JP2729815B2 - Power consumption reduction method of digital temperature compensated oscillator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital temperature-compensated oscillator configured to compensate for a change in oscillation frequency due to a temperature change based on digitally encoded temperature information, and more particularly to a digital signal processing oscillator. The present invention relates to a control method of a digital temperature compensation circuit for minimizing current consumption.

(Prior art) As means for suppressing fluctuations in the oscillation frequency due to temperature changes and always obtaining a stable output, the ambient temperature information is converted into a digital signal, and the control voltage code to be output corresponding to each temperature is stored by this signal. There is a digital temperature-compensated oscillator configured to generate a control voltage to be read from the memory device and to be supplied to the voltage-controlled oscillator based on the control voltage code. This digital temperature-compensated oscillator has attracted attention from the viewpoint of accuracy and adaptability to mass production.

FIG. 2 is a block diagram illustrating a configuration example of a conventional digital temperature compensated oscillator and a control example thereof.

As the voltage controlled oscillator, an oscillator using a crystal oscillator (VCXO) is generally used. Hereinafter, the oscillator using the VCXO will be mainly described, but the present invention is limited to this example. There is no.

In FIG. 2, reference numeral 1 denotes an oscillator as a temperature sensor whose oscillation frequency changes sensitively in response to temperature. For example, 40 KHz at normal temperature (25 ° C.), 20 ppm per degree (1 ppm is 1 / million). The oscillation frequency changes at the ratio of

The output of the sensor oscillator 1 is converted into a low-period pulse waveform by the frequency divider 2 to control the gate circuit of the frequency counter 3.

The frequency counter 3 receives the output of a voltage controlled crystal oscillator (VCXO) 4 to be compensated, divided by a second frequency divider 5 and inputted to the frequency counter 3. The frequency of the VCXO 4 passing through the gate circuit is divided. The number of pulses of the signal is counted.

In this case, since the output frequency of the temperature sensor oscillator 1 fluctuates due to a change in temperature, the number of signal pulses from the VCXO 4 measured by the frequency counter 3 fluctuates with temperature, and this pulse number is used as information representing the temperature at that time. Is extracted.

Therefore, a digital signal of a predetermined bit is created in the next address register 6 based on the result counted by the frequency counter 3, and the digital signal is input to a ROM 7 storing a compensation voltage code to be output as an address signal.

When an address signal is input to the ROM 7, a digital signal stored at each address is output, which is converted into a DC voltage by the D / A converter 8 and applied as a control voltage of the VCXO4.

In this example, the case where temperature information is obtained by counting the output frequency of the VCXO 4 by the output pulse of the sensor oscillator 1 has been shown. However, the frequency counter 3 is changed by changing both the oscillation frequencies or the respective frequency division ratios. The one in which the relationship between the gate control signal and the reference pulse in counting is reversed from that in the above example has been put to practical use.

By the way, in such a digital temperature-compensated oscillator, temperature measurement is performed at a predetermined cycle, that is, a frequency counting operation is performed. In general, digital signal processing requires a relatively large amount of current according to a clock frequency. The required current is consumed every time the temperature compensation operation is performed.

When such an oscillator is used in a small portable device, it is a major issue how to reduce the current consumption in view of a balance between a built-in battery capacity and a use time.

(Object of the Invention) The present invention has been made in view of the above, and provides a method for reducing the current consumption of a digital temperature compensated oscillator. It is an object of the present invention to provide a digital compensated oscillator that prevents an increase in current consumption due to the above-described operation and suppresses the power consumption to a minimum necessary.

(Summary of the Invention) In order to achieve the above object, the present invention provides a digital temperature-compensated oscillator in which the temperature change status from the previous time or several times before is stored before extracting temperature information for compensation,
If there is no temperature change compared to the present result, control is performed so that the compensation voltage is not updated and the interval until the next temperature compensation operation is lengthened.

Further, if necessary, the compensation interval can be shortened when the temperature change is large.

As described above, the present invention is characterized in that the power consumption is reduced by controlling the compensation operation interval time according to the temperature change situation, and the compensation accuracy is improved.

(Embodiment) Hereinafter, a method for reducing power consumption of a digital temperature compensated oscillator according to the present invention will be described in detail based on an embodiment shown in the accompanying drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.
The same parts as those in FIG. 2 are denoted by the same reference numerals, and duplicate description will be omitted.

In this figure, reference numerals 1 to 8 denote temperature sensor oscillator, frequency divider, frequency counter, VCX
O, address register, ROM and D / A converter.

In this embodiment, a controller 9 and a third frequency divider 10 are provided in addition to the above-described blocks, and the controller 9 detects a temperature change situation, and controls the repetition period or interval of frequency counting according to the result. .

The controller 9, the first signal P ₂ which is further divided by the signal pulses P ₁ frequency divider 10 of the frequency divider 2, a digital signal P ₃ of the counting results from the frequency counter 3 and the address register 6 the inputs the output P _4, giving respectively the signal P ₅ which is produced on the basis of these signals to the frequency counter 3 and the address register 6 and ROM7 and the second frequency divider 5.

 The operation of the above configuration will be described.

The output of the temperature sensor oscillator 1 that changes according to the temperature is converted into a pulse P ₁ having a pulse width of 0.01 sec every 0.1 sec by the frequency divider 2 and input to the frequency counter 3. The pulse P ₁ is simultaneously supplied to the controller 9 by the third frequency divider 10 as a pulse P ₂ having a period of 1.6 sec.

