Abstract: A mobile charger includes a housing (1). A cell (2) is provided in the housing (1). A positive power distribution unit (4) and a negative power distribution unit (5) are provided at both ends of the housing (1) relative to the positive and the negative poles (21, 22) of the cell (2) respectively. A conducting piece set (3) is provided in the housing (1). The conducting piece set (3) is connected to the positive power distribution unit (4) and the negative power distribution unit (5). A charging unit (6) and a power supplying unit (7) are provided in the housing (1). The charging unit (6) and the power supplying unit (7) are electrically connected with the positive pole (21) of the cell (2) through the positive power distribution unit (4) and the conducting piece set (3) and electrically connected with the negative pole (22) of the cell (2) through the negative power distribution unit (5).

Abstract: A wireless charging device comprises an electronic switch and a transmitting coil (L1) electrically connected with a power source in sequence. A control end of the electronic switch is connected with a transmitting control unit. The wireless charging device further comprises a current limiting resistance (R1) connected in serial with the transmitting coil. The wireless charging device further comprises a compensation capacitor (C1) connected in parallel with the transmitting coil. An insert total electromagnetic coupling structure is further employed for charging. Such wireless charging device is particularly suitable for electronic cigarette, with low cost, stable and reliable working status and high efficiency, and specific heat sink is not required.

Abstract: A wireless transceiver coupled to a human interface device (HID) having a first coil is provided. The wireless transceiver includes a control module, a port, and a second coil. The control module includes a radio frequency (RF) unit, a conversion unit, and an electricity power unit. The RF unit is used to receive a RF signal outputted from the HID. The conversion unit coupled to the RF receiving unit is used to convert the RF signal to a data packet which is in accordance with the HID. The electricity power signal provides electricity power to the control module by the port. The electricity power unit drives the second coil according to the electricity power signal so that the second coil transmits an electromagnetic wave signal to the first coil of the HID by way of resonance and mutual inductance. Therefore, the wireless transceiver can charge to the HID wirelessly.

Abstract: Disclosed herein are a power receiving device for wireless charging and a portable electronic device having the same. The power receiving device for wireless charging includes a body having a receiving space formed therein; and a charging kit detachably received in the receiving space, and including a coil formed to receive power by magnetic coupling with a power supplying device and a charging circuit configured to charge a battery by electromotive force induced in the coil.

Abstract: Described herein are improved configurations for providing a stranded printed circuit board trace comprising, a plurality of conductor layers, a plurality of individual conductor traces on each of the said conductor layers, and a plurality of vias for connecting individual conductor traces on different said conductor layers, the vias located on the outside edges of the stranded trace. The individual conductor traces of each layer may be routed from vias on one side of the stranded printed circuit board trace to vias on the other side in a substantially diagonal direction with respect to the axis of the stranded printed circuit board trace. In embodiments, the stranded printed circuit board trace configuration may be applied to a wireless power transfer system.

Abstract: A vehicle is able to contactlessly receive electric power from a power transmitting device and to charge a mounted electrical storage device (electric load). The vehicle includes a communication unit that carries out wireless communication with the power transmitting device and a vehicle ECU (control fit) that controls the communication unit. The communication unit is able to switch a communication range between a wide communication range (wire-area communication) and a narrow communication range (narrow-area communication). The vehicle ECU, at the time of identifying a power transmitting device from which electric power should be received, controls the communication unit such that the communication unit communicates with the power transmitting device using the narrow-area communication.

Abstract: Disclosed are a wireless multi-charger system capable of saving the total charging time of a large number of wireless power transmission devices since one wireless multi-power transmission device includes a plurality of the wireless power transmission devices so that a large number of the wireless power transmission devices can be charged with electricity, and preventing the damage of the wireless power transmission devices and the wireless multi-power transmission device although foreign substances are put on charger blocks that are not charged.

Abstract: A wireless charger and controlling method thereof are disclosed, by which a charging area can be displayed in further consideration of user's convenience. The present invention includes a power supply unit configured to supply a power by wireless to a power receiver located in a charging area within a predetermined distance, a light projection unit configured to project a light on an area around the wireless charger, and a control unit configured to control the light projection unit to project the light on the area around the wireless charger to visually discriminate the charging area.

