JPH09103076A - Dc power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC power supply device, in which loss by the on- resistance of a switching element is reduced even in a wide input, which can output DC voltage higher than the peak value of AC input voltage with high efficiency and to which practical load can be connected. SOLUTION: A power-factor improving circuit 6A is constituted so as to satisfy Vo =a.E1 (a: a positive constant) in 0<=E1 <=85V and Vo =b+c.E1 (b, c: the positive constants and a>c) in 85V<=E1 respectively in the relationship of AC input voltage E1 and DC output voltage Vo . Loss Pon by the on resistance of a switching element Q1 is increased with the reduction of the peak value E1 P/Vo of input voltage to output voltage. When output voltage Vo is kept constant, loss Pon is maximized at minimum AC input voltage, but loss Pon at minimum AC input voltage E1 is lowered by varying output voltage Vo in response to the fluctuation of input voltage E1 .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC power supply device, and more particularly to improvement of a power factor correction circuit.

[0002]

2. Description of the Related Art A circuit of a conventional DC power supply device is shown in FIG.

The DC power supply device 1C shown in FIG. 1 includes a pair of AC power supply terminals 2a, to which a commercial AC input voltage E ₁ is applied.
2b, a high frequency removing filter (FIL ₁ ) 3, a rectifying bridge diode (DB ₁ ) 4, and a DC output terminal 5 to which, for example, a DC / DC converter 5 is connected as a load.
a and 5b, and a power factor correction circuit 6C.

The power factor correction circuit 6C is composed of a choke coil L ₁ , a switching element Q ₁ composed of a MOSFET, a reverse current blocking diode D ₁ and a smoothing capacitor C ₁ , and resistors R ₁ and R _2. AC voltage waveform detection circuit 8, a current detection resistor R ₃ , a resistor R ₄ ,
The output voltage detection circuit 9 composed of R ₅ and the switching element control circuit 10C for controlling the switching element Q ₁ are provided.

The switching element control circuit 10C has a first
The operational amplifier (A ₁ ) 12, the multiplier 13, the second operational amplifier (A ₂ ) 14, the flip-flop 15 and the oscillation circuit 16 are provided.

[0006] In such a power factor correction circuit 6C, the DC output voltage V _o of the booster circuit 7, the first operational amplifier 12
Is compared with a reference voltage V _ref, and the difference voltage is multiplied by a pulsating current signal I _sin for causing the AC input current I ₁ to follow the AC input voltage E ₁ . The current flowing through the switching element Q ₁ is detected by the current detection resistor R ₃ and controlled by the output of the multiplier 13. As a result, while follow the AC input current I ₁ to the AC input voltage E _1, the DC output voltage V _o is controlled at higher than the peak value E _1P of the AC input voltage voltage.

Here, considering the loss due to the on-resistance of the switching element Q ₁ , and letting this loss be P _on , P _on = I _1P ² · (1 / 2− (4E _1P ) / (3πV _o )) · R _on (1) However, I _1P : peak value of AC input current E _1P : peak value of AC input voltage V _o : DC output voltage, and loss E _on increases as E _1P / V _o decreases.

[0008]

This power factor correction circuit 6C
Is because they have a step-up circuit 7, the DC output voltage V _o has to be higher than the peak value E _1P of the AC input voltage,
For example, in the case of AC 264V input, the peak value E _1P of the input voltage is 1.41 × 264 = 373V, and when the required output voltage V _o is 390V, the ratio of the peak value E _1P of the input voltage to the output voltage V _o . E _1P / V _{o is, E 1P / V o = 373} /390 = 0.96 , and the loss P _on1 case of AC264V input becomes ^{_{P on1 = 0.094 × I 1P1 2}} · R on.

