Home > Power Circuits > Electric bicycle power control technology

Electric bicycle power control technology

Source: InternetPublisher:傻阿乐 Keywords: power control bicycle Updated: 2021/11/20

Many people are interested in bicycles, so do you know what electric bicycle power control technology is? Around the world, environmental issues are becoming more and more important. Global warming, natural resource scarcity and pollution are issues of heightened sensitivity to institutions, manufacturing companies and ordinary citizens. In this context, electromobility (e-mobility) represents an effective solution to many of the above problems. In particular, electric bicycles (e-bikes) represent an economical, versatile and agile mode of transportation, providing a green alternative to vehicles based on traditional internal combustion engines. Although e-bikes available on the market have completely different technical characteristics and methods of use, there are a few key components present in every e-bike: an electric motor, a battery, a power control circuit, and a set of sensors and actuators to manage vehicle operation. .

The power control system is one of the most important and challenging components of the entire system and therefore requires precise design. Its main functions include the control of the electric motor under each operating condition (changes in road gradient, weight of the load, speed of movement), detection of overvoltage, undervoltage and overcurrent conditions and critical components (such as batteries and power supply equipment) . All functions listed must be performed to ensure maximum vehicle safety. Analysts agree in predicting substantial growth in the e-bike market over the next few years. Efficiency will once again be one of the main factors driving the development of power control systems: high efficiency means longer battery life, longer driving range and lower operating costs.

Electric bicycle power control technology

Electric bicycle power structure

The general electric bicycle power supply architecture is shown in Figure 1. Depending on the specific e-bike model, a direct current (DC) or alternating current (AC) motor can be used. DC motors are controlled using pulse width modulation (PWM) technology, while AC motors require variable frequency. Due to its advantages, the most commonly used motor on e-bikes is the brushless DC motor (BLDC). Brushless DC motors are synchronous motors in which the magnetic fields produced by the stator and rotor have the same frequency. These motors are particularly robust, require no maintenance and guarantee high durability (as the name suggests, they have no brushes). In addition, BLDC motors provide high torque values ​​immediately, reduce power losses, and have high no-load speeds. BLDC motors can be configured as 1-phase, 2-phase or 3-phase schemes. For e-bike applications, the most common configuration is three-phase.

Unlike brushed DC motors, BLDC motors have the advantage of electronic control. Motor rotation is achieved by providing electrical signals generated according to appropriate sequences (waveforms) to the stator windings. The position of Tt must always be known to produce the correct activation sequence, and for this purpose Hall effect sensors (three sensors in the case of a three-phase configuration) are placed on the stator. Recently, sensorless technology is also gaining ground, where the complexity moves from the hardware side (simpler motors can be used) to the software side (more complex algorithms are required). As shown in Figure 1, the power architecture of an electric bicycle includes multiple power devices, such as power MOSFETs for motor control and DC-DC buck converters used in the power supply and power conversion sections.

Regarding batteries, from the first e-bike models using sealed lead-acid (SLA) batteries to the latest versions based on lithium-ion (Li-ion) batteries, we have seen lighter batteries, but improvements are needed. More complex electronic circuits. The increase in battery voltage (nominal voltage up to 54V) also requires the introduction of electronic protection circuits. The latest version of the e-bike power control unit achieves such low weight and size that it can even be accommodated within the frame or under the seat. All electronic components must be selected or designed with special attention to efficiency, space and heat dissipation. For example, consider that increasing efficiency from 80% to 90% increases autonomy by 12.5% ​​and reduces heat dissipation by 50%.

DC-DC converter

The DC-DC converter is the main component of any e-bike control system. Their job is to convert the energy provided by the battery to provide the required voltage and current to the rest of the circuit. Analog Devices, Inc. is a market leader in the design and manufacturing of analog, mixed-signal and DSP integrated circuits, offering the broadest selection of simple, compact inductorless DC-DC converters. By eliminating the inductor, this charge pump family can be used to step up, step down, or invert input voltages. ADI's LTC7821 is based on a proprietary architecture that combines a soft-switching charge pump topology with a synchronous step-down dc-to-dc converter to provide superior efficiency. Using an input voltage VIN of 10V to 72V and a switching frequency of 200kHz to 1.5MHz, the LTC7821 can achieve greater than 97% efficiency. Maxim Integrated also offers a variety of DC-DC converters.

One example is the Maxim MAX17503, which is a 4.5V to 60V, 2.5A, high-efficiency, synchronously rectified step-down DC-DC converter. The power solution operates at a switching frequency of 470 kHz and provides 86.5% power conversion efficiency (VIN = 36V, VOUT = 5V at 2A). Texas Instruments (TI) also offers a variety of motor drivers. Some devices require external FETs, while others have internal power transistors. The DRV8350 is a 9V to 100V triple half-bridge highly integrated gate driver that greatly simplifies the design of three-phase BLDC motor applications, including field-oriented control (FOC), sinusoidal current control and trapezoidal current control. Device variants offer optional integrated current shunt amplifiers to support different motor control schemes and a buck regulator to power gate drivers or external controllers. A simplified schematic of the device is shown in Figure 2 and can be effectively used to support e-bike, e-scooter and electric vehicle applications.

Power Integrations provides power conversion ICs that provide efficient, reliable and low-cost solutions for a variety of power applications up to 600W, including e-bikes. TOPSwitch-JX is PI's latest flagship AC-DC converter series. TOPSwitch-JX integrates a 725V power MOSFET, high-voltage switching current source, multi-mode PWM control, oscillator, thermal shutdown circuit, fault protection and other control circuits on a single device. The device is energy efficient over the entire load range and consumes less than 100mW no-load power at 265 VAC, making it ideal for 10W to 245W applications, such as power supplies for e-bike battery chargers. The above is the power control technology of electric bicycles. I believe that bicycles will become smart in the future.

EEWorld
subscription
account

EEWorld
service
account

Automotive
development
circle

About Us Customer Service Contact Information Datasheet Sitemap LatestNews


Room 1530, 15th Floor, Building B, No.18 Zhongguancun Street, Haidian District, Beijing, Postal Code: 100190 China Telephone: 008610 8235 0740

Copyright © 2005-2024 EEWORLD.com.cn, Inc. All rights reserved 京ICP证060456号 京ICP备10001474号-1 电信业务审批[2006]字第258号函 京公网安备 11010802033920号