JP4300718B2 - Resonant type DC-DC converter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a resonant DC-DC converter and a manufacturing method thereof.
[0002]
[Prior art]
In an electric vehicle including a hybrid vehicle, a dual power supply system in which power is supplied to a traveling motor from a high-voltage main battery and power is supplied to various auxiliary machines from a low-voltage auxiliary battery is advantageous in various respects. Even in a normal internal combustion locomotive, there is a tendency to mount a two-battery power supply system in which both a high-voltage main battery and a low-voltage load power supply auxiliary battery are mounted due to various factors. In this dual power supply vehicle power supply system, it is a reasonable choice in various ways to reduce the capacity of the auxiliary battery and transmit power from the main battery to the auxiliary battery through the DC-DC converter device.
[0003]
The DC-DC converter device for a vehicle includes an inverter that forms a single-phase AC voltage from an input DC voltage, a transformer that steps down the single-phase AC voltage, a rectifier that rectifies the output voltage of the transformer, and a rectified voltage. The smoothing circuit includes a smoothing choke coil and a smoothing capacitor. Since this type of vehicle DC-DC converter needs to cover most of the low-voltage load supply power of the vehicle, the wiring other than the signal transmission line is constituted by a bus bar.
[0004]
Also, a resonance type DC-DC converter using a resonance circuit in order to reduce the loss of the switching element of the inverter is known. In this resonance type DC-DC converter, a resonance phenomenon is generated at the switching frequency (intermittent frequency) of the inverter or its harmonic frequency by using the resonance of the leakage inductance of the transformer coil and its distributed capacitance, capacitor, etc. It aims to reduce loss, heat generation, or improve output due to current reduction during the intermittent transition period of the switching element.
[0005]
In the above-described DC-DC converter for a vehicle, the number of turns of the primary coil of the transformer is larger than that of the secondary coil, and naturally the distributed capacity of the primary coil is larger, so a resonance circuit is configured on the primary coil side of the transformer. It is normal to do.
[0006]
[Problems to be solved by the invention]
However, in the above-described resonance type DC-DC converter, the resonance frequency of the resonance circuit needs to be substantially matched with the switching frequency of the inverter or its harmonic frequency. However, since the resonance circuit includes the leakage inductance of the transformer, High-precision management has not been easy. In particular, in the case of a vehicle, since the transformer coil is constituted by a bus bar, it is not easy to adjust the leakage inductance of the transformer by changing the number of turns.
[0007]
In order to adjust the resonant frequency of the resonant circuit, an inductor (called a resonant coil) connected in series with the transformer coil is added instead of or in addition to the leakage inductance of the transformer. Although it is possible to change the number of turns of the coil, since the optimum number of turns is selected from the resonance coils having various numbers of turns prepared in advance, the number of parts to be prepared increases and the work is also increased. There was a problem of complexity.
[0008]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide a high-current (use bus bar) resonant DC-DC converter that can easily adjust and manufacture a resonance frequency and a method for manufacturing the same. Yes.
[0009]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a resonant DC-DC converter in which an inverter that converts input DC power into AC power by switching of a switching element, a transformer that converts AC power output from the inverter, and a bus bar are wound in a coil shape. A resonance coil that is connected in series with the coil of the transformer and resonates; a resin member that embeds part or all of the resonance coil; and an axial direction of the resonance coil that extends in the axial direction of the resin member. and a heat dissipation plate in close contact with the bottom surface, the resin member is characterized Rukoto which have a core insertion hole of the magnetic core to be inserted into the resonant coil is fitted to be displaceable.
[0010]
That is, according to this configuration, a resonance coil is connected in series with a voltage conversion transformer coil (primary coil or secondary coil) of a DC-DC converter, and leakage of the resonance coil or the transformer coil is caused by this resonance coil. A resonant DC-DC converter is configured by configuring an inductor of the resonant circuit with the inductance. In the present invention, in particular, since the bus bar that is wound a predetermined number of times to form the resonance coil is fixed by the resin member, it is possible to prevent changes in the inductance and distributed capacity of the resonance coil due to deformation due to mechanical vibration or the like. In addition, since the electrical insulation of the bus bar of the resonance coil by covering the resin film can be omitted, the bus bar terminal treatment (insulating film peeling) is not required, and the operation is simplified. That is, mechanical fixation and electrical insulation of the bus bar for the resonance coil can be performed simultaneously.
