JPH1052051A - Pulse width modulation converter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pulse width modulation converter device which can prevent failure in a backup power supply circuit without need for using an isolation transformer. SOLUTION: A converter device is provided with, at a converter 1, a control power supply circuit 16 of a switching regulator system, which is operated by both DC output of a power rectifier 2 and the output of a backup power supply circuit 17, and is operated by supplying electric power to a control circuit 12 of the converter 1. An electromagnetic contactor 18 whose opening/closing is controlled by the control circuit 12 is provided, so that only when a pulse width modulated signal is supplied to a drive circuit 15 and a switching element of the power rectifier 2 conducts a switching operation, a normally-closed contact circuit 12a is opened to turn off the electromagnetic contactor 18, and eliminates loop current which would be generated at the backup power circuit 17 by switching the switching element of the power rectifier 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse width modulation type converter device, and in particular, supplies power required for operation of a control circuit from both a DC output of a forward converter and an output of a backup power supply circuit. The present invention relates to a pulse width modulation converter device of the type.

[0002]

2. Description of the Related Art In an early pulse width modulation (PWM) converter device or an inverter device, a power supply circuit for operating a control circuit (hereinafter referred to as a control power supply circuit) is input from an AC power supply through an insulating transformer. In this case, not only is it easy to cause the effects of power supply fluctuations and instantaneous power failures, but also an insulating transformer having a large size is required in proportion to the required capacity, which is uneconomical.

Therefore, in recent years, this control power supply circuit is constituted by a switching regulator type power supply circuit, which is inexpensive, resistant to power supply fluctuations on the AC power supply side and instantaneous power failure.
In addition, control power circuits with high stability have become available, and more recently, with the increase in the withstand voltage of switching elements used in this switching regulator type power supply, the main circuits of pulse width modulation converters and inverters have been required. A large number of systems in which a switching power supply is operated by directly receiving power supply from a DC unit are employed.

By the way, in this system, when no AC power is supplied to the main circuit, a DC voltage cannot be obtained from the main circuit, so that only the control circuit cannot be operated separately from the main circuit. Also, it is necessary to turn on the power to the main circuit when adjusting the control circuit and analyzing the failure.
For this reason, for example, when applied to electric motor control of an electric vehicle, the main circuit is alive even when adjusting a control circuit or analyzing a failure, and there is a risk that the vehicle may run away while a person is riding on the system. Not safe.

Therefore, a method using a backup power supply circuit in which power is supplied from an AC power supply to a switching power supply independently of the main circuit has been conventionally adopted. At this time, this method is applied to a pulse width modulation converter. If applied, the backup power supply circuit and the DC section of the main circuit will be connected through the DC section of the switching power supply, so a loop current will appear when the pulse width modulation converter operates, causing the backup power supply circuit to fail. A phenomenon occurs.

Therefore, in the prior art, a method of inserting an insulating transformer on the AC input side of the backup power supply circuit has been generally adopted.

[0007]

However, the prior art described above does not sufficiently consider the disadvantages associated with the use of an insulating transformer, and has a problem in terms of cost reduction.
This is because the insulating transformer used for such a converter device is expensive, because it is necessary to specialize the transformer and a general-purpose transformer cannot cope with it.

Specifically, first, it is necessary to match the DC output level of the backup power supply with the DC output level of the converter unit. Next, it is necessary to connect to the power supply side of the switch that turns on and off the main power supply in order to adjust the timing at the time of power failure, so that the transformer becomes a specially designed transformer. Furthermore, when the number of inverters connected in parallel to the DC output of the converter device increases, the capacity needs to be increased.

An object of the present invention is to eliminate the use of an insulating transformer,
An object of the present invention is to provide a pulse width modulation converter device capable of preventing a failure of a backup power supply circuit.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pulse width modulation converter which supplies power required for operation of a control circuit from both a DC output of a forward converter and an output of a backup power supply circuit. A normally closed contact type switch circuit is provided in the connection path between the power supply circuit and the AC power supply,
This is achieved by opening the switch circuit only during the on / off operation of the switching element of the forward conversion unit.

This switch circuit works as follows. First, if the switching element of the forward conversion unit does not perform a switching operation, no loop current occurs between the switching element of the converter unit and the backup power supply circuit, so that the backup power supply circuit does not fail.

Therefore, this switch circuit allows the backup power supply circuit to be connected to the AC power supply only when there is no switching command output to the converter unit or when the protection circuit operates and the switching command is lost. It was made.

