JP2018143010A - Electronic circuit device - Google Patents

Abstract

An electronic circuit device capable of reducing the influence of parasitic inductance as much as possible is provided. A circuit board 3 on which a plurality of circuit elements including switching elements 11 and 12 constituting a regulator are mounted and wiring patterns WPg and WPs for electrically connecting the circuit elements are arranged, and the circuit board 3 An electronic circuit device having a metal housing 4 for holding the switching element 11 and 12 on a main surface 3A of the main surface of the circuit board 3 facing the housing 4. A circuit element is mounted, and a part of the wiring pattern WPg on the ground side among the wiring patterns connecting the circuit elements is replaced with the housing 3. [Selection] Figure 3A

Description

  The present invention relates to an electronic circuit device including a circuit board and a casing for holding the circuit board.

  Patent Document 1 discloses a circuit configuration body that can efficiently cool a bus bar that constitutes a power circuit with a simple structure. The circuit structure includes a plurality of bus bars constituting a power circuit and a heat radiating member for cooling the bus bar. The heat radiating member has a bus bar bonding surface coated with an insulating layer. Each bus bar is directly bonded to the bus bar bonding surface in a state where the plurality of bus bars are arranged on the surface.

  The circuit structure includes, for example, a power distribution circuit in which a plurality of bus bar substrates are stacked, a circuit breaker element and a switch element in the power distribution circuit, and a DC regulator that converts an input DC voltage into a desired output voltage. And is applied to an electrical junction box that distributes power from a common in-vehicle power source to each electronic unit.

  Patent Document 2 discloses a power conversion device (DCDC converter) that is mounted on an electric vehicle or a plug-in hybrid vehicle and performs power conversion from a high voltage storage battery to a low voltage storage battery or power conversion from a low voltage storage battery to a high voltage storage battery. In order to reduce noise mixed in electronic equipment or the like arranged outside the power conversion device, a filter circuit such as an input filter circuit is provided on the input side of the power conversion circuit and an output filter circuit is provided on the output side of the power conversion circuit. A connected electronic device is disclosed. An electronic device that includes a filter circuit that suppresses the influence of electromagnetic noise propagating in space from a circuit board, reduces parasitic inductance, and can output a sufficiently noise-reduced voltage.

  Specifically, the electronic device passes through a housing, a circuit board provided in the housing, and a through-hole provided in the housing, and outputs the output of the circuit board to the outside or from the outside to the circuit board. A filter means having a filter capacitor, a first wiring connecting the external terminal and the filter means, and a housing closer to the external terminal than the filter means. And a second wiring for connecting the body and the filter means. As a result, the parasitic inductance and the electromagnetic induction effect can be reduced, and the filter function can be ensured.

JP 2003-164040 A JP 2013-99057 A

  The power converters such as DC regulators disclosed in Patent Documents 1 and 2 are both surfaces on which circuit elements mounted on each layer are electrically connected via narrow wiring patterns and vias for high-density mounting. Substrates and multilayer substrates are used.

  In such a circuit board, L, C, and R distributed constant circuits are three-dimensionally formed between the wiring pattern of the signal lines and the wiring pattern of the ground lines, between each wiring, vias, and mounted circuit elements. Parasitic capacitance and parasitic inductance are inherent.

  In particular, the value of the parasitic inductance is inversely proportional to the wiring pattern width and tends to be proportional to the wiring length, and is formed on the inner wall of the via to electrically connect the wiring patterns formed on both sides of the circuit board. Since the copper foil pattern is thin, a large parasitic inductance is generated.

  Under the influence of such a parasitic inductance, there is a possibility that a large surge voltage is applied to the semiconductor switching element incorporated in the power conversion device at the time of switching. Therefore, it is necessary to use a semiconductor switching element having a high withstand voltage. There are problems that the on-resistance increases and conduction loss increases, and that the switching time becomes long and the power loss increases.

  The main purpose of the circuit structure disclosed in Patent Document 1 is to cool a plurality of bus bars constituting a power circuit by bringing them into contact with a heat dissipating member, and to eliminate the adverse effects caused by the parasitic inductance generated in the power circuit. There was room for further improvement.

