PMOS Interface Circuit for Power Backflow Blocking
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Solution Overview
Problem
Current backflow of power from a normally powered device to a powered-off device through an interface circuit results in increased power consumption and failure to properly power off the device, as seen in scenarios like a TV powering back current to a set-top box via HDMI.
Innovation Solution
An interface circuit incorporating a PMOS transistor, input signal control circuit, and bias circuit, which controls the PMOS transistor to be in a reverse bias state to prevent current backflow by managing the connection and conduction between power supply and substrate bias voltage generation ends, ensuring normal operation or preventing voltage backflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a simple interface connection is used between host device and self-powered device, then ease of operation is improved, but current backflow occurs causing increased power consumption and failure to power off
Solution Approach 1:
The patent introduces a protection circuit as an intermediary component between the interface circuit and the self-powered device. This protection circuit includes a control circuit that detects power supply states and controls a switching element to open or close, thereby preventing current backflow while maintaining normal interface operations. The switching element acts as a mediator that can block current flow in one direction while allowing normal signal transmission.
2Loss of energy
If a protection circuit is added to prevent current backflow, then power consumption is reduced, but device complexity increases
Solution Approach 1:
The patent combines the protection function with the existing interface circuit by integrating the control circuit and switching element into the interface circuit structure. The control circuit monitors the power supply voltage and controls the switching element to prevent current backflow, merging the protection function with the interface circuit rather than adding a completely separate protection device.
Solution Approach 2:
The control circuit automatically detects the power supply state and controls the switching element without requiring external intervention. When the power supply voltage drops below a threshold (indicating the self-powered device is off), the control circuit automatically opens the switching element to prevent current backflow, making the protection mechanism self-regulating.
3Adaptability or versatility
If the interface circuit allows bidirectional current flow for normal operation, then adaptability is improved, but current backflow to powered-off device occurs
Solution Approach 1:
The patent makes the interface circuit dynamically adaptive by using a controllable switching element whose state changes based on power supply conditions. The switching element can be in a closed state during normal operation to allow bidirectional current flow, and automatically transitions to an open state when current backflow is detected, providing dynamic protection while maintaining operational flexibility.
Data Source
AI summary
An interface circuit, a method for controlling the interface circuit, a chip, and a terminal device are provided. The interface circuit includes a first PMOS transistor, an input signal control circuit, a bias circuit, a signal input end, and an input/output end. The bias circuit includes a substrate bias voltage generation end and a bias voltage generation end. The bias circuit is coupled to a high-level power supply end, the input/output end, and a ground end. The input signal control circuit is connected to the signal input end, the bias voltage generation end, and a gate of the first PMOS transistor; a first electrode of the first PMOS transistor is connected to the high-level power supply end, and a second electrode of the first PMOS transistor is connected to the input/output end.