JPH04181130A - Temperature detecting circuit - Google Patents

Abstract

PURPOSE:To linearize a change in output voltage with respect to temperature to improve accuracy in temperature detection by making constant current flow to a transistor and outputting differential voltage between a base and an emitter by an operational amplifier. CONSTITUTION:When reference voltage obtained by dividing voltage Vcc by resistors 6, 7 is assumed to be Vref, output voltage Vout1 of an operational amplifier 1 is Vref+kT/qX1n(mXn) where (q) is a charge amount, (k) is Boltzmann's constant, T is absolute temperature Kelvin, (m) is a ratio of a current value of a constant current source 5 to a current value of a constant current source, and (n) is a ratio in area of an NPN transistor 3 to an NPN transistor 2. Thus reversed saturated current and temperature characteristics of a current value I1 of the constant current source 4 are canceled so that the voltage Vout1 is completely proportional to the absolute temperature T. An amount in change of the voltage Vout1 with respect to temperature can be set as desired by changing a ratio (m) in current values of the constant current sources 4, 5 and a ratio (n) in area of the transistors 2, 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a temperature detection circuit that outputs a voltage that is proportional or inversely proportional to temperature.

! Conventional technology] FIG. 4 is a circuit diagram of a conventional temperature detection circuit.

In the figure, (1) has diodes (13) to (
15) is connected to a constant current source (12) to which the reference voltage Vt generated is connected, and the output is fed back to the single power source.Next, the operation will be explained. Diode (13) ~ (1
By connecting a constant current source (12) to 5), the generated reference voltage mat becomes as shown in the following equation (1).

q: Electron charge k: l/L/Tumann's constant T: Absolute temperature Kelvin operational amplifier (1
) The temperature detection circuit configured as above utilizes the fact that the diode-generated voltage VD decreases in inverse proportion to the temperature.

[Problem to be solved by the invention] Since the conventional temperature detection circuit was configured as described above, due to the temperature characteristics of the reverse saturation current Is and the temperature characteristics of the constant current I3, the change in VD with respect to temperature is completely It's not a straight line, and the accuracy is poor. Since the amount of change in the output voltage Vout4 with respect to temperature is determined only by the number of 11M diodes, it is restricted by the output voltage level or the power supply voltage, and there are problems such as not being able to freely set the amount of temperature change.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a temperature detection circuit that is highly accurate and can arbitrarily set the amount of change in six voltages with respect to temperature.

Means for Solving the C# Problem] The temperature detection circuit according to the present invention has an emitter connected to an inverting input terminal of an operational amplifier, a base and a collector connected to a short circuit, and a temperature detection circuit connected to an output terminal of the operational amplifier. a first transistor of one conductivity type;
a first constant current source connected to an inverting input terminal of the operational amplifier, a first transistor having an emitter connected to a non-inverting input terminal of the operational amplifier, and a base connected to a reference voltage or a collector to another reference voltage; a second transistor of the same conductivity type and having a different area ratio from that of the first transistor; a second constant current having a different magnitude from that of the first constant current source connected to the non-inverting input terminal of the operational amplifier; [Function] The temperature detection port 17& in this invention outputs the differential voltage between two base-emitter voltages ("JBE") generated by flowing a constant current through the transistor using an operational amplifier. Because of this configuration, the change in output voltage with respect to temperature is completely linear, and the amount of change in output voltage with respect to temperature can be arbitrarily set by changing the area ratio of the transistors or the size of the constant current source.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the temperature detection circuit of the present invention. In the figure, the emitter of (2) is connected to the operational amplifier (1)'s power source and constant current source (5), the base and collector are shorted, and the terminal (a) of the operational amplifier (1) is connected to the (9NPN) terminal.
The other end of the constant current source (5), which may be a transistor, is G
Connected to the ND line.

The emitter of (3) is connected to the operational amplifier (1) and constant current source (4), and the base is a resistor (6
) and (7), and are NPN transistors whose collectors are connected to the Vcc line. Constant current source (4)
The other end of the resistor (7) is connected to GND.
line and the other end of the resistor (6) is VCC
Connected to the line, NPN) Fungistar (
The area ratio of 3) is NPN) D times that of Langinuta (2), which is 1
, the current value of the constant current source (5) is m times the current value of the constant current source (4). Next, the operation will be explained. ・Resistors (6) and (7) K Therefore, Vcc is divided by the resistance. If the reference voltage obtained by
The output voltage Voutl is expressed by the following equation (2).

kT I+ kT mxIIV
out + = Vref −−1n −+ −In
-q nXEs q l5 kT mXnXUIXZs =Vref'+〒1'-Komicho"=Vref'+"In (mXr+)
...-(21IP current value m of constant current source (4) = constant current source (5) for current value of constant current source (4)
Ratio of current values rI: NPN) to transistor (2)
Area ratio of I-transistor (3) In the above equation (2), the temperature characteristics of the reverse saturation current rs and the current r of the constant current source are canceled, and the output voltage Vo
It is clear that ut is perfectly proportional to the absolute temperature T.

In addition, the amount of change in the output voltage moutl with respect to temperature is determined by the ratio m of the current value of the constant current source (5) to the current value of the constant current source (4), and the NPt for the fungistor (2).
1) It can be arbitrarily set by changing the area ratio p of the lung nut (3).

Note that in the above embodiment, NPN) transistors (2) (3
), but PNP) fungistars (8) and (9) may also be used as in other embodiments shown in FIG. ! In addition, if you want to further increase the amount of change in output voltage with respect to temperature, as in another embodiment shown in FIG.
Connect diodes to the emitters of NPN) transistors (2) and (3).
Just add 1). Output voltage in this case ~ out3
is expressed as the following equation (3).

[Effects of the Invention] As described above, according to the present invention, the difference voltage between two base-emitter voltages (VBE) generated by flowing a constant current through a transistor is outputted to r by a v-sational amplifier. With this configuration, the change in output voltage with respect to temperature is completely linear, improving the accuracy of temperature detection, and the amount of change in output voltage with respect to temperature can be controlled by changing the area ratio of the transistor or the size of the constant current source. It has the effect of being able to be set arbitrarily.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a temperature detection circuit that is an embodiment of the present invention, FIGS. 2 and 3 are circuit diagrams of a temperature detection circuit that is another embodiment of the invention, and FIG. This is a circuit diagram of a temperature detection circuit. In the figure, (1) is an operational amplifier, (2)
, (3), (10), (111 is an NPN? transistor, (41, (51 is a constant current source, (8) i9) is a PNP) transistor. In the figures, the same symbols are the same or equivalent. I'll show you the part

Claims (1)

[Claims] a first transistor of a first conductivity type, the emitter of which is connected to the inverting input terminal of the operational amplifier; the base and collector thereof are short-circuited; and the first transistor of the first conductivity type is connected to the output terminal of the operational amplifier; a first constant current source having the same conductivity type as the first transistor having an emitter connected to the non-inverting input terminal of the operational amplifier, a base connected to a reference voltage, and a collector connected to another reference voltage; The second transistor has a different area ratio from the first transistor.
A temperature detection circuit comprising: a transistor; and a second constant current source connected to a non-inverting input terminal of the operational amplifier and having a different size from the first constant current source.