Abstract: Systems, devices, and methods are provided to enable power converters to use two or more sensing elements to reliably detect a short circuit (or soft-short circuit) existing in the power converter and distinguish these conditions from other operating conditions, such as low voltage conditions or normal operating conditions. The disclosed embodiments enable the accurate detection of fault conditions, such as short circuits or soft short conditions, using a number of sensing elements, such as sense resistors and the inherent resistance of switching devices, while preventing the detection of false positives due to other factors such as low input voltage.

Abstract: Provided is a lighting system driver including a damper circuit. A power circuit is coupled to the damper circuit and includes a first portion of a winding of a transformer. Also included is an oscillating control circuit including a second portion of the winding of the transformer.

Abstract: A light emission controller includes: a plurality of stages, including: a first node (n1) controller charging a driving pulse of a gate-on voltage level to a set node (Q) by a reference clock pulse during an active period, a second node controller charging a pull-down voltage having the gate-on voltage level to a reset node during an inactive period, and an output unit controlled by voltage states of the Q and the reset node and outputting an active or inactive state output pulse, the n1 controller including: a first switching transistor supplying the driving pulse of the gate-on voltage level to n1 by the reference clock pulse during the active period, a second switching transistor supplying the driving pulse from n1 to the Q by a turn-on voltage, a first capacitor between the output unit and Q, and a second capacitor between the output unit and n1.

Abstract: A backlight unit of a display apparatus includes a power converter generating a light source power voltage in response to a power control signal, a first node, a second node, a light emitting element connected between the first node and the second node, and a controller connected to the second node. The light emitting element is configured to receive the light source power voltage through the first node, and the controller is configured to output the power control signal for controlling current flowing through the light emitting element in response to a dimming signal. When the dimming signal has a first level, the controller outputs the power control signal to turn off the power converter.

Abstract: A coupled inductor includes a ladder magnetic core, a first common leakage plate formed of a magnetic material, and N windings, where N is an integer greater than one. The ladder magnetic core includes first and second rails and N rungs, where each of the N rungs connects the first and second rails. Each of the N windings includes a respective first portion. Each of the N windings is wound around a respective one of the N rungs, and at least two of the N windings are wrapped at least partially around the first common leakage plate such that a first portion of the winding is disposed between an outer surface of the first rail and an outer surface of the first common leakage plate.

Abstract: A LED current-balance driving circuit having a current-balance coil set, a switching unit, and a control circuit is provided. The current-balance coil set has at least a first coil and a second coil, both of which are in connection with respective LED strings, for balancing currents flowing through the LED strings. The switching unit and a leakage inductance of current-balance coil set are utilized to facilitate the voltage conversion for driving the LED strings. A duty cycle of the switching unit is controlled by the control circuit according to the currents flowing through the LED strings.

Abstract: The present invention provides a DC boost topology circuit for backlight driving, which includes a coupling inductor including a primary coil having an end connected to a DC voltage input terminal and an opposite end connected to a secondary coil and a field-effect transistor that has an end grounded. An energy storage module includes a first capacitor and a first diode. The secondary coil has an end connected to the first capacitor and an opposite end connected to an opposite end of the primary coil and the first diode of which an opposite end connected to an opposite end of the first capacitor. A circuit protection unit has an end connected to a common terminal of the first diode and the first capacitor and an opposite end connected to a DC voltage output terminal. The topology circuit has an output voltage that is multiple times of that of known circuits.

Abstract: A ballast includes a rectifier, DC to DC converter, a dimming sensor, and a light source driver circuit. The rectifier provides rectified power from an AC power source modified by a chopper dimmer. The converter includes a boost inductor having a primary winding and a detection winding. The converter receives the rectified power from the rectifier and provides a DC power rail. The dimming sensor monitors a voltage of the detection winding of the boost inductor and provides a dimming signal as a function of the monitored voltage. The light source driver circuit receives the dimming signal, receives the DC power rail, and provides power from the DC power rail to the light source as a function of the dimming signal. An amount of power provided to the light source by the light source driver circuit corresponds to a dimming level indicated by the dimming signal.

Abstract: A power drive system of light-emitting diode (LED) strings includes an isolation transformer, a current-sharing capacitor, two rectifying units, and a current control integrated circuit (IC). The isolation transformer has a primary-side winding and a secondary-side winding with a dotted terminal and a non-dotted terminal. The current-sharing capacitor is connected to the dotted terminal at one terminal thereof. One rectifying units is connected to the other terminal of the current-sharing capacitor, and the other rectifying unit is connected to the non-dotted terminal of the secondary-side winding. Each rectifying unit is connected to one LED string. The current control IC is connected between common points of the rectifying units and corresponding anode terminals of the LED strings and corresponding cathode terminals of the LED strings.

