JPH02206223A - Frequency synthesizer - Google Patents

Abstract

PURPOSE:To attain low power consumption in a lock state by inputting a pulse outputted from a phase comparator to a select circuit to switch a power supply for a frequency divider and a circuit holding a voltage of a switching low pass filter of a phase locked loop. CONSTITUTION:When a phase locked loop circuit is in operation, a pulse signal is outputted from a phase comparator 4 and the signal is supplied to a select circuit 8. A signal bringing the switches 10, 11 into nonconductive the switch 12 into a conductive state is outputted from the select circuit 8 when the pulse state, i.e., the width is a prescribed value or below. Thus, an output voltage of a low pass filter 5 is inputted to a voltage holding circuit 9 by the switch 12 and it is inputted to a voltage controlled oscillator 1. Thus, even when a loop circuit is interrupted, the same frequency as the lock state is able to be oscillated. Then the phase locked loop is implemented intermittently and the power consumption is reduced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is suitable for wireless devices with low power consumption, such as mobile line devices and portable wireless devices, and performs intermittent operation that operates only when necessary. Regarding frequency synthesizers.

[Conventional technology]

Traditional phase-locked loop frequency synthesizer circuits
It was configured as shown in the figure.

This circuit divides the output of voltage controlled oscillator 1 into frequency divider 2 by 1Ji.
1, and further by a programmable divider 3 whose frequency division ratio is set according to data from the microcomputer. This signal is applied to one input of the phase comparator 4.

The other input of the phase comparator 4 is given a reference frequency obtained by dividing the oscillation frequency generated by the crystal oscillator 6 by a fixed frequency divider 7. The output terminal of the phase comparator 4 outputs a voltage due to the phase difference between the two input signals, which is input to the low-pass filter 5 and then fed back to the voltage controlled oscillator 1. , the oscillation frequency of the voltage controlled oscillator 1 is changed to eliminate the phase difference, and a locked state is achieved, thereby making it possible to obtain the required frequency based on data from the microcomputer.

[Problem to be solved by the invention]

Since the conventional phase-locked loop frequency synthesizer is configured as described above, the battery I! When used in a portable radio device or the like that is operated by a power source, power consumption must be reduced, and there is a problem in that the circuit must be operated intermittently.

The present invention was made to solve the above-mentioned problems, and reduces power consumption by intermittently operating a phase-locked loop! The purpose is to obtain a frequency synthesizer that can perform power ratio.

[Means to solve the problem]

The frequency synthesizer according to the present invention inputs the pulse output from the phase comparator to a selection circuit, and is provided with a switch that opens and closes the power supply of the frequency divider, and a switch that opens and closes the phase-locked loop and the output voltage of the low-pass filter. A switch is provided for sending the signal to the holding circuit, and the above-mentioned switch is controlled by the output signal of the select circuit.

[Effect]

The frequency synthesizer according to the present invention uses a select circuit to open/close the power supply of the frequency divider, open/close the phase lock loop, and open/close the circuit holding the 17 voltage of the low-pass filter, thereby reducing power consumption in the locked state.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a frequency synthesizer according to the present invention. In the figure, 8 is a select circuit that inputs the pulse state from the phase comparator 4 and outputs a signal for controlling the phase-locked loop circuit. do. Reference numeral 9 denotes a voltage holding circuit which holds the output voltage from the low-pass filter (5) when the phase-locked loop circuit is in a locked state and supplies it to the voltage controlled oscillator l. 10, 11.12
is a switch, which is controlled by an output signal from the select circuit 8.

Note that the other symbols are the same as those in the prior art.

The feature of this configuration is that a voltage holding circuit 9 capable of holding the output m voltage of the low-pass filter 5 is provided, and the low-pass filter Switches 10, 11, and 12 are provided between the 5 and the pressure holding circuit 9, respectively, and receive the pulse signal from the phase comparator 4, and output a control signal for opening and closing the switch depending on the state of the switch. The circuit 8 is provided.

Next, the operation will be explained. Switches 10.11 are normally conductive and operate in the same manner as in the prior art described above. At this time, the switch 12 is in a cutoff state.

When the phase-locked loop circuit operates, a pulse-like signal is output from the phase comparator 4, and this signal is given to the select circuit 8. The pulse signal from the phase comparator 4 becomes a whisker-like pulse when the phase lock loop circuit is in a locked state. Follow. The select circuit 8 outputs a signal that turns off the switches 10 and 11 and makes the switches 12 conductive when the state or width of this pulse is below a certain level. Accordingly, the phase-locked loop is cut off by the switch 11, but the output voltage of the low-pass filter 5 is inputted to the voltage holding circuit 9 by the switch 12, and then inputted to the voltage-controlled oscillator 1.

Therefore, even when the loop circuit is in the cutoff state, it can oscillate at the same frequency as in the locked state. Conversely, when the width of the pulse signal input to the select circuit 8 exceeds a certain level, the switches 10 and 11 become conductive and the switches 12 become cut off, allowing the same operation as the conventional one.

Yo. Therefore, the phase-locked loop is performed intermittently, and among the circuits, the frequency divider 2 consumes the most power, making it possible to reduce the power consumption.

〔Effect of the invention〕

As described above, according to the present invention, since the frequency synthesizer is configured to have a phase-locked loop circuit that operates intermittently, there is an effect that power consumption can be reduced.

[Brief explanation of the drawing]

14 is a block diagram showing the configuration of a frequency synthesizer according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of a conventional frequency synthesizer. 1... Town pressure control oscillator, 2.7... Frequency divider, 3...
・Programmable divider, 4...phase comparator, I
5...Low pass filter, 6...Crystal oscillator, 8
...Select circuit, 9...Voltage holding circuit, 10...
・Power switch, 11, 12...switch. In Figure 1, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A voltage controlled oscillator controlled by an input voltage, a frequency divider that divides the output of the oscillator, a programmable divider whose frequency division ratio can be changed based on data from a microcomputer, and a reference frequency created by a crystal oscillator. a fixed frequency divider that divides the frequency; a phase comparator that compares the output of the fixed frequency divider with the output from the programmable divider and outputs a signal according to a phase difference; and an output of the phase comparator. A frequency synthesizer circuit configured to intermittently operate a low-pass filter having a capacitor that is charged and discharged in accordance with a signal, and a phase-locked loop in which the oscillation frequency of the voltage-controlled oscillator is controlled by the output voltage of the low-pass filter, a voltage holding circuit that can hold the output voltage of the low-pass filter; a switch that is placed between the phase comparator and the low-pass filter and that can open and close a phase-locked loop; and a frequency divider that divides the output of the voltage-controlled oscillator. a power switch for opening and closing the power supply; a switch disposed between the low-pass filter and the voltage holding circuit for sending the output voltage of the low-pass filter to the voltage holding circuit; A frequency synthesizer comprising: a select circuit for instructing opening/closing of a switch;