DE2426903A1 - ELECTRONIC CLOCK - Google Patents

Description

Patent attorneys Dipl.-Ing. F. Weickmann, 2426903

Dipl.-Ing. H.Weickmann, Dipl.-Phys. Dr. K. Fincke Dipl.-Ing. F. A. Weickmann, Dipl.-Chem. B. Huber

8 MUNICH 86, DEN

POST BOX S60 820

MÖHLSTRASSE 22, CALL NUMBER 98 3921/22

OPTEL CORPORATION, Box 2215, Princeton, N.J. O85'iO,

United States

Electronic clock

The present invention relates to an electronic watch with a frequency-stable oscillator, the oscillator Coupled frequency dividers for generating output signals with the frequency values required to keep the time constant, a low voltage source, a liquid crystal display that operates at a predetermined bias value works above the voltage of the low voltage source, and with a circuit for transformation the voltage of the low voltage source in the predetermined bias value.

The main components of an electronic watch with a liquid crystal display are the liquid crystal display cell itself, a voltage source, preferably

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a commercially available miniature battery with a voltage of 1.5 V, a crystal oscillator to keep the time constant, Divider circuits for dividing the primary output frequency of the crystal oscillator, counter, decoder and driver circuits for storing the minutes and hours as well as for controlling the liquid crystal display cell, as well as an up-converter for Transformation of the supplied by the voltage source Voltage of 1.5 V into a voltage of typically around 15 V ", which is used to control the counter, decoder and Driver circles as well as the liquid crystal arrow is required.

For practical reasons, the power losses of the electronic circuits and the liquid crystal display be less than 30 microwatts. As a typical display cell with continuous operation has a power loss of around 15 microwatts per year, the entire Power losses of the electronic circuits during continuous operation do not exceed 15 microwatts.

In order to achieve such conditions, an electronic watch of the type mentioned at the outset is by means of the following Features marked:

An inductance with a high quality factor connected to a terminal at the pre-voltage source, a three-electrode switch, as a function of a control signal given to its control electrode between one through a small Impedance value given switching state and a given by a large impedance value switching state of its switching path is switchable and the output of its switching path is connected to the other terminal of the inductance, a control stage that has its input at an output

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retrospectively

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given Fx-equenzvrertes of the frequency divider and with its output at the three-electrode switch is to be switched from the low voltage source in the first switching state of the Dreielckrode switch Sti-otn to lead across the inductance, and one coupled to the inductance Transformation branch that is in the second switching state of the. Three-electrode switch during the first switching state Energy stored in the inductor into the predetermined bias value for the liquid crystal display convicted. _ ^

'CJw following ^ wiirA the. Invention on the basis of the drawings shown in the figures. ee s- single — i dc-

Fiq-4 a Aosföntu ^ gs-fotm der erfittduHgsgemafceoy Ukt ~ fig. 2. Ausfioktungs-forvncu of a & eue.t-icreües and a vfcAo / fetr nacU G & .- i An electronic clock with a liquid crystal display shown in the block diagram of the figure is known in its general form and, for example, in "electronics" from April 10, 19? 2, pages 93 ff.

In the electronic watch according to the figure, a battery 10 is provided, which is for example a, a microbattery supplying a voltage of 1.5 V is formed. Such batteries are also used in, for example Hearing aids used.

The output voltage of this battery 10 can be used by many Clocks used directly, for example, to control a tuned circle in the form of a crystal oscillator will. On the other hand, this voltage can also first be stepped up by a circuit after which this transformed voltage value becomes

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Control of the various circuits of the clock is used.

The electronic clock according to the figure also contains a ZeitkaktosKillator 11. This oscillator is a relatively frequency stable crystal oscillator. Froqueiizstability is necessary in order to be able to that the time constancy is maintained over long periods of time. The output of the oscillator is coupled to frequency divider circuits 12. These frequency divider circuits 12 deliver lower frequency signals in terms of frequency of the stable oscillator output signal, which are a measure of the time constancy.

The oscillator can, for example, at a stable frequency of 32.68 IcHz. swing. The divider circles divide this frequency in such a way that, for example, a signal with 6o pulses per minute representing the seconds and a count is generated from this signal to indicate minutes, hours, days, etc.

The function of these divider circles is known per se.

The divider circuits 12 can use one or more outputs, with a single line to a counter, Decoding and logic module 15 is coupled.

The main function of this counter, decoder and logic module 15 is to generate signals from the divided oscillator signal which are a measure of seconds, minutes and hours.

The module 15 contains counters in the form of integration circuits which are controlled in a manner known per se will.

