Patent Description:
As a screen-to-body ratio of a terminal increases, a camera component is very close to an antenna. In addition, when a complex circuit structure inside a camera matches a length of the antenna, the circuit structure receives a radio signal and reduces antenna efficiency. The circuit structure may also radiate an electromagnetic wave with a corresponding frequency, which reduces sensitivity of the antenna. A design of the antenna requires limiting the use of metal parts on the camera component. Therefore, a camera fastening bracket is a plastic bracket.

A voice coil motor cannot be effectively grounded due to the use of the plastic bracket, resulting in electrostatic discharge (electrostatic discharge, ESD). Electrostatic charge flows to a voice coil motor shell of the camera through a camera lens on a terminal housing, causes secondary discharge to an internal coil, and flows to a camera substrate through the coil. This affects antenna sensitivity, and damage a camera drive circuit, resulting in photographing exceptions such as focusing failure, screen freezing, and artifacts, and other problems such as a system crash. Currently, an electrostatic discharge ESD problem is resolved by attaching a conductive fabric or a conductive copper foil to an outer side of a camera module to effectively avoid suspension of a voice coil motor VCM (Voice Coil Motor, VCM for short). However, this method cannot resolve the problem that the antenna is affected, and the cost increases.

For solving a similar problem <CIT> discloses an interference-suppressing assembly of an actuator with an electric motor. The electric motor is accommodated in a housing of an actuator which is used in a motor vehicle. The electric motor has an electric motor housing with electric motor housing connections as well as a first connecting line and a second connecting line. In the first connecting line, a first coil is arranged, and in the second connecting line, a second coil is arranged. The coils are used in particular for high-frequency interference suppression. The internet citation "Voice coil driver - PCB and Test" with author Andreas Betz and the data sheet of "CN3937 Low Voltage Coil Motor Driver with I2C Interface" each disclose internal structures of voice coil motor drive circuits.

Embodiments of this application provide a voice coil motor VCM protection circuit, to prevent an antenna sensitivity from being affected by the voice coil motor VCM, and to prevent a camera drive circuit from being damaged due to electrostatic discharge, to avoid photographing exceptions such as focusing failure, screen freezing, and artifacts, and a system crash. To resolve the foregoing technical problems, the embodiments of this application provide the following technical solutions.

According to a first aspect, an embodiment of this application provides a voice coil motor VCM protection circuit, including:.

The first circuit and the second circuit are choke circuits including a choke inductor.

According to the invention, the choke circuit may be one of the following cases:.

The foregoing method reduces the influence of the voice coil motor on the antenna at a particular frequency and at several different frequencies. With reference to the first aspect, the first protection module includes a first device and a second device that are connected in parallel, and may be one of the following cases:.

With reference to the first aspect, the second protection module includes a third device and a fourth device that are connected in parallel, and may be one of the following cases:.

With reference to the first aspect, the third protection module includes a fifth device and a sixth device that are connected in parallel, and may be one of the following cases:.

With reference to the first aspect, a model of capacitors of the first protection module and the second protection module is <NUM>, and a capacitance value is <NUM> nF to <NUM>µF.

With reference to the first aspect, for the first protection module, the second protection module, and the third protection module, when electrostatic discharge EDS of a transient voltage suppressor TVS is -<NUM> V or +<NUM> V and a reverse breakdown current is <NUM> mA, a breakdown voltage ranges from <NUM> V to <NUM> V, a turn-off voltage is greater than or equal to <NUM> V, a clamp voltage ranges from <NUM> V to <NUM> V, a maximum peak pulse current is <NUM> A, a junction capacitance is less than <NUM> pF, and general pulse test waveform ranges from <NUM> to <NUM>.

With reference to the first aspect, a capacitance value of the capacitor of the third protection module is <NUM> pF to <NUM> pF.

According to a second aspect according to claim <NUM>, an embodiment of this application provides also a printed circuit board PCB of the voice coil motor VCM protection circuit of claim <NUM>, where a top layer of the PCB includes the first circuit, the second circuit, the first protection module, the second protection module, and the third protection module.

