Relaxation oscillator and method of controlling a relaxation oscillator

Abstract

A relaxation oscillator and a method of controlling a relaxation oscillator are disclosed. The relaxation oscillator includes a reference voltage generation circuit configured to generate a reference voltage based on a transistor-based resistor; a variable voltage generation circuit configured to generate a variable voltage based on the reference voltage and a control switch; a threshold voltage generation circuit configured to generate a threshold voltage using a switched-capacitor resistor circuit; and a switch control circuit configured to output a control signal for controlling the control switch based on the variable voltage and the threshold voltage.

Description

[0001] This application claims the benefit of Korean Patent Application No. 10-2019-0158493, filed on December 2, 2019, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference for all purposes. Technical Field

[0002] The following description relates to relaxor oscillators and methods for controlling relaxor oscillators. Background Technology

[0003] A typical oscillator is a circuit configured to generate a clock signal at a constant frequency and is used in a variety of electronic devices. For example, an oscillator can generate a signal that is stable over time and changes periodically to produce a system clock signal for controlling the timing of a system or a carrier signal that generates the amplitude or frequency of a switching signal. Oscillators can be classified into linear or harmonic oscillators and nonlinear or relaxor oscillators; nonlinear or relaxor oscillators are also called charge / discharge oscillators depending on how they are implemented.

[0004] A relaxor oscillator generates an oscillating signal by charging and / or discharging a capacitor, which serves as an energy storage device, within a threshold voltage defined internally within the circuit. When the voltage across the capacitor reaches the threshold voltage after charging, the relaxor oscillator can repeatedly perform sudden discharge operations on the capacitor, thereby outputting an oscillation frequency whose period is determined based on the charging and / or discharging times. As a non-limiting example, the relaxor oscillator can be used as a low-power oscillator to provide a synchronization clock signal for maintaining synchronization between systems in wireless mobile communications. Summary of the Invention

[0005] The present invention is provided in a simplified form to introduce the choice of concepts further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to help determine the scope of the claimed subject matter.

[0006] In one general aspect, an oscillator includes: a reference voltage generation circuit configured to generate a reference voltage based on a transistor-based resistor; a variable voltage generation circuit configured to generate a variable voltage based on the reference voltage and a control switch; a threshold voltage generation circuit configured to generate a threshold voltage using a switched capacitor resistor circuit; and a switch control circuit configured to output a control signal for controlling a control switch based on the variable voltage and the threshold voltage.

[0007] A transistor-based resistor can be a metal-oxide-semiconductor field-effect transistor (MOSFET) resistor disposed in a chip that implements the oscillator.

[0008] The variable voltage generation circuit may include a capacitor configured to provide a variable voltage. The capacitor may be used together with a transistor-based resistor to form a resistor-capacitor (RC) delay circuit.

[0009] The switching control circuit may include a comparator configured to compare a variable voltage and a threshold voltage, and determine the signal value of a control signal based on the comparison result.

[0010] In response to a variable voltage exceeding a threshold voltage, the switch control circuit can output a control signal to control the switch to be turned on (i.e., closed).

[0011] When the control switch is turned on by a control signal, the variable voltage generation circuit can set the voltage value of the variable voltage to the default voltage value.

[0012] In response to a variable voltage not exceeding a threshold voltage, the switch control circuit can output a control signal to control the control switch to open (i.e., open circuit).

[0013] The reference voltage generation circuit can generate a reference voltage that is independent of the magnitude of the source voltage to be applied to the reference voltage generation circuit.

[0014] The switching control circuit may also include a buffer circuit located at the output of the comparator.

[0015] The threshold voltage generation circuit may include: a frequency divider circuit configured to generate a first clock signal based on the output signal of a comparator; and a clock signal generation circuit configured to generate a second clock signal based on the first clock signal for controlling a switch included in a switched capacitor resistor circuit.

[0016] The clock signal generation circuit can generate multiple non-overlapping second clock signals. Each second clock signal can control the corresponding switching of the switched capacitor resistor circuit.

[0017] The threshold voltage generation circuit may include: a first switched capacitor resistor circuit, including a first capacitor element; and a second switched capacitor resistor circuit, including a second capacitor element.

[0018] The threshold voltage value can be determined based on the capacitance of the first capacitor and the capacitance of the second capacitor.

[0019] The oscillator can be a relaxor oscillator.

[0020] In another general aspect, a method for controlling an oscillator includes: generating a reference voltage using a reference voltage generation circuit including a transistor-based resistor; generating a variable voltage based on the reference voltage and a control switch; generating a threshold voltage using a switched capacitor resistor circuit; comparing the variable voltage and the threshold voltage, and generating a control signal based on the comparison result; and controlling a control switch based on the control signal.

[0021] The step of generating a control signal in response to a variable voltage greater than a threshold voltage may include generating a control signal for controlling the control switch to turn on (i.e., close).

[0022] The step of generating a control signal in response to a variable voltage not exceeding a threshold voltage may include generating a control signal for controlling the control switch to open (i.e., open circuit).

