JP2013021800A - Structure for mounting smoothing capacitor on circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure for mounting a smoothing capacitor on a circuit board, the structure achieving easy stabilization of DC stabilized power supply control even when a smoothing capacitor with small equivalent series resistance (ESR) is used.SOLUTION: A smoothing capacitor on a circuit board is mounted as follows. A choke coil L is mounted between a power line wiring pattern 11a and a power line wiring pattern 11b. Also, the power line wiring pattern 11b has a cut-out shape at a portion where ground wiring patterns 12a,12b are formed, and not-shown one end thereof is connected to an output terminal Vout. Here, the ground wiring pattern 12b is grounded via a via hole 13. Further, a smoothing capacitor C is mounted between the power line wiring pattern 11b in the cut-out part thereof and the ground wiring pattern 12a, and a three-terminal capacitor 3 is mounted between the ground wiring patterns 12a and 12b, and between portions of the cut-out part having a fixed width in the power line wiring pattern 11b.

Description

  The present invention relates to a mounting structure on a circuit board of a smoothing capacitor that smoothes a DC output voltage of a DC stabilized power supply.

  As electronic devices become more advanced and smaller in size, power supply circuits are miniaturized and packaged with high density, as represented by PMIC (Power Management Integrated Circuit). It has become common for voltages to be physically close together. In addition, the IC itself has been downsized due to the high accuracy of semiconductor process technology. Under such circumstances, a switching power supply driver IC is generally used as a component constituting the DC stabilized power supply. The driver IC performs feedback control of on / off of a switching element that switches a DC input voltage by a negative feedback amplifier according to an output voltage. The DC output voltage switched by the switching element is smoothed by the choke coil and the smoothing capacitor.

  As the smoothing capacitor, a functional polymer capacitor with a small equivalent series resistance (ESR: Eqivalent Series Resistance) of several tens of mΩ is often used. As described above, driver ICs and discrete devices have been downsized. Smooth capacitors such as functional polymer capacitors and choke coils are becoming the components that occupy the most mounting area on circuit boards. Functional polymer capacitors use precious metals as electrolytes, so there are concerns about the stable supply in the market, they may burn when they fail, and they are vulnerable to high humidity and have low reliability. . For this reason, it is easy to obtain because it has a stable supply in the market, does not burn when it breaks down, is resistant to high humidity, is highly reliable, and is smaller and cheaper than a functional polymer capacitor. It is desired to use a capacitor as a smoothing capacitor.

  However, a ceramic capacitor has a smaller ESR than a functional polymer capacitor, and when used as a smoothing capacitor in a switching power supply, the ESR is too small to control the output voltage. Conventionally, in such a case, when there is a phase difference between the output voltage and the feedback voltage of the negative feedback amplifier, a resonance circuit is formed by the effective capacitance C and ESR of the smoothing capacitor, and the frequency f (= 1) of this resonance circuit. / (2πC · ESR)) is set so as not to oscillate, and the control is stabilized. Further, the ripple converter disclosed in Patent Document 1 is compared with the reference voltage by comparing the output voltage level with the reference voltage using the IR voltage fluctuation caused by the product (iL × ESR) of the inductor current iL and ESR flowing through the choke coil. Thus, stabilization of control may be achieved.

  In the ripple converter disclosed in Patent Document 1, the output voltage is subjected to waveform control by the waveform conversion means, then compared with a reference voltage, and feedback controlled by a negative feedback amplifier. Since the waveform converting means can convert the waveform of the output voltage into a different waveform, no matter what capacitor is used as the smoothing capacitor, the desired oscillation state can be changed by changing the characteristics of the waveform converting means accordingly. Is maintained and the control is stabilized.

Japanese Patent No. 4107209

  However, in the DC stabilized power source disclosed in the above-mentioned conventional patent document 1, in order to stabilize the control when a low ESR capacitor such as a ceramic capacitor having many advantages described above is used as a smoothing capacitor. For this, it is necessary to design the circuit of the characteristics of the waveform converting means so that a desired oscillation state is maintained, which is troublesome. In addition, a large number of resistance elements and capacitive elements are required to configure the waveform conversion means, and the number of elements increases and costs increase, and the area occupied by the waveform conversion means on the circuit board increases, resulting in downsizing of electronic equipment. Contrary to the request.

