JP5452093B2 - Isolated converter - Google Patents

Description

  According to the present invention, a pair of input terminals and a pair of output terminals are insulated via an insulating transformer, and the voltage between the pair of input terminals is changed to a voltage having another value using the insulating transformer. The present invention relates to an isolated converter that converts and outputs from the pair of output terminals.

  As this type of isolated converter, for example, as can be seen in Patent Document 1 below, a transformer in which a pair of primary coils of a transformer alternately serve as a forward converter and an energy storage coil has been proposed. According to this, the ripple of the output current can be reduced without providing a choke coil on the secondary side of the transformer.

JP 2008-113548 A

  By the way, for example, when the converter is used as an isolated converter that steps down the voltage of a high-voltage battery mounted on a hybrid vehicle and outputs it to a low-voltage battery, a large current flows through the secondary coil. The number of turns is severely limited. In this case, since the degree of freedom for adjusting the output voltage of the isolated converter by the turns ratio of the transformer is reduced, it may be difficult to generate a desired output voltage.

  Note that not only the converter having the above-described configuration, but also an isolated converter, such a situation that the adjustment of the output voltage is likely to be difficult due to the limitation of the turns ratio of the transformer is generally common.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an isolated converter that can suitably relax the restriction on the design of the output voltage due to the restriction on the turn ratio of the insulating transformer. There is.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

In the first invention, the pair of input terminals and the pair of output terminals are insulated via an insulating transformer, and the voltage between the pair of input terminals has a different value using the insulating transformer. In the isolated converter that converts the voltage into an output from the pair of output terminals, the smoothing means that smoothes the output current on the secondary side of the insulation transformer, and the primary side coil of the insulation transformer includes 2 A voltage adjusting transformer in which a secondary coil is connected in series, and a primary coil of the insulating transformer and a secondary coil of the voltage adjusting transformer provided on the primary side of the insulating transformer Voltage applying means for applying a voltage equal to the total magnitude of the applied voltages to the primary coil of the voltage adjusting transformer.

  The isolated converter can adjust its output voltage by changing the voltage applied to the primary coil of the insulating transformer and its period. Therefore, the output voltage can be adjusted by adjusting the voltage applied to the primary coil of the insulating transformer. In the above invention, paying attention to this point, a voltage adjusting transformer is newly provided and applied to the primary coil of the voltage adjusting transformer and the primary coil of the insulating transformer and the secondary coil of the voltage adjusting transformer. A voltage equal to the total voltage magnitude applied is applied. Here, the voltage applied to the primary side coil of the insulating transformer is determined from the total voltage applied to the primary side coil of the insulating transformer and the secondary side coil of the voltage adjusting transformer to the secondary side of the voltage adjusting transformer. This is a value obtained by subtracting the voltage applied to the coil. Therefore, by providing a voltage adjusting transformer, the voltage applied to the primary side coil of the insulating transformer can be adjusted to the voltage applied to the primary side coil of the voltage adjusting transformer with respect to the above total voltage. Changes by the value converted by the turn ratio of the transformer. This is equivalent to changing the turn ratio of the insulating transformer when expressing the relationship between the output voltage and the input voltage using the turn ratio of the insulating transformer. For this reason, the restriction on the design of the output voltage due to the restriction on the turn ratio of the insulating transformer can be preferably relaxed.

According to a second invention, in the first invention, further comprising a series connection body of a first opening / closing means and a second opening / closing means connected in parallel between the pair of input terminals, wherein the first opening / closing means is in a closed state. Thus, a first closed loop circuit including a secondary coil of the voltage adjusting transformer, a primary coil of the insulating transformer, and the first opening / closing means is formed, and the second opening / closing means is closed. Thus, a second closed loop circuit including a primary coil of the voltage adjusting transformer and the second opening / closing means is formed, and the voltage applying means includes the first closed loop circuit, the second closed loop circuit, and the like. It is characterized by comprising the storage means different from each other.

  In the above invention, the voltage applying means can be configured simply.

In a third aspect based on the first aspect , the voltage application means includes a primary side coil of the voltage adjusting transformer and a primary side coil of the insulating transformer and the voltage adjusting transformer connected in series to each other. It is comprised by connecting in parallel with the secondary side coil of this.

  In the above invention, the voltage applying means can be configured simply.

According to a fourth invention, in any one of the first to third inventions, the smoothing means includes a primary side coil of the insulating transformer.

According to a fifth invention, in any one of the first to fourth inventions, the isolated converter is a step-down converter.

  The step-down converter steps down the voltage of the high voltage battery provided in the in-vehicle high voltage system isolated from the in-vehicle low voltage system and outputs the voltage to the low voltage battery provided in the in-vehicle low voltage system. Also good. In this case, since the current of the secondary coil becomes large, the number of turns of the secondary coil tends to be limited. For this reason, the utility value of the voltage adjusting transformer and the voltage applying means is particularly great.

1 is a system configuration diagram according to a first embodiment. FIG. A circuit diagram for explaining operation of a DCDC converter concerning the embodiment. The time chart which shows the operation | movement of the DCDC converter concerning the embodiment. The figure which shows the output voltage of the DCDC converter concerning the embodiment. The system block diagram concerning 2nd Embodiment. The circuit diagram which shows the circuit structure of the DCDC converter concerning 3rd Embodiment. The circuit diagram which shows the circuit structure of the DCDC converter concerning 4th Embodiment. The circuit diagram which shows the circuit structure of the DCDC converter concerning 5th Embodiment. The circuit diagram which shows the circuit structure of the DCDC converter concerning 6th Embodiment. The circuit diagram which shows the circuit structure of the DCDC converter concerning 7th Embodiment. The circuit diagram which shows the circuit structure of the DCDC converter concerning 8th Embodiment. The circuit diagram which shows the circuit structure of the modification of the said 1st Embodiment. The circuit diagram which shows the circuit structure of the modification of the said 1st Embodiment. The circuit diagram which shows the circuit structure of the modification of the said 1st Embodiment. The circuit diagram which shows the circuit structure of the modification of the said 1st Embodiment.

