JP2000260937A - Structure of transistor inverter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce noise generated in a transistor inverter, while miniaturizing a transistor inverter and reducing its weight and cost. SOLUTION: For example, the collector surface of a switch Q1 of upper and lower semiconductor switches Q1 and Q2 which are connected in series between the positive and negative PN poles of a DC power supply is connected directly to a cooling body 1, and the collector surface of the switch Q2 is thermally coupled to the same cooling body 1 via an insulator 2, thus reducing a floating capacity from the collector of the switch Q2 to the case of the ground and suppressing the propagation of noise.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is directed to a structure of a transistor inverter suitable for induction heating, variable speed driving, switching power supply, etc., in particular, to reduce noise, that is, to reduce noise terminal voltage and radiation noise level. The present invention relates to a structure of a transistor inverter.

[0002]

2. Description of the Related Art In the field of power electronics, when a power transistor switches, it is known that noise propagates through cooling fins of the transistor. This will be described below with reference to FIG. FIG. 13A shows a conventional structure and circuit. The two cooling bodies 11 and 12 are structurally
1, Q2 and the like are shown in a circuit diagram. Conventionally, the stray capacitance from the cooling body of Q2 to the case or the ground, that is, the stray capacitance Css is about 30 pF, which greatly affects noise. Note that the specific numerical values are examples in which the capacity of the device is several kW.

FIG. 13B shows a general circuit example from a power supply to a switch. That is, a DC voltage source rectified by the diode D and smoothed by the smoothing capacitor CD is obtained between PN, and two semiconductor switches Q1 and Q2 are provided in series on the upper and lower arms from P to N, and the midpoint O is output. The point is that a square wave voltage output is obtained, which is an extremely general circuit system rather than the conventional example. Here, a ground capacitor CY1 of about 2 nF, a noise filter F, a ground capacitor CY2 of about 1 nF, and the like are provided to suppress the propagation of switching noise to the power supply side.

FIG. 13 (c) shows an example of waveforms of each part,
This is an example of operation at about 30 kHz with a V voltage source. Shows an example of a square wave generated at the output point O as the ON-state voltage VQ2. At the time of switching, a sharp rise of 300V with Q2 off and a fall of Q1 off are observed. . Represents VCY2 which is an example of a noise voltage generated in CY2 at the time of switching, and appears as a value obtained by dividing the high frequency noise component of VQ2 by the capacitance of Css and CY2.
It becomes about several tens of volts. When expressed by a mathematical expression, the following expression is obtained. VCY2 = Css * VQ2 / CY2 indicates VCY1 observed and measured as a noise terminal voltage, a component of 30 kHz to several hundreds kHz attenuated from VCY2 through a noise filter, and 1 MHz or more transmitted spatially. There is a component of 30 MHz or less, and several hundred m
V and several mV are problematic.

[0005]

Conventionally, the cooling body of Q2 is at the potential of the point O including a lot of noise, and since Css is large, a large noise voltage is generated in VCY2, and FC2 is generated.
C (Federal Communications)
Commission) and CISPR (Interna)
Tional Special Committee
A large noise filter is required to pass a standard such as “on RadioInterference” (larger size and higher cost). Also, since the cooling body of Q2 becomes a large antenna and radiates harmonic noise into the space, noise of several MHz or more is observed on the power supply side by jumping over the noise filter F, and the power supply terminal portion is covered by an electrostatic shield metal container. It needs to be covered (increase in size and cost).

If the shield 20 as shown in FIG. 13A is provided, extra large components will be added. However, due to considerations such as opening the air passage, the Css reduction and the noise reduction effect are reduced. Only about 1/2, that is, -6dB
Only about. In addition, CY1 and CY2 cannot be set to several nF or more in order to suppress the leakage current to the ground. Therefore,
An object of the present invention is to provide a small, low-cost, low-noise transistor inverter.

