WO2013164945A1

WO2013164945A1 - Electric circuit

Info

Publication number: WO2013164945A1
Application number: PCT/JP2013/061197
Authority: WO
Inventors: 文典奈良; 里奈澤西
Original assignee: オートリブディベロップメントエービー
Priority date: 2012-05-01
Filing date: 2013-04-15
Publication date: 2013-11-07
Also published as: JP2015073337A

Abstract

To reduce radiation of electromagnetic wave noise from an electric circuit board without using magnetic blocking materials or electromagnetic wave blocking materials, said electric circuit board having a high frequency coil. This electric circuit that includes a voltage converter circuit is characterized in that the voltage converter circuit includes: a voltage converter which includes a first switching element (T1) that interrupts, corresponding to first control signals, a current flowing in a first coil (L1); and a second voltage converter which includes a second switching element (T2) that interrupts, corresponding to second control signals, a current flowing in a second coil (L2). The electric circuit is also characterized in that: the first and second coils (L1, L2) are disposed adjacent to each other on the circuit board; the polarities or the coil current directions of the first and second coils are set such that leakage magnetic fluxes (g1, g2) to be generated by the first and second coils are cancelled out; and operations of the first and second switching elements are substantially synchronized with each other.

Description

electric circuit

The present invention relates to reduction of electromagnetic wave noise (EMI) generated from an electric circuit, and more particularly to an electric circuit designed to reduce electromagnetic wave noise from an electric circuit including a coil through which a high-frequency current flows.

In integrated circuits such as LSI, multiple types of DC voltage are used in the internal circuit. In order to obtain these voltage values (power supply), the output of the DC voltage source is boosted or lowered by a DC-DC converter (switching regulator) to obtain a necessary voltage value. The DC-DC converter includes a direct-current voltage source, a coil, a capacitor, a diode, a switch (transistor), etc., and obtains a boosted voltage or a step-down voltage by intermittently switching the coil current with the transistor, and converts the direct-current voltage of the power source to a desired voltage. Convert to DC voltage.

Such a DC-DC converter operates the switching element with a high-frequency signal to interrupt the coil current, but at that time, the magnetic flux leaks from the coil to the surroundings. When the coil current becomes a high-frequency current, the magnetic flux leaked from the coil is radiated to the surrounding environment as electromagnetic waves and becomes electromagnetic noise. If this electromagnetic wave noise level increases, other electronic components may be influenced by inducing noise, and therefore electromagnetic wave noise reduction measures are required. For example, in a power device having a converter described in Patent Document 1, a magnetized material is disposed between two windings (of a transformer) that are spaced apart from each other, or the entire transformer is covered with a magnetized material and magnetic flux leaks to the outside. (FIGS. 40A and 40B of Patent Document 1).

JP 2004-159485 A

However, when the entire coil is covered with a magnetic material to be magnetically shielded, the shielding material occupies a certain space on the circuit board, which makes it difficult to reduce the size of the mounting circuit board and reduce the occupied space. Moreover, it is necessary to consider separately the heat dissipation countermeasure of the coil interrupted | blocked from the external space by the shielding material. Further, it is expensive to manufacture a shielding structure made of a magnetic material such as ferrite.

The present invention has been made in view of such problems, and an object thereof is to reduce radiation of electromagnetic noise from an electric circuit board having a high frequency coil without using a magnetic shielding material or an electromagnetic shielding material.

An electrical circuit according to an aspect of the present invention for solving the above-described problem is an electrical circuit including a voltage converter circuit, and the voltage converter circuit is configured to intermittently pass a current flowing through the first coil in response to a first control signal. A switching element and a second switching element for intermittently passing a current flowing through the second coil in response to the second control signal, wherein the first and second coils are arranged adjacent to each other on the circuit board, At least one of the polarities of the first and second coils and the direction of the coil current is set so that the leakage magnetic flux generated by the second coil is canceled out, and the operation of the first and second switching elements is substantially the same. It is characterized by being synchronized. Here, the first switching element and the second switching element are provided in circuits of different systems in the electric circuit. A system is a circuit having a certain function (or a circuit of a certain operation system) and is a unified circuit between an entrance portion and an exit portion of an electric signal. Different systems indicate that these systems are different, more specifically, circuits having different functions (or circuits having different operation systems). Originally, electric signals that are mutually used for canceling leakage magnetic flux do not flow in circuits of different systems.

