JPH05236762A - Power supply - Google Patents

Abstract

PURPOSE:To provide a power supply in which the waveform of input current is improved at low cost and surge current is suppressed upon turn ON of power. CONSTITUTION:Switching elements Q1, Q2 are turned ON/OFF alternately at high frequency to start oscillation of an inverter circuit wherein switching operation of the switching element Q1 also serves switching operation of a chopper circuit. Upon turn ON of a switch SW, a diode D4 is inserted into a feedback loop from a choke L0, a capacitor C0, and a diode D3 to an AC power supply AC in the direction reverse to feedback direction in order to block surge current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device.

[0002]

2. Description of the Related Art Conventionally, as a power supply device, a voltage obtained by rectifying and smoothing an AC power supply is used as a power supply, and a high frequency AC cycle is converted by oscillation such as on / off of a switching element, and the AC voltage is further converted into a DC voltage. There is one that outputs the DC voltage. Such a power supply device oscillates by turning on and off the high frequency of the switching element as described above in order to achieve miniaturization and high efficiency, and an AC power supply is generated.
The AC voltage is converted into a high frequency AC voltage. For that purpose, the AC power source must be rectified and smoothed once to be used as a DC power source, and the DC power source must be used as a power source for an oscillation circuit including a switching element. At this time, for example, as a means for rectifying and smoothing an AC power source, a method of rectifying using a diode bridge and smoothing the pulsating voltage with a smoothing capacitor is a simple and well-used method.

However, this method has a drawback that the peak value of the input current is very high and the circuit has a poor power factor due to the relationship of the DC smoothing voltage obtained by rectifying and smoothing the AC power supply. Was. Therefore, in order to improve the power factor,
A so-called chopper circuit is used for a power supply circuit, which is capable of causing an input current to flow in the entire range of an AC input voltage by switching its high frequency using a switching element.

However, when this chopper circuit is used as a power supply circuit, an inverter circuit for converting a DC power supply into a high frequency is required. Therefore, two switching circuits are formed by the chopper circuit and the inverter circuit, and the switching element It has a drawback that the number of devices increases and the cost of the entire device becomes expensive. As a countermeasure, a circuit in which the switching element of the chopper circuit and the switching element of the inverter circuit are shared has been proposed.

FIG. 4 shows an example of the conventional circuit. This conventional circuit operates as follows. First, the chopper circuit is composed of a choke L ₀ , a switching element Q ₁ , a capacitor C _0, and a diode D _3, and when the switching element Q ₁ is on, the input current is choked from the high voltage side of the diode bridge DB, that is, from the positive side. L ₀ , switching element Q ₁ ,
It flows to the low voltage side of the diode bridge DB, and the choke L
Charge electromagnetic energy to _zero . When the switching element Q ₁ is turned off, the choke L ₀ electromagnetic energy capacitor C ₀ which is charged, the diode D _3, a diode bridge DB, the AC power source AC, a diode bridge DB, discharged in a loop of the choke L _0, the capacitor C ₀ To charge.

On the other hand, the inverter circuit uses the capacitor C ₀ as a power source, and the switching elements Q ₁ , Q ₂ , diodes D ₂ , D ₃ , capacitor C ₁ , capacitors C ₁ , C ₂ ,
A so-called half-bridge type inverter circuit is configured by a load R ₀ (including a circuit for converting a direct current to a secondary side by a transformer or the like), and switching elements Q ₁ and Q ₂ are alternately turned on and off at high frequencies. High frequency AC energy is supplied to the load R ₀ .

Although a power supply device having a low cost and improved input distortion has been conventionally proposed by the circuit configuration as described above,

[0008]

FIG. 4 shows the above.
The circuit configuration of the
A source device has been proposed in the past.
In the circuit, switch SW that turns on and off the power supply
When the power is turned on, especially near the peak of the AC input voltage.
Inrush current i when turned on₀As shown by the dotted line in FIG.
From the AC power supply AC to the diode bridge DB,
Ark L₀, Capacitor C₀, Diode D ₃The Daio
Debridge DB, flow in AC power supply AC loop, mechanical
Due to contact welding of switch SW or abnormality of AC power supply AC
It was a cause of adverse effects on other machines.

