HDMI Switch Circuit Prevents Current Leakage in Power-Off State
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Solution Overview
Problem
In HDMI communication systems, connecting a sink device in a power-OFF state to a source device can lead to erroneous operations and inhibited video display due to the source device supplying TMDS signals to the sink device, causing current leakage and inability to recognize the sink device's EDID information.
Innovation Solution
The implementation of an electronic device with a connector having at least first and second pins, where a controller outputs a low-level hot-plug detection signal when the communication unit is inactive, preventing the source device from recognizing a connection in a power-OFF state and thus avoiding current leakage and ensuring accurate EDID information acquisition upon power ON.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If the sink device outputs hot-plug detection signal of +5V when power is OFF, then the source device can read EDID information from nonvolatile memory, but current leakage occurs and erroneous operations happen
Solution Approach 1:
The switch circuit is configured to automatically prevent hot-plug detection signal output when power is OFF, before any signal transmission can occur. This preliminary protective action blocks the harmful current leakage pathway at the source, allowing EDID information to be safely stored in nonvolatile memory without risking erroneous operations in the sink device.
2Reliability
If the sink device outputs hot-plug detection signal of +5V when power is OFF, then connection recognition is enabled, but TMDS signal transmission causes current leakage
Solution Approach 1:
The switch circuit acts as an intermediary control mechanism between power state and hot-plug detection signal output. It monitors the power state and selectively enables or disables the hot-plug detection signal pathway, ensuring that signal transmission only occurs when power is ON, thereby preventing current leakage while maintaining connection recognition functionality.
3Ease of operation
If the sink device is always ready to receive signals, then video display capability is maintained, but accidental operations occur when power is OFF
Solution Approach 1:
The system dynamically adjusts its operational state based on power status. The switch circuit enables the hot-plug detection signal output only when power is ON, creating a dynamic on/off state that matches the power supply condition. This ensures the sink device is ready to receive and display video signals when powered, while automatically preventing accidental operations when power is OFF.
Data Source
AI summary
This electronic device includes connector to which an external device is connected via a communication cable, controller, and output unit. Connector includes at least first and second pins. A predetermined voltage is supplied from the external device to the first pin. Controller includes a communication unit to which a signal is input from the external device via a pin other than the first and second pins of connector, and outputs, when the communication unit is in an activated state, a first signal indicating the activated state. Output unit outputs, when the first signal has not been output, a detection signal indicating that a connection has not been established with the external device to the external device via the second pin.