JPH0376418A - Rtc circuit - Google Patents

Abstract

PURPOSE:To obtain a frequency characteristic with high accuracy and to attain backup a power supply for a long time by using 1st and 2nd backup means for a prescribed time T after interruption of power so as to make the same operation as at the time of energizing and using the 2nd backup means so as to operate only an RTC section after the time T elapses. CONSTITUTION:An oscillation section 2 and a frequency divider section 3 are energized by a battery B1 when no power is applied to the entire device, an RTC section 1 is energized by a battery B2 as the backup power, then the device continues the operation, and the RTC section 1 is operated based on an external clock from the oscillation section 2 the same as at the time of energizing. The battery B1 is discharged out into a no voltage state after a prescribed time T1, and the oscillation section 2 and the frequency divider section 3 stop the operation. Then the RTC section 1 continues its operation by the power supplied from the battery B2 and is operated based on a frequency f1 of a crystal vibrator Y of a self exciting oscillation circuit in such a state, the circuit is cooled to ambient temperature after the non-energized time T1 and the deterioration in the frequency accuracy due to temperature change is prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an RTC (real-time clock) circuit incorporated in various devices having a timer function.
In particular, the present invention relates to an RTC circuit that operates using the power source of the device when the device is energized, and is backed up by a dedicated battery when the device is not energized.

[Prior Art] FIG. 3 shows an RTC circuit using this type of conventional self-oscillation method.

While the device is energized, the switch S4 is on, the switch S2 is off, and the power Vin from the device is supplied to the RTC section l.

When the device is not energized, switch S+ is off and switch S2 is off.
is turned on, and the power supply vb is supplied from the backup battery B to the RTC circuit l. The oscillation frequency in the RTC section I can be adjusted by adjusting the capacitance of capacitors Cr and Ct connected across the crystal oscillator Y.

An RTC-dedicated IC is used for the above RTC part I, but the clock frequency required for this type of IC is usually about 32 KHz, which is extremely low for an oscillation frequency using a crystal oscillator Y. It was very difficult to obtain good temperature characteristics.

Furthermore, in a device in which this RTC unit is incorporated, the internal temperature increases due to the power consumed by the device when the device is energized, and the temperature difference between when energized and when it is not energized becomes a factor that reduces the wave number accuracy of the RTC circuit layer. Ta.

FIG. 4 shows a conventional RTC circuit using an external clock injection method. The oscillator 2 and the crystal oscillator Y' oscillate a clock higher than the frequency required by the RTC section 1, and this clock is divided by the frequency divider 3 to generate the RTC.
It is supplied as a clock for section I.

When the frequency of the crystal oscillator Y° is increased as in this circuit example, it is easy to obtain a crystal oscillator with good temperature characteristics, and an oscillator of I MHz or higher is usually used.

Backup when power is off is oscillation section 21, local section 3, RT
For all of C part l, from battery B to diode D
A power supply vb is supplied via.

[Problems to be Solved by the Invention] However, in the circuit with the above configuration, the current consumption in the oscillation section 2 and the frequency division section 3 increases significantly as the frequency handled increases, and as a result, the period that can be backed up by the battery B becomes significantly shortened. There were some drawbacks.

The present invention was made to eliminate the above-mentioned problems, and an object of the present invention is to provide an RTC circuit that can obtain high frequency accuracy and enable long-time backup.

[Means for Solving the Problems] As shown in FIG.
Self-help oscillation type RTC with one clock oscillation circuit
part A, and a clock frequency f! higher than said frequency fl! an oscillating unit B, a frequency dividing unit C that divides a clock with a frequency f from the oscillating unit into a clock with a frequency “,” and a clock with a frequency rI obtained by the frequency dividing unit C, and a clock with a frequency rI obtained by the frequency dividing unit A clock applying means for applying to the input side of the clock oscillation circuit A second backup means F for backing up the power of the RTC unit A for a desired period of time when the device is not energized;
It is characterized by having the following.

[Function] When the device is energized, the high frequency f2 clock from the oscillator B is powered by the power supply circuit within the device.
The frequency is divided into frequency f by the frequency dividing section C, and the clock of this frequency f2 is applied to the input side of the clock oscillation circuit X of the RTC section A by the clock applying means, so that R
The TC unit A operates based on this externally inputted clock.

On the other hand, when the device is not energized, the oscillation section B and the frequency division section C are operated by the first backup means E, and the RTC section A is operated by the second backup means E.
Since it is powered and operated by the backup means F of
The operation contents are the same as when the device is energized.

When this non-energized state has passed for a predetermined time Th<, the first
Since the backup means E becomes non-voltage, after that,
RTC unit A powered by second backup means F
However, in this state, it operates based on the frequency rl oscillated by the clock oscillation circuit X of the RTC section A.

[Embodiment] Fig. 2 shows an embodiment of a backup device for an RTC circuit according to the present invention, and the same parts as in Figs. 3 and 4 are given the same reference numerals.

