JPH04150762A - Dc/dc converter - Google Patents

Abstract

PURPOSE:To make a smaller DC/DC converter by incorporating more than one of the capacitors of a circuit in a substrate. CONSTITUTION:A dielectric substrate 10 includes high-dielectric-constant regions 11-14, so their surrounding regions have a relatively low dielectric constant. Conducting patterns are formed on both surfaces to provide pairs of electrodes. These pairs of electrodes, together with the dielectric regions, form four capacitors in the substrate. The regions between the electrodes have a properly high dielectric constant to provide capacitors of sufficient capacity for the fundamental structure of a DC/DC converter. An area required for the terminal electrodes is comparatively small, or as large as one electrode, therefore, the packaging efficiency improves.

Description

Detailed Description of the Invention [Industrial Utilization] The present invention relates to a DC-DC converter constructed by assembling various passive and active element parts on a substrate, and particularly to improvements for miniaturizing the DC-DC converter. Regarding.

[Prior Art] DC-DC converters are used for various purposes, but like other electronic circuit devices, these DC-DC converters are also exposed to ever-increasing demands for miniaturization.

In order to cope with this, various attempts have been made to reduce the size of the converter, but in reality, the shape of the converter depends on the output power capacity and other electrical properties required of the DC-DC converter. The actual size had already been determined. For example, when considering a capacitor whose electrical performance is determined, once the required capacitance value is determined, the size of the capacitor as a component that satisfies this requirement is almost determined.

Therefore, conventionally, in order to make the DC-DC converter as small as possible, efforts have been made to simplify the circuit configuration itself and reduce the number of parts.

For example, as is well known, there are different types of DC-DC converters depending on the DC-DC conversion mechanism employed, such as self-help type, passive type or open-loop control type, and closed-loop control type. Ordinary voltage converters can be classified according to the parts used, and the secondary winding and secondary winding are wound completely independently, and as a result of following the principle of mutual induction, insulation separation can be achieved between input and output. In addition to those that use a transformer or a so-called charge pump circuit,
By using a coil and intermittent power supply current flowing through it, a high voltage is obtained according to the self-induction principle, which is then connected to a rectifier diode (
There are some that can be taken out using a catch diode (also called a catch diode), so I tried to choose one that had a small number of components and was relatively small.

In conclusion, among the above types, the type that uses a coil does not have an input/output separation function but can be assembled on the smallest substrate area. If an input/output separation transformer is used, the transformer will be quite large, and if a charge pump circuit is used, the capacitor used to "storage" the stored charge energy will be quite large.

In fact, in cases where miniaturization is the top priority, this coil current intermittent type circuit has traditionally been selected, and there are currently integrated circuits suitable for assembling this type of DC-DC converter. IC) is also available at a relatively low price, and even when obtaining bipolar output, the only external components required are two resistors, two coils, one diode, and a capacitor. It is enough if there are four (
External large capacity capacitors may be used for ripple removal by the user if necessary).

[The problem that the invention tries to solve! l! ] However, as mentioned above, there are limits to miniaturization and space saving by simply selecting a conversion principle or conversion circuit or miniaturizing each component. Even if a coil current intermittent type is used, which is considered to be the smallest in terms of the number of component parts, the area required for each of the parts cannot be reduced.

In other words, no matter which method is adopted, conventionally D
The required board area is inevitably determined by the number of parts and the size of each part required to construct a C-DC converter circuit on a board, and it has not been possible to reduce the board area any further. Even if we try to improve the wiring patterns on the board, there are still limits, and we cannot expect a dramatic reduction in size.

The present invention has been made in view of these circumstances, and no matter what type of circuit configuration is adopted, it can break through the wall of miniaturization that was conventionally thought to be the limit of the circuit, and achieve extremely small size and C. - It aims to provide a DC converter.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides that at least some of the plurality of required capacitors among the circuit components of the DC-DC converter are built-in circuit boards. We propose a DC-DC converter configured using capacitors.

