Patent Description:
Illumination devices that are very low power consuming devices are used in many applications, such as vehicles, household applications, indicators, data communication, and applications involving use of light source. Examples of these devices non-exhaustively include light emitting devices (LEDs) and light amplification by stimulated emission of radiation (LASER) devices. These low power illumination devices are also used as light source in time-of-flight (ToF) imaging applications. ToF cameras work on a principle of illuminating an object by a light source and detecting light reflected from the illuminated object. Further, an image of the illuminated object is constructed based on a phase difference between the light emitted by the illumination device and the light reflected from the illuminated object.

Stringent requirements exist for precise control of emitted power of light from the illumination devices in the ToF cameras, because multiple captures are used for obtaining one frame of data, and each capture has to match the other capture very precisely to minimize depth noise. Even a small change in a signal driving the illumination device (e.g., an LED) results in huge changes, because of the illumination device's I-V characteristics. In a typical ToF camera, each frame of capture may include multiple quadrants of capture operation. Each quadrant has four phases. In a "reset" phase, a sensor inside the ToF camera is reset to clear accumulated signal from the illuminated objects. In an "integration" phase, the sensor and illumination are modulated by a time-of-flight controller (TFC) in the ToF camera, the objects are illuminated, and the sensor acquires a raw ToF signal from the illuminated object. In a "readout phase," the raw ToF signal (a raw pixel data) in a selected region of interest is read out by an analog to digital converter (ADC) and thereafter by the TFC. In a "dead time" phase, the sensor and the ADC are inactive and are in low-power mode. In an implementation, ToF assumes that from quadrant to quadrant, a total emitted power of the light emitted by the ToF camera does not change. A variation in total emitted power results in phase/depth error in processing captured images.

For optimal powering of illumination devices (e.g., LEDs), the ToF camera requires specialized regulators that are capable of providing uniform pulse output and minimizing intensity variations, such as with battery voltage and other operating conditions. Efforts have been made to drive an illumination device in the ToF camera using analog implantations. For example, the illumination device is controlled by a direct current-to-direct current (DC-DC) converter, and the DC-DC converter is controlled by a pulse width modulation (PWM) pulse generated by an analog controller. However, in such implementation of analog control of the DC-DC converter, operating points of a loop (formed by the DC-DC converter and the analog converter) tend to change between the quadrants in the ToF camera. Therefore, a digital loop control (by a digital controller) is increasingly used for controlling the DC-DC converter to maintain that the loop's operating point changes only at a frame boundary and not at quadrant boundary. However, unlike an analog loop, a digital loop has only a few fixed possibilities of duty cycle of the PWM pulse, as the duty cycles are changed in form of step changes. Therefore, it is desirable to have a digital based illumination control circuit that is capable of providing finer control of DC-DC converter and thereby a fine control of a constant current drive of the illumination devices. <CIT> describes a method for dimming control of an electrical load, preferably of a light source, such as an LED or OLED, with a PWM signal with a duty ratio which can be adjusted in discrete steps to achieve a predetermined current or power value for the light source. <CIT> describes an electronic driver circuit for LEDs and LASERs for use in time-of-flight applications featuring a high efficiency of energy conversion and a high precision of distance measurements based on a dual conversion circuit.

The present invention provides a method of controlling an illumination device by an output signal of a DC-DC converter of a pulse width modulation, PWM, illumination control circuit according to claim <NUM> and a pulse width modulation, PWM, illumination control circuit for controlling an illumination device according to claim <NUM>. Embodiments of the method and the apparatus are defined in the dependent claims. In described examples of a method of controlling an illumination device, the illumination device is controlled by an output signal of a DC-DC converter. The method includes receiving a feedback signal corresponding to a variation in the output signal of the DC-DC converter with respect to a predetermined output signal. The method includes controlling the output signal of the DC-DC converter to cause the output signal to be equal to the predetermined output signal for controlling the illumination device. Controlling the output signal includes determining a target duty cycle of a PWM signal based on the feedback signal by a digital controller, where the PWM signal of the target duty cycle is capable of enabling the DC-DC converter to generate the predetermined output. Controlling the output signal further includes providing the PWM signal of an effective duty cycle as equal to the target duty cycle over N switching pulses of the PWM signal to the DC-DC converter. The PWM signal of the effective duty cycle over the N switching pulses is provided by M switching pulses of a first PWM signal of a first duty cycle, and N-M switching pulses of a second PWM signal of a second duty cycle, where M and N are positive integers.