(First embodiment)
Hereinafter, a first embodiment in which an insulated converter according to the present invention is applied to a hybrid vehicle will be described with reference to the drawings.

  FIG. 1 shows a system configuration according to the present embodiment.

  The illustrated DCDC converter 10 converts a DC voltage applied to a pair of input terminals into a DC voltage of another value and outputs it. In particular, the DCDC converter 10 is a step-down converter. Specifically, the DCDC converter 10 steps down the voltage of the high voltage battery 12 (for example, several hundred to several hundreds of volts) to a predetermined low voltage (for example, several to several tens of volts) to reduce the in-vehicle low voltage battery 14. Apply to. The high voltage battery 12 serves as a power source for a motor generator as an in-vehicle main machine, and constitutes an in-vehicle high voltage system that is insulated from the in-vehicle low voltage system. Moreover, the low voltage battery 14 comprises an in-vehicle low voltage system, The negative electrode terminal is connected to the vehicle body. The low voltage battery 14 serves as a power source for in-vehicle auxiliary equipment.

  The DCDC converter 10 includes a series connection body of a pair of switching elements Q1, Q2 connected in parallel to the high voltage battery 12. In this embodiment, N-channel power MOS field effect transistors are illustrated as the switching elements Q1 and Q2. Diodes D1 and D2 are connected in antiparallel to these switching elements Q1 and Q2, respectively. These diodes D1 and D2 are body diodes of the switching elements Q1 and Q2.

  The DCDC converter 10 includes insulating transformers T2 and T3. Here, in the insulating transformers T2 and T3, the primary coils W3 and W4 are connected in series with each other, and the secondary coils W5 and W6 are connected in series with each other. A series connection body of the primary side coil W1 and the secondary side coil W2 of the voltage adjusting transformer T1 is connected in series to the primary side coils W3 and W4 of the insulating transformers T2 and T3. And the serial connection body of secondary side coil W2 and primary side coil W1, W3, W4 is connected in parallel with the serial connection body of switching element Q1, Q2. Specifically, the input side of the switching element Q2 and the primary side coil W1 are connected via a capacitor C2, and the output side of the switching element Q1 and the primary side coil W4 are connected via a capacitor C1. . Also, the connection point of the switching elements Q1, Q2 and the connection point of the primary side coil W1 and the secondary side coil W2 of the voltage adjusting transformer T1 are connected.

  The insulating transformer T2 forms a forward converter when the switching element Q2 is turned on, and the primary coil W3 functions as an energy storage coil when the switching element Q1 is turned on. The insulating transformer T3 forms a forward converter when the switching element Q1 is turned on, and the primary coil W4 functions as an energy storage coil when the switching element Q2 is turned on. This is a function realized by the switching elements Q3 and Q4 for synchronous rectification. In the present embodiment, N-channel power MOS field effect transistors are illustrated as the switching elements Q3 and Q4. The connection between these and the secondary coils W5 and W6 is set so that the body diode does not hinder the realization of the above function.

  A capacitor 16 and a low voltage battery 14 are connected in parallel to the secondary coils W5 and W6 of the insulating transformers T2 and T3. A voltage sensor 20 for detecting the voltage is connected to the capacitor 16, and a current sensor 18 is connected between the capacitor 16 and the low voltage battery 14.

  Control device 30 receives detection values of voltage sensor 20 and current sensor 18 and outputs operation signals MQ1 to MQ4 for operating switching elements Q1 to Q4 based on these values. Here, in order to operate the switching elements Q1 and Q2 in a complementary manner, the operation signals MQ1 and MQ2 are signals whose logic values are inverted from each other. However, in practice, a dead time is provided in order to avoid that both switching elements Q1 and Q2 are simultaneously turned on.

  Next, the operation of the switching elements Q1, Q2 will be described based on FIG.

  FIG. 2A shows a case where the switching element Q1 is on and the switching element Q2 is off. In this case, as shown by the one-dot chain line in the figure, the secondary side coil W2 and the primary side are provided by a closed loop circuit including the primary side coils W4 and W3, the secondary side coil W2, the switching element Q1, and the capacitor C1. The voltage of the capacitor C1 is applied to the side coils W3 and W4. In addition, as shown by a two-dot chain line in the figure, the high-voltage battery 12, the capacitor C2, the primary-side coil W1, and the closed-loop circuit including the switching element Q1 are connected to the primary-side coil W1 by the high-voltage battery 12 and The total voltage of the capacitor C2 is applied.

  FIG. 2B shows a case where the switching element Q1 is in an off state and the switching element Q2 is in an on state. In this case, as indicated by a one-dot chain line in the figure, the voltage of the capacitor C2 is applied to the primary coil W1 by a closed loop circuit including the capacitor C2, the switching element Q2, and the primary coil W1. Further, as shown by a two-dot chain line in the figure, the secondary coil W2 is provided by a closed loop circuit including the high voltage battery 12, the switching element Q2, the secondary coil W2, the primary coils W3 and W4, and the capacitor C1. The total voltage of the high voltage battery 12 and the capacitor C1 is applied to the primary coils W3 and W4.

  Next, the relationship between the time ratio D of the ON time of the switching element Q1 with respect to one cycle of the ON / OFF operation of the switching elements Q1, Q2 and the output voltage Vout is derived. Below, the number of turns N1, N3, N4, N2, N5, N6 of the primary side coils W1, W3, W4 and the secondary side coils W2, W5, W6 and the voltage of the high voltage battery 12 (input voltage Vin) And voltages Vc1 and Vc2 of capacitors C1 and C2. However, here, it is assumed that “N3 / N5 = N4 / N6 = Np / Ns”. Further, the voltages of the primary side coils W1, W3, W4 and the secondary side coil W2 in the ON period of the switching element Q1 and the ON period of the switching element Q2 are set to the voltage Vion and the voltage Vioff (i = 1 to 4). . Incidentally, the “number of turns” refers to the number of times the transformer magnetic path is linked.

