Voltage booster apparatus for power steering system

• US 8,350,510 B2
• Filed: 11/24/2010
• Issued: 01/08/2013
• Est. Priority Date: 11/27/2009
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Ogasawara, Terumoto
• Primary Examiner(s): Ip, Paul
• Application Number:
  US12/954,199
• Publication Number:
  US 20110127936A1
• Time in Patent Office: 776 Days
• Field of Search: 318/400.21, 318/400.22, 318/400.3, 180/65.275, 180/443, 701/43, 323/234, 323/318
• US Class Current: 318/400.3
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load

Abstract

In a voltage booster apparatus, a charge control transistor is turned on to charge a coil output capacitor and a booster output capacitor and then turned off, thereby confirming rise of a coil output voltage and a booster output voltage. A power supply relay is turned on to restore a booster operation thereby to check rise of the booster output voltage. If both of a step-up FET and a step-down FET are not in short-circuit failure, ON state of the power supply relay is fixed thereby to restore a power steering system operation.

Claims

1. A voltage booster apparatus for a power steering system comprising:

a booster power supply terminal for supplying a battery voltage;

a power supply relay;

a booster circuit including a coil, a step-up switching element, a backflow prevention element and an output capacitor, the coil having an input end connected in series with the booster power supply terminal through the power supply relay, the step-up switching element having one end connected to an output end of the coil and an other end connected to a ground, the backflow prevention element having one end connected to the output end of the coil in parallel with the step-up switching element to prevent backflow of a current from an other end thereof to the one end thereof, and the output capacitor having one end connected to the other end of the backflow prevention element and an other end connected to the ground;

a booster circuit control section connected to a control terminal of the step-up switching element to perform voltage boosting control by turning on and off the step-up switching element;

a power supply relay control section configured to supply or interrupt the battery voltage to the input end of the coil by turning on and off the power supply relay;

a voltage monitor section configured to check whether a short-circuit failure is present in the step-up switching element or the backflow prevention element by monitoring at least one of a coil input voltage developed at the input end of the coil, a coil output voltage developed at the coil output end and a boosted voltage developed at the one end of the output capacitor;

the voltage monitor section being configured to control, upon detection of the short-circuit failure, the power supply relay control section to turn off the power supply relay thereby stopping a power steering operation;

a charge power supply terminal provided to supply a reference voltage to the booster circuit;

a charge switching element connected between the output end of the coil and the charge power supply terminal; and

a charge circuit control section connected to a control terminal of the charge switching element for supplying or interrupting the reference voltage to the output end of the coil by turning on and off the charge switching element,

wherein the charge circuit control section is configured to supply the reference voltage to the booster circuit by turning on the charge switching element after the power supply relay is turned off by the power supply relay control section, and the booster circuit control section or the relay control section is configured to perform a predetermined operation, so that the voltage monitor section checks whether the short-circuit failure is present, and

wherein the power supply relay control section is configured to turn on the power supply relay again thereby restoring the power steering operation, when no short-circuit failure is determined.

2. The voltage booster apparatus according to claim 1, wherein:

the charge switching element is connected to supply, when turned on, the reference voltage to the booster circuit for charging the output capacitor by the reference voltage;

the charge circuit control section is configured to turn off the charge switching element after charging the output capacitor; and

the voltage monitor section is configured to check whether the short-circuit failure is present in the step-up switching element based on a rise of the coil output voltage or the boosted voltage after the charge switching element is turned off.

3. The voltage booster apparatus according to claim 2, wherein:

the power supply relay control section is configured to turn on the power supply relay temporarily, when the step-up switching element is determined to have no short-circuit failure, so that the booster circuit performs voltage boosting operation;

the voltage monitor section is configured to check whether the backflow prevention element has the short-circuit failure based on the rise of the boosted voltage produced by the voltage boosting operation of the booster circuit; and

the power supply relay control section is further configured to maintain the power supply relay in an ON state for restoring the power steering operation, when the backflow prevention element is determined to have no short-circuit failure.

4. The voltage booster apparatus according to claim 2, wherein:

the booster control section is configured to turn on the step-up switching element, when the step-up switching element is determined to have no short-circuit failure, so that the output capacitor is discharged through the step-up switching element;

the voltage monitor section is configured to check whether the backflow prevention element has the short-circuit failure by comparing the coil output voltage with the boosted voltage produced after the output capacitor is discharged; and

the power supply relay control section is configured to maintain the power supply relay in an ON state for restoring the power steering operation, when the backflow prevention element is determined to have no short-circuit failure.