In another example for controlling an illumination device, a pulse width modulation (PWM) illumination control circuit includes a DC-DC converter for providing an output signal to drive the illumination device based on a PWM signal. The circuit includes a digital controller coupled to the DC-DC converter for controlling the output signal of the DC-DC converter to cause the output signal to be equal to a predetermined output signal for controlling the illumination device. The digital controller is configured to control the output signal by receiving a feedback signal corresponding to a variation in the output signal of the DC-DC converter with respect to the predetermined output signal, and determining a target duty cycle of the PWM signal, where the PWM signal of the target duty cycle is capable of generating the predetermined output signal. The digital controller also provides the PWM signal of an effective duty cycle as equal to the target duty cycle over N switching pulses of the PWM signal to the DC-DC converter. Providing the PWM signal includes providing M switching pulses of a first PWM signal of a first duty cycle, and providing N-M switching pulses of a second PWM signal of a second duty cycle, where M and N are positive integers.

In another example of a method of controlling an illumination device, the illumination device is controlled by an output signal of a DC-DC converter, where the output signal of the DC-DC converter is controlled by a pulse width modulation (PWM) signal provided by a digital controller. The method includes receiving a feedback signal corresponding to a variation in the output signal of the DC-DC converter with respect to a predetermined output signal. The method includes controlling the output signal of the DC-DC converter to cause the output signal to be equal to the predetermined output signal for controlling the illumination device. Controlling the output signal includes determining a target duty cycle of a PWM signal based on the feedback signal by the digital controller, where the PWM signal of the target duty cycle is capable of enabling the DC-DC converter to generate the predetermined output. The method further includes providing the PWM signal of an effective duty cycle as equal to the target duty cycle over N switching pulses of the PWM signal to the DC-DC converter. Providing the PWM signal includes providing one or more switching pulses of each of two or more PWM signals, where each PWM signal of the two or more PWM signals has a distinct duty cycle, where N is a positive integer.

The drawings are not necessarily drawn to scale.

<FIG> is a block diagram of a pulse width modulation (PWM) illumination control circuit for driving an illumination device, in an example scenario. Some example embodiments may be employed with modifications and improvements in the PWM illumination control circuit of <FIG>, and the same is described with reference to <FIG>.

As shown in <FIG>, a PWM illumination control circuit (hereinafter referred to as control circuit) <NUM> provides an illumination control signal to an illumination device <NUM>. The illumination device <NUM> can be a light emitting diode (LED) or a light amplification by stimulated emission of radiation (LASER) device, and any other such light source used in a time-of-flight (ToF) imaging application. The illumination device <NUM> can also be used in other applications, such as lighting application, flash in camera, optical communication, or any application that includes generation of light source by the LED or LASER, or any similar light sources.

The control circuit <NUM> includes a DC-DC converter <NUM> and a digital controller <NUM> for controlling the DC-DC converter <NUM>. An output signal of the DC-DC converter <NUM> is a controlled DC voltage (the illumination control signal) to the illumination device <NUM>. The controlled DC voltage acts as a constant drive signal for operating the illumination device <NUM>. Examples of the DC-DC converter <NUM> include, but are not limited to, buck converter, boost converter, buck-boost converter and a flyback converter. The digital controller <NUM> includes a duty cycle adjuster (an increment/decrement unit) <NUM> and a PWM pulse generator <NUM>. The duty cycle adjuster <NUM> receives a feedback signal responsive to a variation of the output of the DC-DC converter <NUM> with respect to a reference output. The reference output may be equal to a predetermined output of the DC-DC converter <NUM> that needs to be provided to the illumination device <NUM>.

