JP5652019B2 - Switching power supply module and electrical equipment - Google Patents

Description

  The present invention relates to a switching power supply module and an electric device including the same.

  A switching power supply is a power supply device that uses a switching element to convert and adjust power in a power conversion device that obtains desired output power from input power. Among these are DC-DC converters that convert DC power into another DC power.

A semiconductor element formed using a semiconductor having a wide band gap such as SiC (silicon carbide), GaN (gallium nitride), or diamond on a semiconductor substrate is noted as having the potential to greatly break the performance limit of Si power devices Has been. Accordingly, expectations for wide band gap semiconductor elements are also high in the field of power devices.

  Further, as representative semiconductor elements using wide band gap semiconductors, JFET (junction FET), SIT (electrostatic induction transistor), MESFET (metal-semiconductor-field-effect-transistor), HFET ( There are Heterojunction Field Effect Transistors), HEMTs (High Electron Mobility Transistors), and storage FETs. Currently, many wide bandgap semiconductor elements in practical use have normally-on characteristics, but a wide bandgap semiconductor element having normally-off characteristics can also be obtained.

  Wide bandgap semiconductor elements have excellent characteristics as described above, so they are used as switching elements for switching power supplies and use thin inductors to operate at high frequencies in the region above MHz. Therefore, it can be expected that the switching power supply circuit is made into a module and greatly reduced in size.

JP 2009-283840 A

  However, since the noise component radiated from the mounting device is increased by this high-frequency operation and electromagnetic interference occurs between circuit elements, it is a problem to reduce this electromagnetic interference while maintaining miniaturization.

  Further, in addition to the above problems, the temperature rise of the circuit components due to the heat generated from the circuit components such as the switching elements becomes remarkable with downsizing, so it is also important to reduce the temperature of the circuit components.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a switching power supply module in which mounting density is increased to facilitate downsizing and electromagnetic interference between mounted circuit components is reduced, and an electric device including the same.

According to an embodiment of the present invention, a switching power supply module including a wiring board, a switching device, and an inductor is provided. The wiring board includes an interference prevention layer for preventing interference between the one surface side and the other surface side. The switching device is mounted on the wiring board on one surface side of the interference prevention layer. The inductor is mounted on the wiring board on the other surface side of the interference prevention layer. The switching device includes a switching element, a constant current means, and a diode. The constant current means is connected in series to the switching element, and varies the current flowing through the switching element according to the gate potential. The diode is connected in series with the constant current means.

  According to the present invention, the switching device, which is the main noise radiation source of the switching power supply, and the thin inductor are separately mounted on one side and the other side of the interference prevention layer and mounted on the wiring board, and facing each other. Therefore, even if the mounting area of the thin inductor is relatively large, the mounting area of the switching device is small. Therefore, circuit components other than the switching device and the thin inductor are mainly placed on one side of the wiring board together with the switching device. Since it can be mounted, the switching power supply can be mounted without difficulty, miniaturization is possible, and the switching power supply prevents electromagnetic interference between circuit parts mounted on both sides of the interference prevention layer. A module and an electric device including the module can be provided.

It is a typical sectional view showing a 1st embodiment of a switching power supply module of the present invention. The switching device in 1st Embodiment of the switching power supply module of this invention is shown, (a) is a typical top view when a resist layer is seen, (b) is integration along the AA 'line of (a). It is a typical sectional view of a circuit. FIG. 3 is a schematic partially enlarged and partially sectional perspective view of the thin inductor. 1 is a circuit diagram showing an entire circuit example of a switching power supply that can be employed in a first embodiment of a switching power supply module of the present invention. It is a circuit diagram which similarly shows the circuit arrangement example of a chopper circuit among switching power supplies. It is typical sectional drawing which shows 2nd Embodiment of the switching power supply module of this invention. It is typical sectional drawing which shows 3rd Embodiment of the switching power supply module of this invention. It is a perspective view which shows the LED lighting apparatus which is 1st Embodiment of the electric equipment of this invention.

  (First embodiment of the switching power supply module) will be described.

