Oscillating circuits and methods for automatically correcting duty cycles

Abstract

An oscillating circuit includes an amplifier, a feedback resistor, and a first switching circuit. The amplifier includes an input and an output for inverting and amplifying an oscillating signal received from the input to provide an output oscillating signal to the output. The feedback resistor is coupled between the input and the output. The first switching circuit is coupled in parallel to the feedback resistor for switching the input and output on each other in one of the following situations: (1) the input voltage of the oscillating signal is higher than the output voltage of the output oscillating signal by at least a first threshold; and (2) the output voltage is higher than the input voltage by at least a second threshold. The first switching circuit has a first on-resistance value, which is less than the resistance value of the feedback resistor.

Description

Technical Field

[0001] This invention relates to an electronic oscillator, and more particularly to a quartz oscillator circuit and a method for automatically correcting the duty cycle. Background Technology

[0002] Traditional quartz oscillator systems (such as Pierce oscillators) consist of an amplifier and a quartz crystal, which work together to generate an oscillation signal. To maintain the oscillation signal's duty cycle at 50%, the amplifier's input is typically biased to a fixed voltage. With advancements in semiconductor manufacturing processes, transistor sizes have shrunk to enable high-speed and high-frequency circuits. However, in quartz oscillator systems manufactured using advanced processes, the transistors exhibit significant gate leakage current. This leakage current can cause the amplifier's input to deviate from the aforementioned fixed voltage, thereby causing the oscillation signal's duty cycle to deviate from the 50% mark.

[0003] A frequency multiplier used to boost the frequency of an oscillation signal can be coupled to the output of an amplifier. In some cases, a frequency multiplier can correct the duty cycle of the oscillation signal. However, as the deviation of the oscillation signal's duty cycle increases, the frequency multiplier typically requires a more complex structure to improve its correction capability, which not only increases the overall circuit area but also introduces more noise. Therefore, this correction method is not suitable for quartz oscillator systems manufactured using advanced processes. Summary of the Invention

[0004] This invention provides an oscillation circuit. The oscillation circuit includes an amplifier, a feedback resistor, and a first switching circuit. The amplifier includes an input terminal and an output terminal for inverting and amplifying an oscillation signal received from the input terminal to provide an output oscillation signal to the output terminal. The feedback resistor is coupled between the input terminal and the output terminal. The first switching circuit is coupled in parallel to the feedback resistor for switching the input terminal and the output terminal on each other in one of the following situations: (1) the input voltage of the oscillation signal is higher than the output voltage of the output oscillation signal by at least a first threshold; and (2) the output voltage is higher than the input voltage by at least a second threshold. The first switching circuit has a first on-resistance value, which is less than the resistance value of the feedback resistor.

[0005] This invention provides a method for automatically correcting the duty cycle. The method includes the following steps: receiving an oscillation signal at the input of an amplifier; inverting and amplifying the oscillation signal to provide an output oscillation signal at the output of the amplifier; and turning on a first switching circuit coupled between the input and output in one of the following situations: (1) the input voltage of the oscillation signal is higher than the output voltage of the output oscillation signal by at least a first threshold; and (2) the output voltage is higher than the input voltage by at least a second threshold. A feedback resistor is coupled between the input and output, and the first switching circuit has a first on-resistance value, which is less than the resistance value of the feedback resistor.

[0006] The advantages of the above-mentioned oscillation circuit and automatic correction method are that it can automatically correct the DC bias voltage at the input of the amplifier and avoid introducing additional noise during correction.

[0007] The features, operation, and effects of the present invention will be described in detail below with reference to the accompanying drawings, specifically the preferred embodiments. Attached Figure Description

[0008] Figure 1 This is a simplified functional block diagram of an oscillation system according to an embodiment of the present invention.

[0009] Figure 2 This is a schematic diagram of a switching circuit according to an embodiment of the present invention.

[0010] Figure 3 This is a schematic diagram of a switching circuit according to an embodiment of the present invention.

[0011] Figure 4 This is a schematic diagram of a switching circuit according to an embodiment of the present invention.

[0012] Figure 5 This is a schematic diagram illustrating the total resistance between the input and output terminals according to an embodiment of the present invention.

[0013] Figure 6 This is a schematic diagram of a switching circuit according to an embodiment of the present invention.

[0014] Figure 7 This is a schematic diagram of a switching circuit according to an embodiment of the present invention.

[0015] Figure 8 This is a schematic diagram of a switching circuit according to an embodiment of the present invention.

[0016] Figure 9 This is a schematic diagram illustrating the total resistance between the input and output terminals according to an embodiment of the present invention.

[0017] Figure 10This is a simplified functional block diagram of an oscillation system according to an embodiment of the present invention.

