JPH0449848A - Switching regulator - Google Patents

Abstract

PURPOSE:To improve a power factor and to simplify a circuit scale for stabilizing an output by integrating a power factor improving circuit with an output stabilizer. CONSTITUTION:The output voltage of a rectifying and smoothing circuit 7 is compared with a set voltage by a voltage detector 8, an error signal is applied to a multiplier 9, multiplied by a rectified output voltage, applied to an error amplifier 10, and compared with a sawtooth wave signal of a sawtooth wave generator 11 by a comparator 12. Accordingly, when a period of '1' to be output from the comparator 12 is shortened, a period in which first, second switching elements 4, 5 are simultaneously turned ON, is shortened, an energy to be stored in an inductance 3 is reduced, and the output voltage of the circuit 7 becomes a set voltage. When the period in which the elements 4, 5 are simultaneously turned ON, is lengthened, the energy stored in the inductance 3 is increased, and the output voltage becomes the set voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a switching regulator with improved power factor.

Switching that supplies a stabilized DC voltage from an AC power source to a DC load 1. In the y-giver, the alternating current voltage of the alternating current power supply is rectified, and the rectified output voltage is applied to a bipolar transistor or MOS! -Add the ~ winding wire number of the transformer via L7 through a switching element such as a run lister,
The voltage induced in the secondary winding of the transformer is rectified and smoothed to obtain a DC voltage to be supplied to the direct load t, and the on-period of the switching element is controlled so that the DC voltage becomes the set voltage. It is something.

Further, in the switching L/regulator, a pulsed current flows along with the switching scale, so the current contains less fundamental wave components of the AC voltage, and the power factor decreases. Therefore, it is desired to improve the power factor by controlling the current to flow in a manner similar to a sine wave.

[Conventional technology] A switching l caliper with a conventional power factor improvement configuration.

The rake 1 has, for example, the configuration shown in FIG. 4, where 51 is a rectifier circuit consisting of diodes D1.1 to D14, and 52 is a primary winding 52a, a central winding 52b, and a knee winding 52c. A transformer 5.53 is an inductance, 54.55 is a field effect transistor, and 5
G is a current detector consisting of a resistor, etc., and 57 is a diode D.
15. A rectifying and smoothing circuit consisting of D16, an inductance l-211, and a capacitor C1l, 58 an error amplifier 61
, a comparator 62, a sawtooth wave generator (33), an output stabilizing circuit consisting of an output transistor 4°65, pulse 1 to lance 66, etc., 59 is a reference voltage Vr2 and an error amplifier 676
9 and b; 1 unit '7 Oa multiplier 68 and sawtooth wave generator 7
1, and output transistors 72 and 73; 260 is an AC power supply; L12. C13 is the inductance and capacitor that constitute the input filter, r')17
．． DlB is a diode, and CI2 is a coni/capacitor.

The AC voltage of the AC power supply 60 is 2, and the inductance is 1.12.
It is applied to the rectifier circuit 51 and rectified through an input filter consisting of a capacitor C13 and a capacitor C13, and the rectified output voltage is passed through an inductance 53 and a diode D17 to
41 to the primary winding 52a of the lance 52 and the central winding 52
The current flowing through the primary winding 52a of the transformer 52 is switched by the field effect transistor 54. The current flowing through the primary winding 52a: 1. The voltage Vs induced in the secondary winding 52c by the switching is rectified and normalized by the rectifying and smoothing circuit 57, and becomes a DC voltage Vd to be supplied to the DC load. Also, when field effect 1-ransistor 54 is turned off, lyse throat winding! As the voltage induced in the transformer 52b flows through the diode F'DI8, a voltage is applied to prevent the core of the transformer 52 from magnetic saturation.

In the output stabilization circuit 58, the error amplifier 61 outputs an error signal of the difference between the DC voltage Vd and the reference voltage Vrl to the comparator 62.
and is compared with the sawtooth signal from the sawtooth generator 63, and the comparison output signal causes the output transistor 4.
65 is controlled, and the on-period of the field effect transistor 54 is controlled by its output signal, thereby stabilizing the DC voltage Vd.

Further, when the field effect transistor 55 is turned on, the inductance 7 is passed through the field effect transistor 55 to the inductance 53.
When a current flows and energy is stored, and field effect 1 to transistor 55 are turned off, capacitor CI2 is charged by the energy stored in inductance 53 via diode D17. The charging voltage of the capacitor C12 is applied to the single winding 52a of the transformer 52 via the turned-on field effect transistor 54.

