Abstract: In one implementation, a circuit includes: a comparator; a shift register chain coupled to the comparator; and one or more converters coupled to respective shift registers of the shift register chain, wherein the one or more converters are configured to convert a source of current from a first voltage to a second voltage, and wherein the circuit is configured to selectively transmit an output signal to the one or more converters. In one implementation, the circuit is configured to selectively control modulation for the one or more converters.

Abstract: An N-phase power converter has N phases with outputs connected in parallel and outputs connected in parallel. The converter comprises: N switch units, wherein each phase of the N-phase power converter comprises one of the N switch units; and an integrated inductor unit, comprising M inductor subunits, wherein M is a natural number greater than or equal to 2, each inductor subunit comprises i inductors, i is a natural number greater than or equal to 2, N>M×i or N=M×i, M×i of the inductors in the integrated inductor unit are respectively coupled to M×i of the N switch units, wherein: the i inductors of each of the inductor subunit are inverse-coupled to each other, the coupling coefficient between the M inductor subunits is less than the coupling coefficient between the i inductors in each of the inductor subunits.

Abstract: A system comprising resistive circuit legs coupled with and disposed between (a) a converter that converts electric current for a motor of a powered system and (b) a source of electric current for powering the motor, each of the circuit legs including a braking resistor coupled with the converter, a contactor coupled with the braking resistor such that the braking resistor is between the converter and the contactor, and a semiconductor switch coupled with the contactor such that the contactor is between the semiconductor switch and the braking resistor, where, during a regenerative braking mode of operation of the powered system, the regenerated energy from the motor is conducted to the braking resistor and dissipated as heat.

Abstract: According to some embodiments, a power converter is disclosed. The power converter includes an input electromagnetic interference filter to receive raw AC power and to output filtered AC power. A type-pi filter, and switch, receives the filtered AC power, further filters the received filtered AC power, and receives an indication from a digital controller module that an amplitude, frequency, and phase information of the filtered AC voltage is within a range of acceptable values and outputs the further filtered AC Power. The power conversion circuit receives a signal from the digital controller, receives the further filtered AC power from the type-pi filter and switch, converts the further filtered AC power to a desired voltage and outputs converted AC power. An output electromagnetic interference filter receives the converted AC power from the output electromagnetic interference filter and outputs the filtered converted AC power.

Abstract: A magnetic field sensor includes a magnetic field sensing element to generate a magnetic field signal indicative of a sensed magnetic field, a modulator to modulate the magnetic field signal at a chopping frequency, a front end amplifier coupled to receive the magnetic field signal and generate an amplified signal, and a demodulator configured to demodulate the amplified signal at the chopping frequency. The sensor further includes a low pass filter to process the amplified signal and generate a low pass filtered signal and a Schmitt trigger circuit. The Schmitt trigger circuit includes a comparator having a first input coupled to receive the low pass filtered signal, a second input coupled to receive a reference signal, and an output at which a comparator output signal is provided. The comparator is configured to perform a plurality of comparisons within a chopping time period that is the inverse of the chopping frequency.

Abstract: The invention concerns an electrical vehicle charging station for at least one electric vehicle in a network including at least a house, energy producers, and energy consumers.

Abstract: Embodiments for linking separate eFuse and ORING controllers for output overvoltage protection in power conversion applications. Voltage regulators are configured in parallel. An input circuit includes an input controller, the input circuit being coupled to an input of at least one voltage regulator of the voltage regulators. An output circuit includes an output controller, the output circuit being coupled to an output of the at least one voltage regulator. The output controller is coupled to the input circuit to cause the input circuit to prevent power to the at least one voltage regulator in response to the output controller detecting an overvoltage condition.

Abstract: The present invention relates to a bi-directional power converter (100) for converting an input voltage into an output voltage. The bi-directional power converter (100) may comprise a primary switching unit having a primary switching frequency and a secondary switching unit having a secondary switching frequency: the primary switching frequency being lower than the secondary switching frequency.

Abstract: A multi-port charging system includes a controller having a power input terminal coupled to a DC power output of a converter, multiple power output terminals coupled to the power input terminal, and a communications input terminal. The system includes multiple charger ports, the respective charger ports having a charging power line coupled to a respective one of the power output terminals, and a communications line coupled to the communications input terminal. The controller is configured to control the state of the control output terminal to set a voltage of the DC power output according to a selected highest common compatible voltage of one or more sink devices coupled to one or more respective ones of the charger ports.