[0018] Figure 11 This is a schematic diagram of a plurality of switching circuits according to an embodiment of the present invention.

[0019] Figure 12 This is a schematic diagram illustrating the total resistance between the input and output terminals according to an embodiment of the present invention.

[0020] Figure 13 This is a flowchart of a method for automatically correcting work cycles according to an embodiment of the present invention.

[0021] Symbol Explanation

[0022] 1, 2: Oscillation System

[0023] 10, 100: Oscillating circuit

[0024] 11, 101: Amplifier

[0025] 12, 102, 103: Switching circuits

[0026] VDD: Operating voltage

[0027] Cr: Crystal oscillation signal

[0028] Ou: Output oscillation signal

[0029] Lp, Ln: Leakage current

[0030] Tp, Tn: Transistor

[0031] XI: Input terminal

[0032] XO: Output terminal

[0033] Vin: Input voltage

[0034] Vout: Output voltage

[0035] Rf: Feedback resistor

[0036] Rt: Total resistance value

[0037] P1: First pin

[0038] P2: Second pin

[0039] Qz: Quartz Crystal

[0040] C1: First capacitor

[0041] C2: Second capacitor

[0042] 222, 322, 422, 424, 622, 722, 822, 824, 1122, 1124, 1132, 1134: Transistors

[0043] 324, 426, 724, 826, 1126, 1136: Compensation resistors

[0044] S1, S2, S4, S5, S7, S8, S9: Curves

[0045] S3, S6, S10: line segments

[0046] Vtha: First threshold

[0047] Vthb: Second threshold

[0048] 130: Methods for automatically correcting work cycles

[0049] S132, S134, S136, S138: Process Detailed Implementation

[0050] The embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings, the same reference numerals denote the same or similar components or method flows.

[0051] Figure 1 This is a simplified functional block diagram of an oscillation system 1 according to an embodiment of the present invention. The oscillation system 1 includes an oscillation circuit 10, a first pin P1, a second pin P2, a quartz crystal Qz, a first capacitor C1, and a second capacitor C2. The oscillation circuit 10 forms a feedback system with the quartz crystal Qz to generate an output oscillation signal Ou based on the crystal oscillation signal Cr received from the quartz crystal Qz. For simplicity, other components of the oscillation system 1 are not shown. Figure 1 .

[0052] The oscillation circuit 10 is used to couple a first terminal of the quartz crystal Qz to a first capacitor C1 via a first pin P1, and to couple a second terminal of the quartz crystal Qz to a second capacitor C2 via a second pin P2. In some embodiments, the oscillation circuit 10 may be packaged in a chip, and the first pin P1 and the second pin P2 may be connection pads of the chip. The oscillation circuit 10 includes an amplifier 11, a switching circuit 12, and a feedback resistor Rf. The amplifier 11 includes an input terminal XI and an output terminal XO, which are respectively coupled to the first pin P1 and the second pin P2. The input terminal XI is used to receive a crystal oscillation signal Cr from the quartz crystal Qz via the first pin P1. The amplifier 11 is used to amplify and invert the crystal oscillation signal Cr to provide an output oscillation signal Ou at the output terminal XO, wherein the output oscillation signal Ou is transmitted to the quartz crystal Qz via the second pin P2.

[0053] In this embodiment, amplifier 11 is implemented by an inverter, which includes transistors Tn and Tp, but the invention is not limited thereto. In some embodiments, amplifier 11 can be implemented by various suitable inverting amplifiers. Transistor Tn is coupled between a ground terminal and an output terminal XO, wherein the ground terminal can provide a ground voltage. Transistor Tp is coupled between a power supply terminal and an output terminal XO, wherein the power supply terminal is used to provide the operating voltage VDD. In addition, the control terminals of transistors Tp and Tn are both coupled to the input terminal XI.

[0054] The feedback resistor Rf is coupled between the input terminal XI and the output terminal XO, and is used to provide negative feedback to set the DC bias voltage (indicated by the dashed line) of the input terminal XI, so as to bias transistors Tp and Tn in the linear region. The aforementioned DC bias voltage can be half of the operating voltage VDD (VDD / 2), and is the same as the DC bias voltage of the output terminal XO, so the output oscillation signal Ou will have a 50% duty cycle, but the invention is not limited thereto. To start oscillation, the oscillation circuit 10 requires positive feedback from the first capacitor C1 and the second capacitor C2, therefore the feedback resistor Rf can have a relatively large resistance value to mitigate the negative feedback, thereby preventing the positive feedback from being eliminated. In some embodiments, the feedback resistor Rf can have a resistance value ranging from 1 million ohms (MΩ) to 10 MΩ.