The first circuit and the first protection module are connected and are arranged near a coil connection point of the voice coil motor VCM, and a current return end of the first protection module is directly connected to a DGND by using a through hole of the PCB.

The second protection module is connected to a drive circuit and is arranged near the drive circuit, and a current return end of the second protection module is directly connected to a VCM_GND by using a through hole of the PCB.

The second circuit and the third protection module are connected and are arranged near a coil connection point of the voice coil motor VCM, and a current return end of the third protection module is directly connected to a DGND by using a through hole of the PCB.

With reference to the second aspect, the choke circuit is one of the following cases:.

With reference to the second aspect, the first protection module includes a first device and a second device that are connected in parallel, and may be one of the following cases:.

With reference to the second aspect, second protection module includes a third device and a fourth device that are connected in parallel, and may be one of the following cases:.

With reference to the second aspect, the third protection module includes a fifth device and a sixth device that are connected in parallel, and may be one of the following cases:.

With reference to the second aspect, wires of VCM_VDD and VCM_GND are routed in parallel and are completely wrapped by the DGND.

With reference to the second aspect, a wire between the VCM_VDD and a coil connection point of the voice coil motor VCM, and a wire between the ISINK and a coil connection point of the voice coil motor VCM are routed separately and are completely wrapped by the DGDN.

With reference to the second aspect, areas, that correspond to wires and pads for connecting the first circuit and the second circuit to coil connection points of the voice coil motor VCM, and that are on all layers of the PCB, from the top layer to the bottom layer, are empty. In other words, no copper is coated are routed.

It can be learned from the foregoing technical solutions that, in the embodiments of this application, two ends of a voice coil motor VCM are connected to choke inductors, and protection modules are connected to a circuit at appropriate positions. This can avoid focusing failure, screen freezing, artifacts, and other problems caused by reduced antenna sensitivity and drive circuit failure due to electrostatic discharge.

Specific implementations of this application are described below with reference to the accompanying drawings.

As shown in <FIG>, an embodiment of this application provides a protection circuit <NUM> applied to a terminal camera. The protection circuit includes a drive circuit <NUM>, a voice coil motor VCM <NUM>, a first circuit <NUM>, a second circuit <NUM>, a first protection module <NUM>, a second protection module <NUM>, a third protection module <NUM>, and a mainboard <NUM>.

One end of the voice coil motor VCM <NUM> is connected to one end of the first circuit <NUM> at a first node N, and the other end of the voice coil motor VCM <NUM> is connected to one end of the second circuit <NUM> at a second node G. The other end of the first circuit <NUM> is connected to a power supply end VDD of the voice coil motor drive circuit at a third node D. One end of the first protection module <NUM> is connected to the third node D, and the other end of the first protection module is connected to a digital ground DGND at a fourth node A. One end of the second protection module <NUM> is connected to the third node D, and the other end of the second protection module is connected to a reference ground VCM_GND of the voice coil motor drive circuit at a seventh node. The other end of the second circuit <NUM> is connected to a current return end ISINK of the voice coil motor drive circuit at a fifth node C. One end of the first device <NUM> is connected to the fifth node C, and the other end of the first device <NUM> is connected to the digital ground DGND at a sixth node V The first circuit <NUM> and the second circuit <NUM> are chokes circuit including a choke inductor, and the first device is a transient voltage suppressor TVS.

