CN107317580A - A kind of high stability oscillator circuit and its implementation - Google Patents

Abstract

The invention discloses a high-stability oscillator circuit and its realization method. The oscillator circuit includes: a frequency division driving circuit, which is used to divide the frequency of the oscillation signal whose frequency is Fout output by the voltage-controlled oscillator by N to output The frequency-division signal whose frequency is Fout/N is sent to the charge pump circuit, and the frequency-division signal whose frequency is Fout/N is processed to output the in-phase frequency-division signal and the inverted frequency-division signal to the charge pump circuit; the charge pump circuit is used for Under the control of the in-phase frequency division signal and the inverse frequency division signal, the reference current is compared with the feedback current proportional to the frequency of the frequency-division signal Fout/N frequency output by the frequency-current conversion circuit and an error current is output; the low-pass filter circuit, It is used to convert the error current into a stable control voltage; the voltage-controlled oscillator is used to change the frequency of the output signal under the control of the control voltage. Through the present invention, a low power consumption based on closed-loop frequency control, High Stability Oscillator.

Description

A High Stability Oscillator Circuit and Its Implementation Method

technical field

The invention relates to an oscillator circuit and its realization method, in particular to a high-stability oscillator circuit and its realization method.

Background technique

Oscillators are an important part of modern electronic systems and are widely used in electronics, communications, navigation and aviation and other fields.

Commonly used CMOS on-chip fully integrated oscillators include LC oscillators, ring oscillators, relaxation oscillators, etc., and their oscillation frequency is significantly affected by process angle, power supply voltage, and temperature changes, which is not conducive to practical system applications. At present, the design of high-stability on-chip fully integrated oscillator circuits at home and abroad can be divided into two forms: open-loop and closed-loop. For the open-loop form, the temperature compensation circuit is generally used to directly perform open-loop temperature compensation on the oscillator frequency. The accuracy of its open-loop structure is limited to a certain extent, and it is greatly affected by the change of the process angle, and most of them require complex post-adjustment. Compared with the open-loop fully integrated oscillator, the closed-loop structure can simultaneously Suppressing changes in temperature and power supply voltage makes the output frequency more stable, but the closed-loop structure is relatively complex and consumes a lot of power.

Therefore, it is necessary to provide an oscillator with low power consumption and high stability based on closed-loop frequency control.

Contents of the invention

In order to overcome the shortcomings of the above-mentioned prior art, the object of the present invention is to provide a high stability oscillator circuit and its implementation method, so as to realize a low power consumption and high stability oscillator based on closed-loop frequency control.

In order to achieve the above and other purposes, the present invention proposes a high stability oscillator circuit, comprising:

A frequency-division driving circuit for dividing the frequency of the oscillating signal whose frequency is Fout output by the voltage-controlled oscillator by N to output a frequency-division signal whose frequency is Fout/N to the charge pump circuit, and using the frequency as Fout/N The frequency division signal is processed to output the in-phase frequency division signal and the inverse frequency division signal to the charge pump circuit;

The charge pump circuit is used to compare the reference current Iref with the feedback current If output by the frequency current conversion circuit proportional to the frequency of the frequency division signal Fout/N under the control of the non-phase frequency division signal and the reverse phase frequency division signal, and output an error Current Iout;

A low-pass filter circuit for converting the error current Iout into a stable control voltage Vc;

The voltage-controlled oscillator is used to change the frequency Fout of the output signal under the control of the control voltage Vc.

Further, the frequency-division drive circuit outputs the non-phase frequency-division signal through the transmission gate, and outputs the anti-phase frequency-division signal through the inverter.

Further, the frequency division drive circuit includes an N frequency divider, a transmission gate and an inverter, the input of the N frequency divider is connected to the output of the voltage-controlled oscillator, and the output frequency of the N frequency divider is Fout/ The output signal of N is connected to the input terminal of the transmission gate, the input terminal of the inverter and the frequency input terminal of the frequency current conversion circuit of the charge pump circuit, and the transmission gate and the output terminal of the inverter are connected to the charge pump circuit.

