JP2016123192A - Resonance type step-up converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resonance type step-up converter capable of obtaining a higher-voltage AC output with a simple circuit configuration.SOLUTION: The resonance type step-up converter 100 includes: an insulation type step-up converter 10 which has a first transformer T1 and an inverter circuit 1, converts input power Vin into first high-voltage AC power V1 and outputs the converted power through the first transformer T1; a second transformer T2 which is connected with the first transformer T1, steps up the first high-voltage AC power V1 to second high-voltage AC power V2 and outputs the stepped-up power; and a resonance capacitor Cr.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an insulation type boost converter that boosts input power to high-voltage AC power via a transformer and outputs the boosted power, and more particularly, to a resonance type boost converter that can easily design a resonance circuit connected in front of the transformer.

  As a conventional resonant boost converter, a discharge tube lighting device as shown in FIG. 2 is known (Patent Document 1). A conventional resonant boost converter includes a switching element and a transformer that are connected in a full bridge. An input voltage of about 10 to 20 V is converted into an AC power of about 1.5 kV by a resonance type boost converter and output to a discharge tube.

JP 2005-229794 A

  As a method for obtaining a higher voltage AC power using a conventional resonant boost converter, it is easily considered to increase the turns ratio of the primary winding and the secondary winding of the transformer. However, the resonant step-up converter must limit the frequency range in which the resonance is stable, and the transformer design is very difficult. For example, when the turns ratio of the transformer is increased, the inductance of the primary winding is reduced due to the effect of the line capacitance of the secondary winding. Moreover, if the insulation distance between the primary and secondary of the transformer is increased to make the coupling worse, the influence of the line capacitance is reduced, but the leakage inductance is increased. As described above, in the conventional resonant boost converter, AC power having a higher voltage (for example, 10 kV) cannot be obtained.

  The present invention provides a resonance type boost converter capable of obtaining a higher voltage AC output with a simple circuit configuration.

  According to one aspect of the present invention, an isolated boost converter that includes a first transformer and an inverter circuit, converts input power into first high-voltage AC power, and outputs the first high-voltage AC power via the first transformer; A second transformer connected to the first transformer and boosting and outputting the first high-voltage AC power to a second high-voltage AC power, and a resonance capacitor are provided.

  According to the present invention, the step-up ratio of the first transformer can be suppressed by boosting in two stages using the first and second transformers, so that the degree of freedom in designing the resonant boost converter is increased. Therefore, it is possible to provide a resonant boost converter that can obtain a higher voltage AC output with a simple circuit configuration.

1 is a circuit diagram showing a configuration of a resonant boost converter according to an embodiment of the present invention. FIG. It is a circuit diagram which shows the structure of the conventional resonance type boost converter.

  Next, an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic. Further, the embodiments described below exemplify apparatuses and methods for embodying the technical idea of the present invention, and the embodiments of the present invention have the following structure and arrangement of components. It is not something specific. The embodiment of the present invention can be variously modified within the scope of the claims.

  FIG. 1 is a circuit diagram showing a configuration of a resonant boost converter according to an embodiment of the present invention. The resonant boost converter 100 according to the present embodiment includes an isolated boost converter 10, a second transformer T2, and a resonant capacitor Cr. The insulation type boost converter 10 has a first transformer T1 and an inverter circuit 1, converts an input voltage Vin supplied from an input power source into a first high-voltage AC voltage V1, and converts the first high-voltage AC voltage V1 into Output via the first transformer T1. The second transformer T2 boosts the first high-voltage AC voltage V1 to the second high-voltage AC voltage V2, and outputs it to the load. The load is, for example, a discharge tube or a discharge plate.

  The inverter circuit 1 includes first to fourth switching elements Q1 to Q4 made of MOSFETs, and a drive unit DRV that drives the switching elements Q1 to Q4 by PWM (pulse width modulation). The first and second switching elements Q1 and Q2 are connected in series to each other to form a first bridge circuit having a connection point of each switch as an output terminal. The third and fourth switching elements Q3 and Q4 are connected in series to each other to constitute a second bridge circuit having a connection point of each switch as an output terminal. That is, the switching elements Q1 to Q4 are connected by a full bridge and connected in parallel to the input power supply.

  The first transformer T1 includes at least a first primary winding P1, a first secondary winding S1, and an auxiliary winding that are electromagnetically coupled to each other. Specifically, the first primary winding P1 has two windings P1a and P1b connected in parallel to each other, and the first secondary winding S1 has two windings S1a, The auxiliary winding having S1b has two windings each grounded at the beginning and end of winding. The second transformer T2 includes at least a second primary winding P2 and a second secondary winding S2 that are electromagnetically coupled to each other. Specifically, the second primary winding P2 has three windings P2a, P2b, and P2c connected in parallel with each other, and the second secondary winding S2 has three windings connected in series with each other. S2a, S2b, S2c.

  One end of the first primary winding P1 is connected to the output terminal of the first bridge circuit, and the other end of the first primary winding P1 is connected to the output terminal of the second bridge circuit. The first secondary winding S1 has m times the number of turns of the first primary winding P1 (m> 1, for example, m = 25). The two windings constituting the auxiliary winding are connected to the drive unit DRV via a diode and a capacitor, respectively. The voltage generated in the auxiliary winding is full-wave rectified and smoothed, and is supplied to the drive unit DRV as a drive power supply.

