Abstract: A method for applying power to an electronically commutated motor (ECM) is described. The method includes connecting an AC voltage source to an input of a rectification circuit, connecting a DC voltage source to an output of the rectification circuit, and electrically connecting the DC voltage source and rectification circuit output to operational components of the ECM. The DC voltage source is capable of providing a voltage equal to or greater than a rectified voltage originating from the AC voltage source, and the DC voltage source is connected in parallel with the output of the rectification circuit.

Abstract: A control circuit has an input terminal for receiving an input voltage, an energy accumulator for storing electric energy from the input terminal and supplying power to an electrical load, and an over-voltage protection unit for lowering the voltage at the input terminal when the voltage at an output terminal of the energy accumulator exceeds a predetermined threshold value. A motor device combines the control circuit with an electric motor as the load.

Abstract: A fan system is electrically connected to a power source, and the fan system includes a power reverse protection apparatus, a voltage regulator, a driver, and a fan. The power reverse protection apparatus, electrically connected to the power source, includes a voltage regulator switch and an activating device. The voltage regulator switch receives an input signal and outputs a first output signal according to the input signal. The activating device is electrically connected to the power source and the voltage regulator switch for receiving the input signal and the first output signal, respectively. The activating device outputs a second output signal to the fan according to the first output signal. The voltage regulator is electrically connected to the power source for receiving the input signal from the power source and outputting a regulating signal according to the input signal.

Abstract: A system for moving an aircraft thrust reverser component includes a power drive unit, a thrust reverser actuator assembly, and a tertiary lock system. The power drive unit is operable to rotate and supply a rotational drive force. The thrust reverser actuator assembly receives the rotational drive force from the power drive unit and moves the thrust reverser component between a stowed position and a deployed position. The tertiary lock system selectively engages and disengages the thrust reverser component and includes a tertiary lock power unit, an electromechanical tertiary lock assembly, and a voltage limiting circuit. The voltage limiting circuit limits the voltage magnitude of a control signal supplied to the tertiary lock assembly to a predetermined value.

Abstract: It is presented a protection circuit for a drive circuit of a permanent magnet motor being powered by a main DC source. The protection circuit comprises a protection circuit DC source; a changeover switch being arranged to select an input to a gate of a main drive switch of the drive circuit, the input being selectable between an output of the protection circuit DC source and a second control signal; and a changeover control device connected to control the changeover switch, which changeover control device is arranged to ensure that the changeover switch is connected to the output of the second side of the protection circuit DC source when an overvoltage is detected.

Abstract: An inverter system having a semiconductor device, and a railway vehicle using this inverter, provide a more accurate determination of whether an abnormal heat generation from the inverter is associated with an error of the inverter system or is due to other causes, by use of a plurality of temperature detecting elements at a plurality of sites associated with the semiconductor device. An error detection section applies inputs from the temperature detecting elements, captures a trend of the differential value based on the plurality of temperature inputs using period sampling wherein an error associated with the semiconductor device, and not from some other condition such as outside environment temperature, is determined based on differences from, or a change in, the initial trend.

Abstract: An electric power supply device capable of miniaturizing an FET and wiring and reducing the amount of heat generation even when a motor load goes into a lock state is provided. It is determined whether or not a lock current flows in a motor M1 by comparing various determination voltages with a voltage Vds between a drain and a source of a MOSFET (T1), and in the case of detecting that the lock current flows, an operation of turning off the MOSFET (T1) until a retry cycle to elapses after turning on the MOSFET (T1) for only energization time tb for which lock torque can be caused is repeatedly executed. Then, when a motor current ID becomes smaller than the lock current, control of returning the MOSFET (T1) to a normal operation is performed. Consequently, the lock current can be prevented from flowing continuously.

Abstract: A control portion instructs supply of an offset voltage while a disk remains stopped at the time of start. While the disk remains stopped at the time of start, a differential operational amplifier detects a voltage difference between a first voltage supply line and a second voltage supply line. When the absolute value of the voltage difference output by the differential operational amplifier is equal to or lower than a prescribed threshold value, a failure determination portion determines that a spindle motor has shorted out.

