JPH0556665A - Power supply - Google Patents

Abstract

PURPOSE:To provide a power supply where the higher harmonic components of an input current are few, and the input power factor is high, and the smoothness of the electrolytic capacitor is high, and the rush current at power on is small. CONSTITUTION:This unit is constituted such that a current is made to flow from an AC power source Vs to an inductance L0 through a switching element S1, that the energy accumulated in this inductance L0 is charged in a capacitor C0 through a rectifier DB0 from the secondary winding of the inductance L0, and that DC power is supplied to load circuit IV through a diode D0 from this capacitor C0. Hereby, the rush current from the AC power source Vs can be prevented by controlling the on-off of the switching element S1, and the cost of a product can be cut down by reducing the current resistance of the circuit element. Moreover, the voltage of the capacitor C0 can be set freely by adjusting the winding ratio of the primary winding of the inductance L0 to the secondary winding.

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 and supplying the DC voltage to a load circuit such as an inverter.

[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 circuit such as an inverter. The device is widely used. A conventional example of this type of power supply device (see Japanese Patent Laid-Open No. 59-14021) is illustrated in FIG. In this device, an AC input terminal of a full-wave rectifier DB is connected to an AC power source Vs via a filter circuit FT, and a DC output terminal of the full-wave rectifier DB is connected to a capacitor for smoothing a power source via a reverse current blocking diode D _1. C ₀ is connected, and DC power is supplied from the capacitor C ₀ to the load circuit IV such as an inverter. A series circuit of an inductor L ₁ and a transistor Q ₁ is connected to the DC output terminal of the full wave rectifier DB. Transistor Q ₁
A capacitor C ₀ is connected to both ends of the capacitor via a diode D ₂ .

In the conventional example of FIG. 8, the transistor Q ₁ is turned on and off at a high frequency by the control circuit K ₁ to form a chopper circuit CH. When the transistor Q ₁ is turned on, a current flows through the inductor L ₁ due to the rectified output voltage of the full-wave rectifier DB, and energy is stored in the inductor L ₁ . Then, when the transistor Q ₁ turns off,
A voltage is generated in the inductor L ₁ , this voltage is added to the rectified output voltage of the full-wave rectifier DB, and the capacitor C ₀ is charged via the diode D ₂ . Therefore, a DC voltage higher than the peak value of the rectified output voltage of the full-wave rectifier DB is obtained in the capacitor C ₀ , and the load circuit IV is driven by this DC voltage.

In the circuit of FIG. 8, since the chopper circuit CH is provided between the full-wave rectifier DB and the power source smoothing capacitor C ₀ , the input current is constant even when the rectified output voltage of the full-wave rectifier DB is low. Flow, which improves the input power factor. However, in this circuit configuration, immediately after the AC power supply Vs is turned on, the AC power supply Vs, the filter circuit FT, the full-wave rectifier DB, the diode D ₁ , the capacitor C ₀ , the full-wave rectifier DB, the filter circuit FT, and the AC power supply Vs are connected. There is a problem that an inrush current transiently flows along the path. For this reason, when there is a switch for turning the power on / off, an arc is generated at the contact of the switch, and welding /
Inconvenience such as contact damage occurs. To prevent this, it is necessary to take measures such as using a switch with a large contact capacity or using a high-performance switching mechanism. Further, in order to allow the inrush current to flow, circuit elements having a large current capacity are also required for components such as the filter circuit FT and the full-wave rectifier DB, which causes an increase in cost and an increase in size and shape.

As another conventional example, Japanese Patent Application Laid-Open No. 61-4618.
Japanese Patent No. 1 discloses a power supply device in which a step-down chopper and an inverter also serve as switching elements. In this conventional example, an inrush current is unlikely to occur when the power is turned on, but the power supply of the inverter is a partially smoothed power supply, and there is a problem that a large ripple is generated in the output. Further, the chopper circuit is limited to the step-down type, and there is a problem that the step-up type cannot be used.

As another conventional example, Japanese Patent Application Laid-Open No. 61-9456.
No. 9 discloses a circuit configuration in which a current is supplied to an electrolytic capacitor via a choke of a high frequency inverter in order to prevent an inrush current to the electrolytic capacitor for smoothing a power source. Since it is a choke, there is a problem that it causes magnetic saturation and the effect of suppressing the inrush current is not sufficient. Further, when a low frequency choke made of a silicon steel plate or the like is used, magnetic saturation does not occur but the weight becomes heavy.

