Apparatus for controlling lens module and reducing offset of Hall sensor

An apparatus configured to reduce an offset of a Hall sensor includes a voltage-current conversion circuit and a current mirror circuit. The voltage-current conversion circuit is configured to generate a current configured to decrease when a voltage of an input terminal to which a bias current of a Hall sensor is input increases and increase when the voltage of the input terminal decreases. The current mirror circuit has a current mirror structure configured to feedback the bias current based on the current generated by the voltage-current conversion circuit.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims benefit under 35 USC 119(a) of priority to Korean Patent Application No. 10-2020-0103263 filed on Aug. 18, 2020 in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference for all purposes.

BACKGROUND

The present disclosure relates to an apparatus for controlling a lens module and reducing an offset of a Hall sensor.

2. Description of Related Art

In general, when a lens module moves based on a force received from an external source, a technology for fixing its position relative to the outside of the lens module is widely used.

For example, a camera module may include an optical image stabilizer device fixing the position of the lens module therein, even when the camera module is subjected to an external force.

A Hall sensor may be used to measure the position information of the lens module, and the Hall sensor may output a voltage varying depending on the position of the lens module. The accuracy of optical image stabilization may be higher as the accuracy of the corresponding relationship between the output voltage of the Hall sensor and the position information of the lens module increases.

The output voltage of the Hall sensor may vary slightly depending on external factors such as temperature, and variations in the output voltage due to external factors of the Hall sensor may degrade the accuracy of the corresponding relationship between the output voltage of the Hall sensor and the position information of the lens module.

SUMMARY

In one general aspect, an apparatus configured to reduce an offset of a Hall sensor includes a voltage-current conversion circuit and a current mirror circuit. The voltage-current conversion circuit is configured to generate a current configured to decrease when a voltage of an input terminal to which a bias current of a Hall sensor is input increases and increase when the voltage of the input terminal decreases. The current mirror circuit has a current mirror structure configured to feedback the bias current based on the current generated by the voltage-current conversion circuit.

The current mirror circuit may include a feedback input transistor configured to flow the current generated by the voltage-current conversion circuit between a source terminal and a drain terminal of the feedback input transistor, and a feedback output transistor configured to flow the bias current between a source terminal and a drain terminal of the feedback output transistor. The current mirror circuit may be configured to mirror the current generated by the voltage-current conversion circuit through a gate terminal of the feedback input transistor and a gate terminal of the feedback output transistor.

The voltage-current conversion circuit may include a conversion transistor configured to flow the current generated by the voltage-current conversion circuit between a drain terminal and a source terminal of the conversion transistor. The current mirror circuit may further include a feedback resistor connected between the feedback input transistor and the conversion transistor.

The feedback input transistor may include a first feedback input transistor and a second feedback input transistor connected to each other in series. The feedback output transistor may include a first feedback output transistor and a second feedback output transistor connected to each other in series. The first and second feedback input transistors may mirror the current generated by the voltage-current conversion circuit to the first and second feedback output transistors in parallel.

The feedback resistor may be connected between a gate terminal of the first feedback input transistor and a gate terminal of the second feedback input transistor.

The voltage-current conversion circuit may further include a conversion resistor connected between the conversion transistor and a ground.

The apparatus may further include a conversion operational amplifier having an output terminal connected to a gate terminal of the conversion transistor, receiving a voltage corresponding to a voltage of an input terminal of the hall sensor to one of a plurality of input terminals of the conversion operational amplifier and to a node between the conversion transistor and the conversion resistor through another one of the plurality of input terminals of the conversion operational amplifier.

The voltage-current conversion circuit may further include a buffer configured to invert the voltage of the input terminal of the hall sensor and output a voltage corresponding to the voltage of the input terminal of the hall sensor to the conversion operational amplifier.

The voltage-current conversion circuit may include a conversion transistor configured to flow the current generated by the voltage-current conversion circuit between a drain terminal and a source terminal of the conversion transistor, and a buffer configured to invert a voltage of the input terminal of the Hall sensor and output a voltage corresponding to the voltage of the input terminal of the Hall sensor. The conversion transistor may be configured to generate a current configured to increase when a voltage output from the buffer increases and decrease when a voltage output from the buffer decreases.