[0011]
Further , the resin member has a core insertion hole into which a magnetic core inserted into the resonance coil is inserted so as to be displaceable. According to this configuration, the resin member can secure a core insertion hole that movably accommodates the core inserted in the bus bar for the resonance coil without increasing the number of components, and resonates with a simple structure. It becomes possible to easily adjust the inductance of the coil.
In addition, since it has a metal-grounded heat-radiating plate that extends in the axial direction of the resonance coil and is in close contact with the bottom surface of the resin member, the heat of the inverter and transformer coils can be improved through the resin member and the resonance coil. In addition to being able to dissipate heat, the distributed capacitance of the resonance coil can be increased by increasing the capacitance between the heat dissipation plate and the resonance coil, and the inductance value required for the resonance circuit can be reduced.
[0013]
The arrangement of claim 2 further in resonant DC-DC converter of claim 1, wherein the resonant coil, it therefore is characterized in that the formed trans identical bus bars and the coil, the manufacturing process is simplified Thus, reliability is improved.
[0014]
According to a third aspect of the present invention, in the resonant DC-DC converter according to the first or second aspect , the resin member embeds a coil of the transformer and a bus bar that connects the coil of the transformer to the resonant coil. Therefore, the transformer coil and the resonance coil bus bar can be fixed together, and the leakage inductance and distributed capacitance fluctuations acting between the transformer coil and the resonance coil bus bar can be reduced. Variations in the resonant frequency of the circuit can be reduced.
[0016]
According to a fourth aspect of the present invention, in the method of manufacturing a resonant DC-DC converter according to any one of the first to third aspects, the transformer coil and the resonant coil are embedded in the resin member by insert molding. Since it is a feature, the manufacturing process is simplified.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
A preferred embodiment of a step-down DC-DC converter device for a two-battery mounted vehicle using the DC-DC converter of the present invention will be described with reference to the following examples.
[0018]
[Example 1]
The step-down DC-DC converter device of this embodiment will be described below with reference to the circuit diagram shown in FIG.
(Circuit configuration)
1 is a DC-DC converter and V1 is a high voltage battery.
[0019]
In the DC-DC converter 1, 2 is an inverter, 3 is a transformer, 41 and 42 are a pair of diodes (rectifiers) forming a rectifier, 5 is a choke coil for smoothing, 6 is a smoothing capacitor, 7 is a controller made by a microcomputer, Reference numeral 8 denotes a resonance coil.
[0020]
The transformer 3 has a ferrite core 30, a primary coil 31, a first secondary coil 32, and a second secondary coil 33. The primary coil 31 and the resonance coil 8 are connected by a bus bar 9 for connection. In this embodiment, the bus bar 9 and the bus bar for the resonance coil 8 are composed of the same long plate-like conductor piece (bus bar). Yes. Moreover, you may comprise the primary coil 31, the bus bar 9 for connection, and the bus bar for the resonance coil 8 by the same long plate-shaped conductor piece. One end of the secondary coils 32 and 33 is grounded, and the other end is connected to the choke coil 5 through the diodes 41 and 42.
[0021]
The high-voltage AC voltage output from the inverter 2 constitutes an LC resonance circuit together with the leakage inductance and distributed capacitance seen from the primary side of the transformer 3 and the leakage inductance and distributed capacitance of the resonance coil 8, and switching of the inverter 2 by this LC resonance. Loss during the intermittent transition period of the element is reduced.
[0022]
The transformer 3 steps down the input voltage, and the secondary coils 32 and 33 alternately output half-wave rectified voltages to the external low-voltage load through the diodes 41 and 42 and the choke coil 5 every different half-wave periods. The controller 7 compares the output voltage of the DC-DC converter 1 with a predetermined reference voltage, and based on the comparison result, increases or decreases the PWM duty ratio of the four switching elements (IGBTs) of the inverter 2 and transmits the AC power. Feedback control. Since this type of DC-DC converter is well known, further explanation is omitted, and the features of this embodiment will be described below with reference to FIG. FIG. 2 is a longitudinal sectional view showing the vicinity of the resonance coil 8.
