Temperature compensation circuit and RC oscillator

Abstract

The invention relates to the technical field of electronic circuits, and provides a temperature compensation circuit and an RC oscillator, the temperature compensation circuit comprises a voltage control module and a clock signal generation module, the voltage control module is used for outputting a control signal to the clock signal generation module according to the environment temperature; wherein the frequency of the control signal is related to the temperature of the environment; the clock signal generation module is used for generating a clock signal according to the control signal; wherein the duty ratio of the clock signal is related to the frequency of the control signal. According to the temperature compensation circuit, the clock signal with the duty ratio changing along with the environment temperature can be generated, and the precision of an RC oscillator and other circuits under the influence of the temperature is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic circuits, and particularly relates to a temperature compensation circuit and an RC oscillator. BACKGROUND

[0002] A resistor-capacitor (RC) oscillator can provide an accurate clock for a system. A precise clock is generally realized by a crystal oscillator, which can generate a clock with a precision of 10ppm or less. However, the crystal oscillator needs to be connected with an external crystal, and needs additional PAD pins for electrical and physical connection, which occupies the PAD of the chip and the number of input / output interfaces (IO). The oscillator inside the chip is difficult to achieve the precision of the crystal oscillator. The frequency of a high-precision RC oscillator is determined by the internal resistance and capacitance.

[0003] The RC oscillator has two problems: large process deviation of resistance and capacitance; and the resistance and capacitance have temperature characteristics, and the output frequency changes with temperature.

[0004] The resistance value of the adjustable resistance of a common RC oscillator can be adjusted after the chip is taped out to make the output frequency at room temperature meet the requirements. However, the output deviation of the RC oscillator caused by the temperature characteristics of the resistance and capacitance cannot be solved, resulting in an inaccurate oscillation signal output by the RC oscillator under the influence of temperature. SUMMARY

[0005] Embodiments of the present application provide a temperature compensation circuit and an RC oscillator, which can solve the problem of inaccurate oscillation signal output by the RC oscillator under the influence of temperature.

[0006] In a first aspect, embodiments of the present application provide a temperature compensation circuit, comprising a voltage control module and a clock signal generation module. The voltage control module is configured to output a control signal to the clock signal generation module according to the temperature of an environment; wherein the frequency of the control signal is related to the temperature of the environment. The clock signal generation module is configured to generate a clock signal according to the control signal; wherein the duty cycle of the clock signal is related to the frequency of the control signal.

[0007] Optionally, the voltage control module comprises a temperature sensing circuit and a feedback voltage control circuit. The output end of the temperature sensing circuit is connected to one end of the feedback voltage control circuit and a first input end of the clock signal generation module. The temperature sensing circuit is configured to generate a first control current according to the temperature of the environment. The feedback voltage control circuit is configured to generate a control signal according to the first control current and an output signal of a first output end of the clock signal generation module.

[0008] Optionally, the feedback voltage control circuit comprises a first control branch and a second control branch; An output terminal of the temperature sensing circuit is connected to a first input terminal of the first control branch, a second input terminal of the first control branch, one end of the second control branch, and a first input terminal of the clock signal generation module; a third input terminal of the first control branch is connected to a first output terminal of the clock signal generation module; The first control branch is configured to generate a second control current according to the first control current and an output signal of the first output terminal of the clock signal generation module; The second control branch is configured to charge and discharge according to the second control current to generate a control signal.

[0009] Optionally, the temperature sensing circuit comprises a first switch tube, the first control branch comprises a second switch tube, a third switch tube, and a first switch, the second control branch comprises a first capacitor, and the second control current comprises a charging current and a discharging current; An input terminal of the first switch tube receives an input current; an output terminal of the first switch tube is connected to an input terminal of the second switch tube, a first end of the first switch, a first end of the first capacitor, and a first input terminal of the clock signal generation module; a control terminal of the first switch is connected to a first output terminal of the clock signal generation module; a second end of the first switch is connected to an input terminal of the third switch tube; an output terminal of the second switch tube, an output terminal of the third switch tube, and a second end of the first capacitor are grounded; The first switch is configured to control a charging and discharging state of the first capacitor according to an output signal of the first output terminal of the clock signal generation module.

[0010] Optionally, the clock signal generation module comprises a comparison circuit and a control circuit; A first input terminal of the comparison circuit is connected to an output terminal of the voltage control module; a second input terminal of the comparison circuit receives a reference signal; an output terminal of the comparison circuit is connected to an input terminal of the control circuit; and the output terminal of the comparison circuit outputs a clock signal; The control circuit is configured to output a voltage control signal to adjust a voltage size of the control signal.

[0011] Optionally, the clock signal generation module further comprises a reference voltage control circuit; An output terminal of the reference voltage control circuit is connected to a second input terminal of the comparison circuit; a first control terminal of the reference voltage control circuit is connected to a first output terminal of the control circuit; and a second control terminal of the reference voltage control circuit is connected to a second output terminal of the control circuit; The reference voltage control circuit is configured to adjust a voltage size of an output reference signal according to the voltage control signal.

