JPH04261359A - Power converter - Google Patents

Abstract

PURPOSE:To make the power converter thin and compact by lowering the breakdown strength of circuit parts and make the smoothness by a smoothing capacitor changeable. CONSTITUTION:A diode bridge circuit 12 is connected to an AC power source 11, and a series circuit of a smoothing capacitor 14 and a chock coil 15 is connected to the diode bridge circuit through a diode 13 for discharge. To the series circuit is connected in parallel the primary series circuit of DC-DC capacitors 1611-162m, and to the series circuit of the output terminals of some DC-DC converters 1611-161n is connected load 17, and to the series circuit of the output terminals of the left DC-DC converters 1621-162m is connected, through a diode 18 for charge, the series circuit of a smoothing capacitor 14 and a chock coil 15.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power conversion device comprising a plurality of DC-DC converters.

0002

2. Description of the Related Art Conventionally, a power conversion device shown in FIG. 2 is known. This connects the input terminal of a full-wave rectifier diode bridge circuit 2 to an AC power supply 1, and connects a series circuit of a smoothing capacitor 3, a choke coil 4, and a discharge diode 5 in parallel to the output terminal of the bridge circuit 2. There is. A resonance capacitor 6 is connected to the series circuit of the smoothing capacitor 3, choke coil 4, and discharge diode 5.
A parallel circuit of the primary winding of the resonant transformer 7 and a series circuit of the switching element 8 made of a transistor or the like are connected in parallel, and a connection point between the choke coil 4 and the discharge diode 5 and the resonant capacitor 6 are connected in parallel. A charging diode 9 is connected between the parallel circuit of the primary winding of the resonant transformer 7 and the connection point between the switching element 8 and the switching element 8 . A load 10 is connected to the secondary winding of the resonance transformer 7. In addition, the resonance capacitor 6 and the resonance transformer 7
, the switching element 8 constitutes a single-stone inverter circuit, and the switching element 8 is configured to perform switching operation in a self-excitation type or separately excitation type. In this conventional device, when the AC power supply 1 is turned on, the inverter circuit starts oscillating operation and the switching element 8 repeats on and off operations.

The output voltage of the diode bridge circuit 2 changes as shown by the solid line waveform a in FIG. 3, and the voltage across the smoothing capacitor 3 changes as shown by the dotted line waveform b in FIG. When the output voltage of the diode bridge circuit 2 is higher than the voltage across the smoothing capacitor 3, that is, in the section t1 of FIG.
A charging current flows to the smoothing capacitor 3 via the smoothing capacitor 3. At this time, power is supplied from the diode bridge circuit 2 to the inverter circuit.

Furthermore, when the output voltage of the diode bridge circuit 2 is lower than the voltage across the smoothing capacitor 3, that is, in the interval t2 in FIG. Power is supplied to the inverter circuit. In this way, the oscillation of the inverter circuit continues.

[0005]

However, since one inverter circuit supplies power to the load 10 and supplies charging energy to the smoothing capacitor 3, the resonant capacitor 6, which constitutes the inverter circuit, Circuit components such as the resonant transformer 7 and the switching element 8 had to have a high withstand voltage, and the device could not be made thin and compact. Furthermore, since the charge of the smoothing capacitor 3 is uniquely determined, the degree of smoothness cannot be changed.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a power conversion device that can be made thin and compact, and can also have smoothness that can be set arbitrarily and can be used depending on the application.

[0007]

[Means for Solving the Problems] The present invention connects at least a smoothing capacitor to a power source that rectifies alternating current or a pulsating current power source via a discharge diode in the opposite direction, and connects a series circuit including the discharge diode and the smoothing capacitor. A series circuit in which the primary side input terminals of a plurality of DC-DC converters whose primary and secondary sides are electrically isolated are connected in series is connected in parallel, and a part of each DC-DC converter is connected in parallel. A load is connected to a series circuit formed by connecting the secondary output terminals of the DC-DC converters in series, and a charging diode is connected to the series circuit formed by connecting the remaining secondary output terminals of each DC-DC converter in series. At least smoothing capacitors are connected in parallel in the forward direction.

[0008]

[Operation] In the present invention having such a configuration, when the power is turned on, the divided power supply voltage is supplied to the input terminal of each DC-DC converter, and each DC-DC converter starts its oscillation operation. . As a result, a desired additional DC voltage is generated in the series circuit of some of the secondary output terminals of each DC-DC converter and is supplied to the load.

A desired additional DC voltage is also generated in the series circuit of the remaining secondary output terminals of each DC-DC converter. However, this DC voltage causes a charging current to flow to the smoothing capacitor via the charging diode.

When the charging voltage of the smoothing capacitor is lower than the output voltage of the power supply, charging of the smoothing capacitor continues, and conversely, when the charging voltage of the smoothing capacitor is higher than the output voltage of the power supply, the charge of the smoothing capacitor is discharged. is supplied to the input terminal of each DC-DC converter via a diode.

In this device, by changing the number of DC converters whose secondary output terminals are connected in series to the smoothing capacitor, the charge level of the smoothing capacitor can be changed, so that the degree of smoothness can be changed.

0012

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, an input terminal of a full-wave rectifier diode bridge circuit 12 is connected to an AC power source 11. A series circuit of a smoothing capacitor 14 and a choke coil 15 is connected to the output terminal of the diode bridge circuit 12 via a discharge diode 13 having a polarity opposite to this output.