  In the first embodiment, as shown in FIG. 1, the switching power supply module SMJ includes a wiring board PCB, a switching device IC, a thin inductor L, other circuit components RC, first and second metal radiators MHR1, MHR2 and package PK are included as main components. The switching power supply module SMJ constitutes at least the main part or almost the entire switching power supply SR. Therefore, if the switching power supply module SMJ is connected so as to be interposed between the DC power supply (or AC power supply) and the load, the load can be energized and operated.

  Each of the wiring boards PCB is mounted with a switching device IC, a thin inductor L, and other circuit components RC, which will be described later, and a switching power supply module for the main part or almost the whole of the switching power supply SR having the circuit configuration shown in FIG. Provide wiring means to configure as SMJ. Various known mounting methods can be appropriately employed as the wiring means of the wiring board PCB.

  In the present embodiment, the wiring board PCB has a structure in which two sheets, that is, the first and second wiring boards PC1 and PC2 are overlapped via the interference prevention layer AIL. Reference numerals T1 and T2 in the figure denote terminal lead-out portions of the wiring board PCB, which are connected to external terminals of the switching power supply module SMJ that are not shown. The terminal lead-out portions T1 and T2 are both direct current. The mounting method provided by the wiring board PCB is not particularly limited. In the present embodiment, for example, flip chip mounting and surface mounting are used in combination.

  The interference prevention layer AIL is a means for preventing electromagnetic interference between circuit components that are separated on both sides and mounted on the wiring board PCB. In the present embodiment, the interference prevention layer AIL is configured by using a thin plate or a film-like body made of a conductive metal such as copper or aluminum. And it can be grounded if desired. Further, the interference prevention layer AIL is allowed to be constituted by the ground layer disposed on one or both of the first and second wiring boards PC1 and PC2.

  The switching device IC includes at least a switching element Q1 shown in FIG. 4 that is mounted on the first wiring board PC1 on one side of the interference prevention layer AIL and is in charge of the main switching operation as a switching power supply.

  In the present embodiment, the switching element Q1 is means for switching the switching power supply SR, and may be any of a switching element having a normally-on characteristic, that is, a normally-on switch, and a switching element having a normally-off characteristic, that is, a normally-off switch. .

  In the case of a switching element using a wide bandgap semiconductor, a device having normally-on characteristics is easier to obtain, switching is faster, and the on-resistance is low. The normally-off switch is easy to handle because it is off when the power is turned on, but it requires a start circuit for starting oscillation when operated by self-excited oscillation. In the case of a normally-on switch, it is not necessary to add a starting circuit when the power is turned on, so that the circuit can be simplified and the switching power supply module MJ can be miniaturized. In the case of a normally-on switch, the off operation is preferably performed by the constant current means CCM. Furthermore, when a normally-on switch having a negative switching threshold is used, it is preferable because the off-control using the drive winding DW magnetically coupled to the inductor L1 shown in FIGS. 4 and 5 described later becomes easy. It is. However, even with a normally-off switch, there is no basic problem because a simple start-up circuit may be added.

  When a switching element using a wide band gap semiconductor, for example, GaN-HEMT, is used as the switching element Q1, the switching characteristics at high frequencies are remarkably improved. Therefore, the switching element Q1 is suitable as a switching element Q1 that operates at MHz or higher, preferably at 10 MHz or higher. . When the operating frequency of the switching power supply SR is increased as described above, the switching loss is reduced, and the thin inductor L is also reduced in size, so that the switching power supply SR can be greatly reduced in size. The wide band gap semiconductor may be any semiconductor having a wide band gap such as SiC (silicon carbide), GaN (gallium nitride), or diamond on a semiconductor substrate.

  In the present embodiment, the switching device IC is a constant current means CCM as a circuit element that performs a substantial switching operation accompanying switching of the switching element Q1 of the switching device IC, as shown in FIGS. 4 and 5 and described later. The diode D1 is included after a predetermined circuit connection. That is, the switching element Q1, the constant current means CCM, and the diode D1 of the switching device IC form a serial connection SCB as shown in FIGS. 4 and 5, and in the integrated circuit having five external terminals P1 to P5. It has a form.

  Next, the structure of the switching device IC will be described in detail with reference to FIG. As shown in the schematic top view of the resist layer in FIG. 2A and the schematic cross-sectional view along the line AA ′ in FIG. 2B, the switching device IC has, for example, a GaN-based multichip structure. And is flip-chip mounted on one surface side of the wiring board PCB. If desired, the GaN-based single chip may be configured such that the switching element Q1, the constant current means CCM, and the diode D1 are continuously formed in series.