Here, “adjacent” is a state in which the first coil and the second coil are close to each other at a distance that is affected by the leakage magnetic flux. Desirable for. The “polarity of the coil” represents the winding direction of the coil winding, and it is generally determined whether the conductor is wound clockwise or counterclockwise when the coil is viewed from one direction. However, the direction of the magnetic flux generated from the coil may be indicated by the direction of the current flowing through the coil regardless of the winding direction. Further, “the operations of the first and second switching elements are substantially synchronized” means that the effect of canceling out the leakage magnetic flux of the first and second coils is obtained. This means that there may be a slight deviation between the operation or the first and second control signals. Even if the first and second control signals are synchronized, the phase of the two coil currents may not be the same (there is a deviation) due to the difference in the load of each voltage converter. Even in such a case, if the directions of the magnetic fluxes generated by the two coils are opposite to each other, the leakage magnetic flux is canceled out. The meaning of “cancellation” does not mean that the leakage magnetic flux must be canceled out 100%, but includes a case where the leakage magnetic flux can be reduced by canceling even a little. More preferably, the “cancellation” situation indicates a case where the leakage magnetic flux can be reduced by about 10 dB (μA / m) or more.

Preferably, the voltage converter circuit includes a first voltage converter including the first switching element and a second voltage converter including the second switching element.
Further, when one voltage converter includes two (or plural) coils, the same principle may be applied so that the leakage magnetic flux is canceled between the two (or plural) coils.

By adopting such a configuration, the leakage magnetic flux of the first coil and the second coil is effectively canceled out, the leakage magnetic flux radiated to the outside is reduced, and electromagnetic noise is reduced. Thereby, it is possible to reduce the radiation (EMI) of leakage magnetic flux from the coil of the voltage converter without separately using an electromagnetic shielding component (material). In order to cancel the leakage flux from the coil, it is conceivable to separately provide a compensation coil that creates a magnetic flux in the opposite direction to the leakage flux. However, in this application, two (or a plurality of) coils originally provided in different circuits are adjacent to each other. Leakage magnetic flux can be reduced by devising a signal (more specifically, the polarity of each coil and the current direction of each coil) that flows through each coil. In addition, this eliminates the need to provide an extra leakage flux canceling coil.

Desirably, the first and second control signals are both PWM signals, and the conversion voltage is set according to the on / off ratio. As a result, the current waveform (generated magnetic flux) flowing through the first and second coils is changed to a similar waveform or an approximate waveform, and the amount of cancellation of the leakage magnetic flux (cancellation efficiency) can be increased. In addition, the power (voltage) conversion amount can be adjusted by the on / off ratio of the switching element. It is preferable to use the switching duty ratio at 50% or less because the influence of the canceling magnetic field can be almost ignored and the influence of the conversion efficiency of the voltage converter is almost eliminated.

Desirably, the rising or falling of the waveforms of the first and second control signals are synchronized. As a result, the current waveform (generated magnetic flux) flowing through the first and second coils can be synchronized as much as possible to increase the amount of cancellation of the leakage magnetic flux (cancellation efficiency). Even if the two current waveforms are not completely synchronized due to the difference in the load circuit, the effect of canceling the leakage magnetic flux is recognized as it is.

Desirably, the first voltage converter is a step-up operation (DC voltage up), and the second voltage converter is a step-down operation (DC voltage down). With such a combination, it is recognized that the effect of canceling the leakage magnetic flux becomes higher, and electromagnetic noise is reduced.

Desirably, the first and second voltage converters are both boosted (DC voltage up). With such a combination, since signals of substantially the same level flow, higher leakage flux canceling effects are recognized, and electromagnetic noise is reduced.

