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

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Niimi, Yukihide
• Primary Examiner(s): Callahan, Timothy P.
• Assistant Examiner(s): ENGLUND, TERRY LEE
• Application Number:
  US09/828,123
• Publication Number:
  US 20010030557A1
• Time in Patent Office: 568 Days
• Field of Search: 327/108, 327/109, 327/110, 327/111, 327/112, 327/530, 327/538, 327/543, 327/546, 327/77, 326/82, 326/83, 307/127, 307/131, 307/412, 361/93.1, 361/93.2
• US Class Current: 327/108
• CPC Class Codes: H03K 17/063 in field-effect transistor switches
• CPC Class Codes: H03K 17/0822 in field-effect transistor switches
• CPC Class Codes: H03K 17/693 Switching arrangements with several input- or output-terminals, e.g. multiplexers, distributors logic circuits H03K19/00; code converters H03M5/00, H03M7/00

Abstract

An electrical load driving device is constructed to accurately detect an over-current state in either a high-side output mode or a low-side output mode irrespective of voltage fluctuations of a load power supply. The over-current is detected by a detection voltage which decreases from a battery voltage in proportion to a current flowing through an output transistor being compared with a determination voltage in the high-side output mode. It is detected by a second detection voltage which increases from a ground potential in proportion to the current flowing through the output transistor being compared with a determination voltage in the low-side output mode.

Claims

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.

2. An electrical load driving device as in claim 1, further comprising:

over-current protection means for forcibly turning off the output transistor when the over-current detection signal is outputted from the over-current detection signal outputting means.

3. An electrical load driving device as in claim 1, wherein:

the first current detection signal generating means includes a first resistor for current detection having one end connected to the first output terminal of the output transistor, and a first transistor for current detection having a first output terminal connected to the other end of the first resistor and another output terminal connected to the second output terminal of the output transistor for passing through the first resistor a mirror current proportional to the driving current flowing through the output transistor, and the first current detection signal generating means outputting as the first current detection signal the voltage of a connection point between the first output terminal of the first transistor and the first resistor; and

the second current detection signal generating means includes a second resistor for current detection having one end connected to the second output terminal of the output transistor, and a second transistor for current detection having a first output terminal connected to the first output terminal of the output transistor and another output terminal connected to the other end of the second resistor for current detection for passing through the second resistor a mirror current proportional to the driving current flowing through the output transistor, the second current detection signal generating means outputting as the second current detection signal the voltage of a connection point between the other output terminal of the second transistor for current detection and the second resistor.

4. An electrical load driving device as in claim 1, wherein:

the output transistor, the first current detection signal generating means, the second current detection signal generating means and the over-current detection signal outputting means are formed as an output circuit in a single semiconductor integrated circuit.

5. An electrical load driving device as in claim 4, wherein the electrical load driving device further comprises an additional output circuit formed in the single semiconductor integrated circuit, the additional output circuit including an additional output transistor, an additional first current detection signal generating means, an additional second current detection signal generating means and an additional over-current detection signal outputting means.

6. 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 to function 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;

current detection signal generating means for generating a current detection voltage signal indicative of the driving current flowing in the output transistor, when the output transistor is functioning in either one of a mode in which the output transistor is caused to function as the high-side driving means or a mode in which the output transistor is caused to function as the low-side driving means;

over-current determination voltage generating means for generating an over-current determination voltage to be compared with the current detection voltage signal; and

over-current detection means for comparing the current detection voltage signal with the over-current determination voltage and outputting an over-current detection signal indicating that the driving current flowing through the output transistor is excessive whether the output transistor is caused to function as the high-side driving means or the low-side driving means.

7. An electrical load driving device as in claim 6, wherein the over-current detection means is responsive to the output mode setting signal that determines the output transistor to operate as one of the high-side driving means and the low-side driving means.

8. A method of driving an electrical load, the method comprising:

providing 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 the 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, causing the output transistor to function either as a high-side driver 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 causing the output transistor to function as a low-side driver 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;

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 driver;

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;

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 driver;

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

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 driver, 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 low-side driver.

9. A method as in claim 8, further comprising:

forcibly turning off the output transistor when the over-current detection signal is output.

10. A method of driving an electrical load comprising:

providing 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 the 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, causing the output transistor to function either as a high-side driver 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 causing the output transistor to function as a low-side driver 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;

generating a current detection voltage signal indicative of the current flowing in the output transistor, when the output transistor is functioning in either a mode in which the output transistor is caused to function as the high-side driver or a mode in which the output transistor is caused to function as the low-side driver;

generating an over-current determination voltage to be compared with the current detection voltage signal; and

comparing the current detection voltage signal with the over-current determination voltage and outputting an over-current detection signal indicating that the driving current flowing through the output transistor is excessive.