Voltage-controlled oscillator, phase-locked loop circuit and image sensor

Abstract

The utility model proposes a voltage-controlled oscillator, a phase-locked loop circuit and an image sensor, the voltage-controlled oscillator comprises a linear conversion circuit and an oscillation circuit, the linear conversion circuit receives a first voltage signal output by a charge pump circuit and converts the first voltage signal into a linear change or approximately linear change current signal, and the current signal is output to the oscillation circuit; the oscillating circuit oscillates at a corresponding frequency according to the magnitude of the current signal and outputs a second voltage signal, and the output current and the control voltage of the voltage-controlled oscillator are linearly changed or approximately linearly changed by changing a voltage-to-current module of the voltage-controlled oscillator; finally, the ratio of the output frequency to the input voltage of the voltage-controlled oscillator is a fixed value or close to a fixed value, and when the phase-locked loop circuit works at different frequencies, the stability of an amplitude-frequency curve and the phase margin of a loop are ensured, the jitter of the output frequency is reduced, and the stability of the phase-locked loop circuit is improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of image sensors, and in particular relates to a voltage-controlled oscillator, a phase-locked loop circuit and an image sensor. Background Art

[0002] Phase-locked loop (PLL) circuits are found in a variety of high-frequency applications, from simple clock purification circuits to local oscillators (LOs) for high-performance radio communication links, and ultrafast switching frequency synthesizers in vector network analyzers (VNAs), image sensors, etc.

[0003] The phase-locked loop circuit usually includes a frequency detector, a charge pump circuit and a voltage-controlled oscillator, such as Figure 1 The voltage-controlled oscillator shown in the figure, wherein the first electronic switch tube M1 converts the control voltage output by the charge pump circuit into current, and the inverter chain composed of the second electronic switch tubes M2 and M7 oscillates at different frequencies according to different current sizes. The core parameter of the voltage-controlled oscillator is the coefficient Kvco, which is characterized by the ratio of the frequency of the output signal to the input voltage. The coefficient Kvco of the ideal voltage-controlled oscillator should be a constant.

[0004] The amplitude-frequency characteristic of the loop frequency of the phase-locked loop circuit is directly related to Kvco, while the phase-frequency characteristic is unrelated to Kvco. When the phase-locked loop circuit operates at different frequencies, when the coefficient Kvco is different, it will cause the amplitude-frequency curve to shift up and down, thereby causing the bandwidth of the phase-locked loop circuit to change, and ultimately affecting the phase margin of the loop. In addition, the jitter of the output waveform of the phase-locked loop circuit is also directly related to the coefficient Kvco. Different Kvco at different operating frequencies will cause uncertainty in the output frequency jitter, thereby reducing the output clock quality of the phase-locked loop circuit in practical applications.

[0005] The main reason why the Kvco of the voltage-controlled oscillator is different when it works at different operating frequencies is that the electronic switch tube M1 works in the saturation region and its current is determined by the following formula:

[0006]

[0007] From the formula, we can see that the current and the control voltage Vcont are in a square relationship, and the conversion of the control voltage Vcont into current is not a linear conversion. Therefore, as the control voltage Vcont decreases, the oscillation frequency of the voltage-controlled oscillator increases, and Kvco increases, which ultimately affects the amplitude-frequency characteristics of the phase-locked loop circuit and the output frequency jitter. Utility Model Content

[0008] The utility model aims to provide a voltage-controlled oscillator, aiming to solve the problem of high output frequency jitter and poor stability caused by the change of coefficient Kvco of the voltage-controlled oscillator in the traditional phase-locked loop circuit.

[0009] A first aspect of an embodiment of the utility model provides a voltage-controlled oscillator, which is configured to adjust the frequency and phase of an output second voltage signal according to a received first voltage signal, and the voltage-controlled oscillator includes:

[0010] A linear conversion circuit configured to convert a received first voltage signal into a current signal, wherein a magnitude of the current signal is correlated with a magnitude of the first voltage signal in negative proportion, wherein the correlated change includes a linear change or an approximately linear change;

[0011] The oscillation circuit is connected to the linear conversion circuit and is configured to oscillate at a corresponding frequency according to the magnitude of the current signal and output a second voltage signal, wherein the frequency of the second voltage signal changes in a positive correlation with the magnitude of the current signal.

