JPH0779548B2 - AC / DC conversion circuit - Google Patents

Description

The present invention relates to an AC / DC conversion circuit configured to obtain a DC output voltage higher than a voltage obtained by full-wave rectifying an AC input by a full-wave rectification circuit. Regarding the circuit.

[Conventional technology]

Conventionally, as this type of AC / DC conversion circuit, as shown in FIG. 2, a DC voltage source higher than the full-wave rectified voltage of the AC input is obtained while reducing the harmonics of the AC input current and improving the power factor. It is known that the circuit is configured as follows. That is,
In FIG. 2, reference numerals 10, 12, 14, 16 denote rectifying diodes forming a full-wave rectifying circuit, and an AC filter 20 is connected to an AC input side of the full-wave rectifying circuit via an AC current transformer 18. The connection is arranged. Further, the DC output side of the rectifier circuit is connected to a series connection circuit of a DC reactor 22 and a transistor 24, and the freewheeling diode 26 is connected to the transistor 24 in parallel with a series connection circuit of a capacitor 28, A load 30 is connected in parallel with the capacitor 28. Further, the AC input, the AC current transformer 18 and the capacitor 28 are connected at their respective ends, and the base and emitter terminals of the transistor 24 are connected to the control circuit 32.

In the AC / DC conversion circuit configured as described above, the transistor 24 is operated under the action of the control circuit 32 so that the AC input voltage waveform and the current waveform detected by the AC current transformer 18 become the same. When the on / off operation is performed at a sufficiently higher frequency, a current whose phase and waveform match the AC input voltage flows through the AC input, and the voltage of the capacitor 28 rises. Therefore, when the terminal voltage of the capacitor 28 reaches a predetermined value, the DC output voltage can be kept constant by adjusting the ON / OFF operation ratio of the transistor 24 via the control circuit 32.

[Problems to be solved by the invention]

However, in the conventional AC / DC conversion circuit configured as described above, for example, the AC input voltage is higher than the voltage at the U terminal>
A current passing path when the transistor 24 is turned on / off under the condition of the voltage of the V terminal is as follows. That is, when the transistor 24 is on, the rectifying diode
10 → DC reactor 22 → Transistor 24 → Current I ₁ flows through the path of rectifier diode 16 and when transistor 24 is off, rectifier diode 10 → DC reactor 22 → free wheeling diode 26 → parallel connection of capacitor 28 and load 30 A current I ₂ flows in the path from the circuit to the rectifying diode 16. Similarly,
When the AC input voltage is the voltage at the U terminal <the voltage at the V terminal, the current passage path is as follows. When the transistor 24 is on, the rectifier diode 14 → DC reactor 22 →
Current flows through the path of the transistor 24 → rectifier diode 12, and when the transistor 24 is off, the rectifier diode 14 → DC reactor 22 → free wheeling diode 26 → parallel connection circuit of the capacitor 28 and the load 30 → path of the rectifier diode 12 An electric current flows in.

In the conventional AC / DC conversion circuit that operates in this way, the number of semiconductors through which current passes
Two diodes and one transistor when 24 is on
In addition, when the transistor 24 is in the off state, there are three diodes. Therefore, there are problems that the loss generated by the semiconductor during the operation of the circuit increases and the conversion efficiency of the circuit decreases. Further, a large-sized cooling device is required, which causes a problem that the structure of the device becomes large.

Therefore, an object of the present invention is to obtain an AC / DC for obtaining a DC output voltage higher than a DC voltage obtained by full-wave rectifying an AC input.
An object of the present invention is to provide an AC / DC conversion circuit that can reduce the loss generated by semiconductors, improve the conversion efficiency, and can be configured in a small size.

[Means for solving problems]

An AC / DC conversion circuit according to the present invention is an AC / DC conversion circuit configured to obtain a DC output voltage higher than a voltage obtained by full-wave rectifying an AC input, wherein an AC reactor is provided on an AC input side of the full-wave rectification circuit. And a capacitor connected to the DC output side, and the semiconductor rectifier element arm that constitutes the full-wave rectifier circuit in order to minimize the number of semiconductor elements through which the current passes in the positive and negative half cycles of the AC input. It is characterized in that a self-turn-off type semiconductor switch is connected in antiparallel with half the number of semiconductor rectifiers.

In the AC / DC conversion circuit described above, the AC reactor can be configured by a leakage inductance of a transformer connected to the AC input side, a wiring inductance, or the like. Further, the capacitor can be replaced with a storage means such as a storage battery.

[Action]

According to the AC / DC conversion circuit according to the present invention, the AC reactor is connected to the AC input side of the full-wave rectifier circuit and the capacitor is connected to the DC output side, and the number of semiconductor rectifier element arms constituting the rectifier circuit is further increased. By connecting the self-extinguishing type semiconductor switches in anti-parallel to half of the semiconductor rectifying elements, the number of semiconductors through which the current passes in the positive and negative half cycles of the AC input is minimized, thereby reducing the generated loss, An improvement in conversion efficiency can be easily achieved.