Further, the charge pump circuit includes a PMOS transistor, an NMOS transistor, a reference current source and a frequency current conversion circuit, the gate of the PMOS transistor is connected to the output terminal of the transmission gate, the source is connected to the positive terminal of the power supply, and the drain is connected to the reference The input end of the current source Iref, the output end of the reference current source is connected to the current input end of the frequency current conversion circuit and the low-pass filter circuit, the current output end of the frequency current conversion circuit is connected to the drain of the NMOS tube, The gate of the NMOS transistor is connected to the output terminal of the inverter, and the source is connected to the negative terminal of the power supply.

Further, the frequency-to-current conversion circuit outputs a feedback current proportional to the frequency of the frequency-divided signal Fout/N.

Further, the low-pass filter circuit adopts a first-order low-pass filter or a second-order or multi-order RC low-pass filter.

Further, the low-pass filter circuit includes a capacitor and a resistor R, one end of the resistor is connected to the output end of the reference current source, and the other end is connected to one end of the capacitor and the control end of the voltage-controlled oscillator, and the capacitor The other end is connected to the negative end of the power supply.

Further, the oscillating signal with a frequency of F _out generated by the voltage-controlled oscillator passes through the N frequency divider and then passes through the transmission gate and the inverter to generate the non-phase frequency division signal and the reverse phase frequency division signal. Two switches with opposite phases The signal controls the PMOS transistor and the NMOS transistor switch to be turned on and off at the same time, and the control voltage V _c is charged and discharged periodically.

In order to achieve the above object, the present invention also provides a method for realizing a high-stability oscillator circuit, comprising the following steps:

Step 1, divide the frequency of the oscillating signal whose frequency is Fout output by the voltage-controlled oscillator by N to output a frequency-divided signal whose frequency is Fout/N to the charge pump circuit, and pass the frequency-divided signal whose frequency is Fout/N Process and output the non-phase frequency division signal and the anti-phase frequency division signal to the charge pump circuit;

Step 2, using the charge pump circuit to feed back the reference current Iref output by the reference current source and the frequency current conversion circuit output proportional to the frequency of the frequency division signal Fout/N under the control of the non-phase frequency division signal and the reverse phase frequency division signal The current If is compared and the error current Iout is output;

Step 3, using a low-pass filter circuit to convert the error current Iout into a stable control voltage Vc;

Step 4, using a voltage-controlled oscillator to change the frequency Fout of the output signal under the control of the control voltage Vc.

Further, in step 1, the oscillating signal with a frequency of F _out produced by the voltage-controlled oscillator passes through the N frequency divider and then passes through the transmission gate and the inverter to generate the non-phase frequency-divided signal and the anti-phase frequency-divided signal. The opposite switching signal controls the PMOS transistor and the NMOS transistor switching transistor of the charge pump circuit to be turned on and off at the same time, so as to periodically charge and discharge the control voltage _Vc .

Compared with the prior art, a high-stability oscillator circuit and its implementation method of the present invention divide the frequency of the oscillating signal whose frequency is Fout output by the voltage-controlled oscillator by N so that the output frequency is the frequency division of Fout/N The signal is sent to the charge pump circuit, and the frequency division signal whose frequency is Fout/N is processed to output the non-phase frequency division signal and the reverse phase frequency division signal, so that the charge pump circuit is controlled by the same phase frequency division signal and the reverse phase frequency division signal Next, compare the reference current Iref with the feedback current If output by the frequency-current conversion circuit and the frequency-division signal Fout/N frequency, and output the error current Iout, and use the low-pass filter circuit to convert the error current Iout into a stable Control the voltage Vc, and finally use the voltage-controlled oscillator to change the frequency Fout of the output signal under the control of the control voltage Vc, realizing the purpose of a low-power, high-stability oscillator based on closed-loop frequency control.

Description of drawings

Fig. 1 is the circuit structural diagram of a kind of high stability oscillator circuit of the present invention;

FIG. 2 is a flow chart of steps of a method for implementing a high-stability oscillator circuit in the present invention.

detailed description

The implementation of the present invention is described below through specific examples and in conjunction with the accompanying drawings, and those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific examples, and various modifications and changes can be made to the details in this specification based on different viewpoints and applications without departing from the spirit of the present invention.