[0012] Optionally, the linear conversion circuit includes a first resistor, a first electronic switch tube and a comparator;

[0013] The first end of the first resistor is connected to the positive voltage, the second end of the first resistor, the inverting input end of the comparator and the source of the first electronic switch tube are connected, the non-inverting input end of the comparator constitutes the input end of the linear conversion circuit, the gate of the first electronic switch tube is connected to the output end of the comparator, and the drain of the first electronic switch tube constitutes the output end of the linear conversion circuit.

[0014] Optionally, the linear conversion circuit includes a second resistor and a second electronic switch tube;

[0015] The first end of the second resistor is connected to the positive voltage, the second end of the second resistor is connected to the source of the second electronic switch tube, the gate of the second electronic switch tube constitutes the input end of the linear conversion circuit, and the drain of the second electronic switch tube constitutes the output end of the linear conversion circuit.

[0016] Optionally, the oscillation circuit comprises an odd number of inverter circuits;

[0017] The input and output ends of an odd number of the inverter circuits are connected in sequence to form a ring oscillator, the output end or input end of a corresponding inverter circuit constitutes the output end of the oscillation circuit, and the control ends of an odd number of the inverter circuits are connected together to form the input end of the oscillation circuit.

[0018] Optionally, the inverter circuit comprises an inverter.

[0019] Optionally, the inverter circuit includes a third electronic switch tube and a fourth electronic switch tube;

[0020] The source of the third electronic switch tube constitutes the control end of the inverter circuit, the gate of the third electronic switch tube and the gate of the fourth electronic switch tube are connected to constitute the input end of the inverter circuit, the drain of the third electronic switch tube and the drain of the fourth electronic switch tube are connected to constitute the output end of the inverter circuit, and the source of the fourth electronic switch tube is grounded.

[0021] Optionally, the width-to-length ratio of each electronic switch tube of the oscillator circuit is greater than 20;

[0022] The threshold voltage of each electronic switch tube of the oscillation circuit is less than 300mV.

[0023] A second aspect of the embodiment of the utility model provides a phase-locked loop circuit, comprising a phase frequency detector, a charge pump circuit and the voltage-controlled oscillator as described above, wherein the phase frequency detector, the charge pump circuit and the voltage-controlled oscillator form a series loop, and the signal output end of the voltage-controlled oscillator constitutes the signal output end of the phase-locked loop circuit;

[0024] The frequency and phase detector is configured to detect the frequency and phase difference between the reference signal and the second voltage signal output by the voltage-controlled oscillator, and generate a first control signal and a second control signal;

[0025] The charge pump circuit is configured to charge and discharge according to the received first control signal and second control signal, and output a first voltage signal of corresponding magnitude to the voltage-controlled oscillator;

[0026] The voltage-controlled oscillator is configured to adjust the frequency and phase of the output second voltage signal according to the received first voltage signal, so that the output signal of the phase-locked loop circuit has the same frequency and phase as the reference signal.

[0027] Optionally, the phase-locked loop circuit further includes:

[0028] A frequency divider, wherein the input end of the frequency divider is connected to the output end of the voltage-controlled oscillator, and the output end of the frequency divider is connected to the input end of the frequency detector. The frequency divider is configured to divide the output signal of the voltage-controlled oscillator and output the divided voltage signal to the frequency detector.

[0029] A third aspect of the embodiments of the present utility model provides an image sensor, comprising the phase-locked loop circuit as described above.

