Datasheet

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Off-line Power Supply Controller

• Transformerless Off-line

Applications

• Ideal Primary-side Bias Supply

• Efficient BiCMOS Design

• Wide Input Range

• Fixed or Adjustable

Low Voltage Output

• Uses Low Cost SMD Inductors

• Short Circuit Protected

• Optional Isolation Capability

The UCC1889 controller is optimized for use as an off-line, low power, low voltage,

regulated bias supply. The unique circuit topology utilized in this device can be

visualized as two cascaded flyback converters, each operating in the discontinu-

ous mode, and both driven from a single external power switch. The significant

benefit of this approach is the ability to achieve voltage conversion ratios of 400V

to 12V with no transformer and low internal losses.

The control algorithm utilized by the UCC1889 is to force the switch on time to be

inversely proportional to the input line voltage while the switch off time is made in-

versely proportional to the output voltage. This action is automatically controlled by

an internal feedback loop and reference. The cascaded configuration allows a volt-

age conversion from 400V to 12V to be achieved with a switch duty cycle greater

than 10%. This topology also offers inherent short circuit protection since as the

output voltage falls to zero, the switch off time approaches infinity.

The output voltage can be easily set to 12V or 18V. Moreover, it can be pro-

grammed for other output voltages less than 18V with a few additional compo-

nents. An isolated version can be achieved with this topology as described further

in Unitrode Application Note U-149.

UCC1889

UCC2889

UCC3889

SLUS158A - FEBRUARY 1995 - REVISED FEBRUARY 2003

FEATURES

DESCRIPTION

OPERATION

With reference to the application diagram below, when input voltage is first applied,

the RON current into TON is directed to VCC where it charges the external capacitor,

C3, connected to VCC. As voltage builds on VCC, an internal undervoltage lockout

holds the circuit off and the output at DRIVE low until VCC reaches 8.4V. At this

time, DRIVE goes high turning on the power switch, Q1, and redirecting the current

into TON to the timing capacitor, CT. CT charges to a fixed threshold with a current

ICHG=0.8 • (VIN - 4.5V)/RON. Since DRIVE will only be high for as long as CT

charges, the power switch on time will be inversely proportional to line voltage.

This provides a constant line voltage-switch on time product.

Note: This device incorporates patented technology used under license from Lambda Electronics, Inc.

TYPICAL APPLICATION

UDG-93060-1

Summary of content (14 pages)

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UCC1889 UCC2889 UCC3889 Off-line Power Supply Controller FEATURES • • • • • • • • DESCRIPTION Transformerless Off-line Applications The UCC1889 controller is optimized for use as an off-line, low power, low voltage, regulated bias supply. The unique circuit topology utilized in this device can be visualized as two cascaded flyback converters, each operating in the discontinuIdeal Primary-side Bias Supply ous mode, and both driven from a single external power switch.
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UCC1889 UCC2889 UCC3889 OPERATION (cont.) At the end of the on time, Q1 is turned off and the RON current into TON is again diverted to VCC. Thus the current through RON, which charges CT during the on time, contributes to supplying control power during the off time. IDCHG = (VOUT - 0.7V) / ROFF As VOUT increases, IDCHG increases resulting in the reduction of off time. The frequency of operation increases and VOUT rises quickly to its regulated value.
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UCC1889 UCC2889 UCC3889 ABSOLUTE MAXIMUM RATINGS CONNECTION DIAGRAM ICC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5mA Current into TON Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5mA Voltage on VOUT Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20V Current into TOFF Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250µA Storage Temperature . . . . . . . . . . . . . . . . . . . .
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UCC1889 UCC2889 UCC3889 PIN DESCRIPTIONS resistor connected between VOUT and TOFF. ADJ: The ADJ pin is used to provide a 12V or an 18V regulated supply without additional external components. To select the 12V option, ADJ pin is left open. To select the 18V option, ADJ pin must be grounded. For other output voltages less than 18V, a resistor divider between VOUT, ADJ and GND is needed.
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UCC1889 UCC2889 UCC3889 TYPICAL WAVEFORMS 5
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UCC1889 UCC2889 UCC3889 UNITRODE INTEGRATED CIRCUITS 7 CONTINENTAL BLVD. • MERRIMACK, NH 03054 TEL.
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE OPTION ADDENDUM www.ti.com 11-Apr-2013 TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
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PACKAGE MATERIALS INFORMATION www.ti.com 26-Jan-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant UCC2889DTR SOIC D 8 2500 330.0 12.4 6.4 5.2 2.1 8.0 12.0 Q1 UCC3889DTR SOIC D 8 2500 330.0 12.4 6.4 5.2 2.1 8.0 12.
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PACKAGE MATERIALS INFORMATION www.ti.com 26-Jan-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) UCC2889DTR SOIC D 8 2500 367.0 367.0 35.0 UCC3889DTR SOIC D 8 2500 367.0 367.0 35.
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