Also, the terminal voltage Vc of capacitor C12 and base 1! Voltage Vr2
The error signal from the error amplifier 67 is applied to the multiplier 68, where it is multiplied by the rectified output voltage that has been full-wave rectified by the rectifier circuit 51, and the error signal from the error amplifier 61m is applied to the multiplier output signal from the slag detector 56.
is added to the detection output signal, and the difference signal is sent to the comparator 10L
The output transceivers 72,
73 is controlled, and its output signal causes the capacitor C12 to
The on-period of the C-comi field effect transistor 55 is controlled so that the terminal voltage VC2 of VC2 becomes the set value. Thereby,
The current supplied from the AC power supply 60 approaches a sine wave, and the power factor is improved.

FIG. 5 is an explanatory diagram of the operation of the conventional example, and when the rectified output voltage a full-wave rectified by the rectifier circuit 51 is shown in (a),
When the difference between the terminal voltage Vc of the capacitor CI2 and the reference voltage Vr2 is multiplied by the rectified output voltage a by the multiplier 68, the waveform shown in (b) is obtained, for example. The difference between this multiplication output signal and the detection output signal of the current detector 56 and the sawtooth wave signal C of the sawtooth wave generator 71 have a waveform shown in (C), for example. Therefore, the output signal d of the comparator 70 is (
This output signal d controls the on/off state of the output transistors 72 and 73, and accordingly controls the on/off state of the field effect transistor 550.

At this time, the off period of the field effect transistor 55 is set as Tof.
f, the period of the sawtooth wave signal C of the sawtooth wave generator 71 is T,
Assuming that the rectified output voltage of the rectifier circuit 51 is ■, the terminal voltage Vc of the capacitor C12 is Vc-(TI/To f f
)-V. Therefore, the terminal voltage V of capacitor C12
When c increases, the off-period Toff of the field-effect transistor 55 is lengthened, and when the terminal voltage Vc of the capacitor CI2 decreases, the off-period Toff of the field-effect transistor 55 is controlled to be shortened. Become.

As a result, the current e supplied from the AC power supply 60 is
As shown in (e), the wave becomes close to a sine wave, and the power factor can be improved.

Fig. 3) shows an example of the sawtooth wave signal f of the sawtooth wave generator 63 and the output signal of the error amplifier 61. A signal g that becomes "lo" is output. (g) shows this signal g. Further, (5) is the drain-source voltage Vds of the field effect transistor 54, and (i) is the diode D15. The rectified output voltage Vt due to D16 is shown.

In this case, the period of the sawtooth wave signal f of the sawtooth wave generator 63 is T2, and the on period of the field effect transistor 54 is T2.
When it is on, the DC voltage Vd is Vd= (Ton/T
2) ・Vt. Therefore, when the DC voltage Vd increases, the on-period Ton is shortened and, conversely, the DC voltage Vd
When the on-period Ton decreases, the field effect transistor 54 is controlled to lengthen the on-period Ton.

[Problem to be solved by the invention]

The conventional switching regulator described above transfers the pulse-like input current associated with switching to an inductance 53.
A continuous current is generated using the capacitor C12, the field effect transistor 55, and the power factor correction circuit 59, and the AC power source 6
The output stabilizing circuit 58 and the power factor correcting circuit 59 are each provided with sawtooth wave generators 63 and 71, and are also provided with an error amplifier, a comparator, etc. This has the drawback of increasing the circuit scale and increasing costs.

The present invention aims to simplify the circuit scale for power factor improvement and output stabilization.

[Means to solve the problem]

The switching regulator of the present invention has a simplified circuit scale by integrating a power factor correction circuit and an output stabilization circuit, and will be explained with reference to FIG.

The rectified output voltage of the rectifier circuit 1 that rectifies the AC voltage of the AC power supply is applied to the connection point between the primary winding 2a and the reset winding 2b of the transformer 2 via the inductance 3, and the rectified output voltage is applied to the primary winding 2a of the transformer 2. The first switch switches the flowing current.
a second switching element 5 that switches the current flowing through the reset winding 2b, a current detector 6 consisting of a resistor, etc. that detects the output current of the rectifier circuit 1, and a secondary winding of the transformer 2. 2c, an output voltage detection circuit 8 that compares the output voltage of this rectification and smoothing circuit 7 with a set voltage and outputs an error signal, and this output voltage detection circuit. a multiplier 9 that multiplies the error signal of 8 by the rectified output voltage of the rectifier circuit 1; an error amplifier 10 that outputs the difference between the multiplication output signal of the multiplier 9 and the detection output signal of the current detector 6; A comparator 12 that compares the output signal of the error amplifier 10 and the sawtooth wave signal of the sawtooth wave generator 11, a flip-flop 13 that performs an inverting operation in synchronization with the sawtooth wave signal, and a An OR circuit 14.15 that controls the first and second switching elements 4.5 by the OR signal of the output signals of the positive and negative output terminals Q and Q and the comparison output signal of the comparator 12. It is.

