JP2969985B2 - DC / DC converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC / DC converter,
In particular, it relates to an auxiliary power supply circuit for operating a control circuit of a DC / DC converter.

[0002] With the spread of electronic circuits in recent years, DC / DC converters for supplying a DC voltage to various electronic circuits have been increasingly used. Recent DC /
The DC converter intermittently switches a switching element connected in series to a primary winding of a transformer connected to a DC power supply.
The mainstream is a switching power supply that smoothes the voltage induced in the next winding and supplies it to a load.

In this switching power supply, an output voltage is monitored by a control circuit, and the continuity ratio of the switching element is changed by the voltage to maintain the output voltage at a specified value. However, the control circuit itself is also constituted by an electronic circuit. Therefore, a DC power supply for operation is required. However, the configuration of the DC / DC converter is complicated in order to create a DC power supply (hereinafter, referred to as an auxiliary power supply) for operating the control circuit.
When the output for the auxiliary power supply is taken out from the transformer for outputting the main power supply to simplify the configuration, the output capacity of the main power supply decreases unless the transformer is enlarged.

Therefore, there is a need for a DC / DC converter that has a simple configuration and does not reduce the output capacity of the main power supply.

[0005]

2. Description of the Related Art FIG. 4 is a circuit block diagram of a conventional DC / DC converter, and FIG. 5 is another circuit block diagram of the prior art.

In FIG. 4, the transistor Tr ₁₁ is turned on and off under the control of the main control circuit 14, and the current from the DC power supply 11 flowing through the primary winding of the transformer T ₁₁ is turned on and off. The intermittent current is induced in the secondary winding of the transformer T _11, is supplied to the load is smoothed in the smoothing circuit 12. Its output voltage is monitored in the main control circuit 14, by changing the intermittent ratio of the control pulse is outside the range of the output voltage of the provisions for the transistor Tr ₁₁ maintains the output voltage to a prescribed range.

It is necessary to supply a DC voltage as a power supply for operation to the main control circuit 14 itself which performs the above operation.
In, DC / DC converter comprising a transformer T ₁₂ and the smoothing circuit 13 and the auxiliary control circuit 15 constitutes the auxiliary power supply. When the power is turned on, the auxiliary control circuit 15 does not operate.However, only at the time of startup, the auxiliary control circuit 15 is started by a startup power supply (not shown), and once started, the DC voltage output through the smoothing circuit 13 is mainly controlled. It is supplied as operating power for the circuit 14 and the auxiliary control circuit 15.

Therefore, in the case of FIG. 4, the DC /
Since the DC / DC converter is provided, the scale of the entire DC / DC converter becomes large and the price becomes high.
FIG. 5 is a circuit block diagram of a system that avoids providing two sets of DC / DC converters. In the case of FIG.
The secondary winding ₂₁ is composed of two windings for a main power supply and an auxiliary power supply. Smoothing circuits 22 and 23 are connected to the two windings to supply the former to a load and the latter to a control circuit 24. The operating power of the control circuit 24 at the time of startup is supplied from the DC power supply 21 through the series dropper 25, but the output voltage of the smoothing circuit 23 is
By setting the output voltage to be higher than the output voltage of 25, power supply from the inefficient series dropper 25 is hardly performed after startup.

[0009] scheme in Figure 5 is also low simple pricing structure than the method of FIG. 4, to provide a winding of the auxiliary power supply to the secondary winding of the transformer T _21, that much of the main power supply Output capacity decreases. Further, the transformer T ₂₁ becomes large when not to decrease the output capacity, there is a high possibility that the transformer T ₂₁ is a factor that inhibits contrast demand for miniaturization of the apparatus in recent.

[0010]

SUMMARY OF THE INVENTION DC /
The DC converter is complex and expensive because of the power supply for operating the control circuit.If a simple configuration is adopted, the output capacity of the main power supply decreases, and the transformer becomes large and small. A problem arises that hinders the conversion.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a DC / DC converter having a high efficiency of a main power supply, a simple configuration, and easy downsizing.

[0012]

FIG. 1 is a diagram illustrating the principle of the present invention. In the figure, 1 is a DC power supply supplied to a DC / DC converter, 2 is a switch circuit connected in series to a primary winding of a main transformer 3 for interrupting DC current from the DC power supply 1, and 3 is a primary circuit. A main transformer having one end connected to one pole of the DC power supply 1 and the other end connected to the other pole of the DC power supply 1 via the switch circuit 2, and a secondary winding 4 of the main transformer 3. And a smoothing circuit for smoothing the voltage induced in the secondary winding and outputting the smoothed voltage to the load, and 5 for monitoring the output voltage of the smoothing circuit 4 to control the switch circuit 2 and adjust the output voltage. Control circuit.

