JPH05304777A - Multiple-output switching power supply device - Google Patents

Abstract

PURPOSE:To provide a multiple-output switching power supply device which can improve the setting value of a quasi-stabilization voltage by solving a problem where the setting value of the quasi-stabilization voltage is limited due to restriction conditions in that the number of turns of a transformer is an integer and then slightly modifying a conventional configuration. CONSTITUTION:The title device consists of a switching means 2 which is connected to a primary coil winding 31 of a transformer 3, a choke input type rectification smoothing circuit which is connected to each output coil winding of the transformer 3, and a control circuit 9 which controls the ON/OFF ratio of the switching means 2 for stabilizing one of the output DC voltages and then a fly wheel diode 11 is connected in series with the other output DC voltage, thus improving the setting value of a quasi-stabilization voltage E2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-output switching power supply device for supplying a stable DC voltage to various consumer and industrial electronic devices.

[0002]

2. Description of the Related Art In recent years, switching power supply devices have been required to supply a plurality of stable and stable output DC voltages with high efficiency as electronic devices become smaller and more diversified.

A conventional multi-output switching power supply device will be described below. FIG. 3 shows a circuit configuration of a conventional multi-output switching power supply device. In FIG. 3, 1
Is an input DC current source, and its voltage is Ei. 2 is a switching means, 3 is a transformer, and the primary winding 31
It has output windings 32 and 33 and reset winding 34.
The switching means 2 is connected to the primary winding 31, converts the input DC voltage Ei into a high frequency AC voltage, and inputs the high frequency AC voltage to the primary winding 31. 4 is a forward diode, 5 is a flywheel diode, 6 is a choke coil, 7 is a capacitor, and 8 is a load. A forward input diode 4, a flywheel diode 5, a choke coil 6 and a capacitor 7 constitute a choke input type rectifying and smoothing circuit,
The high frequency AC voltage generated in the output winding 32 is rectified and smoothed, and the output DC voltage E1 is supplied to the load 8. Reference numeral 9 denotes a control circuit, which drives the switching means 2 at a predetermined on / off ratio to stabilize the output DC voltage E1 supplied to the load 8.

Reference numeral 10 is a forward diode, 11 is a flywheel diode, 12 is a choke coil, 13 is a capacitor, and 14 is a series regulator.
1, the choke coil 12 and the capacitor 13 constitute a choke input type rectifying / smoothing circuit, and the output winding 33
The high-frequency AC voltage generated at 1 is rectified and smoothed, and the DC voltage E2 is supplied to the series regulator 14.

Reference numeral 15 is a capacitor, 16 is a load, and the DC voltage E2 is supplied to the load 16 as a stable output DC voltage E3 via the series regulator 14. A diode 17 regenerates the excitation energy of the transformer 3 to the input DC voltage source 1 via the reset winding 34.

The operation of the multi-output switching power supply device configured as described above will be described below. First, the number of turns of each winding of the transformer 3 is N for the primary winding 31.
p and output windings 32 and 33 are N1 and N2, respectively. When the switching means 2 is on, a voltage of (N1 / Np) · Ei is generated in the output winding 32, and the forward diode 4 becomes conductive. Neglecting the forward voltage drop of the diode, the choke coil 6 will have (N1 / N
p). The voltage of Ei-E1 is applied.

Next, when the switching means 2 is off,
The voltage of the choke coil 6 is inverted and the flywheel diode 5 becomes conductive. At this time, -E is applied to the choke coil 6.
A voltage of 1 is applied. When the ON period of the switching means 2 is Ton and the OFF period is Toff, when the output current to the load 8 is sufficiently large and the current flowing through the choke coil 6 is continuous, {(N1 / Np) .Ei-E1} .Ton. =
The relationship of E1 · Toff is established, and the on / off ratio D = To
If n / (Ton + Toff), then E1 = D · (N1
/ Np) · Ei is obtained, and the output DC voltage E1 is stabilized by the control circuit 9 with high accuracy against variations in the input DC voltage Ei and the load 8.

