Abstract: An intelligent power switch (IPS) circuit providing current protection for a power switch, a gate terminal of the power switch being controlled by a first control signal generated by a gate driver. The IPS circuit includes a first circuit to measure a current in the power switch, determine a first difference between a first voltage and a first reference voltage, and reduce the first control signal if the first difference exceeds a first predetermined limit; and a second circuit to measure the current in the power switch and determine a second difference between the first voltage and a second reference voltage, wherein if the second difference exceeds a second predetermined limit the first control signal is set to turn OFF the power switch.

Abstract: The application of electric power from a power source to a load is controlled by detecting the magnitude of electric current flowing to the load and producing a first signal level that is indicative of that magnitude. The first signal level is compared to a reference signal level which comparison produces an output signal. Either the first signal level or the reference signal level is altered in response to variation of voltage applied to the load. This results in the output signal indicating when electric power consumed by the load exceeds a threshold level. The flow of electric current from the power source to the load then is controlled in response to the output signal.

Abstract: A method for driving a semiconductor switch with load current limiting and thermal protection whose maximum load current is limited and which switches off when a predetermined upper temperature is exceeded and switches on again when a predetermined lower temperature is crossed. The semiconductor switch is operated in a normal mode and a fault mode. The semiconductor switch is driven in the fault mode once the predetermined temperature is exceeded; and the load current is limited to a first maximum value in a normal mode and a second maximum value, which is lower than the first maximum value, in a fault mode. Such a circuit configuration with a semiconductor switch has a protection circuit and a sensor circuit.

Abstract: A temperature sensing circuit for a ballast for a HID lamp multiplexes the temperature measurement function with another function to reduce the number of pins required for the temperature measurement function performed by the microcontroller of the ballast. The circuit includes a microcontroller having a first A/D input/output pin, a second A/D input/output pin and a multifunction pin, a temperature measurement circuit connected to the second A/D pin, a timing circuit connected to the first A/D pin, and a switch connected to the multifunction pin, temperature measurement circuit and timing circuit. The switch activates the temperature measurement function by connecting the temperature measurement circuit to the multifunction pin in a first position and deactivates the function by disconnecting the temperature measurement circuit from the multifunction pin in a second position.

Abstract: The invention relates to a method for switching a semi-conductor circuit breaker by means of which the resistance of the breaker gap of the semi-conductor circuit breaker is controlled by a control voltage (Vst), such that the power loss (Pist) from the circuit breaker does not exceed a predetermined setpoint (Psoll). The invention also relates to a device for carrying out said method wherein a transfer gate, which is controlled by a charge pump, is used as a semi-conductor circuit breaker.

Abstract: A float switch system for limiting to desirable levels current and energy entering a tank of combustible liquid comprises: a float switch disposed within the tank; an interface circuit external to the tank and coupled through wiring to the float switch; a passive transient suppression circuit coupled to the wiring external and in proximity to the tank, and operative to limit current and energy entering the tank over the wiring to the desirable levels; and a control circuit coupled to the float switch through the transient suppression circuit and to the interface circuit, the control circuit operative to monitor the status of the float switch with current within the desirable current level and to energize the interface circuit based on the switch status.

Abstract: An electrical control apparatus comprises a current sensor and a current inhibiting circuit that inhibits current flow between first and second terminals of a bicycle dynamo when current sensed by the current sensor is below a selected value.

Abstract: A protection circuit for protecting a switch from a fault includes a first sensing circuit and a second sensing circuit. The first sensing circuit senses a low-side load current through a switch that includes a first terminal, a second terminal and a control terminal. The first terminal is connected to a low-side of the load and the second terminal is connected to ground. The switch provides a conductive path between the first and second terminals responsive to a control signal provided on the control terminal. The first sensing circuit acts to reduce a magnitude of the control signal to limit the low-side load current, carried by the switch, when the low-side load current exceeds a first predetermined value. The second sensing circuit senses a voltage at the low-side of the load and interrupts the low-side load current, when the voltage at the low-side of the load exceeds a second predetermined value.

