JPS60165804A - Circuit for compensating oscillating frequency against temperature of crystal oscillation circuit - Google Patents

Abstract

PURPOSE:To apply temperature compensation at each temperature zone depending on the type of oscillating frequency of a crystal oscillator by providing a selecting means responding to an output from a temperature detecting element, activating selectively a frequency change means thereby keeping the oscillating frequency of the crystal oscillator circuit constant. CONSTITUTION:A temperature correction circuit consists of temperature compensation circuits 4, 7 and 10. A divided voltage at a connecting point P between any of resistors of the temperature compensation circuits 4, 7, 10 and a resistor R14 is applied via a resistor R15. The resistance value of a thermister R40 is increased as temperature rises. Then a current flowing to a circuit comprising resistors R4a, R4b, R40, R14 and R15 is changed. Thus, a voltage given to a varactor diode D2 is dropped. Then the static capacitance of the varactor diode D2 is increased. The load capacitance being a combined capacitance between a capacitor C14 and the varactor diode D2 of the oscillation circuit 20 is increased in this way. Thus, the oscillation frequency is lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to temperature compensation of third-order frequency temperature characteristics of a crystal resonator.

Background technology In the prior art crystal oscillator frequency temperature compensation.

The crystal oscillation circuit itself was kept at a constant temperature using a constant temperature bath or tube. This prior art requires equipment such as a constant temperature bath, and has the disadvantage of requiring a complicated circuit configuration to maintain a constant temperature.

Purpose An object of the present invention is to provide a temperature compensation circuit for a crystal oscillation circuit that performs temperature compensation in each temperature range for each frequency type of a crystal resonator.

Embodiment FIG. 1 is a block diagram of a temperature detection means according to an embodiment of the present invention, and FIG. 2 is a timing chart of the output of the inverting circuit 1.2 and a graph showing the frequency-temperature characteristics of the crystal resonator. Hereinafter, FIG. 1 will be explained with reference to Figure 2 of the palanquin.

The temperature detection means consists of thermistors R1, R3 and selection means S.

The oscillation frequency of a crystal oscillation circuit (not shown) changes depending on the temperature. For this reason, it is necessary to perform temperature compensation for the crystal launch frequency. The present invention provides a circuit for performing temperature compensation.

When the temperature of the crystal resonator (not shown) is in the temperature range indicated by reference mark A, the input signal voltage Vcc is attenuated by thermistor R1 and resistor R2, which are temperature detection elements, and becomes a low level signal. is input. In addition, the input signal voltage Vcc becomes a low level signal due to the thermistor R3 and the resistor R4, which are temperature detection elements.
The signal is input to the inverting circuit 2. The inverting circuit 1.2 is a circuit that inverts an input signal and outputs the inverted signal. Therefore, the low level signal input to the inverting circuit 1.2 (d) is converted to a noy level signal, and is input to the logic circuit 3 via the line /1.l!2Q.The logic circuit 3 receives all input signals. ) This is a circuit that outputs a signal at the no level only when the level is high. Therefore, three logic circuits input a high level signal to the temperature compensation circuit 4 via the line klO. Further, a signal of the no-y level outputted from the inverting circuit 1 is inputted to the inverting circuit 5 via the line 111. The inverting circuit 5 converts the input high level signal into a low level signal, and converts the input high level signal into a low level signal, and converts the input signal to the line l! A low-level signal is input to the logic circuit 6 via 4'. Further, the high level signal output from the inverting circuit 2 is input to the logic circuit 6 via the line 15. It has the same configuration as the logic circuit 3 with six logic circuits. Six logic circuit lines 14'r: A low level signal is input through the line 15, and a high level signal is input through the line 15. Therefore, the logic circuit 6-digit low level signal is sent to line 111? It is output to the temperature compensation circuit 7 via the temperature compensation circuit 7.

The output from the inverting circuit l which has been inverted by the inverting circuit 5 is on the line 16'? : is input to the logic circuit 9 via. Further, a signal of the /N level outputted from the inverting circuit 2 is inputted to the inverting circuit 8 via a line 17. Inversion circuit 8I
ri, converts the input NO-I level signals to all low levels and connects them to the line L! A low level signal is output to the logic circuit 9 via the circuit 8. Logic circuit 9 has a similar configuration to logic circuit 3. A duck crawls into the logic circuit 9/6. A low level signal is input via /8'. Therefore, the logic circuit 9-digit low level signal is sent to line l! 12' to the temperature compensation circuit 10.

In this way, when the crystal resonator is in the temperature band indicated by reference numeral A, a signal of level 7.

Next, the case where the crystal resonator is in the temperature range indicated by reference mark B will be explained. When the crystal resonator is in the temperature range indicated by reference numeral B, the resistance value of the thermistor R1 becomes small. When input signal voltage Vcc is applied to thermistor R1 and resistor R2.

At this time, since the resistance value of the thermistor R1 becomes small, a high level signal is input to the inverting circuit 1.

