JPH10271814A - Switching power supply - Google Patents

Abstract

(57) [Summary] The present invention relates to a switching power supply device used for various electronic devices, and has an object to stabilize a non-control output. SOLUTION: A third rectifier 11 in which a second series circuit including another choke coil 10 and a second smoothing capacitor 7 is connected in parallel to a second winding 3b side of a transformer 3,
A third series circuit including the third rectifier and the second rectifier connected to the winding 3b is provided, and a connection point between the first winding and the first smoothing capacitor is set to a first output. And the power supply to the second output is performed irrespective of the controlled power supply operation of the first output, with the connection point of the other choke coil and the second smoothing capacitor being the uncontrolled second output. Is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply used for consumer or industrial electronic equipment.

[0002]

2. Description of the Related Art A conventional multi-output switching power supply will be described with reference to FIGS.

FIG. 9 is a circuit configuration diagram of a two-output switching power supply device, and FIG. 10 is an operation waveform diagram thereof. According to FIG. 1, reference numeral 1 denotes a chopper type step-down converter for obtaining a controlled first output, and a first input of a transformer 3 serving as a choke coil for a pulse input power supply 2 controlled so that the first output is a constant voltage. Winding 3a and first smoothing capacitor 4
And a diode 5 as a first rectifier for discharging the energy accumulated in the first winding 3a to a controlled first output.
The connection point between the winding 3a and the first smoothing capacitor 4 is a controlled first output, and the second winding 3b of the transformer 3, the diode 6 as the second rectifier, and the second smoothing capacitor 7 A capacitor input type rectifying / smoothing circuit 8 composed of a series connection circuit is connected in parallel, and a connection point between the diode 6 and the second smoothing capacitor 7 is set as an uncontrolled second output.

The operation of the above configuration will be described with reference to FIG. FIG. 10 shows the operation waveform of each part in the circuit configuration of FIG. 9, FIG. 10 (a) shows the voltage waveform of the pulse input power supply 2, and FIG. 10 (b) shows the voltage waveform applied to the first winding 3a of the transformer 3. 10 (c) shows the waveform of the current flowing through the first winding 3a of the transformer 3, FIG. 10 (d) shows the waveform of the voltage across the second winding 3b of the transformer 3, and FIG. Shows the waveform of the current flowing through the second winding 3b.

The period of the pulse voltage of the pulse input power supply 2 is T, the period during which the voltage VIN is output is TON, δ = TON / T,
Although the number of windings of the first winding 3a of the transformer 3 is na, the inductance value is L3a, the number of secondary windings is nb, the leakage inductance value is Lr, and the diodes 5 and 6 have forward voltages. For the sake of simplicity, if the first output voltage controlled to be zero and controlled is denoted by V1, and the uncontrolled second output voltage is denoted by V2, the first winding 3a has V1 during the TON period.
The voltage of IN-V1 is applied, and a voltage of nb / na · (VIN-V1) is generated in the second winding 3b of the transformer 3. However, since the diode 6 is reverse-biased, no current flows and the second control is not performed. No energy is supplied to the output. At this time, the first
A current, which is the sum of the exciting current of the first winding 3a and the output current of the first output, flows through the winding 3a.

Next, during the T-TON period, a voltage V1 having a direction opposite to that of the TON period is applied to the first winding 3a.
a is discharged to the controlled first output via the diode 5, and at the same time, a voltage opposite to the TON period, that is, a forward bias voltage nb / na · V1 of the diode 6, is applied to the second winding 3b. The current generated in the hatched portions (c) and (e) in the drawing flows to the non-controlled second output via the leakage inductance Lr, and energy is supplied.

At this time, the output voltages V1 and V2 of the controlled first output and the uncontrolled second output are respectively V1 = δ · VIN V2 = nb / naV1-2 · Lr / ｛T · (1-δ) {2} · I2 (1) Here, I2 is the output current value of the uncontrolled second output.

From equation (1), the output voltage V of the uncontrolled second output is
2 decreases with an increase in the output current I2.

Further, the uncontrolled second output can extract the excitation energy stored in the first winding 3a during the TON period because a part of the energy discharged to the first output is discharged during the T-TON period. There is a critical power P2max, which is L3a = L3a =
、, P2max = V2 · I2 = {(1−δ) / (1 + δ)} · V1 · I1 = {(1−V1 / VIN) / (1 + V1 / VIN)} · V1 · I1 (2) Becomes Actually, since L3a is finite, P2max is smaller than the above equation (2).

When the output current I2 is further increased from the output current of the non-control second output determined by the above equation (2),
A period t occurs in which the current flowing through the first winding is discontinuous,
As a result, nb / na · V1 · (T−T) in FIG.
ON) and the voltage-time product of V1 · (T-TON) in (b) decrease (black portion), so that the TON time of the pulse input voltage becomes shorter to control the first output to a constant voltage. Tona (the waveform shown by the dotted line in FIG. 10).

For this reason, the output voltage of the uncontrolled second output is further reduced.

