Source Driver Abnormal Detection Circuit for Display Apparatus
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Solution Overview
Problem
In display apparatuses that drive data lines in a time divisional manner, a time difference in operation timing between driver ICs can cause flow-through currents, leading to electromagnetic interference (EMI) noise.
Innovation Solution
A display apparatus with a source driver configured from multiple driver ICs, where each IC includes an output buffer with complementary P-channel and N-channel transistors, and an abnormal detection circuit to synchronize the operation of these buffers, preventing flow-through currents by adjusting the timing of the switching signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple driver ICs are arranged along the extending direction of gate lines to drive a plurality of data lines in a time divisional manner, then the chip area can be suppressed, but flow-through current occurs between the buffers of the left end driver IC and the right end driver IC due to time difference in operation timing
Solution Approach 1:
The abnormal detection circuit proactively detects the timing difference between the left end driver IC and right end driver IC buffers before the flow-through current fully develops. By detecting the state where PMOS and NMOS are simultaneously ON in either buffer, the system can take preliminary corrective action to prevent the harmful flow-through current from occurring, thus resolving the contradiction between maintaining compact chip area and eliminating flow-through current.
Solution Approach 2:
The abnormal detection circuit continuously monitors the operation state of both buffers and provides feedback about timing differences. This feedback mechanism allows the system to detect when the buffers are not operating complementarily (i.e., when both PMOS and NMOS are simultaneously ON in either buffer) and can respond by adjusting the timing or disabling affected buffers, thereby preventing flow-through current while maintaining the time-divisional driving architecture that keeps chip area small.
2Adaptability or versatility
If the buffers of the left end driver IC and the right end driver IC operate with time difference due to signal delay, then the system can handle video signal variations, but electromagnetic interference (EMI) noise occurs due to flow-through current
Solution Approach 1:
The abnormal detection circuit provides continuous feedback on the operational state of both buffers, monitoring for conditions where timing differences cause both PMOS and NMOS to be simultaneously ON. This feedback enables the system to identify when EMI-generating flow-through current is occurring while maintaining the adaptability to handle video signal variations, as the detection circuit can distinguish between acceptable timing variations and harmful simultaneous conduction states.
Solution Approach 2:
The invention converts the potentially harmful timing difference phenomenon into a detectable signal that can be used to prevent EMI. By detecting the abnormal state where timing differences cause simultaneous PMOS and NMOS conduction, the system can then adjust or disable the affected buffer, transforming what would be a source of EMI noise into a controlled condition that actually improves overall system reliability and reduces electromagnetic interference.
Data Source
AI summary
A display apparatus includes a plurality of source drivers outputting a gradation voltage signal and a selector switchably supplying the output gradation voltage signal to a plurality of data lines. The plurality of source drivers include a first source driver that has a first output buffer outputting a switching signal and a second source driver that has a second output buffer. The first output buffer has first and second transistors coupled via output terminals of the switching signal and turned ON and OFF complementarily. The second output buffer has third and fourth transistors coupled via output terminals of the switching signal and turned ON and OFF complementarily. The first and the second output buffers have the output terminals electrically coupled, and the first source driver has an abnormal detection circuit detecting a state causing a flow-through current to occur between the output terminals.