Patent Description:
A driver is often used to provide power to the light sources of a lighting device. For example, a light emitting diode (LED) driver may provide power to one or more LED light sources of one or more lighting fixtures. In general, an LED driver may receive AC (alternating-current) power (e.g., mains electricity) and generate DC (direct-current) power that is provided to one or more light sources. Some AC to DC drivers suffer from poor power factor and high current harmonic distortion at the high end of a universal input voltage, such as between 120V and 277V or above. It is generally required by regulatory agencies for input current total harmonic distortion (THD) by users not to exceed <NUM>%. Typical lighting drivers can meet such a requirement at 120V. However, for drivers that support universal input voltage ranges, when a driver has a maximum universal input voltage of, for example, 305V, it is common for THD to rise above <NUM>% with a corresponding drop in power factor to below <NUM>. A power factor of <NUM> is often a minimum power factor requirement imposed by regulatory agencies. Violation of the THD and power factor requirements can have significant consequences. Thus, a solution that reduces THD while providing an improved power factor of lighting drivers and lighting systems may be desirable.

The present disclosure relates generally to lighting solutions, and more particularly to lighting drivers with low total harmonic distortion and high power factor performance. An example of a lighting driver comprising a negative third harmonic generator, an adder circuit and a controller appears in <CIT>.

A lighting driver is herein disclosed which includes a negative third harmonic generator configured to generate a negative third harmonic signal corresponding to a third harmonic of an AC input voltage shifted by <NUM> degrees. The lighting driver further includes an adder circuit configured to generate an adder output signal by adding the negative third harmonic signal to a voltage divider output signal generated from the AC input voltage. The lighting driver also includes a controller configured to control generation of a DC output voltage provided by the lighting driver based on a control signal generated from the adder output signal.

In another example embodiment, a lighting fixture includes a light source and the above lighting driver whose controller is configured to control, based on a control signal generated from the adder output signal, generation of a DC output voltage provided to the light source by the lighting driver.

These and other aspects, objects, features, and embodiments will be apparent from the following description and the appended claims.

The drawings illustrate only example embodiments and are therefore not to be considered limiting in scope. The elements and features shown in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the example embodiments. Additionally, certain dimensions or placements may be exaggerated to help visually convey such principles. In the drawings, the same reference numerals used in different drawings may designate like or corresponding, but not necessarily identical elements.

In the following paragraphs, example embodiments will be described in further detail with reference to the figures. In the description, well known components, methods, and/or processing techniques are omitted or briefly described. Furthermore, reference to various feature(s) of the embodiments is not to suggest that all embodiments must include the referenced feature(s).

Some power supplies or lighting drivers sample the line voltage from a power source and align the peak switching current with the voltage to reduce total harmonic distortion and increase power factor. Such power supplies/drivers can fail to achieve desired (i.e., low) total harmonic distortion and desired (i.e., high) power factor when the line voltage is a universal input voltage, particularly near the upper limit the line voltage. One of the factors that results in increased total harmonic distortion of the line current and reduced power factor is the third harmonic (i.e., <NUM> or <NUM>) of the line voltage related to the operations of power supplies/drivers. In some example embodiments, the impact of the third harmonic on the total harmonic distortion and the power factor of a power supply/driver may be substantially reduced or eliminated by suppressing the third harmonic as described below.

Turning now to the figures, particular embodiments are described. <FIG> illustrates a lighting driver <NUM> with low total harmonic distortion and high power factor according to an example embodiment. In some example embodiments, the lighting driver <NUM> includes an input port <NUM> designed to be connected to an AC power source (i.e., a constant voltage source such as mains power source). The lighting driver receives a constant AC input voltage from the AC power source via the input port <NUM>. For example, the AC power source may provide to the lighting driver <NUM> a universal input voltage in a range of, for example, between 120V and 277V rms or above. The lighting driver <NUM> also receives a current from the AC power source via through the input port <NUM>, where the current may depend on the load powered by the lighting driver <NUM> as well as the components of the lighting driver <NUM>.

In some example embodiments, the lighting driver <NUM> includes a rectifier circuit <NUM> that rectifies the input AC voltage received via the port <NUM>. The rectifier circuit <NUM> may be coupled to common mode choke that is between the input port <NUM> and the rectifier circuit <NUM>. The lighting driver <NUM> also includes an output transformer <NUM>. The rectifier circuit <NUM> is coupled to the output transformer <NUM> and provides a rectified signal to the output transformer <NUM>. An output unit <NUM> that includes the output transformer <NUM> generates a DC output voltage that is provided via the output port <NUM>. For example, the output port <NUM> may be connected to a load (e.g., one or more lighting fixtures and/or light sources).