Abstract: A power supply in which a feed voltage (Us) is guided through at least one longitudinal branch to at least one output, the at least one branch having a disconnect fuse formed as a controlled semiconductor switch (SW1) and a monitoring unit (UWE) being set up to supply a disconnect signal (s1) to the semiconductor switch when there are changes in voltage or current beyond pre-definable tolerances, in which at least one auxiliary semiconductor switch (H1A), likewise triggered by the monitoring unit (UWE), is connected in parallel to the semiconductor switch (SW1) and in the event of an overload absorbs a substantial portion of the overload current in the branch.

Abstract: A semiconductor device comprises an output transistor for controlling current that flows between a first terminal and a second terminal, a detection transistor connected in parallel with the output transistor, a detection resistor connected in series with the detection transistor, for detecting current that flows through the detection transistor as detection voltage and of which the resistance value is set in proportion to the potential difference between the first terminal and the second terminal and an over-current protection transistor for decreasing the ON current of the output transistor and the detection transistor according to the increase of the detection voltage.

Abstract: A voltage source converter with a line-side diode rectifier, a load-side inverter with an electronic circuit, a power supply for the electronic circuit, and a slim DC link with a DC link capacitor is described. The slim DC link connects a DC output side of the line-side diode rectifier with a DC input side of the load-side inverter. A buffer capacitor is connected across the power supply, and a decoupling diode and a current limiting circuit are electrically connected in series with the buffer capacitor. The serially connected buffer capacitor, decoupling diode and current limiting circuit are connected in parallel with the DC link capacitor. This arrangement results in a voltage source converter that has an improved service reliability even in unstable power grids, without adding circuit complexity to the line input.

Abstract: An overcurrent protection circuit for a voltage regulator has a first transistor having a gate for connection to a gate of an output transistor of the voltage regulator, a resistor connected to a drain of the first transistor, an output voltage detecting transistor having a gate connected to an output terminal of a dividing resistance circuit of the voltage regulator, and a current mirror circuit having an input terminal connected to the drain of the output voltage detecting transistor. A second transistor has a gate connected to the drain of the first transistor and a drain connected to an output terminal of the current mirror circuit. A third transistor has a gate connected to the output terminal of the current mirror circuit and a drain for connection to the gate of the output transistor of the voltage regulator.

Abstract: The voltage generator circuit includes a regulator, a first sensor circuit, and a second sensor circuit. The first sensor circuit includes a first transistor, a first resistor, and an error amplifier. When V1>Vth, the error amplifier senses an overcurrent condition to provide feedback to the operational amplifier to limit an output current. The second sensor circuit includes a second transistor, a second resistor, and a sensing transistor. When the output current exceeds a sense threshold current, the sensing transistor is turned ON to provide feedback to the operational amplifier 12 to limit the output current. The second sensor circuit has a higher setting of sense threshold current than does the first sensor circuit, while having a higher setting of sensing speed than does the first sensor circuit.

Abstract: A control output signal is supplied to a gate electrode of an insulated gate transistor from a control signal output terminal of a control device, however, with regard to the insulated gate transistor, a control output signal is also influenced when that transistor is short-circuited, and a signal waveform different from that in a normal operating state occurs. The short-circuit is detected by monitoring the control output signal of the insulated gate transistor, and in case of the short-circuit, the short-circuit protection of the insulated gate transistor is performed by forcing the control device to stop that control output signal.

Abstract: In an overcurrent protection circuit for a switching power supply having multiple voltage supply sections, an overcurrent in a low voltage supply section is detected to make it possible to take a countermeasure against overload in a transformer winding, using a simple and low cost circuit design. The circuit comprises: a current detection resistor 33 to detect a current in secondary side of the transformer; transistors 53 and 52 to be turned on by the current detection; a photocoupler 50 to be turned on and off by the transistors; and a switching power supply controller 7 to control on-duty of a power MOSFET 6 for removing the overcurrent. The current detection resistor 33 is provided in the line of a secondary winding 30 so as to be able to individually limit a current flowing through the secondary winding 30.

