Abstract: A power-saving control device for operation of an electronic garbage can includes a rotation-blocked current setting register, a sampling resistor, an analog-digital converter, an analog-digital conversion result register, and a comparing unit, which are electrically connected in sequence. The comparing unit compares a current value obtained in real time with a reference current value in the rotation-blocked current setting register, and when the real-time current value is greater than the reference current value, the microcomputer control unit stops supplying power to a motor by controlling the motor positive and negative rotation driving circuit. The power-saving control device has greatly reduced power consumption during operation of an electronic garbage can and a prolonged service life of its battery.

Abstract: The invention relates to fluid drive systems used in fluid wells and brake systems for permanent magnet wellhead direct drives. The braking controller connects or disconnects a brake resistor from a back EMF. A variable frequency drive (VFD) drives the motor and communicates with the control circuitry of the brake controller. The control circuitry monitors the brake resistor and depending on the rotational speed and direction of the motor and operating state of the VFD, disconnects or connects the brake resistor. If the direction of the motor is in reverse and above a threshold speed, it connects the brake resistor. If the direction of the motor is in reverse and below the threshold speed, the control circuitry dissipates stored back EMF through the brake controller. The amount of stored back EMF corresponds to the time to empty a pump.

Abstract: A fan control system has a fan duct, a fan mounted in the duct, an electronic commutator (EC) motor for driving the fan, and a control system hub for controlling the EC motor. A pressure differential sensing system is mounted in association with duct and feeding a pressure differential signal to the control system hub. An input device mounted on the control system hub for scaling an output signal from a low percent extreme to a high percent extreme and sends that output signal to the EC motor. Wherein the control system hub speeds, slows or switches OFF the EC motor according to the pressure differential signal except that the input device sets a speed limit ceiling on the EC motor.

Abstract: A sensorless electric motor control device is provided that completes a phase detection of a rotor before an activation signal is received, so as to shorten a time period from when the activation signal is received to when the rotor reaches a target number of rotations. The control device for a sensorless electric motor 10 includes an inverter 11 that drives the electric motor 10 and a first processor 18 that serves as a phase detection unit that causes the inverter 11 to perform a phase detection before the inverter 11 receives an activation signal that activates the electric motor 10, wherein the phase detection aligns a magnetic pole of a rotor of the electric motor 10 with a predetermined position with respect to a stator.

Abstract: Disclosed is an electric-bicycle driving apparatus.

Abstract: Provided is an apparatus for compensating offset of a current sensor detecting a motor current supplied by an inverter for PWM (Pulse Width Modulation) control of a motor, the apparatus including a current controller providing a PWM signal generated based on the motor current detected by the current sensor to the inverter, calculating an offset using the motor current detected by the current sensor in response to presence and absence of the PWM control of the motor, or offset-compensating the motor current detected by the current sensor.

Abstract: A method for controlling a motor is provided. The method comprises obtaining electrical signals of the motor with a signal unit, the electrical signals comprising a motor torque and an angular velocity, calculating a voltage phase angle of a voltage vector with a calculating component, wherein a command torque, the motor torque, the angular velocity and a voltage amplitude of the voltage vector are inputs of the calculating component, and wherein the voltage phase angle is a variable and the voltage amplitude is a constant. The method further comprises modulating the voltage phase angle and the voltage amplitude to a switching signal for controlling an inverter; converting a direct current voltage to the voltage vector according to the switching signal, and applying the voltage vector to the motor.

Abstract: A rotation speed control circuit is disclosed. The rotation speed control circuit includes a temperature-controlled voltage duty generator, a pulse-width signal duty generator, a multiplier and a rotation speed signal generator. The temperature-controlled voltage duty generator converts temperature-controlled voltage to digital temperature-controlled voltage and executes linear interpolation operation according to a first setting data so as to output temperature-controlled voltage duty signal. The pulse-width signal duty generator coverts pulse-width input signal to a digital pulse-width input signal and executes linear interpolation operation according to a second setting data so as to output a pulse-width duty signal. The temperature-controlled voltage duty signal and the pulse-width duty signal are executed for multiplication by the multiplier so as to output mixing-duty signal.

Abstract: Embodiments of the present method and system permit an effective method for determining the optimum selection of pulse width modulation polarity and type including determining machine parameters, inputting the machine parameters into a predicted duty cycle module, determining the optimum polarity of the pulse width modulation for a predicted duty cycle based on a pulse width modulation generation algorithm, and determining the optimum type of the pulse width modulation for a predicted duty cycle based on the pulse width modulation generation algorithm.

