Universal Serial Bus (USB) port is a power and ground with a bi-directional data port. USB can connect Laptop Battery all types of peripherals, including external drives, storage devices, keyboard, mouse, wireless interfaces, video and still cameras, MP3 players and the countless variety of electronic equipment. Many of these devices use battery-powered, some with built-in battery. For battery charging design, the application of a wide range of USB brings both opportunities and challenges. This paper describes how a simple battery charger with the USB power source interface. Article reviews the USB power bus characteristics, including voltage, current limit, inrush current, connectors and cable connection problem. At the same time introduced a nickel-metal hydride batteries (NiMH) and lithium battery technologies, charging methods, and charge termination techniques. Gives a complete example of circuit used to implement USB port for charging NiMH batteries intelligent, and gives the charging data.
Overview
Universal Serial Bus (USB) port is a power and ground with a bi-directional data port. USB can connect all types of peripherals, including external drives,C1295 laptop battery storage devices, keyboard, mouse, wireless interfaces, video and still cameras, MP3 players and the countless variety of electronic equipment. Many of these devices use battery-powered, some with built-in battery. For battery charging design, the application of a wide range of USB brings both opportunities and challenges. This paper describes how a simple battery charger with the USB power source interface. Article reviews the USB power bus characteristics, including voltage, current limit, inrush current, connectors and cable connection problem. At the same time introduced a nickel-metal hydride batteries (NiMH) and lithium battery technologies, charging methods, and charge termination techniques. Gives a complete example of circuit used to implement USB port for charging NiMH batteries intelligent, and gives the charging data.
USB Features
USB bus can provide power to low-power dell laptop battery electronic devices. Bus-power and power isolation, and has very good stability. However, the available current is limited, while the host or power between the load and there is a potential interoperability problems.
Two-way USB port from 90Ω differential shielded twisted-pair, VBUS (+5 V power supply), and constituted. This is four lines from the aluminum foil and braid shield within the outer shield layer shielding. The latest USB specification version 2.0 standard is available from USB organizations for free. To achieve full compliance with the normative standards, through a functional device and the host controller to achieve two-way communication between the. Specification defines a unit load as 100mA (max). Any equipment allowed to draw the maximum current of 5 units of the load.
USB ports can be divided into low-power port and power port into two categories, low-power port can provide a unit load of current, 1X793 laptop battery high-power port provides up to five units of the load current. When the device is connected to the USB port, the device enumeration process to identify and determine its load requirements. In this process, only to allow the device from the host draw up a unit load of current. Enumeration process is complete, if the host's power management software allows, then the high-power devices can draw a larger current.
Some host systems (including downstream USB hub) through fuses or active current limit detector provides workflow features. If the USB device is not USB port through the enumeration process begins with drawing large currents (more than one unit load), then the host will detect over-current condition and will be closed are using one or more USB ports. The market supply of a number of USB devices, including independent battery charger, do not function controller to handle enumeration process, but the current draw is more than 100mA. In this inappropriate conditions, these devices may cause the host problem. For example, if a drawing 500mA current device into a bus-powered USB hub, and did not correct the enumeration process, it may lead to the hub port and host port 6Y270 laptop battery at the same time overload.
The host operating system, using advanced power management of the situation will be even more complicated, especially notebook computers, it is always hoped that the port currents as low as possible. In some power-saving mode, the computer will suspend issuing commands to the USB device and then think that equipment into a low-power mode. Equipment can be included in a function to communicate with the host controller is always a good practice, even for the same is true for low-power devices.
USB 2.0 specification is very comprehensive and provides for the quality of power supply, connectors, construction, cable material, allowing the voltage drop and inrush current. Low current and high-current power supply port with a different target. This was mainly by the host and the load between the connectors and cable voltage drop on the decision, and includes USB-powered hub to generate voltage drop. Including computer, or self-powered USB hub, including the host, have large 312-0068 laptop battery current port, which provides maximum 500mA of current. Passive, bus-powered USB hub with a low current port. Table 1 shows the high current and low-current USB ports upstream side (power) pin allows the voltage tolerance.
These indicators apply to the upstream end of the host or hub port connector pins. Cables and connectors on the I x R drops need to be considered separately.
Subject to the host USB 2.0 specification, high-power port with the upstream end of 120μF, low ESR capacitors. The connected USB device input capacitance of 10μF or less limited to, in the initial stage of the load connected, allowing the load from the host (or self-powered hub) to draw the maximum charge number of 50μC. As a result, when the new device is connected to the USB port, the upstream port transient voltage drop is less than 0.5V. If the normal work load required a greater input capacitance, you must provide inrush current limiter, in order to ensure Latitude D610 laptop battery a larger capacitor charging current does not exceed 100mA.
When the USB port with a bus-powered USB hub, hub on the access of low-power device, USB port on a permissible DC voltage drop shown in Figure 1. High-power loads and bus-powered hub connection, the voltage drop will exceed the target given in Figure 1, and will cause the bus overload.
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