Abstract: An LED lamp includes a rectifier, a microcontroller, at least one group of LEDs, and at least one MOSFET device. The group of LEDs includes multiple lines of serially connected LEDs, which are connected in parallel to form a first end connected to a DC output of the rectifier and a second end connected to one or more serially connected current-limiting resistors which in turn are connected to a common ground. The gate terminal of the MOSFET device is connected to an output pin of the microcontroller. The drain terminal of the MOSFET device is connected to the second end of the group of LEDs. The source terminal of the MOSFET device is connected to the common ground. A voltage detection circuit is connected between the DC output of the rectifier and an input pin of the microcontroller for detecting the voltage at the DC output of the rectifier.

Abstract: There are disclosed herein various implementations of a power converter having an advanced control integrated circuit (IC). The power converter includes the control IC and a power switch. The control IC includes a driving stage for driving the power switch, and a sensing stage coupled to the driving stage. The sensing stage is configured to produce a control signal for the driving stage based on an output current of the power converter sensed at a high side bus of the power converter.

Abstract: Provided is system including a temperature regulator including at least on regulation component in communication with a semiconductor within a converter, and a peak detector in communication with the semiconductor within the converter configured to identify a maximum temperature of each semiconductor. Also provided is a method for regulating temperature change of semiconductor components including measuring a semiconductor temperature, determining a reference temperature when the semiconductor is energized, summing the first semiconductor temperature and the reference temperature to generate a first temperature sum, comparing the first temperature sum to a coolant temperature to generate a first temperature difference. The method also circulates a fluid configured within the system such that the first temperature difference is adjusted.

Abstract: Control circuits (1) bring power converters (4) in different modes in response to detection results. The power converters (4) exchange possibly rectified first voltage/current signals with electronic halogen transformers (2) and supply second voltage/current signals to light emitting diode circuits (5). The first current signals have, in different modes, different amplitudes. The different amplitudes have different constant values and/or different derivative values. As a result, the first current signal has become a relatively varying first current signal. Then, the halogen transformers (2) no longer experience problems that occur when smaller amounts of power need to be provided than designed to. The detections may comprise polarity detections of and/or zero-crossing detections in the first voltage signals. The halogen transformers (2) comprise self-oscillating switched mode power supplies designed to provide first amounts of power at their outputs.

Abstract: A switch control circuit for controlling an average current flowing into a load through a current control switch that is series-coupled to an input power and the load includes a sensing unit configured to measure a current flowing into the load, a folder unit configured to fold a sensing signal related to the measured current based on a first reference voltage to generate first and second folder output signals based on an initialization voltage, the first and second folder output signals being symmetric to each other, a comparison unit configured to compare the generated first and second folder output signals and a control unit configured to control an operation of the current control switch according to a comparison result in the comparison unit. Such a switch control circuit integrates and compares a sensing signal and a reference signal to effectively perform an average current control.

Abstract: In a power converter, a circuit determines an average value of an inaccessible current from an average value of an accessible current and a value of the operating duty cycle of the converter. A method of measuring an average value of an inaccessible current from a measured value of a current in a power converter by a duty cycle of a pulse width modulation (PWM) signal representing a duty cycle of the power converter. Coupling a voltage representing the measured value to an input of a low pass filter during a time period (D) and coupling the input of the low pass filter to a reference voltage during a time period (1?D).

Abstract: The lighting device of one aspect according to the present disclosure calculates, based on a voltage value of an AC voltage applied to a discharge lamp and a current value of AC current flowing through the discharge lamp, a first power value defined as a value of power supplied to the discharge lamp in a first half period of the AC voltage and a second power value defined as a value of power supplied to the discharge lamp in a second half period of the AC voltage. The lighting device determines that a ground fault has occurred, when an imbalance state in which a difference between the first power value and the second power value is equal to or greater than a threshold value continues for a predetermined time period.

Abstract: Embodiments of the disclosure include an LED lamp driving method and a system in the liquid crystal panel display field. A method of the disclosure includes: adjusting correspondence relations between ports of the LED lamp and channel ports of the LED lamp driving chip first; and then connecting ports of the LED lamp and channel ports of the LED lamp driving chip according to the adjusted the correspondence relations to control light emission of the LED lamp. Aspects of the disclosure include avoiding overheating and even burning of LED lamp driving chips; can be adapted to various LED lamps operation to reduce failure rate of LED lamp operation to the minimum; effectively reduces concentrated heating of the LED lamp driving chip and increases service life of the LED lamp driving chip.