The lighting driver (<NUM>) includes a voltage divider <NUM>, a negative third harmonic generator <NUM>, an adder circuit <NUM>, and a rectifier <NUM>. The voltage divider <NUM> may be coupled to the negative third harmonic generator <NUM> and to the adder circuit <NUM>. The negative third harmonic generator <NUM> is also coupled to the adder circuit <NUM>. The adder circuit <NUM> may be coupled to the rectifier <NUM>. The lighting driver <NUM> may also include a power management controller <NUM>. For example, the controller <NUM> may be LT3799 from Linear Technology-Analog Devices or another equivalent IC or system of components.

In some example embodiments, the voltage divider <NUM> may be coupled to receive input voltage and divide the input voltage to generate a divider output voltage that has a lower voltage level than the input voltage and that is compatible, for example, with the controller <NUM>. The divider output voltage from the voltage divider <NUM> may be used to generate a negative third harmonic from the divider output voltage, which is equivalent to generating a negative third harmonic from the input voltage. The voltage divider <NUM> may be a resistor based voltage divider as can be readily understood by those of ordinary skill in the art with the benefit of this disclosure.

In some example embodiments, the negative third harmonic generator <NUM> generates a negative third harmonic (i.e., the negative of the third harmonic) of the divider output voltage. The negative third harmonic is added to the divider output voltage by the adder circuit <NUM> to generate an adder output. Adding the negative third harmonic to the divider output voltage using the adder circuit <NUM> results in a substantial removal of the third harmonic of the divider output voltage such that the adder output is substantially devoid of the third harmonic of the divider output voltage. As can be readily understood by those of ordinary skill in the art with the benefit of this disclosure, whether the third harmonic of the divider output voltage is entirely or substantially removed by the summation of the negative third harmonic to the divider output voltage depends on phase alignment as well as exact amplitude levels.

The adder output, which is generally equivalent to the divider output voltage without the third harmonic, is provided to the rectifier <NUM> that generates a control signal. The control signal is provided to the power management controller <NUM> via a control input port CTRL of the power management controller <NUM>. The power management controller <NUM> regulates the output voltage provided by the lighting driver <NUM> at the output port <NUM> by controlling the switching of a transistor <NUM> (e.g., a transistor) that controls the operation of the output transformer <NUM>. That is, the power management controller <NUM> controls the operation of the output transformer <NUM> based on the control signal provided to the control input port CTRL by controlling the switch <NUM> coupled to the output transformer <NUM>.

Because the control signal provided to the control input port CTRL is generated after removing the third harmonic of the divider output voltage, the third harmonic of the input voltage has minimal or no impact on the switching of the switch <NUM>, which controls the operation of the output transformer <NUM>. Because the input current drawn by the lighting driver <NUM> via the input port <NUM> depends on the operation of the output transformer <NUM>, the impact of the third harmonic of the input voltage on the input current is significantly reduced and the power factor of the lighting driver <NUM> is improved compared to lighting drivers that do not suppress the effect of the third harmonic of the input voltage.

In some example embodiments, the lighting driver <NUM> may include components other than shown without departing from the scope of this disclosure. In some alternative embodiments, the components of the lighting driver <NUM> may be coupled in a different configuration than shown without departing from the scope of this disclosure. In some alternative embodiments, the input voltage may be provided to the voltage divider <NUM> at a different node than shown without departing from the scope of this disclosure. In some alternative embodiments, another circuit instead of or in addition to the voltage divider <NUM> may be used in the generation of the control signal provided to the controller <NUM>. In some alternative embodiments, a controller other than the controller <NUM> may be used to control the operation of the output amplifier <NUM> via the switch <NUM>.

<FIG> illustrates the negative third harmonic generator <NUM> of <FIG> according to an example embodiment. Referring to <FIG> and <FIG>, in some example embodiments, the negative third harmonic generator <NUM> includes a comparator circuit <NUM>, a low pass filter <NUM>, and a phase shifter <NUM>. The comparator circuit <NUM> includes comparators <NUM>, <NUM>, <NUM>, <NUM>. The comparator circuit <NUM> also includes diodes <NUM>, <NUM>. The output ports of the comparators <NUM>, <NUM> and the input port of the diode <NUM> are connected at a node <NUM>, and the output ports of the comparators <NUM>, <NUM> and the input port of the diode <NUM> are connected at a node <NUM>.