FIG. 5 uses a full-bridge type inverter circuit
It shows a conventional example of a circuit that used to be a switch.
When the SW is turned on, the same rush current as in the conventional circuit of FIG.
Flow i ₀Flows. That is, before the switch SW is turned on
Is the capacitor C₀Since there is no charge on the
When the switch SW is turned on, the AC power supply AC is choked L
₀Resistance and capacitor C₀And diode D₃And with
It will be short-circuited, and inrush current with a high peak value in an instant
Flow i₀Flows, the capacitor C₀To charge. To this
Therefore, there is a problem similar to that of the conventional example shown in FIG.

The present invention has been made in view of the above problems, and an object thereof is to provide a low-cost power supply device in which the input current waveform is improved and the inrush current flowing when the power is turned on is reduced.

[0011]

According to the present invention, one end of a choke and a cathode side of a first diode are connected to a high voltage side of a rectified power source obtained by rectifying an AC power source by a rectifying element, and the choke of the above choke is connected. A first capacitor is connected between the other end and the anode side of the first diode,
In parallel with the capacitor of, a series circuit of a second diode having a cathode connected to the other end of the choke and a third diode having an anode connected to the anode of the first diode is connected, A series circuit of a first switching element and a fourth diode is connected in anti-parallel to the diode, and a second switching element is connected in parallel to the third diode to connect the first switching element and the fourth diode. The point is connected to the low-voltage side of the rectification power source, and the second and third diodes are connected in parallel with an LC resonance circuit or a switching circuit including a load, respectively.

[0012]

According to the present invention, therefore, the first switching element can be shared as a switching element for chopper operation and a switching element for an inverter circuit.
Since the high frequency input current flows in the entire cycle of the AC power supply by turning on / off the switching element in the high frequency, the input current distortion can be improved. Furthermore, when the power is turned on, the choke, the capacitor, the first diode Since the fourth diode is inserted in the feedback loop formed via the diode in the direction opposite to the feedback direction, the inrush current can be blocked.

[0013]

EXAMPLES The present invention will be described below with reference to examples. (Embodiment 1) This embodiment is a half-bridge type inverter.
A circuit is used, and as shown in FIG.
Rectified by a diode bridge DB that is a rectifying element,
A choke L is provided on the high voltage side of the rectified power source obtained by this rectification.₀
End of the first diode D ₁Connect the anode of
On chalk L₀Other end of the first diode D₁Anno
The first capacitor C between₀Connect the first con
Densa C₀Second and third diode D in parallel with₂, D₃
The series circuit of is connected.

Further, the second diode D₂To transistor
A first switching element Q consisting of ₁And the 4th Daio
De D_FourThe series circuit is connected in anti-parallel and the third diode
De D ₃A second switchon consisting of a transistor in parallel with
Element Q₂To connect the first switching element Q₁And the
At the connection point with the diode of 4, connect the low voltage side of the rectified power source
Connected.

The second and third diodes D ₂ and D ₃
The series circuit of the capacitors C ₁ and C ₂ is connected in parallel to the series circuit of No. 2, and the connection point of the capacitors C ₁ and C ₂ and the second and third
A load R ₀ is connected between the connection points of the diodes D ₂ and D ₃ of the above. With the above configuration, the LC resonance circuit including the load R ₀ is connected in parallel to each of the diodes D ₂ and D ₃ .

Thus, in this embodiment, the switching element Q
₁ , Q ₂ are alternately turned on and off at a high frequency by self-excitation or other-excitation or a combination of both, to obtain the oscillation operation of the inverter circuit and the switching operation of the switching element Q ₁ to obtain the chopper operation. That is, FIG.
As shown in (a), when the switching element Q ₁ is turned on, an input current ₁ is caused to flow in the circuit of the diode bridge DB, the choke L ₀ , the switching element Q ₁ and the diode bridge DB, and electromagnetic energy is accumulated in the choke L _0. ,
As shown in FIG. 2B, when the switching element Q ₁ is turned off, the choke L ₀ , the capacitor C ₀ , the diode D ₁ ,
In the closed circuit of the choke L ₀ , a chopper operation is performed in which a chopper current i ₂ caused by electromagnetic energy is passed to charge the capacitor C ₀ .