Abstract: An apparatus for wirelessly charging an energy storage element is disclosed. The apparatus includes a coil, a set of capacitors, a set of switches and a rectifier. The coil, which has multiple taps, is capable of being energized by a charger via inductive coupling. The capacitors are connected to the coil at various taps. The switches selectively connect the rectifier to at least one of the capacitors to charge the energy storage element that is connected to the rectifier.

Abstract: Exemplary embodiments are directed to wireless power transfer. A transmitting device or a receiving device for use in a wireless transfer system may be equipment or a household appliance. The transmitting device includes a transmit antenna to wirelessly transfer power to a receive antenna by generating a near field radiation within a coupling-mode region. An amplifier applies an RF signal to the transmit antenna. A presence detector detects a presence of a receiver device within the coupling-mode region. A controller adjusts a power output of the amplifier responsive to the presence of a receiver device. The presence detector may also detect a human presence. The power output may be adjusted at or below the regulatory level when the presence signal indicates human presence and above a regulatory level when the presence signal indicates human absence.

Abstract: An electrical powered vehicle is equipped with a coil unit capable of receiving electric power from a facility self-resonant coil external to the vehicle. The electrical powered vehicle includes: a pair of side members aligned in a widthwise direction of the vehicle and extending in a fore-aft direction of the vehicle; a vehicle self-resonant coil coupled with the facility self-resonant coil resonantly via an electromagnetic field to be capable of at least one of transmitting electric power and receiving electric power; and a vehicle capacitor provided to the vehicle self-resonant coil between the paired side members.

Abstract: A non-contact charging module with which reduction in thickness can be achieved while reliable insulation is maintained between conducting wire and magnetic sheet. This non-contact charging module comprises: a planar coil section (2) constituted by coiling a conducting wire; a conductive magnetic sheet (3) having the planar coil section (2) arranged thereon, with an insulating sheet (4) therebetween; and a recess (33) or slit (34) provided in the conductive magnetic sheet (3) and extending to an edge of the conductive magnetic sheet (3) from the starting point of the winding of the planar coil section (2). The conducting wire of the planar coil section (2) is stored in the recess (33) or slit (34) by the insulating sheet (4) being pushed into the recess (33) or slit (34). The conducting wire of the planar coil section (2) is insulated from the conductive magnetic sheet (3) by the insulating sheet (4).

Abstract: A method for charging a battery, including: determining a final state of charge and a final temperature of the battery; and calculating charging power and/or cooling power required to reach the two final values within a minimum amount of time.

Abstract: Disclosed herein are representative embodiments of methods, apparatus, and systems relating to electric vehicle charging stations (“EVCSs”) and electric vehicle supply equipment (“EVSE”) that are configured to display advertisements to a user. For example, in one embodiment, advertisements are displayed on a display device of the EVCS or EVSE as the EVCS or EVSE awaits user interaction. An indication is received of user interaction with the EVCS or EVSE. A transaction is facilitated between a user and the EVCS or EVSE by which the user indicates that one or more electric vehicle batteries of an electric vehicle are to be charged via one of one or more charging ports of the EVCS or EVSE. A charging operation is performed that provides an electric charge to the one or more electric vehicle batteries of the electric vehicle via the one of the one or more charging ports.

Abstract: A vehicle that is chargeable using power from an external power source includes: a chargeable electric storage device; a charging device that charges the electric storage device by using the power from the external power source; and a control device that, based on maximum supply power that is able to be supplied to the electric storage device and based on actual charge power actually supplied to the electric storage device, calculates a shortfall with respect to charge power supplied to the electric storage device in a case where charging is performed at the maximum supply power, and stores information relating to a causal factor for the shortfall.

Abstract: An electrical and/or hybrid motor vehicle device includes a charging device for the charging of an accumulator device. The charging device includes a first charging unit with a connector element for the charging of the accumulator device, which is provided for energy transfer by means of contacts. The charging device also includes a second charging unit with an energy transfer unit for the charging of the accumulator device, which is provided for a contactless energy transfer. The charging device has a charging electronic system, which is provided at least in part as an integral construction with the first and second charging units.

Abstract: An intelligent wall-mounted charger comprises a housing (10) mounted on a wall. A power supplying control circuit is provided inside the housing and a display screen (80) is provided on the housing, wherein the display screen is electrically connected with the power supplying control circuit. The intelligent wall-mounted charger is mounted on the wall, and the mounting method of the intelligent wall-mounted charger is similar to that of a conventional wall-mounted switching socket. A charging interface (30) used for a notebook computer and a USB charging interface (50) applied for digital products charged through USB ports are provided on the housing of the charger. The power supplying control circuit is electrically connected with the charging interface for the notebook computer and the USB charging interfaces, and it can automatically and discriminatingly output a charging voltage for the notebook computer.