Abstract: The present disclosure is directed to a solution that provides for continuous adjustment of a reference signal to a control chip to facilitate controlling the average output power. In some aspects, a system may facilitate continuous adjustment of power provided to a device by providing a reference signal with a slope to a control pin (e.g., current control pin) of a control chip (e.g., power regulator or LED driver). Providing a reference signal with a slope (e.g., a triangle or a sinusoidal wave) can increase the control range of the control chip and improve control chip performance. For example, systems and methods of the present disclosure may increase the dimming range of an LED from less than 0.1% to 100%.

Abstract: An illumination light includes: a bridge diode that performs full-wave rectification on an alternating-current signal; a switching converter that includes a switching device and that converts the alternating-current signal on which the full-wave rectification has been performed, into a direct-current signal; a controller that controls on/off timing of the switching device; and a semiconductor light emitting element that is connected to the switching converter and the controller and to which the direct-current signal is output.

Abstract: A power supply device has an output portion that generates an output voltage from an input voltage and supplies the output voltage to a load, an output feedback controller that drives the output portion by performing output feedback control, and a first detector that detects, by means of an electromagnetic induction method, a change in a first monitoring target current due to a load change. The output feedback controller reflects a detection result from the first detector into the output feedback control.

Abstract: An electric circuit of a switchable current source (10) comprises an input path (IP) comprising a first resistor (R1) and a controllable current source (CS) to provide a changeable current (Itrim) and an output current path (OP) including a controllable output driver (MN), a second resistor (R2) and an output terminal (LDR_PIN). A sensing voltage (VSENSE) is tapped at the output current path (OP) and is fed back to a regulator circuit (RC) by a feedback path (FP). The regulator circuit (RC) is connectable to the input path (IP) and the output path (OP) and provides an output signal (Vout2) to control the output current driver (MN). The switchable current source (10) enables to provide an output current (ILDR) at the output terminal (LDR_PIN) in dependence on the first and second resistor (R1, R2) and the changeable current (Itrim).

Abstract: A power controller includes an inductor coupled to an input terminal to which an input voltage is input, a first switch coupled between the inductor and a first power source voltage output terminal, a second switch coupled between the inductor and a ground, a switch controller controlling a voltage output to the first power source voltage output terminal by controlling duties of the first and second switches according to a feedback voltage input to a feedback terminal corresponding to a voltage output to the first power source voltage output terminal, and a diode coupled between the first power source voltage output terminal and the feedback terminal, and preventing a voltage of the first power source voltage output terminal from increasing higher than a breakdown voltage of the first and second switches.

Abstract: The present disclosure is directed to an inexpensive yet intelligent solution for dimming light devices to low level intensities in which the common lighting systems generally have difficulties maintaining stability and flicker-free operation. The systems and method described herein enable a lighting system to utilize a dimmer to dim one or more lighting devices to low level intensities without introducing flickering or inconsistent operation of the lights. More specifically, the systems and methods described herein enable a dimmer to dim lights to anywhere between 0% and 5% of maximum brightness, while ensuring that the lights operate at these levels consistently, smoothly and without any visible flickering.

Abstract: Imaging apparatus, including an imaging unit, which consists of an image sensor, configured to capture images of a region and to output image signals in response to the captured images and an illumination source, configured to illuminate the region. The unit further includes a driver circuit, which is coupled to receive a digital value indicative of a target luminous flux of the illumination source and to generate a pulse-width-modulated (PWM) signal to drive the illumination source with a duty cycle of the signal determined by the value. The apparatus includes a camera control unit, which is configured to process the image signals so as to generate images of the region and to output the digital value indicative of the target luminous flux based on the images. A single cable connects the imaging unit to the camera control unit so as to convey the image signals and the digital value.

Abstract: According to an exemplary embodiment, a display device includes a backlight unit and a display panel. The backlight unit comprises a single light emitting diode string with a plurality of light emitting diodes that are connected to each other in series and configured to emit light. The backlight unit also comprises a detector configured to generate a first voltage and a second voltage with respect to an output voltage for driving the single light emitting diode string, sample the first voltage at a predetermined time interval to generate a sample voltage, and compare a level of the sample voltage with a level of the second voltage to generate a compared result. The display panel is configured to receive light from the backlight unit to display an image. The compared result determines whether the output voltage is applied to the light emitting diode string.