[0030] Compared with the prior art, the beneficial effects of the embodiments of the utility model are as follows: the above-mentioned voltage-controlled oscillator includes a linear conversion circuit and an oscillation circuit, the linear conversion circuit receives the first voltage signal output by the charge pump circuit, and converts it into a current signal that changes linearly or approximately linearly, the current signal is output to the oscillation circuit, the oscillation circuit oscillates at a corresponding frequency according to the size of the current signal, and outputs a second voltage signal, by changing the voltage-to-current module of the voltage-controlled oscillator, so that its output current and the control voltage change linearly or approximately linearly, and finally the ratio of the output frequency of the voltage-controlled oscillator to the input voltage is a constant value or close to a constant value, when the phase-locked loop circuit operates at different frequencies, the stability of the amplitude-frequency curve and the phase margin of the loop are guaranteed, the jitter of the output frequency is reduced, and the stability of the phase-locked loop circuit is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0032] Figure 1 is a circuit diagram of a conventional voltage-controlled oscillator;

[0033] Figure 2 A schematic diagram of the first structure of a voltage-controlled oscillator provided in an embodiment of the utility model;

[0034] Figure 3 A second structural schematic diagram of a voltage-controlled oscillator provided in an embodiment of the utility model;

[0035] Figure 4 A first circuit diagram of a voltage-controlled oscillator provided by an embodiment of the utility model;

[0036] Figure 5 A second circuit diagram of a voltage-controlled oscillator provided by an embodiment of the utility model;

[0037] Figure 6 A third circuit diagram of a voltage-controlled oscillator provided by an embodiment of the utility model;

[0038] Figure 7 A first structural schematic diagram of a phase-locked loop circuit provided in an embodiment of the utility model;

[0039] Figure 8 A second structural schematic diagram of a phase-locked loop circuit provided in an embodiment of the utility model. DETAILED DESCRIPTION

[0040] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present utility model, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0042] A first aspect of an embodiment of the utility model proposes a voltage-controlled oscillator, which is connected to a charge pump circuit of a previous stage and is configured to adjust the frequency and phase of an output second voltage signal Vout according to a received first voltage signal Vcont. The second voltage signal Vout is fed back to a frequency detector and phase detector and compared with a reference signal Vref, for example, the rising edges of the two are compared, and a first control signal and a second control signal are obtained according to the frequency and phase difference comparison between the two. The first control signal and the second control signal are output to the charge pump circuit, and the charge pump circuit performs charging and discharging accordingly, and outputs a changing or stable first voltage signal Vcont to the voltage-controlled oscillator. The voltage-controlled oscillator finally adjusts the frequency and phase of the second voltage signal Vout to be the same as the frequency and phase of the reference signal Vref, that is, adjusts the frequency and phase of the output signal of the phase-locked loop circuit to be the same as the frequency and phase of the reference signal Vref.

[0043] Among them, Figure 2 As shown, in this embodiment, the voltage controlled oscillator 100 includes:

[0044] The linear conversion circuit 10 is configured to convert the received first voltage signal Vcont into a current signal, wherein the magnitude of the current signal is correlated with the magnitude of the first voltage signal Vcont in a negative proportion, wherein the correlated change includes a linear change or an approximately linear change;

[0045] The oscillation circuit 20 is connected to the linear conversion circuit 10 and is configured to oscillate at a corresponding frequency according to the magnitude of the current signal and output a second voltage signal Vout. The frequency of the second voltage signal Vout varies in a positive correlation with the magnitude of the current signal.

[0046] In this embodiment, the signal input end of the linear conversion circuit 10 is connected to the charge pump circuit 300 of the previous stage, and receives the first voltage signal Vcont output by the charge pump circuit 300. The linear conversion circuit 10 performs voltage-current conversion and outputs a current signal, wherein the current signal changes in negative proportion to the first voltage signal Vcont, that is:

[0047] I d =-a*V cont +b;

[0048] Vcont represents the first voltage signal Vcont, Id represents the current signal, a is the proportional coefficient, b is a constant, b can be 0, a can be a constant or close to a constant, that is, the current signal and the first voltage signal Vcont are negatively correlated linearly or negatively correlated approximately linearly. When the first voltage signal Vcont changes, the current signal changes linearly or approximately linearly.

