JPH09252577A - Multioutput dc stabilized power unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multioutput stabilized power unit where the output voltage small in voltage difference can be obtained with high accuracy from each output circuit, with simple circuit constitution. SOLUTION: A main output circuit 12 and a sub output circuit 13 are respectively connected to both ends of the common secondary winding Ls of a main transformer T, and the output of the main transformer T is controlled to fix the main output voltage of the main output circuit 12. Therein, this unit is so constituted as to control the output voltage of the sub output circuit 13 by interposing a saturable reactor SR as a magnetic amplifier between the main transformer T and the sub output circuit 13, and controlling the pulse- shaped signal inputted from the secondary winding Ls of the main transformer T into the sub output circuit 13 by the saturable reactor SR. Therefore, the circuit constitution becomes simple, and output voltage small in voltage difference can be obtained from each output circuit, and the downsizing of the device and the cost reduction can be materialized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-output stabilized DC power supply device for obtaining a plurality of stabilized DC voltages having different ratings from an AC power supply or a DC power supply.

[0002]

2. Description of the Related Art Conventionally, a multi-output DC stabilized power supply device (hereinafter, simply referred to as a stabilized power supply device) has a DC / DC converter connected to an output side of a secondary side main output circuit. There are things.

FIG. 5 is a diagram showing the structure of a stabilized power supply device using this DC / DC converter. As shown in the figure, the DC / DC converter 1 switches the output of the main output circuit 2 and rectifies and smoothes the pulsed signal obtained on the secondary side of the internal transformer to output the output of the main output circuit 2. The voltage (for example, 48V) is converted into a DC voltage below that (for example, 5V) and output. On the other hand, the output voltage of the main output circuit 2 is compared with the reference voltage by the comparator 3, and the signal corresponding to the error is passed through the photocoupler 4 to the PWM of the primary side.
It is fed back to the control circuit 5. The PWM control circuit 5 makes the output voltage of the main output circuit 2 constant by controlling the pulse ON width (duty ratio) of the drive pulse signal supplied to the switching element Q on the primary side based on the error signal.

By the way, the duty ratio (pulse ON width / switching period) of the DC / DC converter is usually set to 0.5 or less in terms of efficiency. Therefore, DC / D
The output voltage of the C converter is 5 times the output voltage of the main output circuit.
It is usually 0% or less. In addition, DC / DC
The output voltage of the DC / DC converter is restricted to a lower level when the voltage drop of the switching element or the rectifying element inside the converter is taken into consideration.

For example, the output voltage of the main output circuit is 5V, the duty ratio is 0.5, the saturation voltage of the switching transistor is 1V, and the forward voltage drop of the rectifying diode is 0.5.
5V, total voltage drop due to smooth choke and wiring is 0.2V
Then, the output voltage Vo of the DC / DC converter becomes Vo <(5-1-0.55-0.2) × 0.5, that is, 1.625V or less.

If the duty ratio of the DC / DC converter is set to 0.5 or more to obtain a DC voltage of 3.3V, the above voltage drop (1 + 0.55 + 0.
2 = 1.75 V is the allowable voltage drop (5-3.
3 = 1.7V) will be exceeded.

As described above, in the system using the DC / DC converter, the output voltage considerably lower than the main output voltage,
Specifically, it is less than 50% of the main output voltage and DC / D
There is a restriction that only a voltage lower than the main output voltage by 3V or more can be obtained in consideration of the voltage drop inside the C converter, and it is difficult to obtain each output having a small voltage difference such as 5V and 3.3V. It was

In the DC / DC converter,
When the load current is large, a heat sink has to be added to the switching element, which poses a problem that the layout is restricted and the power source size is increased.

As a method for reducing such restrictions between output voltages, as shown in FIG. 6, a secondary winding Ls' dedicated to the output circuit of the main transformer T is provided.
There is a method of switching the input from s'to the secondary output circuit 7 in synchronization with the switching on the primary side.