The buffer may include a buffer operational amplifier, a first resistor connected between one of a plurality of input terminals of the buffer operational amplifier and an input terminal of the Hall sensor, a second resistor connected between one of the plurality of input terminals of the buffer operational amplifier and an output terminal of the buffer operational amplifier, and third and fourth resistors connected to another of the plurality of input terminals of the buffer operational amplifier.

The buffer may be configured to apply a reference voltage, different from a ground voltage, to the third and fourth resistors.

In another general aspect, an apparatus configured to control a lens module includes a Hall sensor, an analog-to-digital (AD) converter, a driver, a voltage-current conversion circuit, and a current mirror circuit. The Hall sensor is configured to pass magnetic flux based on a movement of a lens module. The AD converter is configured to output a digital value based on a voltage difference between a first output terminal and a second output terminal of the Hall sensor. The driver is configured to generate a driving signal to control the movement of the lens module based on the digital value. The voltage-current conversion circuit is configured to generate a current configured to decrease when a voltage of an input terminal to which a bias current of the Hall sensor is input increases and increase when the voltage of the input terminal decreases. The current mirror circuit has a current mirror structure configured to feedback the bias current based on the current generated by the voltage-current conversion circuit.

The voltage-current conversion circuit may include a conversion transistor configured to flow the current generated by the voltage-current conversion circuit between a drain terminal and a source terminal of the conversion transistor. The current mirror circuit may inclulde a feedback resistor configured to flow the current generated by the voltage-current conversion circuit.

The current mirror circuit may include a first feedback input transistor and a second feedback input transistor, and a first feedback output transistor and a second feedback output transistor. The first feedback input transistor and the second feedback input transistor may each be configured to flow a current generated by the voltage-current conversion circuit, respectively, between a source terminal and a drain terminal, and connected to each other in series. The first feedback output transistor and the second feedback output transistor may each be configured to flow the bias current, respectively, between a source terminal and a drain terminal, and connected to each other in series. The feedback resistor may be connected between a gate terminal of the first feedback input transistor and a gate terminal of the second feedback input transistor.

The voltage-current conversion circuit ay further include a buffer configured to invert a voltage of an input terminal of the Hall sensor and output a voltage corresponding to the voltage of the input terminal of the Hall sensor, and a conversion resistor connected between the conversion transistor and a ground. The conversion transistor may be configured to generate a current configured to increase when a voltage output from the buffer increases and decrease when a voltage output from the buffer decreases.

The apparatus may further include an amplifier configured to amplify a voltage difference between the first and second output terminals of the Hall sensor. The AD converter may be configured to output the digital value based on an output voltage of the amplifier.

DETAILED DESCRIPTION

FIGS.1A and1Bare views illustrating examples of an apparatus for reducing an offset of a Hall sensor.

Referring toFIG.1A, a Hall sensor300may receive a bias current IHALL1through an input terminal301. The bias current IHALL1passing through the Hall sensor300may flow to the ground through a ground terminal302of the Hall sensor300.

The Hall sensor300may sense magnetic flux passing through the Hall sensor300by using a Hall effect. When magnetic flux passes through the Hall sensor300, the Hall sensor300may generate a bias current IHALL1and a Hall voltage in a direction, perpendicular to the magnetic flux, and a voltage difference between a first output voltage of a first output terminal303and a second output voltage of a second output terminal304may correspond to the Hall voltage. Accordingly, the voltage difference between the first and second output terminals303and304may be used as a measurement value for the magnetic flux passing through the Hall sensor300. Herein, it is noted that use of the term ‘may’ with respect to an example or embodiment, e.g., as to what an example or embodiment may include or implement, means that at least one example or embodiment exists where such a feature is included or implemented while all examples and embodiments are not limited thereto.

An equivalent circuit of the Hall sensor300may be composed of a plurality of resistors. Resistance values of the plurality of resistors may vary due to external factors of the Hall sensor300, such as temperature.

For example, the voltage of each of the first and second output terminals303and304may increase together when the resistance values of the plurality of resistors increase, and when the resistance values of the plurality of resistors decrease, the voltage of each of the first and second output terminals303and304may decrease together.