Abstract: A motor driving apparatus is provided that performs AC/DC conversion by suppressing harmonics of the input at the time of normal operation, while on the other hand, allowing system operation to continue in the event of an overload by avoiding system stoppage.

Abstract: An electronically commutated motor (ECM) includes windings, a power switch, an infrared transceiver and an electromagnetic shield. The power switch is configured to provide pulse width modulated (PWM) power signals to the windings and to generate a substantial level of electromagnetic noises at PWM frequencies during its switching operation. The infrared transceiver is configured to communicate with an external device using infrared signals and convert electrical signals from and to infrared signals that carry data. The electromagnetic shield is configured to substantially shield the infrared transceiver from the electromagnetic noises of PWM frequencies from the power switch.

Abstract: A duty ratio control device includes a duty ratio calculation unit and a parameter setting unit. The duty ratio calculation unit, when an acceleration manipulation is performed, calculates a control duty ratio per predetermined timing based on a value of at least one parameter so that a rotation speed of a motor mounted on an electric power tool reaches a target rotation speed corresponding to the acceleration manipulation. The control duty ratio is calculated to be larger as the value of the at least one parameter is larger. The parameter setting unit sets the value of the at least one parameter. The value of the at least one parameter set for a reacceleration manipulation is larger than the value of the at least one parameter set for an initial acceleration manipulation.

Abstract: When applying a high frequency voltage which alternates on positive and negative sides to a permanent magnet synchronous motor, a driving system of synchronous motor switches the applied voltage phase by 120 degrees successively and applies resultant voltages to three phases. A pulsating current generated by applying a high frequency voltage is detected at timing of elapse of a predetermined time ?t since an output voltage of at least one phase has changed from a state in which all output voltages of the three phases of a power converter are positive or negative. Current detection is conducted by using a DC resistor or a phase current sensor provided on a DC bus. A magnetic pole estimation unit calculates the rotor magnetic pole position of the permanent magnet synchronous motor on the basis of differences between positive side and negative side change quantities in three-phase currents obtained from detected current values.

Abstract: A dynamoelectric machine assembly for connection to a system controller. The assembly includes at least one input contact for receiving a control signal from the system controller and a processor coupled to the input contact. The processor is configured to operate the assembly in a pulse width modulation (PWM) mode when the control signal is a PWM control signal and to operate the assembly in a serial mode when the control signal is a serial communication signal.

Abstract: A control circuit is electrically connected to at least one fan device. The fan device has a motor and generates a sensing signal. The control circuit receives a power-source signal and the sensing signal and includes a power converting unit, a control unit and a switch unit. The power converting unit receives the power-source signal and thus respectively outputs a first power-source signal and a second power-source signal according to the power-source signal. The control unit receives the first power-source signal and the sensing signal and thus generates a control signal according to the sensing signal. The switch unit receives the control signal and generates at least one switch signal according to the control signal. The fan device receives the second power-source signal and the switch signal and drives the motor according to the switch signal.

Abstract: Embodiments of the invention comprise a multi-input range box driven by multiple electric drives. Range shifting involves momentarily increasing the current through all but a given motor, to a level that will carry the entire load, comprising specified constant power. Simultaneously, torque of the given motor is reduced to zero. The given motor is then disconnected from supplying power, is synchronized to the input speed of the new speed range, and is then engaged for the new range. The above sequence is then repeated for each remaining motors, in turn. The motor current is re-equalized for all of the motors, after all the motors have been connected to provide power at the new range. Thus, there is no interruption in power flow during a range shift, and the motors are always used to deliver power, rather than to serve as a brake.

Abstract: Embodiments of the present method and system permit an effective method for determining the optimum selection of pulse width modulation polarity and type including determining machine parameters, inputting the machine parameters into a predicted duty cycle module, determining the optimum polarity of the pulse width modulation for a predicted duty cycle based on a pulse width modulation generation algorithm, and determining the optimum type of the pulse width modulation for a predicted duty cycle based on the pulse width modulation generation algorithm.