For the coil on the high voltage battery 12 side, the et product is expressed by the following equations (c1) to (c4).
D · V1on = (1−D) · V1off (c1)
D · V2on = (1−D) · V2off (c2)
D · V3on = (1-D) · V3off (c3)
D.V4on = (1-D) .V4off (c4)
Here, the voltage Vc2 can be calculated from the above equation (c1).
D · (Vin−Vc2) = (1−D) · Vc2
Vc2 = D · Vin
Further, the voltage Vc1 can be calculated from the total voltage applied to the secondary coil W2 and the primary coils W3 and W4 and the above equations (c2) to (c4).
D · Vc1 = (1-D) (Vin−Vc1)
Vc1 = (1-D) · Vin
From the above, the following equation (c5) is established.
V1off + V2off + V3off + V4off
= Vin-Vc2-Vc1
= 0 (c5)
In the above formula (c5), since V3off = (Np / Ns) Vout, the following formula (c6) is obtained.
-{1+ (N2 / N1)} DVin + (Np / Ns) DVout + V4off
= 0 (c6)
Further, from the above equation (c4), the following equation (c7) is established.
D (Np / Ns) Vout = (1-D) V4off (c7)
From the above formulas (c6) and (c7), the following formula (c8) is obtained.
Vout = (Ns / Np) {1+ (N2 / N1)} D (1-D) Vin (c8)
The output voltage Vout expressed by the above equation (c8) is obtained by multiplying the output voltage of the DCDC converter described in Patent Document 1 by {1+ (N2 / N1)}. For this reason, regardless of restrictions on the turn ratio (Np / Ns) of the insulating transformers T2 and T3, the output voltage Vout can be freely adjusted by the turn ratio (N2 / N1) of the voltage adjusting transformer T1. . This is particularly beneficial for a step-down converter such as this embodiment. That is, in the case of the above application, since the output currents of the insulating transformers T2 and T3 become very large, it is very difficult to increase the number of turns of the secondary coils W5 and W6. Here, when the number of turns Ns of the secondary coils W5 and W6 is limited to “1”, the turns ratio (Ns / Np) is “1/2, 1/3, 1/4,. Thus, only the value “1 / n (n = 1, 2, 3...)” Can be obtained. For this reason, when the duty ratio D and the input voltage range are limited, it may be difficult to control the output voltage Vout to a desired value. On the other hand, according to the present embodiment, the output voltage can be adjusted by the turn ratio (N2 / N1) of the voltage adjusting transformer T1.

  This function is achieved by applying a voltage equal to the voltage applied to the primary coils W3 and W4 of the insulating transformers T2 and T3 and the secondary coil W2 of the voltage adjusting transformer T1 to the voltage adjusting transformer T1. This is realized because it is applied to the secondary coil W1. That is, during the period shown in FIG. 2A, the voltage applied to the primary coils W3 and W4 of the insulating transformers T2 and T3 and the secondary coil W2 of the voltage adjusting transformer T1 is the voltage of the capacitor C1. Vc1 (= (1-D) Vin). On the other hand, during this period, the voltage applied to the primary coil W1 of the voltage adjusting transformer T1 is the total voltage (Vin−DVin) of the voltage of the high voltage battery 12 and the voltage of the capacitor C2. For this reason, the absolute value of both is equal during this period. Also, during the period shown in FIG. 2B, the voltage applied to the primary side coils W3 and W4 of the insulating transformers T2 and T3 and the secondary side coil W2 of the voltage adjusting transformer T1 is high voltage battery 12. And the voltage of the capacitor C1 (Vin− (1−D) Vin = DVin). On the other hand, during this period, the voltage applied to the primary coil W1 of the voltage adjusting transformer T1 is the voltage of the capacitor C2 (Vc2 = DVin). For this reason, the absolute values of both are equal even during this period.

  Further, in this embodiment, the primary side coil W1 and the secondary side coil W2 of the voltage adjusting transformer T1 are connected to the primary side coils W3 and W4 of the insulating transformers T2 and T3 and the voltage in any period. A voltage having a polarity opposite to that applied to the secondary coil W2 of the adjustment transformer T1 is set to be applied to the secondary coil W2 of the voltage adjustment transformer T1. In this case, the voltage V applied to the primary side coils W3 and W4 of the insulating transformers T2 and T3 and the secondary side coil W2 of the voltage adjusting transformer T1 is the primary side coils W3 and W3 of the insulating transformers T2 and T3. Compared with the case where the voltage is applied only to W4, the voltage applied to these is increased by “(N2 / N1) V”. For this reason, the output voltage Vout is generated.

  FIG. 3 shows the measurement results of the output voltage Vout and the like for each of the duty ratios D = 50% and 25%. Specifically, FIG. 3 (a) shows the output voltage Vout, FIG. 3 (b) shows the transition of the voltage between the input and output terminals of the switching element Q1, and FIG. 3 (c) shows the primary coil W1. 3 (d) shows the transition of the voltage V2 of the secondary coil W2, FIG. 3 (e) shows the transition of the voltage V3 of the primary coil W3, and FIG. (F) shows transition of the voltage V4 of the primary coil W4. In this measurement result, the relationship of the above formula (c5) was not strictly established. In the above calculation, an approximate calculation was performed by a tightly coupled transformer, while the actual insulation transformer T2 , T3 and the voltage adjusting transformer T1 are considered to have a leakage magnetic flux.

  FIG. 4 shows measurement results of changes in the output voltage Vout when the turns ratio Np / Ns of the insulating transformers T2 and T3 is fixed and the turns ratio N1 / N2 of the voltage adjusting transformer T1 is adjusted. In the upper left of the figure, it is shown that a transformer having an EE core is used for this measurement.

  It should be noted that a known dead time is provided in order to avoid both of the switching elements Q1 and Q2 being turned on when performing complementary driving in which the switching elements Q1 and Q2 are alternately turned on. This dead time is desirably set so that soft switching is possible based on a time constant determined by the diodes D1 and D2 and the parasitic capacitor connected in parallel to the switching elements Q1 and Q2.

  According to the embodiment described in detail above, the following effects can be obtained.