  Also, when using the resonant circuit with a phase difference between the output voltage and the feedback voltage of the negative feedback amplifier, if the effective capacitance C of the smoothing capacitor is changed, the feedback circuit is reset so that the resonant circuit does not oscillate. Redesigning the power supply circuit to be performed is required separately, and this also requires time.

The present invention has been made to solve such problems,
A mounting structure on a circuit board of a smoothing capacitor that smoothes a DC output voltage of a DC stabilized power supply,
The smoothing capacitor has one end connected to a wiring pattern connected to the output of the DC stabilized power supply and the other end connected to a reference potential via one internal through electrode of the three-terminal capacitor.
The three-terminal capacitor is characterized in that the other internal through electrode is connected in parallel to the wiring pattern.

  According to this configuration, since the wiring pattern connected to the output of the DC stabilized power supply is connected to the reference potential via one internal through electrode of the smoothing capacitor and the three-terminal capacitor, the output of the DC stabilized power supply, the reference potential, In between, a direct current resistance component is formed by adding the direct current resistance component of one internal through electrode of the three-terminal capacitor to the ESR (equivalent series resistance) of the smoothing capacitor. Therefore, even if a capacitor with a low ESR is used as a smoothing capacitor for the output of the power supply circuit, the amount of the ESR is reduced without using a chip resistor or the like. It is supplemented by the DC resistance component of the through electrode. Therefore, even when a low ESR capacitor such as a ceramic capacitor having many advantages described above is used as a smoothing capacitor instead of a functional polymer capacitor, the power supply disclosed in the conventional patent document 1 is used. With the same circuit configuration as when a functional polymer capacitor was used, it is possible to easily stabilize the control of the DC-stabilized power supply without the need for troublesome circuit design. Moreover, control can be stabilized by adding only a three-terminal capacitor, and since many additional elements are not required as in the conventional case, it is possible to suppress an increase in cost and to add to the circuit board. The increase in the area occupied by the element can also be suppressed, and the demand for downsizing of electronic devices can be satisfied. Further, when there is a phase difference between the output voltage and the feedback voltage of the negative feedback amplifier and the resonance circuit is used, the power supply circuit needs to be redesigned separately. Since the internal through electrode of the terminal capacitor can be easily compensated as described above, the redesign is also facilitated.

  In addition, according to this configuration, the other internal through electrode of the three-terminal capacitor is connected in parallel to the wiring pattern from which a DC voltage is output, so that high-frequency noise superimposed on this wiring pattern is referred to via the three-terminal capacitor. The high frequency characteristics are improved as compared with the case where only the smoothing capacitor is connected to the output of the DC stabilized power supply.

  Further, according to the present invention, the three-terminal capacitor has a substantially rectangular parallelepiped shape, and one internal through electrode connected to the reference potential is a hot internal through electrode formed in the long side direction of the substantially rectangular parallelepiped. The other internal through electrode connected to the pattern is a ground internal through electrode formed in the direction of the short side of the substantially rectangular parallelepiped.

  A three-terminal capacitor having a substantially rectangular parallelepiped shape generally has a hot internal through electrode having a long conductor length formed in the long side direction of the substantially rectangular parallelepiped, a power line wiring pattern, and a conductor length formed in the short side direction of the substantially rectangular parallelepiped. The short ground internal through electrode is connected to a reference potential such as a ground potential. However, in this configuration, conversely, the ground internal through electrode with a short conductor length is connected to the wiring pattern, and the hot internal through electrode with a long conductor length is connected to the reference potential. For this reason, the direct current resistance component of the internal through electrode applied to the ESR of the smoothing capacitor becomes a large direct current resistance component of the hot internal through electrode. By appropriately reversing the way of connecting the internal through electrode, a larger direct current resistance component Components can be easily added to the ESR of the smoothing capacitor.

  The present invention is also characterized in that a resistance value adjusting wiring pattern connected in parallel to one internal through electrode of a three-terminal capacitor is formed on a circuit board.