FIG. 1 is a circuit structure diagram of a high stability oscillator circuit according to the present invention. As shown in FIG. 1 , a high-stability oscillator circuit according to the present invention includes: a frequency division drive circuit 10 , a charge pump circuit 20 , a low-pass filter circuit 30 and a voltage-controlled oscillator 40 .

Wherein, the frequency division drive circuit 10 includes an N frequency divider Div1, a transmission gate T1 and an inverter INV1, which are used to divide the frequency of the oscillating signal whose frequency is Fout output by the voltage-controlled oscillator 40 by N so that the output frequency is Fout /N frequency-division signal charge pump circuit, and the frequency-division signal whose frequency is Fout/N outputs the in-phase frequency-division signal S1 through the transmission gate T1, and outputs the inverse frequency-division signal S2 to the charge pump circuit 20 through the inverter INV1; The charge pump circuit 20 includes a PMOS transistor M1, an NMOS transistor M2, a reference current source Iref, and a frequency-current conversion circuit (FIC) F1, which are used to convert the reference current Iref and The frequency current conversion circuit (FIC) F1 output is compared with the feedback current If proportional to the frequency of the frequency division signal Fout/N and outputs the error current Iout; the low-pass filter circuit 30 is a first-order low-pass composed of a resistor R and a capacitor C The filter is used to convert the error current Iout into a stable control voltage Vc, and a second-order or multi-order RC low-pass filter can also be used; the voltage-controlled oscillator 40 is an oscillator with a general voltage control frequency, used for controlling the voltage The frequency Fout of the output signal is changed under the control of Vc.

The output of the voltage-controlled oscillator VCO1 is connected to the subsequent circuit (not shown) and the input terminal of the frequency divider Div1, and the output signal of the frequency Fout/N output by the frequency divider Div1 is connected to the input terminal of the transmission gate T1, the inverting The input terminal of the inverter INV1 and the frequency input terminal of the frequency current conversion circuit (FIC) F1, the output terminal of the transmission gate T1 is connected to the gate of the PMOS transistor M1, and the output terminal of the inverter INV1 is connected to the gate of the NMOS transistor M2, The source of the PMOS transistor M1 is connected to the positive power supply terminal VDD, the source of the NMOS transistor M2 is connected to the negative power supply terminal (ground), the drain of the PMOS transistor M1 is connected to the input terminal of the reference current source Iref, and the output of the reference current source Iref The terminal is connected to the current input terminal of the frequency current conversion circuit (FIC) F1 and one end of the resistor R, the current output terminal of the frequency current conversion circuit (FIC) F1 is connected to the drain of the NMOS transistor M2, and the other end of the resistor R is connected to the capacitor One end of C is connected to the control end of the voltage-controlled oscillator VCO1, and the other end of the capacitor C is connected to the negative end of the power supply (ground); the frequency divider Div1, the transmission gate T1, the inverter INV1, and the voltage-controlled oscillator VCO1 all need to be connected to their respective power and ground.

It can be seen that the voltage-controlled oscillator VCO1 generates a periodic oscillation signal with a frequency of Fout according to the input control voltage VC; the function of the frequency divider Div1 is to reduce the frequency of the oscillation signal by N times; the frequency-current conversion circuit (FIC) converts the input frequency signal is the corresponding current value, which has a linear relationship and satisfies:

The working principle of the present invention is as follows:

The oscillating signal of the frequency F _out generated by the voltage-controlled oscillator VCO1 passes through the frequency divider Div1 and then passes through the transmission gate T1 and the inverter INV1 to generate the in-phase frequency division signal S1 and the inverse frequency division signal S2. Two switching signals with opposite phases control M1 , The M2 switch tube is turned on and off at the same time to periodically charge and discharge the control voltage V _c , and the periodic work of the charge pump circuit helps to reduce the power consumption of the circuit system. The I _ref current generated by the reference current source during the conduction period is compared with the I _f current, and the output current value is the difference between the two:

If I _out >0 → charge V _c → increase voltage V _c → increase frequency → increase current I _f → decrease I _out , repeat this process until I _ref = I _f , the frequency expression of the stable oscillation frequency is:

The resistor R and the capacitor C form a low-pass filter circuit to reduce the ripple of the control voltage Vc and stabilize the frequency Fout of the system output.