Abstract: A method for controlling an electric motor by using the PWM technique including the steps of: applying to the clamps of the electric motor an electric voltage varying in time, which displays a square waveform and consists of a sequence of pulses having a uniform wave period and a variable width; adjusting the average value of the electric voltage by varying the width of the pulses; determining the overall required width variation; subdividing the overall required width variation in a determined number of partial variations, the overall sum of which is equivalent to the overall required width variation; and gradually varying the width amplitude of the pulses of the electric voltage by applying in a sequence a corresponding partial variation to each pulse, so that the difference between the width amplitude of a pulse and the width of a following pulse is equivalent to the corresponding partial variation.

Abstract: A battery-charging device, having a maximum power point tracking (MPPT) function, for a stand-alone generator system includes a DC/DC power converter and a control circuit used to control the DC/DC power converter.

Abstract: Methods and apparatus are provided for sensing currents on a plurality of phases and determining current information therefrom. The multi-phase boost converter includes a single sensor coupled to all of the plurality of phases and a controller coupled to the sensor for determining the current information in response to currents on each of the plurality of phases sensed by the sensor. The sensing method utilizes the gate drive signals and the DC current sensor output to calculate the currents on each of the plurality of phases sensed by the sensor.

Abstract: A system compatible for different types of signals relates to a motor includes a differential amplifier, a comparator, and a transmitting device. The differential amplifier is configured to receive one of a differential digital pulse signals pair and a differential analog signals pair. The differential digital pulse signals pair is converted to a first digital signal, and the differential analog signals pair is converted to an analog signal by the differential amplifier. The comparator is configured to convert the analog signal into a second digital signal. The first digital signal is received and outputted by the comparator. The transmitting device is configured to convert a data signals pair to a binary code, and convert differential reference digital signals pairs to reference digital signals. The reference digital signals, the first and second digital signals are received by an external computing device.

Abstract: A driving apparatus for fan motors, electrically connected between a pulse width modulation (PWM) signal generator and a controller, includes a converter electrically connected to the PWM signal generator, generating a first reference voltage according to the duty cycle of a PWM signal generated by the PWM signal generator; a reference voltage generator electrically connected to an external power source, generating a second reference voltage according to the external power source; and a comparator having a first and second input terminal and an output terminal; wherein the first input terminal is electrically connected to the converter, the second input terminal is connected to the reference voltage generator and the output terminal is connected to the controller, and when the first reference voltage is greater than the second reference voltage, a driving signal is output from the output terminal to the controller to control the rotation speed of the fan motor.

Abstract: The present invention is aimed at provision of a control apparatus for and a control method of controlling a motor for a vehicle driven by a driving circuit that operates according to a pulse width modulation (PWM) signal. Measurement of a duty of an output signal from the driving circuit is executed, and a difference between the measured duty and a target duty in a PWM control is then obtained to further execute setting of a correction value for correcting the target duty based on the above difference and to generate the PWM signal based on the corrected target duty.

Abstract: A control apparatus for a three-phase brushless motor, in which a control circuit includes time interval calculation means (133 in FIG. 4). The time interval calculation means (133) is endowed with at least one time interval calculation mode. In the time interval calculation mode, pluralities of time intervals which correspond to an addition section obtained by adding up two or more Q continuous sections are calculated on the basis of two position detection signals which lie at both the ends of the addition section, among position detection signals successively generated. The control circuit determines pluralities of energization switching timings on the basis of the pluralities of time intervals. The control apparatus for the three-phase brushless motor can decrease the deviations of the energization switching timings attributed to the errors of the mounting positions of position sensors or to the errors of the magnetized positions of a rotor, without requiring any complicated adjustment.

Abstract: A circuit for controlling rotation speed of a computer fan includes a fan header for connecting to a 4-pin fan or a 3-pin fan, a jumper device, an amplifier, and a controller. The jumper device has a first pin for receiving a controlling signal, and connected to a first power source, a second pin connected to the fan header, and a third pin connected to the first power source. The amplifier has an input terminal connected to the third pin of the jumper device via an integrator. The controller has a first terminal connected to an output terminal of the amplifier, a second terminal connected to a second power source, and a third terminal connected to the fan header and connected to a positive input terminal of the amplifier via a resistor. The first pin of the jumper device is selectively connected to the second or third pin.

Abstract: A linear portable actuator including a direct current electric motor (2) rotationally driving a screw with the aid of a reduction element, wherein the motor (2) is controlled by an electronic module (5) comprising means (12) for the acquisition of instantaneous intensity of a supply current for the motor. Further, the electronic module (5) also comprises means (13) for calculating the differential coefficient in relation to supply-current intensity time, which are connected to means (14) for comparing the differential coefficient to a first predetermined value, and a comparing means controlling means (15) for switching off the supply current it the differential coefficient is greater than the first predetermined value.