[0055] like Figure 1 As shown, the crystal oscillation signal Cr and the output oscillation signal Ou have approximately opposite phases. During the positive half-cycle of the crystal oscillation signal Cr, transistor Tn is turned on and may have a leakage current Ln. Similarly, transistor Tp may have a leakage current Lp during the negative half-cycle of the crystal oscillation signal Cr. The leakage currents Ln and Lp may cause the DC bias voltage at input terminal XI to decrease and increase, respectively, thus deviating from half of the operating voltage VDD. Switching circuit 12 is coupled between input terminal XI and output terminal XO, and is connected in parallel to feedback resistor Rf. Switching circuit 12 can stabilize the DC bias voltage at input terminal XI at half of the operating voltage VDD.

[0056] The voltage of the crystal oscillation signal Cr (e.g.) Figure 1 The sine wave shown (hereinafter referred to as "input voltage Vin") can oscillate based on the DC bias voltage at input terminal XI. The voltage of the output oscillation signal Ou (e.g., Figure 1 The square wave shown (hereinafter referred to as "output voltage Vout") can swing based on the DC bias of the output terminal XO. The switching circuit 12 can detect the voltage difference between the input voltage Vin and the output voltage Vout to turn on in one of the following situations: (1) the input voltage Vin is higher than the output voltage Vout by at least a first threshold Vtha (shown on the diagram). Figure 5(2) The output voltage Vout is higher than the input voltage Vin by at least the second threshold Vthb (plotted on...). Figure 9 In the first case, the switching circuit 12, when turned on, can correct the voltage deviation caused by the leakage current Ln. On the other hand, if the switching circuit 12 is designed to be turned on in the second case, the switching circuit 12 can correct the voltage deviation caused by the leakage current Lp.

[0057] Specifically, when the switching circuit 12 is turned on, the turned-on switching circuit 12 operates as an equivalent resistance connected in parallel to the feedback resistor Rf. The on-state resistance of the switching circuit 12 is less than the resistance of the feedback resistor Rf, thereby reducing the total resistance Rt between the input terminal XI and the output terminal XO (as shown in the figure). Figure 5 and Figure 9 Therefore, the DC bias voltage deviated from the input terminal XI will be stabilized by the DC bias voltage of the output terminal XO, and the DC bias voltage of the output terminal XO will be substantially maintained at half of the operating voltage VDD, thereby achieving automatic voltage correction. In some embodiments, the resistance value of the feedback resistor Rf is 10 to 500 times the on-resistance value of the switching circuit 12.

[0058] Please refer to Figures 2-4 The following paragraphs will first introduce several embodiments of the switching circuit 12 being turned on in the first case, where the input voltage Vin is higher than the output voltage Vout.

[0059] Figures 2-4 This is a schematic diagram of a switching circuit 12 according to some embodiments of the present invention. Please refer to [the diagram first]. Figure 2 In this embodiment, the switching circuit 12 includes a transistor 222, which includes a first terminal, a second terminal, and a control terminal. In some embodiments, the transistor 222 may be an N-type transistor. The first terminal and the control terminal of the transistor 222 are both coupled to the input terminal X1, while the second terminal of the transistor 222 is coupled to the output terminal X0. The transistor 222 forms a diode connection, thereby causing the switching circuit 12 of this embodiment to conduct during the positive half-cycle of the crystal oscillation signal Cr. More specifically, the switching circuit 12 of this embodiment conducts when the input voltage Vin is higher than the output voltage Vout by at least the threshold voltage of the transistor 222. Therefore, the first threshold Vtha in the aforementioned first case may be the threshold voltage of the transistor 222. In addition, the on-resistance value of the switching circuit 12 of this embodiment may be the on-resistance value of the transistor 222. The on-resistance value of the transistor 222 is the source-drain resistance value when the transistor 222 is turned on.

[0060] Next, please refer to Figure 3In this embodiment, the switching circuit 12 includes a transistor 322 and a compensation resistor 324, which are connected in series between the input terminal XI and the output terminal XO. The transistor 322 includes a first terminal, a second terminal, and a control terminal. In some embodiments, the transistor 322 may be an N-type transistor. The compensation resistor 324 is coupled between the input terminal XI and the transistor 322. The first terminal, the second terminal, and the control terminal of the transistor 322 are respectively coupled to the compensation resistor 324, the output terminal XO, and the input terminal XI. In some embodiments, the positions of the transistor 322 and the compensation resistor 324 can be interchanged. (This is in conjunction with the aforementioned cooperation.) Figure 2 Similar to the description, the switching circuit 12 in this embodiment will turn on when the input voltage Vin is higher than the output voltage Vout by at least the threshold voltage of transistor 322. Therefore, the first threshold Vtha in the first case described above can be the threshold voltage of transistor 322. The on-resistance value of the switching circuit 12 in this embodiment can be the sum of the on-resistance value of transistor 322 and the resistance value of compensation resistor 324.