  As shown in FIG. 2B, the GaN-based multichip structure is a laminated body including, for example, a metal substrate M, an insulating layer I, a GaN chip GC, a resist layer R, and solder bumps B. In the GaN chip GT, the relatively large square portions indicated by dotted lines in FIG. 4A are the chips of the switching element Q1, the constant current means CCM, and the diode D1, and they are integrated and connected in series. Configured. Note that a relatively small square portion indicated by a solid line in the figure is a bump opening formed in the resist layer R, in which the switching element Q1, the constant current means CCM and the external terminals P1 to P5 are led out. An electrode E forming a schematic terminal portion of the diode D1 faces. Further, a relatively small rectangular portion indicated by a dotted line is a schematic terminal portion similar to the above in which no external terminal is derived. The three solder bumps B shown in FIG. 2B form the external terminals P1, P2, and P3 in FIGS. Except for the solder bumps B, the outer periphery of the switching device IC can be surrounded by a known package (not shown).

  In FIG. 1, the switching device IC flip-chip mounted on one surface side of the wiring board PCB is filled with an underfill UF1 between the space around the solder bump B and the wiring board PCB, so that the moisture resistance of the mounting portion is increased. Is configured to be maintained.

  The thin inductor L is mounted on the other surface side of the interference prevention layer AIL, that is, on the second wiring board PC2 so as to face the switching device, and functions as a main circuit component for chopper operation in cooperation with the switching device IC. . The mounting method of the thin inductor L on the wiring board PCB is not particularly limited. In this embodiment, flip chip mounting is performed as shown in FIG. In the drawing, underfill UF2 is filled between the space around the solder bump B disposed on the thin inductor L1 and the wiring board PCB, so that the moisture resistance of the mounting portion is maintained. ing.

  Further, as shown in FIG. 3, the thin inductor L is formed by winding the inductor L1 and the moving winding DW, for example, by winding a flat coil wire so as to form a spiral shape in a plane. The inside and the periphery are covered with the magnetic layer MG, and the whole is configured to be planar. Then, one end of the inductor L1 and the drive winding DW is located at the center of the coil and constitutes a terminal portion t. Then, a through hole h is formed at the center of the terminal portion t, the other main terminal (anode) conductor of the constant current means CCM of the switching device IC is inserted into the through hole h, and a conductor is injected into the inside. Thus, the inductor L1, the drive winding DW, and the connection conductor of the switching device IC are connected together. Note that the magnetic layer MG is made of, for example, ceramics or plastics in which ferrite fine particles are dispersed, as shown in a cross-sectional view in which a part of FIG. 3 is enlarged on the right side of the drawing.

  In addition, when the operating frequency is in the range of MHz or higher, preferably 10 MHz or higher, the thin inductor L may have a correspondingly small inductance value. It is also permissible to implement directly on That is, the thin inductor L can be formed by forming a coil pattern on a part of the wiring pattern of the wiring board PCB and superimposing a magnetic sheet on the coil pattern.

  The other circuit components RC1 and RC2 are other circuit components excluding the switching device IC and the thin inductor L described above in the switching power supply SR. For example, a rectifier circuit Rec composed of a diode bridge constituting the DC power source DC shown in FIG. 4, capacitors C1 to C3 shown in FIG. 5, an adjustable potential source E1, a resistor constituting the detection circuit associated therewith, a capacitor, and the like It is a control circuit component or the like that is not shown in the figure such as a comparator.

  In the present embodiment, the other circuit components RC1 and RC2 are configured to be mounted on the wiring board PCB by surface mounting using reflow solder. Reference symbol TS denotes external terminals disposed on both side surfaces of the circuit components RC1 and RC2 to be surface-mounted.

  The first and second metal radiators MHR1 and MHR2 are heat radiating means for radiating heat generated in the switching device IC and the thin inductor L to the outside. The first metal heat radiating body MHR1 is in contact with the surface opposite to the wiring board PCB of the switching device IC in a heat conduction relationship via the heat path HP1 so as to dissipate the heat generated by the switching device IC. The second metal radiator MHR2 is in contact with the surface opposite to the wiring board PCB of the thin inductor L1 through the heat path HP2 so as to dissipate the heat generated by the thin inductor L1. . The first and second metal radiators MHR1, MHR2 are preferably arranged so as to be exposed on the outer surface of the package PK described later.