As a more desirable configuration, the present invention also provides the DC
We also propose a DC-DC converter in which all the capacitors necessary to construct a DCC-type circuit are built-in capacitors on a board with a built-in capacitor. In the case where only one capacitor is constructed using a capacitor built into the substrate, we also propose a configuration in which the capacitance values of these capacitors are larger than any of the capacitance values of the remaining capacitors constructed using individual components. In other words, among the capacitors necessary to assemble a DC-DC converter circuit, the capacitors built into the substrate are constructed in order of the largest capacity. however,
A large-capacity capacitor (at least about 10 μF to 100 μF) for ripple removal, which is selectively connected in parallel to the output by the user, is not considered to be a basic component of the DC-DC converter.

According to still another aspect of the present invention, in order to obtain a capacitor with a built-in substrate that is small and has excellent electrical characteristics, the substrate used in the above is made of grain-boundary insulated porcelain containing strontium titanate as a main component. Suggest the use of a board.

[Function] According to the present invention, at least some of the capacitors necessary for the DC-DC converter, preferably all of them, can be configured with built-in capacitors on the board, so that the capacitors as discrete components can be The number can be reduced or eliminated from the board completely.

Naturally, therefore, even if there was a DC-DC converter that could be made the most compact in the past through circuit selection, wiring, etc., it is possible to further reduce the size according to the present invention. This is because other components can be further mounted on the board-embedded capacitor.

Therefore, in short, it can be said that the present invention can overcome the limit of conventional technology in forming the Z-type.

Additionally, using a built-in capacitor on the board increases the reliability of the circuit rather than using a capacitor that is a separate component. This is because the capacitor built into the substrate is strictly controlled during the manufacture of the substrate, and precise trimming and selection are possible, so accuracy can be improved.

In particular, according to another aspect of the present invention, when a grain-boundary insulated ceramic substrate containing strontium titanate as a main component is used as the capacitor-embedded substrate, a high dielectric constant and a high Q value can be obtained, and the temperature Since the coefficient is also excellent, the present invention DC
-DCC-type-temperature characteristics can also be improved.

[Embodiment] Hereinafter, as an embodiment of the present invention, based on FIGS. 1 to 4, a D.
3 shows the steps to build a C-DC converter.

In FIG. 1, there are four high dielectric constant regions 11, 12 in the case of a given slam lever, respectively as stippled.

13 and 14, the front and back sides of the galvanic substrate 10 are shown. Hereinafter, up to and including FIG. 4, each figure (a) shows the configuration seen from the front side, and each figure (b) shows the configuration seen from the back side.

The surroundings of each high dielectric constant region 11, 12, 13, and 14 naturally become a fiducial constant region, but generally when forming such high and low dielectric constant regions, the substrate 10 as a whole has a low dielectric constant. It is not necessary to form a high dielectric constant region and then selectively create a high dielectric constant region according to a predetermined pattern (although that may be the case).
Conversely, when the substrate 10 is fired, the surrounding area surrounding each high dielectric constant portion is often treated to have a relatively low dielectric constant.

There are various processing methods, but for example, a high dielectric constant material is selected from the beginning for the substrate material, and when the substrate is fired, the parts 11, 12, which are left with a high dielectric constant,
13. A particle size growth inhibitor is applied in advance to the front and back surfaces of areas other than 14, and the heat during firing causes the applied inhibitor to be thermally diffused into the substrate, and the high dielectric constant material is applied to the coated area. There is a method to intentionally lower the dielectric constant.

Next, as shown in FIG. 2, for such a board 10, a pair of conductor batts IIET1 are provided on both front and back surfaces of each high conductivity area 11, 12, 13, and 14, respectively.
11, T; 12. T, 12εt; Hc + 1
3ET; 14ET + 14ET are formed facing each other, so that the pair of conductor buttons are respectively used as a pair of terminal electrodes, and the high dielectric constant portions 11 and 12 are formed in between.
, 13 and 14 are the inter-terminal dielectric layers 11. A total of four substrate built-in capacitors are formed. , 12 , 13 , and 14 shall be attached.