[0023] The step of generating the threshold voltage may include: generating a first clock signal using a frequency modulation circuit; and generating a second clock signal based on the first clock signal for controlling a switch included in a switched capacitor resistor circuit.

[0024] In another general aspect, an oscillator includes: a transistor-based resistor, a control switch, a switched capacitor resistor circuit, and a switch control circuit. The transistor-based resistor is configured to generate a reference voltage. The control switch is configured to generate a variable voltage based on the reference voltage. The switched capacitor resistor circuit is configured to generate a threshold voltage. The switch control circuit is configured to output a control signal for controlling the control switch based on the variable voltage and the threshold voltage. The switch control circuit is connected between the control switch and the switched capacitor resistor circuit.

[0025] The reference voltage generation circuit may also include multiple diodes.

[0026] The transistor-based resistor can be a metal-oxide-semiconductor field-effect transistor (MOSFET) resistor disposed in a chip in which the oscillator is implemented, and the oscillator can be a relaxation oscillator.

[0027] The source and gate terminals of the MOSFET can be connected to terminals of the source voltage, and the drain terminal of the MOSFET can be connected to one of the plurality of diodes.

[0028] The capacitor can be connected in parallel with a control switch to generate a variable voltage, and the capacitor can be configured to be combined with a transistor-based resistor to form a resistor-capacitor (RC) delay circuit.

[0029] The switching control circuit may include a comparator configured to compare a variable voltage with a threshold voltage and determine the signal value of a control signal based on the comparison result.

[0030] Other features and aspects will become clear from the following detailed description, the accompanying drawings, and the claims. Attached Figure Description

[0031] Figure 1 This is a diagram showing an example of a relaxation oscillator.

[0032] Figure 2 This is a diagram showing an example circuit for implementing a relaxor oscillator.

[0033] Figure 3 This is a diagram showing an example circuit for implementing a reference voltage generation circuit.

[0034] Figure 4 This is a diagram showing an example circuit for implementing a reference voltage generation circuit.

[0035] Figure 5 This is a diagram illustrating an example of a reference voltage based on the magnitude of the source voltage and a variation based on the transistor's resistance.

[0036] Figure 6 This is a flowchart illustrating an example method for controlling a relaxation oscillator.

[0037] Figure 7 This is a flowchart illustrating an example method for a relaxor oscillator.

[0038] Throughout the accompanying drawings and detailed embodiments, the same reference numerals denote the same elements. The drawings may not be to scale, and for clarity, illustration, and convenience, the relative dimensions, scale, and depiction of elements in the drawings may be exaggerated. Detailed Implementation

[0039] The following detailed embodiments are provided to aid the reader in gaining a comprehensive understanding of the methods, apparatus, and / or systems described herein. However, various changes, modifications, and equivalents of the methods, apparatus, and / or systems described herein will become apparent upon understanding this disclosure. For example, the order of operations described herein is merely illustrative and is not limited to those orders set forth herein, but may be changed as will become clear upon understanding this disclosure, except for operations that must occur in a specific order. Furthermore, for clarity and conciseness, descriptions of known features may be omitted.

[0040] The features described herein may be implemented in different forms and should not be construed as limited to the examples described herein. Rather, the examples described herein have been provided merely to illustrate some of the many feasible ways of implementing the methods, apparatus, and / or systems described herein that will be clear upon understanding the disclosure of this application.

[0041] The terminology used herein is for the purpose of describing particular examples only and is not intended to limit disclosure. Unless the context clearly indicates otherwise, the singular form is intended to include the plural form as used herein. As used herein, the term "and / or" includes any one of the associated listed items and any combination of any two or more. As used herein, the terms "comprising," "including," and "having" indicate the presence of the described features, quantities, operations, elements, components, and / or combinations thereof, but do not exclude the presence or addition of one or more other features, quantities, operations, elements, components, and / or combinations thereof.

[0042] Furthermore, terms such as first, second, A, B, (a), (b), etc., may be used herein to describe components. Each of these terms is not used to define the nature, order, or sequence of the corresponding component, but only to distinguish the corresponding component from one or more other components.

[0043] Throughout the specification, when an element (such as a layer, region, or substrate) is described as being "on" another element, "connected to," or "bonded to" another element, the element may be directly "on" said other element, "connected to," or "bonded to" said other element, or there may be one or more other elements in between. Conversely, when an element is described as being "directly on" another element, "directly connected to," or "directly bonded to" another element, there may be no other elements in between. Similarly, expressions such as "between" and "immediately between," and "adjacent" and "closely adjacent" may be interpreted as described above.

[0044] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains, and as commonly understood after understanding this disclosure. Unless expressly defined herein, terms (such as those defined in a general dictionary) shall be interpreted as having the same meaning as they have in the relevant field and in the context of this disclosure, and shall not be interpreted in an idealized or overly formalized sense.

[0045] Furthermore, in the description of the exemplary embodiments, such descriptions will be omitted when it is believed that a detailed description of the structure or function learned after understanding the disclosure of this application would lead to a vague interpretation of the exemplary embodiments.

