JP3206516B2 - Switching circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a switching circuit having a structure in which a power supply and a switching element are connected by a bus bar.

[0002]

2. Description of the Related Art A strip-shaped, rod-shaped or strip-shaped conductor, that is, a bus bar, has conventionally been used for connection between circuit elements in a power circuit or connection between a circuit element and a power supply or a load (for example, Japanese Utility Model Application Laid-Open No. HEI 3-103). -124785). For example, when the inverter 10 shown in FIG. 10 is realized using a bus bar, the bus bar is arranged as shown in FIG. The inverter 10 shown in FIG. 10 is an IGBT (Insulated Gate Bipolar
Transistor) is a three-phase inverter having switching elements Q _{1 to} Q ₆ and diodes D _{1 to} D ₆ connected in anti-parallel to the switching elements Q _{1 to} Q _{6, and} a control terminal (not shown) of each switching element Q _{1 to} Q ₆ By appropriately supplying a switching control signal to the gate (in the example in the figure), the DC output of the power supply 12 can be converted into a three-phase AC and supplied to the load 14.

In FIG. 11, a total of nine bus bars made of a conductor such as copper are arranged on a substrate 16. Of which the power supply side busbar 18P and 18N, respectively, a bus bar for connecting the switching element Q ₁ to Q ₆ to the positive terminal or negative terminal of the power source 12, the load-side bus bar 20 U, 20V and 20W, respectively, A bus bar for connecting a U-phase, V-phase or W-phase switching element among the switching elements Q _{1 to} Q ₆ to a corresponding phase of the load 14. The power-supply bus bars 18P and 18N are provided in pairs for each phase, and the load-side bus bars 20U, 20V and 20W are respectively connected to the power-supply bus bars 18 of the corresponding phase.
Two-in-one unit 22 in pairs with P and 18N
U, 22V or 22W. Further, the power supply side bus bar 18P is connected to the positive terminal of the power supply 12 by the power supply side wiring 24P, and the power supply side bus bar 18N is connected to the negative side terminal of the power supply 12 by the power supply side wiring 24N. These power supply side wirings 24P and 24N may be formed in a bus bar shape. The switching elements Q _{1 to} Q ₆ are connected between the power supply side bus bar 18P or 18N and the load side bus bar in the two-in-one unit related to the corresponding phase.

[0004]

However, FIG.
In the arrangement of the bus bars as shown in (1), since a flyback voltage is generated at the time of switching due to the inductance (see FIG. 12) distributed to the bus bar and the wiring, there is a problem that high-speed switching is difficult to realize. This problem is realized by implementing a single switching element (for example, Q ₁ ) with a plurality of switching elements (for example, a parallel connection of Q _{1a to} Q _1c ) as shown in a dashed-dotted rectangular frame in FIG. When the bus bar is relatively long.

For example, a large current such as 600 A may flow through each switching element, and the inductance value when viewing the power supply side from each switching element may be 2.
It is assumed to be about 00 nH. When 600A attempts to off at short rise time of about 0.3μsec the switching element is flowing t _f, the induced voltage expressed by the following equation (flyback voltage)

E = −L · dI / dt (1) where L: inductance I: current is as high as 400V. Assuming that the power supply voltage is 288 V, as shown in FIG.
Since 8 V is applied, even a switching element having a withstand voltage performance with a sufficient margin for the power supply voltage, for example, a performance withstanding 600 V is insufficient in the withstand voltage performance. In other words, conventionally, high-speed switching cannot be performed unless a switching element having a very high withstand voltage limit (but expensive) is used. When the switching speed is low, the time required for on / off becomes longer, so that the loss in the switching element increases and heat is generated (see FIG. 14).

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and has an object to reduce the inductance by adding wiring, thereby suppressing the flyback voltage. The purpose is to be able to do.

[0007]

In order to achieve the above object, the present invention provides a switching element and a power supply side bus bar which is a conductor for connecting the switching element to a power supply. DC voltage applied to
A switch that converts the source voltage to AC using a switching element
In the switching circuit, the power supply side bus bar is provided with parallel connection wiring for connecting those having the same polarity, and the power supply side bus bar and the parallel connection wiring form a plurality of mutually parallel conductive paths from the switching element to the power supply. Features.

