Pre-charging circuit applied to voltage-controlled oscillator, voltage-controlled oscillator and digital isolator

Abstract

The utility model provides a pre-charging circuit applied to a voltage-controlled oscillator, the voltage-controlled oscillator and a digital isolator. The pre-charging circuit comprises a switching tube MS5, a current mirror module and a PCC module. The current mirror image module comprises a first mirror image branch with a switch tube MS1 and a second mirror image branch with a switch tube MS2; two ends of the switching tube MS5 are respectively connected with a VOP output node and a VON output node of the voltage-controlled oscillator; the VOP output node is also connected with the grounding end through a first mirror image branch; the VON output node is also connected with the grounding end through a second mirror image branch; and when the voltage-controlled oscillator receives a high-level input signal, a switching tube MS5 of the pre-charging circuit is controlled to be switched off, and a switching tube MS1 and a switching tube MS2 are switched on for a preset time length, so that the oscillation starting effect of the VCO circuit is accelerated, the signal quality is improved, and the transmission rate of the digital isolator is improved to a certain extent.

Description

Technical Field

[0001] The utility model relates to the technical field of oscillators, in particular to a pre-charging circuit, a voltage-controlled oscillator and a digital isolator applied to a voltage-controlled oscillator. Background Art

[0002] Digital isolators are devices that transmit digital signals in an electrically isolated state and are widely used in industrial network environments, especially in harsh environments. Using isolators in the system can eliminate noise caused by ground return on the one hand; on the other hand, it can isolate the manually operated control port from the system execution end where there may be a high-voltage dangerous environment, thereby protecting the devices (people) on the low-voltage side from high-voltage hazards.

[0003] The existing technology adopts antenna coupling and OOK modulation mode to design an isolator, and its structure is as follows: Figure 1 As shown. At the transmitting end, the signal is coupled with the carrier at the voltage-controlled oscillator VCO to form a mixed wave, which is sent to the receiving end on the other side of the isolation through the antenna; after the receiving antenna receives the mixed wave, it amplifies the received signal through the low-noise amplifier LNA, and the demodulator module Demodulator restores the mixed wave to the transmitted signal, which can easily achieve a transmission rate of hundreds of Mbps. Compared with the traditional optocoupler mode, Figure 1 The isolator with the structure shown has a faster transmission speed; compared with the traditional capacitive isolator, Figure 1 The thickness of the isolator in the structure shown can even be as thick as 1 to 2 cm. At this isolation distance, the parasitic capacitance between the two sides of the isolator can be basically ignored, so it can be considered that it will hardly be affected by common-mode transient interference; compared with the on-chip micro-transformer of the magnetic coupling, Figure 1 The structure shown has better isolation and almost no common-mode transient interference.

[0004] However, Figure 1 In the digital isolator structure, every time the system transmits a logic "0", the voltage-controlled oscillator VCO needs to be restarted. If the restart time is too long, the transmission rate will be seriously restricted. Utility Model Content

[0005] The technical problem to be solved by the utility model is to provide a pre-charging circuit, a voltage-controlled oscillator and a digital isolator applied to a voltage-controlled oscillator, which can accelerate the oscillation start-up of the voltage-controlled oscillator and improve the transmission rate to a certain extent.

[0006] In order to solve the above technical problems, the first technical solution adopted by the utility model is:

[0007] A pre-charging circuit applied to a voltage-controlled oscillator comprises a switch tube MS5, a current mirror module and a PCC module; the current mirror module comprises a first mirror branch with a switch tube MS1 and a second mirror branch with a switch tube MS2;

[0008] The two ends of the switch tube MS5 are respectively connected to the VOP output node and the VON output node of the voltage-controlled oscillator; the VOP output node is also connected to the ground terminal via the first mirror branch; the VON output node is also connected to the ground terminal via the second mirror branch; the PCC module is respectively connected to the switch tube MS5, the switch tube MS1 and the switch tube MS2, so that when the voltage-controlled oscillator receives a high-level input signal, the switch tube MS5 is controlled to be turned off, and the switch tubes MS1 and MS2 are turned on for a preset period of time.

[0009] Optionally, the switch tube MS5, the switch tube MS1 and the switch tube MS2 are all N-channel MOS tubes.

[0010] Optionally, the first mirror branch and the second mirror branch are mirror images of each other; the first mirror branch includes a switch tube MS1, a mirror tube MC1 and a mirror tube MC2; the drain of the switch tube MS1 is connected to the VOP output node, the gate is connected to the PCC module, and the source is connected to the drain of the mirror tube MC2; the source of the mirror tube MC2 is connected to the ground terminal, and the gate is respectively connected to the drain and gate of the mirror tube MC1; the source of the mirror tube MC1 is connected to the ground terminal, and the drain is connected to the power supply.

[0011] Optionally, the first mirror branch also includes a switch tube MS3; the drain of the switch tube MS1 is also connected to the power supply via the switch tube MS3; the PCC module is connected to the switch tube MS3 to synchronously output a PREB signal that is inverted from the PRE signal to the switch tube MS3 when outputting the PRE signal to the switch tube MS1, so as to control the switch tube MS3 to be turned on synchronously when the switch tube MS1 is turned on.

[0012] Optionally, the second mirror branch includes a switch tube MS2, a mirror tube MC3 and a mirror tube MC4; the drain of the switch tube MS2 is connected to the VON output node, the gate is connected to the PCC module, and the source is connected to the drain of the mirror tube MC3; the source of the mirror tube MC3 is connected to the ground end, and the gate is respectively connected to the drain and gate of the mirror tube MC4; the source of the mirror tube MC4 is connected to the ground end, and the drain is connected to the power supply.

[0013] Optionally, the second mirror branch also includes a switch tube MS4; the drain of the switch tube MS2 is also connected to the power supply via the switch tube MS4; the PCC module is connected to the switch tube MS4 to synchronously output a PREB signal that is inverted from the PRE signal to the switch tube MS4 when outputting the PRE signal to the switch tube MS2, so as to control the switch tube MS4 to be turned on synchronously when the switch tube MS2 is turned on.