[0023]
The resonance coil 8 is formed by spirally winding a bare long plate-like copper piece (bus bar), and both ends thereof are a connection bus bar 9 extending to the primary coil 31 and a connection bus bar extending to the inverter 2. 10 is constituted.
[0024]
The resonance coil 8 and the bus bars 9 and 10 and the primary coil 31 (not shown) are embedded in a plate-shaped resin plate (resin member referred to in the present invention) 11 formed by resin insert molding. The illustrated end is exposed and connected to one of the pair of output terminals of the inverter 2.
[0025]
The resin plate 11 has a core fitting insertion hole 110 with one end opening formed in the axial direction along the axis of the resonance coil 8, and the rod-shaped ferrite core 80 can be axially displaced in the core fitting insertion hole 11. Has been inserted.
[0026]
12 is a cooling plate made of aluminum flat plate for cooling, and is grounded. The heat radiating plate 12 faces the resonance coil 8 through the thin resin plate 11, and thereby good heat radiation is performed from the resonance coil 11 to the heat radiating plate 12. In addition, a distributed capacitance is formed between the resonance coil 8 and the heat radiating plate 12.
[0027]
In this embodiment, the core 80 is adjusted in the axial direction in order to set the resonance frequency of the resonance circuit to a predetermined value, and then fixed with an adhesive, so that the resonance frequency of the resonance circuit can be easily set to a suitable value.
[0028]
(Modification)
A part of the resonance coil 8 may be exposed from the resin plate 11.
[0029]
A related invention of the present invention will be described below with reference to FIG. FIG. 3 is a longitudinal sectional view showing the vicinity of the resonance coil 8.
[0030]
The feature of this related invention is that the upper half of a part of the turn of the resonance coil 8 described in the first embodiment is exposed from the resin plate 11, and a necessary part of the exposed turn of the resonance coil 8 is further connected to a short-circuit conductor made of copper plate. 13 is short-circuited by soldering. The core 80 is completely embedded in the resin plate 11.
[0031]
In this related invention , the number of effective turns of the resonance coil 8 can be easily adjusted simply by changing the connection location between the short-circuit conductor 13 and the exposed turn of the resonance coil 8 in order to set the resonance frequency of the resonance circuit to a predetermined value. The resonance frequency of the resonance circuit can be easily set to a suitable value.
(Modification)
Finally, the exposed bus bar including the short-circuit conductor 13 may be resin-molded.
(Modification)
In the first embodiment and the related invention , a single capacitor can be additionally provided in the resonance circuit to reduce the required inductance of the resonance circuit.
[Brief description of the drawings]
FIG. 1 is a circuit diagram illustrating a resonant DC-DC converter device according to a first embodiment.
FIG. 2 is a longitudinal sectional view showing the vicinity of a resonance coil in FIG.
FIG. 3 is a longitudinal sectional view showing the vicinity of a resonance coil of a resonance type DC-DC converter according to a related invention .
[Explanation of symbols]
2 Inverter 3 Transformer 41, 42 Diode (rectifier)
5 Choke coil 8 Resonant coil

Claims (4)

An inverter that converts input DC power to AC power by switching elements;
A transformer that converts the AC power output from the inverter into a voltage;
Resonance coil which is formed by winding a bus bar in a coil shape and is connected in series with the coil of the transformer to resonate;
A resin member in which part or all of the resonance coil is embedded;
A heat dissipating plate extending in the axial direction of the resonance coil and closely contacting the bottom surface of the resin member;
Equipped with a,
The resin member, resonant DC-DC converter, wherein Rukoto which have a core insertion hole of the magnetic core to be inserted into the resonant coil is fitted to be displaceable. The resonant DC-DC converter according to claim 1,
The resonance type DC-DC converter is characterized in that the resonance coil is formed of the same bus bar as the coil of the transformer . The resonant DC-DC converter according to claim 1 or 2 ,
A resonance type DC-DC converter , wherein the resin member embeds a coil of the transformer and a bus bar for connecting the coil of the transformer to the resonance coil . In the manufacturing method of the resonance type DC-DC converter in any one of Claims 1 thru | or 3,
The method of manufacturing a resonance type DC-DC converter , wherein the transformer coil and the resonance coil are embedded in the resin member by insert molding .

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