[Effect]

The sawtooth wave signal from the sawtooth wave generator 11 is input to the comparator 12, and a signal synchronized with the sawtooth wave signal is applied to the flip-flop 13.
The output signals of output terminals Q and Q of 3 are the inversions of 1'' and 0''. At this time, the output signal of the comparator 12 is “
1'', the first and second switching elements 4 and 5 are turned on at the same time, and current flows through the inductance 3 to the primary winding 2a and reset winding 2b of the transformer 2.
Since the magnetic fluxes caused by the currents flowing through the primary winding 2a and the reset winding 2b cancel each other out, no voltage is induced in the secondary winding 2c, and energy is stored in the inductance 3.

When the output signal of the comparator 12 is "P0", the output signal of either output terminal Q or Q of the flip-flop 13 becomes "P1". For example, when the output signal of the output terminal Q is "1" , the switching element 5 is turned off, but the switching element 4 continues to be on, the energy stored in the inductance 3 is supplied to the primary winding 2a of the transformer 2, and a voltage is induced in the secondary winding 2c. Also flip flop 13
When the output signal at the output terminal Q of is 1'', the switching element 4 is turned off, but the switching element 5 continues to be on, and the energy stored in the inductance 3 is supplied to the reset winding 2b of the transformer 2. A voltage is induced in the secondary winding 2c.

Further, the output voltage of the rectifying and smoothing circuit 7 is compared with a set voltage in the output voltage detecting circuit 8, and the error signal is added to the multiplier 9, where it is multiplied by the rectified output voltage of the rectifying circuit 1, and the multiplied output signal is The detection output signal of the current detector 6 is applied to the error amplifier 10, and the output signal of the sawtooth wave generator 1 is applied to the comparator 12.
1, so when the output voltage of the rectifying and smoothing circuit 7 rises above the set voltage, the error signal increases, the multiplier output signal of the multiplier 90 also increases, and the output signal of the error amplifier 10 also increases. Become. Therefore, the period of "1" output from the comparator 12 is shortened, and the period of "1" output from the comparator 12 is shortened. Since the period during which the second switching elements 4 and 5 are simultaneously turned on becomes shorter and the energy stored in the inductance 3 also becomes smaller, the output voltage of the rectifying and smoothing circuit 7 becomes the set voltage.

Also, if the output voltage falls below the set voltage, the situation is opposite to the above case, and the first. The period during which the second switching element 45 is simultaneously turned on becomes longer, the energy stored in the inductance 3 also becomes larger, and the output voltage becomes the set voltage.

Therefore, a pulsed current is supplied by switching by releasing the energy stored in the inductance 3,
Since a current corresponding to the AC waveform can be passed through the inductance 3, the power factor can be improved. Also the first
．． By controlling the on-periods of the second switching elements 4 and 50, the output voltage can be stabilized.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a circuit diagram of an embodiment of the present invention, where 2] is a rectifier circuit consisting of diodes 1'Dl to D4, and 22 is a primary winding 2.
2a, a transformer consisting of a reset winding 22b and a secondary winding 22c, 23 an inductance, 24.25 a first . 26 is a current detector consisting of a resistor, etc.; 27 is a diode D5. 28 is an error amplifier 39, a comparator 40.
Photocoupler 41. An output voltage detection circuit consisting of an i quasi-voltage 42, etc., 29 a multiplier, 30 an error amplifier, 31 a sawtooth wave generator, 32 a comparator, 33 a flip-flop, 3
4.35 is an OR circuit, 36 is an AC power supply, 37.38 is an inductance and a capacitor that constitute an input filter,
R1 and R2 are resistors.

C2 is a capacitor.