Desirably, the first and second voltage converters both perform step-down operation (DC voltage down). With such a combination, since signals of substantially the same level flow, higher leakage flux canceling effects are recognized, and electromagnetic noise is reduced.

Desirably, the first and second voltage converters are two of the plurality of voltage converters whose switching element ON or OFF timing is approximate. Thus, the invention can be realized without separately providing a synchronization circuit between the switching operations by utilizing the switching operations of the voltage converters of different (power supply) systems. Thereby, size reduction, weight reduction, and power saving can be achieved.

Preferably, the apparatus further includes a first control circuit that generates the first control signal and a second control circuit that generates the second control signal, and the first and second control circuits use a common clock signal. Is. Thereby, the switching operations of the first voltage converter and the second voltage converter can be actively synchronized. For example, the first and second control signals are used as PWM (pulse width modulation) signals, and the rising and falling edges of the signal waveform are synchronized, and the on / off ratio is set separately, whereby different power is supplied to the first and second voltage converter circuits. It is possible to set the conversion amount. If the PWM waveforms of the control signals are not the same, but have similar waveforms (if magnetic fluxes in opposite directions are generated in the two coils), there is an effect of reducing leakage magnetic flux. These eliminate the need for an extra leakage flux canceling coil.

According to the electric circuit of the present invention, since the coils of two voltage converters having similar switching operations are arranged adjacent to each other and cancel each other in the opposite direction, the leakage of magnetic flux to the outside is reduced. Further, without using a magnetic shielding material or an electromagnetic shielding material, an additional coil for canceling the leakage magnetic flux is not required, and it is possible to reduce radiation of electromagnetic waves (mainly magnetic waves) noise from the coil.

It is explanatory drawing explaining the electric circuit board containing the some DC-DC converter of this invention. It is explanatory drawing explaining the example which arrange | positions each coil of two DC-DC converters of this invention adjacently. It is explanatory drawing explaining the example of the magnetic flux generated by two coils. It is explanatory drawing explaining cancellation of the leakage magnetic flux by two coils. It is a circuit diagram explaining an example of a step-up DC-DC converter. It is a circuit diagram explaining an example of a step-down DC-DC converter. FIG. 5 is a circuit diagram illustrating an example in which two boost DC-DC converters are arranged so that two coils are close to each other. FIG. 5 is a circuit diagram for explaining an example in which two step-down DC-DC converters are arranged so that two coils are close to each other. FIG. 5 is a circuit diagram illustrating an example in which two coils are brought close to each other in a step-up DC-DC converter and a step-down DC-DC converter. It is a wave form diagram explaining the magnetic flux change of two coils of a reference example. It is a wave form diagram explaining the magnetic flux change of the two coils of an Example. It is explanatory drawing explaining the experimental result of a sample.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the corresponding part in each figure.

First, the concept of the present invention will be described with reference to FIGS. FIG. 1 shows an example in which an LSI (Large Scale Integrated Circuit) 14 such as a CPU is provided on the electric circuit board 1. The CPU requires a plurality of types of DC voltage sources as circuit power supplies. For this reason, a constant voltage such as 24 volts, 12 volts, and 5 volts supplied from a power supply device (not shown) is boosted or lowered to a desired level of DC voltage by a voltage converter circuit. As indicated by dotted lines in FIG. 1, a plurality of DC-DC converters (or DC-DC converter units) 11 are provided on the electric circuit board 1 in order to obtain a plurality of DC voltages. A voltage converter circuit is configured including the plurality of DC-DC converters 11. Each DC-DC converter 11 includes a switching element. Each DC-DC converter 11 uses a coil L. When the DC-DC converter 11 is operated at a high frequency (switching is performed at a high frequency), electromagnetic waves may leak from the coil L.

