Frequency division system

• US 4,244,043 A
• Filed: 03/29/1979
• Issued: 01/06/1981
• Est. Priority Date: 03/31/1978
• Status: Expired due to Term

• Current Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Original Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Inventors: Tsuzuki, Akira, Sekiya, Fukuo, Fujita, Hiro, Ebiha, Heihachiro
• Primary Examiner(s): Jackmon, Edith S.
• Application Number:
  US06/025,048
• Time in Patent Office: 649 Days
• Field of Search: 58/23 R, 58/23 AC, 331/25, 368/62, 368/85, 368/156
• US Class Current: 368/85
• CPC Class Codes: G04G 3/02 Circuits for deriving low frequency timing pulses from pulses of higher frequency pulse frequency dividers in general H03K23/00 - H03K29/00
• CPC Class Codes: H03L 7/191 using at least two different signals from the frequency divider or the counter for determining the time difference H03L7/193, H03L7/195 take precedence
• CPC Class Codes: Y10S 331/03 Logic gate active element oscillator

Abstract

A system for performing frequency division of a high frequency signal by intermittent operation of a frequency dividing counter circuit and by a phase lock loop circuit, in which phase lock is periodically achieved with an output of the counter circuit. Phase lock loop circuit is of novel design which provides exact phase lock without cyclic variations from the reference phase.

Claims

1. A frequency division system for producing a phase locked signal of relatively low frequency which is synchronized in phase with a signal of relatively high frequency and whose frequency is an integral submultiple of said relatively high frequency, comprising:

frequency divider circuit means responsive to said relatively high frequency signal for producing a reference signal of said relatively low frequency;

a voltage controlled oscillator circuit for generating said phase locked signal, comprising a first control element for controlling the frequency of said phase locked signal and a second control element for controlling the phase of said phase locked signal in an instantaneous manner;

a phase comparator circuit for comparing the phase of said phase locked signal and the phase of said reference signal and for producing a first control signal if the phase of said phase locked signal is lagging that of said reference signal and for also producing a second control signal if the phase of said phase locked signal is leading the phase of said reference signal, whereby one of said first and second control signals is applied to said second control element of said voltage controlled oscillator circuit to cause the phase of said phase locked signal to come into coincidence with said reference signal phase; and

a charge pump circuit comprising a capacitor, charge control means responsive to said first control signal for increasing the amount of charge in said capacitor and discharge control means responsive to said second control signal for decreasing the amount of charge in said capacitor, the voltage appearing across said capacitor being applied to said first control element of said voltage controlled oscillator circuit so as to cause the frequency and phase of said phase locked signal to come into coincidence with the frequency and phase of said reference signal.

2. A frequency division system according to claim 1, and further comprising means for producing a third control signal for selectively setting said frequency division system in a pre-scaling mode of operation and in a phase locked mode of operation, and furthermore comprising electronic switch means responsive to said third control signal for applying said reference signal to said phase comparator circuit to be compared in phase with said phase locked signal in said pre-scaling mode of operation and for inhibiting operation of said frequency divider circuit means and applying said relatively high frequency signal to said phase comparator circuit to be compared in phase with said phase locked signal in said phase locked mode of operation, whereby said phase locked signal is brought into phase and frequency coincidence with said reference signal during said pre-scaling mode of operation and is held in phase coincidence with said relatively high frequency signal during said phase locked mode of operation.

3. A frequency division system according to claim 2, and further comprising;

timer circuit means for measuring a predetermined duration of said phase locked operating mode and for producing a fourth control signal when said predetermined duration has elapsed;

phase coincidence detection circuit means coupled to receive said phase locked signal and said first and second control signals for detecting a condition of phase and frequency coincidence between said phase locked signal and said reference signal, and for producing a fifth control signal when said condition of phase and frequency coincidence is detected; and

control circuit means responsive to said fourth and fifth control signals for producing said third control signal, whereby said pre-scaling mode of operation is entered when said predetermined duration of said phase locked mode of operation has elapsed and whereby said phase locked mode of operation is entered when said condition of phase and frequency coincidence between said phase locked signal and said reference signal is detected during said pre-scaling mode of operation.

