KR101759258B1 - Dc/dc converter with couple inductor and snubber circuit - Google Patents

Abstract

More particularly, the present invention relates to a DC / DC converter, in which a couple inductor is provided in parallel with an inductor of a filter unit, a reverse voltage is applied to the transformer by a voltage applied to the couple inductor, , A couple inductor with a snubber circuit to absorb and discharge the surge voltage generated by the coupled inductor, thereby reducing the surge voltage applied to the diode so that a diode having a low voltage rating can be used. / DC converter.

Description

[0001] DC / DC CONVERTER WITH COUPLE INDUCTOR AND SNUBBER CIRCUIT WITH COUPLING INDUCTOR AND SNEBER CIRCUIT [0002]

More particularly, the present invention relates to a DC / DC converter, in which a coupled inductor is provided in parallel with an inductor of a filter unit, a reverse voltage is applied to the transformer by a voltage applied to the coupled inductor, , A couple inductor with a snubber circuit to absorb and discharge the surge voltage generated by the coupled inductor, thereby reducing the surge voltage applied to the diode so that a diode having a low voltage rating can be used. / DC converter.

In order to supply energy to an electronic circuit requiring a relatively high voltage, it is necessary to increase the voltage to a high voltage in order to be used in an application field in connection with the system. In addition, depending on the electronic circuit, it may be necessary to lower the voltage by using a high voltage. One of the various step-down and step-up converters for this purpose is a DC / DC converter.

In recent years, electric vehicles (EVs) are future fusion convergence technology, which is drawing attention not only from international organizations but also from governments and corporations, along with the global green growth policy.

Such an electric vehicle receives electric energy from the outside, charges it into the battery, and obtains a mechanical energy as a voltage charged in the battery. A vehicle charger is a device that provides the necessary voltage for an electric vehicle to charge low voltage and high voltage and requires a DC / DC converter capable of supplying a DC voltage from a DC input power source to the output using a single output circuit. do.

1, the DC / DC converter 10 includes a switching unit 11 including a plurality of switching elements S1 to S8 for alternately switching a DC input power source Vin to apply a current, A transformer 12 which is induced in the secondary winding and outputs an AC power when a current applied in accordance with the switching operation of the switching unit 11 is applied to the primary winding and a diode rectifier circuit A rectifier 13 which rectifies the AC power outputted from the secondary winding side of the transformer 12 to DC power and outputs an output voltage, an inductor Lo, a rectifier 15 composed of a capacitor Co, And a filter unit 14 for filtering an output voltage of the inverter. At this time, input capacitors C1 and C2 are connected between the DC input power source Vin and the switching unit 11 to be connected to the DC input power source Vin so as to divide the power source into half, and the switching unit 11 is provided with a circulating diode D1 to D4 are provided.

As shown in FIG. 2, in the DC / DC converter 10, when the switching unit 11 is alternated, the circulating current period in the switching devices S2, S7, S3, and S6 becomes long, S3, and S6 increases.

In addition, a high voltage is applied to the diode of the rectifying part at the time of high voltage output, so that the diode voltage rating should be large. However, a diode having a high breakdown voltage has a problem that loss is large due to VF (forward drop voltage).

Korean Patent No. 10-1548528 Korean Patent No. 10-0799856

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a coupled inductor in parallel with an inductor of a puller and minimize a conduction loss by minimizing a circulating current section by applying a reverse voltage to a transformer with a voltage applied to the coupled inductor And a DC / DC converter having a couple inductor and a snubber circuit.

Also, the present invention provides a coupled inductor and a snubber circuit which can reduce a surge voltage applied to a diode by using a snubber circuit installed in a coupled inductor to absorb and discharge a surge voltage generated in a coupled inductor, The DC / DC converter includes a DC / DC converter.

According to an aspect of the present invention,

A switching unit including a plurality of switching elements S1 to S8 for alternately switching a DC input power supply Vin to apply a current to the secondary winding, And a rectifier circuit for rectifying the alternating current power output from the secondary winding side of the transformer to a direct current power source and outputting an output voltage by forming a bridge rectifying circuit by diodes D5 to D8, DC converter comprising a capacitor (Co) and an inductor (Lo), and a filter unit for filtering an output voltage of the rectifier unit, the DC / DC converter comprising: a transformer connected in parallel between an inductor (Lo) A couple inductor unit for minimizing a conduction loss by applying a reverse voltage to a secondary winding of the secondary winding to minimize a circulation current period; And a snubber circuit connected in parallel between the coupled inductor part and the rectified part to absorb and discharge a surge voltage generated in the coupled inductor part.

Here, the coupled inductor section is connected in series with a coupled inductor L1 and a forward-circuited diode Df at the rear end of the coupled inductor L1 to apply a voltage.

