Abstract: A fan controlling circuit for detecting rotational speed of a fan, includes a comparison circuit and a controlling chipset. The comparison circuit receives a rotational speed signal from the fan at one input terminal, a reference voltage at another input terminal, and outputs a filtered rotational speed signal at an output terminal. The controlling chipset receives the filtered rotational speed signal, and outputs control signals to control the rotational speed of the fan.

Abstract: A motor control is provided with both open loop and closed loop controllers. The open loop and closed loop controllers provide commutation signals back to gate drives for an inverter, wherein the commutation signals utilize sinusoidal signals in open loop control, and utilize six step commutation in closed loop control.

Abstract: The invention relates to a machine tool comprising an electric motor (2) which serves to drive a tool and which has an adjustable, electric brush arrangement (3), and comprising a mode selector switch (6) having various switch positions. Provision is made for an adjusting device (8) to displace the brush arrangement (3) as a function of the switch position of the mode selector switch (6). Furthermore, the invention relates to a corresponding method.

Abstract: An electric commutator motor comprising a housing and a shaft which is solidly connected to a rotor. The housing comprises a stator and supply brushes which can be connected to an electric power source. The rotor is solidly connected to a commutator with bars, and comprises a set of wound turns, the ends of which are connected to two successive bars of the commutator. The housing comprises at least one additional brush which is positioned close to at least one of the supply brushes, known as the monitor brush, at a distance less than the width of a bar. The additional brush and the monitor brush are of the same thickness and are disposed symmetrically in relation to a diametrical plane of the rotor. The additional brush is connected electrically to a means for counting the pulses generated directly on the additional brush when the monitor brush leaves a bar of the commutator.

Abstract: The invention relates to a drive and evaluation unit for displacing an object to be displaced, particularly for raising and lowering a side window in a motor vehicle. The drive includes a commutator motor with a stator having two diametrically opposed permanent magnets. The magnets have cross-sectional shapes of a respective peripheral contour segment, having a radial inner peripheral contour segment which encompasses an armature over a respective inner peripheral angle. The armature is provided with ten grooves spaced around its periphery for holding armature windings that are configured as lap windings. The evaluation unit includes a device for determining the rotational position of the armature by evaluating the ripple count of the armature current. According to the invention, the armature windings are configured as short pitch windings, and the inner peripheral angle of the radial inner peripheral contour segment of at least one of the magnets is between 101° and 111°.

Abstract: A method and apparatus for controlling a brushless DC (BLDC) motor over a wide range of angular speeds is presented. Analog magnetic sensors provide continuous signal measurements related to the rotor angular position at a sample rate independent of rotor angular speed. In one embodiment, analog signal measurements are subsequently processed using an arctangent function to obtain the rotor angular position. The arctangent may be computed using arithmetic computation, a small angle approximation, a polynomial evaluation approach, a table lookup approach, or a combination of various methods. In one embodiment, the BLDC rotor is used to drive a Roots blower used as a compressor in a portable mechanical ventilator system.

Abstract: Disclosed is a starting device and method for eliminating a peak current introduced when an inductive circuit such as a motor or a direct-current (DC) motor is actuated, The starting device includes a signal generator electrically connected to the inductive circuit and generating a first signal corresponding to a signal output by the inductive circuit, a comparative circuit electrically connected to the signal generator for converting the first signal to a second signal to be compared with a reference signal to generate a control signal, and a controlling device electrically connected with the inductive circuit and the comparative circuit for receiving the control signal and gradually increasing a current input into the inductive circuit corresponding to the control signal, thereby eliminating the peak current introduced when the inductive circuit is actuated.

Abstract: In accordance with the principles of the invention, an integrated circuit comprises a substrate having a first FET formed on the substrate. The first FET has a first terminal coupleable to a load, a second terminal and a control terminal. The second terminal is connected to the substrate. The substrate comprises a parasitic body diode coupled between the first terminal and the substrate. The body diode is disposed such that it becomes conductive when a reverse voltage across the FET first terminal and the substrate is at least a first diode forward voltage. A voltage detector is formed on the substrate. The voltage detector has a first input coupled to the FET first terminal, a second input coupled to the substrate, and an output coupled to the FET control terminal. The voltage detector is responsive to a reverse voltage level at the FET first terminal that is less than the first diode forward voltage to turn the FET on for the duration of a reverse voltage having at least said reverse voltage level.