On the other hand, the power factor correction circuit 6C is
0V (AC85 to 132V) and AC200V (AC
When corresponding to the input 170 to 264V) is "Wide Input corresponding", for example in the case of AC85V _{input, E 1P / V o = 1.41} × 85/390 = 0.31 P on2 = 0.369 × since the ratio P _on2 / P _on1 loss of AC85V input to I _1P2 ² · R _on AC264V input is about _{I 1P2 / I 1P1 = 264/} 85, P on2 / P on1 = 0.396 × (264/85 ) ² · I _1P1 ² · R _on /(0.094I _1P1 ² · R _on ) = 0.396 × (264/85) ² /0.094=40.6, which causes a problem of extremely poor efficiency. there were.

Therefore, the present invention has been made in view of the above, and it is possible to output a DC voltage higher than the peak value of the AC input voltage with high efficiency, even in the case of a wide input, by reducing the loss due to the ON resistance of the switching element. Moreover, it is an object of the present invention to provide a DC power supply device capable of connecting a practical load.

[0011]

To achieve the above object, the present invention provides an AC power supply terminal to which an AC input voltage E ₁ of V _m or more is applied, and a rectifying circuit connected to the AC power supply terminal. In a DC power supply device having a DC output terminal and a power factor correction circuit having a booster circuit connected between the rectifier circuit and the DC output terminal, an AC input voltage E ₁ and a DC output voltage V of the booster circuit are provided. The relationship with _o is 0 ≦ E ₁ ≦ V _n
In (V _n ≦ V _m ), the relational expression of V _o = a · E ₁ (a: positive constant), and in V _n ≦ E ₁ V _o = b + c · E ₁ (b, c: positive constant and a >
The power factor correction circuit is configured so as to satisfy the respective relational expressions of c).

The loss P _on due to the on resistance of the switching element Q ₁ is P _on = I _1P ² · (1 / 2− (4E _1P ) / (3πV _o )) · R _on, where I _{1P is the} AC input current. Peak value E _1P : peak value of AC input voltage V _o : DC output voltage, and loss P _on increases as E _1P / V _o decreases.

Therefore, if the output voltage V _o is constant, the loss P _on becomes maximum at the minimum input voltage E ₁ .

Therefore, when V _n ≤E ₁ , V _o = b + c
· By configuring the power factor correction circuit to satisfy E _1, by varying the output voltage V _o in response to variations in the input voltage E _1, to reduce the loss P _on at the minimum input voltage E _1.

Further, by properly selecting the constants a, b, and c, a DC output voltage V _o higher than the peak value E _{1P of} the AC input voltage can be obtained, and with respect to the fluctuation range of the AC input voltage E ₁ ,
By reducing the fluctuation width of the DC output voltage V _o, a practical DC / DC converter or the like can be connected as a load.

In order to satisfy the relational expression, the power factor correction circuit smoothes the output of the rectifier circuit, and two resistors connected in series to the output side of the smoothing circuit. and a Zener diode, thereby connecting the connecting point between the two resistors to one input terminal, may be those of the voltage proportional to the output voltage V _o with an operational amplifier that is applied to the other input terminal, wherein A smoothing circuit for smoothing the output of the rectifying circuit, two resistors connected in series on the output side of the smoothing circuit, and a connection point between the two resistors are connected to one input terminal and the output voltage V The operational amplifier of the previous stage that applied a voltage proportional to _o to the other input terminal, and the output of this operational amplifier of the previous stage was applied to one input terminal, and the reference voltage was applied to the other input terminal. It may have an operational amplifier.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit diagram of a DC power supply device according to a first embodiment of the present invention.

The DC power supply device 1A of the present invention includes, for example, a pair of AC power supply terminals 2a and 2b to which a commercial AC input voltage E ₁ of 50 Hz is applied, and a high frequency removing filter (which is connected to the AC power supply terminals 2a and 2b). FIL ₁ ) 3, a rectifying bridge diode (DB ₁ ) 4 connected to the subsequent stage of the high frequency removing filter 3, and a load such as DC / DC
A pair of DC output terminals 5a, 5 to which the converter 5 is connected
b, the rectifying bridge diode 4, the DC output terminal 5a,
5b and a power factor correction circuit 6A connected to the power source 5b.

