KR100219289B1 - Dc-dc converter - Google Patents

Abstract

The first switching element (transistor) 12 is connected to one end of the primary winding 11 connected to the power supply 10, and is connected to the connection point 16a of the primary winding 11 and the switching element 12. A first output voltage V1 output through the rectifying diode 13a; Second rectifying diodes 13b and 13c are connected to the output side of the secondary windings 14b and 14c which are magnetically coupled to the primary winding 11, and are output through the second rectifying diodes 13b and 13c. A second output voltage V2; And a third output voltage V3; In the DC-DC converter having the capacitor, capacitors 15b and 15c are connected between the output side of the secondary windings 14b and 14c and the second rectifying diodes 13b and 13c, and the capacitors 15b and 15c are connected to each other. Third rectifying diodes 18b and 18c are formed between the connection points 16b and 16c with the second rectifying diodes 13b and 13c and the grounds 17b and 17c. By such a configuration, the present invention aims to provide a multi-output type DC-DC converter capable of controlling each output voltage and having high conversion efficiency.

Description

DC-DC converter

1 is a circuit diagram of one embodiment of a DC-DC converter according to the present invention.

2 is a circuit diagram of another embodiment of the DC-DC converter according to the present invention.

3 is an operational waveform diagram showing characteristics of the output voltage.

4 is a circuit diagram of a conventional DC-DC converter.

5 is a circuit diagram of another conventional DC-DC converter.

* Explanation of symbols for main parts of the drawings

10: power source 11-primary winding

12: switching element (transistor) 13a: first rectifying diode

13b, 13c: 2nd rectifier diode 14b, 14c: secondary winding

15b, 15c: condenser 16a, 16b, 16c: connection point

17b, 17c: ground 18b, 18c: third rectifier diode

19: control circuit

The present invention relates to a DC-DC converter, and more particularly, to a multi-output DC-DC converter having a good conversion efficiency.

4 shows a conventional DC-DC converter. This is a circuit called a flyback converter, and the first output voltage V1, the second output voltage V2, and the third output voltage V3 are magnetically coupled to the primary winding 41, respectively. It is output from the secondary windings 42a, 42b and 42c which are through the rectifying diodes 43a, 43b and 43c. By adjusting the number of turns of the secondary windings 42a, 42b and 42c and the polarity of the rectifying diodes 43a, 43b and 43c, an arbitrary positive or negative output voltage is output. It is possible. In this circuit, each output voltage Vn (n = 1, 2, 3, ...) is represented by the equation (1).

Here, Vin denotes an input voltage, D denotes an on duty of the switching element 44, np denotes the number of turns of the primary winding, and nsn denotes the number of turns of the nth secondary winding.

This method detects any one output voltage, for example, the first output voltage V1, controls d to control V1 to be a constant voltage, and then (D / 1-D) × Vin It is always a constant value. Accordingly, the second output voltage V2 and the third output voltage V3 also have a ratio of (ns1 + ns2) / np and (ns1 + ns2 + ns3) / np between the number of turns of the secondary winding and the number of turns of the primary winding. Therefore, the constant voltage is controlled.

5 shows another conventional DC-DC converter. This is a circuit called a boost chopper method. In this circuit, the first output voltage V1 is directly output from the primary winding 41 through the rectifying diode 43a. The second output voltage V2 and the third output voltage V3 are rectified diodes from the secondary windings 42b and 42c magnetically coupled to the primary winding 41, similarly to the flyback converter of FIG. It is output through 43b and 43c. By inverting the polarities of the rectifying diodes 43a, 43b and 43c, it is possible to invert the polarity of the output voltage.

This method has the advantage that the conversion efficiency for directly outputting the output voltage from the primary winding 41 connected to the input voltage Vin with respect to the first output voltage V1 is good.

However, in the flyback converter, since the primary winding 41 and the secondary windings 42a, 42b and 42c are completely separated from each other, the primary winding 41 and the secondary windings 42a, 42b and 42c are used. The coupling between) contributes greatly to the conversion efficiency. That is, if the coupling degree is not high, there is a problem that the conversion efficiency does not increase. In order to increase the coupling degree, it is necessary to use a means such as using a shielding core in the transformer.