Abstract: A circuit configuration has a first semiconductor switch and a first protection circuit. The protection circuit has a second semiconductor switch whose load path is connected between a control terminal and a load path terminal of the first semiconductor switch. The second semiconductor switch is switched on by a comparator circuit, in each case for a predefined time period, in dependence on a comparison between a load path voltage and a reference voltage, or between a load path current and a reference current.

Abstract: An inverter circuit overcurrent protection device in which an overcurrent detection resistor (Rs) is incorporated in a hybrid integrated circuit, in which a detection voltage from the overcurrent detection resistor (Rs) is divided by voltage dividing resistors (R1 and R2) and is compared with a reference voltage in an overcurrent detection circuit, for carrying out an overcurrent protection, and an external resistor is connected in series or in parallel with one of the voltage dividing resistors (R1 and R2) to change a division ratio so that the level of overcurrent protection can be adjusted; and an embodiment wherein, in the vicinity of a current detection terminal, a first pad (P1) is connected to a detection voltage from the overcurrent detection resistance, a second pad (P2) is connected to a detection voltage from the amplifier, and a third pad (P3) is connected to the voltage dividing resistors, and a bonding wire (10) is connected between the current detection terminal one of said pads, to select one

Abstract: A high side current monitor circuit includes an op amp which is coupled across a sensing element which carries a current Isense and develops a shunt voltage Vsense. A feedback transistor driven by the op amp output conducts an output current Iout through a resistor to a current output node necessary to make the op amp inputs equal, such that Iout is proportional to Isense. Iout is conducted through a resistor to generate a ground-referred voltage proportional to Vsense. When the common mode voltage of Vsense is greater than the op amp's breakdown voltage, a discrete transistor is connected between the current output node and ground to stand off the voltage across the amp. The monitor circuit is arranged such that it can be powered with a limited fraction of the common mode voltage when used with a discrete transistor, and is self-biased when used without a discrete transistor.

Abstract: A current limit circuit regulates the current flow through a power switch 90 by measuring the current through the switch 90 and comparing it to a reference voltage VREF that represents the limit current. When the current through the power switch 90 is greater than the limit current, the current in the power switch 90 is pulled lower by a driver circuit 92 which controls the power switch 90. By using a current limit reference voltage that has two levels, the power switch 90 has two current limit thresholds. Using a comparator 94 to compare the input voltage of the power switch 90 to the output voltage of the power switch 90, an output signal is generated to control the current limit threshold. When the input voltage and output voltage has a large differential voltage, a lower current limit threshold voltage is selected. When the input voltage and output voltage has a small differential voltage, an upper limit threshold voltage is selected.

Abstract: An overcurrent protection circuit using a shunt resistor and the voltage drop across a switch to program a user-defined current limiting level. This protects the switch and the input power supply, as well as the load. The shunt resistor is connected to the input or output of the switch, and a temperature dependent current source, so that a voltage drop is generated across the shunt resistor. An amplifier is used to sense the voltage across the shunt resistor and the voltage drop across the switch. When the voltage drop across the switch exceeds the voltage drop across the shunt resistor, the amplifier will regulate the switch so that a voltage drop across the switch is equal to the voltage drop across the shunt resistor. In this way, a constant current through the switch can be achieved. A constant ratio between the current limiting level to the shunt resistor value can be achieved with this method, so the current limiting level is programmable by selecting the resistor value.

Abstract: In a semiconductor protection circuit comprising a low speed protection circuit having an overcurrent detector for detecting an overcurrent of a predetermined switching element and turning off the semiconductor switching element following detection of the overcurrent, and a high speed protection circuit turning off the semiconductor switching element based on a voltage signal proportional to an output voltage of the semiconductor switching element.

