Switched Capacitor Regulator Output Current Estimation With Mirrored Sensing
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Solution Overview
Problem
Existing methods for measuring the output current of switched capacitor (SC) regulators are inefficient in terms of power usage, as they incur significant power loss due to the I2R loss in series resistors, and may require higher precision analog-to-digital converters to sense small voltage values.
Innovation Solution
The proposed solution involves circuits and methods that measure the output current of SC regulators by measuring input current, output voltage, and input voltage, and calculating the output current using an efficiency estimate. This approach can include using a small switch and resistor in parallel with the SC regulator to estimate the output current with reduced power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a series resistor is used to measure output current, then current measurement is achieved, but power loss increases due to I2R loss
Solution Approach 1:
The patent introduces a current sense resistor connected in parallel with the output capacitor, which acts as an intermediary element. This sense resistor measures the AC ripple current component rather than the full DC output current, significantly reducing I2R power loss while still providing usable current information for regulation purposes.
Solution Approach 2:
The patent segments the current measurement function by separating the DC current path from the AC measurement path. The output capacitor blocks DC current from flowing through the sense resistor while allowing AC ripple current to pass through, enabling measurement of current characteristics without having the full DC current flow through the measurement element.
2Loss of energy
If a small series resistor is used to reduce power loss, then power loss decreases, but voltage sensing becomes more difficult
Solution Approach 1:
The patent changes the measurement parameter from measuring the voltage across a small series resistor (which would be very small and difficult to sense) to measuring the voltage across a sense resistor that only carries the AC ripple current component. This parameter change allows using a larger effective resistance for measurement without subjecting it to the full DC current, thus achieving both low power loss and easy voltage sensing.
3Difficulty of detecting and measuring
If a large series resistor is used to improve voltage sensing, then voltage sensing becomes easier, but power loss increases
Solution Approach 1:
The output capacitor acts as an intermediary that blocks DC current from flowing through the sense resistor while allowing AC ripple current to pass. This enables the use of a larger sense resistor value for easier voltage sensing without subjecting it to the full DC current that would cause excessive 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 method reduces power loss by measuring input current and using an efficiency estimate to calculate output current, rather than directly measuring output current with a series resistor. It also allows for more accurate measurement with less I2R loss, although it may be less accurate than direct measurement methods.
Implementation Method 1
a capacitor having a first side and a second side
Implementation Method 2
a plurality of switches that, when in a first state, couple the capacitor in parallel with the load and, when in a second state, coupled the capacitor in series with the load
Implementation Method 3
a first resistor having a first side and a second side, wherein the first side of the first resistor is connected to the second side the third switch
Implementation Method 4
a hardware processor that measures a current flowing through the first resistor and estimates the current provided to the load based on the current measured as flowing through the first resistor
Data Source
AI summary
Circuits comprising: a capacitor; switches that, when State0, couple the capacitor in parallel with the load and, when State1, couple the capacitor in series with the load, wherein a first of the switches connects the capacitor to ground when in State0 and wherein a second of the switches connects the capacitor to an input voltage when in State1; a third switch, wherein a first side of the third switch is connected to the capacitor identically to one of the first switch and the second switch (OFWSW), wherein the third switch switches identically to the OFWSW, wherein the third switch is smaller than the OFWSW; a first resistor connected to the second side of the third switch; and a hardware processor that measures a current flowing through the first resistor and estimates the current provided to the load based on the current measured as flowing through the first resistor.