Hitachi, Ltd.

Hitachi Haramachi Semi-conductor, Ltd.

Masayuki Wada

Kazunori Umeda

Eiichi Sudou

Hideki Miyazaki

Kenichi Onda

Tomoyuki Tanaka

Koichi Suda

Kouzou Watanabe

Tatsuo Shimura

Shoichi Ozeki

Hitoshi Matsuzaki

Chooji Shiina

Tadaki Kariya

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.

Programmable controller

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.

An inverter includes first, second, and third dc voltage sources, first and second switching elements which are connected in series to the first dc voltage source, a signal generator section for producing first and second control signals on the basis of the output voltage from the third dc voltage source, first and second signal level converter sections for converting voltage levels of the first and second control signals based on the output voltage from the second dc voltage source and thereby respectively generating first and second output signals, and first and second driver sections responsive to the first and second output signals for supplying the first and second switching element with first and second driving signals on the basis of the output voltage from the second dc voltage source and thereby respectively turning the first and second switching elements on or off. At least either one of the first and second signal level converter sections includes a turn-off section responsive when at least either one of the output voltages respectively from the second and third dc voltage sources is lower than a predetermined voltage level for turning the first or second switching element off irrespective of the first and second control signals.

Inverter

A switching circuit providing detection circuit for detecting a current which flows through a main P-channel MOSFET detection of a floating voltage dependent upon a power supply potential, a reference-voltage generating circuit for generating a reference voltage which is a floating voltage dependent upon the power supply potential and has a constant value independently of variations in power supply potential, a comparator circuit operated on a supply voltage which is a floating voltage dependent upon the power supply potential, for comparing a detected voltage from the detection circuit with the reference voltage from the reference-voltage generating means, to convert the detected voltage into a logic voltage signal (i.e., a bi-level voltage signal and a conversion circuit for converting the logic voltage outputted by the comparator circuit into a voltage measured from a ground potential.

High-side switch with overcurrent protecting circuit

A turn-off control circuit for a gate turn-off thyristor is used in a state where one end of an inductive load is connected therewith on the cathode side. The turn-off control circuit includes a first turning-off transistor, which takes-out electric current through the gate at the first stage of the turn-off operation of the gate turn-off thyristor, and a second turning-off transistor, which takes-out electric current through the gate at the second stage of the turn-off operation of the gate turn-off thyristor so as to surely effect the turn-off operation.

Growing community of inventors

Katsuta, Japan

Masayuki Wada