On the other hand, in the step-up chopper method, the first output voltage V1 is represented by the formula (2), and the nth output voltage Vn (n = 2, 3,...) Output from the (n-1) th secondary windings. ) Is represented by equation ③.

Here, Vin denotes an input voltage, D denotes an on duty of the switching element 44, np denotes the number of turns of the primary winding, and nsn denotes the number of turns of the (n-1) th secondary winding.

In this system, if the first output voltage V1 is controlled to be constant, (1 / (1 / D)) × Vin becomes constant, but the second output voltage V2 and the third output voltage V3 are constant. Cannot be controlled. As a result, since the variation value D also exists in the first term in addition to (1 / (1-D)) × Vin of the second term in the formula (3), when the input voltage Vin changes, the second output voltage V2 and the third There is a problem that the output voltage V3 also fluctuates.

An object of the present invention is to provide a multi-output DC-DC converter capable of controlling each output voltage and having high conversion efficiency.

In order to solve the above problems, the present invention, the switching element is connected to one end of the primary winding connected to the power supply, and output through the first rectifying diode connected to the connection point between the primary winding and the switching element Output voltage; A second rectifying diode is connected to an output side of at least one secondary winding that is magnetically coupled to the primary winding, and an output voltage corresponding to the number of the secondary windings output through the second rectifying diode; In a DC-DC converter having a capacitor, a capacitor is connected between an output side of the secondary winding and the second rectifying diode, and a third rectifier is connected between the capacitor and the second rectifying diode and ground. It is a DC-DC converter characterized by the diode being connected.

An anode of the second rectifying diode and the capacitor are connected, and an anode of the third rectifying diode and the ground are connected.

The cathode of the second rectifying diode is connected to the capacitor, and the cathode of the third rectifying diode is connected to the ground.

The DC-DC converter according to claim 1, wherein in the DC-DC converter, a capacitor is connected between the output side of the secondary winding and the second rectifying diode, and is connected between the connection point of the capacitor and the second rectifying diode and ground. Since the three rectifier diodes are connected, all amplitude values of the AC voltage generated in the (n-1) th secondary winding as the nth output voltage Vn can be derived.

The first output voltage V1 can be output directly from the primary winding through the first rectifying diode.

In the DC-DC converter according to claim 2, the anode and the capacitor of the second rectifying diode are connected, and the anode and the ground of the third rectifying diode are connected. Positive output voltage can be derived.

In the DC-DC converter according to claim 3, since the cathode and the capacitor of the second rectifying diode are connected, and the cathode and the ground of the third rectifying diode are connected, the nth output voltage Vn Negative output voltage can be derived.

Hereinafter, exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

1 shows an embodiment of a DC-DC converter according to the present invention. In this circuit, the switching element (transistor) 12 is connected to one end of the primary winding 11 connected to the power supply 10, and the connection point 16a between the primary winding 11 and the switching element 12 is connected. The first rectifying diode 13a is connected to the.

The first output voltage V1 is directly output from the connection point 16a of the primary winding 11 and the switching element 12 through the rectifying diode 13a.

Further, capacitors 15b and 15c and second rectifying diodes 13b and 13c are connected to the output sides of the two secondary windings 14b and 14c magnetically coupled to the primary winding 11, respectively. The third rectifying diodes 18b and 18c are connected between the connection points 16b and 16c of the capacitors 15b and 15c and the second rectifying diodes 13b and 13c and the grounds 17b and 17c, respectively. .

The second output voltage V2 and the third output voltage V3 are supplied from the respective output sides of the secondary windings 14b and 14c through the capacitors 15b and 15c and the second rectifying diodes 13b and 13c. Is output. At this time, since the third rectifying diodes 18b and 18c are connected between the connection points 16b and 16c between the capacitors 15b and 15c and the second rectifying diodes 13b and 13c and the grounds 17b and 17c. All amplitude values of the AC voltage generated in the secondary windings 14b and 14c as the second output voltage V2 and the third output voltage V3 can be derived.

In the DC-DC converter according to the present invention, the first output voltage V1 is represented by the formula ④, and the nth output voltage Vn (n = 2, output from the (n-1) th secondary winding) is output. 3,…) is expressed by equation (5).