The duty cycle adjuster <NUM> determines a duty cycle of a PWM signal that should be provided to the DC-DC converter <NUM> to mitigate the variation of the output of the DC-DC converter <NUM> from the reference output. For example, the duty cycle adjuster <NUM> can include a digital counter for generating a control signal based on the variation of the output of the DC-DC converter <NUM>. The control signal may be generated in response to the count states of the digital counter. For example, the digital counter can count up to a "Ton" time and up to a "Ttotal" time for each individual switching pulse of the PWM signal, and the control signal can be generated based on counts up to the Ton time and counts up to the Ttotal time, and switching pulses of the PWM signal can be generated by the PWM pulse generator <NUM>. The duty cycle adjuster <NUM> is configured to dynamically provide the control signal corresponding to the determined duty cycle, and the PWM pulse generator <NUM> generates switching pulses of the PWM signal of the updated duty cycle. Further, the DC-DC converter <NUM>, operating on the PWM signal received from the PWM pulse generator <NUM>, provides the constant current drive signal to drive the illumination device <NUM>.

In a conventional control circuit, such as the control circuit <NUM>, a high frequency clock signal can be required for a precise control of the duty cycle of the PWM signal, and this drawback can be understood with the following example. In one example, a switching frequency of the DC-DC converter <NUM> is <NUM>, and a clock frequency of a digital clock signal in the digital controller <NUM> is <NUM>. In this example, a PWM pulse may be generated with varying duty cycles of N/<NUM>, where N represents an integral number of clock cycles of the digital clock signal. For example, if the counter inside the duty cycle adjuster <NUM> counts to <NUM> (e.g., N is equal to <NUM>), the PWM pulse generator <NUM> generates the PWM signal of <NUM>% duty cycle. Similarly, if the counter of the duty cycle adjuster <NUM> counts to <NUM> (e.g., N is equal to <NUM>), the PWM pulse generator <NUM> generates the PWM signal of <NUM>% duty cycle. In this example, the step size (or resolution) of the duty cycle can be <NUM>% around a current duty cycle. For example, if the current duty cycle is <NUM>%, the closest duty cycles that can be generated by the PWM pulse generator <NUM> are +/-<NUM>% of PWM duty cycle of <NUM>%, such as either <NUM>% or <NUM>%.

In this example, the resolution (a minimum duty cycle step) of change in the duty cycle of the PWM signal is <NUM>%, due to the digital clock signal frequency (<NUM>) and the switching frequency (<NUM>) of the DC-DC converter <NUM>. In the control circuit <NUM>, a step size finer than <NUM>% or any fractional step size for changing the duty cycle of the PWM signal is difficult to achieve. Fundamentally, such step sizes of the change in duty cycle can be achieved by making changes in the switching frequency of the DC-DC converter <NUM> or in the clock frequency of the digital clock signal. For example, a step size of <NUM>% can be achieved by applying the digital clock signal of <NUM> while keeping the switching frequency as <NUM>. However, using the high frequency clock (e.g., <NUM>) can be an impractical solution in digital controllers. For example, phase locked loops (PLLs) in such systems can be incapable of running at such high frequencies. Alternatively, the switching frequency can be reduced to <NUM> while maintaining the digital clock signal of <NUM>. However, as the switching frequency is reduced, sizes of storage elements in a filter network would typically go up.

Various embodiments provide solutions that are capable of providing PWM signals of finer duty cycles to the DC-DC converters to thereby offer constant current drive for the illumination devices, and these solutions overcome the above described and other limitations, in addition to providing currently unavailable benefits. Various embodiments are herein disclosed in conjunction with <FIG>.

<FIG> is a block diagram of an illumination control circuit for driving an illumination device, in an example embodiment. A PWM illumination control circuit (hereinafter referred to as control circuit) <NUM> provides an illumination control signal to an illumination device <NUM>. The illumination device <NUM> may be a LED or a LASER, and any other such light source used in a time-of-flight (ToF) imaging application. The illumination device <NUM> can be LED or LASER, which can also be used in other applications, such as lighting application, flash in camera, optical communication, or any application that includes generation of light by LED or LASER, or any similar light-sources.

