JPH07312862A - Switching regulator - Google Patents

Abstract

PURPOSE:To cope with, for example, AC 100V input and AC 200V input by a smoothing filter consisting of a choke coil and a capacitor. CONSTITUTION:When a transistor Q1 is turned on at positive and negative half cycles of AC signal while a selection switch SW1 is short-circuited, energy is accumulated at choke coils L11 and L21 which are electrically connected. At the same time, voltage charged to capacitors is discharged and flows via the transistor Q2 and then energy is accumulated in a primary winding L1 of a high-frequency transformer T. When the transistor Q1 is turned off at positive and negative half cycles, current flows from the choke coils L11 and 522 to capacitors C21 and C22 and energy of the choke coils L11 and L12 move to the capacitors C21 and C22, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching regulator that smoothes a rectified voltage by a filter circuit composed of a choke coil and a capacitor.
The present invention relates to a switching regulator compatible with a V input and an AC200V input.

[0002]

2. Description of the Related Art In recent power supply circuits, a circuit for smoothing a rectified voltage by a filter circuit composed of a choke coil and a capacitor is used instead of a so-called capacitor input type which directly smoothes a rectified voltage by a large-capacity electrolytic capacitor. Are known. Conventionally, as a switching regulator of this kind, which corresponds to a single AC voltage, for example, one in which the first and second switching elements are shared as shown in JP-A-2-21358, and a 92 'switching power supply symposium Material (February 24, 1990-) S7-
3-1 to S7-3-11, a method of superposing a high frequency dither signal on a control signal of a non-linear circuit is known as shown in "Improving input current waveform of switching power supply by dither rectifier circuit".

[0003]

By the way, for example, AC
To support 100V input and 200V AC input,
A method of doubling voltage rectification when AC100V is input and full-wave rectification when AC200V is input can be considered. However, in each switching regulator configured to support an AC100V input and an AC200V input by using a smoothing filter circuit composed of a choke coil and a capacitor, the parameters of the circuit elements used are completely different. Voltage rectified, A
There is a problem in that even if switching is made so as to perform full-wave rectification at the time of C200V input, it cannot be dealt with at the time of AC100V input and AC200V input.

In view of the above-mentioned conventional problems, it is an object of the present invention to provide a switching regulator which can handle AC100V input and AC200V input by using a smoothing filter circuit including a choke coil and a capacitor.

[0005]

In order to achieve the above object, the present invention provides a first filter for smoothing a half-wave rectified DC voltage by a first choke coil and a first capacitor, and a half wave. A second filter for smoothing the rectified DC voltage by a second choke coil and a second capacitor magnetically coupled to the first choke coil, and an AC voltage for double voltage rectification. The positive side and the negative side take out each half-wave rectified direct current voltage and apply it to the first filter during the positive side period of the alternating voltage and apply it to the second filter during the negative side period of the alternating voltage. And a switching means for extracting a DC voltage obtained by full-wave rectifying the AC voltage during the wave rectification and applying the DC voltage to the first and second filters.

The present invention is also characterized in that saturable choke coils are connected in series to the first and second choke coils, respectively. The present invention is also characterized in that the cores of the saturable choke coils are integrally formed with the cores of the first and second choke coils, respectively. The present invention also further switches the voltage passing through the first filter during the positive side of the alternating voltage during double voltage rectification and the voltage passing through the second filter during the negative side of the alternating voltage. Switching elements for switching the voltage passing through the first and second filters during full-wave rectification, and first and second switching elements.
A smoothing circuit for further smoothing the voltage smoothed by the filter, and turning on the switching element so that the voltage smoothed by the smoothing circuit becomes a predetermined DC voltage,
And a chopper control circuit for controlling OFF.

[0007]

In the present invention, each of the first and second filters,
Since the second choke coil is magnetically coupled to each other, the half-wave rectified direct current voltage is smoothed by both the first and second filters during the positive side and the negative side of the alternating voltage. Voltage doubler rectification, and thus AC
It can support 100V input. Further, during full-wave rectification, the DC voltage obtained by full-wave rectifying the AC voltage passes through the first and second filters and is smoothed.
It can support 200V input. Therefore, by using a smoothing filter circuit composed of a choke coil and a capacitor, for example, AC100V input and AC200V input can be supported.