In the present invention, a plurality of parallel conductive paths are formed as conductive paths from the switching element to the power supply, and as a result, a parallel circuit of inductance is generated. Therefore, the value of the inductance when the power supply is viewed from the switching element is reduced, so that the flyback voltage is also reduced, and the switching can be performed at a higher speed than before.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. The same or corresponding members as those in the related art shown in FIGS. 10 to 14 are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 1 shows a bus bar arrangement according to a first embodiment of the present invention. This embodiment is suitable for realizing the inverter 10 shown in FIG. 10, and includes a loop wiring 26P as a parallel connection wiring for connecting the power supply bus bars 18P on the opposite side to the power supply wiring 24P, and a power supply side. The power supply side bus bars 18N are connected to each other on the side opposite to the wiring 24N.
It differs from the arrangement of FIG. 11 in that it has a looped wiring 26N that is a parallel connection wiring . These loop wirings 26P and 26P connecting the power supply side bus bars of the same polarity to each other.
6N has a function to reduce the inductance when viewed power source side switching element Q ₁ to Q _6.

[0011] Here, for the sake of simplicity, the inductance also L ₁ of either power bus bar, also the power supply-side wire and the looped wires together its inductance is assumed to be L _2. Since the power supply 12 to AC can be regarded as short, distribution of inductance in the circuit connecting the switching element Q ₁ to Q ₆ to the power supply 12 is, in this embodiment a distribution as shown in FIG. When the power supply 12 side is viewed from the position P in the figure, the value of the inductance is:

L = (L ₁ + L ₂ ) // (L ₂ + L ₁ // (L ₁ + 2 × L ₂ )) (2) This formula includes the parallel connection indicated by the symbol //. Have been. On the other hand, in the conventional arrangement shown in FIG.
Since the inductance distribution is as shown in FIG. 12, when the power supply 12 side is viewed from the position P, the value of the inductance is:

L = 2 × L ₁ + 2 × L ₂ (3), and no parallel connection is included. When L ₁ = L ₂ , the inductance given by equation (2) is 1.
866... L ₁ , and the inductance given by equation (3) is 4 L ₁ ,
According to the present embodiment, compared to the prior art shown in FIG.
Inductance decreases. Thus, in the present embodiment, suppression of the flyback voltage and high-speed switching are realized.

On the other hand, by providing the looped wirings 26P and 26N, the flyback voltage generated in one phase goes around to the other phase via the looped wiring, and may act as a fluctuation of the power supply voltage. I can think. However, usually, the output current waveform of each phase of the inverter 10 when the DC output from the power supply 12 is converted into a three-phase AC and supplied to the load 14 is as shown in FIG. That is, at timing (d) where a large flyback voltage is likely to occur in a certain phase (for example, U phase), the other phases (V phase and W phase)
Is small, even if the above-mentioned wraparound occurs, the operation of the switching element of the other phase is hardly affected.

A voltage for controlling each switching element (a voltage applied to a control terminal of each switching element) is usually generated by comparing a triangular wave or a sawtooth wave with a three-phase sine wave. Therefore, as shown in FIG. 4 in which the vicinity of the timing d is enlarged in time, the rising / falling timing of the voltage for controlling the switching element (output voltage in the figure) does not coincide between the phases. That is, for example, the timing at which the flyback voltage is generated in the U phase, the V phase, and the W phase
Since the timing of switching in the phases generally does not match, even if the flyback voltage sneak occurs,
A situation in which flyback voltages overlap with each other does not occur.

FIG. 5 shows a bus bar arrangement according to a second embodiment of the present invention. In this embodiment, the U-phase power supply side bus bar 18P and the V-phase power supply side bus bar 18P are constituted by a single power supply side bus bar 18P,
Similarly, the W-phase power supply-side bus bar 18N and the V-phase power supply-side bus bar 18N are constituted by the same power supply-side bus bar 18N. Since the inductance distribution in this embodiment is as shown in FIG. 6, the inductance L when the power supply 12 side is viewed from the position P in FIG.

