JP2006271099A - Series resonance converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel DC series resonance converter which can control the output even under a light load. <P>SOLUTION: The DC series resonance converter having a DC power supply Vin as an input, insulating the primary and the secondary by a transformer T and provided with a bridge circuit 1 equipped with semiconductor switch elements Q1-Q4 on the primary, comprises a first resonance circuit 2 provided with a series circuit of an inductor Lr and a capacitor Cr at one end of the primary winding of the transformer T, and a second resonance circuit 3 comprising a series circuit of a second inductor Lr1 and a second capacitor Cr1 connected in parallel with the primary winding of the transformer T. Predetermined numbers of second inductors and second capacitors are set such that a second resonance frequency generated from the second resonance circuit becomes higher than a first resonance frequency generated from the first resonance circuit, and the switching frequency of the semiconductor switch elements is controlled to come between first resonance frequency and the second resonance frequency. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a series resonance type converter in which a DC power source is used as an input, a primary circuit and a secondary circuit are insulated by a transformer, and a bridge circuit including a semiconductor switch element is provided on the primary side.

  A conventional series resonant converter is shown in FIG. The series resonant converter shown in FIG. 6 has a DC power supply Vin as an input, a primary bridge and a secondary secondary are insulated by a transformer T, and a full bridge type bridge circuit including semiconductor switch elements Q1, Q2, Q3, and Q4 on the primary side. 1A and a rectifier circuit 11 having rectifier diodes D5, D6, D7, and D8 on the secondary side. The bridge circuit 1A has a reference inverter 5 composed of switch elements Q1 and Q2 and a control inverter 6 composed of switch elements Q3 and Q4.

A first resonance circuit 2 having a series circuit of an inductor Lr and a capacitor Cr is connected to one end of the primary winding of the transformer T. In addition, a control circuit (hereinafter referred to as “phase shift control”) by a method of increasing the frequency (hereinafter referred to as “frequency control”) or a method of controlling ON / OFF of the semiconductor switches Q1, Q2, Q3, Q4 by phase shift (hereinafter referred to as “phase shift control”). (For example, refer to Patent Document 1 for the phase shift).
JP-A-9-117156

  Conventional series resonance type converters generally use frequency control. In frequency control, the switching frequency becomes higher at light loads, so the upper limit of the operating frequency is determined by the operating speed of the switching element, and there is a problem that it cannot be controlled, and control is possible even if it is similar to phase shift control However, there is a problem in the soft switching range in addition to the problem that the switching element is difficult to switch to zero voltage and the efficiency is lowered.

  The present invention has been made in view of the above problems, and provides a novel series resonance type converter capable of controlling the output even at a light load.

  In order to solve the above-described problems, a series resonance converter according to the present invention is a series circuit in which a DC power supply is input, a primary and a secondary are insulated by a transformer, and a bridge circuit including a semiconductor switch element is provided on the primary side. In the resonant converter, a first resonant circuit including a series circuit of an inductor and a capacitor at one end of the primary winding of the transformer, a second inductor and a second capacitor in parallel with the primary winding of the transformer, A second resonance circuit composed of a series circuit of the second resonance circuit, wherein the second resonance frequency generated from the second resonance circuit is higher than the first resonance frequency generated from the first resonance circuit. A constant is set for the second inductor and the second capacitor, and the switching frequency at which the semiconductor switch element switches is the first resonance frequency and the second resonance frequency. Characterized in that are controlled to come between.

  Further, in a series resonance type converter in which a DC power source is input, a primary and a secondary are insulated by a transformer, and a bridge circuit having a semiconductor switch element on the primary side is provided, an inductor is provided at one end of the primary winding of the transformer. A first resonance circuit including a series circuit of a capacitor and a capacitor, and a second resonance circuit including a series circuit of a second inductor and a second capacitor in parallel with the secondary winding of the transformer, The second inductor and the second capacitor are set to be constant so that the second resonance frequency generated from the second resonance circuit is higher than the first resonance frequency generated from the first resonance circuit, Control is performed so that a switching frequency at which the semiconductor switch element switches is between the first resonance frequency and the second resonance frequency.

