KR20160110678A - Resonance-type dc-dc converter - Google Patents

Abstract

The present invention relates to a resonance-type DC-DC converter comprising: a transformer to supply output voltage of values converted for input voltage in accordance with winding ratios of a first, a second, and a third coil; a first bridge circuit part which has multiple switching devices, is connected to a coil at a first side of the transformer and is applied with a power source; a second bridge circuit part which is connected to a coil at a second side of the transformer and is applied with inductive voltage in accordance with winding ratios of a first side coil and a third side coil to output DC voltage; and a resonance part serially connected to a third side coil of the transformer. According to the present invention, the converter has an advantage of being appropriate for converter application since the converter has a broad voltage variation with a small frequency variation in accordance with voltage variation.

Description

RESONANCE-TYPE DC-DC CONVERTER BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

The present invention relates to a resonance type DC-DC converter, and more particularly, to a resonance type DC-DC converter capable of satisfying a wide input /

Type resonant DC-DC converter.

In a high-frequency step-up DC converter for converting a low input voltage to a high output voltage, a conventional converter main circuit can be generally divided into a voltage-fed converter and a current-fed converter.

1 shows a circuit diagram of a voltage type full bridge DC converter. In general, a voltage-type full bridge direct current converter at a medium capacity is applied to the primary bridge main switching elements (S1, S2, S3, S4) by applying a phase-shift PWM method. Since the switching loss can be reduced by providing the voltage switching operation, it is widely applied as a step-up DC converter. However, since the voltage type full bridge direct current converter requires a high transformer turn ratio to increase the voltage, the duty loss due to the increase of the leakage inductance of the transformer occurs.

The circulating current flowing during the duty loss period does not transfer energy to the secondary side but flows through the primary main switching element to increase the conduction loss. This causes a problem of deteriorating the efficiency characteristics of the converter.

Fig. 2 shows a circuit diagram of a conventional current type DC / DC converter. The current type converter has a step-up inductor L attached to the input terminal to store energy in the step-up inductor L during the short-circuit interval, and the sum of the input voltage and the voltage stored in the step-up inductor L during the transfer period, The energy is transmitted by applying the voltage.

At this time, since the current flowing through the step-up inductor L is a predetermined DC current having a small ripple current, it is a desirable feature as a DC DC-DC step-up converter that supplies a low input voltage and a large current.

However, in the conventional current type DC converter, the current flowing through the step-up inductor L causes a parasitic capacitance and a ringing phenomenon in the switching element when the main switching elements S1, S2, S3, and S4 are turned off , Thereby increasing the voltage stress of the switching element. In order to solve this problem, an RCD snubber circuit is attached to both ends of the DC connection part of the switching element so that a current path passing through the boost inductor when the switching element is turned off flows through the snubber diode and the snubber capacitor, Can be suppressed.

However, the application of such an RC or RCD snubber circuit consumes the energy stored in the snubber capacitor during the discharge through the snubber resistor. Therefore, the higher the switching frequency, the larger the switching loss and the energy conversion efficiency is reduced.

In order to solve such a problem, an LLC serial resonance converter which can operate both the step-up mode and the step-down mode, can control a wide range of input / output voltage in a relatively narrow frequency control range, Korean Patent No. 10-0871676 is an applied step-up DC conversion device.

3 shows a conventional LLC series resonant converter circuit. Referring to FIG. 3, the LLC series resonant converter circuit uses a transformer in which an inductor and a transformer are integrated by a single transformer in order to increase power density and efficiency characteristics.

However, since the LLC series resonant converter of FIG. 3 is operated by boosting the voltage from a low input voltage to a high output voltage, a series resonant capacitor, which is one of the resonant means of the LLC series resonant converter, There is a problem that the series resonance capacitor is deteriorated to change characteristics.

In addition, due to the difficulty of high integration due to the increase in the size of the capacitor and the increase of the application cost, various problems are caused to be used in the primary side.

In addition, such an LLC series resonant converter has a disadvantage that a frequency variation range due to input / output voltage fluctuation is wide. In order to narrow the frequency fluctuation width, if the inductance is reduced, not only the circulation current increases but also the loss of the transformer due to the air gap of the transformer becomes large.

Also, when the load capacitance is increased, the current rating of the resonance capacitor connected in series with the input becomes large, making it difficult to apply the resonance capacitor to a large capacity.

Therefore, the present invention is to provide a resonant DC-DC converter circuit suitable for applications having a small voltage variation due to voltage fluctuation compared with a conventional LLC converter.

Further, the present invention can reduce the current rating of the resonant capacitor, making it suitable for high power applications

Type resonant DC-DC converter circuit.

According to an aspect of the present invention, there is provided a resonance type DC-DC converter comprising: a transformer for supplying an output voltage having a converted value to an input voltage according to a winding ratio of a first, second, and third winding coils; A first bridge circuit part having a plurality of switching elements and connected to a primary winding coil of the transformer and receiving power; A second bridge circuit part connected to the secondary winding coil of the transformer and receiving an induced voltage according to the turns ratio of the primary winding coil and the tertiary winding coil to output a DC voltage; And a resonance part connected in series to the tertiary winding coil of the transformer.