  (1) When the insulating transformers T2, T3, etc. are approximated by a tightly coupled transformer, application to the primary side coils W3, W4 of the insulating transformers T2, T3 and the secondary side coil W2 of the voltage adjusting transformer T1 A voltage equal to the total voltage was applied to the primary coil W1 of the voltage adjusting transformer T1. As a result, the restriction on the degree of freedom in adjusting the output voltage Vout due to the restriction of the turns ratio of the insulating transformers T2 and T3 can be relaxed suitably.

  (2) It further includes a series connection body of switching elements Q1 and Q2 connected in parallel between a pair of input terminals, and the secondary coil W2 of the voltage adjusting transformer T1 when the switching element Q1 is closed. The primary side coils W3 and W4 of the insulating transformers T2 and T3, the capacitor C1 included in the first closed loop circuit including the switching element Q1, and the primary of the voltage adjusting transformer T1 when the switching element Q2 is closed. The capacitor C2 included in the second closed loop circuit including the side coil W1 and the switching element Q2 is used as a different storage device. As a result, a voltage equal to the total magnitude of the voltages applied to the primary side coils W3 and W4 of the insulating transformers T2 and T3 and the secondary side coil W2 of the voltage adjusting transformer T1 is set to the primary of the voltage adjusting transformer T1. It can be applied to the side coil W1.

  (3) The means (smoothing means) for smoothing the output current on the secondary side of the insulating transformers T2 and T3 is constituted by the primary coils W3 and W4 of the insulating transformers T2 and T3. As a result, a means for smoothing the output current can be configured without providing a choke coil on the secondary side of the insulating transformers T2 and T3.

  (4) The DCDC converter 10 is a step-down converter. Thereby, since the current of the secondary coil increases, the number of turns of the secondary coil tends to be limited. For this reason, the utility value of the voltage adjusting transformer T1 is particularly great.

(Second Embodiment)
Hereinafter, the second embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  FIG. 5 shows a system configuration diagram according to the present embodiment. In FIG. 5, members corresponding to those shown in FIG. 1 are given the same reference numerals for convenience.

  As shown in the drawing, in the present embodiment, a coil for smoothing the output current on the secondary side of the insulating transformer T <b> 2 is configured by a choke coil 32. For this reason, the insulating transformer T2 is a single transformer. FIG. 5 shows an example in which energy is output from the primary side to the secondary side of the insulating transformer T2 when the switching element Q2 is turned on.

  Even in such a configuration, the output voltage is expressed by the above equation (c8).

  According to this embodiment described above, the effects (1), (2), and (4) of the first embodiment can be obtained.

(Third embodiment)
Hereinafter, the third embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  FIG. 6 shows a circuit configuration of the DCDC converter according to the present embodiment. In FIG. 6, members corresponding to those shown in FIG. 1 are given the same reference numerals for convenience.

  As shown in the figure, in the present embodiment, the secondary coil of the voltage adjusting transformer T1, the primary coils W3 and W4 of the insulating transformers T2 and T3, and the capacitor C1 are connected in parallel to the switching element Q1. Yes. Further, the primary side coil W1 of the voltage adjusting transformer T1 is connected in parallel with the secondary side coil of the voltage adjusting transformer T1 and the primary side coils W3 and W4 of the insulating transformers T2 and T3.

  In addition, when the switching element Q2 is turned on, the secondary side of the insulating transformers T2 and T3 prevents current from flowing through the secondary coil W5, and when the switching element Q1 is turned on. Means (diode D4) for allowing a current to flow through the secondary coil W5 is provided. In addition, when the switching element Q1 is turned on, the secondary side of the insulating transformers T2 and T3 prevents current from flowing through the secondary coil W6 and when the switching element Q2 is turned on. Means (diode D3) for allowing a current to flow through the secondary coil W6 is provided.

  Even with such a configuration, a voltage having a magnitude equal to the voltage applied to the secondary coil W2 of the voltage adjusting transformer T1 and the primary coils W3 and W4 of the insulating transformers T2 and T3 is equal to the voltage of the voltage adjusting transformer T1. It is applied to the primary coil W1. In particular, by adjusting the connection between the primary side coil W1 and the secondary side coil W2 of the voltage adjusting transformer T1, the secondary side coil of the voltage adjusting transformer T1 and the primary side of the insulating transformers T2 and T3. A voltage having a polarity opposite to that applied to the coils W3 and W4 is applied to the secondary coil W2 of the voltage adjusting transformer T1. For this reason, the output voltage of the DCDC converter 10 is also expressed by the above equation (c8).

  This DCDC converter 10 is basically a circuit in which a voltage adjusting transformer T1 is added to the circuit described in Japanese Patent Application Laid-Open No. 2007-74830. Here, the output voltage of the converter described in the above publication is the same as that described in Patent Document 1.

  Also according to the present embodiment described above, the following effects can be obtained in addition to the effects (1), (3), and (4) of the first embodiment.

  (5) The primary coil W1 of the voltage adjusting transformer T1 is connected in parallel to the primary coils W5 and W6 of the insulating transformers T2 and T3 and the secondary coil W2 of the voltage adjusting transformer T1. As a result, a voltage equal to the total magnitude of the voltages applied to the primary side coils W3 and W4 of the insulating transformers T2 and T3 and the secondary side coil W2 of the voltage adjusting transformer T1 is set to the primary of the voltage adjusting transformer T1. It can be applied to the side coil W1.

(Fourth embodiment)
Hereinafter, the fourth embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  FIG. 7 shows a circuit configuration of the DCDC converter according to the present embodiment. In FIG. 7, members corresponding to those shown in FIG. 1 are given the same reference numerals for the sake of convenience.

  As shown in the figure, the high voltage battery 12 is connected in parallel with a series connection body of a secondary coil W2 of the voltage adjusting transformer T1, a primary coil W3 of the insulating transformer T2, and a switching element Q1. ing. A series connection body of a capacitor C1 and a switching element Q2 is connected in parallel to the secondary side coil W2 of the voltage adjusting transformer T1 and the primary side coil W3 of the insulating transformer T2. Further, the primary side coil W1 of the voltage adjusting transformer T1 is connected in parallel to the secondary side coil W2 of the voltage adjusting transformer T1 and the primary side coil W3 of the insulating transformer T2.

