Load control device and method

• US 7,907,376 B2
• Filed: 03/09/2007
• Issued: 03/15/2011
• Est. Priority Date: 04/04/2006
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Yoshimura, Satoshi, Yamada, Masao
• Primary Examiner(s): Fureman; Jared J
• Assistant Examiner(s): WILLOUGHBY, TERRENCE RONIQUE
• Application Number:
  US11/715,898
• Publication Number:
  US 20070230224A1
• Time in Patent Office: 1,467 Days
• Field of Search: 361/90, 361/86, 361/88, 361/91.2, 361/92, 361/93.7
• US Class Current: 361/92
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/4903 Connectors having different sizes, e.g. different diameters
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/13055 Insulated gate bipolar transistor [IGBT]
• CPC Class Codes: H01L 2924/13091 Metal-Oxide-Semiconductor Field-Effect Transistor [MOSFET]
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 1/36 Means for starting or stopping converters
• CPC Class Codes: H02M 3/1555 for the generation of a regulated current to a load whose impedance is substantially inductive
• CPC Class Codes: H02P 29/0241 the fault being an overvoltage

Abstract

A load control device includes a control circuit and a protection circuit. The control circuit controls driving of an electric load. The protection circuit monitors a power supply voltage supplied to the control circuit and stops control of driving the load by the control circuit, when the power supply voltage drops below a threshold value. The protection circuit provides the threshold value with a hysteresis characteristic having a width determined by a product of a wiring resistance of a path for supplying a driving current to the load and a maximum value of the driving current.

Claims

1. A load control device comprising:

a power source for supplying a power supply voltage;

a control circuit that controls driving of a load;

a protection circuit that monitors the power supply voltage supplied to the control circuit and stops control by the control circuit when the power supply voltage drops below a threshold value;

a first wiring that supplies a current to the load from a terminal to which the power supply voltage is supplied, the first wiring including a smoothing inductor; and

a second wiring that is directly connected to the terminal and supplies the power supply voltage to the control circuit from the terminal of the power supply voltage, the second wiring being different from the first wiring and connected between the smoothing inductor and the terminal of the power supply voltage, wherein

the protection circuit has a means to provide the threshold value with a hysteresis characteristic having a width equal to or larger than a voltage drop level based on a wiring resistance of a path for supplying a driving current to the load and a maximum value of the driving current.

2. The load control device of claim 1, wherein

the protection circuit includes:

an integration circuit that smoothes the power supply voltage; and

a comparator that compares the power supply voltage of the integration circuit with a threshold reference.

3. The load control device of claim 1, wherein

the protection circuit includes:

a timer that causes the control circuit to resume control only after a predetermined time has elapsed from restoration of the power supply voltage, when the protection circuit once stops the control.

4. The load control device of claim 1, wherein

the control circuit includes:

a slow start circuit that, when the control circuit resumes control, starts driving of the load from a lowest level and gradually increases a level to a level corresponding to a command value externally applied at that point of time.

5. The load control device of claim 1, wherein

the load is an electric motor.

6. The load control device of claim 1, wherein

the load is a device that outputs sonic wave signals.

7. The load control device of claim 1, wherein

the load is a device that outputs optical signals.

8. The load control device of claim 1, wherein:

the control circuit and the protection circuit are integrated in an IC chip;

the IC chip and other circuit element chips are mounted on a lead frame and package-molded as a hybrid IC.

9. The load control device of claim 8, wherein

one of the circuit element chips is a transistor for supplying the current to the load.

10. The load control device of claim 9, wherein

the load is an inductive load, and another of the circuit element chips is a flywheel diode connected in parallel with the transistor.

11. The load control device of claim 1, further comprising:

a third wiring that connects ground with the load, the first and third wirings forming the path for supplying the driving current to the load; and

a fourth wiring that connects ground with the control circuit, the second and fourth wirings being dedicated power wires that form a power system different from that which powers the load through the first and third wirings.

12. A load control method comprising the steps of:

monitoring a power supply voltage supplied by a power source to a control circuit for controlling driving of a load;

stopping control by the control circuit when the power supply voltage drops below a threshold value;

changing the threshold value by adding a hysteresis when the control is stopped, the hysteresis having a width equal to or larger than a voltage drop level determined based on a wiring resistance of a path for supplying a driving current to the load and a maximum value of the driving current;

resuming the control by the control circuit when the power supply voltage rises above the threshold value changed with the hysteresis;

supplying the power supply voltage from a terminal of the power source to the load through a first wiring; and

supplying the power supply voltage from the terminal of the power source to the control circuit through a second wiring, the second wiring being directly connected to the terminal of the power source, being different from the first wiring, and having a lower resistance than the first wiring.

13. The load control method of claim 12, further comprising:

integrating the power supply voltage, wherein

the step of monitoring monitors the power supply voltage integrated by the step of integrating.

14. The load control method of claim 12, further comprising:

resuming the control by the control circuit only when a predetermined time has elapsed after the power supply voltage is restored to be above the threshold value, when the control is stopped.

15. The load control method of claim 12, further comprising:

resuming the control of diving of the load from a lowest level and a level is gradually increased to a level corresponding to a command value externally given at that point of time, when the power supply voltage is restored to be above the threshold value.

16. The load control method of claim 12, wherein

the load is an electric motor.

17. The load control method of claim 12, wherein

the load is a device that outputs sonic wave signals.

18. The load control method of claim 12, wherein

the load is a device that outputs optical signals.

19. The load control method of claim 12, wherein

the width of the hysteresis is determined to be larger than a product of the wiring resistance and the maximum value of the driving current.

20. The load control method of claim 12, wherein

supplying the power supply voltage from the terminal of the power source to the load through a first wiring includes supplying the power supply voltage through a smoothing conductor;

and

supplying the power supply voltage from the terminal of the power source to the control circuit includes supplying the power supply voltage directly from the terminal of the power source to the control circuit.

21. The load control method of claim 12, wherein:

the path for supplying the driving current to the load includes the first wiring and a third wiring that connects ground with the load, and

the control circuit is connected with ground through a fourth wiring, the second and fourth wirings being dedicated power wires that form a power system different from that which powers the load through the first and third wirings.