VOLTAGE STEP-UP/DOWN CONVERTER

• US 20100181946A1
• Filed: 01/20/2010
• Published: 07/22/2010
• Est. Priority Date: 01/22/2009
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Ogasawara, Terumoto
• Granted Patent: US 8,148,934 B2
• Time in Patent Office: Days
• US Class Current: 318/139
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 3/1582 Buck-boost converters H02M3/1584 takes precedence

Abstract

A motor control apparatus includes a step-up/down converter and an inverter. The converter includes a coil, MOSFETs, capacitors and a control circuit. The control circuit turns on the MOSFET in the high potential side, while tuning off the MOSFET in the low potential side. After a predetermined time, the control circuit turns off the MOSFET in the high potential side and then turns on the MOSFET in the low potential side. It is checked whether the MOSFET, which is switched in the step-down operation, is normal or abnormal based on the voltages of the capacitors. The capacitors produce specific changes in the respective voltages in correspondence to the check result. Thus, the abnormality of the MOSFET can be determined based on the changes.

Claims

1. A voltage step-up/down converter comprising:

a coil;

a first switch having one end connected to one end of the coil and the other end grounded;

a first rectifier connected in parallel to the first switch to allow current flow only from the other end to the one end of the first switch;

a second switch having one end connected to a junction between the coil and the first switch;

a second rectifier connected in parallel to the second switch to allow current flow only from the one end to the other end of the second switch;

a first capacitor having one end connected to the other end of the coil and the other end grounded for smoothing a DC voltage outputted to the other end of the coil;

a second capacitor having one end connected to the other end of the second switch and the other end grounded for maintaining a DC voltage outputted to the other end of the second switch;

a third switch having one end connected to a circuit power source and the other end connected to a junction among the coil, the first switch and the second switch; and

a control circuit configured to turn on and off the first switch in a voltage step-up operation, in which the DC voltage at the other end of the coil is stepped up and outputted from the other end of the second switch, and the control circuit configured to turn on and off the second switch in a voltage step-down operation, in which the DC voltage at the other end of the second switch is stepped down and outputted from the other end of the coil,

wherein the control circuit is further configured to check whether the second switch is normal or abnormal based on voltages of the first capacitor and the second capacitor, by turning on the third switch while turning on the first switch, then turning off the third switch and then turning on the first switch.

2. The voltage step-up/down converter according to claim 1,

wherein the control circuit is configured to turn on the second switch when the third switch is turned on, and turn off the second switch when the third switch is turned off.

3. The voltage step-up/down converter according to claim 1,

wherein the control circuit is configured to determine that the second switch is normal if the voltage of the second capacitor is higher than that of the first capacitor.

4. The voltage step-up/down converter according to claim 1,

wherein the control circuit is configured to determine that the second switch is in short-circuit failure, if the voltage of the second capacitor falls to be lower than immediately before the first switch is turned on.

5. The voltage step-up/down converter according to claim 4,

wherein the control circuit is configured to determine that the second switch is in the short-circuit failure, if the voltage of the second capacitor is less than a voltage threshold.

6. The voltage step-up/down converter according to claim 4, wherein the control circuit is configured to determine that the second switch is in the short-circuit failure, if a change of the voltage of the second capacitor between before and after the first switch is turned on.

7. The voltage step-up/down converter according to claim 1,

wherein the control circuit is configured to determine that the second switch is in the short-circuit failure, if a difference between the voltages of the first capacitor and the second capacitor is less than a voltage threshold.

8. The voltage step-up/down converter according to claim 1,

wherein the other end of the coil and the one end of the first capacitor are connected to a battery of a vehicle so that a DC voltage of the battery is stepped up by turning on and off of the first switch, and the other end of the second switch and the one end of the capacitor are connected to an inverter so that a DC voltage outputted from the inverter is stepped down by turning on and off of the second switch.