LED color and brightness control apparatus and method

Abstract

The present disclosure relates to an LED color and brightness control apparatus and method. An apparatus includes a bandgap voltage reference configured to generate a current reference for controlling a plurality of light emitting diode channels, a plurality of MOSFET devices connected in parallel and coupled between a cathode of a light emitting diode channel and ground, wherein the plurality of MOSFET devices are configured to control a current flowing through the light emitting diode channel, and a control circuit configured to generate a gate drive signal for the plurality of MOSFET devices, wherein the gate drive signal is configured to adjust the current flowing through the light emitting diode channel based on a predetermined color and a predetermined brightness level of the light emitting diode channel.

Description

Technical Field

[0001] Embodiments of the present invention relate to devices and methods for controlling the color and brightness of light-emitting diodes, and more specifically, to RGB-based LED systems. Background Technology

[0002] A light-emitting diode (LED) is a semiconductor light source. When a voltage is applied to an LED, current flows through it. In response to the current flowing through the LED, electrons and holes recombine in the PN junction of the diode. During this recombination process, energy is released in the form of photons. Photons with different wavelengths and / or frequencies produce different colors of light. The primary colors of LEDs are red, green, and blue (RGB). Mixing these colors in different proportions can generate almost all colors of visible light.

[0003] To produce different colors, three RGB colors of varying intensities are combined. The light intensity produced by the LED is proportional to the current flowing through it. Adjusting the current flowing through the LED changes its intensity, thereby altering the intensity of the RGB colors to achieve different colors.

[0004] RGB-based LED systems play a crucial role in lighting technology, which is widely used in areas such as automotive / industrial / architectural lighting, smart home appliances, wearable and handheld devices, and the like. An RGB-based LED system can include multiple RGB modules (e.g., 12 RGB modules). Each RGB module contains three light-emitting diodes: a red LED, a green LED, and a blue LED. In most lighting applications, due to the proximity of the three LEDs within an RGB module, the human eye perceives the light emitted from a single RGB module as a single point light source.

[0005] This module mixes the three RGB colors of an RGB module into a single color and a single brightness level. The color and brightness level of the RGB module can be changed by adjusting the current flowing through the three LEDs. Various colors can be generated by mixing the three RGB colors with different light emission intensities of red, green, and blue. The brightness level of the RGB module comes from the total emission intensity of the three combined LEDs. The brightness level of a channel (LED) is proportional to the average current flowing through the LED channel.

[0006] The process of controlling the average current or emission intensity of an LED is commonly referred to as dimming. Dimming can be divided into two categories: analog dimming and PWM (Pulse Width Modulation) dimming. In conventional RGB control methods, two complex control schemes are used to control the color and brightness levels of an RGB-based LED system. In the first RGB control method, a brightness PWM control scheme is applied to all RGB modules. In other words, the brightness and color of each RGB module are controlled individually. This is a zone control scheme. In the second RGB control method, a single function control bit is used to control the color and brightness level of the corresponding RGB module. This is a bundled control scheme. Zoned or bundled control schemes result in complex and expensive systems. These complex and expensive systems have many drawbacks, such as a lack of design flexibility, poor reliability, and the like. A simple control device and method are desired to effectively control the color and brightness levels of an RGB-based LED system. Summary of the Invention

[0007] These and other problems are generally solved or circumvented and technical advantages are generally achieved by providing preferred embodiments of the present disclosure of light-emitting diode (LED) color and brightness control devices and methods.

[0008] According to an embodiment, an apparatus includes: a bandgap voltage reference configured to generate a current reference for controlling a plurality of light-emitting diode (LED) channels; a plurality of MOSFET devices connected in parallel and coupled between the cathodes of the LED channels and ground, wherein the plurality of MOSFET devices are configured to control the current flowing through the LED channels; and control circuitry configured to generate gate drive signals for the plurality of MOSFET devices, wherein the gate drive signals are configured to adjust the current flowing through the LED channels based on a predetermined color and a predetermined brightness level of the LED channels.

[0009] According to another embodiment, a method for controlling the brightness and color of a group of red, green, and blue light-emitting diode (LED) channels includes: in an illumination module including a red LED channel, a green LED channel, and a blue LED channel, determining three color digital values ​​based on a predetermined color and storing the three color digital values ​​in three corresponding color registers; determining a brightness digital value based on a predetermined brightness level and storing the brightness digital value in a brightness register; and multiplying the three color digital values ​​by the brightness digital value to generate three PWM signals to control the current flowing through the red LED channel, the green LED channel, and the blue LED channel, respectively.

[0010] According to another embodiment, a system includes: a plurality of lighting modules, each including a red light-emitting diode (LED) channel, a green LED channel, and a blue LED channel; and an LED control device including: a bandgap voltage reference configured to generate a current reference for controlling the plurality of lighting modules; a plurality of MOSFET devices connected in parallel and coupled between the cathode and ground of one LED channel, wherein the plurality of MOSFET devices are configured to control the current flowing through the LED channel; and a control circuit configured to generate gate drive signals for the plurality of MOSFET devices, wherein the gate drive signals are configured to adjust the current flowing through the LED channel based on a predetermined color and a predetermined brightness level of the LED channel.

[0011] The foregoing has provided a fairly general overview of the features and technical advantages of this disclosure in order to better understand the following detailed description. Additional features and advantages of this disclosure, which form the subject matter of the claims, will be described below. Those skilled in the art will understand that the disclosed concepts and specific embodiments can be readily used as the basis for modifying or designing other structures or processes for carrying out the same purpose of this disclosure. Those skilled in the art will also recognize that such equivalent constructions should not depart from the spirit and scope of this disclosure as set forth in the appended claims. Attached Figure Description

[0012] To more fully understand this disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:

[0013] Figure 1 A block diagram illustrating a control device for a light-emitting diode system according to various embodiments of the present disclosure;

[0014] Figure 2 Description of various embodiments of the present disclosure for control Figure 1 The image shows multiple PWM generators for LEDs;

[0015] Figure 3 Description of various embodiments according to this disclosure Figure 1 A schematic diagram of the control equipment shown in the image;

[0016] Figure 4 Description of various embodiments according to this disclosure Figure 1 The block diagram of the light-emitting diode system shown in the figure; and

[0017] Figure 5 Description of control according to various embodiments of the present disclosure Figure 1 The flowchart of the LED system shown in the figure.