The AC voltage from the AC power supply 36 is applied to the rectifier circuit 21 via the input filter, where it is rectified, and then connected via the inductance 23 to the primary winding 22a of the transformer 22 and the reset winding 22.
b, and the secondary winding 22 of the transformer 22
The voltage induced in c is rectified and smoothed by the rectifying and smoothing port 127, and the DC voltage Vd is supplied to the DC load. This DC voltage Vd is stabilized by controlling the on period of the field effect transistor 24. Such operation is similar to the conventional example.

In the present invention, as described above, the power factor correction circuit and the output stabilization circuit are integrated, and the output voltage detection circuit 28 generates an error signal indicating the difference between the DC voltage Vd and the reference voltage 42. The difference signal between the multiplied output signal and the detection output signal of the current detector 26 is applied to the comparator 32, and the sawtooth wave signal of the sawtooth wave generator 31 is When the difference signal level from the comparator 32 is higher than the sawtooth wave signal level, a signal of "1°" is output. It corresponds to the magnitude of the signal, the rectified output voltage waveform, and the magnitude of the rectified output current.

Further, the sawtooth wave signal is differentiated by a differentiating circuit including a capacitor C2 and a resistor R1°R2, and the differentiated output signal is applied to the clock terminal CK of the flip-flop 33, so that the output terminals Q and 11+ of the flip-flop 33 are
ZIIQ" is inverted according to the period of the sawtooth wave signal. Note that the clock signal applied to the clock terminal CK of the flip-flop 33 only needs to be synchronized with the falling edge of the sawtooth wave signal. It is also possible to form it by means.

Also, from the OR circuit 34 to the output terminal Q of the flip-flop 33
The output signal of the output terminal Q of the flip-flop 33 and the comparison output signal of the comparator 32 are applied from the OR circuit 135 to the gate of the field effect transistor 25, and the comparison output signal of the comparator 32 is applied to the gate of the field effect transistor 25. applied to the gate of transistor 24. Therefore, the comparison output signal of the comparator 32 of °°1" causes the field effect transistor 24.25
are simultaneously turned on, current I flows through the primary winding 22a of the transformer 22, and current I2 flows through the reset winding 22b. In this case, the current I,,1. Since the magnetic fluxes due to the above directions cancel each other out, no voltage is induced in the secondary winding. And the inductance 23 has I+ +Iz
-IL current flows and energy is stored.

Next, the comparison output signal of the comparator 32 becomes °"OI+, and the output signal of the output terminal Q of the flip-flop 33 becomes °'
o'', when the output signal at the output terminal Q is 111 I+, the field effect transistor 24 continues to be on, the field effect transistor 25 is turned off, and the energy stored in the inductance 23 is supplied to the primary winding 22a of the transformer 22. , a voltage is induced in the secondary winding 22c.

Next, the comparison output signal of the comparator 32 becomes "1" and the electron effect transistors 24 and 25 are turned on at the same time. Next, when the comparison output signal of the comparator 32 becomes "0°", the flip-flop 33 performs an inversion operation. Therefore, the output terminal Q of the flip-flop 33 becomes "1", the output terminal Q becomes "'0", and the field effect transistor 24 turns off, but the field effect transistor 25 continues to turn on, and the inductance 2
The stored energy of 3 is supplied to the reset winding 22b, a voltage is induced in the secondary winding 22c, and a voltage is induced in the secondary winding 22c.

By repeating the above-mentioned operation, the DC voltage Vd is stabilized, and the rectified output current can be changed in accordance with the AC waveform by storing and discharging energy by the inductance 23. Therefore, the AC power supply 36 It is possible to improve the power factor seen from

FIG. 3 is an explanatory diagram of the operation of the embodiment of the present invention, in which (a) shows the sawtooth wave signal a1 and the output signal a2 of the error amplifier 30, and (b) shows a clock synchronized with the sawtooth wave signal a1. (C) and (d) are the output terminals Q and Q of the flip-flop 33, and (e) is the comparison output signal of the comparator 32.
is the output signal of the OR circuit 35, (9) is the output signal of the OR circuit 34, (5) is the current flowing through the field effect transistor 24, , (i) is the output signal of the field effect transistor 25
A current 1.0 flowing through the clock signal shown in example 7(b) is the sawtooth signal a of the sawtooth generator 31,
It is also possible to obtain it by differentiating it using a differentiating circuit as shown in Fig. 2.1, With this clock signal, the output signal of the output terminals Q and Q of the flip-flop 33 is expressed as (C).
, as shown in (d), is inverted in synchronization with the sawtooth signal. The output signal of the comparator 32 is "1" when the level of the output signal a of the error amplifier 30 is higher than the level of the sawtooth signal a1, and during this "1" period, the field effect Transistors 24 and 25 are turned on at the same time and energy is stored in inductance 23.

