Voltage Generation Circuit for LCD AVDD Stability
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Solution Overview
Problem
Current liquid crystal display devices face significant voltage drop and ripple issues in the analog voltage AVDD due to increasing load, leading to overheating of the source driver and instability in reference voltage generation.
Innovation Solution
A voltage generation circuit comprising a buck circuit and a double boost charge pump circuit, which generates an auxiliary voltage to reduce the voltage difference between AVDD and reference voltage Vref, utilizing a PMOS transistor and diodes to stabilize the output and connect to a low dropout linear regulator or precision voltage stabilizing source for precise voltage generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a boost circuit is used to generate analog voltage AVDD, then voltage conversion capability is improved, but voltage drop and ripple increase under heavy load
Solution Approach 1:
The voltage generation system is divided into two independent parts: a boost circuit for generating AVDD and a buck circuit for generating Vref. This segmentation allows each circuit to be optimized for its specific function, with the buck circuit providing stable reference voltage unaffected by the boost circuit's load variations.
Solution Approach 2:
The patent introduces a separate buck circuit as an intermediary to generate the reference voltage Vref independently from the boost circuit. This intermediary circuit isolates the reference voltage generation from the heavy load effects on the boost circuit, ensuring stability.
2Reliability
If a large voltage difference is maintained between AVDD and Vref, then reference voltage stability is improved, but source driver overheating increases
Solution Approach 1:
By segmenting the voltage generation into separate boost and buck circuits, the patent enables the reference voltage to be generated at an appropriate level without requiring a large voltage difference, thus reducing power loss and heat generation in the source driver while maintaining stability.
Solution Approach 2:
The patent changes the generation method of reference voltage from being derived from AVDD through LDO to being generated independently by a buck circuit. This parameter change allows Vref to be generated at the optimal voltage level, reducing the voltage difference and associated heat generation.
3Device complexity
If analog voltage AVDD is used to generate reference voltage Vref through LDO, then circuit simplicity is improved, but voltage ripple affects reference voltage stability
Solution Approach 1:
The patent introduces a buck circuit as an intermediary specifically for reference voltage generation. Although this adds a circuit component, it effectively isolates the reference voltage from the ripple and instability of the boost circuit output, significantly improving reliability.
Solution Approach 2:
The patent changes the input voltage parameter for the reference voltage generation from AVDD (which has ripple) to the output of a buck circuit (which provides stable voltage). This parameter change fundamentally improves reference voltage stability despite increased 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
This solution reduces power consumption and temperature effects while maintaining stable reference voltage output, unaffected by load changes, and does not require changes to existing chip applications.
Implementation Method 1
When the first switching transistor Q1 is closed, the first inductor L1 converts the electric energy into a magnetic energy and stores the magnetic energy. When the first switch Q1 is turned off, the first inductor L1 converts the stored magnetic energy into electric energy
Implementation Method 2
the first inductor L1 converts the stored magnetic energy into electric energy, and superimposed with the input voltage VIN through the first diode
Implementation Method 3
a third capacitor C3 and a fourth capacitor C4, the third capacitor C3 and the fourth capacitor C4 are connected in parallel between the digital voltage output terminal and the ground
Data Source
AI summary
A voltage generation circuit is disclosed. The circuit includes: a buck circuit and a charge pump circuit; the buck circuit includes a second switching transistor, a second diode for freewheeling and a second inductor for storing energy, wherein a first end of the second switching transistor is connected to an input voltage, a second end is connected to a cathode of the second diode, a control end is connected with a control signal; an anode of the second diode is connected to a ground; a first end of the second inductor is connected to the cathode of the second diode, a second end is connected to a digital voltage output terminal; the cathode of the second diode is connected to the charge pump circuit, voltage on the cathode of the second diode is outputted as an auxiliary voltage for generating a reference voltage after boosted by the charge pump circuit.