JPH04335565A - Voltage detection circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a voltage detection circuit, and in particular, it generates a voltage using two resistors connected between power supplies.
The present invention relates to a voltage detection circuit that detects and outputs the voltage using a bandgap type constant current circuit.

0002

2. Description of the Related Art FIG. 4 shows a basic conventional voltage detection circuit. In this circuit, two dividing resistors R1 and R2 connected between the power supplies are used to determine the reference voltage Va.
, and a current Ia (
A comparison is made between the collector current of transistor Q1) and the constant current Ib (collector current of transistor Q3) generated from a bandgap type constant current circuit configured with transistors Q1 to Q4 and resistor R3. The circuit configuration is such that when more current flows, transistor Q5 is turned on and output is output via Q6.

0003

However, the above-described circuit configuration has a drawback in that when the power supply voltage Vcc is high, the transistor Q5 is turned on and the circuit current increases.

The relationship between power supply voltage Vcc and circuit current is shown in the following equation. Note that the circuit current generated by the dividing resistors R1 and R2 and the bandgap type constant current circuit is determined by the respective resistance values of R1 to R4, and there is no difference from the present invention, so only the transistor Q5, which is different from the conventional circuit, will be described. calculate.

[Vcc/(R1 +R2) ×R2-V
BE]×1/R4=Ia(K×T/q)×lnN×
1/R3=IbIa −Ib=Q5IB Q5IB × h fe =Q5IC

Here, VBE is the base-emitter voltage of the transistor Q1, K is the Boltzmann constant, T is the absolute temperature, q is the electron charge, and N is the voltage between the base and emitter of the transistor Q1.
The emitter size of Q2, Ia is the transistor Q
1, Ib is the collector current of transistor Q3, and Q5IB is the base current of Q5. Q5IC represents the collector current, and ln is the natural logarithm symbol. Since the emitter of transistor Q5 is connected to the power supply,
Collector current Q5IC is added as is as a circuit current.

That is, as can be seen from the above equation, when the power supply voltage Vcc increases, the collector current Ia of the transistor Q1 increases, and since the collector current Ib of the transistor Q3 is constant, the base and collector currents of the transistor Q5 increase. Each current increases. Therefore, there is a drawback that the circuit current increases in proportion to the power supply voltage.

The present invention was devised in view of the above-mentioned circumstances, and is a novel method that makes it possible to reduce the circuit current by using the current generated when the transistor Q1 is saturated as the base current of the output transistor Q6. The purpose is to provide circuit configurations.

[0009]

[Means for Solving the Problems] A voltage detection circuit according to the present invention includes a first transistor whose base is connected to the midpoint of two resistors connected between power supplies, and an emitter transistor whose base is connected to the midpoint of two resistors connected between power supplies. In a bandgap type constant current circuit configured by a second transistor having a large area and a resistor connected between each of its emitters, a current generated by the bandgap type constant current circuit and the emitter of the first transistor The circuit compares the current generated by the resistor connected between It is a feature.

0010

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit configuration diagram of the present invention, FIG. 2 is a plan view showing the electrode configuration of a transistor Q1 having a saturation detection terminal, and FIG. 3 is a cross-sectional view taken from section line A in FIG. 2.

In FIG. 1, Q1, Q2 and Q6 are NPN
transistors, Q3 and Q4 are PNP transistors,
R1 to R4 are resistors, Vcc is a power supply, and GND is a ground. Reference voltage Va generated by resistors R1 and R2, transistors Q1 to Q4, and resistors R3 and R4
Both of the band gap type constant current circuits constructed by the above circuit have the same circuit configuration as the conventional circuit, but due to the structural difference of the transistor Q1, the PNP transistor Q5 and the resistor R5 of the conventional circuit are omitted.

Next, the operation of the embodiment of the present invention will be explained. The circuit operation of comparing and outputting the collector current Ia of the transistor Q1 and the collector current Ib of the transistor Q3 based on the reference voltage Va generated by the resistors R1 and R2 is the same as described in the prior art.

In FIG. 2, transistor Q1 is an NPN
A saturation detection terminal is formed by surrounding the transistor with a P diffusion layer 4, and a transistor Q is connected via the terminal.
Connected to the base of 6. As shown in FIG. 3, this transistor Q1 comprises an N+ buried layer 6 in a silicon semiconductor substrate 5, an N layer 7 grown on this N+ buried layer 6, and P+ isolation layers 8 and 9 formed on the N layer 7. After that, a P layer 10 is formed by base diffusion, an N layer 11 is formed by emitter diffusion, a silicon oxide film 12 is formed on the entire surface, and the silicon oxide film 12 is patterned to form a P layer 10. A base wiring terminal 14 and a saturation detection terminal 16 are separately deposited, and a collector wiring terminal 13 and an emitter wiring terminal 1 are also deposited on the N layer 11.
5 by vapor deposition.

[0014] When the collector reaches saturation, some of the holes are recombined with electrons in the N diffusion layer region, but the remaining holes reach the P diffusion for saturation detection and a current flows. Thereby, the saturation of the transistor Q1 can be detected by the current flowing from the saturation detection terminal. As described above, by using the current flowing when the transistor Q1 is saturated as the base current of the transistor Q6, it is possible to minimize the circuit current during operation at a high power supply voltage.

[0015]

As described above, according to the present invention, it is possible to construct a voltage detection circuit that minimizes the increase in circuit current caused by the power supply voltage.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram according to the present invention.

FIG. 2 is a drawing according to the present invention, and is a plan view showing an electrode configuration of a transistor Q1 having a saturation detection terminal.

FIG. 3 is a drawing according to the present invention, showing a section line A in FIG. 2;
FIG.

FIG. 4 is a circuit configuration diagram according to the prior art.

[Explanation of symbols]

5 Silicon semiconductor substrate 6 N+ buried layer 7 N layer 8 P+ separation layer 9 P+ separation layer 10 P layer 11 N layer 12 Silicon oxide film 13 Collector wiring terminal 14 Base wiring terminal 15 Emitter wiring terminal 16 Saturation detection terminal

Claims (1)

[Claims] Claim 1: A first transistor whose respective bases are connected to the midpoint of two resistors connected between power supplies, a second transistor having an emitter area N times that of the first transistor, and between each of the emitters. In a bandgap type constant current circuit configured by a resistor connected to the bandgap type constant current circuit, a current generated by the bandgap type constant current circuit and a current generated by the resistor connected between the emitter of the first transistor and ground. In a voltage detection circuit that compares , detects that the first transistor is saturated, and outputs,
A voltage detection circuit characterized by minimizing circuit current during operation.