Voltage tripler using a charge pump having a single multiplexed charge transfer capacitor

• US 5,397,928 A
• Filed: 06/17/1994
• Issued: 03/14/1995
• Est. Priority Date: 01/17/1992
• Status: Expired due to Term

• Current Assignee: Exar Corporation (Maxlinear Incorporated)
• Original Assignee: Sipex Corporation
• Inventors: Chan, Paul S., Chow, Raymond W. B.
• Primary Examiner(s): Pellinen, A. D.
• Assistant Examiner(s): Krishnan, Aditya
• Application Number:
  US08/261,754
• Time in Patent Office: 270 Days
• Field of Search: 307/109-110, 363/60, 363/59, 363/61, 321/15
• US Class Current: 307/109
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps

Abstract

A voltage tripler which uses a charge pump with a single charge transfer capacitor to produce the required voltage is disclosed. The voltage tripler in conjunction with an inverter is useful for producing voltages with negative polarities. The voltage tripler when used in conjunction with a variable frequency oscillator circuit is useful in optimizing the power consumption by the charge pump of the voltage tripler when the tripler is not operating under load conditions. The tripler is useful in supplying power to a combination RS232 and RS422 or RS232 and RS485 interface, as well as other monolithic interface products.

Claims

1. A voltage tripler circuit comprising a charge transfer capacitor in selective communication with a supply voltage, a first storage capacitor, and a second storage capacitor, wherein said charge transfer capacitor is first employed to generate a first voltage on said first storage capacitor which is approximately twice said supply voltage and said charge transfer capacitor employed to generate a second voltage on said second storage capacitor which is approximately triple said supply voltage.

2. A voltage multiplier comprising:

a voltage tripler circuit comprising a charge transfer capacitor in selective communication with a supply voltage, a first storage capacitor, and a second storage capacitor wherein said charge transfer capacitor is first employed to generate a first voltage which is approximately twice said supply voltage on said first storage capacitor and said charge storage capacitor employed to generate a second voltage on said second storage capacitor which is approximately triple said supply voltage; and

a power management circuit, wherein said power management circuit is employed to control the amount of time during which said charge transfer capacitor is coupled to said supply voltage.

3. A voltage multiplier comprising:

a voltage tripler circuit comprising;

power supply input terminals for providing a power supply input voltage;

a first voltage storage capacitor;

a second voltage storage capacitor; and

a charge transfer capacitor in switchable communication with said first voltage storage capacitor, said second voltage storage capacitor, and said power supply input terminals,

said charge transfer capacitor being switchably connected during first selected time periods to said power supply input terminals to charge said charge transfer capacitor to approximately said power supply voltage,

being switchably connected during second selected time periods to one of said power supply input terminals and said first voltage storage capacitor so as to permit the charging of said first voltage storage capacitor to a first voltage approximately twice said power supply voltage, and

being switchably connected to said first voltage storage capacitor and said second voltage storage capacitor so as to charge said second voltage storage capacitor to a voltage approximately three times said power supply voltage.

4. The voltage multiplier of claim 3 wherein said charge transfer capacitor is switchably connected to said power supply input terminals during first selected time periods to charge said charge transfer capacitor to approximately said power supply voltage,

subsequent to being switchably connected to one of said power supply input terminals and said first voltage storage capacitor so as to permit the charging of said first voltage storage capacitor to approximately twice said power supply voltage, and

prior to being switchably connected to said first voltage storage capacitor and said second voltage storage capacitor so as to charge said second voltage storage capacitor to approximately three times said power supply voltage.

5. The voltage multiplier of claim 3 further comprising:

an inverter circuit; and

an output terminal,

wherein said inverter circuit is in communication with said second voltage storage capacitor, and

wherein said inverter circuit is operative to produce an output voltage at said output terminal which is approximately equal to said voltage on said second voltage storage capacitor but with a polarity which is inverted with respect to the polarity of said voltage on said second voltage storage capacitor.

6. The voltage multiplier of claim 3 further comprising a power management circuit, said power management circuit including a variable oscillator for generating a switching rate at which said charge transfer capacitor is sequentially switchably connected to said power supply input terminals, said first voltage storage capacitor, and said second voltage storage capacitor,

said switching rate being responsive to the power supplied by said voltage tripler circuit to a load in communication with said voltage tripler circuit.

