JPH04285468A - Switching regulator - Google Patents

Abstract

PURPOSE:To suppress a variation in output voltages even if a load current is increased. CONSTITUTION:In structures in which outputs of first, second rectifiers 2, 3 are output in parallel and in series and the outputs are separately output (load currents are substantially equal), a current transformer 5 is not bypassed by bypass diodes 6, 7, currents I1, I2 of secondary windings of a transformer 1b for power conversion are balanced, and variations in output voltages V01, V02 are suppressed to a predetermined value or less. If load currents of the first, second outputs are largely different in the case of independent outputs, primary and secondary side induced voltages V1, V2 of the transformer 5 become a forward drop voltage Vd or more of the diode, and are bypassed by the diodes 6, 7. As a result, it becomes the same as the case where no transformer 5 exists to prevent variations in the voltages V01, V02 of first, second smoothing circuits 2, 3 to a predetermined value or more through the transformer 5.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is directed to switching regulators.
In particular, the DC voltage input to the primary winding of a transformer is intermittent, a predetermined DC voltage is generated from the first and second secondary windings having the same number of turns, and these DC voltages are This invention relates to a switching regulator that supplies current to a load in parallel, in series, or independently.

[0002] DC input/DC output power supply circuits such as DC/DC converters are generally used as power supplies for communication equipment used in exchanges and transmission equipment. A power supply with a voltage of 48V is converted to an output voltage of ±5V or ±12V and used as a power supply for communication equipment. For example, as an example of the power supply rating of communication equipment, input 4
8V, output 5V, current capacity 2-3A, output voltage fluctuation ±5
% or less, and is used as a power source for small capacity switching equipment.

0003

2. Description of the Related Art FIG. 3 is a block diagram of a conventional switching regulator. Reference numeral 1 denotes a power converter, which includes a capacitor 1a for power supply, and two first and second capacitors having the same number of windings. It has a transformer 1b having secondary windings C21 and C22, and a switching circuit 1c such as a transistor or FET that connects and disconnects the DC voltage input to the primary winding C11 of the transformer. Reference numerals 2 and 3 indicate first and second rectifying and smoothing circuits that rectify and smooth the output voltages of the first and second secondary windings, respectively, each of which is composed of two diodes, a coil, and a capacitor. There is. 4 turns on/off the switching circuit 1c based on the output voltage value V02 of the second rectifying and smoothing circuit 3.
A voltage control unit (CONT) which turns off and intermits the DC voltage input to the primary winding C11 of the transformer 1b, 5 has a primary winding C51 and a secondary winding C52 with the same number of windings, and has a power supply Current I on the first and second secondary windings of the conversion transformer 1b
It is a current transformer that balances 1 and I2.

According to this switching regulator,
For example, an output voltage of 5 V and 1 A can be obtained from the first and second rectifying and smoothing circuits 2 and 3, respectively.

Then, as shown in FIG. 4, the output terminals T11 and T21 of the first and second rectifying and smoothing circuits 2 and 3 are connected, and the output terminals T12 and T22 are connected, and the terminals T11 and T22 are connected.
By connecting the load between T22, 5V
, 2A, and a capacity of 10W. In this power supply circuit with a parallel connection configuration, the voltage control unit 4 detects the output voltage V02 (=V02=V0) and outputs the reference voltage V02.
r (=5V), and depending on the difference, the switching circuit 1c is turned on and off to intermittent the input voltage Vin, and is controlled so that V02=Vr at all times.

The current transformer 5 also functions as an impedance matching circuit that balances the secondary winding currents I1 and I2 of the power conversion transformer 1b. That is, the current transformer 5 matches the impedance so that the terminal voltages V1 and V2 at both ends of the primary winding C51 and the secondary winding C52 are the same, and connects the first and second secondary windings to the load. The same current is supplied from For example, when the secondary winding current I1 becomes larger than I2, the secondary winding C5 of the current transformer 5
A voltage V2 (>V1) is induced in V2, increasing I2, and as a result, I1 decreases, so that I1=I2. The same applies when the secondary winding current I2 becomes larger than I1.

On the other hand, as shown in FIG. 5, the output terminals T12 and T21 of the first and second rectifying and smoothing circuits 2 and 3 are connected,
By connecting a load between the terminals T11 and T22, a power source of 10V, 1A, and capacity 10W can be formed. In this series-connected power supply circuit, the voltage control section 4 detects the output voltage V02 and detects the reference voltage Vr(
= 5V), and according to the difference, the switching circuit 1c
The input voltage Vin is intermittent by turning on and off, and the input voltage Vin is always V0.
Control is performed so that 2=5V. Note that the same currents I1 and I2 constantly flow through the primary and secondary windings C51 and C52 of the current transformer 5 and are balanced, so that V1
= V2, and a stabilized output can be obtained.

Note that the voltage control section 4 can vary the output voltage by 120% or more, and in the case of parallel connection, the output voltage can be varied up to 6 V, the output current 1.6 A, and the capacity up to 10 W.
In addition, in the case of series connection, the output voltage is 12V and the output current is 0.
The capacity can be varied up to 8A and 10W.