Abstract: A motor control strategy for a motor in a front steering system for a vehicle that reduces vibrations from the motor being transferred to a vehicle hand-wheel. The control strategy also includes operating the electric motor in a commutation freeze mode if a position error signal is less than a first predetermined threshold by sending signals to coils of the motor to prevent to the motor from rotating, operating the electric motor in a commutation normal mode if the position error signal is greater than a second predetermined threshold that is greater than the first predetermined threshold, and operating the electric motor in an angle step mode if the position error signal is between an intermediate threshold and the second threshold where the angle step mode provides a signal to the motor to move the motor forward or backward a predetermined number of motor steps, one step at a time.

Abstract: An exemplary device for controlling rotation speed of a computer fan includes an identifying device and a control circuit. The identifying device is configured for identifying the type of the computer fan. The control circuit configured for controlling rotation speed of the computer fan includes an electric switch, an integrated circuit, a first output terminal, and a second output terminal. The electric switch has a first terminal coupled to the identifying device to receive an identifying signal, a second terminal coupled to a super I/O chip to receive a PWM signal. The integrated circuit is configured to convert the PWM signal to an analog voltage signal. The first output terminal is configured to output the PWM signal to a PWM control pin of a fan header. The second output terminal is configured to output the analog voltage signal to a power pin of the fan header.

Abstract: The invention relates to a regulator circuit for controlling the power fed to an electric motor from a voltage source, wherein the regulator circuit comprises a semiconductor switching element connected in series to the electric motor and the voltage source for the purpose of controlling the power fed to the electric motor, a control circuit for controlling the semiconductor switching element, and a first operating element for operating the control circuit by means of an operating signal generated by the operating element and fed to the control circuit, wherein a microprocessor is incorporated in the control circuit. The microprocessor can be adapted to control numerous functions within the regulator circuit, in particular monitoring and safety functions. It is however also possible for the microprocessor to be adapted to control the power fed to the electric motor subject to the operating signal.

Abstract: A motor control module designed to control operation of a plurality of different motors in a plurality of different tools a power tool uses an electronic clutch in the module in conjunction with a mechanical clutch in the tool to protect the tool against an overload event. The module is adapted to implement methods to provide aural and/or tactile feedback to a tool user as a warning of an impending or current fault condition in the tool. The module can prevent power from inadvertently turning on either after an overload event has cleared with the tool plugged in and its power switch on, or after plugging in the tool within the power switch on. The control module is adapted to provide torque control for the power tool, to estimate tool motor temperature and to inform a tool user when a servicing need in the tool is required.

Abstract: A drive system for a multi-phase brushless motor comprises a single current sensor drive circuit, including switch means, switchable between a plurality of states. A controller is arranged to provide pulse width modulated drive signals to control the switch means so as to control the time that the drive circuit switches between said states in each of a series of pulse width modulation periods, and to: determine a demanded voltage parameter set, identify PWM periods during which the demanded voltage parameter set is such that neither two nominal corresponding state times, nor a higher number of equivalent state times producing the same net voltage, in a single PWM period, would allow a predetermined minimum time to be spent in a predetermined number of active states sufficient for current sensing.

Abstract: A delta type inverter is used in conjunction with a closed-loop motor controller to provide a control device for driving a three phase brushless direct current motor. The delta inverter has one-half of the solid state switching devices and diodes required by conventional bridge type inventers, thereby improved reliability, and enabling the motor control device to have reduced size, cost and weight. The closed-loop motor controller may include a torque loop for reducing torque ripple during operation of the motor.

Abstract: A fan motor is driven under a pulse width modulation (PWM) control. PWM signals to be supplied to a circuit for driving the fan motor are formed from carrier waves having a specified frequency and a duty ratio of the PWM control. Rotational speed of the fan motor is increased by increasing the duty ratio. In a low speed region, the fan motor is driven with a high carrier frequency to suppress driving noises of the fan motor, while it is driven with a low carrier frequency in a high speed region to reduce switching losses in semiconductor elements. The carrier frequency may be continuously decreased when the fan motor speed reaches the high speed region, or it may be stepwise decreased. The low carrier frequency used in the high speed region is set to such a frequency that guarantees a sufficient number of switching times at a maximum speed of the fan motor.