[0061] Please refer to Figure 4 In this embodiment, the switching circuit 12 includes transistor 422, transistor 424, and compensation resistor 426. Each of transistors 422 and 424 includes a first terminal, a second terminal, and a control terminal. In some embodiments, transistor 422 may be an N-type transistor, and transistor 424 may be a P-type transistor. Compensation resistor 426 is coupled between transistors 422 and 424. The first terminal, second terminal, and control terminal of transistor 422 are respectively coupled to compensation resistor 426, output terminal XO, and input terminal XI. The first terminal, second terminal, and control terminal of transistor 424 are respectively coupled to input terminal XI, compensation resistor 426, and output terminal XO. The switching circuit 12 of this embodiment will turn on when the input voltage Vin is higher than the output voltage Vout by at least the absolute value of the threshold voltage of transistor 422 or at least the threshold voltage of transistor 424. That is, the first threshold Vtha in the aforementioned first case may be the absolute value of the threshold voltage of transistor 422 or the threshold voltage of transistor 424. The on-resistance value of the switching circuit 12 in this embodiment can be the sum of the on-resistance value of transistor 422, the on-resistance value of transistor 424, and the resistance value of compensation resistor 426.

[0062] In some embodiments, Figure 4 The compensation resistor 426 can be omitted. The first terminal of transistor 422 can be directly coupled to the second terminal of transistor 424.

[0063] Figure 5 This is a schematic diagram illustrating the total resistance value Rt according to an embodiment of the present invention. The total resistance value Rt is provided between the input terminal X1 and the output terminal XO by the switching circuit 12 and the feedback resistor Rf. In this embodiment, the switching circuit 12 can be provided by... Figures 2-4 This can be implemented using any of the embodiments discussed. The voltage difference obtained by subtracting the output voltage Vout from the input voltage Vin is represented by curve S1. Curve S2 represents the total resistance value Rt when the switching circuit 12 is turned on. Line segment S3 represents the total resistance value Rt when the switching circuit 12 is turned off.

[0064] like Figure 5 As shown, when the input voltage Vin is not higher than the first threshold Vtha by the output voltage Vout, the switching circuit 12 is turned off, so the total resistance value Rt is the resistance value of the feedback resistor Rf (segment S3).

[0065] On the other hand, when the input voltage Vin is higher than the output voltage Vout by at least the first threshold Vtha, the switching circuit 12 is turned on. Therefore, the total resistance value Rt is composed of the on-resistance value of the switching circuit 12 and the resistance value of the feedback resistor Rf (curve S2). In this case, the total resistance value Rt can be expressed by the following formula:

[0066]

[0067] In Formula 1, the symbol "Rost" represents the on-resistance value of switch circuit 12.

[0068] Furthermore, since the on-resistance of a transistor can vary with the source-drain voltage, when the input voltage Vin is higher than the output voltage Vout, the switching circuit 12 (when...) Figures 2-4 In the embodiments discussed, the on-resistance value is negatively correlated with the input voltage Vin. For example, for... Figure 4 The switching circuit 12 of the embodiment, when Figure 4 When the switching circuit 12 is turned on, the total resistance value Rt can be expressed by the following formula:

[0069]

[0070] The symbols "Rc", "Ron", and "Rop" represent the resistance values ​​of compensation resistor 426, the on-resistance values ​​of transistor 422 and transistor 424, respectively. The on-resistance values ​​of transistor 422 and transistor 424 decrease as the input voltage Vin increases, resulting in... Figure 4 The on-resistance of the switching circuit 12 is negatively correlated with the input voltage Vin. Therefore, the total resistance Rt between the input terminal XI and the output terminal XO decreases as the input voltage Vin increases. Reducing the total resistance Rt makes it easier for the DC bias voltage of the input terminal XI to be stabilized by the DC bias voltage of the output terminal XO, thus helping to mitigate the effect of the large leakage current Ln caused by the high input voltage Vin.

[0071] Please refer to Figures 6-8In the following embodiments, the switching circuit 12 will be turned on in the second case described above to mitigate the effect of leakage current Lp.

[0072] Figures 6-8 This is a schematic diagram of a switching circuit 12 according to some embodiments of the present invention. Please refer to... Figure 6 In this embodiment, the switching circuit 12 includes a transistor 622, which includes a first terminal, a second terminal, and a control terminal. In some embodiments, the transistor 622 may be an N-type transistor. The first terminal of the transistor 622 is coupled to the input terminal X1, and the second terminal of the transistor 622 is coupled to the control terminal and connected to the output terminal X0. The transistor 622 forms a diode connection, such that the switching circuit 12 of this embodiment will conduct during the negative half-cycle of the crystal oscillation signal Cr. That is, the switching circuit 12 of this embodiment will conduct when the output voltage Vout is higher than the input voltage Vin by at least the threshold voltage of the transistor 622. Therefore, the second threshold Vthb in the aforementioned second case may be the threshold voltage of the transistor 622. In addition, the on-resistance value of the switching circuit 12 of this embodiment may be the on-resistance value of the transistor 622.

