Image Signal Input Circuit Without External Capacitor
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Solution Overview
Problem
Conventional image signal input circuits require a capacitor to hold sink chip voltage constant, which is impractical for downsized electronic devices due to space constraints and circuit size reduction needs.
Innovation Solution
An image signal input circuit with a clamp function that includes a clamp circuit, a level shift circuit, and an electric current source, allowing direct connection to a previous stage device without an external capacitor, by using transistors and current sources to maintain sink chip voltage at a predetermined value, including a protection circuit for voltage protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a capacitor is used to hold sink chip voltage constant, then voltage stability is improved, but circuit size increases
Solution Approach 1:
The invention extracts the voltage holding function from the capacitor and implements it through an active clamp circuit using transistors Q1 and Q2. The capacitor is removed from the circuit entirely, with its voltage holding function replaced by the transistor-based clamp circuit that actively maintains the sink chip voltage at a predetermined level through feedback control.
Solution Approach 2:
The invention replaces the passive capacitor-based voltage holding mechanism with an active electronic control system using transistors. The clamp circuit uses transistor Q1 as a switch controlled by transistor Q2, creating an active feedback system that dynamically maintains voltage stability instead of relying on passive capacitor storage.
2Stability of the object's composition
If an external capacitor is mounted for connection, then voltage holding function is achieved, but device compactness is reduced
Solution Approach 1:
The invention merges the voltage holding function into the driver IC itself by integrating the clamp circuit with transistors Q1 and Q2 directly in the chip. This eliminates the need for external capacitors and allows direct connection to previous stage devices, achieving both voltage stability and device compactness through functional integration.
Solution Approach 2:
The driver IC becomes self-sufficient by incorporating the clamp circuit internally. The circuit uses its own transistors Q1 and Q2 to maintain sink chip voltage without requiring external passive components, making the device independent and compact while maintaining voltage stability functionality.
3Stability of the object's composition
If a clamp circuit with transistor is used, then sink chip voltage is held constant, but circuit complexity increases
Solution Approach 1:
Transistor Q1 serves multiple functions: it acts as a switch for voltage holding, a current amplifier, and part of the feedback control system. Transistor Q2 controls Q1's operation while also providing biasing. This multi-functionality reduces the need for additional components, maintaining voltage stability without proportionally increasing circuit complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables the direct connection of the image signal input circuit to a previous stage device without an external capacitor, maintaining sink chip voltage stability and reducing circuit size, while providing protection against disruptive voltages.
Implementation Method 1
the capacitor C1 receives an electric charge from the power source Vcc via the transistor Q1. Then, the sink chip voltage rises
Data Source
AI summary
An image signal input circuit includes an input terminal configured to receive an image signal, a clamp circuit configured to hold a sink chip voltage contained in the image signal to be a constant value, a level shift circuit that includes a first emitter follower having a first transistor and a first current source, and a second emitter follower having a second transistor and a second current source, a base of the second transistor being connected to an emitter of the first transistor, and that is configured to shift a level of the sink chip voltage which is held constant, and an electric current source configured to attract a base current of the first transistor.