Preferably, the resonant portion includes an inductance and a capacitor, and the inductance and the capacitor can be connected in series. In this case, the inductance may be the leakage inductance of the winding coil of the tertiary winding of the transformer.

Preferably, the capacitor resonates with the inductance of the first, second and third winding coils of the transformer. In this case, the resonance section has a characteristic of a notch filter that reduces the gain at a point where the resonance frequency and the switching frequency are the same.

The resonant type DC-DC converter according to the present invention is advantageous to applications having a wide voltage fluctuation because the frequency fluctuation due to voltage fluctuation is smaller than that of a conventional LLC converter.

Further, the resonance type DC-DC converter according to the present invention

As the resonance structure, since the leakage inductance of the transformer can be used as an inductance component used for resonance, there is an advantage that the number of elements used in the converter is reduced.

Also, since the resonance type DC-DC converter according to the present invention can minimize the current flowing through the resonance capacitor using the tertiary winding of the transformer, it is advantageous to provide a converter that is easy to apply to large power.

Fig. 1 shows a circuit diagram of a conventional voltage full bridge direct current converter.
Fig. 2 shows a circuit diagram of a conventional current type DC / DC converter.
3 shows a circuit diagram of a conventional LLC series resonant converter.
Figure 4 is a block diagram of an embodiment of the present invention,

Type resonator type converter.
FIG. 5 is a block diagram of an alternative embodiment of the present invention

Circuit structure of a bidirectional resonant converter.
6 (a) shows a resonant portion equivalent circuit of a conventional converter, and Fig. 6 (b) shows an equivalent circuit of a resonant portion according to the embodiment of the present invention.
7 (a) shows the gain characteristics of the resonator connected in series, and FIG. 7 (b) shows the gain characteristics of the resonator connected in parallel.
8 (a) shows a resonant equivalent circuit of a conventional LLC converter, and Fig. 8 (b) shows a resonant equivalent circuit according to an embodiment of the present invention

This figure shows a resonant equivalent circuit of a resonant converter.
9 (a) shows a gain curve by a resonant equivalent circuit of a conventional LLC converter, and Fig. 9 (b)

And shows the gain curve by the resonance equivalent circuit of the resonant converter.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to or limited by the exemplary embodiments. Like reference numerals in the drawings denote members performing substantially the same function.

Figure 4 is a block diagram of an embodiment of the present invention,

Type resonator type converter. Referring to Figure 4,

The resonance converter may include a transformer 70, a first bridge circuit unit 10, a second bridge circuit unit 30, and a resonance unit 50.

The transformer 70 can supply the output voltage of the converted value with respect to the input voltage 20 according to the winding ratios n1, n2 and n3 of the first, second and third winding coils.

The first bridge circuit unit 10 has a plurality of switching elements S1, S2, S3 and S4 and is connected to the primary winding coil n1 of the transformer and receives the power supply 20 from the outside.

The second bridge circuit unit 30 is connected to the secondary winding coil n2 of the transformer and receives an induced voltage according to the turns ratio of the primary winding coil n1 and the tertiary winding coil n3 to output a DC voltage have.

The resonance portion 50 is connected in series to the tertiary winding coil n3 of the transformer 70. [ The resonance part 50 according to the present embodiment includes an inductance

And a capacitor Cr.

In this case, the capacitor Cr is connected to the first, second and third inductances of the transformer 70

,

,

). The first, second and third inductances of the transformer 70

,

,

May be a separate inductor element connected in series with the winding coil, or it may be the leakage inductance of the transformer 70.

According to the present embodiment, the resonance portion 50 is formed on the tertiary side of the transformer 70. [ The tertiary inductance of the transformer 70 (

) Connected in series with the capacitor (Cr) has the characteristics of a notch filter on the converter.

Figure 5 is a graphical representation of an < RTI ID = 0.0 >

Circuit diagram of a resonant converter. Referring to FIG. 5, the second bridge circuit unit 30 may include a plurality of switching elements to transmit power in a forward or reverse direction. The bidirectional converter circuit according to the present embodiment can be applied to various fields such as an uninterruptible power supply system, a hybrid electric vehicle, and a grid connection system.

6 (a) shows a resonant part equivalent circuit of a conventional converter, and Fig. 6 (b) shows an equivalent circuit of the resonator part 50 according to the embodiment of the present invention.

6A, the resonance unit formed on the primary side or the secondary side of the conventional transformer can be represented by an equivalent circuit in which a capacitor Cr, an inductance Lr, and a load resistance R are connected in series. In this case, the gain gain characteristic has a maximum gain of 1 regardless of the load at the same resonance frequency and switching frequency.

Therefore, the LLC converter has a constant gain regardless of load at the same resonance frequency and switching frequency. However, if the load is reduced in the region above the resonance frequency, there is a disadvantage that a large frequency fluctuation is required when the input / output voltage fluctuates.