[0007]

In order to solve such a problem, according to the first aspect of the present invention, of the upper and lower semiconductor switch elements connected in series as the upper and lower arms between the positive and negative electrodes of a DC power supply, The collector surface of the semiconductor switch element on the side where the voltage does not fluctuate is directly joined to the cooling body, and the collector surface of the semiconductor switch element on the side where the potential fluctuates is thermally coupled to the cooling body via an insulator. . In the first aspect of the present invention, the cooling bodies of the upper and lower semiconductor switching elements can be common (the invention of the second aspect), or the cooling bodies of the upper and lower semiconductor switching elements are individually provided. Thus, the cooling members can be coupled with low impedance (the invention of claim 3).

According to a fourth aspect of the present invention, upper and lower semiconductor switch elements connected in series as upper and lower arms between the positive and negative electrodes of a DC power supply are respectively insulated and joined to individual cooling bodies,
It is characterized in that each of the cooling bodies is coupled to the positive electrode or the negative electrode with low impedance. According to a fifth aspect of the present invention, a transistor module configured by insulating upper and lower semiconductor switch elements connected in series as upper and lower arms between positive and negative electrodes of a DC power supply and joining them to a metal base is installed in the cooling body. This cooling body is characterized in that it is joined to either the positive electrode or the negative electrode with low impedance. According to the invention of claim 6, the collector surface of the semiconductor switch molded part on the side where the potential does not fluctuate among the upper and lower semiconductor switch molded parts connected in series as the upper and lower arms between the positive and negative electrodes of the DC power supply is cooled. And soldering to a circuit pattern provided by insulating the collector surface of the semiconductor switch molded part on the side where the potential fluctuates from the cooling body surface.

According to the present invention, the collector surface of the semiconductor switch element chip on the side where the potential does not fluctuate among the upper and lower semiconductor switch element chips connected in series as the upper and lower arms between the positive and negative electrodes of the DC power supply is cooled. Solder directly to the body, solder the collector surface of the semiconductor switch element chip on the side where the potential fluctuates to the circuit pattern provided insulated on the cooling body surface, and electrically connect the circuit pattern and the semiconductor switch element chip to each other. And sealed with a resin. According to the eighth aspect of the present invention, the collector surface of the semiconductor switch element on which the potential does not fluctuate among the upper and lower semiconductor switch elements connected in series as the upper and lower arms between the positive and negative electrodes of the DC power supply is directly joined to the metal base. The collector surface of the semiconductor switch element on the side where the potential fluctuates is joined to a metal base via an insulator, and the metal base is joined to a cooling body via another insulator.

In any one of the first to third or sixth to eighth aspects of the present invention, the area or the number of chips of the semiconductor switch element on the side where the potential fluctuates is made smaller than that of the semiconductor switch element on the side where the potential does not fluctuate. Can also be increased (the invention of claim 9). In the invention of claim 10,
A transistor module formed by insulating upper and lower semiconductor switch elements connected in series as upper and lower arms between the positive and negative electrodes of a DC power supply and joining them to a metal base is installed on a cooling body via an insulator, and It is characterized in that the base is joined to either the positive electrode or the negative electrode with low impedance. According to the tenth aspect, the transistor module can be mounted on the cooling body after being joined to another metal base via an insulator (the invention of the eleventh aspect).

[0011]

FIG. 1 is an explanatory view for explaining a first embodiment of the present invention. FIG. 1 (a) is a structural sectional view, and FIG. 1 (b) is a plan view thereof (as viewed from the back side). (C) is a structure and a circuit diagram thereof. (A),
As is clear from FIG.
2 is insulated by an insulator 2 such as an insulating sheet and attached to the main circuit board 4 with screws 3. Since Q2 increases the thermal resistance of the insulator 2 and lowers the current-carrying capacity, two Q2s are arranged in parallel as shown in FIGS. Q2 can be two or more, and the area can be increased instead of plural. This is common when only one of Q1 and Q2 is insulated. Q1 is one and is attached directly to its cooling body 1 with screws 3 via heat transfer grease 5, so that the cooling body 1 is now connected to P potential with low impedance. It should be noted that a general transistor having a shape as shown in FIG.
In the P, TO220 type and the like, the surface to be attached to the cooling body 1 is a metal base and has a collector potential. Recently, there is also an insulation type, and by using two types properly, the person who insulates can use it without an insulation sheet.