[0046] In the following description, examples will be described in detail with reference to the accompanying drawings, and the same reference numerals in the drawings always denote the same elements.

[0047] Figure 1 This is a diagram showing an example of a relaxation oscillator.

[0048] The relaxor oscillator 100 is a device configured to generate a signal (such as a clock signal) with a predetermined period. The relaxor oscillator 100 generates the oscillation signal by charging or discharging an energy storage device (such as a capacitor) within a threshold voltage range internally set in the circuit. In one example, when the energy storage device is being charged, the relaxor oscillator 100 can repeatedly discharge the energy storage device when the voltage of the energy storage device reaches or exceeds the threshold voltage, thereby providing an oscillation frequency with a predetermined time period.

[0049] The relaxor oscillator 100 can be used, for example, in systems that use a low-power clock signal generator to operate at a precise frequency (such as a wake-up timer or an attachable or implantable micro-medical device). However, the use of the relaxor oscillator 100 is not limited to the aforementioned example application areas, and the relaxor oscillator 100 can be used wherever a low-power relaxor oscillator is suitable or desired.

[0050] Typically, low-power clock signal generators (such as wake-up timers) can use resistive voltage dividers to reduce frequency variations based on changes in the supply voltage. In such cases, a trade-off exists between power consumption and the area used due to the use of common resistors. For example, when using common resistors with high resistance values ​​(e.g., fixed resistors) to reduce the power consumption of the relaxation oscillator, a relatively large area is expected for such common resistors. Conversely, when using common resistors with low resistance values ​​to reduce the area to be used, the power consumption of the relaxation oscillator can be relatively higher.

[0051] Although described in more detail below, the relaxor oscillator 100 can use switched-capacitor resistors and transistor-based resistors, and thus eliminates the trade-off between power consumption and required area size, reducing both the power consumption and area of ​​the relaxor oscillator 100. Furthermore, the relaxor oscillator 100 can use switched capacitors and transistor-based resistors, and therefore provides robust stability to variations in the manufacturing process, source voltage, and temperature of the relaxor oscillator 100.

[0052] exist Figure 1 In the process, the relaxor oscillator 100 includes a reference voltage generation circuit 110, a variable voltage generation circuit 120, a threshold voltage generation circuit 130, and a switching control circuit 140.

[0053] The reference voltage generation circuit 110 can generate a reference voltage from the source voltage. The reference voltage can have a constant voltage value. The reference voltage generation circuit can generate the reference voltage based on a transistor-based resistor. The transistor-based resistor can be, for example, a metal-oxide-semiconductor field-effect transistor (MOSFET) resistor disposed in the chip implementing the relaxation oscillator 100. The MOSFET resistor can have a relatively excellent resistance value that is continuously maintained with respect to the source voltage. For example, the MOSFET resistor can have a resistance value of tera-ohms. When a MOSFET resistor with such a high resistance value is arranged in the chip, the MOSFET resistor can form a resistor-capacitor (RC) delay circuit of the relaxation oscillator 100. Here, it should be noted that the use of the term "may" (e.g., what may be included or implemented in an example or embodiment) with respect to examples or embodiments indicates the existence of at least one example or embodiment that includes or implements such a feature, while all examples and embodiments are not limited thereto.

[0054] By using a transistor-based resistor that can be implemented on a chip, the reference voltage generation circuit 110 can reduce the area to be used and generate a reference voltage that is independent of the magnitude or variation of the source voltage to be applied to the reference voltage generation circuit 110. Therefore, the source voltage does not affect the output frequency of the relaxation oscillator 100. Furthermore, using a transistor-based resistor as the resistor in the RC delay circuit allows for a considerably large resistance value to be obtained with only a small area, thereby reducing the power consumption of the relaxation oscillator 100.

[0055] A reference voltage generated in the reference voltage generation circuit 110 can be provided to the variable voltage generation circuit 120. The variable voltage generation circuit 120 can generate a variable voltage that varies over time. The variable voltage generation circuit 120 can generate the variable voltage based on the reference voltage generated in the reference voltage generation circuit 110 and a control switch, and includes an energy storage device for providing the variable voltage. For example, the energy storage device can be a capacitor. As the energy accumulated in the capacitor changes over time, the voltage value of the variable voltage can change over time. The capacitor can be repeatedly charged and discharged by the control switch, and the operation of the control switch can be controlled by a control signal sent from the switch control circuit 140. The capacitor may include one or more capacitors or other capacitive elements.

[0056] In one example, when the capacitor is discharged, the variable voltage supplied to the capacitor can become ground (GND). When the capacitor is charged, the variable voltage can begin to increase from GND to a reference voltage. In this example, while the variable voltage is increasing, it can decrease back to GND when the control switch is turned on by a control signal. Here, the term "on" indicates that the switch is closed, and the term "off" indicates that the switch is open.