[0012] Optionally, the reference voltage control circuit comprises a second switch and a third switch, and the voltage control signal comprises a first control signal and a second control signal; The first end of the second switch receives a first reference signal, and the first end of the third switch receives a second reference signal. The control end of the second switch is connected to the second output end of the control circuit, and the control end of the third switch is connected to the first output end of the control circuit. The second end of the second switch and the second end of the third switch are both connected to the second input end of the comparison circuit. The control circuit is specifically configured to output the first control signal and the second control signal to adjust the voltage of the control signal and the reference signal. The voltage of the first reference signal is higher than the voltage of the second reference signal, and the first control signal and the second control signal are opposite.

[0013] Optionally, the control circuit comprises a first inverting unit and a second inverting unit connected in series. The input end of the second inverting unit is connected to the output end of the comparison circuit, the output end of the second inverting unit is connected to the control end of the second switch, the input end of the first inverting unit is connected to the output end of the second inverting unit, and the output end of the first inverting unit is connected to the control end of the third switch. The first inverting unit is configured to generate the first control signal according to the output signal of the comparison circuit. The second inverting unit is configured to generate the second control signal according to the output signal of the comparison circuit.

[0014] In a second aspect, an embodiment of the present application provides an RC oscillator, comprising a temperature compensation circuit, a load adjustment circuit, a reference signal generation circuit and an oscillation circuit. The output end of the temperature compensation circuit is connected to the control end of the load adjustment module, the load adjustment circuit is connected in parallel with the load module in the reference signal generation circuit, and the output end of the reference signal generation circuit is connected to the input end of the oscillation circuit. The load adjustment circuit is configured to adjust the resistance value of the reference signal generation circuit according to the clock signal generated by the temperature compensation circuit. The resistance value of the reference signal generation circuit is related to the duty cycle of the clock signal. The reference signal generation circuit is configured to generate a reference signal according to the resistance value thereof. The oscillation circuit is configured to perform reverse compensation on the oscillation circuit according to the reference signal to generate an oscillation signal irrelevant to the ambient temperature.

[0015] Optionally, the load adjustment circuit comprises a switch tube. The second end of the switch tube is connected to the output end of the temperature compensation circuit, the first end of the switch tube is connected to the first end of the load module, and the third end of the switch tube is connected to the second end of the load module.

[0016] Optionally, the load module comprises a first load, and the reference signal generation circuit further comprises a second load, a third load, a PMOS tube and a filter capacitor. The drain of the PMOS tube is connected to the first end of the third load, and the common end of the connection is used as the output end of the reference signal generation circuit; the first end of the second load is connected to the third load; the second end of the second load is commonly connected to the first end of the first load, the first end of the switch tube and the first end of the filter capacitor; the second end of the first load is commonly connected to the third end of the switch tube and the second end of the filter capacitor, and the common end of the connection is grounded.

[0017] The above-mentioned scheme of the present application has the following beneficial effects: In the embodiment of the present application, the temperature compensation circuit comprises a voltage control module for outputting a control signal to the clock signal generation module according to the temperature of the environment, and a clock signal generation module for generating a clock signal according to the control signal, so that the duty cycle of the clock signal generated by the temperature compensation circuit can change according to the temperature of the environment. When the temperature compensation circuit is applied to the RC oscillator, the resistance of the RC oscillator is adjusted according to the clock signal generated by the temperature compensation circuit, thereby reducing the influence of temperature on the oscillation signal output by the RC oscillator, and further improving the precision of the oscillation signal. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0019] Figure 1 The structural schematic diagram of the temperature compensation circuit provided by an embodiment of the present application is shown in the figure. Figure 2 The structural schematic diagram of the voltage control module provided by an embodiment of the present application is shown in the figure. Figure 3 The structural schematic diagram of the feedback voltage control circuit provided by an embodiment of the present application is shown in the figure. Figure 4 The structural schematic diagram of the clock signal generation module provided by an embodiment of the present application is shown in the figure. Figure 5 The specific structural schematic diagram of the temperature compensation circuit provided by an embodiment of the present application is shown in the figure. Figure 6 The structural schematic diagram of the RC oscillator provided by an embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0020] In the following description, for purposes of explanation and not limitation, specific details are set forth such as particular architectures, techniques, etc. in order to provide a thorough understanding of the embodiments of the present application. However, it will be apparent to those skilled in the art that the present application can be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known methods, devices, circuits, and

[0021] It is to be understood that the terminology "includes", "has", "holds", "contains" and / or "comprising", "including", "having" and their conjugates, as used herein, means "including but not limited to", and not to the exclusion of any other term or aspect.

[0022] It is also to be understood that the terminology "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items, and that the term "at least one of A and B" is equivalent to "A, B, or A and B".

[0023] As used in the description of the application and the appended claims, the term "if' can be interpreted to mean "when" or "upon" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrase "if it is determined" or "if [a described condition or event] is detected" can be interpreted to mean "upon determining" or "in response to determining" or "upon [the described condition or event] being detected" or "in response to [the described condition or event] being detected", depending on the context.

[0024] In addition, the terms "first", "second", "third", etc. as used in the description of the application and the appended claims are not used to denote or imply relative importance but are used to distinguish one element from another.