One inverting circuit converts the input no-y level signal into a low-level signal, and then converts the input signal to the line l! It is input to the logic circuit 3 via lk. Thermistor R, 3rI′! , when the crystal resonator is in the temperature range indicated by reference mark B, the resistance value does not change. Therefore, when the input signal voltage VCC is applied to the thermistor R3 and the resistor R4, the input signal voltage becomes low level and is input to the inverting circuit 2. The inversion circuit converts the 2-digit low-level signal to 7-high level and sends it to the logic circuit 3 via the line /2t.
A low level signal is input through line I!, and a high level signal is input through line 12, so the low level signal is input to line I! 10 to the temperature compensation circuit 4.

Also, the low level signal output from the inverting circuit 1 is on the line l! It is input to the inverting circuit 5 via 3f.

The inversion circuit 5 converts all low level signals to high level,
Line l! 4t- to the logic circuit 6 via.

Further, the high level signal output from the inverting circuit 2 is input to the logic circuit 6 via the line 17'ft.

A high level signal is input from the logic circuit 6 line/4.775, so the high level signal is input to line 111? It is input to the temperature compensation circuit 7 via the temperature compensation circuit 7.

Further, the high level signal output from the inverting circuit 5 is input to the logic circuit 9 via the line 16.

Further, the high level signal output from the inverting circuit 2 is input to the inverting circuit 8 via the line 17'ft.

Inverting circuit 8#-1' converts all input high-level signals into low-level signals and sends them to logic circuit 9 via line 18.
Enter. A high level signal is input from the logic circuit 9 line/6. A low level signal is input from line 18. At this time, a low level signal from the logic circuit 9I/i is inputted to the temperature compensation circuit IO via the line 112'f.

In this manner, when the crystal resonator is in the temperature band indicated by reference numeral B, a high level signal is input to the temperature compensation circuit 7 and it is activated. Further, a low level signal is input to the temperature compensation circuit 4, IO, and the temperature compensation circuit is disabled.

Next, the case where the crystal resonator is in the temperature range indicated by reference mark C will be explained. At this time, the resistance value of thermistor R1 becomes small, so the input signal voltage ■CC increases to the thermistor R1.
When applied to I and resistor R2, the input signal voltage becomes a high level signal and is input to the 1 inverting circuit 1. Inversion circuit 1
inputs a low level signal to the logic circuit 3 via the line 11. The resistance value of the thermistor R3 also becomes small at this time. Therefore, the input signal voltage VCC is thermistor R3
When applied to the resistor R4, the input signal voltage becomes high level and is input to the 0 inversion circuit 2.

Ru. Two inverting circuits convert the high level signal into a low level signal, and input the low level signal to the logic circuit 3 via the line 12. Logic circuit 3 has lines el, l! Since a low level signal is input through line I!2, at this time the low level signal is input to line I! It is input to the temperature compensation circuit 4 via IO'e.

The low level signal output from the inverting circuit l is connected to line l.
! 3' to the inverting circuit 5. The inverting circuit converts the 5-digit low-level signal into a low-level signal, and then converts the signal to line I! 4' to the logic circuit 6. Also, the low level signal output from the inverting circuit 2 is on line l! 5 to the logic circuit 6. Logic circuit 6 lines 1
A signal of no-y level is input from line I! A low level signal is input from 5. At this time, is the logic circuit 6 digit low level signal? It is input to the temperature compensation circuit 7 via the line ell'.

The high level signal output from the inverting circuit 5 is on line I.
! 6? The signal is input to the logic circuit 9 via the signal gh. Also, inverting circuit 2
The low level signal output from.

The signal is input to the inverting circuit 8. The inverting circuit converts the low level signal inputted through the line E7 into a low level signal and inputs it to the logic circuit 9 through the line f8e.

Logic circuit 9t/'i line I! Since a high level signal is input from 6.18, at this time the high level signal is input to the temperature compensation circuit 10 via the line /12t-.

In this way, the temperature compensation circuit 10 receives the input signal, and the temperature compensation circuit 10 is activated. At this time, a low level signal is input to the temperature compensation circuit 4.7, so
The temperature compensation circuit 4.7 is disabled.

As described above, when the crystal resonator is in the temperature band indicated by reference numeral A, the temperature compensation circuit 4 is activated. Further, when the crystal oscillator is in the temperature range indicated by mark B, the temperature compensation circuit 7 is activated. When the crystal oscillator is in the temperature band indicated by reference C, the temperature compensation circuit IO is activated. The below-zero temperature compensation circuit in which the temperature compensation circuits 4, 7, and 10 perform temperature compensation of the oscillation frequency according to the characteristics of the crystal resonator will be described in detail.

FIG. 3 is an electrical circuit diagram of the temperature compensation circuit. Oscillation circuit 2
0(d) This is a so-called high-order overtone crystal oscillation circuit.Resistors R11 and R12 are connected in connection with the crystal resonator XT,
A transistor Q1 is connected to the transistor Q1. Transistor Q1 includes capacitors C12 and C13 and resistor R1.
3 is connected, and the coil L1 that also constitutes the tank circuit
2. A capacitor C14 and a voltage dependent variable capacitance diode D2 are connected. Although the oscillation circuit 20 can oscillate at the same frequency, frequency deviations occur due to temperature.