[0057] The variable voltage generation circuit 120 can be connected to the reference voltage generation circuit 110. The capacitors included in the variable voltage generation circuit 120 can form an RC delay circuit together with the transistor-based resistors included in the reference voltage generation circuit 110. The variable voltage generation circuit 120 can also be connected to the switch control circuit 140 and provide the generated variable voltage to the switch control circuit 140. Furthermore, the variable voltage generation circuit 120 can receive control signals from the switch control circuit 140 for controlling a control switch.

[0058] Threshold voltage generation circuit 130 generates a threshold voltage for use as a reference for comparison with a variable voltage. Threshold voltage generation circuit 130 may use a switched capacitor resistor circuit to generate the threshold voltage. In one example, threshold voltage generation circuit 130 may include multiple switched capacitor resistor circuits, a frequency divider circuit, and a clock signal generation circuit. For example, the switched capacitor resistor circuit may include a first switched capacitor resistor circuit containing a first capacitor element and a second switched capacitor resistor circuit containing a second capacitor element. In this example, the voltage value of the threshold voltage generated by threshold voltage generation circuit 130 may be determined based on the capacitance of the first capacitor element and the capacitance of the second capacitor element. Using switched capacitor resistor circuits instead of ordinary resistors reduces the area and power consumption required to generate the threshold voltage.

[0059] The frequency divider circuit can generate a first clock signal based on the output signal of the comparator in the switch control circuit 140. For example, the frequency divider circuit can convert the comparator's output signal into a first clock signal with a 50% duty cycle and output the first clock signal. The clock signal generation circuit can generate a second clock signal for controlling the switch included in the switched capacitor resistor circuit based on the first clock signal generated by the frequency divider circuit. Here, the clock signal generation circuit can generate non-overlapping second clock signals, and each second clock signal can control a corresponding switch in the switched capacitor resistor circuit.

[0060] The switch control circuit 140 can generate a control signal for controlling the control switch of the variable voltage generation circuit 120 based on the variable voltage and a threshold voltage, and output the generated control signal. The control signal can periodically control the control switch to turn on or off, so as to periodically charge or discharge the capacitor of the variable voltage generation circuit 120.

[0061] In one example, the switch control circuit 140 may include a comparator configured to compare a variable voltage with a threshold voltage and determine a control signal value based on the comparison result. In response to the variable voltage being higher than the threshold voltage, the comparator may output a control signal to control the control switch to turn on (i.e., close). When the control switch of the variable voltage generation circuit 120 is turned on by the control signal, the variable voltage generation circuit 120 may set the voltage value of the variable voltage to a default voltage value (e.g., the GND voltage value). In response to the variable voltage not being higher than the threshold voltage, the comparator may output a control signal to control the control switch to turn off (i.e., open circuit). When the control switch of the variable voltage generation circuit 120 is turned off by the control signal, the capacitor of the variable voltage generation circuit 120 may continue to charge, and the voltage value of the variable voltage may gradually increase.

[0062] According to one example, the switch control circuit 140 may also include a buffer circuit disposed at the output of the comparator. The buffer circuit can connect the comparator to other components to prevent electrical problems or faults from occurring between the comparator and other components providing the comparator's output. The buffer circuit may include two inverters connected in series, and make the waveform of the comparator's output signal sharper.

[0063] The relaxor oscillator 100 can generate a constant frequency independent of or unrelated to the source voltage using transistor-based resistors, and can be implemented on-chip with relatively large resistance values ​​and relatively small area. Furthermore, by using transistor-based resistors as resistors in an RC delay circuit, the relaxor oscillator 100 can be implemented as a low-power relaxor oscillator within a limited area. Moreover, with this configuration, the frequency of the relaxor oscillator 100 can be robustly generated in response to changes in ambient temperature.

[0064] Figure 2 This is a diagram illustrating an example circuit implementation of a relaxation oscillator.

[0065] exist Figure 2 In this example, as a non-limiting example, the relaxor oscillator includes a reference voltage generation circuit 210, a variable voltage generation circuit 220, a switch control circuit 230, and a threshold voltage generation circuit.

[0066] The reference voltage generation circuit 210 receives the source voltage VDD and provides a reference voltage V with a constant voltage value independent of the source voltage VDD. REF The reference voltage generation circuit 210 generates a reference voltage V based on a transistor-based resistor. REFFor example, a transistor-based resistor can be a MOSFET resistor implemented in-chip. To achieve low power in the relaxation oscillator, a resistor with a relatively large resistance value can be used. Therefore, by using MOSFET resistors that can be implemented in-chip, the effect of the source voltage VDD on the frequency of the relaxation oscillator can be reduced or eliminated with various reductions in design area and unit production cost.