Abstract: An LED drive circuit is disclosed, comprising an electronic controller which is arranged to monitor LED current as a first input. The controller also receives a second input from a sensor associated with the LED. The controller serves to monitor, based on its inputs, at least one further operating parameter of the LED which is either LED junction temperature or LED luminous intensity. The further operating parameter may be directly sensed by the sensor or may be calculated from the inputs to the controller. The controller is adapted to implement a closed loop control on LED current and to thereby limit current as necessary to maintain both the LED current and the further operating parameter below predetermined maximum values.

Abstract: In an overcurrent protection circuit for a switching power supply having multiple voltage supply sections, an overcurrent in a low voltage supply section is detected to make it possible to take a countermeasure against overload in a transformer winding, using a simple and low cost circuit design. The circuit comprises: a current detection resistor 33 to detect a current in secondary side of the transformer; transistors 53 and 52 to be turned on by the current detection; a photocoupler 50 to be turned on and off by the transistors; and a switching power supply controller 7 to control on-duty of a power MOSFET 6 for removing the overcurrent. The current detection resistor 33 is provided in the line of a secondary winding 30 so as to be able to individually limit a current flowing through the secondary winding 30.

Abstract: A protection circuit (10) is formed to protected a load (11) when a short circuit develops during operation of the load (11). A load transistor (18) is formed to couple the load to a voltage return terminal. A disable transistor (19) is formed to disable the load transistor (18) when a short circuit occurs.

Abstract: A power MOSFET has a main current carrying section and a sense current carrying section, with separate source electrodes. The source electrode of the main section is connected to the device source terminal. The source electrode of the sense section is connected through a current sensing resistance to the same terminal. Both sections have separate gate electrodes. By comparing a reference voltage with the sense voltage across the sensing resistance, a first control signal is provided for the gate electrode of the sense section. A control circuit includes an adjustment circuit coupled to the first control signal and to the sense voltage and provides a second control signal to the gate electrode of the main section. This second control signal maintains the gate-source voltage of the main section equal to the gate source voltage of the sense section.

Abstract: A bias circuit for preventing excessive emission from light emitting diodes includes a switch connected to power. A light emitting diode connects to the switch output. Two bias current legs, electrically connected in parallel, interpose the light emitting diode and ground. A fault comparator connects to the bias current legs and a logic OR gate. Four fault comparators can be implemented, each detecting a unique fault condition. The logic OR gate has an output connected to the input of the switch.

Abstract: The present invention is directed to a main element of a surge protector device and its fabrication method which uses breakdown phenomenon of a single high resistive film. A breakdown voltage and a place where breakdown occurs can be precisely controlled. The surge protector device changes from its non-conductive state to conductive state very quickly when a surge is induced and returns quickly to the non-conductive state when a surge is removed if said element is surrounded by oxidizing agent. The main element of the surge protector device of the present invention has a single high resistive film on a single metal bar. The high resistive film has a part or parts where electric field concentrates when a surge induced. A breakdown voltage can be controlled precisely by controlling a size including a thickness of the high resistive film of the part. The part is called a fuse part. The main element includes also at least two parts on said metal bar which are continuous to said fuse part.

Abstract: In an overcurrent detecting circuit, a judgment circuit comprises a reference voltage generating circuit for detecting an overcurrent flowing to an output circuit by utilizing resistor of a wire that connects a lead member provided in an IC package and the output circuit formed on a semiconductor chip and switching transistors for generating a judgment signal indicative of detection of the overcurrent by controlling the reference voltage generating circuit.

Abstract: A programmable controller has an overcurrent detection portion, an overcurrent indication portion and a transistor for interrupting a load current at the time of occurrence of an overcurrent are provided in an output circuit portion of the programmable controller. An overcurrent detection resistor is provided in the output transistor circuit, and a detected voltage across the resistor is compared with a reference voltage in an overcurrent detection circuit to judge an overcurrent. If an overcurrent is recognized, the overcurrent indication portion is operated, and the base current of the output transistor circuit is controlled to perform protection of the output circuit from the overcurrent. Accordingly, when an overcurrent is flowing and an input signal is in ON state, the output transistor is turned OFF automatically and, the overcurrent state is showed to a user.