[0012]

A second winding in which a capacitor input type rectifying / smoothing circuit 8 is connected to a transformer 3 of a step-down converter which obtains a first output controlled to a constant voltage as in the above-mentioned conventional switching power supply device. 3b from the second winding 3b to the second winding 3d during the discharge period of the energy stored in the first winding 3a of the transformer to the controlled first output.
b. Capacitor input type rectifying / smoothing circuit connected to b
In the configuration in which the current flowing through the first winding 3a of the transformer 3 is in a continuous operation state, stable power can be supplied to the uncontrolled second output in the configuration in which the energy is supplied to the non-controlled second output. Since the power supply is performed via the leakage inductance Lr of the first winding 3a and the second winding 3b of the transformer 3, the output current I of the uncontrolled second output is obtained from the above equation (1).
2 is the leakage inductance Lr
, The voltage stability of the uncontrolled second output is poor (load fluctuation is large).

When the current flowing through the first winding 3a of the transformer 3 is in a discontinuous state, a stable output cannot be obtained for the power supply to the uncontrolled second output, and stable power supply to the uncontrolled second output is performed. Is expressed by the above equation (2), and there is a limit (it is limited by the power of the first output).

The uncontrolled second output is the first winding 3 during the TON period.
Since the excitation energy stored in the first winding 3a is obtained by extracting a part of the energy discharged to the first output during the T-TON period, the operation of the current flowing through the first winding 3a to the discontinuous state is promoted. In order to stabilize the uncontrolled second output, the transformer 3 determined by the minimum output current of the first output
In this case, an inductance value larger than the inductance value of the first winding is required.
In addition, the non-control second output can handle only a small amount of power for the size of the transformer 3. Furthermore, the ripple current of the current flowing through the first winding 3a increases, and the ripple current of the first smoothing capacitor 4 of the converter that obtains the first output increases, so that the first smoothing capacitor 4 cannot be downsized.

Since the power supply to the uncontrolled second output is performed via the capacitor input type rectifying and smoothing circuit 8, the ripple current of the second smoothing capacitor 7 becomes large and the second smoothing capacitor 7 cannot be downsized. There were challenges.

The present invention solves the above-mentioned conventional problems, and can stabilize the uncontrolled output connected to the second winding of the transformer, increase the power, reduce the size of the transformer, and reduce the size of the smoothing capacitor. It is intended to provide a simple switching power supply device.

[0017]

In order to solve the above-mentioned problems, a switching power supply according to the present invention has a first rectifier connected in parallel to a pulse input power supply and a first rectifier connected in parallel to the first rectifier. A first winding and a first winding of a transformer acting as a choke coil for obtaining a first output that is stably controlled.
A first series circuit composed of a smoothing capacitor, a third rectifier in which another choke coil and a second series circuit composed of a second smoothing capacitor are connected in parallel, and a third rectifier connected in parallel with a second winding of the transformer. The third rectifying means and the second
And a third series circuit comprising a rectifier means, the connection point between the first winding and the first smoothing capacitor is set to a first output, and the other choke coil and the second
The power supply to the second output can be performed irrespective of the controlled power supply operation of the first output. The output voltage can be stabilized by the output current of the output, and the uncontrolled second output composed of the second winding provided in the transformer acting as a choke coil for obtaining the controlled first output can be stabilized, and large power can be obtained. It is possible to reduce the size of the switching power supply device.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, a first rectifying means connected in parallel to a pulse input power supply, and a stable and controlled parallel connection to the first rectifying means. A first winding composed of a first winding of a transformer acting as a choke coil for obtaining a first output and a first smoothing capacitor.
And a third rectifying unit in which a second series circuit composed of another choke coil and a second smoothing capacitor is connected in parallel, and the third rectifier connected in parallel to a second winding of the transformer. A third series circuit comprising a rectifier and a second rectifier, wherein a connection point between the first winding and the first smoothing capacitor is set to a first output, and the other choke coil and the The connection point of the second smoothing capacitor is used as an uncontrolled second output, and power supply to the uncontrolled second output can be performed irrespective of the controlled power supply operation of the first output. The output voltage of the control second output can be stabilized by the output current, and the second transformer provided in the transformer serving as a choke coil for obtaining the controlled first output can be obtained.
This makes it possible to stabilize the uncontrolled second output composed of windings, increase the power, reduce the size of the transformer 3, reduce the size of the smoothing capacitor 4, and reduce the size of the first output smoothing capacitor 7.

According to a second aspect of the present invention, there is provided a first rectifier connected in parallel to a pulse input power supply,
Of a transformer acting as a choke coil for obtaining a stably controlled first output connected in parallel to
A first series circuit consisting of a winding and a first smoothing capacitor; a second series circuit consisting of another choke coil and a second smoothing capacitor; a second winding of the transformer;
A third series circuit comprising rectification means, and a third rectification means connected between a connection point of the second series circuit and the third series circuit and the first smoothing capacitor,
A connection point between the first winding and the first smoothing capacitor is set to a first output, and a connection point between the other choke coil and the second smoothing capacitor is set to an uncontrolled second output. The third rectifier of claim 1 is connected between a connection point between the second rectifier and the choke coil and the first output. In addition to the effects of the invention of claim 1, a second winding of a transformer is provided. , The transformer is reduced in size and loss by reducing the number of windings, the choke coil constituting the non-controlled second output is reduced in operating voltage, the choke coil is reduced in size and loss is reduced, the second rectifying means and the third An object of the present invention is to enable a reduction in loss by reducing the operation applied voltage of the rectifier, a further stabilization of the output voltage of the uncontrolled second output, and a downsizing of the transformer.