[0014] Optionally, the first mirror branch includes a switch tube MS1, a dummy tube MD2, a mirror tube MC1 and a mirror tube MC2; the second mirror branch includes a switch tube MS2 and a dummy tube MD1; the dummy tube MD2 and the switch tube MS2 are N-channel MOS tubes;

[0015] The drain of the switch tube MS1 is divided into two paths, one of which is connected to the power supply via the Dummy tube MD2, and the other is connected to the VOP output node; the gate of the Dummy tube MD2 is connected to the power supply; the source of the switch tube MS1 is connected to the drain of the mirror tube MC2; the source of the mirror tube MC2 is connected to the ground terminal, and the gate is respectively connected to the drain and gate of the mirror tube MC1; the source of the mirror tube MC1 is connected to the ground terminal, and the drain is connected to the power supply;

[0016] The source and gate of the Dummy tube MD1 are both connected to the ground terminal, and the drain is divided into two paths, one is connected to the power supply via the switch tube MS2, and the other is connected to the VON output node;

[0017] The PCC module is connected to the gate of the switch tube MS1 and the gate of the switch tube MS2 respectively, so as to output a PRE signal to the switch tube MS1 and synchronously output a PREB signal which is inverted from the PRE signal to the switch tube MS2, so that the switch tube MS1 and the switch tube MS2 are synchronously turned on.

[0018] The second technical solution adopted by the utility model is:

[0019] A voltage-controlled oscillator comprises the above-mentioned pre-charging circuit.

[0020] Optionally, a VOC circuit is further included; the VOC circuit includes a MOS tube M1, a MOS tube M2, a capacitor C1, a capacitor C2, a capacitor C3, an inductor L1, an inductor L2 and an inductor L3;

[0021] The source of the MOS tube M1 and the source of the MOS tube M2 are connected to the ground terminal; the gate of the MOS tube M1 and the gate of the MOS tube M2 are connected; the drain of the MOS tube M1 is respectively connected to one end of the capacitor C3 and one end of the inductor L1; the drain of the MOS tube M2 is respectively connected to the other end of the capacitor C3 and the other end of the inductor L1; one end of the capacitor C1 is connected to the drain of the MOS tube M1, and the other end is connected to the gate of the MOS tube M2; one end of the capacitor C2 is connected to the drain of the MOS tube M2, and the other end is connected to the gate of the MOS tube M1; one end of the capacitor C3 is used as a VOP output node, and the other end is used as a VON output node;

[0022] The inductor L1 is also connected to a power supply; the inductor L2 is connected in parallel to the capacitor C3; the inductor L3 is coupled to the inductor L2, one end of the inductor L3 is connected to the ground, and the other end is connected to the transmitting antenna.

[0023] Optionally, the VOC circuit includes a MOS tube M1, a MOS tube M2, a capacitor C1, a capacitor C2, a capacitor C3, an inductor L1 and an inductor L2;

[0024] The source of the MOS tube M1 and the source of the MOS tube M2 are grounded; the gate of the MOS tube M1 and the gate of the MOS tube M2 are connected; the drain of the MOS tube M1 is respectively connected to one end of the capacitor C3 and one end of the inductor L1; the drain of the MOS tube M2 is respectively connected to the other end of the capacitor C3 and the other end of the inductor L1; one end of the capacitor C1 is connected to the drain of the MOS tube M1, and the other end is connected to the gate of the MOS tube M2; one end of the capacitor C2 is connected to the drain of the MOS tube M2, and the other end is connected to the gate of the MOS tube M1; one end of the capacitor C3 is used as a VOP output node, and the other end is used as a VON output node;

[0025] The inductor L1 is also connected to a power source; the inductor L2 is coupled to the inductor L1; one end of the inductor L2 is connected to a ground terminal, and the other end is connected to a transmitting antenna.

[0026] Optionally, the VOC circuit also includes a resistor R1 and a resistor R2; the gate of the MOS tube M1 is connected to the gate of the MOS tube M2 via the resistor R1 and the capacitor R2 connected in series; the resistor R1 and the capacitor R2 are also connected to the PCC module to output a VBN signal corresponding to the signal to be transmitted after the pre-charging circuit completes pre-charging.

[0027] The third technical solution adopted by the utility model is:

[0028] A digital isolator comprises the above-mentioned voltage-controlled oscillator and a millimeter-wave transmitting antenna connected to the voltage-controlled oscillator.

[0029] The beneficial effect of the utility model is that by adding a pre-charge circuit in the voltage-controlled oscillator, when the voltage-controlled oscillator needs to start, the pre-charge circuit can be started, the two output nodes of the VCO circuit are isolated, and the capacitors at the two output nodes are charged by its current mirror module, so that the voltage-controlled oscillator can quickly enter the normal operating state, thereby achieving the effect of accelerating the start-up of the VCO circuit, thereby improving the signal quality and, to a certain extent, increasing the transmission rate of the digital isolator. According to simulation data verification, the voltage-controlled oscillator provided by the utility model can not only significantly shorten the start-up time of the voltage-controlled oscillator; at the same time, it can also obtain the expected start-up time by controlling the size of the pre-charge current, and compromise between the start-up time and power consumption to obtain the most suitable solution to ensure the normal operation of the voltage-controlled oscillator. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of an isolator structure designed by using an antenna coupling method and combining an OOK modulation mode in the prior art;

[0031] Figure 2 A schematic diagram of key node signals of a pre-charging circuit structure and a PCC module applied to a voltage-controlled oscillator provided in an embodiment of the utility model;

[0032] Figure 3 A schematic diagram of key node signals of a pre-charging circuit structure and a PCC module provided in a specific embodiment of the utility model;

[0033] Figure 4 A schematic diagram of key node signals of a pre-charging circuit structure and a PCC module provided in another specific embodiment of the utility model;

[0034] Figure 5 A schematic diagram of key node signals of a pre-charging circuit structure and a PCC module provided by another specific embodiment of the utility model;

[0035] Figure 6 A schematic diagram of the structure of a VCO circuit in a voltage-controlled oscillator provided in an embodiment of the utility model;

[0036] Figure 7 A schematic diagram of the structure of a VCO circuit in a voltage-controlled oscillator provided in another embodiment of the utility model. DETAILED DESCRIPTION

[0037] In order to explain the technical content, achieved objectives and effects of the present invention in detail, the following is an explanation in conjunction with the implementation modes and the accompanying drawings.