  According to this configuration, the resistance value adjusting wiring pattern is connected in parallel to one internal through electrode of the three-terminal capacitor connected in series to the smoothing capacitor. Therefore, the DC resistance component added to the ESR of the smoothing capacitor is a parallel composite value of the DC resistance components of the internal through electrode and the resistance value adjusting wiring pattern. For this reason, the DC resistance component applied to the ESR of the smoothing capacitor can be easily adjusted to an arbitrary value by appropriately setting the shape of the resistance value adjusting wiring pattern connected in parallel.

  According to the present invention, even when a low ESR capacitor such as a ceramic capacitor is used as a smoothing capacitor, it is possible to easily stabilize the control of the DC stabilized power supply without the need for designing a circuit that requires labor. I can do it. In addition, since many additional elements are not required as in the conventional case, it is possible to suppress an increase in cost, and it is also possible to suppress an increase in the area occupied by the additional elements on the circuit board, thereby satisfying the demand for downsizing of electronic devices. .

(A) is a partial plan view of a circuit board showing a mounting structure of a smoothing capacitor to a circuit board according to an embodiment of the present invention, (b) is an equivalent circuit diagram of the mounting structure shown in (a), and (c). FIG. 3 is a circuit diagram of a switching power supply using the mounting structure shown in FIG. (A) is an external perspective view of the three-terminal capacitor shown in FIG. 1, and (b) is an exploded perspective view showing its internal configuration. FIG. 7 is a partial plan view of a circuit board showing a mounting structure of a smoothing capacitor on a circuit board according to a first modification of the embodiment shown in FIG. 1. FIG. 9 is a partial plan view of a circuit board showing a mounting structure of a smoothing capacitor on a circuit board according to a second modification of the embodiment shown in FIG. 1.

  Next, the case where the mounting structure of the smoothing capacitor on the circuit board according to the embodiment of the present invention is applied to the output circuit of the switching power supply will be described.

  FIG.1 (c) is a circuit diagram of this switching power supply 1 which comprises a direct current | flow stabilized power supply.

  The switching power supply 1 includes a PNP transistor Q, a flywheel diode D, a choke coil L, a smoothing capacitor C, a feedback circuit 2, and a three-terminal capacitor 3. The emitter of the transistor Q is connected to the input terminal Vin, the collector is connected to the output terminal Vout via the choke coil L, and is connected to the reference potential via the flywheel diode D. In the present embodiment, this reference potential is set to the ground potential and is connected to the input ground terminal GND and the output ground terminal GND. The output terminal Vout is connected to a reference potential through a smoothing capacitor C and a ground internal through electrode 23 described later of the three-terminal capacitor 3. The feedback control circuit 2 includes a comparator 4 and a reference voltage source Vref. The non-inverting input terminal of the comparator 4 is connected to the output terminal Vout, and the inverting input terminal is connected to the other end of the reference voltage source Vref having one end connected to the reference potential. The output of the comparator 4 is connected to the base of the transistor Q.

  The transistor Q switches a DC voltage input to the input terminal Vin. The flywheel diode D passes a current through the choke coil L when the transistor Q is off, and the DC voltage switched by the transistor Q is smoothed by the choke coil L and the smoothing capacitor C and output from the output terminal Vout. The feedback control circuit 2 compares the magnitude of the fluctuation of the output voltage with the reference voltage of the reference voltage source Vref by the comparator 4, and feedback-controls the switching of the transistor Q according to the comparison result to stabilize the DC output voltage. To the predetermined value.

  FIG. 1A is a partial plan view of a circuit board showing a mounting structure of the output circuit portion of the switching power supply 1 on the circuit board of the smoothing capacitor C according to the present embodiment. In the figure, components mounted on the circuit board are indicated by dotted lines, and wiring patterns formed on the surface of the circuit board are indicated by solid lines.

  On the surface of the circuit board, power line wiring patterns 11a and 11b and ground wiring patterns 12a and 12b are formed. One ground wiring pattern 12b is formed in the inner layer of the circuit board through the via hole 13. It is connected to a ground plane layer (not shown). The ground plane layer is connected to the ground potential and is connected to the input ground terminal GND and the output ground terminal GND.