L = (L ₁ + L ₂ ) // (L ₁ + L ₂ ) + L ₁ // (L ₁ + 2 × L ₂ ) (4)

Here, the same modification as that required to realize the present embodiment by modifying the first embodiment described above is applied to the conventional technique shown in FIG.
The configuration is as shown in FIG. The inductance distribution in this configuration is as shown in FIG. 8. Therefore, the inductance when the power supply 12 is viewed from the position P is:

L = 2 × L ₁ + L ₂ (5) When L ₁ = L ₂ , the inductance L in the present embodiment is 1.75 × L ₁ , whereas the inductance L in the reference example shown in FIGS. 7 and 8 is 3 × L ₁ . It can also be seen that the effect of reducing the inductance is obtained in the same manner as in the first embodiment.

FIG. 9 shows a bus bar arrangement according to a third embodiment of the present invention. In this embodiment, the connection between the power supply side bus bars 18P and 18N and the power supply 12 is made at a substantially central position of each of the power supply side bus bars 18P and 18N. Further, looped wirings 26P and 26N
Are provided at the left and right ends of the power supply side bus bars 18P and 18N. Even in such a configuration, the same effect as in the first embodiment can be obtained. Further, the present embodiment can be modified in the same manner as the modification necessary for obtaining the second embodiment from the first embodiment.

In the above description, the present invention has been described by taking the three-phase inverter 10 as an example. However, the present invention can be applied to a power circuit other than the inverter, The present invention can also be applied to phase exchange. At that time, it is preferable to perform control for shifting the switching timing.

In the above description, the loop wiring 26
Although detailed configurations of P and 26N have been omitted,
These can be realized, for example, as bus bar-shaped conductors. At this time, for example, a place where the looped wiring 26P and the looped wiring 26N intersect needs to be a so-called three-dimensional intersection, that is, an intersection via an insulator.

[0019]

As described above, according to the present invention,
Conductive paths from switching elements to power supply are connected in parallel
Since a plurality of paths are provided in parallel with each other by providing the wiring , the inductance when the power supply is viewed from the switching element is reduced, so that the flyback voltage can be reduced and high-speed switching can be realized.

[Brief description of the drawings]

FIG. 1 is a plan view showing a bus bar arrangement in an inverter according to a first embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram showing an inductance distribution in this embodiment.

FIG. 3 is a diagram showing a current waveform of a three-phase inverter.

FIG. 4 is a timing chart showing a method for generating a switching element control voltage in a three-phase inverter.

FIG. 5 is a plan view showing a bus bar arrangement in an inverter according to a second embodiment of the present invention.

FIG. 6 is an equivalent circuit diagram showing an inductance distribution in this embodiment.

FIG. 7 is a plan view showing a bus bar arrangement in an inverter according to a reference example.

FIG. 8 is an equivalent circuit diagram showing an inductance distribution in this reference example.

FIG. 9 is a plan view showing a bus bar arrangement in an inverter according to a third embodiment of the present invention.

FIG. 10 is a diagram showing a circuit configuration of an inverter according to one related art.

FIG. 11 is a plan view showing a bus bar arrangement in an inverter according to the related art.

FIG. 12 is an equivalent circuit diagram showing an inductance distribution according to the related art.

FIG. 13 is a diagram illustrating a flyback voltage.

FIG. 14 is a diagram illustrating a loss caused by low-speed switching.

[Explanation of symbols]

10 inverter, 12 power supply, 14 load, 16 substrate, 18P, 18N power supply side bus bar, 20U, 20V,
20W load side bus bar, 22U, 22V, 22W two-in-one unit, 24P, 24N power supply side wiring, 2
6P, 26N looped wiring.

Claims (1)

(57) [Claims] 1. A power supply voltage comprising: a switching element; and a power supply side bus bar which is a conductor for connecting the switching element to a power supply, and a DC power supply voltage applied to the power supply side bus bar.
To convert AC into AC by switching element
In the circuit, the power supply side bus bars having the same polarity are connected to each other.
A switching circuit comprising a parallel connection wiring , wherein a plurality of parallel conductive paths from the switching element to the power supply are formed by the power supply side bus bar and the parallel connection wiring .