JPH033356A - Hybrid integrated circuit - Google Patents

Abstract

PURPOSE:To obtain a safe device capable of stably detecting a large current independently of temperature change by providing a conducting path, the main circuit of a power inverter, and a protecting circuit on an integrated circuit substrate composed of metal, and fusing a bonding wire of a power semiconductor element when an excessive current which can not be protected by the protecting circuit generates. CONSTITUTION:The following are provided; an integrated circuit substrate 7 composed of metal, a conducting path 9 of desired shape formed on the substrate 7, the main circuit 8a of a power inverter composed of a plurality of power semiconductor elements 8 which are connected with the conducting path 9 and controls a current supplied from a power supply to a load, and a protecting circuit 8b formed in order to prevent the destruction of power semiconductor elements caused by an excessive current or voltage by using a part of the conducting path 9 stretched in the vicinity of the power semiconductor elements 8 constituting the above main circuit 8a. When the excessive current or voltage which can not be protected by the protecting circuit 8b generates, a bonding wire 8c connecting the power semiconductor element 8 and the adjacent conducting path 9 is fused, thereby cutting off the current supplied from a power source.

Description

[Detailed description of the invention] B) Industrial application field The present invention relates to a hybrid integrated circuit, and more particularly to a hybrid integrated circuit in which a protection circuit for overcurrent protection and temperature protection is integrated using a low-resistance resistor. It is something.

(B) Prior Art Conventionally, a bridge circuit is one of the means for detecting current. As shown in Figure 7, the bridge circuit for current detection is connected in series with resistor R, (22), resistor R*<Z3>, resistor R6 (21) for current detection, and resistor R, (21). The resistor R, (25), the resistor R, (24), and the resistor R,
(22) and resistance R, (23) connection point and resistance R, (2
5) and a comparator (26) input to the connection point of the resistor R4 (24).

Next, to briefly explain the operation, the resistor R for current detection (25) has a current of 1. Suppose that is flowing. This electrician to be measured. When the maximum value of flows through the resistor R, (25), each resistor R1 (22
) , R, (23) and R, (24) are set.

In such a bridge circuit, the resistor R, (25) has a current of 1. If a current less than the maximum value of comparator 26
), for example, a signal of level "rL" is output from the current to be measured 1. continues to flow, and the current flows through the resistance R, (21). If the maximum current of
゜ is cut off and becomes a protection circuit.

Such a bridge circuit is described in Japanese Patent Laid-Open No. 53-9747.

Also, a temperature protection circuit is constructed using a part of such a bridge circuit.

When the above-mentioned bridge circuit is used in a thick film IC, the current is 1.
Ni plating was mainly used for the resistor R8 that detects the . However, since Ni plating has a small fusing current, it is possible to detect small currents, but when detecting large currents, the area of the resistor must be increased or the resistor must be made thicker in order to increase the fusing current. Therefore, there are problems such as a reduction in the board mounting area and an increase in plating processing time, and it has been considered almost impossible to detect a large current of, for example, 40A.

This problem can be solved by using copper foil or Ag paste, which has a large fusing current, as the resistor of the current detection resistor R8.

(c) Problems to be Solved by the Invention It is possible to detect large currents by using Ag paste or copper foil, which has a large fusing current, as a detection resistor. However, the TCR (temperature coefficient of resistance) of copper foil and Ag paste is 3800 ± 200 ppm and 2150 ± 1
Since the current was extremely high at 50 p4, there was a problem that current detection could not be performed accurately in response to temperature changes.

(D) Means for Solving the Problems The present invention has been made in view of the above-mentioned problems, and includes an integrated circuit board made of metal, a conductive path of a desired shape formed on the board, and a conductive path formed on the board. a main circuit of a power inverter comprising a plurality of power semiconductor elements connected to a conductive path and controlling a current supplied from a power source to a load; and a conductive path extending near the power semiconductor elements constituting the main circuit. and a protection circuit formed to prevent destruction of the power semiconductor element due to overcurrent or overvoltage using a part of the power semiconductor element, and when an overcurrent or overvoltage that cannot be protected by the protection circuit occurs, the power semiconductor element The present invention is characterized in that the current supplied from the power source is cut off by melting a bonding wire connecting the conductive path and the conductive path in the vicinity.

(*) Effect As described above, according to the present invention, a large current flows in the main circuit of the power inverter by forming a protection circuit using a part of the conductive path formed from low-resistance @ foil as a detection resistor. Even if the detection resistor generates heat, a stable large current can be detected regardless of temperature changes.

In addition, when an overcurrent or overvoltage that cannot be protected by the above-mentioned protection circuit occurs, the hybrid integrated circuit can It is possible to protect the entire system of electronic devices that implement this.