However, the control circuit 9 for switching the switching element Q2 of the secondary output circuit 7 in synchronism with the primary side switching element Q1 has a large-scale and complicated structure, which makes the apparatus large and increases the cost. It is inevitable to invite. Further, since there are a plurality of control circuits equipped with oscillators, it becomes necessary to take measures against beats and noise.

[0011]

As described above, DC / D
In the multiple output DC stabilized power supply device using the C converter, there is a problem that it is very difficult to obtain an output voltage with a small voltage difference between the output circuits. Also, in a device that has a secondary winding dedicated to the secondary output circuit of the main transformer so that an output voltage with a small voltage difference between the output circuits can be obtained, the input from the secondary winding to the secondary output circuit is applied to the primary side. There is a problem that a complicated control circuit for switching in synchronism with the above switching is required, resulting in an increase in size of the device and an increase in cost.

The present invention is intended to solve such a problem, and provides a stabilized multi-output power supply device with a simple circuit configuration and capable of obtaining an output voltage with a smaller voltage difference than each output circuit with high accuracy. Has an aim.

[0013]

In order to achieve the above object, a multi-output stabilized DC power supply device according to claim 1 of the present invention has a transformer, a switching element for switching a direct current supplied to the transformer, and an output of the transformer. A first output circuit that rectifies and smoothes the first DC voltage and outputs a first DC voltage, and a transformer that rectifies and smoothes the output of the first DC voltage within the range of 50% to 95% of the first DC voltage. A second output circuit that outputs a second DC voltage having a voltage difference of 3 V or less, and an error between the output voltage of the second output circuit and the reference voltage is detected, and a reset signal corresponding to the error is output. And a magnetic amplifier that controls the input of electric power from the transformer to the second output circuit so as to make the output voltage of the second output circuit constant based on the reset signal output from the control means. I will do it.

According to a second aspect of the present invention, in the multi-output stabilized DC power supply device, the first output circuit rectifies and smoothes the pulsed signal output to at least the secondary winding of the transformer to generate a direct current. It is characterized by comprising a diode for obtaining a current, a choke coil and a capacitor.

Further, in the multi-output stabilized DC power supply device according to claim 3 of the present invention, the second output circuit is a magnetic amplifier for controlling the input of the pulsed signal output to at least the secondary winding of the transformer. Of saturable reactor and pulsed signal input controlled by this saturable reactor,
It is characterized by comprising a diode, a choke coil and a capacitor which are smoothed to obtain a direct current.

According to a fourth aspect of the stabilized DC power supply device of the present invention, a saturable reactor for reducing noise is connected in series to the diode.

Further, a multi-output stabilized DC power supply device according to a fifth aspect of the present invention is characterized in that a snubber circuit is connected in parallel with at least the diode.

As described above, according to the present invention, the output voltage of the second output circuit on the low voltage side is in the range of 50% to 95% of the output voltage of the first output circuit on the high voltage side, and the voltage difference is 3V. In the case where the above conditions are satisfied, the power input from the transformer to the second output circuit on the low voltage side is controlled by the magnetic amplifier, so that the control width of the second output circuit on the low voltage side is controlled. Becomes wider. Therefore, with a simple circuit configuration, an output voltage having a smaller voltage difference than each output circuit can be obtained with high accuracy, and the device can be downsized and the cost can be reduced.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a multi-output DC stabilized power supply device (hereinafter simply referred to as a stabilized power supply device) which is an embodiment of the present invention.
FIG. 3 is a circuit diagram showing the configuration of FIG. As shown in the figure, this stabilized power supply device includes a main transformer T, an input circuit 11 connected to a primary winding Lp of the main transformer T, and a common secondary winding Ls of the main transformer T. It has a first output circuit 12 and a second output circuit 13 which are connected to each other. Hereinafter, the first output circuit 12 is called a main output circuit, and the second output circuit 13 is called a sub output circuit 13.

The input circuit 11 includes a bridge circuit 13 composed of four diodes for full-wave rectifying the input alternating current to convert it into a direct current, a capacitor C1 for smoothing the direct current after the full-wave rectification, and a main transformer T. And a switching element Q such as a transistor for switching DC power supplied to the primary winding Lp at a high frequency, and is connected to a PWM control circuit 14 for controlling the pulse ON width (duty ratio) of the switching element Q in a constant cycle. ing.

