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  • UCC28720 Constant-Voltage, Constant-Current Controller With Primary-Side Regulation

    • SLUSBE8B May   2013  – September 2015 UCC28720

      PRODUCTION DATA.  

  • CONTENTS
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  • UCC28720 Constant-Voltage, Constant-Current Controller With Primary-Side Regulation
  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Detailed Pin Description
    4. 7.4 Device Functional Modes
      1. 7.4.1 Primary-Side Voltage Regulation
      2. 7.4.2 Primary-Side Current Regulation
      3. 7.4.3 Valley Switching
      4. 7.4.4 Start-Up Operation
      5. 7.4.5 Fault Protection
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Stand-by Power Estimate
        2. 8.2.2.2 Input Bulk Capacitance and Minimum Bulk Voltage
        3. 8.2.2.3 Transformer Turns Ratio, Inductance, Primary-Peak Current
        4. 8.2.2.4 Transformer Parameter Verification
        5. 8.2.2.5 Output Capacitance
        6. 8.2.2.6 VDD Capacitance, CDD
        7. 8.2.2.7 VS Resistor Divider, Line Compensation, and Cable Compensation
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Device Nomenclature
        1. 11.1.1.1 Definition of Terms
          1. 11.1.1.1.1  Capacitance Terms in Farads
          2. 11.1.1.1.2  Duty Cycle Terms
          3. 11.1.1.1.3  Frequency Terms in Hertz
          4. 11.1.1.1.4  Current Terms in Amperes
          5. 11.1.1.1.5  Current and Voltage Scaling Terms
          6. 11.1.1.1.6  Transformer Terms
          7. 11.1.1.1.7  Power Terms in Watts
          8. 11.1.1.1.8  Resistance Terms in Ω
          9. 11.1.1.1.9  Timing Terms in Seconds
          10. 11.1.1.1.10 Voltage Terms in Volts
          11. 11.1.1.1.11 AC Voltage Terms in VRMS
          12. 11.1.1.1.12 Efficiency Terms
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information
  13. IMPORTANT NOTICE

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DATA SHEET

UCC28720 Constant-Voltage, Constant-Current Controller With Primary-Side Regulation

1 Features

  • < 10-mW No-Load Power
  • Primary-Side Regulation (PSR) Eliminates Opto-Coupler
  • ±5% Voltage and Current Regulation Across Line and Load
  • 700-V Start-Up Switch
  • 80-kHz Maximum Switching Frequency Enables High-Power Density Charger Designs
  • Quasi-Resonant Valley-Switching Operation for Highest Overall Efficiency
  • Wide VDD Range Allows Small Bias Capacitor
  • Dynamic BJT Drive
  • Overvoltage, Low-Line, and Overcurrent Protection Functions
  • Programmable Cable Compensation
  • SOIC-7 Package

2 Applications

  • USB-Compliant Adapters and Chargers for Consumer Electronics
    • Smart phones
    • Tablet computers
    • Cameras
  • Standby Supply for TV and Desktop
  • White Goods

3 Description

The UCC28720 flyback power supply controller provides isolated-output Constant-Voltage (CV) and Constant-Current (CC) output regulation without the use of an optical coupler. The devices process information from the primary power switch and an auxiliary flyback winding for precise control of output voltage and current.

An internal 700-V start-up switch, dynamically-controlled operating states and a tailored modulation profile support ultra-low standby power without sacrificing start-up time or output transient response.

Control algorithms in the UCC28720 allow operating efficiencies to meet or exceed applicable standards. The output drive interfaces to a bipolar transistor power switch. Discontinuous conduction mode (DCM) with valley switching reduces switching losses. Modulation of switching frequency and primary current peak amplitude (FM and AM) keeps the conversion efficiency high across the entire load and line ranges.

The controller has a maximum switching frequency of 80 kHz and always maintains control of the peak-primary current in the transformer. Protection features help keep primary and secondary component stresses in check. The UCC28720 allows compensation for voltage drop in the cable to be programmed with an external resistor.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)
UCC28720 SOIC (7) 3.91 mm × 4.90 mm
  1. For all available packages, see the orderable addendum at the end of the data sheet.