[0073] Please refer to Figure 7 In this embodiment, the switching circuit 12 includes a transistor 722 and a compensation resistor 724, which are connected in series between the input terminal XI and the output terminal XO. The transistor 722 includes a first terminal, a second terminal, and a control terminal. In some embodiments, the transistor 722 may be an N-type transistor. The compensation resistor 724 is coupled between the transistor 722 and the output terminal XO. The first terminal, second terminal, and control terminal of the transistor 722 are respectively coupled to the input terminal XI, the compensation resistor 724, and the output terminal XO. In some embodiments, the positions of the transistor 722 and the compensation resistor 724 can be interchanged. Similar to the aforementioned arrangement... Figure 6 As described, the switching circuit 12 of this embodiment will turn on when the output voltage Vout is higher than the input voltage Vin by at least the threshold voltage of transistor 722. Therefore, the second threshold Vthb in the aforementioned second case can be the threshold voltage of transistor 722. In addition, the on-resistance value of the switching circuit 12 in this embodiment can be the sum of the on-resistance value of transistor 722 and the resistance value of compensation resistor 724.

[0074] Please refer to Figure 8In this embodiment, the switching circuit 12 includes transistor 822, transistor 824, and compensation resistor 826. Each of transistors 822 and 824 includes a first terminal, a second terminal, and a control terminal. In some embodiments, transistor 822 may be an N-type transistor, and transistor 824 may be a P-type transistor. The compensation resistor 826 is coupled between transistors 822 and 824. The first terminal, second terminal, and control terminal of transistor 822 are respectively coupled to input terminal X1, compensation resistor 826, and output terminal X0. The first terminal, second terminal, and control terminal of transistor 824 are respectively coupled to compensation resistor 826, output terminal X0, and input terminal X1. The switching circuit 12 of this embodiment will turn on when the output voltage Vout is higher than the input voltage Vin by at least the absolute value of the threshold voltage of transistor 822 or at least the threshold voltage of transistor 824. That is, the second threshold Vthb in the aforementioned second case may be the absolute value of the threshold voltage of transistor 822 or the threshold voltage of transistor 824. The on-resistance value of the switching circuit 12 in this embodiment can be the sum of the on-resistance values ​​of transistor 822, transistor 824, and compensation resistor 826.

[0075] In some embodiments, Figure 8 The compensation resistor 826 can be omitted. The second terminal of transistor 822 can be directly coupled to the first terminal of transistor 824.

[0076] Figure 9 This is a schematic diagram illustrating the total resistance value Rt according to an embodiment of the present invention. The total resistance value Rt is provided between the input terminal X1 and the output terminal XO by the switching circuit 12 and the feedback resistor Rf. The switching circuit 12 can be composed of... Figures 6-8 The implementation is carried out in any of the embodiments discussed. The voltage difference obtained by subtracting the output voltage Vout from the input voltage Vin is represented by curve S4. Curve S5 represents the total resistance value Rt when the switching circuit 12 is turned on. Line segment S6 represents the total resistance value Rt when the switching circuit 12 is turned off.

[0077] like Figure 9 As shown, when the output voltage Vout is not higher than the second threshold Vthb by the input voltage Vin, the switching circuit 12 is turned off, and therefore the total resistance value Rt is the resistance value of the feedback resistor Rf (segment S6).

[0078] On the other hand, when the output voltage Vout is higher than the input voltage Vin by at least the second threshold Vthb, the switching circuit 12 is turned on, and thus the total resistance value Rt is composed of the on-resistance value of the switching circuit 12 and the resistance value of the feedback resistor Rf (curve S5).

[0079] Furthermore, since the on-resistance of a transistor can vary with the source-drain voltage, when the output voltage Vout is higher than the input voltage Vin, the switching circuit 12 (when...) Figures 6-8 In the embodiments discussed, the on-resistance value is positively correlated with the input voltage Vin. Therefore, the total resistance Rt between the input terminal X1 and the output terminal XO decreases as the input voltage Vin decreases. Reducing the total resistance Rt as the input voltage Vin decreases helps to mitigate the effects of the large leakage current Lp caused by the low input voltage Vin.