Further, in the present invention, since the saturable choke coils are connected in series to the first and second choke coils respectively, the timing of the voltage applied to the first and second choke coils depends on the saturable choke coil. Slowed by the coil. Therefore, when the switching pulse width becomes narrow when the load is light, the charging voltage of the first and second capacitors drops first, so that the smoothing circuit in the subsequent stage can operate stably. As the second capacitor, it is possible to use a small capacitor having a low breakdown voltage.

Further, according to the present invention, since the cores of the saturable choke coils are integrally formed with the cores of the first and second choke coils, respectively, the size can be reduced. Further, in the present invention, since the voltage smoothed by the first and second filters and the circuit at the subsequent stage for further smoothing this voltage are controlled by one switching element, for example, an AC100V input and an AC200V input can be realized by a small circuit. Can correspond to.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of a switching regulator according to the present invention. In FIG. 1, the changeover switch SW1 is at the time of inputting AC100V (at the time of voltage doubler rectification)
Is set to a short-circuit state, and, on the other hand, when AC200V is input (at the time of full-wave rectification), an open state is set. AC
A diode bridge 2 is connected to a commercial AC power source 1 of 100 V or 200 V AC, and in the diode bridge 2, the full-wave rectified DC signal is output from the output side 21 to the first power conversion unit 3 and returns to the input side 22.

An AC signal that is not rectified by the diode bridge 2 is output from the output side 21 to the first power conversion unit 3 in the positive half cycle section, and the AC power is supplied via the changeover switch SW1 and the connection point 23. Return to side 1. On the other hand, in the half-cycle section on the negative side, the AC power source 1 returns to the input side 22 to the first power conversion unit 3 via the connection point 23 and the changeover switch SW1. Therefore, the diode bridge 2 and the changeover switch SW1 are configured to half-wave rectify the AC signal in the positive side section and the negative side section.

The first power converter 3 includes a diode D11,
D12, a MOS transistor Q1 which is a switching element, choke coils L11 and L12, saturable choke coils L21 and L22, a smoothing capacitor C21,
C22 and flywheel diodes D21 and D22
And resistors R1 and R2 and capacitors C31 and C32.

Choke coil L11 and smoothing capacitor C21, choke coil L12 and smoothing capacitor C2
Reference numeral 2 denotes a positive filter (L11, C2) that chops and smoothes each half-wave rectified voltage on the positive side and the negative side of the AC voltage by turning on and off the transistor Q1.
1), a negative filter (L12, C22) is configured, and
The choke coils L11 and L12 are magnetically coupled to each other. In addition, the lower 2 in the first power conversion unit 3
In the digit reference numbers, the reference symbol of the positive circuit component shown above the transistor Q1 ends with "1", and the reference of the negative circuit component shown below the transistor Q1. "2" is added to the end of the symbol.

A second power conversion unit 4 is connected to a stage subsequent to the first power conversion unit 3, and the second power conversion unit 4 includes the transistor Q1, capacitors C21 and C22, a diode D3, and a high frequency transformer. T (primary winding L1 and secondary winding L2 in the figure), a rectifying diode D4 and a smoothing capacitor C4. Therefore, the transistor Q1 and the capacitors C21 and C22 are shared by the first and second power conversion units 3 and 4. A load RL is connected to both ends of the smoothing capacitor C4, and a DC voltage is detected by the chopper control unit 5 from the connection point between the diode D4 and the smoothing capacitor C4. The transistor Q1 is pulsed so that this DC voltage becomes a predetermined value. Width control (PW
M).

The above configuration will be described in detail. The output side 21 and the input side 22 of the diode bridge 2 are respectively one ends of capacitors C11 and C21 for noise absorption (not smoothing capacitors) and a saturable choke coil L21,
It is connected to each one end of L22, the cathode of diode D21 and the anode of diode D22, and one end of each of resistors R1 and R2. On the other hand, the connection point 23 is connected to the other ends of the capacitors C11 and C21, the anode of the diode D11, and the cathode of the diode D12 via the changeover switch SW1.