According to a third aspect of the present invention, a first rectifying means connected in parallel to a pulse input power supply,
Of a transformer acting as a choke coil for obtaining a stably controlled first output connected in parallel to
A first series circuit comprising a winding and a first smoothing capacitor, and a second series circuit comprising another choke coil and a second smoothing capacitor.
And a third rectifier connected in parallel with the second series circuit, a second rectifier connected in series with the third rectifier, and a second winding of a transformer. And the third series circuit connected in series with the third rectifying means is connected in parallel to the first smoothing capacitor, and the first winding and the first smoothing capacitor are connected. The first smoothing capacitor according to claim 1, wherein a connecting point of the first choke coil and the second smoothing capacitor is a non-control second output. A third rectifier in which a series circuit of a choke coil and a second smoothing capacitor are connected in parallel, a second rectifier and a third series circuit of a second winding of the transformer are connected in parallel, In addition to the effects of the invention according to claim 1, a transformer Transformer downsizing and loss reduction by reducing the number of windings of the second winding, uncontrolled Choke coil downsizing and loss reduction by reducing the operating applied voltage of the choke coil constituting the second output, second rectifier And loss reduction by reduction of the operation applied voltage of the third rectifier, non-control second
This enables further stabilization of the output voltage of the output.

According to a fourth aspect of the present invention, a first rectifier connected in parallel to a pulse input power supply and a first output that is stably controlled and connected in parallel to the first rectifier are obtained. A first series circuit consisting of a first winding of a transformer and a first smoothing capacitor serving as a choke coil for
A second series circuit including another choke coil and a second smoothing capacitor; a third series circuit including a second winding of the transformer and a second rectifier; and a parallel circuit with the third series circuit. And a third rectifier connected to the second series circuit and the third series circuit connected in series, and these are connected in parallel to the first smoothing capacitor, so that the first winding and the third winding are connected to each other. The connection point of the first smoothing capacitor is a first output, and the connection point of the other choke coil and the second smoothing capacitor is an uncontrolled second output. A third series circuit comprising a third rectifier, a choke coil, and a second smoothing capacitor in which a third series circuit comprising a second winding of a transformer and a second rectifier is connected in parallel to the first smoothing capacitor. Are connected in parallel. Claim 1, in which can be obtained together the effect of the invention of claim 2 and claim 3.

According to a fifth aspect of the present invention, the first rectifying means, the second rectifying means and the third rectifying means according to the first or second or third or fourth aspect are field-effect transistors. In synchronization with the high level of the pulse input power supply, the field effect transistor serving as the second rectifier is turned on, the field effect transistors serving as the first rectifier and the third rectifier are turned off, and the low level of the pulse input power is turned off. Switching means for turning on the field effect transistor, which is the first rectification means and the third rectification means, and turning off the field effect transistor, which is the second rectification means, in synchronization with the rectification means. By using a field-effect transistor, the power consumed by the rectifier can be reduced, and the efficiency of the switching power supply can be increased.

An embodiment of the present invention will be described below with reference to FIGS. Note that the same parts as in the prior art will be described with the same reference numerals.

(Embodiment 1) FIG. 1 is a circuit diagram of a switching power supply according to an embodiment of the present invention.
Is an operation waveform diagram of the same. According to FIG. 1, reference numeral 1 denotes a chopper type step-down converter for obtaining a controlled first output, and a chopper type step-down converter 1 for a transformer 3 serving as a choke coil for a pulse input power supply 2 controlled so that the first output has a constant voltage. A first series circuit of one winding 3a and a first smoothing capacitor 4 is connected in parallel with a diode 5 as first rectifying means for discharging energy accumulated in the first winding 3a to a first output. The connection point of the first winding 3a and the first smoothing capacitor 4 is a controlled first output, and the choke coil 10 and the second smoothing capacitor 7 are connected to the second winding 3b of the transformer 3. The third in which two series circuits are connected in parallel
Is connected in parallel with a diode 11 as a rectifier, and a third series circuit of a diode 9 as a second rectifier and a second winding 3b of the transformer 3 is connected in parallel to the choke coil 10 and the second smoothing capacitor 7. The connection point is configured to be a non-control second output.

The operation of the above configuration will be described with reference to FIG. 2A and 2B show operation waveforms of respective parts in the circuit configuration of FIG. 1, FIG. 2A shows a voltage waveform of the pulse input power supply 2, and FIG. 2B shows a voltage waveform applied to the first winding 3 a of the transformer 3. 2 (c) shows a current waveform flowing through the first winding 3a of the transformer 3, FIG. 2 (d) shows a voltage waveform across the second winding 3b of the transformer 3, and FIG. 2 (f) shows a waveform of a current flowing through the choke coil 10. FIG.