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The module 15 is coupled to a driver stage 16, which, for example, a series of amplifiers, such as integrated MOS field effect transistor circuits for The amplification of the signals supplied by the counters and the associated decoding circuits contains and these Signals into a liquid crystal display 17 feeds.

This liquid crystal display 17 is preferably driven by a pulsating current, as is described in US Pat. No. 3,7kk 0 ^ 9.

This liquid crystal display 17 is typically a numeric digit display cell with several Digit segments formed, with at least four digit segments are provided. One such at known liquid crystal cell 17 generally consists of a hermetically sealed structure with a liquid crystal material between two electrodes, one of which is an electrode as common Electrode for all display elements and the other electrode is divided into segments. Such with Displays provided with segments are used in a manner known per se for all types of display media. In the context of the invention, it is essential to control such a liquid crystal display from the voltage source.

This is because the liquid crystal display 17 typically requires a voltage of approximately 15 V. in order to ensure good contrast and good brightness. In general, such a liquid crystal display can be used in a voltage range of 4 - kO V.

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operate. Such a liquid crystal display can operated from a battery with a voltage of 15 V. However, such batteries are not compact enough; if they are, they are extremely expensive. The battery must therefore be so small as possible, but the required operating conditions must be guaranteed. One battery for A digital electronic watch must be able to provide sufficient energy to power the watch to be able to operate for about a year. In addition, it must be sufficiently small. Commercially available Batteries deliver output voltages of 1.3 - 1.5 V "with a capacity of I65 - 250 milliampere-hours. A single compact battery with an output voltage of 1.5 V. can be used continuously for over one Supply about 30 microwatts a year. When using a Liquid crystal display 17 and a low power semiconductor circuit can use a single battery meet these requirements with a voltage of 1.5 V. However, the voltage of 1.5 V. must be increased by a factor of at least three to ten, stepped up to typical liquid crystal displays available in conjunction with low power circuits to ensure a good brightness and a good one To be able to reliably control contrasts.

The battery 10 with a voltage of 1 _f 5 V. therefore feeds an upward transforming circuit, which is designed as an inductive charging circuit and works with good efficiency. For this purpose, the battery 10 is coupled to a rectifier or a diode circuit 21 via an inductance 20.

A capacitance 22 is coupled to the connection point between the battery 10 and the inductance 20,

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which are used to linearize the battery voltage over long periods of time or for the internal resistance of the Battery 10 affecting large temperature changes serves. Furthermore, this capacitance supports the supply of the larger current into the inductance 20 in their charging interval.

The inductance 20 has a relatively large quality factor Q. Your inductance word. is selected as a function of the required power values and switching frequencies.

A switch 2 ^l k is coupled to the connection point between the inductance 20 and the rectifier 21. This switch 2k can be formed by a transistor, a field effect transistor or another controllable switching element. This switch forms a small impedance in a first switching state and a large impedance in a second switching state. During the first switching state, the output terminal of the inductance 20 is practically grounded, while in the second switching state it is idle or at a very large impedance.

The switch 2k is switched between its first and its second switching state by a control stage 23, which responds to a signal from the divider circuits 12, which in turn are controlled by the crystal oscillator 11.

For example, if the crystal oscillator 11 is at a frequency of 32 j 768 kHz. oscillates, the divider circles 12 can be formed by a nine-stage binary counter. Output signals from these divider circuits can be at 256 Hz and 6k Hz. The signal with the frequency of 256 Hz. Is fed into the control stage 23 to

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to control the switch 2k . The operating frequency of the switch 2k is therefore also at a frequency of 256 Hz, so that a structurally small capacitance 29 can be used at the output of the rectifier 21.

If the switch 2k is formed by a transistor, this should have a large beta O100) and a low saturation voltage to ensure good efficiency.

At the output of the rectifier 21, a Zener diode 30 is connected in parallel with the capacitor 29. This zener diode 30 is used to set the output voltage to a value of I5 V. The Zener diode 30 can still a current sensing resistor 31 can be connected in series. The connection point between this resistor and the Zener diode 30 is coupled to the control stage. This results in feedback control for stabilization of a signal on a line 331 which couples the control stage 23 to the rectifier 21.

The rectifier 21 can be a synchronous rectifier which is controlled by the control stage 23 which also controls the switch 2k.

The synchronous control of the rectifier, which is not absolutely necessary, further improves the efficiency.

As already stated above, the inductance 20 has a relatively large quality factor Q so that losses are so small as possible and to improve efficiency.

As is known, the current flowing through an inductor cannot change instantaneously. If the current flowing in an inductor current _t be interrupted. Sjo-creates a large voltage spike. the

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Aniplittide and the duration of this voltage spike is one Function of the size of the inductance as well as the amount and the time with which the dex * current is changed.

