Power conversion device and refrigeration/air-conditioning system

• US 9,531,250 B2
• Filed: 03/04/2011
• Issued: 12/27/2016
• Est. Priority Date: 03/04/2011
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Arisawa, Koichi, Shimomugi, Takuya, Shinomoto, Yosuke
• Primary Examiner(s): Tran, Thienvu
• Assistant Examiner(s): Sun, Pinping
• Application Number:
  US14/002,173
• Publication Number:
  US 20130334884A1
• Time in Patent Office: 2,125 Days
• US Class Current: 1/1
• CPC Class Codes: H02M 1/0051 Diode reverse recovery losses
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H02M 7/06 using discharge tubes without control electrode or semiconductor devices without control electrode
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A power conversion device according to the present invention includes a power supply, a booster unit (a reactor, a switch) that boosts a voltage supplied from the power supply by switching control, a smoothing circuit that smoothes an output voltage from the booster unit, a rectifier that is arranged between the booster unit and the smoothing circuit to prevent a current reverse flow toward the booster unit, and a commutation unit that is connected to the rectifier in parallel to commutate a current flowing through the rectifier toward itself.

Claims

1. A power conversion device comprising:

a power supply unit;

a booster unit that boosts a voltage supplied from the power supply unit by switching control;

a smoothing unit that smoothes an output voltage from the booster unit;

a backflow prevention element that is arranged between the booster unit and the smoothing unit to prevent a current reverse flow toward the booster unit;

a commutation unit that is connected to the backflow prevention element in parallel to commutate a current flowing through the backflow prevention element in a predetermined period before a short-circuit current begins to flow in response to the switching control of the booster unit; and

a determination unit that determines a duty ratio of the switching control and an implementation period of a commutation operation by the commutation unit, based on a plurality of thresholds and a comparison target signal that is a triangle-wave signal or a sawtooth signal, wherein

the thresholds include a first threshold, a second threshold that is equal to or larger than the first threshold, and a third threshold that is equal to or smaller than the first threshold, and

the determination unit determines the duty ratio based on a comparison result between the first threshold and the comparison target signal, and determines the implementation period based on a comparison result between the third threshold and the comparison target signal.

2. The power conversion device according to claim 1, wherein

the booster unit includes

a reactor that is connected to the power supply unit, and

a switch that short-circuits a connection point between the reactor and the backflow prevention element and a negative side of the power supply unit.

3. The power conversion device according to claim 2, wherein the commutation unit commutates a current flowing through the backflow prevention element in a predetermined period before the switch is turned on.

4. The power conversion device according to claim 2, wherein the commutation unit finishes a commutation operation after a predetermined period has passed after the switch is turned on.

5. The power conversion device according to claim 1, wherein

the commutation unit includes

a transformer,

a switch that drives the transformer,

a power supply that supplies power to the transformer and the switch, and

a backflow prevention element that is serially connected to a secondary winding of the transformer to prevent a current reverse flow.

6. The power conversion device according to claim 5, wherein the backflow prevention element of the commutation unit is formed of a wide bandgap semiconductor.

7. The power conversion device according to claim 6, wherein the wide bandgap semiconductor is formed of silicon carbide, a gallium nitride-based material, or diamond.

8. The power conversion device according to claim 1, wherein the first threshold, the second threshold, and the third threshold are variable.

9. The power conversion device according to claim 1, further comprising an adjustment unit that adjusts a duty ratio of the switching control based on a comparison result between a voltage value having been smoothed by the smoothing unit and a predetermined target value.

10. The power conversion device according to claim 9, wherein the target value is variable.

11. The power conversion device according to claim 1, further comprising an adjustment unit that adjusts a duty ratio of the switching control based on a comparison result between a current value of a current flowing through the booster unit and a predetermined target value.

12. The power conversion device according to claim 11, wherein the target value is variable.

13. The power conversion device according to claim 1, wherein the determination unit is realized by using a one-shot pulse generation function of a microcomputer.

14. The power conversion device according to claim 1, wherein the power supply unit includes a DC power supply or an AC power supply and a rectifying circuit that rectifies a voltage of the AC power supply.

15. A refrigeration/air-conditioning system comprising the power conversion device according to claim 1.

16. A power conversion device comprising:

a power supply unit;

a booster unit that boosts a voltage supplied from the power supply unit by switching control;

a smoothing unit that smoothes an output voltage from the booster unit;

a backflow prevention element that is arranged between the booster unit and the smoothing unit to prevent a current reverse flow toward the booster unit;

a commutation unit that is connected to the backflow prevention element in parallel to commutate a current flowing through the backflow prevention element in a predetermined period before a short-circuit current begins to flow in response to the switching control of the booster unit; and

a determination unit that determines a duty ratio of the switching control and an implementation period of a commutation operation by the commutation unit, based on a plurality of thresholds and a comparison target signal that is a triangle-wave signal or a sawtooth signal, wherein

the determination unit includes

a reference-signal generation unit that generates a plurality of reference signals as the thresholds,

a comparison-target signal generation unit that generates the comparison target signal,

a comparison unit that compares each of the thresholds with the comparison target signal to determine the duty ratio and the implementation period based on a comparison result, and

a control-signal generation unit that generates a determination-result output control signal having a variable ON/OFF timing, which is a control signal instructing whether to output an implementation period determined by the comparison unit as an effective determination result.

17. A power conversion device comprising:

a power supply unit;

a booster unit that boosts a voltage supplied from the power supply unit by switching control;

a smoothing unit that smoothes an output voltage from the booster unit;

a backflow prevention element that is arranged between the booster unit and the smoothing unit to prevent a current reverse flow toward the booster unit;

a commutation unit that is connected to the backflow prevention element in parallel to commutate a current flowing through the backflow prevention element in a predetermined period before a short-circuit current begins to flow in response to the switching control of the booster unit; and

a determination unit that determines a duty ratio of the switching control and an implementation period of a commutation operation by the commutation unit, based on a threshold and a plurality of comparison target signals, each of which is a triangle-wave signal or a sawtooth signal, wherein

the plurality of comparison target signals include a first comparison target signal, a second comparison target signal having a phase and an amplitude coincident with those of the first comparison target signal and always having a level equal to or larger than that of the first comparison target signal, and a third comparison target signal having a phase and an amplitude coincident with those of the first comparison target signal and always having a level equal to or smaller than that of the first comparison target signal, and

the determination unit determines the duty ratio based on a comparison result between the threshold and the first comparison target signal, and determines the implementation period based on a comparison result between the threshold and the second comparison target signal and a comparison result between the threshold and the third comparison target signal.

18. The power conversion device according to claim 17, wherein the levels of the first comparison target signal, the second comparison target signal, and the third comparison target signal are variable.