On the other hand, the DC voltage E2 is also E2 = D.
(N2 / Np) · Ei = (N2 / N1) · E1.
However, the DC voltage E2 is not precisely stabilized by the control circuit 9 like the output DC voltage E1.
Further, the series regulator 14 is used in order to obtain the desired output DC voltage E3 which is stabilized with high precision, under the constraint that the number of turns is an integer. In this case, output winding 3
The number of turns N2 of 3 is set to the minimum integer that satisfies E2> E3 in consideration of the loss of the series regulator 14.

Hereinafter, what has a feedback control system such as the control circuit 9 for stabilizing the output DC voltage E1 by the switching means 2 is called a representative stabilized output voltage.
A voltage that does not have a feedback control system and is determined by the turns ratio of the transformer, like the DC voltage E2, is called a quasi-stabilized voltage.

[0010]

However, the above-mentioned conventional configuration has a problem that the setting value of the metastabilized voltage such as the DC voltage E2 is limited due to the constraint condition that the number of turns is an integer. Switching power supplies can be downsized by increasing the switching frequency,
Therefore, the number of turns of the transformer tends to decrease, and the set value of the meta-stabilization voltage becomes more and more limited. For example, when 5V and 12V are desired as the stabilized output DC voltage, and the number of turns of the 5V output winding 32 is set to one turn and this voltage is representatively stabilized, in order to obtain the stabilized 12V, Set the number of turns of the output winding 33 to 3 turns and once set 15
Series regulator 1 with V as meta-stabilized voltage E2
It must be 12V via 4. When the load of 12V output requires 1A as the output current, the loss in the series regulator 14 becomes 3W.

Further, the output current of the representative regulated output voltage E1 in the above-mentioned conventional configuration becomes small, and the current flowing through the choke coil 6 is discontinuous (that is, the current flowing through the flywheel diode 5 during the off period Toff is 0 A). In such a case), the representative stabilized output voltage E1 tries to rise, and the ON / OFF ratio D of the switching means 2 is controlled to be small in order to stabilize it. At this time, the metastabilization voltage E2, which is determined by the on / off ratio D and the turns ratio, decreases, and there is also a problem that the condition of E2> E3 is not satisfied.

The present invention solves the above-mentioned conventional problems. The setting value of the meta-stabilization voltage E2 is improved and the representative stabilization output voltage E1 of the representative stabilization output voltage E1 is improved by slightly modifying the conventional configuration. It is an object of the present invention to provide a multi-output switching power supply device that makes the current flowing through the choke coil continuous even if the output current is small.

[0013]

In order to achieve this object, a multi-output switching power supply device of the present invention comprises a transformer having a primary winding and a plurality of output windings, and one of the transformers.
One of a switching means connected to the next winding, a choke input type rectifying / smoothing circuit connected to each output winding of the transformer, and an output DC voltage obtained from each of the choke input type rectifying / smoothing circuits. It comprises a control circuit for controlling the on / off ratio of the switching means to stabilize, and has a configuration in which at least one flywheel diode of each choke input type rectifying and smoothing circuit is connected in series with another output DC voltage. ..

[0014]

With this configuration, the DC voltage obtained from the choke input type rectifying / smoothing circuit having the flywheel diode connected in series with the other output DC voltage is such that when the other output DC voltage is E, the number of turns of the transformer is increased. The voltage of (1-D) .E is increased from the conventional meta-stabilized voltage determined by the ratio and the on / off ratio D of the switching means. By selecting an appropriate turns ratio and combining with another output DC voltage E, The meta-stabilized voltage can be brought close to the set value, which was impossible with the conventional configuration. Further, if the other output DC voltage is set to the representative stabilized output voltage, current is supplied to the improved meta-stabilized voltage via the choke coil, and the output from the representative stabilized output current is obtained. Even if the current becomes small, the current flowing through the choke coil can maintain a continuous state.