Abstract: A method for operating a HID lamp using a bi-power electromagnetic ballast. The method includes applying a full power level to the lamp to produce full brightness and applying a dimmed power level to the lamp to produce a dimmed brightness. The lamp may be dimmed by switching the lamp power from the full power level to the dimmed power level and then applying a full power pulse to the lamp. The dimmed power level is less than the full power level.

Abstract: The invention relates to a current converter of the forward converter type for converting a three-phase primary voltage into a plurality of secondary voltages, with a magnetic intermediate circuit including at least three transformer secondary windings, wherein the current converter on its primary side includes at least three transformers with respectively two primary windings wound in opposition directions and respectively at least one secondary winding, and that two electronic switches are provided, wherein the first switch respectively controls a primary winding of the three transformers via a set of diodes and wherein the second switch respectively controls another primary winding of the three transformers via a second set of diodes.

Abstract: The present invention provides an illumination device, an illumination system, and a lamp. The illumination system includes the illumination device and a light modulation module. The illumination device includes a light emitting diode (LED) array, an alternating current (AC) current source, and an output power control module. The AC current source is electrically coupled to the LED array. The output power control module is electrically coupled to the LED array and the AC current source. The LED array, the AC current source, and the output power control module together form a closed-loop control loop. The light modulation module is electrically coupled to the closed-loop control loop for modulating illumination brightness of the LED.

Abstract: A drive circuit for realizing accurate constant current of multiple LEDs is disclosed. The drive circuit comprises a high-frequency impulse Alternating Current (AC) power carrying N circuit units with same structure. Each of the circuit unit comprises a rectifier filter circuit, a blocking capacitor C1 and two LED loads. The rectifier filter circuit comprises two independent half-wave rectifier circuits, and two filter capacitors. Each of the two half-wave rectifier circuits comprises two diodes connected in series to supply power for the corresponding LED load. The filter capacitor is connected in parallel with the two ends of an LED load respectively, and the blocking capacitor C1 is connected in series with the input end of the rectifier filter circuit. The circuit also comprises N?1 equalizing transformers, each of which connects in series between two adjacent circuit units.

Abstract: The present invention relates to a multi-output current-balancing circuit, which in one embodiment can include: (i) a transformer having a primary winding and a plurality of secondary windings, where the primary winding receives an AC input current; (ii) a plurality of first and second rectifier circuits and a plurality of first current balancing components, where each of the first and second rectifier circuits and the first current balancing components is coupled to a corresponding secondary winding, where each the first current balancing component is configured for current balancing between each of the first and second rectifier circuits of the corresponding secondary winding; and (iii) at least one second current balancing component, where each second current balancing component is coupled to a pair of the second rectifier circuits that correspond to different secondary windings, where the second current balancing components are configured for current balancing between different the secondary windings.

Abstract: Aspects of the disclosure provide a lighting system. The lighting system includes a transformer having a primary winding on a receiving path and a secondary winding on a delivering path. The receiving path receives electric energy regulated based on a dimming angle. The delivering path delivers the received electric energy. According to an aspect of the disclosure, the lighting system includes a secondary switch, and a dimming controller. The secondary switch is switched on to couple a light source, such as an LED array, and the like, with the delivering path to emit light in response to the delivered electric energy and is switched off to decouple the light source from the delivering path. The dimming controller is configured to detect the dimming angle based on an electrical property of the delivering path. Then, the dimming controller switches on and switches off the secondary switch based on the dimming angle.

Abstract: A serial-type LED device includes p light source units and a dimming circuit. Each light source unit includes first and second terminals, m light strings and m current balance units. Each light string includes LEDs coupled in series to have a first terminal coupled to the first terminal of a corresponding light source unit and a second terminal coupled to the second terminal of the corresponding light source unit through a corresponding current balance unit. The first terminal of the first light source unit is coupled to a second DC voltage, and the second terminal of the i-th light source unit is coupled to the first terminal of the (i+1)-th light source unit, where m and p are integers greater than or equal to 2 and i is any integer from 1 to (p?1). The dimming circuit coupled to the second terminal of the p-th light source unit controls the second DC voltage according to a current outputted from the p-th light source unit.