A common voltage change value of the first and second output terminals303and304according to external factors of the Hall sensor300, such as a temperature, may be defined as an offset of the Hall sensor300.

Since the voltage difference between the first and second output terminals303and304compared to unit magnetic flux passing through the Hall sensor300may be proportional to the voltages of the first and second output terminals303and304, an offset of the Hall sensor300may affect a voltage difference between the first and second output terminals303and304compared to the unit magnetic flux passing through the Hall sensor300.

That is, the voltage difference between the first and second output terminals303and304compared to the unit magnetic flux passing through the Hall sensor300may vary depending on the magnetic flux and an offset passing through the Hall sensor300.

Therefore, from the viewpoint of extracting magnetic flux information passing through the Hall sensor300from the voltage difference between the first and second output terminals303and304, an effect of an offset may be determined as a part of the magnetic flux information passing through the Hall sensor300, and accuracy of the extracted magnetic flux information may be lowered.

An apparatus for reducing an offset of a Hall sensor100aaccording to one or more embodiments of the present disclosure may reduce an offset of the Hall sensor300. For example, the apparatus for reducing an offset of a Hall sensor100amay be implemented as an integrated circuit (IC), may be mounted on a substrate such as a printed circuit board, and may be electrically connected to the Hall sensor300through the substrate.

Referring toFIG.1A, the apparatus for reducing an offset of a Hall sensor100aaccording to one or more embodiments of the present disclosure may include a voltage-current conversion circuit110and a current mirror circuit120a.

The voltage-current conversion circuit110may be configured to generate a current IHALL2decreasing when the voltage VTOP of the input terminal310, to which the bias current IHALL1is input, increases and increasing when the voltage VTOP of the input terminal301decreases.

The current mirror circuit120amay be configured to feedback the bias current IHALL1based on the current IHALL2generated by the voltage-current conversion circuit110by a current mirror structure.

Accordingly, the bias current IHALL1of the Hall sensor300may decrease when the voltage VTOP of the input terminal301increases, and may increase when the voltage VTOP of the input terminal301decreases.

That is, the voltage VTOP of the input terminal301may increase as the resistance value of the Hall sensor300increases, and may decrease when the bias current IHALL1decreases. The voltage VTOP of the input terminal301may decrease as the resistance value of the Hall sensor300decreases, and may increase when the bias current IHALL1increases.

The apparatus for reducing an offset of a Hall sensor100aaccording to one or more embodiments of the present disclosure may have a structure in which a start and an end of a process of reducing an offset of the Hall sensor300is a bias current IHALL1or an input terminal301, so the efficiency, accuracy, and stability of the process can be improved overall.

The current mirror circuit120amay include feedback input transistors M4and M5configured such that the current IHALL2generated by the voltage-current conversion circuit110flows between a source terminal and a drain terminal, and may include feedback output transistors M2and M3configured such that the bias current IHALL1flows between the source terminal and the drain terminal.

The current mirror circuit120amay mirror through gate terminals of the feedback input transistors M4and M5and gate terminals of the feedback output transistors M2and M3. For example, a voltage of the gate terminals of the feedback input transistors M4and M5and a voltage of the gate terminals of the feedback output transistors M2and M3may be shared with each other, and the gate terminals of the feedback input transistors M4and M5may be electrically connected to drain terminals of the feedback input transistors M4and M5.

Accordingly, the magnitude of the bias current IHALL1may be determined to be proportional to the current IHALL2generated by the voltage-current conversion circuit110at a preset ratio (e.g., a one to one (1:1) ratio). Here, the preset ratio may be determined based on a W/L of the feedback input transistors M4and M5and a W/L of the feedback output transistors M2and M3.

In addition, since an influence of external factors (e.g., temperature) of the feedback input transistors M4and M5and an influence of external factors of the feedback output transistors M2and M3may be common to each other, a ratio (e.g., 1 to 1) between the current IHALL2generated by the voltage-current conversion circuit110and the bias current IHALL1may not be substantially affected by external factors.

Therefore, the apparatus for reducing an offset of a Hall sensor100aaccording to one or more embodiments of the present disclosure may more stably reduce an offset of the Hall sensor300.

