Charge pump mode transition control

• US 6,512,411 B2
• Filed: 03/11/2002
• Issued: 01/28/2003
• Est. Priority Date: 08/05/1999
• Status: Expired due to Term

• Current Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Original Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Inventors: Thurber, Charles R. Jr., Meng, David D.
• Primary Examiner(s): Callahan, Timothy P.
• Assistant Examiner(s): ENGLUND, TERRY LEE
• Application Number:
  US10/095,899
• Publication Number:
  US 20020130705A1
• Time in Patent Office: 323 Days
• Field of Search: 327/536, 327/537, 327/538, 327/540, 327/541, 327/543, 307/110, 363/59, 363/60
• US Class Current: 327/536
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps
• CPC Class Codes: H02M 3/072 adapted to generate an output voltage whose value is lower than the input voltage

Abstract

A mode transitioning system (10) for a charge pump (12), which may optionally be embodied in an integrated circuit (28). A number of switches (30a-i) are operated based on an input detection sub-circuit (32) and an output detection sub-circuit (34) to controllably connect a number of flying capacitors (24, 26) in a variety of manners producing alternate input voltage to output voltage step ratios. One example embodiment of the mode transitioning system (10) proceeds from an idle state (52a), through start-up and fault testing states (52b-c), and then selects among alternate step-down ratios of 1:1, 2:3, and 1:2 based on suitability and efficiency for respective operating states (52d-f).

Claims

1. A method for operating a charge pump to convert an input signal exhibiting an input voltage to an output signal exhibiting an output voltage, wherein the charge pump includes an oscillator producing clock cycles in which a plurality of flying capacitors are charged during first halves of the clock cycles and discharged during the other halves of the clock cycles, the method comprising the steps of:

(a) operating the charge pump for at least one of the clock cycles in a first step mode defined by a first interconnecting combination of the plurality of flying capacitors while they are both charged and discharged;

(b) determining whether the charge pump is within regulation based on whether the output voltage is within a desired range;

(c) comparing the input voltage and the output voltage to determine whether the charge pump can operate in a second step mode defined by a second interconnecting combination of the plurality of flying capacitors while they are both charged and discharged; and

(d) transitioning operation of the charge pump from said first step mode to said second step mode whether both said step (b) and said step (c) evaluate as true.

2. The method of claim 1, wherein it is more efficient to operate the charge pump in said second step mode than in said first step mode.

3. The method of claim 1, further comprising:

(e) checking whether evaluation of said step (b) as true has only occurred within the last of a pre-set quantity of the clock cycles, to determine whether the charge pump has only recently achieved regulation;

(f) repeating said step (c); and

(g) transitioning operation of the charge pump from said second step mode back to said first step mode whether said step (e) evaluates as true and whether said step (f) now evaluates as false.

4. The method of claim 1, wherein the charge pump performs step-up voltage conversion, wherein the input voltage is lower than the output voltage and a first step ratio is greater than a second step ratio.

5. The method of claim 1, wherein the charge pump performs step-down voltage conversion, wherein the input voltage is greater than the output voltage and a first step ratio is lower than a second step ratio.

6. The method of claim 1, further comprising:

(e) operating the charge pump in said second step mode for at least one of the clock cycles;

(f) repeating said step (b);

(g) comparing the input voltage and the output voltage to determine whether the charge pump can operate in a third step mode defined by a third interconnecting combination of the plurality of flying capacitors while they are both charged and discharged; and

(h) transitioning operation of the charge pump from said second step mode to said third step mode whether both said step (f) and said step (g) evaluate as true.

7. The method of claim 6, wherein it is more efficient to operate the charge pump in said third step mode than in said second step mode and it is also more efficient to operate the charge pump in said second step mode than in said first step mode.

8. The method of claim 6, further comprising:

(i) checking whether evaluation of said step (f) as true has only occurred within the last of a pre-set quantity of the clock cycles, to determine whether the charge pump has only recently achieved regulation;

(j) repeating said step (g); and

(k) transitioning operation of the charge pump from said third step mode back to said second step mode whether said step (i) evaluates as true and whether said step (j) now evaluates as false.

9. The method of claim 6, wherein the charge pump performs step-up voltage conversion, wherein the input voltage is lower than the output voltage, a first step ratio is greater than a second step ratio, and said second step ratio is greater than a third step ratio.

10. The method of claim 6, wherein the charge pump performs step-down voltage conversion, wherein the input voltage is greater than the output voltage, a first step ratio is lower than a second step ratio, and said second step ratio is lower than a third step ratio.

11. A charge pump for converting an input signal exhibiting an input voltage to an output signal exhibiting an output voltage, the charge pump comprising:

an input terminal, an output terminal, and a common terminal, wherein the input signal is received across said input terminal and said common terminal and the output signal is produced across said output terminal and said common terminal;

a plurality of flying capacitors;

a plurality of switches capable of connecting at least some of said flying capacitors together into a plurality of interconnected combinations;

said plurality of switches further capable of connecting at least some of said plurality of interconnected combinations across said input terminal and said common terminal as an input combination;

said plurality of switches yet further capable of connecting at least some of said plurality of interconnected combinations across said output terminal and said common terminal as an output combination, to transfer a charge quanta to the output signal;

an input detector suitable for determining a voltage relationship between the input voltage and the output voltage;

an output detector suitable for determining a regulation condition based on whether the output voltage is within a desired range;

an oscillator circuit producing clock cycles;

a control circuit able to selectively operate the charge pump in a plurality of step modes, wherein each said step mode is defined by how said input combination and said output combination of said interconnected combinations of said plurality of flying capacitors produce a step ratio between the input voltage and the output voltage;

said control circuit further able to determine from said regulation condition and said voltage relationship whether to selectively attempt operation of the charge pump in a more desirable of said step modes or to attempt operation in a more capable of said step modes; and

said control circuit yet further able to direct connection of said input combination during one half of a said clock cycle and connection of said output combination during the other half of a said clock cycle, to obtain said charge quanta from the input signal and transfer said charge quanta to the output signal.

12. The charge pump of claim 11, wherein said plurality of switches are capable of connecting less than all of said flying capacitors which are contributively connected into either of said input combination or said output combination, to increase the quantity of said interconnected combinations and thus also said step ratios between the input voltage and the output voltage of the charge pump which are possible.

13. The charge pump of claim 11, wherein said plurality of switches includes MOSFETs.

14. The charge pump of claim 11, wherein said input detector includes a plurality of comparators, each of said plurality of comparators corresponding to a respective one of said step modes.

15. The charge pump of claim 11, wherein said output detector includes:

a voltage reference producing a reference signal; and

a comparator receiving said reference signal and a portion of the output signal exhibiting the output voltage and said comparator producing a regulation signal there from.

16. The charge pump of claim 15, wherein said oscillator circuit includes a gate controlled by said regulation signal to selectively provide and cease providing said clock cycles, and thus transference of said charge quanta, based on said regulation condition.

17. The charge pump of claim 11, wherein said step modes produce voltage relationships between the input signal and the output signal which include at least one member of the set consisting of voltage step-up, voltage step down, and voltage inversion.

18. The charge pump of claim 11, wherein:

said more desirable of said step modes is more desirable because operation of the charge pump is more efficient in it than in a present said step mode; and

said more capable of said step modes is more capable because operation of the charge pump in it provides more output current than in a present said step mode.

19. The charge pump of claim 11, wherein said plurality of switches and said oscillator circuit are integrated within a monolithic integrated circuit.

20. The charge pump of claim 19, wherein said input detector and said output detector are further integrated within said monolithic integrated circuit.