The pulse cycle of the pulse input power supply 2 is T, the cycle at which the voltage VIN is output is TON, TON / T = δ, the number of turns of the first winding 3a of the transformer 3 is na, and the inductance value is L3a, 2 The number of the next windings is nb, the inductance value L10 of the choke coil 10, the diode 5, the diode 9
Although the diode 11 has a forward voltage, it is assumed to be zero for simplicity of explanation, the first output voltage is set to V1, the second
When the output voltage is led to V2, a voltage of VIN-V1 is applied to the first winding 3a during the TON period, and a voltage of nb / na. (VIN-V1) is applied to the second winding 3b of the transformer 3. Is generated, a voltage of nb / na · (VIN−V1) −V2 is applied to the choke coil 10 via the diode 9, and the exciting current of the choke coil 10 and the output current of the uncontrolled second output flow. The first winding 3a has a first winding 3
The current of the sum of the exciting current a, the controlled output current of the first output, the exciting current of the choke coil 10 flowing through the second winding 3b, and the output current of the uncontrolled second output flows.

Next, during the T-TON period, T
The voltage V1 in the opposite direction to the ON period is applied, and the excitation energy of the first winding 3a is controlled via the diode 5 in the first period.
At the same time as the voltage is supplied to the output, a voltage nb / na · V1 in the opposite direction to the TON period is applied to the second winding 3b, so that the diode 9 is reverse biased and turned off, and the choke coil 1
To 0, a voltage V2 in the opposite direction to the TON period is applied, and the excitation energy of the choke coil 10 is supplied to the non-control second output via the diode 11.

At this time, the controlled voltage V1 of the first output and the voltage V2 of the uncontrolled second output are respectively: V1 = δ · VIN (3) V2 = nb / na · (1-δ) · V1 ... (4)

The condition under which the uncontrolled second output can be stabilized is when the current flowing through the first winding 3a of the transformer 3 is in a continuous state, and the controlled output current of the first output is I1. I1 ≧ (VIN−V1) / (2 · L3a) · TON ≧ V1 / (2 · L3a) · (T−TON) (5), and the output current I at which the second output is stable under the above conditions
The range of 2 is: I2 ≧ {nb / na · (1-δ) · V1−V2} / (2 · L10) · TON ≧ V2 / (2 · L10) · (T-TON) (6) Becomes

As described above, the power supply to the uncontrolled second output is controlled by the transformer 3 for supplying power to the controlled first output.
Energy is stored in the choke coil 10 via the second winding 3b of the transformer 3 and the diode 9 during the storage period (TON period) of the first winding 3a, and is stored in the first winding 3a of the transformer 3. Energy controlled first
During the period of discharging to the output (T-TON period), energy is supplied from the choke coil 10 in which energy is stored to the uncontrolled second output, so that the second output is not subject to the power limitation of the first output. . In addition, since the second output is not a power supply via the leakage inductance Lr, there is no voltage drop due to the leakage inductance Lr, and the voltage stability is good. Further, in the discharging operation of the energy stored in the first winding 3a of the transformer 3 to the controlled first output, a part of the discharging energy is not taken out to the uncontrolled second output, so that the current flowing through the first winding 3a is controlled. Can be reduced, the size of the smoothing capacitor 4 can be reduced, and the size of the transformer 3 can be reduced. Further, since the non-controlled second output has the configuration of the choke input type rectifying / smoothing circuit 12, the voltage stability is good and the ripple current of the second smoothing capacitor 7 is also small, so that the second smoothing capacitor 7 can be downsized. As a result, it is possible to stabilize the uncontrolled second output, increase the power, reduce the size of the transformer 3, and reduce the size of the smoothing capacitors 4 and 7.

In this embodiment, the controlled first
A two-output configuration of output and non-control second output is used. However, the transformer 3 is provided with third and fourth windings and the like, and an uncontrolled multi-output configuration comprising a choke input type rectifying and smoothing circuit of three or more outputs. It is good.

Further, the period T of the pulse input power supply 2 is fixed,
Although the TON width control is used, a period T control, a TON width fixed control method, or the like may be used.

(Embodiment 2) Next, another embodiment of the switching power supply of the present invention will be described. In the following description of each of the embodiments, mainly the differences from the first embodiment will be mainly described.

FIG. 3 is a circuit diagram, and FIG. 4 is an operation waveform diagram. 1 is a chopper type step-down converter,
A first series circuit comprising a pulse input power supply 2, a first winding 3a of a transformer 3, a first smoothing capacitor 4, and a diode 5 is provided. The first winding 3a of the first series circuit is connected to a first series circuit. The connection point of the smoothing capacitor 4 is a controlled first output, a third series circuit including the second winding 3b of the transformer 3 and the diode 9, and a second series circuit including the choke coil 10 and the second smoothing capacitor 7. A series circuit is connected in series, a diode 11 is connected between a connection point between the diode 9 and the choke coil 10 and the first output, and a connection point between the choke coil 10 and the second smoothing capacitor 7 is set as an uncontrolled second output. It consists of a configuration.

The operation of the above configuration will be described with reference to FIG. 4. FIG. 4 (a) shows the voltage waveform of the pulse input power supply 2, and FIG. 4 (b) shows the voltage waveform applied to the first winding 3a of the transformer 3. FIG. 4C shows a waveform of a current flowing through the first winding 3 a of the transformer 3, and FIG.
FIG. 4E shows a voltage waveform applied to the choke coil 10, and FIG. 4F shows a current waveform flowing through the choke coil 10.

