JPS6023987Y2 - Variable capacitance diode temperature compensation circuit - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a temperature compensation circuit for a variable capacitance diode.

In electronic tuning tuners using variable capacitance diodes, variations in the tuning frequency occur due to changes in capacitance due to temperature changes.

Therefore, a temperature compensation circuit is required.

The present invention changes the bias voltage in response to temperature changes,
Therefore, fluctuations in capacitance value are suppressed.

Figure 1 is a capacitance change-temperature characteristic diagram using the bias voltage V3 of the variable capacitance diode as a parameter, and Figure 2 is a temperature-bias voltage fluctuation value characteristic diagram when capacitance change is compensated for by bias voltage fluctuation. .

That is, the vertical axis in FIG. 2 shows the variation value of the bias voltage necessary to keep the capacitance constant despite temperature changes.

Therefore, if a bias circuit having the temperature characteristics shown in FIG. 2 can be realized at each bias voltage, capacitance changes due to temperature will be completely compensated for.

Comparing the case with a high bias voltage and the case with a low bias voltage from the characteristic diagram of FIG. 2, it is found that a large bias variation is required in the case of a high bias voltage.

The present invention takes this point into consideration, and a specific example thereof is shown in FIG.

1 is a constant voltage diode, 2 is a general silicon diode, and the breakdown voltage of diode 1 is appropriately selected depending on the operating voltage of the variable capacitance diode.

The voltage applied across diode 1 has a positive temperature coefficient, and the voltage applied to diode 2 has a negative temperature coefficient.

The diodes 1 and 2 are combined, and a voltage whose voltage (Vl) has an appropriate positive temperature coefficient is applied to the variable resistor 3 and the tungsten lamp 4 as a whole.

That is, V□=V1+αT・・・・・・・・・■ The following formula holds true.

On the other hand, the resistance value R of the tungsten lamp 4 increases approximately in proportion to the temperature.

R=Hikiju βT・・・・・・・・・■ Therefore, the voltage taken out from the movable terminal of the variable resistor 3 (
Vout) is Vout V, +crT -R7R+R8+β1 (Ro +βT +RVR・k)・
......■.

Here, (k) is a coefficient corresponding to the rotation of the variable resistor 3.

Here, if we rearrange the formula as βT<Ro×RVR, Vout=1, RVR−Ro[■1(Ro×RVR−k)+(βv1
+α(Ro+RvR−k))T].

According to this equation, it can be seen that the coefficient of (T) increases as the bias voltage increases.

In reality, (RVR) is about IOKΩ, and (R) is 500Ω.
By appropriately selecting the values of α and β, a device having characteristics close to those shown in FIG. 2 can be obtained.

According to the present invention described above, based on temperature changes (because the variation in bias voltage is proportional to the bias voltage value,
Accurate temperature compensation is possible.

[Brief explanation of drawings]

Figure 1 is a capacitance change-temperature characteristic diagram of a variable capacitance diode.
FIG. 2 is a temperature-bias voltage characteristic diagram when capacitance changes are compensated for by variations in bias voltage, and FIG. 3 is a temperature compensation circuit diagram of a variable capacitance diode according to the present invention. 1.2 is a diode, 3 is a variable resistor, and 4 is a lamp.

Claims (1)

[Scope of utility model registration request] A series circuit of a variable resistor and a lamp is connected in parallel to a series circuit of a backward-connected diode with positive temperature characteristics and a forward-connected diode with negative temperature characteristics, and the power supply voltage is applied to this parallel circuit. A variable capacitance diode temperature compensation circuit configured to derive a bias voltage having positive temperature characteristics to be applied to the variable capacitance diode from between the movable terminal of the variable resistor and one end of the lamp.