[0015]

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the first of the present invention.
2 shows a circuit configuration of a multi-output switching power supply device in the embodiment of FIG. In FIG. 1, 1 is an input DC voltage source, and its voltage is Ei. 2 is a switching means, 3 is a transformer, and a primary winding 31 and an output winding 32
33 and reset winding 34. The switching means 2 is connected to the primary winding 31, converts the input DC voltage Ei into a high frequency AC voltage, and inputs the high frequency AC voltage to the primary winding 31. 4 is a forward diode, 5 is a flywheel diode, 6 is a choke coil, 7 is a capacitor, and 8 is a load. A forward input diode 4, a flywheel diode 5, a choke coil 6 and a capacitor 7 constitute a choke input type rectifying and smoothing circuit to rectify and smooth the high frequency AC voltage generated in the output winding 32 and supply the output DC voltage E1 to the load 8. To do.

Reference numeral 9 is a control circuit, which drives the switching means 2 at a predetermined ON / OFF ratio so as to stabilize the output DC voltage E1 supplied to the load 8. 10 is a forward diode, 11 is a flywheel diode, 12 is a choke coil, 13 is a capacitor, 14 is a series regulator, and a forward diode 10, a flywheel diode 11, a choke coil 12, and a capacitor 13 choke input type rectification smoothing circuit. The high frequency AC voltage generated in the output winding 33 is rectified and smoothed to supply the DC voltage E2 to the series regulator 14.

Reference numeral 15 is a capacitor, 16 is a load, and the DC voltage E2 is supplied to the load 16 as a stable output DC voltage E3 via the series regulator 14. A diode 17 regenerates the excitation energy of the transformer 3 to the input DC voltage source via the reset winding 34.

The circuit configuration of this embodiment is the same as the circuit configuration of the conventional example shown in FIG. 3 except that the anode of the flywheel diode 11 is connected to the output DC voltage E1. The functions of the components are also the same, so the same reference numerals are given.

The operation of the multi-output switching power supply device configured as described above will be described below. First, the number of turns of each winding of the transformer 3 is N for the primary winding 31.
p and output windings 32 and 33 are N1 and N2, respectively. When the switching means 2 is on, a voltage of (N1 / Np) · Ei is generated in the output winding 32, and the forward diode 4 becomes conductive. Neglecting the forward voltage drop of the diode, the choke coil 6 will have (N1 / N
p). The voltage of Ei-E1 is applied.

Next, when the switching means 2 is off,
The voltage of the choke coil 6 is inverted and the flywheel diode 5 becomes conductive. At this time, -E is applied to the choke coil 6.
A voltage of 1 is applied. When the ON period of the switching means 2 is Ton and the OFF period is Toff, when the output current to the load 8 is sufficiently large and the current flowing through the choke coil 6 is continuous, {(N1 / Np) .Ei-E1} .Ton. =
The relationship of E1 · Toff is established, and the on / off ratio D = To
If n / (Ton + Toff), then E1 = D · (N1
/ Np) · Ei is obtained, and the output DC voltage E1 is stabilized by the control circuit 9 with high accuracy against variations in the input DC voltage Ei and the load 8.

On the other hand, during the ON period of the switching means 2, a voltage of (N2 / Np) .Ei is generated in the output winding 33, and the forward diode 10 becomes conductive. At this time, a voltage of (N2 / Np) .Ei-E2 is applied to the choke coil 12. Next, during the off period, the voltage of the choke coil 12 is inverted, and the flywheel diode 11 becomes conductive. At this time, the voltage of E1-E2 is applied to the choke coil 12. Therefore, {(N2 / Np) · Ei-E
2} · Ton = (E2-E1) · Toff, and E2 = D · (N2 / Np) · Ei + (1-D) ·
The relational expression of E1 = {(N2 / N1) + 1-D} .E1 is obtained. The series regulator 14 is used to obtain the desired stabilized output DC voltage E3, and the number of turns N2 of the output winding 33 is a minimum integer that satisfies E2> E3 in consideration of the loss of the series regulator 14. Is set in the same manner as in the case of the conventional example described in FIG.