For example, the feedback input transistors M4and M5may include a first feedback input transistor M5and a second feedback input transistor M4connected to each other in series. For example, the feedback output transistors M2and M3may include a first feedback output transistor M2and a second feedback output transistor M3connected to each other in series.

The first and second feedback input transistors M5and M4may be mirrored in parallel to the first and second feedback output transistors M2and M3. That is, the voltage of the gate terminal of the first feedback input transistor M5and the voltage of the gate terminal of the first feedback output transistor M2may be shared with each other, and the voltage of the gate terminal of the second feedback input transistor M4and the voltage of the second feedback output transistor M3may be shared with each other, but the voltage of the gate terminal of the first feedback input transistor M5and the voltage of the gate terminal of the second feedback output transistor M3may be separated from each other, and the voltage of the gate terminal of the second feedback input transistor M4and the voltage of the gate terminal of the first feedback output transistor M2may be separated from each other.

Accordingly, the current mirror circuit120amay more stably mirror the current IHALL2generated by the voltage-current conversion circuit110to feedback the bias current IHALL1, and may further widen a range of an offset of the Hall sensor300that can be decreased.

The current mirror circuit120amay be disposed so that the current IHALL2generated by the voltage-current conversion circuit110flows, and may further include a feedback resistor R6electrically connected between the gate terminal of the first feedback input transistor M5and the gate terminal of the second feedback input transistor M4.

That is, the feedback resistor R6may form a bias voltage of a path through which the current IHALL2generated by the voltage-current conversion circuit110flows, and may also form a difference voltage between the voltage of the gate terminal of the first feedback input transistor M5and the voltage of the gate terminal of the second feedback input transistor M4.

The feedback resistor R6may be electrically connected between the feedback input transistors M4and M5and the conversion transistor M1, and may form a bias voltage of a path through which the current IHALL2generated by the voltage-current conversion circuit110flows.

The voltage-current conversion circuit110may include a buffer111and a conversion core circuit112, and the conversion core circuit112may include at least one of a conversion transistor M1, a conversion resistor R5, and a conversion operational amplifier OP2.

The conversion transistor M1may be configured such that the current IHALL2generated by the voltage-current conversion circuit110flows between the drain terminal and the source terminal.

Since the conversion transistor M1may generate the current IHALL2based on the voltage of the gate terminal, a voltage-current conversion operation may be performed.

The conversion resistor R5may be electrically connected between the conversion transistor M1and ground. Accordingly, the stability of the bias voltage of the conversion transistor M1may be improved.

The conversion operational amplifier OP2may have a structure in which an output terminal is electrically connected to the gate terminal of the conversion transistor M1, a voltage corresponding to the voltage VTOP of the input terminal301of the Hall sensor is input to one of a plurality of input terminals, and a node between the conversion transistor M1and the conversion resistor R5is electrically connected to the other one of the plurality of input terminals. Accordingly, the voltage-current conversion circuit110may perform a voltage-current conversion operation more stably.

For example, when a positive input voltage VP of the conversion operational amplifier OP2increases, a voltage of the gate terminal of the conversion transistor M1may increase, and a current between the drain terminal and the source terminal of the conversion transistor M1may increase, and a negative input voltage VN of the conversion operational amplifier OP2may increase as the current flowing through the conversion resistor R5increases.

For example, when the positive input voltage VP of the conversion operational amplifier OP2decreases, the voltage of the gate terminal of the conversion transistor M1may decrease, and a current between the drain terminal and the source terminal of the conversion transistor M1may decrease, and a negative input voltage VN of the conversion operational amplifier OP2may decrease as the current flowing through the conversion resistor R5decreases.

That is, the conversion transistor M1may generate a current IHALL2that increases when the voltage output from the buffer111increases and decreases when the voltage output from the buffer111decreases.

The buffer111may invert the voltage VTOP of the input terminal301of the Hall sensor300and output a positive input voltage VP corresponding to the voltage VTOP to a conversion operational amplifier OP2.

Since the buffer111may have an input impedance higher than the output impedance of the buffer111, the influence of the voltage-current conversion circuit110on the voltage VTOP may be reduced.