4. A frequency division system according to claim 1, wherein said voltage controlled oscillator further comprises a combination of resistive and capacitative elements to determine a time constant which defines the frequency of said phase locked signal, and wherein said first control element is coupled to at least a part of said resistive and capacitative elements to control the value of said time constant and thereby to control the frequency of said phase locked signal.

5. A frequency division system according to claim 4, wherein said second control element is coupled to at least a part of said resistive and capacitative elements for selectively enabling and disenabling charging and discharging of said capacitative elements through said resistive elements, to thereby control the phase of said phase locked signal in response to one of said first and second control signals from said phase comparator circuit.

6. A frequency division system according to claim 4, wherein said second control element is connected across at least a part of said capacitative elements, for selectively establishing an open circuit and a closed circuit condition in response to one of said first and second control signals from said phase comparator.

7. A frequency division system according to claim 4, wherein said second control element is connected between a part of said combination of resistive and capacitative elements and a source of a fixed voltage, for thereby selectively connecting and disconnecting said part of said combination of resistive and capacitative elements to and from said fixed voltage source, in response to one of said first and second control signals from said phase comparator.

8. A frequency division system according to claim 4, wherein said first control element comprises a field effect transistor having source and drain terminals connected across at least a part of said resistive elements of said voltage controlled oscillator, and having a gate terminal coupled to receive said voltage appearing across said capacitor of said charge pump circuit.

9. A frequency division system according to claim 5, wherein said second control element comprises an electronic switch connected in series with a part of said resistive elements and having a control electrode coupled to receive one of said first and second control signals from said phase comparator.

10. A frequency division system according to claim 1, wherein said phase comparator comprises:

a first data-type flip-flop having a data terminal coupled to a high logic level potential, a clock terminal coupled to receive said reference signal, and a reset terminal coupled to receive said phase locked signal from said voltage controlled oscillator circuit; and

a second data-type flip-flop having a data terminal coupled to said high logic level potential, a clock terminal coupled to receive said phase locked signal, and reset terminal coupled to receive said reference signal.

11. A frequency division system according to claim 10, wherein said first control signal is produced from the inverting output terminal of said first data type flip-flop and said second control signal is produced from a normal output terminal of said second data type flip-flop.

12. A frequency division system according to claim 10, wherein said phase comparator circuit further comprises:

a third data type flip-flop having a clock terminal coupled to receive said relatively high frequency signal, and a data terminal coupled to receive said phase locked singal;

a fourth data type flip-flops having a clock terminal coupled to receive said phase locked signal and a data terminal coupled to receive said relatively high frequency signal;

a fifth data type flip-flop having a data terminal coupled to a normal output terminal of said third data type flip-flop and a clock terminal coupled to receive said relatively high frequency signal;

first AND gate means having an input terminal coupled to an inverting output terminal of said third data type flip-flop and another input terminal coupled to receive said phase locked signal;

second AND gate means having an input terminal coupled to an inverting output terminal of said fourth data type flip-flop and another input terminal coupled to said normal output of said third data type flip-flop;

NAND gate circuit means having an input terminal coupled to a normal output terminal of said fifth data type flip-flop and another input terminal coupled to an output of said second AND gate means;

first electronic switch means coupled to said normal output terminal of said second data type flip-flop and to an output of said first AND gate means, for producing a signal indicating that the phase of the phase locked signal is leading that of said reference signal during the pre-scaling operation mode, and for producing a signal indicating that the phase of the phase locked signal is leading that of said relatively high frequency signal during tha phase locked operation mode; and

second electronic swtich means coupled to said inverting output terminal of said first data type flip-flop and to an output terminal of said NAND gate means, for producing a signal indicating that the phase of said phase locked signal is legging that of said reference signal during said pre-scaling operation mode, and for producing a signal indicating that the phase of said phase locked signal is lagging that of said relatively high frequency signal during said phase locked operation mode.