Here, E1 = 5V and E3 = 12V, and E
In order to stabilize 1 to 5V, considering an adjustment range of D = 0.2 to 0.4, E1 = 1 turn, E2 = 2 turns (3 turns in the conventional example), and E2 = 13V ~
It becomes 14V (15V in the case of the conventional example). If the output current of 12 V is 1 A, the loss of the series regulator 14 is 1 to 2 W (3 W in the case of the conventional example), and the effect of loss reduction is obtained as compared with the case of the conventional example. Further, since the current supplied to the DC voltage E2 during the off period is obtained from the representative stabilized output E1 via the flywheel diode 11, even if the output current of the representative stabilized output E1 becomes small, the current flowing through the choke coil. Can maintain a continuous state as compared with the case of the conventional example.

Further, under the output condition that the number of turns of the output winding 33 is the same, the number is smaller than that of the conventional example, so that the reverse voltage applied to the forward diode 10 and the flywheel diode 11 can also be reduced. The effect is obtained.

As described above, according to this embodiment, the choke input type rectifying / smoothing circuit for supplying the output stabilized DC voltage E1 has the conventional configuration, and the flywheel diode of another choke input type rectifying / smoothing circuit is used. 11
Is connected in series with the representative stabilized output E1,
The set value of the metastabilized voltage E2 can be improved as compared with the case of the conventional example, and the loss of the series regulator 14 can be reduced. Further, even if the output current of the representative stabilized output E1 becomes small, the current flowing through the choke coil 6 can be maintained in a continuous state as compared with the case of the conventional example. Furthermore, since the number of turns of the output winding 33 is reduced, the reverse voltage applied to the forward diode 10 and the flywheel diode 11 can also be reduced.

(Embodiment 2) A second embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows a circuit configuration of a multi-output switching power supply device according to the second embodiment of the present invention. In FIG. 2, 1 is an input DC voltage source, 2 is switching means, 3 is a transformer, and
Next winding 31, output windings 32 and 33, reset winding 34
Have. 4 is a forward diode, 5 is a flywheel diode, 6 is a choke coil, 7 is a capacitor, and 8 is a load. The forward diode 4, the flywheel diode 5, the choke coil 6 and the capacitor 7 constitute a choke input type rectifying / smoothing circuit, and the output DC voltage E1 is supplied to the load 8.

A control circuit 9 drives the switching means 2 at a predetermined ON / OFF ratio to stabilize the output DC voltage E1. 10 is a forward diode, 11 is a flywheel diode, 12 is a choke coil, 13 is a capacitor, 14 is a series regulator, and 10 is a forward diode, a flywheel diode 11,
The choke coil 12 and the capacitor 13 constitute a choke input type rectifying / smoothing circuit to supply the DC voltage E2 to the series regulator 14.

Reference numeral 15 is a capacitor, 16 is a load, and the DC voltage E2 is supplied to the load 16 as a stable output DC voltage E3 via the series regulator 14. A diode 17 regenerates the excitation energy of the transformer 3 to the input DC voltage source 1 via the reset winding 34.

The above is the same as the configuration of FIG. The difference from the configuration of FIG. 1 is that the choke coil 6 is provided with another winding 61, the diode 18 and the capacitor 19 are connected so as to rectify and smooth the voltage generated during the OFF period of the switching means 2, and the output DC voltage E4 is obtained. The point is that a configuration for supplying the load 20 is added.

Regarding the multi-output switching power supply device configured as described above, the operation common to the structure of FIG. 1 of the present embodiment is the same as that of the operation, and therefore the description thereof is omitted.
The operation of the additional components will be described. As described in the first embodiment, the voltage applied to the choke coil 6 is equal to the representative stabilized output voltage E1 during the off period of the switching means 2. Therefore, the number of turns of the choke coil 6 is N
6, the number of turns of the additional winding 61 provided on the choke coil 6 is N7.
Then, the output DC voltage E4 is E4 = (N7 / N6)
-It becomes a metastabilized voltage represented by E1.