Abstract: Various embodiments provide a voltage regulator circuit including two or more discontinuous conduction mode (DCM) phases coupled to an output node and coupled in parallel with one another. A control circuit may detect a trigger and switch all of the two or more DCM phases to a first state (charge state) responsive to the detection. The control circuit may switch a first DCM phase, of the two or more DCM phases, to a second state (discharge state) after a first predetermined time period in the first state and may switch a second DCM phase, of the two or more DCM phases, to the second state after a second predetermined time period in the first state, wherein the second predetermined time period is different than the first predetermined time period. Other embodiments may be described and claimed.

Abstract: An on-board charging apparatus is provided to implement high-power charging. The on-board charging apparatus includes an alternating current (AC) to direct current (DC) conversion circuit (AC/DC conversion circuit), a power factor correction (PFC) circuit, and a DC/DC conversion circuit. An alternating current terminal of the AC/DC conversion circuit is connected to an alternating current terminal of the PFC circuit. The AC/DC conversion circuit is configured to: receive a first alternating current voltage at the alternating current terminal of the AC/DC conversion circuit, and convert a first component of the first alternating current voltage into a first direct current voltage. The PFC circuit is configured to: convert a second component of the first alternating current voltage into a second direct current voltage. The DC/DC conversion circuit is configured to: convert the first direct current voltage and the second direct current voltage into a third direct current voltage.

Abstract: The invention relates to an LLC stage for an LED driver (100), comprising a half bridge or full-bridge circuit (100a) comprising two switches (M40, M41), connected in series, a control circuitry (100e), such as e.g. a microcontroller or ASIC, for controlling switching operations of the switches (M40, M41), wherein the control circuitry (100e) for switches is arranged to monitor the middle point voltage between the two switches (M40, M41) and enables the switch on of one of the switches (M40, M41) only if the middle point voltage meets defined criteria. The control circuitry (100e) is designed to issue an error signal, if a dead time, during which both switches are non-conducting and resulting from the monitoring of the midpoint voltage, is greater than a preset threshold value.

Abstract: The present disclosure aims to avoid a situation where a drive unit to be used for precharge does not drive due to a drop in power supply voltage. The power supply device is provided with the first voltage conversion unit and the control unit. The first voltage conversion unit performs a third voltage conversion operation in which a voltage applied to a second conductive path is boosted and an output voltage is output to a first conductive path to which a capacitive component is electrically connected. The control unit supplies the third control signal to only some of the plurality of first voltage conversion units, thereby causing the some of the first voltage conversion units to perform the third voltage conversion operation.

Abstract: A power system includes first and second power supplies, and a control circuit. The control circuit is configured to control the first power supply to regulate its output voltage at a first value, enable the second power supply, increase the output voltage of the first power supply to a second value in response to the second power supply being enabled, increase an output voltage of the second power supply to a third value, and decrease an output current of the first power supply and increase an output current of the second power supply to transition between electrically powering the load with the first power supply and electrically powering the load with the second power supply. Other example power system and methods for controlling a power transition between power supplies are also disclosed.

Abstract: A drum washing machine, and a control method and a control apparatus for same are provided. The control method for the drum washing machine comprises the following steps: acquiring an average starting power of a drum in a starting process of the drum; acquiring a load range to which a current load of the drum belongs according to the average starting power; and setting a weighing protection velocity fluctuation threshold according to the load range to which the current load of the drum belongs. A value of the current load is obtained by using a correspondence between load with different weights and average starting powers. A weighing protection velocity fluctuation threshold is set according to the value of the current load to avoid the collision with the drum and non-dehydration in case of only one piece of clothing.

Abstract: A conversion apparatus with a three-level switching circuit includes a DC conversion module, a three-level circuit, and a control unit. The three-level circuit includes a bridge arm assembly and a capacitor assembly. The capacitor assembly includes a first capacitor and a second capacitor connected to the first capacitor in series. The DC conversion module has a positive output end and a negative output end, and the positive output end and the negative output end are coupled to the bridge arm assembly. The control unit controls the switching of a second switch unit and a third switch unit to make the three-level circuit operate in a first state where the positive output end and the negative output end are connected to the first capacitor, and operate in a second state where the positive output end and the negative output end are connected to the second capacitor.