13. A frequency division system according to claim 1, wherein said phase comparator circuit comprises:

a first data type flip-flop having a data terminal connected to a high logic level potential, a clock terminal coupled to receive said reference signal, and a reset terminal coupled to receive said phase locked signal;

a second data type flip-flop having a data terminal connected to a low logic level potential, a clock terminal coupled to receive the inverse of said phase locked signal, and a set terminal coupled to a normal output terminal of said first data type flip-flop;

an OR gate having an input terminal coupled to a normal output terminal of said second data type flip-flop and another input terminal coupled to receive said reference signal;

a third data type flip-flop having a data terminal connected to a high logic level potential, a reset terminal coupled to an output of said OR gate, whereby an output signal is produced from an output terminal of said first data type flip-flop indicating that said phase locked signal is logging in phase with respect to said reference signal, and an output signal is produced from an output terminal of said third data type flip-flop indicating that said phase locked signal is leading in phase with respect to said reference signal, and furthermore whereby phase comparison between said phase locked signal and said reference signal is significantly independent of the duty cycle of said reference signal.

14. A frequency division system according to claim 1, wherein said charge control means of said charge pump circuit comprises a P-channel field effect transistor and a resistor, with the source terminal of said P-channel field effect transistor being connected to a high potential, a drain terminal thereof connected to one end of said resistor, and a gate terminal thereof connected to receive said first control signal, and wherein said discharge control means comprises an N-channel field effect transistor having a source terminal connected to a low potential, a gate terminal thereof connected to receive said second control signal, and a drain terminal thereof connected to the junction of said resistor and said drain terminal of said P-channel field effect transistor, and wherein the other end of said resistor is connected to one terminal of said capacitor.

15. A frequency division system according to claim 1, wherein said charge pump circuit comprises:

a first P-channel field effect transistor with the gate and drain terminals thereof connected together and the source terminal connected to a high logic level potential;

a resistor with one end connected to said drain terminal of said first field effect transistor

a first N-channel field effect transistor having the gate and drain terminals thereof connected together and to the other end of said resistor and having the source terminal thereof connected to a low logic level potential;

a second P-channel field effect transistor having a source terminal connected to said high logic level potential and a gate terminal connected to the drain terminal of said first P-channel field effect transistor;

a third P-channel field effect transistor having a source terminal connected to the drain terminal of said second P-channel transistor and a gate terminal connected to receive said first control signal from said phase comparator circuit;

a second N-channel field effect transistor having a source terminal connected to said low logic level potential and a gate terminal connected to said drain terminal of said first N-channel field effect transistor;

a third N-channel field effect transistor having a source terminal connected to a drain terminal of said second N-channel field effect transistor, drain terminal connected to the drain terminal of said third P-channel field effect transistor, and a gate terminal coupled to receive said second control signal from said phase comparator circuit; and

a capacitor having one terminal connected to the drain terminals of said third P-channel field effect transistor and said third N-channel field effect transistor and having another terminal connected to said low logic level potential.

16. A frequency division system according to claim 1, wherein said charge pump circuit comprises;

a first P-channel field effect transistor with gate and drain terminals thereof connected together and with the source terminal thereof connected to a high logic level potential;

a resistor with one end connected to said drain terminal of said first P-channel field effect transistor;

a first N-channel field effect transistor having the gate and drain terminals thereof connected together and to the other end of said resistor, and having a source terminal thereof connected to a low logic level potential;

a second P-channel field effect transistor having a source terminal thereof connected to said high logic level potential, a drain terminal connected to the drain terminal of said first P-channel field effect transistor, and a gate terminal coupled to receive said first control signal from said phase comparator circuit;

a third P-channel field effect transistor having a source terminal thereof connected to said high logic level potential and a gate terminal connected to the drain terminal of said second P-channel field effect transistor;

a second N-channel field effect transistor having source and drain terminals thereof connected to the source and drain terminals respectively of said first N-channel field effect transistor, and having a gate terminal coupled to receive said second control signal from said phase comparator circuit;

a third N-channel field effect transistor having a source terminal connected to said low logic level potential, a gate terminal connected to the drain terminal of said second N-channel field effect transistor and a drain terminal connected to the drain terminal of said third P-channel field effect transistor; and

a capacitor having one terminal connected to said drain terminals of said third N-channel and P-channel transistors and having another terminal connected to said low logic level potential.

