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US 2003/0197532 A1Published application
Overcurrent protection structure of load driving circuit
AssigneeDenso Corporation
InventorMasahiro Tsuchida
Life of this patent
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AssigneeDenso Corporation
InventorMasahiro Tsuchida
Estimating the term…
An electrical load driving circuit is provided which includes an insulated gate transistor and a control voltage limiting circuit. The transistor works to supply the power to an electrical load selectively. The control voltage limiting circuit includes a control circuit and a switching circuit. The control circuit works to limit a voltage applied to the transistor selectively to one of a higher controlled voltage and a lower controlled voltage. The switching circuit is disposed across the transistor and closed selectively to limit the voltage applied to the transistor to the second controlled voltage through the control circuit when it is determined that an overcurrent has occurred which flows through the transistor.
An electrical load driving circuit comprising:
An electrical load driving circuit further comprising an overcurrent determining circuit working to provide an overcurent signal indicating occurrence of an overcurrent when said comparator continues to output the close control signal after the elapse of a given period of time from output of the close control signal from said comparator.
Dependencies are inferred from the claim text.
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From the US filing history. Foreign family members aren’t listed.
Backward citations are indexed for grants only.
By feedback from the output to the control circuit: in field-effect transistor switches
Pulse technique
Term end not estimated
1. Technical Field of the Invention
The present invention relates generally to a load driving circuit designed to drive a current flowing through an electrical load using an insulated gate transistor, and more particularly to an overcurrent protection structure of such a load driving circuit equipped with with an overcurrent detector and an overcurrent limiter.
2. Background Art
The present invention will be understood more fully from the detailed description given hereinbelow and from the accompanying drawings of the preferred embodiments of the invention, which, however, should not be taken to limit the invention to the specific embodiments but are for the purpose of explanation and understanding only.
In the drawings:
FIG. 1 is a circuit diagram which shows an electrical load driving circuit according to the first embodiment of the invention;
Referring to the drawings, wherein like reference numbers refer to like parts in several views, particularly to FIG. 1, there is shown a load driving circuit 21 according to the first embodiment of the invention which is fabricated on an IC 22 installed in an ECU (Electronic Control Unit) of an automotive vehicle and works to drive a resistive and inductive electrical load 23 such as a relay coil or an LED. In practice, the IC 22 has disposed thereon as many channels, i.e., driving circuits 21 as electrical loads to be actuated.
The IC 22 has a power supply terminal 22a and a ground terminal 22b connected to positive and negative terminals of a battery 24, respectively. The electrical load 23 is connected between an output terminal 22c and the ground terminal 22d of the IC 22. An external capacitor 25 (i.e., a capacitive load) is disposed between the power supply terminal 22a and the output terminal 22c for enhancing the ability of the IC 22 to withstand ESD (electrostatic discharge).
The load driving circuit 21 has disposed between the power supply terminal 22a and the output terminal 22c an N-channel MOSFET 26 (i.e.,. an insulated gate transistor) and a current detector 29 made up of a resistor 27 and an N-channel MOSFET 28 connected in series which works as a high-side switch for the load 23.