Typical Application

UCC28720 alt_v13090_lusbe8.gif

4 Revision History

Changes from A Revision (January 2014) to B Revision

  • Added ESD Ratings table, Feature Description section, Device Functional Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information section. Go

Changes from * Revision (May 2014) to A Revision

  • Changed CDD equation.Go

5 Pin Configuration and Functions

D PACKAGE
7-PIN SOIC
Top View
UCC28720 pin_lusbe8.gif

Pin Functions

PIN I/O DESCRIPTION
NAME NO.
VDD 1 I VDD is the bias supply input pin to the controller. A carefully-placed bypass capacitor to GND is required on this pin.
VS 2 I Voltage sense is an input used to provide voltage and timing feedback to the controller. This pin is connected to a voltage divider between an auxiliary winding and GND. The value of the upper resistor of this divider is used to program the AC-mains run and stop thresholds and line compensation at the CS pin.
CBC 3 I Cable compensation is a programming pin for compensation of cable voltage drop. Cable compensation is programmed with a resistor to GND.
GND 4 — The ground pin is both the reference pin for the controller and the low-side return for the drive output. Special care must be taken to return all AC decoupling capacitors as close as possible to this pin and avoid any common trace length with analog signal return paths.
CS 5 I Current sense input connects to a ground-referenced current-sense resistor in series with the power switch. The resulting voltage is used to monitor and control the peak primary current. A series resistor can be added to this pin to compensate the peak switch current levels as the AC-mains input varies.
DRV 6 O Drive is an output used to drive the base of an external high voltage NPN transistor.
HV 7 I The high-voltage pin connects directly to the rectified bulk voltage and provides charge to the VDD capacitor for start-up of the power supply.

6 Specifications

6.1 Absolute Maximum Ratings(1)

MIN MAX UNIT
VHV Start-up pin voltage, HV 700 V
VVDD Bias supply voltage, VDD 38 V
IDRV Continuous base current sink 50 mA
IDRV Continuous base current source Self- limiting mA
IVS Peak current, VS −1.2 mA
VDRV Base drive voltage at DRV −0.5 Self- limiting V
VS Voltage −0.75 7 V
CS, CBC −0.5 5 V
TJ Operating junction temperature −55 150 °C
Lead temperature 0.6 mm from case for 10 seconds 260 °C
TSTG Storage temperature −65 150 °C
(1) Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. These are stress ratings only and functional operation of the device at these or any other conditions beyond those indicated under “Recommended Operating Conditions” is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect device reliability. All voltages are with respect to GND. Currents are positive into, negative out of the specified terminal. These ratings apply over the operating ambient temperature ranges unless otherwise noted.

6.2 ESD Ratings

VALUE UNIT
V(ESD) Electrostatic discharge Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001(1) ±2000 V
Charged-device model (CDM), per JEDEC specification JESD22-C101(2) ±500 V
(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
(2) JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.

6.3 Recommended Operating Conditions

over operating free-air temperature range (unless otherwise noted)
MIN NOM MAX UNIT
VDD Bias supply operating voltage 9 35 V
CVDD VDD bypass capacitor 1.0 10 µF
RCBC Cable-compensation resistance 10 kΩ
IVS VS pin current −1 mA
TJ Operating junction temperature −40 125 °C

6.4 Thermal Information

THERMAL METRIC(1) UCC28720 UNIT
D (SOIC)
7 PIN
RθJA Junction-to-ambient thermal resistance 141.5 °C/W
RθJC(top) Junction-to-case (top) thermal resistance 73.8 °C/W
RθJB Junction-to-board thermal resistance 89.0 °C/W
ψJT Junction-to-top characterization parameter 23.5 °C/W
ψJB Junction-to-board characterization parameter 88.2 °C/W
(1) For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.

