US-12627260-B2 - Oscillating circuit and electronic device

Abstract

An oscillation circuit which includes a Pierce circuit and a Colpitts circuit that share an oscillator and an input node to respective amplifiers and switches connected to output nodes of the respective amplifiers of the Pierce circuit and the Colpitts circuit. The switches are controlled to cause the oscillation circuit output oscillation signals of the Pierce circuit at the time of oscillation start-up and output oscillation signals of the Colpitts circuit at the time of steady-state oscillation.

Inventors

• Masaya Nohara
• Takehito Ishii
• Noritoshi Kimura

Assignees

• INTER-UNIVERSITY RESEARCH INSTITUTE CORPORATION HIGH ENERGY ACCELERATOR RESEARCH ORGANIZATION
• PIEZO STUDIO INC.

Dates

Publication Date

20260512

Application Date

20220623

Claims (11)

1. 1 . An oscillation circuit including an oscillator, the oscillation circuit comprising: a Pierce circuit and a Colpitts circuit that include a first amplifier and a second amplifier, respectively, and share the oscillator and an input node the first amplifier and the second amplifier; a first switch connected to an output node of the first amplifier, and a second switch connected to an output node of the second amplifier, wherein the first switch and the second switch are controlled to cause the oscillation circuit output oscillation signals of the Pierce circuit at the time of oscillation start-up and output oscillation signals of the Colpitts circuit at the time of steady-state oscillation.
2. 2 . An oscillation circuit comprising a Pierce circuit including include a first amplifier (A 1 ) and a first oscillation capacitance (C 1 ), a Colpitts circuit including a second amplifier (A 2 ) and a second oscillation capacitance (C 2 ), a first switch (SW 1 ) connected in parallel to the first oscillation capacitance (C 1 ) between an output of the first amplifier (A 1 ) and the ground, a second switch (SW 2 ) connected in parallel to the second oscillation capacitance (C 2 ) between an output of the second amplifier (A 2 ) and the ground, an oscillator (X 1 ) between an input and an output of the first amplifier (A 1 ), and a third oscillation capacitance (C 3 ) between an input and an output of the second amplifier (A 2 ), wherein he Pierce circuit and the Colpitts circuit share an input node to the first amplifier and the second amplifier, the first switch (SW 1 ) is open and the second switch (SW 2 ) is closed in a first mode at the time of oscillation start-up, and the first switch (SW 1 ) is closed and the second switch (SW 2 ) is open in a second mode at the time of steady-state oscillation.
3. 3 . The oscillation circuit according to claim 2 , wherein the oscillator is an oscillator using a Langasite type piezoelectric single crystal.
4. 4 . The oscillation circuit according to claim 2 , wherein switching from the first mode to the second mode is carried out when the oscillation amplitude of the Pierce circuit at oscillation start-up reaches 70-95% of the final convergence amplitude.
5. 5 . The oscillation circuit according to claim 4 , wherein the switching from the first mode to the second mode is carried out on the basis of a control signal from an oscillation detection circuit which compares the oscillation amplitude of the Pierce circuit with a predetermined reference value.
6. 6 . The oscillation circuit according to claim 2 , wherein the first amplifier includes a configuration in which a plurality of amplifier circuits are connected in series, a first stage amplifier circuit of the plurality of amplifier circuits includes a capacitive feedforward path, and the second amplifier is a source follower in which an NMOS transistor and a PMOS transistor are cascaded.
7. 7 . An electronic device including the oscillation circuit according to claim 1 .
8. 8 . The oscillation circuit according to claim 2 , further comprising an oscillation detection circuit configured to output a control signal according to the oscillation amplitude of the Pierce circuit to control the first switch (SW 1 ) and the second switch (SW 2 ).
9. 9 . The oscillation circuit according to claim 3 , wherein the first amplifier includes a configuration in which a plurality of amplifier circuits are connected in series, a first stage amplifier circuit of the plurality of amplifier circuits includes a capacitive feedforward path, and the second amplifier is a source follower in which an NMOS transistor and a PMOS transistor are cascaded.
10. 10 . The oscillation circuit according to claim 4 , wherein the first amplifier includes a configuration in which a plurality of amplifier circuits are connected in series, a first stage amplifier circuit of the plurality of amplifier circuits includes a capacitive feedforward path, and the second amplifier is a source follower in which an NMOS transistor and a PMOS transistor are cascaded.
11. 11 . The oscillation circuit according to claim 5 , wherein the first amplifier includes a configuration in which a plurality of amplifier circuits are connected in series, a first stage amplifier circuit of the plurality of amplifier circuits includes a capacitive feedforward path, and the second amplifier is a source follower in which an NMOS transistor and a PMOS transistor are cascaded.