Here, Vin denotes an input voltage, D denotes an on duty of the switching element 12, np denotes the number of turns of the primary winding, and nsn denotes the number of turns of the (n-1) th secondary winding.

In the circuit of this embodiment, when the first output voltage V1 is detected and D is controlled to control V1 to be a constant voltage, (1 / (D-1)) × Vin is always a constant value from equation (4). Therefore, the second output voltage V2 and the third output voltage V3 are also shown in the equation ⑤, where the ratio of the number of turns of the secondary winding and the number of turns of the primary winding is (np + ns2) / np, (np + Constant voltage control is performed according to ns2 + ns3) / np.

2 shows another embodiment of a DC-DC converter according to the present invention. This circuit is a case where the negative output voltage is derived as the second output voltage V2 by inverting the polarities of the rectifying diodes 13b and 18b.

As described above, in the DC-DC converter of the present invention, high efficiency can be realized not only in the first output voltage but also in the n-th output voltage.

Also, by controlling the first output voltage V1, the second output voltage V2 and the third output voltage V3 can also be controlled in a constant voltage according to the ratio of the number of turns of the secondary winding and the number of turns of the primary winding.

3 illustrates the operation of each generated voltage over time. Here, the voltage generated at each connection point is called a generated voltage.

First, the primary winding in the case where the connection point between the primary winding and the switching element and the anode of the first rectifying diode (hereinafter referred to as connection 1), the switching element, and the first rectifying electrode The voltage generated between the anode of the diode and the junction (hereinafter referred to as junction 1) is referred to as Va.

The capacitor and the anode of the second rectifying diode when the anode of the capacitor and the second rectifying diode are connected, and the anode of the third rectifying diode and the ground are connected (hereinafter referred to as connection 2). And the generated voltage at the connection point (called connection point 2) to the cathode of the third rectifying diode is referred to as Vb.

The capacitor and the cathode of the second rectifying diode are connected, the cathode of the third rectifying diode is connected to the ground (hereinafter referred to as connection 3), and the cathode of the second rectifying diode. And the generated voltage at the connection point (called connection point 3) to the anode of the third rectifying diode is referred to as Vc.

The operating waveforms of the generated voltages at each connection are shown in FIG. 3, the horizontal axis represents time t, the vertical axis represents the base voltage Vs of the switching element 12, the generated voltage Va of the connection point 1, the generated voltage Vb of the connection point 2, The generated voltage Vc at the connection point 3 and the AC voltage Vd generated in the secondary winding.

First, when t is 0 (before startup; the point of ① in Fig. 3), each voltage Vs, Va, Vb, Vc, Vd is also zero.

Subsequently, when Vs is applied to the base voltage of the switching element 12, and the switching element 12 is turned on (area in Fig. 3), the AC voltage generated in the primary winding in connection 1 is a ground potential (large ground). Since the voltage is generated, the generated voltage Va of the connection point 1 becomes zero. In addition, the AC voltage Vd generated in the secondary winding becomes Vd2, which is a negative portion of the amplitude. In connection 2, the second rectifying diode is connected in the reverse direction to the Vd2, and the third rectifying diode is attached in the forward direction. Therefore, the generated voltage Vb of the connection point 2 becomes zero. On the other hand, in connection 3, since the second rectifying diode is attached in the forward direction and the third rectifying diode is in the reverse direction with respect to Vd2, the generated voltage Vc at the connection point 3 becomes -Vd2. The above is called operation 1.

Subsequently, when -Vs is applied to the base voltage of the switching element 12 and the switching element is turned off (area of 3 in Fig. 3), in the connection 1, the AC voltage generated in the primary winding becomes Va, so that the connection point 1 The generated voltage Va becomes Va. In addition, since the AC voltage generated in the secondary winding is Vd1, which is a positive part of the amplitude, at the connection 2, the second rectifying diode is forward and the third rectifying diode is attached in the reverse direction with respect to Vd1. The generated voltage Vb of the connection point 2 becomes Vd1. On the other hand, in connection 3, since the second rectifying diode is attached in the reverse direction with respect to Vd1 and the third rectifying diode is in the forward direction, the generated voltage Vc at the connection point 3 becomes zero. The above is called operation 2.

Subsequently, when + VS is applied to the base voltage of the switching element 12 and the switching element 12 is turned on (region ④ in Fig. 3), in the connection 1, the AC voltage generated in the primary winding becomes the ground potential. The generated voltage Va of the connection point 1 becomes zero. The AC voltage generated in the secondary winding becomes Vd2, which is a negative portion of the amplitude. In connection 2, the second rectifying diode is reversed to the Vd2, and the third rectifying diode is attached in the forward direction. The generated voltage Vb of 2 becomes zero. On the other hand, in connection 3, since the second rectifying diode b is attached in the forward direction and the third rectifying diode is in the reverse direction with respect to Vd2, the generated voltage Vc at the connection point 3 is the sum of -Vd1 and -Vd2. It becomes Vd. The above is called operation 3.

Subsequently, when -Vs is applied to the base voltage of the switching element 12, and the switching element 12 is turned off (region ⑤ in Fig. 3), the AC voltage generated in the primary winding in connection 1 becomes Va. The generated voltage Va of the connection point 1 becomes Va. The AC voltage generated in the secondary winding becomes Vd1, which is the positive portion of the amplitude, and in connection 2, the second rectifying diode is forward and the third rectifying diode is reversed with respect to Vd1. The voltage Vb becomes Vd which is the sum of Vd1 and Vd2. On the other hand, in connection 3, since the second rectifying diode is attached in the reverse direction with respect to Vd1 and the third rectifying diode is in the forward direction, the generated voltage Vc at the connection point 3 becomes zero. The above is called operation 4.

Thereafter, the operation 3 and the operation 4 are sequentially repeated, and as a result, a positive generated voltage is generated to the generated voltage Va, a positive generated voltage to the generated voltage Vb, and a negative generated voltage to the generated voltage Vc. Is output.

Therefore, the first, second, and third output voltages V1, V2, and V3 in FIG. 1 become positive, positive, and positive output voltages, respectively, and the first, second, and third output voltages in FIG. V1, V2, and V3) become positive, negative, and positive output voltages, respectively.

As in the above embodiment, the nth output voltage Vn can derive all amplitude values of the AC voltage generated in the (n-1) th secondary winding.

The polarity of the output voltage can be selected by selecting the polarities of the first rectifying diode, the second rectifying diode, and the third rectifying diode.

In addition, compared to the flyback converter shown in FIG. 4, the multi-output is possible with a small number of turns. For example, in the case of three outputs, in the flyback converter shown in FIG. 4, four windings are required in combination with the primary winding and the secondary winding, but three windings are required in the present invention.

In the DC-DC converter according to claim 1, since the nth output voltage Vn can derive all amplitude values of the AC voltage generated in the (n-1) th secondary winding, High efficiency can be realized not only in the first output voltage V1 but also in the nth output voltage Vn.

Further, by controlling the first output voltage V1, the n-th output voltage Vn is also controlled to be constant voltage in accordance with the ratio of the number of turns of the secondary winding and the number of turns of the primary winding.

In addition, since the first output voltage V1 is directly output from the primary winding through the rectifying diode, the output voltage V1 can be multiplied by one less winding number than the flyback converter.

In the DC-DC converter according to claims 2 and 3 of the claims, the polarity of the output voltage can be selected by selecting the polarities of the first rectifying diode, the second rectifying diode, and the third rectifying diode. Therefore, when used in a DC-DC converter, positive and negative output voltages can be arbitrarily output, and design freedom is increased, which is effective.

Claims (3)

An output voltage connected to one end of the primary winding connected to the power supply and output through a first rectifying diode connected to a connection point between the primary winding and the switching element; A second rectifying diode is connected to an output side of at least one secondary winding that is magnetically coupled to the primary winding, and an output voltage corresponding to the number of the secondary windings output through the second rectifying diode; In the DC-DC converter having a capacitor, a capacitor is connected between the output side of the secondary winding and the second rectifying diode, and is connected to the third rectifying point between the capacitor and the second rectifying diode and ground. DC-DC converter, characterized in that the diode is connected. The DC-DC converter according to claim 1, wherein an anode of the second rectifying diode and the capacitor are connected, and an anode of the third rectifying diode and the ground are connected. The DC-DC converter according to claim 1, wherein a cathode of said second rectifying diode and said capacitor are connected, and a cathode of said third rectifying diode and said ground are connected.