The main output circuit 12 includes rectifying diodes D1 and D2, a choke coil L1 and a capacitor C2 for rectifying and smoothing the pulsed signal output to the secondary winding Ls of the main transformer T to obtain a DC voltage of 5V. It consists of Then, the main output circuit 12 compares the main output voltage with an internal reference voltage and outputs an error signal, and the error signal of the comparator 15 is PWM.
A photocoupler 16 for returning to the control circuit 14 and the like are connected.

The slave output circuit 13 acts as a reactance on the pulsed signal output to the secondary winding Ls of the main transformer T to control the input of the pulsed signal, and a saturable reactor SR as a magnetic amplifier. Diodes D3 and D for rectifying and smoothing a pulsed signal input controlled by the saturable reactor SR to obtain a DC voltage of 3.3V
4, a choke coil L2 and a capacitor C3. The secondary output circuit 13 detects an error between the secondary output voltage and the internal reference voltage and supplies a reset current corresponding to the error to the saturable reactor SR through the resistor R1 and the backflow prevention diode D5. The control circuit 17 is connected.

Next, the operation of this stabilized power supply device will be described.

The alternating current input to the input circuit 11 is full-wave rectified by the bridge circuit 13 and converted into direct current, and then smoothed by the capacitor C1. The direct current is supplied to the primary winding Lp of the main transformer T as a pulse signal by the switching of the switching element Q at a high frequency, and is output to the secondary winding Ls as a pulse signal transformed.

The main output circuit 12 performs full-wave rectification on the pulsed signal output from the main transformer T by the diodes D1 and D2, rectifies and smoothes it by the choke coil L1 and the capacitor C2, and outputs a DC voltage of 5V. Supply to the load.
Here, the output voltage of the main output circuit 12 is divided by the resistors R2 and R3 and input to the comparator 15. The comparator 15 compares the detected output voltage with the internal reference voltage, and feeds back the error signal to the PWM control circuit 14 through the photocoupler 16. The PWM control circuit 14 controls the pulse ON width (duty ratio) of the drive pulse signal supplied to the switching element Q based on the error signal. As a result, stabilization control of the main output voltage is executed.

On the other hand, in the slave output circuit 13, among the pulsed signals output from the main transformer T, the pulsed signal which conducts one diode D3 is controlled in pulse width by the saturable reactor SR and then the other pulsed signal. A choke coil L together with a pulsed signal that conducts the diode D4
It is smoothed by 2 and the capacitor C3, and is applied to the load as a DC voltage of 3.3V. Here, the sub output circuit 13
The output voltage of the control circuit 17 is compared with the internal reference voltage, and the error signal is sent as a reset current through the resistor R1 and the backflow prevention diode D5 to the saturable reactor S.
Sent to R. The saturable reactor SR is magnetized by the reset current to a state before saturation during the period when the switching element Q is OFF, and prevents the pulse-like signal from flowing from the secondary winding Ls of the main transformer T after the switching element Q is turned ON. Block for a period of time depending on the degree of magnetization.
After the above time has elapsed, the secondary winding L of the main transformer T
The saturable reactor SR is saturated by the pulsed signal from s, the inductance is reduced, and the pulsed signal passes through the diode D3. In this way, by controlling the reset current flowing through the saturable reactor SR to control the blocking time of the pulsed signal that conducts the diode D3,
The slave output voltage is controlled.

In this stabilized power supply device, a high voltage (5
The main output circuit 12 on the V) side and the sub output circuit 13 on the low voltage (3.3 V) side are respectively connected to both ends of the common secondary winding Ls of the main transformer T, and the output of the main transformer T is the main output. The main output voltage of the circuit 12 is controlled to be a constant voltage. Then, the stabilized power supply device controls the pulsed signal input from the secondary winding Ls of the main transformer T to the low voltage side slave output circuit 13 by the saturable reactor SR to output the output voltage of the slave output circuit 13. Is configured to control.