6 is a diode, 7 is a primary winding and an auxiliary power transformer in which the diode 6 connected in series with the primary winding is connected in parallel with the primary winding of the main transformer 2. 8 is an auxiliary power supply smoothing circuit that is connected to the secondary winding of the auxiliary power supply transformer 7 and smoothes the voltage induced in the secondary winding, and supplies as an operating power supply for the control circuit 5.
Reference numeral 9 denotes a series dropper for inputting a DC voltage from the DC power supply 1 to reduce the voltage and supplying the power supply voltage of the control circuit 5 at the time of starting.

[0014]

The switching circuit 2 in FIG. 1 is interrupted by a control pulse (not shown) from the control circuit 5 in a steady state. As a result, the DC current from the DC power supply 1 flowing through the primary winding of the main transformer 3 is interrupted, and a voltage is induced in the secondary winding. This induced voltage is smoothed in the smoothing circuit 4 and supplied to the load. The output voltage to the load is monitored by the control circuit 5, and when the output voltage deviates from the specified range, the control circuit 5 changes the on / off ratio of the control pulse to the switch circuit 2 to adjust the output voltage.

At this time, the intermittent current also flows through the primary winding of the auxiliary power supply transformer 7 connected in parallel with the main transformer 3, so that a voltage is induced in the secondary winding and the auxiliary power supply smoothing circuit 8 A DC voltage is output via the. This DC voltage is supplied to the control circuit 5 as a power supply for operation of the control circuit 5. The diode 6 prevents the current flowing through the auxiliary power supply transformer 7 from causing a ripple due to the electromotive force induced in the main transformer 3 when the switch circuit 2 is turned off.

The operation in the steady state has been described above. At startup, the DC voltage for operation of the control circuit 5 is supplied through the series dropper 9 by reducing the voltage of the DC power supply 1.
Once started, the control circuit 5 operates with the DC voltage output from the auxiliary power supply smoothing circuit 8 as described above. As described in the related art, after the startup, the output voltage from the auxiliary power supply smoothing circuit 8 set to a value higher than the DC voltage from the series dropper 9 is mainly used.

In the above configuration, the DC / DC dedicated to the auxiliary power supply is used.
Since a converter is not used, the circuit configuration is simplified,
A low-cost DC / DC converter can be realized. Further, since the auxiliary power transformer 7 is provided separately from the main transformer 3,
The DC power output from the main transformer 3 does not decrease because of the auxiliary power supply, and therefore, it is not necessary to increase the size of the main transformer 3 for securing capacity. Usually, the largest component used in one device limits the miniaturization of the device. However, in the DC / DC converter having the above configuration, the main transformer 3 which is likely to be the largest component is large. Since it is not necessary to reduce the size of the device, it is possible to eliminate the obstacles to the miniaturization of the device.

[0018]

2 and 3 show a circuit block diagram of an embodiment of the present invention.
FIG. In the figure, the same objects as those in FIG.
Shown, Tr_{twenty one}Is a transistor constituting the switch circuit 2
Ta, T₃₁Is the main transformer, T₇₁Is the auxiliary power transformer, D
_41,D ₄₂, D_61,D_81,D₈₂Is a diode, L_41,L₈₁
Is a coil, C_41,C₈₁Is a capacitor.

FIG. 2 is a circuit block diagram showing an embodiment according to the principle diagram of FIG. 1, and its operation and effect are shown in FIG.
The operation is simply described because it is the same as that described above. Although the control circuit 5 is not shown in detail, it is of a well-known technique. The transistor Tr ₂₁ is turned on and off by the control pulse sent from the control circuit 5 to the transistor Tr ₂₁ ,
While intermittently current flowing through the primary winding of the transformer T _31, the transistor Tr ₂₁ is the power induced in the secondary winding side of the transformer T ₃₁ The longer in the ON increases. The control circuit 5 monitors the output voltage of the smoothing circuit 4, and when the output voltage is out of the specified range, changes the continuity ratio to secure the output voltage in the specified range.

As described above, the transistor Tr ₂₁
Because There electromotive force is generated in the direction of the transformer T ₃₁ and T ₇₁ the current flowing to it when turned off, generating power is larger than the transformer T ₃₁ large capacity,
So that this electromotive force is not generated ripple voltage by flowing to the transformer T _71, the diode D in the direction shown in Figure 2
₆₁ is inserted.

The configuration of FIG. 2 is simple because it does not need to have two sets of DC / DC converters including a control circuit as shown in FIG.
The capacity of the main transformer does not decrease due to the winding of the auxiliary power transformer as in the above.