[0049] The generated current signal is output to the oscillation circuit 20. The oscillation circuit 20 oscillates at different frequencies according to different current magnitudes. The oscillation frequency changes in a positive correlation with the magnitude of the current signal and changes linearly. Its positive proportional coefficient is K, that is, the frequency of the second voltage signal Vout output by the oscillation circuit 20 changes linearly with the current signal. Therefore, the frequency of the second voltage signal Vout output by the oscillation circuit 20 changes linearly or approximately linearly with the magnitude of the first voltage signal Vcont. The second voltage signal Vout of the oscillation circuit 20 is the output signal of the voltage-controlled oscillator 100. The first voltage signal Vcont is the input voltage of the voltage-controlled oscillator 100. Through indirect comparison of the current signal, the ratio of the output frequency of the voltage-controlled oscillator 100 to the input voltage of the voltage-controlled oscillator 100 is Ka. Ka is a constant or close to a constant, that is, the coefficient Kvco is a constant or close to a constant. Therefore, when the phase-locked loop circuit operates at different frequencies, the coefficient Kvco of the voltage-controlled oscillator 100 can be guaranteed to be consistent at each operating frequency, thereby ensuring the phase margin of the phase-locked loop circuit and the stability of the output jitter.

[0050] The linear conversion circuit 10 can use corresponding resistors, transistors, amplifiers and other structures to achieve linear conversion of voltage to current. In an optional embodiment, Figure 4 As shown, the linear conversion circuit 10 includes a first resistor R1, a first electronic switch tube M1 and a comparator U1;

[0051] The first end of the first resistor R1 is connected to the positive voltage AVDD, the second end of the first resistor R1, the inverting input end of the comparator U1 and the source of the first electronic switch tube M1 are connected, the non-inverting input end of the comparator U1 constitutes the input end of the linear conversion circuit 10, the gate of the first electronic switch tube M1 is connected to the output end of the comparator U1, and the drain of the first electronic switch tube M1 constitutes the output end of the linear conversion circuit 10.

[0052] In this embodiment, the comparator U1, the first electronic switch tube M1 and the first resistor R1 form a negative feedback circuit, and the formula of the current signal is:

[0053]

[0054] Right now When the first voltage signal Vcont changes, the current signal changes linearly. The linearly changing current signal is output to the oscillation circuit 20. The oscillation circuit 20 oscillates at different frequencies according to different current sizes. The oscillation frequency changes in a positive correlation with the size of the current signal and changes linearly. Therefore, the frequency of the second voltage signal Vout output by the oscillation circuit 20 changes linearly with the size of the first voltage signal Vcont. Through indirect comparison of the current signal, the ratio of the output frequency of the voltage-controlled oscillator 100 to the input voltage of the voltage-controlled oscillator 100 is Ka. Ka is a constant, that is, the coefficient Kvco is a constant. Therefore, when the phase-locked loop circuit operates at different frequencies, it can ensure that the coefficient Kvco of the voltage-controlled oscillator 100 is consistent at each operating frequency, thereby ensuring the phase margin of the phase-locked loop circuit and the stability of the output jitter.

[0055] In another alternative embodiment, if Figure 5 As shown, the linear conversion circuit 10 includes a second resistor R2 and a second electronic switch tube M2;

[0056] The first end of the second resistor R2 is connected to the positive voltage AVDD, the second end of the second resistor R2 is connected to the source of the second electronic switch tube M2, the gate of the second electronic switch tube M2 constitutes the input end of the linear conversion circuit 10, and the drain of the second electronic switch tube M2 constitutes the output end of the linear conversion circuit 10.

[0057] In this embodiment, the second resistor R2 and the second electronic switch tube M2 form a source negative feedback circuit to achieve an approximately linear conversion of voltage-current. In the source negative feedback in the figure, the ratio of its current signal to the first voltage signal Vcont is Gm, that is, the equivalent transconductance is

[0058]

[0059] Among them, g m represents the transconductance of the second electronic switch tube M2, R2 is the resistance value of the second resistor R2, g m*R2 is larger, such as g m *R2>10, the equivalent transconductance Gm is approximately equal to 1 / R2. At this time, the current signal and the first voltage signal Vcont are approximately linearly related, that is, the current signal and the first voltage signal Vcont are negatively correlated and approximately linearly changed. When the first voltage signal Vcont changes, the current signal changes approximately linearly.

