Capacitive Isolation Charge Pump With Controlled Current and Low EMI
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Solution Overview
Problem
Existing power transfer technologies across isolated capacitive barriers face inefficiencies, high costs, and significant electromagnetic interference (EMI) in low-power applications, particularly in sensor transmitters, where transformer-based solutions are costly and layout-constrained, and fail to provide adequate power transfer efficiency and reduced EMI.
Innovation Solution
A capacitively isolated current-loaded charge pump circuit that uses controlled current sources to maintain voltage and current through isolation capacitors as square waves, reducing EMI and increasing efficiency by operating at lower switching frequencies and using off-chip capacitors for flexible layout and lower costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If transformer-based solutions are used for power transfer across isolated capacitive barriers, then power transfer capability is achieved, but cost increases and layout flexibility is constrained
Solution Approach 1:
The patent extracts the isolation function from traditional transformer-based solutions and implements it using separate off-chip isolation capacitors. This allows the power transfer circuit to use simpler capacitive coupling while maintaining isolation, reducing cost and improving layout flexibility without sacrificing power transfer capability
Solution Approach 2:
The patent replaces the magnetic field-based power transfer mechanism of transformers with an electric field-based capacitive coupling mechanism. This substitution eliminates the need for complex transformer windings and magnetic shielding, significantly reducing cost and improving layout flexibility while maintaining effective power transfer
2Power
If traditional charge pump circuits are used for power transfer, then power transfer is achieved, but electromagnetic interference increases and efficiency decreases
Solution Approach 1:
The patent employs synchronous switching of the charge pump circuit where the switching frequency is synchronized with the isolation capacitor charging/discharging cycles. This periodic action creates controlled current square waves that reduce electromagnetic radiation and improve power transfer efficiency by minimizing parasitic effects
Solution Approach 2:
The patent changes the operating parameters of the charge pump circuit by using controlled current sources that maintain square wave current through the isolation capacitors. This parameter change optimizes the switching behavior to reduce EMI and improve efficiency while maintaining effective power transfer
3Loss of energy
If higher switching frequencies are used in charge pump circuits, then power transfer efficiency may improve, but electromagnetic interference increases and component stress increases
Solution Approach 1:
The patent uses dynamically controlled current sources that adjust the switching behavior based on load conditions and voltage levels. This dynamic control allows the circuit to operate at optimized switching frequencies that maintain high efficiency while minimizing EMI and component stress through adaptive rather than fixed-frequency operation
Solution Approach 2:
The patent implements feedback control mechanisms where the controlled current sources monitor voltage and current levels across the isolation capacitors and adjust switching parameters accordingly. This feedback ensures optimal efficiency while preventing excessive EMI and component stress by automatically adapting operating conditions
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 achieves greater than 80% efficiency with reduced EMI and lower component stress, allowing for smaller component design and lower costs compared to transformer-based solutions, while providing flexible layout options and efficient power transfer in low-power applications.
Implementation Method 1
a first isolation capacitor coupled at a first end to the first primary terminal and at a second end to the first secondary terminal, and a second isolation capacitor coupled at a first end to the second primary terminal and at a second end to the second secondary terminal
Implementation Method 2
at least one of a secondary-side controlled current source coupled between the secondary switching bridge and the output capacitor and configured to maintain an output voltage across the output capacitor to within a tolerance, and to maintain current through the first and second isolation capacitors as a square wave
Data Source
AI summary
In one example, an apparatus comprises: a primary side bridge coupled between a power input and a first ground terminal, the primary side bridge having first switching terminals coupled to first capacitor terminals; and a secondary side bridge coupled between a power output and a second ground terminal, the secondary side bridge having second switching terminals coupled to second capacitor terminals.