Description

TECHNICAL FIELD The present invention relates to an oscillation circuit using an oscillator. BACKGROUND ART In recent years, among mobile phones and Internet-of-things (IoT) devices that connect all kinds of things to the Internet, small cordless electronic devices with wireless circuits have been required to extend the battery life. Therefore, reducing the power consumption of the electronic circuits and electronic components used in those devices has become an important technical objective. Inverter-based Pierce circuits using quartz oscillators as shown in FIG. 10A have been widely used for oscillation circuits used in small IoT communication devices, and have been used for decades due to their simple circuit configurations. However, slow oscillation start-up due to the voltage component for the oscillation being not large enough and large power consumption for steady-state current flow have been technical issues. CITATION LIST Document 1: Masaya Miyahara, Yukiya Endo, Kenichi Okada, and Akira Matsuzawa, “A 64 μs Start-Up 26/40 MHz Crystal Oscillator with Negative Resistance Boosting Technique Using Reconfigurable Multi-Stage Amplifier”, Proc. IEEE Symp. VLSI Circuits, 2018Document 2: Zule Xu, Noritoshi Kimura, Kenichi Okada, and Masaya Miyahara, “Ultralow-Power Class-C Complementary Colpitts Crystal Oscillator”, IEEE Journal of Solid-State Circuits, Letters, VOL. 3, 2020 SUMMARY OF THE INVENTION Document 1 proposes a circuit, which is shown in FIG. 10B, in which a boost circuit is added for speeding up the oscillation start-up, in order to overcome the problem of slow oscillation start-up in Pierce circuits. Meanwhile, Document 2 proposes a circuit, shown in FIG. 11B, which can reduce steady-state current at the time of oscillation. This circuit is different from a Pearce circuit and is based on a source follower-based Colpitts circuit shown in FIG. 11A. If it is possible to achieve both advantages of the above two circuits, i.e., the fast oscillation start-up in the circuit shown in FIG. 10B and the reduction of the steady-state current during oscillation in the circuit shown in FIG. 11B, the power consumption can be reduced furthermore as compared to the Pierce circuit. However, there is a problem that it is difficult to incorporate one of the circuits into the other circuit because the base circuit type is different. The present invention has been achieved to solve the above problems, and an object of the present invention is to provide an oscillation circuit that achieves both fast start-up and low current consumption. An oscillation circuit according to an aspect of the present invention comprises: a Pierce circuit and a Colpitts circuit that share an oscillator and a node which serves as inputs to respective amplifiers; andswitches connected to output nodes of the respective amplifiers of the Pierce circuit and the Colpitts circuit, whereinthe switches are controlled to cause the oscillation circuit output oscillation signals of the Pierce circuit at the time of oscillation start-up and output oscillation signals of the Colpitts circuit at the time of steady-state oscillation. An oscillation circuit according to an aspect of the present invention includes a Pierce circuit and a Colpitts circuit, wherein a first amplifier (A1) in the Pierce circuit and a second amplifier (A2) in the Colpitts circuit share a node which serves as inputs to the respective amplifiers,the oscillation circuit includes a first oscillation capacitance (C1) and a first switch (SW1) connected in parallel to the first oscillation capacitance (C1) between an output of the first amplifier (A1) and the ground,the oscillation circuit includes a second oscillation capacitance (C2) and a second switch (SW2) connected in parallel to the second oscillation capacitance (C2) between an output of the second amplifier (A2) and the ground,the oscillation circuit includes an oscillator (X1) between said input and said output of the first amplifier (A1),the oscillation circuit includes a third oscillation capacitance (C3) between said input and said output of the second amplifier (A2), andthe oscillation circuit is configured to oscillate in a first mode at the time of oscillation start-up in which the first switch (SW1) and the second switch (SW2) are open and closed, respectively, and in a second mode at the time of steady-state oscillation in which the first switch (SW1) and the second switch (SW2) are closed and open, respectively. In accordance with the present invention, it is possible to provide an oscillation circuit that achieves both fast start-up and low current consumption. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a configuration example of an oscillation circuit according to an embodiment of the present invention. FIG. 2A is for explaining the states of switches in the oscillation circuit according to the embodiment of the present invention at the time of oscillation start-up. FIG. 2B is for explaining the states of the s