[0025] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" or "in other embodiments" or "in still other embodiments" in various places throughout this specification are not necessarily all referring to the same embodiment, unless otherwise specified. Furthermore, the terms "comprise", "comprises", "comprising", "include", "includes", "including" and the like are synonymous with the term "contain", "contains", "containing" or "has", "has", "having" and are used in the sense of "including but not limited to", unless otherwise specified.

[0026] In view of the problem that the output oscillation signal of the existing RC oscillator under the influence of temperature is not accurate, the embodiment of the present application provides a temperature compensation circuit and an RC oscillator. The temperature compensation circuit comprises a voltage control module configured to output a control signal to a clock signal generation module according to the temperature of an environment, and a clock signal generation module configured to generate a clock signal according to the control signal, so that the duty cycle of the clock signal generated by the temperature compensation circuit can change with the temperature of the environment. When the temperature compensation circuit is applied to the RC oscillator, the resistance of the RC oscillator is adjusted according to the clock signal generated by the temperature compensation circuit, the influence of temperature on the output oscillation signal of the RC oscillator is reduced, and the accuracy of the oscillation signal is improved.

[0027] Next, the temperature compensation circuit provided by the present application is exemplarily described.

[0028] As shown in Figure 1 The temperature compensation circuit provided by the present application comprises a voltage control module and a clock signal generation module.

[0029] The voltage control module is configured to output a control signal to the clock signal generation module according to the temperature of an environment. The frequency of the control signal is related to the temperature of the environment.

[0030] The clock signal generation module is configured to generate a clock signal according to the control signal. The duty cycle of the clock signal is related to the frequency of the control signal.

[0031] Exemplarily, the temperature of the environment is the temperature of the environment where the temperature compensation circuit is located, or the temperature of the environment where the circuit or device to which the temperature compensation circuit is applied is located. For example, when the temperature compensation circuit is applied to the RC oscillator, the temperature of the environment is the temperature of the environment where the RC oscillator is located.

[0032] It should be noted that the voltage control module outputs a control signal related to the ambient temperature to the clock signal generation module, and the clock signal generation module generates a clock signal according to the control signal. In some embodiments, the frequency of the control signal output by the voltage control module is related to the ambient temperature, and the specific correlation characteristics can be flexibly switched according to the requirements of the application scenario. The present embodiment does not limit this. For example, the control signal can be set to have a shorter rising time and a longer falling time when the temperature rises, or the control signal can be set to have a longer rising time and a shorter falling time when the temperature rises, and the rising time and the falling time will affect the frequency of the control signal. In addition, the duty cycle of the clock signal is related to the frequency of the control signal, and the duty cycle characteristics of the clock signal can respond to the requirements of the application scenario, that is, when the temperature rises, the rising time of the control signal becomes shorter, the falling time becomes longer, and the duty cycle of the clock signal becomes smaller. At the same time, the duty cycle characteristics of the clock signal can be that when the temperature rises, the duty cycle of the clock signal increases. Specifically, it can be flexibly switched according to the requirements of the application scenario, so that the clock signal changes with the temperature, which is convenient for temperature compensation of the RC oscillator using the clock signal, and improves the precision of the oscillation signal generated by the RC oscillator under the influence of temperature.

[0033] The voltage control module will be described below.

[0034] As shown in Figure 2 , the voltage control module includes a temperature sensing circuit and a feedback voltage control circuit.

[0035] The output end of the temperature sensing circuit is commonly connected with one end of the feedback voltage control circuit and the first input end of the clock signal generation module.

[0036] The temperature sensing circuit is configured to generate a first control current according to the temperature of the environment.

[0037] The feedback voltage control circuit is configured to generate a control signal according to the first control current and an output signal of the first output end of the clock signal generation module.

[0038] It should be noted that the size of the first control current is related to the ambient temperature, the current of the temperature sensing circuit is a positive temperature coefficient current, the first control current is positively correlated with the temperature, when the current of the temperature sensing circuit is a negative temperature coefficient current, the first control current is negatively correlated with the temperature. The voltage size of the control signal is related to the first control current, for example, the voltage size of the control signal is proportional to the first control current. The temperature sensing circuit outputs the first control current according to the change of the temperature, the feedback voltage control circuit generates the control signal according to the first control current and the output signal of the clock signal generation module, the clock signal generation module generates the clock signal according to the control signal, so that the duty cycle of the clock signal changes according to the change of the temperature. When the current of the temperature sensing circuit is a positive temperature coefficient, the temperature rises, the first control current becomes larger, and the duty cycle of the clock signal becomes smaller. When the current of the temperature sensing circuit is a negative temperature coefficient, the temperature rises, the first control current becomes smaller, and the duty cycle of the clock signal becomes larger.

[0039] The feedback voltage control circuit will be described below.

[0040] As shown in Figure 3 The feedback voltage control circuit includes a first control branch and a second control branch.

[0041] The output end of the temperature sensing circuit is commonly connected with the first input end of the first control branch, the second input end of the first control branch, one end of the second control branch, and the first input end of the clock signal generation module, and the third input end of the first control branch is connected with the first output end of the clock signal generation module.

