PWM Charge Pump Gate Drive for In-Rush Current Limiting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing solutions for reducing excessive in-rush current between a dc-dc converter and a load circuit during turn-on processes are inefficient, requiring additional circuitry and increased silicon area, and often result in power losses and inefficient silicon utilization.
Innovation Solution
A PWM-controlled charge pump with a single driver that uses a variable slope ramp signal and feedback loop to limit in-rush current, eliminating the need for a dedicated slew rate driver and external capacitors, and enabling linear charging from 0 to Vpump without complex voltage domain transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a slew rate controlled driver is used to avoid excessive in-rush current, then in-rush current is limited, but device complexity increases due to additional circuitry
Solution Approach 1:
The patent combines the charge pump and slew rate controlled driver into a single integrated circuit block. The charge pump generates the boosted voltage while simultaneously controlling the slew rate through integrated capacitance, eliminating the need for separate driver circuitry and reducing overall device complexity while maintaining in-rush current limitation
Solution Approach 2:
The integrated charge pump serves multiple functions: it provides voltage boosting to exceed battery level, acts as a slew rate controlled driver to limit in-rush current, and eliminates the need for external capacitors. This multi-functionality reduces the number of components and simplifies the overall power management architecture
2Speed
If the size of the charge pump or external capacitor is increased to reduce turn-on time, then turn-on time is reduced, but device area increases
Solution Approach 1:
The patent embeds the slew rate control capacitance within the charge pump circuit itself, nesting the capacitance function inside the existing charge pump structure. This eliminates the need for large external capacitors while maintaining fast turn-on performance, as the integrated capacitance is efficiently utilized within the compact charge pump architecture
Solution Approach 2:
The patent optimizes the capacitance value within the charge pump to achieve the desired turn-on speed without requiring large component sizes. By carefully selecting and integrating the capacitance parameter within the charge pump, the circuit achieves fast switching while minimizing silicon area occupation
3Object-generated harmful factors
If two drivers are used to control voltage domain transitions, then in-rush current is controlled, but device complexity and silicon area increase
Solution Approach 1:
The patent merges the functions of multiple drivers into a single integrated charge pump with built-in slew rate control. The charge pump directly drives the switch gate while internally controlling the charging rate, eliminating the need for separate drivers and their associated control circuitry for voltage domain transitions
Solution Approach 2:
The single charge pump circuit performs multiple functions that previously required two separate drivers: it provides voltage boosting, controls in-rush current through integrated slew rate control, and manages the complete gate charging process from 0 to Vpump, eliminating the need for complex multi-driver coordination
4Object-generated harmful factors
If a current limit resistor is used in the charge pump, then in-rush current is limited, but power dissipation increases
Solution Approach 1:
The patent uses an intermediate capacitance element within the charge pump to control the in-rush current by limiting the charging rate of the switch gate. This capacitive approach replaces resistive current limiting, achieving in-rush current control through voltage ramping rather than resistive dissipation, thereby reducing power loss
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 in-rush current by 63% and minimizes silicon area and power dissipation, achieving efficient and simple in-rush current management with reduced complexity and increased efficiency.
Implementation Method 1
a converter, such as a charge pump, able to supply the driver to a voltage above the battery level
Implementation Method 2
A possible solution would be to increase either the size of the charge pump itself or the size of the external capacitor C3
Data Source
AI summary
Circuits and methods to limit an in-rush current of a load circuit such as a processor are disclosed. A charge pump is used as driver for switches with pulse modulation width (PWM) control on the duty cycle of a clock. A clock generator generates a ramp signal with variable slope and a reference voltage. The slope of the ramp signal is dependent on the in-rush current of the switch. No dedicated slew rate driver or an external capacitor is required. The main building blocks are: a charge pump used as driver connected to single supply domain, one external (or internal) switch device, a single capacitive feedback between the switch device and the PWM control, and a PWM control comprising a fix frequency voltage triangular pulse generator with variable slope proportional to the in-rush current measurement.