Therefore, in the present invention, as shown by 1 in FIG. 2, two coils L having similar waveforms of the leakage magnetic flux from the coil L in different circuits are extracted so that the leakage magnetic flux cancels each other. The two coils L are arranged adjacent to each other (or adjacent to each other). As described above, “adjacent” is a state in which the distance between the two coils is such that the leakage magnetic flux can be offset. The leakage magnetic flux is canceled by adjusting the direction of two adjacent coil currents or the winding direction (polarity) of the two coils L. The inductance values of the two coils L need not be the same value. The leakage magnetic flux can be measured by bringing the probe of the measuring instrument close to the coil L. These two coils may be searched for on the same substrate, or those on another circuit substrate may be brought on the same substrate in the form of transplanting some of the functions. The two coils may be arranged on the same substrate so that coils existing separately in separate electric circuit systems (for example, voltage converters) having different functions are adjacent to each other.

3 and 4 are diagrams for explaining the leakage magnetic flux in the coils L1 and L2. FIG. 3 shows an example in which magnetic fluxes Φ1 and Φ2 in the same direction are generated in the coils when the currents of the two coils L1 and L2 flow in opposite directions. FIG. 4 shows that when the currents of the two coils L1 and L2 flow in opposite directions, the direction of one coil (winding direction) is reversed so that the magnetic fluxes Φ1 and Φ2 in the opposite directions are generated in the coils L1 and L2. An example that occurs is shown. When magnetic fluxes Φ1 and Φ2 in opposite directions are generated in the two coils L1 and L2, respectively, the leakage magnetic flux g1 and g2 of each coil are also offset in the opposite direction, and the leakage magnetic flux of the two coils L1 and L2 as a whole is Decrease. Therefore, if the waveforms of the currents flowing through the two coils are similar, more desirably, if the current waveforms are synchronized, electromagnetic wave leakage from the coils L1 and L2 is reduced. The direction of the coil current and the direction of the magnetic flux generated in the coil are explained by the so-called right-handed screw law.

Therefore, in the embodiment, as shown in FIGS. 1 and 2, two of the plurality of DC-DC converters included in the electric circuit board that approximate the magnetic flux waveform of the coil L are selected, and one coil is selected. The coils are arranged close to each other by changing the winding direction of L so that the leakage magnetic flux from the two coils is canceled. In addition, the leakage magnetic flux from a coil should just be canceled, and the number of the coils arrange | positioned closely is not limited to two. Even if there are three, four, or more (plural) coils, it is only necessary to cancel the leakage magnetic flux from the coils.

Before describing an example of a DC-DC converter in which the two coils L are adjacent to each other, two types of DC-DC converters will be described.

5A and 5B are circuit diagrams illustrating an example of a step-up DC-DC converter including the coil L described above. The step-up DC-DC converter includes a coil L and a high-frequency rectifier diode (for example, a Schottky barrier diode SBD) connected in series between an input terminal VIN and an output terminal VOUT to which a DC voltage is supplied, An FET transistor Tr connected between the connection point of the diode SBD and the ground potential GND, a capacitor C holding a boosted voltage connected between the output terminal VOUT and the ground GND, and the like.

The gate G of the transistor Tr is a pulse control signal (PWM) from a controller (not shown) as a control circuit (can be included in a commercially available IC chip, custom IC, CPU, etc., or can be created with a transistor). A signal is supplied. The controller adjusts the duty of the pulse width modulation signal in accordance with the difference between the output voltage and the target voltage. Each controller has its own internal oscillator (OSC), but a clock signal common to the system (electric circuit board 1) may be used.

Next, the operation of the step-up DC-DC converter will be described. As shown in FIG. 5A, when the transistor Tr is turned on by the control signal supplied to the gate, the connection point between the coil L and the diode SBD is grounded, and the diode SBD is reverse biased and cut off. Thereby, a current flows through the coil L by the terminal voltage VIN and energy is stored (energy is stored in the form of a magnetic field).

Next, as shown in FIG. 5B, when the transistor Tr is turned off by the control signal, the potential at the connection point rises, and the diode SBD is forward biased and becomes conductive. A voltage VL induced in the coil L is added to the terminal voltage VIN and supplied to the output terminal VOUT. As a result, a voltage (VIN + VL) obtained by boosting the terminal voltage VIN is obtained at the output terminal VOUT. The voltage boosting operation is performed by repeating the operations shown in FIGS. The boosted voltage is set by appropriately setting the ratio (duty) of the on-time and off-time of the transistor Tr.

