Charge Pump EMI Mitigation via Dynamic Current Limiting
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Solution Overview
Problem
Conventional charge pump circuitry generates large current spikes that cause electromagnetic interference (EMI), negatively impacting nearby electronic circuitry, particularly radio frequency (RF) receivers due to parasitic inductances.
Innovation Solution
A charge pump system incorporating current limit circuitry and a charge pump controller that limits current through the charge pump circuitry during a current limit mode, reducing EMI by controlling switches and capacitors to manage voltage and current levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the charge pump operates in normal mode with high current, then the voltage multiplication efficiency is improved, but electromagnetic interference increases
Solution Approach 1:
The charge pump controller dynamically switches between normal mode and current limit mode based on operating conditions. The system adjusts the current level through which the charge pump operates, allowing high current for efficient voltage multiplication when needed, and reducing current to limit EMI when nearby RF circuitry is active. This dynamic operation mode adjustment resolves the contradiction between productivity and harmful emissions.
Solution Approach 2:
The system changes the operational parameters of the charge pump by adjusting the current level. In normal mode, the charge pump operates at higher current levels for efficient voltage multiplication. When EMI mitigation is required, the current limit circuitry reduces the current parameter to a controlled level, thereby reducing electromagnetic interference while maintaining voltage multiplication functionality.
2Object-generated harmful factors
If the charge pump limits current to reduce EMI, then electromagnetic interference is reduced, but the voltage multiplication capability is degraded
Solution Approach 1:
The charge pump controller dynamically adjusts operational parameters based on real-time conditions. When current limiting is activated to reduce EMI, the system modifies switching timing and duration to compensate for reduced current, thereby maintaining adequate voltage multiplication capability. This dynamic adaptation allows the system to operate effectively in both EMI-sensitive and non-sensitive environments.
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
The solution effectively mitigates EMI by limiting current spikes, thereby reducing RF interference and maintaining the performance of nearby communication circuitry while still efficiently driving higher voltage devices.
Implementation Method 1
The charge pump circuitry includes switches and at least one capacitor, has an input coupled to a supply input node and has an output for developing a drive voltage. The charge pump controller controls the switches of the charge pump circuitry to control coupling of the at least one capacitor to increase the drive voltage above a supply voltage provided to the supply input node.
Implementation Method 2
The operation of switching capacitive devices of the charge pump, however, tends to generate large current spikes that are driven through conductors with parasitic inductance. The higher currents flowing through the parasitic inductances generates electromagnetic fields that may interfere with surrounding circuitry.
Data Source
AI summary
A charge pump system including charge pump circuitry, a charge pump controller, and current limit circuitry. The charge pump circuitry has an input coupled to a supply input node and has an output for developing a drive voltage. The charge pump controller controls the charge pump circuitry to increase the drive voltage above a supply voltage provided to the supply input node. The current limit circuitry limits current through the charge pump circuitry to a limited current level that is less than a maximum current level during a current limit mode to reduce current spikes at the nodes of the charge pump system that may generate EMI. A current mirror may be used as the current limit circuitry to directly limit current through switches of the charge pump circuitry. The timing of the charge pump switches may also be modified such as inserting strategic delays to reduce the current spikes.