Imaging Driver Circuit With Stepped Voltage Switching for Lower Power
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Solution Overview
Problem
Existing driver circuits for imaging devices face high power consumption issues due to the need for step-up and step-down circuits to output voltages beyond the power supply and ground potential, which hinders high integration and increases thermal design challenges.
Innovation Solution
A driver circuit configuration that includes step-up and step-down switches to sequentially select voltages in ascending and descending order, respectively, dispersing the load for charging and discharging, along with control circuits to manage these switches based on a trigger signal, and incorporates a capacitor for current supply and bias circuits for voltage and current control within transistor withstand limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a step-up circuit and step-down circuit are used to output voltages higher than power supply voltage or lower than ground potential, then drive capability is improved, but power consumption increases
Solution Approach 1:
The drive signal is precharged to the power supply voltage before the rising edge transition, and predischarged to ground potential before the falling edge transition. This preliminary action reduces the voltage swing required from the step-up and step-down circuits, thereby reducing their power consumption while maintaining the necessary drive capability.
Solution Approach 2:
The voltage transition process is segmented into distinct phases: precharging phase, rising edge phase, predischarging phase, and falling edge phase. Each phase is controlled by specific control signals that activate particular switches, allowing the step-up and step-down circuits to operate only when necessary rather than continuously, thus reducing overall power consumption.
2Power
If gate-to-source voltage is increased to improve drive capability, then current flowing between source and drain increases, but this requires additional voltage generation circuits
Solution Approach 1:
The step-up circuit and step-down circuit serve multiple functions: they generate the necessary voltage swings for drive signal transitions, and they enable the driver circuit to operate with reduced power consumption by working in conjunction with the precharging and predischarging mechanisms. This multi-functionality reduces the need for additional dedicated circuits.
3Power
If step-up circuit and step-down circuit are used to achieve high drive capability, then thermal design becomes more challenging
Solution Approach 1:
By precharging the drive signal to the power supply voltage before rising edges and predischarging to ground potential before falling edges, the energy that would otherwise be dissipated as heat during large voltage swings is reduced. This preliminary action minimizes the power consumption of the step-up and step-down circuits, thereby improving thermal design.
4Reliability
If voltage swing is maximized for optimal pixel driving, then power consumption of voltage generation circuits increases
Solution Approach 1:
The voltage transition is segmented into precharging, rising edge, predischarging, and falling edge phases. During precharging and predischarging, local capacitors store energy at intermediate voltage levels, allowing the step-up and step-down circuits to operate only during the actual transition edges. This segmentation maintains optimal voltage swings for pixel driving while reducing the duration and intensity of power consumption.
Data Source
AI summary
To reduce power consumption of a driver circuit used in a vertical drive circuit of an image processing device.In the driver circuit, a drive signal output circuit outputs a drive signal in accordance with a predetermined trigger signal. Furthermore, at a time of rising of the drive signal, a step-up switch sequentially selects a plurality of voltages in ascending order, and supplies the selected voltage to the drive signal output circuit. Moreover, at a time of falling of the drive signal, a step-down switch sequentially selects a plurality of voltages in descending order, and supplies the selected voltage to the drive signal output circuit.