Charge Pump Switchable Impedance Startup Ripple Control
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Solution Overview
Problem
Charge pump systems face issues with ripple and startup time due to the delay caused by voltage dividers and capacitors, which result in undesirable noise and prolonged charging times.
Innovation Solution
A charge pump system with a switchable impedance is introduced, where a low impedance is used during startup to quickly charge the capacitor and a high impedance during steady-state operation to reduce ripple, allowing for faster feedback and reduced overshoots and undershoots in the output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a capacitor is coupled between Vout and the voltage divider to reduce ripple, then the differential input to the comparator is increased during steady state operation, but an RC delay is created during startup transition
Solution Approach 1:
The patent applies the dynamics principle by making the impedance of the voltage divider switchable between two states: a first impedance during startup that allows fast charging of the capacitor, and a second impedance during steady-state operation that reduces ripple. This is achieved through a switchable impedance element (such as a transistor or switch) that changes the resistance value based on the operational phase, thereby dynamically optimizing the circuit performance for different conditions without creating RC delays during startup.
2Reliability
If a voltage divider is used to provide feedback to the comparator, then the system can regulate Vout to a target voltage, but large ripple results due to attenuation of the differential input to the comparator
Solution Approach 1:
The patent applies the parameter changes principle by changing the impedance parameter of the voltage divider based on the operational state. During steady-state operation, the impedance is increased to reduce ripple and noise, while during startup, the impedance is decreased to enable fast charging. This parameter switching allows the system to maintain reliable voltage regulation while minimizing harmful noise effects in different operational phases.
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 reduces startup delay and ripple in the output voltage, enabling the charge pump system to quickly reach the desired target voltage while maintaining stability during steady-state operation.
Implementation Method 1
a capacitor having a first terminal coupled to the output of the charge pump and a second terminal coupled to the first input of the comparator
Implementation Method 2
a switchable impedance coupled between the output of the charge pump and a first input of the comparator... During the start-up operation, the switchable impedance has a low impedance which allows for the capacitor to quickly charge
Data Source
AI summary
A charge pump system includes a charge pump, a switchable impedance, a comparator, and a capacitor. The switchable impedance has an input coupled to the output of the charge pump. The comparator has a first input coupled to the output of the switchable impedance, a second input coupled to a reference, and an output coupled to the input of the charge pump. The capacitor has a first terminal coupled to the output of the charge pump and a second terminal coupled to the first input of the comparator. The switchable impedance causes a first impedance between the first and second terminals of the capacitor during a start-up operation of the charge pump system and a second impedance between the first and second terminals of the capacitor during a steady-state operation of the charge pump system, wherein the first impedance is lower than the second impedance.