Abstract: A charger includes a charging body having a base body, two insertion pins apart assembled to a front end of the base body, and at least one USB port equipped in a rear end of the base body. A power plug includes a plug part, a socket part mounted to the plug part and defining two inserting slots, and two electrical terminals located between the socket part and the plug part and each having a pair of contact portions. The plug part has a group of power pins of which one end electrically connects with the electrical terminals and the other end projects outward for plugging in a wall socket. The power plug can be removably attached to the charging body by means of plugging the insertion pins into the corresponding inserting slots to electrically clamp the insertion pin between the contact portions of the corresponding electrical terminal respectively.

Abstract: A portable, rechargeable lithium battery power supply device that can power home electronics or home lights or appliances is disclosed in the present invention. Said device comprises a lithium ion battery, an AC/DC inverter, a diode, a charger and a outlet. Said device provides 120 volt direct current power to home electronics or home light or appliances.

Abstract: A video game controller charging system is provided. The video game controller charging system includes a base; at least one structure on the base for providing physical support to at least one video game controller while it is being charged; and at least one DC port on the base configured to couple to and provide DC power to a power input port of the at least one video game controller. The video game controller charging system may also include a current detector, a charging status indicator, at least one docking bay, and/or an AC-to-DC converter adapted to convert externally supplied power to the DC power provided to the power input port of at least one video game controller. The base of a charging station may include a recess having at least one electrical contact and a power input for connection to a power supply.

Abstract: A battery includes a plurality of battery modules which are arranged in battery strings and are selectively activated or deactivated by driving. The battery module voltage of a respective battery module contributes to an output voltage of the corresponding battery string of the battery in the activated state. The battery further includes a switching converter topology which is coupled to the battery strings and is configured to selectively generate currents flowing into one or more of the battery strings.

Abstract: A battery pack that has a configuration in which a plurality of secondary battery cells are connected in series at time of discharge and are connected in parallel at time of charge, and that has a configuration and a structure with which the charge and the discharge are allowed to be performed without any trouble even if an abnormal-state secondary battery cell exists is provided. A battery pack 10 includes a plurality of secondary battery cells 21 and a control circuit 11. Under control of the control circuit 11, the plurality of secondary battery cells 21 are connected in series at time of discharge, and are connected in parallel at time of charge.

Abstract: Embodiments of an electronic circuit for monitoring a battery stack enable cell balancing while conserving pin-count of the circuit package. The illustrative electronic circuit comprises a battery monitoring integrated circuit configured for monitoring a plurality of cells in the battery stack. The battery monitoring integrated circuit is arranged to share a common node pin between two adjacent battery cells in the battery stack for the purpose of cell balancing.

Abstract: An energy store includes a rechargeable primary energy store having a first electrode which generates anions and which conducts anions, a second electrode which accepts anions and/or which conducts anions, an electrolyte which is arranged between the first electrode and the second electrode and which conducts anions and is embodied as a solid, and a first redox pair which forms the second electrode or is in contact with same and which includes an oxidation reactant and an oxidation product. The store includes at least one storable second oxidation reactant that belongs to a second redox pair and a secondary energy store which is designed as a store for the second oxidation reactant. A connecting line is provided between the primary energy store and the secondary energy store, the connecting line allowing the second oxidation reactant to be conducted from the primary energy store to the secondary energy store and back.

Abstract: A battery system including a battery pack having a plurality of battery cells and a charger control circuit configured to receive unregulated power from a source and to provide regulated power to the battery pack. The battery system also includes a battery management system configured to individually monitor and control the plurality of battery cells and the charger control circuit.

Abstract: A storage battery control system comprises multiple storage batteries disposed in a power grid, and a storage battery control apparatus. The storage battery control apparatus is communicably coupled to the multiple storage batteries and an energy management system. The storage battery control apparatus acquires storage battery information comprising a charging-discharging performance and a remaining capacity from each of the storage batteries, acquires power supply-demand prediction information showing a prediction of power supply and demand in a prescribed range from the energy management system, decides an individual charging-discharging rate for each of the storage batteries based on the storage battery information and the power supply-demand prediction information, and sends the decided individual charging-discharging rate to each of the storage batteries. Each of the storage batteries operates based on the individual charging-discharging rate received from the storage battery control apparatus.