  One end (not shown) of the power supply line wiring pattern 11a is connected to the collector of the transistor Q, and the choke coil L is mounted between the power supply line wiring pattern 11b that is electrically insulated and separated. The power supply line wiring pattern 11b has a shape in which the ground wiring patterns 12a and 12b are notched, and one end (not shown) is connected to the output terminal Vout. A smoothing capacitor C is mounted between the power line wiring pattern 11b and the ground wiring pattern 12a at the notch. Further, a three-terminal capacitor 3 is mounted between the ground wiring patterns 12a and 12b that are electrically insulated and separated, and between the power supply line wiring patterns 11b that are notched at a predetermined distance.

  2A is an external perspective view of the three-terminal capacitor 3, and FIG. 2B is an exploded perspective view showing an internal configuration thereof.

  The three-terminal capacitor 3 is a multilayer ceramic chip capacitor, and includes a hot internal through electrode 22 and a ground internal through electrode 23 in a dielectric body 21 in which a ceramic layer 20 is laminated to form a substantially rectangular parallelepiped shape. Yes. The hot internal through electrode 22 is provided so as to pass through the dielectric 21 in a straight line, and both ends of the substantially rectangular parallelepiped in the long side direction are connected to the pair of hot electrodes 3a and 3b. The ground internal through electrode 23 is provided in a substantially cross shape, and both ends in the short side direction of a substantially rectangular parallelepiped are connected to the pair of ground electrodes 3 c and 3 d to form a capacitance with the hot internal through electrode 22. . In the dielectric 21, a plurality of hot internal through electrodes and ground internal through electrodes (not shown) similar to the hot internal through electrodes 22 and the ground internal through electrodes 23 are alternately stacked to form a plurality of capacitors. Similarly to the hot internal through electrode 22 and the ground internal through electrode 23, these hot internal through electrode and ground internal through electrode (not shown) are also connected to the hot electrodes 3a and 3b and the ground electrodes 3c and 3d, respectively.

  In the three-terminal capacitor 3, the ground electrode 3d is connected to the ground wiring pattern 12a shown in FIG. 1A, the ground electrode 3c is connected to the ground wiring pattern 12b, and the hot electrodes 3a and 3b are respectively connected to the power supply line wiring pattern. 11b. FIG. 1B is an equivalent circuit diagram of the mounting structure shown in FIG. In FIG. 2B, the same parts as those in FIGS. 2A and 2C and FIG.

  Therefore, the smoothing capacitor C that smoothes the DC output voltage of the switching power supply 1 has one end connected to the power supply line wiring pattern 11 b connected to the output terminal Vout of the switch power supply 1 and the other end connected to the ground of the three-terminal capacitor 3. Connected to the ground potential through one ground internal through electrode 23 and via hole 13 between electrodes 3c and 3d. In the three-terminal capacitor 3, both ends of the other hot internal through electrode 22 are connected in parallel to the power line wiring pattern 11b via the hot electrodes 3a and 3b.

  In the switching power supply 1 having such a configuration, the DC resistance component between the output terminal Vout and the ground potential is the ESR of the smoothing capacitor C, the DC resistance component of the ground wiring pattern 12a, and between the ground electrodes 3c and 3d of the three-terminal capacitor 3. , The DC resistance component from the ground electrode 3c of the ground wiring pattern 12b to the via hole 13, and the DC resistance component of the via hole 13. However, it is the DC resistance component between the ESR of the smoothing capacitor C and the ground electrodes 3 c and 3 d of the three-terminal capacitor 3 that mainly contributes as resistance among these DC resistance components. The DC resistance component between the ground electrodes 3c and 3d depends on the shape of the ground internal through electrode 23, and can be changed to an arbitrary DC resistance value by appropriately setting the shape of the ground internal through electrode 23. . Each ESR between the ground electrodes 3c and 3d of the three-terminal capacitor 3 and between the hot electrodes 3a and 3b has substantially the same value as the ESR of the functional polymer capacitor.