The output of the oscillator 2, which has a self-excited oscillation circuit using a crystal oscillator Y°, is input to the frequency divider 3, and the output of the frequency divider 3 is input to the emitter of the PNP transistor Q. The collector is connected to one terminal of the crystal oscillator Y of the RTC section l via a capacitor C8. The base of the transistor Q is grounded via a resistor R.

The oscillating section 2 and the frequency dividing section 3 are supplied with the power Vin through the switch S3, and are also supplied with the power from the battery B1 through the switch S5.

A switch S4 is connected between the power supply Vin and the battery Bl.

On the other hand, the RTC section 1 is connected to the power supply Vin via the switch S6.
At the same time, power from battery B2 is supplied via switch S7. The frequency of the crystal oscillator Y of the RTC section 1 is equal to the frequency rI required by the RTC section 1, and the crystal oscillator Y of the oscillation section 2 is an easily available and highly stable oscillation element, and its oscillation frequency r, is the eye frequency which is considerably higher than the frequency rl.

Next, the operation of the circuit having the above configuration will be explained.

When the devices in the circuit are energized, switch S3. B4. Turn on B6 and S7 and turn off switch S5. As a result, the RTC section I1 oscillation section 2 and frequency dividing section 3 are powered and operated by the power supply Vin of the device. Also, battery B
1 and B2 are charged by the power supply Vin.

During this energization, the oscillator 2 oscillates a clock of frequency f2 by the crystal oscillator Y°, and this clock is divided by the frequency divider 3 into a clock of frequency rl.

The frequency f obtained by this frequency dividing section 3.

The clock of R
The TC unit 1 operates based on this externally applied clock having a frequency f. In this operating state, as described with reference to FIG. 4, highly accurate frequency characteristics are obtained in the RTC section 51.

On the other hand, when the device is de-energized, switch S3. B4 and B
6 is turned off and switches S5 and S7 are turned on.

As a result, the oscillating section 2 and the frequency dividing section 3 are connected to the battery B1.
Furthermore, the RTC unit 1 is supplied with power from the battery B2 and is backed up, so that it continues to operate, and the RTC unit 1 operates based on the external clock from the oscillation unit 2 in the same way as when it is energized. As mentioned above, since the oscillation section 2 and the frequency division section 3 handle high frequencies, their power consumption is large.
After a certain period of time T1, the battery Bl is exhausted and has no voltage, and the oscillation section 2 and frequency division section 3 stop operating. After this, the RTC section i continues to operate by being supplied with power from the battery B2, and in this state it operates based on the frequency r of the crystal oscillator Y of the self-excited oscillation circuit, but at this point,
That is, after the de-energization time T1, the device has been cooled down to the ambient temperature, and when de-energized, the RTC section!
Since there is no subsequent temperature change, it is possible to prevent the frequency accuracy from decreasing due to changes in salinity, as described in connection with Figure 3, and battery B2 provides a stable power backup for the desired period of time. becomes possible.

In the above embodiment, two batteries Bl and B2 are provided as the first and second backup means, but one battery is used, and a timer etc. Accordingly, the power supply to the oscillation section 2 and frequency division section 3 may be turned off.

[Effects of the Invention] As explained above, during a certain period T after de-energization, the first or second backup means performs the same operation as when energized, and when the time T elapses, the By using the backup means described in 2, only the RTC section is operated, so that the clock of the RTC section has highly accurate frequency characteristics during the time T as when the power is turned on, and after the time T has elapsed. , since the device is cooled to ambient temperature, highly accurate frequency characteristics are obtained and long.

Power backup over time is possible.

[Brief explanation of drawings]

FIG. 1 is a claim correspondence diagram of an RTC circuit of the present invention, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIGS. 3 and 4 are block diagrams of conventional RTC circuits. ■...RTC section, 2...Oscillation section, 3...Frequency division section, Y, Y'...Crystal oscillator, B
l, B2...Battery, Q...Transistor, C
a, C+, C+', Ct, Ct"" capacitor, 64~
S7...Switch. Patent applicant Furuno Electric Co., Ltd.

Claims (2)

[Claims] (1) A self-oscillation type RTC unit having a clock oscillation circuit with a frequency f_1, an oscillation unit with a clock frequency f_2 higher than the frequency f_1, and a clock with a frequency f_2 from the oscillation unit with a frequency f_
a frequency dividing unit that divides the frequency into a clock of 1; a clock applying means that applies the clock of frequency f_1 obtained by the frequency dividing unit to the input side of the clock oscillation circuit of the RTC unit; when the device is not energized, A first backup means for backing up the power of the oscillation section and the frequency dividing section for a predetermined period of time; and a second backup means for backing up the power of the RTC section for a desired period of time when the device is not energized. An RTC circuit characterized by: (2) The RTC circuit according to claim 1, wherein the clock applying means applies the clock obtained by the oscillation section and the frequency dividing section to the input side terminal of the clock oscillation circuit of the RTC section via a PNP transistor and a capacitor. .