Abstract: Information indicative of the placement of spindle motor components may be obtained and used to provide a correction to one or more BEMF-derived attributes used to control the spindle speed. In some implementations, first and second signals indicative of BEMF of different stator windings may be used to determine a speed-related characteristic. The speed related characteristic may be used to determine an error amount, which may be used to determine a correction factor to control the speed of the spindle motor.

Abstract: A motor controller calculates a motor torque command based on motor speed and causes a motor to generate a torque corresponding to the motor torque command, to drive a machine load coupled to the motor. The motor controller includes a speed compensator that makes, when a speed compensation torque is calculated based on the motor speed, frequency characteristics of the speed compensation torque for the motor speed exhibit a low frequency cutoff characteristic so that steady-state gain in frequency response is less than a maximum gain value. A torque adder generates a motor torque command by adding to the existing motor torque command an externally input feedforward torque signal and the speed compensation torque.

Abstract: A drive control device is provided with a determining section and a voltage increasing section. The determining section determines if the actual acceleration is deficient in comparison with the acceleration requested by the driver or if the generator output is deficient in comparison with the acceleration requested by the driver. The voltage increasing section increases the voltage supplied to the electric generator from a vehicle mounted electric power source when the determining section determines that the actual acceleration or the generator output is deficient. As a result, the generator output deficiency is eliminated and the required motor torque is produced, thereby enabling the vehicle to start into motion appropriately in accordance with the acceleration requested by the driver.

Abstract: A motor drive device (10) including a velocity command preparing means for preparing a velocity command value of a motor (20), a velocity detecting means (21) for detecting a velocity of the motor, a torque command value preparing means (12) for preparing a torque command value of a torque applied to the motor based on the velocity command value and a velocity detection value, and a disturbance load torque estimating means (18) for estimating a disturbance load torque applied to the motor based on a velocity detection value detected by the velocity detecting means and a torque command value prepared by the torque command preparing means, which motor drive device (10) is further provided with at least one of a first filtering means (31) for removing a noise component in the velocity detection value and supplying the velocity detection value to the disturbance load torque estimating means and a second filtering means (32) for removing a noise component in the torque command value and supplying the torque comman

Abstract: An apparatus is used for controlling a rotating direction of a fan. The apparatus comprises a power source, a signaling unit, a switching unit, and an activating module. The power source is used for supplying power for the apparatus. The signaling unit is used for generating direction-control signals. The switching unit is connected to the power source and the signaling unit, and used for controlling the switching unit to work. The activating module is connected to the switching unit and the fan, and used for driving the fan to selectively rotate in one of two opposite directions based on the direction-control signals. A method for driving the fan in the two directions is also disclosed.

Abstract: A system and method is provided for improved monitoring and controlling of mechanically commutated DC motors. The system and method include DC motors, pulse-count driver circuitry for driving the motors, motor position sensing circuitry, and motor control circuitry. The system and method provide for improved motor current waveform sensing that is able to effectively reject false brake pulses, avoid erroneous processing due to fluctuating battery voltage levels, and reduce the sensitivity to variations in motor current signals due to dynamic motor load, manufacturing variation, system aging, temperature, brush bounce, EMI, and other factors. The system and method also include an improved ability to multiplex additional external motor drivers to the motor control circuitry, select between sequential and simultaneous drive modes using an SPI bit, and monitor the system controller for an error condition and simultaneously driver motors in response to the error condition.