[0038] The key concept of the utility model is that the pre-charging circuit can isolate the two output nodes of the VCO circuit, and the current mirror module thereof charges the capacitors at the two output nodes, so that the voltage-controlled oscillator can quickly enter the normal operation state, thereby achieving the effect of accelerating the oscillation of the VCO circuit.

[0039] In the prior art, since the VCO circuit in the voltage-controlled oscillator needs to restart each time it transmits a logic "1", if the restart time is too long, the transmission efficiency will be seriously restricted. The embodiment of the utility model accelerates the VCO restart by adding a pre-charging circuit, thereby improving the signal quality and increasing the transmission rate of the digital isolator to a certain extent.

[0040] Please refer to Figure 2 , Figure 2 A schematic diagram of key node signals of a pre-charging circuit structure and a PCC module applied to a voltage-controlled oscillator provided in an embodiment of the utility model.

[0041] like Figure 2 As shown, the present embodiment provides a pre-charge circuit for a voltage-controlled oscillator, which includes a switch tube MS5, a current mirror module and a PCC module. The PCC module is a pre-charge circuit control signal modulation module (pre-charge control cell, used to generate a control signal in the pre-charge circuit according to input data; wherein the current mirror module includes a first mirror branch with a switch tube MS1 and a second mirror branch with a switch tube MS2.

[0042] Specifically, the switch tube MS5 is arranged between the VOP output node and the VON output node of the VCO circuit in the voltage-controlled oscillator; the VOP output node is connected to the ground terminal via the first mirror branch of the pre-charging circuit; the VON output node is connected to the ground terminal via the second mirror branch of the pre-charging circuit; the PCC module is respectively connected to the switch tube MS5, the switch tube MS1 and the switch tube MS2, so as to control the switch tube MS5 to be turned off when the VCO circuit needs to start oscillation, and the switch tube MS1 and the switch tube MS2 are turned on for a preset time.

[0043] Figure 2In the key node signal diagram of the PCC module shown, Data is the signal that the voltage-controlled oscillator needs to transmit, that is, the signal to be transmitted; VBP is the signal that controls the on and off of the switch tube MS5, which corresponds to the start of the pre-charge circuit; PRE is the pre-charge switch signal, when the low level turns to the high level, the pre-charge starts, and when it turns from the high level to the low level, the pre-charge is completed; VBN is the Data characterization signal, that is, the Data input to the PCC module is converted into a VBN signal representation and output to the voltage-controlled oscillator, and the VCO circuit is controlled to start oscillation immediately after the pre-charge is completed, so as to achieve the purpose of transmitting the "Data signal"; VOP / N are the two output node signals of the VCO circuit, which are synchronized with the VBN signal.

[0044] The pre-charge working principle of this embodiment is: when the VCO circuit needs to be started to transmit the signal to be transmitted, that is, when the signal to be transmitted Data is at a high level, the pre-charge circuit is turned on. At this time, the VBP control signal generated by the PCC module will be pulled low to control the switch tube MS5 to turn off, so as to isolate the VOP output node and the VON output node; at the same time, the PCC module will control the switch tube MS1 and the switch tube MS2 in the current mirror module to be turned on by pulling up the PRE control signal, so that the current mirror module charges the capacitors at the VOP output node and the VON output node, thereby quickly providing the voltage-controlled oscillator with part of the current Ipre for normal operation. After a short period of pre-charge, the PCC module will control the switch tubes MS1 and MS2 in the current mirror module to turn off by pulling down the PRE control signal, ending the pre-charge. At the same time, the VBN control signal potential will rise to control the VCO circuit to start oscillation. The potential rise of the VBN control signal will turn on the two MOS tubes M1 and M2 of the VCO circuit. At this time, the power supply current directly flows into the MOS tubes M1 and M2 and continues to increase until the VCO circuit of the voltage-controlled oscillator operates normally.

[0045] The time from the VBN control signal potential rising to the oscillation stability at the VOP / VON output node is defined as the VCO start-up time Tstart, and the case without a pre-charge circuit is defined as Ipre is 0. Please refer to the following Table 1 for the simulation results.

[0046] Ipre(mA) Tstart(ns) Improvement(%) 0 2.348 0 2 1.807 23.04 6 1.767 24.74

[0047] Table 1

[0048] It can be seen from Table 1 that when the voltage-controlled oscillator has no pre-charging circuit, the VCO start-up time is 2.348ns, and when there is a pre-charging circuit and the pre-charging current is 2mA and 6mA respectively, the VCO start-up time is 1.807ns and 1.767ns. It can be seen that when the pre-charging circuit provided in this embodiment is applied to the voltage-controlled oscillator, the start-up time of the voltage-controlled oscillator is reduced by 23% and 24.7% respectively compared with the case where the voltage-controlled oscillator has no pre-charging circuit.

[0049] From the above, it can be seen that the pre-charge circuit provided in this embodiment can significantly improve the startup time of the VCO, and the improvement effect is better as the pre-charge current increases. It is also noted that this trend is not linear, but will weaken rapidly, so the circuit structure used in this embodiment should be able to balance the startup time and power consumption at the same time.