(F) Embodiments Below, embodiments of the present invention will be described in detail based on the embodiments shown in FIGS. 1 to 6.

As shown in FIG. 1, the hybrid integrated circuit of the present invention includes an integrated circuit board (7), a conductive path (9) of a desired shape formed on the board (7), and a power supply The main circuit (8a) of the power inverter consists of a plurality of power semiconductor elements (8>) that control the current supplied from the load (not shown) to the load (not shown), and the power semiconductor elements (8a) constituting the main circuit (8a). 8) and a protection circuit (8b) formed by using a part of the conductive path (9) extending near the detection resistor as a detection resistor.

A printed circuit board or a metal board is used as the integrated circuit board (1), and here a metal board with excellent heat dissipation is used.

An aluminum substrate is used as the metal substrate, and an aluminum oxide film is formed on its surface by anodic oxidation. An insulating thin layer of resin such as epoxy resin or polyimide resin is formed on the main surface of the metal substrate (1) on which the aluminum oxide film is formed. Although an aluminum oxide film was formed here, it is also possible to form an insulating thin layer of polyimide or the like directly on the metal substrate.

The conductive path (9) has a thickness of 35 mm through a thin insulating layer on the metal substrate.
After the μ copper foil is pasted and etched into a desired pattern, such as a bridge circuit,
Ni plating is applied to the part to be bonded.

A plurality of power semiconductor elements (8) constituting the main circuit (8a) and other circuit elements such as chip resistors, chip capacitors, monolithic ICs, etc. are fixedly formed on the conductive path (9), and the protection circuit (2) is formed on the conductive path (9). Resistors R1, Ra, Rs, Ra, Rs
, an R diode D and first and second comparators (5) and (6) are fixed. Each resistor is formed by screen printing using resistor paste, and a diode D
A chip component is used and is bonded to a nearby conductive path (9) by ultrasonic bonding or the like.

FIG. 2 is a circuit diagram showing the protection circuit (8b), which is composed of a bridge circuit as shown in FIG. is connected. In detail, the protection circuit (2)
are the first and second resistors RI and Rt, the detection resistor R1 whose resistor is the low-resistance metal through which the current to be measured flows, and the fourth and third resistors R4 and R connected to the detection resistor R.
a bridge circuit including a diode D connected to the second resistor R3 and correcting the temperature dependence of the detection resistor R6 made of a low-resistance metal; A first comparator (5) inputs and compares the voltage at the connection point of the second resistor R, , R, and the voltage at the connection point of the third and fourth resistors Rs and Ra, and a first comparator (5) for temperature protection. The pressure at the connection point of the first and second resistors Rt and Rm and the voltage of the Zener diode D, which keeps the voltage of the bridge circuit constant, is applied to the fifth and sixth resistors Ra.
, and a second comparator (6) which inputs and compares the divided voltages divided by Re.

As described above, the first comparator (5) inputs the voltage at the connection point of the first and second resistors R+ and Rx and the voltage at the connection point of the third and fourth resistors R, , R, After comparison, a cutoff signal for cutting off the current flowing through the detection resistor R1 is output. In addition, the second comparator (6)
By inputting and comparing the voltage at the connection point of the resistors R, R and the voltage at the connection point of the fifth and sixth resistors R* and Ra, a cutoff signal is generated to detect an abnormality due to temperature and cut off the current. Output.

A diode D connected to the first resistor R+ is a detection resistor R
It is possible to correct variations in resistance with respect to zero temperature changes and to perform temperature-based protection operations.

The operating principle of the temperature correction method using diodes will be explained below.

In Figure 2, the Zener voltage v2 at the Zener diode
(at this time, Ov is the anode side of the Zener voltage v2). The midpoint voltage V, , V, of the bridge circuit when the current I0 is flowing through the detection resistor R, is given by the following equation.

Equation (2) above is for electric current. There is a dependence on electrician. When is large, the midpoint voltage V becomes a low voltage. When the electric current is small, the midpoint voltage V, , V, becomes V, < V, and
Current 1 becomes the dog. (MA!), the midpoint voltage V I +V becomes equal to Vt-Vt, and at this time the output of the comparator is inverted and the current is cut off.

The temperature change of the detection resistor R0 (in this case, the temperature change of the copper foil) is as shown in FIG. 3, and when the temperature is 25°C, the resistance value is r. , and this can be expressed as the following formula.

Ro-foe(1+ (! (T-25))”
""""""" (3) Here, r and . are the Cu pattern resistance values at 25°C, and α is the TCR of Cu.
2) Substituting into the formula gives V.

The temperature change of is given as follows.

The temperature change of the diode is shown in FIG. 4, and when the temperature is 25° C., the voltage '/D is VDD, which is expressed as follows.