The snubber circuit further includes a capacitor Csn having one end connected between the coupled inductor L1 and the circulating diode Df and the other end connected between the inductor Lo of the filter unit and the rectifying unit; A resistor Rsn connected between the coupled inductor L1 and the capacitor Csn; And a diode Dsn having an anode connected to the capacitor Csn and a cathode connected between the inductor Lo of the filter unit and the rectifying unit.

Here, the switching unit is any one selected from a half bridge, a full bridge, a three-level half bridge, and a three-level full bridge.

According to the DC / DC converter including the coupling inductor and the snubber circuit of the present invention, the coupling inductor is provided in parallel to the inductor of the filter portion, and a reverse voltage is applied to the transformer by the voltage applied to the coupling inductor, The conduction loss can be minimized by minimizing the interval.

In addition, according to the present invention, a snubber circuit is provided in a coupled inductor to absorb and discharge a surge voltage generated in a coupled inductor, thereby reducing a surge voltage applied to the diode and using a diode having a low diode voltage rating.

1 is a circuit diagram showing a typical three-level full-bridge DC / DC converter.
2 is a graph for explaining the operation of FIG.
3 is a circuit diagram showing a DC / DC converter including a coupled inductor and a snubber circuit according to the present invention.
4 is a graph illustrating the operation of the DC / DC converter including the coupled inductor and the snubber circuit according to the present invention in a state where the snubber circuit is removed.
5 is a graph for explaining the operation of a DC / DC converter having a coupled inductor and a snubber circuit according to the present invention.

Hereinafter, the configuration of a DC / DC converter including a coupled inductor and a snubber circuit according to the present invention will be described in detail with reference to the accompanying drawings.

In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions of the present invention, and these may be changed according to the intention of the user, the operator, or the like. Therefore, the definition should be based on the contents throughout this specification.

3 is a circuit diagram showing a DC / DC converter including a coupled inductor and a snubber circuit according to the present invention.

3, a DC / DC converter 10 including a coupled inductor and a snubber circuit according to the present invention includes a switching unit 110, a transformer 120, a rectifying unit 130, (140), a coupled inductor unit (150), and a snubber circuit (160).

First, the switching unit 110 includes first to eighth switching elements S1 to S8 for alternately switching the DC input power source Vin to apply a current. Here, the switching unit 110 is selected from a half bridge, a full bridge, a three-level half bridge, and a three-level full bridge. In FIG. 3, a three-level full bridge is shown as an example. The switching unit 110 is provided with input capacitors C1 and C2 for dividing the DC input power supply Vin by half and includes first to fourth circulating diodes D1 to D4 between the switching elements S1 to S8, And the first to fourth circulating diodes D1 to D4 are electrically connected to the input capacitors C1 and C2. It is preferable that the first to eighth switching elements S1 to S8 are MOSFETs.

When the current applied in accordance with the switching operation of the switching unit 110 is applied to the primary winding, the transformer 120 is induced in the secondary winding and outputs AC power.

The rectifying unit 130 rectifies the AC power outputted from the secondary winding side of the transformer 120 to DC power and outputs an output voltage. The rectifying unit 130 includes a fifth diode D5 and a sixth diode D6 connected to both ends of the secondary winding of the transformer unit 120 in the forward direction and a fifth diode D5 and a sixth diode D6 connected to both ends of the secondary winding of the transformer unit 120, And a seventh diode D7 and an eighth diode D8, which are connected to each other in the reverse direction.

The filter unit 140 includes an inductor Lo and a capacitor Co to filter the output voltage of the rectifying unit 130. [

The coupled inductor part 150 is connected in parallel between the inductor Lo of the filter part 140 and the rectifying part 130 so that a reverse voltage is applied to the secondary winding of the transformer part 120 to minimize the circulating current section A coupling inductor L1 that minimizes conduction loss and a circulating diode Df are connected in series in a forward direction to the rear end of the coupling inductor L1 to apply a voltage to the coupling inductor L1.

The snubber circuit 160 is connected in parallel between the coupled inductor L1 of the coupled inductor unit 150 and the rectified unit 130 to absorb the surge voltage generated in the circulating diode Df of the coupled inductor unit 150 And discharges. The snubber circuit 160 has one end connected between the coupled inductor L1 and the circulating diode Df and the other end connected between the inductor Lo of the filter unit 140 and the rectifying unit 130. [ An anode is connected to the resistor Rsn and a capacitor Csn connected between the coupled inductor L1 and the capacitor Csn and the inductor Lo and the rectifying unit 130 of the filter unit 140 are connected to each other, And a diode Dsn to which a cathode is connected.

Hereinafter, the operation of the DC / DC converter including the coupled inductor and the snubber circuit according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 4 is a graph for explaining an operation of the DC / DC converter including the coupled inductor and the snubber circuit according to the present invention in a state in which the snubber circuit is removed, FIG. 5 is a graph showing the operation of the coupled inductor and the snubber circuit DC converter according to the present invention.

Referring to FIG. 4, in operation of the DC / DC converter 100 having the coupled inductor and the snubber circuit according to the present invention in a state in which the snubber circuit 160 is removed, the switching element 110 of the switching unit 110 S2), the circulating current section is shorter than that in FIG.

That is, when the first, second, seventh and eighth switching elements S1, S2, S7 and S8 are turned on, the DC input power source 750V is connected to the first and second switching elements S1 and S2 of the input capacitor C1. Through the primary winding of the transformer unit 120 and the seventh and eighth switching devices S7 and S8 and the input capacitor C1 through the output terminal (not shown).

Then, an AC current is generated by the secondary winding of the transformer 120, and an AC voltage is generated, which is converted into a DC voltage through the rectifier 130 and the filter 140 to charge the battery Vbatt.

Subsequently, when the first and eighth switching elements S1 and S8 are turned off, the residual current of the primary winding of the transformer 120 flows through the seventh switching element S7 and the fourth and one rectifier diodes D4 and D1. , And then circulated through the second switching element (S2) to the primary winding of the transformer (120) again and is destroyed.

At this time, the circulating diode Df of the coupled inductor unit 150 is turned on to apply a voltage to the coupled inductor Ll, and the voltage applied to the coupled inductor Ll causes a reverse voltage to be applied to the secondary winding of the transformer unit 120 To minimize circulating current.

When the second and seventh switching elements S2 and S7 are turned off and the fourth and fifth switching elements S4 and S5 and the third and sixth switching elements S3 and S6 are turned on, Is applied to the reverse side of the primary winding of the transformer 120 through the positive terminal of the input capacitor C2 and the fifth and sixth switching elements S5 and S6 and then the third and fourth switching elements S3 and S4 and the input Flows to the - end of the capacitor C2.

Then, an AC voltage is generated by the secondary winding of the transformer 120, which is converted into a DC voltage through the rectifying unit 130 and the filter unit 140 to charge the battery Vbatt.

Subsequently, when the fourth and fifth switching elements S4 and S5 are turned off, the residual current of the primary winding of the transformer 120 is applied to the third switching element S3, the second and third rectifying diodes D2 and D3, The sixth switching element S6, and is then discharged to the primary winding of the transformer 120 again.

At this time, the circulating diode Df of the coupled inductor unit 150 is turned on to apply a voltage to the coupled inductor Ll, and the voltage applied to the coupled inductor Ll causes a reverse voltage to be applied to the secondary winding of the transformer unit 120 To minimize circulating current.

Then, the above process is repeated again.

On the other hand, as shown in FIG. 4, the voltage vDf applied to the circulating diode Df by the inductance of the coupled inductor L1 is about 1,400 V, and therefore, the circulating diode Df must have a high withstand voltage, There is a limit to apply a large capacity due to loss due to VF (forward drop voltage) of the diode. At this time, the voltage applied to the fifth diode D5 of the rectifying unit 130 is as high as about 800V.

Thus, the snubber circuit 160 is applied to both ends of the coupled inductor L1 to absorb and discharge the surge voltage applied to the coupled inductor L1.

As a result, as shown in FIG. 5, the voltage vDf applied to the circulating diode Df is reduced to about 800 V, which is lower than that of the conventional one.

Also, it can be seen that the voltage applied to the fifth diode D5 of the rectifying part 130 is also about 600 V, which is 200 V less than the conventional one.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It is to be understood, however, that the invention is not to be limited to the specific forms thereof, which are to be considered as being limited to the specific embodiments, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. .

11, 110: switching unit 12, 120: transformer
13, 130: rectification section 14, 140: filter section
150: Snubber circuit 160: Coupled inductor part

Claims (4)

A switching unit formed of any one selected from a half bridge, a full bridge, a three-level half bridge, and a three-level full bridge having a plurality of switching elements for alternately switching a DC input power supply Vin to apply a current, A transformer for rectifying the alternating current power output from the secondary winding side of the transformer to a direct current power to output an output voltage; And a filter portion having an inductor (Lo) and a capacitor (Co) for filtering an output voltage of the rectifying portion, the DC / DC converter comprising:
A couple inductor L1 is connected in parallel between the inductor Lo of the filter unit and the rectifying unit to apply a reverse voltage to the secondary winding of the transformer unit to minimize a circulation current period to minimize conduction loss, A coupled inductor unit having a circulating diode Df connected in series in a forward direction to a rear end of the coupled inductor L1;
And a snubber circuit which is connected in parallel between the coupled inductor unit and the rectifying unit to absorb and discharge a surge voltage generated by the inductance of the coupled inductor L1 to lower a reverse voltage applied to the circulating diode Df, ,
The snubber circuit includes:
A resistor Rsn having one end connected between the coupled inductor L1 and the circulating diode Df and connected between the coupled inductor L1 and the capacitor Csn; And
And a diode Dsn having an anode connected to the capacitor Csn and a cathode connected between the inductor Lo and the rectifying unit of the filter unit. Converter. delete delete delete

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