  In addition, the electronic device disclosed in Patent Document 2 is intended to reduce the influence of noise caused by parasitic inductance generated in the wiring of the filter circuit, and the viewpoint of reducing the influence of parasitic inductance generated in the power converter itself. There was room for further improvement as well.

  In view of the above-described problems, an object of the present invention is to provide an electronic circuit device that can reduce the influence of parasitic inductance as much as possible.

  In order to achieve the above-described object, an electronic circuit device according to the present invention is a circuit board on which a plurality of circuit elements including switching elements constituting a DC regulator are mounted and wiring patterns for electrically connecting the circuit elements are arranged. And a metal casing that holds the circuit board, wherein the circuit element includes the switching element on a main surface of the main surface of the circuit board that faces the casing. Is mounted, and a part of the wiring pattern on the ground side among the wiring patterns connecting the respective circuit elements is replaced with the housing.

  ADVANTAGE OF THE INVENTION According to this invention, the electronic circuit device which can reduce the influence of parasitic inductance as much as possible can be provided.

It is sectional drawing of the principal part of an electronic circuit device. It is a circuit diagram of a DC regulator. It is explanatory drawing of the switching waveform of the high side switching element in case a parasitic inductance is large. It is explanatory drawing of the switching waveform of the high side side switching element in case a parasitic inductance is small. It is explanatory drawing of the current pathway of the electronic circuit apparatus of this invention. It is explanatory drawing of the equivalent circuit of the principal part of a switching element. It is explanatory drawing of the principal part of the electronic circuit device which shows another embodiment. It is sectional drawing of the principal part of the conventional electronic circuit device. It is explanatory drawing of the equivalent circuit of the principal part of a switching element.

[Description of Embodiment of the Invention]
First, the contents of the embodiment of the present invention will be listed and described.
(1) An electronic circuit device according to the present embodiment includes a circuit board on which a plurality of circuit elements including switching elements that constitute a DC regulator are mounted, and a wiring pattern that electrically connects each circuit element is disposed; An electronic circuit device comprising a metal casing for holding a substrate, wherein a circuit element including a switching element is mounted on a main surface of the main surface of the circuit board opposite to the casing, and each circuit element A part of the wiring pattern on the ground side of the wiring pattern for connecting is replaced with a housing.

  A circuit element including a switching element is mounted on the main surface of the circuit board opposite to the housing, and a part of the wiring pattern on the ground side among the wiring patterns for electrically connecting the circuit elements is the housing. It is electrically connected via. In other words, since the wiring portion replaced by the housing can be configured to have the shortest length with a substantially wide pattern width, the parasitic inductance is greatly reduced. In addition, since the circuit element including the switching element is mounted on the main surface of the main surface of the circuit board that faces the housing, the corresponding circuit elements can be electrically connected without vias. This makes it possible to reduce the parasitic inductance more effectively.

  (2) The electronic circuit device is provided with a fixing portion that fastens and fixes the circuit board and the housing with screws, and a connection portion that electrically connects the ground-side wiring pattern and the housing in the vicinity of the fixing portion. It is preferable that In the vicinity of the fixing portion that is fastened and fixed with screws, a high contact pressure can be secured between the ground-side wiring pattern and the housing, and a good ohmic contact can be realized.

  (3) It is more preferable that a convex portion is formed on either the ground side wiring pattern or the casing of the connecting portion, and a reliable and good ohmic contact can be realized through the convex portion.

  (4) It is preferable that a recess is formed in the housing, and a circuit element mounted on the circuit board is accommodated in the recess. The circuit element mounted on the circuit board is accommodated in the recess formed in the casing, so that the flat wiring pattern on the circuit board is directly opposed to the casing without distortion such as bending. In addition, the ground potential can be stabilized and the noise resistance can be improved by the electromagnetic shielding effect.

  (5) The DC regulator is a synchronous rectification step-down regulator in which a capacitor is connected in parallel to a series circuit of a high-side switching element and a low-side switching element, and the wiring pattern on the ground side of the low-side switching element and the capacitor is a housing. It is preferable that it is replaced with.

  Synchronous rectifier buck regulators have the advantage of significantly reducing power loss compared to asynchronous rectifier buck regulators, but large parasitic inductance values can cause switching losses and make it difficult to ensure dead time. Or a high surge voltage may be applied to the high-side switching element to cause damage.

