Voice Coil Motor (VCM) is the core driving element of modern optical system, and its performance directly determines the accuracy and speed of automatic focusing (AF) and optical anti-shake (OIS). Different types of VCM motors need to be matched with specific driver chips to achieve optimal performance,From the basic open-loop structure to high-precision closed-loop control, to the complex optical anti-shake system, the technical scheme presents a diversified development. Adapt to end-side AI deployment requirements, can be equipped with lightweight intelligent reasoning model locally on the device, to achieve local autonomous decision-making of focusing strategy, anti-shake logic, power consumption control, without relying on cloud computing power,Perfect adaptation to the end-side intelligent imaging hardware ecology. In this paper, the system analyzes the four mainstream technical solutions of open-loop VCM, closed-loop VCM, optical anti-shake VCM and SMA alternatives, and combines the latest driver chip cases to reveal its design principles, performance boundaries and application scenarios.
1. Open-loop VCM motor drive scheme
Open-loop VCM is the most widely used low-cost auto-focus solution. Its structure is composed of permanent magnets, coils and elastic support mechanisms, and the lens displacement is realized through current control. This kind of motor has no position feedback sensor and completely depends on the current control accuracy and algorithm compensation of the drive chip. Its core driving requirements are reflected in:
Current control accuracy: the lens movement should be completed within 20ms, and the current fluctuation should be less than 5%. Awinic is an electronic two-in-one driver IC in AW86018CSR, which is packaged by WLCSP, supports 2.3V-3.6V voltage input, integrates 11-bit DAC, and realizes ± 100mA/± 130mA two-level current output,Digital control is realized through I²C interface (address 0x 18h). Sufficient interface bandwidth and computing resources can quickly dock AI visual perception data on the end side and jointly complete intelligent focusing prediction.
Figure 1 AW86018 product block diagram
Algorithm coordination: Awinic for electronic AW86018CSR needs to cooperate with VRC focusing algorithm (VCM Ring Control) to realize fast contrast focusing by predicting the motion track of the lens. This solution is suitable for the main camera, end-side AI and ultra-wide-angle lens of low-end mobile phones, and the cost is reduced by about 30% compared with the closed-loop system.
This kind of driver chip adopts WLCSP small package, and the typical power consumption is controlled below 5MW to meet the needs of portable devices. However, due to the open-loop characteristics, its repeated positioning accuracy is only ± 10μm, and focus drift is prone to occur in high-power zoom scenes.
2. Closed-loop VCM motor drive scheme
The closed-loop system feeds back the lens position in real time through the Hall sensor to achieve micron-level focusing accuracy. Its driver chip needs to have three core capabilities:
High-precision data conversion: AW86022CSR default drive current ± 150mA, supports 1.7V-3.6V voltage input, integrates 14-bit ADC (analog-to-digital conversion) and 13-bit DAC (digital-to-analog conversion), position detection resolution of ± 1μm, current control error <1.5%。
High-frequency communication interface: support I²C 3.4MHz high-speed mode, to ensure that each frame of image (30fps) can complete at least 3 position correction.
Scenario-specific pain points: In a ball-like motor application scenario, Awinic developed a SmartHolding intelligent algorithm for electronics due to the power loss caused by maintaining a holding current to resist unnecessary static friction. The algorithm significantly reduces unnecessary drive currents used to resist static friction through an innovative algorithm control loop mechanism,This in turn significantly reduces power consumption.
The closed-loop scheme is mainly used in flagship mobile phone main camera, medical endoscope lens and other scenes.
Figure 2 AW86022CSR Product Block Diagram
3. Optical anti-shake (OIS)VCM drive scheme
3.1 "cloud shaking" algorithm: OIS optical anti-shake algorithm
Awinic's self-developed "shuddering cloud" algorithm is integrated in the OIS driver chip. Through real-time monitoring of gyroscope data, the compensation displacement required by the lens is calculated to realize the "stable, accurate and fast" anti-shake effect:
Steady: ± 5 ° anti-shake angle (higher than the industry's common ± 3 °), supporting six-axis anti-shake.
Quasi: millisecond response, dynamic tracking jitter trajectory, reduce motion blur.
Fast: Low-delay closed-loop control to improve focus speed.
3.2 Algorithm Advantages
Compatible with various motor types such as VCM (suspension wire, Reed, ball), SMA (shape memory alloy), Piezo (Piezoelectric), etc., and is suitable for different module designs.
3.3 integrated and discrete driver chip
Integrated OIS driver chip: Built-in MCU main control core, integrated gyroscope data processing, motor drive and algorithm, providing "single chip solution".
Awinic is electronic has two-channel drive AW86064CSR, which can meet the application of conventional vertical OIS (including suspension wire, shrapnel and ball):
Figure 3 AW86064 Product Block Diagram
Table 1 AW86064 product specifications
At the same time, Awinic has introduced high-precision, three-channel drive AW86068CSR to meet the application of telephoto teleconverter anti-shake/focus control:
Product Specifications:
64KByte Flash Memory
32Kbyte SRAM provides SDK to support customer secondary development and Awinic control scheme integration.