The other ends of the saturable choke coils L21 and L22 are connected to the one ends of the choke coils L11 and L12, respectively, and the transistor Q1 is connected between the other ends of the choke coils L11 and L12. The other ends of the choke coils L11 and L12 are also connected to the cathode of the diode D11 and the anode of the diode D12, respectively, and one ends of the smoothing capacitors C21 and C22. The other ends of the smoothing capacitors C21 and C22 are connected to the anode of the diode D21 and the cathode of the diode D22, respectively, and the resistors R1 and R2 and the capacitor C3 are respectively connected to both ends of the diodes D21 and D22.
A series circuit of C1 and C32 is connected.

The other end of the smoothing capacitor C21 is also connected to the cathode of the diode D3, and the primary winding L1 of the high frequency transformer T is connected between the anode of the diode D3 and the other end of the smoothing capacitor C22. A smoothing capacitor C4 is connected in parallel to both ends of the secondary winding L2 of the high frequency transformer T via a rectifying diode D4. Next, the operation of the above embodiment will be described. First, with reference to FIG. 2, the operation when AC100V is input (the changeover switch SW1 is in a short state) will be described. When the transistor Q1 is turned on in the positive half cycle, the current i1 from the commercial power source 1 flows from the output side 21 of the diode bridge 2 to the saturable choke coil L21 → choke coil L11 → transistor Q1 as shown in FIG. 2 (a). → Diode D
21 → changeover switch SW1 → flows to the connection point side 23.

In this case, a rising current i1 as shown in FIG. 3C flows and the voltage Vin1 is applied to the saturable choke coil L21 and the choke coil L11.
Energy is accumulated in the choke coil L11,
Energy is also accumulated in the choke coil L21 which is magnetically coupled to the choke coil L11. At the same time, the voltage charged in the smoothing capacitors C21 and C22 is discharged, and a rising discharge current i3 as shown in FIG. 3 (f) flows through the transistor Q1 to the primary winding L1 of the high frequency transformer T. Energy is stored. Further, the rectifying diode D4 of the second power converter 4 is turned off,
Further, the charging voltage of the smoothing capacitor D4 is discharged and supplied to the load RL.

Next, when the transistor Q1 is turned off in the positive half cycle, as shown in FIG. 2B, the choke coils L11 and L12 are respectively fed into FIG. 3D.
Falling currents i2 and i2 ′ as shown in (e) flow into the smoothing capacitors C21 and C22, and the choke coil L
The energy of 11 and L12 is the smoothing capacitor C2, respectively.
1, move to C22. At the same time, one of the high frequency transformer T
The secondary winding L is generated by the energy stored in the secondary winding L1.
The falling current i4 as shown in FIG. 3 (g) from 2 flows through the rectifying diode D4 and the smoothing capacitor C4
Is charged, and the charging voltage of the smoothing capacitor D4 is further supplied to the load RL.

Next, when the transistor Q1 is turned on in the negative cycle, the current i1 from the commercial power source 1 is connected to the connection point 23 → changeover switch SW1 → diode D11 → transistor Q1 → choke coil as shown in FIG. 2 (c). L12 → saturable choke coil L22 → flows to the input side 22 of the diode bridge 2, and similarly, energy is stored in the magnetically coupled choke coils L11 and L12. At the same time, the smoothing capacitor C21,
The voltage charged in C22 is discharged, and the discharge current i3
Flows through the transistor Q1 and energy is stored in the primary winding L1 of the high frequency transformer T. Further, the rectifying diode D4 of the second power conversion unit 4 is turned off, and
The charging voltage of the smoothing capacitor D4 is discharged and supplied to the load RL.