Furthermore, the first output can be obtained independently from the terminals T11 and T12, and the second output from the terminals T21 and T22, without connecting the output terminals of the rectifying and smoothing circuits 2 and 3. For example, +5V, 1A, 5 from terminals T11 and T12
Outputs of -5V, 1A, and 5W can be obtained from W and terminals T21 and T22. In such an independent output configuration, even if the output voltage V02 of the rectifying and smoothing circuit 3 varies depending on the load, it is maintained at a constant value by feedback.

0010

[Problems to be Solved by the Invention] From the above, according to the configuration of the conventional switching regulator, the parallel connection output,
Series-connected outputs and independent outputs are possible, and one switching regulator has the advantage of being capable of three types of outputs.

However, in a configuration in which outputs are obtained independently from the rectifying and smoothing circuits 2 and 3, there is no problem if the currents I01 and I02 supplied to the load from each rectifying and smoothing circuit are approximately equal, but if they are significantly different, for example, I02 >When it comes to I01,
A problem arises in which the output voltage V01 of the first rectifying and smoothing circuit 2 fluctuates beyond a specified value. This is due to the following reasons. That is, the output voltage V02 of the second rectifying and smoothing circuit 3 is controlled to the reference voltage 5V by feedback control, but the output voltage V01 of the first rectifying and smoothing circuit 2 is not subjected to feedback, and Primary winding C of current transformer 5
A large voltage V1 corresponding to the difference between the primary and secondary currents (=I02-I01) is induced in the transformer 1b.
is synthesized with the secondary winding voltage Vn1 of output voltage V01 (=
This is because V1+Vn1) and fluctuates greatly.

From the above, it is an object of the present invention to provide parallel connection outputs,
It is an object of the present invention to provide a switching regulator which is capable of serially connected outputs and separate and independent outputs, and which can suppress fluctuations in each output voltage even in the case of independent outputs.

[0013]

[Means for Solving the Problems] FIG. 1 is a diagram illustrating the principle of the present invention. 1 has a power conversion transformer 1b having first and second secondary windings with the same number of windings, and a switching circuit 1c for intermittent DC voltage input to the primary winding of the transformer. A power converter, 2 and 3 are first and second rectifying and smoothing circuits that rectify and smooth the first and second secondary winding side output voltages Vn1 and Vn2, respectively; 4 is a second rectifying and smoothing circuit; A voltage control unit that turns on and off the switching circuit 1c based on the output voltage value to intermittently connect the DC voltage Vin input to the primary winding of the transformer 1b; 5 is a unit with the same number of windings;
The first winding in the transformer 1b has a secondary winding and a secondary winding.
A current transformer that balances the second secondary winding side currents I1 and I2, 6 and 7 are bypass diodes connected in parallel to the primary winding and secondary winding of the current transformer 5, respectively.

[0014]

[Operation] Output terminal T11 of the first and second rectifier circuits 2 and 3
and T21, and output terminals T12 and T22.
A parallel connection configuration in which the output terminals T12 and T21 are connected and a load is connected between the terminals T11 and T22, a series connection configuration in which the output terminals T12 and T21 are connected and a load is connected between the terminals T11 and T22, and a rectification smoothing circuit 2 and 3. Do not connect the output terminal, connect terminal T11
, T12 and the second output from terminals T21 and T22 (however, the load currents of the first and second outputs are approximately equal), the current transformer 5
are not bypassed by the bypass diodes 6 and 7, and the secondary winding side currents I1 and I2 operate in a balanced manner, suppressing fluctuations in the output voltages V01 and V02 to below specified values.

However, in the independent output configuration, if the load currents of the first and second outputs are significantly different, the induced voltages V1 and V2 on the primary and secondary sides of the current transformer 5 will be reduced by the forward drop of the bypass diode. The voltage becomes higher than Vd (≈0.6V) and is bypassed by bypass diodes 6 and 7. As a result, it is the same as if the current transformer 5 were not present, and it is possible to prevent the output voltage V01 of the first rectifying and smoothing circuit 2 from fluctuating beyond a specified value via the current transformer.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Overall Structure FIG. 2 is a block diagram of an embodiment of a switching regulator according to the present invention, and the same parts as in FIG. 1 are given the same reference numerals.

In the figure, reference numeral 1 denotes a power conversion section, which is equipped with a capacitor 1a for power supply and two secondary windings C21 and C22 with the same number of turns. It has a transformer 1b and a switching circuit 1c such as a transistor or FET that connects and disconnects the DC voltage Vin input to the primary winding C11 of the transformer.

Reference numerals 2 and 3 indicate first and second rectifying and smoothing circuits that rectify and smooth the output voltages of the first and second secondary windings, respectively, each consisting of two diodes, a coil, and a capacitor. It is configured. 4 is a voltage control unit (CONT) that turns on and off the switching circuit 1c based on the output voltage value V02 of the second rectifying and smoothing circuit 3 to intermittent the DC voltage Vin input to the primary winding C11 of the transformer 1b. ,
5 is a current transformer that has a primary winding C51 and a secondary winding C52 with the same number of windings, and balances the first and second secondary winding side currents I1 and I2 of the transformer 1b for power conversion;
6 and 7 are bypass diodes connected in parallel to the primary winding and secondary winding of the current transformer 5, respectively.

