JPS6140527A - Temperature measuring oscillation circuit - Google Patents

Abstract

PURPOSE:To reduce the rising in the temp. of each circuit element and the heat generation of a temp. sensitive element itself, by controlling the start and stop of oscillation operation by a control signal. CONSTITUTION:A feedback signal is applied to one input terminal of an AND circuit G and a control signal Sc is applied to the other input terminal thereof. The output of the circuit G is amplified by first and second complementary push-pull amplifier (constituted of resistors R1, R2, capacitors C1, C2 and transistors Q1, Q2) having mutual reverse phase outputs and the feedback signal is applied to one input terminal of the AND circuit G from the output of each amplifier through one of feedback circuits. A temp. sensitive element TH is inserted in one of the feedback circuits in series and a capacitor CT is inserted in the other feedback circuit in series and the start and stop of oscillation operation are controlled by a control signal and a pulse like signal with a cycle proportional to temp. is obtained.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an oscillation circuit for temperature measurement that generates a pulse-like signal with a period corresponding to temperature. "Temperature and humidity detection device" filed separately
(Utility Model Publication No. 54-32954),
A first inverter and a second inverter are connected in cascade,
Positive feedback is applied from the output of the second inverter to the input of the first inverter via a series circuit of a capacitor and a resistor, and between the output of the first inverter and the common connection point of the capacitor and resistor. A temperature detecting element such as a thermistor is connected to the oscillator, and the oscillation frequency is controlled by changing the resistance value of the temperature detecting element according to the temperature, thereby obtaining a pulse signal having a frequency inversely proportional to the temperature. ing.

However, when using this method, the oscillation frequency must be set high when high accuracy is required for temperature measurement, and in order to process the oscillation signal by a digital circuit such as a processor, the frequency must be divided by a frequency divider. The device configuration becomes complicated and expensive, and continuous oscillation is required, resulting in heat generation due to temperature rise of the circuit elements and energization of the temperature detection element itself. This method has drawbacks such as easy measurement errors.

Generally, a method is also adopted in which the temperature detection element is used as one side of the bridge circuit, and the unbalanced state of the bridge circuit due to a change in the resistance value of the temperature detection element is detected as a voltage.
In this case, when the detection output is processed by a digital circuit, an analog-to-digital converter (hereinafter referred to as ADC) is required, which has the same disadvantage of being expensive as described above.

[Summary of the invention]

The present invention has the purpose of fundamentally solving such drawbacks of the conventional art, and provides a feedback signal to one input of an AND circuit, and a control signal to the other input, thereby controlling the output of the AND circuit. Each of the first
and a second complementary push-pull amplifier,
A feedback signal is given from the output of each amplifier to one input of the AND circuit through the first and second feedback circuits, and the resistance value is set depending on the temperature of either one of the feedback circuits. Insert temperature-sensitive elements that change in series, and insert five capacitors in series in one of the other feedback circuits,
The present invention provides an extremely effective temperature measurement oscillation circuit that controls the start and stop of oscillation by a control signal and obtains a pulsed signal with a period proportional to temperature.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to figures showing examples.

Figure 1 is a basic circuit diagram in which a feedback signal is given to one input of a NAND gate G as an AND circuit via a resistor R1, and the other input is given a feedback signal via a resistor R1. , a control signal So of "H" (high level) is given from the input IN, and the NAND gate G turns on and performs oscillation only while this is @H", while this is @L" (low level). If so, the NAND gate G will be turned off, so
It is designed to stop the oscillation operation.

The output of NAND gate G is connected to resistor R2+R3, capacitor C1+C2 and transistors Qt, Q2K
It is inverted and amplified by a first complementary push-pull amplifier (hereinafter referred to as CPA), which has a multiplicity of configurations, and an inverter I
Through N, resistor R4+ R5, capacitor C3+C4
and transistor Q3. The outputs are inverted and amplified by the second CPA consisting of Qa, and the outputs, which are in opposite phases to each other, are connected to a NAND gate via a resistor R1.
For each input of G, the thermistor T as a temperature sensing element
A feedback signal is given to each individual through a first feedback circuit in which a capacitor CT is inserted in series and a second feedback circuit in which a capacitor CT is inserted in series.