  As a result of the switching power supply module SMJ having the above-described configuration, the switching device IC and the thin inductor L are sandwiched between the first and second metal radiators MHR1 and MHR2. Therefore, the first and second metal radiators MHR1 and MHR2 function as a shield for the switching device IC and the thin inductor L. In order to further improve the function as an electromagnetic shielding member and the function as a heat sink, the areas of the first and second metal heat sinks MHR1 and MHR2 are as shown in FIG. It can be set clearly larger than that of the above surface.

  The package PK surrounds the entire switching power supply module SMJ and protects the circuit components and the circuit housed therein, and facilitates handling of the module SMJ. In the present embodiment, a resin mold is used for the package PK. However, it is needless to say that other known packages mainly made of materials such as ceramics and metal can be adopted as appropriate.

In the case of this embodiment, since the first and second metal radiators MHR1 and MHR2 are exposed on the outer surface of the package PK, the switching power supply module SMJ is simply attached to the mounted body. The generated heat can be conducted to the mounted body. For this reason, if the heat dissipation of the attached body is good, the heat generated by the switching power supply module SMJ can be dissipated to suppress the temperature rise. The first metal heat radiating body MHR1 that is in contact with the switching device IC in the heat conduction relationship is attached to the attached body so that the temperature rise is further suppressed and the generation of noise is reduced. This is because when comparing the switching device IC and the thin inductor L, the former generates more heat and noise radiation than the latter.

  Next, a circuit configuration example of the switching power supply module SMJ will be described with reference to FIG. That is, the switching power supply SR includes a DC power supply DC and a chopper circuit CHC, an input terminal is connected to the AC power supply AC, and a load circuit LC is connected to the output terminal. The chopper circuit CHC portion can be configured as the switching power supply module SMJ. However, the whole including the direct current power source DC may be configured as the switching power source module SMJ if desired.

  The chopper circuit CHC is a concept including various choppers such as a step-down chopper, a step-up chopper, and a step-up / step-down chopper. Each of the choppers described above is configured with a switching device IC and a thin inductor L as main components. Then, by turning on the switching element Q1 of the switching device IC, an increased current flows from the DC power source DC to the inductor L1. Further, by turning off the switching element Q1, the operation of decreasing current flowing through the diode D1 due to the release of electromagnetic energy accumulated in the inductor L1 is repeated. This is common in that the voltage of the DC power supply DC is DC-DC converted and a DC voltage is output to the output terminal.

  The chopper circuit CHC includes a drive winding DW that is magnetically coupled to the inductor L1. When the switching element Q1 is turned on and an increased current flows through the inductor L1, the drive winding DW detects this and maintains the switching element Q1 in the off state with the output voltage.

  Further, the chopper circuit CHC includes DC input terminals t1 and t2 and DC output terminals t3 and t4, and the inside thereof is configured by any one of various known choppers such as a step-down chopper, a step-up chopper, and a step-up / step-down chopper.

  The DC power source DC is means for inputting a DC voltage before conversion to the above-described chopper circuit CHC. Further, any configuration may be used as long as a DC voltage is output. For example, a rectifier circuit Rec is mainly used, and a smoothing circuit including a smoothing capacitor may be provided as desired. In this embodiment, the rectifier circuit Rec is preferably a bridge-type rectifier circuit, and full-wave rectifies an AC voltage of an AC power source AC, for example, a commercial AC power source, to output a DC voltage.

  When the switching power supply SR described above operates in a frequency range of MHz or higher, preferably in a frequency range of 10 MHz or higher, the external terminals arranged in the switching power supply module SMJ are all DC and only DC input / output is provided. Therefore, the operation is stable and the switching power supply SR can be significantly reduced in size. For this reason, the switching power supply SR can be arranged adjacent to the load circuit LC, for example, the light emitting diode of the lighting device, which contributes to a significant downsizing of the entire load of the lighting device or the like.