  Even in such a case, the wiring pattern of the low-side switching element and the capacitor on the ground side, that is, a part of the switching loop is replaced with the housing, so that the value of the parasitic inductance is greatly reduced, and the switching loss. Thus, a dead time can be easily secured, and a low-breakdown-voltage switching element with low on-resistance and low conduction loss can be used.

[Details of the embodiment of the invention]
Next, the embodiment of the present invention will be described more specifically. In addition, this invention is not limited to these illustrations, is shown by the attached claim, and is intended that all the changes within the meaning and range equivalent to the claim are included. .

FIG. 1 shows an example of an electronic circuit device 1 that employs a synchronous rectification step-down regulator.
The electronic circuit device 1 is a vehicle-mounted electronic circuit device 1 that includes a circuit board 3 that constitutes a voltage conversion circuit, and a metal casing 4 that holds the circuit board 3, specifically, an aluminum casing 4. It is prepared for. The housing 4 is provided with a fixing portion 5 that fastens and fixes the above-described circuit board 3 with screws 6, and is formed with screw holes (not shown) for fixing the housing 4 itself to a vehicle frame or the like. The housing 4 is grounded to the vehicle frame by screws screwed into the screw holes.

  The circuit board 3 is composed of, for example, a glass epoxy resin double-sided board, and a plurality of circuit elements including switching elements 11 and 12 constituting a DC regulator 10 as an example of a voltage conversion circuit are mounted on one main surface 3A. A wiring pattern WP for electrically connecting each circuit element is arranged. The wiring pattern WP includes a signal wiring pattern WPs and a ground wiring pattern WPg.

  As shown in FIG. 2A, the DC regulator 10 supplies various auxiliary devices mounted on the vehicle by reducing the output voltage of a DC48V high-voltage storage battery such as a lithium ion battery to a low-voltage DC12V, or a lead storage battery or the like. It is a non-insulated synchronous rectification step-down regulator used for charging a low-voltage storage battery.

  The step-down regulator 10 is connected in parallel to the electrolytic capacitor C1 for voltage stabilization connected between the input terminals T1 and T2, the bypass capacitor C2 connected in parallel to the electrolytic capacitor C1, and the capacitors C1 and C2. The switching circuit SC is composed of a choke coil L1 and a smoothing capacitor C3.

  The switching circuit SC is configured by a series circuit of a high-side switching element 11 and a low-side switching element 12, and a choke coil L1 is connected between the connection portion N1 of the switching elements 11 and 12 and the output terminal T3, and the output terminal A smoothing capacitor C3 is connected between T3 and T4. As the switching element, a MOS-FET or IGBT is preferably used. The symbol IL indicates an insulating coating layer.

  The gate voltage is controlled so that the high-side switching element 11 and the low-side switching element 12 are alternately turned on with a certain dead time when both are turned off. When the high-side switching element 11 is turned on, the smoothing capacitor C3 is charged from the input terminal T1 via the high-side switching element 11 and the choke coil L1. At this time, energy is accumulated in the choke coil L1.

  Thereafter, when the high-side switching element 11 is turned off and the low-side switching element 12 is turned on with a dead time interposed therebetween, the energy accumulated in the choke coil L1 is released along a closed loop including the low-side switching element 12. Thus, the smoothing capacitor C3 is charged.

  By adjusting the switching cycle of the high-side switching element 11 and the low-side switching element 12, a desired DC voltage is output between the output terminals T3 and T4. Although not shown in the figure, the step-down regulator 10 is further provided with a control circuit that monitors the voltage between the output terminals T3 and T4 and controls the gate voltages of the high-side switching element 11 and the low-side switching element 12. It has been.

  FIG. 5A shows a configuration of a conventional electronic circuit device 1. 2A, the capacitor C2 is mounted on the main surface 3B of the main surface of the circuit board 3 opposite to the housing 4 and corresponds to the circuit portion in the area surrounded by the broken line shown in FIG. A high-side switching element 11 and a low-side switching element 12 are mounted on 3A.

  One end of the capacitor C2 is connected to the drain terminal of the high-side switching element 11 via the wiring pattern WP1 and via V1, and the other end of the capacitor C2 is connected to the drain terminal of the low-side switching element 12 via the wiring pattern WP2 and via V2. Further, the source terminal of the high-side switching element 11 and the drain terminal of the low-side switching element 12 are connected by the wiring pattern WP3. In the figure, a loop indicated by a broken-line arrow indicates a current flow. In the present embodiment, the term “via” is used as a concept including a through hole.