However, the output of CPA by transistors Ql and Q2 is in phase with the input of NAND gate G, and transistor Qs
, the output of CPA by Q4 is in reverse phase with the input of NAND gate G, and is connected to capacitor cT via thermistor TH.
The terminal voltage of the capacitor 0 is given as a feedback signal, and each CP
The output impedance of A is sufficiently low (it is possible to supply sufficient voltage and current for driving the input of the NAND gate G and driving the charging and discharging of the capacitor cT, as well as grounding to the common potential.

Therefore, when the control signal So becomes IH', it starts oscillating at a period corresponding to the capacitance value of the capacitor cT and the resistance value of the thermistor TH, and the waveforms of each part in Fig. 1 are shown in Fig. 2). , the feedback signal (a) given to the input of the NAND gate G changes according to the charging and discharging of the capacitor 0, which undergoes waveform shaping and inversion in the NAND gate G and becomes the output (b). The inverter INK can be inverted and become the output (c), and the output O
It will be sent from the UT.

Also, for outputs (b) and (e), transistor Q
The output (d) of the CPA by Q1+Q2 and the output (@) of the CPA by the transistor Qs+Q4 are each inverted, so that the output (d) is @H'' and the output (e) is @L''.
At this time, a charging current passes from the output (d) to the output (e) via the capacitor cT and thermistor TH, and the resulting terminal voltage of the thermistor TH is applied to the input of the NAND game (G) as a feedback signal (a).

This feedback signal (a) is high at the beginning of charging of the capacitor cT, decreases as charging ends, and initially the output (b
) is set to "L", but when it drops to the input response threshold voltage VTR of the NAND gate G, the output (b)
changes to @H”, and accordingly, the output (a) changes to “L”, the output (・) changes to @H#, and at this time, the capacitor CT
The voltage remaining as charge charge to 'H# is the power supply voltage v
If it is equal to nn, it becomes VDD -VTR, which causes the output (d) @L# to use the positive side as the reference potential, so the feedback signal (l> goes in the negative direction until -(Vnn-VTa). Then, the output (@) is charged in the opposite direction, and the terminal voltage of the capacitor 0 becomes the feedback signal (&), with the initial output value being @H#. However, when the feedback signal (1) gradually rises and reaches the VTR, the output (b) becomes 1L" and the output (e) becomes -H', so the output (d) becomes @H" and the output (・) changes to 'L', and at this time, the voltage VT remaining as charge in the capacitor cT
The feedback signal (a) rises to VDD + VTH due to the sum of R and VDD, after which the discharge and output (d
), and the above operation is repeated.

Here, each rising and falling period of the feedback signal (a) due to charging and reverse charging of the capacitor cT is t,
If l t2, the period T is given by the following equation.

T = t 1 + t z ・・・・・・・・・・・・ (1) However, Rτ: resistance value of thermistor T, V7H: NA
NI) Input response threshold voltage of gate G VDD: Power supply voltage Therefore, vTn = "/2" VDn ttL
tf, Equation (1) C, becomes the following equation.

T Medium 1・IRr110+1・IR・cT;2・2R
T@CT ・・・・・・・・・・・・・Old・・・・・・・−(
2), e7.9. ,c,81,1□. Ahhh. Yoyo 2
If the temperature changes, the temperature can be measured by detecting the period T by counting clock pulses or the like.

In FIG. 1, the CPA is provided for feedback to the input of the NAND gate G.
and the output impedance yy of the inverter IN is C-M
OS (Complementary-Metal O
xldeSemiconductor, ),
This is because it is as high as 5,000 to several Ω, making it impossible to obtain sufficient output voltage, current, and ground fault effect, causing errors in the charging and discharging period of the capacitor cT, and making it difficult to obtain the conditions of equations (1) and (2). Ashi, resistor R2 ~ Capacitor 01 ~ in parallel with Rs
C4 shortens the response time of transistors Q1-Q4,
The purpose is to make the waveform change steeper.

