switched capacitor dc dc converters topologies and applications l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Switched Capacitor DC-DC Converters: Topologies and Applications PowerPoint Presentation
Download Presentation
Switched Capacitor DC-DC Converters: Topologies and Applications

Loading in 2 Seconds...

play fullscreen
1 / 25

Switched Capacitor DC-DC Converters: Topologies and Applications - PowerPoint PPT Presentation


  • 1048 Views
  • Uploaded on

Switched Capacitor DC-DC Converters: Topologies and Applications. Bill Tsang and Eddie Ng. Outline. Motivations Dickson’s Charge Pump Other Various Charge Pumps Applications Conclusion. Motivations. Inductorless On-chip integration Low cost High switching frequency

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

Switched Capacitor DC-DC Converters: Topologies and Applications


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
switched capacitor dc dc converters topologies and applications

Switched Capacitor DC-DC Converters: Topologies and Applications

Bill Tsang and Eddie Ng

outline
Outline
  • Motivations
  • Dickson’s Charge Pump
  • Other Various Charge Pumps
  • Applications
  • Conclusion
motivations
Motivations
  • Inductorless
  • On-chip integration
  • Low cost
  • High switching frequency
  • Easy to implement (open-loop system)
  • Fast transient but large ripple
  • High efficiency but limited output power
ideal dickson s charge pump phase 1
Ideal Dickson’s Charge Pump(Phase 1)

2VDD-Vt

VDD

VDD-Vt

VDD-Vt

VDD-Vt

0

VDD

  • Clk=0, Clk_bar=VDD
  • Finite diode voltage drops, Vt
ideal dickson s charge pump phase 2
Ideal Dickson’s Charge Pump(Phase 2)

3VDD-2Vt

2VDD-Vt

VDD

2VDD-2Vt

VDD-Vt

VDD-Vt

VDD

0

  • Clk=VDD, Clk_bar=0
  • Maximum voltage stress on diodes 2VDD-Vt => reliability issue
  • Maximum voltage stress on capacitors VCn =n(VDD-Vt) => reliability issue
dickson s charge pump
Dickson’s Charge Pump

C1=C2=C3=C

(Body effect can be significant at later stages)

non idealities
Non-idealities
  • Threshold voltage drop [Mos charge pumps for low-voltage operation]
  • Parasitic capacitor divider voltage drop
  • Low conversion efficiency and pumping gain
  • Limited maximum number of stages

[An on-chip High-voltage generator circuit for

EEPROMs with a power supply voltage below 2V]

modified switch
Modified Switch

CTS

  • Static Charge Transfer Switches (CTS)
  • Eliminate transistor threshold drop
modified dickson s charge pump 1 ncp 1
Modified Dickson’s Charge Pump #1 (NCP-1)

Conditions:

1, Clk=Vdd,Clk_bar=0: v2, v3+V

To turn on transistor Ms2; Vgs = 2V

2, Clk=0,Clk_bar=VDD: v1, v2+V,v3

To turn off transistor Ms2; Vgs = 2V

impossible

modified dickson s charge pump 1 ncp 110
Modified Dickson’s Charge Pump #1 (NCP-1)
  • Static Charge Transfer Switches (CTS)
  • Better voltage pumping gain than diodes
  • Lower voltage equals upper voltage of pervious stage
  • Utilizing higher voltage from following stage to drive CTS
  • Reverse charge sharing since CTS cannot turn off completely
modified switch 2
Modified Switch #2

MN1 used to turn off MS1

MP1 used to turn on MS1

MN1

MP1

Next stage

  • Eliminate transistor threshold drop
  • Complete turn-off of switch, MS1
modified dickson s charge pump 2 ncp 2
Modified Dickson’s Charge Pump #2 (NCP-2)

Conditions:

1, Clk=Vdd,Clk_bar=0: v2, v3+V

To turn on transistor MP2 and MS2; Vgs = 2V

2, Clk=0,Clk_bar=VDD: v1, v2+V,v3

To turn on transistor MN2 and turn off MS2; Vgs = 2V

complete circuit ncp 2
Complete Circuit(NCP-2)
  • Careful PMOS well connection to prevent latch-up
  • Diode-connected output stage used
modified dickson s charge pump 3 ncp 3
Modified Dickson’s Charge Pump #3 (NCP-3)

NCP-3 uses boosted clock at output stage

optimum capacitance selection
Optimum Capacitance Selection
  • [A Low-Ripple Switched-Capacitor DC-DC Up converter for Low-voltage applications]
efficiency and output impedance
Efficiency and Output Impedance

[Performance limits of switched-capacitor DC-DC Converter]

  • Power loss due to: Vth, Rds(on), ESR, Cp, etc
  • Efficiency estimation
  • Output impedance (slow switching)

M=ideal conversion ratio

[Performance limits of switched-capacitor DC-DC Converter]

Ts=switching period

i= parasitic time constant

q=charge supplied to the source Vout

cross coupled charge pump
Cross-Coupled Charge Pump
  • PMOS to transmit 2VDD to output
  • Bodies tied to source(highest voltage) to avoid forward biasing junction diodes

[Area-efficient CMOS Charge Pumps for LCD Drivers]

h bridge topology
H-bridge Topology
  • Commercial products (Linear Technology, Fairchild, Maxim …)
  • Buck or Boost functions
  • Negative voltage generation
h bridge topologies
H-bridge Topologies

Phase 1: transistors in red are on

Phase 2: transistors in blue are on

Vout = 2Vin

Vout = -Vin

Vout = 0.5 Vin

application 1 flash memory
Application (1): Flash Memory
  • Floating gate programming
  • Control gate voltage >> Vdd

[ee141 lecture]

application 2 sample switches
Application (2): Sample Switches
  • S/H circuit– constant vgs sampling with all input level
  • Reduces distortion
  • Reduces Rds(on)

Voltage doubler

application 3 low voltage amplifier
Application (3): Low voltage Amplifier
  • Positive zero in Miller compensation
  • 1/gm pole-zero cancellation [charge-pump assisted low-power/low-voltage CMOS Opamp Design]

>2VGS

conclusion
Conclusion
  • Different Dickson’s SC converters discussed
  • Optimal Capacitor size selection
  • Discussion of cross-coupled doublers
  • Commercial product: Full H-bridge
  • Applications: Flash, ADC, Amplifier, LCD driver