Abstract: A protective redundancy circuit is provided for a power tool having an electric motor. The protective redundant subsystem is comprised of: a motor switch coupled in series with the motor; a motor control module that controls the switching operation of the motor switch; and a protective control module that monitors switching operation of the motor switch and disables the power tool when the switching operation of the motor switch fails. In the context of an AC powered tool, the switching operation of the motor switch is correlated to and synchronized to the waveform of the AC input signal. During each cycle or half cycle, the motor control module introduces a delay period before closing the motor switch and the protective control module determines the operational status of the motor switch by measuring the voltage across the motor switch during the delay period.

Abstract: A cooling system is provided with a motor drive device, a fan motor, and a Hall element. The motor drive device includes a lock protection circuit and a lock controller. When a control signal instructing rotation of the fan motor that is to be driven instructs stoppage of the motor for a predetermined time-period or longer, the lock controller has the lock protection circuit inactive. At an occasion when the control signal has continued to instruct stoppage of the fan motor for a first time-period or longer, a standby controller starts time measurement, and after a further predetermined second time-period has elapsed, makes at least a part of the motor drive device transition to a standby mode.

Abstract: A protection circuit is configured to change control modes in a drive control process of a drive circuit for a motor when overvoltage is applied to a power source line while the motor is driven. With overvoltage applied, the control process is changed to a control mode to perform forced commutation control. When a predetermined time period passes after the voltage of the power source line returns to a predetermined level, the control process is changed to a sensorless control mode using a position detection circuit. This configuration can provide a motor drive apparatus capable of performing an overvoltage protection operation appropriately even when the sensorless control mode is adopted.

Abstract: A programmable logic controller is disclosed. The programmable logic controller includes control circuitry integrally arranged with a current path and at least one micro electromechanical system (MEMS) switch disposed in the current path. The programmable logic controller further includes a hybrid arcless limiting technology (HALT) circuit connected in parallel with the at least one MEMS switch facilitating the opening of the at least one MEMS switch. The programmable logic controller also may include a MEMS switch and a voltage sensor for measuring the voltage across the MEMS switch. The MEMS switches are arranged to transmit or receive logic signals.

Abstract: A control system is disclosed. The control system has an electric machine coupled to provide power to or receive power from a DC bus and a controller in communication with the electric machine and the DC bus. The controller is configured to receive a voltage from the DC bus, compare the voltage from the DC bus to a characteristic indicative of a fault of at least one winding of the electric machine, and take a precaution based on the comparison.

Abstract: A disc apparatus which can judge accurately whether or not a spindle motor is at fault due to a short circuit is provided. A disc apparatus (1) includes a spindle motor (3) which rotates a disc (2), a differential operational amplifier (5) which successively detects output voltages of the spindle motor (3), and a failure judgment unit (10) which calculates an average voltage of the plural output voltages and judges whether or not the spindle motor (3) is at fault in accordance with the average voltage and the output voltages. When counting number of occurrences of a specific state which indicates that one of the two output voltages detected successively is larger than the average voltage and other of the two output voltages is smaller than the average voltage, the failure judgment unit (10) judges that the spindle motor (3) is at fault.

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 windscreen wiper, including a protection device for an electric motor for drive thereof, and corresponding method. The windscreen wiper includes a DC motor with first, second, and third carbon contacts rubbing on a rotor thereof. The first carbon contact is ground, the second is selectively connected to a DC current supply, and the third is connected to neither the ground nor the DC current supply. A sub-assembly for detection of sticking of the electric motor provides information on the sticking of the motor. A voltage measuring device between the first and the third carbon contacts permits taking a first measured voltage value that is compared to a first threshold value to generate further second information on the sticking of the electric motor if the voltage is lower than the first threshold value.

Abstract: There is provided an electronic control unit including: input terminals connected to output terminals of a magneto generator driven by an engine; DC output terminals; a control power supply circuit that converts an AC voltage input between the input terminals into a DC voltage equal to a set value; and a microprocessor that controls electrical components of the engine, wherein the electronic control unit further includes an interruption signal generation circuit that compares an output voltage of the control power supply circuit with a certain abnormality determination voltage and generates an interruption signal when the output voltage of the control power supply circuit becomes the abnormality determination voltage or less, and an abnormality state storage unit for storing that an abnormality occurs in a power supply portion when the interruption signal is generated.