[0060] The current signal with approximately linear variation is output to the oscillation circuit 20. The oscillation circuit 20 oscillates at different frequencies according to different current magnitudes. The oscillation frequency varies in positive correlation with the magnitude of the current signal. The frequency of the second voltage signal Vout output by the oscillation circuit 20 varies approximately linearly with the magnitude of the first voltage signal Vcont. Through indirect comparison of the current signal, the ratio of the output frequency of the voltage-controlled oscillator 100 to the input voltage of the voltage-controlled oscillator 100 is Ka. Ka is close to a constant, that is, the coefficient Kvco is close to a constant. Therefore, when the phase-locked loop circuit operates at different frequencies, it can be ensured that the coefficient Kvco of the voltage-controlled oscillator 100 is close to the same at each operating frequency, thereby ensuring the phase margin of the phase-locked loop circuit and the stability of the output jitter.

[0061] The oscillation circuit 20 may be a transistor, an inverter U2, etc. In an optional embodiment, Figure 3 As shown, the oscillation circuit 20 includes an odd number of inverter circuits 21;

[0062] The input and output ends of an odd number of inverter circuits 21 are connected in sequence to form a ring oscillator. The output end or input end of a corresponding inverter circuit 21 constitutes the output end of the oscillation circuit 20. The control ends of the odd number of inverter circuits 21 are connected together to form the input end of the oscillation circuit 20.

[0063] In this embodiment, an odd number of inverter circuits 21 form an inverter chain, which oscillates at different frequencies according to current signals of different sizes. The second voltage signal Vout generated by the oscillation is output from the input end or the output end of the corresponding inverter circuit 21. The ratio of the oscillation frequency of the second voltage signal Vout to the input voltage of the linear conversion circuit 10, i.e., the first voltage signal Vcont, is a constant or close to a constant value. Therefore, when the phase-locked loop circuit operates at different frequencies, the coefficient Kvco of the voltage-controlled oscillator 100 can be guaranteed to be consistent at each operating frequency, thereby ensuring the phase margin of the phase-locked loop circuit and the stability of the output jitter.

[0064] The inverter circuit 21 can be composed of a corresponding switch tube and an inverter U2. In an optional embodiment, Figure 6As shown, the inverter circuit 21 includes an inverter U2, the power supply end of the inverter U2 is connected to the output end of the linear conversion circuit 10, the input end and the output end of an odd number of inverters U2 are connected in sequence to form a ring oscillator, and the odd number of inverters U2 form an inverter chain. The inverter U2 oscillates at different frequencies according to the received current signal, and the second voltage signal Vout generated by the oscillation is output by the input end or the output end of the corresponding inverter U2. When the phase-locked loop circuit operates at different frequencies, the coefficient Kvco of the voltage-controlled oscillator 100 can be guaranteed to be consistent at each operating frequency, thereby ensuring the phase margin of the phase-locked loop circuit and the stability of the output jitter.

[0065] like Figure 5 As shown, in another optional embodiment, the inverter circuit 21 includes a third electronic switch tube M3 and a fourth electronic switch tube M4;

[0066] The source of the third electronic switch tube M3 constitutes the control end of the inverter circuit 21, the gate of the third electronic switch tube M3 and the gate of the fourth electronic switch tube M4 are connected to constitute the input end of the inverter circuit 21, the drain of the third electronic switch tube M3 and the drain of the fourth electronic switch tube M4 are connected to constitute the output end of the inverter circuit 21, and the source of the fourth electronic switch tube M4 is grounded.

[0067] In this embodiment, the source of the third electronic switch tube M3 inputs a current signal, and the third electronic switch tube M3 and the fourth electronic switch tube M4 oscillate according to the received current signal and output a second voltage signal Vout from a corresponding commonly connected gate position.

[0068] Among them, the reason why the Kvco of the voltage-controlled oscillator 100 is different when it works at different working frequencies is also related to the on-resistance of the third electronic switch tube M3 and the fourth electronic switch tube M4. Since the switch on-resistance of the inverter circuit 21 composed of multiple third electronic switch tubes M3 and fourth electronic switch tubes M4 changes with the output voltage of the linear conversion circuit 10, when the oscillation frequency is low, the output voltage of the linear conversion circuit 10 is low. At this time, the Vgs of the third electronic switch tube M3 and the fourth electronic switch tube M4 are small, and the on-resistance is large. The input and output delay of the inverter circuit 21 is mainly determined by the on-resistance; when the oscillation frequency is high, the output voltage of the linear conversion circuit 10 is high. At this time, the Vgs of the third electronic switch tube M3 and the fourth electronic switch tube M4 are large, and the on-resistance is small. The input and output delay of the inverter circuit 21 is mainly determined by the on-resistance. It is determined by the current. In order to solve the problem of different Kvco caused by devices, in an optional embodiment, the width-to-length ratio of each electronic switch tube of the oscillation circuit 20 is greater than 20, the threshold voltage of each electronic switch tube of the oscillation circuit 20 is less than 300mV, and the third electronic switch tube M3 and the fourth electronic switch tube M4 of each inverter circuit 21 adopt a larger width-to-length ratio and a smaller threshold voltage, thereby ensuring that at different operating frequencies of the phase-locked loop circuit, the on-impedance of the third electronic switch tube M3 and the fourth electronic switch tube M4 of the inverter circuit 21 is small, thereby ensuring that the oscillation frequency of the voltage-controlled oscillator 100 is determined by the current signal and is independent of the switch on-impedance of the inverter circuit 21, thereby ensuring that the coefficient Kvco of the voltage-controlled oscillator 100 is consistent at each operating frequency, thereby ensuring the phase margin of the phase-locked loop circuit and the stability of the output jitter.

[0069] Compared with the prior art, the embodiments of the utility model have the following beneficial effects: the voltage-controlled oscillator 100 includes a linear conversion circuit 10 and an oscillation circuit 20. The linear conversion circuit 10 receives the first voltage signal Vcont output by the charge pump circuit 300, and converts it into a current signal that changes linearly or approximately linearly. The current signal is output to the oscillation circuit 20. The oscillation circuit 20 oscillates at a corresponding frequency according to the magnitude of the current signal, and outputs a second voltage signal Vout. By changing the voltage-to-current module of the voltage-controlled oscillator 100, its output current and the control voltage change linearly or approximately linearly, and finally the ratio of the output frequency of the voltage-controlled oscillator 100 to the input voltage is a constant or close to a constant. When the phase-locked loop circuit operates at different frequencies, the stability of the amplitude-frequency curve and the phase margin of the loop are guaranteed, the jitter of the output frequency is reduced, and the stability of the phase-locked loop circuit is improved.

[0070] like Figure 7As shown, the embodiment of the utility model further proposes a phase-locked loop circuit, comprising a frequency detector 200, a charge pump circuit 300 and the voltage-controlled oscillator 100 as above, the frequency detector 200, the charge pump circuit 300 and the voltage-controlled oscillator 100 form a series loop, and the signal output end of the voltage-controlled oscillator 100 constitutes the signal output end of the phase-locked loop circuit;

[0071] The frequency detector 200 is configured to detect the frequency and phase difference between the reference signal Vref and the second voltage signal Vout output by the voltage controlled oscillator 100, and generate a first control signal up and a second control signal down;

[0072] The charge pump circuit 300 is configured to charge and discharge according to the received first control signal up and the second control signal down, and output a first voltage signal Vcont of a corresponding magnitude to the voltage controlled oscillator 100;

[0073] The voltage controlled oscillator 100 is configured to adjust the frequency and phase of the output second voltage signal Vout according to the received first voltage signal Vcont, so that the output signal of the phase-locked loop circuit has the same frequency and phase as the reference signal Vref.

[0074] In this embodiment, the frequency detector 200 compares the reference signal Vref and the output signal of the phase-locked loop circuit, for example, compares the rising edges of the two, and obtains the first control signal up and the second control signal down according to the frequency and phase difference comparison between the two. Specifically, in the phase-locked loop circuit, if the reference signal Vref has a rising edge, but the output signal does not have a rising edge, the first control signal up is a high level, and the second control signal down is a low level. If the reference signal Vref has a rising edge and the output signal has a rising edge, the frequency detector 200 simultaneously outputs the first control signal up and the second control signal down of a low level. If the reference signal Vref does not have a rising edge, but the output signal has a rising edge, the first control signal up is a low level, and the second control signal down is a high level.

[0075] The charge pump circuit 300 charges and discharges according to the high and low levels of the first control signal up and the second control signal down. When the first control signal up is a high level signal and the second control signal down is a low level signal, the charge pump circuit 300 charges and the output first voltage signal Vcont increases; and when the first control signal up is a low level signal and the second control signal down is a high level signal, the charge pump circuit 300 discharges and the output first voltage signal Vcont decreases; and, when the first control signal up and the second control signal down are both high level signals or low level signals, the charge pump circuit 300 charges and discharges simultaneously, or both charges and discharges simultaneously. At this time, the charge pump circuit 300 outputs a constant first voltage signal Vcont, and the constant voltage signal may be a zero voltage or a preset voltage.

[0076] The voltage-controlled oscillator 100 adjusts the frequency and phase of the second voltage signal Vout, i.e., the output signal of the phase-locked loop circuit, according to the first voltage signal Vcont output by the charge pump circuit 300. When the received first voltage signal Vcont increases, the voltage-controlled oscillator 100 increases the frequency of the output signal to catch up with the frequency and phase of the reference signal Vref until the frequencies and phases of the two are the same. The first control signal up and the second control signal down are at the same level, and the frequency detector 200 is reset to complete the frequency detection and phase locking operation.

[0077] And when the received voltage signal decreases, the voltage-controlled oscillator 100 reduces the frequency of the output signal, making it gradually approach the frequency and phase of the reference signal Vref, until the frequencies and phases of the two are the same, the first control signal up and the second control signal down are at the same level, the frequency detector 200 is reset, and the frequency detection and phase locking operation is completed.

[0078] The phase and frequency detector 200 may be composed of structures such as a D flip-flop, a logic gate, etc., and the charge pump circuit 300 may be composed of a current source, a controllable switch, and an energy storage element.

[0079] like Figure 8 As shown, in an optional embodiment, the phase-locked loop circuit further includes:

[0080] The frequency divider 400 has an input end connected to the output end of the voltage-controlled oscillator 100, and an output end of the frequency divider 400 is connected to an input end of the frequency detector 200. The frequency divider 400 is configured to divide the output signal of the voltage-controlled oscillator 100, and output the divided voltage signal to the frequency detector 200. The frequency detector 200, the charge pump circuit 300 and the voltage-controlled oscillator 100 perform frequency detection and phase locking on the divided voltage signal and the reference signal Vref, so that the frequency and phase of the divided voltage signal are the same as the frequency and phase of the reference signal Vref, and the phase-locked loop circuit realizes an N-fold frequency multiplication function.

[0081] The utility model also provides an image sensor, which includes a phase-locked loop circuit. The specific structure of the phase-locked loop circuit refers to the above embodiment. Since the image sensor adopts all the technical solutions of all the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here. Among them, the phase-locked loop circuit acts as a high-speed clock generator to provide the image sensor with a clock signal that meets the working requirements of each module.

[0082] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention.

Claims

1. A voltage-controlled oscillator, configured to adjust the frequency and phase of a second voltage signal output according to a received first voltage signal, characterized in that: The voltage controlled oscillator comprises: A linear conversion circuit configured to convert a received first voltage signal into a current signal, wherein a magnitude of the current signal is correlated with a magnitude of the first voltage signal in negative proportion, wherein the correlated change includes a linear change or an approximately linear change; The oscillation circuit is connected to the linear conversion circuit and is configured to oscillate at a corresponding frequency according to the magnitude of the current signal and output a second voltage signal, wherein the frequency of the second voltage signal changes in a positive correlation with the magnitude of the current signal.

2. The voltage controlled oscillator according to claim 1, wherein: The linear conversion circuit includes a first resistor, a first electronic switch tube and a comparator; The first end of the first resistor is connected to the positive voltage, the second end of the first resistor, the inverting input end of the comparator and the source of the first electronic switch tube are connected, the non-inverting input end of the comparator constitutes the input end of the linear conversion circuit, the gate of the first electronic switch tube is connected to the output end of the comparator, and the drain of the first electronic switch tube constitutes the output end of the linear conversion circuit.

3. The voltage controlled oscillator according to claim 1, wherein: The linear conversion circuit includes a second resistor and a second electronic switch tube; The first end of the second resistor is connected to the positive voltage, the second end of the second resistor is connected to the source of the second electronic switch tube, the gate of the second electronic switch tube constitutes the input end of the linear conversion circuit, and the drain of the second electronic switch tube constitutes the output end of the linear conversion circuit.

4. The voltage controlled oscillator according to claim 1, wherein: The oscillation circuit comprises an odd number of inverter circuits; The input and output ends of an odd number of the inverter circuits are connected in sequence to form a ring oscillator, the output end or input end of a corresponding inverter circuit constitutes the output end of the oscillation circuit, and the control ends of an odd number of the inverter circuits are connected together to form the input end of the oscillation circuit.

5. The voltage controlled oscillator according to claim 4, characterized in that: The inverter circuit includes an inverter.

6. The voltage controlled oscillator according to claim 4, characterized in that: The inverter circuit includes a third electronic switch tube and a fourth electronic switch tube; The source of the third electronic switch tube constitutes the control end of the inverter circuit, the gate of the third electronic switch tube and the gate of the fourth electronic switch tube are connected to constitute the input end of the inverter circuit, the drain of the third electronic switch tube and the drain of the fourth electronic switch tube are connected to constitute the output end of the inverter circuit, and the source of the fourth electronic switch tube is grounded.

7. The voltage controlled oscillator according to claim 6, characterized in that: The width-to-length ratio of each electronic switch tube of the oscillator circuit is greater than 20; The threshold voltage of each electronic switch tube of the oscillation circuit is less than 300mV.

8. A phase-locked loop circuit, characterized in that: It comprises a frequency detector, a charge pump circuit and a voltage controlled oscillator as claimed in any one of claims 1 to 7, wherein the frequency detector, the charge pump circuit and the voltage controlled oscillator form a series loop, and the signal output end of the voltage controlled oscillator constitutes the signal output end of the phase-locked loop circuit; The frequency and phase detector is configured to detect the frequency and phase difference between the reference signal and the second voltage signal output by the voltage-controlled oscillator, and generate a first control signal and a second control signal; The charge pump circuit is configured to charge and discharge according to the received first control signal and second control signal, and output a first voltage signal of corresponding magnitude to the voltage-controlled oscillator; The voltage-controlled oscillator is configured to adjust the frequency and phase of the output second voltage signal according to the received first voltage signal, so that the output signal of the phase-locked loop circuit has the same frequency and phase as the reference signal.

9. The phase-locked loop circuit according to claim 8, characterized in that: The phase-locked loop circuit also includes: A frequency divider, wherein the input end of the frequency divider is connected to the output end of the voltage-controlled oscillator, and the output end of the frequency divider is connected to the input end of the frequency detector. The frequency divider is configured to divide the output signal of the voltage-controlled oscillator and output the divided voltage signal to the frequency detector.

10. An image sensor, characterized in that: Comprising the phase-locked loop circuit as claimed in claim 8 or 9.

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