  Further, in a series resonance type converter in which a DC power source is input, a primary and a secondary are insulated by a transformer, and a bridge circuit having a semiconductor switch element on the primary side is provided, an inductor is provided at one end of the primary winding of the transformer. And a first resonance circuit including a series circuit of a capacitor and an auxiliary winding magnetically coupled to the primary winding of the transformer, and a second inductor and a second in parallel with the auxiliary winding. A second resonance circuit comprising a series circuit with a capacitor, so that a second resonance frequency generated from the second resonance circuit is higher than a first resonance frequency generated from the first resonance circuit. A constant is set for the second inductor and the second capacitor, and a switching frequency at which the semiconductor switch element switches is between the first resonance frequency and the second resonance frequency. Characterized in that are controlled to so that.

  According to the present invention, a second resonance circuit comprising a series circuit of a second inductor and a second capacitor is provided in parallel with the primary winding of the transformer, and the second resonance generated from the second resonance circuit. By setting the constant so that the frequency is higher than the first resonance frequency generated from the first resonance circuit, the output can be controlled at the maximum load, and even when the load is light, series resonance occurs, Since both ends approach the direction in which they are short-circuited, energy is hardly transmitted to the secondary side, and as a result, there is an effect that the output can be controlled at a light load.

  A circuit diagram of the best mode for carrying out the invention is shown in FIG. The series resonance type converter shown in FIG. 1 is a full bridge type bridge having DC power supply Vin as an input, primary and secondary are insulated by a transformer T, and semiconductor switching elements Q1, Q2, Q3, and Q4 are provided on the primary side. A rectifier circuit 11 having a circuit 1A and rectifier diodes D5, D6, D7, and D8 on the secondary side is provided. The bridge circuit 1A has a reference inverter 5 composed of switch elements Q1 and Q2 and a control inverter 6 composed of switch elements Q3 and Q4. A first resonance circuit 2 having a series circuit of an inductor Lr and a capacitor Cr is connected to one end of the primary winding of the transformer T.

  The series resonance type converter according to the present invention includes a second resonance circuit 3 formed of a series circuit of a second inductor Lr1 and a second capacitor Cr1 in parallel with the primary winding of the transformer T. Have Further, the second inductor Lr1 and the second capacitor Cr1 are set so that the second resonance frequency fr2 generated from the second resonance circuit 3 is higher than the first resonance frequency fr1 generated from the first resonance circuit. Is set as a constant. Further, the switching frequency fs at which the semiconductor switch elements Q1, Q2, Q3, and Q4 are switched is controlled to be between the first resonance frequency fr1 and the second resonance frequency fr2. As for the control means for the switching frequency fs, for example, means for providing a control circuit (not shown) between the conventionally known converter output section and the gate terminals of the semiconductor switch elements Q1, Q2, Q3, Q4, etc. However, the control means is not limited in the present invention.

  The series resonance type converter configured as described above operates as follows. First, the operation at the maximum load, that is, at the rated output will be described. In this case, since the resonance frequency fr1 of the first resonance circuit 2 becomes the switching frequency fs, the second resonance circuit 3 is hardly affected. Therefore, the operation is the same as that of a conventional series resonance type converter.

  Describing in detail with reference to FIG. 1, first, when the gate signals of the semiconductor switches Q2 and Q3 are turned off from the state where the semiconductor switches Q2 and Q3 are turned on, a back electromotive force is generated in the first inductor Lr. The internal capacitors C2 and C3 of the semiconductor switches Q2 and Q3 are charged up to the input power source Vin, and the semiconductor switches Q2 and Q3 perform a zero voltage switching operation. The energy accumulated in the first inductor Lr flows to the secondary side via the transformer T while being regenerated to the input power source Vin, and supplies energy to the load side. Thereafter, a zero current switching operation is performed because the gate signals of the semiconductor switches Q1 and Q4 are turned on in a state where current flows through the internal diodes D1 and D4 of the semiconductor switches Q1 and Q4. Thereafter, a resonance action occurs in the first resonance circuit 2, and a sinusoidal current flows in the first resonance circuit 2 to supply energy to the load.