[0018] Unless otherwise indicated, corresponding numbers and symbols in different figures generally refer to corresponding parts. The figures are drawn to clearly illustrate relevant aspects of various embodiments and are not necessarily drawn to scale. Detailed Implementation

[0019] The following describes in detail the making and use of the presently preferred embodiments. However, it should be understood that this disclosure provides many applicable inventive concepts that can be embodied in various specific contexts. The specific embodiments discussed are merely illustrative of specific ways of making and using this disclosure and do not limit the scope of this disclosure.

[0020] This disclosure will be described with reference to preferred embodiments in a specific context (i.e., RGB-based LED systems). However, this disclosure is also applicable to various LED systems. Various embodiments will be explained in detail below with reference to the accompanying drawings.

[0021] Figure 1 This diagram illustrates a control device for a light-emitting diode (LED) system according to various embodiments of the present disclosure. The LED system includes multiple lighting modules (e.g., lighting modules 101 and 112). Each lighting module includes a red LED channel, a green LED channel, and a blue LED channel. In some embodiments, up to 12 lighting modules may be present in the LED system.

[0022] like Figure 1 As shown, the first lighting module 101 includes three channels. Each channel includes a light-emitting diode (LED). In some embodiments, D0 is a red LED, D1 is a green LED, and D2 is a blue LED. The first lighting module 101 is a first RGB module. The second lighting module 112 includes three channels. Each channel includes an LED. In some embodiments, D33 is a red LED, D34 is a green LED, and D35 is a blue LED. The second lighting module 112 is a second RGB module.

[0023] It should be noted that Figure 1 Only two lighting modules of a light-emitting diode system are described herein, but the system may contain hundreds of such lighting modules. The number of lighting modules described herein is limited to clearly illustrating the inventive aspects of various embodiments. This disclosure is not limited to any particular number of lighting modules.

[0024] Control device 100 is a mixed-signal RGB controller that combines analog dimming and PWM dimming to control an array of RGB modules (e.g., lighting modules 101 and 112). Color generation of the lighting modules is achieved by setting the color control register for each channel of the lighting modules. Brightness generation of the lighting modules is achieved by setting the brightness control register for each lighting module. The output of control device 100 is configured to generate a PWM signal for each channel. In some embodiments, the PWM signal has a 12-bit PWM resolution and operates at an ultrasonic frequency of 30 kHz. High PWM resolution (e.g., 12-bit PWM resolution) helps the RGB controller achieve a smooth dimming effect. Selecting the ultrasonic operating frequency prevents the RGB controller from generating audible noise.

[0025] During operation, the control device 100 is configured to control the flow. Figure 1 The current of the corresponding LEDs is shown in the diagram. By controlling the current flowing through the three channels in the lighting module, the color and brightness of the lighting module can be adjusted accordingly.

[0026] like Figure 1 As shown, the control device 100 includes multiple output terminals from Out0, Out1, and Out2 to Out33, Out34, and Out35. Each output terminal (e.g., Out0) is connected to a corresponding light-emitting diode (e.g., D0) and ground (not shown but...). Figure 3 (as explained in the description). Inside the control device 100, multiple functional units are connected to output terminals (e.g., Out0). These multiple functional units are configured such that the current flowing through the channels (light-emitting diodes) of the lighting module (e.g., lighting module 101) is determined based on the color and brightness settings of this lighting module.

[0027] In some embodiments, the multiple functional units connected to the output terminal include a bandgap voltage reference, multiple MOSFET devices, and control circuitry. The bandgap voltage reference is configured to generate a current reference for controlling multiple channels of the LED system. The multiple MOSFET devices are connected in parallel and... Figure 3 M1 is coupled between the cathode of the LED and ground. Multiple MOSFET devices are configured to control the current flowing through the LED. Control circuitry is configured to generate gate drive signals for the multiple MOSFET devices. The gate drive signals are configured to achieve a predetermined color and a predetermined brightness level. The following will discuss... Figure 3 Detailed diagrams illustrating multiple functional units are provided.

[0028] Figure 1 Further explanation of the connection in I REF Setting resistor R between terminal and ground SET Set resistor R SET Used to set the flow Figure 1The maximum current of the LED shown is [value]. Capacitor C VCC Connected between the VCC terminal and ground. Capacitor C VCC Used to keep the voltage at the VCC terminal constant and stable.

[0029] In operation, the lighting module (e.g., lighting module 101) includes a red LED channel (e.g., D0), a green LED channel (e.g., D1), and a blue LED channel (e.g., D2). Based on a predetermined color, the control device 100 determines three digital values ​​for setting the color of the lighting module. These three digital values ​​are stored in three corresponding color registers. Next, based on a predetermined brightness level, the control device 100 determines a brightness digital value and stores it in a brightness register. Furthermore, the control device 100 multiplies the three color-setting digital values ​​with the brightness digital value to generate three PWM signals. These three PWM signals are used to control the current flowing through the red, green, and blue LED channels, respectively.

[0030] Figure 2 Description of various embodiments of the present disclosure for control Figure 1 The diagram shows multiple PWM generators for the light-emitting diodes. The current flowing through each light-emitting diode is controlled by a PWM signal. In some embodiments, the PWM signal is an exemplary 12-bit resolution PWM signal generated by the PWM generator.

[0031] like Figure 2 As shown, the color mixing unit is configured to generate multiple color control signals according to the color settings of the corresponding light-emitting diodes. In some embodiments, each color control signal is an 8-bit color control signal. This 8-bit color control signal is stored in the corresponding color register.

[0032] like Figure 2 As shown, the 8-bit color control signal R0 is used to determine the current flowing through the red LED in the first lighting module. The 8-bit color control signal G0 is used to determine the current flowing through the green LED in the first lighting module. The 8-bit color control signal B0 is used to determine the current flowing through the blue LED in the first lighting module. By configuring these three color control signals, the color of the first lighting module can be determined accordingly. Similarly, the 8-bit color control signal R11 is used to determine the current flowing through the red LED in the twelfth lighting module. The 8-bit color control signal G11 is used to determine the current flowing through the green LED in the twelfth lighting module. The 8-bit color control signal B11 is used to determine the current flowing through the blue LED in the twelfth lighting module. By configuring these three color control signals, the color of the twelfth lighting unit can be determined accordingly.

