JP2006067780A - Power supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply device capable of supplying power, while maintaining a prescribed voltage across a wide output current range that includes the region with a large output current. <P>SOLUTION: The output of a generator 2 which is driven by an engine 1 is rectified by an AC-DC conversion part 3. The output of the AC-DC conversion part 3 is boosted by a DC-DC conversion part 5 consisting of a boosting DC-DC converter, while being regulated for voltage. It is further converted into the AC output of a prescribed frequency by a power conversion part 4 consisting of an inverter. The DC-DC conversion part 5 is switching-driven so that the input voltage of the power conversion part 4 is kept at a prescribed voltage. The generator 2 consists of, for example, a multi-pole magnet generator. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power supply device, and more particularly to a power supply device that converts a direct current output generated using a generator driven by an engine or the like as a power source into alternating current power by an inverter and outputs the alternating current power.

  Power generation devices such as engine-driven generators are widely used as power supply devices for various purposes from portable to emergency. Such a power supply device has a feature that it can be configured on a small scale.

  FIG. 5 is a functional block diagram of a conventional power supply device. As shown in the figure, the power supply device includes a generator 2 driven by the engine 1, an AC-DC converter 3 that performs AC-DC conversion (rectification), and a power converter 4 that performs DC-AC conversion. The AC-DC converter 3 is composed of a thyristor regulator that also serves as a rectifier circuit, and the power converter 3 is composed of an inverter.

The output of the generator 2 is AC-DC converted and voltage-adjusted by the AC-DC converter 3. The output of the AC-DC converter 3 is DC-AC converted by the power converter 4. For example, the output voltage of the generator 2 is AC400V, the AC-DC converter 3 rectifies and adjusts the voltage of AC400V, and the input side voltage DC340V (≈240√) sufficient for the power converter 4 to output AC240V. 2V) is output. The power converter 4 outputs 240V AC. Such power supply devices are described in Patent Documents 1 and 2.
Japanese Patent No. 2540305 JP 2001-309666 A

  The above-described conventional power supply device is rationally configured because rectification and adjustment of the input voltage to the power conversion unit 4 are simultaneously performed by a thyristor regulator also serving as a rectifier circuit that constitutes the AC-DC conversion unit 3. It can be said. However, there is a problem that the efficiency of the power supply apparatus is greatly influenced by the operation efficiency of the generator itself.

  For example, if the inverter that constitutes the power conversion unit 4 outputs the output voltage V1, it is necessary to apply a DC voltage of √2 × V1 or more to the input, but a normal generator increases the output current. Accordingly, since the output voltage decreases, the DC voltage required by the power conversion unit 4 cannot be obtained from the generator when the output current increases. Therefore, in the region where the output current is large, the output voltage applied from the power conversion unit 4 to the load is insufficient.

  In order to prevent this, the generator can be made to have a high output, but especially when a multi-pole magnet generator is used as the generator, the output voltage accompanying the increase in the output current in the high load region is reduced. Since the decrease is large, it is necessary to use a generator with a remarkably high voltage specification in order to secure a DC voltage of the above-mentioned √2 × V1 or more at the peak power, and an element with a high withstand voltage is required.

In addition, when the output current decreases and the output voltage of the generator rises, the thyristor of the AC-DC converter 3 (thyristor regulator) is turned off for a predetermined period so that the input voltage of the power converter does not become excessive. Since the output during a predetermined period when the thyristor is turned off is discarded, the efficiency of the power supply apparatus is greatly reduced.
An object of the present invention is to solve the above-described problems and provide a power supply device capable of high-efficiency operation over a wide output current range including a region where the output current is large.

  In order to solve the above-described problems, the present invention provides an AC generator, a rectifier circuit that rectifies the output of the AC generator, and a DC output of the rectifier circuit that is converted into AC power having a predetermined frequency and a predetermined output voltage for output. In the power supply apparatus including the inverter, a boost DC-DC converter is provided in which the DC output is boosted to a predetermined voltage necessary for maintaining the output voltage of the inverter by a switching operation and supplied to the inverter. It is a feature.

  Further, according to the present invention, the step-up DC-DC converter performs a step-up operation so as to compensate for a decrease in the direct current output of the rectifier circuit accompanying an increase in the output current of the inverter, and the input side voltage of the inverter is set to a predetermined voltage The second feature is to maintain the value.

  Furthermore, the third feature of the present invention is that the AC generator is a multipolar magnet generator.

  According to the first feature of the present invention, the direct current output of the rectifier circuit is boosted by the step-up DC-DC converter and applied to the inverter, so that the input required by the inverter even in a region where the output current is large. A voltage can be secured, and power supply can be performed while maintaining a predetermined voltage to the load over a wide output current range. Therefore, stable power supply is possible even if the DC output of the rectifier circuit is relatively low.