5. The voltage booster apparatus according to claim 2, wherein:

the booster control section is configured to turn on the step-up switching element, when the step-up switching element is determined to have no short-circuit failure, so that the output capacitor is discharged through the step-up switching element;

the voltage monitor section is configured to check whether the backflow prevention element has the short-circuit failure based on a speed of fall of the boosted voltage produced after the output capacitor is discharged; and

the power supply relay control section is configured to maintain the power supply relay in an ON state for restoring the power steering operation, when the backflow prevention element is determined to have no short-circuit failure.

6. The voltage booster apparatus according to claim 3, wherein:

the voltage monitor section is configured to check whether the booster power supply terminal has a short-circuit failure by comparing the coil output voltage or the boosted voltage with the battery voltage, when the power supply relay is turned on temporarily.

7. The voltage booster apparatus according to claim 1, wherein:

the voltage monitor section is configured to confirm, before the charge switching element is turned on, that the coil output voltage and the boosted voltage change less than a predetermined amount in a predetermined time.

8. A voltage booster apparatus for a power steering system comprising:

a battery for supplying a battery voltage;

a booster circuit including a coil, a step-up switching element, an output capacitor and a current flow control element, the coil having an input end for receiving the battery voltage, the step-up switching element being connected in series with the coil at an output end of the coil, the output capacitor being connected in series with the coil in parallel relation with the step-up switching element, and the current flow control element being connected between the output end of the coil and one end of the capacitor for preventing a current flow from the capacitor to the coil;

a charge switching element connected to the output end of the coil for supplying a reference voltage to the output end of the coil when turned on;

a control unit configured to control a voltage boosting operation of the booster circuit by turning on and off the step-up switching element so that the coil produces a coil output voltage at the coil output end a boosted voltage is produced from the output capacitor;

the control unit being configured to interrupt supply of the battery voltage to the booster circuit upon detection of a short-circuit failure of the step-up switching element or the current flow control element;

the control unit being configured to turn on the charge switching element to supply the reference voltage to the output end of the coil for charging the output capacitor by the reference voltage in response to interruption of the battery voltage;

the control unit being configured to turn on the step-up switching element in a predetermined manner after the output capacitor is charged with the reference voltage;

the control unit being configured to check whether the step-up switching element and the current flow control element have the short-circuit failure based on the coil output voltage and the boosted voltage produced after the charge switching element is turned on to supply the reference voltage; and

the control unit being configured to restore the supply of the battery voltage to the booster circuit after both of the step-up switching element and the current flow control element are determined to have no short-circuit failure.

9. The voltage booster apparatus according to claim 8, further comprising:

a power supply relay connected between the battery and the booster circuit to supply and interrupt the battery voltage when turned on and off, respectively, the power supply relay being turned off upon detection of the short-circuit failure by the control unit,

wherein the control unit is configured to turn on temporarily the power supply relay after the reference voltage is supplied to the output end of the coil by the charge switching element is turned on,

wherein the control unit is configured to turn on and off the step-up switching element for boosting the battery voltage, and

wherein the control unit is configured to turn on and off the power supply relay when the boosted voltage rises or does not rise, respectively, as a result of turning on and off the step-up switching element after the reference voltage is supplied.

10. The voltage booster apparatus according to claim 8, further comprising:

a power supply relay connected between the battery and the booster circuit to supply and interrupt the battery voltage when turned on and off, respectively, the power supply relay being turned off upon detection of the short-circuit failure by the control unit,

wherein the control unit is configured to turn on the step-up switching element after the reference voltage is supplied to the output end of the coil by the charge switching element is turned on,

wherein the control unit is configured to compare the coil output voltage with the boosted voltage produced after the step-up switching element is turned on, and

wherein the control unit is configured to turn on the power supply relay again only when a comparison result indicates that the boosted voltage is much higher than the coil output voltage.

11. The voltage booster apparatus according to claim 8, further comprising:

a power supply relay connected between the battery and the booster circuit to supply and interrupt the battery voltage when turned on and off, respectively, the power supply relay being turned off upon detection of the short-circuit failure by the control unit,

wherein the control unit is configured to turn on the step-up switching element after the reference voltage is supplied to the output end of the coil by the charge switching element is turned on,

wherein the control unit is configured to check whether a speed of rise of the boosted voltage is less than a predetermined speed, and

wherein the control unit is configured to turn on the power supply relay again only when a check result indicates that the speed of rise of the boosted voltage is less than the predetermined speed.