Abstract: In one aspect, an apparatus for charging a device includes a charger and a controller. The charger includes a capacitance and has a charger input and a charger output. The charger input receives an AC input voltage waveform, and the charger output outputs an output voltage waveform and an output current waveform. The controller determines whether an amplitude of the output voltage waveform is within a voltage range. In response to determining that the amplitude of the output voltage waveform is within the voltage range, the controller directs an amplitude of the output current waveform to be substantially proportional to an amplitude of the AC input voltage waveform. In response to determining that the amplitude of the output voltage waveform is not within the voltage range, the controller increases the capacitance of the charger to adjust the amplitude of the output voltage waveform to be within the voltage range.

Abstract: A power supply system includes data circuitry as well as power circuitry to generate DC power for use by a portable electronic device having a rechargeable battery. The DC power, ground and two signaling lines are provided in a power supply connector which detachably mates with an electronic device power input port. In response to a first signal from the electronic device transmitted over one of the signaling lines, the data circuitry provides an analog signal to the electronic device over the other signaling line. The electronic device determines a parameter level, such as a current level, of the analog signal, and based on the determined parameter level controls charging of its battery.

Abstract: A battery state-of-charge (SOC) estimator uses a robust H? filter design by taking into account the battery parameter uncertainties, which is due to battery age, variation, and operating conditions such as temperature and SOC level. Each of the time-varying battery parameter values and their variation rates are bounded. By utilizing the parameter variation bounds and parameter variation rate bounds into the design process and minimizing the H? gain from the measured current signal to the estimation error of Voc, the battery SOC estimator can achieve enhanced robustness to the variations of battery age, variation, and operating conditions that include temperature and SOC level.

Abstract: An excavator includes an electric load, an electrical energy storage unit including an electrical energy storage part (19) that supplies electric power to the electric load, and a control unit (30) that controls an amount of charge to the electrical energy storage part (19) so that a charge rate of the electrical energy storage part (19) is between a system control upper limit value and a system control lower limit value. The control unit (30) controls the amount of charge to the electrical energy storage part (19) based on a changing trend of a detection value of the charge rate.

Abstract: A high voltage dc power source for providing a charging current to an electronic device, including one or more strings connected in parallel, each string being subdivided into dc power source units connected in series and each string being provided with a solid-state switch configured to connect and disconnect the string, and a control unit adapted to turn on and turn off the solid-state switch, and the control unit is configured, upon receiving an order to connect the string, to control the switch of the string to be alternately turned on and off so that a soft charging of the electronic device is achieved.

Abstract: A shaft-driven generator system has a generator connected to a converter. An inverter supplies an AC voltage on a network side. The converter and the inverter are linked via a DC link circuit. The inverter has at least two phase modules, which each have an upper and a lower valve branch, which each have a plurality of two-pole sub-systems connected electrically in series. Each sub-system has a unipolar storage capacitor, to which a series circuit of two gate-controlled turn-off semiconductor switches is connected electrically in parallel. Each semiconductor switch has a diode connected antiparallel therewith. Thus, a shaft-driven generator system is obtained that has a DC-link converter as a static frequency converter for complying with the required network feedback and for managing transient operating states.

Abstract: A power converter apparatus for driving an electronic load is disclosed. The power converter apparatus includes a rectifier module, an active switch unit, a driving module, an input voltage detection module, an output voltage detection module, a current detection module and a digital processor module. The active switch unit is shunt connected to the electronic load. The input voltage detection module is used for sampling out an input sampled voltage waveform. The output voltage detection module is used for sampling out an output sampled voltage waveform. The current detection module is used for sampling o out a practical input current waveform. The digital processor module generates a current reference command according to the input sampled voltage waveform and the output sampled voltage waveform. The digital processor module dynamically switches the active switch unit according to the current reference command and the practical input current waveform.

Abstract: A circuit comprises a cascode core circuit and a current adjustor circuit. The cascode core circuit has an output node and a current path (ID). The current adjustor circuit is configured to change a current on the current path in response to a change in a voltage at the output node. The cascode core circuit comprises a first transistor, a second transistor, and a third transistor. A first terminal of the first transistor is coupled to a second terminal of the second transistor and to a third terminal of the third transistor. A first terminal of the second transistor is configured as the output node. A first terminal of the third transistor is coupled to a third terminal of the second transistor. The current path is through the first terminal of the third transistor.