By turning on / off the switching element Q ₁ at a high frequency in this manner, a high frequency input current i ₁ flows in the entire cycle of the AC power supply AC, and the waveform is shaped by a filter circuit (not shown). The power factor is 1
An input current close to is obtained. On the other hand, in the half-bridge inverter circuit including switching elements Q _1, Q ₂ and has a configuration in which a diode D _1, D ₄ is added to the conventional circuit of FIG. 4, the diode D _4,
The inrush current can be prevented from flowing when the switch SW is turned on. That is, when viewed from the AC power supply AC side, when the switch SW is turned on, the AC power supply A is connected to the choke L ₀ , the capacitor C ₀ , and the diode D _3.
Since the diode D ₄ is inserted in the loop returning to C in the direction opposite to the feedback direction, no inrush current flows. And it does not affect the operation of the inverter circuit,
Moreover, the operation of the chopper circuit can be performed.

(Second Embodiment) In the first embodiment, a half-bridge type circuit is constructed as an inverter circuit, but in this embodiment, a full bridge type inverter circuit is constructed as shown in FIG. That is, the switching elements Q ₄ , Q are connected to the series circuit of the second and third diodes D ₂ , D _3.
The series circuit of _{5 and} the series circuit of the fifth and sixth diodes D ₅ and D ₆ are connected in parallel, respectively, and the connection point of the second and third diodes D ₂ and D ₃ and the switching element Q ₄ , A load R ₀ is connected between the connection point of Q _{5 and} the connection points of the fifth and sixth diodes D ₅ and D ₆ .

That is, the second and third diodes D₂, D₃
Each has a switching circuit connected in parallel.
ing. Thus, the switching element Q is also used in this embodiment.₁A little
Switching device for inverter operation and inverter circuit
Also serves as a touching element. In addition, as in the first embodiment,
AC power supply AC and choke L when the switch SW is turned on₀,
C Densa C₀, Diode D₃Return from AC power supply AC
Diode D in the opposite direction to the feedback direction _FourIs inserted
Since it is turned on, the inrush current can be blocked.
It

In addition to the configurations of the inverter circuits of the first and second embodiments, various inverter circuit configurations such as a modified half bridge circuit are conceivable depending on the circuit configuration connected to the diodes D ₂ and D ₃ , particularly the first embodiment. It is not limited to two.

[0021]

Since the present invention is configured as described above, the first switching element can be used both as a chopper operation switching element and an inverter circuit switching element, and the first switching element is turned on at a high frequency.・ By turning off, high-frequency input current flows through the entire cycle of the AC power supply, so distortion of the input current can be improved, and when the power is turned on, it is formed from the AC power supply via the choke, the capacitor, and the first diode. Since the fourth diode is inserted in the feedback loop in the direction opposite to the feedback direction, an inrush current can be blocked, and the circuit configuration is simple, so that there is an effect that it can be manufactured at low cost.

[Brief description of drawings]

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

FIG. 2 is an operation explanatory diagram of the first embodiment of the present invention.

FIG. 3 is a circuit diagram of a second embodiment of the present invention.

FIG. 4 is a circuit diagram of a conventional example.

FIG. 5 is a circuit diagram of another conventional example.

[Explanation of symbols]

Q _1, Q ₂ switching elements D ₁ to D ₄ diode DB diode bridge R ₀ load C ₀ -C ₂ capacitors L ₀ choke AC AC power SW power switch

Claims (1)

[Claims] 1. A high voltage side of a rectified power source obtained by rectifying an AC power source by a rectifying element, one end of a choke and a cathode side of a first diode are connected, and the other end of the choke and the first diode are connected. A first capacitor connected to the anode of the second diode, the second diode having the cathode connected to the other end of the choke in parallel with the first capacitor, and the anode connected to the anode of the first diode. And a third diode connected in series, and a second diode connected in series with a first switching element and a fourth diode in anti-parallel, and a third diode connected in a second switching element. Is connected in parallel, the connection point of the first switching element and the fourth diode is connected to the low voltage side of the rectified power supply, and the second and third diodes each include a LC resonance including a load. Road or power supply, wherein a switching circuit connected in parallel.