  Further, a direct current output is generated by the generator and the rectifier circuit, and the AC-DC converter that converts the AC output of the generator into a DC output is configured by dividing the rectifier circuit and the step-up DC-DC converter, that is, the rectifier circuit. Output voltage of the generator is boosted by the step-up DC-DC converter, so the output voltage of the generator may be low. This eliminates the need for the generator itself to have a high breakdown voltage specification. Further, it is not necessary to use a high voltage element in the rectifier circuit, and only the control element of the step-up DC-DC converter is required as the high voltage element, so that the cost can be reduced.

  Further, according to the second feature, the boost type DC-DC converter is boosted so as to compensate for a decrease in the DC output of the rectifier circuit accompanying an increase in the output current of the inverter, and the input side voltage of the inverter is predetermined. Since the voltage value is maintained, power can be supplied in accordance with the output current.

  Furthermore, according to the third feature, even when a multipolar magnet generator is used as an AC generator, high-efficiency operation is possible over a wide output current range including a region where the output current is large. Become.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a functional block diagram showing a power supply device according to the present invention. In FIG. 1, the same or equivalent parts as in FIG.

  The generator 2 driven by the engine 1 is composed of, for example, a three-phase multipolar magnet generator. The AC-DC conversion unit 3 includes a rectifying element that is bridge-connected, and functions as a rectifying circuit that rectifies the output of the generator 2. The DC-DC converter 5 is composed of a step-up DC-DC converter, boosts the output voltage of the AC-DC converter 3 and adjusts the voltage to provide it to the power converter 5 in the next stage. The power conversion unit 4 includes an inverter, and converts the output of the DC-DC conversion unit 5 into AC power having a predetermined frequency and outputs it.

  The input voltage of the power conversion unit 4 needs to be equal to or higher than a predetermined DC voltage so that a specified AC voltage peak value is obtained on the output side. The DC-DC conversion unit 5 is an AC-DC conversion unit. 3 is boosted to output a DC voltage required on the input side of the power converter 4.

  For example, the output voltage of the generator 2 is AC180V, and the AC-DC conversion unit rectifies the AC180V by three-phase full-wave and outputs DC250V having a peak value. The DC-DC converter 5 boosts DC 250V to 340V, and the power converter 4 outputs AC 240V.

  FIG. 2 is a circuit diagram showing a specific circuit example of the power supply device according to the present invention. In addition, the same number is attached | subjected to the same or equivalent part as FIG.

  The generator 2 has a three-phase output winding 2-1. The AC-DC conversion unit 3 includes rectifying elements 3-1 to 3-6 and performs three-phase full-wave rectification on the output of the generator 2. As described above, in the present invention, the AC-DC conversion unit 3 can be configured by only a rectifying element (diode), and it is not necessary to use a thyristor.

  The DC-DC converter 5 includes a MOSFET 5-1, a choke coil 5-2, capacitors 5-3 and 5-4, and a rectifying element 5-5. When the MOSFET 5-1 is turned on, the DC-DC converter 5 stores energy in the choke coil 5-2, and boosts the stored energy by discharging it to the output side when the MOSFET 5-1 is turned off. It functions as a DC-DC converter.

  The voltage detector 10 detects the output voltage of the DC-DC converter 5. The control unit 11 controls the driver 12 according to the detected voltage, and PWM-modulates the ON period of the MOSFET 5-1 so that the output voltage of the DC-DC conversion unit 5 is maintained at a predetermined value. The control unit 11 also controls a driver 12 of the power conversion unit 4 described later according to the output voltage of the DC-DC conversion unit 5.

  The power conversion unit 4 includes an inverter configured by bridge-connecting four MOSFETs 4-1 to 4-4. As is well known, the driver 12 drives the inverter by alternately turning on and off the pair of MOSFETs 4-1 and 4-4 and the pair of 4-2 and 4-3. The control unit 11 also controls the driver 12 to PWM modulate the on periods of the MOSFETs 4-1 to 4-4 so that predetermined power supply is performed.

  FIG. 3 shows the characteristics (a) of the generator that can be used in the present invention and the characteristics (b) of the generator that is used in the prior art in order to show the difference between the present invention and the prior art. In the figure, characteristic A shows the relationship between the generated voltage and current of the generator, and characteristic B shows the relationship between the output and current of the generator. The generated voltage and output represent values on the output side of the AC-DC converter, that is, values on the input side of the power converter.

  In the present invention, since the output voltage of the AC-DC converter 3 is boosted by the DC-DC converter 5 to be the input voltage of the power converter 4, the boosted DC voltage is equal to the output AC voltage of the power converter 4. The output voltage of the generator 2 may be low because it needs to be √2 or more. Therefore, the rectifying elements 3-1 to 3-6 constituting the generator 2 and the AC-DC converter 3 do not need to have a high breakdown voltage specification.