The following further describes the embodiment of this application by using an operating process of the protection circuits of the camera. A power supply end VDD_2V8 of the mainboard <NUM> supplies power to the circuit <NUM>. A ground end of the mainboard <NUM> is separately grounded: One is connected to the digital ground DGND, and the other is connected to a reference ground VCM_GND of the voice coil motor. The power supply end VDD_2V8 of the mainboard <NUM> supplies power to the circuit <NUM>. When the current flows to the third node D, the current is divided into two currents, and one current flows to the first circuit <NUM>. The first circuit <NUM> is configured to avoid impact of the voice coil motor on the antenna in a driving process. An inductance value of the choke inductor is selected according to a type of the antenna and a corresponding frequency, to reduce the impact of the voice coil motor drive circuit on the antenna. The first protection module <NUM> and the third protection module <NUM> are separately arranged near the voice coil motor coil <NUM>, and are configured to release static electricity generated by electrostatic discharge ESD at two ends of the voice coil motor coil. The second protection module <NUM> is arranged near the drive circuit <NUM> and cooperates with the first protection module <NUM> and the third protection module <NUM>, to protect the drive circuit <NUM> when the first protection module <NUM> and the third protection module <NUM> cannot achieve a good suppression effect on electrostatic discharge ESD. This can avoid problems such as focusing failure and screen freezing caused by drive circuit <NUM> failure. The other current flows to a VDD end of the drive circuit, and supplies power to the drive circuit.

In the foregoing embodiments, the first circuit and the second circuit are choke circuits including a choke inductor, and the choke circuits are configured to reduce the impact of the voice coil motor in the camera module on the antenna. When the choke circuits are one-stage filter circuits, the choke circuits reduce impact on an antenna at a specific frequency in the camera module. For example, when an inductance value of the selected choke inductor is <NUM> nH, an SFR of the choke inductor is about <NUM>, and then the one-stage filter circuit relatively reduces the impact of the voice coil motor on the antenna at a frequency within <NUM> to <NUM>.

<FIG> are two cases in which choke circuits are one-stage filter circuits.

<FIG>, which does not correspond to the invention, is a possible case in which a choke circuit <NUM> is a one-stage filter circuit and includes two choke inductors that are connected in parallel. One end of a choke inductor <NUM> and one end of a choke inductor <NUM> are connected to a first node D, and the other end of the choke inductor <NUM> and the other end of the choke inductor <NUM> are connected to a third node M.

Further, a quantity of choke inductors that are connected in parallel may be increased or decreased based on an actual situation.

In an embodiment of the invention, as shown in <FIG>, the choke circuit <NUM> includes a choke inductor <NUM> and a capacitor <NUM> that are connected in parallel.

Further, the quantity of choke inductors that are connected in parallel and a quantity of capacitors that are connected in parallel may be increased or decreased based on an actual situation.

When the choke circuit is a two-stage filter circuit, the choke circuit can reduce the impact of the voice coil motor on the antenna at different frequencies. For example, the choke inductors in the two-stage filter circuit may reduce the impact of the voice coil motor on the antenna at two different frequencies: a low frequency within <NUM> to <NUM> and a high frequency within <NUM> to <NUM>.

<FIG> and <FIG> are two cases in which the choke circuits are two-stage filter circuits.

<FIG>, which does not correspond to the invention, is a case in which a choke circuit <NUM> is a two-stage filter circuit. One end of a choke inductor <NUM> is connected to a second node G, the other end of the choke inductor <NUM> is connected in series to a choke inductor <NUM> at a node P, and the other end of the choke inductor <NUM> is connected to a fifth node C.

Further, a quantity of choke inductors that are connected in series may be increased or decreased based on an actual situation.

In an embodiment of the invention, as shown in <FIG>, in the choke circuit <NUM>, a choke inductor <NUM> and a capacitor <NUM> are connected in parallel between a second node G and a node P, and then connected in series with a choke inductor <NUM> at the node P.

Further, quantities of choke inductors and capacitors that are connected in parallel, and a quantity of other choke inductors that are connected in series with the foregoing choke inductors and capacitors may be increased or decreased based on an actual situation.

Both the choke circuit <NUM> and the choke circuit <NUM> in the foregoing embodiments may be applied to the first circuit <NUM> and the second circuit <NUM>. For example, the first circuit <NUM> is a choke circuit <NUM>, and the second circuit <NUM> is a choke circuit <NUM>. Alternatively, both the first circuit <NUM> and the second circuit <NUM> are choke circuits <NUM>. This is not enumerated herein.

In a possible design, for the first circuit and the second circuit, through-current capabilities are greater than or equal to <NUM> mA, direct current impedances are less than <NUM>Ω, and self-resonance frequencies SFRs are not less than an operating frequency of a neighboring antenna.

