Ripple Current Reduction Circuit for Charge Pump Stability
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Solution Overview
Problem
Charge pumps and other electronic circuits with switching mechanisms often produce undesirable ripple voltages due to periodic switching, which can degrade the output of operational amplifiers and other load devices.
Innovation Solution
A ripple current reduction circuit that includes a supply node coupled to the output of a voltage source, with a first current mirror mirroring a current to a second node and a shunt circuit connected between the second node and a common point to shunt a portion of the ripple current, reducing the ripple component in the output current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a charge pump uses switching mechanisms to convert DC voltages, then voltage conversion efficiency is improved, but ripple voltage is generated in the output
Solution Approach 1:
The circuit extracts and removes the harmful ripple voltage component from the charge pump output through a dedicated ripple reduction circuit, separating the useful DC voltage from the harmful AC ripple component
Solution Approach 2:
An intermediary ripple reduction circuit is introduced between the charge pump and the load, using current mirrors and shunt circuits to filter out ripple voltage while passing the DC component to the load
2Stability of the object's composition
If a reservoir capacitor is added to smooth output waveform, then output voltage stability is improved, but considerable ripple remains due to switching requirements
Solution Approach 1:
An intermediary ripple reduction circuit is introduced between the charge pump and the load, using current mirrors and shunt circuits to filter out ripple voltage while passing the DC component to the load
Solution Approach 2:
The circuit changes the operating parameters by using current mirrors to convert voltage ripple into current ripple, then using shunt circuits to divert the ripple current, fundamentally changing how ripple is handled from a voltage filtering problem to a current diversion problem
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 circuit effectively reduces the magnitude of ripple current at the output node, improving the stability and quality of the output voltage for load devices by shunting excess ripple current to a common point, thereby minimizing its impact on the load.
Implementation Method 1
A first current mirror is referred to the supply node, and arranged to mirror a current I1 provided by a first current source to a second node; the mirrored current (I3) has an associated ripple current induced by the ripple voltage
Implementation Method 2
A second current mirror is referred to the second node, and arranged to mirror a current I2 provided by a second current source to an output node
Implementation Method 3
A shunt circuit is connected between the second node and a circuit common point, and arranged to shunt a portion of the ripple current provided at the second node to the common point
Data Source
AI summary
A ripple current reduction circuit includes a supply node coupled to the output of a high ripple voltage source such as a charge pump. A first current mirror is referred to the supply node and mirrors a current I1 to a second node, the mirrored current (I3) including a ripple current induced by the ripple voltage. A second current mirror is referred to the second node and mirrors a current I2 to an output node, which provides a current ILOAD to a load. The mirrors are sized such that the current provided at the second node is greater than the current required by the second mirror to provide ILOAD. The excess current, at least a portion of which includes a ripple component induced by the ripple voltage, is shunted to ground. As such, the magnitude of the ripple component in ILOAD is less than that present in I3.