JPS6051458A - Dc/dc converter - Google Patents

Abstract

PURPOSE:To simplify a circuit configuration by forming a coupling choke coil in a DC/DC converter of 2-output construction of ringing choke coil type in a tapped choke coil, thereby reducing the number of parts. CONSTITUTION:An input power source Vin is connected through a switching transistor 11 between one end of a winding 20P of a choke coil with taps operating as a coupling choke coil and the tap 21. A rectifying and smoothing circuit which has a diode 25a and a condenser 25b is connected to both ends of the winding 20P, a rectifying and smoothing circuit which has a diode 23a and a condenser 23b is connected to both ends of the winding 20S, and two output voltages are supplied to loads 26a, 26b. Accordingly, since the choke coil 20 with the taps of substantially 100% of coupling rate is used as the choke coil, a snubber CR circuit can be eliminated, and the choke coil itself can be reduced in size.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a ringing choke coil type DC-DC
Concerning converters.

[Technical background of the invention and its problems]

FIG. 1 is a circuit diagram showing an example of a conventional ringing choke coil type two-output DC-DC converter. In FIG. 1, the input voltage vIn is, for example, a smoothed direct current (DC) voltage of 5V. 10 is a coupling choke coil, which has a primary winding 10P on the input side and 2 on the output side.
The next winding consists of 1081.10S2. Furthermore, 11 is a switching transistor, which is controlled on and off by a control signal from a control circuit 12, and output voltages VO, VO,
Perform 2 stabilization. This control circuit 12 includes, for example, an error amplifier, and this error amplifier has an output voltage Vol,
The configuration is such that a voltage proportional to one or the combined value of vo2 is applied to one input terminal, and a reference voltage is applied to the other input terminal. Then, a pulse signal based on the output of the error amplifier is supplied to the switching transistor 11 as a control signal.

On the output side, rectifying diodes 13&, 13b and output voltage smoothing capacitors 14m, 14b are connected to each of the secondary windings 1081 and 10S2, respectively. Output terminals 15m and 15b are connected to one terminal of each of the capacitors 14a and 14b, and output DC voltages vO1 and Vo of 12V and -12V, for example, are output from these output terminals 15a and 15b. Further, the other terminal of each of the capacitors 14a and 14b is a common terminal 16a.

16b.

With the above-mentioned converter, it is possible to obtain two predetermined output DC voltages Vo 1 and Vo 2 for the input DC voltage "in." Here, the above-mentioned converter has a There is a snubber (5nubbe) on the input side.
A capacitor 17a and a resistor 17b constituting the CR circuit 17 for r) are provided. This snubber CR circuit 17 is provided to suppress transient voltage when the switching transistor 11 is turned off. As a result, it is possible to reduce the leakage inductance from the primary winding of the coupling choke coil 100 and the leakage voltage when the transistor 1 is turned on, thereby stabilizing the voltage conversion operation of the converter.

However, by providing the snubber CR circuit 17, the number of components in the conventional converter increases, and in a two-output configuration, the coupling choke coil 10 has three windings, which makes the circuit configuration complicated. .

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide DC-D with a simple circuit configuration even in the case of a two-output configuration.
C voltage conversion can be realized and the number of parts can be reduced D
An object of the present invention is to provide a C-DC converter.

[Summary of the invention]

In the present invention, a ringing choke coil type DC-D
In the C converter, a tapped choke coil is provided as a coupling choke coil. An output common terminal is connected to the tap of this tapped choke coil, and a first rectifying and smoothing circuit consisting of a capacitor and a diode is provided between this tap and one end of the choke coil. Further, a second rectifying and smoothing circuit consisting of a capacitor and a diode is provided between the tap and the other end of the tip coil. The first and second rectifiers are connected to one end of each capacitor of the first and second rectifier and smoothing circuits.
output terminal is connected. With such a configuration, the circuit configuration around the coupling choke coil can be simplified, and the snubber CR circuit can be omitted.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a circuit diagram showing the configuration of a DC-DC converter according to one embodiment. In Figure 2, 11
is a switching transistor, and a positive voltage, for example, is supplied to the collector from the input DC power supply vIn. 20 is a tapped choke coil that operates as a coupling choke coil, and input D Clj pressure is supplied from the emitter of transistor 1 to one end on the primary winding 20P side.

In this tapped choke coil 20, the negative voltage of the input DC power supply vin is supplied to a tap (C center tap) 21, and the tap is further connected to an output common terminal 22 on the output side. Also, the secondary winding z of the tapped choke coil 2θ
The anode side of a diode 23a is connected to one end on the oS side, and one output terminal 24a is connected via this diode 23a. The diode 23a has one end connected to the output terminal 24th and a capacitor 23b on the cathode side, and forms a rectifying and smoothing circuit together with the capacitor 23b.

The other end of the capacitor 23b is connected to the output common terminal 22 together with the tap 21 of the choke coil 6-20.