[0067] The following will refer to Figure 3 An example circuit is described that can implement a reference voltage generation circuit 210. Figure 3 In this circuit, the reference voltage generation circuit 210 can be connected to a terminal from which the source voltage VDD is supplied, and the source voltage VDD can be supplied to the MOSFET M1 310, which is a transistor device. The MOSFET M1 310 can function as a resistor and can be incorporated into a chip implementing a relaxation oscillator. The reference voltage generation circuit 210 may include a plurality of diodes 320 connected in series, with a current I... DC The current flows through diode 320. The source and gate terminals of MOSFET M1 310 are connected to the terminal from which the supply source voltage VDD is obtained, and the drain terminal of MOSFET M1 310 is connected to one of the diodes 320 and the output terminal 330. A reference voltage V with a constant voltage value is provided. REF Based on MOSFET M1 310 and current I DC It is generated and output through output terminal 330. Reference voltage V REF It can be sent to the variable voltage generation circuit 220. The MOSFET M1 310 can be used as a resistor in the RC delay circuit that forms the relaxation oscillator.

[0068] Figure 4 This is a diagram illustrating an example circuit for implementing the reference voltage generation circuit 210. Figure 4 In, similar to Figure 3 In the example shown, the reference voltage generation circuit 210 can be connected to a terminal from which the source voltage VDD is supplied, and the source voltage VDD is supplied to the MOSFET M1 410, which is a transistor device. For example, Figure 4 The reference voltage generation circuit 210 may include a current I DC Multiple transistor devices 420 flowing within it, rather than as Figure 3 The multiple diodes shown. The reference voltage generation circuit 210 is based on MOSFET M1 410 and current I. DC Generate a reference voltage V with a constant voltage value REF Reference voltage V REFThe voltage can be sent to the variable voltage generation circuit 220 via output terminal 430. The source and gate terminals of MOSFET M1 410 are connected to the terminals from which the source voltage VDD is supplied. The drain terminal of MOSFET M1 410 is connected to one of the transistor devices 420 and output terminal 430.

[0069] Return to reference Figure 2 The variable voltage generation circuit 220 receives the reference voltage V generated by the reference voltage generation circuit 210. REF The variable voltage generation circuit 220 includes a capacitor C0222 and a control switch 224. The capacitor C0222 accumulates voltage from the reference voltage V. REF The supplied charge. The voltage across capacitor C0222 corresponds to the variable voltage V2 generated by variable voltage generation circuit 220. Control switch 224 can be turned on or off via a control signal generated by switch control circuit 230. When control switch 224 is on (i.e., closed), both ends of capacitor C0222 are connected to GND voltage, and capacitor C0222 is discharged. When control switch 224 is off (i.e., open circuit) after capacitor C0222 has discharged, capacitor C0222 is based on reference voltage V... REF Charge accumulates again, and the variable voltage V2 begins to increase. This increase in variable voltage V2 corresponds to the charging of capacitor C0 222. By controlling switch 224, capacitor C0 222 can be repeatedly charged or discharged, thus forming a period. Capacitor C0 222, together with the transistor-based resistor included in the reference voltage generation device 210, forms the RC delay circuit of the relaxation oscillator.

[0070] The threshold voltage generation circuit generates a threshold voltage V1. The threshold voltage generation circuit includes multiple switched capacitor and resistor circuits 242 and 246, a frequency divider circuit 252, and a clock signal generation circuit 254.

[0071] The first switched capacitor resistor circuit 242 includes a first capacitor C1 244, and the second switched capacitor resistor circuit 246 includes a second capacitor C2 248. Each switch included in each of the switched capacitor resistor circuits 242 and 246 can be controlled by a control signal generated by a clock signal generation circuit 254. The resistance value of the first switched capacitor resistor circuit 242 can be determined by the operating cycle of the switching operation of the switch included in the first switched capacitor resistor circuit 242 and the capacitance of the first capacitor C1 244. The resistance value of the second switched capacitor resistor circuit 246 can be determined by the operating cycle of the switching operation of the switch included in the second switched capacitor resistor circuit 246 and the capacitance of the second capacitor C2 248. One end of the first switched capacitor resistor circuit 242 is connected to the source voltage VDD, and the first switched capacitor resistor circuit 242 and the second switched capacitor resistor circuit 246 are connected in series. With this circuit structure, the switched capacitor resistor circuits 242 and 246 can perform the function of a voltage divider. Using switched capacitor resistor circuits 242 and 246 as voltage dividers reduces the power consumption and area required for the relaxation oscillator compared to a typical oscillator.

[0072] The threshold voltage V1 generated by the threshold voltage generation circuit can have a constant voltage value and can be determined by the capacitance C1 of the first capacitor C1 244 included in the first switched capacitor resistor circuit 242 and the capacitance C2 of the second capacitor C2 248 included in the second switched capacitor resistor circuit 246. For example, the threshold voltage V1 can be determined as shown in Equation 1.

[0073] Equation 1:

[0074]

[0075] The frequency divider circuit 252 generates a first clock signal based on the output signal of the switch control circuit 230. In one example, the waveform of the output signal of the switch control circuit 230 (or more specifically, the waveform of the output signal of the comparator 232) may have a spike, and the frequency divider circuit 252 can convert the output signal of the switch control circuit 230 into a first clock signal with a 50% duty cycle and output the first clock signal. The first clock signal, as the output signal of the frequency divider circuit 252, is sent to the clock signal generation circuit 254.