[0033] The brightness control unit is configured to generate multiple brightness control signals based on the brightness settings of the corresponding lighting modules. In some embodiments, each brightness control signal is an 8-bit brightness control signal. This 8-bit brightness control signal is stored in the corresponding brightness register.

[0034] like Figure 2 As shown, the color control signal of the lighting module is multiplied by the corresponding brightness control signal to generate a PWM signal for the lighting module. For example, the 8-bit color control signal R0 is multiplied by the 8-bit brightness control signal of the first lighting module. The product of this multiplication is a 16-bit signal. Depending on design requirements, the four least significant bits of this product are omitted. Therefore, a 12-bit PWM signal is generated for the red LED of the first lighting module. Figure 3 In the embodiment shown, MG3 may contain six exemplary MOSFET devices controlled by a 6-bit global analog dimming control signal. The gate of each MOSFET device is configured to... Figure 3 The PWM generator 304 shown in the image receives 12-bit resolution PWM signals.

[0035] Figure 3 Description of various embodiments according to this disclosure Figure 1 The diagram shows the control equipment. (See attached image.) Figure 3 As shown, the anode of LED D1 is connected to the power supply Vs. The cathode of LED D1 is connected to the OUT node. LED D1 can be used as... Figure 1 Any LEDs shown in the diagram. The OUT node is connected to... Figure 1 The corresponding output terminals are shown in the image.

[0036] The control equipment includes a bandgap voltage reference VG, a first amplifier A1, a current mirror formed by MP1 and MP2, and a setting resistor R. SET The system includes an auxiliary transistor M2, a sampling and holding circuit 302 formed by switches S1, S2, S3 and capacitor C0, a control circuit 300, a second amplifier A2, transistor M1 and multiple MOSFET device groups MG1, MG2, MG3 and MG4.

[0037] In operation, the bandgap voltage reference VG is configured to generate a signal for controlling multiple LED channels (e.g., ...). Figure 3 The current reference for D1) is shown in the diagram. In some embodiments, the bandgap voltage reference is equal to 700mV. The bandgap voltage reference is determined by... Figure 3All channels shown share a single bandgap voltage reference. An advantageous feature of all LED channels having a single bandgap voltage reference is that this single reference contributes to improved channel-to-channel accuracy. In some embodiments, channel-to-channel accuracy can be controlled within 2%. It should be noted that this high channel-to-channel accuracy is achieved without using common tuning options such as fuse tuning.

[0038] Multiple MOSFET device groups MG1, MG2, MG3 and MG4 are connected in parallel and via Figure 3 M1 is coupled between the cathode of LED D1 and ground. Multiple MOSFET device groups MG1, MG2, MG3, and MG4 are configured to control the current flowing through LED D1. Control circuit 300 is configured to generate gate drive signals for the multiple MOSFET device groups MG1, MG2, MG3, and MG4. The gate drive signals are configured to adjust the current flowing through LED D1 based on a predetermined color and a predetermined brightness level of LED D1.

[0039] like Figure 3 As shown, the inputs of current mirrors MP1 / MP2 are coupled to the bandgap reference voltage VG via the first operational amplifier A1. Resistor R is set... SET Coupled to a current mirror. For example... Figure 3 As shown, the current mirror includes a first current mirror transistor MP1 and a second current mirror transistor MP2. The gates of MP1 and MP2 are connected together and further connected to the output of a first operational amplifier A1. The inverting input of the first operational amplifier A1 is connected to a bandgap voltage reference VG. The non-inverting input of the first operational amplifier A1 is connected to a setting resistor R. SET And the common node of the first current mirror transistor MP1.

[0040] like Figure 3 The first current mirror transistor MP1 and the setting resistor R are shown in the figure. SET A series connection is made between the bias voltage Vb and ground. The current / voltage converter is coupled to the output of the current mirror. In some embodiments, the current / voltage converter is implemented as an auxiliary transistor M2 operating in the transistor region. In other words, the auxiliary transistor M2 acts as a resistor. Figure 3 As shown, auxiliary transistor M2 and second current mirror transistor MP2 are connected in series between the bias voltage Vb and ground. The gate of auxiliary transistor M2 is connected to the bias voltage Vb. Note that Vb is a logic high voltage. Vb is also connected to the gate of the devices in MG1, MG2, MG3, and MG4.

[0041] like Figure 3As shown, the second operational amplifier A2 is coupled between the output of the current mirror (the drain of MP2) and the gate of transistor M1. The non-inverting input of the second operational amplifier A2 is connected to the common node of the auxiliary transistor M2 and the second current mirror transistor MP2 via the sample-and-hold circuit 302. The inverting input of the second operational amplifier A2 is connected to the source of transistor M1. The output of the second operational amplifier A2 is connected to the gate of transistor M1.

[0042] Multiple MOSFET device groups include a first MOSFET device group MG1, a second MOSFET device group MG2, a third MOSFET device group MG3, and a fourth MOSFET device group MG4 connected in parallel between the source of transistor M1 and ground.

[0043] The sample-and-hold circuit 302 includes a first switch S1, a second switch S2, a third switch S3, and a capacitor C0. The first switch S1 is connected between the common node of the auxiliary transistor M2 and the second current mirror transistor MP2 and the non-inverting input of the second operational amplifier A2. The second switch S2 and the third switch S3 are connected in series between the common node of the auxiliary transistor M2 and the second current mirror transistor MP2 and the inverting input of the second operational amplifier A2. The capacitor C0 is connected between the non-inverting input of the second operational amplifier A2 and the common node of the second switch S2 and the third switch S3. The sample-and-hold circuit 302 and the second operational amplifier A2 form an auto-zero amplifier.