FIG. 2 shows the control width on the low voltage side by the saturable reactor SR in comparison with the control width by the conventional DC / DC converter. As is clear from the figure, the control width on the low voltage side by the saturable reactor SR goes into the control range on the high voltage side, which is much wider than the control width by the conventional DC / DC converter.

With this configuration, even when the difference between the rated output voltages of the main and slave output circuits 12 and 13 is small, the constant voltage control of the slave output circuit 13 on the low voltage side has a sufficient power margin. It will be possible to do. That is,
According to this configuration, a multi-output type stabilized power supply device is achieved in which the ratio of the sub output voltage to the main output voltage is 50% or more and the difference between the main and sub output voltages is within 3V.

If a material having a high squareness ratio and a good saturation characteristic is used for the saturable reactor SR, the voltage drop value of the saturable reactor SR can be small, and as a result, the secondary output of about 95% of the main output voltage can be obtained. It is also possible to obtain a voltage.

Furthermore, by using a material having a low iron loss for the saturable rear tuttle SR, heat generation can be suppressed to a low level and a heat sink becomes unnecessary.

In the above embodiments, the main output voltage is controlled by the PWM control of the primary side switching element, but the present invention is not limited to the voltage control system on the main output side. Any other method may be used.

Further, in the above embodiment, each output circuit 1 is provided at both ends of the common secondary winding Ls of the main transformer T.
Although 2 and 13 are connected, two secondary windings having the same number of turns may be independently provided and the main output circuit and the slave output circuit may be connected to each secondary winding. Further, each output circuit may be connected to two secondary windings having the same number of turns and having the same ground side.

Further, the present invention is not limited to the forward type and can be applied to a flyback type power supply device,
In addition, self-excited switching drive system on the primary side
I don't care about encouragement.

[0036]

Next, embodiments of the present invention will be described.

FIG. 3 is a circuit diagram showing a multiple output DC stabilized power supply device according to an embodiment of the present invention. In this stabilized power supply device, the rated output voltage of the main output circuit is 5V and the rated output voltage of the slave output circuit is 3.3V. A saturable reactor SR is connected for voltage control of the slave output circuit. Further, in order to reduce noise, saturable reactors SR11, SR12, SR21, SR22 are connected in series with diodes D11, D12, D21, D22 in each output circuit.

As the saturable reactor, in order to prevent the saturable reactor from being unnecessarily reset due to the leakage current of the diode, for example, a Co type amorphous core having a high squareness ratio and a good saturation characteristic is used. More specifically, a core of Co type amorphous alloy having a toroidal shape having an outer diameter of 12 mm, an inner diameter of 8 mm and a height of 4.5 mm was put in a case, and a 1.0 mm diameter wire was made into three para wires and subjected to 5 turns. I used one.

Half-wave excitation (applied magnetic field 600 A / m,
The control range of the output pulse width of the main transformer is expanded by using a saturable reactor with a magnetic flux change of 100 mT or less in the saturation characteristic (right half surface due to the CMC characteristic) due to the frequency 100 kHz), and the voltage control of the secondary output circuit is performed. The accuracy of was improved. Furthermore, AC magnetic characteristics (applied magnetic field 80A
/ M, frequency 100 kHz), coercive force is 27 A
/ M or less, the reset current for controlling the saturable reactor can be reduced, and the iron loss can be further reduced to improve efficiency and heat generation surface, and no heat sink is required. .

In the control circuit of the slave output circuit, a shunt regulator IC21 having good temperature compensation is used to generate a reference voltage to be compared with the output voltage, and the reference voltage is 1.
It was set to 26V. A suitable ratio of the reference voltage to the output voltage is 0.3 to 0.76.

When the regulation characteristics of the load were confirmed in the above stabilized power supply device, the error with respect to the target of each of the master and slave output voltages could be suppressed within ± 0.8%.

