JPH02301151A - Transistor with current detection function - Google Patents

Abstract

PURPOSE:To eliminate necessity of adding a new external resistor for main current detection to eliminate wasteful electric power loss by a method wherein main current is detected by utilizing voltage drop of resistor component present in an existing electrode wiring. CONSTITUTION:At the tip of one electrode Sa constituting a part of a comb-like source electrode S, a terminal S1 for detecting current is provided while at the foot of the other electrode Sb distant from the electrode Sa the other terminal S2 for detecting current is provided. A part (shaded part) between the two terminals S1, S2 of the source electrode S is used as a resistor RS for detecting current. According to gate current IS flowing via a gate electrode G drain current ID flows to a drain electrode D, and source current IS flows to the source electrode S. Since current (current for detection) ISS flows also to the resistor RS for detecting current which is a part of the source electrode S, the amount of main current can be detected by measuring voltage VSS between the terminals S1, S2.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a transistor with a current detection function,
In order to enable current detection without adding an external resistor and eliminate extra power loss associated with current detection, a part of the electrode wiring through which the main current flows is used as a current detection resistor, and the voltage drop due to this resistance is Based on this, the magnitude of the main current is detected.

[Industrial application field]

The present invention relates to a transistor having a current detection function for detecting the magnitude of a main current, and is applied to various transistors such as bipolar transistors, static induction transistors, and field effect transistors.

[Conventional technology]

2. Description of the Related Art Conventionally, some power transistors that require a large current to flow are equipped with a current detection function in order to prevent damage to one member due to excessive current. The current detection method is as follows:
For example, it has been common practice to connect an external resistor to a main electrode such as an emitter electrode or a source electrode, and measure the voltage drop due to this external resistance to detect the magnitude of the main current.

(Problems to be Solved by the Invention) The conventional current detection method described above has a problem in that it is necessary to newly add an external resistor to the transistor, and the extra power loss due to this resistor is large.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a current that enables current detection without adding an external resistor and eliminates extra power loss associated with current detection. An object of the present invention is to provide a transistor with a detection function.

[Means to solve the problem]

The transistor with a current detection function of the present invention uses a part of the electrode wiring through which the main current flows as a resistor for current detection,
The present invention is characterized in that the magnitude of the main current is detected based on the voltage drop caused by the resistor.

[For production]

Since the electrode wiring also contains a resistance component, a part of it can be used as a resistance for current detection. That is, since a voltage drop corresponding to the main current is obtained from both ends of a portion of the electrode wiring used as this resistor, the magnitude of the main current can be detected based on this voltage drop.

In this way, in the present invention, current detection is performed using the voltage drop of the resistance component existing in the existing electrode wiring, so there is no need to add a new external resistor, and extra power loss associated with current detection is eliminated. will also be zero.

[Examples] Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view showing an electrode pattern on the upper surface of an embodiment of the transistor with current detection function of the present invention. In this embodiment, a current detection function is provided to an existing bipolar static induction transistor having a multi-emitter structure.

In the transistor of this embodiment, as shown in FIG. 1, a comb-shaped source electrode S made of aluminum or the like is formed on a large number of source regions (not shown) arranged in parallel on the surface of the transistor. At the same time, a comb-shaped gate electrode G made of aluminum or the like is formed on a gate region (not shown) disposed surrounding the source region mentioned above, and these source electrodes S and gate electrodes G are connected to each other. are arranged in mesh with each other. Although not shown in Figure 1,
A train electrode is formed on the entire back surface of the chip (drain region).

Furthermore, one terminal S+ for current detection is provided at the tip of one electrode S forming a part of the comb-shaped source electrode S, and the other terminal S+ is provided at a distance from the electrode S. Another terminal S2 for current detection is provided at the base of the two electrodes S. The portion of the source electrode S sandwiched between the two terminals S2 and S2 (hatched portion) is used as a current detection resistor R8. A schematic circuit diagram of this configuration is shown in FIG. 2. However, the case of an n-channel static induction transistor is shown here.

In the transistor of this embodiment having the above configuration, depending on the gate current 1c flowing through the gate electrode G, the drain current flows through the drain electrode G! 0 flows, and a source current ■ flows through the source electrode S.

(!-i drain current to) flows. At this time, the current detection resistor R5, which is a part of the source electrode S, is also connected to the terminal S.
Since a current (detection current) tss flows from l to terminal S2, the voltage drop due to resistor Rs, that is, terminal S,
By measuring the voltage VSS between , S, the main current (
The magnitude of the source current Is) can be detected.

According to this embodiment, as described above, the existing source electrode S
Since current detection can be performed using the voltage drop of the resistance component existing in the sensor, there is no need to add a new external resistor, and additional power loss associated with current detection can be reduced to zero.