Abstract: A method of voltage supply management for an electric drive system includes receiving a voltage signal (1002) indicative of a voltage in a supply link, and one or more condition signals that are indicative of an operating condition of the electric drive system. A difference between a desired voltage value (1008), which is calculated based on the voltage signal (1002) and the one or more condition signals, and the voltage signal (1002) yields a voltage error signal (1014). The voltage error signal (1014) is evaluated to indicate an over-voltage condition or an under-voltage condition. Power is dissipated from the supply link when an over-voltage condition is present and a torque command limit with respect to the one or more electric drive motors (210) is imposed when an under-voltage condition is present.

Abstract: A method for controlling a motor (2) which drives a disk-shaped tool (4) of a power tool (1) and to which a motor voltage in the amount of a nominal value is applied in an “on” position of a motor switch (6), includes determination of an actual motor current (IM) applied to the motor (2) and comparing it to a first predetermined threshold (GW1), and automatically triggering of a control process for protecting the motor (2) when an overload condition which is defined in that the first predetermined threshold (GW1) is exceeded beyond a first predetermined limiting time period (grDt1), is met, the control process including reduction of the motor voltage applied to the motor (2) by a magnitude that can be perceived by the user as a choke value.

Abstract: A current sensor of a motor controller detects the current applied to a motor drive circuit and thus a phase where a failure cannot be detected would occur without taking any measures. However, an abnormal current monitor section contained in a microcomputer receives a voltage signal of an average value of the currents detected in the current sensor by allowing a signal to pass through a first LPF having a cutoff frequency sufficiently lower than the frequency of a PWM signal. Therefore, whether or not the value is within a predetermined normal range is checked, whereby whether or not some failure containing a failure of the current sensor occurs can be easily determined about every phase.

Abstract: A car power source apparatus includes a battery array that has a plurality of battery units connected in series, a battery over-charge and over-discharge detection circuit, selection switches that sequentially input battery unit voltages to the over-charge and over-discharge detection circuit, a reference voltage circuit that inputs reference voltages to the over-charge and over-discharge detection circuit, and a control circuit that controls selection switches and the reference voltage circuit. The control circuit controls the selection switches to input battery unit voltages to the over-charge and over-discharge detection circuit to determine over-charge and over-discharge.

Abstract: A wiper control circuit is provided for invalidating the state of a wiper operation switch to suppress unnecessary operations of a wiper in an automotive vehicle upon starting an engine using a remote control engine starter. The wiper control circuit is configured to suppress generation of a sneak current and thereby reduce the likelihood that an erroneous operation instruction is received.

Abstract: To provide a cordless power tool which can suppress heat generation of a protection unit and prevent the erroneous operation. A cordless power tool 1 includes a body casing 10; a battery 20 which is detachably attached to the body casing 10 and can supply electric power; a motor 30 which is housed in the body casing 10, and generates rotation force by the electric power of the battery 20; a cooling fan 40 which rotates by the rotation force of the motor 30; and a protection unit 50 which shuts off the power supply to the motor 30, in accordance with a detection result of the state of the battery 20, so that the battery 20 does not enter an overdischarge state or an overcurrent state. Herein, a passage of cool air generated by the cooling fan 40 is formed in the body casing 10, and the 16 protection unit 50 is arranged so that at least its part is located in the passage of the cool air.

Abstract: A method and apparatus for a pump control system. One or more embodiments of the invention include a pump controller that can perform a self-calibrating procedure, can provide precise motor speed control, can provide a limp mode before shutting down the motor when system parameters are exceeded and/or fault conditions occur, can detect fault conditions, and can store fault conditions for later retrieval.

Abstract: A power supply protecting circuit configured to protect an electronic device includes a normally open switch, a voltage dropping circuit, a first rectifier, and a relay having a coil and switch. A power terminal of the electronic device is connected to a power terminal of a power supply, the other power terminal of the electronic device is connected to the other power terminal of the power supply via the normally open switch. The power terminal of the electronic device is connected to the other power terminal of the electronic device via the voltage dropping circuit, the first rectifier, and the coil of the relay in turn. The switch of the relay is connected in parallel to the normally open switch.

Abstract: An over-voltage and under-voltage protection system for protecting an electrical device includes a comparison device, a signal controller, a switch controller, and a switch. The comparison device receives an input voltage and compares the input voltage with a predetermined voltage. If the input voltage is greater than the predetermined voltage, the comparison device outputs an over-voltage signal to the switch controller via the signal controller. If the input voltage is less than the predetermined voltage, the comparison device outputs an under-voltage signal to the switch controller via the signal controller. The switch controller controls the switch to turn the electrical device off when the over-voltage or the under-voltage signals are received from the signal controller.