The control circuit <NUM> includes a DC-DC converter <NUM> and a digital controller <NUM> for controlling an output signal of the DC-DC converter <NUM>. The DC-DC converter <NUM> provides the output signal, such as a controlled DC voltage (the illumination control signal) to the illumination device <NUM>. The output signal (controlled DC voltage) acts as a constant drive signal for operating the illumination device <NUM>. The DC-DC converter <NUM> can take form of a converter including, but not limited to, buck converter, boost converter, buck-boost converter and a flyback converter.

The digital controller <NUM> includes a duty cycle adjuster <NUM>, a dithering module <NUM> and a PWM pulse generator <NUM>. The duty cycle adjuster <NUM> is configured to receive a feedback signal corresponding to a variation in an output signal <NUM> received from an output <NUM> of the DC-DC converter <NUM> with respect to a predetermined output signal. In an example embodiment, the duty cycle adjuster <NUM> includes a comparator that compares the output signal <NUM> to the predetermined output signal, and determines the variation, such as error in the output signal <NUM>. In this example embodiment, the predetermined output signal can be a constant output signal that is to be provided to the illumination device <NUM> for controlling the illumination device <NUM>. In another example embodiment, the comparator can be configured to compare a signal generated in accordance with the output signal <NUM> to the predetermined output signal. In this example embodiment, the signal can be a compensated signal generated in responsive to the output signal <NUM>, and the predetermined output signal can be a signal in accordance to the constant output signal that is to be provided to the illumination device <NUM> for controlling the illumination device <NUM>.

The duty cycle adjuster <NUM> is configured to determine a target duty cycle of a PWM signal <NUM> that is capable of generating the predetermined output signal at the output <NUM> of the DC-DC converter <NUM> to effectively control the illumination device <NUM>. The duty cycle adjuster <NUM> is configured to determine the target duty cycle based on the feedback signal. In some cases, the target duty cycle can be a value of duty cycle that lies between two predetermined duty cycles. For example, the target duty cycle of the PWM signal <NUM> may be D+Δd, where Δd may be a decimal number. For example, if the predetermined duty cycles generated by the PWM pulse generator <NUM> are integer percentage numbers (e.g., <NUM>%, <NUM>%, <NUM>%. <NUM>%) in some scenarios, the target duty cycle can be <NUM>% lying between two predetermined duty cycles <NUM>% and <NUM>%. Herein, the term "predetermined duty cycles" represents those duty cycles of the PWM signal <NUM> that can be fundamentally generated by the digital controller <NUM> due to step duty cycle changes, and the values of the predetermined duty cycles depend upon the switching frequency of the DC-DC converter <NUM> and the clock frequency used in the digital controller <NUM>.

The dithering module <NUM> is configured to determine a combination of two or more types of PWM signals, where each type of PWM signal has a distinct duty cycle. The dithering module <NUM> is further configured to provide a PWM control signal <NUM> to the PWM pulse generator <NUM>. The PWM control signal <NUM> is generated, such that the PWM pulse generator <NUM> generates a combination of the two or more types of PWM signals based on the PWM control signal <NUM>. In an example embodiment, the dithering module <NUM> provides the PWM control signal <NUM> to the PWM pulse generator <NUM>, where the PWM control signal <NUM> is generated based on the determined combination of the two or more types of PWM signals. Accordingly, the PWM pulse generator <NUM> generates the PWM signal <NUM> based on the PWM control signal <NUM>, and the PWM signal <NUM> is provided to the DC-DC converter <NUM> to generate the predetermined output signal for driving the illumination device <NUM>.