[0042] The first control branch is configured to generate a second control current according to the first control current and the output signal of the first output end of the clock signal generation module.

[0043] The second control branch is configured to charge and discharge according to the second control current to generate the control signal.

[0044] It should be noted that the second control current includes a charging current and a discharging current, when the second control current is the charging current, the second control branch charges according to the charging current to generate the control signal, when the second control current is the discharging current, the second control branch discharges to generate the control signal.

[0045] The charging current is related to the first control current and the third control current (the third control current is the current output by the first control branch, usually 0.5 times the zero temperature coefficient current Ic), and the discharging current is related to the first control current, the third control current and the fourth control current (i.e. another current output by the first control branch, usually the zero temperature coefficient current Ic).

[0046] When the temperature sensing circuit is a positive temperature coefficient current, the temperature rises, the third control current and the fourth control current in the first control branch remain unchanged, the first control current of the output of the temperature sensing circuit becomes larger, the charging current becomes larger, and thus the charging time becomes smaller, the discharging current becomes smaller, and thus the discharging time becomes larger, the frequency of the control signal of the voltage control module rises, and the duty cycle of the clock signal generated by the clock signal generation module decreases, so that the duty cycle of the clock signal decreases with the temperature rise.

[0047] The specific structure of the clock signal generation module will be described below.

[0048] As shown in Figure 4 The clock signal generation module includes a comparison circuit and a control circuit.

[0049] The first input end of the comparison circuit is connected with the output end of the voltage control module, the second input end of the comparison circuit receives a reference signal, the output end of the comparison circuit is connected with the input end of the control circuit, and the output end of the comparison circuit outputs the clock signal.

[0050] The control circuit is configured to output a voltage control signal to adjust the voltage of the control signal. The first output end of the control circuit serves as the first output end of the clock signal generation module, and the second output end of the control circuit serves as the second output end of the clock signal generation module.

[0051] The clock signal generation module further includes a reference voltage control circuit.

[0052] The output end of the reference voltage control circuit is connected with the second input end of the comparison circuit, the first control end of the reference voltage control circuit is connected with the first output end of the control circuit, and the second control end of the reference voltage control circuit is connected with the second output end of the control circuit. The reference voltage control circuit is configured to adjust the voltage of the reference signal output according to the voltage control signal.

[0053] It should be noted that the comparison circuit compares the voltage between the reference signal output by the reference voltage control circuit and the control signal output by the voltage control module to output the clock signal. The frequency of the control signal is related to the temperature of the environment. When the voltage of the control signal is greater than the voltage of the reference signal, the clock signal is at a low level. When the voltage of the clock signal is less than the voltage of the reference signal, the clock signal is at a high level. The comparison circuit generates the clock signal according to the control signal and the reference signal, so that the duty cycle of the clock signal changes with the temperature.

[0054] The specific structure of the voltage control module and the clock signal generation module will be described below.

[0055] As shown in Figure 5The temperature sensing circuit in the voltage control module includes a first switch tube (PMOS2) in the first control branch, the first control branch includes a second switch tube (NMOS1), a third switch tube (NMOS2) and a first switch (Sw3_clka), the second control branch includes a first capacitor (C0), and the second control current includes a charging current and a discharging current. Figure 5 Figure 5 Figure 5 Figure 5 Figure 5

[0056] The input end of the first switch tube receives an input current, the output end of the first switch tube is connected with the input end of the second switch tube, the first end of the first switch, the first end of the first capacitor and the first input end of the clock signal generation module, the control end of the first switch is connected with the first output end of the clock signal generation module, the second end of the first switch is connected with the input end of the third switch tube, and the output end of the second switch tube, the output end of the third switch tube and the second end of the first capacitor are grounded.

[0057] The first switch is used for controlling the charging and discharging state of the first capacitor according to the output signal of the first output end of the clock signal generation module.

[0058] The control end of the first switch tube is connected with a first bias voltage (Vn), the control end of the second switch tube and the control end of the third switch tube are connected with a second bias voltage (Vc). Figure 5 Figure 5

[0059] It should be noted that the first switch tube is used for outputting a first control current according to the input current Iptat and the bias voltage Vn, the first switch tube controls the input current Iptat to flow into the feedback voltage control circuit, the second switch tube is used for shunting the first control current, and the third control current 0.5 Ic is controlled according to the bias voltage Vc, and the third switch tube is used for inputting a fourth control current Ic controlled according to the bias voltage Vc.

[0060] The charging time of the first capacitor is negatively related to Ic and positively related to Iptat, and the discharging time is positively related to Ic and negatively related to Iptat.

[0061] When the input current Iptat is a positive temperature coefficient current, the temperature rises, the charging current becomes larger, the charging time of the first capacitor becomes shorter, and the charging time of the first capacitor becomes shorter, that is, the control signal (Vout) becomes smaller. Figure 5 ​​​​​​​The voltage of VFB quickly rises to a level greater than the reference signal voltage. The high-level duration of the clock signal output by the comparator circuit becomes shorter, while the discharge current decreases. The discharge time of the first capacitor becomes longer, and the voltage drop rate of VFB slows down. Therefore, the low-level duration of the clock signal output by the comparator circuit becomes longer. This is true when Iptat is a negative temperature coefficient current, and vice versa. Thus, the clock signal (…) Figure 5 The duty cycle of CLK_TEMP is related to the ambient temperature, and the duty cycle characteristics of the clock signal can be flexibly set according to the needs of the application scenario; among them, the first switch, the second switch and the third switch can be used as long as they can control the current on and off, and the specific type is not limited in this embodiment.