Abstract: A two level lighting ballast is provided, which includes a self-oscillating inverter circuit and a control circuit. The inverter includes an input; an output to selectively provide current to energize a lamp; a switching circuit operating at a switching frequency; a feedback transformer; and an impedance component. The feedback transformer is connected to the output, and drives the switching circuit based on the lamp current. The impedance component is connected in parallel with the feedback transformer, and is operated by the control circuit. When the control circuit enables the impedance component, the switching circuit operates in a first frequency range, and a first lamp current is provided. When the control circuit disables the impedance component, the switching circuit operates in a second frequency range, and a second lamp current is provided. The first frequency range is lower than the second, and the first lamp current is greater than the second.

Abstract: The present invention relates to a multi-output current-balancing circuit, which in one embodiment can include: (i) a transformer having a primary winding and a plurality of secondary windings, where the primary winding receives an AC input current; (ii) a plurality of first and second rectifier circuits and a plurality of first current balancing components, where each of the first and second rectifier circuits and the first current balancing components is coupled to a corresponding secondary winding, where each the first current balancing component is configured for current balancing between each of the first and second rectifier circuits of the corresponding secondary winding; and (iii) at least one second current balancing component, where each second current balancing component is coupled to a pair of the second rectifier circuits that correspond to different secondary windings, where the second current balancing components are configured for current balancing between different the secondary windings.

Abstract: An LED lighting device includes two or more switching circuits connected between a power source and an LED (light emitting diode) unit, an inrush current limiting circuit which limits an inrush current flowing through the LED lighting device when power is turned on and a trigger circuit which generates a trigger signal of an operation/non-operation of the inrush current limiting circuit from the switching circuits. Further, the inrush current limiting circuit is set in a non-operation state when any one of the switching circuits is started first.

Abstract: A lighting ballast and associated methods balance current through resonant inductors that have inductance variation, and are further effective to balance lamp currents in the range from full brightness to full dimming. The ballast includes a lighting power source, a balancing transformer having a plurality of windings, a first resonant tank circuit having one or more transformer windings and a second resonant tank circuit having a like number of transformer windings. Each of the windings for the first resonant tank are reversed in direction in association with a corresponding winding for the second resonant tank, such that the only current passing through the windings is a current difference between the two windings.

Abstract: An apparatus is disclosed for supplying power to a luminous load. The apparatus includes a transformer having a primary winding, and a control circuit adapted to generate an alternating current through the primary winding to develop an alternating voltage. The alternating current is based on a first signal derived from the input voltage, a second signal derived from the current, and a third signal varying substantially in-phase with the input voltage. The first and second signals are used to regulate the power delivered to the load, and the third signal is used to improve the power factor. A load interface circuit is provided to generate an output voltage for the luminous load based on the alternating voltage from the transformer. An over-temperature sensor may be provided to cause a reduction in power to the load when the ambient temperature exceeds a threshold.

Abstract: A driving circuit system for a gas discharge lamp includes a power circuit having a switch for converting an input voltage into a lamp voltage for driving the gas discharge lamp, a lamp current detecting circuit connected to the power circuit or the gas discharge lamp for detecting a lamp current, a feedback circuit connected to the lamp current detecting circuit for generating a lamp current feedback signal, a constant power control circuit for generating a corrected current reference signal, and a power control circuit connected to the feedback circuit, the constant power control circuit, and the switch of the power circuit for generating a first modulating signal in accordance with the lamp current feedback signal and the corrected current reference signal for driving the switch to turn on or off, thereby substantially maintaining a lamp power of the gas discharge lamp at a constant value.

Abstract: A radiofrequency plasma generating device including: a supply circuit including a switch controlled by a control signal for applying a voltage on an output of the control circuit at a control frequency; at least two plasma-generating circuits connected in parallel at the output of the supply circuits, each circuit having its own resonance frequency and being capable of generating plasma when a high voltage level is applied to the output of the supply circuit at a frequency substantially equal to the resonance frequency of the plasma generation circuit; and a supply control device determining the control frequency from the resonance frequencies of the plasma generation circuits to selectively control each circuit according to the control frequency used.

Abstract: An alternating current chopper circuit with low noise is disclosed. The circuit includes a switching circuit, a first freewheel circuit, and a second freewheel circuit. The switching circuit has a control switching unit, which turns on and or off accordingly to a control signal. The first freewheel circuit and the second freewheel circuit are for providing a current-conducting path to the motor, when the control switching unit is turned off.

