Charge-Pump LDO In-Rush Current Control via Pre-Charge Path
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Solution Overview
Problem
Conventional charge pump regulators are inefficient and costly for mobile communication devices, as they struggle to generate multiple voltage reference levels and smoothly transition between them in a power-efficient and reliable manner, particularly for components like Class-G amplifiers, and suffer from high in-rush currents during LDO mode operation.
Innovation Solution
A charge-pump low-dropout (LDO) regulator with in-rush current control is implemented, utilizing a comparator, pass transistor, and pre-charge switches to pre-charge capacitive loads to a lower voltage level, reducing the in-rush current by allowing the capacitive load to charge through a pre-charge path during the pre-charge mode, thereby minimizing the need for large switches and wider metallization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional charge pump regulators are used to generate multiple voltage reference levels, then the device complexity and cost increase, but the ability to provide multiple supply voltages for components like Class-G amplifiers is insufficient
Solution Approach 1:
The charge pump regulator is designed to perform multiple functions by generating different voltage reference levels (first and second voltage references) using a single device. The regulator can selectively charge capacitors to different voltage levels and provide these multiple references to different components, eliminating the need for separate regulators for each voltage level.
Solution Approach 2:
The regulator dynamically transitions between different operating modes (first mode and second mode) to provide different voltage reference levels. The switching between modes allows the same hardware to adaptively provide different voltage outputs based on the requirements of connected components, such as Class-G amplifiers.
2Adaptability or versatility
If conventional charge pump regulators with multiple fly-back capacitors or switching regulators are used, then multiple voltage levels can be generated, but efficiency decreases and cost increases
Solution Approach 1:
The patent combines the functions of multiple fly-back capacitors and switching regulators into a single charge pump regulator with selective charging capability. By merging these functions, the design achieves multiple voltage output capability while improving power efficiency and reducing component count, thereby lowering cost and energy loss.
3Reliability
If charge-pump LDO regulator operates in LDO mode with capacitive load, then regulation is maintained with small dropout voltage, but high in-rush current occurs during startup
Solution Approach 1:
The regulator implements a startup sequence where it first generates a first voltage reference and uses it to charge the capacitive load before transitioning to the second voltage reference for full LDO operation. This preliminary charging action prevents high in-rush current by gradually bringing the capacitive load online rather than charging it directly at full voltage.
Solution Approach 2:
The startup process is segmented into distinct phases: first generating a lower voltage reference to charge the capacitive load, then transitioning to the full voltage reference. This segmentation of the charging process into stages reduces the peak in-rush current while maintaining the ability to provide stable regulation.
4Object-generated harmful factors
If larger switches and wider metallization are used to handle in-rush current, then current handling capability improves, but device area and cost increase
Solution Approach 1:
By implementing preliminary charging through the first voltage reference before full LDO operation, the regulator avoids the need for large switches and wide metallization to handle peak in-rush current. The gradual charging approach reduces peak current demands, allowing the use of smaller, more area-efficient switches while still protecting against harmful in-rush effects.
Data Source
AI summary
A circuit for a charge-pump low-dropout (LDO) regulator may include a comparator circuit configured to control a pass transistor based on an error signal. A pre-charge path may be provided between a supply voltage and an output node of the regulator. The pre-charge path may be configured to allow charging of an output capacitor to a pre-charge voltage during a pre-charge operation mode. The output capacitor may be coupled between the output node of the regulator and ground potential. The pass transistor may be configured to allow charging of the output capacitor during an LDO mode of operation. A charge-pump circuit may be configured to provide a current for charging the output capacitor during the LDO mode of operation.