[0062] For example, the first switch is used to control whether Ic flows. The first switch can also be a MOSFET. Specifically, the first switch only needs to be able to control the on and off of the circuit. This embodiment does not limit the specific type.

[0063] When the output signal of the first output terminal of the clock signal generation module is high, the first switch is turned on, the first capacitor is charged, and the charging current is the first preset value.

[0064] When the output signal of the first output terminal of the clock signal generation module is low, the first switch is turned off, the first capacitor discharges, and the discharge current is the second preset value.

[0065] For example, the first preset value is Iptat-0.5Ic, and the second preset value is Ic+0.5Ic-Iptat.

[0066] The aforementioned reference voltage control circuit includes a second switch ( Figure 5 Sw1_clkb and the third switch (in Figure 5 Sw2_clka in the code includes a first control signal and a second control signal.

[0067] The first terminal of the second switch receives the first reference signal. Figure 5 In VH), the first terminal of the third switch receives the second reference signal ( Figure 5 In the circuit, the control terminal of the second switch is connected to the second output terminal of the control circuit, the control terminal of the third switch is connected to the first output terminal of the control circuit, and the second terminals of both the second and third switches are connected to the second input terminal of the comparator circuit.

[0068] For example, the second and third switches mentioned above can also be MOSFETs. Specifically, the second and third switches only need to be able to control the on and off of the circuit, and this embodiment does not limit the specific type.

[0069] The aforementioned control circuit is specifically used to output the first control signal ( Figure 5 clka) and the second control signal ( Figure 5 The clkb in the control signal is used to adjust the voltage of the control signal and the reference signal; wherein the voltage of the first reference signal is higher than the voltage of the second reference signal, and the first control signal and the second control signal are out of phase.

[0070] It should be noted that when the output of the comparator circuit is high, the first control signal is low, the second control signal is high, the second switch is on, and the first and third switches are off (i.e., Figure 5 When clk=1 swon), the first control branch outputs a charging current, the magnitude of which is a first preset value. The first capacitor charges according to the charging current, and the clock signal is high. When the output of the comparator circuit is low, the first control signal is high, the second control signal is low, the first and third switches are turned on, the second switch is turned off, the first control branch outputs a charging current, the first capacitor discharges, the discharge current is a second preset value, and the clock signal is low.

[0071] For example, the comparator circuit can be a comparator ( Figure 5 CMP in (the context of CMP).

[0072] The control circuit includes a first inverting unit and a second inverting unit connected in series.

[0073] The input terminal of the second inverting unit is connected to the output terminal of the comparator circuit, the output terminal of the second inverting unit is connected to the control terminal of the second switch, the input terminal of the first inverting unit is connected to the output terminal of the second inverting unit, and the output terminal of the first inverting unit is connected to the control terminal of the third switch.

[0074] The first inverting unit is used to generate a first control signal based on the output signal of the comparator circuit.

[0075] The second inverting unit is used to generate a second control signal based on the output signal of the comparator circuit.

[0076] For example, such as Figure 5 As shown, the first inverting unit includes one inverter, and the second inverting unit includes two inverters connected in series.

[0077] It should be noted that when the temperature of the environment is the preset temperature (such as 40℃), Iptat=Ic, after the circuit is powered on, VFB is a low voltage, the output of the comparison circuit is a high level, the first control signal is a low level, the second control signal is a high level, the first switch and the third switch are turned off, the second switch is turned on, the first capacitor is charged, the charging current is Iptat-0.5Ic, the clock signal at the output end of the comparison circuit is a high level, and the charging causes VFB to rise. When VFB rises to be greater than VH, the output of the comparison circuit flips to be a low level, the first control signal is a high level, the second control signal is a low level, the first switch and the third switch are turned on, and the second switch is turned off. The first capacitor is discharged, the discharging current is Ic+0.5Ic-Iptat, and the clock signal at the output end of the comparison circuit is a low level.

[0078] The high level maintenance time of the clock signal is related to the charging time of the first capacitor, the charging time of the first capacitor is related to the size of the charging current, the low level duration of the clock signal is related to the discharging time of the first capacitor, and the discharging time of the first capacitor is related to the size of the discharging current.

[0079] When the temperature of the environment is the preset temperature, the charging current is equal to the discharging current, that is, the charging time of the first capacitor is equal to the discharging time, the high level duration of the clock signal is equal to the low level duration, and the duty cycle is 50%.

[0080] When the temperature of the environment rises and the input current Iptat is a positive temperature coefficient current, Ic is unchanged and Iptat becomes larger, the charging current Iptat-0.5Ic becomes larger, the charging time becomes shorter, the discharging current Ic+0.5Ic-Iptat becomes smaller, the discharging time becomes longer, that is, the high level maintenance time of the clock signal becomes shorter, the low level duration becomes longer, and the duty cycle of the clock signal becomes smaller. According to the above process, the duty cycle of the clock signal can be represented as Duty=1.5-(Iptat / Ic) or Duty=(Iptat / Ic)-0.5.