The power factor correction circuit 6A includes a booster circuit 7 composed of a choke coil L ₁ , a switching element Q ₁ composed of a MOSFET, a reverse current blocking diode D ₁ and a smoothing capacitor C _1, and an output stage of a rectifying bridge diode 4. AC voltage waveform detection circuit 8 consisting of resistors R ₁ and R ₂ for detecting pulsating current signal Isin from switching element Q ₁
In a current detection resistor R ₃ for detecting a current flowing through the DC output terminals 5a, and the output voltage detection circuit 9 composed of a resistor R _4, R ₅ connected between 5b, the switching element control circuit for controlling the switching element Q ₁ It has 10A.

The switching element control circuit 10A includes a diode D connected to the output of the rectifying bridge diode 4.
a and a capacitor Ca, a smoothing circuit 11, resistors Ra and Rb for dividing the voltage of the capacitor Ca, and a resistor Rb.
Zener diode Db connected in series with the resistor R
The first operational amplifier (A _{1) in} which the connection point between a and the resistor Rb is connected to the plus side input terminal, and the connection point between the resistors R ₄ and R ₅ of the output voltage detection circuit 9 is connected to the minus side input terminal ) 12, a multiplier 13 for multiplying the pulsating current signal Isin from the AC voltage waveform detection circuit 8 and the output of the first operational amplifier 12, an output side of the multiplier 13 is connected to a plus side input terminal, and switching is performed. The second operational amplifier (A ₂ ) 14 in which the connection point between the element Q ₁ and the current detection resistor R ₃ is connected to the negative side input terminal, and the switching element Q
_The flip-flop 15 in which the output terminal Q is connected to the control terminal (gate) 1 and the output of the second operational amplifier 14 is connected to the set terminal S, and the oscillation circuit for inputting the reset signal to the reset terminal R of the flip-flop 15 16
And

Next, the operation of the DC power supply device 1A will be described.

When the AC voltage E ₁ is applied to the pair of power supply terminals 2a and 2b by connecting the power switch S, a full-wave rectified voltage waveform is obtained at the output stage of the rectifying bridge diode 4.

When a voltage is obtained at the output stage of the rectifying bridge diode 4, a reset signal is given from the oscillation circuit 16 to the reset terminal R of the flip-flop 15 based on this voltage, and the switching element Q is output by the output terminal Q of the flip-flop 15. ₁ turns on.

When the switching element Q ₁ is turned on, a current flows through the circuit composed of the choke coil L ₁ and the switching element Q _1, and energy is accumulated in the choke coil L ₁ . The current of the choke coil L ₁ gradually increases during the ON period of the switching element Q ₁ .

The current during this ON period is the current detection resistor R ₃
Is detected by, and is input to the negative side input terminal of the second operational amplifier 14, is compared with the sine wave corresponding to the input power supply voltage given from the multiplier 13, and the triangular wave of the current detected by the current detection resistor R ₃ is a sine wave. When the output of the second operational amplifier 14 is reached, the set signal is given to the set terminal S of the flip-flop 15, the Q output of the flip-flop 15 becomes low level, and the switching element Q ₁ is turned off. .

[0027] The OFF period of the switching element Q _1, the energy stored in the choke coil L ₁ is transferred to the capacitor C ₁ through the diode D _1. At this time, the capacitor D ₁ is charged with a voltage obtained by adding the voltage of the choke coil L ₁ to the power supply voltage, and the capacitor C ₁ is charged with a voltage higher than the AC input voltage E ₁ .

Further, in the OFF period of the switching element Q _1, and decreases with the current of the choke coil L ₁ time, the release of energy of the choke coil L ₁ is completed, a reset terminal R of the flip-flop 15 from the oscillation circuit 16
To the switching element Q ₁ again.
Turns on.