[0044] In some embodiments, when the PWM signal has a 100% duty cycle, an automatic zeroing function can be achieved through a duty cycle compensation method. For example, a 100% duty cycle is desired. The PWM signal may have a 97% duty cycle, with the remaining portion (3%) used to achieve the automatic zeroing function provided by the sample-and-hold circuit 302. To compensate for losses caused by duty cycle mismatch (3% duty cycle), a duty cycle compensation current can be used. This duty cycle compensation current can be implemented as a bleed current. This duty cycle compensation current can cover the losses caused by duty cycle mismatch.

[0045] exist Figure 3In this configuration, MG3 is the primary channel current regulator controlling approximately 97% of the channel current. MG1, MG2, and MG4 are auxiliary channel current regulators controlling approximately 3% of the channel current. MG1 is configured to provide bleed current. MG1 contains 24 exemplary devices (e.g., MOSFET devices) for 24-bit programming. The gate of each device is configured to receive a DC voltage equal to 0V or Vb. MG2 is configured to provide delay compensation current. MG2 contains six exemplary devices (e.g., MOSFET devices) for 6-bit programming. The gate of each device is configured to receive a DC voltage equal to 0V or Vb. MG3 is configured to simultaneously provide 12-bit exemplary PWM dimming and 6-bit exemplary analog dimming. MG3 contains six exemplary devices (e.g., MOSFET devices) for 6-bit analog dimming, and the gate of each device is configured to receive a 12-bit exemplary PWM signal from PWM generator 304. MG4 is configured to provide current accuracy tuning. The MG4 contains four exemplary devices (e.g., MOSFET devices) for 4-bit tuning, and the gate of each device is configured to receive a DC voltage equal to 0V or Vb.

[0046] It should be noted that the gates of the MOSFET devices in MG1, MG2, MG3, and MG4 are bound to Vb when a logic high signal is applied to these gates. Additionally, the drains of the MOSFET devices in MG1, MG2, MG3, and MG4 are maintained at a voltage level equal to Vref2. By setting the gate and drain voltages as described above, the current flowing through M1 can be accurately controlled.

[0047] During operation, during the PWM off phase where the PWM signal applied to the gate of MG3 is in a logic low state, the first switch S1 and the third switch S3 are turned on and the second switch S2 is turned off. Therefore, an offset voltage is stored in capacitor C0. During the PWM on phase where the PWM signal applied to the gate of MG3 is in a logic high state (Vg equals Vb), the first switch S1 and the third switch S3 are turned off and the second switch S2 is turned on. Therefore, the voltage stored in capacitor C0 is added to the non-inverting input of the second operational amplifier A2 to cancel the offset voltage.

[0048] During operation, the maximum current flowing through transistor M1 is determined by the setting resistor R. SET Sure.

[0049] The current flowing through MP1 can be expressed by the following equation:

[0050] I = VG / R SET (1)

[0051] The ratio of the current mirrors MP1 / MP2 is 1:m. In other words, the current flowing through MP2 is m times the current flowing through MP1. M2 is used as a resistor because it is configured to operate in the transistor region. The resistance of M2 is denoted as Ron_M2.

[0052] The current flowing through MP2 can be expressed by the following equation:

[0053] Iref = m × VG / R SET (2)

[0054] The voltage at the common node of MP2 and M2 is denoted as Vref1. Given equation (2), Vref1 can be expressed by the following equation:

[0055]

[0056] According to the operating principle of the second amplifier A2, Vref2 equals Vref1. For example... Figure 3 As shown, four MOSFET devices are connected in parallel between Vref2 and ground. The on-resistance of each MOSFET in the four MOSFET device groups is inversely proportional to the channel width W. Therefore, the maximum current flowing through M1 can be expressed as:

[0057] Imax = Vref2 / Ron_total (4)

[0058] In equation (4), Ron_total is the total resistance of the group of four MOSFET devices connected in parallel. In some embodiments, Ron_total is inversely proportional to the equivalent width W_total. The resistance of M2 (Ron_M2) is inversely proportional to the width of M2 (W_2).

[0059] It should be noted that W_total is the equivalent width, given the widths of the devices in MG1, MG2, MG3, and MG4. Furthermore, the duty cycle of the device in MG3 can be considered when calculating W_total. For example, the width of the device in MG3 is W_MG3. When the duty cycle of the device in MG3 is 50%, the corresponding width of the device in MG3 is equal to 0.5 × W_MG3. Additionally, there is a 6-bit analog dimming register that selects the equivalent width W_total from the six devices in MG3.

[0060] Given equation (3), equation (4) can be expressed as:

[0061]

[0062] In equation (5), m, W_total, and W_2 can be replaced by the general parameter K. The maximum current Imax can be simplified to:

[0063]

[0064] Equation (6) indicates that the maximum current flowing through M1 is determined by R. SET And the 6-bit analog dimming register that controls the equivalent width W_total of MG3 is determined. This is achieved by selecting different R... SET The maximum current flowing through M1 can vary accordingly. In some embodiments, Imax is equal to 70mA.

[0065] As described above, LED emission (current) control can be categorized into a control scheme that combines analog dimming and PWM dimming to control multiple LED channels. Setting Imax via Equation (6) is essentially an analog dimming process, which is achieved by setting the global dimming control signal / register of MOSFET device groups MG1, MG2, MG3, and MG4. In analog dimming, multiple predetermined MOSFET devices (e.g., the MOSFET device in MG3) are enabled, and the remaining devices are disabled. When calculating W_total in Equation (5), only the enabled MOSFET devices contribute to W_total. In PWM dimming, only MG3 is controlled by the PWM dimming signal generated by PWM generator 304. It should be noted that in PWM dimming, only the enabled MOSFET device in MG3 undergoes PWM dimming control. Therefore, the current flowing through M1 is regulated by applying PWM dimming to Imax.

[0066] In operation, if the signal applied to the gate of M1 immediately changes from a low voltage (e.g., 0V) to a high voltage potential (e.g., the supply voltage), then the amount of time that the second amplifier A2 takes to charge the gate of M1 above the turn-on threshold voltage of M1 is limited. This transition introduces a significant error. To avoid this error, a discharge current provided by MG1 is used to keep M1 always on to compensate for it. In some embodiments, this discharge current is adjustable.

[0067] like Figure 3 As shown, the first MOSFET device group MG1 is controlled by a first global dimming control signal with 24 control bits. Under the first global dimming control signal, the first MOSFET device group MG1 is configured to provide a discharge current to compensate for the limited amount of time required to charge the gate of transistor M1 from a low voltage potential (e.g., 0V) to a high voltage potential (e.g., the supply voltage).