  Next, a circuit configuration example when the chopper circuit CHC is a step-down type will be described with reference to FIG. In this circuit configuration example, the chopper circuit CHC is a step-down type, and GaN-HEMT is used for the switching element Q1 and the constant current means CCM of the switching device IC, respectively, and the inductor L1 is connected between the load circuit LC and the input terminal t2. Connected between. The drive winding DW is connected between the external terminals P4 and P3 of the switching device IC via the load circuit LC and the coupling capacitor C2, that is, the control terminal (gate) of the switching element Q1 and the other main terminal of the constant current means CCM ( Source).

  The switching device IC has an external terminal P1 connected to the input terminal t1, an external terminal P2 connected to the input terminal t2, and an external terminal P3 connected to one end of the load circuit LC.

  Reference symbol C1 in the figure is a high-frequency bypass capacitor connected between the input ends t1 and t2 of the chopper circuit CHC. Reference sign A is a first circuit, and reference sign B is a second circuit. The symbol LED of the load circuit LC is a light emitting diode, and C3 is an output capacitor.

  The first circuit A includes an input terminal t1, a switching element Q1, a constant current means CCM, a parallel circuit of an output capacitor C3 and a load circuit LC, an inductor L1, and a series circuit of an input terminal t2. The second circuit B is configured by a closed circuit of a parallel circuit of an inductor L1, a diode D1, an output capacitor C3, and a load circuit LC.

The constant current means CCM makes the constant current value variable by making the gate potential variable using the adjustable potential source E1. That is, the adjustable potential source E1 is connected between the control terminal (gate) of the constant current means CCM and the other main terminal (source) via the external terminal P5 of the switching device IC and the load circuit LC. . Reference numeral D2 in the figure, the control terminal of the switching element Q1 (gate) - a clamping diode for main terminal (source) between the voltage V _GS is clamped so as not more than 0.6V.

  Next, circuit operation will be described.

When the DC power source DC is turned on, since the switching element Q1 of the chopper circuit CHC is turned on, a current flows out of the first circuit A from the DC power source DC via the switching element Q1 and the constant current means CCM. The current increases linearly. As a result, electromagnetic energy is accumulated in the inductor L1. Note that the gate-source voltage V _GS of the switching element Q1 is 0 during the period when the switching element Q1 is on. When the increasing current reaches the constant current value of the constant current means CCM, the increasing tendency of the current is stopped and held at the constant current. Note that while the increasing current flows in the inductor L1, the terminal voltage of the inductor L1 is positive.

  When the increasing current reaches the constant current value of the constant current means CCM, the current flowing through the inductor L1 further increases, so the voltage of the constant current means CCM increases in a pulse shape. Accordingly, the main terminal (source) potential of the switching element Q1 becomes higher than the potential of the control terminal (gate), and as a result, the control terminal becomes a relatively clearly negative potential, so that the switching element Q1 is turned off. . For this reason, the increasing current flowing into the inductor L1 is cut off by the switching element Q1 being turned off.

  At the same time when the switching element Q1 is turned off, the electromagnetic energy stored in the inductor L1 starts to be released, and a decreasing current flows out to the second circuit B. Note that while the decreasing current flows, the voltage polarity of the inductor L1 is reversed and becomes negative, and the drive winding DW is induced with a voltage at which the control terminal of the switching element Q1 has a negative potential. Since the voltage is applied between the control terminal (gate) of the switching element Q1 and the other main terminal (source) via the constant current means CCM, the switching element Q1 is maintained in the OFF state.

  When the decreasing current flowing through the second circuit B becomes 0, the negative voltage applied to the control terminal (gate) of the switching element Q1 is not induced, and at the same time, the voltage at which the control terminal becomes positive due to the back electromotive force. Is induced in the drive winding DW, the switching element Q1 is turned on again, and the circuit operation similar to that described above is repeated thereafter.

In the above operation, the step-down chopper circuit has an output voltage lower than the input voltage because Vout = Vin · α when the on-duty of the switching element Q1 is α, the input voltage is Vin, and the output voltage is Vout. It is done.

  As is apparent from the above circuit operation, the chopper circuit CHC performs a step-down chopper operation, and an output current in which an increasing current and a decreasing current alternately flow in the load circuit LC connected between the output terminals t3 and t4. The light emitting diodes LED are lit with these DC components, and the output capacitor C3 bypasses the high frequency components.