Now, the pulse cycle of the pulse input power supply 2 is T,
The period during which the voltage VIN is output is TON, δ = TON / T, the number of turns of the first winding 3a of the transformer 3 is na, the inductance value is L3a, and the number of secondary windings is nb.
Although a forward voltage exists in the inductance value L10 of 0, the diode 5, the diode 9 and the diode 11, the first output voltage is set to zero for clarity of explanation.
1, if the second output voltage is V2, the first winding 3
a, a voltage of VIN-V1 is applied, and a voltage of nb / na · (VIN-V1) is generated in the second winding 3b of the transformer 3;
A voltage of nb / na · (VIN−V1) −V2 is applied to 0, and the exciting current of the choke coil 10 and the output current of the uncontrolled second output flow. Further, the exciting current of the first winding 3a, the output current of the controlled first output, and the second
A current, which is the sum of the exciting current of the choke coil 10 flowing through the winding 3b and the output current of the uncontrolled second output, flows.

Next, during the T-TON period, the first winding 3a has T
The voltage V1 in the opposite direction to the ON period is applied, and the excitation energy of the first winding 3a is controlled via the diode 5 in the first period.
At the same time as the voltage is supplied to the output, a voltage nb / na · V1 in the opposite direction to the TON period is applied to the second winding 3b, so that the diode 9 is reverse biased and turned off, and the choke coil 1 is turned off.
0, a voltage V2-V1 in the opposite direction to the TON period is applied, and the excitation energy of the choke coil 10 is reduced by the diode 5,
It is supplied to the uncontrolled second output via the diode 11.

At this time, the controlled voltage V1 of the first output and the voltage V2 of the uncontrolled second output are respectively V1 = δ · VIN (7) V2 = (nb / na + 1) · (1-δ) · V1 (8)

The condition under which the uncontrolled second output can be stabilized is when the current flowing through the first winding 3a of the transformer 3 is in a continuous state. If the output current of the first output is I1, then I1 ≧ ( VIN−V1) / (2 · L3a) · TON−I2 ≧ V1 / (2 · L3a) · (T−TON) −I2 (9), and the uncontrolled second output is a stable output under the above conditions. The range of the current I2 is I2 ≧ {nb / na · (VIN−V1) −V2} / (2 · L10) · TON ≧ (V2−V1) / (2 · L10) · (T-TON) (10)

As described above, the power supply to the uncontrolled second output is performed by accumulating the energy in the first winding 3a of the transformer 3 for the controlled power supply to the first output (a TON period).
Energy is stored in the choke coil 10 via the second winding 3b of the transformer 3 and the diode 9 therein, and the transformer 3
During the period in which the energy stored in the first winding 3a is discharged to the controlled first output (T-TON period), the energy is stored in the choke coil 10 in the diode 5, the first winding 3a, and the like. Non-control second via diode 11
Since energy is supplied to the output, in addition to the effects of the first embodiment, the expressions (3), (4), (7), and (8)
As is clear from FIG. 4, the second winding number nb of the transformer 3 can be reduced, the transformer 3 can be reduced in size and loss can be reduced, and the diode 9 and the third
Since the reverse applied voltage of the diode 11 as the rectifying means can be reduced, an element having a small voltage rating can be used, and high efficiency and low cost can be achieved.

As is clear from the equations (6) and (10), the range of the output current I2 of the non-control second output can be expanded (the minimum current value of I2 can be further reduced). . In other words, if the minimum output current of the uncontrolled second output is the same as in the first embodiment, the inductance value L10 of the choke coil 10 can be reduced, so that the choke coil 10 can be reduced in size and loss can be reduced.

In the T-TON period, the choke coil 10
Control to suppress the transition of the current flowing through the first winding 3a to the discontinuous operation due to the decrease of the output current of the first output, which is controlled such that the discharging current of the first winding 3a also flows through the diode 5 and the first winding 3a. It is possible to expand the range of the output current I1 of the output of the first output (the minimum current value of I1 can be further reduced). In other words, if the controlled minimum output current of the first output is the same as that of the first embodiment, the inductance value of the first winding 3a can be reduced, so that the size of the transformer 3 can be reduced.
The loss can be reduced.

Further, during the T-TON period, the choke coil 1
0 discharge current also flows through the diode 5 and the first winding 3a, and a voltage drop occurs due to the current, so that the voltage of the controlled first output also drops, but TON is used to keep the output voltage constant.
The period changes and this change acts to compensate for a part of the voltage drop due to the line impedance of the uncontrolled second output, so that the uncontrolled second output can be more stabilized than in the first embodiment. As a result, further stabilization of the second output, downsizing of the choke coil 10, downsizing and high efficiency of the transformer 3 can be achieved.

In this embodiment, the transformer 3
And a third winding, a fourth winding or the like, and an uncontrolled multi-output configuration comprising a choke input type rectifying / smoothing circuit having three or more outputs.

Further, the period T of the pulse input power supply 2 is fixed,
Although the TON width control is used, a period T control, a TON width fixed control method, or the like may be used.