In any case, in this way, the substrate lO is effectively utilized in its thickness direction, and each capacitor 11, 12, 13, 1
If the pair of terminal electrodes 4 sandwich the substrate 10, and if the dielectric layer between the terminals is made to have a fairly high dielectric constant, a capacitor with sufficient capacity for the basic configuration of the DC-DC converter can be obtained. In addition, the planar area required for the terminal electrodes is relatively small, and since the area is only one electrode, the mounting efficiency is improved.

In addition, the applicant has already developed a dielectric substrate containing strontium titanate as a main component, and in addition, a composition containing, for example, calcium titanate, lanthanum oxide, titanium oxide, or even strontium oxide as an additive. He also proposes dielectric substrates containing antimony, so if these are used, capacitors with extremely high dielectric constants and Q values, as well as good temperature coefficients, can be obtained, and fairly large capacitors can be obtained. Even with a capacitance value, a sufficiently small substrate area can be obtained.

In this way, if all four capacitors necessary for constructing the DC-DC converter of this embodiment are configured as board-embedded capacitors 11, 12, 13, and 14, then Figures 3 (a) and (b) ), an insulating layer 15 of an appropriate material is formed on the front and back main surfaces of the substrate,
A conductor batten is formed thereon according to the required wiring batten. Furthermore, as will be clear from the explanation regarding FIG. 5 later, the DC-DC converter to be constructed in this embodiment requires two resistors, so these resistors 17 and 18
is also formed at a corresponding predetermined location by a known method (for example, printing).

Furthermore, along with the formation of the conductor button, there are also via holes 16, which are shown slightly larger in the figure to make them more conspicuous.
・Place each electrode of each built-in capacitor on the corresponding conductor button through the .

Then, as shown in Figures 4 (a) and (b),
A commercially available integrated circuit module 21, 22 for a DC-DC converter and coils 23, 24 are respectively attached to one of the front and back surfaces of the substrate 10 by a known method, and a diode 25 is also attached to the back side of the substrate. 10
Build and complete the planned DC-DC converter on top.

As is clear, the DC-DC converter of this embodiment is so-called double-sided mounted on the board 10, and conversion circuits for positive polarity and negative polarity are assembled on the front side and the back side, respectively. ing.

In the present invention, the circuit configuration itself of the applied DC-DC converter does not matter, but for reference, the DC-DC converter in the embodiment examined above has a circuit as shown in FIG. There is.

Each component corresponding to the symbol used in FIG.
~4 The integrated circuit modules 21 and 22 for DC-DC converters used in the figures correspond to the components indicated by the same reference numerals as those used in the figures, and are the MAX630 series manufactured by Maxim Corporation.The positive polarity side will be explained as follows. It behaves like this.

The current from the external DC power supply 30 through the coil 23 flows from the LX terminal of the integrated circuit module 21 to the GNDI terminal, but a switching element is built in between this and is turned on and off at a certain frequency by the built-in oscillation source. As a result of repeating this, a pulsating high voltage is generated at both ends of the coil 23 due to self-induction.

Therefore, this pulsating high voltage is rectified by a built-in catch diode and output to the output terminal vO, but a relatively large value of about 0.1 to 0.47 μF is connected between this output terminal vO and the ground. A noise removal capacitor 12 is connected. In this embodiment, this capacitor 12 is constituted by the above-mentioned substrate built-in capacitor 12.

In addition, the voltage appearing at the output terminal vO is fed back into the module 21, and compared with the built-in reference voltage source, the error is extracted by the built-in error amplifier, and the coil current is intermittent depending on the magnitude and direction. Turn on/off the switching element
The off state or duty is controlled to maintain the output voltage at a predetermined voltage value. Another capacitor 11, which is externally attached to this module and is also constituted by a capacitor built into the substrate in this embodiment, is, for example, about 5009F, and is used for the error amplifier built into the module. It is inserted in parallel to one of the resistors of the piezoresistive circuit, and is used as a bypass capacitor for response compensation and to eliminate the adverse effects of ripples being superimposed on the divided voltage value.