Still another conventional example is Japanese Patent Laid-Open No. 58-1.
Japanese Patent No. 70378 discloses a circuit configuration in which an output of a high frequency transformer of an inverter is fed back to charge an electrolytic capacitor. However, since it is a partial smoothing method, there is a problem that a large ripple is generated in the output of the inverter. Further, since the input current waveform in the steady state includes higher harmonic components, there is room for improvement in the input current distortion.

[0008] As another conventional example, as a practical example, Shokai 63-1
Japanese Patent No. 34500 discloses a circuit configuration in which high frequency power of an inverter is rectified via a transformer and is supplied to an electrolytic capacitor for power supply. However, a large ripple occurs in the output of the inverter and a large input current distortion occurs. There is a problem. In addition, a similar circuit configuration is disclosed in Japanese Patent Laid-Open No. 3-211065, but this also has a problem that an inrush current is generated.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is an object of the present invention to provide a high input power factor, a high input power factor, and a high input power factor in an electrolytic capacitor. The object of the present invention is to provide a power supply device having a high smoothness and a small inrush current when the power is turned on.

[0010]

FIG. 1 shows a power supply device according to the present invention.
3 is a circuit diagram showing the basic configuration of FIG. Below is the circuit configuration
explain about. AC power supply Vs has a filter circuit FT
AC input terminal of full-wave rectifier DB is connected via
It Power switch on the DC output terminal of the full-wave rectifier DB
SW₀The chopper circuit CH is connected via.
The chopper circuit CH is an inductor L with a secondary winding.₀
With an inductor L between the input terminals₀And switch
Element S₁Connect a series circuit of and switch between the output terminals.
Holding element S₁Are connected. Chopper circuit CH
A diode D is placed between the output terminals.₀And capacitor C₀Directly
The column circuit is connected. Diode D₀Is a capacitor
C ₀Are connected in such a polarity as to allow the discharge current to flow. Ko
C Densa C₀Is the inductor L of the chopper circuit CH₀
Secondary winding output of the full-wave rectifier DB₀By the voltage rectified by
Will be charged. Between the output terminals of the chopper circuit CH,
A load circuit IV such as an inverter is connected.

[0011]

The operation of the circuit shown in FIG. 1 will be described below. In this circuit, the diode D ₀ connected in series with the electrolytic capacitor C ₀ is connected with a polarity that prevents the capacitor C ₀ from being charged. Therefore, when the power switch SW ₀ is turned on, the output of the full-wave rectifier DB is output. No rush current flows through the capacitor C ₀ due to the voltage. When the switching element S ₁ of the chopper circuit CH is turned on, a current flows in a path passing through the full-wave rectifier DB, the power switch SW ₀ , the inductor L ₀ , the switching element S ₁ , and the full-wave rectifier DB, and the inductor L ₀ flows. Energy is stored. Next, when the switching element S ₁ is turned off, the inductor L
_A voltage is generated at both ends of ₀ , and this voltage is superimposed on the output voltage of the full-wave rectifier DB and supplied to the load circuit IV. By the operation of the chopper circuit CH, a high frequency voltage is induced in the secondary winding of the inductor L ₀ . The high frequency voltage is full-wave rectified by the full-wave rectifier DB _0, it is charged in the capacitor C _0. The charging voltage of the capacitor C ₀ is supplied to the load circuit IV via the diode D ₀ .

[0012]

FIG. 2 is a circuit diagram of a first embodiment of the present invention.
The circuit configuration of this embodiment will be described below. The bridge circuit composed of the diodes D ₁ , D ₂ , D ₃ , and D ₄ constitutes a full-wave rectifier, and the series circuit of the transistors Q ₁ and Q ₂ and the capacitors C ₁ and C are provided between the DC output terminals thereof.
_Two series circuits are connected in parallel. The connection point of the transistors Q ₁ and Q ₂ is connected to the connection point of the diodes D ₃ and D ₄ . A load R is connected between the connection point of the transistors Q ₁ and Q _{2 and} the connection point of the capacitors C ₁ and C ₂ . The connection points of the diodes D ₁ and D ₂ are the primary winding n ₁ of the inductor T ₀ and the inductor Lf,
It is connected to one end of the AC power supply Vs via the power switch SW ₀ . The other end of the AC power source Vs is connected to the connection point of the diodes D ₃ and D ₄ and the capacitor C
It is connected via f to the connection point between the primary winding n ₁ of the inductor T ₀ and the inductor Lf. The inductor Lf and the capacitor Cf form a filter circuit FT for removing high frequency components. Secondary winding n of inductor T ₀
AC input terminals of the full-wave rectifier DB ₀ is connected to _2. An electrolytic capacitor C ₀ is connected to the DC output terminal of the full-wave rectifier DB ₀ . The capacitor C ₀ is connected to the series circuit of the transistors Q ₁ and Q ₂ via the diode D ₀ having the illustrated polarity.