VD-vDD-β (T-25) ・・・・・・
・・・・・・・・・(5) Here, β is the amount of temperature change of the P-N junction V, which is approximately -2 mV/''C per one. By substituting, the temperature change of vl is given as follows.

The temperature is 25℃. ``The midpoint voltage Vt at II (MAI), Vt is equal to Vt-Va, and the midpoint voltage V
, , V, (7) If the amount of temperature change is the same, even if the temperature changes, 1°-I.

The midpoint voltage V at (MAz), −V, holds true.

First, when we differentiate equation (4) with respect to temperature T......(7) Next, when we differentiate equation (6) with respect to temperature, we get -ro. (1+a ('l-25))'Iecl, Ax
)......4> Also, the midpoint voltage V+-V* at a temperature of 25° C. is expressed as follows.

・・・・・・・・・(10) When rearranged by ratio, the following two-dimensional simultaneous equations are given.

Since equations (13) and (14) are initial constants, R
A and Rs are also determined by only one constant. Therefore, as shown in equations (13) and (14), if RA and Rm are determined, the midpoint voltage V, = It is possible to detect the current generated by the

Next, temperature protection will be explained.

Resistor R used for temperature correction of the above-mentioned detection resistor R0
1, R1 and diode D connected in series, resistor R
The change in v1 due to temperature change at the connection point v1 of ,,R, is expressed as V,
Temperature protection is provided compared to

V, , V, are given by the following formula.

Solving the equations (11) and (12) above gives the following equations.

As mentioned above, ■ゎ is '/El when the temperature is 25°C, and this can be expressed by the following formula.

V, -V D, -β(T-25) -
−−−−−−−−−−−−−(5)<5) Expression (1)
Substituting into the expression gives

When the temperature is low, Vs < Vt, but when the temperature is high < (IW
aX ) becomes V 1111!1 V 1, the output signal of the second comparator (6) is inverted, and the signal is cut off.

FIG. 6 is an equivalent circuit diagram showing a control circuit that controls to cut off the large current flowing through the power semiconductor element (8) via the detection resistor R0 when a signal of level rH is output from the comparator. is the detection resistor R0 for current detection provided in the bridge circuit, and now the comparator (6
), the transistor Trt (16) turns on and the photocoupler DCI
(17) is turned on, and transistor 'rr* (18) is turned off. By turning off the transistor τrs (1B), the large current is cut off and the power semiconductor element (8) is protected. Needless to say, the above-mentioned control circuit also includes a protection circuit (
Similarly to 2), it is not connected to the conductive path (9) formed on the substrate (7).

In this embodiment, a part of the conductive path (9) is used for the detection resistor R0, and here, a point a near the power semiconductor element (8) is used.
-b is used as the detection resistor R0. A bridge circuit for current detection is formed near the detection resistor R0, and a key-shaped protrusion (10) for adjusting the detection resistor R0 is further formed at the end of the detection resistor R0. This protrusion (10) is used to adjust the resistance of the detection resistor R0 between points a and b, and the adjustment method will be described below.

The protrusion (10) and the detection resistor R6 are connected by a connecting body (11) such as Ni plating. Here, Ni plating is used for the connecting body (11), but any type can be used as long as it connects the protrusion (10) and the detection resistor R6. The internal resistance of the detection resistor R0 at the part connected by the connection body (11) is wide and has an extremely low resistance that can be ignored, and the resistance of the entire detection resistor R0 is the distance connected by the connection body (12), i.e. , protrusion (
1G)j! Any point of t! ! Internal resistance from to point a and arbitrary point 1. It is the sum of the internal resistance of the super resistance value from to .

Therefore, the resistance of the detection resistor R0 can be adjusted by changing the arbitrary point 18 on the protrusion (10) L of the detection resistor R8. That is, an arbitrary point is determined by the distance between the trimming slit (13) of the connecting body (12), and the internal resistance at the distance from point a to arbitrary point lx becomes the resistance value of the detection resistor R0, and fine adjustment can be easily performed.

By forming the above-mentioned protection circuit (8b) on the substrate (7), stable current detection can be performed and damage to the power semiconductor element (8) can be prevented. However, in reality, overcurrent or overvoltage that cannot be protected by the protection circuit may occur. In this case, the protection circuit or control circuit may not operate normally due to destruction of the peripheral circuit formed on the substrate (7) or malfunction due to unpredictable reasons such as external noise. At this time, even if an overcurrent or overvoltage occurs, protection can be provided in the case of normal operation, but in this case, protection is not possible, and the power semiconductor element (8) is destroyed, becomes conductive, and a large current continues to flow.

As a result, when a hybrid integrated circuit for an inverter is mounted on an electronic device such as an air conditioner, there is a problem that the motor may stop or malfunction. Furthermore, current paths such as AC hood wires generate heat, which poses a major problem that can lead to secondary disasters such as fire.