Basically speaking, the voltage peak is all the greater the greater the current and the shorter the time in which the current flow is to be interrupted. This known relationship is through the equation

given, where V is the voltage,

L is the inductance

i the electricity and

t mean the time.

The switch 2k controlled by the control stage 23 switches alternately between current interruption and current flow as a function of its two switching states indicated above.

The switching frequency between the first and second switching state is equal to 256 Hz, although if necessary larger or smaller values (100 - 1,000 Hz.) can also be set. The ones supplied by the tax bracket Pulses are relatively narrow; in a specific example, at a repetition rate of 256 Hz, they are 15 microseconds wide.

During the first switching state, the switch 2k is switched through, so that current flows from the battery 10 via the inductance 20 and the switch 2k to earth. The inductance 20 stores energy due to this current flow and generates a magnetic field. The amount of this saved. Energy depends of course on the width of the pulse which the switch 2k in the

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Saturation or switches into its first switching state, the size of the inductance 20 also being important is. Therefore, by controlling the pulse width, the energy can be controlled.

If the switch 24 is locked or in its second Switched state, the current flowing through the inductance changes because the impedance to earth changes changes. This change in the switching state is associated with a voltage pulse which causes the inductance 20 transmits stored energy via the rectifier 21. The rectifier 21 generates from the pulse train a DC voltage with a large voltage amplitude. This rectified voltage is filtered and converted into the capacity 29. saved.

The output power is preferably achieved by changing the pulse repetition frequency via the feedback from the Zener diode 30 to control stage 23 (line 5O) controlled. the Changing the pulse repetition frequency is mainly used to control the output power. The output signal consists of very narrow peaks with a repetition frequency, which is determined by the repetition frequency of the repetition frequency supplied by the divider circuits 12 is determined. This pulse train is generated by the control stage modified so that the average available power by monitoring the rectified. Output voltage and regulated by changing the pulse repetition frequency according to the power required at the load. Is more If power is required, the pulse is reduced or the frequency increased. Is less power if necessary, the reverse is the case. Although the pulse repetition rate is preferred for changing the power is used, the pulse width can of course also be changed, with a definition of the output power as well he follows. A pulse width change can

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without any change in the pulse sequence frequency.

If the rectifier 21 is controlled by the control stage, the result is an improved mode of operation. When the switch 2k is switched on, the rectifier 21 is switched off, so that the entire current flows through the inductance 20 and the switch 2k , whereby the greatest possible energy is stored, since the shunt path formed by leakage currents is practically switched off via an ordinary rectifier . The pulse-shaped signal which switches off the switch 2k also switches on the rectifier 21 so that the maximum energy is transferred to the capacitance 29.

The control stage 23 can set a variable pulse width for control purposes. For this purpose, the control stage can be designed as a monostable multivibrator, the pulse width of which can be changed as a function of the current flowing through the resistor. If the power requirement at the load (counter, decoding and logic module 15t driver stage 16 and liquid crystal display 17) increases, the current flowing through resistor 31 decreases. This decrease in current has the effect that the control stage holds the switch 2k in its one switching state for a longer period of time, as a result of which more energy is stored in the inductance 20 and thus more power is available.

The divider circles 12 and the control stage 23 can in an can be built up in a number of forms, as is known. For this purpose, for example, multivibrators, Find gates, etc. use.

The step-up circuit described above a voltage offers the advantage that any design of the overall circuit is structurally small Switching elements can be used, which by a time

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clock cycle can be controlled, which is already present in clocks to ensure time constancy. Specifically, therefore, a small battery with a small voltage can be used, from which a larger voltage can be used can be generated to control a liquid crystal display.

Claims

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Fig. 2 shows a practical embodiment of the control stage 23 and switch 24.

The control stage 23 contains two transistors Q 1 and Q p * which are connected together to form a trigger stage. For this purpose, the collectors G of the transistors Q. and Q ^ are each via a resistor R. and R _1, respectively. connected to a positive potential with respect to earth + V, while their emitters

CC

E lie directly on earth. The transistors GL and Qp are reciprocally fed back in such a way that the collector 0 of the transistor Q. via a capacitance Cp at the base B of the Transistor Qp and the collector C of transistor Qp a resistor R. is connected to the base B of the transistor Q. Furthermore, the base B of the transistor Q, is not over one specified resistance at a voltage V ,,.

The frequency divider circuits 12 are on via a capacitance C. the base B of the transistor Q. coupled. Furthermore is that of the connection point between the zener diode 30 and the Resistor 31 outgoing line 50 (see own. 1) via a Resistor Rp coupled to the junction between the capacitance Op and the base B of the transistor Q ^.