7. The voltage multiplier of claim 3 wherein said charge transfer capacitor is switchably connected to said power supply input terminals during first selected time periods to charge said charge transfer capacitor to approximately said power supply voltage prior to being switchably connected to one of said power supply input terminals and said first voltage storage capacitor so as to permit the charging of said first voltage storage capacitor to approximately twice said power supply voltage.

8. The voltage multiplier of claim 3 wherein said switching rate responsive to the power supplied by the voltage tripler circuit to said load in communication with said voltage tripler circuit increases as current supplied to said load increases.

9. A voltage multiplier comprising:

a voltage tripler circuit comprising;

first and second supply voltage input terminals for providing a supply voltage;

a charge transfer capacitor having a first terminal and a second terminal;

a first switch connected between said first supply voltage input terminal and said first terminal of said charge transfer capacitor;

a second switch connected between said second terminal of said charge transfer capacitor and said second supply voltage input terminal;

a third switch connected between said second terminal of said charge transfer capacitor and said first supply voltage input terminal;

a fourth switch connected between said first terminal of said charge transfer capacitor and a first voltage storage capacitor;

a fifth switch connected between said second terminal of said charge transfer capacitor and said first voltage storage capacitor; and

a sixth switch connected between said first terminal of said charge transfer capacitor and a second voltage storage capacitor,

wherein said first and second switches are conductive simultaneously, said third and fourth switches are conductive simultaneously, and said fifth and sixth switches are conductive simultaneously,

wherein each said switches is switched in response to a four cycle clock, said first and second switches being conductive during a first and third clock cycles, said third and fourth switches being conductive during a second clock cycle, and said fifth and sixth switches being conductive during a fourth clock cycle, and

wherein said charge transfer capacitor is charged to approximately said supply voltage during said first and third clock cycles,

wherein said first voltage storage capacitor is charged to approximately twice said supply voltage during said second clock cycle and

wherein said second voltage storage capacitor is charged to approximately triple said supply voltage during said fourth clock cycle.

10. The voltage multiplier of claim 9 further comprising a power management circuit in communication with said four cycle clock, said four cycle clock having a clock rate determined by said power management circuit in response to power supplied to a load in communication with said voltage tripler circuit.

11. The voltage multiplier of claim 10 wherein said power management circuit comprises:

an oscillator in communication with said four cycle clock; and

an oscillator controller in communication with said oscillator,

said oscillator controller controlling the rate of oscillation of said oscillator in response to said power supplied to said load in communication with said voltage multiplier.

12. The voltage multiplier of claim 11 in which said oscillator comprises:

an oscillator capacitor having a first terminal and a second terminal, said first terminal of said oscillator capacitor being grounded;

a first oscillator switch in series communication between said second terminal of said oscillator capacitor and an oscillator power supply;

a second oscillator switch in series communication between said second terminal of said oscillator capacitor and said oscillator power supply;

a third oscillator switch in series communication between said second terminal of said oscillator capacitor and ground; and

a fourth oscillator switch in series communication between said second terminal of said oscillator capacitor and ground;

wherein when said second oscillator switch and said fourth oscillator switch are non-conductive and said first oscillator switch and said third oscillator switch are alternately and sequentially conductive and non-conductive, said oscillator capacitor charges and discharges at a first rate and generates a first oscillator frequency, and

wherein when said second oscillator switch and said fourth oscillator switch are conductive and said first oscillator switch and said third oscillator switch are alternately and sequentially conductive and non-conductive, said oscillator capacitor charges and discharges at a second rate and generates a second oscillator frequency.

13. The voltage multiplier of claim 11 in which said oscillator controller comprises a voltage comparator, having an input and an output, said input in communication with said second voltage capacitor, and said output in communication with said second oscillator switch and said fourth oscillator switch,

wherein said voltage comparator causes said second oscillator switch and said fourth oscillator switch to conduct when said voltage comparator determines said voltage on said second voltage capacitor is below a predetermined value.

14. The voltage multiplier of claim 9 further comprising:

an inverter circuit; and

an output terminal,

wherein said inverter circuit is in communication with said sixth switch and in communication with said second voltage storage capacitor, said inverter circuit for producing a voltage at said output terminal which is substantially equal to said voltage on said second voltage storage capacitor and having a polarity which is inverted with respect to said voltage on said second voltage storage capacitor.