Next, when the transistor Q1 is turned off in the negative cycle, as in the case of the positive half cycle, as shown in FIG. 2B, the choke coil L1 is turned on.
The falling currents i2 and i2 ′ from the L1 and L21 as shown in FIGS.
1 and C22, and the energies of the choke coils L11 and L12 are transferred to the smoothing capacitors C21 and C22, respectively. Further, at the same time, the energy accumulated in the primary winding L1 of the high frequency transformer T causes the secondary winding L2 to move to the state shown in FIG.
A falling current i4 as shown in (g) flows through the rectifier diode D4 to charge the smoothing capacitor C4, and the charging voltage of the smoothing capacitor D4 is supplied to the load RL.

In this case, the output voltage supplied to the load RL is detected by the chopper control unit 5 so as to be constant,
As shown in FIG. 3B, the pulse width Ton that turns on the transistor Q1 is controlled. That is, the input voltage Vin1
, Vin2 increases, choke coil L1
The charging voltages Vc1 and Vc2 of the smoothing capacitors C21 and C22 increase with the increase of the current i1 flowing in 1 and L12. As a result, the current i3 increases and the output voltage supplied to the load RL increases, and the chopper control unit 5 performs control to stabilize the output voltage by narrowing the pulse width Ton according to this increase.

On the other hand, when the input voltages Vin1 and Vin2 decrease, the smoothing capacitor C2 increases as the current i1 flowing through the choke coils L11 and L12 decreases.
1, the charging voltages Vc1 and Vc2 of C22 decrease. As a result, the current i3 decreases and the output voltage decreases, and the chopper control unit 5 performs control to stabilize the output voltage by widening the pulse width Ton according to this decrease.

Next, the operation when AC200V is input (changeover switch SW1 is open) will be described. When the transistor Q1 is turned on, a full-wave rectified signal is sent from the output side 21 of the diode bridge 2 to the saturable choke coil L21 → choke coil L11 → transistor Q1 → choke coil L12 → saturable choke coil L22 → diode as shown in FIG. It flows to the input side 22 of the bridge 2.

Therefore, the choke coils L11 and L2
1 accumulates energy, and at the same time, the voltage charged in the smoothing capacitors C21 and C22 is discharged.
A rising discharge current i3 as shown in (f) flows through the transistor Q1 and energy is accumulated in the primary winding L1 of the high frequency transformer T. Further, the rectifying diode D4 of the second power converter 4 is turned off, and the charging voltage of the smoothing capacitor D4 is discharged and supplied to the load RL.

Next, when the transistor Q1 is turned off, as shown in FIG. 2B, the choke coils L11 and L12 are respectively fed from the choke coils L11 and L12 as shown in FIG.
Falling currents i2 and i2 ′ as shown in (e) flow into the smoothing capacitors C21 and C22, and the choke coil L
The energy of 11 and L12 is the smoothing capacitor C2, respectively.
1, move to C22. At the same time, one of the high frequency transformer T
The secondary winding L is generated by the energy stored in the secondary winding L1.
The falling current i4 as shown in FIG. 3 (g) from 2 flows into the smoothing capacitor C4 to charge the smoothing capacitor C4, and the charging voltage of the smoothing capacitor D4 is changed to the load RL.
Is supplied to. Also, in the case of this AC200V input, as in the case of AC100V input, the chopper control unit 5 detects the current supplied to the load RL to be constant and controls the pulse width Ton for turning on the transistor Q1. It

Therefore, according to the above embodiment, since the choke coils L11 and L12 are magnetically coupled,
Energy can be accumulated in both the choke coils L11 and L12 in the positive side section and the negative side section of the AC signal to perform voltage doubler rectification.
AC100V input and AC200V input can be supported by using a positive and negative smoothing filter circuit composed of 11, L12 and smoothing capacitors C21, C22.

Here, when the pulse width Ton for turning on the transistor Q1 at a light load becomes narrow, the second power is generated due to a slight difference between the pulse width applied to the transformer T and the pulses applied to the choke coils L11 and L12. The operation of the conversion unit 4 is stopped, and as a result, the primary smoothing capacitor C21,
The charging voltage of C22 will rise. Therefore, the saturable choke coils L21 and L22 are provided, and the choke coil L
By delaying the voltage applied to 11 and L12 for a certain period of time, a difference is generated between the pulse width applied to the transformer T and the pulse width applied to the choke coils L11 and L12, and the primary smoothing capacitor C21 is used when the load is light. , C22, the second power converter 4 can be operated in a stable manner by lowering the charging voltage of the capacitors C21,
The breakdown voltage of C22 can be lowered.

