Reference Voltage Generator Dynamic Switching for Noise and Power
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Solution Overview
Problem
Existing band-gap reference circuits for liquid crystal drivers in mobile devices face challenges in maintaining stable reference voltage during normal operation while minimizing current consumption in standby mode, with insufficient power supply noise rejection leading to degraded display quality.
Innovation Solution
A reference voltage generator with a switchable configuration that uses a constant current source in standby mode for low current consumption and an output transistor in normal operation mode for high noise resistance, allowing the circuit to adapt between Pch and Nch driving types based on operational states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a band-gap reference circuit is used to ensure stable reference voltage output, then the stability of output voltage is improved, but current consumption increases during standby mode
Solution Approach 1:
The patent implements dynamic switching between two operational modes (first mode with Pch driving type and second mode with Nch driving type) based on the state of the liquid crystal display driver. This allows the reference voltage generator to adapt its characteristics - achieving low current consumption during standby while maintaining stable output voltage during normal operation, thus resolving the contradiction between reliability and energy use
2Device complexity
If a conventional BGR circuit configuration is used, then the circuit scale is reduced, but power supply noise rejection ratio deteriorates
Solution Approach 1:
The patent dynamically switches between Pch driving type and Nch driving type based on operational requirements. The Nch driving type provides high power supply noise rejection ratio, while the Pch driving type maintains compact circuit scale. This dynamic adaptation resolves the contradiction between device complexity and resistance to harmful factors
Solution Approach 2:
The patent changes the driving type parameter (Pch/Nch) of the reference voltage generator based on operational state. By switching the type of transistor used for driving (PMOS or NMOS), the circuit characteristics are changed to optimize for either noise rejection or circuit scale, thus resolving the contradiction between these two parameters
3Reliability
If the reference voltage generator operates in high stability mode during normal operation, then output voltage stability is improved, but current consumption increases during standby mode
Solution Approach 1:
The patent implements dynamic mode switching between first mode (Pch driving) and second mode (Nch driving) based on whether the liquid crystal display driver is in standby or normal operation. During standby, the circuit operates in a mode optimized for low power consumption, while during normal operation it switches to a mode optimized for output voltage stability, thus resolving the contradiction between reliability and energy use by stationary object
Data Source
AI summary
A reference voltage generator includes an output terminal, a load circuit connected between the output terminal and a ground voltage terminal, an output transistor connected between the output terminal and a power supply voltage terminal, a first constant current source connected between the output terminal and the power supply voltage terminal, a first switch circuit that selectively connects the output terminal with the output transistor or the first constant current source, and a control circuit that controls a band-gap current to be supplied to the load circuit. In a first state, the first switch circuit connects the output terminal with the output transistor, and the control circuit controls an activation state of the output transistor. In a second state, the first switch circuit connects the output terminal with the first constant current source, and the control circuit controls the amount of current drawn from the first constant current source.