JPH0556659A - Power supply - Google Patents

Abstract

PURPOSE:To provide a power unit wherein the higher harmonic components of the input current are few and the rush current at power on is small. CONSTITUTION:A capacitor C1 for supplying an inverter A with DC power through a diode D4 is so constituted as to be charged through a diode D3 at power regeneration of the inverter A. Moreover, one part of the load circuit of the inverter A is connected to the output of a full wave rectifier DB through an impedance like a capacitor C4. Hereby, the rush current to the capacitor C1 at the initial stage of the power on of an AC power source Vs is checked by the diode D4. Even in the period where the instantaneous value of the input voltage from the AC power source Vs is low, an input current can be made to flow through an impedance element as the capacitor C4, so the input factor can be improved by reducing the higher harmonic components of the input 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 for converting an AC input voltage from an AC power supply into a DC voltage, converting the DC voltage into a high frequency by an inverter, and supplying the high frequency to a load.

[0002]

2. Description of the Related Art Conventionally, in order to drive a high-frequency lighting device for a fluorescent lamp, an AC input voltage from an AC power supply is rectified and smoothed, converted into a DC voltage, and the DC voltage is supplied to a load such as an inverter. Is widely used. Such a power supply device has the following two problems.

Input current harmonics problem. In other words, the waveform of the input current becomes a distorted waveform with respect to the sinusoidal input voltage from the AC power supply, and it contains many harmonic components. There is a problem that it becomes a cause.

Inrush current problem when power is turned on. That is,
Since the smoothing capacitor has a large capacity, when the power is turned on, the smoothing capacitor is rapidly charged. As a result, an inrush current flows from the AC power supply. Since this inrush current has a very high peak value, there is a problem that it may cause the fuse to be blown or the breaker to be cut off.

Conventionally, in order to solve such a problem,
A circuit as shown in FIG. 10 has been proposed (Japanese Patent Laid-Open No. 59-59).
-22,081). This circuit is designed so that the rectifier D
B, capacitor C1, inductor L2, diode D
3, the input current flows through the path passing through the transistor Q2 and the rectifier DB, and the capacitor C1 is charged. This circuit has the structure of a step-down chopper, and the rush current can be reduced by devising the on / off control of the switching element Q2 by the drive circuit K. However, since it is a step-down chopper, a quiescent period occurs in the input current. Therefore, there is a problem that the harmonic component of the input current is relatively large.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to reduce the harmonic components of the input current and to reduce the inrush current when the power is turned on. To provide a power supply device.

[0007]

In order to solve the above-mentioned problems, the power supply device of the present invention provides an AC power supply Vs and an AC input voltage from the AC power supply Vs as shown in FIG. Full-wave rectifier DB for full-wave rectification and full-wave rectifier DB
An inverter A having a load circuit including an LC resonance system and connected to the output of the capacitor C1, a capacitor C1 for supplying DC power to the inverter A, and a charging device for supplying a charging current to the capacitor C1 when the inverter A regenerates power. Like the diode D3, the discharging diode D4 for supplying DC power from the capacitor C1 to the inverter A, and the capacitor C4 for connecting a part of the load circuit of the inverter A to the output of the full-wave rectifier DB. And an impedance element.

[0008]

In the present invention, the capacitor C1 for supplying DC power to the inverter A through the diode D4.
Is configured to be charged through the diode D3 when the power of the inverter A is regenerated, so that the rush current into the capacitor C1 at the initial stage of power-on of the AC power supply Vs is blocked by the diode D4. Further, since the capacitor C1 is charged through the diode D3 when the power of the inverter A is regenerated, the voltage of the capacitor C1 can be gradually increased by devising the switching control of the inverter A. Inrush current can be prevented. In addition, since a part of the load circuit of the inverter A is connected to the output of the full-wave rectifier DB via an impedance element such as the capacitor C4, even when the instantaneous value of the input voltage from the AC power supply Vs is low, the input A current can be passed, the harmonic component of the input current can be reduced, and the input power factor can be improved. Further, by causing a current flowing from the full-wave rectifier DB through an impedance element such as the capacitor C4 to flow through the capacitor C1 through the other part of the load circuit and the charging diode D3, an impedance component is generated in the capacitor C1. A charging current can be passed through the charging current, and the voltage of the capacitor C1 can be gradually increased while preventing an inrush current.

