JPH01144820A - Oscillating circuit - Google Patents

Abstract

PURPOSE:To constitute an oscillating circuit with no adjusting part and without increasing the number of oscillators by controlling the oscillation frequency of a voltage or current controlled type oscillating circuit with the aid of a loop constituted of a reference oscillating circuit, a phase-shifting circuit, a phase comparing circuit and a low-pass filter. CONSTITUTION:The feedback loop is constituted so as to change the phase delay quantity (or the lead quantity) alpha of the circuit 3, to change the output 1/2cosalpha of the low-pass filter(LPF) 4 as the result of that and to lower (or to decrease) the voltage (or the current) of the control terminal of the circuit 3 when the voltage (or the current) of the control terminal of the phase-shifting circuit 3 is raised (or increased). Therefore, the feedback loop is made to be a steady state at the state that the output of the LPF 4 is zero, that means, the phase delay quantity (or the lead quantity) alpha is 90 deg.. Then, when the voltage or the current controlled type oscillating circuit 5 or 6 is set so as to be the oscillation frequency obtained by the voltage value (the current value) of the control terminal of the circuit 3 in the steady state, the oscillation frequency can be kept constant. Thus, the oscillating circuit can be constituted with no adjusting part.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an oscillation circuit in which the oscillation frequency is not adjusted, and particularly to an oscillation circuit in which the oscillation frequency of an oscillation circuit built in an integrated circuit is automatically controlled and the oscillation frequency is not adjusted. Regarding.

[Conventional technology]

Conventionally, an oscillation circuit built into an integrated circuit has been adjusted externally when the oscillation frequency requires high precision due to the absolute precision of the resistor or capacitor that forms the internal circuit of the integrated circuit. For example, as shown in FIG. 2, an oscillation circuit 9.
A variable resistor 8 was connected to the adjustment terminal 10 to adjust the oscillation frequency.

Further, when the oscillation frequency is not adjusted, an oscillation circuit is constructed using an oscillator 7 such as a crystal oscillator as shown in FIG.

[Problem that the invention seeks to solve]

The above-described conventional oscillation circuit has the disadvantage that in the example shown in FIG. 2, the oscillation frequency must be adjusted by the variable resistor 8, which increases the number of man-hours, and in the example shown in FIG. If a plurality of oscillation circuits are required, it is necessary to use as many oscillators as there are oscillation circuits, which has the drawback of increasing the number of parts and increasing the cost.

SUMMARY OF THE INVENTION An object of the present invention is to provide an oscillation circuit that eliminates such drawbacks and can obtain a required number of oscillation outputs without adjustment.

[Means for solving problems]

The configuration of the oscillation circuit of the present invention includes a reference oscillation circuit that oscillates using an oscillator, and a phase shifter that inputs the output signal of this reference oscillation circuit and controls the voltage (or current) using a control signal to change the phase of the output signal. a phase comparison circuit that performs a phase shift comparison between the output of this phase shift circuit and the output of the reference oscillation circuit; a low-pass filter that outputs a reduced component of the output of this phase comparison circuit; The present invention is characterized in that it includes a plurality of voltage (or current) controlled oscillation circuits that change the oscillation frequency by controlling voltage (or current), and the output of the low-pass filter is used as a control signal for the phase shift circuit.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention.

This embodiment includes a reference oscillation circuit 1 that oscillates with an oscillator 7, a phase shift circuit 3 controlled by voltage (or current), a phase comparison circuit 2, and a low-pass filter (hereinafter referred to as L).
(referred to as PF) 4 and voltage (or current) controlled oscillation circuits 5 and 6 that are controlled by voltage (or current), and compares the phase of the output end of the reference oscillation circuit 1 with the input end of the phase shift circuit 3. connected to the first input end of circuit 2, phase shift circuit 3
The output of the phase comparison circuit 2 is connected to the second input terminal of the phase comparison circuit 2, and the output of the phase comparison circuit 2 is connected to the control input terminal of the phase shift circuit 3 and the voltage (or current) controlled oscillation circuits 5, 6 through the LPF 4.
is connected to the control input terminal of the

The output signal of the reference oscillation circuit 1 is cosω. t.

The amount of phase delay (or amount of advance) generated in phase shift circuit 3 is α
Then, the input signal of the phase comparison circuit 2 is cosωOt+
and cos (ω, 1+α).

Furthermore, the output signal of the phase comparator circuit 2 is a signal that is the product of two input signals, and is expressed as follows, and this signal is an LPF
The first term on the right side of equation (1) to pass through 4 disappears,
The output signal of the LPF 4 becomes a DC signal of -cosα. This DC signal is input to the control input terminal of the transfer sum circuit 3.

When the voltage (or current) at the control terminal of the phase shift circuit 3 rises (or increases), the phase delay amount (or advance amount) α of the phase shift circuit 3 changes, and as a result, the output of the LPF 4 -c
A feedback loop is constructed so that the voltage (or current) at the control terminal of the phase circuit 3 decreases (or decreases) as osα changes.

As a result, the output of LPF4 becomes 0. That is, the feedback loop is in a steady state when the phase delay amount (or lead amount) α is 90°. Therefore, if the voltage or current controlled oscillation circuit 5 or 6 is set so that the oscillation frequency is determined by the control terminal voltage value (or current value) of the phase shift circuit 3 in this steady state, the oscillation frequency can be kept constant. This allows an oscillation circuit to be constructed without any adjustment.

Note that although there are only two voltage (or current) controlled oscillation circuits 5.6 in this embodiment, it is also possible to further increase the number of oscillation circuits.

〔Effect of the invention〕

As explained above, the present invention controls the oscillation frequency of the voltage- or current-controlled oscillator circuit using the loop composed of the reference oscillation circuit, the phase shift circuit, the phase comparator circuit, and the low-pass filter 4. Although adjustment of the oscillation frequency was required, there is an effect that adjustment can be eliminated without increasing the number of oscillators.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, FIG.
The figures are block diagrams of two examples of conventional oscillation circuits. 1... Reference oscillation circuit, 2... Phase comparison circuit, 3...
・Phase shift circuit, 4... LPF, 5, 6... Voltage (or current) controlled oscillation circuit, 7... Oscillator, 8... Variable resistance, 9.10.11... Oscillation circuit.

Claims (1)

[Claims] A reference oscillation circuit that oscillates with an oscillator, a phase shift circuit that receives the output signal of this reference oscillation circuit and controls the voltage (or current) using a control signal to change the phase of the output signal, and the output of this phase shift circuit. a phase comparison circuit that performs a phase shift comparison between the output of the reference oscillation circuit and the output of the reference oscillation circuit, a low-pass filter that outputs a reduced component of the output of the phase comparison circuit, and a voltage (or current) that is controlled by the output of the low-pass filter. An oscillation circuit comprising a plurality of voltage (or current) controlled oscillation circuits that change the oscillation frequency, the output of the low-pass filter being used as a control signal for the phase shift circuit.