As shown in FIG. 1B, a rectifier diode D is also attached to the cooling body 1. The lead terminals of the transistor and the diode are bent at a right angle near the element and are soldered to the main circuit board 4 in the shortest distance. The screw 3 of the main circuit board 4 has a large hole through which the head of the screw passes sufficiently, so that the screw 3 can be attached and detached. FIG.
(C) shows an example in which the load is the heating coil L. The point O, which is noisy, is connected to the center of the spiral so that noise is not emitted as much as possible. Capacitance Ccf with cooling body
Is made as large as about 100 pF because it is adhered with a thin insulator, but the Css in question is drastically reduced to about 3 pF and 1/10.

In the above description, the switching element is IGB
Although T (insulated gate bipolar transistor) is assumed, an FET or another transistor can be used. When Q1 and Q2 in FIG. 1 are viewed as transistors, they are of the so-called NPN type. For example, if a PNP type as shown in FIG. 2 is used, the collector of Q1 is connected via an insulator. It will be joined to the cooling body. That is, the collector surface of the semiconductor switch element on the side where the potential fluctuates (point O) is joined to the cooling body via the insulator.

1 and 2, the following effects 1) to 4) can be expected. 1) Since the value of Css is reduced by one digit, the noise voltage level of VCY2 is reduced by one digit; -20 dB, and the noise filter can be reduced. Even if Css becomes smaller,
In the case where the output conductor O is long, such as a motor drive, Css is not reduced as a result, so that the effect is small. Therefore, the effect is great for an electromagnetic cooker, a switching power supply, or the like having a short or no output conductor. 2) The cooling body is connected to a potential with low noise, and the collector of Q2 is covered by the cooling body and the main circuit board, so that the noise cannot be radiated. If the wiring of the output conductor O from the transistor to the load is prevented from radiating noise, the effect of radiation noise can be reduced to 1/10 or less. 3) Ccf is equivalently the C between POs in FIG.
oss (parasitic capacitance in Q1) has the same effect. As a result, the rising and falling slopes of VQ2 are relaxed, and the capacitance is effective for reducing noise. 4) Since only one cooling body is used and is stably soldered and supported on the main circuit board at a large number of points, no special cooling body support parts are required, and the number of parts is reduced, the weight is reduced, and the weight is reduced. It becomes costly. This effect is achieved by one set of upper and lower arms in each figure; not only a half bridge but also two full bridges and three sets
The present invention extends to various inverter circuits such as a three-phase bridge, and has an advantage that it can be constituted by one cooling body.

FIG. 3 is a block diagram showing a second embodiment of the present invention, in which a cooling body is divided into 11 and 12 parts. In such a case, the cooling bodies 11 and 12 are connected by a low impedance connection 7 as shown in the figure. FIG. 4 is a block diagram showing a third embodiment of the present invention, in which the cooling body is divided into 11 and 12, and the cooling body 11 is set to the P potential and the cooling body 12 is Connect to N potential.
In FIG. 4, the cooling body 11 is connected to the P potential and the cooling body 12 is connected to the N potential. However, the cooling body 11 may be connected to the N potential and the cooling body 12 may be connected to the P potential. The effects shown in FIGS. 3 and 4 are exactly the same as those in FIG. At this time, it is important to note that connecting the insulated cooling body to the case, the ground potential, or the like in the same manner as in the past increases noise instead.