[0050] In some specific implementations of this embodiment, based on the low-level VBP control signal generated by the PCC module, the switch tube MS5 needs to be controlled to be turned off, so the switch tube MS5 uses an N-channel MOS tube (high-level conduction). In addition, since the switch tubes MS1 and MS2 are turned on based on the high-level PRE control signal, a high-level conduction N-channel MOS tube can be selected.

[0051] See also Figure 3 , Figure 3 This is a schematic diagram of the key node signals of the pre-charging circuit structure and PCC module provided by a specific embodiment of the utility model. Figure 3 As shown, Figure 2 In a specific implementation of the current mirror module in the embodiment, the first mirror branch and the second mirror branch in the current mirror module are mirror images of each other.

[0052] Specifically, the first mirror branch includes a switch tube MS1, a mirror tube MC1 and a mirror tube MC2; the drain of the switch tube MS1 is respectively connected to the power supply and the VOP output node in the VCO circuit, the gate is connected to the PCC module, and the source is connected to the drain of the mirror tube MC2; the source of the mirror tube MC2 is connected to the ground end, and the gate is respectively connected to the drain and gate of the mirror tube MC1; the source of the mirror tube MC1 is connected to the ground end, and the drain is connected to the current source.

[0053] The second mirror branch, which is a mirror image of the first mirror branch, includes a switch tube MS2, a mirror tube MC3 and a mirror tube MC4; the drain of the switch tube MS2 is connected to the VON output node in the VCO circuit, the gate is connected to the PCC module, and the source is connected to the drain of the mirror tube MC3; the source of the mirror tube MC3 is connected to the ground end, and the gate is respectively connected to the drain and gate of the mirror tube MC4; the source of the mirror tube MC4 is connected to the ground end, and the drain is connected to the current source.

[0054] The switch tube MS1 in the first mirror branch and the switch tube MS2 in the second mirror branch are both connected to the PRE control signal output terminal of the PCC module. After the pre-charging circuit is started, the PRE control signal output by the PCC module will rise in potential within a certain period of time, so that the switch tubes MS1 and MS2 are turned on, and then the first current mirror composed of the mirror tubes MC1 and MC2 of the first mirror branch charges the capacitor (including parasitic capacitance) at the VOP output node; similarly, the second current mirror composed of the mirror tubes MC3 and MC4 of the second mirror branch charges the capacitor (including parasitic capacitance) at the VON output node, so as to quickly provide the VCO circuit with a part of the current Ipre for its normal operation, and after the time is reached, the potential is pulled down, the switch tubes MS1 and MS2 are turned off, and the current mirror stops charging.

[0055] See also Figure 4 , Figure 4 This is a schematic diagram of the key node signals of the pre-charging circuit structure and the PCC module provided by another specific embodiment of the utility model. Figure 4 As shown, Figure 2 Another specific implementation of the current mirror module in the embodiment, this specific implementation is Figure 3 Based on the specific implementation, the first mirror branch further includes a switch tube MS3;

[0056] Specifically, the drain of the switch tube MS1 in the first mirror branch is also connected to the power supply via the switch tube MS3; the PCC module is connected to the switch tube MS3 to synchronously output a PREB signal that is inverted from the PRE signal to the switch tube MS3 when outputting the PRE signal to the switch tube MS1, so as to control the switch tube MS3 to be turned on synchronously when the switch tube MS1 is turned on.

[0057] Optionally, the second mirror branch may also include a switch tube MS4; the drain of the switch tube MS2 is also connected to the power supply via the switch tube MS4; the PCC module is connected to the switch tube MS4 to synchronously output a PREB signal that is inverted from the PRE signal to the switch tube MS4 when outputting the PRE signal to the switch tube MS2, and control the switch tube MS4 to be synchronously turned on when the switch tube MS2 is turned on.

[0058] In this specific embodiment, a switch tube MS3 is newly added in the first mirror branch, and a switch tube MS4 is newly added in the second mirror branch, and both are connected to the PREB control signal output port of the PCC module. Since the control signals output by the PREB control signal output port and the PRE control signal output port are in opposite phases, when the PRE control signal output port outputs a high level, the PREB control signal output port will synchronously output a low level. In other words, when the switch tube MS1 in the first mirror branch is turned on by the high-level PRE control signal, the switch tube MS3 will be synchronously turned on by the low-level PREB control signal; accordingly, when the switch tube MS2 in the second mirror branch is turned on by the high-level PRE control signal, the switch tube MS4 will be synchronously turned on by the low-level PREB control signal. The conduction of the switch tubes MS1 and MS3 in the first mirror branch will enable the current mirror composed of the mirror tubes MC1 and MC2 to charge all the capacitors at the VOP output node; the conduction of the switch tubes MS2 and MS4 in the second mirror branch will enable the current mirror composed of the mirror tubes MC3 and MC4 to charge all the capacitors at the VON output node, which can quickly provide the inductor in the VCO circuit with part of the current Ipre when the VCO circuit is in normal operation, thereby precharging the VCO circuit. In other words, since the switch tubes MS3 and MS4 are newly added in this specific embodiment, the speed of charging the capacitors at the VOP output node and the VON output node can be further accelerated, thereby further accelerating the speed at which the VCO circuit enters a normal operating state.

[0059] In this specific implementation, the switch tube MS3 and the switch tube MS4 are P-channel MOS tubes that are turned on at a low level.

[0060] Optionally, the switch tube MS3 and the switch tube MS4 may also be high-level N-channel MOS tubes, and directly connected to the PRE control signal output terminal of the PCC module, so as to achieve synchronous conduction with the switch tube MS1 and the switch tube MS2.

[0061] See also Figure 5 , Figure 5 This is a schematic diagram of the key node signals of the pre-charge circuit structure and PCC module provided by another specific embodiment of the utility model. Figure 5 As shown, Figure 2 In another specific implementation of the current mirror module in the embodiment, the first mirror branch and the second mirror branch in the current mirror module have different structures.