  Further, by adjusting the reference potential using the adjustable potential source E1, the constant current value of the constant current means CCM can be varied, so that it is easy to set a desired load current. At the same time, if the adjustable potential source E1 is feedback-controlled with respect to the power supply voltage fluctuation, the light output fluctuation of the light emitting diode with respect to the power supply voltage fluctuation can be suppressed. Further, the voltage drop of the constant current means CCM and the load circuit LC is added to the negative voltage of the drive winding DW applied to the control terminal of the switching element Q1.

  (Second Embodiment of Switching Power Supply Module) will be described.

  In the second embodiment, as shown in FIG. 6, the switching device IC is provided with the first metal radiator MHR1 that contacts the heat conduction relationship, but the thin inductor L is provided with a metal radiator. Not set up. In the figure, the same parts as those in FIG.

  As described above, if the switching device IC generates more heat and noise radiation than the thin inductor L, and the metal radiator can be omitted from the latter, this embodiment may be used. The structure is simplified.

  (Third embodiment of the switching power supply module) will be described.

  In the third embodiment, as shown in FIG. 7, the metal radiator that contacts the switching device IC and the thin inductor L in a heat conduction relationship is not provided. In the figure, the same parts as those in FIG.

  For example, when the generated heat and noise radiation of the switching device IC and the thin inductor L are low due to the low switching frequency, it is not necessary to dispose a special metal radiator in the switching power supply module SMJ. This embodiment may be used.

  Therefore, according to the present embodiment, the structure of the switching power supply module SMJ is simplified and less expensive than the first and second embodiments.

(Embodiment of electrical equipment) will be described.
In the present embodiment, the electric device EA is an LED lighting device shown in FIG. This LED illumination device is configured by arranging and arranging a plurality of sets of LED modules LM and switching power supply modules SMJ on a support substrate BP.

  The support substrate BP is made of a member having good thermal conductivity such as aluminum. The switching power supply module SMJ is the embodiment described above, and is attached so that the switching device IC shown in FIG. 1, FIG. 6, or FIG. 7 is located between the wiring board PCB and the support board BP.

  With the above configuration, the switching device IC that generates a large amount of heat and noise is sandwiched between the support substrate BP and the interference prevention layer AIL of the wiring substrate PCB, and the switching device IC is relatively close to the substrate BP. Ascending and radiation noise can be reduced easily. In particular, in the case of the switching power supply module SMJ having the configuration shown in FIG. 1 or FIG. Since they are in contact, the temperature rise of the switching device IC and the reduction of radiation noise are effectively suppressed.

  Further, according to the present embodiment, since it is common to arrange the LED module LM and the switching power supply module SMJ constituting the set adjacent to each other on the support substrate BP, not only maintenance is facilitated, but also the appearance It is also refreshing and good.

  AIL ... interference prevention body, B ... solder bump, CCM ... constant current means, D1 ... diode, DW ... drive winding, HP1, HP2 ... heat path, IC ... switching device, L ... thin inductor, L1 ... inductor, MHR1 ... 1st metal radiator, MHR2 ... 2nd metal radiator, P1, P2, P3, P4, P5 ... External terminal, PCB, ... Wiring board, PC1 ... 1st wiring board, PC2 ... 2nd wiring board , PK ... package, Q1 ... switching element, RC1, RC2 ... other circuit parts, SMJ ... switching power supply module, SR ... switching power supply, T1, T2 ... terminal output, TS ... external terminal, UF1, UF2 ... underfill

Claims (3)

A wiring board provided with an interference prevention layer for preventing interference between the one side and the other side;
A switching device in one side of the interference preventing layer is mounted on the wiring board;
And inductor to the other surface of the interference preventing layer is mounted on the wiring board;
Equipped with,
The switching device is
A switching element;
Constant current means connected in series to the switching element and varying a current flowing through the switching element in accordance with a gate potential;
A diode connected in series to the constant current means;
Switching power supply module and having a. Switching power supply according to claim 1, characterized by comprising a first metal heat radiator that is thermally coupled to the switching device, and a second metal radiator body that is thermally coupled to the inductor, at least one. With the electrical equipment body;
And disposed claims 1 or 2 switching power supply module according to the electric apparatus unit;
An electrical apparatus comprising:

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