Abstract: Aspects of the invention overcome a monolithic approach to conventional low-frequency LPTs by using a high-frequency solid-state alternating current ac/ac modular power-conversion approach. Embodiments of the invention enable the ability to incorporate new technologies without in all cases redoing a LPT design from scratch. Furthermore, given that LPTs are for the long term, aspects of the invention ensure that they are durable, efficient, and fault tolerant with overloading capability.

Abstract: One aspect of the present disclosure is a power-supply apparatus to supply an electric power to an electric working machine including a trigger switch, a motor, and a tool. The power-supply apparatus includes a connection detector, a trigger detector, and a signal outputter. In response to (i) the connection detector detecting connection of the electric working machine to the power-supply apparatus, and also to (ii) the trigger detector detecting an ON state of the trigger switch, the signal outputter outputs, to the electric working machine, a discharge prohibition signal prohibiting supply of the electric power to the motor, until an OFF state of the trigger switch is detected once by the trigger detector.

Abstract: A switching mode power supply preventing a first switch from being falsely triggered. The switching mode power supply detects a peak of an input signal and starts timing a period of time since the arrival of the peak of the input signal is detected. The first switch starts performing the on and off switching operations when the period of time expires.

Abstract: A multi-phase signal control circuit includes: a comparator, configured to compare a triangular wave signal with a feedback control signal to output a first pulse width modulation signal, where the feedback control signal is a signal fed back by the power stage circuit; a phase switch circuit, configured to receive a phase switch signal and the first pulse width modulation signal to generate a first phase signal and a second phase signal, where the first phase signal and the second phase signal are used to control the power stage circuit to generate an output voltage signal.

Abstract: Induction cooker having an induction coil, a supporting structure, a ferromagnetic element and a non-ferromagnetic element. The induction coil is arranged to receive a varying electric current and produce a corresponding varying electromagnetic field. The supporting structure is arranged to support a ferromagnetic object above the induction coil, the ferromagnetic object being placed in the corresponding varying electromagnetic field to be magnetically coupled to the induction coil, thereby determining a mutual inductance between the induction coil and the ferromagnetic object. The ferromagnetic element and the non-ferromagnetic element are arranged to be located between the supporting structure and the induction coil and selectively move in the corresponding varying electromagnetic field based on a mutual inductance between the induction coil and the ferromagnetic object.

Abstract: An injection control device controls fuel injection to an internal-combustion engine by driving a fuel injection valve with an electric current to open and close the valve. The injection control device includes a boost circuit boosting a battery voltage; a boost controller controlling the boosting of the boost circuit; and a charge control setter setting charge permission or charge prohibition of the boost circuit to the boost controller. The charge control setter sets the charge permission or charge prohibition of the boost circuit to the boost controller according to a magnitude of an influence of a drive current error.

Abstract: A zero-crossing detection circuit coupled to a power factor correction (PFC) controller of a power supply system includes a zener diode configured to generate a zener reference signal, and an operational amplifier coupled to the zener diode and configured to receive the zener reference signal and a feedback signal corresponding to an output current of the power supply system, and to generate a zero-crossing signal to a zero-crossing input of the PFC controller.

Abstract: According to one embodiment, the X-ray high voltage apparatus includes a plurality of converters and control circuitry. The plurality of converters converts AC power to DC power. Each converter includes choke coils and three-phase rectifier circuits. Each choke coil has a main winding and is provided on each phase line of three-phase AC power supply lines. Each three-phase rectifier circuit includes a switching device. The control circuitry is configured to interleave the plurality of converters. Each choke coil of the each converter has the single main winding and two correction windings of a first correction winding and a second correction winding. Each of currents flowing through the respective two correction windings is a sum of currents flowing through the plurality of converters performing interleaving operation, and flows so as to cancel a magnetic flux generated in the main winding.

Abstract: A power converter is capable to convert an electrical input power into a bipolar output power and to deliver the bipolar output power to at least two independent plasma processing chambers. The power converter includes a power input port for connection to an electrical power delivering grid, at least two power output ports each for connection to one of the plasma processing chambers, and a controller configured to control the power converter to deliver the bipolar output power to the power output ports, using at least one of control parameters including power, voltage, current, excitation frequency, and threshold for protective measures. The controller includes a virtual power supply for each power output port, and each virtual power supply includes a separate complete set of all fixed and time varying parameters and internal states associated with the operation of the individual power output port.