Furthermore, by providing the terminal S1 at the tip of the electrode S and providing the terminal S2 at the base of the other electrode S as in this embodiment, the terminal S2 receives not only the current from the electrode S1 but also the current from the electrode S1. Current from each electrode sandwiched between electrodes Sj and S also flows in, and the voltage drop due to all these currents is detected as a voltage drop due to the resistor Rs. It is possible to detect every voltage drop. For example, even if the material of the source electrode S is aluminum, which has a small resistivity, it is possible to obtain a resistance R5 of about 0.1Ω by appropriately setting the width W and length l of each electrode that forms part of the source electrode S. Therefore, when the source current Is is made to flow in the order of tens of magnitude, a sufficient voltage drop of around 100 mV can be obtained by the resistor Rs.

Next, FIG. 3 is a block diagram showing an example of an overcurrent protection circuit for protecting the transistor T itself from overcurrent using the transistor T with a current detection function of the above embodiment, and FIG. 4 is a more detailed circuit diagram of FIG. 3; FIG.

In FIG. 3, the drain electrode of the transistor T is connected to the positive side of the DC power supply 2 through the load l, the source electrode S is connected to the negative side of the DC power supply 2 through the common terminal 3, and , a gate current IG output from the transistor drive circuit 4 flows into the gate electrode G.

Furthermore, a current detection resistor R provided in the transistor T
5 (the voltage between terminals St and Sz) is input to the DC amplifier 5, and the output voltage obtained by amplification here is input to the judgment control circuit 7 together with the reference voltage VIIEF of the reference voltage source 6. be done. This judgment control circuit 7
An output voltage corresponding to the determination result is supplied to the transistor drive circuit 4 as a control input. Here, the fourth
As is clear from the figure, the DC amplifier 5 is composed of an operational amplifier operating on a single power supply, the judgment control circuit 7 is composed of a comparator with an open collector output, and the reference voltage source 6 is a Zener diode. , a resistor and a capacitor. Further, the transistor drive circuit 4 includes an amplification circuit including a transistor Q1 and a current mirror circuit including transistors Q2 and Q3.

The operation of the overcurrent protection circuit having the above configuration will be explained below.

First, when a drive signal is input to the drive input terminal d of the transistor drive circuit 4, the transistor drive circuit 4 supplies the gate current 6 to the gate electrode G of the transistor T.

As a result, the transistor T becomes conductive, and the source current ts (!=i drain current to) flows through the load l. At this time, the detection current ISS, which is a part of the source current Is, also flows through the current detection resistor Rs, so that a voltage corresponding to the magnitude of the source current Is is generated across the resistor Rs. This voltage is converted to K (K
is a constant).

The output voltage of the DC amplifier 5 is input to the judgment control circuit 7,
It is compared with a reference voltage V 11EF. If the load 1 is short-circuited for some reason and the source current 1° becomes excessive, and the output voltage of the DC amplifier 5 becomes higher than the reference voltage V RfF, the judgment control circuit 7
A control signal is sent to the control terminal S of. As a result, the transistor drive circuit 4 reduces the supply of the gate current Is to the transistor T, and the source current Is (-drain current +
1. ) decrease. Due to this negative feedback loop,
Transistor T, load l, and DC power supply 2 are protected from overcurrent.

Note that the positions of the current detection terminals S5 and S2 shown in FIG.
+ and Sz, the resistor Rs may be placed at any position as long as a voltage drop sufficient to enable current detection is obtained.

Further, the electrode material is not limited to the above-mentioned aluminum, and other metals, polysilicon, etc. can also be used.

Furthermore, although only an n-channel electrostatic induction transistor is shown in FIG. 2, the present invention may of course be applied to a p-channel transistor, or to an ordinary bipolar transistor, field effect transistor, or the like.

[Effects of the Invention] According to the present invention, the main current is detected using the voltage drop of the resistance component existing in the existing electrode wiring, so there is no need to add a new external resistor, and the current detection It is also possible to reduce the loss of extra power to zero.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an electrode bump on the top surface of an embodiment of the transistor with current detection function of the present invention, FIG. 2 is a circuit diagram schematically showing the transistor of the embodiment, and FIG. 3 is the same embodiment. FIG. 4 is a circuit diagram showing the circuit shown in FIG. 3 in more detail. S... Source electrode, G... Gate electrode, D... Drain electrode, Rs... Resistor for current detection, S, , S2... Terminal for current detection.

Claims (1)

[Claims] A transistor with a current detection function, characterized in that a part of the electrode wiring through which the main current flows is used as a resistance for current detection, and the magnitude of the main current is detected based on the voltage drop caused by the resistance.