Overall operation (a) Output terminals T11 and T21 of the first and second rectifier circuits 2 and 3 connected in parallel
In a parallel connection configuration in which output terminals T12 and T22 are connected, a load is connected between terminals T11 and T22. The voltage control unit 4 controls the output voltage V02 (=V0
2=V0) is detected and compared with the reference voltage Vr, and depending on the difference, the switching circuit 1c is turned on and off to intermittent the input voltage Vin, and control is performed so that V02=Vr.

In this parallel connection configuration, the primary and secondary voltages V1 and V2 of the current transformer 5 are lower than the forward drop voltage Vd (≈0.6V) of the bypass diode. Therefore, the current transformer 5 is not bypassed by the bypass diode, and the transformer 1b
It operates to balance the secondary winding side currents I1 and I2, and supplies the same value of load current to the load from the first and second secondary winding sides.

(b) Series connection configuration: Output terminals T12 and T21 of the first and second rectifier circuits 2 and 3
The terminals are connected in series, and a load is connected between the terminals T11 and T22. As in the case of parallel connection, the voltage control section 4 detects the output voltage V02, compares it with the reference voltage Vr, and turns on/off the switching circuit 1c according to the difference to control the input voltage Vi.
n is intermittently controlled so that V02=Vr.

In such a series connection configuration, the secondary winding currents I1 and I2 of the transformer 1b are always equal, and therefore the primary and secondary induced voltages V1 and V of the current transformer 5 are
2 is the forward drop voltage Vd of the bypass diode (≒0
．． 6V) or less, and therefore the current transformer 5 is not bypassed by the bypass diode.
Stable output can be obtained.

(c) The output terminals of the independent output configuration rectifier and smoothing circuits 2 and 3 are not connected to each other,
A first load is connected between terminals T11 and T12, and terminal T2
A second load is connected between T1 and T22.

[0024] In such an independent output configuration, the first and second
The load currents I01 and I0 output from the rectifier circuits 2 and 3 of
2 are substantially equal, the primary side of the current transformer 5,
The secondary side induced voltages V1 and V2 are lower than the forward drop voltage Vd (≈0.6V) of the bypass diode. Therefore, the current transformer 5 is not bypassed by the bypass diodes 6, 7, and the secondary winding side currents I1,
Even if there is a slight difference in I2, fluctuations in the output voltages V01 and V02 can be suppressed to below a specified value.

However, when the load currents I01 and I02 output from the first and second rectifier circuits 2 and 3 are significantly different (for example, I01<I02), one of the current transformers 5
The next side induced voltage V1 becomes higher than the forward drop voltage Vd (≒0.6V) of the bypass diode, and the bypass diode
Bypassed by mode 6. As a result, it is the same as if the current transformer 5 did not exist, and the load currents I01 and I0
2 is large, the output voltage V01 of the first rectifying and smoothing circuit 2 is prevented from fluctuating beyond a specified value via the current transformer 5. The same applies to the case of I01>I02.

The present invention has been explained above using examples, but
The present invention can be modified in various ways according to the gist of the present invention as described in the claims, and the present invention does not exclude these modifications.

[0027]

As described above, according to the present invention, since a current transformer is provided that balances the currents on the first and second secondary winding sides of a power conversion transformer, a single switching regulator can provide parallel connection output and series connection output. Three types of outputs are possible: connected output and independent output, and when the load current of each output is significantly different in the case of independent output, the primary and secondary windings of the current transformer are bypassed with a bypass diode. Because of this configuration, it is possible to eliminate the negative effects of the current transformer when the load current varies greatly, and it is possible to suppress voltage fluctuations of each output within the specified range.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the present invention.

FIG. 2 is a configuration diagram of an embodiment of the present invention.

FIG. 3 is a configuration diagram of a conventional switching regulator.

FIG. 4 is a configuration diagram of a conventional parallel connection.

FIG. 5 is a configuration diagram of a conventional series connection.

[Explanation of symbols]

1. Power conversion section 1b...trans 1c...Switching circuit 2, 3...first and second rectifying and smoothing circuits 4...Voltage control section 5. Current transformer 6, 7... Bypass diode

Claims (1)

[Claims] 1. A power converter unit comprising a transformer having first and second secondary windings having the same number of windings, and a switching circuit that intermittents a DC voltage input to the primary winding of the transformer. , first and second rectifying and smoothing circuits that rectify and smooth the output voltages of the first and second secondary windings, respectively, and a primary winding and a secondary winding having the same number of windings. , turning on and off the switching circuit based on the output voltage value of a current transformer that balances the first and second secondary winding currents in the transformer and one of the first and second rectifying and smoothing circuits; The current transformer is characterized by comprising a voltage control section that intermittents the DC voltage input to the primary winding of the transformer, and bypass diodes connected in parallel to the primary winding and the secondary winding of the current transformer, respectively. switching regulator.