Abstract: An LED drive circuit and drive method thereof are provided. The drive circuit comprises: a rectifier circuit receiving a phase-control dimming signal with a conduction angle, and outputting a rectified signal; a converter comprising a switching element, with an input end coupled to the rectifier circuit and an output end coupled to an LED; and a controller having a first input end receiving the rectified signal, a second input end receiving a first sampling signal and an output end outputting a control signal according to the rectified signal and the sampling signal; wherein the switching element receives the control signal from the controller, thus executing an on/off operation to control current flowing through the LED.

Abstract: The present disclosure describes a boost converter for supplying current to a series connection of light-emitting diodes (LEDs). A duty ratio of the main switch of the converter is configured to be controlled on the basis of a current feedback signal. The current feedback signal is formed as a weighted average of at least two signals including a first signal representing the current through the series connection of LEDs and a second signal representing a current through the main switch.

Abstract: A lighting module includes a compatible part to transform and output an output voltage from a ballast, a transformation part to transform and output an output voltage from the compatible part, and a lighting part to emit light using an output voltage from the transformation part as a driving voltage. In the compatible part, a number of ports to receive the output voltage from the ballast is different form a number of ports to output the transformed output voltage to the transformation part.

Abstract: In one embodiment, an igniter circuit may include a circuit to determine if the current through a load switch exceeds a threshold value, and to responsively disable a second switch that couples DC power to the igniter circuit.

Abstract: When supplying an LED light source with a first output voltage that is equal to or higher than a threshold voltage, an LED driver causes a DC power supply to output a first DC voltage and causes a switching regulator to supply the LED light source with the first output voltage. When supplying the LED light source with a second output voltage that is below the threshold voltage, the LED driver causes the DC power supply to output a second DC voltage lower than the first DC voltage and causes the dropper regulator to supply the LED light source with the second output voltage.

Abstract: A physiological monitoring system may use photonic signals to determine physiological parameters. The system may vary parameters of a light drive signal used to generate the photonic signal from a light source such that power consumption is reduced or optimized. Parameters may include light intensity, firing rate, duty cycle, other suitable parameters, or any combination thereof. In some embodiments, the system may use information from a first light source to generate a light drive signal for a second light source. In some embodiments, the system may vary parameters in a way substantially synchronous with physiological pulses, for example, cardiac pulses. In some embodiments, the system may vary parameters in response to an external trigger.

Abstract: The LED tube lamp includes a lamp tube configured to receive an external driving signal; a rectifying circuit configured to rectify the external driving signal to produce a rectified signal; a filtering circuit coupled to the rectifying circuit, and configured to filter the rectified signal to produce a filtered signal, wherein the filtering circuit has a first filtering output terminal and a second filtering output terminal; an LED lighting module coupled to the filtering circuit, wherein the LED lighting module includes a driving circuit having a first driving output terminal and a second driving output terminal and configured to receive the filtered signal to produce a driving signal, and an LED module configured to receive the driving signal and emit light; and a mode switching circuit coupled to at least one of the first and the second filtering output terminal and at least one of the first and the second driving output terminal, and configured to determine to perform one of a first driving mode and a se

Abstract: The invention relates to an LED illumination system (BA), with at least one lighting means, the lighting means being controlled by at least one operating device (1, 1?, 1? . . . ) according to commands of a central control unit (12), the operating devices (1, 1?, 1? . . . ) being supplied with a voltage by the central control unit (12), and the operating devices (1, 1?, 1? . . . ) having an address (A), the address (A) to be assigned to the operating device (1, 1?, 1? . . . ) is associated on the basis of a temporally defined load behavior of the operating device (1, 1?, 1? . . . ).

Abstract: A universal load control module may include a power supply that operates over a wide voltage range, a microcontroller, and one or more functional control blocks. A functional control block may include a dimmer circuit for controlling a lighting load that provides reverse phase cut mode dimming, forward phase cut mode dimming, and hybrid phase cut mode dimming, as well as thermal protection. One or more universal control modules may be housed in a cabinet that include a cabinet control module. The cabinet may include additional thermal protection measures.