[0080] In some embodiments, Figures 2-3 In the embodiment, the transistor of the switching circuit 12 can be implemented using a P-type transistor, thereby enabling... Figures 2-3 In the embodiment, the switching circuit 12 can be turned on in the second case to mitigate the effect of leakage current Lp.

[0081] In other embodiments, Figures 6-7 In the embodiment, the transistor of the switching circuit 12 can be implemented using a P-type transistor, thereby enabling... Figures 6-7 In the embodiment, the switching circuit 12 can be turned on in the first case to mitigate the effect of leakage current Ln.

[0082] Figure 10 This is a simplified functional block diagram of an oscillation system 2 according to an embodiment of the present invention. The oscillation system 2 includes an oscillation circuit 100 and includes the aforementioned cooperation. Figure 1 The discussion focuses on the first pin P1, the second pin P2, the quartz crystal Qz, the first capacitor C1, and the second capacitor C2. For simplicity, the remaining components of the oscillation system 2 are not shown. Figure 10 In the middle, the oscillation circuit 100 is used to form a feedback system with the quartz crystal Qz to generate an output oscillation signal Ou based on the crystal oscillation signal Cr received from the quartz crystal Qz. The oscillation circuit 100 includes an amplifier 101, a feedback resistor Rf, a switching circuit 102, and a switching circuit 103. Due to Figure 10 The oscillating circuit 100 is similar to Figure 1 The oscillating circuit 10, for Figure 10 The components in, if their corresponding components have been coordinated as described above Figure 1 As described above, the relevant details will be omitted below.

[0083] Each of switching circuits 102 and 103 is coupled between the input terminal XI and the output terminal XO (i.e., coupled in parallel to the feedback resistor Rf). Switching circuit 102 is turned on when the input voltage Vin is higher than the output voltage Vout by at least a first threshold Vtha (i.e., the first case) to mitigate the effect of leakage current Ln. On the other hand, switching circuit 103 is turned on when the output voltage Vout is higher than the input voltage Vin by at least a second threshold Vthb (i.e., the second case) to mitigate the effect of leakage current Lp. The on-resistance value of each of switching circuits 102 and 103 is less than the resistance value of the feedback resistor Rf.

[0084] In some embodiments, the switching circuit 102 may be composed of Figures 2-4 The switching circuit 12 of any of the embodiments is implemented, or by Figures 6-7 The switching circuit 12 of any of the embodiments is implemented, and its transistor is a P-type transistor. The switching circuit 103 can be implemented by... Figures 6-8 The switching circuit 12 of any of the embodiments is implemented, or by Figures 2-3 The switching circuit 12 of any of the embodiments is implemented, and its transistor is a P-type transistor. The following will be used in conjunction with... Figure 11 Explanation Figure 4 The switching circuit 12 and Figure 8 The switching circuit 12 implements the configuration methods of switching circuits 102 and 103 respectively.

[0085] Figure 11 This is a schematic diagram of a switching circuit 102 and a switching circuit 103 according to an embodiment of the present invention. Switching circuit 102 includes transistor 1122, transistor 1124, and a compensation resistor 1126. Each of transistors 1122 and 1124 includes a first terminal, a second terminal, and a control terminal. In some embodiments, transistor 1122 may be an N-type transistor, and transistor 1124 may be a P-type transistor. The compensation resistor 1126 is coupled between transistors 1122 and 1124. The first terminal, second terminal, and control terminal of transistor 1122 are respectively coupled to the compensation resistor 1126, the output terminal XO, and the input terminal XI. The first terminal, second terminal, and control terminal of transistor 1124 are respectively coupled to the input terminal XI, the compensation resistor 1126, and the output terminal XO.

[0086] The switching circuit 103 includes transistors 1132 and 1134, and a compensation resistor 1136. Each of transistors 1132 and 1134 includes a first terminal, a second terminal, and a control terminal. In some embodiments, transistor 1132 may be an N-type transistor, and transistor 1134 may be a P-type transistor. The compensation resistor 1136 is coupled between transistors 1132 and 1134. The first terminal, second terminal, and control terminal of transistor 1132 are respectively coupled to input terminal X1, compensation resistor 1136, and output terminal X0. The first terminal, second terminal, and control terminal of transistor 1134 are respectively coupled to compensation resistor 1136, output terminal X0, and input terminal X1.

[0087] Switching circuit 102 can provide current from input terminal XI to output terminal XO, while switching circuit 103 can provide another current flowing in the opposite direction. That is, switching circuit 102 and switching circuit 103 are inversely parallel connected to avoid switching circuits 102 and 103 being turned on at the same time.

[0088] In some embodiments, compensation resistors 1126 and / or 1136 may be omitted. The first terminal of transistor 1122 may be directly coupled to the second terminal of transistor 1124, and the second terminal of transistor 1132 may be directly coupled to the first terminal of transistor 1134.