In this embodiment, the switch 24 is formed by a TraiELStor, the base B of which is connected to the collector C of the transistor Qp, its emitter E to earth and its collector C to the inductance 20 lies.

The mode of operation of these stages 23 and 24 is as follows: In the interval between the pulses coming from the divider circuits 12, the voltage V ,, which has its positive pole on earth and its negative pole on the unspecified resistor, blocks the transistor Q In the control stage Apart from the transient state, the transistor Qo is also blocked, since in the circuit + V, R ", O ₀ and base-emitter-

cL CC I £.

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Path of the transistor Q ₂ when the capacitance C _{2 is} charged, no base current can flow in the transistor Q _2. Then the collector C of the transistor Q _{2 is} practically at the positive potential + V, because its collector-emitter path is a

CC

Represents open circuit, i.e. the switch transistor 24 is switched on, so that the inductive charging current of the inductance 20 can flow through its collector-emitter path.

A positive pulse from the divider circuits 12 now switches the transistor Q. through, so that its collector potential practically drops to ground potential, because switching through to saturation is also supported by the positive potential supplied via the voltage divider K ^ ,, R, - . This means that the capacity C ₂ must be reloaded. The recharge current is the base current for the transistor C. so that this transistor is also turned on. Thus, its collector potential drops practically to ground potential because its collector-emitter path represents a short circuit, that is, the switch transistor 24 is blocked.

This switching of the switch Trarastor 24 takes place in time the frequency of the pulses supplied by the divider circles 12 in the above using £ ig. 1 described sense.

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Claims (10)

■ - vf - JIf Claims 1, Electronic. Clock with a frequency stable Oscillator, frequency dividers coupled to the oscillator for generating output signals with currently required constant Frequency values, a voltage source, a liquid crystal display, which at a given voltage value above the Voltage of the low voltage source works, and with a circuit for transformation the voltage of the low voltage source in the specified voltage value, characterized by one with a clamp on the bias source (10) lying inductance (20) with a high quality factor, a three-electrode switch (24), which functions as a a control signal given to its control electrode between a switching state given by a small impedance value and one given by a large impedance value given switching state of its switching path is switchable and that with the output its switching path is at the other terminal of the inductance (20), a control stage (23) the with its input at an output predetermined frequency value of the frequency divider (12) and with its The output at the three-electrode switch (24) is to be switched from the low-voltage source (10) in the first switching, state of the three-electrode switch (24) current over to lead the inductance (20), and through a transformation circuit coupled to the inductance (20), which in the second switching state of the three-electrode switch (24) the energy stored in the inductance during the first switching state converted into the predetermined bias value for the liquid crystal display (17). 409885/1223 - 14 - 4t 2. Electronic clock according to claim 1, characterized in that the frequency value at which the three-electrode switch (2k) responds is above 100 Hz. 3. Electronic clock according to claim 1 and 2, characterized in that the three-electrode switch (2k) is formed by a transistor with a low saturation voltage between the collector and emitter, the base of which forms the control electrode and the collector of which is coupled to the inductance (20). k. Electronic clock according to one of Claims 1 to 3, characterized in that the transformation circuit coupled to the inductance (20) contains a Zener diode (30) with one terminal on the inductance (20), the other terminal of which is at reference potential and the leads to the setting of the bias value current. 5. Electronic clock according to one of claims 1 to 4, characterized by a capacitance (29) lying parallel to the Zener diode (30). 6. Electronic watch according to one of claims 1 to 51 characterized in that the voltage of the low voltage source (10) is between 1 and 2 V. 7. Electronic clock according to one of claims 1 to 6, characterized in that the predetermined bias value is between k and 20 V. 8. Electronic clock according to one of claims 1 to 7, characterized by a branch (31) coupled to the transformation circuit for generating a display signal when the predetermined bias 409885/1223 value falls below a given amount and by a feedback loop coupled to the control stage (23) (50), over which the duration of the first switching state of the switch (24) varies as a function of the display signal is cash. 9. Electronic clock according to one of claims 1 to 8, characterized in that the feedback branch has a Contains rectifier (21) with a first terminal to the second output terminal of the inductance (20) and is coupled with a second clamp to the liquid crystal display (17) and that during the second Switching state of the switch (24) transfers energy to the liquid crystal display ■ (17). 10. Electronic clock according to one of claims 1 to 9s characterized in that the rectifier (21) is coupled to the control stage (23) via a synchronous loop (33) is, the rectifier (21) during a switching state of the switch (24 ^ iH the conductive state is controlled. 409885/1223