6 and (B) are circuit diagrams illustrating an example of a step-down DC-DC converter including the coil L described above. The step-down DC-DC converter includes a transistor Tr and a coil L connected in series between an input terminal VIN and an output terminal VOUT to which a DC voltage is supplied, and a connection point between the transistor Tr and the coil L and a ground potential GND. And a capacitor C holding a step-down voltage connected between the output terminal VOUT and the ground GND, and the like.

A gate control signal which is a pulse width modulation signal is supplied to the gate G of the transistor Tr from a controller chip (not shown) as in the above boosting example. The controller chip adjusts the duty of the pulse width modulation signal in accordance with the difference between the output voltage and the target voltage. Each controller chip has its own internal oscillator (OSC), but a lock signal common to the system may be used. The boosted voltage is set by appropriately setting the ratio (duty) of the on-time and off-time of the transistor Tr.

Next, the operation of the step-down DC-DC converter will be described. As shown in FIG. 6A, when the transistor Tr is turned on by the control signal supplied to the gate, the diode SBD is reverse-biased and cut off, and the terminal voltage VIN is supplied to the output terminal VOUT. , Energy is stored in the coil L (energy is stored in the form of a magnetic field).

Next, as shown in FIG. 6 (B), when the transistor Tr is turned off by the control signal, the coil L acts to maintain the immediately preceding current, and the diode SBD is made conductive. At this time, since the left end of the coil L is grounded via the diode, the voltage at the terminal VOUT decreases. By appropriately setting the ratio (duty) of the on-time and off-time of the transistor Tr, a voltage lower than the terminal voltage VIN is set at the output terminal VOUT. The step-down operation is performed by repeating the operations of FIGS. 6 (A) and 6 (B).

7 to 9 show the leakage flux by arranging the coils L1 and L2 of two DC-DC converters (voltage converters) provided in the voltage converter circuit provided on the electric circuit board 1 next to each other (adjacent). It is a circuit diagram explaining the example which reduces this.

A control circuit for the transistors T1 and T2, which are switching elements, is not shown, but a commercially available IC chip or the like can be used as described above. The IC chip adjusts the duty ratio of the control signal (PWM) supplied to the gate of the switching transistor based on the difference signal between the detection voltage and the target value. A first control signal is generated by a first IC chip corresponding to the first DC-DC converter, and a second control signal is generated by a second IC chip corresponding to the second DC-DC converter. However, these IC chips can be incorporated into the LSI 12 described above. In this case, it becomes easier to set the first and second control signals to the same switching frequency or to synchronize the signal waveforms by the common clock signal inside the LSI.

As described above, the first and second control signals are used as PWM (pulse width modulation) signals, and the rising and falling edges of the signal waveform are synchronized, and the on / off ratio is set separately, so that the first and second voltage converter circuits Although it is possible to set different power conversion amounts, if the PWM waveform of the control signal is not the same, but has a similar waveform (if two magnetic fluxes are generated in opposite directions), the leakage flux can be reduced. effective. In addition, if the magnetic fluxes in opposite directions are generated in the two coils, the control signal may be a PAM signal, a signal for changing the pulse frequency, a sine wave signal, or the like.

The example shown in FIG. 7 shows an example in which two step-up DC-DC converter coils L are arranged side by side. The first step-up DC-DC converter corresponds to a first voltage converter circuit including a first switching element (T1) for intermittently passing a current flowing through the first coil (L1) in response to a first control signal. The second step-up DC-DC converter corresponds to a second voltage converter circuit including a second switching element (T2) that intermittently passes a current flowing through the second coil (L2) in response to a second control signal. . The first and second coils (L1, L2) are arranged adjacent to each other on the circuit board, and the first and second coils are offset so that the leakage magnetic flux generated by the first and second coils (L1, L2) is offset. The polarity (winding direction) of the (L1, L2) or the direction of the coil current is set, and preferably the first and second control signals have waveforms that are approximate to each other.