Abstract: An arc discharge detecting circuit includes; a voltage dividing part which divides a driving voltage provided to a light source, a detecting part which includes a loop-shaped wiring spaced apart from the voltage dividing part and which detects a current corresponding to an arc discharge flowing through the voltage dividing part using a coupling capacitance generated between the loop-shaped wiring of the detecting part and a wiring of the voltage dividing part, and an output part connected to the detecting part to output a detection voltage corresponding to the arc discharge. Accordingly, the arc discharge detecting circuit may improve a sensitivity of detecting an arc discharge as a current source type using the coupling capacitors, a design may be simplified, and manufacturing costs may be decreased.

Abstract: A load current balancing circuit that operates with a direct current (DC) power supply includes at least one transformer having a first inductive element adapted to couple in series with a first load and a second inductive element adapted to couple in series with a second load. The first load is parallel to the second load. The load balancing circuit further includes at least one switch adapted to operate at one or more switching frequencies associated with at least one driving signal. The switch is configured to periodically interrupt respective current flows through the first inductive element and second inductive element substantially simultaneously.

Abstract: An ignition transformer for a discharge lamp is provided having a transformer core whose material and dimensions are selected in such a manner that the Curie temperature of the material after the ignition which is achieved by means of the ignition transformer can be achieved by a voltage drop across a secondary winding of the ignition transformer.

Abstract: The instant disclosure relates to a LED backlight driving module. The driving module utilizes a plurality of second power isolation transformers interconnected to each other in series and connected to a secondary winding of a first power isolation transformer in parallel to produce a plurality of second driving signals with uniform current, and driving corresponding LED light bars with uniform brightness. Optionally, a base voltage circuit can be used to provide a base voltage with negative voltage level on the other end of LED light bars, so as to lower the positive voltage level of the second driving signals. Thus, it is beneficial that the LED backlight driving module provides higher power conversion efficiency and has lower design cost.

Abstract: The current invention provides a power supply that includes an igniter that generates an ignition voltage for igniting a DC lamp; an auxiliary power stage that outputs an auxiliary voltage for sustaining sufficient current in the DC lamp after the DC lamp is ignited; a voltage conversion stage coupled to the auxiliary power stage and generating a voltage at a level that is higher than the auxiliary voltage; and a switch that couples the auxiliary voltage to the DC lamp and the voltage conversion stage for a predefined period of time.

Abstract: A fluorescent lamp includes three transformers, a power supply, a converter, and four lamp tubes. The converter converts a direct current (DC) provided by the power supply into an alternating current (AC) generated in a first transformer and a second transformer for driving the four lamp tubes to emit light. The third transformer is connected to the four lamp tubes to balance working electric potentials of the four lamp tubes.

Abstract: An output voltage monitoring circuit monitors an output voltage of a capacitor charging circuit. A first sample-and-hold circuit samples and holds a voltage of a connection point of a primary coil of a transformer and a switching transistor. A first monitoring comparator compares output of the first sample-and-hold circuit with a predetermined first reference voltage. When the output of the first sample-and-hold circuit exceeds the first reference voltage, a signal processor executes predetermined signal processing. The first sample-and-hold circuit starts a sampling period after a predetermined first time has elapsed after the switching transistor is turned OFF. When a voltage drop across a detection resistor reaches a third reference voltage, the first sample-and-hold circuit ends the sampling period.

Abstract: An electronic ballast circuit includes a filament drive circuit that can adjust the pulse width of a pulsed heating signal in accordance with the lamp current to a gas-discharge lamp. A logic device, such as an SR flip-flop, is used to control a switch that is coupled to the primary winding of a filament drive transformer coupled to the lamp filaments. The logic device opens and closes the switch device to generate the pulses of the pulsed heating signal and thus controls the pulse width of the pulses. A clock signal triggers logic device to start a pulse while the end of the pulse is determined by a signal level across a resistor in series with the primary winding of filament drive transformer. Once this signal level is at or above a threshold level, logic device switches the switch device to end the pulse.

Abstract: A circuit arrangement is provided, which may include an input; an output; an inverter, configured to provide an AC supply voltage from a DC supply voltage; a control device configured to drive the inverter, the control device being configured to initiate a preheating phase once a preheating criterion has been met; a resonant circuit having a resonant inductor and having a resonant capacitor; and a transformer configured to preheat electrodes of a gas discharge lamp; wherein the primary winding of the transformer is connected in series with the resonant capacitor and is connected directly to the reference potential of the control device, and an electrical switch is coupled in parallel with the primary winding of the transformer, which switch has a control connection, which is coupled to the control device being configured to transfer the electrical switch into its electrically conducting switching state once the starting criterion has been met.