The operation of this embodiment will be described below.
When the power switch SW ₀ is turned on during the positive half cycle of the AC power supply Vs, the AC power supply Vs and the power switch S
Although a current is about to flow through W ₀ , the inductor Lf of the filter circuit FT, the primary winding n ₁ of the inductor T ₀ , the diode D ₁ , the transistor Q ₁ , and the AC power supply Vs, the chopper operation by the transistor Q ₁ occurs. It is possible to prevent an excessive current from flowing into the capacitor C ₀ via the secondary winding n ₂ of the inductor T ₀ and the full-wave rectifier DB ₀ by controlling Further, if the peak value of the current flowing through the transistor Q ₁ when the power is turned on is to be suppressed to the same level as the peak value of the current flowing through the transistor Q ₁ during steady operation, the control for shortening the ON period of the transistor Q ₁ ( For example, PWM control), power switch SW ₀
After the power is turned on, it may be performed for several cycles of the commercial AC power supply Vs. When the AC power supply Vs has a negative half cycle, the transistor Q ₂ may be controlled.

In this embodiment, the capacitor C₀In series with
Iodo D₀Since they are connected with the polarity shown in the figure,
Source switch SW₀When the filter is turned on, the filter circuit F
T, diode D₁, D₂, D₃, D_FourConsisting of
A condenser for smoothing the power supply is provided through the ion bridge circuit.
SA C₀It is possible to prevent inrush current from flowing into. here
Then, the capacitor Cf of the filter circuit FT and the inverter
Capacitor C₁, C ₂Is a small capacity for high frequency bypass
This is a large-capacity electrolytic capacitor C ₀Flow
Only a small amount of current flows compared to the current that flows in. did
Therefore, the power switch SW₀Will not damage. Shi
However, nevertheless, these small capacitors will not work.
If you want to suppress the current that flows in, turn the inductor Lf
Limit current using line DC equivalent resistance and inductance component
It is possible that

In the circuit shown in FIG. 2, the capacitor C ₀
Voltage Vc ₀ resulting in the winding n ₁ of inductor T _0,
It can be freely set by the turns ratio of n ₂ . When this voltage Vc ₀ is higher than the input voltage Vi of the inverter throughout the commercial cycle, the inverter is supplied with the ripple-free power supply voltage from the capacitor C ₀ , and the envelope of the output voltage of the inverter is It will be constant. In addition, the input voltage Vi of the inverter is the capacitor C _0.
When there is a period in which the voltage becomes larger than the voltage Vc ₀ of, the partially smoothed power supply voltage with many ripples is supplied to the inverter. That is, in the period when the Vi ≧ Vc _0, the power from the AC power source Vs to the inverter is supplied through the diode D ₁ or D _2, in the period when the Vi <Vc _0, via the diode D ₀ from the capacitor C ₀ Power is supplied to the inverter. Therefore, the voltage Vc ₀ of the capacitor C ₀ may be set appropriately according to the application.

FIG. 3 is a waveform diagram for explaining the operation of the circuit shown in FIG. In the figure, (a) is a power switch SW ₀
Shows an on / off state of the AC power source Vs.
The input voltage from is shown. Further, (c) shows the inrush current of the conventional example when the diode D ₀ , the full-wave rectifier DB _0, and the secondary winding n ₂ are not provided. On the contrary,
2 (d) and (e) show the waveforms of the current flowing through the primary winding n ₁ of the inductor T ₀ and the input current from the AC power supply Vs in the circuit shown in FIG. 2, respectively. This Figure 3
As is clear from a comparison between the input current waveform of the present invention shown in (e) and the input current waveform of the conventional example shown in FIG. 3 (c), in the present invention, the input current when the power is turned on is excessive. No inrush current occurs.

FIG. 4 is a circuit diagram of the second embodiment of the present invention. In this embodiment, in the circuit of FIG. 2, the diode D
By inserting ₅ and D ₆ , the charging efficiency of the capacitor C ₀ is improved. The charging efficiency of the capacitor C ₀ depends on the inductor T ₀ from the primary winding n ₁ to the secondary winding n _2.
Is dominated by the efficiency of conversion of energy into. The energy of the primary winding n ₁ of the inductor T ₀ is equal to the secondary winding n ₂
It is desirable that the conversion efficiency be 100%, but in reality, the conversion efficiency does not reach 100%, which causes a decrease in the charging efficiency of the capacitor C ₀ . Among the factors that reduce the conversion efficiency, the core loss and the DC resistance loss of the winding are unavoidable, but the energy accumulated due to the leakage inductance component of the inductor T ₀ is released by the diode as shown in FIG. It can be prevented by inserting D ₅ and D ₆ .