[0068] During operation, due to the added discharge current, the gate voltage of M1 needs to change to support the increased current when the PWM signal changes from a low voltage (e.g., 0V) to a high voltage potential (e.g., the supply voltage). The increased current means that the current is the sum of the discharge current and the maximum current set by formula (6). In addition, when the MOSFET device group, for example MG3, is turned on, the voltage on node VMG drops. In order to maintain Vref2 equal to Vref1, the second operational amplifier A2 must increase the voltage on the gate of M1, thereby increasing the current flowing through M1. The increased current flowing through M1 charges VMG to a level equal to Vref1. Due to the various parasitic capacitors coupled to VMG, a delay error may exist. To avoid this delay error, a small current is provided by MG2 to compensate for this delay error. Specifically, the second MOSFET device group MG2 is controlled by a second global dimming control signal with 6 exemplary control bits. Under the second global dimming control signal, the second MOSFET device group MG2 is configured to provide a delay compensation current for compensating for the delay error.

[0069] In operation, the third MOSFET device group MG3 is controlled by a third global dimming control signal with six control bits. Under the third global dimming control signal, the third MOSFET device group MG3 is configured to provide PWM current flowing through transistor M1. More specifically, the MOSFET devices in the third MOSFET device group MG3 are selectively enabled by the third global dimming control signal with six control bits. Under the third global dimming control signal, the enabled MOSFET devices in the third MOSFET device group MG3 are configured to provide PWM current flowing through transistor M1. The PWM current is generated based on the PWM signal generated by PWM generator 304.

[0070] During operation, systematic errors caused by factors such as layout mismatch between different channels can lead to channel-to-channel inaccuracies. This channel-to-channel inaccuracy can be corrected using adjustment options. Under these adjustment options, current can be added or removed from M1 to minimize channel-to-channel inaccuracies. Figure 3 As shown, the fourth MOSFET device group MG4 is controlled by a trimming control signal with six control bits. Under the trimming control signal, the fourth MOSFET device group MG4 is configured to adjust the current flowing through transistor M1 to balance the current flowing through different channels. In some embodiments, the trimming control signal is input via a suitable digital interface (e.g., I2C, Universal Asynchronous Receiver-Transmitter (UART), and the like) to adjust the current flowing through transistor M1.

[0071] have Figure 3One advantage of the control device shown is the ability to reduce the voltage across the drain of M1. In some embodiments, the voltage across the drain of M1 is as low as 350mV. This low voltage helps reduce power dissipation in the control device. This advantage of reduced power dissipation is achieved through the A2 operational amplifier loop, where the VMG voltage is regulated to a precisely low value, such as approximately 200mV.

[0072] It should be noted that Figure 3 This is a simplified representation showing only one of many LED channels. In a light-emitting diode system, the first amplifier A1, the current mirror MP1, and the setting resistor R... SET It is unique and shared by all LED channels. The circuit 350 within the dashed rectangle is used to control the current flowing through one channel. The following will discuss... Figure 4 Describe a detailed implementation scheme for a light-emitting diode system.

[0073] It should be further noted that the method for generating Vref1 is very flexible. In some embodiments, the control device may generate a single Vref1 for all channels. Alternatively, the control device may generate a dedicated Vref1 for each channel (e.g., Figure 4 (The system configuration shown in the diagram). This is a trade-off between design simplicity and matching accuracy. Furthermore, in some embodiments, three reference signals may be used to control all channels. Specifically, the control device is configured to generate a first Vref1 shared by all red LED channels. The control device is configured to generate a second Vref1 shared by all green LED channels. The control device is configured to generate a third Vref1 shared by all blue LED channels.

[0074] Figure 4 Description of various embodiments according to this disclosure Figure 1 The diagram shows a block diagram of a light-emitting diode (LED) system. The LED system contains 36 channels (D0 to D35). Figure 4 Each circuit 350 shown is used to drive one channel. Each circuit 350 has three inputs connected to Vb, Vg, and Vb respectively. Figure 4 As shown, the first amplifier A1, MP1 and R SET Shared by all 36 channels. Vb is the bias voltage. Vg is tapped from the gate of MP1.

[0075] It should be noted that Figure 4 This description focuses on 36 channels of a light-emitting diode system, which may contain hundreds of such channels. The number of channels described herein is limited to clearly illustrating the inventive aspects of various embodiments. This disclosure is not limited to any particular number of channels.

[0076] Figure 5 Description of control according to various embodiments of the present disclosure Figure 1 The flowchart of the LED system shown in the figure. Figure 5 The flowchart shown is merely an example and should not unduly limit the scope of the claims. Many variations, substitutions, and modifications will be appreciated by those skilled in the art. For example, additions, removals, substitutions, rearrangements, and repetitions may be made. Figure 5 The various steps described herein.

[0077] Return to reference Figure 1 and 3 The light-emitting diode system includes multiple lighting modules (e.g., Figure 1 The lighting modules 101 and 112 shown are illustrated. Each lighting module includes a red LED channel, a green LED channel, and a blue LED channel. In some embodiments, up to 12 lighting modules may be present. Each module has three channels. The LED system comprises 36 exemplary channels.

[0078] Devices controlled by light-emitting diodes (e.g.) Figure 1 The control device 100 shown herein controls the color and brightness of the LED system. The LED control device includes a bandgap voltage reference (e.g., ...). Figure 3 The VG shown in the image), and multiple MOSFET devices (e.g. Figure 3 The devices shown in MG1, MG2, MG3 and MG4), and control circuits (e.g. Figure 3 The control device 100 and PWM generator shown in the figure.

[0079] A bandgap voltage reference is configured to generate a current reference for controlling multiple LED channels in the LED system. For each channel, multiple MOSFET devices (e.g., Figure 3 The devices in MG1, MG2, MG3 and MG4 shown in the figure are connected in parallel and through Figure 3 M1 in this channel is coupled between the cathode of the LED and ground. Multiple MOSFET devices are configured to control the current flowing through the LED in this channel. Control circuitry is configured to generate gate drive signals for the multiple MOSFET devices. The gate drive signals are configured to adjust the current flowing through the LED based on a predetermined color and a predetermined brightness level of the channel.

