Inverter device with improved 3-phase pulse width modulation and vehicle air conditioner using the same
View Patent ↗The inverter device contains three sets of series circuit formed by connecting two switching elements ( 2 ) in series between a positive terminal and a negative terminal of DC power supply ( 1 ). Connecting points of the two switching elements are connected to motor ( 11 ). DC voltage of DC power supply ( 1 ) is switched by PWM 3-phase modulation so that a sinusoidal wave-shaped AC current is fed to the motor. Upper-arm switching elements connected to the positive terminal of the DC power supply increase or decrease an ON period equally in all phases for a carrier cycle in the PWM 3-phase modulation so as to provide two conducting period in the carrier cycle.
1. An inverter device comprising:
three sets of series circuits formed by connecting two switching elements of each set of series circuits in series between a positive terminal and a negative terminal of a DC power supply, each set of series circuits including an upper-arm switching element and a connecting point connected to a motor; and
a control circuit configured to switch DC voltage of the DC power supply by PWM 3-phase modulation so that a sinusoidal wave-shaped AC current is fed to the motor,
wherein the control circuit allows the upper-arm switching elements to add the same ON-period to all phases or to subtract the same ON-period from all phases for a carrier cycle in the PWM 3-phase modulation so as to provide two conducting periods in the carrier cycle.
2. The inverter device of claim 1 , wherein when there is a phase in which the upper-arm switching element has an ON period that accounts for 0% or at most 5% of the carrier cycle, the ON-period for adjustment is equally increased in all the phases.
3. The inverter device of claim 1 , wherein when there is a phase in which the upper-arm switching element has an ON period that accounts for 100% or at least 95% of the carrier cycle, the ON-period for adjustment is equally decreased in all the phases.
4. The inverter device of claim 1 , wherein the ON-period for adjustment is increased or decreased in a middle of the carrier cycle.
5. The inverter device of claim 1 , wherein the ON-period for adjustment is equally increased or decreased in all phases so that a period during which all of the upper-arm switching elements turn on is equivalent in length to a period during which all of the upper-arm switching elements turn off.
6. The inverter device of claim 1 , wherein the ON-period for adjustment is determined so as to form a continuous transition without a gap between the phases.
7. The inverter device of claim 1 , wherein the ON-period for adjustment, which is to be increased or decreased equally in the phases, becomes greater as the PWM 3-phase modulation takes a higher modulation degree.
8. A vehicle air conditioner that employs the inverter device described in claim 1 .
9. A vehicle air conditioner that employs the inverter device described in claim 2 .
10. A vehicle air conditioner that employs the inverter device described in claim 3 .
11. A vehicle air conditioner that employs the inverter device described in claim 4 .
12. A vehicle air conditioner that employs the inverter device described in claim 5 .
13. A vehicle air conditioner that employs the inverter device described in claim 6 .
14. A vehicle air conditioner that employs the inverter device described in claim 7 .