In some example embodiments, the input voltage (i.e., the divider output voltage from the voltage divider <NUM> in <FIG>) is provided an input to the comparators <NUM>-<NUM>. A first reference voltage Vref1 is provided to the comparator <NUM>, and a second reference voltage Vref2 is provided to the comparator <NUM>. An input port of each of the comparators <NUM>, <NUM> are connected to ground. Thus, the comparator <NUM> generates an output based on the comparison of the input voltage to the reference voltage Vrefl, the comparator <NUM> generates an output based on the comparison of the input voltage to the reference voltage Vref2, and the comparators <NUM>, <NUM> generate a respective output based on the comparison of the input voltage to ground.

<FIG> illustrates the relationship between the input voltage and reference voltages Vref1 and Vref2 used in generating a negative third harmonic signal by the negative third harmonic generator <NUM> of <FIG> according to an example embodiment. Referring to <FIG>, in some example embodiments, the reference voltage Vref2 intersects the input voltage at <NUM> degrees and <NUM> degrees in a cycle of the input voltage level having a period T as shown in <FIG>. Also as shown in <FIG>, the reference voltage Vref1 intersects the input voltage at <NUM> degrees and <NUM> degrees in the cycle of the input voltage level. In general, reference voltage Vref1 is at a voltage level of -<NUM> of the peak voltage level of the input voltage, and the reference voltage Vref2 is at voltage level of <NUM> of the peak voltage level. The output ports of the diodes <NUM>, <NUM> of the comparator circuit of <FIG> are connected at a node <NUM> coupled to the low pass filter <NUM>.

<FIG> illustrates a comparator output voltage generated by the comparator circuit <NUM> of the negative third harmonic generator <NUM> of <FIG> and the divider output voltage corresponding to the input voltage provided to the lighting driver <NUM> of <FIG> according to an example embodiment. <FIG> illustrates a waveform of a filtered output signal generated by the low pass filter <NUM> of the negative third harmonic generator <NUM> of <FIG> according to an example embodiment. Referring to <FIG>, in some example embodiments, the low pass filter <NUM> of <FIG> filters the comparator output voltage from the comparator circuit <NUM> and generates the filtered output voltage shown in <FIG>. In general, the filtered output voltage from the low pass filter <NUM> is a phase shifted version of the negative third harmonic of the divider output voltage provided by the voltage divider <NUM>. As described above, the divider output voltage is generated from the input voltage provided to the lighting driver <NUM> as shown in <FIG>.

In some example embodiments, the filtered output voltage from the low pass filter <NUM> is provided to the phase shifter <NUM>. The phase shifter <NUM> is designed to shift the phase of the filtered output voltage and generate a phase shifted output voltage. In general, the phase shifter <NUM> may introduce a phase shift to the filtered output voltage from the low pass filer <NUM> such that the phase shifted output voltage is <NUM> degrees shifted from the third harmonic of the divider output voltage. That is, the phase shifted output voltage generated/provided by the phase shifter <NUM> is a negative (i.e., <NUM> degrees shifted) of the third harmonic of the divider output voltage from the voltage divider <NUM>. The amount of required phase shift may be determined from measurement or by calculation based on particular elements of the negative third harmonic generator <NUM> as can be readily understood by those of ordinary skill in the art with the benefit of this disclosure. The amplitude of the phase shifted output voltage may also be set based on the amplitude of the divider output voltage as can be readily understood by those of ordinary skill in the art with the benefit of this disclosure.

The phase shifted output voltage is the output voltage of the negative third harmonic generator <NUM> that is provided to the adder <NUM> of the lighting driver <NUM> of <FIG>. <FIG> shows the relationship between the fundamental component of the divider output voltage, which is equivalent to the fundamental component of the input voltage provided to the lighting driver <NUM>, and the negative third harmonic generated by the third harmonic generator of <FIG> according to an example embodiment.

In general, the phase shifter <NUM> of <FIG> may be implemented in a number of ways as can be readily understood by those of ordinary skill in the art with the benefit of this disclosure. For example, the phase shifter <NUM> may include an operational amplifier based circuit. In some example embodiments, the phase shifter <NUM> may include an all-pass filter that introduces a desired phase shift as can be readily understood by those of ordinary skill in the art with the benefit of this disclosure.