Based on the PWM control signal <NUM>, the PWM pulse generator <NUM> is configured to generate the PWM signal <NUM>, where the PWM signal <NUM> has an effective duty cycle as equal to the target duty cycle over N switching pulses of the PWM signal <NUM>. In an example, the PWM signal <NUM> of the effective duty cycle is provided by generating M switching pulses of a first PWM signal of a first duty cycle and generating N-M switching pulses of a second PWM signal of a second duty cycle. In this example, the M switching pulses of the first PWM signal and N-M switching pulses of the second PWM signal provide the effective duty cycle of the PWM signal <NUM> over the N switching pulses of the PWM signal <NUM>.

An example representation of generation of the effective duty cycle as equal to the target duty cycle is shown in <FIG>, in which a PWM signal of effective duty cycle of <NUM>% is illustrated. In this example, the switching frequency of the DC-DC converter <NUM> is considered as <NUM>, and a clock frequency of a digital clock signal in the digital controller <NUM> is <NUM>. In a representation <NUM>, switching pulses of a first PWM signal and a second PWM signal over <NUM> switching pulses (T1-T10) of PWM signals are shown. As shown in the representation <NUM>, within time periods T1, T2, T3, T4, T5 and T6, six switching pulses of the first PWM signal of <NUM>% duty cycle are generated. Within the time periods T7, T8, T9 and T10, four switching pulses of the second PWM signal of <NUM>% duty cycle are generated. Within the time periods T1-T6, a count value (for duty cycle) selected by the dithering module <NUM> is <NUM> (e.g., <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>), and accordingly the first PWM signal of <NUM>% duty cycle is generated. Further, within the time periods T7-T10, a count value selected by the dithering module <NUM> is <NUM> (e.g., <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>), and accordingly the second PWM signal of <NUM>% duty cycle is generated. The effective duty cycle of a combination of the first PWM signal and the second PWM signal over a period of <NUM> switching pulses (T1-T10) is <NUM> (the target duty cycle).

The effective duty cycle of <NUM>% can be generated by any pattern of combinations of the first PWM signal and the second PWM signal. For example, in a representation <NUM> shown in <FIG>, six switching pulses of the first PWM signal (e.g., during the time periods T1, T3, T4, T6, T7 and T9) and four switching pulses of the second PWM signal (e.g., during the time periods T2, T5, T8 and T10) generate a PWM of effective duty cycle of <NUM>% over ten switching pulses.

In an example embodiment, the effective duty cycle that can be generated by combination of the two or more types of PWM signals is also dependent upon a value of locations of poles in the DC-DC converter <NUM> and the digital controller <NUM>. For example, typically, a passive network in the DC-DC converter <NUM> has poles at about <NUM>/M times of the switching frequency of the DC-DC converter <NUM>. Some example values of M can lie between <NUM> and <NUM>. In an example, if the value of M is <NUM>, duty cycles can be generated in integral multiple of <NUM> around the predetermined duty cycles (e.g., <NUM>±N*<NUM>, where N is <NUM> to <NUM>), and if the value of M is <NUM>, then the duty cycles can be generated in the integral multiple of <NUM> around the predetermined duty cycles (e.g., <NUM>±N*<NUM>, where N is <NUM> to <NUM>).

<FIG> is a flowchart of an example method <NUM> of controlling an illumination device, in an example embodiment. The method <NUM> can be performed in an illumination device, such as the PWM illumination control circuit <NUM> explained with reference to <FIG>.

At <NUM>, the method <NUM> includes receiving a feedback signal corresponding to a variation in an output signal of a DC-DC converter (e.g., the DC-DC converter <NUM>) with respect to a predetermined output signal. In an example, the feedback signal can be a difference of the output signal of the DC-DC converter and the predetermined output signal, where the predetermined output signal can be a drive input required to control the illumination device (e.g., for providing a constant current drive to the illumination device).

The method <NUM> further includes controlling the output signal of the DC-DC converter to cause the output signal to be equal to the predetermined output signal for controlling the illumination device. Controlling the output signal is performed by operations of the blocks <NUM> and <NUM>. At <NUM>, the method <NUM> includes determining a target duty cycle of a PWM signal based on the feedback signal by a digital controller (e.g., the digital controller <NUM> of <FIG>). The target duty cycle is determined, such that the PWM signal of the target duty cycle is capable of enabling the DC-DC converter to generate the predetermined output signal. For example, the duty cycle adjuster <NUM> (<FIG>) is capable of determining the target duty cycle based on the feedback signal.