Abstract: Disclosed are a Darlington transistor drive circuit, a Darlington transistor drive method implemented based on such Darlington transistor drive circuit, and a constant current switching power supply including such Darlington transistor drive circuit. The Darlington transistor drive circuit includes a drive current circuit, two switch units, and a drive control circuit used for controlling the two switch units to be switched off during the switching-on cycle of the Darlington transistor and to be switched on during a switching-off cycle of the Darlington transistor, and for changing an equivalent resistance of the two switch units at different stages during the switching- off cycle of the Darlington transistor. The switching-off time delay of the Darlington transistor is greatly reduced while achieving the EMI optimization. In additional, the switch loss of Darlington transistor is small when it is switched off, and the efficiency is improved.

Abstract: The present application includes an uninterruptable power supply device for connection of a 3-wire multiphase AC source to a 3-wire multiphase load, whereby the UPS device is provided for multiphase operation, including a converter part, which is connected to at least one power source and the load, and a 3-wire bypass, which interconnects the AC source to the load, whereby the bypass includes a bypass switch, which includes an independently controlled switching unit for each phase of the AC source, and the UPS device includes a control unit, which controls the converter part and the bypass switch, whereby the control unit controls the bypass switch to power one of the three phases of the load directly via the bypass by one phase of the AC source, and the control unit controls the converter part to power the remaining two phases of the load.

Abstract: The present disclosure provides a forward converter with secondary LCD connected in parallel to realize forward and backward energy transmission, comprising a forward converter main circuit and an energy transfer and transmission circuit. The forward converter main circuit includes a high-frequency transformer T, a switching tube S, a diode D1, a diode D2, an inductance L1, and a capacitor C1. The energy transfer and transmission circuit includes a diode D3, a capacitor C2 and an inductance L2.

Abstract: An apparatus, such as an adjustable frequency drive (AFD), includes an inverter configured to be selectively coupled to a motor in a first mode and an AC line in a second mode and a control circuit configured to operate the inverter as a motor drive in the first mode and as a power compensator in the second mode. The power compensator may provide power factor correction. The control circuit may include a scalar controller configured to control the inverter according to a voltage vs. frequency characteristic determined by a field weakening point reference and the control circuit may vary the field weakening point reference in the second mode. The inverter may have an input coupled to a DC bus and the control circuit may be configured to adjust a frequency of the inverter in the second mode to increase a voltage on the DC bus.

Abstract: A multi-mode uninterruptible power supply (UPS) is provided. The multi-mode UPS includes a first path including a rectifier and an inverter, and a second path in parallel with the first path, wherein the multi-mode UPS is operable in an economy mode in which power flows from a utility to a load through the second path while at least one of the rectifier and the inverter is activated, the at least one of the rectifier and the inverter operable to perform at least one of DC voltage regulation, reactive power compensation, and active damping.

Abstract: A galvanically connected AC charger is provided having a monitoring and diagnostic system for the AC charging of an electric, fuel cell or hybrid vehicle.

Abstract: This disclosure describes vehicle systems and methods for controlling charging of an auxiliary battery of an electrified vehicle. Exemplary charging methods align the charge management of an auxiliary battery to occur only during low cost charging windows.

Abstract: A Direct Current (DC) chopper may be integrated into the Modular Multilevel Converter (MMC) cells of a power converter. The integrated DC chopper may include chopper resistors that may also be advantageously integrated into a heat sink for a power module including at least the power transistors of the MMC cell. The safe discharge of both cell capacitors and DC-link capacitors in different operating conditions is performed using Insulated-Gate Bipolar Transistors (IGBTs) and chopper resistors of an MMC cell.

Abstract: The switching power supply is provided with a voltage converter including a switching element for inputting a voltage from an input terminal, and has a spread spectrum function of varying a switching frequency in the switching element within a predetermined variation range. The switching power supply has a frequency setting unit that sets the variation range of the switching frequency and raises a lower limit value of the set variation range when a value of the voltage input from the input terminal is equal to or more than a predetermined threshold, and a signal generator that generates a control signal for driving the switching element by varying the switching frequency within the variation range set by the frequency setting unit.