Here, even if the input of the AC power supply to the forward converter is stopped, the charge stored in the smoothing capacitor on the DC side of the forward converter does not immediately disappear. Therefore, the drive power supply for the control circuit does not run out immediately.

Therefore, even when a power failure occurs, a closing signal can be sent from the control circuit to the switch circuit for connecting the backup power supply circuit and the switching power supply circuit. , The drive power of the control circuit is normally maintained, and the switch circuit is maintained in the closed state, so that the backup function can be reliably maintained.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a pulse width modulation converter according to the present invention will be described in detail with reference to one embodiment shown in the drawings.

FIG. 1 shows an embodiment in which a pulse width modulation converter device according to the present invention is applied to an inverter device. In the drawing, reference numeral 1 denotes a converter unit, which is a forward conversion unit comprising a main circuit switching element. The main circuit system, which is configured as a voltage-type pulse-width modulation converter having a power conversion circuit 2 and operates in a pulse width modulation system, mainly includes a forward converter 2, an electromagnetic switch 4, an AC reactor 5, a current detector 6,
It has a smoothing capacitor 6.

During the powering operation, the three-phase AC power supply 3
The three-phase AC power taken from the DC converter is converted to DC by the forward converter 2 and serves to supply DC power to the DC terminals P and N. In the regenerative operation, on the contrary, the DC power taken from the DC terminals P and N Is converted into a three-phase alternating current by the forward converter 2 and regenerated to the three-phase alternating current power supply 3.

Reference numeral 8 denotes an inverter, which is constituted as a voltage-type pulse width modulation inverter, and includes, in a main circuit system, an inverse converter 9 operating in a pulse width modulation system and a smoothing capacitor 1.
0 is provided. During the power running operation, the DC power taken from the DC terminals P and N of the converter unit 1 is converted into a three-phase AC having a desired frequency by the inverse converter 9, and the three-phase AC having an arbitrary voltage and frequency is supplied to the motor 11 serving as a load. Conversely, during the regenerative operation, the three-phase AC power taken from the motor 11 is converted into DC by the inverse converter 9 and the DC power is supplied to the DC terminals P and N. It operates to regenerate to the power supply 3.

That is, when the motor 11 is in a power running operation, electric power is supplied from the AC side of the converter unit 1, and from the DC side of the converter unit 1 to the DC side of the inverter unit 8 and to the motor 11 via the inverse conversion unit 9. When electric power is supplied and the electric motor 11 is in regenerative operation, the regenerative electric power passes from the AC side of the inverter unit 8 to the DC side and from the DC side of the converter unit 1 to the three-phase AC power supply 3 through the forward conversion unit 2. It will be regenerated.

Next, in the converter section 1, a control circuit 12 is a transformer 1 for detecting the phase of the AC power supply.
3, a detector 4 for detecting the magnitude and phase of the AC input current, and a detector 14 for detecting the magnitude of the DC voltage, and fetching respective information to generate a pulse width modulation signal necessary for controlling the pulse width modulation converter. It works to happen.

Reference numeral 15 denotes a drive circuit, which receives a supply of a pulse width modulation signal from the control circuit 12 and serves to drive a switching element of the forward converter 2. Reference numeral 16 denotes a control power supply circuit, which is configured as a switching regulator type power supply circuit which receives a supply of DC power from the DC terminals P and N via a backflow preventing diode 20 as shown in FIG. 12 and a function of supplying a plurality of electrically independent electric powers at desired voltages required for the operation of the drive circuit 15 and the like.

A backup power supply circuit 17 includes a single-phase bridge type diode rectifier circuit 21 and a smoothing capacitor 2.
2. It is composed of a backflow preventing diode 23 and
It functions to separately supply backup DC power to the control power supply circuit 16.

Therefore, since the control power supply circuit 16 operates by receiving power supply from the DC side of the converter section 1, the electromagnetic switch 4 is turned on and power is supplied from the three-phase AC power supply 3 in a normal operation state. When it is supplied, it operates with the DC power supplied from the DC parts P and N of the main circuit via the diode 20, thereby supplying power to the control circuit 12, the drive circuit 15, and other circuits. .

On the other hand, the backup power supply circuit 17 is adapted to receive a single-phase AC supply from the three-phase AC power supply 3 in front of the electromagnetic switch 4, and includes a single-phase bridge type diode rectifier circuit 21 and a smoothing capacitor. 22 is designed to generate a DC at the same level as the DC voltage (P-N voltage) of the main circuit. As a result, even if the electromagnetic switch 4 is open, the DC is supplied to the control power supply circuit 16. It can be supplied and performs a backup function that enables the operation of the control circuit 12 and the like.