In the example shown in FIG. 1, saturable choke coils L21 and L22 and choke coils L11 and L12.
However, as shown in FIG. 5B, the cores 7 of the partially saturable choke coils L21 and L22 are incorporated in the cores 6 of the choke coils L11 and L12 so that one core is integrated. May be. Next, a second embodiment will be described with reference to FIG. In FIG. 6, in the circuit configuration shown in FIG. 1, a high-frequency transformer T ′ is composed of a positive primary winding L31, a negative primary winding L32, and a secondary winding L2. A diode D5 and a choke coil L3 are added to the power conversion unit 4. Of course, the choke coils L11, L12 are likewise magnetically coupled to each other.

In such a configuration, when AC100V is input (switch SW1 is on), when the transistor Q1 is turned on in the positive half cycle, the current from the output side 21 of the diode bridge 2 is changed to the choke coil L11. → saturable choke coil L21 → diode D21 → transistor Q1 → diode D12 → switch SW1 → flow to connection point side 23, and capacitor C
A current also flows through 21 → primary winding L31 → transistor Q1 and capacitor C22 → transistor Q1 → primary winding L32.

In this case, the choke coils L11 and L12
Energy is stored in the smoothing capacitor C2
1, the voltage charged in C22 is discharged and the voltage is applied to the primary windings L31, L32 of the high frequency transformer T ',
As a result, a current flows through the secondary winding L2, and this voltage becomes the second
Is smoothed by the power conversion unit 4. Next, when the transistor Q1 is turned off in the positive half cycle, current flows from the choke coils L11 and L12 to the diode D5.
Capacitor C2 via 1, D12, D11, D52
1 and C22, the energy of the choke coils L11 and L12 is transferred to the capacitors C21 and C22.

Next, when the transistor Q1 is turned on in the negative half cycle, the current from the commercial power supply 1 is supplied to the connection point 23 → the changeover switch SW1 → the diode D1.
1 → transistor Q1 → diode D22 → saturable choke coil L22 → choke coil L12 → input side 22 of the diode bridge 2, and similarly, energy is stored in the magnetically coupled choke coils L11 and L12. Also in this case, a current flows through the secondary winding L2 by the same operation as the positive half cycle, and this voltage is smoothed by the second power conversion unit 4.

Next, when the transistor Q1 is turned off in the negative cycle, the current from the choke coils L11 and L12 is supplied to the diode D as in the positive half cycle.
Capacitor C2 via 51, D12, D11, D52
1 and C22, the energy of the choke coils L11 and L12 is transferred to the capacitors C21 and C22. AC200
When the transistor Q1 is turned on at the time of V input (switch SW1 is off), the full-wave rectified signal is output from the output side 21 of the diode bridge 2 to the choke coil L11 → saturable choke coil L21 → diode D21 → transistor Q1 → diode D22. → Saturable choke coil L2
2 → choke coil L12 → flows to the input side 22 of the diode bridge 2, and the capacitors C21 and C22 are discharged through the transistor Q1 in the primary windings L31 and L32. Next, when the transistor Q1 is turned off, the energy of the choke coils L11 and L12 is transferred to the diode D5.
1 and D52 to charge the capacitors C21 and C22.

A saturable choke coil is not used in the third embodiment shown in FIG. In the case of AC100V input (switch SW1 is on), when the transistor Q1 is turned on during the positive half cycle, the current from the output side 21 of the diode bridge 2 is changed to the choke coil L.
11 → primary winding L31 → transistor Q1 → diode D82 → diode D62 → switch SW1 → connection point side 23.

In this case, the choke coils L11 and L12
Energy is stored in the capacitors C21 and C2
The voltage of 2 is the primary winding L31, L3 of the high frequency transformer T '.
2 and a current flows through the secondary winding L2. Then
When the transistor Q1 turns off, the choke coil L1
1, the current from L12 is smoothing capacitor C21, C22
Energy of the choke coils L11 and L12 is transferred to the smoothing capacitors C21 and C22.