Abstract: A power converting apparatus includes: a first arm including a switching element and a switching element connected in series; a second arm including a switching element and a switching element connected in series, the second arm being connected in parallel with the first arm; a reactor having one end connected to the switching element and the switching element and an opposite end connected to an alternating-current power supply; and a smoothing capacitor connected in parallel with the first arm and the second arm. The loss characteristic of the switching element and the second switching element that occurs in each switching event is better than the loss characteristic of the switching element and the switching element that occurs in each switching event.

Abstract: An in-vehicle DC-DC converter includes a gain setting unit that sets a gain to be used for feedback computation, a duty ratio determination unit that determines a duty ratio, and a drive unit that outputs, to a switching element, a PWM signal that is based on the duty ratio to be used determined by the duty ratio determination unit. The duty ratio determination unit includes a computation unit that repeatedly performs feedback computation for calculating a duty ratio of a PWM signal, so as to approximate a voltage value of an output-side conductive path to a target voltage value, based on a voltage value detected by the voltage detection unit and the gain to be used set by the gain setting unit. The gain setting unit sets the gain to be used, based on a voltage value detected by the voltage detection unit.

Abstract: A boost converter includes a first inductor, a power switch element, an output stage circuit, a controller, a resonant circuit, and a discharging circuit. The first inductor receives an input voltage. The power switch element includes a parasitic capacitor. The output stage circuit includes a first resistor. The output stage circuit generates an output voltage. The controller detects the resistive voltage of the first resistor, and generates a clock voltage, a first control voltage, and a second control voltage according to the resistive voltage. The resonant circuit is coupled to the first inductor, and is selectively enabled or disabled according to the first control voltage. When the resonant circuit is enabled, the resonant circuit resonates with the first inductor and the parasitic capacitor, so as to fine-tune an inductive current flowing through the first inductor.

Abstract: A power electronic converter can utilize exemplary double synchronous unified virtual oscillator control (DSUVOC) logic or circuitry to convert direct current to alternating current that is input into a power grid. An exemplary DSUVOC controller of the present disclosure includes a double synchronous space vector oscillator component, a sequence extraction component, a fault detection component, a pre-synchronization component, a virtual impedance component, a terminal voltage compensation component, and/or an active damping component, wherein the double synchronous unified virtual oscillator controller is capable of controlling a grid following or a grid forming power electronic converter enabling synchronization and fault ride-through under both balanced and unbalanced conditions.

Abstract: A smart circuit breaker is configured for installation within a panel assembly. The smart circuit breaker includes a breaker device positioned between a power source and a subcircuit, the breaker device having a moveable contactor configured to change from an open state to a closed state, wherein in the closed state power flows from the power source to the subcircuit via a power line, and wherein in the open state power does not flow from the power source to the subcircuit. The smart circuit breaker further includes a power meter configured to measure a power characteristic of the subcircuit. The smart circuit breaker further includes a processing circuit configured to receive a power characteristic measurement from the power meter, the processing circuit having a communications interface configured to communicate power consumption data to an external device, the power consumption data based on the power characteristic.

Abstract: A power conversion system includes a first and a second energy storage element, a first boost circuit, a switching element, a control circuit and a detection circuit. The first boost circuit is coupled between the first and the second energy storage element. The switching element is coupled to the first boost circuit in parallel. When the first voltage value is lower than a first preset level, the control circuit turns off the switching element and drives the first booster circuit to maintain a second voltage value according to the first voltage value, so that the power conversion system operates in a first state. When the first voltage value is equal to or larger than the first preset level, the control circuit turns on the switching element and turns off the first boost circuit, so that the power conversion system operates in a second state.

Abstract: A step-up switching power supply circuit executes a step-up operation for stepping up an input voltage supplied through an input terminal. The step-up switching power supply circuit includes: an inductor; a switching element enlarging a current flowing through the inductor when the switching element is turned on; a step-up control circuit controlling the switching element to execute the step-up operation; a fault detection control circuit controlling the switching element to detect a fault of the switching element; a current detection unit detecting a current flowing through the switching element; and a switching unit executing switchover between the step-up control circuit and the fault detection control circuit to control the driving the switching element, Prior to execution of the step-up operation, the switching unit switches the fault detection control circuit to control the switching element.

Abstract: A semiconductor device includes an amplifier that has an output terminal and that outputs via the output terminal a signal commensurate with an input signal fed to the amplifier, a signal conductor that is connected to the output terminal and that conducts a target voltage signal based on the output signal of the amplifier, a shield conductor that is laid along the signal conductor, and a shield drive circuit that controls the voltage on the shield conductor based on the target voltage signal.