15. The voltage multiplier of claim 14 wherein said inverter circuit comprises:

an output terminal;

a inverting capacitor having a first terminal and a second terminal;

a seventh switch in series communication between said first terminal of said inverting capacitor and said sixth switch;

an eighth switch in series communication between said first terminal of said inverting capacitor and said second supply voltage input terminal;

a ninth switch in communication between said second terminal of said inverting capacitor and said second supply voltage input terminal; and

a tenth switch in communication between said output terminal and said second terminal of said inverting capacitor,

said seventh switch and said ninth switch being conductive during said first and third clock cycles, and

said eighth switch and said tenth switch being conductive during said second clock cycle.

16. A communications interface circuit comprising:

an output terminal;

a first communications driver in communication with said output terminal;

a second communications driver in communication with said output terminal;

a voltage tripler in communication with said first communications driver and second communications driver, said voltage tripler for supplying a voltage to said first communications driver and said second communications driver, said voltage tripler circuit comprising a charge transfer capacitor in selective communication with a supply voltage a first storage capacitor, and a second storage capacitor wherein said charge transfer capacitor is first employed to generate a first voltage which is approximately twice said supply voltage on said first storage capacitor and wherein said charge transfer capacitor is employed to generate a second voltage which is approximately triple said supply voltage on said second storage capacitor;

an oscillator in communication with said voltage tripler, said oscillator for controlling said second voltage supplied by said voltage tripler; and

an oscillator controller in communication with said oscillator and in communication with said voltage tripler, said oscillator controller for causing said oscillator to oscillate at a first frequency when said second voltage supplied by said voltage tripler exceeds a first predetermined value and for causing said oscillator to oscillate at a second frequency when said second voltage supplied by said voltage tripler is below a second predetermined voltage.

17. A method of voltage tripling using a charge transfer capacitor having first and second connections comprising the steps of:

switchably connecting said first and second charge transfer capacitor connections to respective first and second power supply input terminals providing a power supply input voltage;

charging said charge transfer capacitor approximately to said power supply input voltage;

switchably connecting said second charge transfer capacitor connection to said first power supply input terminal to provide a voltage equal to approximately two times said power supply input voltage on said first charge transfer capacitor connection;

switchably connecting a first connection of a first voltage storage capacitor to said first connection of said charge transfer capacitor and switchably connecting a second connection of said first voltage storage capacitor to said second power supply input terminal to charge said first voltage storage capacitor to approximately two times said power supply voltage;

switchably connecting said second connection of said charge transfer capacitor to said first connection of said first voltage storage capacitor to provide a voltage equal to approximately three times said power supply input voltage on said first connection of said charge transfer capacitor; and

switchably connecting a first connection of a second voltage storage capacitor to said first connection of said charge transfer capacitor and switchably connecting a second connection of said second voltage storage capacitor to said second power supply input terminal to charge said second voltage storage capacitor to approximately three times said power supply voltage.

18. A voltage tripler circuit comprising:

power supply input terminals for connection to a power supply input voltage;

a first voltage storage capacitor;

a second voltage storage capacitor; and

a charge transfer capacitor in switchable communication with said first voltage storage capacitor, said second voltage storage capacitor, and said power supply input terminals,

said charge transfer capacitor being switchably connected across said power supply input terminals at selected times to charge said charge transfer capacitor to approximately said power supply voltage,

being switchably connected between one of said power supply input terminals and said first voltage storage capacitor so as to produce a voltage on said first voltage storage capacitor of approximately twice said power supply voltage, and

being switchably connected between said first voltage storage capacitor and said second voltage storage capacitor so as to produce a voltage on said second voltage storage capacitor of approximately three times said power supply voltage.

19. The voltage tripler circuit of claim 20 wherein said charge transfer capacitor is switchably connected across said power supply input terminals at selected times to charge said charge transfer capacitor to said power supply voltage,

subsequent to being switchably connected between one of said power supply input terminals and said first voltage storage capacitor so as to produce a voltage on said first voltage storage capacitor of approximately twice said power supply voltage, and

prior to being switchably connected between said first voltage storage capacitor and said second voltage storage capacitor to produce a voltage on said second voltage storage capacitor to approximately three times said power supply voltage.