For example, the buffer111may include at least one of a buffer operational amplifier OP1, a first resistor R1, a second resistor R2, a third resistor R3, and a fourth resistor R4.

The first resistor R1may be electrically connected between one of the plurality of input terminals of the buffer operational amplifier OP1and the input terminal301of the Hall sensor300.

The second resistor R2may be electrically connected between one of the plurality of input terminals of the buffer operational amplifier OP1and the output terminal of the buffer operational amplifier OP1.

The third and fourth resistors R3and R4may be electrically connected to the other one of the plurality of input terminals of the buffer operational amplifier OP1.

That is, since the buffer111may have an inverting amplifier structure, the voltage VTOP of the input terminal301of the Hall sensor300may be inverted, and the voltage VTOP of the input terminal301may be amplified by a gain based on the relationship between resistance values of the first, second, third, and fourth resistors R1, R2, R3, and R4.

For example, the buffer111may be configured to apply a reference voltage VREF different from the ground voltage to the third and fourth resistors R3and R4. Accordingly, the positive input voltage VP of the conversion operational amplifier OP2can be easily set, and the current IHALL2of the conversion transistor M1can be easily adjusted. For example, according to the control of the reference voltage VREF, the on-off of the conversion transistor M1may be controlled, and on-off of the apparatus for reducing an offset of the Hall sensor100aaccording to one or more embodiments of the present disclosure may be controlled.

Referring toFIG.1B, when the voltage VTOP of the input terminal301of the Hall sensor300increases/decreases, the positive input voltage VP of the conversion operational amplifier OP2may decrease/increase, the current of the conversion transistor M1can be decreased/increased, the current IHALL2of the feedback input transistors M4and M5can be decreased/increased, and the current IHALL1of the feedback output transistors M2and M3can be decreased/increased.

That is, the bias current IHALL1of the Hall sensor300decreases when the voltage VTOP of the input terminal301increases, and may increase when the voltage VTOP of the input terminal301decreases.

FIGS.2A and2Bare diagrams illustrating examples of a modified structure of a current mirror circuit of an apparatus for reducing an offset of a Hall sensor.

Referring toFIG.2A, the feedback input transistor M5and the feedback output transistor M2of a current mirror circuit120bof an apparatus for reducing an offset of a Hall sensor100baccording to one or more embodiments of the present disclosure may be one, respectively. Here, the feedback resistor shown inFIG.1Amay be omitted. The number of the feedback input transistor M5and the feedback output transistor M2may be determined based on a threshold voltage of the feedback input transistor M5and the feedback output transistor M2and a power supply VDD.

Referring toFIG.2B, since the current mirror circuit120cof the apparatus for reducing an offset of a Hall sensor100caccording to one or more embodiments of the present disclosure may be implemented as an NMOS, and it may be a different type from the PMOS of the current mirror circuit shown inFIG.1A.

FIGS.3and4are views illustrating examples of an apparatus for reducing an offset of a Hall sensor and an apparatus for controlling a lens module.

Referring toFIG.3, an apparatus for controlling a lens module100daccording to one or more embodiments of the present disclosure may include the apparatus for reducing an offset of a Hall sensor shown inFIG.1A, and may include at least one of first and second current sources151and152.

The first and second current sources151and152may generate a bias current IHALL1and a current IHALL2of the feedback input transistors M4and M5, respectively. For example, the first and second current sources151and152may receive first and second control signals (control1and control2), and may generate a bias current IHALL1and a current IHALL2that the magnitudes thereof are determined based on the first and second control signals (control1and control2).

Referring toFIG.3, at least one of a Hall sensor300, an amplifier130, an analog-to-digital (AD) converter140, and a driver may be included in the apparatus for controlling a lens module100d.

The amplifier130may amplify a voltage difference between the first and second output terminals303and304of the Hall sensor300. For example, the amplifier130may be implemented as a (non) inverting amplifier circuit in which an operational amplifier and a plurality of resistors are combined, and may generate a voltage amplified in proportion to the voltage difference between the first and second output terminals303and304.

A gain of the amplifier130may be determined according to a relationship between resistance values of the plurality of resistors. The amplifier130having a low gain may be advantageous when a wide magnetic flux sensing range of the Hall sensor300is required, and the amplifier130having a high gain may be advantageous when a high magnetic flux sensing resolution of the Hall sensor300is required.