In a possible implementation, recommended inductance values of the choke inductors in the first circuit and the second circuit are <NUM> nH.

As shown in <FIG>, an embodiment of this application provides a first protection module <NUM>, including a first device <NUM> and a second device <NUM> that are connected in parallel between a third node D and a fourth node A.

The first device <NUM> is a transient voltage suppressor TVS (transient voltage suppressor, TVS for short), and the second device <NUM> is a capacitor.

In a possible implementation, in the first protection module <NUM>, the first device <NUM> is a capacitor, the second device is not configured, and a branch circuit corresponding to the second device is disconnected.

In a possible implementation, in the first protection module <NUM>, the first device <NUM> is a transient voltage suppressor TVS, the second device is not configured, and a branch circuit corresponding to the second device is disconnected.

In the foregoing embodiments, a capacitance value of the capacitor is <NUM> nF to <NUM>µF, and a model of the capacitor is <NUM>.

As shown in <FIG>, an embodiment of this application provides a second protection module <NUM>, including a third device <NUM> and a fourth device <NUM> that are connected in parallel between a third node D and a seventh node M. The third device <NUM> is a transient voltage suppressor TVS, and the fourth device <NUM> is a capacitor.

In a possible implementation, in the second protection module <NUM>, the third device <NUM> is a capacitor, the fourth device is not configured, and a branch circuit corresponding to the second device is disconnected.

As shown in <FIG>, an embodiment of this application provides a third protection module <NUM>, including a fifth device <NUM> and a sixth device <NUM> that are connected in parallel between a fifth node C and a sixth node V. The fifth device <NUM> is a transient voltage suppressor TVS, and the sixth device <NUM> is a capacitor.

In a possible implementation, the fifth device is a transient voltage suppressor TVS, the sixth device is not configured, and a branch circuit corresponding to the second device is disconnected.

In a possible implementation, a capacitance value of the sixth device <NUM>, namely a capacitor, is <NUM> pF to <NUM> pF.

For the transient voltage suppressors TVSs in all the foregoing embodiments, when an electrostatic discharge EDS is -<NUM> V or +<NUM> V and a reverse breakdown current is <NUM> mA, a breakdown voltage ranges from <NUM> V to <NUM> V, a turn-off voltage is greater than or equal to <NUM> V, a clamp voltage ranges from <NUM> V to <NUM> V, a maximum peak pulse current is <NUM> A, a junction capacitance is less than <NUM> pF, and general pulse test waveform ranges from <NUM> to <NUM>.

<FIG> is a schematic diagram of a printed circuit board PCB circuit of a voice coil motor VCM, which does not correspond to the invention. The PCB has four circuit layers with a through hole, and devices of the voice coil motor VCM protection circuit are all arranged on a top layer.

Further, the top layer of the PCB includes a first circuit <NUM>, a second circuit <NUM>, a first protection module <NUM>, a second protection module <NUM>, and a third protection module <NUM>. The first circuit <NUM> and the first protection module <NUM> are connected and are arranged near a coil connection point of the voice coil motor VCM, and a current return end of the first protection module <NUM> is directly connected to a DGND by using a through hole of the PCB. The second protection module <NUM> is connected to the drive circuit and is arranged near the drive circuit, and a current return end of the second protection module is directly connected to a VCM_GND by using a through hole of the PCB. The second circuit <NUM> and third protection module <NUM> are connected and are arranged near a coil connection point of the voice coil motor VCM, and a current return end of the third protection module is directly connected to a DGND by using a through hole of the PCB.

Further, the first circuit <NUM> and the second circuit <NUM> are choke circuits including a choke inductor.

In <FIG>, differently as according to the invention, the first circuit <NUM> and the second circuit <NUM> include only one choke inductor, and the second protection module <NUM> includes only a capacitor. The third protection module <NUM> includes only a transient voltage suppressor TVS.