[0089] Figure 12 This is a schematic diagram illustrating the total resistance value Rt according to an embodiment of the present invention. The total resistance value Rt is provided between the input terminal X1 and the output terminal XO by switching circuits 102 and 103 and feedback resistor Rf. The voltage difference obtained by subtracting the output voltage Vout from the input voltage Vin is represented by curve S7. Curve S8 represents the total resistance value Rt when switching circuit 102 is on and switching circuit 103 is off. Curve S9 represents the total resistance value Rt when switching circuit 102 is off and switching circuit 103 is on. Line segment S10 represents the total resistance value Rt when both switching circuits 102 and 103 are off.

[0090] like Figure 12 As shown, when the input voltage Vin is higher than the output voltage Vout by at least a first threshold Vtha, the switching circuit 102 is turned on and the switching circuit 103 is turned off. The total resistance value Rt (curve S8) is composed of the on-resistance value of the switching circuit 102 and the resistance value of the feedback resistor Rf. Therefore, the total resistance value Rt is negatively correlated with the input voltage Vin.

[0091] On the other hand, when the output voltage Vout is higher than the input voltage Vin by at least the second threshold Vthb, the switching circuit 103 is turned on and the switching circuit 102 is turned off. The total resistance value Rt (curve S9) is composed of the on-resistance value of the switching circuit 103 and the resistance value of the feedback resistor Rf. Therefore, the total resistance value Rt is positively correlated with the input voltage Vin.

[0092] Furthermore, when the input voltage Vin is higher than the output voltage Vout but the difference between them is less than the first threshold Vtha, or when the output voltage Vout is higher than the input voltage Vin but the difference between them is less than the second threshold Vthb, both switching circuits 102 and 103 will be turned off. Therefore, the total resistance value Rt is the resistance value of the feedback resistor Rf.

[0093] When the input and output voltages of an amplifier have similar voltage levels (i.e., when they intersect), some oscillating circuits may be more susceptible to noise. Figure 5 , 9 As can be seen from 12, the oscillation circuits 10 and 100 in the above embodiments can not only automatically correct the DC bias voltage of the input terminal XI, but also prevent the introduction of additional noise by disabling the correction operation (i.e., turning off all switching circuits) when the crystal oscillation signal Cr and the output oscillation signal Ou have similar voltage levels.

[0094] Figure 13 This is a flowchart of a method 130 for automatically correcting work cycles according to an embodiment of the present invention. Any combination of features of method 130 or other methods described herein may be implemented by a plurality of instructions stored in a non-transitory computer-readable medium. When these instructions are executed by one or more processors, they cause some or all of the aforementioned plurality of methods to be executed. It should be understood that any method described herein may contain more or fewer processes than shown in the flowchart, and the processes in the method may be executed in any suitable order. For ease of explanation, the following will be used in conjunction with... Figure 10 The method 130 is described with respect to the oscillation circuit 100, but the invention is not limited thereto. Method 130 is applicable to any of the various oscillation circuits described in the above embodiments.

[0095] In process S132, amplifier 101 receives crystal oscillation signal Cr from quartz crystal Qz through its input terminal XI.

[0096] In process S134, amplifier 101 provides an output oscillation signal Ou at its output terminal XO through the inverting crystal oscillation signal Cr.

[0097] In process S136, the switching circuit 102 is turned on based on the voltage difference between the input voltage Vin and the output voltage Vout. Specifically, the switching circuit 102 is turned on in one of the following situations: (1) when the input voltage Vin is higher than the output voltage Vout by at least a first threshold Vtha; and (2) when the output voltage Vout is higher than the input voltage Vin by at least a second threshold Vthb. For example, the switching circuit 102 will turn on when the input voltage Vin is higher than the output voltage Vout by at least the first threshold Vtha.

[0098] In process S138, the switching circuit 103 is turned on based on the voltage difference between the input voltage Vin and the output voltage Vout. The switching circuit 103 is used to turn on in another of the above-mentioned multiple cases. For example, the switching circuit 103 will turn on when the output voltage Vout is higher than the input voltage Vin by at least a second threshold Vthb.

[0099] Certain terms are used in the specification and claims to refer to specific components. However, those skilled in the art will understand that the same component may be referred to by different names. The specification and claims do not distinguish components by differences in name, but by differences in function. The term "comprising" in the specification and claims is an open-ended term and should therefore be interpreted as "comprising but not limited to". Furthermore, "coupled" here includes any direct and indirect means of connection. Therefore, if the text describes a first component coupled to a second component, it means that the first component can be directly connected to the second component via electrical connection or signal connection such as wireless transmission or optical transmission, or indirectly electrically or signalally connected to the second component via other components or connection means.