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 circuit and a method for controlling the rotating speed of a brushless direct current (BLDC) motor are provided, whose goal is solving the stall problem encountered by conventional BLDC motors driven by pulse width modulation (PWM). The circuit includes a closed-loop control mechanism for adjusting the duty cycle of the motor current of the BLDC motor, thus controlling the rotating speed of the motor. The closed-loop control is based on the comparison of a signal proportional to the actual rotating speed and another signal proportional to the predetermined target rotating speed.

Abstract: Improvements to a compressor which consists in that, as soon as the measured outlet temperature (TO) reaches a certain hysteresis upper temperature limit (HMAX), the actual rotational speed of the compressor element is either lowered with a speed jump (DS) when the measured rotational speed is situated in the higher speed range close to the maximum rotational speed (SMAX), or is increased with a speed jump (DS) when the measured rotational speed is situated in the lower speed range close to the minimum rotational speed (SMIN).

Abstract: A medical handle comprises a drive unit and a control device or circuit for driving a medical tool. The control device or circuit comprises a control and/or regulating circuit for controlling and/or regulating the drive unit, the drive unit comprises at least one magnetic element and a sensor system for determining the alignment of the at least one magnetic element. To achieve simpler assembly and a greater resistance to the ambient conditions that prevail during sterilization in comparison with known handles, the sensor system and the control and/or regulating circuit are combined in a joint control module, and the at least one magnetic element is arranged in the medical handle in such a way that at least a part of the control module can be positioned in the immediate vicinity of the at least one magnetic element and that the sensor system is arranged in the control module in such a way that it can be positioned in the immediate vicinity of the at least one magnetic element.

Abstract: A constant voltage power supply circuit includes oscillation means; a step-up or step-down circuit including coil means and capacitive means; detecting means that detects an outputted voltage value of the step-up or step-down circuit, and compares the detected value with a predetermined reference value to output a detected information, at which either the detected value exceeds the reference value or becomes lower than the reference value; and control means that controls, based on the detected information of the detecting means, supply of the pulse signals outputted from the oscillation means to the step-up or step-down circuit.

Abstract: Information indicative of the placement of spindle motor components may be obtained and used to provide a correction to one or more BEMF-derived attributes used to control the spindle speed. In some implementations, first and second signals indicative of BEMF of different stator windings may be used to determine a speed-related characteristic. The speed related characteristic may be used to determine an error amount, which may be used to determine a correction factor to control the speed of the spindle motor.

Abstract: A system for controlling a motor for use in a ventilation system may include a motor, a voltage adjustment system, a user interface, and a motor controller. The voltage adjustment system may be configured to adjust a voltage applied to the motor. The user interface may be configured to receive patient settings input from a user and communicate target ventilation parameters to the motor controller. The motor controller may include a calculation engine configured to calculate motor performance parameters for achieving the target ventilation parameters, and based at least on the calculated motor performance parameters, perform a voltage adjustment analysis for controlling the voltage adjustment system. The motor controller may further include a voltage adjuster controller configured to activate the voltage adjustment system based on a first result of the voltage adjustment analysis and to not activate the voltage adjustment system based on a second result of the voltage adjustment analysis.

Abstract: A motor is provided that includes multiple sets of independent stator windings that are not magnetically coupled, which allows the motor to be driven by multiple independent current drivers, and thereby increases the overall torque generated by the motor. In one embodiment, the motor is a brushless DC motor that includes a rotor and a stator. The rotor is configured for rotation, and the stator surrounds at least a portion of the rotor and has multiple sets of independent stator windings wound thereon. Each set of independent stator windings is configured to be independently energized and, when energized, magnetically independent of the other sets of independent stator windings.

Abstract: A power supply with performance display is disclosed. The computer power supply mainly has a power converter, a control module, and a display. The control module receives and processes the operating signals from the power converter, and then sends those processed signals to a display in a numerical value form. The power supply can be applied in a computer, an adapter, or other electronic products, which is convenient for users to know the operating status of the power converter.

Abstract: Each connection point of three series circuits formed by connecting two MOSFETs in series between positive and negative terminals of a direct-current power source is connected to a driving coil of a motor. The MOSFET is composed of an FET main body, and a parasitic element group, and its current tolerance is a sum of maximum value of a first current flowing in the FET main body when the MOSFET is turned on, and maximum value of a second current flowing in the parasitic element group upon transition of the MOSFET from on to off state.