Abstract: A light-emitting diode arrangement includes a piezoelectric transformer having at least one output connection position, and a high-voltage light-emitting diode including a high-voltage light-emitting diode chip including at least two active regions connected in series with one another, wherein the high-voltage light-emitting diode is electrically connected to the output connection position of the piezo transformer.

Abstract: Infinite dimming circuits, devices, systems, and methods of use are provided herein. In one embodiment, a dimming driver integrated circuit (IC) is configured to compensate for flicker caused by alternating current (AC) waveform valleys of an operational reference provided by an AC source, the dimming driver IC having a main interface and a secondary interface, the main interface receiving the operational reference, the secondary interface receiving a compensating reference which is relative to the operational reference, the dimming driver IC using both the operational reference and the compensating reference to create a compensated waveform that drives the semiconductor light while removing flicker at any luminance level.

Abstract: A lighting device includes an electricity storage electrically connected in parallel with a solid light source, a switching circuit that produces a current to supply the current to the electricity storage, and a control circuit that controls, according to a dimming level, burst dimming by controlling the switching circuit so that the solid light source is lit intermittently. When the dimming level is a threshold level or more, the control circuit sets an electricity storage capacity of the electricity storage to a first capacity, and sets a frequency by the burst dimming to a first frequency. When the dimming level is below the threshold level, the control circuit sets the electricity storage capacity to a second capacity smaller than the first capacity, and sets the frequency by the burst dimming to a second frequency higher than the first frequency.

Abstract: A system for controlling a level of light output by a solid state lighting load controlled by a dimmer includes a phase angle detector and a power converter. The phase angle detector is configured to detect a phase angle of the dimmer based on a rectified voltage from the dimmer and to determine a power control signal based on comparison of the detected phase angle with a predetermined first threshold. The power converter is configured to provide an output voltage to the solid state lighting load, the power converter operating in an open loop mode based on the rectified voltage from the dimmer when the detected phase angle is greater than the first threshold, and operating in a closed loop mode based on the rectified voltage from the dimmer and the determined power control signal from the detection circuit when the detected phase angle is less than the first threshold.

Abstract: A method for controlling an angular distribution of a light-beam emitted by a light-output device (102, 200) comprising a first set of light-sources (105, 211) comprising at least one light-source configured to emit light within a first angular range (221, 231, 241) and second set of light-sources (107, 210) comprising at least one light-source configured to emit light within a second angular range (222, 232, 242), wherein the first angular range is different from the second angular range. The method comprises the steps of: receiving (401) a dimmer setting (VDS) from a dimmer (101); controlling (404), if the dimmer setting is within a first predetermined range, the first set of light-sources to emit light within the first angular range; and controlling (405), if the dimmer setting is within a second predetermined range, the second set of light-sources to emit light within the second angular range.

Abstract: In a method according to embodiments of the invention, a light emitting structure comprising a plurality of light emitting diodes (LEDs) is provided. Each LED includes a p-contact and n-contact. A first mount and a second mount are provided. Each mount includes anode pads and cathode pads. The anode pads are aligned with the p-contacts and the cathode pads are aligned with the n-contacts. The method further includes mounting the light emitting structure on one of the first and second mounts. An electrical connection on the first mount between the plurality of LEDs differs from an electrical connection on the second mount between the plurality of LEDs. The first mount is operated at a different voltage than the second mount.

Abstract: A display system, having an emissive body, emitting light in a way that is color temperature controllable. The light emission can be from zones. The emissive body can be a FIPEL type device with a first transparent conductive coating over a light emitting substrate. The zones are each separately controllable for color temperature.

Abstract: A lighting device includes: a drive circuit that supplies power to a light source; a switch connected in series with the light source; and a controller that controls pulse modulation for visible light communication executed through switching ON and OFF of the switch in a first interval, and stops the pulse modulation in a second interval. The controller controls a peak value, which is a high value of a pulsed current supplied from the drive circuit to the light source, to match an average current value in the first interval with an average current value in the second interval.

Abstract: A device for supplying a plurality of LED units with power includes a common DC/DC converter which delivers a regulated output voltage and to which a plurality of sections are connected, each having a buck converter and an LED unit connected thereto, and means for regulating or setting the section currents to be supplied to the LED units. In order to simplify the device, the means for regulating or setting the section currents are formed by a central, common processor, which is supplied with actual values in keeping with the individual section currents and connected to corresponding control inputs of the respective buck converters for applying control values calculated on the basis of the actual values.