[0009]

1 is a circuit diagram of a first embodiment of the present invention.
The circuit configuration of this embodiment will be described below. The AC power supply Vs is connected to the AC input terminal of the full-wave rectifier DB. A series circuit of transistors Q1 and Q2 is connected between the DC output terminals of the full-wave rectifier DB via a diode D5. Diodes D1 and D2 are connected in antiparallel to the transistors Q1 and Q2, respectively. An inductor L1 for current limiting and resonance is provided at both ends of the transistor Q2.
And through the coupling capacitor C3 for cutting the DC component,
A parallel circuit of a resonance capacitor C2 and a load F is connected. The parallel circuit of the capacitor C2 and the load F is connected between the DC output terminals of the full-wave rectifier DB via the capacitor C4. Further, a smoothing capacitor C1 is provided at both ends of the transistor Q2 via a charging diode D3.
Is connected to the capacitor C1, and a series circuit of transistors Q1 and Q2 is connected to the capacitor C1 via a discharging diode D4. In the figure, a circuit surrounded by a broken line constitutes a half-bridge inverter A.

The operation of this embodiment will be described below.
In the present embodiment, since the diode D4 is provided, the smoothing capacitor C1 is not directly charged by the input current from the AC power supply Vs when the power is turned on, and thus the inrush current can be prevented. Smoothing capacitor C1
Is charged by the regenerative current of the inverter A. First,
When the transistor Q2 turns on, the full-wave rectifier D
B, capacitor C4, capacitor C3, inductor L
1, the input current flows through the path passing through the transistor 1, the transistor Q2, and the full-wave rectifier DB. Also, capacitor C3 and inductor L
1, a current also flows through a path passing through the transistor C2, the parallel circuit of the capacitor C2 and the load F, and the capacitor C3. As a result, energy is stored in the inductor L1. Next, when the transistor Q2 is turned off, the stored energy of the inductor L1 causes the inductor L1 to pass through the diode D3, the capacitor C1, the parallel circuit of the capacitor C2 and the load F, and the inductor L3.
The regenerative current flows in the route returning to 1. The smoothing capacitor C1 is charged by this regenerative current. Then, the DC voltage charged in the capacitor C1 becomes the power supply voltage of the half-bridge inverter A via the diode D4. As described above, since a current flows through the capacitor C1 via the diode D3 during power regeneration, the diode D1 antiparallel to the transistor Q1 may be omitted.

The diode D5 is connected to the capacitor C4.
To discharge the electric charge in the inductor L1 and the capacitor C3 when the transistor Q1 is turned on, and
It is provided to disconnect the output of the full-wave rectifier DB from the output of the capacitor C1 via the diode D4 when the switch 1 is turned on. When the transistor Q2 is turned on, the input current flows into the inverter A via the capacitor C4 because the potential of one end of the load F to which the capacitor C4 is connected oscillates in a high frequency and the negative of the full-wave rectifier DB. This is because there is always a period when the potential is lower than the output terminal,
Therefore, the input current can always flow regardless of the instantaneous value of the power supply voltage. This eliminates the idle period of the input current, can reduce the harmonic components of the input current, and can further increase the input power factor. When the power is turned on, only the transistor Q2 is turned on / off to charge the smoothing capacitor C1 by the chopper action, and after the voltage of the capacitor C1 has sufficiently risen, the transistors Q1 and Q2 are turned on / off alternately.
By turning off, it is possible to effectively prevent inrush current when the power is turned on.

FIG. 2 is a circuit diagram of the second embodiment of the present invention. In this embodiment, in the circuit of FIG. 1, the full-wave rectifier D
The inductor L2 is inserted immediately after the DC output of B. The reason why the input current flows even when the instantaneous value of the input voltage from the AC power supply Vs is low is the same as in the embodiment of FIG. When the power is turned on, the full-wave rectifier DB,
Inductor L2, diode D5, transistor Q1,
An input current flows through a path that passes through the diode D3, the capacitor C1, and the full-wave rectifier DB to form a step-down chopper that charges the capacitor C1. In this step-down chopper, if the on / off control of the transistor Q1 is devised, the capacitor C1 can be gradually charged, whereby the inrush current can be prevented. In the embodiment shown in FIG. 1, since the inductor L2 is not provided, a control system in which only the transistor Q2 is turned on / off without turning on / off the transistor Q1 at the initial stage of power-on is adopted. In the embodiment shown in, the inductor L2 is provided immediately after the DC output of the full-wave rectifier DB,
The transistors Q1 and Q2 can be alternately turned on and off from the initial stage of power-on. Of course, like the embodiment shown in FIG. 1, it goes without saying that a control system in which only the transistor Q2 is turned on / off at the initial stage of power-on may be adopted.