[0076] The clock signal generation circuit 254 generates a second clock signal based on the first clock signal to control the switches included in the switched capacitor resistor circuits 242 and 246. The second clock signals generated by the clock signal generation circuit 254 can be non-overlapping in terms of on-time, and each second clock signal can control the corresponding switch of the switched capacitor resistor circuits 242 and 246.

[0077] The switch control circuit 230 generates a control signal for controlling the control switch 224 of the variable voltage generation circuit 220. A threshold voltage V1 and a variable voltage V2 are input to the switch control circuit 230. The switch control circuit 230 includes a comparator 232 configured to compare the input threshold voltage V1 and the input variable voltage V2, and output different values ​​of output signals based on the comparison result.

[0078] In response to a variable voltage V2 being greater than a threshold voltage V1, comparator 232 outputs a control signal (e.g., a high logic value) to control switch 224 to turn on (i.e., close). When the control signal turns on control switch 224, capacitor C0 222 is discharged. Conversely, in response to a variable voltage V2 not being greater than a threshold voltage V1, comparator 232 outputs a control signal (e.g., a low logic value) to control switch 224 to turn off (i.e., open). When control switch 224 is turned off by the control signal, capacitor C0 222 discharges based on a reference voltage V1. REF It is continuously charged, and the variable voltage V2 gradually increases.

[0079] When the continuously increasing variable voltage V2 becomes higher than the threshold voltage V1, comparator 232 outputs a control signal to turn on control switch 224, and correspondingly, capacitor C0 222 is discharged again. When capacitor C0 222 is discharged, the variable voltage V2 is initialized to the GND voltage value or 0V. Therefore, the variable voltage V2 input to comparator 232 becomes less than the threshold voltage V1, and comparator 232 then outputs a control signal to turn off control switch 224. Thus, capacitor C0 222 begins to be recharged.

[0080] According to one example, the switch control circuit 230 may also include a buffer circuit 234 disposed at the output of the comparator 232. For example, the buffer circuit 234 may include two inverters connected in series and is used to make the waveform of the output signal of the comparator 232 sharper.

[0081] Furthermore, whenever a short pulse appears in the output signal of the switch control circuit 230, the output of the frequency divider circuit 252 is toggled. For example, whenever a short pulse appears in the output signal of the switch control circuit 230, the output of the frequency divider circuit 252 can change from a high logic value to a low logic value, or from a low logic value to a high logic value.

[0082] Figure 5 This is a diagram illustrating an example of a reference voltage based on the magnitude of the source voltage and a variation based on the transistor's resistance.

[0083] Figure 5 Indicates the instruction in Figure 3 or Figure 4 The reference voltage V shown in the circuit diagram appears when the source voltage VDD increases. REF The change and resistance R of MOSFET M1 M1 The graph shows the change in voltage. Referring to the graph, when the source voltage VDD becomes greater than or equal to the threshold voltage V... TH At that time, the reference voltage V REF and the resistance R of MOSFET M1 M1 Saturation is constant. Threshold voltage V TH This corresponds to the minimum gate-source voltage required to generate a conduction path between the source and drain terminals of MOSFET M1. As described above, MOSFET M1, as a transistor device, can be used as a resistor in the RC delay circuit of a relaxation oscillator, thus enabling the generation of a constant-frequency relaxation oscillator independent of changes in the source voltage VDD.

[0084] Figure 6 This is a flowchart illustrating an example method for controlling a relaxation oscillator.

[0085] exist Figure 6 In operation 610, the relaxor oscillator uses a reference voltage generation circuit including a transistor-based resistor to generate a reference voltage. The reference voltage may have a constant value independent of the magnitude of the source voltage applied to the reference voltage generation circuit. The transistor-based resistor may be a MOSFET resistor disposed in the chip implementing the relaxor oscillator. The transistor-based resistor may form an RC delay circuit together with a capacitor configured to provide a variable voltage.

[0086] In operation 620, the relaxor oscillator can generate a variable voltage using a variable voltage generation circuit. The variable voltage generation circuit may include a capacitor and a control switch. The capacitor is configured to accumulate charge based on a reference voltage, and the control switch is configured to control the variable voltage reflecting changes in the amount of charge on the capacitor. The variable voltage generation circuit can generate the variable voltage under the control of the control switch. The capacitor can be repeatedly charged and discharged via the control switch, and the operation of the control switch can be controlled by a control signal generated by a switch control circuit.

[0087] In operation 630, the relaxor oscillator generates a threshold voltage using a threshold voltage generation circuit that includes a switched capacitor resistor circuit. The threshold voltage can be used as a reference to be compared with a variable voltage. In one example, the relaxor oscillator can use a frequency modulation circuit to generate a first clock signal, and based on the generated first clock signal, generate a second clock signal for controlling the switches included in the switched capacitor resistor circuit. The second clock signal can periodically control the operation of the switches included in the switched capacitor resistor circuit, so each switched capacitor resistor circuit can perform the function of a resistor. The threshold voltage value can be determined based on the resistance value of the switched capacitor resistor circuit and the source voltage.