The example shown in FIG. 8 shows an example in which two step-down DC-DC converter coils L are arranged adjacent to each other. The first step-down DC-DC converter corresponds to a first voltage converter circuit including a first switching element (T1) that intermittently passes a current flowing through the first coil (L1) in response to a first control signal. The second step-down DC-DC converter corresponds to a second voltage converter circuit including a second switching element (T2) that intermittently passes a current flowing through the second coil (L2) in response to a second control signal. . The first and second coils (L1, L2) are arranged adjacent to each other on the circuit board, and the first and second coils are offset so that the leakage magnetic flux generated by the first and second coils (L1, L2) is offset. The polarity of (L1, L2) or the direction of the coil current is set, and preferably the first and second control signals have waveforms that are approximate to each other.

The example shown in FIG. 9 shows an example in which a step-up DC-DC converter coil L1 and a step-down DC-DC converter coil L2 are arranged adjacent to each other. The step-up DC-DC converter corresponds to a first voltage converter circuit including a first switching element (T1) that intermittently passes a current flowing through the first coil (L1) in response to a first control signal. For example, DC 13.5 volts is boosted to DC 33.1 volts. The step-down DC-DC converter corresponds to a second voltage converter circuit including a second switching element (T2) that intermittently passes a current flowing through the second coil (L2) in response to the second control signal. For example, DC 33.1 volts is stepped down to DC 9 volts. The first and second coils (L1, L2) are arranged adjacent to each other on the circuit board, and the first and second coils are offset so that the leakage magnetic flux generated by the first and second coils (L1, L2) is offset. The polarity of (L1, L2) or the direction of the coil current is set, and preferably the first and second control signals have waveforms that are approximate to each other.

7 to 9, at least one of the winding direction (polarity) and the coil current direction of each coil L is adjusted so that the leakage flux of the two coils L is canceled out. Is done.

FIGS. 10 and 11 are examples in which the levels of the magnetic flux Φ1 of the coil L1 of the step-up DC-DC converter and the magnetic flux Φ2 of the coil L2 of the step-down DC-DC converter in the example shown in FIG. It is explanatory drawing shown. The horizontal direction of the screen is the time axis, and the vertical direction is the signal level. The example shown in FIG. 10 shows an example (see FIG. 3) in which the magnetic flux Φ1 of the coil L1 and the magnetic flux Φ2 of the coil L2 are substantially in phase (the magnetic flux is in the same direction). In this case, the leakage magnetic flux from the two coils increases.

On the other hand, the example shown in FIG. 11 shows an example (see FIG. 4) in which the magnetic flux Φ1 of the coil L1 and the Φ2 of the coil L2 are in substantially opposite phases (the magnetic flux is directed in the reverse direction). The magnetic flux Φ1 of the coil L1 and the magnetic flux Φ2 of the coil L2 change in a complementary manner, thereby canceling out the leakage magnetic flux (radiated magnetic field) and greatly reducing electromagnetic noise.

The first and second control signals supplied to the gates of the transistors are not shown, but it is desirable that the rise or fall of the waveform of the PWM control signal be synchronized and have the same pulse frequency. Thereby, it is possible to synchronize the magnetic flux waveforms (generated magnetic fluxes) flowing through the first and second coils and to increase the amount of cancellation (cancellation efficiency) of the leakage magnetic flux. However, the two magnetic flux waveforms (or waveform phases) flowing in the first and second coils do not have to be completely synchronized, and if there is a complementary level change tendency in the two magnetic flux waveforms, the effect of canceling the leakage magnetic flux is recognized. (See FIG. 11). In this embodiment, the transistor switching duty ratio is set to a ratio necessary for voltage conversion of 50% or less as appropriate. Thereby, the influence of the canceling magnetic fields can be almost ignored, and the influence on the conversion efficiency of the voltage converter due to the cancellation of the magnetic flux can be almost eliminated.