FIG. 3 is a circuit diagram of a third embodiment of the present invention. In this embodiment, in the circuit of FIG.
The inductor L2 is inserted in series with the circuit 4, and the rest of the configuration is the same as the circuit of FIG. In this example,
By inserting the inductor L2, the input current becomes a little easier to flow than the circuit of FIG. The reason is,
This is because the voltage of the inductor L2 oscillates at a high frequency, the voltage across the inductor L2 overlaps with the output voltage of the full-wave rectifier DB, and there is always a period in which the input current from the AC power supply Vs can easily flow. Note that the harmonic components of the input current are reduced and the effect of reducing the inrush current is the same as in the circuit of FIG.

FIG. 4 is a circuit diagram of a fourth embodiment of the present invention. In the present embodiment, the arrangement of the load F, the capacitors C2 and C3, and the inductor L1 in the circuit of FIG. 3 is exchanged, and the connection point of the series circuit of the capacitor C4 and the inductor L2 is changed. Even in the case of such a circuit configuration, the harmonic components of the input current are reduced, and the inrush current when the power is turned on can be reduced.

FIG. 5 is a circuit diagram of the fifth embodiment of the present invention. In the present embodiment, in the circuit of FIG. 1, the parallel circuit of the load F and the capacitor C2 and the arrangement of the capacitor C3 are exchanged, the inductor L2 is inserted in series with the diode D4, and the diode D5 is omitted. The capacitance of the capacitor C4 is set smaller than that of the capacitor C3. In this embodiment, the transistor Q1 is turned off and only the transistor Q2 is turned on / off at high frequency in the initial stage of power-on. When the transistor Q2 is turned on, the input current from the AC power supply Vs causes the full-wave rectifier DB, the capacitor C4, the load F and the capacitor C2.
Of the parallel circuit, the inductor L1, the transistor Q2, and the full-wave rectifier DB. Then, when the transistor Q2 is turned off, a regenerative current due to the energy stored in the inductor L1 flows into the capacitor C1 via the diode D3 to charge the capacitor C1. The transistor Q1 is not turned on until the voltage of the capacitor C1 rises. This makes it possible to prevent an inrush current at the initial stage of power-on.

FIG. 6 is a circuit diagram of a sixth embodiment of the present invention. In the present embodiment, in the circuit of FIG. 2, the parallel circuit of the load F and the capacitor C2 and the arrangement of the capacitor C3 are exchanged, and the diode D5 is omitted. In this embodiment, as in the circuit of FIG. 2, the inductor L2 is inserted immediately after the DC output of the full-wave rectifier DB, so when the power is turned on, the full-wave rectifier DB, the inductor L2, the transistor Q1, the diode D3, A step-down chopper that charges the capacitor C1 by input current flowing through the path passing through the capacitor C1 and the full-wave rectifier DB is configured. In this step-down chopper, if the on / off control of the transistor Q1 is devised, the capacitor C1 can be gradually charged, whereby the inrush current can be prevented.

FIG. 7 is a circuit diagram of a seventh embodiment of the present invention. In the present embodiment, the arrangement of the smoothing capacitor C1 and the discharging diode D4 is replaced with the arrangement of the inductor L2 in the circuit of FIG. The direction of the diode D3 for charging the capacitor C1 is opposite to that in FIG. At power-on, full-wave rectifier DB, inductor L2, capacitor C
1, diode D3, transistor Q2, full-wave rectifier D
An input current flows through the path passing through B to form a step-down chopper that charges the capacitor C1. In this step-down chopper, if the on / off control of the transistor Q2 is devised, the capacitor C1 can be gradually charged,
As a result, inrush current can be prevented.