[0062] Specifically, the first mirror branch includes a switch tube MS1, a dummy tube MD2, a mirror tube MC1 and a mirror tube MC2; the second mirror branch includes a switch tube MS2 and a dummy tube MD1; the dummy tube MD2 and the switch tube MS2 are P-channel MOS tubes;

[0063] The drain of the switch tube MS1 is divided into two paths, one of which is connected to the power supply via the Dummy tube MD2, and the other is connected to the VOP output node of the VCO circuit; the gate of the Dummy tube MD2 is connected to the power supply; the source of the switch tube MS1 is connected to the drain of the mirror tube MC2; the source of the mirror tube MC2 is connected to the ground terminal, and the gate is respectively connected to the drain and gate of the mirror tube MC1; the source of the mirror tube MC1 is connected to the ground terminal, and the drain is connected to the power supply;

[0064] The source and gate of the Dummy tube MD1 are both connected to the ground terminal, and the drain is divided into two paths, one is connected to the power supply via the switch tube MS2, and the other is connected to the VON output node of the VCO circuit;

[0065] The PCC module is connected to the gate of the switch tube MS1 and the gate of the switch tube MS2 respectively, so as to output a PRE signal to the switch tube MS1 and synchronously output a PREB signal which is inverted from the PRE signal to the switch tube MS2, so that the switch tube MS1 and the switch tube MS2 are synchronously turned on.

[0066] In this specific embodiment, combined with the key node signal diagram of the PCC module, it can be seen that when the pre-charging circuit is started and the switch tube MS5 is turned off, the PRE control signal output end of the PCC module will output a high level within a certain period of time, and the PREB control signal output end will output a low level at the same time, so that the switch tube MS1 and the switch tube MS2 are turned on synchronously, and the Dummy tube MD2 in the first mirror branch and the Dummy tube MD1 in the second mirror branch are used to make the parasitic environment at the VOP output node and the VON output node symmetrical, so as to ensure that the normal operation of the VCO circuit will not be affected by the imbalance of artificial design.

[0067] The current mirror module provided in this specific embodiment is Figure 3 or Figure 4 The difference between the current mirror modules provided in the specific implementation is that: considering that the VCO circuit needs a trigger to start oscillating, its essence is to introduce an initial imbalance between the VOP output node and the VON output node of the VCO circuit, and the VCO circuit gradually changes to the oscillating state in this initial imbalance state. Based on this, this specific implementation increases this imbalance artificially at the beginning of the VCO circuit oscillation, as shown in the following example. Figure 5As shown in FIG. 1 , by providing only one-side current mirror to precharge one side of the VCO circuit, the imbalance state of the VCO circuit at the initial oscillation is increased. This will be achieved compared to Figure 3 or Figure 4 For the current mirror module provided in the specific implementation, the time required for the VCO circuit to start oscillation is further shortened. At the same time, since the current mirror circuit structure on one side can be reduced, the component composition of the mirror branch on one side is greatly simplified, so that the overall structure of the pre-charging circuit is also simplified, and the power consumption of the pre-charging circuit part is also reduced. In this way, it is also possible to simultaneously reduce the cost of the pre-charging circuit, reduce the space occupied by the pre-charging circuit in the voltage-controlled oscillator, and facilitate the integration effect, achieving multiple goals at one stroke.

[0068] It can be understood that the positions of the first mirror branch and the second mirror branch described in this specific embodiment can be interchanged, and the working principles of the two are the same. That is, the first mirror branch is arranged on the VON output node side of the VCO circuit; and the second mirror branch is arranged on the VOP output node side of the VCO circuit.

[0069] Based on Figure 2 The same definitions as those in Table 1 are used in the embodiments. The simulation results of the pre-charging circuit formed by the improved current mirror module provided in this specific implementation manner can be found in Table 2 below.

[0070] Ipre(mA) Tstart(ns) Improvement(%) 0 2.348 0 2 0.998 57.5 6 0.818 65.16

[0071] Table 2

[0072] As shown in Table 2, when the pre-charge current is 2mA and 6mA respectively, the start-up time of the VCO circuit is 0.998ns and 0.818ns respectively, which is 57.5% and 65.16% better than that without the pre-charge circuit. Figure 3 or Figure 4 DETAILED DESCRIPTION OF THE EMBODIMENTS A pre-charging circuit is provided.

[0073] The present invention also provides a voltage-controlled oscillator, which includes the pre-charging circuit described in any one of the above embodiments. The specific structure of the pre-charging circuit is not repeated here, and please refer to the description of the above embodiments for details.

[0074] The voltage-controlled oscillator provided in this embodiment, due to the addition of a pre-charge circuit, can start the pre-charge circuit when the voltage-controlled oscillator needs to start oscillation, isolate the two output nodes of the VCO circuit, and use its current mirror module to charge the capacitors at the above two output nodes, quickly provide the voltage-controlled oscillator with normal operating current, thereby achieving the effect of accelerating the start-up of the VCO circuit, thereby improving the signal quality and, to a certain extent, increasing the transmission rate of the digital isolator. According to simulation data verification, the voltage-controlled oscillator provided by the utility model can not only significantly shorten the startup time of the voltage-controlled oscillator; but also achieve a balance between startup time and power consumption by controlling the pre-charge current, and can ensure the normal operation of the voltage-controlled oscillator.

[0075] See also Figure 6 , Figure 6 This is a schematic diagram of the structure of a VCO circuit in a voltage controlled oscillator provided in an embodiment of the utility model. Based on the voltage controlled oscillator provided in the previous embodiment, this embodiment further expands the VCO circuit therein.

[0076] like Figure 6 As shown, the VCO circuit in the voltage-controlled oscillator provided in this embodiment specifically includes a MOS transistor M1, a MOS transistor M2, a capacitor C1, a capacitor C2, a capacitor C3, an inductor L1, an inductor L2 and an inductor L3.

