Progressive start-up circuit for activating a charge pump

Abstract

A charge pump power converter efficiently provides electrical power by dynamically controlling a switch matrix of the charge pump. Instead of open-loop oscillator-based control, a dynamic controller provides power upon demand by sensing the output voltage and changing the operating frequency of the charge pump in response. Moreover, this closed-loop dynamic control intrinsically voltage regulates the output voltage of the charge pump power converter without the inefficient addition of a step-down voltage regulator, downstream of the power converter. In addition, this closed-loop dynamic control allows for maintaining a desired output voltage even with variations in the input voltage. Also, the dynamic control accommodates the advantages of using ultra-capacitors in the charge pump. The power converter is capable of operating with a sub-one volt input voltage incorporating low-threshold, low on-resistance power MOSFET switches in the switch matrix of the charge pump. A progressive start-up circuit further allows the power converter to start from a discharged state even with a sub-one volt input voltage.

Description

[0001] The present invention relates to DC / DC power supply controllers, and more particularly to regulated charge pump power converters for integrated power management systems.[0002] Advances in electronics technology have enabled the design and cost-effective fabrication of portable electronic devices. Thus, usage of portable electronic devices continues to increase both in the number of products available and the types of products. Examples of the broad spectrum of portable electronic devices include pagers, cellular telephones, music players, calculators, laptop computers, and personal digital assistants, as well as others.[0003] The electronics in a portable electronic device generally require direct current (DC) electrical power. Typically, one or more batteries are used as an energy source to provide this DC electrical power. Ideally, the energy source would be perfectly matched to the energy requirements of the portable electronic device. However, most often the voltage and c...

AI Technical Summary

Benefits of technology

[0132] The series resistances encountered during the charge (R.sub.CHG) and discharge (R.sub.DIS) phases have the most significant effect on the maximum current capacity of the power output stage 44, as shown by the three operating point columns in Table 1. Although larger fly (C.sub.F) and load (C.sub.L) capacitors improve this capability, the amount of improvement is mitigated as their resistance increases. Increasing the capacitor values appears to have a greater proportional effect on reducing the output voltage ripple V.sub.RIP, rather than the current capacity.

[0181] Furthermore, the aspects of the invention related to dynamically adapting to the input voltage, especially with regard to a low input voltage, allow for applications wherein the input voltage is volatile or otherwise unsuitable for generally known power converters. For example, photovoltaic cells provide power in relation to the surface area and the amount of incident radiant energy. Consequently, devices using photovoltaic cells may often be inoperable due to insufficient light, may have to limit functionality to remain within the typical amount of available power, and / or have to increase the surface area devoted to photovoltaic cells. Thus, a power converter 40A may allow for smaller photovoltaic cells and use in a wider range of lighting conditions.

Problems solved by technology

The disadvantage of the short self-discharge time for electronic capacitors means that oscillator-based charge pumps 20 must operate at duty cycles that are between the rate in which the electronic capacitor can be charged and discharged and the rate at which the electronic capacitor will self-discharge.

Consequently, known oscillator-based charge pumps 20 cannot take advantage of ultra-capacitors and similar high storage devices that have self-discharge times measured in weeks or months.

Moreover, as will become apparent below, the power converter 40A may readily be implemented as an integrated circuit and thus be of small size and cost.

For example, the energy source may have a safety limitation on the amount of current that can be provided, perhaps for a certain duration.

This represents situations where the various protection measures may result in a situation where the power converter needs to be restarted.

In addition, the Schottky diode consumes power during normal operation of the oscillator-controlled power converter 20, thereby reducing efficiency.

This is due to the non-compensated nature of the comparator.

However, the current capability of this one small MOSFET is insufficient to charge the load capacitor C.sub.L.

For example, common-mode signals may be induced noise on the inputs.

Consequently, devices using photovoltaic cells may often be inoperable due to insufficient light, may have to limit functionality to remain within the typical amount of available power, and / or have to increase the surface area devoted to photovoltaic cells.

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