  Further, even in a voltage range where the output voltage of the generator is less than the input voltage of the power conversion unit 4, it is possible to supply power while maintaining a predetermined voltage to the load. Therefore, the generator is operated in a range not reaching the high voltage range. In addition, since the output can be used as it is, it is possible to supply power with a predetermined voltage stably maintained over a wide output current range. In addition, since it is not necessary to discard some outputs for voltage adjustment, the efficiency of the power supply device can be increased.

  On the other hand, in the prior art, it is not possible to perform an operation in a region where the output voltage of the generator falls below √2 times the output AC voltage. Moreover, since the output in the high-efficiency voltage region of the generator is not used as it is and the output is partially discarded by the AC-DC converter 3 so that the input voltage of the power converter 4 becomes 340V, The efficiency of the power supply device is reduced accordingly.

  FIG. 4 is a circuit diagram specifically showing an embodiment of the power supply device according to the present invention. The same or equivalent parts as those in FIG. 2 are denoted by the same reference numerals. The three-phase generator 2 is an engine-driven generator that is connected to the engine and driven by the engine. Here, the three-phase generator 2 is an electric generator that can also operate as an engine starting electric motor.

  The generator 2 is connected to an engine (not shown). The AC-DC conversion unit 3 connected to the output side of the generator 2 includes rectifying elements 3-1 to 3-6 that are bridge-connected, and rectifies the output of the generator 2. In addition, switching elements such as MOSFETs are connected in parallel to each rectifying element of the AC-DC converter 2, and these switching elements convert DC voltage into three-phase AC voltage by on / off to generate power. A drive inverter to be applied to the machine 1 is configured. The rectifying element of the AC-DC converter 3 may be a parasitic diode of a MOSFET switching element, or may be a separately connected junction diode.

  Since the DC-DC converter 5 and the power converter 4 connected to the output side of the AC-DC converter 3 are the same as those in FIG.

  The connection point between the AC-DC converter 3 and the DC-DC converter 5 is connected to the secondary side of the bidirectional DC-DC converter 6, and the primary side of the DC-DC converter 6 is made of, for example, a battery (12 V). Connected to battery 7.

  The bidirectional DC-DC converter 6 interchanges power bidirectionally between the battery 7 and the output of the DC converter 2, and includes a primary side low-voltage side winding 6-1-1 and a secondary side. A transformer 6-1 including a high voltage side winding 6-1-2 is included. The step-up ratio of the bidirectional DC-DC converter 6 is determined by the winding ratio of the low-voltage side winding 6-1-1 and the high-voltage side winding 6-1-2.

  The low voltage side switching unit 6-2 is inserted into the low voltage side winding 6-1-1 side, and the high voltage side switching unit 6-3 is inserted into the high voltage side winding 6-1-2. The low-voltage side switching unit 6-2 is configured by, for example, four MOSFETs 6-2-1 to 6-2-4 being bridge-connected, and the high-voltage side switching unit 6-3 is similarly configured with four MOSFETs 6-3-1 to 6. 6-3-4.

  Rectifier elements such as diodes are connected in parallel to the MOSFETs 6-2-1 to 6-2-4 and 6-3-1 to 6-3-4 of the low-voltage side switching unit 6-2 and the high-voltage side switching unit 6-3. Is done. These rectifying elements may also be MOSFET parasitic diodes or may be separately connected junction diodes. If the rectifying elements connected in parallel are combined, the low-voltage side switching unit 6-2 and the high-voltage side switching unit 6-3 can be considered as switching / DC conversion units, respectively.

  An LC resonance circuit 6-4 is inserted on the high voltage side winding 6-1-2 side of the transformer 6-1. The LC resonance circuit 6-4 makes a current that flows when at least one of the low-voltage side switching unit 6-2 and the high-voltage side switching unit 6-3 is driven into a sine wave, reduces switching loss, and is caused by a large current. It functions so as not to cause MOSFET destruction. This is because the MOSFET can be turned on and off near the zero cross point of the sinusoidal current. The LC resonance circuit 6-4 may be provided on the primary side instead of the secondary side.

  The MOSFETs 6-2-1 to 6-2-4 of the low-voltage side switching unit 6-2 and the MOSFETs 6-3-1 to 6-3-4 of the high-voltage side switching unit 6-3 are control circuits (not shown) including a CPU or the like. Z)). Capacitors 8 and 9 connected to the primary side and the secondary side are output smoothing capacitors.