(Embodiment 3) FIG. 5 is a circuit configuration diagram of a multi-output switching power supply according to another embodiment of the present invention, and FIG. 6 is an operation waveform diagram thereof. According to FIG. 1, reference numeral 1 denotes a chopper type step-down converter, and a pulse input power supply 2
And the first winding 3a of the transformer 3 and the first smoothing capacitor 4
, And a connection point between the first winding 3a and the first smoothing capacitor 4 is set as a controlled first output, and the first smoothing capacitor 4 is connected to the choke coil 10 and A second series circuit including a second smoothing capacitor 7 is connected in parallel to a diode 11 serving as a third rectifier, and the diode 11, a diode 9 serving as a second rectifier, and a second winding 3b of a transformer are connected. Is connected in parallel to the first smoothing capacitor 4, and the choke coil 10 and the second
The connection point of the smoothing capacitor 7 is set as the uncontrolled second output.

Next, the operation will be described with reference to FIG.
6A shows a voltage waveform of the pulse input power supply 2, FIG. 6B shows a voltage waveform applied to the first winding 3a of the transformer 3, and FIG. 6C shows a current waveform flowing through the first winding 3a of the transformer 3. , FIG.
(D) shows a voltage waveform across the second winding 3b of the transformer 3,
FIG. 6E shows a waveform of a voltage applied to the choke coil 10, and FIG. 6F shows a waveform of a current flowing through the choke coil 10.

Now, the pulse cycle of the pulse input power supply 2 is T,
The period during which the voltage VIN is output is TON, δ = TON / T, the number of turns of the first winding 3a of the transformer 3 is na, the inductance value is L3a, and the number of secondary windings is nb. A forward voltage exists in the diode 11, but the first output voltage is set to V1 and the second output voltage is set to V2 for simplicity of explanation.
A voltage of VIN−V1 is applied to the winding 3a, and nb / na · (VIN−V1) is applied to the second winding 3b of the transformer 3.
1) is generated, and a voltage of nb / na · (VIN−V1) + V1−V2 is applied to the choke coil 10 via the diode 9, and the exciting current of the choke coil 10 and the output current of the uncontrolled second output Flows.

The first winding 3a has an exciting current of the first winding 3a, an output current of the controlled first output, and a second winding 3b.
, A current, which is the sum of the exciting current of the choke coil 10 and the output current of the uncontrolled second output, flows through the choke coil 10.

Next, during the T-TON period, T
The voltage V1 in the opposite direction to the ON period is applied, and the excitation energy of the first winding 3a is controlled via the diode 5 in the first period.
At the same time as the voltage is supplied to the output, a voltage nb / na · V1 in the opposite direction to the TON period is applied to the second winding 3b, so that the diode 9 is reverse biased and turned off, and the choke coil 1 is turned off.
To 0, a voltage V2 in the opposite direction to the TON period is applied, and the excitation energy of the choke coil 10 is supplied to the non-control second output via the diode 11.

At this time, the controlled first output voltage V1 and the uncontrolled second output voltage V2 are respectively V1 = δ · VIN (11) V2 = {δ + nb / na · (1-δ)} · V1 (12)

The condition under which the uncontrolled second output can be stabilized is when the current flowing through the first winding 3a of the transformer 3 is in a continuous state. If the output current of the first output is I1, then I1 ≧ ( VIN−V1) / (2 · L3a) · TON ≧ V1 / (2 · L3a) · (T−TON) (13) where the second output is a stable output current I under the above conditions.
The range of 2 is: I2 ≧ {nb / na · (VIN−V1) + v1−V2} / (2 · L10) · TON ≧ V2 / (2 · L10) · (T−TON) (14) .

As described above, the power supply to the uncontrolled second output is performed by accumulating the energy in the first winding 3a of the transformer 3 for the controlled power supply to the first output (TON period).
Energy is stored in the choke coil 10 via the second winding 3b of the transformer 3 and the diode 9 therein, and the transformer 3
During the period (T-TON period) during which the energy stored in the first winding 3a is discharged to the controlled first output (T-TON period), the diode 1
Since the energy is supplied to the uncontrolled second output via the first control unit 1, the equation (3)
As is clear from (4), (11) and (12), the second winding number nb of the transformer 3 can be reduced, and the second output can be controlled even when the output voltage value VIN of the pulse input voltage 2 varies. And the transformer 3 can be further stabilized, the size of the transformer 3 can be further reduced, the loss can be reduced, and the reverse applied voltage of the diode 9 as the second rectifier and the diode 11 as the third rectifier can be reduced. Therefore, an element having a small voltage rating can be used, and high efficiency and low cost can be achieved.

As is clear from the equations (6) and (14), the range of the output current I2 of the non-control second output can be expanded (the minimum current value of I2 can be further reduced). . In other words, if the minimum output current of the uncontrolled second output is the same as that of the first embodiment, the inductance value L10 of the choke coil 10 can be reduced, so that the effect that the choke coil 10 can be downsized and the loss can be reduced is obtained. Further, the uncontrolled second output can be further stabilized, the size of the choke coil 10 can be reduced, the size of the transformer 3 can be reduced, and the efficiency can be increased.

The first embodiment controlled in this embodiment as well.
Although a two-output configuration of an output and an uncontrolled second output is used, an output configuration of three or more outputs may be used as in the above-described embodiment.

Further, the period T of the pulse input power supply 2 is fixed,
Although the TON width control is used, a period T control, a TON width fixed control method, or the like may be used.