Further, in the circuit of FIG. 7, the inductor L2 also has a function of reducing the harmonic component of the input current. Because, when the transistor Q2 is turned on, a current flows in a path that passes through the capacitor C1, the inductor L2, the capacitor C4, the parallel circuit of the load F and the capacitor C2, the inductor L1, the transistor Q2, and the diode D4.
At this time, a voltage is generated in the inductor L2 in the right direction in the figure, and the input current flows even if the power supply voltage is lower than the voltage of the capacitor C1.

FIG. 8 is a circuit diagram of an eighth embodiment of the present invention. In this embodiment, in the circuit of FIG.
2, a capacitor C5 is inserted in series, and a diode D5 is connected in parallel with the series circuit of the inductor L2 and the capacitor C5 with the polarity shown. Due to the oscillating current flowing through the series circuit of the inductor L2 and the capacitor C5, there is a period during which the power supply voltage is lower than the voltage of the capacitor C1 and conduction is possible. As a result, the pause of the input current is reduced, the harmonic components of the input current are reduced, and the input power factor is improved. Since the series circuit of the diode D5, the capacitor C1, the diode D3, and the transistor Q2 is connected between the DC output terminals of the full-wave rectifier DB, the transistor Q2 is turned off and the transistor Q1 is turned on at the initial stage of power-on.
Only needs to be turned on and off. Then, after the voltage of the capacitor C1 rises sufficiently, the transistor Q1,
AC power supply V
It is possible to prevent a rush current from s to the capacitor C1.

FIG. 9 is a circuit diagram of the ninth embodiment of the present invention. In the present embodiment, the arrangement of the series circuit of the transistors Q1 and Q2 and the series circuit of the capacitors C3 and C4 in the circuit of FIG. 7 is replaced. Other configurations are
It is the same as the circuit of FIG. When the transistor Q2 is turned on at the initial stage of power-on, an input current flows in a path passing through the full-wave rectifier DB, the inductor L2, the capacitor C1, the diode D3, the transistor Q2, and the full-wave rectifier DB, and the inductor L2 is a component of the step-down chopper. Becomes By devising the on / off control of the transistor Q2, the voltage of the capacitor C1 can be gradually increased, which can prevent an inrush current when the power is turned on. Regarding that the inductor L2 also acts as an element for reducing the harmonic component of the input current,
It is the same as the circuit of FIG.

In the power supply device of the present invention, the load F is not particularly limited, but it is conceivable to use, for example, a fluorescent lamp load or an incandescent lamp load.

[0022]

According to the present invention, in a power supply device including a full-wave rectifier for full-wave rectifying an AC power supply, a capacitor for smoothing the output of the full-wave rectifier, and an inverter driven by the DC power from the capacitor. , By adding an impedance element for connecting a part of the load circuit of the inverter to the output of the full-wave rectifier and a diode for charging and discharging the capacitor, the harmonic component of the input current is reduced and the power is turned on. There is an effect that the initial inrush current can be prevented.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram of a second embodiment of the present invention.

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

FIG. 4 is a circuit diagram of a fourth embodiment of the present invention.

FIG. 5 is a circuit diagram of a fifth embodiment of the present invention.

FIG. 6 is a circuit diagram of a sixth embodiment of the present invention.

FIG. 7 is a circuit diagram of a seventh embodiment of the present invention.

FIG. 8 is a circuit diagram of an eighth embodiment of the present invention.

FIG. 9 is a circuit diagram of a ninth embodiment of the present invention.

FIG. 10 is a circuit diagram of a conventional example.

[Explanation of Codes] A Half Bridge Inverter Vs AC Power Supply DB Full Wave Rectifier Q1 Transistor Q2 Transistor L1 Inductor F Load D1, ..., D5 Diode C1, ..., C4 Capacitor

Claims (1)

[Claims] 1. An AC power supply, a full-wave rectifier for full-wave rectifying an AC input voltage from the AC power supply, an inverter including a load circuit connected to the output of the full-wave rectifier and including an LC resonance system, and a DC power supply for the inverter. A capacitor for supplying electric power, a charging diode for supplying a charging current to the capacitor during power regeneration of the inverter, a discharging diode for supplying DC power from the capacitor to the inverter, and a load circuit for the inverter. A power supply device, comprising: an impedance element for connecting a part thereof to an output of the full-wave rectifier.