Referring to FIG. 6B, the resonator 50 according to the embodiment of the present invention may be represented by an equivalent circuit in which the capacitor Cr and the inductance Lr are connected in parallel with the load resistor R. FIG. In this case, the gain gain characteristic has a minimum gain of 0 regardless of the load at the same resonance frequency and switching frequency. The characteristic

In the resonant converter, the converter has a constant gain irrespective of the load even in the region above the resonance frequency. This will be described later with reference to FIG.

7A shows the gain characteristics of the resonance unit connected in series, and FIG. 7B shows the gain characteristics of the resonance unit 50 connected in parallel. Referring to FIG. 7 (b), the resonator unit 50 according to the embodiment of the present invention has a gain characteristic such as a notch filter.

In the case of having the same gain characteristics as the resonator portion 50 according to the embodiment of the present invention,

The resonant converter is characterized in that the frequency fluctuation width decreases when the input / output voltage fluctuates. And a resonance part 50 in which a capacitor Cr is connected in series to the tertiary side of the transformer 70

The equivalent circuit of the resonant converter is shown in Fig.

8 (a) shows a resonant equivalent circuit of a conventional LLC converter. FIG. 8 (b) is a schematic view of an embodiment of the present invention

This figure shows a resonant equivalent circuit of a resonant converter. FIG. 9A shows a gain curve by the circuit of FIG. 8A, and FIG. 9B shows a gain curve by the circuit of FIG. 8B.

 Referring to FIGS. 8A and 9A, in the case of an LLC converter in which a resonance capacitor Cr is connected in series on the primary side, when the load decreases in an area above the resonance frequency, It can be confirmed that a large frequency fluctuation is required when the input / output voltage fluctuates.

Referring to FIG. 8 (b), in accordance with an embodiment of the present invention

The resonant converter has a tertiary leakage inductance (

And a resonance capacitor Cr are connected in series, which can be represented by an equivalent circuit connected in parallel with the secondary side load R.

Referring to FIG. 9 (b), in accordance with an embodiment of the present invention

The resonant converter has a gain of zero (zero point) regardless of the load at the same resonance frequency and switching frequency. Also, unlike LLC converters,

The resonant converter has a constant gain characteristic regardless of the load in the region of the Above region. In this case, there is an advantage that the frequency fluctuation width due to the voltage fluctuation is smaller than that of the LLC converter at the light load.

Experimental Example 1

According to an embodiment of the present invention

In order to verify the characteristics of the resonant converter, the following design specifications were prepared and the experimental waveforms were measured.

(P = 1 kW, Vi = 380 V, Vo = 100-410 V, L1 = 51 H, L2 = 35 H, L3 = 2 H, Cr = 0.0033 F)

Results of Experimental Example 1

<Figure 1>

Figure 1 shows the primary side inductance current and the resonant capacitor current waveform. The difference between the two currents is transmitted to the secondary side of the transformer.

<Figure 2>

Figure 2 shows the switch voltage and current waveforms showing that all switches are switched to zero voltage.

<Figure 3>

<Figure 3> shows that the zero-current switching is performed by the secondary current and the diode voltage waveform.

The output voltage ranges from 100 to 400 V, which is very wide,

The frequency range of the resonant converter is very small, ranging from 175kHz to 220kHz.

According to an embodiment of the present invention

The resonant converter has a characteristic that the resonant capacitor (Cr) is connected in parallel with the load (R), and the frequency variation due to the voltage fluctuation is very small compared with that of the LLC converter, . Further, if the turn ratio of the tertiary winding n3 of the transformer 70 is appropriately adjusted, the current rating of the resonant capacitor Cr can be reduced, which is suitable for high power applications.

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. will be. Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be determined by all changes or modifications derived from the scope of the appended claims and equivalents of the following claims.

10: first bridge circuit part 20: power source
30: second bridge circuit part 50: resonance part
70: Transformer
n1, n2, n3: turns ratio

Claims (5)

A transformer for supplying an output voltage having a converted value with respect to an input voltage according to a winding ratio of the first, second and third winding coils;
A first bridge circuit part having a plurality of switching elements and connected to a primary winding coil of the transformer and receiving power;
A second bridge circuit part connected to a secondary winding coil of the transformer and receiving an induced voltage according to a winding ratio of the primary winding coil and the tertiary winding coil to output a DC voltage; And
And a resonance unit connected in series to the tertiary winding coil of the transformer.
The method according to claim 1,
The resonator may include:
Including inductance and capacitors,
Wherein the inductance and the capacitor are connected in series.
3. The method of claim 2,
Wherein the inductance is a leakage inductance of a third winding coil of the transformer.
3. The method of claim 2,
Wherein the capacitor resonates with an inductance of the first, second and third winding coils of the transformer.
The method according to claim 1,
Wherein the resonance unit includes a notch filter that reduces the gain at a point where the resonance frequency and the switching frequency are the same.

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