(Embodiment 4) FIG. 7 is a circuit diagram of a switching power supply according to another embodiment of the present invention, and FIG. 8 is an operation waveform diagram thereof. Referring to FIG. 1, reference numeral 1 denotes a chopper type step-down converter, which includes a pulse input power supply 2 and a transformer 3
Of the first winding 3a and the first smoothing capacitor 4
, And a connection point between the first winding 3a of the first series circuit and the first smoothing capacitor 4 is a controlled first output, and the second winding 3b of the transformer 3 And the third rectifying means of the diode 9
In parallel with a series circuit of
1 and to the first smoothing capacitor 4,
A second series circuit including a choke coil 10 and a second smoothing capacitor 7 is connected in parallel between the diode 11 and the first smoothing capacitor 4, and a connection point between the choke coil 10 and the second smoothing capacitor 7 is not connected. This is a configuration in which the control is the second output, and is a configuration in which the above-described second and third embodiments are combined.

The operation in the above configuration will be described with reference to FIG. 8A shows a voltage waveform of the pulse input power supply 2, FIG. 8B shows an applied voltage waveform of the first winding 3a of the transformer 3, and FIG. 8C shows a first winding 3a of the transformer 3. 8 (d) shows a voltage waveform across the second winding 3b of the transformer 3, FIG. 8 (e) shows a voltage waveform applied to the choke coil 10, and FIG. 2 shows a waveform of a current flowing through.

Now, the pulse period of the pulse input power supply 2 is T,
The period during which the voltage VIN is output is TON, δ = TON / T, the number of turns of the first winding 3a of the transformer 3 is na, the inductance value is L3a, and the number of secondary windings is nb. A forward voltage exists in the diode 11, but the first output voltage is V1 and the second output voltage is V2.
A voltage of VIN−V1 is applied to the winding 3a, and nb / na · (VIN−V1) is applied to the second winding 3b of the transformer 3.
1) is generated, and a voltage of nb / na · (VIN−V1) + V1−V2 is applied to the choke coil 10 via the diode 9, and the exciting current of the choke coil 10 and the output current of the uncontrolled second output Flows.

The first winding 3a has an exciting current of the first winding 3a, an output current of a controlled first output, and a second winding 3a.
b, the choke coil 1 flowing through the diode 9
A current of the sum of the excitation current of 0 and the output current of the uncontrolled second output flows.

Next, during the T-TON period, T
The voltage V1 in the opposite direction to the ON period is applied, and the excitation energy of the first winding 3a is discharged through the first output and the diode 5, and at the same time, the voltage in the second winding 3b is opposite to the voltage in the TON period. Since nb / na · V1 is applied, the diode 9 is reverse biased and turned off, and the choke coil 10 has TON
The voltage V2-V1 in the opposite direction to the period is applied, and the excitation energy of the choke coil 10 is reduced by the diode 5 and the transformer 3
Is supplied to the uncontrolled second output via the first winding 3a and the diode 11.

At this time, the voltage V1 of the first output and the voltage V2 of the second output are respectively V1 = δ · VIN (15) V2 = {1 + nb / na · (1-δ)} · V1 (16) ).

The condition under which the uncontrolled second output can be stabilized is when the current flowing through the first winding 3a of the transformer 3 is in a continuous state, and the controlled output current of the first output is I1. I1 ≧ (VIN−V1) / (2 · L3a) · TON ≧ V1 / (2 · L3a) · (T−TON) (17), and the output current I at which the second output is stable under the above conditions is obtained.
The range of 2 is as follows: I2 ≧ {nb / na · (VIN−V1) + V1−V2} / (2 · L3a) · TON ≧ (V2−V1) / (2 · L10) · (T-TON) 18)

As described above, the power supply to the uncontrolled second output is performed by accumulating energy in the first winding 3a of the transformer 3 for controlling the supply of power to the first output (a TON period).
Energy is stored in the choke coil 10 via the second winding 3b of the transformer 3 and the diode 9 therein, and the transformer 3
During the period (T-TON period) in which the energy stored in the first winding 3a is discharged to the controlled first output (T-TON period), the diode 5
And the first output 3a of the transformer 3 and the non-controlled second output via the diode 11, so that the effects of the second and third embodiments can be obtained in addition to the effects of the first embodiment. Becomes

In the present embodiment, a two-output configuration of a controlled first output and a non-controlled second output is also used. 4th
It is also possible to adopt a multi-output non-control output configuration.

Also, the period T of the pulse input power supply 2 is fixed,
Although the TON width control is used, a cycle T control, a control method for fixing the TON width, or the like may be used.

(Embodiment 5) Although the other embodiment is not particularly shown, the first rectifying means described in each of Embodiment 1, Embodiment 2, Embodiment 3 or Embodiment 4 is applicable. The certain diode 5, the diode 9 as the second rectifier, and the diode 11 as the third rectifier are field effect transistors, and the field effect transistor as the second rectifier is synchronized with the high level of the pulse input power supply 2. 9
Is turned on, the field effect transistors 5 and 11 as the first rectifier and the third rectifier are turned off, and the electric field as the first rectifier and the third rectifier is synchronized with the low level of the pulse input power supply 2. Turn on effect transistors 5 and 11,
A known switching means (not shown) for turning off the field effect transistor 9, which is the second rectifying means, is provided.