Therefore, in this embodiment, the hybrid integrated circuit is mounted by actively blowing out the bonding wire (8c) connecting the power semiconductor element (8) and the conductive path (9) to prevent overcurrent or overvoltage that cannot be protected by the above-mentioned protection circuit. This protects the entire system of electronic equipment that has been exposed.

That is, the diameter of the bonding wire (8C) that connects the power semiconductor element (8) and the conductive path (9) is set to a diameter that will melt when an overcurrent or overvoltage that cannot be protected by the protection circuit occurs. Bonding wire (8C
) to protect the system.

A gold wire or an aluminum wire is used as the bonding wire (8c), and the diameter thereof varies depending on the setting of overcurrent or overvoltage, but is, for example, 0.1.
If the distance is in the range of a to 0.5 m, the bonding wire (8c) can be fused with an overcurrent of 208 to 100 A, as shown in FIG.

Therefore, by setting in advance the case where an overcurrent voltage that cannot be protected by the protection circuit occurs, and by setting the diameter of the wire (8C), even if an overcurrent or voltage occurs, secondary disasters such as fire can be prevented. It can be prevented.

(G) Effects of the Invention As detailed above, according to the present invention, by forming a protection circuit on a substrate using a portion of a conductive path formed of low-resistance copper foil as a detection resistor, It is possible to provide a highly reliable hybrid integrated circuit for an inverter that can perform stable current detection regardless of temperature changes even if a large current flows through the main circuit of the power inverter and the detection resistor generates heat.

Also, the detection resistance is f! 1111, it has the advantage that even if a low-resistance resistor is formed, there is no need to increase the resistor area.

Furthermore, in the present invention, even if an overcurrent or voltage that cannot be protected by the above-mentioned protection circuit occurs, the bonding wire that connects the power semiconductor element and the conductive path is fused, so even if an overcurrent or voltage occurs, the hybrid integrated circuit An extremely safe hybrid integrated circuit for an inverter can be provided because the hybrid integrated circuit for an inverter does not destroy the entire system of an electronic device such as an air conditioner in which the hybrid integrated circuit for an inverter is mounted.

[Brief explanation of drawings]

FIG. 1 is a plan view of the main parts showing the hybrid integrated circuit of this embodiment, FIG. 2 is a circuit diagram showing this embodiment, FIG. 3 is a resistance temperature characteristic diagram, FIG. 4 is a voltage temperature characteristic diagram, Fig. 5 is a temperature characteristic diagram of the detected current corrected by the present invention, and Fig. 6 is a diagram of the temperature characteristic of the detected current corrected by the present invention.
FIG. 7 is a circuit diagram illustrating a conventional control circuit. (7)...Integrated circuit board, (8)...Power semiconductor element, (9)...Conducting path, (8a)...Inverter main circuit, (8b)...Protection circuit, ( 8C
)...bonding wire. Figure 2 [ , X Figure 3 Figure 4 5121 O 7th r:A

Claims (5)

[Claims] (1) A power source consisting of an integrated circuit board made of metal, a conductive path of a desired shape formed on the substrate, and a plurality of power semiconductor elements connected to the conductive path and controlling the current supplied from the power source to the load. A main circuit of an inverter and a part of the conductive path extending near the power semiconductor elements constituting the main circuit are used to prevent destruction of the power semiconductor elements due to overcurrent or overvoltage. and a protection circuit that, when an overcurrent or overvoltage that cannot be protected by the protection circuit occurs, melts a bonding wire connecting the power semiconductor element and the nearby conductive path to cut off the current supplied from the power source. A hybrid integrated circuit characterized by: (2) The protection circuit includes first and second resistors, a detection resistor whose resistor is the low-resistance copper foil through which the current to be measured flows, fourth and third resistors connected to the detection resistor, and the Second
a bridge circuit including a diode connected to the resistor to correct the temperature dependence of the detection resistor made of copper foil, and a voltage at the connection point of the first and second resistors to provide overcurrent protection; a first comparator that inputs and compares the voltage at the connection point of the third and fourth resistors, and a voltage at the connection point of the first and second resistors and the voltage of the bridge circuit for temperature protection; 2. The hybrid integrated circuit according to claim 1, further comprising a second comparator which inputs and compares the divided voltage of the Zener diode which is kept constant. (3) The hybrid integrated circuit according to claim 2, wherein the Zener diode is powered by a current flowing through the detection resistor. (4) The hybrid integrated circuit according to claim 1, wherein the semiconductor element mounted on the substrate is mounted as a chip. (5) The hybrid integrated circuit according to claim 1, wherein the integrated circuit board is an aluminum substrate whose surface is insulated.