FIG. 12 is an explanatory diagram for explaining the effect of the embodiment. In this example, two coils L1 and L2 of a step-up DC-DC converter and a step-down DC-DC converter on a mounting circuit board (substrate finished product, not shown) to which the present invention is applied are arranged adjacent to each other. Product) and the leakage magnetic flux around the substrate (for example, above, left, right, front, back, etc.) is measured. The maximum leakage value at the measurement location when two DC-DC converters are operated in the switching frequency range of 100 kHz to 200 kHz is shown. The measured value is a current value dB (μA / m) detected in the probe (coil) by the leakage magnetic flux around the coil. For measurement, ESU26 made by ROHDE & SCHWARZ and 7604 made by loop antenna ETS / RINDGREN were used. Measurement was performed at an upper position at a distance of 70 mm from the product.

As shown in FIG. 12, the leakage flux amount of the mounting circuit board before the countermeasure was 73.0 dB (μA / m) at the operating frequency of 100 kHz to 200 kHz. Thus, 58.5, 60.8, and 60.6 dB (μA / m) were all good values. The numerical value is improved by about 10 dB (μA / m) as compared with a conventional mounting circuit board that does not take electromagnetic wave shielding measures.

The device (electric equipment) including the electric circuit board to which the above-described countermeasure against electromagnetic wave noise is applied has an advantage that the electromagnetic radiation energy (electromagnetic wave noise) from the apparatus is also reduced because the noise from the board is reduced.

As described above, according to the embodiment of the present invention, in an electric circuit board including a plurality of DC-DC converters, two DC-DC converters approximating the waveform of magnetic flux generated by a coil are selected, and both converters are selected. The coils are arranged next to each other so that the leakage magnetic fluxes cancel each other. Thereby, electromagnetic noise from the coil of the converter can be greatly reduced without using special parts (or additional parts) such as a magnetic shielding material, an electromagnetic shielding material, and a magnetic shielding member as much as possible. .

The embodiments described above are preferred examples of the present invention, and embodiments other than those described in this specification can be implemented or performed by various methods. The present invention is not limited to the shape, size, type, configuration, and the like of the parts shown in the present specification and the accompanying drawings unless otherwise specified in the present specification. In addition, expressions and terms used in the present specification are for the purpose of explanation, and are not limited to those unless specifically stated.
For example, the coil may be a sheet coil in which a spiral coil sheet is laminated in addition to a conductor wound. The voltage converter circuit includes not only a DC-DC converter but also a DC-AC converter.
Further, although not shown, the DC-DC converter may be of a boost / buck type.

The present invention is advantageous when applied to an electric circuit board on which a plurality of voltage converters are arranged, and can also be applied to an electric device including such an electric circuit board.

1 Electric Circuit Board 11 DC-DC Converter 12 LSI
L, L1, L2 Coil Tr, T1, T2 FET transistor SBD (Schottky barrier) diode

Claims

An electrical circuit including a voltage converter circuit,
The voltage converter circuit is:
A first switching element that interrupts the current flowing through the first coil in response to the first control signal; and a second switching element that interrupts the current flowing through the second coil in response to the second control signal;
The first and second coils are arranged next to each other on the circuit board, and the polarity of the first and second coils and the direction of the coil current so that the leakage magnetic flux generated by the first and second coils is offset. An electrical circuit in which at least one of them is set and the operations of the first and second switching elements are substantially synchronized.
The voltage converter circuit is:
A first voltage converter including the first switching element;
A second voltage converter including the second switching element;
The electric circuit according to claim 1.
The electric circuit according to claim 1 or 2, wherein both the first and second control signals are PWM signals, and a conversion voltage of the voltage converter is set by an on / off ratio.
4. The electric circuit according to claim 2, wherein the first voltage converter is a step-up operation and the second voltage converter is a step-down operation.
The voltage converter circuit includes a plurality of voltage converters;
5. The electric circuit according to claim 2, wherein the first and second voltage converters are two of the plurality of voltage converters whose switching element ON or OFF timings are approximated. 6.
And a first control circuit for generating the first control signal and a second control circuit for generating the second control signal.
The electric circuit according to claim 1, wherein the first and second control circuits use a common clock signal.
An apparatus comprising the electric circuit according to any one of claims 1 to 6.