At <NUM>, the method <NUM> includes providing the PWM signal of an effective duty cycle as equal to the target duty cycle over N switching pulses of the PWM signal to the DC-DC converter. The operation of the block <NUM> is performed by the blocks <NUM> and <NUM>. Operations at the blocks <NUM> and <NUM> can be performed in any order. At <NUM>, M switching pulses of a first PWM signal of a first duty cycle are generated; and at <NUM>, N-M (N minus M) switching pulses of a second PWM signal of a second duty cycle are generated. M and N are positive integer values. The effective duty cycle over N switching pulses is achieved by a combination of the M switching pulses of the first PWM signal (of the first duty cycle) and the N-M switching pulses of the second PWM signal (of the second duty cycle).

<FIG> is a flow diagram of an example method <NUM> of generating a PWM signal of an effective duty cycle as equal to the target duty cycle over N switching pulses of the PWM signal, according to an example embodiment. An example of switching frequency for the DC-DC converter (switching frequency of the PWM signal) as <NUM>, and a clock frequency in a digital controller controlling the DC-DC converter as <NUM> is assumed to explain the generation of the PWM signal of <NUM> % duty cycle. For example, the duty cycle adjuster <NUM> (<FIG>) determines the target duty cycle as <NUM>% based on the feedback signal, and it is determined that six switching pulses of a first PWM signal and four switching pulses of a second PWM signal should be generated to generate an effective duty cycle of <NUM>% over ten switching pulses.

At <NUM>, the method <NUM> includes setting a PWM output as high and setting a count value as equal to zero (<NUM>). For example, starting at the count zero (<NUM>), a first PWM signal is set as high. In an example embodiment, the control signal (the PWM control signal <NUM> explained in <FIG>) is generated, such that the output of the PWM pulse generator (<NUM> of <FIG>) is set as high (due to the first PWM signal).

At <NUM>, the count is incremented by <NUM>. As each count is incremented in the digital controller <NUM> (<FIG>) with a frequency of <NUM>, a time duration for incrementing each count is equal to a time period of <NUM> ns. At <NUM>, it is determined whether the count is equal to a duty cycle count (e.g., <NUM>). If the count is not equal to the duty cycle count, the method <NUM> proceeds to <NUM>, otherwise the method <NUM> proceeds to <NUM>.

At <NUM>, it is determined whether the count is equal to a "total count" (e.g., equal to <NUM>). If the count is not equal to the "total count," the method <NUM> proceeds to the block <NUM>, and the count is incremented. At <NUM>, it is again determined whether the count is equal to the "duty cycle count. " If the count is equal to the "duty cycle count," at <NUM>, the PWM output is switched to zero, and it is maintained as zero until the count becomes equal to "total count. " If the count becomes equal to the "total count," generation of a first switching pulse of the first PWM signal is completed.

At <NUM>, it is determined if the duty cycle is to be dithered. For example, a decision is made as to which PWM signal among the two or more PWM signals should be generated by the dithering module <NUM> (<FIG>) for a subsequent switching pulse. In an example embodiment, whether the duty cycle should be dithered is dependent upon combination of the two or more PWM signals. For example, it is determined that six switching pulses of the first PWM signal of duty cycle count <NUM>, and four switching pulses of the second PWM signal of duty cycle count <NUM> need to be generated. Accordingly, in an example, after the six switching pulses of the first PWM signal of <NUM>% duty cycle (where the "duty cycle count" is <NUM>) are generated, a decision is made at the block <NUM> to dither the duty cycle for subsequent switching pulses of the ten switching pulses. Accordingly, at <NUM>, the "duty cycle count" is updated from <NUM> to <NUM>, and the <NUM>th switching pulse to <NUM>th switching pulse of the PWM signal (the second PWM signal) are generated with the duty cycle of <NUM>%. As discussed in reference to <FIG>, the effective duty cycle over the ten switching pulses (<NUM>st to <NUM>th of the first PWM signal and <NUM>th to <NUM>th of the second PWM signal) is <NUM>%, and this process is repeated until a change is determined in the target duty cycle by the duty cycle adjuster <NUM> (<FIG>).