As shown in FIG. 2 (3), the frequency-temperature characteristic Vi of the crystal resonator XT forms a cubic curve. In order to cancel out this three-dimensional change, it is considered to change the resonant frequency of the tank circuit. The relationship between the oscillation frequency and the tank circuit resonance frequency is shown in FIG. Further, the relationship between the tank circuit resonance chest wave number and the capacitor capacity is shown in FIG. Further, the relationship between the oscillation frequency and the capacitance of the tank circuit is shown in FIG. As shown in FIG. 6, as the capacitance increases, the oscillation frequency decreases, so temperature correction of one oscillation frequency can be performed by changing the capacitance.

All temperature correction can be performed by changing the capacitance of the capacitor as shown in FIG. 7 111. However, it is difficult to change the capacitor's capacitance three-dimensionally, as shown in Figure 11.

Therefore, the three-dimensional curve of capacitance change is approximated by three straight lines in each temperature range. Capacitors for each temperature range A and B.

The diagram when changing linearly in C is shown in Figure 7 (2).
It is shown in

Referring to the IS3 diagram, a temperature compensation circuit 21, which is a frequency changing means, is composed of temperature compensation circuits 4, 7, and 10. The voltage of the voltage-dependent variable capacitance diode D2 is applied via a resistor R15 as a divided voltage at a connection point P between one of the resistors of the temperature compensation circuit 4, 7.10 and the resistor R14.

As shown in FIG. 10, the capacitance of the variable capacitance diode D2 changes depending on the voltage.

A high level signal is input to the base of the transistor QIO of the temperature compensation circuit 4 via the line flO'. and,
The collector and emitter of transistor QIO are electrically connected. When the temperature of the thermistor R40 rises, the resistance value increases. Therefore, the resistance R4a.

The current flowing through the circuit consisting of R4b, R411, R14, and R15 changes. Therefore, the variable capacitance diode D2
When the voltage is not applied to the current, the voltage decreases. Therefore, variable capacitance D2
The capacitance of increases. In this way, the load capacitance, which is the combined capacitance of the capacitor CI4 and the variable capacitance diode D2 of the oscillation circuit 20, increases. Therefore, the oscillation frequency becomes low. As described above, when the crystal resonator is in the temperature range indicated by reference mark A, the thermistor R40 shows a change in accordance with the temperature, and the capacitance of the variable capacitance diode D2 changes. In this way, temperature compensation of the crystal oscillator is performed.

A high level signal is applied to the base of the transistor Qll of the temperature compensation circuit 7 via the line lll'fr,
The collector and emitter of transistor Qll are electrically connected. As the temperature rises, the resistance of thermistor R41 decreases. Therefore, the resistance R4a +R4b, R40, R14, R
The current flowing through the circuit consisting of 15 changes. Therefore, the voltage applied to the variable capacitance diode D2 increases.
Therefore, the capacitance of the variable capacitance diode D2 decreases.Thus, the load capacitance, which is the combined capacitance of the capacitor C14 of the oscillation circuit 20 and the variable capacitance diode D2, decreases. Therefore, the oscillation frequency becomes high. Further, since the thermistor R41 changes according to the temperature, an appropriate voltage is applied to the variable capacitance diode D2, and the oscillation frequency of the oscillation circuit 20 becomes constant.

When a voltage is applied to the base of transistor Q12 of temperature compensation circuit 10 through line 112, transistor Q1
2 collector and emitter are electrically connected. The following operation is similar to that of the temperature compensation circuit 4.

In the embodiment shown in the first figure, temperature correction is performed by dividing one frequency characteristic into three, but it is also possible to perform temperature correction by dividing it in multiple stages. Is there a temperature detection element? It is also possible to use one unit to detect the temperature in one step.

Effects As described above, according to the present invention, temperature compensation can be performed in each temperature range for each type of oscillation frequency of a crystal resonator.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the temperature detection means according to an embodiment of the present invention, FIG. circuit diagram. Figure 4 is a graph showing the relationship between oscillation frequency and tank circuit resonance frequency, No. 51S! 4 is a graph showing the relationship between tank circuit resonance frequency and capacitor capacitance, Figure 6 is a graph showing the relationship between oscillation frequency and capacitor capacitance, and Figure 7 is the operation of the temperature compensation circuit. r[For clarity, Figure 1g8 is a diagram showing the relationship between capacitance and voltage of a variable capacitance diode. 1.2, 5.8... Inversion circuit, 3, 6.9... Logic circuit, 4, 7.10... Temperature compensation circuit, 20... Oscillation circuit, 21... Temperature compensation circuit , R1, R3, R40
R4], R42... Thermistor agent Patent attorney Kei Nishi Part Figure 1 Figure 4 Figure 5 Figure 6 Stone t Capacity 1 Voltage

Claims (1)

[Claims] A crystal oscillation circuit. a plurality of frequency changing means for changing the oscillation frequency in a plurality of predetermined ways depending on the temperature; With temperature detection element. Oscillation frequency temperature compensation for a crystal oscillation circuit, comprising selection means for selectively activating one frequency changing means in response to an output from a temperature detection element, thereby keeping the oscillation frequency of the crystal oscillation circuit constant. circuit.