FIG. 3 is a circuit block diagram of an embodiment in which two sets of DC / DC converters are used. Assume that converter A and converter B in the figure have exactly the same configuration,
Internal components are indicated by the same symbols.

In FIG. 3, each of the converters A and B has a control circuit 5, but the operating power is supplied from the same auxiliary power supply circuit. The input of the auxiliary power circuit is drawn from the converter A side,
The operation does not change at all even if it is pulled in from the converter B side. Since the DC voltage output from the series dropper 9 of the auxiliary power supply circuit and the auxiliary power supply smoothing circuit 8 is supplied in parallel to the control circuits 5 of the converters A and B, both the converters A and B are the same as those in FIG. Perform the operation.

In the case of FIG. 3, since only one set of auxiliary power supply circuit is required for two sets of DC / DC converters, the structure is much simpler and more economical than, for example, the structure shown in FIG. 4 of the prior art. It is also advantageous. Further, when two sets of DC / DC converters are formed by the conventional technique shown in FIG. 5 to form one set of auxiliary power supply, for example, one converter has the auxiliary power supply as shown in FIG. FIG.
It is necessary to use different types of converters, such as a configuration having no auxiliary power supply like the converter B.
Further, since the capacity of the auxiliary power supply shown in FIG. 5 changes depending on the number and scale of the control circuits to be supplied, it is necessary to prepare a plurality of combinations in the converter of FIG. 5 depending on the capacity of the main converter and the capacity of the auxiliary power supply. The type of converter becomes complicated. In the method of FIG. 3, even when the number of DC / DC converters is two or more, the main converters each have an optimum capacity, and the auxiliary power supply has a capacity corresponding to the number of main converters to be supplied and the total capacity. Can be provided independently, so that there is an advantage that the type and configuration are simplified.

The embodiment of the present invention has been described above with reference to FIGS. 2 and 3. However, FIGS. 2 and 3 merely show the embodiment of the present invention. Of course, the configuration is not limited. For example, it is clear that the same effect can be obtained even if the configuration of the smoothing circuit 4 is different from those shown in FIGS.
The transistor Tr ₂₁ constituting a is not limited to the embodiment shown is of course. Further, although the DC power supplies 1 of the converter A and the converter B in FIG. 3 are shown separately, it is needless to say that the same power supply may be used, and the present invention does not exclude these modifications.

[0026]

As described above, according to the present invention,
The configuration of the auxiliary power supply portion in the DC / DC converter is simplified, and the capacity of the main transformer of the converter is not reduced due to the auxiliary power supply, so that the efficiency of the main power supply is improved and the main transformer is prevented from being enlarged. DC / D
The downsizing of the C converter is not hindered. Also,
When a plurality of DC / DC converters are used, it is easy to provide an independent auxiliary power supply having a simple configuration in common to the plurality of DC / DC converters.
The complexity of the type of C / DC converter can be avoided, and the entire converter system can be configured simply and economically.

As described above, the present invention greatly contributes to the downsizing of the DC / DC converter and the efficiency of the main power supply.

[Brief description of the drawings]

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

FIG. 2 is a circuit block diagram of an embodiment of the present invention (1).

FIG. 3 is a circuit block diagram of an embodiment of the present invention (2).

FIG. 4 is a circuit block diagram of a conventional technique (1).

FIG. 5 is a circuit block diagram of a conventional technique (2).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DC power supply 2 Switch circuit 3 Main transformer 4 Smoothing circuit 5 Control circuit 6 Diode 7 Auxiliary transformer 8 Auxiliary power supply smoothing circuit 9 Series dropper

Claims (1)

(57) [Claims] A primary transformer having one end of a primary winding connected to one pole of a DC power supply (1) and the other end connected to the other pole of the DC power supply (1) via a switch circuit (2). 3) a smoothing circuit (4) connected to the secondary winding of the main transformer (3) for smoothing the voltage induced in the secondary winding and outputting the smoothed voltage to the load; Monitoring the output voltage and the switch circuit (2)
And a control circuit (5) for controlling the output voltage and controlling the output voltage.
In the C / DC converter, a primary winding and a diode (6) connected in series to the primary winding are connected to the main transformer.
Auxiliary power transformer connected in parallel with the primary winding of (2)
And (7) an auxiliary power supply smoothing circuit connected to the secondary winding of the auxiliary power transformer (7) for smoothing the voltage induced in the secondary winding and supplying it as an operating power supply for the control circuit (5). (8)
And a series dropper (9) for inputting a DC voltage from the DC power supply (1) to reduce the voltage and supplying a power supply voltage of the control circuit (5) at the time of startup. DC converter.