Reference numeral 18 denotes an electromagnetic contactor which is controlled by the control circuit 12 and has a function of turning on and off the supply of power from the AC power supply 3 to the backup power supply circuit 17. For this reason, the control circuit 12 includes a normally closed contact circuit 12a, supplies a pulse width modulation signal to the drive circuit 15, and operates the normally closed contact circuit only when the switching element of the forward conversion unit 2 performs the switching operation. The electromagnetic contactor 18 is turned off by opening 12a.

Reference numeral 19 denotes an external operation power supply output terminal, which functions to allow the AC power whose ON / OFF is controlled by the contact of the electromagnetic contactor 18 from the AC power supply 3 to be taken out of the converter unit 1.

Next, a control system of the inverter unit 8 will be described. Reference numeral 24 denotes a control circuit which controls the inverter device based on information from a frequency setting device 30 and a detector 36 for detecting the magnitude and phase of an alternating current flowing through the motor 11 as a load. A drive circuit 25 receives a pulse width modulation signal from the control circuit 24 and has a function of driving the switching element of the inverse converter 9 by pulse width modulation.

Reference numeral 26 denotes a control power supply circuit which serves as a power supply for operating circuits such as the control circuit 24 and the drive circuit 25. The control power supply circuit 26 is a switching regulator type circuit that operates by inputting a DC voltage, similarly to the control power supply device 16 in the converter unit 1. 3
When the DC power is supplied from the forward converter 2 of the converter 1 and the DC output is obtained from the
From the DC terminals P and N through a diode 28 for preventing backflow, and operates.

Reference numeral 27 denotes a backup power supply circuit. Reference numeral 29 denotes an operation power supply input terminal. This terminal 29 is connected to an external operation power supply output terminal 19 of the converter 1 as shown in the figure.

The backup power supply circuit 27
Is composed of a single-phase bridge-type diode rectifier circuit 31, a smoothing capacitor 32, and a backflow preventing diode 33, and is configured to output a DC voltage substantially equal to the DC voltage (P-N voltage) of the main circuit. With this voltage, the DC power is supplied to the control power supply circuit 26 even when the DC power is not supplied from the converter unit 1, and the operation of the control circuit 12 is enabled.

Therefore, in this embodiment, the electromagnetic contactor 1
8 and an operation power supply output terminal 19 are provided. However, not only that, the control power supply circuit 1 having the same configuration is provided in both the converter unit 1 and the inverter unit 8.
6 and 26 and backup power supply circuits 17 and 27 are provided as structural features.

Next, the reason why the electromagnetic contactor 18 and the operation power output terminal 19 are provided and their functions will be described. Before that, first, in the embodiment of FIG. FIG. 2 shows what kind of problem will occur if the device is not provided.

FIG. 2 is a diagram showing only the parts necessary for explaining the problem extracted from the converter unit 1 of the embodiment shown in FIG. 1. Here, the forward conversion unit 2 comprises six switching elements Q1. To Q6 and six flywheel diodes D1 to D6 connected in anti-parallel to each other. The single-phase bridge-type diode rectifier circuit 21 of the backup power supply circuit 17 includes four diodes D7 to D10. It is configured.

At this time, since there is no electromagnetic contactor 18 in FIG.
Of the three-phase AC power supply 3, for example, the R-phase and the T-phase.

In this configuration, first, the switching elements Q1 to Q6 of the forward converter 2 do not perform a switching operation, and
When the FF is set, the power supply to the control power supply circuit 16 is controlled by the diodes D1 to D6.
, And the rectified output of the diodes D7 to D10 are supplied from the lower one of the power supply impedances, but in this case, no particular problem occurs.

However, when the converter unit 1 is in the operating state, that is, when the switching elements Q1 to Q6 are performing a switching operation, a loop passing through the switching element of the forward conversion unit 2 and the rectifier diode of the backup power supply circuit 17 is provided. A current is generated, causing the back power supply circuit 17 to fail.

For example, assuming that the R-phase of the three-phase AC power supply 3 has a positive polarity and the T-phase has a negative polarity. Here, if the switching element Q4 is turned on,
From the phase, through the switching element Q4, through the rectifier diode D10 of the backup power supply circuit 17, and back to the T phase;
An almost short-circuited path is formed as shown by a line L1 with an arrow, and a loop current is generated here.