[0077] The source of the MOS tube M1 and the source of the MOS tube M2 are connected to the ground terminal; the gate of the MOS tube M1 and the gate of the MOS tube M2 are connected; the drain of the MOS tube M1 is respectively connected to one end of the capacitor C3 and one end of the inductor L1; the drain of the MOS tube M2 is respectively connected to the other end of the capacitor C3 and the other end of the inductor L1; one end of the capacitor C1 is connected to the drain of the MOS tube M1, and the other end is connected to the gate of the MOS tube M2; one end of the capacitor C2 is connected to the drain of the MOS tube M2, and the other end is connected to the gate of the MOS tube M1; one end of the capacitor C3 is used as a VOP output node, and the other end is used as a VON output node;

[0078] The inductor L1 is also connected to a power supply; the inductor L2 is connected in parallel to the capacitor C3; the inductor L3 is connected to the inductor L2 via electromagnetic induction coupling, one end of the inductor L3 is connected to the ground, and the other end is connected to the transmitting antenna.

[0079] In some specific implementations of this embodiment, a resistor R1 and a resistor R2 are further included; the gate of the MOS tube M1 is connected to the gate of the MOS tube M2 via the resistor R1 and the capacitor R2 connected in series; the resistor R1 and the capacitor R2 are also connected to the PCC module to output a VBN signal corresponding to the signal to be transmitted after the pre-charging circuit completes the pre-charging. Here, the role of the resistor R1 and the resistor R2 is to block the AC signal coupled to the gates of the MOS tubes M1 and M2 through the capacitors C1 and C2 after the VCO starts oscillating, so as to prevent the AC transient signal from causing serious interference to the DC signal at VBN.

[0080] In some specific implementations of this embodiment, the capacitor C3 is a variable capacitor, which can better adjust the LC resonance frequency to make it fall on the expected frequency.

[0081] In this embodiment, the VBN signal provides the MOS transistor M1 and the MOS transistor M2 in the VCO circuit with a DC level required for turning on the VBN signal, which is directly output and controlled by the PCC module.

[0082] The working principle of the VCO circuit described in this embodiment is as follows: after the pre-charging circuit completes the pre-charging, that is, the PCC module controls the switch tube MS1 and the switch tube MS2 in the current mirror module to turn off through the control signal, and after the pre-charging is stopped, the control output is used to represent the VBN signal to be transmitted to the VCO circuit; at this time, the VBN signal potential rises, that is, the VBN signal coupled into the gate of the MOS tube M1 and the MOS tube M2 in the VCO circuit is high level (logic "1"), which provides a DC bias for the gate of the MOS tube M1 and the MOS tube M2, and the MOS tube M1 and the MOS tube M2 are turned on. At this time, the power supply current directly flows into the MOS tube M1 and the MOS tube M2, and continues to increase until the VCO circuit operates normally. After the VCO starts normally, the inverted signals at the VOP output node and the VON output node of the VCO circuit are coupled to the gate of the MOS tube M1 and the MOS tube M2 through the capacitor C1 and the capacitor C2, respectively, so that the MOS tube M1 and the MOS tube M2 are alternately turned on and off, promoting the LC resonance of the inductor L1 and the capacitor C3. At the same time, the signal at the VOP / N output node is coupled to the inductor L3 through the inductor L2, and then sent out through the transmitting antenna, and the receiving end receives the logic "1" signal. When the input VBN signal becomes a low level (logic "0"), the VBN is 0, the MOS tube M1 and the MOS tube M2 are turned off, and the VOP / N output node no longer oscillates. At this time, the transmitting antenna does not transmit a signal, which means that the receiving end receives a logic "0" in the OOK modulation mode.

[0083] See also Figure 7 , Figure 7A schematic diagram of the structure of a VCO circuit in a voltage controlled oscillator provided in another embodiment of the utility model. Figure 6 On the basis of the embodiment, the VCO circuit is further improved by reusing the inductor L1 therein so as to reduce the use of one inductor (L3); thus saving a large chip area and reducing the chip cost.

[0084] like Figure 7 As shown, the VCO circuit in the voltage-controlled oscillator provided in this embodiment specifically includes a MOS transistor M1, a MOS transistor M2, a capacitor C1, a capacitor C2, a capacitor C3, an inductor L1 and an inductor L2.

[0085] The source of the MOS tube M1 and the source of the MOS tube M2 are grounded; the gate of the MOS tube M1 and the gate of the MOS tube M2 are connected; the drain of the MOS tube M1 is respectively connected to one end of the capacitor C3 and one end of the inductor L1; the drain of the MOS tube M2 is respectively connected to the other end of the capacitor C3 and the other end of the inductor L1; one end of the capacitor C1 is connected to the drain of the MOS tube M1, and the other end is connected to the gate of the MOS tube M2; one end of the capacitor C2 is connected to the drain of the MOS tube M2, and the other end is connected to the gate of the MOS tube M1; one end of the capacitor C3 is used as a VOP output node, and the other end is used as a VON output node;

[0086] The inductor L1 is also connected to a power source; the inductor L2 is connected to the inductor L1 through electromagnetic induction coupling; one end of the inductor L2 is connected to a ground terminal, and the other end is connected to a transmitting antenna.

[0087] In some specific implementations of this embodiment, a resistor R1 and a resistor R2 are further included; the gate of the MOS tube M1 is connected to the gate of the MOS tube M2 via the resistor R1 and the capacitor R2 connected in series; the resistor R1 and the capacitor R2 are also connected to the PCC module to output a VBN signal corresponding to the signal to be transmitted after the pre-charging circuit completes the pre-charging. Here, the role of the resistor R1 and the resistor R2 is to block the AC signal coupled to the gates of the MOS tubes M1 and M2 through the capacitors C1 and C2 after the VCO starts oscillating, so as to prevent the AC transient signal from causing serious interference to the DC signal at VBN.

[0088] In some specific implementations of this embodiment, the capacitor C3 is a variable capacitor, which can better adjust the LC resonance frequency to make it fall on the expected frequency.