[0081] It can be understood that in the above process, Iptat is a positive temperature coefficient current, and the current size increases with the rise of the temperature. When Iptat is set to a negative temperature coefficient current in actual application, the current size decreases with the rise of the temperature, and the effect achieved is opposite to the above process, that is, the temperature of the environment rises, Ic is unchanged and Iptat becomes smaller, the charging current Iptat-0.5Ic becomes smaller, the charging time becomes longer, the discharging current Ic+0.5Ic-Iptat becomes larger, the discharging time becomes shorter, and the duty cycle of the clock signal increases.

[0082] In addition, the correlation between the duty cycle of the clock signal and the temperature can be changed by adding inverters to the output of the comparison circuit, or the clock signal can be inverted after being generated to change the correlation between the duty cycle of the clock signal and the temperature.

[0083] The clock signal generation module further includes a third inverting unit.

[0084] The input end of the third inverting unit is connected to the output end of the comparison circuit, and the output end of the third inverting unit is connected to the input end of the second inverting unit.

[0085] The third inverting unit is configured to generate a clock signal according to the voltage signal output by the comparison circuit.

[0086] As shown in the example, Figure 6 the third inverting unit includes two inverters connected in series, which is specifically configured to: enhance the driving capability: the output driving capability of a single comparator is limited, especially in the case of large load or long signal transmission distance, the output signal may be attenuated. By connecting multiple inverters in series at the output end of the comparator, the driving capability can be enhanced to ensure that the signal can be stably transmitted to the load, and the anti-interference capability can be improved: the inverter has threshold characteristics and can resist noise interference of the input signal to a certain extent. By connecting multiple inverters in series, the anti-interference capability of the circuit can be further enhanced to ensure stable output of the signal in a noisy environment; waveform shaping and conversion: the inverter can be used for waveform shaping and conversion to convert the input waveform (such as sine wave, triangular wave) into a square wave or other required waveform. By connecting multiple inverters in series, the waveform quality can be further optimized to meet specific application requirements.

[0087] Next, the RC oscillator provided by the present application is exemplarily described.

[0088] As shown in the example, Figure 6 the RC oscillator includes a temperature compensation circuit, a load adjustment circuit, a reference signal generation circuit, and an oscillation circuit.

[0089] The output end of the temperature compensation circuit is connected to the control end of the load adjustment module, the load adjustment circuit and the load module in the reference signal generation circuit are connected in parallel, and the output end of the reference signal generation circuit is connected to the input end of the oscillation circuit.

[0090] The load adjustment circuit is configured to adjust the resistance value of the reference signal generation circuit according to the clock signal (CLK_TEMP) generated by the temperature compensation circuit. Figure 6 The resistance value of the reference signal generation circuit is related to the duty cycle of the clock signal.

[0091] The reference signal generation circuit is configured to generate a reference signal according to its own resistance value.Figure 6 Vr in the formula (1).

[0092] The oscillation circuit is used to inversely compensate the oscillation circuit according to the reference signal to generate an oscillation signal irrelevant to the ambient temperature. Figure 6 CLK in the formula (1).

[0093] It should be noted that the frequency of the reference signal is related to the change of the resistance value of the reference signal generating circuit, the greater the resistance value of the reference signal generating circuit, the smaller the frequency of the reference signal, and the smaller the resistance value of the reference signal generating circuit, the greater the frequency of the reference signal.

[0094] When the frequency of the oscillation signal output by the RC oscillator is directly proportional to the temperature, the duty cycle of the clock signal output by the temperature compensation circuit is inversely proportional to the temperature, the resistance value of the reference signal generating circuit is inversely proportional to the duty cycle of the clock signal, the frequency of the oscillation signal is inversely proportional to the resistance value of the reference signal generating circuit, and the oscillation circuit reduces the frequency of the oscillation signal under the action of the reference signal. When the frequency of the oscillation signal output by the RC oscillator is inversely proportional to the temperature, the duty cycle of the clock signal output by the temperature compensation circuit is directly proportional to the temperature, the resistance value of the reference signal generating circuit is inversely proportional to the duty cycle of the clock signal, the frequency of the oscillation signal is inversely proportional to the resistance value of the reference signal generating circuit, and the oscillation circuit increases the frequency of the oscillation signal under the action of the reference signal.

[0095] The load adjusting circuit includes a switch tube, which is used to control whether the load module is connected to the reference signal generating circuit according to the clock signal. Specifically, the switch tube can only realize the control of the short-circuit state of the load module, and the specific type of the switch tube is not limited in the embodiment.

[0096] The second end of the switch tube is connected to the output end of the temperature compensation circuit, the first end of the switch tube is connected to the first end of the load module, and the third end of the switch tube is connected to the second end of the load module.