  Thereafter, the semiconductor switch elements Q1 and Q4 are turned off, and the charges of the internal capacitors C1 and C4 of the semiconductor switch elements Q1 and Q4 are sufficiently charged by the energy (resonant current) accumulated in the first inductor Lr, and the semiconductor switch element Q2 , Q3, the internal capacitors C2 and C3 are discharged to 0V. When the charging / discharging of the internal capacitors C1, C2, C3, and C4 is completed, the energy stored in the first inductor Lr is regenerated to the power source through the internal diodes D2 and D3 of the semiconductor switch elements Q2 and Q3. Thereafter, the gate signals of the semiconductor switch elements Q2 and Q3 are turned on, and the same operation as when the gate signals of the semiconductor switch elements Q1 and Q4 are turned on is performed.

  Subsequently, an operation at a light load will be described. In this case, the switching frequency fs approaches the second resonance frequency fr2, and the second resonance circuit 3 causes series resonance. For this reason, both ends of the transformer T approach the direction in which the two ends are short-circuited, energy is not easily transmitted to the secondary side, voltage is not generated in the load, and current flowing through the load is reduced.

  More specifically, when the semiconductor switches Q1, Q2, Q3, and Q4 are turned on / off at a frequency higher than the first resonance frequency fr1, a sinusoidal current flows in the first resonance circuit, and both ends of the transformer T A rectangular wave voltage synchronized with the switching frequency is generated. When this rectangular wave voltage approaches the resonance frequency fr2 of the second resonance circuit 3, series resonance occurs in the second resonance circuit 3, current flows in the second resonance circuit 3, and both ends of the transformer T Approaches the direction of short circuit. As a result, energy is hardly transmitted to the secondary side, load voltage is not generated, and current flowing through the load is reduced.

  With the above action, the output can be controlled at the maximum load, and even at light loads, by causing series resonance, the both ends of the transformer approach the direction in which they are short-circuited, making it difficult for energy to be transmitted to the secondary side. As a result, the output can be controlled at a light load.

  A circuit diagram of the first embodiment of the invention is shown in FIG. The series resonant converter shown in FIG. 2 is characterized in that a half-bridge type bridge circuit 1B including semiconductor switch elements Q1 and Q2 is provided on the primary side.

  The configuration of this example is a form in which the semiconductor switch elements Q3 and Q4 are omitted from the above embodiment, but the semiconductor switch element Q1 and the semiconductor switch element Q2 cannot be turned on at the same time. It is almost the same as the form. Therefore, explanation of the operation is omitted. Therefore, in the present embodiment as well as in the above embodiment, the output can be controlled at the maximum load, and even at the light load, by causing a series resonance, both ends of the transformer approach the direction in which the both ends are short-circuited. As a result, the output can be controlled at light load.

  A circuit diagram of the second embodiment of the invention is shown in FIG. The series resonant converter shown in FIG. 3 has a DC power supply Vin as an input, a primary / secondary circuit is insulated by a transformer T, and a bridge circuit 1C having semiconductor switch elements Q1 and Q2 on the primary side is provided. It is a push-pull type converter in which a center tap is provided in the primary winding and a DC power source Vin is connected to one end of the center tap. A first resonance circuit 2 having a series circuit of an inductor Lr and a capacitor Cr is provided in the center tap. In addition, the series resonance type converter according to the present embodiment includes a second resonance circuit 3 formed of a series circuit of a second inductor Lr1 and a second capacitor Cr1 in parallel with the primary winding of the transformer T. .

  The series resonance type converter according to the present embodiment is a push-pull type converter, but the operation is almost the same as that of the full bridge type converter shown in FIG. Therefore, explanation of the operation is omitted. Therefore, in this embodiment as well as in the previous embodiment, the output can be controlled at the maximum load, and even at the light load, by causing series resonance, both ends of the transformer approach the direction in which the both ends are short-circuited. As a result, the output can be controlled at light load.