Abstract: A switching circuit is connected to an output side of a DC power supply, includes a low-side switch circuit and a high-side switch circuit, and generates high frequency power by switching of the low-side switch circuit and the high-side switch circuit. Snubber circuits are connected between both ends of the low-side switch circuit and both ends of the high-side switch circuit. The snubber circuits include series circuits including inductors and capacitors, and include diodes that are connected in parallel with the inductors.

Abstract: An apparatus is provided for minimizing the peak power demand on an inverter in a power supply with one or more switched reactive loads comprising an AC semiconductor bypass switch connected in parallel with the inverter and a bypass control device. The bypass control device includes filters for selecting load current signals with specific frequencies of interest from the switched reactive loads; a signal processor for sampling and transforming the selected load current signals into frequency domain to identify frequency components of the selected load current signal; an amplitude detector for detecting peak current amplitudes of the identified frequency components of the selected load current signal; and a bypass driver.

Abstract: A power converter can be configured to convert an AC input voltage into a regulated DC output voltage while maintaining the input current in phase with the rectified AC input voltage. A control circuit of the power converter may be configured to selectively enable switching of at least one switching device of the power converter responsive to a determination that the input voltage is greater than a threshold voltage and to selectively disable switching of the at least one switching device responsive to a determination that the rectified AC input voltage is less than the threshold voltage. The control circuit may be configured to selectively enable and disable switching using an active burst mode signal having a frequency lower than a switching frequency of the converter. The control circuit may be still further configured to operate at least one switching device of the converter in a zero voltage switching condition.

Abstract: A power converter circuit included in a computer system may include an adiabatic charge pump which includes multiple capacitors different numbers of which are used to charge and discharge a switch node coupled to regulated power supply node via an inductor. A control circuit may control the dividing ratio of the charge pump circuit as well as determine respective durations of when the charge pump circuit is charging and discharging the switch node.

Abstract: A charging and discharging apparatus includes, in some implementations, an alternating current charging and discharging unit, a bidirectional alternating current/direct current conversion unit, a bidirectional direct current/direct current isolated conversion unit, and a first energy storage unit that are sequentially connected in series, and further including at least one switch unit, a direct current/direct current isolated conversion unit, and a second energy storage unit. A first end of each switch unit is connected to the bidirectional direct current/direct current isolated conversion unit, a second end of each switch unit is connected to a first end of the direct current/direct current isolated conversion unit, and a second end of the direct current/direct current isolated conversion unit is connected to the second energy storage unit.

Abstract: A sub-module based hybrid converter is provided. By setting a half-controlled charging link of changing full bridge sub-modules from a blocked state to a half-blocked state one by one in a charging process, and raising the voltages of half bridge sub-modules to reach the starting point of a half bridge sub-module based self-powered supply in an uncontrolled stage of the half bridge sub-modules, the starting point of the sub-module based self-powered supply is increased, and the design difficulty of the sub-module based self- powered supply is reduced. The present invention also includes another charging method for a sub-module based hybrid converter.

Abstract: In a method of compensating for a DC offset of a high-voltage AC output from a Modular Multilevel Converter (MMC) including at least one phase leg, the MMC is connected to a three-phase high-voltage AC grid via a grid transformer. The method includes, in at least one DC offset correcting device, measuring the DC offset by in each of the at least one DC offset correcting device: obtaining a high-voltage AC signal in the MMC, removing high-voltage AC components from the obtained high-voltage AC signal by means of a passive higher-order filter to obtained an analogue filtered signal, converting the analogue filtered signal to a digital signal by means of an analogue-to-digital converter, removing remaining AC components from the digital signal by means of a digital filter to obtain the DC offset, and in a controller comparing the obtained offset with a reference value and forming a control signal based on said comparing.

Abstract: A battery monitor control system has a load plate, two or more lead wires connected to two or more busbars in a string of batteries, and a digital signal processor. The load plate has one or more primary switches connected to two or more terminals of the batteries in the string of batteries. The load plate also has a load resistor and a current sensor. The primary switches are turned on and off to produce a ripple current in the string of batteries. The digital signal processor determines the real portion of the complex impedance of at least one of the batteries by analyzing the voltage and current waveform of the ripple current. The primary switches may be turned on and off with a sine wave modulation.