[0097] For example, the switch tube can be an NMOS tube (NMOS2 in the formula (1)), a PMOS tube, etc. Figure 6

[0098] The load module includes a first load (R3 in the formula (1)), and the reference signal generating circuit further includes a second load (R2 in the formula (1)), a third load (R1 in the formula (1)), a PMOS tube (PMOS1 in the formula (1)), and a filter capacitor (C1 in the formula (1)). Figure 6 Figure 6 Figure 6 Figure 6 Figure 6

[0099] ​​​​​​The drain of the PMOS tube is connected to the first end of the third load, and the common end of the connection is the output end of the reference signal generation circuit; the first end of the second load is connected to the third load; the second end of the second load is commonly connected to the first end of the first load, the first end of the switch tube and the first end of the filter capacitor; the second end of the first load is commonly connected to the third end of the switch tube and the second end of the filter capacitor; and the common end of the connection is grounded.

[0100] ​ I1 is the current of the source of the PMOS tube in the reference signal generation circuit, Vbias is the bias voltage, I2 is the current of the source of the PMOS2 in the oscillation circuit, VFB is the input voltage of the inverting input end of the comparator CMP, C0 is the charge and discharge capacitor of the oscillation circuit, NMOS1 is the switch tube for controlling the charge and discharge capacitor in the oscillation circuit, D, Q, CK and QN are all ports of the D flip-flop.

[0101] For example, the load adjustment circuit can be a device capable of controlling the on-off of the circuit (such as a switch tube, a switch, etc.), and the reference signal generation circuit can be a combination of a switch tube and a load device (such as a resistor, a bulb, etc.).

[0102] It should be noted that the noise introduced by the continuous closing of the NMOS2 can be filtered by the filter capacitor C1 to reduce the jitter.

[0103] When the frequency of the oscillation signal output by the RC oscillator is positively correlated with the temperature, that is, the frequency of the oscillation signal is positively correlated with the temperature, the frequency of the oscillation signal increases with the increase of the temperature, and the duty cycle of the clock signal output by the temperature compensation circuit is inversely proportional to the temperature, so the duty cycle of the clock signal becomes smaller with the increase of the temperature. When the clock signal output by the temperature compensation circuit is at a high level, the load adjustment circuit shorts the first load R3, and when the clock signal is at a low level, the load adjustment circuit is disconnected to connect R3. The shorter the high level maintenance time of the clock signal, the shorter the time of shorting R3, so that the overall resistance of the reference signal generation circuit becomes larger, the frequency of the reference signal becomes smaller, and thus the frequency of the oscillation signal output by the RC oscillator becomes smaller, thereby realizing reverse compensation of the RC oscillator.

[0104] When the frequency of the oscillation signal output by the RC oscillator is negatively correlated with temperature, that is, the frequency of the oscillation signal output by the RC oscillator is negatively correlated with temperature, when the temperature rises, the frequency of the oscillation signal decreases, by connecting an inverter at the output end of the temperature compensation circuit, etc. Method, reverse the level of the clock signal output by the temperature compensation circuit, so that the duty cycle of the clock signal output by the temperature compensation circuit is inversely proportional to the temperature, so when the temperature rises, the duty cycle of the clock signal becomes larger, which is equivalent to the time of R3 access becomes shorter, the resistance of the reference signal generation circuit as a whole becomes smaller, so that the frequency of the reference signal becomes larger, the frequency of the oscillation signal output by the RC oscillator becomes larger, and the RC oscillator is compensated in the opposite direction.

[0105] It is worth mentioning that the temperature compensation circuit includes a voltage control module for outputting a control signal to the clock signal generation module according to the temperature of the environment, and a clock signal generation module for generating a clock signal according to the control signal, so that the duty cycle of the clock signal generated by the temperature compensation circuit can change with the temperature of the environment. Apply the temperature compensation circuit to the RC oscillator, so that the resistance of the RC oscillator is adjusted according to the clock signal generated by the temperature compensation circuit to generate a reference signal, and then the oscillation circuit is compensated in the opposite direction according to the reference signal to generate an oscillation signal independent of the temperature of the environment, eliminating the influence of temperature on the resistance and capacitance of the RC oscillator, and further improving the precision of the oscillation signal.

[0106] The above is the preferred embodiment of the present application. It should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which should also be considered as the protection scope of the present application.

Claims

1. A temperature compensation circuit, characterized by, The temperature compensation circuit comprises a voltage control module and a clock signal generation module; The voltage control module is configured to output a control signal to the clock signal generation module according to the temperature of the environment, wherein the frequency of the control signal is related to the temperature of the environment; The clock signal generation module is configured to generate a clock signal according to the control signal, wherein the duty cycle of the clock signal is related to the frequency of the control signal.

2. The temperature compensation circuit of claim 1, wherein, The voltage control module comprises a temperature sensing circuit and a feedback voltage control circuit; An output end of the temperature sensing circuit is connected to one end of the feedback voltage control circuit and a first input end of the clock signal generation module; The temperature sensing circuit is configured to generate a first control current according to the temperature of the environment; The feedback voltage control circuit is configured to generate the control signal according to the first control current and an output signal of a first output end of the clock signal generation module.