[0080] The following method is used to control the brightness and color of a group of red, green, and blue LED channels in a light-emitting diode system.

[0081] In step 502, in the lighting module including a red LED channel, a green LED channel, and a blue LED channel, three color digital values ​​are determined based on a predetermined color and stored in three corresponding color registers.

[0082] In step 504, a digital value of brightness is determined based on a predetermined brightness level and stored in a brightness register.

[0083] In step 506, the three color digital values ​​are multiplied by the brightness digital value to generate three PWM signals to control the current flowing through the red LED channel, the green LED channel, and the blue LED channel, respectively.

[0084] The method further includes: determining the maximum current flowing through the red LED channel, the green LED channel, and the blue LED channel by selecting the value of a set resistor; adjusting the maximum current flowing through the red LED channel, the green LED channel, and the blue LED channel by selecting a predetermined set of MOSFET devices; and adjusting the current flowing through one of the red LED channel, the green LED channel, and the blue LED channel by using a PWM signal, wherein the PWM signal is configured to modulate the maximum current.

[0085] The method further includes: applying a bandgap voltage to a setting resistor via a first operational amplifier to generate a first reference current; converting the first reference current to a second reference current via a current mirror; converting the second reference current to a first reference voltage by passing the second reference current through an auxiliary transistor operating in the transistor region; generating a second reference voltage equal to the first reference voltage via a second operational amplifier; and applying the second reference voltage to a plurality of MOSFET devices connected in parallel and coupled between the cathode and ground of one of a red light-emitting diode channel, a green light-emitting diode channel, and a blue light-emitting diode channel.

[0086] transistors (e.g.) Figure 3 M1 in the diagram is one of the red LED channel, green LED channel, and blue LED channel (e.g., M1 in the diagram). Figure 3 D1 in the series connection. The current mirror includes a first current mirror transistor (e.g., D1 in the series connection). Figure 3 MP1 in the middle) and the second current mirror transistor (e.g. Figure 3 MP2 in the middle), which has connected together and further connected to the first operational amplifier (e.g. Figure 3 The gate of the output of A1). The first current mirror transistor and the setting resistor (e.g. Figure 3 R in SET ) connected in series with the bias voltage (e.g. Figure 3 The first operational amplifier's inverting input is connected to the bandgap voltage (e.g., Vb) and ground. Figure 3(VG in the first operational amplifier). The non-inverting input of the first operational amplifier is connected to the common node of the setting resistor and the first current mirror transistor. An auxiliary transistor operating in the transistor region (e.g., Figure 3 M2 in the transistor is connected in series with the second current mirror transistor between the bias voltage and ground. The gate of the auxiliary transistor operating in the transistor region is connected to the bias voltage. The second operational amplifier (e.g., Figure 3 The non-inverting input of A2 in the sample and hold circuit (e.g.) passes through the sample and hold circuit. Figure 3 S1, S2, S3, and C0 in the second operational amplifier are connected to the common node of the auxiliary transistor and the second current mirror transistor operating in the transistor region. The inverting input of the second operational amplifier is connected to the source of the transistor. The output of the second operational amplifier is connected to the gate of the transistor. Multiple MOSFET devices originate from a group of first MOSFET devices connected in parallel between the source and ground of the transistor (e.g., ...). Figure 3 MG1 in the middle), the second MOSFET device group (e.g. Figure 3 MG2 in the middle), the third MOSFET device group (e.g. Figure 3 MG3 in the middle) and the fourth MOSFET device group (e.g. Figure 3 (MG4 in the middle).

[0087] The method further includes providing a discharge current to compensate for the limited amount of time required to charge the transistor gate from a low voltage potential to a high voltage potential by applying a first global dimming control signal having 24 control bits to the gate of a MOSFET device in a first MOSFET device group.

[0088] The method further includes providing a delay compensation current to compensate for delays caused by voltage variations on the gates of transistors by applying a second global dimming control signal having six control bits to the gates of MOSFET devices in the second MOSFET device group.

[0089] The method further includes modulating the maximum current to generate a PWM current flowing through the transistor by applying a PWM signal to the gate of a MOSFET device enabled by a third global dimming control signal having 6 control bits.

[0090] The method further includes adjusting the current flowing through the transistor by applying a trim control signal with 6 control bits to the gate of the MOSFET device in the fourth MOSFET device group in order to balance the current flowing through different channels.

[0091] Sample and hold circuit (e.g.) Figure 3 The sampling and holding circuit 302 in the middle includes a first switch (e.g., Figure 3 S1 in the middle), the second switch (e.g. Figure 3 S2 in the middle), the third switch (e.g. Figure 3 S3 in the middle) and capacitors (e.g. Figure 3 (C0 in the example). The first switch is connected to the auxiliary transistor (e.g., C0). Figure 3 M2) and the second current mirror transistor (e.g. Figure 3 The common node of MP2 in the second operational amplifier (e.g.) Figure 3 The second and third switches are connected in series between the non-inverting input of the second operational amplifier (A2). A capacitor is connected between the non-inverting input of the second operational amplifier and the common node of the second and third switches.

[0092] The method further includes: during the PWM off phase, turning on the first switch and the third switch and turning off the second switch to store the offset voltage in the capacitor; and during the PWM on phase, turning off the first switch and the third switch and turning on the second switch to offset the offset voltage.

[0093] Although embodiments of the present disclosure and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations may be made herein without departing from the spirit and scope of the disclosure as defined by the appended claims.

[0094] Furthermore, the scope of this application is not intended to be limited to specific embodiments of the processes, machines, manufactures, compositions of matter, components, methods, and steps described in the specification. Those skilled in the art will readily understand from the disclosure of this release that processes, machines, manufactures, compositions of matter, components, methods, or steps that are currently existing or will be developed thereafter can be utilized to perform substantially the same functions or achieve substantially the same results as the corresponding embodiments described herein. Therefore, the appended claims are intended to encompass such processes, machines, manufactures, compositions of matter, components, methods, or steps within their scope.