Abstract: A DC-DC converter includes a current control stage configured to provide a threshold based on an output voltage, an input voltage, and a reference voltage for the DC-DC converter. An off time control can be configured to receive the threshold and control an off time for the DC-DC converter based on the threshold such that the off time is inversely proportional to the peak current generated by the DC-DC converter.

Abstract: An isolated switching mode power supply, having: a transformer having a primary winding, a secondary winding and a third winding; a current limit comparator configured to provide a current limit signal based on the current sense signal and the peak current signal; a logic circuit configured to provide a logic control signal based on the frequency control signal and the current limit signal; a startup control circuit configured to generate a startup control signal based on the current sense signal; a load detecting circuit configured to provide a load detecting signal based on the second feedback signal and the switching signal; and a selector configured to provide the logic control signal or the startup control signal based on the load detecting signal.

Abstract: The embodiments of the present invention disclose a charge-pump voltage divider and associated start-up method. The charge-pump voltage divider comprises a start-up circuit that can regulate an inrush current during start up. The start-up circuit comprises a switch, which operates in linear region state during start-up, and operates in switching state after the start-up completes. The charge-pump voltage divider may further comprise a load control switch configured to ensure the start-up is independent of a load current.

Abstract: An integrated circuit (IC) device is provided that includes at least one internal voltage regulator arranged to receive a voltage supply signal at a first input thereof, receive a control signal at a second input thereof, regulate the received voltage supply signal in accordance with the received control signal, and provide a regulated voltage supply signal at an output thereof. The IC device further includes at least one voltage regulation power control module operably coupled to the second input of the at least one internal voltage regulator and arranged to provide the control signal thereto. The voltage regulation power control module is further arranged to receive at least one IC device conditional indication, and generate the control signal for the at least one internal voltage regulator based at least partly on an available thermal power budget for the IC device corresponding to the at least one IC device conditional indication.

Abstract: A power control circuit and method of formation is provided, which in one embodiment includes a low voltage detection circuit to process a rectified input voltage from at least one alternating current (AC) voltage source and to output a low voltage indication signal upon detection of an initiation of an increase in the rectified input voltage; and a driver circuit configured to receive a signal representative of the low voltage indication signal and, in response, to output a drive signal to the switch control input of the power switch to turn on the power switch.

Abstract: A predictive current feedback system for a switched mode regulator including a sample and hold network for sampling voltage across a lower switch of the regulator and for providing a hold signal indicative thereof, and a predictive current feedback network which adds an offset adjustment to the hold signal based on a duration of a pulse width of a pulse control signal developed by the regulator. Sampling may be done while the lower switch is on for providing a hold value indicative of inductor current while the pulse control signal is low. The offset adjustment may be added to the hold signal in response to a transient event when the pulse signal is high. The offset may be incremental values after each of incremental time periods after a nominal time period, or may be a time-varying value. Adjustment may be made while the pulse signal is low as well.

Abstract: A regulator circuit includes a comparator configured to compare a feedback voltage obtained by dividing an output voltage with a reference voltage to output a comparison signal; a controller configured to control an electric potential of an internal node according to the comparison signal; a current supply unit configured to increase an electric potential of an output node by applying a pump voltage received from a pump circuit according to the electric potential of the internal node; and a discharge unit configured to reduce the potential of the output voltage by discharging the electric potential of the output node according to the electric potential of the internal node.

Abstract: The present invention related to a switch control circuit, a coupled inductor boost converter including the same, and a driving method thereof. The coupled inductor boost converter includes a first inductor connected between an input voltage and a first node, a second inductor connected between the first node and a second node, and a power switch connected between the first node and a ground, and a switch control circuit. The switch control circuit receives a voltage of the second node and turn on the power switch by using the voltage of the second node at a time when a voltage of the first node becomes a zero voltage.

Abstract: An exemplary embodiment of the present invention generates a plurality of clock signals having a frequency according to an output voltage, a plurality of low clock signals of which frequencies are half of frequencies of the plurality of clock signals, and a phase signal corresponding to the output voltage by subtracting an average phase error from a count signal sampled by being synchronized with a reference clock signal from the count result of a first clock signal having the earliest phase among the plurality of clock signals. The average phase error is generated according to a comparison result of a first low clock signal corresponding to the first clock signal and each of other low clock signals among the plurality of low clock signals by being synchronized with the reference clock signal.