Abstract: In order to create a method and an apparatus for anti-trap protection detection for displaceable window and door elements by means of which faster and more stable adjustment to current physical conditions can be achieved during system actuation, in the system the motor (1) is controlled using parameter values generated in real-time using a closed-loop control unit, preferably a PID controller, to keep the speed in the system constant during a learning run and during operational use and to ensure timely trapping detection.

Abstract: A method is specified for controlling a polyphase brushless electric motor, wherein the motor phase currents which are associated with the phases are produced by clocked variation of the respectively applied electrical potential. In this case, the motor phase currents flow back from the electric motor via a common return line with the peak current value in the return line being detected and being included in a controlled variable. Furthermore, a circuit configuration is specified, which is provided in a corresponding manner in order to carry out the control method. The control method and the circuit configuration allow the motor phase currents to be taken into account in the control of the electric motor in a simple and cost-effective manner.

Abstract: A motor controller is provided with: an estimated temperature calculating means that calculates an estimated temperature of a motor; and a control unit that can perform a driving control of the motor only when the estimated temperature is not larger than a predetermined value. A mode switching means switches the control unit and the estimated temperature calculating means between in a normal operation mode in which they can drive the motor and in a sleep mode in which electric power consumption thereof is smaller than in the normal operation mode in accordance with a predetermined condition while the motor is stationary. An activating means activates the estimated temperature calculating means in the sleep mode for a predetermined active time every time a predetermined sleep time is elapsed.

Abstract: A controller is operable in one of a plurality of operational modes, which include an estimated temperature computation performing mode for performing computing of an estimated temperature of the motor and an estimated temperature computation non-performing mode for stopping the computing of the estimated temperature of the motor. An operational mode of the controller is changed from the estimated temperature computation performing mode to the estimated temperature computation non-performing mode according to a predetermined condition in a stopped state of the motor.

Abstract: A motor driving apparatus is provided which can minimize ripple current flowing through a DC link capacitor, and downsize the motor driving apparatus. It synchronizes the frequency of the inverter carrier signal for driving an inverter with the frequency of the DC/DC converter carrier signal for driving a DC/DC converter, and carries out control in such a manner that the center of a period during which the input current of the inverter is zero and the center of a period during which the output current of the DC/DC converter is zero are matched.

Abstract: According to some preferred embodiments of the present invention, a motor driving circuit includes a phase detection circuit configured to detect a rotation phase of a motor and output a phase detection signal, a first amplifier configured to amplify the phase detection signal and output an amplified detection signal, and a second amplifier configured to amplify the amplified detection signal in accordance with a power supply voltage and output a driving signal to the motor. The motor driving circuit is further provided with a controlling circuit configured to detect the power supply voltage and increase/decrease amplitude of the amplified detection signal outputted from the first amplifier in response to an increase/decrease of the detected power supply voltage, whereby heat generation and noise generation can be restrained, irrespective of the increase/decrease of the power supply voltage.

Abstract: A method and device for control of a low-cost DC motor such as that suitable for portable or battery-powered applications are disclosed such that an intended behavior for the motor may be programmed without reliance on external equipment or specific expertise. The invention enables programming of a motor controlling device by means of physical manipulation of the motor. In other words, the invention allows for the training of a motor by demonstrating the intended behavior for the motor. The invention specifies a method of parsing an observation of the motor system into storable commands, while preserving information on motor response and conditions for execution. A motor controller device comprising an implementation of this method is also presented.

Abstract: A method is specified for controlling a multiphase motor that is commutated by an inverter-side bridge circuit, in the course of which a particularly precise and technically simple detection of a control-relevant variable of a considered motor phase, in particular of a motor phase current and/or a back EMF voltage and/or a variable derived therefrom, takes place. It is provided here to determine the control-relevant variable with the aid of the current state of a freewheeling diode that is disposed in a phase half bridge, assigned to the respective motor phase, of the bridge circuit, the current state being detected during an on time in which a power switch, connected in parallel with the freewheeling diode, of the phase half bridge exhibits a conducting state, and a power switch connected in series with the freewheeling diode exhibits a blocking state.