The T-phase of the three-phase AC power supply 3 has a positive polarity and R
The same applies when the phase becomes negative. In this case, when the switching element Q6 is turned on, the T phase of the power supply 3 passes through the switching element Q6, passes through the rectifier diode D9 of the backup power supply circuit 17, and changes to the R phase. Return, a short-circuited path is also formed, and a loop current is generated.

Since this loop current almost flows through a short-circuited path, it immediately exceeds the rated current of the rectifier diode, and thus causes the back power supply circuit 17 to fail.

However, in the embodiment shown in FIG. 1, the electromagnetic contactor 18 is provided, and as described above, the switching elements Q1 to Q6 of the forward conversion unit 2 perform the ON-OFF operation in the switching state. In this case, the contact of the electromagnetic contactor 18 is opened and the backup power supply circuit 17 is disconnected from the three-phase AC power supply 3, so that there is no risk of generation of a loop current, and the backup power supply circuit 17 can be reliably protected. Can be done.

Here, a backup power source is required only when a DC output cannot be obtained from the forward converter 2.
Since it is unnecessary when DC output is obtained, the forward conversion unit 2
Of the switching elements Q1 to Q6
Even if the contact of the electromagnetic contactor 18 is opened during the N-OFF operation, there is no danger that the power supply to the control power supply circuit 16 will be interrupted. On the other hand, the switching elements Q1 to Q6 stop switching and the backup power supply Is required, the contacts of the electromagnetic contactor 18 are closed and power is input from the three-phase AC power supply 3 to the backup power supply circuit 17, so that the backup function can be reliably obtained. .

Even when the input of the AC power to the forward converter 2 is stopped due to a power failure or the like, the electric charge stored in the smoothing capacitor 7 on the DC side of the forward converter 2 does not disappear immediately. Since the operation of the control power supply circuit 16 is continued by the charge, the control circuit 12
Drive power supply is not lost.

Therefore, even when a power failure occurs, a closing signal can be sent from the normally closed contact circuit 12a of the control circuit 12 to the electromagnetic contactor 18, and thereafter, power is supplied from the backup power supply circuit 17 and the control power supply circuit 16 , The drive power of the control circuit is normally maintained, and the switch circuit is maintained in the closed state, so that the backup function can be reliably maintained.

Therefore, according to this embodiment, without providing an insulating transformer between the three-phase AC power supply 3 and the backup power supply circuit 17, the generation of loop current is reliably suppressed, and the backup power supply circuit 17 is prevented from failing. Can be prevented.

In the embodiment shown in FIG. 1, the supply of AC power to the backup power supply circuit 27 of the inverter unit 8 is configured to be obtained from the external operation power supply output terminal 19 via the operation power supply input terminal 29. Yes, so
The occurrence of loop current on the inverter section 8 side can also be suppressed, and the occurrence of failure can be reliably suppressed without impairing the backup function of the backup power supply circuit 27.

That is, the AC power supply of the backup power supply circuit 27 on the side of the inverter unit 8 is not passed through the electromagnetic contactor 18,
If it is connected to the AC power supply 3 as it is, the DC output of the converter unit 1 and the DC input of the inverter unit 7 are connected in common, and the backup power supply circuit 27 and the control power supply circuit 2
6 has a configuration similar to that of the backup power supply circuit 17 and the control power supply circuit 16 on the converter unit 1 side, and as described with reference to FIG. The back power supply circuit 27 in 10 will be broken.

In this embodiment, however, the external operation power supply output terminal 19 is provided, and power is supplied to the backup power supply circuit 26 of the inverter section 8 through the contact of the electromagnetic contactor 18. , Inverter section 8
Also on the side, protection of the backup power supply circuit 26 and retention of the backup function can be reliably obtained.

Although the use of an insulating transformer as in the prior art can suppress the generation of the loop current, the cost increases in this case. this is,
As described above, this is because the insulating transformer used in such a converter device is expensive.

That is, first, it is necessary to match the DC output level of the backup power supply with the DC output level of the converter section. Next, it is necessary to connect to the power supply side of the switch that turns on and off the main power supply in order to adjust the timing at the time of power failure, so that the transformer becomes a specially designed transformer. Furthermore, when the number of inverters connected in parallel to the DC output of the converter device increases, it is necessary to use a dedicated transformer because of the need to increase the capacity, etc. Because.

