JPH01292906A - Current detecting circuit - Google Patents

Abstract

PURPOSE:To execute current detection with high accuracy without using a resistor for shunting even in a semiconductor composite circuit due to a bipolar transistor by causing an emitter part to be multi-structure and fetching a detecting current. CONSTITUTION:Darlington connection is executed for two bipolar transistors 1 and 2 and the transistor 1 is made in the multi-emitter structure to have two emitters E1 and E2, and the area ratio of the emitters E1 and E2 is set nearly '1'. A current to be proportional to a main current flows to the transistor 1 in the front step of this semiconductor composite circuit and on the other hand, the current to be proportional to the main current appears with being shunted between the plural emitters E1 and E2 to be multiplexed in this transistor 1 of the front step. Accordingly, when a current value to appear in these plural multiplexed emitters E1 and E2 are observed, the main current can be detected. Thus, even in the semiconductor composite circuit due to the bipolar transistor, the current detection of the high accuracy can be executed without using the resistor for shunting.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a current detection circuit in a semiconductor composite circuit in which a plurality of transistors are connected in cascade, and particularly to a current detection circuit suitable for a semiconductor composite circuit in which a Darlington connection is made. Regarding circuits.

[Prior Art] Semiconductor composite circuits including power transistors are often used to control various electrical loads such as automotive electrical components, but in order to obtain accurate control, It is desirable to sense and control the current being supplied to this load.

By the way, in the past, it was customary to mainly use a shunt resistor in such cases, but from the standpoint of eliminating heat generation and power loss caused by the shunt resistor, for example, US Pat. , 553.084,
A method has been proposed in which the sources of MOS transistors constituting a semiconductor composite circuit are multiplied.

In this method, as shown in FIG. 2, a current detection MOS transistor 10 is connected to a power MOS transistor 20 through which a current to be detected flows, and the drain of the current detection transistor 10 is connected to a current detection terminal 30. That is.

Load current 6 current, 2 MOS transistors 10°2o
Therefore, the area of the source of each of these MOS transistors 10.20 is divided by a predetermined ratio of 1:
If it is set so that N (N>1), the current flow is taken out from the current detection terminal 30. By calculating the load current I using the above ratio N, the main current (load current) can be detected without using a shunt resistor.

[Problems to be Solved by the Invention] The above-mentioned conventional technology utilizes the fact that multi-source MOS transistors are easy in terms of R manufacturing technology, including accurate setting of the above-mentioned area ratio. Yes, therefore,
No consideration was given to the application of this method to bipolar transistors, and as a result, there was a problem in that the scope of its application was limited.

An object of the present invention is to provide a current detection circuit that can be applied to semiconductor composite circuits using any type of transistors, including bipolar transistors, and that can always perform highly accurate current detection without using a shunt resistor. Our goal is to provide the following.

[Means for Solving the Problem] The above object is to convert a part of the transistors in the previous stage into multi-emitters or multi-collectors in a semiconductor composite circuit such as a Darlington-connected bipolar transistor circuit, and to convert these multi-emitters or This is achieved by determining the main current by the current flowing through one of the collectors.

[Operation] A current proportional to the main current flows through the transistor at the front stage of the semiconductor composite circuit. On the other hand, a current proportional to the main current appears as a branch between the plurality of emitters or collectors of the transistors in the previous stage.

Therefore, if we look at the current value appearing at one of these multiple multi-emitters or collectors.

Main current can be detected.

The magnitude of the current that appears in the emitter or collector at this time is a reciprocal of the current amplification factor of the subsequent transistor, and the current value is sufficiently small compared to the main current, so it is generated for current value detection. It is possible to sufficiently suppress voltage drop, power loss, heat generation, etc.

[Example] Hereinafter, a current detection circuit according to the present invention will be explained in detail with reference to an illustrated example.

Figure 1 shows an embodiment of the present invention, in which the present invention is applied to a semiconductor composite circuit consisting of Darlington connections of bipolar transistors. ,2
are Darlington connected, and the current amplification factor is h
Fix + h Flax. transistor 1 is 2
It is made into a multi-emitter structure having emitters E, E2, and emitters E1. The area ratio of E is set to approximately 1.

Note that this does not necessarily have to be 1, but from the perspective of the baton design, there is an advantage that the same baton can be used.

Now, load current 1. , is flowing at the base of transistor 2, the load current ■ is flowing at the base of transistor 2. A current IL/hp'□ that is the reciprocal of the current amplification factor flows in, and this is the base current■!
It becomes l□. On the other hand, since the areas of the two emitter currents E2 of the transistor 1 are set equal, the base current I of the transistor 2 is transmitted from the current detection terminal 3.
The same current as n□ flows out. In other words, engineering==i! 12
Since hp□=Izs”hp□, the detection current rxs flowing out from the 1! current detection terminal 3 can represent the load current ■.

Next, FIG. 3 shows another embodiment of the present invention, which is the same as the embodiment shown in FIG. 1 in that two transistors 1 and 2 are connected in Darlington, but transistor 1 is It has a multi-collector structure, and its two collectors C and C
The difference is that the area ratio of 2 is set to approximately 1, and one of them is used as the current detection terminal 31.