FIG. 5 is a block diagram showing a fourth embodiment of the present invention. This shows an example of a transistor module M having a standard structure, in which the metal base 8 is insulated from the transistor circuit. Conventionally, the insulated cooling body 1 is connected to a case, grounded or opened. For this reason, in each case, a noise transmission structure for transmitting large noise to the power supply is provided. Therefore, as shown in the figure, the noise is reduced by connecting the cooling body 1 to, for example, the N potential with low impedance.
At this time, there are the internal coupling S1 and the external coupling S2, but the internal coupling S1 connected inside the connection module has a lower impedance structure. Here, the cooling body 1
Is connected to the N potential, but may be connected to the P potential. In this example, although the insulation between the cooling body and the case is required again, the size and cost of the noise filter can be reduced.

FIGS. 6 and 7 show a fifth embodiment of the present invention, in which a collector of a semiconductor switch molded part Q1 molded, for example, into a cooling body 1 is soldered 9. FIG. Here is an example. Soldering 9 can be dealt with by using a copper alloy for the cooling body, or by electroless plating aluminum. It is desirable that the semiconductor switch molded component Q2 side has an insulative mounting structure that can be soldered in accordance with Q1. 6 shows an example in which the main circuit wiring is provided on the main circuit board 4, and FIG. 7 shows an example in which a part of the main circuit wiring is provided on the surface of the cooling body. Reference numeral 30 denotes an insulating circuit pattern or DBC (Direct
2 shows a (T Bonding Copper) substrate. According to the examples of FIGS. 6 and 7, screws for attaching components to the cooling body are not required, and the number of components can be further reduced. By eliminating the screws, the thickness of the cooling body can be made as thin as possible. For example, an ultralight cooling body of 1 mm or less can be obtained. In addition, soldering improves the coupling between electricity and heat.

FIGS. 8 and 9 are block diagrams showing a sixth embodiment of the present invention. This is an example in which the transistor semiconductor chip itself is directly soldered 9 to the cooling body and the main circuit wiring is carried out by wire bonding 10 or the like.
It is almost the same. FIG. 9 shows an example in which the cooling body is a water-cooled type. According to the examples of FIGS. 8 and 9, the size and weight can be further reduced as compared with the examples of FIGS.

In the above examples, the cooling body was connected to the main circuit potential and could not be grounded. Or a free potential such as the ground or the human body. At this time, it is important for the noise reduction that the metal plate sandwiched between the double insulations is connected with a low impedance to the P or N potential where the potential in the inverter does not fluctuate. FIG. 10 shows an example in which the insulator 21 and the metal base 81 are added to FIG. 1, and the cooling body 1 can be grounded. FIG. 11 shows that the insulator 21 is inserted between the transistor module M having the standard structure of FIG.
This is an example in which the metal base 8 is connected S to the N potential. Of course, it may be coupled to the P potential. FIG. 12 shows a transistor module M having the standard structure shown in FIG.
This is an example of a special module in which a metal base 8 is internally connected to an N potential S. The cooling module 1 is installed on a metal base 81 with a noise-reduced and easily mountable module that can be freely installed anywhere. The metal base 8 may be coupled to the P potential as in the case of FIG.

[0020]

According to the present invention, the noise generated at the time of switching of the transistor inverter can be reduced in size and weight,
The advantage that the cost can be reduced while reducing the cost is obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a first embodiment of the present invention.

FIG. 2 is an explanatory diagram in the case where the types of switch elements are different in FIG.

FIG. 3 is a schematic diagram showing a second embodiment of the present invention.

FIG. 4 is a schematic diagram showing a third embodiment of the present invention.

FIG. 5 is a schematic diagram showing a fourth embodiment of the present invention.

FIG. 6 is an explanatory diagram illustrating a fifth embodiment of the present invention.

FIG. 7 is an explanatory diagram illustrating a modification of FIG.

FIG. 8 is an explanatory diagram illustrating a sixth embodiment of the present invention.

FIG. 9 is a schematic diagram showing a modification of FIG.

FIG. 10 is an explanatory diagram illustrating a seventh embodiment of the present invention.

FIG. 11 is a schematic diagram showing an eighth embodiment of the present invention.