Abstract: A control circuit is electrically connected to at least one fan device. The fan device has a motor and generates a sensing signal. The control circuit receives a power-source signal and the sensing signal and includes a power converting unit, a control unit and a switch unit. The power converting unit receives the power-source signal and thus respectively outputs a first power-source signal and a second power-source signal according to the power-source signal. The control unit receives the first power-source signal and the sensing signal and thus generates a control signal according to the sensing signal. The switch unit receives the control signal and generates at least one switch signal according to the control signal. The fan device receives the second power-source signal and the switch signal and drives the motor according to the switch signal.

Abstract: A control circuit for a direct current motor is described. In accordance with the principles of the invention, a duty cycle comparator is provided to control the speed of the motor.

Abstract: An aspect of the invention is a method and a device for controlling a rotating field machine having several phase windings, which can be controlled by means of pulse width modulation, wherein a pulse width modulation controller is adapted in such a way that an individual winding of the phase windings of the rotating field machine is energized at a specifiable sampling time.

Abstract: The invention relates to a drive device for an electric motor, in particular for a brushless DC motor in an electrical tool, which is powered by a rechargeable battery. The drive device has at least one power semiconductor, in particular for controllable application of an electrical voltage to the electric motor, a control circuit for controlling the power semiconductor, and a mounting plate which, for example, is in the form of a printed circuit board. At least one portion of the control circuit, in particular electrical and/or electronic components as well as the conductor tracks (which connect the electrical and/or electronic components) of the control circuit, is arranged on the mounting plate. The power semiconductor is arranged on the mounting plate and/or on a mount element, which is mounted on the mounting plate.

Abstract: A drive system for a three phase brushless AC motor that is operative to optimize a transistor switching pattern to improve power output while allowing current measurement in all of the phases using a single sensor. This is achieved by defining a voltage demand vector where more than two states are required to meet a minimum state time requirement determined by the single sensor and calculating three or more state vectors that produce the demand vector while still allowing single current sensing.

Abstract: A control and motor arrangement in accordance with the present invention includes a motor configured to generate a locomotive force for propelling the model train. The control and motor arragement further includes a command control interface configured to receive commands from a command control unit wherein the commands correspond to a desired speed. The control and motor arrangement still further includes a plurality of detectors configured to detect speed information of the motor, and a process control arrangement configured to receive the speed information from the sensors. The process control arrangement is further configured and arranged to generate a plurality of motor control signals based on the speed information for controlling the speed of said motor. The control and motor arrangement yet still further includes a motor control arrangement configured to cause power to be applied to the motor at different times in response to the motor control signals.

Abstract: An abnormality monitoring device monitors a PWM driving signal output from a driving section of an associated motor control system to judge whether the driving section is operating abnormally. By monitoring the output of the driving section, the monitoring device can detect an abnormality of the driving section before the motor can respond to the abnormal drive signal to a significant degree (e.g., to a degree readily discernable to a rider of a motorcycle on which the motor control system is employed in combination with an electronic throttle system).

Abstract: A controller of a pulse width modulation signal-driven device, includes: an instruction input of operating the pulse width modulation signal-driven device; a control section generating a control clock which operates the pulse width modulation signal-driven device; a frequency modulator frequency-modulating the control clock, to thereby give to the control clock a frequency variation in a predetermined frequency range; a frequency varier generating a modulation signal inputted to the frequency modulator; and a first switching member driving the switching element which flows a predetermined drive current to the pulse width modulation signal-driven device based on the frequency-modulated control clock. The frequency varier includes: a first signal generator setting a range of diffusing a switching noise in a frequency range, and a unit for shifting a frequency band of the switching noise by giving a predetermined offset voltage to an output voltage of the first signal generator.

Abstract: A system and method for reducing fan noise by controlling the drive current to the fan motor. In one embodiment the system approximates a linear drive using a number of transistors in parallel and sequentially deploying the transistors. In another embodiment, a scheme is used to activate and deactivate transistors in discrete steps thereby achieving the benefits of the linear controller topology.

Abstract: A motor drive circuit includes a switching circuit having an input node that receives a drive signal and a control node that receives a control signal. The switching circuit couples the input node to an output node responsive to the control signal. A bias element receives an input signal and is coupled to the output node of the switching circuit. The bias element automatically develops a bias voltage on the output responsive to the input signal. The drive circuit may be used, for example, in a motor control system to control the speed of a DC motor, such as in a power supply for a computer system.