  Therefore, as shown in FIG. 5B, large parasitic inductances L (WP1), L (WP2), L (WP3), L (V1), L (V2) are present in the wiring patterns WP1, WP2, WP3 and the vias V1, V2. Has occurred. In the figure, the size of the figure showing the inductances L (WP1), L (WP2), L (WP3), L (V1), and L (V2) imitates the size of the parasitic inductance. The value of the parasitic inductance is large, and a small figure indicates that the value of the parasitic inductance is small.

  FIG. 2B shows a voltage waveform Vh and a current waveform Ih across the high-side switching element 11 of the electronic circuit device 1 shown in FIG. 5A. When the high-side switching element 11 shifts from the on state to the off state at time t0, it is confirmed that a large surge voltage is applied to the drain of the high-side switching element 11 and that the drain current falls slowly. Is done.

  In order to prevent the element from being damaged by such a large surge voltage, it is necessary to employ an expensive switching element having a large withstand voltage as the high-side switching element 11. In addition, since the current that flows when the high-side switching element 11 transitions from the on-state to the off-state leads to heat loss, the power loss is less than that of an asynchronous rectification step-down regulator that uses a diode instead of the low-side switching element. There is a problem that the advantage is impaired.

  As shown in FIG. 3A, in the electronic circuit device 1 according to the present invention, a circuit element including a switching element, that is, a high-side switching element 11 and a main surface 3A facing the casing 4 among the main surfaces of the circuit board 3 The low-side switching element 12 and the capacitor C2 are mounted, and a part of the ground-side wiring pattern WPg among the wiring patterns connecting the circuit elements 11, 12, and C2 is replaced by the housing 4.

  Specifically, a fixing portion 5 is provided to fasten and fix the circuit board 3 and the housing 4 with screws 6, and a connection for electrically connecting the ground-side wiring pattern WPg and the housing 4 in the vicinity of the fixing portion 5. A portion 7 (a region surrounded by a broken-line circle in the drawing) is provided.

  By tightening and fixing with the screws 6, a good ohmic contact is obtained between the ground-side wiring pattern WPg formed on the circuit board 3 and the housing 4. In the figure, the symbol IL is an insulating coating layer.

  Furthermore, a recess 4A is formed in the housing 4, and circuit elements C2, 11, 12 and the like mounted on the circuit board 3 are accommodated in the recess 4A. As a result, the flat wiring pattern on the circuit board 3 can be brought into contact with the housing 4 in a state of being directly opposed without distortion such as bending, and the ground potential can be stabilized and the electromagnetic shielding effect can be obtained. As a result, the noise resistance performance is improved.

  FIG. 3B shows the parasitic inductance characteristic of the electronic circuit device 1 so that it can be compared with the parasitic inductance characteristic of the conventional electronic circuit device 1 (see FIG. 5B). As shown in FIG. 3B, the parasitic inductances L (V1) and L (V2) corresponding to the conventional via are eliminated, and the parasitic inductance L (WP2) corresponding to the wiring pattern WP2 is extremely small. This is because the case 4 replaces the wiring pattern WP2 corresponding to the parasitic inductance L (WP2).

  FIG. 2C shows the switching characteristics of the high-side switching element 11 provided in the electronic circuit device 1 shown in FIG. 3A. When the high-side switching element 11 shifts from the on state to the off state at time t0, a large surge voltage is not applied to the drain of the high-side switching element 11 and the drain current falls quickly. It is confirmed that That is, it can be seen that even a low withstand voltage switching element that has the advantage that the switching loss is greatly reduced and the on-resistance is small functions sufficiently.

  The electrolytic capacitor C1, the choke coil L1, and the smoothing capacitor C3 shown in FIG. 2A are mounted on the main surface 3A of the circuit board 3, and further, a voltage detection circuit that monitors the voltage between the output terminals T3 and T4, A control circuit that controls the gate voltage of the switching element 11 and the low-side switching element 12, a driver circuit that drives the switching elements 11 and 12, and the like are mounted.

