Charge pump and method of having negative output voltage tracking positive output voltage thereof

Patent metadata

Field	Value
Publication number	US-9236796-B2
Application number	US-201414290715-A
Country	US
Kind code	B2
Filing date	May 29, 2014
Priority date	May 29, 2013
Publication date	Jan 12, 2016
Grant date	Jan 12, 2016

Abstract

A method having a negative output voltage at a negative output terminal of a charge pump tracking a positive output voltage at a positive output terminal of the charge pump. The charge pump comprises a plurality of switches and each of the plurality of switches has a serially coupled resistance. The method comprises selecting the serially coupled resistance for at least one of the plurality of switches to be different to each of the other respective serially coupled resistances associated to the other switches.

First claim

We claim:

1. A method of having a negative output voltage at a negative output terminal of a charge pump tracking a positive output voltage at a positive output terminal of the charge pump, wherein the charge pump comprises a first switch, a second switch, a third switch, a fourth switch, an inductor, a first output capacitor, a flying capacitor and a second output capacitor, wherein:
the inductor having a first end and a second end, wherein the first end is coupled to an input terminal;
the first switch having a first end, a second end and a control end, wherein the first end of the first switch is coupled to the second end of the inductor, and the second end of the first switch is coupled to a reference ground;
the second switch having a first end, a second end and a control end, wherein the first end of the second switch is coupled to the second end of the inductor, and the second end of the second switch is coupled to the positive output terminal;
the first output capacitor having a first end and a second end, wherein the first end of the first output capacitor is coupled to the second end of the second switch, and the second end of the first output capacitor is coupled to the reference ground;
the flying capacitor having a first end and a second end, wherein the first end of the flying capacitor is coupled to the second end of the inductor;
the third switch having a first end, a second end and a control end, wherein the first end of the third switch is coupled to the second end of the flying capacitor and the second end of the third switch is coupled to the negative output terminal;
the second output capacitor having a first end and a second end, wherein the first end of the second output capacitor is coupled to the second end of the third switch, and the second end of the second output capacitor is coupled to the reference ground; and
the fourth switch having a first end, a second end and a control end, wherein the first end of the fourth switch is coupled to the second end of the flying capacitor and the second end of the fourth switch is coupled to the reference ground;
the method comprising selecting a serial resistance for the second switch in its ON state to be at least twice higher than the serial resistance for each of the first switch, the third switch and the fourth switch in their ON states.

2. The method of claim 1 , wherein selecting the serial resistance for the second switch comprises selecting a doping concentration or layout for the second switch different from those for the first switch, the third switch and the fourth switch, and wherein the first switch, the second switch, the third switch and the fourth switch are manufactured on a same semiconductor substrate.

3. The method of claim 1 , wherein the charge pump comprises a boost charge pump.

4. The method of claim 1 ,
further comprising:
during a first time period of a cycle period, turning ON the second switch and the fourth switch, and turning OFF the first switch and the third switch; and
during a second time period of the cycle period, turning OFF the second switch and the fourth switch, and turning ON the first switch and the third switch.

5. The method of claim 1 , further comprising starting charging the first output capacitor and the flying capacitor at the same time at startup.

6. The method of claim 1 , wherein the method of selecting the serial resistance for the second switch at least twice higher than the serial resistance for each of the first switch, the third switch and the fourth switch comprises: coupling a discrete resistor to the second switch in series.

7. The method of claim 4 , further comprising:
blocking a body diode of the second switch and a body diode of the fourth switch during startup when the first switch, the second switch, the third switch and the fourth switch are in OFF state; and
releasing the body diode of the second switch and the body diode of the fourth switch at the same time for normal operation.

8. The method of claim 4 , comprising:
coupling an under voltage lockout (UVLO) signal to the second switch and the fourth switch; and
blocking a body diode of the second switch and a body diode of the fourth switch when the UVLO signal is in an active state.

9. The method of claim 4 , further comprising adjusting an on-resistance of the second switch by controlling a voltage on the control end of the second switch, wherein the on-resistance of the second switch is adjusted based on the negative output voltage and the positive output voltage.

10. The method of claim 4 , further comprising coupling a switch between the input terminal and the inductor, and wherein the switch is turned OFF when the input voltage is below a threshold voltage.

11. A charge pump, having an input terminal configured to receive an input voltage, a positive output terminal configured to provide a positive output voltage and a negative output terminal configured to provide a negative output voltage, the charge pump comprising a first switch, a second switch, a third switch, a fourth switch, an inductor, a first output capacitor, a flying capacitor and a second output capacitor, wherein:
the inductor having a first end and a second end, wherein the first end is coupled to an input terminal;
the first switch having a first end, a second end and a control end, wherein the first end of the first switch is coupled to the second end of the inductor, and the second end of the first switch is coupled to a reference ground;
the second switch having a first end, a second end and a control end, wherein the first end of the first switch is coupled to the second end of the inductor, and the second end of the second switch is coupled to the positive output terminal;
the first output capacitor having a first end and a second end, wherein the first end of the first output capacitor is coupled to the second end of the second switch, and the second end of the first output capacitor is coupled to the reference ground;
the flying capacitor having a first end and a second end, wherein the first end of the flying capacitor is coupled to the second end of the inductor;
the third switch having a first end, a second end and a control end, wherein the first end of the third switch is coupled to the second end of the flying capacitor and the second end of the third switch is coupled to the negative output terminal;
the second output capacitor having a first end and a second end, wherein the first end of the second output capacitor is coupled to the second end of the third switch, and the second end of the second output capacitor is coupled to the reference ground; and
the fourth switch having a first end, a second end and a control end, wherein the first end of the fourth switch is coupled to the second end of the flying capacitor and the second end of the fourth switch is coupled to the reference ground; wherein
the serial resistance for the second switch in its ON state is at least twice higher than each serial resistance for the first switch, the third switch and the fourth switch in their ON states.

12. The charge pump of claim 11 , wherein a transistor for the second switch has a doping concentration or layout different from those for the first switch, the third switch and the fourth switch, and wherein the first switch, the second switch, the third switch and the fourth switch are manufactured on a same semiconductor substrate.

13. The charge pump of claim 11 , wherein
during a first time period of a cycle period, the second switch and the fourth switch are configured to be turned ON, and the first switch and the third switch are configured to be turned OFF;
during a s

Assignees

• Chengdu Monolithic Power Sys
• Chengdu Monolithic Power Sys

Inventors

• Liu Bairen
• Qin Hongqiang
• Yang Eric
• Qu Song
• Ueunten Paul

Classifications

• H02M3/1588

  comprising at least one synchronous rectifier element (H02M3/1582, H02M3/1584 take precedence) · CPC title

• H02M3/07 Primary

  using capacitors charged and discharged alternately by semiconductor devices with control electrode {, e.g. charge pumps} · CPC title

• H02M2003/071

  Electricity · mapped topic

• H02M3/071

  adapted to generate a negative voltage output from a positive voltage source · CPC title

• Y02B70/10

  Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes · CPC title