Next, when the transistor Q1 is turned on in the negative half cycle, the current i from the commercial power source 1
1 flows from the connection point 23 to the changeover switch SW1 to the diode D61 to the diode D81 to the transistor Q1 to the primary winding L32 to the choke coil L12 to the input side 22 of the diode bridge 2, and similarly to the magnetically coupled choke. Energy is stored in the coils L11 and L12. In this case, the primary winding L31 of the high frequency transformer T ',
L32 has a transistor C1 through a capacitor C21,
By applying the voltage of C22, a current flows through the secondary winding L2.

Next, when the transistor Q1 is turned off in the negative cycle, the currents from the choke coils L11 and L12 flow into the smoothing capacitors C21 and C22, and the energy of the choke coils L11 and L12 is transferred to the capacitor C2.
1, move to C22. AC200V input (switch SW
When the transistor Q1 is turned on, the full-wave rectified signal is output from the output side 21 of the diode bridge 2 to the choke coil L11 → primary winding L31 → transistor Q1 → primary winding L32 → choke coil L12 → It flows to the input side 22 of the diode bridge 2. In this case, similarly, the choke coils L11 and L1 that are magnetically coupled to each other.
Energy is stored in 2 and capacitors C21, C
22 is discharged through the primary windings L31 and L32, and when the transistor Q1 is turned off, the capacitor C2 is discharged.
1, C22 is charged.

In the fourth embodiment shown in FIG. 8, a saturable choke coil is not used, and the high frequency transformer T has a primary winding L1 and a secondary winding L2. In the case of AC 100 V input (switch SW1 is on), when the transistor Q1 is turned on in the positive half cycle, the current from the output side 21 of the diode bridge 2 is choke coil L11 → primary winding L1 → transistor Q1. → choke coil L12 → diode D72 → diode D62 →
The current flows from the switch SW1 to the connection point side 23. In this case, energy is accumulated in the choke coils L11 and L12, and the voltages of the capacitors C21 and C22 are applied to the primary winding L1 of the high frequency transformer T ′ and discharged. As a result, a current flows through the secondary winding L2.

Next, when the transistor Q1 is turned off, the currents from the choke coils L11 and L12 flow into the smoothing capacitors C21 and C22 and the choke coil L1.
Energy of 1, L12 is smoothing capacitors C21, C22
Move on to. Next, when the transistor Q1 is turned on in the negative half cycle, the current from the commercial power source 1 causes a current to flow from the connection point 23 → changeover switch SW1 → diode D61 →
Diode D71 → choke coil L12 → primary winding L
1 → transistor Q1 → choke coil L12 → flows to the input side 22 of the diode bridge 2, and similarly, energy is stored in the magnetically coupled choke coils L11 and L12. In this case, the capacitors C21 and C22 are discharged by the same operation as the positive half cycle, and a current flows through the secondary winding L2.

Next, when the transistor Q1 is turned off in the negative cycle, the currents from the choke coils L11 and L12 flow into the smoothing capacitors C21 and C22, and the energy of the choke coils L11 and L12 is transferred to the smoothing capacitors C21 and C22. When AC200V is input (switch SW1 is off), when the transistor Q1 is turned on, the full-wave rectified signal is output to the output side 2 of the diode bridge 2.
A current flows from 1 to the choke coil L11 → primary winding L1 → transistor Q1 → choke coil L12 →→ the input side 22 of the diode bridge 2, and the choke coils L11 and L12 magnetically coupled to the primary winding L1. Energy is stored in. In this case, the smoothing capacitors C21 and C22 discharge through the primary winding L1 by the same operation as when AC100V is input, and a current flows through the secondary winding L2. Then, when the transistor Q1 is turned off, the capacitors C21 and C2 are
2 is charged by the primary windings L1 and L2.