  On the other hand, the insulating transformer T2 includes secondary coils W4 and W5. These secondary coils W4 and W5 are connected in parallel to the capacitor 16 via the choke coil 44, respectively. Further, the secondary coil W4 allows the current of the secondary coil W4 when the switching element Q1 is turned on, and the secondary coil W4 receives a current when the switching element Q2 is turned on. A means (diode 40) for blocking the flow is connected. Further, the secondary coil W5 allows the current of the secondary coil 5 to be allowed when the switching element Q2 is turned on, and the current to the secondary coil W5 when the switching element Q1 is turned on. A means (diode 42) for blocking the flow is connected.

  The DCDC converter 10 is basically obtained by adding a voltage adjustment transformer T1 to a classic active clamp type converter described in Japanese Patent Laid-Open No. 5-276651. Here, depending on the setting of the connection polarity between the primary side coil W1 and the secondary side coil W2 of the voltage adjusting transformer T1, the primary side coils W3 and W4 of the insulating transformers T2 and T3 and the voltage adjusting transformer T1 are two. A voltage having a polarity opposite to the polarity of the voltage applied to the secondary coil W2 is applied to the secondary coil W2 of the voltage adjusting transformer T1. For this reason, the output voltage Vout of the DCDC converter 10 is obtained by multiplying the output voltage of the classic converter by {1+ (N2 / N1)}.

  According to the present embodiment described above, the effects (1) and (4) of the previous first embodiment, the effect (5) of the previous third embodiment, and the like can be obtained. .

(Fifth embodiment)
Hereinafter, a fifth embodiment will be described with reference to the drawings, focusing on differences from the first embodiment.

  FIG. 8 shows a circuit configuration of the DCDC converter according to the present embodiment. In FIG. 8, members corresponding to those shown in FIG. 1 are given the same reference numerals for convenience.

  As shown in the figure, the DCDC converter 10 includes a pair of secondary coils W5 and W6 as secondary coils of the insulating transformer T2. These secondary coils W5 and W6 are connected in parallel to the capacitor 16 via synchronous rectification switching elements Q3 and Q4, respectively.

  The DCDC converter 10 includes a series connection body of a pair of capacitors C1 and C2 and a series connection body of the switching elements Q1 and Q2, and these series connection bodies are connected in parallel to each other. Between the connection point of the switching elements Q1 and Q2 and the connection point of the pair of capacitors C1 and C2, the secondary coil W2a of the voltage adjusting transformer T1a and the primary coil W3 of the insulating transformer T2 Is connected. The insulation transformer T2 further includes a boosting coil (primary coil W4) connected between the connection point of the switching elements Q1 and Q2 and the positive electrode of the high voltage battery 12 as the primary coil. I have.

  The primary coil W1a of the voltage adjusting transformer T1a is connected in parallel to the secondary coil W2a of the voltage adjusting transformer T1a and the primary coil W3 of the insulating transformer T2. Further, the secondary coil W2b of the voltage adjusting transformer T1b is connected in series to the primary coil W4 of the insulating transformer T2, and the voltage adjusting transformer is connected to the primary coil W4 and the secondary coil W2b. The primary coil W1b of T1b is connected in parallel.

  This DC-DC converter 10 is basically obtained by adding voltage adjusting transformers T1a and T1b to the circuit described in Japanese Patent Laid-Open No. 2003-79142. In the converter of the above publication, primary coils W3 and W4 of the insulating transformer T2 are configured to be applied with the same voltage. In the present embodiment, in view of this point, the voltage applied to the primary side coils W3 and W4 is equal to each other by providing the primary side coils W3 and W4 with different voltage adjusting transformers T1a and T1b. Change only the amount. Incidentally, in the previous third embodiment, the insulating transformers T2 and T3 are connected in series, and the voltage applying means (the high voltage battery 12 and the capacitor C1) are connected in parallel thereto. One voltage adjusting transformer is provided for T1 and T2.

  According to such a configuration, a voltage having a magnitude equal to the total voltage applied to the primary side coil W3 of the insulating transformer T2 and the secondary side coil W2a of the voltage adjusting transformer T1a is set to 1 of the voltage adjusting transformer T1a. It can be applied to the secondary coil W1a. Further, a voltage having a magnitude equal to the total voltage applied to the primary side coil W4 of the insulating transformer T2 and the secondary side coil W2b of the voltage adjusting transformer T1b is set to the primary side coil W1b of the voltage adjusting transformer T1b. Can be applied. In particular, the connection between the primary side coil W1a and the secondary side coil W2a of the voltage adjusting transformer T1a is applied to the primary side coil W3 of the insulating transformer T2 and the secondary side coil W2a of the voltage adjusting transformer T1a. A voltage having a polarity opposite to that of the voltage is set to be applied to the secondary coil W2a of the voltage adjusting transformer T1a. Further, the connection between the primary side coil W1b and the primary side coil W2b of the voltage adjusting transformer T1b is applied to the primary side coil W4 of the insulating transformer T2 and the secondary side coil W2b of the voltage adjusting transformer T1b. A voltage having a polarity opposite to the voltage is set so as to be applied to the secondary coil W2b of the voltage adjusting transformer T1b.

  As a result, the DCDC converter 10 is obtained by multiplying the output voltage of the converter described in the above publication by {1+ (N2 / N1)}.

  According to the present embodiment described above, the effects (1), (3), (4) of the previous first embodiment, the effects (5) of the previous third embodiment, and the like. Can be obtained.

(Sixth embodiment)
Hereinafter, the sixth embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  FIG. 9 shows a circuit configuration of the DCDC converter according to the present embodiment. In FIG. 9, members corresponding to those shown in FIG. 1 are given the same reference numerals for convenience.

  As illustrated, in the DCDC converter 10 according to the present embodiment, a series connection body of capacitors C1 and C2 and a series connection body of switching elements Q1 and Q2 are connected in parallel to the high voltage battery 12. . Between the connection point of the capacitors C1 and C2 and the connection point of the switching elements Q1 and Q2, the secondary coil W2 of the voltage adjustment transformer T1, the primary coil W3 of the insulation transformer T2, and the insulation transformer. The series connection body with the primary side coil W4 of T3 is connected. The series connection body of the secondary coil W2 of the voltage adjusting transformer T1, the primary coil W3 of the insulating transformer T2, and the primary coil W4 of the insulating transformer T3 includes a primary of the voltage adjusting transformer T1. The side coil W1 is connected in parallel. The capacitances of the capacitors C1 and C2 are set equal to each other.