Assuming that a load current is flowing now, a current of I,/hFil flows into the base of transistor 2. Then, generally hpx>1, so the collector electric current. The relationship between and emitter current I2 can be considered to be I0, and the current flowing into the collector of transistor 1 is approximately equal to the base current 1□ of transistor 2. Furthermore, since the two collectors C1 and C of the transistor l are set to have the same area, a current that is 1/2 of the base current I5 of the transistor 2 flows into the current detection terminal 31.

In other words, I c, = h y! z・engineering, □valve 2・h2
Since it is □・Ics, the load current can be represented by the detected current flowing into the current detection terminal 31.

In this embodiment, the collector section has a multi-structure to take out the detection current, so the range of potential of the current detection terminal can be greatly expanded compared to the embodiment shown in FIG. , the voltage at current detection terminal 3 must be set to the base-emitter voltage).

In the examples so far, the semiconductor composite circuit has been described as having two transistors connected by Darlington, but this is not necessarily an essential condition of the present invention.
As in the embodiment shown in FIG. 4, the current can be detected even if the collector 4 of the first stage transistor 1 is made independent from the collector of the transistor 2.

Further, the transistor may be not only a bipolar element but also a MOS element or a composite connection of these elements.

FIG. 5 shows a combination of a bipolar element 2 and a MOS element 1 in which the present invention is implemented.

Furthermore, FIG. 6 shows another embodiment of the present invention.

This embodiment uses a PNP type transistor as the front-stage transistor 1, and this embodiment has the effect of making it easy to integrate the entire circuit (PNP multi-collector structure or multi-emitter structure is easy to make as rc). ).

FIG. 7 shows an embodiment in which the present invention is integrated into a semiconductor chip. In this embodiment, the circuit shown in Fig. 1 was realized as an IC using a bipolar process, and one transistor
is the collector with the n-type region 9, the base with the P-type region 10, and the n"
The type region 11 is formed as an emitter, and the multi-emitter structure is achieved by forming two n+ regions 11 and 12 inside the P-required region 10, with one n+ region 12 being used as the current detection terminal 3. The silicon substrate 5 is connected by the terminal SB to the lowest potential of the circuit and serves to electrically isolate the transistor 1.2.

According to this embodiment, since the circuit can be integrated, the effects of miniaturization and high reliability can be expected.

FIG. 8 shows another embodiment of the semiconductor chip of the present invention. In this embodiment, the circuit of FIG. 6 is implemented using a bipolar process in the same manner as the embodiment of FIG. 7, and the structure of the transistor 2 is the same as that of the embodiment of FIG. On the other hand, a PNP transistor 1 having a multi-collector structure is realized by forming P-required regions 10, 11, and 12 in an n-type region 9 corresponding to the base, and uses one region 12 for detection. Set it as terminal 3.

According to this embodiment, it is possible to easily create a multi-collector structure of a PNP transistor (it is relatively easy to create a multi-collector structure of an NPN transistor).

[Effects of the Invention] According to the present invention, even in a semiconductor composite circuit using bipolar transistors, it is possible to
Current detection can be performed with high accuracy.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the current detection circuit according to the present invention, FIG. 2 is a circuit diagram showing a conventional example, FIGS.
FIGS. 5 and 6 are circuit diagrams showing other embodiments of the present invention, and FIGS. 7 and 8 are explanatory diagrams each showing an integrated embodiment of the present invention. 1... Transistor in front stage, 2... Transistor in rear stage, 3, 30, 31... Current detection terminal. Fig. 1 1.2: NPN tofunjis 7 3: t, *detection js child Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6L

Claims (1)

[Claims] 1. A semiconductor composite circuit comprising at least two transistors in a front stage and a rear stage and connected so that the output of the transistor in the front stage directly controls the transistor in the latter stage, wherein the transistor in the front stage is connected to a plurality of emitters. A current characterized in that the output is taken out from one of the plurality of emitters, and the current taken out from the other emitter represents the value of the main current flowing through the semiconductor composite circuit. detection circuit. 2. In a semiconductor composite circuit comprising at least two transistors in a front stage and a rear stage and connected so that the output of the transistor in the front stage directly controls the transistor in the latter stage, the transistor in the front stage has a multi-collector structure consisting of a plurality of collectors. A current detection circuit characterized in that the current flowing into one of the plurality of collectors is configured to represent the value of the main current flowing through the semiconductor composite circuit. 3. In claim 1 or 2, the area ratio of each of the plurality of emitters of the multi-emitter structure and the area ratio of each of the collectors of the multi-collector structure are both set to approximately 1. A current detection circuit characterized by: 4. The current detection circuit according to claim 1 or 2, wherein the semiconductor composite circuit is composed of two bipolar transistors connected in a Darlington connection. 5. The current detection circuit according to claim 1 or 2, wherein the transistor at the front stage is a unipolar transistor, and the transistor at the rear stage is a bipolar transistor.