17. A frequency division system according to claim 1, wherein said charge pump circuit further comprises a source of an operation initiation control signal which is produced when operation of said frequency division system is initiated, and moreover comprises electronic switch means coupled between said capacitor and said charge and dishcarge control means, responsive to said operation initiation control means, responsive to said operation initiation control signal for connecting said capacitor to a high logic level potential for a predetermined period of time when operation of said frequency division system is initiated, to charge said capacitor to said high logic level potential, and for thereafter connecting said capacitor to said charge and discharge control means.

18. An electronic timepiece powered by a battery, comprising:

a source of a standard signal of relatively high frequency;

first frequency divider circuit means responsive to said relatively high frequency signal for producing a signal of relatively low frequency which is an integral submultiple of said relatively high frequency;

a voltage controlled oscillator circuit for generating a phase locked signal which is in phase and frequency coincidence with said relatively low frequency signal, comprising a first control element for controlling the frequency of said phase locked signal and a second control element for controlling the phase of said phase locked signal in an instantaneous manner;

electronic switch means coupled to receive said relatively high frequency signal;

phase comparator circuit menas for comparing the phase of said phase locked signal with that of said relatively low frequency signal when said first frequency divider circuit is enabled by said electronic switch means in a first operation mode and for comparing the phase of said relatively high frequency signal with that of said phase locked signal when said relatively high frequency signal is applied to said phase comparator circuit by said electronic switch means in a second operation mode of said timepiece, and for producing a first control signal indicating that the phase of said phase locked signal is lagging that of said relatively low frequency signal when said timepiece is in said first operation mode and for indicating that the phase of said phase locked signal is lagging that of said relatively high frequency signal when said timepiece is in said second operation mode, and further for producing a second control signal indicating that the phase of said phase locked signal is leading that of said relatively low frequency signal when said timepiece is in said first operation mode and for indicating that the phase of said phase locked signal is leading that of said high frequency signal when said timepiece is in said second operation mode, whereby said second control signal is applied to said second, control element of said voltage controlled oscillator circuit for controlling the phase of said phase locked signal;

charge pump circuit means comprising a capacitor, charge control means responsive to said first control signal from said phase comparator circuit for increasing the amount of charge in said capacitor, and discharge control means responsive to said second control signal for reducing the amount of charge in said capacitor, the voltage across said capacitor being applied to said first control element of said voltage controlled oscillator circuit;

second frequency divider circuit means responsive to said phase locked signal for producing a standard time signal; and

time display means responsive to said standard time signal for providing a display of time.

19. An electronic timepiece according to claim 18, and further comprising:

timer circuit means for measuring a predetermined duration of said second operation mode and for producing a first mode control signal when said time duration has elapsed;

phase coincidence detection circuit means coupled to receive said phase locked signal and said relatively low frequency signal for detecting a condition of phase and frequency coincidence between them in said first operation mode and for producing a second mode control signal when said condition of phase and frequency coincidence is detected; and

control circuit means coupled to said electronic switch means and responsive to said first mode control signal for setting said timepiece in said first operation mode and further responsive to said second mode control signal for setting said timepiece in said second operation mode.

20. An electronic timepiece according to claim 18, and further comprising:

a battery load prediction circuit for detecting a condition of said timepiece in which a significant change in the voltage of said battery is about to occur and for producing a first mode control signal when such a condition is detected;

phase coincidence detection circuit means coupled to receive said phase locked signal and said relatively low frequency signal for detecting a condition of phase and frequency coincidence between them in said first operation mode, and for producing a second mode control signal when said condition of phase and frequency coincidence is detected; and

control circuit means responsive to said first mode control signal for setting said timepiece in said first operation mode, and responsive to said second mode control signal for setting said timepiece in said second operation mode if said first mode control signal is not being produced.