Claims

1. An LED color and brightness control device, comprising: A bandgap voltage reference, configured to generate a current reference for controlling multiple LED channels; The transistor connected in series with the light-emitting diode channel; A plurality of MOSFET devices are connected in parallel and coupled between the source of the transistor and ground, wherein the plurality of MOSFET devices include a first MOSFET device group, a second MOSFET device group, a third MOSFET device group and a fourth MOSFET device group, and wherein the plurality of MOSFET devices are configured to control the current flowing through the light-emitting diode channel; and A control circuit configured to generate gate drive signals for the plurality of MOSFET devices, wherein the gate drive signals are configured to adjust the current flowing through the light-emitting diode channel based on a predetermined color and a predetermined brightness level of the light-emitting diode channel, wherein: The first MOSFET device group is controlled by a first global dimming control signal and configured to provide discharge current; The second group of MOSFET devices is controlled by a second global dimming control signal and configured to provide delay compensation current; The MOSFET devices in the third MOSFET device group are selectively enabled by a third global dimming control signal, and the enabled MOSFET devices in the third MOSFET device group are configured to provide PWM current flowing through the transistor based on a PWM signal generated by a PWM generator; and The fourth MOSFET device group is controlled by a trim control signal and configured to adjust the current flowing through the transistor to balance the current flowing through the different light-emitting diode channels.

2. The LED color and brightness control device according to claim 1, further comprising: A current mirror having an input coupled to the bandgap voltage reference via a first operational amplifier; A resistor is provided that is coupled to the current mirror; A current-to-voltage conversion device coupled to the output of the current mirror; and A second operational amplifier is coupled between the output of the current mirror and the gate of the transistor.

3. The LED color and brightness control device according to claim 2, wherein: The maximum current flowing through the transistor is determined by the set resistor.

4. The LED color and brightness control device according to claim 2, wherein: The current mirror includes a first current mirror transistor and a second current mirror transistor, whose gates are connected together and further connected to the output of the first operational amplifier. The first current mirror transistor and the setting resistor are connected in series between the bias voltage and ground; The inverting input of the first operational amplifier is connected to the bandgap voltage reference; The non-inverting input of the first operational amplifier is connected to the common node of the setting resistor and the first current mirror transistor; The current / voltage conversion device includes an auxiliary transistor connected in series with the second current mirror transistor between the bias voltage and ground, wherein the gate of the auxiliary transistor is connected to the bias voltage; The non-inverting input of the second operational amplifier is connected to the common node of the auxiliary transistor and the second current mirror transistor via a sample-and-hold circuit; and The inverting input of the second operational amplifier is connected to the source of the transistor, and the output of the second operational amplifier is connected to the gate of the transistor.

5. The LED color and brightness control device according to claim 4, wherein: The sampling and holding circuit includes a first switch, a second switch, a third switch, and a capacitor, wherein: The first switch is connected between the common node of the auxiliary transistor and the second current mirror transistor and the non-inverting input of the second operational amplifier; The second switch and the third switch are connected in series between the common node of the auxiliary transistor and the second current mirror transistor and the inverting input of the second operational amplifier; and The capacitor is connected between the non-inverting input of the second operational amplifier and the common node of the second switch and the third switch.

6. The LED color and brightness control device according to claim 4, wherein: The first MOSFET device group is controlled by a first global dimming control signal having 24 control bits, wherein, under the first global dimming control signal, the first MOSFET device group is configured to provide the discharge current to compensate for the limited amount of time required to charge the gate of the transistor from a low voltage potential to a high voltage potential.

7. The LED color and brightness control device according to claim 4, wherein: The first MOSFET device group is controlled by a first global dimming control signal having 24 control bits, wherein, under the first global dimming control signal, the first MOSFET device group is configured to provide the discharge current for keeping the transistor in the on state.

8. The LED color and brightness control device according to claim 4, wherein: The first MOSFET device group is controlled by a first global dimming control signal having 24 control bits, wherein, under the first global dimming control signal, the first MOSFET device group is configured to provide the discharge current to compensate for the duty cycle loss caused by the sample and hold circuit.

9. The LED color and brightness control device according to claim 4, wherein: The second MOSFET device group is controlled by a second global dimming control signal having 6 control bits, wherein, under the second global dimming control signal, the second MOSFET device group is configured to provide the delay compensation current to compensate for the delay caused by voltage variations on the gate of the transistor.

10. The LED color and brightness control device according to claim 4, wherein: The MOSFET devices in the third MOSFET device group are selectively enabled by the third global dimming control signal having 6 control bits, and wherein, under the third global dimming control signal, the enabled MOSFET devices in the third MOSFET device group are configured to provide the PWM current flowing through the transistor, and wherein the PWM current is generated based on a PWM signal generated by a PWM generator.

11. The LED color and brightness control device according to claim 4, wherein: The fourth MOSFET device group is controlled by the trim control signal having 6 control bits, wherein, under the trim control signal, the fourth MOSFET device group is configured to adjust the current flowing through the transistor to balance the current flowing through the different light-emitting diode channels.

12. The LED color and brightness control device according to claim 11, wherein: The adjustment control signal is input via a digital interface for adjusting the current flowing through the transistor.

13. A method for controlling the brightness and color of a group of red, green, and blue light-emitting diode channels, comprising: In a lighting module that includes a red LED channel, a green LED channel, and a blue LED channel, three color digital values ​​are determined based on a predetermined color and the three color digital values ​​are stored in three corresponding color registers; A digital value for brightness is determined based on a predetermined brightness level and the digital value for brightness is stored in a brightness register; The three color digital values ​​are multiplied by the brightness digital value to generate three PWM signals to control the current flowing through the red LED channel, the green LED channel, and the blue LED channel, respectively. The maximum current flowing through the red LED channel, the green LED channel, and the blue LED channel is determined by selecting and setting the value of the resistor. The maximum current flowing through the red LED channel, the green LED channel, and the blue LED channel is adjusted by selecting a predetermined set of MOSFET devices configured for analog dimming; and The current flowing through one of the red LED channel, the green LED channel, and the blue LED channel is adjusted by applying the corresponding PWM signal of the three PWM signals to a selected set of predetermined MOSFET devices, wherein the corresponding PWM signal of the three PWM signals is configured to modulate the maximum current.

