Charge Pump Circuit Precharge Mechanism for Low Output Impedance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The inefficiency of charge-pump circuits in semiconductor devices leads to high output resistance and increased power consumption, particularly in liquid crystal drivers, where higher resolution and touch detection functions require higher electric current, necessitating a reduction in output impedance without increasing transistor size.
Innovation Solution
Incorporating a precharge circuit that precharges the stabilization capacitance to the third voltage before the voltage-boosting operation, allowing the charge pump to alternately switch capacitive electrodes between first and second voltages, thereby reducing the on-resistance of MOS switch circuits and achieving a lower output impedance without increasing transistor size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-voltage MOS switch circuits are used to achieve the required withstand voltage, then the withstand voltage requirement is met, but the on-resistance increases and transistor size must be increased
Solution Approach 1:
The voltage boosting function is divided into two independent stages: a first voltage boosting circuit that boosts the first voltage to a second voltage, and a second voltage boosting circuit that boosts the third voltage to a fourth voltage. Each stage uses MOS switch circuits with withstand voltages matched to their specific requirements, avoiding the need for high-voltage MOS switches in the first stage.
Solution Approach 2:
A capacitor is introduced as an intermediary element between the two voltage boosting circuits. This capacitor stores the boosted second voltage and enables the second voltage boosting circuit to function, allowing the system to achieve high output voltage without requiring all MOS switches to withstand the maximum voltage.
2Loss of energy
If transistor size is increased to reduce on-resistance, then the on-resistance decreases, but the chip area increases
Solution Approach 1:
The voltage boosting function is divided into two independent stages: a first voltage boosting circuit that boosts the first voltage to a second voltage, and a second voltage boosting circuit that boosts the third voltage to a fourth voltage. Each stage uses MOS switch circuits with withstand voltages matched to their specific requirements, avoiding the need for high-voltage MOS switches in the first stage.
3Device complexity
If conventional charge-pump circuit configuration is used, then the circuit structure is simple, but the output impedance is high and power consumption is excessive
Solution Approach 1:
The voltage boosting function is divided into two independent stages: a first voltage boosting circuit that boosts the first voltage to a second voltage, and a second voltage boosting circuit that boosts the third voltage to a fourth voltage. Each stage uses MOS switch circuits with withstand voltages matched to their specific requirements, avoiding the need for high-voltage MOS switches in the first stage.
Solution Approach 2:
The charge pump circuit alternately switches a capacitive electrode of one of pumping capacitances between first and second voltages and in parallel, periodically applies a third voltage to a capacitive electrode of the other pumping capacitance. The charge-pump circuit lifts up the third voltage thus applied each time the input of the pumping capacitance is switched from the first voltage to the second voltage, thereby successively supplying the resultant boost voltage to a stabilization capacitance through an output MOS switch circuit.
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 approach effectively lowers the output impedance of charge-pump circuits, reducing power wastage and enabling more efficient voltage boosting while maintaining a compact chip size, applicable to various driver ICs including liquid crystal drivers.
Implementation Method 1
a charge-pump circuit alternately switches a capacitive electrode of one of pumping capacitances between first and second voltages and in parallel, periodically applies a third voltage to a capacitive electrode of the other pumping capacitance. The charge-pump circuit lifts up the third voltage thus applied each time the input of the pumping capacitance is switched from the first voltage to the second voltage
Data Source
AI summary
The booster precharges a boost-voltage-output terminal to a predetermined voltage before voltage-boosting start by a charge-pump circuit in the booster. While alternately switching one capacitive electrode of a pumping capacitance between first and second voltages, the charge-pump circuit periodically applies a third voltage to the other capacitive electrode, in which the voltage is boosted by lifting up the third voltage each switching. The resultant boost voltage is successively supplied to a stabilization capacitance through a MOS switch circuit for output. Thus, a boost voltage boosted to a sum voltage of the second and third voltages can be obtained. Using a precharge voltage produced by the precharge circuit in the booster as the third voltage can make a MOS switch circuit operable to supply the third voltage and the MOS switch circuit for boost voltage output smaller than a voltage under the sum voltage of the second and third voltages.