In addition, in Fig. 1, the causes of measurement errors are: la, the nonlinear characteristic of the temperature sensing element lb, and the variation in VTH due to the temperature of the gate circuit 1eS
response delay time of us 1 dS gp fluctuation of output voltage due to temperature le,
Variations in capacitance value due to temperature of the capacitor cT, etc. can be eliminated by the following measures or reasons.

2m, corrected by processor processing or correction circuit.

2b, C-MO8 circuit jVyu/jθ=-3m
When V/°C is used and θ=θ to 50°C, it is 0.06% F8 or less and can be ignored.

2e, υ can be ignored by increasing the period T.

, 2a, In the case of the C-MO8 circuit, there is no particularly large variation and can be ignored.

2Q1 Select one with temperature characteristics that do not cause any problems within the allowable range.

Therefore, NAND game) G% inverter INK C
- By using an equivalent MO8 circuit tfc and applying each of the conditions 2- and 2., it is possible to obtain a sufficiently large period T.J), the conditions 2c are also satisfied, and it is stable and Realizes highly accurate temperature measurement.

In addition, M is not required, and by making the period T large, a frequency divider, etc. is not required), the whole device becomes cheaper, and the polling signal etc. are used only during measurement as the control signal It is possible to freely perform the oscillation operation only at this time, reducing power consumption, temperature rise of each circuit element, and self-heating of the temperature sensing element, and improving measurement accuracy. .

FIG. 3 is a circuit diagram showing another embodiment), in this case, the resistor Rtt t R12 and the capacitor C11zC1
2 and the first C by transistor Qtt TQ12
PA, resistor RIM +R14, capacitor C13r
C14 and a second CPA formed by transistor Q13*Qr< are connected in cascade, and inverters IN1 and IN2 are connected in parallel with each of them, and the in-phase output of CPA by transistor Qn JQ12 is connected to NAND through resistor R1. A capacitor cT is inserted in series in the first feedback circuit between the input of the gate G, while a second By inserting a he thermistor TH in series in the feedback circuit, the phase of the pulsed signal from the output OUT is inverted compared to that shown in Fig. 1, but the operating situation is the same as that shown in Fig. 1. .

However, the input resistor voltage of each CPA is fixed by the base-emitter voltage VBX of the transistors Q1t to Q14, which is approximately 1.4V, whereas the C-M
The input resistor voltage of the O8 circuit goes low at approximately 2.5V, and the response to the rise from @L" to @H" is for each CPA.
Even if IN1. Since IN is faster, each CPA and inverters IN, IN, and IN2 are connected in parallel with each other in order to make the multi-waveform change steeper due to faster response operations.

In addition, in FIG. 3, a CP with sufficient front drive output
A is connected in cascade), the operation is more stable than in FIG.

In addition to the thermistor TH, other equivalent elements may be used as the temperature sensing element depending on the conditions, and the same effect may be obtained by using a gate, inhibit gate, etc. in place of the NAND gate G. It is sufficient that each CPA generates outputs in phase opposite to each other, and various modifications are possible, such as by appropriately inserting an inverter or the like on the input side according to situation 1.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, a pulse-like signal having a period corresponding to the temperature can be immediately obtained, and in particular, an AD
It does not require a C1 frequency divider, has an overall inexpensive configuration, and can be operated only when it is not needed, reducing the temperature rise of each circuit element and the self-heating of the temperature sensing element. Since the temperature is reduced, the measurement situation is stable and accurate, and a remarkable effect can be obtained in various temperature measurements.

[Brief explanation of drawings]

The figure shows an embodiment of the present invention, and FIG. 1 is a basic circuit diagram;
Figure 2 shows the waveforms of each part in Figure 1. IN11 IN
2@...Inverter, Q1~Q4, Qt+~Q14
...transistor, TH...fist? -Mister (temperature sensing element), CT...capacitor, Sc...-
Control signal.

Claims (1)

[Claims] an AND circuit to which a feedback signal is given to one input and a control signal to the other input; a first and a second exhibiting an output impedance;
a complementary push-pull amplifier, first and second feedback circuits each providing a feedback signal from each output of each of the amplifiers to the one input; 1. A temperature measurement oscillation circuit comprising: a temperature sensing element whose resistance value changes depending on the temperature; and a capacitor inserted in series with one of the feedback circuits.