Abstract: A multimode integrated modulation circuit for controlling the fan rotating speed mainly includes a voltage regulating circuit, an integrated modulation circuit and a fan motor driving circuit. The voltage regulating circuit is used to receive an external voltage signal and regulate the external voltage signal to a suitable range of workable voltage and then a first output voltage is generated. The integrated modulation circuit that is electrically connected with the voltage regulating circuit is used to receive a PWM signal with a duty cycle and a second output voltage is accordingly generated depending on the product of the duty cycle of PWM signal and the first output voltage. The fan motor driving circuit is used to receive the second output voltage and decide the fan motor rotating speed depending on the second output voltage. Therefore, the present invention substantially adopts low-price circuit elements to integrate voltage regulating mode and PWM mode for controlling the fan rotating speed.

Abstract: A PWM controller for a direct current brushless motor comprising first and second windings includes a motor drive circuit receiving pulse width modulation control signals to drive the first and the second windings; and a control circuit having inputs coupled to the first and second windings to control a pulse width modulation control circuit such that pulse width modulated control signals are provided to the motor drive circuit only when the voltage across the first and second windings are at a predetermined level.

Abstract: An electric motor drives a belt spool of a seatbelt retractor in a vehicle using a micro-controller and a drive circuit that drives the electric motor. A plurality of PWM control signal sources are provided each of which has a trigger input and a control signal output. Each control signal source, upon application of a trigger pulse to its trigger input, provides on its control signal output a control pulse of a duration different from durations of control pulses of all other control signal sources. A set of motor control programs are permanently stored in the micro-controller. A program selection signal is sent to the micro-controller from a central sensor unit in the vehicle. Trigger pulses are sent by the micro-controller to the trigger inputs of the control signal sources. Particular ones of the control signal sources are selected for application of their signal outputs to the drive circuit in a control sequence defined by a selected control program.

Abstract: The speed control apparatus comprises a plurality of Hall sensors, a plurality of switches, a turn-on control circuit, and a gate drive logic. The Hall sensors are configured to detect magnetic rotor sections of a poly-phase brushless DC motor at different positions. The switches apply voltages on a plurality of windings to respectively produce magnetic north or south on stator poles of the poly-phase BLDC motor. The turn-on control circuit generates a conduction time reduction after each output transition of the Hall sensors. The gate drive logic separately turns on or turns off the switches according to different output transitions of the Hall sensors to respectively apply voltages on the windings with the conduction time reduction.

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 method and apparatus for controlling the speed of a DC electric motor receives a periodic commutation signal having a fixed duration on cycle and an off cycle. The commutation signal then is modified to form a periodic modified commutation signal having substantially the same period duration as the commutation signal. The modified commutation signal has a single on cycle per period. The method and apparatus then determine a desired speed of the motor, and vary the duration of the on cycle of the commutation signal to form the on cycle of the modified commutation signal. The on cycle of the modified commutation signal has a duration that is less than the fixed duration. By varying in this manner, the rotor rotates at substantially the desired speed.

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: Practically ideal electrical resonance is employed to soley provide armature power, and stator power if desired, to run DC motors. A practically ideal parallel resonant tank circuit (PIPRC) is used wherein the quotient of the “tank current” divided by the “line current” (called the “quality” or “Q” of the tank) is (1) greater than one, (2) large enough to allow the percent efficiency of the electric motor to be equal to or greater than 95%, and (3) removes enough back emf or enough of the influence thereof so that criteria (1) and (2) can be realized throughout the entire operating range of the motor. Only one PIPRC is needed for a DC motor. Recontrolling and/or redesigning is done for two reasons.