The operation is the same as in each of the embodiments, and a description thereof will be omitted. However, in this embodiment, rectification loss can be reduced and higher efficiency can be achieved as compared with a diode by using each rectifier as a field effect transistor. Is possible.

Although the embodiments have been described above, a multi-output switching power supply having a plurality of stable outputs by combining the embodiments may be used.

Further, the pulse input power supply 2 may have a DC power supply and a switching element whose on / off time is controlled in series in order to stably control the first output. Further, the first output may be stabilized. The secondary winding of the transformer of the isolated switching power supply to be controlled and the rectifying element may be connected in series.

Further, in the description of the embodiment of the present invention, 1 is a chopper type step-down converter, but the same effect can be obtained by a step-up converter or a polarity inversion converter.

[0072]

As described above, since the switching power supply of the present invention is constructed, it is possible to increase the power and obtain a stable uncontrolled second output, and to obtain the third, fourth,. By providing the winding, the effects such as the non-control third, the non-control fourth,... That a plurality of stable outputs can be obtained, and the second rectifier and the third rectifier The effect of increasing the efficiency by reducing the reverse applied voltage, downsizing the choke coil, downsizing the transformer, and the like can be obtained, and a multi-output switching power supply device that can be downsized with high efficiency can be realized.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of an embodiment of a switching power supply device of the present invention.

FIG. 2 is an operation waveform diagram of the same.

FIG. 3 is a circuit configuration diagram of another embodiment.

FIG. 4 is an operation waveform diagram of the same.

FIG. 5 is a circuit configuration diagram of another embodiment.

FIG. 6 is an operation waveform diagram of the same.

FIG. 7 is a circuit configuration diagram of another embodiment.

FIG. 8 is an operation waveform diagram of the same.

FIG. 9 is a circuit configuration diagram of a conventional switching power supply device.

FIG. 10 is an operation waveform diagram of the same.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Chopper type step-down converter 2 Pulse input power supply 3 Transformer 3a First winding 3b Second winding 4 First smoothing capacitor 5 Diode 6 Diode 7 Second smoothing capacitor 8 Capacitor input type rectifying and smoothing circuit 9 Diode 10 Choke coil 11 Diode 12 Choke input type rectifying and smoothing circuit

Claims (5)

[Claims] 1. A first rectifying means connected in parallel to a pulse input power supply, and a first transformer connected in parallel to the first rectifying means and serving as a choke coil for obtaining a stably controlled first output. A first series circuit comprising one winding and a first smoothing capacitor; a third rectifier in which a second series circuit comprising another choke coil and a second smoothing capacitor are connected in parallel; A third series circuit comprising the third rectifier and the second rectifier connected in parallel to a second winding is provided, and a connection point between the first winding and the first smoothing capacitor is connected to a second winding. A switching power supply device having one output and having a connection point between the other choke coil and the second smoothing capacitor as a non-control second output. 2. A first rectifier connected in parallel to a pulse input power supply, and a first transformer connected in parallel with the first rectifier and acting as a choke coil for obtaining a stable and controlled first output. A first series circuit including one winding and a first smoothing capacitor; a second series circuit including another choke coil and a second smoothing capacitor; a second winding of the transformer and a second rectifier; And a third rectifying means connected between a connection point of the second series circuit and the third series circuit and the first smoothing capacitor, and A switching power supply device in which a connection point between one winding and the first smoothing capacitor is a first output, and a connection point between the other choke coil and the second smoothing capacitor is an uncontrolled second output. 3. A first rectifying means connected in parallel to the pulse input power supply, and a first rectifying means connected in parallel with the first rectifying means and serving as a choke coil for obtaining a stably controlled first output. A first series circuit composed of one winding and a first smoothing capacitor, a second series circuit of another choke coil and a second smoothing capacitor, and a third series circuit connected in parallel to the second series circuit. A rectifier, a second rectifier connected in series with the third rectifier, and a third series circuit including a second winding of the transformer, which is connected in series with the third rectifier. A third series circuit is connected in parallel to the first smoothing capacitor, a connection point between the first winding and the first smoothing capacitor is set to a first output, and the other choke coil is connected to the second smoothing capacitor. No control of the smoothing capacitor connection point Switching power supply with power. 4. A first rectifier connected in parallel to the pulse input power supply, and a first transformer connected in parallel with the first rectifier and acting as a choke coil for obtaining a stable and controlled first output. A first series circuit including one winding and a first smoothing capacitor; a second series circuit including another choke coil and a second smoothing capacitor; a second winding of the transformer and a second rectifier; Means, a third rectifier connected in parallel with the third series circuit, and a second series circuit connected in series with the third series circuit. The first smoothing capacitor is connected in parallel, the connection point between the first winding and the first smoothing capacitor is set to a first output, and the connection point between the other choke coil and the second smoothing capacitor is not controlled. Switching power for the second output Source equipment. 5. The first rectifier, the second rectifier and the third rectifier are field-effect transistors, and the field-effect transistor as the second rectifier is turned on in synchronization with a high level of a pulse input power supply. , The first rectifying means and the third
The field effect transistor as the rectifier is turned off, the first rectifier and the field effect transistor as the third rectifier are turned on in synchronization with the low level of the pulse input power supply, and the field effect transistor as the second rectifier is turned on. A switching means for turning off the transistor is provided.
The switching power supply device according to any one of the above.