3. The temperature compensation circuit of claim 2, wherein, The feedback voltage control circuit comprises a first control branch and a second control branch; An output end of the temperature sensing circuit is connected to a first input end of the first control branch, a second input end of the first control branch, one end of the second control branch and a first input end of the clock signal generation module, and a third input end of the first control branch is connected to a first output end of the clock signal generation module; The first control branch is configured to generate a second control current according to the first control current and an output signal of the first output end of the clock signal generation module; The second control branch is configured to charge and discharge according to the second control current to generate the control signal.

4. The temperature compensation circuit of claim 3, wherein, The temperature sensing circuit comprises a first switch tube, the first control branch comprises a second switch tube, a third switch tube and a first switch, the second control branch comprises a first capacitor, and the second control current comprises a charging current and a discharging current; An input end of the first switch tube receives an input current, an output end of the first switch tube is connected to an input end of the second switch tube, a first end of the first switch, a first end of the first capacitor and a first input end of the clock signal generation module, a control end of the first switch is connected to a first output end of the clock signal generation module, a second end of the first switch is connected to an input end of the third switch tube, and output ends of the second switch tube and the third switch tube and a second end of the first capacitor are grounded; The first switch is configured to control the charging and discharging state of the first capacitor according to an output signal of the first output end of the clock signal generation module.

5. The temperature compensation circuit of claim 1, wherein, The clock signal generation module comprises a comparison circuit and a control circuit; A first input end of the comparison circuit is connected to an output end of the voltage control module, a second input end of the comparison circuit receives a reference signal, an output end of the comparison circuit is connected to an input end of the control circuit, and the output end of the comparison circuit outputs the clock signal; The control circuit is configured to output a voltage control signal to adjust the voltage of the control signal.

6. The temperature compensation circuit of claim 5, wherein, The clock signal generation module further comprises a reference voltage control circuit; An output terminal of the reference voltage control circuit is connected with a second input terminal of the comparison circuit, a first control terminal of the reference voltage control circuit is connected with a first output terminal of the control circuit, and a second control terminal of the reference voltage control circuit is connected with a second output terminal of the control circuit. The reference voltage control circuit is configured to adjust a voltage of an output reference signal according to the voltage control signal.

7. The temperature compensation circuit of claim 6, wherein, The reference voltage control circuit comprises a second switch and a third switch, and the voltage control signal comprises a first control signal and a second control signal. A first terminal of the second switch receives a first reference signal, a first terminal of the third switch receives a second reference signal, a control terminal of the second switch is connected with the second output terminal of the control circuit, a control terminal of the third switch is connected with the first output terminal of the control circuit, and a second terminal of the second switch and a second terminal of the third switch are both connected with the second input terminal of the comparison circuit. The control circuit is specifically configured to output the first control signal and the second control signal to adjust the voltage of the control signal and the reference signal, wherein the voltage of the first reference signal is higher than the voltage of the second reference signal, and the first control signal and the second control signal are opposite.

8. The temperature compensation circuit of claim 6, wherein, The control circuit comprises a first inverting unit and a second inverting unit connected in series. An input terminal of the second inverting unit is connected with an output terminal of the comparison circuit, an output terminal of the second inverting unit is connected with the control terminal of the second switch, an input terminal of the first inverting unit is connected with an output terminal of the second inverting unit, and an output terminal of the first inverting unit is connected with the control terminal of the third switch. The first inverting unit is configured to generate the first control signal according to an output signal of the comparison circuit. The second inverting unit is configured to generate the second control signal according to the output signal of the comparison circuit.

9. An RC oscillator characterized by, The temperature compensation circuit, the load adjustment circuit, the reference signal generation circuit and the oscillation circuit according to any one of claims 1 to 8 are included. An output terminal of the temperature compensation circuit is connected with a control terminal of the load adjustment module, the load adjustment circuit is connected in parallel with a load module in the reference signal generation circuit, and an output terminal of the reference signal generation circuit is connected with an input terminal of the oscillation circuit. The load adjustment circuit is configured to adjust a resistance of the reference signal generation circuit according to a clock signal generated by the temperature compensation circuit, wherein the resistance of the reference signal generation circuit is related to a duty cycle of the clock signal. The reference signal generation circuit is configured to generate a reference signal according to the resistance thereof. The oscillation circuit is configured to perform reverse compensation on the oscillation circuit according to the reference signal to generate an oscillation signal irrelevant to the ambient temperature.

10. The RC oscillator of claim 9, wherein, The load adjustment circuit comprises a switch tube. A second terminal of the switch tube is connected with an output terminal of the temperature compensation circuit, a first terminal of the switch tube is connected with a first terminal of the load module, and a third terminal of the switch tube is connected with a second terminal of the load module.

11. The RC oscillator of claim 10, wherein, The load module comprises a first load, and the reference signal generation circuit further comprises a second load, a third load, a PMOS tube and a filter capacitor; The drain of the PMOS tube is connected with the first end of the third load, and the common end of the connection serves as an output end of the reference signal generation circuit; the first end of the second load is connected with the third load; the second end of the second load is commonly connected with the first end of the first load, the first end of the switch tube and the first end of the filter capacitor; the second end of the first load is commonly connected with the third end of the switch tube and the second end of the filter capacitor, and the common end of the connection is grounded.

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