As a countermeasure against unnecessary resetting of the saturable reactor and noise reduction, as shown in FIG. 4, the secondary winding Ls of the main transformer T for absorbing the leakage current of the rectifier diode to the secondary output circuit is absorbed. For example, capacitors C31 and C32 and resistors R31 and R in parallel with the input line of the pulse signal, that is, at least in parallel with the diode.
It is preferable to connect a snubber circuit composed of 32 series circuits. The snubber circuit is not limited to the series circuit of the capacitor and the resistance described above, but may be a circuit including only the capacitor or another impedance circuit. In the case of the flyback method, it is preferable to connect an impedance circuit in parallel with the main transformer.

Since the smaller the reset current is, the smaller the electric power can be controlled, it is preferable that the saturable reactor has a short average magnetic path length. Further, in order to reduce the reset drop due to the leakage current of the diode, the ratio 1 / h of the core average magnetic path length 1 and the height h is preferably 4 to 14.

Further, in FIG. 3, the positive side of the reset current controlling transistor Q21 and the positive side of the output voltage detecting resistor R22 in the control circuit of the secondary output circuit are connected to the positive output side of the secondary output circuit. However, by connecting this to the positive side of the main output circuit, it is possible to stop the operation of the slave output circuit when the output of the main output circuit goes down due to an abnormality.

[0045]

As described above, according to the multiple output DC stabilized power supply device of the present invention, the output voltage of the second output circuit on the low voltage side is the same as the output voltage of the first output circuit on the high voltage side. Fifty
% To 95% and satisfying the condition that the voltage difference is within 3 V, the control range of the second output circuit on the low voltage side is widened, so that the output circuit is simpler than each output circuit. An output voltage with a small voltage difference can be obtained with high accuracy, and the device can be downsized and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a multiple output DC stabilized power supply device that is an embodiment of the present invention.

FIG. 2 is a diagram showing a control width of the saturable reactor of FIG. 1 in comparison with a control width of a conventional DC / DC converter.

FIG. 3 is a circuit diagram showing a configuration of a multiple output DC stabilized power supply device that is an embodiment of the present invention.

FIG. 4 is a diagram for explaining unnecessary resetting of the saturable reactor and measures against noise.

FIG. 5 is a circuit diagram showing a configuration of a multi-output DC stabilized power supply device using a conventional DC / DC converter.

FIG. 6 is a circuit diagram showing the configuration of another conventional multi-output stabilized DC power supply device.

[Explanation of symbols]

 T: Main transformer Q: Switching element SR: Saturable reactor 12: First output circuit 13: Second output circuit 14: PWM control circuit Q 17: Control circuit

Claims (5)

[Claims] 1. A transformer, a switching element for switching a direct current supplied to the transformer, a first output circuit for rectifying and smoothing an output of the transformer and outputting a first direct current voltage, and an output of the transformer. A second output circuit that rectifies and smoothes the first DC voltage and outputs a second DC voltage within a range of 50% to 95% of the first DC voltage and having a difference from the first DC voltage of 3 V or less. A control unit that detects an error between the output voltage of the second output circuit and the reference voltage and outputs a reset signal according to the error; and the second output based on the reset signal output from the control unit. A multi-output stabilized DC power supply device, comprising: a magnetic amplifier that controls the input of electric power from the transformer to the second output circuit so as to make the output voltage of the circuit constant. 2. The first output circuit rectifies a pulsed signal output to at least a secondary winding of the transformer,
The multi-output stabilized DC power supply device according to claim 1, further comprising a diode, a choke coil, and a capacitor that are smoothed to obtain a DC current. 3. The saturable reactor as a magnetic amplifier that controls the input of the pulsed signal output to at least the secondary winding of the transformer, and the second output circuit is input controlled by the saturable reactor. 2. The stabilized multi-output power supply device according to claim 1, further comprising a diode, a choke coil, and a capacitor that obtain a direct current by rectifying and smoothing the pulsed signal. 4. The multi-output stabilized DC power supply device according to claim 2, wherein a saturable reactor for noise reduction is connected in series to the diode. 5. The multiple output stabilized DC power supply device according to claim 2, wherein a snubber circuit is connected in parallel with at least the diode.