Abstract: The invention relates to an operating circuit for an LED series, having: a converter, particularly a DC-DC converter, having a controllable switch (S1) and an inductor (LBUCK) for converting an input voltage (Vin) fed to the operating circuit into a supply voltage for the LED series; —a control unit (SR) for driving the switch (S1); —a secondary-side inductor (L2) coupled to the inductor (LBUCK); —an envelope curve demodulator (30) for detecting the envelope curve of the voltage (V?LED) present at the secondary-side inductor (L2); and—a compensating circuit (31) for compensating an error caused by the envelope curve demodulator (30) relating to the detection of the envelope curve.

Abstract: A surge protection device provides a dimming control signal to an LED driving system upon failure of surge protection components. Impedance networks are coupled between respective first, second and third input lines for an AC mains. The impedance networks include thermal fuses and metal oxide varistors, with a dimming control circuit having a resistive network coupled between each respective series circuit of fuses and MOV's. The resistive network generates a 0-10V analog dimming signal to an LED device controller, wherein a lighting device operates in full lighting mode while the surge protection device is in normal, high impedance mode, but operates in a dimming mode when one or more of the impedance network devices fail and cause the 0-10V signal to drop below 10 volts. Detection of a dimmed but operable lighting device may serve as warning to an operator that the associated surge protection device component should be replaced.

Abstract: A method for controlling a portable lighting device. The device has a switched-mode power supply, a light source, a high frequency switch, a controller controlling the operation of the light source and a user interface for inputting commands to the controller. A DC power source has a negative pole that is connected by only one single electric contact with the lighting device tail. The method for controlling a portable lighting device includes connecting a DC power source, an inductor, a light source, a high frequency switch and a resistor in series, measuring a voltage across the resistor, and controlling the high frequency switch dependent on the voltage measured across the resistor.

Abstract: The present disclosure relates to a circuit compensation circuit includes a current compensator configured to perform a charging or a discharging of a capacitive element according to whether a sensing voltage is less than or greater than a certain voltage and to delay a turn-off point of a driving switching element until a corresponding discharging quantity is identical to a corresponding charging quantity and a switching controller configured to provide a switching control signal at the delayed turn-off point of the driving switching element. The present disclosure also relates to a light emitting diode apparatus that includes such a current compensation circuit, and a related method of driving such a current compensation circuit.

Abstract: Disclosed is an AC light emitting device. The AC light emitting device is electrically connected to an AC power, and the AC power is rectified by a rectification module and inputs an input voltage. The AC light emitting device comprises a buck module, a switching unit, a control module and an AC lighting emitting module. The buck module is electrically connected to the rectification module. The switching unit is electrically connected to the rectification module and the buck module. The control module is electrically connected to the switching unit and the buck module. The AC lighting emitting module is electrically connected to the switching unit. The control module outputs a pulse waveform signal to the switching unit according to the input voltage and a dimming signal, and the switching unit turns on or off the AC lighting emitting module according to the pulse waveform signal.

Abstract: Adaptation circuits (1) allow discharge lamps to be replaced by light circuits (45) with light emitting diodes, while keeping ballast circuits (8) designed for connection to the discharge lamps. The adaptation circuits (1) comprise conversion circuits (2) for converting input voltage and current signals coming from the ballast circuits (8) into output voltage and current signals destined for the light circuits (45). The conversion circuits (2) reduce amplitudes of the input voltage signals to values below predefined values during predefined time intervals after energy from the ballast circuits (8) has been transferred to the conversion circuits (2). The time intervals are synchronized with periods of the input voltage signals. Between first draining states for draining energy and second releasing states for releasing the energy, third states such as holding states for holding the energy have been introduced.

Abstract: A drive circuit with an external mode-adjusting pin includes an operational mode control circuit and a drive processing circuit. The operational mode control circuit further includes a current mirror circuit, a resistor, a capacitor and a comparator. The first comparator input port receives a reference voltage. The second comparator input port couples the second output port of the current mirror and the capacitor. The current mirror circuit bases on a resistor current to generate a charge current for charging the capacitor. As the charge voltage at the second comparator input port reaches a reference voltage, a trigger signal is outputted to the drive processing circuit for controlling the switches thereof. The external pin is defined to one end of the resistor or the capacitor for varying the resistance or the capacitance respectively to determine the operational mode for the driven circuit.