One or more of the example embodiments generate finer duty cycles of PWM signal for controlling the output of the DC-DC converter, where the DC-DC converter is used for a constant current drive for an illumination device. Various example embodiments offer generation of those values of duty cycles that lie between predetermined duty cycles (e.g., duty cycles that are generated due to step duty cycle change) of the PWM signal. Various example embodiments are capable of generating finer duty cycles of the PWM signal without using additional components or without using any higher frequency phase locked loop (PLL) in a digital controller of the DC-DC converter.

For example, the various circuits etc. described herein can be enabled and operated using hardware circuitry (e.g., complementary metal oxide semiconductor (CMOS) based logic circuitry), firmware, software and/or any combination of hardware, firmware, and/or software (e.g., embodied in a machine-readable medium). For example, the various electrical structures and methods can be embodied using transistors, logic gates, and electrical circuits (e.g., application specific integrated circuit (ASIC) circuitry and/or in digital signal processor ("DSP") circuitry).

Particularly, the duty cycle adjuster <NUM>, the dithering module <NUM>, and the PWM pulse generator <NUM> may be enabled using software and/or using transistors, logic gates and electrical circuits (e.g., integrated circuit circuitry, such as ASIC circuitry). Embodiments of this disclosure include one or more computer programs stored or otherwise embodied on a computer-readable medium, wherein the computer programs are configured to cause a processor to perform one or more operations, for methods <NUM> and <NUM>. A computer-readable medium storing, embodying or encoded with a computer program or similar language may be embodied as a tangible data storage device storing one or more software programs that are configured to cause a processor to perform one or more operations. Such operations may be any of the steps or operations described herein. Also, a tangible data storage device may be embodied as one or more volatile memory devices, one or more non-volatile memory devices, and/or a combination of one or more volatile memory devices and non-volatile memory devices.

Also, techniques, devices, subsystems and methods described and illustrated in the various embodiments as discrete or separate can be combined or integrated with other systems, modules, techniques or methods. Other items shown or discussed as directly coupled or communicating with each other can be coupled through some interface or device, such that the items can no longer be considered directly coupled to each other but can still be indirectly coupled and in communication, whether electrically, mechanically or otherwise, with one another.

Various embodiments of this disclosure, as discussed above, are practiced with steps and/or operations in a different order, and/or with hardware elements in different configurations.

Claim 1:
A method (<NUM>) of controlling an illumination device (<NUM>) by an output signal of a DC-DC converter (<NUM>, <NUM>) of a pulse width modulation, PWM, illumination control circuit (<NUM>), the method (<NUM>) comprising:
receiving (<NUM>) a feedback signal based on the output signal of the DC-DC converter (<NUM>, <NUM>); and
controlling the output signal of the DC-DC converter (<NUM>, <NUM>) by:
determining (<NUM>) a target duty cycle of a target pulse width modulation, PWM, signal over N switching pulses based on comparing the feedback signal with a reference output signal of the DC-DC converter (<NUM>, <NUM>),
selecting, by a dithering module (<NUM>) of the PWM illumination control circuit (<NUM>) and based on the determined target duty cycle of the target PWM signal, a first count value associated with a first duty cycle and a second count value associated with a second duty cycle,
generating, a first PWM signal with the first duty cycle based on the first count value and generating a second PWM signal with the second duty cycle based on the second count value,
determining a combination of M switching pulses of the first PWM signal of the first duty cycle and N-M switching pulses of the second PWM signal of the second duty cycle such that the combination results in the target PWM signal over N switching pulses of the PWM signal, wherein M and N are positive integers, and
generating the target PWM signal based on the combination of the M switching pulses of the first PWM signal and the N-M switching pulses of the second PWM signal.