Abstract: The present invention relates to a technique of limiting an overcurrent of a power semiconductor element (1) such as an IGBT. In a background art overcurrent protection circuit (10P), when an emitter current (i) and a current sense current (is) do not show the same behavior even in a transient state, the current sense current tends to momentarily increase at a turnoff, and in such a case, the energizing capability of a MOSFET (2P) in the overcurrent protection circuit increases and the turnoff speed of an IGBT (1P) becomes much faster than necessary and as a result, a surge voltage disadvantageously increases. Then, in the present invention, a diode (5) having a forward voltage set not lower than a threshold voltage of the MOSFET (2) is so provided as a voltage clamping circuit (4) between a gate electrode (2G) and a source electrode (2S) as to be biased in the forward direction in an overcurrent protection circuit (10) of an IGBT (1).

Abstract: In an over current protection circuit of a semiconductor switching device, a change in a main current of a semiconductor switching device with respect to a change in the detected voltage of the resistor for current detection connected to the current detection terminal of the semiconductor switching device becomes gentle in the vicinity of a location where the semiconductor switching device is turned off. With the provision of the current protection circuit, the variation in the cut-off level of the over current with respect to the variation in the detected voltage of the resistor for current detection connected to the current detection terminal of the semiconductor switching device is suppressed so that the semiconductor switching device can be protected from being breakdown due to the over current flow.

Abstract: A solid state fuse type protective circuit is provided in which a series MOSFET is connected in series with the load and its voltage source and a shunt MOSFET is connected in parallel with the load. A control circuit turns the series MOSFET on and the shunt FET off under normal operation; and turns the series FET off and applies a turn on signal to the shunt FET under a fault condition. An indicator LED is connected across the series FET and turns on when the series FET turns off.

Abstract: A motor driver high current protector includes a voltage source, a current sensor, a comparator, a switch, a delay circuit, and an inhibitor. The current sensor is configured to sense current passing through the motor driver and output a voltage responsive to the sensed current. The comparator has an output and is configured to generate a low voltage at its output while the output of the current sensor exceeds a first reference voltage. The switch has an input, an output, and a base. The base is activated by a low voltage at the output of the comparator to close the switch. Closing the switch provides electrical connection between the input and the output of the switch. The input of the switch is connected to the voltage source. The delay circuit is connected to the output of the switch and is configured to delay the voltage at the output of the switch while the switch is open. The delay circuit may include a resistor and a capacitor each connected to the output of the switch.

Abstract: An electrical power distribution system is disclosed that includes a gateway module (100) including logic (112) to interface to a vehicle management computer (VMC) (50) via a dual redundant standard data bus (1). The gateway module (100) has redundant microcontrollers (114, 116) operably connected to the VMC (50) for selectively controlling supply of electrical power to a plurality of separate electrical loads (120). A plurality of Load Management Modules (300) is provided. Each Load Management Module (300) includes a local microcontroller (310); power switching devices (320); and application specific integrated circuits ASICs (330) for interfacing the power switching devices (320) to the local microcontroller (310). Each ASIC (330) can be connected to a corresponding digital potentiometer (600) that is used to program an over current protection characteristic.

Abstract: In the electrophotographic copying apparatus or printer, a current proportional to the output current of the high voltage output circuit for supplying the charger etc. with a high voltage is detected by a current detection circuit, and the detection output is supplied to a smoothing circuit and a peak hold circuit. The outputs of the smoothing circuit and the peak hold circuit are supplied to a comparator and are compared with a reference value. If the output of the smoothing circuit or the peak hold circuit exceeds the reference value, the output of the high voltage output circuit is lowered or terminated.

Abstract: A programmable controller has an overcurrent detection portion, an overcurrent indication portion and a transistor for interrupting a load current at the time of occurrence of an overcurrent are provided in an output circuit portion of the programmable controlled. An overcurrent detection resistor is provided in the output transistor circuit, and a detected voltage across the resistor is compared with a reference voltage in an overcurrent detection circuit to judge an overcurrent. If an overcurrent is recognized, the overcurrent indication portion is operated, and the base current of the output transistor circuit is controlled to perform protection of the output circuit from the overcurrent. Accordingly, when an overcurrent is flowing and an input signal is in ON state, the output transistor is turned OFF automatically and, the overcurrent state is showed to a user.