It can be analyzed from the final output frequency expression that since the frequency division ratio N and the frequency-to-current conversion coefficient α are all fixed values, the oscillation frequency obtained after feedback control is only related to Iref, so through design and process angle, power supply voltage, The temperature-independent reference current source can obtain the same high-stability oscillation signal.

FIG. 2 is a flow chart of steps of a method for implementing a high-stability oscillator circuit in the present invention. As shown in Figure 2, a method for realizing a high-stability oscillator circuit of the present invention includes the following steps:

Step 201, divide the frequency of the oscillating signal whose frequency is Fout output by the voltage-controlled oscillator by N to output a frequency-divided signal whose frequency is Fout/N to the charge pump circuit, and pass the frequency-divided signal whose frequency is Fout/N Process and output the non-phase frequency division signal and the anti-phase frequency division signal to the charge pump circuit;

Step 202, the charge pump circuit under the control of the non-phase frequency division signal and the reverse phase frequency division signal, the reference current Iref of the reference current source and the feedback current proportional to the frequency of the frequency division signal Fout/N output by the frequency current conversion circuit If compares and outputs the error current Iout;

Step 203, using a low-pass filter circuit to convert the error current Iout into a stable control voltage Vc;

Step 204, using a voltage controlled oscillator to change the frequency Fout of the output signal under the control of the control voltage Vc.

Specifically, the oscillating signal with the frequency F _out generated by the voltage-controlled oscillator passes through the N frequency divider and then passes through the transmission gate and the inverter to generate the non-phase frequency-divided signal and the anti-phase frequency-divided signal. Two switching signals with opposite phases , the charge pump circuit compares the reference current Iref with the feedback current If proportional to the frequency of the frequency-division signal Fout/N output by the frequency-current conversion circuit under the control of the in-phase frequency-division signal and the reverse-phase frequency-division signal to output an error current Iout To a low-pass filter circuit (comprising a capacitor and a resistor), in a specific embodiment of the present invention, the in-phase frequency division signal and the anti-phase frequency division signal respectively control the PMOS tube and the NMOS tube switch tube of the charge pump circuit to be turned on and switched on simultaneously. Turn off, and then periodically charge and discharge the control voltage _Vc , the periodic work of the charge pump circuit helps to reduce the power consumption of the circuit system.

In summary, a high-stability oscillator circuit and its implementation method of the present invention divide the frequency of the oscillation signal whose frequency is Fout output by the voltage-controlled oscillator by N to output a frequency-divided signal whose frequency is Fout/N to A charge pump circuit, and the frequency division signal whose frequency is Fout/N is processed to output a non-phase frequency division signal and an inverted frequency division signal, so that the charge pump circuit will be controlled by the same phase frequency division signal and the reverse phase frequency division signal. The reference current Iref is compared with the feedback current If output by the frequency-current conversion circuit proportional to the frequency of the frequency division signal Fout/N, and the error current Iout is output, and the error current Iout is converted into a stable control voltage by using a low-pass filter circuit Vc, and finally use the voltage-controlled oscillator to change the frequency Fout of the output signal under the control of the control voltage Vc, realizing the purpose of a low-power, high-stability oscillator based on closed-loop frequency control.

The above-mentioned embodiments only illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Any person skilled in the art can modify and change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be listed in the claims.

Claims (10)

1. a kind of high stability oscillator circuit, including：

Drive circuit is divided, for the frequency that exports voltage controlled oscillator for the frequency divided by N of Fout oscillator signal to export Frequency exports same phase for Fout/N fractional frequency signal to charge pump circuit, and by the frequency for Fout/N fractional frequency signal through processing Fractional frequency signal and anti-phase fractional frequency signal to charge pump circuit；

Charge pump circuit, for this with phase fractional frequency signal and anti-phase fractional frequency signal control under by reference current Iref and frequency electricity The feedback current If proportional to fractional frequency signal Fout/N frequencies that circuit output is changed in circulation is compared and output error electric current Iout；

Low-pass filter circuit, for error current Iout to be converted into stable control voltage Vc；

Voltage controlled oscillator, the frequency Fout for changing output signal under control voltage Vc control.

