Inverter

• US 20070189048A1
• Filed: 07/19/2005
• Published: 08/16/2007
• Est. Priority Date: 07/20/2004
• Status: Active Grant

• Current Assignee: Panasonic Automotive Systems Company of America (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Goto, Naomi
• Granted Patent: US 7,583,523 B2
• Time in Patent Office: Days
• US Class Current: 363/95
• CPC Class Codes: B60H 1/00428 electric
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 7/53871 with automatic control of output voltage or current
• CPC Class Codes: H02M 7/5395 by pulse-width modulation
• CPC Class Codes: H02P 6/18 without separate position detecting elements
• CPC Class Codes: Y02T 10/88 Optimized components or subsystems, e.g. lighting, actively controlled glasses

Abstract

A small and highly vibration-proof inverter capable of detecting a phase current without requiring the development of complicated control software and without causing any current distortion is provided. Shunt resistors (15, 16) serving as a kind of current detector are provided, respectively, between lower arm switching elements (X, Y, Z) in only two phases and the minus side of a DC power supply. An identical ON period is reduced from the ON periods of upper arm switching elements (U, V, W) in the carrier cycle entirely for three phases. Consequently, phase current is detected for the two phases provided with the shunt resistors (15, 16). The inverter can detect the phase current without complicating the control software and without causing any current distortion, by controlling inverter circuit (10) with control software incorporated in control circuit (14) through connection lines (18).

Claims

1. An inverter comprising an upper arm switching element connected with a plus side of a direct-current power source and a lower arm switching element connected with a minus side of the direct-current power source for three phases for outputting sine wave-like three phase alternating current by switching a direct-current voltage of the direct-current power source by means of PWM three phase modulation, wherein

a current detector for detecting a current which flows between the lower arm switching element and the minus side of the direct-current power source is provided in two phases among the three phases, and

a control circuit detects a phase current of the two phases provided with current detector by deducting identical ON periods in all the three phases from ON periods of the upper arm switching element within a carrier cycle.

2. The inverter of claim 1, wherein

the deduction of the ON period with the upper arm switching element in all the three phases is conducted when there exists a phase in which an ON period of the lower arm switching element is 0% or close to 0% within a carrier cycle.

3. The inverter of claim 1, wherein the deduction of the ON period with the upper arm switching element in all the three phases is conducted avoiding a term in which ON periods of all the upper arm switching element are 0% or close to 0%.

4. The inverter of claim 1, wherein

the deduction of the ON period with the upper arm switching element in all the three phases is conducted so that a time length of a term in which all the upper arm switching elements are ON approximately equals to that of a term in which all the upper arm switching elements are OFF.

9. The inverter of claim 1, wherein the current detector is a shunt resistor.

10. The inverter of claim 1, wherein

the sine wave-like three phase alternating current is outputted to a sensorless DC brushless motor, and a position of a rotor of the sensorless DC brushless motor is judged based on the detected two phase currents.

11. The inverter of claim 10, wherein the inverter is mounted on an electric compressor which is driven by a sensorless DC brushless motor.

12. The inverter of claim 1, wherein the inverter is used on board a vehicle.

5. An inverter comprising an upper arm switching element connected with a plus side of a direct-current power source and a lower arm switching element connected with a minus side of the direct-current power source for three phases for outputting sine wave-like three phase alternating current by switching a direct-current voltage of the direct-current power source by means of PWM three phase modulation, wherein

a current detector for detecting a current which flows between the upper arm switching element and the plus side of the direct-current power source is provided in two phases among the three phases, and

a control circuit detects a phase current of the two phases provided with current detector by adding identical ON periods in all the three phases to ON periods of the upper arm switching element within a carrier cycle.

6. The inverter of claim 5, wherein

the addition of the ON period with the upper arm switching element in all the three phases is conducted when there is a phase in which the ON period of the upper arm switching element is 0% or close to 0% within a carrier cycle.

7. The inverter of claim 5, wherein

the addition of the ON period with the upper arm switching element in all the three phases is conducted avoiding a term in which ON periods of all the lower arm switching element are 0% or close to 0%.

8. The inverter of claim 5, wherein

the addition of the ON period with the upper arm switching element in all the three phases is conducted so that a time length of a term in which all the upper arm switching elements are ON approximately equals to that of a term in which all the upper arm switching elements are OFF.

13. The inverter of claim 5, wherein the current detector is a shunt resistor.

14. The inverter of claim 5, wherein

the sine wave-like three phase alternating current is outputted to a sensorless DC brushless motor, and a position of a rotor of the sensorless DC brushless motor is judged based on the detected two phase currents.

15. The inverter of claim 5, wherein the inverter is used on board a vehicle.