Abstract: A current driver capable of generating a controlled current in the form of a pulse-width modulation (PWM) signal suitable for controlling an electronic device such as a solenoid is disclosed. The current driver has a feedback loop incorporating a dual-slope integrator. During an integration phase, which has a duration of one or more PWM periods, the dual-slope integrator integrates a signal indicative of the current flowing through the device. During a de-integration phase, the time required for the integrated signal to discharge at a known rate is measured. The measured time and integration phase duration are used to determine average output current. Any error between the measured and desired average output current is corrected by way of a multiplicative corrective factor or an additive corrective factor. The integration and de-integration phases may occur during alternating PWM periods.

Abstract: A system and method for measuring the speed of a fan is presented. The duty cycle of a pulse width modulated (PWM) power signal may control speed of the fan. The fan may generate tachometer pulses used for monitoring RPM of the fan. Very low frequency test pulses may be generated and provided via a test signal multiplexed with the PWM signal to obtain tachometer pulses present even when the PWM signal is deasserted. The frequency of the test signal may be determined based on the duty cycle of the PWM signal and may be dynamically updated using frequency divider values stored in a user programmable look-up table. The tachometer pulses may be used to reset a flip-flop whose data input is held high and a down counter, which may be operated at a frequency slightly lower than the frequency of the test signal, with the output of the down counter clocking the flip-flop.

Abstract: A driving circuit for switches of direct current fan motor is disclosed. The driving circuit includes a plurality of switches, a first control circuit, and a second circuit. The switches are driven by a first pulse width modulation signal and a second pulse width modulation signal, and they are electrically connected with the direct current fan motor in a bridge manner. A third pulse width modulation signal is used to drive the first control circuit connected to at least one of the switches driven by the first pulse width modulation signal. A fourth pulse width modulation signal is used to drive the second control circuit connected to at least one of the switches driven by the second pulse width modulation signal. Especially, either the first pulse width modulation signal or the second pulse width modulation signal is selected as the third pulse width modulation signal or the fourth pulse width modulation signal.

Abstract: A power tool such as an electric drill typically contains a gear train that couples the output spindle of the motor to the tool bit-receiving chuck. The control circuit for the power tool is operable in a ratcheting or pulse mode that causes the output spindle to rotate in discrete incremental amounts. Corresponding methods for controlling the operation of the electric motor of a power tool are also disclosed.

Abstract: An apparatus for controlling a rotational speed of a motor, coupled to a sensing unit capable of outputting a sensing signal. The apparatus includes a controlling unit, coupled to the sensing unit, for outputting a controlling signal according to the sensing signal and independently of the rotational speed of the motor. The controlling signal is a square wave and has a duty ratio that is determined by the sensing signal. The apparatus also includes a driving unit, coupled to the controlling unit, for outputting a driving signal to a motor rotor according to the duty ratio of the controlling signal. The driving signal also is a square wave. The rotational speed of the motor rotor is determined by the duty ratio of the driving signal.

Abstract: An electronically commutatable motor having field windings activatable in sequence with a commutation frequency via semiconductor output stages using control signals connectable and disconnectable from a direct voltage supply, the control signals being clocked using pulse width modulation. Noise generation from connection and disconnection of the current applied to field windings is minimized by flattening of the rising and/or falling edges of the current in the field windings. The pulse width ratio increases in the rising edges of the control signals from a low initial value to an operating value assigned to the setpoint as a function of a selected setpoint for the motor speed or output, and, in the falling edges of the control signals, the pulse width ratio starts from the existing operating value and is reduced to a lower final turn-off value as a function of the existing actual value of the speed or the output of the motor.

Abstract: Disclosed is a circuit for regulating a power supply. In one embodiment, the circuit includes a signal generator for generating a square wave signal that varies in magnitude between a first voltage and a second voltage, and a voltage regulation circuit. A duty cycle of the square wave generated by the signal generator varies according to a signal provided to the signal generator. The voltage regulation circuit, coupled to the signal generator, outputs a DC voltage in response to the circuit receiving the square wave signal. The magnitude of the DC voltage varies between the first voltage and a third voltage, wherein the third voltage is greater than the second voltage, and wherein the magnitude of the DC voltage varies directly with the duty cycle of the square wave signal.