FIG. 5 is a waveform diagram for explaining the operation of this embodiment. In the figure, In ₁ is the primary winding n _{1 of the} inductor T ₀
Is the current that flows through. This current In ₁ is the AC power supply Vs
In the positive half cycle of, flows through diode D ₁ ,
In the negative half cycle, it will flow through diode D ₂ .
Now, assuming that the AC power supply Vs has a positive half cycle, when the transistor Q ₁ is turned on, the primary winding n ₁ of the inductor T ₀ , the diode D ₁ , and the transistor Q ₁
Current In ₁ flows through _one, this current In ₁ linearly increases. Next, when the transistor Q ₁ is turned off, the current In ₁ drops as shown by the shaded area. At this time,
Without the diode D _5, the first path through the diode D ₁ , the capacitor C ₁ and the load R, or the second path through the diode D ₁ , the capacitors C ₁ and C ₂ and the diode D ₄ , The current in the shaded area flows, and this current is not converted to the secondary winding n ₂ of the inductor T ₀ . Similarly, if the AC power supply Vs has a negative half cycle,
When transistor Q ₂ is turned on, the transistors Q _2, diode D _2, a current In ₁ flows through the primary winding n ₁ of the inductor T _0, the current In ₁ linearly increases. Next, when the transistor Q ₂ turns off,
The current In ₁ drops as shown by the shaded area. At this time, if diode D ₆ is not present, load R, capacitor C
_2, a first path through the diode D _2, or, diode D _3, capacitor C ₁ and C _2, through a second path through the diode D _2, the current of the shaded portion flows, this current inductor T It is not converted to the secondary winding n _{2 of 0} .

As is clear from the above description, the circuit shown in FIG.
In the road, diode D_Five, D₆By providing
Current In shown in 5₁Block the current in the shaded area
The inductor T₀Secondary winding n₂Converted to
The current that is emitted without
Duct T₀The energy conversion efficiency of
C₀The charging efficiency of can be improved. Well
And diode D₁, D ₂No extra current has to flow
Therefore, it is necessary to use a large capacity high frequency diode.
There is no need, and the circuit configuration can be economical.

FIG. 6 is a circuit diagram of the third embodiment of the present invention. In this embodiment, the primary winding n ₁ of the inductor T ₀ is arranged on the rectified output side of the full-wave rectifier DB. Therefore, a current flows only in one direction in the primary winding n ₁ of the inductor T ₀ , and the diode D ₁₀ for half-wave rectification is connected between the secondary winding n ₂ and the capacitor C _0. Just good. Also, since only the transistor Q ₂ is also used as the switching element for the chopper,
The diodes D ₁ and D ₂ are unnecessary.

FIG. 7 is a circuit diagram of the fourth embodiment of the present invention. In this embodiment, the capacitors C ₀₁ and C ₀₂ of the half-bridge type inverter are also used as capacitors for smoothing the power supply. In this case, it is necessary to connect the diodes D ₀₁ and D ₀₂ with the polarities shown in order to prevent inrush current from the power supply. Suppose Without diode D _01, when the power is turned on, the positive half cycle of the AC power source Vs, the diode D _1, the capacitor C _01, the load R, the first through the primary winding n ₁ of inductor T ₀ path Alternatively, an inrush current will flow in the second path that passes through the diode D ₁ , the capacitors C ₀₁ and C ₀₂ , the diode D ₄ , and the primary winding n ₁ of the inductor T ₀ . Also, the diode D ₀₂
If there is not, the first path through the primary winding n ₁ , the load R, the capacitor C ₀₂ , the diode D ₂ of the inductor T ₀ , or the inductor T in the negative half cycle of the AC power supply Vs when the power is turned on. _An inrush current flows through the second path passing through the primary winding n _{1 of 0} , the diode D ₃ , the capacitors C ₀₁ and C ₀₂ , and the diode D ₂ . Therefore,
To prevent these inrush currents, the diode D ₀₁ ,
D ₀₂ is required.