Abstract: A cascaded DC-DC converter architecture has an upstream converter stage and a downstream converter stage, which derives its input voltage from the upstream stage. Cascading the two converter stages enables functionality of control and monitoring (including soft start and overcurrent detection) circuitry of the upstream stage to be used for the downstream stage, to reduce chip area, cost, and complexity. A voltage window regulator in the downstream converter ensures that, during shutdown, its output voltage will be maintained within a prescribed window of its regulated output voltage, so that no soft start delay is needed when the second converter stage is turned back on.

Abstract: A bias circuit for preventing excessive emission from light emitting diodes includes a switch connected to power. A light emitting diode connects to the switch output. Two bias current legs, electrically connected in parallel, interpose the light emitting diode and ground. A fault comparator connects to the bias current legs and a logic OR gate. Four fault comparators can be implemented, each detecting a unique fault condition. The logic OR gate has an output connected to the input of the switch.

Abstract: It is an object to provide a semiconductor device comprising a short circuit protecting system capable of enhancing the detection precision of a collector current, thereby carrying out a reliable short circuit protection. An IGBT (1) having a collector (C) connected to a terminal (T1) and an emitter (E) connected to a terminal (T2) is provided, and has a sense emitter (SE) connected to a terminal (T2) through a variable resistor (VR1) to be a current and voltage converting section. A sense potential is output from an end on the sense emitter (SE) side of the variable resistor (VR1) and is given to a terminal (T11) of a current ratio detecting section (15). A gate of the IGBT (1) is connected to a terminal (T3) and an output of the current ratio detecting section (15) is connected to a terminal (T4).

Abstract: A novel motor driver with an active snubber circuit. The motor driver is interposed between an external electrical power source and an electrical motor. The electrical motor is driven in first and second states such that the electrical motor produces an inductive flyback current when it switches torque direction. The motor driver comprises a reverse voltage protector in series between the power source and the electrical motor allowing flow of electrical power to the motor; and a capacitor arranged in parallel circuit with the motor between the motor and the diode (or other reverse voltage protector). The active snubber circuit is in parallel circuit with the motor between the diode and the electrical motor. The active snubber circuit comprises a switch having a sensor responsive to increases in the bus voltage resulting from the inductive flyback current and a resistor in series with the switch regulating electrical current flow.

Abstract: A solid state circuit breaker is disclosed for use in connection with a voltage bus, the voltage bus supplying electrical current to a load. The solid state circuit breaker includes a current controller for controlling the magnitude of current supplied by the voltage bus. A first current sensor senses the magnitude of the electrical current supplied by the voltage bus, the first current sensor having an output in communication with the current controller. An inductor is included within the first current sensor, the inductor providing a back electromotive force on the voltage bus. The back electromotive force is proportional to the rate of change of current flowing through the voltage bus.

Abstract: A power distribution module is especially suited to vehicular applications. An input/output module port is adapted for connection to an external multiplexed communication path, with transceiver circuitry being operative to send and receive messages over the communication path in digital form. The module is flexible enough to support a standard or user-defined commination protocol. An input is adapted for connection to a source of power. A plurality of controllable power switches are used to selectively route power from the source to a plurality of power output ports each port being associated with one of the switches. Control circuitry, operatively connected to the transceiver circuitry and to each power switch, facilitates the sending and receiving of messages over the communication path and provides control signals to the switches in accordance with a message received.

Abstract: A fault detection circuit and method for monitoring a power converter system to identify faults. The detection circuit includes two comparator circuits each having one input connected to the dc bus of the power converter system and responsive to the voltage spikes that occur as a result of faults. The other inputs of the comparator circuits are respectively connected to first and second sources of reference voltages having preset limits. The outputs of the two comparator circuits are combined on an output lead, and a fault signal will be produced on the output lead when the voltage spike on the dc bus exceeds the limits.

