USB interface charging circuit

Abstract

Embodiments of the invention provide a USB interface charging circuit, and relates to auto parts. The circuit can compensate for charging voltages according to USB line losses so that the voltage dropcaused by the line losses can be compensated for, and thus, the USB charging voltages can accord with related certification rules. The circuit includes a voltage dividing resistor, a voltage detection unit, a CPU and a PWM voltage modulation module; the control end of the PWM voltage modulation module is connected to the PWM end of the CPU; the input end of the PWM voltage modulation module is connected to the input end of a power supply; the output end of the PWM voltage modulation module is connected to the first end of the voltage dividing resistor; and the PWM voltage modulation module isused for receiving a PWM control signal, and adjusts the duty ratio of the conducting time of the input end and output end of the PWM voltage modulation module according to the PWM control signal soas to adjust the voltages output by the power supply pins of a USB interface. The embodiment of the invention is used for the USB interfaces.

Description

technical field [0001] Embodiments of the present invention relate to the field of electronic technology, in particular to a USB interface charging circuit. Background technique [0002] In recent years, in-vehicle USB (Universal Serial Bus, Universal Serial Bus) charging has become more and more widespread. The system structure using USB charging is as follows: figure 1 As shown, the main power supply B / U supplies power to the USB power management module, the CPU (Central Processing Unit, central processing unit) controls the USB power management module to supply power to the USB interface, and the USB interface charges the connected external device (through the power lead of the USB interface Pin VBUS and ground pin GND), in order to realize the USB charging function. In addition, the USB interface can also send the received differential data signal (transmitted through the differential signal pins D+ and D-) to the CPU for processing. For the USB charging function, due...

AI Technical Summary

Problems solved by technology

In addition, because the sampling resistor of the USB power supply has a deviation, the output voltage also has a deviation, and the output voltage setting is close to the specification limit value. If the output voltage is slightly higher, it will not meet the requirements of the certification rules during the mass production load inspection.

[0007] In short, the prior art cannot provide a USB interface charging circuit that fully meets the requirements of the certification rules

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