1611, 1612, 1613,...161
n and 1621...162m are DC-DC converters,
These DC-DC converters 1611, 1612, 16
The primary side input terminals of 13,...161n, 1621...162m are connected in series with each other, and one end of the series circuit, that is, one end of the primary side input terminal of the DC-DC converter 1611 is connected to the full-wave rectifier diode bridge circuit 12. It is connected to the connection point between the positive side of the output terminal of the output terminal and the cathode of the discharge diode 13, and the other end of the series circuit, that is, the DC -
The other end of the primary input terminal of the DC converter 162m is connected to the connection point between the negative electrode side of the output terminal of the full-wave rectifier diode bridge circuit 12 and the choke coil 15.

[0015] Each of the DC-DC converters 1611, 1
612, 1613,...161n, 1621...162m are electrically insulated on the primary and secondary sides, respectively.
A resonant circuit in which a resonant capacitor 21 and a primary winding of a resonant transformer 22 are connected in parallel, and a series circuit of a switching element 23 for operating this resonant circuit are connected between the primary side input terminals, and the switching element 23 is diode 24
A DC-AC conversion circuit is provided that connects the two in parallel. Incidentally, as the switching element 23, for example, a MOS type FET (field effect transistor) or the like is used, and this M
The OS type FET is switched by a well-known self-excited oscillation control circuit.

The transformer 22 has a primary winding and a secondary winding electrically insulated from the primary winding.
An output capacitor 26 is connected in parallel to the next winding via a rectifying diode 25.

A portion of each of the DC-DC converters, ie, the output terminals of each of the DC-DC converters 1611 to 161n, are connected in series, and a load 17 is connected between both ends of the series circuit.

[0018] Also, the remainder of each DC-DC converter,
That is, each of the DC-DC converters 1621 to 162
The output terminals of m are connected in series with each other, and a series circuit of the smoothing capacitor 14 and choke coil 15 is connected in parallel between both ends of the series circuit through a charging diode 18 in the forward direction.

In this embodiment having such a configuration, when the AC power supply 11 is turned on, each DC-DC converter 1
A full-wave rectified waveform from the full-wave rectifying diode bridge circuit 12 is applied to the input-side series circuits 611 to 161n and 1621 to 162m. The full-wave rectified pulsating current voltage is divided into 1/(n+m) and applied to each DC-DC converter 1611 to 161n and 1621 to 162m. In this way, each DC-DC converter 1611~
161n and 1621 to 162m start oscillating operation.

In this way, each DC-DC converter 161
The pulsating current voltage is 1/1 to 161n and 1621 to 162m.
Since only the voltage divided into (n+m) is applied,
The withstand voltage of the circuit components that make up each converter has been reduced to 1/(
n+m). Therefore, low-voltage circuit components can be used, and components can be shared. Therefore, the circuit components can be made smaller and thinner, allowing higher integration, and the entire device can be made thinner and more compact.

Since the voltage obtained by adding the output voltages of the DC-DC converters 1611 to 161n is applied to the load 17, a voltage sufficient to drive the load 17 can be obtained, and a discharge lamp or the like can be used as the load. Suitable when used.

[0022] Also, each DC-DC converter 1621 to 1
A voltage obtained by adding the output voltages of each DC-DC converter 1621 to 162m is generated in the series circuit of the output terminal of 62m. This voltage is then applied to the series circuit of the smoothing capacitor 14 and the choke coil 15 via the charging diode 18. In this way, the smoothing capacitor 14 is charged.

When the charging voltage of the smoothing capacitor 14 becomes higher than the output voltage of the diode bridge circuit 12, the charging voltage of the smoothing capacitor 14 is transferred to the discharging diode 13.
Each DC-DC converter 1611 to 161n,
It is supplied to the input side series circuit of 1621 to 162m.

In this case, each DC-DC converter 1611 to 161n and each DC-DC converter 1621
~ If you change the usage ratio of 162m, the smoothing capacitor 14
The voltage applied to the load 17 and the voltage applied to the load 17 can be changed arbitrarily. This makes it possible to set the optimum power supply and smoothness for the load 17. Therefore, when a discharge lamp is used as a load, it is possible to optimize the luminous efficiency of the lamp.

[0025] In the above embodiments, a full-wave rectified AC power source was used, but the power source is not necessarily limited to this, and any DC power source containing a pulsating current component may be used. .

[0026]

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide a power conversion device that can be made thin and compact, and can also be used according to the purpose by arbitrarily setting the degree of smoothness. It is.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a conventional example.

FIG. 3 is an output waveform diagram of each part of the conventional example.

[Explanation of symbols]

12... Full-wave rectifier diode bridge circuit, 13... Discharge diode, 14... Smoothing capacitor, 1611-16
1n, 1621~162m...DC-DC converter, 1
7...Load, 18...Charging diode.

Claims (1)

[Claims] 1. At least a smoothing capacitor is connected to a power source that rectifies alternating current or a pulsating current power source via a discharge diode in the opposite direction, and the primary and secondary sides of the series circuit including the diode and the smoothing capacitor are electrically connected. A series circuit formed by connecting the primary side input terminals of a plurality of DC-DC converters insulated in series with each other is connected in parallel, and a part of the secondary side output terminals of each DC-DC converter is connected in series with each other. A load is connected to a series circuit formed by connecting the remaining secondary output terminals of the DC-DC converters to each other in series, and a charging diode is connected in the forward direction to at least the smoothing circuit. A power conversion device characterized by connecting capacitors in parallel.