Abstract: The subject matter disclosed herein relates to a system for controlling strings of lights. This system can include a host controller, one or more strings of lights, and an effects modulator. Each string of light can include at least one LED light. The effects modulator can be operatively connected to the host controller and to the strings of light. The effects modulator can include a microcontroller and an inverter. The inverter can include a high side driver circuit and one or more low side driver circuits operatively connected to the high side driver circuit. Each low side driver circuit can be operatively connected to one of the strings of light. The microcontroller can be configured to receive one or more control signals from the host controller and control the strings of light via the inverter in accordance with the control signals. Related apparatus, methods, and techniques are also described.

Abstract: Exit and egress lighting, emergency lighting or emergency light fixture, having internal supercapacitor power sources are recharged after a power outage using a staggered power up process. For example, once an emergency light fixture detects a power-on transition from power being unavailable on a power source to power being available from the power source, the fixture waits a predetermined time to recharge a supercapacitor based on a charge time delay value. The predetermined time may be selected to be unique for one or several emergency light fixtures so as to distribute a combined peak power demand of the fixtures. After the predetermined time has expired, the supercapacitor is electrically coupled to a power source to in order to recharge the supercapacitor.

Abstract: To protect electromagnetic ballasts against damage, driver circuits for coupling the electromagnetic ballasts to light circuits comprising light emitting diodes are provided with rectifier bridges for exchanging first current signals with the electromagnetic ballasts and for providing second current signals to the light circuits, and with protection circuits for protecting the electromagnetic ballasts against parameters of the first current signals obtaining values larger than threshold values. The parameters may be direct-current components of the first current signals and may be average values of rectified versions of the first current signals/peak values of the first current signals. The rectifier bridges may comprise first diode elements. The protection circuits may comprise second diode elements serially coupled to the first diode elements.

Abstract: A light emitting diode (LED) controller provides constant current regulation for a converter circuit providing current to an LED. The LED controller senses an inductor voltage and determines an inductor reset time from the sensed inductor voltage. Based on the determined inductor reset time, a switch on time and a switch period, the LED controller generates a control signal modifying the state of a switch coupling the converter circuit to an input voltage.

Abstract: A short circuit detection circuit for detecting short circuit of a series of light-emitting diodes includes a constant current source, a rectifier, and a detector. The constant circuit source provides a setting current. The rectifier is coupled between a feedback node and the constant current source. The feedback node is coupled to a terminal of the series of light-emitting diodes. When a feedback voltage of the feedback node exceeds a short reference voltage, the rectifier allows the setting current sinks the feedback node. The detector detects the feedback voltage of the feedback node. When the feedback voltage exceeds a predetermined value, short-circuit protection is triggered to make the series of light-emitting diodes be turned off.

Abstract: A lighting system is disclosed having a plurality of luminaires in which the energy usage of each luminaire can individually be metered using a luminaire controller having a metering circuit.

Abstract: Various examples directed to phase-dimming LED driver input circuitry having multiple bleeder circuits activated by a controller with multi-bleeder mode control are disclosed. In one example, the input circuitry may include multiple bleeder circuits controlled by the controller in an open-loop or closed-loop configuration. The controller may selectively activate or deactivate the multiple bleeder circuits based on the input line voltage, the dimming state, and the type of dimming being implemented to improve performance of the LED driver by preventing or reducing shimmering/blinking and by reducing bleeder loss.

Abstract: GaN-based half bridge power conversion circuits employ control, support and logic functions that are monolithically integrated on the same devices as the power transistors. In some embodiments a low side GaN device communicates through one or more level shift circuits with a high side GaN device. Both the high side and the low side devices may have one or more integrated control, support and logic functions. Some devices employ electro-static discharge circuits and features formed within the GaN-based devices to improve the reliability and performance of the half bridge power conversion circuits.

Abstract: A power supply apparatus includes a rectification circuit, a power factor correction circuit, an auxiliary boost circuit and a direct current to direct current conversion circuit. The auxiliary boost circuit includes an input contact, an output contact, a voltage detection unit, a control unit, a boost unit and a boost bypass unit. When a voltage value of a power factor correction power is not greater than a predetermined voltage value, the control unit is configured to turn off the boost bypass unit and turn on the boost unit, so that the boost unit boosts the power factor correction power and then the power factor correction power is sent to the direct current to direct current conversion circuit through the boost unit and the output contact.