14. The method of claim 13, further comprising: A first reference current is generated by applying a bandgap voltage to the set resistor via a first operational amplifier. The first reference current is converted into a second reference current using a current mirror; The second reference current is converted into a first reference voltage by passing the second reference current through an auxiliary transistor operating in the transistor region; A second reference voltage equal to the first reference voltage is generated by a second operational amplifier; and The second reference voltage is applied to a plurality of MOSFET devices connected in parallel and coupled between the cathode of one of the red LED channel, the green LED channel and the blue LED channel and ground.

15. The method according to claim 14, wherein: The transistor is connected in series with one of the red light-emitting diode channels, the green light-emitting diode channels, and the blue light-emitting diode channels; The current mirror includes a first current mirror transistor and a second current mirror transistor, whose gates are connected together and further connected to the output of the first operational amplifier. The first current mirror transistor and the setting resistor are connected in series between the bias voltage and ground; The inverting input of the first operational amplifier is connected to the bandgap voltage; The non-inverting input of the first operational amplifier is connected to the common node of the setting resistor and the first current mirror transistor; The auxiliary transistor operating in the transistor region is connected in series with the second current mirror transistor between the bias voltage and ground, and the gate of the auxiliary transistor operating in the transistor region is connected to the bias voltage. The non-inverting input of the second operational amplifier is connected to the common node of the auxiliary transistor operating in the transistor region and the second current mirror transistor via a sample-and-hold circuit; The inverting input of the second operational amplifier is connected to the source of the transistor, and the output of the second operational amplifier is connected to the gate of the transistor; and The plurality of MOSFET devices are from a first group of MOSFET devices, a second group of MOSFET devices, a third group of MOSFET devices, and a fourth group of MOSFET devices connected in parallel between the source of the transistor and ground.

16. The method of claim 15, further comprising: A discharge current is provided to compensate for the limited amount of time required to charge the gate of the transistor from a low voltage potential to a high voltage potential by applying a first global dimming control signal with 24 control bits to the gate of the MOSFET device in the first MOSFET device group.

17. The method of claim 15, further comprising: A delay compensation current is provided to compensate for the delay caused by voltage variations on the gate of the transistor by applying a second global dimming control signal with 6 control bits to the gate of the MOSFET device in the second MOSFET device group.

18. The method of claim 15, further comprising: The maximum current is modulated by applying the PWM signal to the gate of a MOSFET device enabled by a third global dimming control signal with 6 control bits to generate a PWM current flowing through the transistor.

19. The method of claim 15, further comprising: The current flowing through the transistor is adjusted by applying a trim control signal with 6 control bits to the gate of the MOSFET device in the fourth MOSFET device group in order to balance the current flowing through different channels.

20. The method of claim 15, wherein: The sampling and holding circuit includes a first switch, a second switch, a third switch, and a capacitor, wherein: The first switch is connected between the common node of the auxiliary transistor and the second current mirror transistor and the non-inverting input of the second operational amplifier; The second switch and the third switch are connected in series between the common node of the auxiliary transistor and the second current mirror transistor and the inverting input of the second operational amplifier; and The capacitor is connected between the non-inverting input of the second operational amplifier and the common node of the second switch and the third switch.

21. The method of claim 20, further comprising: During the PWM shutdown phase, the first switch and the third switch are turned on and the second switch is turned off to store the offset voltage in the capacitor; and During the PWM on-phase, the first switch and the third switch are turned off and the second switch is turned on to counteract the offset voltage.

22. An LED color and brightness control system, comprising: Multiple lighting modules, each of which includes a red LED channel, a green LED channel, and a blue LED channel; and LED control device, comprising: A bandgap voltage reference, configured to generate a current reference for controlling the plurality of lighting modules; The transistor connected in series with the light-emitting diode channel; A plurality of MOSFET devices are connected in parallel and coupled between the source and ground of the transistor, wherein the plurality of MOSFET devices include a first MOSFET device group, a second MOSFET device group, a third MOSFET device group, and a fourth MOSFET device group, and wherein the plurality of MOSFET devices are configured to control the current flowing through the light-emitting diode channel; and A control circuit configured to generate gate drive signals for the plurality of MOSFET devices, wherein the gate drive signals are configured to adjust the current flowing through the light-emitting diode channel based on a predetermined color and a predetermined brightness level of the light-emitting diode channel, wherein: The first MOSFET device group is controlled by a first global dimming control signal and configured to provide discharge current; The second group of MOSFET devices is controlled by a second global dimming control signal and configured to provide delay compensation current; The MOSFET devices in the third MOSFET device group are selectively enabled by a third global dimming control signal, and the enabled MOSFET devices in the third MOSFET device group are configured to provide PWM current flowing through the transistor based on a PWM signal generated by a PWM generator; and The fourth MOSFET device group is controlled by a trim control signal and configured to adjust the current flowing through the transistor to balance the current flowing through the different light-emitting diode channels.

23. The LED color and brightness control system according to claim 22, wherein the light-emitting diode control device further comprises: A current mirror having an input coupled to the bandgap voltage reference via a first operational amplifier; A resistor is provided that is coupled to the current mirror; A current-to-voltage conversion device coupled to the output of the current mirror; and A second operational amplifier is coupled between the output of the current mirror and the gate of the transistor connected in series with the light-emitting diode channel.

24. The LED color and brightness control system according to claim 23, wherein: The current mirror includes a first current mirror transistor and a second current mirror transistor, whose gates are connected together and further connected to the output of the first operational amplifier. The first current mirror transistor and the setting resistor are connected in series between the bias voltage and ground; The inverting input of the first operational amplifier is connected to the bandgap voltage reference; The non-inverting input of the first operational amplifier is connected to the common node of the setting resistor and the first current mirror transistor; The current / voltage conversion device includes an auxiliary transistor connected in series with the second current mirror transistor between the bias voltage and ground, wherein the gate of the auxiliary transistor is connected to the bias voltage; The non-inverting input of the second operational amplifier is connected to the common node of the auxiliary transistor and the second current mirror transistor via a sample-and-hold circuit; and The inverting input of the second operational amplifier is connected to the source of the transistor, and the output of the second operational amplifier is connected to the gate of the transistor.

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