  On the other hand, the secondary coil W5 of the insulating transformer T2 and the secondary coil W6 of the insulating transformer T3 are connected in series with each other. These secondary coils W5 and W6 are connected in parallel to the capacitor 16, respectively. Further, the secondary side coil W6 allows a current to flow through the secondary side coil W6 when the switching element Q1 is turned on, and the secondary side coil when the switching element Q2 is turned on. A means (diode 40) for preventing a current from flowing through W6 is connected. The secondary side coil W5 allows a current to flow through the secondary side coil W5 when the switching element Q2 is turned on, and the secondary side coil W5 when the switching element Q1 is turned on. A means (diode 42) for preventing a current from flowing through W5 is connected.

  The insulating transformers T2 and T3 have the same turn ratio n.

  Here, the DCDC converter 10 can control the output voltage Vout by turning on the switching elements Q1 and Q2 alternately. In particular, the DCDC converter 10 has a time ratio that is a ratio of on-time to one cycle of the on / off operation of the switching element Q1, and a time ratio that is a ratio of on-time to one cycle of the on / off operation of the switching element Q2. Are operated with the same time ratio D (≦ 0.5).

  Here, the DCDC converter 10 according to the present embodiment is basically one in which a voltage adjusting transformer T1 is added to the converter described in Japanese Patent Laid-Open No. 2007-74830. In particular, in this embodiment, the primary side coil W1 and the secondary side coil W2 of the voltage adjusting transformer T1 are connected to the secondary side coil W2 of the voltage adjusting transformer T1 and the primary side coil of the insulating transformer T2. A voltage having a polarity opposite to the voltage applied to the series connection body between W3 and the primary side coil W4 of the insulating transformer T3 is set to be applied to the secondary side coil W2 of the voltage adjusting transformer T1. Therefore, the output voltage Vout of the converter of the above publication becomes “D · Vin / (2n)” according to the time ratio D, whereas the output voltage Vout of the DCDC converter 10 is expressed as {1+ (N2 / N1) } It will be multiplied.

  According to the present embodiment described above, the effects (1), (3), (4) of the previous first embodiment, the effects (5) of the previous third embodiment, and the like. Can be obtained.

(Seventh embodiment)
Hereinafter, the seventh embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  FIG. 10 shows a circuit configuration of the DCDC converter according to the present embodiment. In FIG. 10, members corresponding to those shown in FIG. 1 are given the same reference numerals for convenience.

  As shown in the figure, the DCDC converter 10 according to the present embodiment includes a full bridge circuit. That is, a series connection body of switching elements Q1 and Q2 and a series connection body of switching elements Q3 and Q4 are connected in parallel to the high voltage battery 12. Here, the switching elements Q3 and Q4 are also N-channel power MOS field effect transistors. Between the connection point of the switching elements Q1, Q2 and the connection point of the switching elements Q3, Q4, the secondary side coil W2 of the voltage adjusting transformer T1 and the primary side coil W3 of the insulating transformer T are connected. Yes.

  The secondary side of the insulating transformer T includes a pair of secondary side coils W5 and W6. The secondary coils W5 and W6 are connected in series with each other, and the secondary coils W5 and W6 are connected in parallel to the capacitor 16 via the choke coil 44, respectively. Here, the secondary coil W5 allows a current to flow through the secondary coil W5 during a period in which the switching elements Q2 and Q3 are in the on state, and a period in which the switching elements Q1 and Q4 are in the on state. Is connected to a means (diode 40) for preventing current from flowing through the secondary coil W5. On the other hand, the secondary coil W6 allows a current flowing through the secondary coil W6 during the period in which the switching elements Q1, Q4 are turned on, and is 2 during the period in which the switching elements Q2, Q3 are turned on. A means (diode 42) for preventing current from flowing through the secondary coil W6 is connected.

  Here, the first closed loop circuit formed by turning on switching elements Q1 and Q4 and the second closed loop circuit formed by turning on switching elements Q2 and Q3 are alternately formed. The Further, the ratio of the formation time of the first closed loop circuit to the period of the formation time of the second closed loop circuit with respect to one cycle of the alternate formation process of the closed loop circuit is equal to the time ratio D (≦ 0.5). It has become.

  The DCDC converter 10 is obtained by adding a voltage adjusting transformer T1 to a known full bridge type converter. The voltage applied to the primary coil W2 of the voltage adjusting transformer T1 and the primary coil W3 of the insulating transformer T2 is connected to the primary coil W1 and the secondary coil W2 of the voltage adjusting transformer T1. Is set so that a voltage of the opposite polarity is applied to the secondary coil W2 of the voltage adjusting transformer T1. As a result, the output voltage Vout of the DCDC converter 10 is obtained by multiplying the output voltage of a known full bridge converter by {1+ (N2 / N1)}.

  According to the present embodiment described above, the effects (1) and (4) of the previous first embodiment, the effect (5) of the previous third embodiment, and the like can be obtained. .

(Eighth embodiment)
Hereinafter, the eighth embodiment will be described with reference to the drawings with a focus on differences from the previous seventh embodiment.

  FIG. 11 shows a circuit configuration of the DCDC converter according to the present embodiment. In FIG. 11, members corresponding to those shown in FIG. 10 are given the same reference numerals for convenience.

  As shown in the figure, the present embodiment employs a configuration in which two DCDC converters 10 according to the previous seventh embodiment are connected in series. That is, the DCDC converter 10 according to the present embodiment includes a pair of DCDC converters 10a and 10b.

  On the other hand, a series connection body of capacitors C1 and C2 is connected to the high voltage battery 12 in parallel. These capacitors C1 and C2 have the same capacitance. For this reason, these capacitors C1 and C2 divide the voltage of the high voltage battery 12 into two. The input terminals of the DCDC converters 10a and 10b are connected to the capacitors C1 and C2, respectively. According to such a configuration, the input voltages of the DCDC converters 10a and 10b can be made equal to each other.