  Note that other circuit elements necessary for the DC regulator other than the capacitor C2 and the switching elements 11 and 12 may be mounted on the main surface 3B of the circuit board 3. For example, a voltage detection circuit and a control circuit may be mounted on the main surface 3B except for the driver circuit described above. In this case, what is necessary is just to electrically connect with the circuit element mounted in the main surface 3A side via the via | veer. By limiting the number of circuit elements to be mounted on the main surface 3A of the circuit board 3, the shape of the recess 4A formed in the housing 4 is simplified, and the processing step of the recess 4A for that purpose can be simplified. .

FIG. 4 shows another embodiment of the electronic circuit device 1 according to the present invention.
In the present embodiment, a convex portion 8 is formed on the surface of the housing 4 among the connection portions 7 that electrically connect the ground-side wiring pattern WPg and the housing 4 (see the upper part of FIG. As the substrate 3 is fastened and fixed to the housing 4, a more reliable ohmic contact can be obtained between the convex portion 8 and the wiring pattern WPg (see the lower part of FIG. 4).

  Instead of forming the protrusions 8 on the surface of the housing 4, the protrusions 8 may be formed on the wiring pattern WPg side, that is, on the circuit board 3 side. Furthermore, you may interpose the arbitrary conductive spacers which function as a convex part. Furthermore, the convex portions 8 may be formed on both the ground-side wiring pattern WPg and the housing 4.

  In the above-described embodiments, the case where the DC regulator is a synchronous rectification step-down regulator has been described. However, the DC regulator to which the present invention can be applied is not limited to a non-isolated synchronous rectification step-down regulator, but is an asynchronous rectification step-down regulator. Needless to say, the present invention can be applied to a boost regulator and a buck-boost regulator, and can also be applied to an isolated buck regulator, a boost regulator, and a buck-boost regulator.

  The present invention can be applied to any regulator circuit using a switching element in addition to a DC regulator, and can be widely applied to, for example, a full-bridge inverter circuit and a half-bridge inverter circuit.

  In the above-described embodiments, the case made of aluminum has been described. However, the metal constituting the case is not limited to aluminum, and may be a highly conductive metal such as copper. Further, the constituent material of the circuit board 3 is not limited to glass epoxy resin, and a known material may be used as appropriate.

  The embodiment described above is merely an example of an electronic circuit device to which the present invention is applied, and the specific circuit configuration of each part and the configuration of the wiring pattern of the circuit board are within the scope where the effects of the present invention are exhibited. Needless to say, the design can be changed as appropriate.

  The electronic circuit device of the present invention can be applied to electronic circuit devices for various uses that need to reduce the influence of parasitic inductance.

1: Electronic circuit device 3: Circuit board 4: Housing 5: Fixing part 6: Screw 7: Connection part 8: Convex part 10: DC regulator (step-down regulator)
11: High-side switching element 12: Low-side switching element C1: Electrolytic capacitor C2: Capacitor C3: Smoothing capacitor L1: Choke coil

Claims (5)

A circuit board on which a plurality of circuit elements including a switching element constituting a regulator are mounted and a wiring pattern for electrically connecting each circuit element is provided, and a metal casing that holds the circuit board. Electronic circuit device,
A circuit element including the switching element is mounted on a main surface of the main surface of the circuit board facing the housing, and a part of the ground-side wiring pattern among the wiring patterns connecting the circuit elements is the housing. Electronic circuit devices that are replaced by the body.   A fixing portion for fastening and fixing the circuit board and the housing with screws is provided, and a connection portion for electrically connecting the ground-side wiring pattern and the housing in the vicinity of the fixing portion is provided. The electronic circuit device according to claim 1.   The electronic circuit device according to claim 2, wherein a convex portion is formed on either the wiring pattern on the ground side of the connection portion or the housing.   4. The electronic circuit device according to claim 1, wherein a concave portion is formed in the housing, and a circuit element mounted on the circuit board is accommodated in the concave portion. 5. The regulator is a synchronous rectification step-down regulator in which a capacitor is connected in parallel to a series circuit of a high-side switching element and a low-side switching element, and a wiring pattern on the ground side of the low-side switching element and the capacitor is the housing The electronic circuit device according to claim 1, wherein the electronic circuit device is replaced by any one of claims 1 to 4.

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