Abstract: Embodiments of the present invention beneficially provide circuits and methods which isolate downhole electronics of a well pump assembly from a power surge. The pump assembly includes a motor and a housing, including head, base, and manifold plate. The head has a hollow interior and a shoulder. The head is mounted to the motor so that, in operation, oil from the motor fills the interior of the head. The base has an outside diameter to fit snugly inside the head. The manifold plate is located between an upper end of the base and the shoulder of the head so that the axis of the manifold plate is perpendicular to the axis of housing. A gauge circuit and an isolation circuit are mounted to the manifold plate. The isolation circuit includes active semiconductor elements to detect excessive voltage and to protect the gauge circuit from the excessive voltage.

Abstract: An accurate slip calculation for providing monitoring and protection to an electric motor. The slip calculation is made using a minimum value of stator resistance as the initial stator resistance, where the minimum value of stator resistance is the minimum value of stator resistance calculated during an initiation period of the motor. The initiation period may be a predetermined time period or a predetermined number of cycles during the motor startup. The initiation period may start after a predetermined settling time or after a predetermined condition is met.

Abstract: A disc apparatus which can accurately judge whether or not a spindle motor is at fault due to a short circuit is provided. A disc apparatus (1) includes a spindle motor (3) which rotates a disc (2), a differential operational amplifier (5) which detects a difference between voltages of a positive terminal and a negative terminal of the spindle motor (3) as a detecting voltage level, a failure judgment unit (10) which judges whether or not the spindle motor (3) is at fault based on the detecting voltage level, and a disc determination means (12) which determines a type of the disc (2). The failure judgment unit (10) judges that the spindle motor (3) is at fault when the detecting voltage level becomes lower than a predetermined threshold level five times continuously during a start-up that the spindle motor (3) starts driving when the disc (2) is in stopped state while the disc determination means (12) determines the type of the disc (2).

Abstract: Methods and apparatus are provided for protecting a motor control circuit in a permanent magnet electric motor system. The permanent magnet electric motor system includes a permanent magnet electric motor having a predetermined number of windings corresponding to the phases of the permanent magnet electric motor and a direct current (DC) bus coupled to a power source for providing operational power for the electric motor system. A motor control circuit is connected to the DC bus for receiving the operational power therefrom and is connected to the windings of the permanent magnet electric motor for controlling the permanent magnet electric motor. A protection circuit is connected to the DC bus for receiving the voltage therefrom for operation of the protection circuit and for detecting predetermined motor control circuit fault conditions from voltage sensed on the DC bus and in response thereto providing protection for the motor control circuit.

Abstract: Detection accuracy of a short circuit state in a load driving circuit is improved thereby operation efficiency of a motor may be enhanced. A gate control circuit 25 turns off NMOS transistors Q1 and Q4, turns on an NMOS transistor Q3, and turns on and off an NMOS transistor Q2 intermittently so as to control rotation of a motor 10. A detection circuit 30a detects a voltage Va at a connection node a between the NMOS transistor Q2 and the motor 10 a predetermined time after the NMOS transistor Q2 is turned on. A control circuit 20 turns off the NMOS transistor Q2 so as to cut off a current from a power supply to the motor 10 if the voltage Va at the connection node a is within a range in which the motor 10 is determined to be short-circuited.

Abstract: A method and associated apparatus for operating an electrical machine includes providing a brushless excitation system including at least one rectifier having at least one diode. The method also includes providing at least one voltage amplitude limiter assembly including at least one resistor and at least one transient voltage suppressor (TVS) electrically coupled with the at least one resistor to form at least one voltage suppression unit. The method further includes transmitting an electrical signal having a current and a voltage to each voltage suppression unit, the voltage having an amplitude. The method also includes electrically coupling the at least one voltage amplitude limiter assembly to the at least one diode. The method further includes transmitting the electrical signal through the rectifier and the voltage suppression unit such that voltage amplitude excursions of the electrical signal are facilitated to be reduced.