  One end of the first secondary winding S1 is connected to one end of the second primary winding P2 of the second transformer via a leakage inductance (for example, a leakage reactor Lr) and a resonance capacitor Cr. The other end of the first secondary winding S1 is connected to the other end of the second primary winding P2 of the second transformer. That is, the first secondary winding S1 and the second primary winding P2 are connected to each other to form a closed loop.

  One end of the first secondary winding S1 is connected to one end of the leakage reactor Lr. The other end of the leakage reactor Lr is connected to one end of the resonance capacitor Cr. The other end of the resonance capacitor Cr is connected to one end of the second primary winding P2. That is, the leakage reactor Lr and the resonance capacitor Cr are connected in series with each other and connected to a closed loop constituted by the first secondary winding S1 and the second primary winding P2.

  The second secondary winding S2 has n times the number of turns of the second primary winding P2 (n> m, for example, n = 50). The second transformer T2 generates a second high-voltage AC voltage V2 between one end and the other end of the second secondary winding S2, and outputs it to a load (not shown). Connected to the second transformer T2 is a power detection circuit that detects the output power of the resonant boost converter 100 and feeds it back to the drive unit DRV. Therefore, the resonant boost converter 100 generates the second high-voltage AC voltage V2 from the input voltage Vin by PWM driving the switching elements Q1 to Q4 so that the output power of the resonant boost converter 100 becomes a desired magnitude. .

  As described above, the resonant boost converter 100 performs two-stage boosting using the first transformer T1 and the second transformer T2. Since the turns ratio of each transformer can be reduced, the design of the transformer is facilitated, and even if the turns ratio of the first transformer T1 is reduced, the turn ratio of the second transformer T2 is increased, so that a higher voltage can be obtained. AC voltage is obtained. Further, since the primary windings P1 and P2 of each transformer have a configuration in which a plurality of windings are connected in parallel, the current flowing through each primary winding P1 and P2 is dispersed, and the heat generation of the transformer is suppressed.

  In addition, the resonance capacitor Cr also serves to couple the first and second transformers T1 and T2 with each other, so that adverse effects on the primary circuit including the inverter circuit 1 can be suppressed even when the output impedance is reduced. . Further, when the resonance capacitor Cr is connected to the secondary side of the first transformer T1, the ripple current flowing through the resonance capacitor Cr when the input voltage Vin is low is reduced. Is secured.

  The resonant step-up converter 100 performs a resonance operation with the secondary side leakage inductance of the first transformer T1, the leakage reactor Lr, the resonance capacitor Cr, and the primary side leakage inductance of the second transformer T2. Therefore, when the leakage reactor Lr is provided, the resonance frequency of the resonant boost converter 100 can be easily adjusted by adjusting the inductance value and the capacitance value of the resonance capacitor Cr. For example, the resonance frequency is reduced by using the leakage reactor Lr having a large inductance value, thereby reducing the oscillation frequency of each of the switching elements Q1 to Q4, and the resonant boost converter 100 having low output power suitable for driving a capacitive load is configured. Is done. Alternatively, by adjusting the resonance frequency to the oscillation frequency of each of the switching elements Q1 to Q4, it is possible to suppress a voltage drop at the leakage reactor Lr and the resonance capacitor Cr and improve the power conversion efficiency.

  As mentioned above, although this invention was described by embodiment, it should not be understood that the description and drawing which form a part of this indication limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art. That is, it goes without saying that the present invention includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description. For example, a third transformer may be used in addition to the first and second transformers T1 and T2. Further, the primary winding of each transformer does not need to have a configuration in which a plurality of windings are connected in parallel, and the presence or absence of an auxiliary winding can be selected according to the control method of the converter. The leakage reactor Lr may be replaced with the leakage inductances of the first and second transformers T1 and T2.

DESCRIPTION OF SYMBOLS 1 Inverter circuit 10 Insulation type | mold boost converter 100 Resonance type | mold boost converter Q1-Q4 Switching element DRV drive part T1 1st transformer P1a, P1b 1st primary winding S1a, S1b 1st secondary winding T2 2nd transformer P2a, P2b, P2c Second primary winding S2a, S2b, S2c Second secondary winding Lr Leakage reactor Cr Resonance capacitor

Claims (6)

An isolated boost converter that has a first transformer and an inverter circuit, converts input power into first high-voltage AC power, and outputs the first high-voltage AC power via the first transformer;
A second transformer connected to the first transformer and boosting and outputting the first high-voltage AC power to a second high-voltage AC power;
A resonance type boost converter comprising: a resonance capacitor.   The first transformer includes a first primary winding and a first secondary winding that are electromagnetically coupled to each other, and the second transformer includes a second primary winding that is electromagnetically coupled to each other. The first secondary winding and the second primary winding are connected to each other to form a closed loop. Resonant boost converter.   The resonant boost converter according to claim 2, wherein the resonant capacitor is connected to the first transformer and the second transformer.   The resonant boost converter according to claim 3, wherein the resonant capacitor is connected to the closed loop.   5. The resonant boost converter according to claim 4, further comprising a leakage inductance connected in series with the resonant capacitor in the closed loop.   6. The resonant boost converter according to claim 5, wherein the inverter circuit includes a switching element connected in a full bridge.

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