greater than the transition current.

38. The LED driver of claim 37, wherein the control circuit is configured to generate a frequency control signal for controlling the operating frequency of the LED driving circuit, and the control circuit is configured to control the periodic signal to have a constant on-time and to be synchronized with the frequency control signal.

39. The LED driver of claim 38, wherein the maximum duty cycle is 100%.

40. The LED driver of claim 38, wherein the maximum duty cycle is greater than 90%.

41. A method for controlling the intensity of a lighting load, the method comprising: The intensity of the lighting load is adjusted between low and high intensity by controlling the magnitude of the load current conducted through the load regulation circuit. The current feedback signal received from the load regulation circuit is filtered to generate a filtered feedback signal; In response to the filtered feedback signal, the magnitude of the load current is adjusted toward the target current; as well as When the target current is less than the set transition current value, the operating frequency of the load regulation circuit is adjusted in response to the target current. The filtering of the current feedback signal includes: filtering the current feedback signal during a periodically repeated filter window when the target current is less than a set transition current value, and continuously filtering the current feedback signal when the target current is greater than or equal to the set transition current value.

42. The method of claim 41, wherein filtering the current feedback signal comprises: When the target current is less than the transition current, the current feedback signal is filtered during the filter window period, and when the target current is greater than the transition current, the current feedback signal is continuously filtered.

43. The method of claim 42, further comprising: During each operating cycle of the load regulation circuit, for the on-time, the semiconductor switch of the load regulation circuit is turned on.

44. The method of claim 43, further comprising: maintaining the operating frequency of the load regulating circuit constant when the magnitude of the target current is greater than the transition current; and adjusting the on-time of the semiconductor switch of the load regulating circuit in response to the target current.

45. The method of claim 44, further comprising: When the target current is greater than the transition current, the magnitude of the target current control signal is adjusted to adjust the on-time of the semiconductor switch of the load regulation circuit. as well as When the target current is less than the transition current, the magnitude of the target current control signal is kept constant, and the operating frequency of the load regulation circuit is adjusted in response to the target current.

46. ​​The method of claim 44, further comprising: Generate the target current control signal; In response to the target current control signal, the semiconductor switch of the load regulation circuit is controlled by the analog control loop circuit to control the magnitude of the load current; as well as When the target current is less than the transition current, the magnitude of the target current control signal is kept constant, and the operating frequency of the load regulation circuit is adjusted in response to the target current.

47. The method of claim 42, wherein filtering the current feedback signal comprises filtering the current feedback signal using a filter circuit.

48. The method of claim 47, further comprising: When the target current is less than the transition current, the filter circuit is controlled by a periodic signal. as well as When the target current is greater than the transition current, the filter circuit is controlled by a constant signal.

49. The method of claim 48, wherein the periodic signal has a maximum duty cycle when the magnitude of the target current is greater than the transition current.

50. The method of claim 49, wherein the maximum duty cycle is 100%.

51. The method of claim 49, wherein the maximum duty cycle is greater than 90%.

52. The method of claim 48, further comprising: A frequency control signal is generated to control the operating frequency of the load regulation circuit, wherein the periodic signal for controlling the filter circuit has a constant on-time and is synchronized with the frequency control signal.

53. The method of claim 52, wherein the on-time of the periodic signal used to control the filter circuit is equal to the minimum period of the frequency control signal.

54. A method for controlling the intensity of a lighting load, the method comprising: The intensity of the lighting load is adjusted by controlling the magnitude of the load current conducted through the lighting load through the load regulation circuit. The current feedback signal received from the load regulation circuit is filtered to generate a filtered feedback signal; In response to the filtered feedback signal, the magnitude of the load current is adjusted toward the target current; as well as When the target current of the lighting load is less than the transition current, the operating frequency of the load regulation circuit is adjusted in response to the target current. The filtering of the current feedback signal includes: filtering the current feedback signal during a periodically repeated filter window when the magnitude of the target current of the lighting load is less than the transition current, and continuously filtering the current feedback signal when the magnitude of the target current of the lighting load is greater than the transition current.

55. The method of claim 54, further comprising: During each operating cycle of the load regulation circuit, for the on-time, the semiconductor switch of the load regulation circuit is turned on; as well as When the target current is greater than the transition current, the operating frequency of the load regulation circuit is kept constant.

56. The method of claim 55, further comprising: When the magnitude of the target current is greater than the transition current, the on-time of the semiconductor switch of the load regulation circuit is adjusted in response to the target current. as well as When the target current is less than the transition current, the operating frequency of the load regulation circuit is adjusted in response to the target current.

57. The method of claim 55, further comprising: Generate the target current control signal; In response to the target current control signal, the semiconductor switch of the load regulation circuit is controlled by the analog control loop circuit to control the magnitude of the load current; as well as When the target current is less than the transition current, the magnitude of the target current control signal is kept constant, and the operating frequency of the load regulation circuit is adjusted in response to the target current.

58. The method of claim 54, wherein filtering the current feedback signal comprises filtering the current feedback signal using a filter circuit, and the method further comprises: The filter circuit is controlled by a periodic signal when the magnitude of the target current is less than the transition current, and by a constant signal when the magnitude of the target current is greater than the transition current.

59. The method of claim 58, further comprising generating a frequency control signal for controlling the operating frequency of the load regulation circuit, wherein the periodic signal for controlling the filter circuit has a constant on-time and is synchronized with the frequency control signal.

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