Abstract: The invention concerns a motor starter circuit for an induction motor, particularly a single-phase AC induction motor, with a main winding (4) and an auxiliary winding (5) supplied with current, particularly AC, via current supply connections (24, 25), and with a starter switch arrangement (15), which serves the purpose of interrupting the current flow through the auxiliary winding (5) after the start of the motor, the starter switch arrangement (15) interacting with a measuring arrangement serving the purpose of measuring the voltage across the auxiliary winding (5).

Abstract: An engine control apparatus in which, when it is detected by a starter switch that a starter has changed-over from a drive state into a non-drive state, an ECU (engine control unit) predicts a time period in which an engine is completely stopped, on the basis of a revolution speed of the engine at that time, so as to turn OFF an output of a starting motor relay for the predicted period.

Abstract: HVAC systems implementing micro-electromechanical system based switching devices. Exemplary embodiments include a HVAC system, including a load motor, a main breaker micro electromechanical system (MEMS) switch, and a variable frequency drive (VFD) disposed between and electrically coupled to the load motor and the main breaker MEMS switch.

Abstract: A power supply device and a method for controlling the power supply device in which a fusion checking process for the cathode side relay and the anode side relay is easily performed within a short period of time. A battery ECU (controller) measures a first voltage between a high potential output terminal and an anode terminal of the rechargeable battery when a cathode side relay arranged between the high potential output terminal and a cathode terminal of the rechargeable battery and an anode side relay arranged between a low potential output terminal and the anode terminal of the rechargeable battery are open to determine whether or not a cathode side relay is fused. The battery ECU also measures a second voltage between the low potential output terminal and the cathode terminal of the rechargeable battery to determine whether or not the anode side relay is fused.

Abstract: To provide a motor control apparatus, including a rotational number detecting means for detecting the rotational number of a motor; a current detecting means for detecting a motor current; a voltage detecting means for detecting an impressed voltage to be supplied to a motor; a temperature estimating means for obtaining a motor temperature from the rotational number of a motor, the motor current, and the impressed voltage; and a protection signal generating means for generating an operational signal in order to protect the motor when the obtained motor temperature exceeds a predetermined value.

Abstract: The present invention provides a power module, power converter, and vehicular electric machine system capable of reducing inductance of a peripheral section of an output terminal in a power module, and additionally, reducing a surge voltage. A positive emitter conductor 3 connected to an emitter electrode of a positive power semiconductor element Mpu and an output terminal U are electrically interconnected by using a plurality of aluminum wires 7, a negative collector conductor 4 connected to a collector electrode of a negative power semiconductor element Mnu and the output terminal U are electrically interconnected by using a plurality of aluminum wires 9, and the positive emitter conductor 3 connected to the emitter electrode of the positive power semiconductor element Mpu and the negative collector conductor 4 connected to the collector electrode of the negative power semiconductor element Mnu are further electrically interconnected by using a plurality of aluminum wires 8.

Abstract: Circuits and methods for protecting polarity-sensitive components, such as light emitting diodes, electrolytic capacitors or integrated circuits, operating from a DC current source including a DC motor, an inductor or relay having a positive terminal and a negative terminal for receiving current from the current source, a protection diode connected parallel with the positive and negative terminals of the motor in a reverse bias configuration, at least one polarity-sensitive component connected in parallel with the protection diode and the DC motor, and a polarity protection transistor connected either between the nominally positive current source terminal and the positive motor terminal, or between the nominally negative current source terminal and the negative motor terminal.

Abstract: In an inverter system including of an electric-power converter and an ac rotating machine, over-voltage generated in the ac rotating machine is controlled by a low-cost system configuration. The system includes: an electric-power converter; a three-phase ac rotating machine; and a four-core non-coaxial cable, having a ground line and three-phase electric-power supplying lines, connecting the electric-power converter to the three-phase ac rotating machine. One or two capacitors are connected between the ground line and one or two of the electric-power supplying lines, at electric-power supplying terminals on the rotating machine, so that respective capacitances between the three-phase electric-power supplying lines and the ground line are approximately equal to each other.

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: Provided is a method and apparatus for controlling a motor of a disk drive. The method is used to stably control the startup current of a motor by considering a voltage drop and the disk drive uses the method. The method includes managing power-on reset retry information generated during the startup of the motor and determining the startup current of the motor that corresponds to a power-on reset retry count included in the power-on reset retry information.

