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Electrical load driving device

  • US 6,472,910 B2
  • Filed: 04/09/2001
  • Issued: 10/29/2002
  • Est. Priority Date: 04/12/2000
  • Status: Active Grant
First Claim
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1. An electrical load driving device comprising:

  • an output transistor having a first output terminal and a second output terminal connected in series in an electrical current supply path for passing a driving current through an electrical load, the output transistor supplying the driving current to the electrical load by assuming an ON state;

    in accordance with an output mode setting signal, the output transistor being caused to function either as high-side driving means which, with the first output terminal connected to the high-potential side of a load power supply and the second output terminal connected to one terminal of the electrical load having its other terminal connected to the low-potential side of the load power supply, by assuming the ON state in accordance with a driving signal, passes the driving current to the electrical load, or being caused as low-side driving means which, with the first output terminal connected to the one terminal of the electrical load having its other terminal connected to the high-potential side of the load power supply and the second output terminal connected to the low-potential side of the load power supply, by assuming the ON state in accordance with the driving signal, draws the driving current from the electrical load;

    first current detection signal generating means for generating as a first current detection signal a voltage dropped from the high-potential side of the load power supply by a voltage proportional to the driving current flowing through the output transistor, when the output transistor is functioning as the high-side driving means;

    first over-current determination voltage generating means for generating as a first over-current determination voltage, the first over-current determination voltage to be compared with the first current detection signal, a voltage dropped from the high-potential side of the load power supply by a predetermined voltage;

    second current detection signal generating means for generating as a second current detection signal a voltage raised from the low-potential side of the load power supply by a voltage proportional to the driving current flowing through the output transistor, when the output transistor is functioning as the low-side driving means;

    second over-current determination voltage generating means for generating as a second over-current determination voltage, the second over-current determination voltage to be compared with the second current detection signal, a voltage raised from the low-potential side of the load power supply by a predetermined voltage; and

    over-current detection signal outputting means for comparing the first current detection signal with the first over-current determination voltage and outputting an over-current detection signal indicating that the driving current flowing through the output transistor is excessive when the first current detection signal falls below the first over-current determination voltage when the output transistor is being caused to function as the high-side driving means, and for comparing the second current detection signal with the second over-current determination voltage and outputting the over-current detection signal when the second current detection signal rises above the second over-current determination voltage when the output transistor is being caused to function as the lowside driving means.

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