2. a kind of high stability oscillator circuit as claimed in claim 1, it is characterised in that：The frequency dividing drive circuit is by passing Defeated door exports this with phase fractional frequency signal, and inverted device exports the anti-phase fractional frequency signal.

3. a kind of high stability oscillator circuit as claimed in claim 2, it is characterised in that：The frequency dividing drive circuit includes N Frequency divider, transmission gate and phase inverter, the input of the Fractional-N frequency device connect the output end of the voltage controlled oscillator, and the Fractional-N frequency device is defeated The frequency gone out is connected to the input of the transmission gate, the input of the phase inverter and charge pump electricity for Fout/N output signal The output end of the frequency input of the frequency-current conversion circuit on road, the transmission gate and the phase inverter is connected to charge pump electricity Road.

4. a kind of high stability oscillator circuit as claimed in claim 3, it is characterised in that：The charge pump circuit includes one PMOS, NMOS tube, reference current source and frequency-current conversion circuit, the grid of the PMOS connect the output of the transmission gate End, source electrode connects power positive end, and drain electrode connects reference current source Iref input, and the output end of the reference current source is connected to this The current input terminal and low-pass filter circuit of frequency-current conversion circuit, the current output terminal of the frequency-current conversion circuit connect The drain electrode of the NMOS tube is connected to, the grid of the NMOS tube connects the output end of the phase inverter, and source electrode connects power supply negative terminal.

5. a kind of high stability oscillator circuit as claimed in claim 4, it is characterised in that：The frequency-current conversion circuit is defeated Go out the feedback current being directly proportional to fractional frequency signal Fout/N frequencies.

6. a kind of high stability oscillator circuit as claimed in claim 4, it is characterised in that：The low-pass filter circuit is used Low-pass first order filter or second order or multistage RC low pass filters.

7. a kind of high stability oscillator circuit as claimed in claim 6, it is characterised in that：The low-pass filter circuit includes One electric capacity and resistance R, one end of the resistance connect the output end of the reference current source, the other end be connected to the electric capacity one end and The control end of the voltage controlled oscillator, another termination power supply negative terminal of the electric capacity.

8. a kind of high stability oscillator circuit as claimed in claim 4, it is characterised in that：The frequency that the voltage controlled oscillator is produced Rate is F_outOscillator signal this is produced with phase fractional frequency signal, anti-phase frequency dividing by the transmission gate and phase inverter after the Fractional-N frequency device The switching signal of signal two-way opposite in phase controls the PMOS, NMOS tube switching tube to simultaneously turn on and turn off, periodically to control Voltage V processed_cCarry out discharge and recharge.

9. a kind of implementation method of high stability oscillator circuit, comprises the following steps：

Step one, the frequency divided by N for the oscillator signal for being Fout by the frequency that voltage controlled oscillator is exported are using output frequency as Fout/ N fractional frequency signal to charge pump circuit, and by the frequency for Fout/N fractional frequency signal through processing output with phase fractional frequency signal with Anti-phase fractional frequency signal is to charge pump circuit；

Step 2, using the charge pump circuit this with phase fractional frequency signal and anti-phase fractional frequency signal control under reference current source is defeated The feedback current proportional with fractional frequency signal Fout/N frequencies that the reference current Iref gone out is exported to frequency-current conversion circuit If is compared and output error electric current Iout；

Step 3, stable control voltage Vc is converted to using low-pass filter circuit by error current Iout；

Step 4, changes the frequency Fout of output signal using voltage controlled oscillator under control voltage Vc control.

10. a kind of implementation method of high stability oscillator circuit as claimed in claim 9, it is characterised in that：In step one In, the frequency that the voltage controlled oscillator is produced is F_outOscillator signal to produce this by transmission gate and phase inverter after Fractional-N frequency device same Phase fractional frequency signal, the switching signal of anti-phase fractional frequency signal two-way opposite in phase control the PMOS of the charge pump circuit, NMOS tube Switching tube is simultaneously turned on and turned off, with periodicity to control voltage V_cCarry out discharge and recharge.