12.5MHz I3C high-speed communication interface
3x16bit high precision ADC
VM = 1.5V to 3.6V support dynamic voltage regulation
WLCSP3.555mmx1.255mmx0.3mm-27B
Figure 4 AW86068 product block diagram
Awinic is the OIS VCM drive scheme with the "shake cloud" algorithm as the core, through the deep integration of software and hardware, in the anti-shake accuracy, power consumption control, scene adaptation and other aspects of significant advantages. Its products cover a variety of forms from integrated to discrete, adapting to the diversified needs of mobile phones, PTZ, plug-in lenses, etc., and have become the preferred solution for head manufacturers such as mobile phones and industrial cameras,And continue to promote the localization of optical anti-shake technology breakthrough.
Discrete OIS control driver chip: improve the anti-shake precision and system flexibility, IC motor built-in, support with external processor cooperation, algorithm development.
Fig.5 Block diagram of AW86033A application scheme
Figure 6 AW86033A product block diagram
Table 2 AW86033A product specifications
4. SMA drive scheme (VCM alternative technology)
Shape memory alloy (SMA) as an emerging drive technology, by Ai for electronics to launch the first domestic drive chip, its program has a significant differentiation advantage:
Ultra-high thrust density: Single-wire SMA wire can generate 50gf thrust, and the 8-wire parallel scheme (supported by electronic chips) has a thrust of 400gf, which is 10 times that of VCM at the same level, and is suitable for driving ultra-telephoto Periscope units.
Thermal control innovation: The chip integrates 32bit ARM MCU(96MHz), stores the resistance-displacement curve at different temperatures through 128KB Flash, and realizes nonlinear compensation.
Ultra-thin structure: SMA wire thickness is only 0.1mm, which reduces the Z height of the module by 30%, and is suitable for the folding screen mobile phone design.
However, the SMA drive needs to meet the thermal management challenge: the Awinic chip uses Time-Division Multiplexing technology (Time-Division Multiplexing) to independently control the 8-wire SMA for PWM to avoid the response lag caused by concentrated heat. The program has landed mainstream flagship smartphone high-end imaging module,However, the focus speed is still about 15ms slower than that of the VCM (typical value is 40ms).
Figure 7 AW86100 product block diagram
5. Piezoelectric drive scheme (VCM alternative technology)
Piezoelectric drive technology is an innovative drive solution in the field of camera motors, and its core principle is based on the special physical properties of piezoelectric materials.
In camera module applications, piezoelectric motors serve two core functions: Autofocus (AF) and Optical Image Stabilization (OIS). As a focus Motor (AF Motor),It changes the relative position of the lens and the image sensor through precision displacement control to ensure that the subject forms a clear image on the sensor; As an anti-shake actuator, it compensates for the jitter effect of handheld devices by quickly fine-tuning the lens position. The working frequency of modern piezoelectric motors is usually designed above 20kHz (ultrasonic frequency band),It not only exceeds the audible range of the human ear to avoid noise interference, but also achieves higher energy conversion efficiency through high-frequency vibration.
Awinic has 8 channels of PWM output, 13Bit ADC AW86102FOR piezoelectric motor applications:
ARM 32-bit STARCU processor, equipped with FPU and DSP, frequency up to 96MHz,128KB flash memory, static random access memory: 64KB for program storage, 16KB for data storage, 8KB read-only memory.
Product Specifications:
Simulation: VAVDD = 2.6V to 3.6V,
Drive: VVM = 1.8V to 3.6V,
Input/Output: VIOVDD = 1.1V to 3.6V
Each PGA offset (8 channels, 10-bit DAC) can be independently adjusted PWM driver
Sigma-delta ADC(13Bit), configurable 12/14/16 bit resolution.
SPI (dual channel), configurable master/slave/monitor mode, support 3/4-wire bus configuration
I2C(2 channels), configurable master/slave mode.
Support I3C Slave devices and UART.
Supports hardware CORDIC with digital filters.
Figure 8 AW86102 Product Block Diagram
6. VCM scenario, Awinic is a long-term exploration of electronic all-round OIS solutions
In summary, the VCM driver chip scheme has formed a technical gradient of open loop → closed loop → OIS, while the SMA scheme achieves a differentiated breakthrough in special scenarios. Design selection needs to comprehensively consider the four-dimensional requirements of precision, speed, space and cost: the open-loop VCM still dominates the cost-effective market, and the closed-loop scheme meets the mainstream flagship demand,OIS chips help high-end image breakthroughs, while SMA drives serve ultra-thin high-thrust scenarios. With the maturity of multi-physics collaborative control algorithms, the next generation of driver chips will further integrate temperature compensation, vibration suppression and energy consumption optimization functions to promote the evolution of optical systems to higher integration.
In the long run, Awinic will continue to explore better solutions in VCM all-round control technology. Besides the products described in this article, AI Wei electronics will continue to invest in PWM control and advanced process to reduce the direction of substrate current, and continue to optimize the chip adaptation performance in the fields of smart wear, medical treatment, consumer electronics, end-side AI, etc,Create a complete motor drive solution.
To learn more about the selection of Awinic for VCM Driver products, please log on to Awinic for official website:
https://www.awinic.com
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