In some alternative embodiments, the negative third harmonic generator <NUM> may include other components without departing from the scope of this disclosure. In some alternative embodiments, the components of the negative third harmonic generator <NUM> may be coupled in a different configuration than shown without departing from the scope of this disclosure. In some alternative embodiments, some of the components of the negative third harmonic generator <NUM> may be integrated into a single component. For example, the functions of the low pass filter <NUM> and the phase shifter <NUM> may be integrated a single component. In some alternative embodiments, the function of the comparator circuit <NUM> may be implemented with different components than shown without departing from the scope of this disclosure.

<FIG> illustrates a comparator circuit <NUM> for use in the negative third harmonic generator <NUM> of <FIG> according to another example embodiment. For example, the comparator circuit <NUM> may be used instead of the comparator circuit <NUM> of <FIG>. Referring to <FIG>, in some example embodiments, the comparator circuit <NUM> includes comparators <NUM>-<NUM>, AND logic gates <NUM>, <NUM>, and an OR logic gate <NUM>. The input voltage corresponding to the divider output voltage from the voltage divider <NUM> is provided to the comparators <NUM>-<NUM>. The first reference voltage Vref1 is provided to comparator <NUM>, the second reference voltage Vref2 is provided to comparator <NUM>, and a respective input of the comparators <NUM>, <NUM> are coupled to ground. The reference voltages Vref1 and Vref2 are described above with respect to <FIG>. The outputs of the comparators <NUM>, <NUM> are provided to the AND gate <NUM>, and the outputs of the comparators <NUM>, <NUM> are provided to the AND gate <NUM>. The outputs of the AND gates <NUM>, <NUM> are provided to the OR gate <NUM> that generates the comparator output voltage on the connection <NUM>.

In general, the waveform labelled comparator output in <FIG> represents the comparator output voltage on the connection <NUM>. The connection <NUM> may be coupled to the low pass filter <NUM> of <FIG>, and the low pass filter <NUM> may filter the comparator output voltage to generate the filtered output voltage that is provided to the phase shifter <NUM> as described above.

In some alternative embodiments, the comparator circuit <NUM> may include other components without departing from the scope of this disclosure. In some alternative embodiments, the some of the components of the comparator circuit <NUM> may be integrated into a single component without departing from the scope of this disclosure. In some alternative embodiments, different logic gates than shown may be used to limit the function of the comparator circuit <NUM> without departing from the scope of this disclosure.

<FIG> illustrates a lighting driver <NUM> with low total harmonic distortion and high power factor according to another example embodiment. In some example embodiments, the lighting driver <NUM> includes the same components described above with respect to the lighting driver <NUM> of <FIG>. To illustrate, in some example embodiments, the lighting driver <NUM> includes the input port <NUM>, the rectifier circuit <NUM>, the output transformer <NUM>, and the output port <NUM>. The lighting driver <NUM> may also include a current sense circuit <NUM>, the voltage divider <NUM>, a filter and phase shifter circuit <NUM>, a difference amplifier <NUM>, and the rectifier <NUM>. The lighting driver <NUM> may also include the power management controller <NUM>. The rectifier circuit <NUM> is coupled to the output transformer <NUM> and provides the rectified input voltage to the output transformer <NUM>. The voltage divider <NUM> may be coupled to generate a divider output voltage as described with respect to <FIG>. The voltage divider <NUM> is coupled to and provides the divider output voltage to the difference amplifier <NUM>.

In some example embodiments, the current sense circuit <NUM> is coupled to sense the current from the AC power source and to generate a representative current sense output signal that is provided to the filter and phase shifter circuit <NUM>. The filter and phase shifter circuit <NUM> is coupled to the difference amplifier <NUM> that generates a difference output signal representing the difference between the divider output voltage and the output voltage from the filter and phase shifter circuit <NUM>. The difference amplifier <NUM> is coupled to the rectifier <NUM> that is coupled to the controller <NUM> and that provides a control signal to the control input port CTRL port of the controller <NUM>. The controller <NUM> controls the switch <NUM> and thus the output transformer <NUM> based on the control signal in a similar manner as described above with respect to <FIG>.