FIG. 12 is a schematic diagram showing a modification of FIG.

FIG. 13 is an explanatory diagram for explaining a conventional example.

[Explanation of symbols]

1, 11, 12: cooling body, 2, 21: insulator, 3: screw, 4: main circuit board, 5: heat transfer grease, 6: case,
7 ... low impedance connection, 8,81 ... metal base, 9
... Soldering, 10 ... Wire bonding, 20 ... Shield, 30 ... Insulated circuit pattern (or DBC), M ... Standard transistor module.

Claims (11)

[Claims] 1. An upper and lower semiconductor switch element connected in series as an upper and lower arm between a positive electrode and a negative electrode of a DC power supply,
The collector surface of the semiconductor switch element on the side where the potential does not fluctuate is directly joined to the cooling body, and the collector surface of the semiconductor switch element on the side where the potential fluctuates is thermally coupled to the cooling body via an insulator. Structure of a transistor inverter. 2. The structure of the transistor inverter according to claim 1, wherein a cooling body for the upper and lower semiconductor switch elements is shared. 3. The structure of the transistor inverter according to claim 1, wherein the cooling bodies of the upper and lower semiconductor switching elements are separated from each other, and the cooling bodies are coupled with low impedance. 4. An upper and lower semiconductor switch element connected in series as an upper and lower arm between the positive and negative electrodes of a DC power source is insulated and joined to individual cooling bodies, and each of the cooling bodies has a low impedance with a positive electrode or a positive electrode. A transistor inverter structure coupled to a negative electrode. 5. A cooling module comprising a transistor module comprising upper and lower semiconductor switch elements connected in series as upper and lower arms between the positive and negative electrodes of a DC power supply and insulated and joined to a metal base. A structure of a transistor inverter, wherein a body is joined to one of a positive electrode and a negative electrode with low impedance. 6. The collector surface of the semiconductor switch molded part on the side where the potential does not fluctuate among the upper and lower semiconductor switch molded parts connected in series as the upper and lower arms between the positive and negative electrodes of the DC power supply is directly connected to the cooling body. Solder,
A structure of a transistor inverter, wherein a collector surface of a semiconductor switch molded part on a side where a potential fluctuates is soldered to a circuit pattern provided insulated from a cooling body surface. 7. The collector surface of the semiconductor switch element chip on the side where the potential does not fluctuate among the upper and lower semiconductor switch element chips connected in series as the upper and lower arms between the positive and negative electrodes of the DC power supply is directly soldered to the cooling body. Then, the collector surface of the semiconductor switch element chip on the side where the potential fluctuates is soldered to a circuit pattern provided insulated on the cooling body surface, and the circuit pattern and the semiconductor switch element chip are electrically connected to each other, A transistor inverter structure characterized by being sealed. Structure of a transistor inverter. 8. An upper and lower semiconductor switch element connected in series as an upper and lower arm between positive and negative electrodes of a DC power supply,
The collector surface of the semiconductor switch element on the side where the potential does not fluctuate is directly joined to the metal base, the collector surface of the semiconductor switch element on the side where the potential fluctuates is connected to the metal base via an insulator, and this metal base is A transistor inverter structure which is joined to a cooling body via another insulator. 9. The semiconductor switching device according to claim 1, wherein the area or the number of chips of the semiconductor switching element on the side where the potential fluctuates is larger than that of the semiconductor switching element on the side where the potential does not fluctuate. 9. The structure of the transistor inverter according to any one of 6 to 8. 10. A transistor module formed by insulating upper and lower semiconductor switch elements connected in series as upper and lower arms between positive and negative electrodes of a DC power supply and joining them to a metal base is connected to a cooling body via an insulator. A transistor inverter structure, wherein the metal base is installed at a low impedance to one of a positive electrode and a negative electrode. 11. The structure of the transistor inverter according to claim 10, wherein said transistor module is joined to another metal base via an insulator and then installed on said cooling body.