Abstract: A regulator system with dynamic droop including a regulator control network which is adapted to control regulation of an output voltage to a reference level, a DC droop network which provides a droop signal to modify the reference level based on output load according to a predetermined DC load line, and a dynamic droop network which adjusts the droop signal to delay recovery to the predetermined DC load line within an AC load line tolerance in response to a load transient. A transient reduction network may be included to reduce transient overshoot for load insertion or release depending upon duty cycle type. The dynamic droop network adjusts the droop signal to optimize utilization of an AC delay parameter while transitioning between an AC offset voltage allowance and the predetermined DC load line.

Abstract: Disclosed herein are a circuit of outputting a temperature compensation power voltage from variable power and a method thereof, the circuit including: a regulator circuit unit converting the variable power into a predetermined voltage desired by a system; a resistance compensation circuit unit provided at an output terminal of the regulator circuit unit, and compensating for a change in resistance value due to the temperature change; and a temperature sensor sensing a change in surrounding temperature of an electronic circuit system employing the regulator circuit unit and supplying an output value corresponding to the sensed temperature change to the resistance compensation circuit unit, to thereby allow the resistance compensation circuit unit to compensate for the change in resistance value due to the temperature change.

Abstract: A low side driver includes a first transistor coupled in series with a second transistor at a low side voltage node for a load. A capacitance is configured to store a voltage and a voltage buffer circuit has an input coupled to receive the voltage stored by the capacitance and an output coupled to drive a control node of the second transistor with the stored voltage. A current source supplies current through a switch to the capacitance and the input of the voltage buffer circuit. The switch is configured to be actuated by an oscillating enable signal so as to cyclically source current from the current source to the capacitance and cause a stepped increase in the stored voltage which is applied by the buffer circuit to the control node of the second transistor.

Abstract: This document discusses, among other things, apparatus and methods configured to accurately identify accessories coupled to mobile electronic devices over a wide range of temperature, In an example, an apparatus can include a reference voltage generator configured to provide a reference voltage, a comparator configured to compare the reference voltage to a voltage across an accessory-resistor, a current supply configured to be coupled to the accessory resistor and to provide the voltage to the comparator using the accessory resistor. The current supply can include a first sense resistor having a first temperature dependency and a second sense resistor having a second temperature dependency. In an example, the second temperature dependency can be configured to compensate for at least a portion of the first temperature dependency. In an example, at least one of the first or second temperature dependencies can be configured to control a temperature dependency of the apparatus.

Abstract: A start-up circuit for activating a bandgap voltage generation circuit is disclosed. The bandgap voltage generation circuit includes a bandgap input end, a first bandgap output end and a second bandgap output end. The start-up circuit includes a comparator having a first input end coupled to the first bandgap output end, a second input end coupled to the second bandgap output end, and an output end for outputting an output voltage, a first transistor including a gate coupled to the bandgap input end, a first source/drain coupled to a first system voltage, where a voltage of the gate is generated according to the output voltage, and a first resistor having an end coupled to a second source/drain of the first transistor, another end coupled to a second system voltage.

Abstract: In a power converter, a reference signal generator generates a reference signal with a predetermined period. A current detector detects a current flowing in the converter. When a value of the detected current is larger than a value of a predetermined current command, a reset signal generator generates a reset signal. A driving unit drives a switch. The switch is turned on, and subsequently is turned off: (i) in synchronization with the reference signal when the reset signal is not outputted before the reference signal is outputted; and (ii) in synchronization with the reset signal when the reset signal is outputted before the reference signal is outputted. However, the switch is turned off in synchronization with the reset signal during a predetermined time including a first predetermined time before an output timing of the reference signal and a second predetermined time after the output timing of the reference signal.

Abstract: An exemplary discharge test circuit for testing whether there is current on a circuit board includes a comparison module, a switch module, a control module and a display module. The comparison module receives a first direct current (DC) voltage from the circuit board, compares the first DC voltage with a reference voltage, and outputs a switch signal according to a result of the comparison. The switch module receives the switch signal, and output a control signal accordingly. The control module receives the control signal, determines a status of the circuit board according to the control signal, and outputs a display signal corresponding to the status of the circuit board. The display module receives the display signal, and displays whether there is current on the circuit board according to the display signal.