6.5 Electrical Characteristics

over operating free-air temperature range, VVDD = 25 V, HV = open, RCBC = open, TA = –40°C to 125°C, TA = TJ
(unless otherwise noted)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
HIGH-VOLTAGE START UP
IHV Start-up current out of VDD VHV = 100 V, VVDD = 0 V, start state 100 225 500 µA
IHVLKG Leakage current at HV VHV = 400 V, run state, TJ = 25 ºC 0.01 0.25 µA
BIAS SUPPLY INPUT
IRUN Supply current, run IDRV = 0, run state 2.00 2.65 mA
IWAIT Supply current, wait IDRV = 0, wait state 95 150 µA
ISTART Supply current, start IDRV = 0, VVDD = 18 V, start state, IHV = 0 18 30 µA
IFAULT Supply current, fault IDRV = 0, fault state 95 150 µA
UNDERVOLTAGE LOCKOUT
VVDD(on) VDD turn-on threshold VVDD low to high 19 21 23 V
VVDD(off) VDD turn-off threshold VVDD high to low 7.35 7.7 8.15 V
VS INPUT
VVSR Regulating level Measured at no-load condition, TJ = 25°C(1) 4.01 4.05 4.09 V
V
VVSNC Negative clamp level IVS = -300 µA, volts below ground 190 250 325 mV
IVSB Input bias current VVS = 4 V -0.25 0 0.25 µA
CS INPUT
VCST(max) Max CS threshold voltage VVS = 3.7 V 735 780 815 mV
VCST(min) Min CS threshold voltage VVS = 4.35 V 175 190 215 mV
KAM AM control ratio VCST(max) / VCST(min) 3.6 4.0 4.4 V/V
VCCR Constant current regulating level CC regulation constant 317 330 344 mV
KLC Line compensation current ratio IVSLS = -300 µA, IVSLS / current out of CS pin 24.0 25.0 28.6 A/A
TCSLEB Leading-edge blanking time DRV output duration, V CS = 1 V 230 290 355 ns
DRIVER
IDRS(max) Maximum DRV source current VDRV = 2 V, VVDD = 9 V, VVS = 3.85 V 32 37 41 mA
IDRS(min) Minimum DRV source current VDRV = 2 V, VVDD = 9 V, VVS = 4.30 V 16 19 22 mA
RDRVLS DRV low-side drive resistance IDRV = 10 mA 1 2.4 Ω
VDRCL DRV clamp voltage VVDD = 35 V 5.9 7 V
RDRVSS DRV pull-down in start state 20 25 kΩ
VOVP Over-voltage threshold At VS input, TJ = 25°C(1) 4.51 4.60 4.73 V
V
VOCP Over-current threshold At CS input 1.4 1.5 1.6 V
IVSL(run) VS line-sense run current Current out of VS pin increasing 190 225 275 µA
IVSL(stop) VS line-sense stop current Current out of VS pin decreasing 70 80 100 µA
KVSL VS line sense ratio IVSL(run) / IVSL(stop) 2.45 2.80 3.05 A/A
TJ(stop) Thermal shut-down temperature Internal junction temperature 165 °C
CABLE COMPENSATION
VCBC(max) Cable compensation maximum voltage Voltage at CBC at full load 2.9 3.1 3.5 V
VCVS(min) Minimum compensation at VS VCBC = open, change in VS regulating level at full load -55 -15 25 mV
VCVS(max) Maximum compensation at VS VCBC = 0 V, change in VS regulating level at full load 275 320 380 mV
(1) The regulating level and over voltage at VS decreases with temperature by 0.8 mV/˚C. This compensation is included to reduce the power supply output voltage variance over temperature.

Switching Characteristics

over operating free-air temperature range (unless otherwise noted)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
fSW(max) + Maximum switching frequency VVS = 3.7 V 74 80 87 kHz
fSW(min) Minimum switching frequency VVS = 4.35 V 580 650 740 Hz
tZTO Zero-crossing timeout delay 2.5 3.1 3.6 µs

6.6 Typical Characteristics

VDD = 25 V, unless otherwise noted.
UCC28720 C001_SLUSBE8.png Figure 1. Bias Supply Current vs. VDD Voltage
UCC28720 C003_SLUSBE8.png Figure 3. VS Pin Regulation Voltage vs. Junction Temperature
UCC28720 C005_SLUSBE8.png Figure 5. Current Sense Threshold vs. Temperature
UCC28720 C007_SLUSBE8.png Figure 7. Minimum Switching Frequency vs. Junction Temperature
UCC28720 C008_SLUSBE8.png Figure 9. Driver Output Source Current vs. Junction Temperature
UCC28720 C010_SLUSBE8.png Figure 11. Over Voltage Protection Threshold vs. Junction Temperature
UCC28720 C002_SLUSBE8.png Figure 2. Operating Current vs. Junction Temperature
UCC28720 C004_SLUSBE8.png Figure 4. VS Pin Start and Stop Thresholds vs. Junction Temperature
UCC28720 C006_SLUSBE8.png Figure 6. Constant Current Regulation Level vs. Junction Temperature
UCC28720 C012_SLUSBE8.png Figure 8. Maximum Switching Frequency vs. Junction Temperature
UCC28720 C009_SLUSBE8.png Figure 10. Driver Pull Down Resistance vs. Junction Temperature
UCC28720 C011_SLUSBE8.png Figure 12. HV Charging Current vs. Junction Temperature

 
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