Further, wires connected to the power supply end VCM_VDD and the reference ground VCM_GND of the drive circuit are routed in parallel and are completely wrapped by the DGND, to be isolated from other signals. A wire between the VCM_VDD and a connection point of the voice coil motor, and a wire between a circuit current return end ISINK and a connection point of the voice coil motor are routed separately and are completely wrapped by the DGND, to be isolated from other signals.

Further, areas, that correspond to wires and pads for connecting the first circuit and the second circuit to coil connection points of the voice coil motor VCM, and that are on all layers of the PCB, from the top layer to the bottom layer, are empty. In other words, no copper is coated are routed.

Further, three types of signal wires of the power supply end VCM_VDD, the reference ground VCM_GND, and the circuit current return end ISINK may be implemented on one or more layers of a top layer, a second layer and a third layer of the PCB according to a design.

In a possible design, the first circuit and the second circuit are choke circuits. When the choke circuit is a one-stage filter circuit, the choke circuit may be one of the following cases not corresponding to the invention:.

According to the invention, when the choke circuit is a one-stage filter circuit, the choke circuit is:
one or more choke inductors connected in parallel with one or more capacitors.

Further, when the choke circuit is a two-stage filter circuit, in examples not according to the invention, the choke circuit may be:
a plurality of choke inductors are connected in series.

According to the invention, when the choke circuit is a two-stage filter circuit, the choke circuit is:
one or more choke inductors and one or more capacitor connected in parallel and the connected in series with one or more choke inductors.

Further, in a possible design, the first circuit and the second circuit may be a one-stage filter circuit or two-stage filter circuit based on an actual requirement.

In a possible design, the first protection module includes a first device and a second device that are connected in parallel, and the first protection module <NUM> may be one of the following cases:.

In a possible design, the second protection module <NUM> includes a third device and a fourth device that are connected in parallel, and may be one of the following cases:.

In a possible design, the third protection module <NUM> includes a fifth device and a sixth device that are connected in parallel, and may be one of the following cases:.

Further, in a possible design, a capacitor of the choke circuit may be implemented as a lumped capacitor or a coupling capacitor, for example, formed by coupling on a PCB.

Further, the choke inductors described in the foregoing embodiments are an inductor that acts as a choke, and a model of the choke inductors is selected based on an actual requirement.

The foregoing descriptions are merely specific implementations of this application, but are not intended to limit the protection scope of this application. Any variation or replacement readily figured out by a person skilled in the art within the technical scope of the appended claims shall fall within the protection scope of this invention.

Claim 1:
A voice coil motor VCM protection circuit (<NUM>), comprising:
a voice coil motor VCM (<NUM>), wherein two ends of the voice coil motor VCM (<NUM>) are separately connected to a first circuit (<NUM>) and a second circuit (<NUM>);
a VCM drive circuit (<NUM>);
the first circuit (<NUM>), wherein the first circuit (<NUM>) is a choke circuit (<NUM>, <NUM>) comprising a choke inductor, one end of the first circuit (<NUM>) is connected to one end of the voice coil motor VCM (<NUM>) at a first node (N), and the other end of the first circuit (<NUM>) is connected to a power supply end VDD of the VCM drive circuit (<NUM>) at a third node (D); and
the second circuit (<NUM>), wherein the second circuit (<NUM>) is a choke circuit (<NUM>, <NUM>) comprising a choke inductor, one end of the second circuit (<NUM>) is connected to the other end of the voice coil motor VCM (<NUM>) at a second node (G), and the other end of the second circuit (<NUM>) is connected to a current return end ISINK of the VCM drive circuit (<NUM>) at a fifth node (C);
characterized in that
the third node (D) is configured to receive a supplied current, wherein the supplied current is divided into two currents, one current flowing to the first circuit (<NUM>) and the other current flowing to the power supply end VDD of the VCM drive circuit (<NUM>), and in that
each of the choke circuits (<NUM>, <NUM>) is one of the following cases:
one or more choke inductors (<NUM>) are connected in parallel with one or more capacitors (<NUM>); or
one or more choke inductors (<NUM>) and one or more capacitors (<NUM>) are connected in parallel and then are connected in series with one or more choke inductors (<NUM>).