[0041]

As described above, according to the present invention, since the first and second choke coils of the first and second filters are magnetically coupled to each other, the positive and negative sides of the AC voltage are negative. The DC voltage that has been half-wave rectified in the side period is the first and second DC voltages.
Are smoothed by both filters, and thus can accommodate, for example, a 100 VAC input. Also, during full-wave rectification, the DC voltage obtained by full-wave rectifying the AC voltage is the first
And, since it passes through the second filter and is smoothed, for example, AC200V input can be supported. Therefore, by using a smoothing filter circuit including a choke coil and a capacitor, for example, AC100V input and AC200V
Can respond to input.

Further, in the present invention, since the saturable choke coils are connected in series to the first and second choke coils, respectively, the timing of the voltage applied to the first and second choke coils is the saturable choke. The coil slows down, and therefore, when the switching pulse width becomes narrow at a light load, the charging voltage of the first and second capacitors decreases first, so that the smoothing circuit in the subsequent stage can operate stably. Also, as the first and second capacitors, it is possible to use small capacitors having a low breakdown voltage.

The present invention can also be miniaturized because the cores of the saturable choke coils are formed integrally with the cores of the first and second choke coils, respectively. The present invention also controls the voltage smoothed by the first and second filters and the subsequent circuit for smoothing this voltage by a single switching element, so that a small circuit, for example, AC100V input and AC200V input. Can correspond to.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a switching regulator according to the present invention.

FIG. 2 is an explanatory diagram showing an operation during voltage doubler rectification in the switching regulator of FIG.

FIG. 3 is a timing chart showing main currents at the time of voltage doubler rectification in FIG.

FIG. 4 is an explanatory diagram showing an operation during full-wave rectification in the switching regulator of FIG.

FIG. 5 is a configuration diagram showing the choke coil and the saturable choke coil of FIG.

FIG. 6 is a circuit diagram showing a switching regulator according to a second embodiment.

FIG. 7 is a circuit diagram showing a switching regulator according to a third embodiment.

FIG. 8 is a circuit diagram showing a switching regulator of a fourth embodiment.

[Explanation of symbols]

1: AC power supply 2: Diode bridge 3: First power conversion unit 4: Second power conversion unit 5: Chopper control unit 6, 7: Core 21: Output side 22: Input side 23: Connection point SW1: Changeover switch Q1: Transistor L11, L12, L3: Choke coil L21, L22: Saturable choke coil T, T ': Transformer L1, L31, L32: Primary winding L2: Secondary winding C11, C21, C21, C22, C31 , C32, C
4: Capacitors D11, D12, D21, D22, D3, D4, D5
D51, D52, D61, D62, D71, D72: Diode R1, R2: Resistor RL: Load

Claims (4)

[Claims] 1. A first filter for smoothing a half-wave rectified DC voltage with a first choke coil and a first capacitor; and a half-wave rectified DC voltage for the first choke coil. The second choke coil and the second capacitor, which are magnetically coupled to each other, smooth the second filter, and the positive and negative sides of the AC voltage are half-wave rectified at the time of double voltage rectification. A DC voltage obtained by taking out and applying to the first filter during the positive side of the AC voltage and to the second filter during the negative side of the AC voltage, the AC voltage being full-wave rectified during full-wave rectification. A switching regulator having a switching means for taking out and applying it to the first and second filters. 2. The switching regulator according to claim 1, wherein saturable choke coils are connected in series to the first and second choke coils, respectively. 3. A switching regulator according to claim 2, wherein the cores of the saturable choke coils are integrally formed with the cores of the first and second choke coils, respectively. . 4. The switching regulator according to any one of claims 1 to 3, further comprising: a first side in a period on a positive side of an AC voltage during double voltage rectification.
Switching the voltage passing through the filter, switching the voltage passing through the second filter during the period of the negative side of the AC voltage, and switching the voltage passing through the first and second filters during full-wave rectification. One switching element, a smoothing circuit that further smoothes the voltage smoothed by the first and second filters, and the smoothing circuit so that the voltage smoothed by the smoothing circuit becomes a predetermined DC voltage. A switching regulator having a chopper control circuit for controlling on / off of a switching element.