Abstract: A method of protecting an electromechanical power transfer system from excessive peak electrical potentials, the power transfer system comprising a prime mover, a dynamoelectric machine coupled to the prime mover for generating multiphase alternating current (AC) power, and at least one multiphase AC electrical load coupled to the dynamoelectric machine by way of a multiphase AC power bus, the dynamoelectric machine having a control coil responsive to control current for varying power supplied to the electrical load, comprises the steps of: analysing electrical potentials on the power bus to generate analysed power bus characteristics; comparing the analysed power bus characteristics to predetermined power bus characteristics; simultaneously shunting power across the power bus and reducing control current to the control coil for the dynamoelectric machine when the analysed power bus characteristics approximate the predetermined power bus characteristics to reduce the measured electrical potentials; and simult

Abstract: A signaling device includes an electrical circuit which discharges an electrical energy storage device through an electrically powered alert mechanism via a biased open transition switch upon disruption of electrical power in an electrical system of a work machine. A work machine is further provided having an alert device coupled with a normally closed electrical power circuit, the alert device being activated upon opening of the normally closed electrical circuit via a transistor switch. An associated method includes using the signaling device to alert a work machine operator to a predetermined condition by closing a normally open electrically switch to connect an electrical energy storage device with an electrically powered alert mechanism, via an electronic controller or via interruption of electrical power in a normally closed electrical circuit of a work machine.

Abstract: A system for sensing short circuits and open circuits prior to operation of a motor (i.e., while the motor is in a static state), thereby sparing the electrical system from destructive effects of these electrical problems. In addition, the system may detect a short circuit during operation of the motor (i.e., while the motor is in a dynamic state). Still yet, the system may detect an open circuit at the motor. The motor may be any electromechanical motor, such as a direct current (DC) motor, used in a vehicle or otherwise for controlling motion of a mechanical device.

Abstract: A control system is disclosed. The control system has an electric machine coupled to provide power to or receive power from a DC bus and a controller in communication with the electric machine and the DC bus. The controller is configured to receive a voltage from the DC bus, compare the voltage from the DC bus to a characteristic indicative of a fault of at least one winding of the electric machine, and take a precaution based on the comparison.

Abstract: Methods and apparatus are provided for protecting a motor control circuit in a permanent magnet electric motor system. The permanent magnet electric motor system includes a permanent magnet electric motor having a predetermined number of windings corresponding to the phases of the permanent magnet electric motor and a direct current (DC) bus coupled to a power source for providing operational power for the electric motor system. A motor control circuit is connected to the DC bus for receiving the operational power therefrom and is connected to the windings of the permanent magnet electric motor for controlling the permanent magnet electric motor. A protection circuit is connected to the DC bus for receiving the voltage therefrom for operation of the protection circuit and for detecting predetermined motor control circuit fault conditions from voltage sensed on the DC bus and in response thereto providing protection for the motor control circuit.

Abstract: A motor driving circuit comprising: a synchronous rectification driving circuit to carry out synchronous rectification, to energize a driving coil connected between a first connection point at which a first source and first sink side transistors are connected in series and a second connection point at which a second source and second sink side transistors are connected in series; a backflow detecting resistor connected to electrodes of the first and second sink side transistors, the electrodes being on an opposite side of the first and second sink side transistors to the first and second connection points; a backflow detecting comparator to output a comparison signal indicating a result of comparison of voltage between a first and second terminals of the backflow detecting resistor, and a backflow prevention circuit to prohibit the synchronous rectification when the comparison signal indicates that the second terminal is higher in voltage than the first terminal.

Abstract: A protection circuit is configured to change control modes in a drive control process of a drive circuit for a motor when overvoltage is applied to a power source line while the motor is driven. With overvoltage applied, the control process is changed to a control mode to perform forced commutation control. When a predetermined time period passes after the voltage of the power source line returns to a predetermined level, the control process is changed to a sensorless control mode using a position detection circuit. This configuration can provide a motor drive apparatus capable of performing an overvoltage protection operation appropriately even when the sensorless control mode is adopted.

Abstract: A specially designed rotation speed controller for fans, in addition to basic components like variable resistor, the controller has also been equipped with special components such as TRIAC, micro limit switch, and glass tube fuse, which allows said controller to precisely control the on/off status and the rotation speed of the fan, and the controller also provides power-off protection against power overload.