In some example embodiments, the filter and phase shifter circuit <NUM> may include a band pass filter that passes a range of frequency components of the current sense output signal from the current sense circuit <NUM> and filters out/rejects other frequency components of the current sense output signal. In general, the band pass filter may reject at least the fundamental harmonic of the current sense output signal and pass at least the third harmonic of the current sense output signal. An example band pass filter <NUM> that may be included in the filter and phase shifter circuit <NUM> is shown in <FIG>.

Referring to <FIG> and <FIG>, in some example embodiments, the values of resistors R1, R2 and capacitors C1, C2 of the band pass filter <NUM> may be selected to pass the third harmonic, the fifth harmonic, and the seventh harmonic of the current sense output signal from the current sense circuit <NUM> and substantially filter out/reject other frequencies. For example, for a <NUM> AC input power provided to the lighting driver <NUM>, the band pass filter <NUM> may substantially reject frequency components below <NUM> and above <NUM>. In some alternative embodiments, the band pass filter <NUM> may pass the third harmonic and the fifth harmonic and reject harmonics that are below the third harmonic and above the fifth harmonic. In some alternative embodiments, instead of a band pass filter, the filter and phase shifter circuit <NUM> may include a high pass filter that passes frequencies corresponding to the third and higher harmonics of the current sense output signal while rejecting frequencies below the frequency corresponding to the third harmonic.

The filter and phase shifter circuit <NUM> includes a phase shifter that shifts the phase of the filtered output voltage from the filter circuit of the filter and phase shifter circuit <NUM>. For example, the phase shifter may be an all-pass filter that shifts the phase of the filtered output voltage from the band pass filter <NUM> to align the harmonics that pass through the filter <NUM> with the corresponding harmonics of the divider output voltage. The amount of phase shifting required may be determined from measurement or by calculation based on particular elements of the filter <NUM> and other relevant elements of the lighting driver <NUM> as can be readily understood by those of ordinary skill in the art with the benefit of this disclosure.

In some example embodiments, the difference amplifier <NUM> generates the difference output signal representing the difference between the divider output voltage and the output voltage from the filter and phase shifter circuit <NUM>. Because the output signal from the filter and phase shifter circuit <NUM> includes at least the phase-shifted third harmonic of the current sense output signal from the current sensor <NUM>, the difference output signal generated by the difference amplifier <NUM> does not include the third harmonic of the divider output voltage provided to the difference amplifier <NUM>. The difference output signal generated by the difference amplifier <NUM> is provided to the rectifier <NUM> that rectifies the difference output signal and generates a control signal to the control input port CTRL port of the controller <NUM>. As described above, the controller <NUM> controls the switching of the switch <NUM> based on the control signal, and the operation of the output transformer <NUM> depends on the switching of the switch <NUM>. Because the third harmonic of the divider output voltage generated by the voltage divider <NUM> is removed before generating the control signal provided to the controller <NUM>, the impact of the third harmonic of the divider output voltage (and thus, impact of the third harmonic of the input voltage provided to the lighting driver <NUM>) on the total harmonic distortion of the input current drawn by the lighting driver <NUM> from the AC power source is significantly reduced.

In some example embodiments, the lighting driver <NUM> may include other components without departing from the scope of this disclosure. In some alternative embodiments, the voltage divider <NUM> and the current sense circuit <NUM> may be coupled at different nodes than shown without departing from the scope of this disclosure. In some alternative embodiments, the components of the lighting driver <NUM> may be coupled in a different configuration than shown without departing from the scope of this disclosure. In some alternative embodiments, another circuit instead of or in addition to the voltage divider <NUM> may be used in the generation of the control signal provided to the controller <NUM>. In some alternative embodiments, a controller other than the controller <NUM> may be used to control the operation of the output amplifier <NUM> via the switch <NUM>.

<FIG> is a graph illustrating a waveform of an input current with high total harmonic distortion. For example, the total harmonic distortion of the input current, such as the input current received via the input port <NUM> of the lighting drivers <NUM>, <NUM>, may be approximately <NUM>%, which is extremely high. In some example embodiments, the significant contributor to the high total harmonic distortion of the input current of the input current is the third harmonic of the input voltage.

<FIG> is a graph illustrating a waveform of an input current with relatively low total harmonic distortion when using the lighting drivers <NUM>, <NUM> of <FIG> and <FIG> according to an example embodiment. By eliminating or reducing the effect of the third harmonic of the input voltage (by eliminating or reducing the third harmonic of the divider voltage output generated from the input voltage) on the operation of the output transformer <NUM>, the unwanted impact of the third harmonic of the input voltage on the total harmonic distortion of the input current is eliminated or significantly reduced. For example, the total harmonic distortion of the input current represented by the waveform shown in <FIG> may be approximately <NUM>%, which is a significant improvement over the <NUM>% total harmonic distortion of the input current shown in <FIG>.