[0088] In operation 640, the relaxor oscillator uses a comparator to generate a control signal for controlling the control switch of the variable voltage generation circuit. The comparator compares the variable voltage generated in operation 620 with the threshold voltage generated in operation 630. Based on the comparison result, the comparator generates a control signal for controlling the control switch. In response to the variable voltage being greater than the threshold voltage, the comparator generates a control signal for controlling the control switch to turn on (i.e., close). Conversely, in response to the variable voltage not being greater than the threshold voltage, the comparator generates a control signal for controlling the control switch to turn off (i.e., open circuit).

[0089] In operation 650, the relaxor oscillator can control the control switch of the variable voltage generation circuit based on the control signal generated in operation 640. When the control switch is turned on by the control signal, the capacitor of the variable voltage generation circuit can be discharged, and the variable voltage can be set to a default voltage value. Subsequently, as the variable voltage changes, a control signal for turning off the control switch can be generated, and the control switch can then be turned off, and the capacitor can be charged. As the capacitor is charged, the variable voltage can gradually increase. When the gradually increasing variable voltage becomes greater than a threshold voltage, the control signal for turning the control switch on can be generated again, and the capacitor can be discharged again.

[0090] As described above, the variable voltage can be changed over time by a capacitor that is repeatedly charged and discharged based on time, and the relaxation oscillator can generate a periodic signal based on the variable voltage and a fixed threshold voltage.

[0091] Figure 7 This is a flowchart illustrating an example method for a relaxor oscillator.

[0092] exist Figure 7 In operation 710, an initial threshold voltage value is generated for the threshold voltage generation circuit. During the initial phase of the relaxor oscillator, the source voltage VDD is initially supplied, and the clock signal is not yet supplied to the switched capacitor-resistor circuit of the threshold voltage generation circuit. Therefore, for example, the initial threshold voltage value can be set to the value of VDD / 2. Furthermore, the reference voltage generation circuit begins operation based on the source voltage VDD, and a constant reference voltage is generated from the reference voltage generation circuit.

[0093] In operation 720, the variable voltage generation circuit can start operating based on the reference voltage generated from the reference voltage generation circuit, and the variable voltage, which is the output signal of the variable voltage generation circuit, can start to increase.

[0094] In operation 730, the variable voltage and the threshold voltage are compared by a comparator included in the control signal generation circuit. In operation 740, a low logic value output signal can be output from the comparator in response to the variable voltage not being greater than the threshold voltage. In operation 750, a high logic value output signal can be output from the comparator in response to the variable voltage being greater than the threshold voltage.

[0095] When the comparator outputs a low logic value, the control switch of the variable voltage generation circuit remains open, operation 720 is executed, and the variable voltage continues to increase. Conversely, when the comparator outputs a high logic value, the control switch of the variable voltage generation circuit is turned on, and the variable voltage is initialized in operation 760. Subsequently, the initialized variable voltage can be input to the comparator, and a low logic value output signal is output from the comparator via operation 730. Therefore, the control switch of the variable voltage generation circuit is turned off, operation 720 is executed, and the variable voltage begins to increase. When the comparator outputs a high logic value output signal after a short time, the low logic value output signal is output again. The low logic value output signal is held until just before the variable voltage becomes greater than the threshold voltage, so the comparator's output signal can be represented as a periodically repeating short pulse signal.

[0096] The comparator's output is sent to the frequency divider circuit. When a high logic value is output from the comparator, the clock signal output through the frequency divider circuit and the clock signal generation circuit is switched in operation 770. In operation 780, the clock signal switched in operation 770 is supplied to the switch of the switched capacitor resistor included in the threshold voltage generation circuit, and a constant threshold voltage is generated by the clock signal and sent to the comparator.

[0097] Although this disclosure includes specific examples, it will be clear upon understanding this disclosure that various changes in form and detail may be made in these examples without departing from the spirit and scope of the claims and their equivalents. The examples described herein are to be considered descriptive only and not for limiting purposes. The description of features or aspects in each example should be considered applicable to similar features or aspects in other examples. Suitable results may be achieved if the described techniques are performed in a different order, and / or if components in the described system, architecture, apparatus, or circuit are combined in a different manner, and / or replaced or supplemented by other components or their equivalents.

[0098] Therefore, the scope of the disclosure is not limited by the specific embodiments, but by the claims and their equivalents, and all variations within the scope of the claims and their equivalents should be interpreted as included in the disclosure.

Claims

1. An oscillator comprising: a reference voltage generation circuit configured to generate a reference voltage using a transistor-based resistor; a variable voltage generation circuit configured to generate a variable voltage based on the reference voltage and a control switch; a threshold voltage generation circuit configured to generate a threshold voltage using a switched-capacitor resistor circuit; and a switch control circuit configured to output a control signal for controlling the control switch based on the variable voltage and the threshold voltage, wherein the variable voltage generation circuit comprises: a capacitive device configured to provide the variable voltage, wherein the capacitive device is configured to form a resistor-capacitor delay circuit with the transistor-based resistor used to generate the reference voltage. The transistor-based resistor is a metal-oxide-semiconductor field-effect transistor resistor provided in a chip in which the oscillator is implemented.