[0089] In this embodiment, the VBN signal provides the MOS transistor M1 and the MOS transistor M2 in the VCO circuit with a DC level required for turning on the VBN signal, which is directly output and controlled by the PCC module.

[0090] The working principle of the VCO circuit described in this embodiment is as follows: after the pre-charging circuit completes the pre-charging, that is, the PCC module controls the switch tube MS1 and the switch tube MS2 in the current mirror module to turn off through the control signal, and after the pre-charging stops, the control output is used to represent the VBN signal to be transmitted to the VCO circuit; at this time, the VBN signal potential rises, that is, the VBN signal coupled into the gate of the MOS tube M1 and the MOS tube M2 in the VCO circuit is high level (logic "1"), which provides a DC bias for the gate of the MOS tube M1 and the MOS tube M2, and the MOS tube M1 and the MOS tube M2 are turned on. At this time, the power supply current directly flows into the MOS tube M1 and the MOS tube M2, and continues to increase until the VCO circuit operates normally. After the VCO starts oscillating normally, the signals at the VOP output node and the VON output node of the VCO circuit are coupled to the inductor L2 through the inductor L1, and then sent out through the transmitting antenna, and the receiving end receives the logic "1" signal. When the input VBN signal becomes low level (logic "0"), VBN is 0, MOS tube M1 and MOS tube M2 are turned off, and the VOP / N output node no longer oscillates. At this time, the transmitting antenna does not transmit a signal, which means that the receiving end receives logic "0" in the OOK modulation mode.

[0091] It can be seen that the VCO circuit structure of this embodiment is different from that of Figure 6 As for the VCO circuit structure of the embodiment, by reusing the inductor L1, the use of one inductor can be reduced, thereby saving considerable chip area (the on-chip implementation of the inductor requires a relatively large chip area, and reducing one inductor can reduce the area on the chip by about 150um*150um), and at the same time, it can also reduce the chip cost to a certain extent.

[0092] Understandably, whether Figure 6 The VCO circuit described in the embodiment is also Figure 7 The VCO circuits described in the embodiments are both designed by using antenna coupling to transmit signals. Their working principles are that at the transmitting end, the signal to be transmitted is coupled with the carrier at the voltage-controlled oscillator to form a mixed wave, and then sent to the receiving end through the transmitting antenna.

[0093] As a preferred embodiment of the utility model, the voltage-controlled oscillator described in the above embodiment and the transmitting antenna coupled thereto are all millimeter-wave transmitting antennas. That is to say, in this preferred embodiment, the voltage-controlled oscillator is used in the transmitting end that adopts millimeter-wave wireless transmission, and the receiving end also adopts millimeter-wave wireless reception. This design can not only easily achieve a transmission rate of hundreds of Mbps, but also has a faster transmission speed than the traditional optical coupling transmission method; compared with the pure capacitive coupling method, it can eliminate the influence of common-mode transient interference; compared with the magnetic coupling transmission method, it greatly simplifies the process difficulty and cost. Therefore, this preferred embodiment will have a broader and more practical application prospect in the field of wireless transmission.

[0094] The present invention also provides a digital isolator, comprising the voltage-controlled oscillator described in any of the above embodiments and a millimeter wave transmitting antenna connected to the voltage-controlled oscillator. The specific structure of the voltage-controlled oscillator will not be repeated here, please refer to the above embodiments for details.

[0095] The digital isolator provided in this embodiment has all the effects listed in the above preferred embodiments because it adopts millimeter wave wireless transmission technology for isolation transmission; at the same time, the voltage-controlled oscillator in the digital isolator provided in this embodiment has the effect of accelerating the oscillation of the VCO circuit because a pre-charging circuit is added, thereby improving the signal quality and increasing the transmission rate of the digital isolator to a certain extent.

[0096] In some specific implementations of this embodiment, please refer to the specific structure of the digital isolator. Figure 1 In particular, the voltage-controlled oscillator in this embodiment not only includes Figure 1 The VCO circuit shown in FIG. Figures 2 to 7 The pre-charging circuit structure described in any embodiment.

[0097] The above description is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent transformations made using the contents of the specification and drawings of the present invention, or directly or indirectly applied in the relevant technical field, are also included in the patent protection scope of the present invention.

Claims

1. A pre-charging circuit for a voltage-controlled oscillator, characterized in that: It includes a switch tube MS5, a current mirror module and a PCC module; the current mirror module includes a first mirror branch with a switch tube MS1 and a second mirror branch with a switch tube MS2; The two ends of the switch tube MS5 are respectively connected to the VOP output node and the VON output node of the voltage-controlled oscillator; the VOP output node is also connected to the ground terminal via the first mirror branch; the VON output node is also connected to the ground terminal via the second mirror branch; the PCC module is respectively connected to the switch tube MS5, the switch tube MS1 and the switch tube MS2, so that when the voltage-controlled oscillator receives a high-level input signal, the switch tube MS5 is controlled to be turned off, and the switch tubes MS1 and MS2 are turned on for a preset period of time.

2. The precharge circuit for voltage-controlled oscillator as claimed in claim 1, wherein The switch tube MS5, the switch tube MS1 and the switch tube MS2 are all N-channel MOS tubes.

3. The precharge circuit applied to a voltage controlled oscillator as claimed in claim 1, characterized in that, The first mirror branch and the second mirror branch are mirror images of each other; The first mirror branch includes a switch tube MS1, a mirror tube MC1 and a mirror tube MC2; the drain of the switch tube MS1 is connected to the VOP output node, the gate is connected to the PCC module, and the source is connected to the drain of the mirror tube MC2; the source of the mirror tube MC2 is connected to the ground end, and the gate is respectively connected to the drain and gate of the mirror tube MC1; the source of the mirror tube MC1 is connected to the ground end, and the drain is connected to the current source.