[0100] As used herein, the term "and / or" includes any combination of one or more of the listed items. Furthermore, unless otherwise specified in the specification, any singular form of the term also includes the meaning of the plural form.

[0101] Although preferred and feasible embodiments of the present invention have been disclosed above, these embodiments are not intended to limit the present invention. Those skilled in the art can make changes to the technical features of the present invention based on the explicit or implicit content of the present invention. All such changes fall within the scope of patent protection sought by the present invention. In other words, the scope of patent protection of the present invention shall be determined by the scope defined in the claims of this application.

Claims

1. An oscillation circuit, characterized in that, The oscillation circuit includes: An amplifier, comprising an input and an output, is used to invert and amplify an oscillating signal received from the input to provide an output oscillating signal to the output. A feedback resistor is coupled between the input terminal and the output terminal; as well as A first switching circuit, coupled in parallel to the feedback resistor, is used to connect the input terminal and the output terminal to each other in one of the following situations: (1) The input voltage of the oscillation signal is higher than the output voltage of the output oscillation signal by at least a first threshold; and (2) The output voltage is higher than the input voltage by at least a second threshold. The first switching circuit has a first on-resistance value, which is less than the resistance value of the feedback resistor. The first switching circuit includes: A first transistor includes a first terminal, a second terminal, and a control terminal, wherein the second terminal of the first transistor and the control terminal are respectively coupled to the output terminal and the input terminal; and The second transistor includes a first terminal, a second terminal, and a control terminal, wherein the first terminal and the control terminal of the second transistor are respectively coupled to the input terminal and the output terminal.

2. The oscillation circuit as described in claim 1, characterized in that, The second terminal of the second transistor is coupled to the first terminal of the first transistor.

3. The oscillation circuit as described in claim 1, characterized in that, The first switching circuit further includes: A first compensation resistor is coupled between the first terminal of the first transistor and the second terminal of the second transistor.

4. The oscillation circuit as described in claim 1, characterized in that, The oscillation circuit further includes a second switching circuit, which is connected in parallel to the feedback resistor and is used to connect the input terminal and the output terminal to each other in another of the plurality of cases, wherein the second switching circuit has a second on-resistance value, which is less than the resistance value of the feedback resistor.

5. The oscillation circuit as described in claim 4, characterized in that, The second switching circuit includes a third transistor, which includes a first terminal, a second terminal, and a control terminal, wherein the first terminal of the third transistor is coupled to the input terminal, and the second terminal of the third transistor is coupled to the control terminal and the output terminal.

6. The oscillation circuit as described in claim 4, characterized in that, The second switching circuit includes: A third transistor includes a first terminal, a second terminal, and a control terminal, wherein the first terminal and the control terminal of the third transistor are respectively coupled to the input terminal and the output terminal; and The fourth transistor includes a first terminal, a second terminal, and a control terminal, wherein the first terminal, the second terminal, and the control terminal of the fourth transistor are respectively coupled to the second terminal, the output terminal, and the input terminal of the third transistor.

7. The oscillation circuit as described in claim 4, characterized in that, The second switching circuit includes: The third transistor includes a first terminal, a second terminal, and a control terminal, wherein the first terminal and the control terminal of the third transistor are respectively coupled to the input terminal and the output terminal; The fourth transistor includes a first terminal, a second terminal, and a control terminal, wherein the second terminal of the fourth transistor and the control terminal are respectively coupled to the output terminal and the input terminal; as well as The second compensation resistor is coupled between the second terminal of the third transistor and the first terminal of the fourth transistor.

8. The oscillation circuit as described in claim 1, characterized in that, The resistance value of the feedback resistor is 10 to 500 times the first on-resistance value of the first switching circuit.

9. A method for automatically correcting work cycles, characterized in that, The method includes: The oscillation signal is received through the input of the amplifier; The oscillation signal is inverted and amplified by the amplifier to provide an output oscillation signal at the output of the amplifier; The first switching circuit coupled between the input and the output is turned on in one of the following situations: (1) An input voltage of the oscillation signal is at least a first threshold higher than the output voltage of the output oscillation signal; as well as (2) The output voltage is higher than the input voltage by at least a second threshold. The feedback resistor is coupled between the input terminal and the output terminal, and the first switching circuit has a first on-resistance value, which is less than the resistance value of the feedback resistor. The first switching circuit includes: A first transistor includes a first terminal, a second terminal, and a control terminal, wherein the second terminal of the first transistor and the control terminal are respectively coupled to the output terminal and the input terminal; and The second transistor includes a first terminal, a second terminal, and a control terminal, wherein the first terminal and the control terminal of the second transistor are respectively coupled to the input terminal and the output terminal.

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