Abstract: In a device for driving LEDs with variable light intensity, a supply stage has a first operating mode, in which a controlled supply current is generated, and a second operating mode, in which a controlled supply voltage is generated. A LED is connected to the supply stage, receives the controlled supply current or voltage, and has a turning-on threshold voltage higher than the controlled supply voltage. A current sensor generates a current-feedback signal that is correlated to the current flowing in the LED and is supplied to the supply stage in the first operating mode. An intensity-control stage generates a mode-control signal that is sent to the supply stage and controls sequential switching between the first and the second operating modes of the supply stage.

Abstract: A circuit arrangement for operating at least one discharge lamp may include: a first and a second input terminal for connecting a supply voltage; an inverter, which includes at least one first switch and one second switch, which are coupled in series between the first and the second input terminal and between which a bridge center point is defined; a drive circuit for at least the first switch and the second switch with an input for receiving a control signal; an apparatus for generating an auxiliary voltage.

Abstract: A lamp ballast capable of lighting a discharge lamp and an incandescent lamp each at an optimum condition. The lamp ballast has a DC-DC converter, an inverter that converts an output of DC-DC converter into an AC power for applying the same to a lamp load, a starting circuit generating a high voltage pulse from the AC power to provide the same to the lamp load, and a controller that controls the DC-DC converter and the inverter to provide a variable DC voltage and the AC power of variable frequency. The controller has a starting mode of operating the inverter at a starting frequency to generate the high voltage, and a lighting mode of operating the inverter at a lighting frequency lower than the starting frequency.

Abstract: A discharge lamp operating system has first and second discharge lamp operating circuits. The first discharge lamp operating circuit includes first and second primary windings, a first secondary winding, a first discharge lamp connected to the first primary winding, and a second discharge lamp connected to the second primary winding. The second discharge lamp operating circuit includes third and fourth primary windings, a second secondary winding, a third discharge lamp connected to the third primary winding, and a fourth discharge lamp connected to the fourth primary winding. The first secondary winding and the second secondary winding are connected in series.

Abstract: A high-voltage discharge lamp lighting device provides a starting pulse voltage sufficient to turn on a high-voltage discharge lamp having terminal wire connections of variable length. A power conversion circuit is coupled to a commercial AC power source input and rectifies the AC input into a predetermined DC voltage output. A charging capacitor is coupled to the power conversion circuit. A full bridge circuit is coupled to the power conversion circuit and the charging capacitor and provides a rectangular wave AC output signal to a transformer primary winding circuit of at least a capacitor, a single switching element and a primary winding of a transformer. A low pulse voltage is induced in the primary winding and a transformer secondary winding is connected on one end to the high-voltage discharge lamp, wherein the low pulse voltage is stepped up to a high pulse voltage and applied to the high-voltage discharge lamp.

Abstract: A gas-discharge lamp igniter is disclosed which has a group of gas-discharge lamps, such as those for LCD backlighting, connected in parallel with one another between the pair of outputs of an AC power supply. Provided one for each lamp to be energized, current-balancing transformers have their secondary windings serially interconnected. The lamps are connected to one of the pair of outputs of the AC power supply via the respective primary windings of the current-balancing transformers and the serial connection of the secondary windings thereof.

Abstract: A power supply including a transformer primary coil coupled to an input power source and a secondary coil coupled to an output terminal, a first switch coupled to the primary coil of the transformer, a duty cycle of the first switch controlling a voltage of the output terminal, first and second resistors coupled to the output terminal in series, a third resistor having a first terminal coupled to a node common to the output terminal and the first resistor, a second switch having a first terminal coupled to a second terminal of the third resistor and having a second terminal coupled to a node common to the first and second resistors, the second switch controlled based on an accumulated driving time, and a switching controller configured to receive a feedback voltage varying according to an on/off of the second switch, and configured to control the duty cycle.

Abstract: The invention relates to an electronic ballast for a lamp, supplied with electrical energy from a power source, different to the mains AC network, comprising at least one electronic switch element for conversion of the supplied electrical power. According to the invention, a microcontroller controls the electronic switch element.