  Next, the operation of FIG. 4 will be described. The low-voltage side switching unit 6-2 and the high-voltage side switching unit 6-3 are driven in perfect synchronization, that is, with the same drive signal so that the bidirectional DC-DC converter 6 automatically performs bidirectional power conversion. To do. As is well known, in the low voltage side switching unit 6-2, this driving is performed by alternately turning on the pair of MOSFETs 6-2-1 and 6-2-4 and the pair of MOSFETs 6-2-2 and 6-2-3. In the high voltage side switching unit 6-3, the pair of MOSFETs 6-3-1 and 6-3-4 and the pair of MOSFETs 6-3-2 and 6-3-3 are alternately turned on and off. .

  When the engine is started, power conversion is performed from the primary side to the secondary side of the bidirectional DC-DC converter 6, and the DC voltage of the battery 7 boosted thereby is supplied to the drive inverter (AC-DC converter) 3. Given. The driving inverter 3 converts this DC voltage into a three-phase AC voltage and applies it to the generator 2 to start it as an engine starting motor. This start-up is performed by PWM driving the MOSFET of the drive inverter as is well known. At this time, it is possible to determine the phase using the fact that the current distribution is changed by the counter electromotive voltage according to the movement of the generator (motor) 2 and to perform synchronous driving without a sensor.

  When the engine is started, the generator 2 is driven by the engine to generate an output. The output of the generator 2 is rectified by an AC-DC converter (drive inverter) 3. At this time, the MOSFET constituting the drive inverter is not driven, and the output of the generator 2 is full-wave rectified by the rectifying elements 3-1 to 3-6 of the AC-DC converter 3. The output of the AC-DC converter 3 is boosted by the DC-DC converter 5 and voltage-adjusted. The adjustment of the DC voltage is performed by, for example, PWM modulating the MOSFET 5-1. The output of the DC-DC converter 5 is further converted into an AC output of a predetermined frequency by the power converter 4 and output.

  At this time, if the remaining capacity of the battery 7 is small, the bidirectional DC-DC converter 6 performs power conversion from the secondary side to the primary side, and the battery 7 is charged with the output of the stepped-down AC-DC converter 2. . If the output of the generator 2 cannot handle the load due to an overload state, power conversion is performed so that power is also supplied from the battery 7 through the bidirectional DC-DC converter 6.

  In this way, the bidirectional DC-DC converter 6 automatically exchanges power between the primary side and the secondary side according to the relative voltage difference between the primary side and the secondary side according to the winding ratio of the transformer 6-1. Accommodate electricity.

  The present invention can be applied not only to a direct current power source including a generator and an AC-DC converter (rectifier circuit) but also to a direct current power source such as a fuel cell.

  Although the embodiment has been described above, the present invention can be variously modified. For example, by providing a step-down DC-DC converter together with a step-up DC-DC converter and using them separately, it is possible to supply power from a single DC power supply to systems with different voltage values, such as 200V system and 100V system. become.

It is a functional block diagram which shows the power supply device which concerns on this invention. It is a circuit diagram which shows the specific circuit example of the power supply device which concerns on this invention. It is explanatory drawing for demonstrating the difference of this invention and a prior art. 1 is a circuit diagram specifically showing an embodiment of a power supply device according to the present invention. It is a functional block diagram of the conventional power supply device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Generator, 2-1 ... Output winding, 3 ... AC-DC conversion part (drive inverter), 3-1 to 3-6, 5-5 ..Rectifying element, 4... Power conversion unit, 4-1 to 4-4, 5 ... MOSFET, 5 ... DC-DC conversion unit, 5-2 ... Coil, 5-3 , 5-4, 8, 9 ... capacitor, 6 ... bidirectional DC-DC converter, 6-1 ... transformer, 6-1-1 ... low-voltage side winding, 6-1-2 ... High voltage side winding, 6-2 ... Low voltage side switching unit, 6-3 ... High voltage side switching unit, 6-4 ... LC resonance circuit, 7 ... Battery, 10 ... Voltage detection unit, 11 ... control unit, 12, 13 ... driver 1

Claims (3)

In a power supply apparatus comprising an AC generator, a rectifier circuit that rectifies the output of the AC generator, and an inverter that converts the DC output of the rectifier circuit into AC power having a predetermined frequency and a predetermined output voltage, and outputs the AC power.
A power supply apparatus comprising: a step-up DC-DC converter that boosts and adjusts the direct current output to a predetermined voltage necessary for maintaining the output voltage of the inverter by switching operation. The step-up DC-DC converter performs a step-up operation so as to compensate for a decrease in the DC output of the rectifier circuit accompanying an increase in the output current of the inverter, and maintains the input side voltage of the inverter at a predetermined voltage value. The power supply device according to claim 1. The power supply device according to claim 1, wherein the AC generator is configured by a multipolar magnet generator.