On the other hand, a diode 25 is connected to one end of the choke coil 20 on the primary winding 20P side along with the emitter of the transistor 11.
m is connected to the cathode side thereof, and the other output terminal 24b is connected via this diode 25m. The diode 25a has an output terminal 24b and one end of a capacitor 25b connected to its anode side, and forms a rectifying and smoothing circuit together with the capacitor 25b. The other end of the capacitor 25b is connected to the output common terminal 22 together with the tap 2 of the choke coil 20. The output common terminal 22 and each output terminal 24a.

A load resistor 26a is provided between each of 24b and 24b.

26b is provided. Note that the transistor 11 is turned on and off by a control signal from a control circuit (similar to that shown in FIG. 1) 12.

The operation of the DC-DC converter having such a configuration will be explained. First, switching transistor 1
1 is turned on, the input DC voltage Vin is applied to the primary winding m20P side of the choke coil 20, and the current in the choke coil 20 is accumulated over time according to the on period of the transistor 1. Then, when the transistor 11 is turned off at a predetermined time, the current accumulated in the choke coil 20 flows from the primary winding 20P through the capacitor 25b and the diode 25a, and an output voltage o2 is generated at the load resistor 26b, that is, the output terminal 24b. . at the same time,
A current from the secondary winding 2O8 of the choke coil 20 flows through the diode 23a and the capacitor 23b, producing an output voltage VO1 at the load resistor 26a or output terminal 24a.

Here, if the coupling rate between each winding 20P and 208 is 1.00%, the voltage v8 induced in the secondary winding 20S is as follows. N1: Number of turns of the primary winding 20P N2: Secondary Number of turns Vo2 of the winding 20S: voltage between terminals of the capacitor 25b vF: forward voltage drop of the diode 25IL.

From the above formula (1), the output voltage v01, that is, the capacitor 23
The voltage between the terminals of b is as follows, where V, , : is the forward voltage drop of the diode 23h. That is, the output voltage V. , , is determined by the ratio (N2/Nl) of the number of windings of each winding 20P, 20S of the vo2fd choke coil 20. Further, the number of 8-pins is determined from the inductance of the choke coil 20 used in the converter.

As described above, a given output DC@voltage V for an input DC voltage V in . , , Vo can be converted into voltage and output. In this case, since no transient voltage is generated when the transistor 11 is off, the capacitor and resistor of the conventional snubber CR circuit can be eliminated.
In the conventional converter (FIG. 1), since the coupling ratio of the coupling choke coil is not 100 tI), a snubber CR circuit is required to absorb the magnetic energy due to the leakage inductance of the primary winding. On the other hand, in the present invention, a tapped choke coil with a coupling ratio of approximately 100 inches is used as the coupling choke coil, so the snubber CR circuit can be made unnecessary. In addition, in a two-output configuration, conventional choke coils were used with three windings, but in the present invention, as shown in FIG. The configuration can be simplified. Furthermore, C for snubber
Since the R circuit can be eliminated, loss of excitation energy due to the snubber CR circuit can be prevented, and voltage conversion efficiency can be improved.

〔Effect of the invention〕

As detailed above, according to the present invention, a snubber CR circuit can be made unnecessary by using a tapped choke coil as a coupling choke coil in a ringing choke coil type DC-DC converter. can. Therefore, the capacitor and resistor used in the snubber CR circuit can be eliminated, and the number of parts required for the circuit configuration can be significantly reduced. Furthermore, even in the case of a two-output configuration, since it can be realized using a tapped choke coil, the coupling choke coil can be downsized, and as a result, the circuit configuration of the entire converter can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of a conventional DC-DC converter, and FIG. 2 is a circuit diagram showing the configuration of a DC-DC converter according to an embodiment of the present invention. 11...Switching transistor, 13a. 13b123a, 25a...Diode, 14a. 14b, 23b, 25b... Capacitor, 20...
Choke coil with tap, 22...Output common": f,
f, 24a, 24b...output terminals. 11- Figure 1 Figure 2

Claims (1)

[Claims] A ringing choke coil type DC-DC converter includes a switching transistor whose operating state is controlled based on the fed-back output DC voltage, and which controls the operation of the switching transistor. Accordingly, the input DC voltage is supplied to one end and the output common terminal is connected to the tap.
a first rectifying and smoothing circuit consisting of a diode and a capacitor connected in series between the output common terminal connected to the tap of the tapped choke coil and one end of the tapped choke coil; A second rectifier consisting of a diode and a capacitor connected in series between the other end of the choke coil and the output common terminal. a smoothing circuit, the first rectifier; a first output terminal connected to one end of the capacitor of the smoothing circuit to generate a first output DC voltage; and the second rectifier. The second output D is connected to the other end of the capacitor of the smoothing circuit.
A DC-DC converter comprising a second output terminal that generates a C voltage.