2. The oscillator of claim 1, wherein, The switch control circuit comprises:

3. The oscillator of claim 1, wherein, a comparator configured to compare the variable voltage and the threshold voltage and set a signal value of the control signal based on a result of the comparison. The switch control circuit further comprises:

4. The oscillator of claim 3, wherein, a buffer circuit provided at an output of the comparator. The threshold voltage generation circuit comprises:

5. The oscillator of claim 3, wherein, a frequency divider circuit configured to generate a first clock signal based on an output signal of the comparator; and a clock signal generation circuit configured to generate a second clock signal for controlling a switch included in the switched-capacitor resistor circuit based on the first clock signal. The clock signal generation circuit is configured to generate a plurality of non-overlapping second clock signals, 6. The oscillator of claim 5, wherein, wherein each of the second clock signals is configured to control a respective switch of the switched-capacitor resistor circuit. In response to the variable voltage being greater than the threshold voltage, the switch control circuit is configured to output the control signal for controlling the control switch to turn on.

7. The oscillator of claim 1, wherein, The variable voltage generation circuit is configured to set a voltage value of the variable voltage to a default voltage value based on the control switch turning on.

8. The oscillator of claim 7, wherein, The switch control circuit is configured to output the control signal for controlling the control switch to turn off based on the variable voltage not being greater than the threshold voltage.

9. The oscillator of claim 1, wherein, The reference voltage generation circuit is configured to generate the reference voltage regardless of a magnitude of a source voltage applied to the reference voltage generation circuit.

10. The oscillator of claim 1, wherein, The threshold voltage generation circuit comprises:

11. The oscillator of claim 1, wherein, a first switched-capacitor resistor circuit including a first capacitive device; and a second switched-capacitor resistor circuit including a second capacitive device. A voltage value of the threshold voltage is determined based on a capacitance of the first capacitive device and a capacitance of the second capacitive device.

12. The oscillator of claim 11, wherein, The oscillator is a relaxation oscillator.

13. The oscillator of claim 1, wherein, 14.A method of controlling an oscillator, the method comprising: generating a reference voltage using a transistor-based resistor of a reference voltage generation circuit; generating a variable voltage based on the reference voltage and a control switch; generating a threshold voltage using a switched-capacitor resistor circuit; comparing the variable voltage and the threshold voltage and generating a control signal based on a result of the comparison; and controlling the control switch based on the control signal, wherein the transistor-based resistor used to generate the reference voltage forms a resistor-capacitor delay circuit with a capacitive device configured to provide the variable voltage. The transistor-based resistor is a metal-oxide-semiconductor field-effect transistor resistor provided in a chip in which the oscillator is implemented. ​ 15. The method of claim 14, wherein, ​ 16. The method of claim 14, wherein, The reference voltage generation circuit generates a reference voltage that is independent of a magnitude of a source voltage applied to the reference voltage generation circuit.

17. The method of claim 14, wherein, The step of generating the control signal includes: in response to the variable voltage being greater than the threshold voltage, generating the control signal for controlling the control switch to turn on.

18. The method of claim 14, wherein, The step of generating the control signal includes: in response to the variable voltage not being greater than the threshold voltage, generating the control signal for controlling the control switch to turn off.

19. The method of claim 14, wherein, The step of generating the threshold voltage includes: generating a first clock signal using a frequency modulation circuit; and generating a second clock signal for controlling a switch of the switched capacitor resistor circuit based on the first clock signal.

20. An oscillator comprising: a reference voltage generation circuit including a transistor-based resistor configured to generate a reference voltage; a control switch configured to generate a variable voltage based on the reference voltage; a switched capacitor resistor circuit configured to generate a threshold voltage; and a switch control circuit configured to output a control signal for controlling the control switch based on the variable voltage and the threshold voltage, wherein the switch control circuit selectively connects the control switch and the switched capacitor resistor circuit, wherein a capacitor device is connected in parallel with the control switch to generate the variable voltage, and the capacitor device is configured to form a resistor-capacitor delay circuit with the transistor-based resistor for generating the reference voltage. The reference voltage generation circuit further includes a plurality of diodes connected in series to generate a current.

21. The oscillator of claim 20, wherein, The transistor-based resistor is a metal oxide semiconductor field effect transistor resistor provided in a chip in which the oscillator is implemented, and the oscillator is a relaxation oscillator.

22. The oscillator of claim 21, wherein, A source terminal and a gate terminal of the metal oxide semiconductor field effect transistor resistor are connected to a terminal of the source voltage, and a drain terminal of the metal oxide semiconductor field effect transistor resistor is connected to one of the plurality of diodes.

23. The oscillator of claim 22, wherein, The switch control circuit includes:

24. The oscillator of claim 20, wherein, a comparator configured to compare the variable voltage with the threshold voltage, and determine a signal value of the control signal based on a result of the comparison. ​

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