  Thus, according to the mounting structure of the smoothing capacitor C on the circuit board according to the present embodiment, one ground internal through electrode 23 of the three-terminal capacitor 3 is provided between the output terminal Vout of the switching power supply 1 and the ground potential. A DC resistance component is formed by adding the DC resistance component to the ESR of the smoothing capacitor C. Therefore, even if a ceramic capacitor with a smaller ESR than a functional polymer capacitor is used as the smoothing capacitor C for the output of the power circuit, the amount of ESR that has been reduced is not necessary to eliminate noise without using a chip resistor or the like. This is compensated by the DC resistance component of the ground internal through electrode 23 of the three-terminal capacitor 3. Therefore, even when a low ESR capacitor such as the ceramic capacitor of the present embodiment having many advantages described above is used as the smoothing capacitor C instead of the functional polymer capacitor, it is disclosed in the conventional patent document 1. It is possible to easily stabilize the control of the switching power supply 1 with the same circuit configuration as when a functional polymer capacitor is used, without the need for designing a circuit that requires time as in the case of a ripple converter. In addition, the control can be stabilized by adding only the three-terminal capacitor 3, and many additional elements such as a resistance element and a capacitive element are not required as in the prior art disclosed in Patent Document 1, An increase in cost can be suppressed, and an increase in the area occupied by the additional elements on the circuit board can also be suppressed, thereby satisfying the demand for downsizing of electronic devices. Further, when there is a phase difference between the output voltage and the feedback voltage of the negative feedback amplifier and the resonant circuit is used, the power supply circuit needs to be redesigned separately. Can be easily compensated for by the ground internal through electrode 23 of the three-terminal capacitor 3 as described above, so that the redesign is also facilitated.

  Further, according to the mounting structure of the smoothing capacitor C on the circuit board according to the present embodiment, since the hot internal through electrode 22 of the three-terminal capacitor 3 is connected in parallel to the power line wiring pattern 11b, the power line wiring pattern The high frequency noise superimposed on 11a and 11b is released to the ground potential via the three-terminal capacitor 3, and the high frequency characteristics are improved as compared with the case where only the smoothing capacitor C is connected to the output terminal Vout of the switching power supply 1. .

  FIG. 3 is a partial plan view of the circuit board showing the mounting structure of the smoothing capacitor C on the circuit board according to the first modification of the embodiment described above. In the figure, the same parts as those in FIG. 1A are denoted by the same reference numerals, and the description thereof is omitted.

  As described above, the three-terminal capacitor 3 usually has a hot internal through electrode 22 having a long conductor length formed in the long side direction of the substantially rectangular parallelepiped, and a conductor in which the power line wiring pattern is formed in the short side direction of the substantially rectangular parallelepiped. A short ground internal through electrode 23 is connected to a reference potential such as a ground potential. However, in the configuration according to the first modification, as shown in FIG. 3, one internal through electrode connected to the ground potential via the via hole 13 is used in the long side direction of the substantially rectangular parallelepiped. The hot internal through electrode 22 is formed, and the other internal through electrode connected to the power line wiring pattern 11b is the ground internal through electrode 23 formed in the short side direction of the substantially rectangular parallelepiped.

  Accordingly, the ground internal through electrode 23 having a short conductor length is connected to the power line wiring pattern 11b via the ground electrodes 3c and 3d, and the hot internal through electrode 22 having a long conductor length is connected to the ground potential via the hot electrodes 3a and 3b. Is done. For this reason, the direct current resistance component of the internal through electrode applied to the ESR of the smoothing capacitor C becomes a large direct current resistance component of the hot internal through electrode 22, and the way of connecting the internal through electrode is appropriately reversed as in this modification. Thus, a larger DC resistance component can be easily added to the ESR of the smoothing capacitor C, and the DC resistance component formed between the output terminal Vout of the switching power supply 1 and the ground potential can be easily adjusted. The direct current resistance component between the hot electrodes 3a and 3b depends on the shape of the hot internal through electrode 22, and can be changed to an arbitrary direct current resistance value by appropriately setting the shape of the hot internal through electrode 22.

