Charge Pump Control Circuit Suppressing Rush Current
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Solution Overview
Problem
Conventional charge pump circuits experience a rush current issue due to the charging and discharging of capacitors, which can lead to inefficiencies and potential circuit reliability problems when the switching device is turned on, especially when the ON-time is short.
Innovation Solution
The proposed solution involves a control circuit for a charge pump circuit that includes specific switch configurations and a driver to manage the charging and discharging of flying and output capacitors through precharge periods and normal switching operations, ensuring that the first input voltage is applied only during precharge periods to prevent rush currents. This includes using a driver to turn on specific switch pairs during high and low periods of a pulse signal, and adjusting the ON-resistance of input switches to control charging currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switching device is turned on with short ON-time to improve switching efficiency, then switching losses are reduced, but rush current flows through the flying capacitor or output capacitor
Solution Approach 1:
The patent applies preliminary action by turning on the first and fourth switches during a predetermined precharge period before normal switching operations. This precharges the output capacitor to the first input voltage level, ensuring that when normal switching begins, the voltage difference across the capacitor is minimized, thereby preventing rush current while maintaining efficient short ON-time switching
Solution Approach 2:
The patent implements dynamics by making the ON-resistance of the input switch adjustable. During the precharge period, the ON-resistance is set to a first value that limits rush current, and during normal switching operations, it is switched to a second value that allows efficient power transfer. This dynamic adjustment resolves the contradiction between limiting rush current and maintaining switching efficiency
2Reliability
If the first input voltage is applied continuously to charge the output capacitor, then the output voltage is maintained, but rush current occurs when the switching device turns on
Solution Approach 1:
The patent applies periodic action by dividing the operation into distinct periods: a precharge period where the first and fourth switches are turned on to charge the output capacitor, followed by normal switching operations with alternating switch pairs. This periodic structure ensures the output capacitor is properly charged before normal operation begins, maintaining voltage stability while preventing rush current during switching transitions
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 suppresses rush currents by limiting the impedance of the charging path and ensuring that the first input voltage is only applied during precharge periods, thereby improving the efficiency and reliability of the charge pump circuit by stabilizing the output voltage without the need for additional regulators.
Implementation Method 1
a first switch arranged between a first input terminal to which a first input voltage is applied and one end of the flying capacitor; a fourth switch arranged between the one end of the flying capacitor and one end of the output capacitor
Implementation Method 2
a driver which turns on any one of a first pair consisting of the first and second switches and a second pair consisting of the third and fourth switches during a period corresponding to a high period of a pulse signal and which turns on the other pair during a period corresponding to a low period of the pulse signal
Data Source
AI summary
A charge pump circuit includes a first switch to a fourth switch, a flying capacitor, and an output capacitor. A driver turns on the first switch and the fourth switch during a predetermined precharge period from the start of activation of the charge pump circuit to charge the output capacitor. Thereafter, on the basis of a pulse signal, the driver alternately turns on and off a first pair and a second pair.