<FIG> illustrates a lighting system <NUM> including a lighting driver <NUM> according to an example embodiment. For example, the lighting driver <NUM> may correspond to the lighting driver <NUM> of <FIG> or the lighting driver <NUM> of <FIG>. An AC power source (e.g., a power source of a power generation or distribution company) may provide AC power to the lighting driver <NUM>.

In some example embodiments, the lighting system <NUM> may include a lighting fixture <NUM>, and the lighting driver <NUM> may provide power to the lighting fixture <NUM>. For example, the lighting driver <NUM> may provide DC power (e.g., DC in a range of 12V - 24V) to the lighting fixture <NUM>. In some example embodiments, the lighting fixture <NUM> may include a light source <NUM> (e.g., a light emitting diode (LED) light source or another type of light source) that provides illumination light and/or other light (e.g., indicator light). The lighting fixture <NUM> may be an indoor or outdoor lighting fixture. In some example embodiments, the lighting fixture <NUM> may also include one or more other components <NUM>, such as a sensor, a camera, etc., that may be powered by the lighting driver <NUM>.

By using the lighting driver <NUM>, which suppresses the third harmonic of the input voltage provided by AC power source, the total harmonic distortion of the input current provided by the AC power source is reduced and the power factor of the lighting driver <NUM> is improved compared to lighting drivers that do not suppress the impact of the third harmonic of the input voltage.

In some alternative embodiments, the lighting system <NUM> may include other components without departing from the scope of this disclosure. For example, the lighting system <NUM> may include other lighting fixtures that are powered by the lighting driver <NUM>. In some alternative embodiments, the lighting fixture <NUM> may include other components than shown without departing from the scope of this disclosure.

<FIG> illustrates a lighting fixture <NUM> including a lighting driver <NUM> according to an example embodiment. For example, the lighting driver <NUM> may correspond to the lighting driver <NUM> of <FIG> or the lighting driver <NUM> of <FIG>. An AC power source (e.g., a power source of a power generation or distribution company) may provide AC power to the lighting fixture <NUM>. The lighting driver <NUM> may generate DC power (e.g., DC in a range of 12V - 24V) from the AC power and provide the DC power to a light source <NUM> of the lighting fixture <NUM>. The light source <NUM> (e.g., a light emitting diode (LED) light source or another type of light source) may provide illumination light and/or other light (e.g., indicator light).

In some example embodiments, the lighting driver <NUM> may also provide DC power generated from the AC power to one or more other components <NUM> (e.g., sensors, camera, etc.) of the lighting fixture <NUM>. The lighting fixture <NUM> may be an indoor or outdoor lighting fixture.

By using the lighting driver <NUM>, which suppresses the third harmonic of the input voltage provided by AC power source, the total harmonic distortion of the input current provided by the AC power source is reduced, and the power factor of the lighting driver <NUM> is improved compared to lighting drivers that do not suppress the impact of the third harmonic of the input voltage.

In some alternative embodiments, the lighting fixture <NUM> may include other components than shown without departing from the scope of this disclosure. In some alternative embodiments, the lighting driver <NUM> may provide power to components that are external to the lighting fixture <NUM> without departing from the scope of this disclosure.

Claim 1:
A lighting driver (<NUM>), comprising:
a negative third harmonic generator (<NUM>) configured to generate a negative third harmonic signal corresponding to a third harmonic of an AC input voltage shifted by <NUM> degrees,
an adder circuit (<NUM>) configured to generate an adder output signal by adding the negative third harmonic signal to a voltage divider output signal generated from the AC input voltage; and
a controller (<NUM>) configured to control generation of a DC output voltage provided by the lighting driver (<NUM>) based on a control signal generated from the adder output signal; characterised in that:
the negative third harmonic generator (<NUM>) comprises a comparator circuit (<NUM>), a low pass filter (<NUM>), and a phase shifter (<NUM>), wherein the low pass filter (<NUM>) is configured to generate a filtered output signal from an output signal of the comparator circuit (<NUM>), and wherein the phase shifter (<NUM>) is configured to shift the generated negative third harmonic signal to compensate for the phase shift of the low pass filter (<NUM>).