〔Example〕

Next, embodiments of an AC / DC conversion circuit according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of an AC / DC conversion circuit according to the present invention. For the sake of convenience of explanation, the same components as those of the conventional circuit shown in FIG. In FIG. 1, reference numerals 10, 12, 14, 16 denote rectifying diodes as semiconductor rectifying elements that constitute a full-wave rectifying circuit, and an AC current transformer 18 and AC filter 20 via AC reactor 34
Are connected. A capacitor 28 and a load 30 are connected in parallel on the DC output side of the rectifier circuit. In the circuit of this embodiment, transistors 36 and 38 are connected to the rectifying diodes 10 and 12 in antiparallel with them. In addition, AC input, AC current transformer 18
Also, both ends of the capacitor 28 are connected to the control circuit 32, and the base and emitter terminals of the transistors 36 and 38 are connected to the control circuit 32.

In the AC / DC conversion circuit of the present embodiment configured in this manner, the transistors 36 and 38 are sufficiently higher than the frequency of the AC input so that the AC input voltage waveform and the current waveform detected by the AC current transformer 18 match. When the on / off operation is performed at the frequency, a current having the same phase and waveform as the AC input voltage flows through the AC input, and the voltage of the capacitor 28 rises. Therefore, when the terminal voltage of the capacitor 28 reaches a predetermined value, the DC output voltage can be kept constant by adjusting the ON / OFF operation ratio of the transistors 36 and 38 via the control circuit 32. You can

Further, the current paths in the circuit configured as described above are as follows. For example, AC input voltage is U terminal voltage>
Under the voltage condition of the V terminal, when the transistor 36 is turned off and the transistor 38 is turned on, the AC input (U terminal) → AC filter 20 → AC reactor 34 → transistor 38 → rectifier diode 16 → AC current transformer 18 Current in the path I ₁
Flows, and energy is stored in the AC reactor 34. Next, when the transistor 38 is turned off, the energy stored in the AC reactor 34 is rectified by the rectifier diode 10 →
Parallel connection circuit of capacitor 28 and load 30 → rectifier diode
16 → Commutes as a current I ₂ through the path of the AC current transformer 18.
Similarly, under the condition that the AC input voltage is the voltage of the U terminal <the voltage of the V terminal, when the transistor 38 is turned off and the transistor 36 is turned on, the AC input (V terminal) → AC current transformer 18 → rectifier diode A current flows through the route of 14 → transistor 36 → AC reactor 34. Next, the transistor 36
When turning off, AC input (V terminal) → AC current transformer
18 → Rectifier diode 14 → Parallel connection circuit of capacitor 28 and load 30 → Rectifier diode 12 → Current flows through the path of AC reactor 34.

In this way, according to the circuit of this embodiment, the number of semiconductors through which the current passes is one diode and one transistor when the transistor 36 or 38 is in the ON state, and when the transistors 36 and 38 are in the OFF state. Diode 2
It becomes an individual. Therefore, the number of diodes through which the current passes is reduced by one as compared with the above-mentioned conventional circuit.

The preferred embodiment of the AC / DC conversion circuit according to the present invention has been described above, but the present invention is not limited to this embodiment, and for example, as a transistor connected in antiparallel with a rectifier diode, An arc-extinguishing semiconductor switch can be generally used, and a circuit configuration that utilizes the leakage inductance and wiring inductance of a transformer instead of the AC reactor connected to the AC input side, or a capacitor provided on the DC output side Instead of this, it is possible to use a power storage means such as a storage battery, and it is needless to say that various design changes can be made without departing from the spirit of the present invention.

〔The invention's effect〕

As is apparent from the above-mentioned embodiments, according to the present invention,
As an AC / DC conversion circuit that can obtain a DC voltage source that is higher than the voltage obtained by full-wave rectifying an AC power supply, connect an AC reactor in series to the AC input side of the full-wave rectification circuit and connect it to the DC output side. By connecting a capacitor and connecting a self-extinguishing type semiconductor switch in antiparallel with half the number of arms of the rectifying diodes that compose the full-wave rectifier circuit, the passage of current in each positive and negative half cycle of the AC input. The number of semiconductors to be used can be reduced as compared with the conventional circuit, which can reduce the generated loss, improve the conversion efficiency, downsize the cooling device, and downsize the overall structure of the device.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of an AC / DC conversion circuit according to the present invention, and FIG. 2 is a circuit diagram of a conventional AC / DC conversion circuit. 10,12,14,16 …… Rectifier diode 18 …… AC current transformer, 20 …… AC filter 28 …… Capacitor, 30 …… Load 32 …… Control circuit, 34 …… AC reactor 36,38 …… Transistor

Claims (2)

[Claims] 1. In an AC / DC conversion circuit configured to obtain a DC output voltage higher than a voltage obtained by full-wave rectifying an AC input, an AC reactor is connected in series to an AC input side of the full-wave rectification circuit. , A capacitor is connected to the DC output side, and in order to minimize the number of semiconductor elements through which the current passes in the positive and negative half cycles of the AC input, the semiconductor rectifier element has half the number of semiconductor rectifier elements constituting the full wave rectifier circuit. An AC / DC conversion circuit characterized by connecting a self-extinguishing semiconductor switch in antiparallel with the element. 2. The AC / DC conversion circuit according to claim 1, wherein the AC reactor is composed of a leakage inductance of a transformer connected to the AC input side, a wiring inductance, etc., and the capacitor is a storage means such as a storage battery. AC / DC conversion circuit that is replaced by.