  A circuit diagram of the third embodiment of the invention is shown in FIG. The series resonant converter shown in FIG. 4 includes a full-bridge type bridge circuit 1A including semiconductor switch elements Q1, Q2, Q3, and Q4 on the primary side as in the embodiment shown in FIG. The rectifier circuit 11 includes rectifier diodes D5, D6, D7, and D8. A first resonance circuit 2 having a series circuit of an inductor Lr and a capacitor Cr is connected to one end of the primary winding of the transformer T.

  The series resonance type converter according to the present embodiment includes a second resonance circuit 13 formed of a series circuit of a second inductor Lr1 and a second capacitor Cr1 in parallel with the secondary winding of the transformer T. It has the characteristics. Similarly to the embodiment, the second inductor is set so that the second resonance frequency fr2 generated from the second resonance circuit 13 is higher than the first resonance frequency fr1 generated from the first resonance circuit. Lr1 and the second capacitor Cr1 are set as constants. Further, the switching frequency fs at which the semiconductor switch elements Q1, Q2, Q3, and Q4 are switched is controlled to be between the first resonance frequency fr1 and the second resonance frequency fr2.

  The series resonance type converter configured as described above operates as follows. First, at the maximum load, the resonance frequency fr1 of the first resonance circuit 2 becomes the switching frequency fs, so that the second resonance circuit 13 is hardly affected. Therefore, the same operation as in the above embodiment is performed.

  Subsequently, an operation at a light load will be described. In this case, the switching frequency fs approaches the second resonance frequency fr2, and series resonance occurs between the first resonance circuit 2 and the second resonance circuit 13. In the present embodiment, current flows through the primary winding and the secondary winding of the transformer T, but almost no current flows after the rectifier diode 11 connected to the secondary winding. A current flows through the second resonance circuit 13 connected in parallel. As a result, both ends of the secondary winding of the transformer T approach the direction in which they are short-circuited, making it difficult for energy to be transmitted to the output side, no load voltage is generated, and the current flowing through the load decreases. Although the operation is different from the embodiment shown in FIG. 1 in the above points, the result is the same as that of the embodiment shown in FIG.

  As described above, the output can be controlled at the maximum load, and even when the load is light, the resonance of the transformer approaches the direction where both ends of the transformer are short-circuited. The output can be controlled at light load.

  A circuit diagram of the fourth embodiment of the invention is shown in FIG. The series resonance type converter shown in FIG. 5 includes a full-bridge type bridge circuit 1A having semiconductor switch elements Q1, Q2, Q3, and Q4 on the primary side, as in the embodiment shown in FIG. The rectifier circuit 11 includes rectifier diodes D5, D6, D7, and D8. A first resonance circuit 2 having a series circuit of an inductor Lr and a capacitor Cr is connected to one end of the primary winding of the transformer T.

  The series resonance type converter according to the present embodiment includes an auxiliary winding magnetically coupled to the primary winding of the transformer T. In parallel with the auxiliary winding, a second inductor Lr1 and a second capacitor Cr1 are provided. A second resonance circuit 23 formed of a series circuit is provided. Similarly to the embodiment, the second inductor is set so that the second resonance frequency fr2 generated from the second resonance circuit 23 is higher than the first resonance frequency fr1 generated from the first resonance circuit. Lr1 and the second capacitor Cr1 are set as constants.

  The series resonance type converter configured as described above operates as follows. First, at the maximum load, the resonance frequency fr1 of the first resonance circuit 2 becomes the switching frequency fs, so that the second resonance circuit 13 is hardly affected. Therefore, the same operation as in the above embodiment is performed.

  Subsequently, an operation at a light load will be described. In this case, the switching frequency fs approaches the second resonance frequency fr2, and the second resonance circuit 23 causes series resonance. In this case, as in the embodiment shown in FIG. 1, a current flows through the second resonance circuit 23, and both ends of the auxiliary winding of the transformer T approach the direction in which they are short-circuited. As a result, the energy is hardly transmitted to the secondary side, the load voltage is not generated, and the current flowing through the load is reduced. Therefore, the same operation as in the above embodiment is performed.