Since the number of turns of the choke coil 6 is larger than the number of turns of the output winding of the transformer 3, a suitable additional winding is provided for this to obtain another output of a relatively small capacity as a metastabilized voltage. Has been known for a long time. However, when the metastabilized voltage E4 as described above is also used in the configuration of the conventional example, when the output current of the representative stabilized output becomes small and the current flowing through the choke coil 6 becomes discontinuous, the on / off ratio D of the switching means 2 becomes small. Controlled to be smaller,
There was a problem that the voltage dropped. With the configuration of this embodiment, if the output current of the representative regulated output voltage E1 or the output current of the other output E3 is sufficiently large, the current flowing through the choke coil 6 maintains a continuous state, and the meta-stabilized voltage is obtained. The effect that the operating region where the voltage of E4 is lowered is reduced.

[0031]

As described above, the present invention has a transformer having a primary winding and a plurality of output windings, switching means connected to the primary winding of the transformer, and each output winding of the transformer. And a control circuit for controlling the on / off ratio of the switching means so as to stabilize one of the output DC voltages obtained from the choke input type rectifying and smoothing circuits. In the output switching power supply device, by connecting at least one flywheel diode of each of the choke input type rectifying and smoothing circuits in series with another output DC voltage, it is connected in series with another output DC voltage. The DC voltage obtained from the choke input type rectifying and smoothing circuit having the flywheel diode is
By selecting an appropriate turns ratio and combining it with other output DC voltage, it is possible to bring the meta-stabilized voltage closer to the set value that was not possible with the conventional configuration, and to connect a series regulator at the subsequent stage. Moreover, the loss can be reduced, the number of turns of the output winding can be reduced, and the reverse voltage of the diode can be reduced. In addition, if the other output DC voltage is set to the representative stabilized output voltage, through the choke coil,
Current is supplied to the improved meta-stabilized voltage, and even if the output current from the representative stabilized output voltage becomes small, the current flowing through the choke coil can maintain a continuous state. It is possible to realize an excellent multi-output switching power supply device capable of preventing an improved drop in the metastabilized voltage.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a multi-output switching power supply device according to a first embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of a multi-output switching power supply device according to a second embodiment of the present invention.

FIG. 3 is a circuit configuration diagram of a conventional multi-output switching power supply device.

[Explanation of symbols]

 1 Input DC voltage source 2 Switching means 3 Transformer 4 Forward diode 5 Flywheel diode 6 Choke coil 7 Capacitor 8 Load 9 Control circuit 10 Forward diode 11 Flywheel diode 12 Choke coil 13 Capacitor 14 Series regulator 15 Capacitor 16 Load 17 Diode

Claims (3)

[Claims] 1. A transformer having a primary winding and a plurality of output windings, a switching means connected to the primary winding of the transformer, and a choke input type rectifier connected to each output winding of the transformer. Each of the choke input type rectifying and smoothing circuits includes a smoothing circuit and a control circuit for controlling the on / off ratio of the switching means so as to stabilize one of the output DC voltages obtained from the choke input type rectifying and smoothing circuits. Multi-output switching power supply device in which at least one of the flywheel diodes is connected in series with another output DC voltage. 2. A first choke-input type rectifying / smoothing circuit for supplying a first output DC voltage stabilized by a control circuit, and at least one flywheel diode of another choke-input type rectifying / smoothing circuit. The multi-output switching power supply device according to claim 1, wherein the multi-output switching power supply device is connected in series with the first output DC voltage. 3. A choke coil of the first choke input type rectifying / smoothing circuit is provided with another winding, and the generated voltage is rectified and smoothed to obtain another output voltage.
The multi-output switching power supply device described.