Abstract: A fan motor speed control circuit is disclosed. The circuit includes a digital/analog converting unit and a driving unit. The digital/analog converting unit takes charge of receiving a pulse width modulation (PWM) signal and converting it into a voltage signal. The driving unit is connected with the digital/analog converting unit in series for receiving the voltage signal, while the driving unit provides a first predetermined voltage level and a second predetermined voltage level as references. The fan motor is kept to run with a low constant rotation speed when the voltage signal level is higher than the first predetermined voltage level, with a full constant rotation speed when the voltage signal level is lower than the second predetermined voltage level, and with a variable rotation speed when the voltage signal level is lower than the first predetermined voltage level and higher than the second predetermined voltage level.

Abstract: Systems and methods of detecting an overload condition. In one embodiment, a method of monitoring a load of a DC motor includes intermittently de-energizing the motor; monitoring a first voltage; and measuring a first interval of time between a starting time and an ending time, wherein the starting time comprises the time at which the motor is de-energized and the ending time comprises a time at which the first voltage and a reference voltage have substantially similar values.

Abstract: A self-startup circuit for a DC fan includes a voltage sampling device receiving a first control signal, a comparator, and a self-startup device. The comparator includes two input terminals and an output terminal. One input terminal is connected to an output terminal of the voltage sampling device. The self-startup device has a switching device and a diode connected in parallel. The self-startup device has an input terminal connected to the output terminal of the comparator, and outputs a second control signal for keeping the DC fan rotating even when the first control signal has a very low duty cycle.

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: Disclosed are systems and methods for receiving and manipulating the travel of a sheet material, such as paper, from a device such as an imaging device. One embodiment of a system can be implemented as a system for handling a sheet material including a flipper device that has a shaft for accelerating a sheet material, such as paper. The flipper device also has a drive system for causing the shaft to rotate. A drive system is also provided that has a direct current motor configured to drive the shaft.

Abstract: A system and method for powered surgical handpiece capable of powering various micro-cutting instruments is described. The system is comprised of a controller adapted for controlling/interfacing with a powered surgical handpiece based upon user-defined procedural information. A data entry device is used for entering the user-defined procedural information used by the controller for configuring and operating the motor control system.

Abstract: The invention provides an electrically movable vehicle drivable by a simplified mode of control and a control program for driving the vehicle. A normalized value Y? representing translation motion and a normalized value X? representing turning motion are fed from a command value input unit 110 to a velocity command value calculating unit 120. The calculating unit 120 determines a translation velocity command value Vg—trg based on the normalized value Y?. The calculating unit 120 determines a turn angular velocity command value ?f—trg that will always satisfy Expression (2–4) for preventing the vehicle from falling down. The translation velocity command value Vg—trg and the turn angular velocity command value ?f—trg determined by the unit 120 are fed to a control command value calculating unit 130, which calculates control command values for left and right drive wheels. The control command values are fed to a motor control unit 140 to control motors Mr, Ml and control the drive wheels.

Abstract: Amperage control of a power tool motor is provided by pulse width modulation of current from a power supply. The pulse width modulation may be varied according to the determined motor current and measured power supply voltage. The power supply preferably includes a battery, such a lithium ion or nickel cadmium.

Abstract: A serial fan set and rotation speed-matching curve generation method thereof are provided. The serial fan set comprises a rotation speed control module, a first fan and a second fan, in which the rotation speed control module is used to receive the power signal and produce the rotation speed driving signal corresponding to the power signal in accordance with the relations of the rotation speed-matching curve, so that the first fan and the second fan are operated at the matching rotation speed, thus producing the optimum operation efficiency and achieving the purpose of controlling the serial fan set.

Abstract: The invention relates to a method to optimize the efficiency of a motor operated under a load having an essentially quadratic characteristic curve, the motor being connected to a motor control with whose aid at least one free motor parameter w can be changed to influence the efficiency. According to the invention, the rotational speed n and the input power PE are determined and the motor parameter w is adjusted to a value at which the value E representing the quotient of the cube of the rotational speed n and the input power PE attains a maximum.