KR920007364B1 - Ic protected from heat - Google Patents

Abstract

The prevention circuit compensates the thermal shutdown temperature error caused by base to emitter voltage variation in manufacturing process. The circuit comprises a positive and a negative temperature coefficient bias circuit (11,13) having positive and negative temperature coefficient, and a comparator (12) for generating control signal when temperature rises upper limit by comparing the output voltage levels of the positive and negative temperature coefficient bias circuit (11,13).

Description

Thermal break prevention circuit

1 is a conventional thermal damage prevention circuit diagram.

FIG. 2 is a diagram illustrating the multiple shut down characteristic according to FIG. 1.

3 is a thermal damage prevention circuit diagram of the present invention.

4 is a characteristic diagram of a mulberry town in accordance with the present invention.

* Explanation of symbols for main parts of the drawings

11: static temperature coefficient bias circuit 12: comparison circuit

13: Negative temperature coefficient virus circuit Vo: Control output

The present invention relates to a thermal protection circuit (thermal protection), in particular to prevent the thermal shutdown due to variations in the element-emitter voltage (V _BE ) of the device in the process to operate at an appropriate temperature It relates to a thermal damage prevention circuit for.

The conventional thermal damage prevention circuit will be described with reference to the accompanying drawings.

FIG. 1 is a conventional thermal damage prevention circuit diagram. As shown in FIG. 1, a multi-collector PEN P transistor Q1 having a reference voltage Vref applied to an emitter and connected one of the multi-collectors to its base, The output Vo is connected to a collector connected to one of the multiple collectors of the transistor Q1, and a base Q2 is connected to one collector of the PNP transistor Q1, and the PNP transistor Q1. A base is connected through a base of bias) and bias adjustment resistors R1 and R2, and a collector thereof is connected to the base of the transistor Q2 to constitute a transistor Q3 for controlling the transistor Q2.

Referring to the operation and problems of the conventional thermal damage prevention circuit configured as described above are as follows.

The resistors R1 and R2 having appropriate resistance values with respect to the reference voltage Vref are selected so that the transistor Q3 is not turned on when the base voltage of the transistor Q3 is below a specific temperature. The base-emitter voltage V _BE of transistor Q1 is expressed as a function of temperature as follows.

V _BE (T) = _{BE, STD} + α. △ _T

Here, V _{BE, STD} is the V _BE voltage at 25 ℃ temperature at a particular current, α will have had the characteristic section of about -2mV / ℃ in temperature coefficient of V _BE, △ _T is the temperature rise shown.

2 is a change characteristic diagram of V2 in the conventional thermal damage prevention circuit, where V _BE is the turn-on potential of transistor Q3, point A is a normal shutdown, and point A is to the left of process A. This is a characteristic diagram showing abnormal shut down caused by _BE change.

When the temperature rises, the V _BE voltage of the transistor Q1 decreases and its base voltage V1 rises, so that the base voltage V2 of the transistor Q3 goes up, and finally the transistor Q3 at a specific temperature, which is a further shutdown temperature. ) Is turned on and the output state changes.

Thus the conventional circuit, the deomeol shut-down temperature is influenced in V _BE turn-on voltage, V _BE turn-on voltage because of a problem in the process according may cause an error of approximately ± 0.05 [V], the deomeol shut down temperature ± 25 ℃ An error of degree may occur and cause a malfunction.

The present invention has been devised a circuit for operating at an appropriate temperature to prevent the thermal shutdown temperature change caused by the variation of the V _BE voltage in the process to solve such a conventional problem, will be described with reference to the accompanying drawings As follows.

3 is a circuit break prevention circuit diagram of the present invention, in which the transistors Q2, Q3, Q1 for the current source and the input virus and the transistors Q4, Q5, for determining the temperature coefficient, and A static temperature coefficient bias circuit 11 composed of resistors R1 to R3, varactor diodes D1, and D2, which acts as a band gap circuit and exhibits a static temperature coefficient; Similar to the characteristic temperature coefficient bias circuit 11, the transistors Q8, Q9, Q10, transistors Q11, Q12, resistors R4 to R6, and varactor diodes D3 and D4 are used. The output voltages V1 and V2 of the negative characteristic temperature coefficient bias circuit 13 and the positive and negative characteristic temperature coefficient bias circuits 11 and 13, which are configured to exhibit the negative characteristic temperature coefficient, are compared. And a comparison circuit section 12 that outputs Vo.

Referring to the operation and effects of the present invention configured as described above are as follows.

Here, the switches SW1 and SW2 are turned on only at the start of operation so that the inventive circuit is operated.

First, the temperature coefficient determination of the static temperature coefficient bias circuit 11 is determined by the following equations (1 to 3).

The temperature coefficient of the negative temperature coefficient bias circuit 13 is determined by the following equations (4 to 6).

Where m and n are base-emitter voltages V _{BE and Q4} and V _{BE and Q12} of transistors Q4 _{and Q12} .

The output voltage V1 of the static characteristic temperature coefficient bias circuit 11 is set lower than the output voltage V2 of the negative characteristic temperature coefficient bias circuit 13 according to the temperature coefficient determined by the above equations (1 to 6). do. Under these conditions, if the temperature rises, the output voltage V1 of the positive temperature coefficient bias circuit 11 rises because the temperature coefficient is positive, and the output voltage V2 of the negative temperature coefficient bias circuit 13 becomes a temperature coefficient. Since it is a negative characteristic, it falls. As a result, the output (Vo) state changes above a certain temperature. Since the voltages V1 and V2 are determined by the above equations (1) and (4), both are determined by the V _BE voltage drop.

If V _BE is changed due to process factors, both V1 and V2 are changed in the same direction so that the operating temperature of the multiple shut down does not change.

That is, as shown in the characteristic diagram according to the circuit of the invention of FIG. 4, the normal shut-down time of point (A) and the shutdown point due to V _BE error in the process of point (B) are at the same temperature (To). Will be located.

As described above, the present invention has an effect of not causing circuit protection and malfunction in the integrated circuit since the error of the thermal shutdown temperature is hardly generated.

Claims (1)

In the thermal damage prevention circuit which generates a control signal by protecting the integrated circuit when the temperature is higher than a predetermined temperature, when the temperature rises, the output voltages V1 and V2 rise and fall to the positive and negative characteristic temperature coefficients. According to the band gap function, the positive and negative temperature coefficient bias circuits 11 and 13 and the output voltage V1 of the positive and negative temperature coefficient bias circuits 11 and 13 And a comparison circuit (12) which compares (V2) and makes a control output (Vo).

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