  Here, in the present embodiment, the primary side coil of one voltage adjustment transformer T1 of the DCDC converters 10a and 10b is magnetically coupled to the secondary side coil of the other voltage adjustment transformer T1. Even in such a configuration, the input voltages of the DCDC converters 10a and 10b are equal to each other. Therefore, as long as these switching elements are operated in synchronization, the DCDC converters 10a and 10b are applied to the primary side coil of the voltage adjusting transformer T1. Is equal to the voltage applied to the secondary coil of the other voltage adjusting transformer T1 and the primary coil of the insulating transformer. For this reason, the output voltage of these DCDC converters 10a and 10b can be {1+ (N2 / N1)} times the output voltage of a known full-bridge converter.

(Other embodiments)
Each of the above embodiments may be modified as follows.

  In the first embodiment, the arrangement mode of the capacitors C1 and C2 is not limited to that illustrated in FIG. For example, as shown in FIG. 12 (a), the capacitor C2 is disposed at a connection point between the switching element Q1 and the switching element Q2 and a connection point between the primary side coil W1 and the secondary side coil W2 of the voltage adjusting transformer T1. You may change between. In this case, when the switching element Q1 is in the closed state, in the closed loop circuit including the primary side coils W3, W4, the secondary side coil W2, and the switching element Q1, the primary side coils W3, W4, and the secondary side coil The power storage means for applying a voltage to the side coil W2 are capacitors C1 and C2. In addition, when the switching element Q2 is in the closed state, the power storage means for applying a voltage to the primary side coil W1 in the closed loop circuit including the primary side coil W1 and the switching element Q2 is the capacitor C2. In this way, the power storage means of both are different. Alternatively, the arrangement location of the capacitor C1 is changed between the connection point of the switching element Q1 and the switching element Q2 and the connection point of the primary side coil W1 and the secondary side coil W2 of the voltage adjusting transformer T1. May be. These changes can also be applied to the second embodiment.

  Further, for example, the capacitor C1 is disposed between the primary side coil W3 of the insulation transformer T2 and the primary side coil W4 of the insulation transformer T3, or for the insulation with the secondary side coil W2 of the voltage adjustment transformer T1. It may be changed between the primary side coils W3 of the transformer T2. These changes can also be applied to the second embodiment.

  Further, for example, as shown in FIG. 12B, a capacitor C3 is provided between the connection point of the switching element Q1 and the switching element Q2 and the connection point of the primary side coil W1 and the secondary side coil W2 of the voltage adjusting transformer T1. May be added. In this case, when the switching element Q1 is in the closed state, in the closed loop circuit including the primary side coils W3, W4, the secondary side coil W2, and the switching element Q1, the primary side coils W3, W4, and the secondary side coil The power storage means for applying a voltage to the side coil W2 are capacitors C1 and C3. In addition, when the switching element Q2 is in the closed state, the power storage means for applying a voltage to the primary side coil W1 in the closed loop circuit including the primary side coil W1 and the switching element Q2 is the capacitors C2 and C3. In this way, the power storage means of both are different. These changes can also be applied to the second embodiment.

  The structure of the voltage adjusting transformer T1 and the insulating transformers T2 and T3 is such that the secondary coil W2 of the voltage adjusting transformer T1 and the primary coils W3 and W4 of the insulating transformers T2 and T3 are independent. It is not limited to what is configured. For example, as shown in FIG. 13, by winding a common winding around the magnetic legs of the voltage adjusting transformer T1 and the insulating transformers T2 and T3, the secondary coil W2 of the voltage adjusting transformer T1 and the insulating transformer You may comprise the primary side coils W3 and W4 of T2, T3. In this case, although the degree of freedom of the turns ratio is reduced, there is an advantage that it is easy to further downsize the magnetic component including the voltage adjusting transformer T1 and the insulating transformers T2 and T3. In FIG. 13, the measurement result of the change in output voltage is also shown in correspondence with FIG.

  In the first embodiment, the applied voltage polarity of the secondary coil W2 of the voltage adjusting transformer T1, the primary coils W3 and W4 of the insulating transformers T2 and T3, and the secondary side of the voltage adjusting transformer T1. Although the applied voltage polarity of the coil W2 is reversed, it is not limited to this and may be the same. This can be realized by connecting the winding ends of the primary side coil W1 and the secondary side coil W2 of the transformer T1, for example, as shown in FIG. In this case, when the output voltage Vout is “Np / Ns = N3 / N5 = N4 / N6”, the following expression is obtained.

Vout == (Ns / Np) {1+ (N2 / N1)} D (1-D) Vin
Similarly, also in the second to seventh embodiments, the voltage polarity applied to the secondary coil W2 of the voltage adjusting transformer T1 and the primary coil of the insulating transformer and the secondary side of the voltage adjusting transformer T1. A change may be made so that the polarity of the voltage applied to the coil W2 is the same. In this case, the output voltage Vout is obtained by changing the term {1+ (N2 / N1)} to {1- (N2 / N1)}.

  In the first embodiment, the voltage adjusting transformer T1 is connected to the positive electrode side (the high potential side input terminal side of the DCDC converter 10) of the high voltage battery 12. However, the present invention is not limited to this. For example, as shown in FIG. 14B, a voltage adjusting transformer T1 may be connected to the negative electrode side of the high voltage battery 12 (the low potential side input terminal side of the DCDC converter 10). Further, the primary side coil W1 and the secondary side coil W2 of the voltage adjusting transformer T1 are not limited to those connected without interposing other electronic components therebetween. For example, in FIG. 1, the primary coil W1 of the voltage adjusting transformer T1 and the primary coil W3 of the insulating transformer T2 are connected, and the primary coil W3 of the insulating transformer T2 and the insulating transformer T3 are connected. The secondary coil W2 of the voltage adjusting transformer T1 may be connected to the primary coil W4. FIG. 15A illustrates a case where an EE core is adopted as a transformer in this case. Such a change can also be applied to the configuration shown in FIG. This is illustrated in FIG. These changes can also be applied to the second embodiment.