Further, when the load R of the inverter includes an inductive element, a path for flowing a flywheel current is required, so that in the present embodiment, the diodes D ₃ and D _{3 are used} .
₄ are connected as shown. When the transistor Q ₁ is on and the transistor Q ₂ is off, a current flows through the path passing through the capacitor C ₀₁ , the diode D ₀₁ , the transistor Q ₁ , the load R, and the capacitor C ₀₁ , and the load R is supplied with power. After that, when the transistor Q ₁ is turned off, the flywheel current flows through the path passing through the load R, the capacitor C ₀₂ , the diode D ₄ , and the load R due to the stored energy of the inductive load R. After that, the transistor Q ₂ is turned on, and a current flows through a path that passes through the capacitor C ₀₂ , the load R, the transistor Q ₂ , the diode D ₀₂ , and the capacitor C ₀₂ , and the load R is supplied with power. After that, when the transistor Q ₂ is turned off, the flywheel current flows in the path passing through the load R, the diode D ₃ , the capacitor C ₀₁ , and the load R due to the stored energy of the inductive load R. After that, the transistor Q ₁ is turned on, and
By repeating the same operation, high frequency power is supplied to the load R, and the load R operates as a half-bridge type inverter.

The capacitors C ₀₁ and C ₀₂ are charged by a chopper circuit consisting of a series circuit of a diode D ₁ , a transistor Q ₁ and a primary winding n ₁ of an inductor T ₀ in the positive half cycle of the AC power source Vs. AC power supply Vs
In the negative half cycle of, the primary winding n _{1 of the} inductor T ₀
It is charged by a chopper circuit consisting of a series circuit of a transistor Q ₂ and a diode D ₂ . In the primary winding n ₁ of the inductor T ₀ , currents of opposite polarities flow between the positive half cycle and the negative half cycle of the AC power supply Vs, so the full-wave rectifier DB ₀ flows in the secondary winding n _2. A series circuit of capacitors C ₀₁ and C ₀₂ is connected via.

As a modification of this embodiment, a capacitor
C₀₁, C₀₂Connect a small capacitor for high frequency in parallel with
It is possible to continue. In this case, a large capacity electrolytic
Densa C ₀₁, C₀₂Is responsible for smoothing the DC power supply,
The capacitor for the high frequency of the capacity is
You will be responsible for the work.

In each of the above embodiments, a capacitor is connected in parallel to one or both of the primary winding n ₁ and the secondary winding n ₂ of the inductor T _{0 so} as to be parallel to the inductance component of the winding. You may resonate. At this time, the energy of the primary winding n ₁ of the inductor T ₀ flows through the capacitor forming the inverter and the anti-parallel diode of the transistors Q ₁ and Q ₂ , and the transistor Q _1
The effects of reducing the stress of ₁ and Q ₂ and boosting the power supply voltage supplied to the inverter are obtained.

The primary windings n ₁ and 2 of the inductor T ₀ are
A plurality of taps may be provided in advance on the next winding n ₂ , and the taps may be selected according to the application.

[0027]

According to the present invention, a current is made to flow from an AC power supply to a inductor via a switching element, and the energy accumulated in this inductor is charged from a secondary winding of the inductor to a capacitor via rectifying means. Since this capacitor is configured to supply DC power to the load circuit via the diode, it is possible to prevent inrush current from the AC power supply when the power is turned on by controlling the on / off of the switching element. Therefore, there is an effect that the current withstand amount of the circuit element can be reduced and the cost of the device can be reduced. Further, by flowing a high-frequency current from the AC power supply to the inductor, it is possible to eliminate the pause of the input current, reduce the harmonic component of the input current, and improve the input power factor. In addition, the voltage obtained in the capacitor can be set freely by adjusting the turns ratio of the primary winding and secondary winding of the inductor, so the capacitor is charged with a voltage higher than the peak value of the rectified voltage of the AC power supply. Then, there is also an effect that it is possible to apply a DC power with a small ripple and a high smoothness to the load circuit.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a basic configuration of the present invention.

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

FIG. 3 is a waveform diagram for explaining the operation of the first embodiment of the present invention.

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

FIG. 5 is a waveform diagram for explaining the operation of the second embodiment of the present invention.

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

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

FIG. 8 is a circuit diagram of a conventional example.

[Explanation of symbols]

Vs AC power supply FT filter circuit DB full-wave rectifier SW ₀ power switch L ₀ inductor S ₁ switching element CH chopper circuit D ₀ diode C ₀ capacitor IV load circuit DB ₀ full-wave rectifier

Claims (1)

[Claims] 1. A load circuit driven by DC power, and a capacitor for supplying DC power to the load circuit,
A diode that constitutes a supply path of DC power from the capacitor to the load circuit, a switching element that is turned on / off at high frequency, and a chopper for storing energy by a current flowing from an AC power supply through the switching element. And an rectifying means for rectifying the secondary winding output of the inductor to charge the capacitor.