Abstract: A backlight module control system includes a power supply, a first backlight sub-module, a second backlight sub-module, a first transformer and a second transformer. The power supply is utilized for providing an operating power to the backlight module control system. A primary side and a secondary side of the first transformer are respectively coupled to the power supply and a first node of the first backlight sub-module. A primary side of the second transformer is coupled to the power supply, and a secondary side of the second transformer is coupled to the secondary side of the second transformer and a first node of the second backlight sub-module.

Abstract: A series load circuit is a circuit formed by connecting a light-emitting device unit 851 (the first load circuit) and a light-emitting device unit 852 (the second load circuit) in series. A voltage generating circuit 111 generates voltage to be applied to the series load circuit. A current detecting circuit 112 detects electric current flowing through the light-emitting device unit 851. A controlling circuit 114 controls the voltage generating circuit 111 so that the electric current detected by the current detecting circuit 112 becomes a predetermined current value.

Abstract: A fluorescent tube power supply including a rectification circuit, a smoothing circuit, an inverter, and a control circuit for controlling the inverter, further includes a current detecting unit for detecting an input current of the inverter. The control circuit is stopped based on an output signal of the current detecting unit when the input current increases.

Abstract: A discharge lamp controlling apparatus includes a detector for detecting a discharge condition of a discharge lamp; a frequency changing unit for gradually changing a frequency of a voltage to be applied to the discharge lamp until the discharge condition reaches a predetermined lighting condition; and a voltage controller for controlling the voltage to be applied to the discharge lamp on the basis of the frequency changed by the frequency changing unit.

Abstract: A lamp drive circuit used for driving a number of lamps is provided. The lamps are used in a backlight module. The backlight module is used for providing a light source when a liquid crystal display displays. The lamps are respectively electrically connected to a coil. The coils have the same number of turns and have the same magnetic circuit, so that the currents flowing through the lamps are balanced.

Abstract: An electronic control gear for a HID lamp receives an input signal for operating the lamp and frequency modulates the input signal to generate a frequency modulated output signal that drives an arc of the lamp. The frequency modulation of the output signal sweeps continuously between a low frequency modulation and a high frequency modulation, the low frequency modulation being a frequency f1 in a range of 125 kHz to 150 kHz and the high frequency modulation being a frequency f2 in a range of 230 kHz to 300 kHz, where f2?f1 is at least 0.4*f1. A power amplifier changes an amplitude of the frequency modulated output signal during the low frequency modulations so that a current amplitude of the frequency modulated output signal is substantially constant, and a variable gain transformer adjusts a voltage of the frequency modulated output signal during starting of the lamp.

Abstract: A circuit with a magnetically variable inductor that is placed in close proximity to an independently wound control coil and connected in parallel to a current transformer having primary and secondary windings wound on a magnetic core wherein the transformer core with associated windings. The inductor core is placed within the bore of the control coil and an optional focusing armature concentrates the magnetic field at the poles. Application of a control current forms poles at the control coil extremities and causes a change in magnetic properties of the inductor core thereby altering the power output of the current transformer inversely to the magnitude of the control current. The control current from the output of the secondary coil of a current transformer in series with the load and conditioned by a feedback conditioning circuit modulates the level of the control current. The magnetically variable inductor controls a D.C. to A.C.

Abstract: An apparatus and method for driving a lamp are provided. In one embodiment, an inverter having four switching elements is split into two inverter arms that are deployed at separate terminals of a floating lamp structure to achieve even light output. A controller drives both inverter arms such that power switching lines do not cross the floating lamp structure. In one embodiment, the controller adjusts the brightness of the lamp structure by adjusting the phase difference between outputs of a first inverter arm relative to a second inverter arm. In one embodiment, the controller adjusts the brightness by symmetrically pulse width modulating the outputs of the first inverter arm and the second inverter arm.

Abstract: A power-supply circuit is described. In particular, the power-supply circuit includes an input node configured to receive a power-supply signal, an output node configured to output a modulated power-supply signal, and a modulation mechanism coupled between the input node and the output node. This modulation mechanism is configured to modulate the power-supply signal to produce the modulated power-supply signal. Furthermore, the modulation mechanism may be configured to modulate the power-supply signal using both a first modulation and a second modulation. This first modulation is a duty-cycle modulation which controls the power output of the piezoelectric transformer signal, and the second modulation spreads harmonic energy associated with the first modulation over a range of frequencies. By spreading the harmonic energy, the perceived acoustical noise generated by the piezoelectric transformer is reduced.