By the way, the voltage rectified by the rectifying bridge diode 4 is smoothed by the smoothing circuit 11 including the diode Da and the capacitor Ca. The voltage V _{1 of the} capacitor Ca is divided by the resistors Ra and Rb, and the voltage V ₂ between the resistor Rb and the Zener diode Db is input to the positive side input terminal of the first operational amplifier 12. Output voltage V _o
The sense voltage V _{s obtained by} dividing the voltage by the resistors R ₄ and R ₅ of the output voltage detection circuit 9 is input to the negative side input terminal of the first operational amplifier 12.

That is, the sense voltage V _s is not compared with the reference voltage, but is compared with the input voltage V ₂ to the plus side input terminal of the first operational amplifier 12, and the control is performed.
The output voltage V _o varies in response to changes in the input voltage V _2. The voltage V ₁ is equal to the AC input voltage E _{1 as} shown in FIG.
The input voltage V ₂ becomes higher than the voltage V ₁
Rises at V ₂ = V ₁ until the voltage exceeds the zener voltage V _z of the zener diode Db, but when it exceeds the zener voltage V _z , V ₂ = k ₁ + k ₂ · V ₁ (2) However, k ₁ = V _z · (Ra−rz) / (Ra +
Rb) k ₂ = (Rb + rz) / (Ra + Rb) rz: operating resistance of Zener diode Db

Utilizing this characteristic of the input voltage V ₂ , as shown in FIG. 3, the relationship between the AC input voltage E ₁ and the output voltage V _o of the booster circuit 6A is V when 0 ≦ E ₁ ≦ V _n ). _o = a · E ₁ (a: positive constant), where V _b ≦ E ₁ V _o = b + c · E ₁ (b, c: positive constant, and a>
The power factor correction circuit 10A can be designed so as to satisfy the respective relational expressions of c). For example, AC input voltage E ₁ = 264
It can be designed so that the output voltage V _o = 390 V when V, and the output voltage V _o = 250 V when the AC input voltage E ₁ = 85 V. Note that V _n may be set to the minimum input voltage (85 V) V _m or less.

According to the DC power supply device 1A according to the first embodiment, when the AC input voltage E ₁ decreases, the DC output voltage V _o also decreases.
When the C input voltage E ₁ varies from AC85V to AC264V, the output voltage V _o from 250V DC DC39
If it is designed to fluctuate to 0V, the switching element Q when the AC input voltage E ₁ is AC85V
_The loss P _on3 due to the ON resistance of ₁ is P _on3 = 0.296 × I _1p ² · R _on , and the AC input voltage E ₁ is AC85V and the output voltage V _o
There can be lowered by about 20% compared to the loss P _on2 in the case of 390 V.

Further, the fluctuation range of the AC input voltage E ₁ (264
-85) /264=67.8Pasento respect, since the smaller the fluctuation range (390-250) /390=35.9Pasento output voltage V _o, the practical DC / DC converter 5 as a load Can be used.

Further, the AC input current I ₁ is converted to the AC input voltage E
While following the _1, and controls the output voltage V _o is always higher voltage than the peak value E _1P of the AC input voltage.

Further, it is effective when the reference voltage of the output voltage control operational amplifier of the power factor correction circuit control IC can be changed externally or when the IC is assembled independently.

FIG. 4 is a circuit diagram of a DC power supply device according to the second embodiment of the present invention.

The switching element control circuit 10B of the present DC power supply apparatus 1B is the same as the switching element control circuit 10A of the DC power supply apparatus 1A shown in FIG.
Is omitted, a third operational amplifier (A ₃ ) 17 is added, the sense voltage V _s is applied to the negative side input terminal of the third operational amplifier 17, and the resistance Rb is applied to the positive side input terminal of the third operational amplifier 17. applying a by divided voltage V _in, is applied with the reference voltage V _ref to the positive input terminal of the first operational amplifier 12, applies the output of the third operational amplifier 17 to the negative input terminal of the first operational amplifier 12 It was done.