Furthermore, in the illustrated embodiment, the voltage across the DC power supply 30 is divided by a voltage divider circuit including resistors 18, 17 and applied to the terminal LBI of the module 21, which is also compared with a reference voltage source and If the voltage drops abnormally, a detection signal can be obtained at the terminal LBO (actually, the line connected to this terminal LBO is grounded).

The operation of the integrated circuit module 22 on the negative polarity side is similar, except that this commercially available module requires one more diode 25 than the one on the positive polarity side. Also,
The capacitor 14 parallel to the DC power supply 30 and the capacitor 13 parallel to the negative output side each have a voltage of 0.1 to 0, for example.
．． The value is approximately 47 .mu.F, and in this embodiment, both of the capacitors are built-in capacitors on the substrate.

As described above, in the case of the illustrated embodiment, the capacitor 11 necessary for the DC-DC converter according to the fifth illustrated circuit configuration is
, 12, 13, and 14 are all constructed with built-in capacitors on the board, so there is no need for any external capacitors as individual components. We succeeded in reducing the substrate area by about 50%.

Further, as mentioned above, since the capacitor built into the substrate can be controlled extremely strictly, the reliability of the characteristics as a DC-DC converter can be significantly improved.

However, even if only some of the capacitors are required instead of all of them, the area occupied by the board can certainly be reduced by that amount. DC-1) The circuit configuration of the C converter itself is also arbitrary, and a DC converter with a circuit configuration other than the illustrated embodiment
- When building a DC converter, a small C-DC converter embodying the present invention can be similarly obtained by using some of the necessary capacitors as built-in capacitors on the substrate.

Of course, whether or not the substrate is mounted on both sides as shown in the illustrated embodiment is not an essential issue for the present invention, and it is best to use a substrate mainly composed of strontium titanate as described above. However, this is not the case if only the most basic constituent requirements of the present invention need to be satisfied.

[Effect] According to the present invention, regardless of the operating principle or circuit configuration,
As a DC-DC converter built on a substrate, it can break the conventional miniaturization limitations, and the board footprint required for at least some capacitors can be greatly reduced.

Moreover, since the substrate built-in capacitor is stable in quality and has good characteristics, the characteristics and reliability of the DC-DC converter are also improved.

[Brief explanation of the drawing]

Figures 1 to 1J4 each show the schematic structure of the front and back surfaces of the substrate at the end of each process for obtaining a DC-DC converter as an embodiment of the present invention.
The figure shows a circuit diagram of an example of a DC-DC converter built on a board. In the figure, 10 is a substrate, 11, 12, 13, and 14 are high dielectric constant regions or substrate-built-in capacitors that constitute the galvanic layer between the terminals of the capacitor, IIE? , 12ET'l 1
3ET + 14tt is the terminal electrode of each board built-in capacitor, 16 is the via hole, 17.18 is the resistor, 21
, 22 is an integrated circuit module for DC-DC:ff inverter, 23.24 is a coil, 25 is a diode, 30
is a DC power supply. Applicant: NOF Corporation Figure 5

Claims (4)

[Claims] (1) D constructed by mounting the necessary circuit components on the board
A C-DC converter; wherein the substrate is a capacitor-embedded substrate; and at least one of a plurality of capacitors included in a circuit constituting the DC-DC converter is incorporated in the capacitor-embedded substrate. A DC-DC converter comprising a capacitor. (2) The capacitance value of the at least one capacitor constituted by the capacitor built into the capacitor built-in board shall be the same as that of all the remaining capacitors constituted by individual components other than the capacitor of the capacitor built-in board. The DC-DC converter according to claim 1, characterized in that: the DC-DC converter is larger than the capacitance value. (3) The capacitors constituted by the capacitors built into the capacitor built-in board are all capacitors included in the circuit constituting the DC-DC converter; DC converter. (4) The DC-DC according to claim 1, 2 or 3, wherein the substrate is a grain boundary insulated semiconductor ceramic substrate containing strontium titanate as a main component.
converter.