The AD converter140may output a digital value based on an analog value corresponding to the voltage difference between the first and second output terminals301and302of the Hall sensor300or to the output voltage of the amplifier130.

The driver may generate a driving signal to control the movement of the lens module based on the digital value output from the AD converter140.

Referring toFIG.4, an apparatus for controlling a lens module100eaccording to one or more embodiments of the present disclosure may include an apparatus for reducing an offset of a Hall sensor, and may be electrically connected to the Hall sensor300.

The Hall sensor300may be disposed so that magnetic flux based on the movement of the lens module210passes.

The driver220may receive an output value of the apparatus for controlling a lens module100ecorresponding to magnetic flux information passing through the Hall sensor300, and may generate positional information of the lens module210through the magnetic flux information.

For example, the driver220may be included in the apparatus for controlling a lens module100eor may be implemented as a separate integrated circuit for the apparatus for controlling a lens module100e.

The driver220may include an optical image stabilization (OIS) control structure, may determine the magnitude of a driving current based on the magnetic flux information, and output a driving signal including the determined driving current to the driving coil230.

The driving coil230may generate magnetic flux based on a driving current included in the driving signal, and may be disposed near the magnetic member211of the lens module210. For example, the driving coil230and the Hall sensor300may be disposed on the first substrate240.

The lens module210may move according to force received by the magnetic member211in response to the magnetic flux of the driving coil230. In this case, the lens module210may move to change the magnetic flux in a direction opposite to the change of the magnetic flux passing through the Hall sensor300. Accordingly, an absolute position of the lens module210may be substantially fixed, and an image obtained by the lens module210may be stable.

Meanwhile, the processor270may be implemented as an image signal processor (ISP), receive image information from the image sensor262on the first support member261, and transmit the processed information to the driver220.

The lens module210may move one-dimensionally or two-dimensionally, according to the rotation of the plurality of guide balls212on the second support member213, and may be surrounded by the housing250.

A structure including most of the lens module, peripheral components of the lens module210, and the housing250may be defined as a camera module.

FIG.5is a graph showing an example of a main voltage/current of the apparatus for reducing an offset of a Hall sensor and the apparatus for controlling a lens module.

Referring toFIG.5, a resistance value RHALLof the Hall sensor may be set to increase from 900 ohms to 1100 ohms step by step for a time of 1 ms. That is, the resistance value RHALLof the Hall sensor may be set to increase from 90% of 1000 ohms to 110% of 1000 ohms.

A voltage VTOP of the input terminal of the Hall sensor may increase as the resistance value RHALLincreases, and a positive input voltage VP and a negative input voltage VN of the conversion operational amplifier can decrease, and a current IHALL2of the feedback input transistor may decrease, and a current IHALL1of the feedback output transistor may decrease.

The voltage VTOP of the input terminal of the Hall sensor may be a voltage of about 99.47% of 1V when the resistance value RHALLof the Hall sensor is 90% of 1000 ohms, and when the resistance value RHALLof the Hall sensor is 110% of 1000 ohms, it may be a voltage of about 100.43% of 1V.

In other words, the change in the voltage VTOP of the input terminal of the Hall sensor can be very small compared to the change in the resistance value RHALLof the Hall sensor, and the change in the voltage VTOP of the input terminal of the Hall sensor may correspond to an offset of the Hall sensor, such that the apparatus for reducing an offset of a Hall sensor and the apparatus for controlling a lens module according to one or more embodiments of the present disclosure may effectively reduce an offset of the Hall sensor.

As set forth above, according to one or more embodiments of the present disclosure, since an apparatus for reducing an offset of a Hall sensor and an apparatus for controlling a lens module may have a structure in which a start and an end of a process of reducing an offset of a Hall sensor is a bias current, efficiency, accuracy and stability of the process may be improved overall.

Since the apparatus for reducing an offset of a Hall sensor and the apparatus for controlling a lens module can self-reduce an offset without an external element (e.g., temperature) sensing structure (e.g., a temperature sensor, a Hall sensor to be compared), it can be more easily simplified/miniaturized.