The output voltage V ₃ of the added third operational amplifier 17 is subtracted from the sense voltage V _s by the voltage V _{in obtained by} dividing the voltage V ₁ of the capacitor Ca which changes according to the AC input voltage E ₁ . It becomes an output. Since the output voltage V ₃ is controlled by the reference voltage V _ref , the output voltage V _o is V _o = k ₃ · V _ref + k ₄ · V ₁ (3) However, k ₃ and k ₄ are constants.

The formula (3) has the same form as the formula (2), and can be designed in the same manner as the first form.

Further, in contrast to the configuration of the conventional example shown in FIG.
Since only the smoothing circuit 11 and the third operational amplifier 17 are added, the IC used in the conventional example of FIG. 5 can be realized.

The third operational amplifier 17 is an example of a circuit that subtracts the V _in signal from the V _s signal, and a circuit for realizing this can be realized by a discrete structure.

[0042]

As described above in detail, according to the present invention, the DC output voltage is changed according to the level of the AC input voltage, so that the loss due to the ON resistance of the switching element is prevented even in the wide input. It is possible to realize a power factor correction circuit that can reduce the DC voltage higher than the peak value of the AC input voltage with high efficiency.

Further, since the fluctuation range of the DC output voltage can be made smaller than the fluctuation range of the AC input voltage, it is possible to connect a practical DC / DC converter or the like as a load.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a DC power supply device according to a first embodiment of the present invention.

FIG. 2 V ₂ characteristic diagram

[Fig. 3] Characteristic diagram of V _o

FIG. 4 is a circuit diagram of a DC power supply device according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram of a conventional DC power supply device.

[Explanation of symbols]

1A, 1B DC power supply device 2a, 2b AC power supply terminal 3 High frequency removing filter (FIL ₁ ) 4 Rectifying bridge diode (DB ₁ ) 5 DC / DC converter 5a, 5b DC output terminal 6A, 6B Power factor improving circuit 7 Step-up circuit 8 AC voltage waveform detection circuit 9 Output voltage detection circuit 10A, 10B Switching element control circuit 11 Smoothing circuit 12 First operational amplifier 13 Multiplier 14 Second operational amplifier 15 Flip-flop 16 Oscillation circuit Db Zener diode Ra, Rb Resistance Q ₁ switching element

Claims (3)

[Claims] 1. An AC power supply terminal to which an AC input voltage E ₁ of V _m or more is applied, a rectifier circuit connected to the AC power supply terminal, a DC output terminal, and the rectifier circuit and the DC output terminal. in direct-current power supply and a power factor improvement circuit formed by connecting a boosting circuit between the relationship of the AC input voltage E ₁ and the DC output voltage V _o of the booster _{circuit, 0 ≦ E 1 ≦ V n} (V _{In the case of n} ≦ V _m ), the relational expression of V _o = a · E ₁ (a: positive constant), in the case of V _n ≦ E ₁ V _o = b + c · E ₁ (b, c: positive constant, and a>
A DC power supply device characterized in that the power factor correction circuit is configured so as to satisfy the respective relational expressions of c). 2. The power factor correction circuit includes a smoothing circuit for smoothing an output of the rectifier circuit, two resistors and a zener diode connected in series to an output side of the smoothing circuit, and a resistor between the two resistors. thereby connecting the connection point to the one input terminal, a DC power supply device according to claim 1, characterized by comprising an operational amplifier which applies a voltage proportional to the output voltage V _o to the other input terminal. 3. The power factor correction circuit includes a smoothing circuit for smoothing the output of the rectifier circuit, two resistors connected in series on the output side of the smoothing circuit, and a connection point between the two resistors. The output voltage V is connected to one of the input terminals.
_Equipped with a front-stage operational amplifier that applies a voltage proportional to _o to the other input terminal, and a rear-stage operational amplifier that applies the output of this front-stage operational amplifier to one input terminal and a reference voltage to the other input terminal. The DC power supply device according to claim 1, wherein