Abstract: A switching device includes a commanding device (813, Q51) which commands a driving of a load, a driving device (111) which outputs a drive signal in response to a drive command signal from the commanding device (813, Q51) and a first switching device (QA) inserted in a power supply circuit connecting a power supply (101) and the load (102). The first switching device (QA) is adapted to conduct in response to the drive signal and close the power supply circuit. A reference resistor (Rr1, Rr2) generates a reference voltage by receiving a current from the power supply, and a second switching device (QB, QC) is inserted in a shunt circuit connecting the power supply and the reference resistor. The second switching device (QB, QC) is adapted to conduct in response to the drive signal and close the shunt circuit. An abnormality determining device (CMP1, CMP2) determines an abnormality by comparing an output voltage from the first switching device (QA) and the reference voltage.

Abstract: An electrical protection system on a power distribution side includes a control element of a series combination of a PTC device thermally coupled with a resistive device, and a relay coil coupled with relay contacts. If the relay contacts are open the only way in which they can be closed is by supplying current to the relay coil through a resistance-capacitance network. An electronic control module on a control side includes an electronic control module for monitoring a voltage present in the system, and a switch for opening a current path feeding the system upon detection of a fault condition. An indicator indicates presence of a sensed fault condition.

Abstract: A programmable controller has an overcurrent detection portion, an overcurrent indication portion and a transistor for interrupting a load current at the time of occurrence of an overcurrent are provided in an output circuit portion of the programmable controller. An overcurrent detection resistor is provided in the output transistor circuit, and a detected voltage across the resistor is compared with a reference voltage in an overcurrent detection circuit to judge an overcurrent. If an overcurrent is recognized, the overcurrent indication portion is operated, and the base current of the output transistor circuit is controlled to perform protection of the output circuit from the overcurrent. Accordingly, when an overcurrent is flowing and an input signal is in ON state, the output transistor is turned OFF automatically and, the overcurrent state is showed to a user.

Abstract: A pulse-width modulator for controlling a semiconductor circuit-breaker in a switched-mode power supply has a comparator circuit for generating control pulses determined by an oscillator signal. Whereby a duration of the individual control pulses depends on a first control signal and a second control signal. A measuring configuration is provided for generating a load-current signal that is dependent on a load current of the circuit-breaker. Furthermore, the modulator has a feedback branch for feeding back the load-current signal to the comparator circuit whereby the feedback branch has a low-pass configuration. The low-pass configuration has an input which receives the load-current signal and an output at which the second control signal can be picked off.

Abstract: A circuit for detecting and automatically responding to ground faults. A passive protection PTC resistor is coupled in series with an active protection switch, the active protection switch being controlled by a control circuit to open the switch when excess current is detected to be flowing in the common path of one of the channels. Floating and grounded versions are described.

Abstract: A method of detecting absence of connection of an external ground to a ground connection point associated with an AC supply circuit of a power supply. The AC supply circuit has hot and neutral conductors, with the neutral conductor externally connected to ground. The math involves (a) passing a current from the hot conductor to the neutral conductor via the ground connection point, (b) detecting passage of the current, (c) shutting down operation of the power supply upon detection of the current, and (d) bypassing at least an effective portion of the current from the ground connection point to external ground on connection of the ground connection point to external ground, thereby disabling the detection of passage of the current.

Abstract: A programmable controller has an overcurrent detection portion, an overcurrent indication portion and a transistor for interrupting a load current at the time of occurrence of an overcurrent are provided in an output circuit portion of the programmable controller. An overcurrent detection resistor is provided in the output transistor circuit, and a detected voltage across the resistor is compared with a reference voltage in an overcurrent detection circuit to judge an overcurrent. If an overcurrent is recognized, the overcurrent indication portion is operated, and the base current of the output transistor circuit is controlled to perform protection of the output circuit from the overcurrent. Accordingly, when an overcurrent is flowing and an input signal is in ON state, the output transistor is turned OFF automatically and, the overcurrent state is showed to a user.