  In all the embodiments of the series resonance converter according to the present invention, the rectifier circuit 11 including the rectifier diodes D5, D6, D7, and D8 is provided on the secondary side. For example, the secondary side may be a center tap system. Further, although the full bridge type converter is used in the third and fourth embodiments, it can be applied to a half bridge type converter and a push-pull type converter.

  According to the present invention, a second resonance circuit comprising a series circuit of a second inductor and a second capacitor is provided in parallel with the primary winding of the transformer, and the second resonance generated from the second resonance circuit. By setting the constant so that the frequency is higher than the first resonance frequency generated from the first resonance circuit, the output can be controlled at the maximum load, and even when the load is light, series resonance occurs, Since both ends approach the direction in which they are short-circuited, energy is not easily transmitted to the secondary side, and as a result, the output can be controlled at light loads and can be used industrially.

1 is a circuit diagram showing the best embodiment of the present invention. It is a circuit diagram which shows the 1st Example which concerns on this invention. It is a circuit diagram which shows the 2nd Example which concerns on this invention. It is a circuit diagram which shows the 3rd Example which concerns on this invention. It is a circuit diagram which shows the 4th Example which concerns on this invention. It is the circuit diagram which showed the prior art example.

Explanation of symbols

Vin Input power source RL Load T Transformer Co Output capacitor Cr, Cr1 Resonant capacitors C1, C2, C3, C4 Capacitors Lr, Lr1 Resonant inductors D5, D6, D7, D8 Rectifier diodes Q1, Q2, Q3, Q4 Semiconductor switch elements 1A, 1B , 1C Bridge circuit 2 First resonance circuit 3, 13, 23 Second resonance circuit 5 Reference inverter 6 Control inverter 11 Rectifier circuit

Claims (3)

In a series resonance type converter in which a DC power source is input, a primary and a secondary are insulated by a transformer, and a bridge circuit having a semiconductor switch element on the primary side is provided, an inductor and a capacitor at one end of the primary winding of the transformer And a second resonant circuit comprising a series circuit of a second inductor and a second capacitor in parallel with the primary winding of the transformer, and the second resonant circuit. The second inductor and the second capacitor are set constant so that the second resonance frequency generated from the first resonance circuit is higher than the first resonance frequency generated from the first resonance circuit, and the semiconductor switch A series resonance type converter characterized in that the switching frequency at which the element switches is controlled to be between the first resonance frequency and the second resonance frequency. Data. In a series resonance type converter in which a DC power source is input, a primary and a secondary are insulated by a transformer, and a bridge circuit having a semiconductor switch element on the primary side is provided, an inductor and a capacitor at one end of the primary winding of the transformer And a second resonant circuit comprising a series circuit of a second inductor and a second capacitor in parallel with the secondary winding of the transformer, and A constant value is set for the second inductor and the second capacitor so that a second resonance frequency generated from the second resonance circuit is higher than a first resonance frequency generated from the first resonance circuit; A series resonance type converter characterized in that the switching frequency at which the switching element switches is controlled to be between the first resonance frequency and the second resonance frequency. Data. In a series resonance type converter in which a DC power source is input, a primary and a secondary are insulated by a transformer, and a bridge circuit having a semiconductor switch element on the primary side is provided, an inductor and a capacitor at one end of the primary winding of the transformer A first resonance circuit including a series circuit of the transformer, an auxiliary winding magnetically coupled to the primary winding of the transformer, and a second inductor and a second capacitor in parallel with the auxiliary winding. A second resonance circuit composed of a series circuit of the second resonance circuit, wherein the second resonance frequency generated from the second resonance circuit is higher than the first resonance frequency generated from the first resonance circuit. A constant is set for the second inductor and the second capacitor, and the switching frequency at which the semiconductor switch element switches is between the first resonance frequency and the second resonance frequency. Series resonant converter, characterized in that are controlled to.

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