  FIG. 4 is a partial plan view of the circuit board showing the mounting structure of the smoothing capacitor C on the circuit board according to the second modification of the embodiment described above. In the figure, the same parts as those in FIG. 1A are denoted by the same reference numerals, and the description thereof is omitted.

  In the second modification, a resistance value adjusting wiring pattern 31 is formed on the surface of the circuit board between the ground wiring patterns 12a and 12b, and the inside of the ground formed between the ground electrodes 3c and 3d of the three-terminal capacitor 3 is formed. Only the point that the through electrode 23 is connected in parallel to the resistance value adjusting wiring pattern 31 is different from the above-described embodiment.

  According to the configuration of the present modification, the resistance value adjusting wiring pattern 31 is connected in parallel to the ground internal through electrode 23 of the three-terminal capacitor 3 connected in series to the smoothing capacitor C. In addition to the ESR of the smoothing capacitor C, The DC resistance component to be obtained is a parallel composite value of the DC resistance components of the ground internal through electrode 23 and the resistance value adjusting wiring pattern 31. For this reason, also by this modification, the DC resistance component applied to the ESR of the smoothing capacitor C can be easily adjusted to an arbitrary value by appropriately setting the shape of the resistance value adjusting wiring pattern 31 connected in parallel. .

  In the mounting structure of the first modified example shown in FIG. 3 described above, a resistance value adjusting wiring pattern is formed on the surface of the circuit board between the ground wiring patterns 12a and 12b as in this modified example. You may comprise so that the hot internal through electrode 22 comprised between the hot electrodes 3a and 3b of the capacitor | condenser 3 may be connected in parallel with the resistance value adjustment wiring pattern. According to this configuration, the DC resistance component applied to the ESR of the smoothing capacitor C is a parallel composite value of the DC resistance components of the hot internal through electrode 22 and the resistance value adjustment wiring pattern, and the resistance value adjustment wiring connected in parallel. By appropriately setting the shape of the pattern, the direct current resistance component applied to the ESR of the smoothing capacitor C can be easily adjusted to an arbitrary value.

  In the present embodiment, the case where the mounting structure of the smoothing capacitor C on the circuit board is applied to the switching power supply 1 has been described. However, the mounting structure of the smoothing capacitor C on the circuit board according to the present invention is not limited to the switching power supply 1 and can be similarly applied to other DC stabilized power supplies. The same effects as those of the above-described embodiment can be obtained.

DESCRIPTION OF SYMBOLS 1 ... Switching power supply 2 ... Feedback control circuit 3 ... 3 terminal capacitor | condenser 3a, 3b ... Hot electrode 3c, 3d ... Ground electrode 4 ... Comparator 11a, 11b ... Power supply line wiring pattern 12a, 12b ... Ground wiring pattern 13 ... Via hole 20 ... Ceramic layer 21 ... Dielectric 22 ... Hot internal through electrode (the other internal through electrode)
23: Ground internal through electrode (one internal through electrode)
Q ... Transistor D ... Flywheel diode C ... Smoothing capacitor L ... Choke coil

Claims (3)

A mounting structure on a circuit board of a smoothing capacitor that smoothes a DC output voltage of a DC stabilized power supply,
The smoothing capacitor has one end connected to a wiring pattern connected to the output of the DC stabilized power supply and the other end connected to a reference potential via one internal through electrode of the three-terminal capacitor.
The three-terminal capacitor has the other internal through electrode connected in parallel to the wiring pattern. A smoothing capacitor mounting structure on a circuit board.   The three-terminal capacitor has a substantially rectangular parallelepiped shape, and the one internal through electrode connected to the reference potential is a hot internal through electrode formed in a long side direction of the substantially rectangular parallelepiped, and the wiring pattern 2. The structure for mounting a smoothing capacitor to a circuit board according to claim 1, wherein the other internal through electrode connected to the ground is a ground internal through electrode formed in a short side direction of the substantially rectangular parallelepiped.   3. The smoothing capacitor circuit according to claim 1, wherein a resistance value adjusting wiring pattern connected in parallel to the one internal through electrode of the three-terminal capacitor is formed on the circuit board. 4. Mounting structure on the board.

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