4. The precharge circuit applied to a voltage controlled oscillator as claimed in claim 3, characterized in that, The first mirror branch also includes a switch tube MS3; the drain of the switch tube MS1 is also connected to the power supply via the switch tube MS3; the PCC module is connected to the switch tube MS3 to synchronously output a PREB signal that is inverted from the PRE signal to the switch tube MS3 when outputting the PRE signal to the switch tube MS1, so as to control the switch tube MS3 to be synchronously turned on when the switch tube MS1 is turned on.

5. The precharge circuit applied to a voltage controlled oscillator as claimed in claim 3, characterized in that, The second mirror branch includes a switch tube MS2, a mirror tube MC3 and a mirror tube MC4; the drain of the switch tube MS2 is connected to the VON output node, the gate is connected to the PCC module, and the source is connected to the drain of the mirror tube MC3; the source of the mirror tube MC3 is connected to the ground end, and the gate is respectively connected to the drain and gate of the mirror tube MC4; the source of the mirror tube MC4 is connected to the ground end, and the drain is connected to the power supply.

6. The precharge circuit applied to a voltage controlled oscillator as claimed in claim 5, characterized in that, The second mirror branch also includes a switch tube MS4; the drain of the switch tube MS2 is also connected to the power supply via the switch tube MS4; the PCC module is connected to the switch tube MS4 to synchronously output a PREB signal that is inverted from the PRE signal to the switch tube MS4 when outputting the PRE signal to the switch tube MS2, and control the switch tube MS4 to be synchronously turned on when the switch tube MS2 is turned on.

7. The precharge circuit applied to a voltage controlled oscillator as claimed in claim 1, characterized in that, The first mirror branch includes a switch tube MS1, a dummy tube MD2, a mirror tube MC1 and a mirror tube MC2; the second mirror branch includes a switch tube MS2 and a dummy tube MD1; the dummy tube MD2 and the switch tube MS2 are N-channel MOS tubes; The drain of the switch tube MS1 is divided into two paths, one of which is connected to the power supply via the Dummy tube MD2, and the other is connected to the VOP output node; the gate of the Dummy tube MD2 is connected to the power supply; the source of the switch tube MS1 is connected to the drain of the mirror tube MC2; the source of the mirror tube MC2 is connected to the ground terminal, and the gate is respectively connected to the drain and gate of the mirror tube MC1; the source of the mirror tube MC1 is connected to the ground terminal, and the drain is connected to the power supply; The source and gate of the Dummy tube MD1 are both connected to the ground terminal, and the drain is divided into two paths, one is connected to the power supply via the switch tube MS2, and the other is connected to the VON output node; The PCC module is connected to the gate of the switch tube MS1 and the gate of the switch tube MS2 respectively, so as to output a PRE signal to the switch tube MS1 and synchronously output a PREB signal which is inverted from the PRE signal to the switch tube MS2, so that the switch tube MS1 and the switch tube MS2 are synchronously turned on.

8. A voltage-controlled oscillator, characterized in that: The pre-charging circuit comprises the pre-charging circuit described in any one of claims 1 to 7.

9. The voltage controlled oscillator according to claim 8, characterized in that: It also includes a VOC circuit; the VOC circuit includes a MOS tube M1, a MOS tube M2, a capacitor C1, a capacitor C2, a capacitor C3, an inductor L1, an inductor L2 and an inductor L3; The source of the MOS tube M1 and the source of the MOS tube M2 are connected to the ground terminal; the gate of the MOS tube M1 and the gate of the MOS tube M2 are connected; the drain of the MOS tube M1 is respectively connected to one end of the capacitor C3 and one end of the inductor L1; the drain of the MOS tube M2 is respectively connected to the other end of the capacitor C3 and the other end of the inductor L1; one end of the capacitor C1 is connected to the drain of the MOS tube M1, and the other end is connected to the gate of the MOS tube M2; one end of the capacitor C2 is connected to the drain of the MOS tube M2, and the other end is connected to the gate of the MOS tube M1; one end of the capacitor C3 is used as a VOP output node, and the other end is used as a VON output node; The inductor L1 is also connected to a power supply; the inductor L2 is connected in parallel to the capacitor C3; the inductor L3 is coupled to the inductor L2, one end of the inductor L3 is connected to the ground, and the other end is connected to the transmitting antenna.

10. The voltage controlled oscillator according to claim 8, characterized in that: It also includes a VOC circuit; the VOC circuit includes a MOS tube M1, a MOS tube M2, a capacitor C1, a capacitor C2, a capacitor C3, an inductor L1 and an inductor L2; The source of the MOS tube M1 and the source of the MOS tube M2 are grounded; the gate of the MOS tube M1 and the gate of the MOS tube M2 are connected; the drain of the MOS tube M1 is respectively connected to one end of the capacitor C3 and one end of the inductor L1; the drain of the MOS tube M2 is respectively connected to the other end of the capacitor C3 and the other end of the inductor L1; one end of the capacitor C1 is connected to the drain of the MOS tube M1, and the other end is connected to the gate of the MOS tube M2; one end of the capacitor C2 is connected to the drain of the MOS tube M2, and the other end is connected to the gate of the MOS tube M1; one end of the capacitor C3 is used as a VOP output node, and the other end is used as a VON output node; The inductor L1 is also connected to a power source; the inductor L2 is coupled to the inductor L1; one end of the inductor L2 is connected to a ground terminal, and the other end is connected to a transmitting antenna.

11. The voltage controlled oscillator according to claim 9 or 10, characterized in that: The VOC circuit also includes a resistor R1 and a resistor R2; the gate of the MOS tube M1 is connected to the gate of the MOS tube M2 via the resistor R1 and the capacitor R2 connected in series; the resistor R1 and the capacitor R2 are also connected to the PCC module to output a VBN signal corresponding to the signal to be transmitted after the pre-charging circuit completes pre-charging.

12. A digital isolator, characterized in that: It comprises the voltage-controlled oscillator according to any one of claims 8 to 11 and a millimeter wave transmitting antenna connected to the voltage-controlled oscillator.

Images