Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With specific source of supply or bias voltage
Reexamination Certificate
1999-09-04
2001-06-05
Cunningham, Terry D. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
With specific source of supply or bias voltage
C327S390000
Reexamination Certificate
active
06242970
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
Cross reference is made to the following patent applications, each assigned to the same assignee, the teachings of which are incorporated herein by reference:
Patent
Filing
No.
Serial No.
Date
Inventor
Title
TBD
09/389,811
Herewith
Grant
Integration of
Synchronous
Rectifier Restoration
of Boot Capacitor
into Charge-Pump
TBD
09/389,691
Herewith
Grant
Charge-Pump
Closely Coupled
to Switching
Converter to
Improve Area
Efficiency
TBD
09/389,810
Herewith
Martinez et al
Controlled Linear
Start-Up in a
Linear Regulator
TECHNICAL FIELD OF THE INVENTION
This invention relates generally to integrated circuits, more specifically to a charge-pump device and a method of dynamically sequencing charge-pump switches to improve the efficiency of a charge-pump circuit.
BACKGROUND OF THE INVENTION
As integrated circuits (ICs), such as digital signal processors (DSPs) and mixed signal analog circuits, are required to operate at faster speeds, and continue to be designed and built smaller, more electrical power is used per unit of wafer surface area. Using more electrical power per unit of wafer surface area causes the operating temperature of ICs to increase. Since the power consumed by a device is a function of the current flowing through the IC and the upon the voltage placed across the IC, lower working voltages are sometimes implemented to lower the power used by the IC.
Likewise, as overall system sizes have continued to decrease, power supply designs with smaller sizes and higher efficiencies are used to supply power to these smaller circuits that operate at lower voltages. Switch mode power supplies (also known as direct current (DC) to DC converters, are typically used in electrical devices, such as digital signal processors (DSPs) and mixed signal analog circuits. These devices are commonly used in products such as modems, television receivers and cell phones, for example. DC to DC converters convert the voltage of a primary source (such as a device battery) to the operating voltage required by the electrical circuitry or IC of the electrical device. Likewise, it is often necessary to re-convert the voltage of the electrical device from the voltage of the electrical circuitry or IC to a higher operating voltage used by the device. For instance, a 2.8 volt supply voltage provided to a BiCMOS IC may need to be increased internally to 5.0 volts to operate internal CMOS circuitry. Sometimes, a charge-pump is used to generate a larger power supply voltage from a smaller one.
Unfortunately, the performance of a charge-pump is not very efficient during the charge-up period of the charge-pump. In addition, during the charge-up period, an IC coupled to the charge-pump may be damaged due to an over-voltage condition.
Also, the performance of charge-pumps is limited due to the time it takes to charge-up the charge-pump. Furthermore, if the output voltage of the charge-pump exceeds it's input voltage, the charge-pump may forward bias back diodes and inject noise into the IC. All of these factors contribute to reducing the efficiency of the charge-pump.
Therefore it is desired to have a charge-pump circuit and a method for implementing a charge-pump that increases start-up speed, increases charge-pump efficiency, prevents over-voltage conditions, and reduces the likelihood of noise injection. The present invention provides such a device and method.
SUMMARY OF THE INVENTION
The present invention achieves technical advantages as a charge-pump and a method of operating a charge-pump that has one switching sequence for the start-up operation of the charge-pump, and a second switching sequence for the steady-state operation of the charge-pump. This dual-mode switching sequence provides advantages over charge-pumps that are designed to charge-up and operate using the same switching sequence that is typically based on the charge-pump's steady state (non charge-up) operation. Accordingly, the charge-pump of the present invention provides the advantages of better start-up speeds, increased charge-pump efficiency, the prevention of over-voltage conditions, and the reduced likelihood of noise injection.
The invention comprises a method of operating a charge-pump. The method includes the steps of charging a first capacitor, and then choosing between two switching sequences based on the determined relative values of the input voltage and the output voltage of the charge pump. When the input voltage is greater than the output voltage, the method applies a first switching sequence to discharge the first capacitor into a second capacitor by first partially discharging the first capacitor into the second capacitor, then fully discharging the first capacitor into the second capacitor. When the input voltage is determined to be less than or equal to the output voltage, the method uses a second switching sequence to prevent the discharge of the second capacitor into the first capacitor by electrically isolating the first capacitor.
The invention further comprises a charge-pump configuration. The charge-pump configuration includes an input voltage defined as the voltage between a first node and a connection to ground, as well as an output voltage defined as the voltage between a fifth node and a connection to ground. The charge-pump has several switches, including a first switch coupled between the first node and a second node, a second switch coupled between the first node and a third node, a third switch coupled between the third node and the connection to ground, and a fourth switch coupled between the second node and the fifth node. Furthermore, the charge-pump includes a first capacitor coupled between the second node and the third node, and a second capacitor coupled between the fifth node and the connection to ground.
Using the invention, one method of operating the charge-pump includes sequentially charging a first capacitor by closing the first switch, closing the third switch, opening the second switch, and opening the fourth switch. The method then applies a first switching sequence comprising the steps of sequentially closing the fourth switch to partially discharge the first capacitor into the second capacitor in a first sub-step, and then opening the third switch to isolate the first capacitor from the ground connection in a second sub-step. Then, in a third sub-step the method closes the second switch to fully discharge the first capacitor into the second capacitor. The method also uses a second switching sequence comprising the steps of sequentially opening the third in a first sub-step, closing the fourth switch in a second sub-step, and closing the second switch in a third sub-step. The first switching sequence is selected when an output voltage is determined to be less than an input voltage, and the second switching sequence is selected when an output voltage is determined to be greater than or equal to an input voltage.
The invention allows the implementation of NMOS transistors for the first or the third switch, and PMOS transistors for the second switch or the fourth switch. The first capacitor could be a 1 uF (micro-farad) capacitor. Likewise, the second capacitor could be a 10 uF capacitor.
In another aspect, the present invention is a method of operating a charge-pump during charge-up. Using the disclosed charge-pump, the method comprises the steps of closing the first switch, closing the third switch, opening the second switch, and opening the fourth switch to charge the first capacitor in a first sub-step. Then, the method proceeds by closing the fourth switch to partially discharge the first capacitor into the second capacitor in a second sub-step. Afterwards, the third switch is opened to isolate the first capacitor from ground in a third sub-step. Lastly of these sub-steps, the method closes the second switch to fully discharge the first capacitor into the second capacitor. This method is designated for use particularly when the output voltage that is less than the input voltage.
REFERENCES:
patent: 4679134 (1987-07-01), Bingham et al.
pat
Grant David
Martinez Robert
Brady III W. James
Cunningham Terry D.
Hernandez Pedro P.
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
LandOfFree
Charge-pump device and method of sequencing charge-pump... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Charge-pump device and method of sequencing charge-pump..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Charge-pump device and method of sequencing charge-pump... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2492091