When the output signal of the comparator 32 becomes 0, one of the output terminals Q and Q of the flip-flop 33 becomes 0.
, the other is 1'', and for example, when the output signal of the output terminal Q is ``1'', the field effect transistor 240 continues to be on, and as described above, the inductance 23
is supplied to the primary winding 22a of the transformer 22, and the secondary SI! A voltage is induced at 22c. Further, when the output signal of the output terminal Q of the flip-flop 33 is "1", the field effect transistor 25 continues to be in the on state,
The stored energy of the inductance 23 is reset by the winding 22
b, and a voltage is induced in the secondary winding 22c.

Therefore, the comparison output signal of the comparator 32 shown in (e) is “1”.
Energy is stored in the inductance 23 during period t + of ``, and the stored energy is released during periods 1 and 2 of 0''. In addition, the current IL flowing through the inductance 23
(-II +12) has a waveform shown by the dotted line in OJ, and the reset winding 22b can be effectively used to improve the power factor and stabilize the output.

The present invention is not limited to the above-described embodiments, and various additions and changes can be made. For example, the OR circuits 34, 35, etc. can be replaced with logic circuits corresponding to the configuration of the switching elements. It is possible.

[Effects of the Invention] As explained above, the present invention integrates the conventional power factor correction circuit and output stabilization circuit, thereby making it possible to reduce the circuit scale and reduce costs. can.

Also, number 1. The second switching element 4.5 is turned on at the same time to flow current through the primary winding 2a and reset winding 2b of the transformer 2 at the same time, and when no power is transmitted to the secondary winding 2C, energy is transferred to the inductance 3. By turning on the first switching element 4, the stored energy is transferred to the primary winding 2a of the transformer 2 and the second
By turning on the switching element 5, power is supplied to the reset winding 2b of the transformer 2 and transmitted to the secondary winding 2c, and the current flowing through the inductance 3 is controlled according to the AC waveform. This makes it possible to improve the power factor.

Also, number 1. By controlling the on period of the second switching element 4.5, the output voltage of the rectifying and smoothing circuit 7 can be stabilized.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the present invention, FIG. 2 is a circuit diagram of an embodiment of the present invention, FIG. 3 is a diagram explaining the operation of an embodiment of the present invention, and FIG.
The figure is a circuit diagram of a conventional example, and FIG. 5 is an explanatory diagram of the operation of the conventional example. 1 is a rectifier circuit, 2 is a transformer, 3 is an inductance, 4 is
, 5 is the first. 2nd switching element, 6 is a current detector, 7 is a rectifier smoothing circuit, 8 is an output voltage detection circuit, 9 is a multiplier, 10 is an error amplifier, 11 is a sawtooth wave generator, 12 is a comparator, 13 is Fri-knob-flo-knob, 14.15 is an OR circuit. Patent applicant: Fujitsu Denso Co., Ltd. Representative patent attorney: Shoji Aitani

Claims (1)

[Claims] Applying a rectified output voltage of a rectifier circuit (1) that rectifies the AC voltage of an AC power source to a connection point between the primary winding and the reset winding of a transformer (2) via an inductance (3), A first switching element (4) that switches the current flowing through the primary winding of the transformer (2) and a second switching element (5) that switches the current flowing through the reset winding; and the rectifier circuit (1). A current detector (
6), a rectifying and smoothing circuit (7) that rectifies and smoothes the voltage induced in the secondary winding of the transformer (2), and the rectifying and smoothing circuit (7);
an output voltage detection circuit (8) that compares the rectified output voltage of 7) with a set voltage and outputs an error signal;
a multiplier (9) that performs multiplication with the rectified output voltage of 1); and a multiplier output signal of the multiplier (9) and the current detector (6).
an error amplifier (10) that outputs the difference between the detection output signal of the error amplifier (10) and the sawtooth wave generator (1);
A comparator (12) that compares the sawtooth wave signal with the sawtooth wave signal of 1), a flip-flop (13) that performs an inversion operation in synchronization with the sawtooth wave signal, and positive and negative output terminals of the flip-flop (13). The logical sum output signal of the output signal and the comparison output signal of the comparator (12) causes the first and second switching elements (4
, 5) and an OR circuit (14, 15).