On the other hand, electromagnetic contactors are widely used for various electric devices and can also be used as switches in general, so that they are versatile, have a wide variety of capacity types, and are considerably less expensive than insulating transformers. And, compared to the contact capacity,
The power required for the contact operation is small, and even if a plurality of control power supply circuits are driven, only one power supply is required. Therefore, according to the above-described embodiment, the increase in cost can be sufficiently suppressed.

Next, another embodiment of the present invention will be described with reference to FIGS. The embodiment of FIGS. 3 and 4 is different from the embodiment of FIG.
Instead of providing an electromagnetic contactor 18 on the AC input side of 7,
It is provided on the DC output side.

At the same time, the DC power output from the backup power supply circuit 17 is taken out from the external operation power supply output terminal 19 instead of the AC power supply 3 from the external operation power supply output terminal 19, so that the inverter is not used. The backup power supply on the part 8 side is
It is obtained from the backup power supply circuit 17 on the side.

Therefore, according to these embodiments, only one backup power supply circuit is required for the entire inverter device having the pulse width modulation type converter, and the cost can be further suppressed.

Here, the difference between the embodiment of FIG. 3 and the embodiment of FIG. 4 lies in the insertion position of the contact of the electromagnetic contactor 18 as is apparent from the drawing. In the embodiment of FIG. The contact 18 is connected to the outside of the backup power supply circuit 17, but in the embodiment of FIG.

The backup power supply circuit 17 may be unitized as shown by a broken line. In this case, as in the embodiment shown in FIG. 4, the contact of the electromagnetic contactor 18 is backed up. It is difficult to provide the power supply circuit in the power supply circuit 17, and in this case, the embodiment shown in FIG.

In each of the above embodiments, the electromagnetic contactor 18 is used to disconnect the backup power supply circuit 17 from the AC power supply, but a semiconductor switch such as a thyristor or a transistor may be used instead. May be.

[0057]

According to the present invention, the generation of loop current can be reliably eliminated without impairing the backup function only by using an inexpensive switch circuit such as an electromagnetic contactor. An abundant converter device can be easily provided at low cost.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment in which a pulse width modulation converter device according to the present invention is applied to an inverter device.

FIG. 2 is a circuit diagram for explaining generation of a loop current in the pulse width modulation converter device.

FIG. 3 is a circuit diagram showing another embodiment in which the pulse width modulation converter device according to the present invention is applied to an inverter device.

FIG. 4 is a circuit diagram showing still another embodiment in which the pulse width modulation converter device according to the present invention is applied to an inverter device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Converter part 2 Forward conversion part 3 Three-phase AC power supply 4 Electromagnetic switch 5 Reactor 6, 36 Current detector 7, 10, 22, 32 Smoothing capacitor 8 Inverter part 9 Inverting part 11 Motor (load) 12 Control circuit 12a Always Closed contact circuit 13 Transformer for phase detection 14 Detector for DC voltage detection 15, 25 Drive circuit 16, 26 Control power supply circuit 17, 27 Backup power supply circuit 18 Electromagnetic contactor (switch circuit) 19 External operation power supply output terminal 20, 23 Diode for preventing backflow 20 21 Single-phase bridge type diode rectifier circuit 29 External operation power input terminal

Continuing from the front page (72) Inventor Hiroyuki Kazusa 7-1-1 Higashi Narashino, Narashino City, Chiba Prefecture Inside Hitachi Keiyo Engineering Co., Ltd.

Claims (3)

[Claims] 1. A pulse width modulation converter device for supplying power required for operation of a control circuit from both a DC output of a forward converter and an output of a backup power supply circuit. A pulse width modulation converter device, wherein a normally closed contact type switch circuit is provided on a connection path, and the switch circuit is opened only when the switching element of the forward conversion unit is on / off. 2. The pulse width modulation converter according to claim 1, further comprising an external operation power supply output terminal connected to the contact of the switch circuit on the side of the backup power supply circuit. 3. A pulse width modulation converter of a type in which power required for operation of a control circuit is supplied from both a DC output of a forward converter and an output of a backup power supply circuit, wherein the backup power supply circuit and the control circuit A normally closed contact type switch circuit is provided in the connection path, and the switch element of the forward conversion unit is configured to open the switch circuit only during ON / OFF operation, and is connected to the control circuit side of the contact of the switch circuit. A pulse width modulation converter device, further comprising an external operation power output terminal.