The frequency counter 3 are inputted oscillation output of 12.8MHz of VCXO4 becomes the 6.4MHz by the second frequency divider 5, this signal frequency is counted pulses P ₁ from the divider 2 as a gate pulse The count value is converted into an address signal in the address register 6 and then input to the ROM 7.

At this time, the latest address value is stored in the address register 6 until the next counting is performed.

In ROM7, a compensation code is stored in correspondence with each address value, and this compensation code is stored in VCXO4
Represents the control voltage to be applied to the DA converter 8
Is converted into a DC voltage.

The DC voltage generated in this way is applied to the VCXO4 as a frequency control voltage, and the VCXO
The signal of 4 is given to the necessary device as an oscillation output.

The above control is based on the cycle of the output pulse P1 of the _first frequency divider 2.
It is performed every 0.1 sec.
The address register 6, the ROM 7, and the D / A converter 8 operate, and a relatively large current is consumed by this operation.

Therefore, in the present invention, current consumption is reduced by causing the controller 9 to function as follows.

The output P ₁ of the frequency divider 2 is supplied to the controller 9 as a third frequency divider.
Has been further frequency-divided by applying periodic pulse P ₂ next 1.6sec by 10, firstly, the counting result of the previous stored frequency count result by 0.1sec period ahead in the address register 6 (previous) Compare.

This comparison is performed by the controller 9 by comparing the signal P ₃ (current measurement result) and P ₄ (previous measurement result) inputted thereto. performs frequency measured after 0.1sec based on pulse P _1, similarly as compared with the previous measurement result to detect the change.

As described above, the compensation operation is performed every 0.1 second while the temperature change is detected, and the control voltage based on the sequentially updated address code is supplied to the VCXO 4.

Next, when there is no temperature change, the previous measurement result and the present result are the same, so at this time, the contents of the address register 6 are not updated and the access to the ROM 7 is not performed, and thereafter, the operation is rapidly performed. Assuming that there is no temperature change, the controller 9 immediately outputs the pulse P ₅ (disable signal) and stops the operations of the frequency counter 3, the frequency divider 5, the address register 6 and the ROM 7.

During this time, the compensation code by the D / A converter 8 is fixed to that immediately before the disable signal is output.
The control voltage to VCXO4 is fixed at the value at that time.

At the same time, the controller 9 sets a 1.6-sec synchronization pulse P ₂
When but entering said releasing the disable pulse P _5, and starts counting again, thereby comparing the results with previous count result obtained in the same manner as if it finds a difference count value of the time performs updating of the address register as an address, performs the following counting operation after 0.1sec by P ₁ pulse. If the result both of the following measurements are the same, and outputs a disable pulse P ₅ from Kotorora 9 again.

In this way, if no temperature change is detected,
If the counting operation is performed every 1.6 seconds, unnecessary counting operation can be omitted and current consumption can be greatly reduced.

In the above example, when there is no temperature change, the following compensation operation is performed as 1.
Although the interval is fixed at 6 seconds, the present invention is not limited to this and various modifications are possible.

For example, if none of the temperature changes were detected as a result of performing the past several times of compensation operations with an interval of 1.6 seconds,
By further increasing the interval, power consumption can be further reduced.

For this purpose, the number of times that the temperature change is not recognized is stored in memory, and when the number exceeds a predetermined number, the interval until the next compensation operation is further divided by two to divide the signal P ₂ by 3.2 seconds. P 'and produce a ₂ becomes pulse, carried out according to this timing.

As a further modified example, when a large temperature change is found in the comparison between the previous temperature measurement result and the current result, the interval until the next time can be shorter than 0.1 sec.

According to this method, more accurate compensation can be performed following a rapid temperature change.

Each numerical value shown in the above embodiment is an example, and the present invention is not limited to this.
c, 1.6 sec, etc. may be arbitrarily changed according to the surrounding environment in which these oscillators are used, and can be widely applied not only to VCXOs but also to voltage-controlled oscillators and the like.

Further, one memory in the controller 9 is added, and the count values of the previous one and two times are respectively stored in each memory, and these two previous count values are compared with the present count value. When the three match, the interval until the next count is extended, and when the previous two counts do not match the current count, the interval until the next measurement may be shortened. . Alternatively, two or three memories may be added, and the measured values three times before and four times before may be compared with the current measurement.

(Effects of the Invention) As is clear from the above description, the present invention reduces the compensating operation during the period in which there is no temperature change in the digital temperature compensated oscillator as much as possible, so that the current consumption can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional digital temperature compensated oscillator. Reference numeral 1: temperature sensor oscillator, 2, 5, and 10 ... frequency divider 3 ... frequency counter 4 ... VCXO, 6 ... address register, 7 ... ROM, 8 ... DA converter, 9 ...
controller

Claims (1)

(57) [Claims] 1. A temperature sensor oscillator whose oscillation frequency changes according to temperature, a voltage control oscillator which controls the oscillation frequency by voltage, and a gate circuit controlled by the output of one of these two oscillators to output the other oscillator. A frequency counting circuit for counting the frequency,
And a digital temperature-compensated oscillator that generates a control voltage to be supplied to the voltage-controlled oscillator based on the counting result of the frequency counting circuit. A method for reducing power consumption of a digital temperature-compensated oscillator, characterized in that: