Annular voltage-controlled oscillator for micro-display

Abstract

The invention provides an annular voltage-controlled oscillator for a micro-display. The annular voltage-controlled oscillator comprises a band-gap reference current source, an oscillator delay circuit, a temperature sensor and a voltage-controlled gain adjusting circuit, the temperature sensor is connected with the band-gap reference current source and is used for generating a control code SWA and controlling a current value generated by the band-gap reference current source; the band-gap reference current source is connected with the control end of the oscillator delay circuit and is used for copying a generated current value to the oscillator delay circuit; and the voltage-controlled gain adjusting circuit is connected with the output end of the oscillator delay circuit and is used for generating a control code SWB and controlling the oscillation frequency of the oscillator delay circuit. By adopting the temperature compensation and voltage-controlled gain adjustment circuit, the basic current and the load capacitance are adjusted according to the change of the temperature and the change of the control voltage, so that the output frequency of the ring oscillator does not change along with the temperature, and the constant voltage-controlled gain is realized under different control voltages.

Description

Technical Field

[0001] This application relates to the field of oscillators, and more particularly, to a ring voltage-controlled oscillator for a microdisplay. Background Art

[0002] Currently, the output frequency of known ring voltage-controlled oscillators varies significantly with temperature, resulting in unstable operation of digital circuits when they provide a reference clock for digital circuits.

[0003] At the same time, the frequency variation of known ring voltage-controlled oscillators with the control voltage (voltage-controlled gain) is not constant, and the varying voltage-controlled gain is not conducive to the application of ring voltage-controlled oscillators in phase-locked loops. Summary of the Invention

[0004] In view of the deficiencies in the prior art, an object of this application is to provide a ring voltage-controlled oscillator for a microdisplay.

[0005] In a first aspect of this application, there is provided a ring voltage-controlled oscillator for a microdisplay, including a bandgap reference current source, an oscillator delay circuit, a temperature sensor, and a voltage-controlled gain adjustment circuit;

[0006] The temperature sensor is connected to the bandgap reference current source and is configured to generate a control code SWA to control the current value generated by the bandgap reference current source;

[0007] The bandgap reference current source is connected to the control terminal of the oscillator delay circuit and is configured to copy the generated current value to the oscillator delay circuit;

[0008] The voltage-controlled gain adjustment circuit is connected to the output terminal of the oscillator delay circuit and is configured to generate a control code SWB to control the oscillation frequency of the oscillator delay circuit.

[0009] Optionally, the temperature sensor includes a temperature sensing unit and an analog-to-digital converter;

[0010] The temperature sensing unit is connected to the analog-to-digital converter, and the analog-to-digital converter is connected to the bandgap reference current source;

[0011] [[ID=3,7]]The temperature sensing unit generates a voltage signal that is positively correlated with temperature and inputs it to the analog-to-digital converter;

[0012] The analog-to-digital converter converts the voltage signal into an N-bit control code SWA <n:1>;

[0013] Optionally, the bandgap reference current source includes N parallel switch current mirrors;

[0014] The N parallel switch current mirrors are connected to the analog-to-digital converter and receive the control code SWA <n:1>, control the on / off of the N parallel switch current mirrors to adjust the output reference current value;

[0015] The output ends of the N parallel switch current mirrors are connected to the input end of the oscillator delay circuit, and are used to copy the adjusted reference current value to the oscillator delay circuit.

[0016] Optionally, the N-bit control code SWA <n:1>An N-bit binary number is used to control the on / off number of the switching current mirror.

[0017] Optionally, the oscillator delay circuit includes four main inverters INV1, INV2, INV3, and INV4 connected in a ring;

[0018] The four main inverters INV1, INV2, INV3, and INV4 are connected in series to form a ring structure, and the voltage-controlled gain adjustment circuit is connected between adjacent two of the main inverters to adjust the voltage-controlled gain of the oscillator output frequency;

[0019] The PMOS source of each main inverter is connected to the power supply, and the NMOS source is grounded through two parallel tail current transistors;

[0020] Wherein, one of the tail current transistors is connected to the N parallel switching current mirrors for copying the current value;

[0021] The other tail current transistor is connected to an external control voltage.

[0022] Optionally, the oscillator delay circuit further includes four auxiliary inverters INV5, INV6, INV7, and INV8, which are respectively arranged between adjacent two of the main inverters;

[0023] Wherein: the inverting inputs of INV5 and INV6 are respectively connected to the outputs of INV1 and INV3; the inverting inputs of INV7 and INV8 are respectively connected to the outputs of INV2 and INV4 for coupling the input and output of the main inverter.

[0024] Optionally, the voltage-controlled gain adjustment circuit includes M parallel switching capacitors;

[0025] The M parallel switching capacitors are connected between adjacent two of the main inverters.

[0026] Optionally, the voltage-controlled gain adjustment circuit further includes a reference voltage generation module and a multiplex comparator module;

[0027] The reference voltage module is connected to the multiplex comparator module to generate M reference voltages V evenly divided between 0 and VDD REF <m:1>, and comparing the external control voltage with M reference voltages through the multiplex comparator module to generate an M-bit control code SWB <m:1>Adjust the equivalent capacitance value of the M parallel-connected switched capacitors.

[0028] Optionally, the M-bit control code SWB <m:1>An M-bit binary number is used to control the on / off of the switching capacitor;

[0029] Wherein, the capacitance value of the switching capacitor is the additional capacitance value required to achieve a constant voltage-controlled gain under its corresponding control voltage.

[0030] A ring voltage-controlled oscillator for a microdisplay provided by this application adopts technical means of adding a temperature compensation and voltage-controlled gain adjustment circuit, which can adjust the basic current and load capacitance according to the changes in temperature and control voltage, so that the frequency output by the ring oscillator is basically independent of temperature changes, and a constant voltage-controlled gain technical effect is achieved under different control voltages, overcoming the problems that the output frequency of the existing ring voltage-controlled oscillator changes greatly with temperature and the voltage-controlled gain changes greatly with the input voltage.

[0031] Other technical effects brought by the additional features will be further elaborated in the corresponding embodiments. Brief Description of the Drawings

[0032] By reading the detailed description of the non-restrictive embodiments with reference to the following drawings, other features, purposes and advantages of this application will become more obvious:

[0033] Figure 1 It is a schematic circuit diagram of a ring voltage-controlled oscillator for a microdisplay shown according to an exemplary embodiment;

[0034] Figure 2 It is a schematic diagram of the principle that the positive temperature coefficient voltage signal generated by the temperature sensing unit is converted into a 3-bit control code SWA<3:1> through an analog-to-digital converter according to an exemplary embodiment;

[0035] Figure 3 It is a schematic diagram of the temperature compensation effect of the 3-bit control code SWA<3:1> on the curve of the output frequency changing with temperature shown according to an exemplary embodiment;

[0036] Figure 4 It is a schematic diagram of the constant voltage-controlled gain control effect of the 5-bit control code SWB<5:1> on the curve of the output frequency changing with the control voltage shown according to an exemplary embodiment. Detailed Description of the Embodiments

[0037] The following will describe this application in detail with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand this application, but do not limit this application in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of this application, several deformations and improvements can still be made, and these all belong to the protection scope of this application. Parts not described in detail in the following embodiments can be implemented using existing technologies.

[0038] In the description of the embodiments of the present application, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. are based on the orientation or positional relationships shown in the drawings. These are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of the present application.

[0039] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0040] In the description of the embodiments of the present application, the meaning of "a plurality" is two or more, unless otherwise specifically defined. In the present application, unless otherwise clearly specified and defined, the terms "mounted", "connected", "coupled", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0041] In the embodiments of the present application, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products, or devices.

[0042] In view of the situation that the output frequency of the existing ring voltage-controlled oscillator varies greatly with temperature and the voltage-controlled gain varies greatly with the input voltage. Based on the above problems, the embodiments of the present application provide a ring voltage-controlled oscillator with temperature compensation and voltage-controlled gain to solve the above existing problems.

[0043] Refer to Figure 1 As shown, in an embodiment of the present application, a ring voltage-controlled oscillator for a microdisplay includes a bandgap reference current source, an oscillator delay circuit, a temperature sensor, and a voltage-controlled gain adjustment circuit.

[0044] The temperature sensor is connected to the bandgap reference current source and is used to generate a control code SWA to control the current value generated by the bandgap reference current source; the bandgap reference current source is connected to the control end of the oscillator delay circuit and is used to copy the generated current value to the oscillator delay circuit; the voltage-controlled gain adjustment circuit is connected to the output end of the oscillator delay circuit and is used to generate a control code SWB to control the oscillation frequency of the oscillator delay circuit.

[0045] Specifically, by adding a temperature sensor and a voltage-controlled gain adjustment circuit to the ring voltage-controlled oscillator, the output end of the temperature sensor is connected to the bandgap reference current source, and the output end of the bandgap reference current source is connected to the control end of the oscillator delay circuit, so as to obtain the temperature change value through the temperature sensor and adjust the basic current of the bandgap reference current source, making the frequency output by the ring oscillator basically not change with temperature, realizing dynamic adjustment and solving the problem of frequency drift of the traditional ring oscillator caused by temperature change; at the same time, in combination with the connection between the voltage-controlled gain adjustment circuit and the input end of the oscillator delay circuit, the load capacitance of the oscillator delay circuit is controlled, and a constant voltage-controlled gain is achieved under different control voltages.

[0046] In the above embodiments of the present application, by adopting a temperature sensor and a voltage-controlled gain adjustment circuit, temperature compensation and voltage-controlled gain adjustment are realized. The basic current and the load capacitance can be adjusted according to the temperature change and the control voltage change, so that the frequency output by the ring oscillator basically does not change with temperature, and a constant voltage-controlled gain is achieved under different control voltages, solving the problems that the output frequency of the existing ring voltage-controlled oscillator changes greatly with temperature and the voltage-controlled gain changes greatly with the input voltage.

[0047] In order to achieve the purpose of controlling the bandgap reference current source by the temperature sensor, in some specific embodiments of the present application, the temperature sensor includes a temperature sensing unit and an analog-to-digital converter.

[0048] The temperature sensing unit is connected to the analog-to-digital converter, and the analog-to-digital converter is connected to the bandgap reference current source; the temperature sensing unit generates a voltage signal that is positively correlated with temperature and inputs it to the analog-to-digital converter; the analog-to-digital converter converts the voltage signal with a positive temperature coefficient into an N-bit control code SWA <n:1>。

[0049] Specifically, the temperature sensor includes a temperature sensing unit and an analog-to-digital converter. The temperature sensing unit can generate a voltage signal that is positively correlated with the temperature according to the temperature change and input it into the analog-to-digital converter. The analog-to-digital converter can generate different control codes SWA according to different temperatures <n:1>.

[0050] Among them, the control code is an N-bit binary number, which can control the on and off of the switching current mirror in the bandgap reference current source to generate different output currents. The output current is copied to the oscillator delay circuit, affecting the delay time of each level of delay unit, thereby affecting the output frequency of the oscillator.

[0051] By setting an appropriate current mirror replication ratio and an appropriate correspondence between the control code and the switch, an output frequency that is independent of temperature can be obtained.

[0052] According to Figure 2 As shown, in one embodiment of the present application, the voltage signal generated by the temperature sensing unit increases as the temperature rises. The voltage signal can be converted into a three-bit control code SWA<3:1> by the analog-to-digital converter to control the on and off of the three parallel switch current mirrors. For example, when the temperature is low, such as -40°C, the control code output by the analog-to-digital converter is <000> , which means that all three switch current mirrors are turned off, and the current is the lowest at this time; when the temperature rises to -20 degrees, the control code output by the analog-to-digital converter is <001> , indicating that the first current mirror is turned on. At this time, the current increases and is copied to the delay unit of the ring oscillator, which speeds up the charge and discharge speed of the delay unit and increases the frequency of the ring oscillator, compensating for the frequency drop of the ring oscillator due to temperature rise.

[0053] In the above-mentioned embodiment of the present application, the temperature sensor uses a temperature sensing unit to collect a positive temperature-related voltage signal in real time, combines it with an analog-to-digital converter to generate a digital control code, and dynamically adjusts the output current of the bandgap reference current source to compensate for the impact of temperature changes on the oscillator delay circuit. Through a closed-loop feedback mechanism of temperature-voltage-current-frequency, the output frequency is decoupled from the temperature, ensuring that the system maintains stable timing characteristics over a wide temperature range. The use of a digitally controlled switching current mirror structure improves the accuracy and flexibility of current regulation, while reducing the temperature drift and noise interference of the analog circuit.

[0054] In order to control the output current of the bandgap reference current source, in some specific embodiments of the present application, the bandgap reference current source includes N parallel switching current mirrors.

[0055] N parallel switched current mirrors are connected to the analog-to-digital converter and receive the control code SWA <n:1>, control the on / off of N parallel switch current mirrors to adjust the output reference current value; the output ends of the N parallel switch current mirrors are connected to the input end of the oscillator delay circuit to copy the adjusted reference current value to the oscillator delay circuit.

[0056] Among them, the N-bit control code SWA <n:1>An N-bit binary number is used to control the on / off number of the switched current mirrors.

[0057] It should be noted that the bandgap reference current source is the bandgap reference current source of the operational amplifier structure in the prior art.

[0058] Specifically, the current output terminal of the bandgap reference current source is composed of N parallel switched current mirrors, which can copy the output current in a certain proportion; the control signals of these switches are controlled by the built-in temperature sensor; the frequency of the ring oscillator has a negative temperature coefficient, and the digital N-bit digital code output by the temperature sensor is directly proportional to the temperature, that is, the higher the temperature, the more current mirrors are turned on, injecting more basic current into the oscillator delay circuit; in this way, the temperature characteristics of the ring oscillator are calibrated, and the frequency can be made almost invariant with temperature.

[0059] Refer to Figure 3 As shown, in an embodiment of the present application, the SWA control code generated by the temperature sensor compensates for the frequency that changes negatively with temperature. Exemplarily, the temperature sensor generates a three-bit control code SWA<3:1>. When the temperature is -40 degrees, the corresponding control code is <000>, indicating that the first, second, and third current mirrors are all turned off, and no additional current is injected into the delay unit of the oscillator. When the temperature rises to 0 degrees, the control code is <010>, indicating that the first and third current mirrors are turned off and the second current mirror is turned on. At this time, a small amount of current is injected into the delay unit of the oscillator, and the output frequency of the oscillator rises by approximately 10%, which is close to the output frequency at -40 degrees. When the temperature rises to 100 degrees, the corresponding control code is <111>, representing that the first, second, and third current mirrors are all turned on. At this time, a large amount of current is injected into the delay unit of the oscillator, and the output frequency of the oscillator rises by approximately 5 times, which is close to the output frequency at -40 degrees.

[0060] In the above embodiment of the present application, through the collaborative design of N parallel switched current mirrors and the analog-to-digital converter, the digital precise regulation of the output current of the bandgap reference current source is realized. The number of turned-on current mirrors is dynamically selected by using the N-bit binary control code, combined with the proportional replication characteristics of the current mirrors; at the same time, through the directly proportional digital code output by the temperature sensor, the multi-gear current mirror combination is adjusted in real time, so that the negative temperature coefficient of the ring oscillator and the positive temperature characteristics of the compensation current form a dynamic balance, significantly improving the frequency stability; the parallel current mirror structure has both coarse-tuning and fine-tuning functions, can achieve continuous current compensation in a wide temperature range, breaks through the accuracy limitation of traditional analog compensation, and can finely adjust the reference current value injected into the ring oscillator.

[0061] In order to achieve precise regulation of the oscillator, in some specific embodiments of the present application, the oscillator delay circuit includes four main inverters INV1, INV2, INV3, and INV4 connected in a ring.

[0062] Four main inverters INV1, INV2, INV3, and INV4 are connected in series to form a ring structure. A voltage-controlled gain adjustment circuit is connected between two adjacent main inverters for adjusting the voltage-controlled gain of the output frequency of the ring oscillator. The source of the PMOS of each main inverter is connected to the power supply, and the source of the NMOS is grounded through two parallel tail current transistors.

[0063] Wherein, one tail current transistor is connected to N parallel switch current mirrors for copying the current value; the other tail current transistor is connected to an external control voltage.

[0064] Specifically, the oscillator delay circuit includes four main inverters INV1, INV2, INV3, and INV4. The connection relationship of the main inverters is INV1-INV2-INV3-INV4, that is, the drain (output terminal) of the main inverter INV1 is connected to the gate (input terminal) of the main inverter INV2, the drain of the main inverter INV2 is connected to the gate of the main inverter INV3, the drain of the main inverter INV3 is connected to the gate of the main inverter INV4, and finally the output terminal of INV4 is connected back to the input terminal of INV1; the source terminal of the PMOS of each main inverter is connected to the power supply, and the source terminal of the NMOS is connected to two NMOSs serving as tail current transistors (for example, the source terminal of the NMOS of the main inverter INV1 is connected to NM1A and NM1B) and then grounded. NM1A, NM2A, NM3A, and NM4A (i.e., one tail current transistor) are all connected to the switch current mirror in the bandgap reference current source to copy the current generated by the bandgap reference current source; NM1B, NM2B, NM3B, and NM4B (i.e., the other tail current transistor) are all connected to an external control voltage to control the output frequency of the ring oscillator. The connection line between two main inverters is connected to N parallel switch capacitors, and the switch capacitors are controlled by the voltage-controlled gain adjustment circuit to change the oscillation frequency of the ring oscillator by changing the load capacitance of the ring oscillator.

[0065] It should be noted that the tail current transistors are respectively transistor NM1A, transistor NM2A, transistor NM3A, transistor NM4A, transistor NM1B, transistor NM2B, transistor NM3B, and transistor NM4B.

[0066] In some specific embodiments of the present application, the oscillator delay circuit further includes four auxiliary inverters INV5, INV6, INV7, and INV8, which are respectively arranged between two adjacent main inverters.

[0067] Wherein: the inverting inputs of the auxiliary inverters INV5 and INV6 are respectively connected to the outputs of the main inverters INV1 and INV3; the inverting inputs of the auxiliary inverters INV7 and INV8 are respectively connected to the outputs of the main inverters INV2 and INV4, forming an enhanced ring oscillation topology for coupling the input and output of the main inverter, thereby ensuring that a loop formed by an even number of main inverters can oscillate stably, and a loop formed by four main inverters can generate four orthogonal phases with a phase difference of 90 degrees.

[0068] It should be noted that in the ring voltage-controlled oscillator, it includes four-stage main inverters connected end to end and two pairs of cross-coupled auxiliary inverters connected in the middle of the main loop. This is a typical ring oscillator with a pseudo-differential structure, which can provide orthogonal phases with inverters as basic units. Two tail current transistors are connected to the main inverters as additional control transistors. Among them, the tail current transistors NM1A, NM2A, NM3A, and NM4A are connected to the bandgap reference current module to obtain a certain basic current; the tail current transistors NM1B, NM2B, NM3B, and NM4B are connected to the control voltage to realize the function of the voltage-controlled oscillator.

[0069] In the above embodiments of the present application, through the collaborative design of the main inverter ring structure and the switched capacitor array, the dual regulation functions of temperature compensation and voltage-controlled gain are realized; the tail current transistors of the main inverter are respectively connected to the temperature compensation current mirror and the external control voltage, which not only introduces temperature-adaptive current to offset process deviations, but also can dynamically adjust the transconductance gain through the external voltage; M parallel switched capacitors are precisely adjusted under the drive of the control code SWB to adjust the equivalent capacitance value of the node and realize the digital fine-tuning of the oscillation frequency.

[0070] In some specific embodiments of the present application, in order to achieve a constant voltage-controlled gain for the oscillator delay circuit, the voltage-controlled gain adjustment circuit includes M parallel switched capacitors; M parallel switched capacitors are connected between adjacent two main inverters.

[0071] Specifically, the connection line between two main inverters is connected to M parallel switched capacitors, that is, the connection points of the mutually connected main inverters are respectively connected to M parallel switched capacitors. The switched capacitors are controlled by the voltage-controlled gain adjustment circuit, and the oscillation frequency of the ring oscillator is changed by changing the load capacitance of the ring oscillator.

[0072] In some specific embodiments of the present application, the voltage-controlled gain adjustment circuit further includes a reference voltage generation module and a multi-channel comparator module.

[0073] The reference voltage generation module is connected to the multi-channel comparator module to generate M reference voltages V evenly distributed between 0 and VDD REF <m:1>, and compare the external control voltage with M reference voltages through a multiplex comparator module to generate an M-bit control code SWB <m:1>Adjust the equivalent capacitance value of M parallel-connected switched capacitors.

[0074] Specifically, the reference voltage generation module (V REF ) is connected to the multi-channel comparator, and the other end of the multi-channel comparator is connected to M parallel-connected switched capacitors. Among them, the transistor NM3B is connected to the multi-channel comparator, and the voltage-controlled gain adjustment circuit is the Kvco adjustment circuit. The reference voltage generation module can generate M reference voltages V evenly distributed between 0 and VDD REF <m:1>, these M reference voltages are compared with the control voltage by a comparator, and a control code SWB with a bit width of M is output <m:1>, different control voltages output different control codes. The multi-channel comparator module compares the reference voltage generated by the reference voltage generation module and the control voltage of the voltage-controlled ring oscillator to control the size of the load capacitance of the voltage-controlled ring oscillator, thereby changing the output frequency and achieving a constant voltage-controlled gain.

[0075] It should be noted that the M-bit control code SWB <m:1>An M-bit binary number is used to control the on / off of the switched capacitor.

[0076] Among them, the capacitance value of the switched capacitor is the additional capacitance value required to achieve a constant voltage-controlled gain under its corresponding control voltage.

[0077] Exemplarily, assuming that the voltage-controlled gain is small when the control voltage is close to 0 and this voltage-controlled gain is the value to be maintained, and the voltage-controlled gain increases when the control voltage rises, then more switched capacitors can be turned on when the control voltage rises to reduce the speed of the delay unit, thereby reducing the oscillation frequency and achieving a constant voltage-controlled gain.

[0078] Referring to Figure 4 As shown, in an embodiment of the present application, the switched capacitor is controlled by the SWB control code converted from the control voltage through a comparator to achieve a constant voltage-controlled gain. The solid line is the curve of the frequency varying with the control voltage without constant voltage-controlled gain control, indicating that the voltage-controlled gain increases with the increase of the control voltage. As the control voltage increases, additional switched capacitors can be successively turned on to reduce the charge and discharge speed of the delay unit to reduce the output frequency of the oscillator, thereby achieving a constant voltage-controlled gain. Exemplarily, when the control voltage rises from 0V to 0.2V, the control code is <00001>, indicating that among the 5 switched capacitors, the first switched capacitor is turned on and the second to fifth switched capacitors are turned off. At this time, the output frequency is reduced by about 10%; when the control voltage rises to 1V, the control code is <11111>, indicating that all 5 switched capacitors are turned on. At this time, the output frequency is reduced by about 50%. Through this control method, a constant voltage-controlled gain of the ring oscillator is achieved.

[0079] In the above embodiments of the present application, through the combination of the switched capacitor and the linear control code, the non-linear limitation of the traditional voltage-controlled gain is solved, and a constant output of the gain-voltage characteristic is achieved; the multi-channel comparator compares the external control voltage with these reference voltages in parallel, improving the response speed and noise tolerance, ensuring that stable gain adjustment can still be maintained in a complex electromagnetic environment, and improving the overall dynamic performance and reliability of the ring oscillator.

[0080] In the above embodiments, each preferred feature can be used alone in any one embodiment, and can also be used in any combination on the premise of not conflicting with each other. In addition, the parts not described in detail in the embodiments can be implemented by using the prior art.

[0081] Some specific embodiments of the present application have been described above. It should be understood that the present application is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which do not affect the essence of the present application. The above preferred features can be used in any combination on the premise of not conflicting with each other.

Claims

1. A ring voltage-controlled oscillator for a microdisplay, characterized in that, Comprising: A bandgap reference current source, an oscillator delay circuit, a temperature sensor, and a voltage-controlled gain adjustment circuit; The temperature sensor is connected to the bandgap reference current source and is used to generate a control code SWA to control the current value generated by the bandgap reference current source; The bandgap reference current source is connected to the control end of the oscillator delay circuit and is used to copy the generated current value to the oscillator delay circuit; The voltage-controlled gain adjustment circuit is connected to the output end of the oscillator delay circuit and is used to generate a control code SWB to control the oscillation frequency of the oscillator delay circuit.

2. The ring voltage-controlled oscillator for a microdisplay according to claim 1, wherein The temperature sensor includes a temperature sensing unit and an analog-to-digital converter; The temperature sensing unit is connected to the analog-to-digital converter, and the analog-to-digital converter is connected to the bandgap reference current source; The temperature sensing unit generates a voltage signal that is positively correlated with temperature and inputs it to the analog-to-digital converter; The analog-to-digital converter converts the voltage signal into an N-bit control code SWA <n:1> 。< / n:1> 3. The ring voltage-controlled oscillator for a microdisplay according to claim 2, characterized in that, The bandgap reference current source includes N parallel-connected switched current mirrors; The N parallel switch current mirrors are connected to the analog-to-digital converter and receive the control code SWA <n:1>, controlling the on / off of the N parallel-connected switched current mirrors to adjust the output reference current value; < / n:1> The output ends of the N parallel-connected switched current mirrors are connected to the input end of the oscillator delay circuit and are used to copy the adjusted reference current value to the oscillator delay circuit.

4. The ring voltage-controlled oscillator for a microdisplay according to claim 3, characterized in that, The N-bit control code SWA <n:1>An N-bit binary number is used to control the number of on / off of the switched current mirrors. < / n:1> 5. A ring voltage-controlled oscillator for a microdisplay according to claim 3, characterized in that, The oscillator delay circuit includes four main inverters INV1, INV2, INV3, and INV4 connected in a ring; The four main inverters INV1, INV2, INV3, and INV4 are connected in series to form a ring structure, and a connection is made between adjacent two of the main inverters and the voltage-controlled gain adjustment circuit to adjust the voltage-controlled gain of the oscillator output frequency; The PMOS source of each main inverter is connected to the power supply, and the NMOS source is grounded through two parallel-connected tail current transistors; Among them, one of the tail current transistors is connected to the N parallel-connected switched current mirrors and is used to copy the current value; The other tail current transistor is connected to an external control voltage.

6. The ring voltage-controlled oscillator for a microdisplay according to claim 5, characterized in that The oscillator delay circuit further includes four auxiliary inverters INV5, INV6, INV7, and INV8, which are respectively arranged between adjacent two of the main inverters; Among them: the inverting input ends of INV5 and INV6 are respectively connected to the output ends of INV1 and INV3; the inverting input ends of INV7 and INV8 are respectively connected to the output ends of INV2 and INV4, and are used to couple the input and output of the main inverters.

7. A ring voltage-controlled oscillator for a microdisplay according to claim 5, characterized in that, The voltage-controlled gain adjustment circuit includes M parallel-connected switched capacitors; The M parallel-connected switched capacitors are connected between adjacent two of the main inverters.

8. The ring voltage-controlled oscillator for a microdisplay according to claim 6, wherein, The voltage-controlled gain adjustment circuit further includes a reference voltage generation module and a multi-channel comparator module; The reference voltage module is connected to the multi-channel comparator module to generate M reference voltages V evenly divided between 0 and VDD REF <m:1>, and comparing an external control voltage with M reference voltages through the multiplex comparator module to generate an M-bit control code SWB <m:1>Adjusting the equivalent capacitance value of the M parallel-connected switched capacitors. < / m:1> 9. A ring voltage-controlled oscillator for a microdisplay according to claim 8, characterized in that, The M-bit control code SWB <m:1>An M-bit binary number is used to control the on / off of the switched capacitors; < / m:1> Among them, the capacitance value of the switched capacitor is the additional capacitance value required to achieve a constant voltage-controlled gain under its corresponding control voltage.

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