  In the first embodiment, the turn ratio “N3 / N5” of the transformer T2 and the turn ratio “N4 / N6” of the transformer T3 are the same, but may be different from each other.

  The voltage adjusting transformer T1 and the insulating transformers T2 and T3 are not limited to those having an EE core structure.

  In the first embodiment, the diodes D1 and D2 are body diodes, but may be discrete components. A capacitor as a discrete component may be connected in parallel to the switching elements Q1 and Q2.

  In the fourth embodiment, the capacitor C1 is connected to the positive electrode side of the high voltage battery 12, but the present invention is not limited to this. For example, the switching element Q1 may be connected to the positive side of the high voltage battery 12, and the capacitor C1 and the switching element Q2 may be connected to the negative side of the high voltage battery 12.

  In the fifth embodiment, the primary coil W4 of the insulating transformer T2 is made independent of the insulating transformer T2, and instead, the secondary side of the insulating transformer T2 is used as in the second embodiment. A choke coil 32 may be provided.

  In the sixth embodiment, one of the capacitors C1 and C2 may be deleted.

  In the eighth embodiment, the primary sides of the DCDC converters 10a and 10b may be connected in parallel. Further, the secondary side circuits of the DCDC converters 10a and 10b may be shared. Further, the primary side coil W1 and the secondary side coil W2 of the voltage adjusting transformer T1 of each of the DCDC converters 10a and 10b may be magnetically coupled. Further, the primary side coil W1 of one voltage adjusting transformer T1 of the DCDC converters 10a and 10b is constituted by the secondary side coil W2 of the other voltage adjusting transformer T1 and the primary side coil W3 of the insulating transformer T2. May be.

  In the first and fifth embodiments, the switching elements Q3 and Q4 for synchronous rectification are provided. However, the present invention is not limited to this. For example, as in the second to fourth and sixth to eighth embodiments, the diodes 40 and 42 are provided. It may be replaced with.

  In the second to fourth and sixth to eighth embodiments, the secondary diode may be replaced with a synchronous rectification switching element.

  In the fourth, seventh and eighth embodiments, instead of providing the choke coil 44 on the secondary side, the primary side of the transformer is different from the first embodiment with respect to the second embodiment. One insulating transformer may be added so that the coil functions as an energy storage coil.

  In each of the above embodiments, N-channel power MOS field effect transistors are used as the switching elements Q1, Q2, etc., but this is not restrictive, and any power field effect transistor such as a P-channel power MOS field effect transistor may be used. There may be. For example, an insulated gate bipolar transistor may be used.

  The DCDC converter 10 is not limited to being mounted on a hybrid vehicle, but may be mounted on an electric vehicle, for example. Furthermore, it is not limited to an in-vehicle converter.

  The DCDC converter 10 is not limited to a step-down converter, and may be a step-up converter or a step-up / step-down converter.

  DESCRIPTION OF SYMBOLS 10 ... DCDC converter, 12 ... High voltage battery, 14 ... Low voltage battery, Q1, Q2 ... Switching element, T1 ... Voltage adjustment transformer, T2, T3 ... Insulation transformer.

Claims (5)

The pair of input terminals and the pair of output terminals are insulated via an insulating transformer, and the voltage between the pair of input terminals is converted into a voltage having another value using the insulating transformer. In an isolated converter that outputs from a pair of output terminals,
Smoothing means for smoothing the output current on the secondary side of the insulating transformer;
A voltage adjusting transformer in which a secondary coil is connected in series to the primary coil of the insulating transformer;
The voltage adjustment is performed on a voltage equal to the total voltage applied to the primary side coil of the insulation transformer and the secondary side coil of the voltage adjustment transformer. An insulating converter comprising: a voltage applying means for applying to a primary side coil of the transformer. Further comprising a series connection body of first opening and closing means and second opening and closing means connected in parallel between the pair of input terminals,
When the first opening / closing means is closed, a first closed loop circuit including a secondary coil of the voltage adjusting transformer, a primary coil of the insulating transformer, and the first opening / closing means is formed. ,
When the second opening / closing means is closed, a second closed loop circuit including a primary coil of the voltage adjusting transformer and the second opening / closing means is formed,
2. The isolated converter according to claim 1, wherein the voltage applying unit includes power storage units different from each other in the first closed loop circuit and the second closed loop circuit.   The voltage applying means is configured by connecting a primary side coil of the voltage adjusting transformer in parallel to a primary side coil of the insulating transformer and a secondary side coil of the voltage adjusting transformer connected in series with each other. The insulated converter according to claim 1, wherein Further comprising a series connection body of first opening and closing means and second opening and closing means connected in parallel between the pair of input terminals,
When the first opening / closing means is closed, a first closed loop circuit including a secondary coil of the voltage adjusting transformer, a primary coil of the insulating transformer, and the first opening / closing means is formed. ,
When the second opening / closing means is closed, a second closed loop circuit including a primary coil of the voltage adjusting transformer and the second opening / closing means is formed,
The insulating transformer is a first insulating transformer and a second insulating transformer,
The primary coil of the insulation transformer is a primary coil of each of the first insulation transformer and the second insulation transformer connected in series.
The secondary coils of the first insulating transformer and the second insulating transformer are connected in series with each other,
On the secondary side of the first insulation transformer and the second insulation transformer, the first insulation transformer and the second insulation transformer when the first opening / closing means is closed. A first current that prevents current from flowing through one of the secondary coils and allows current to flow through the one secondary coil when the second opening / closing means is closed. Means are provided,
A secondary side of the first insulating transformer and the second insulating transformer is provided on the secondary side of the first insulating transformer and the second insulating transformer when the second opening / closing means is closed. Second means for preventing current from flowing through the other secondary coil and allowing current to flow through the other secondary coil when the first opening / closing means is closed. Is provided,
4. The smoothing means comprises the first insulating transformer , the second insulating transformer, the first means, and the second means . The insulated converter of any one of Claims.   The insulated converter according to claim 1, wherein the insulated converter is a step-down converter.

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