UC1852N_技术文档

UC1852

UC2852

UC3852

High Power-Factor Preregulator

FEATURES

DESCRIPTION

The UC1852 provides a low-cost solution to active power-factor correction (PFC)

for systems that would otherwise draw high peak current pulses from AC power

lines. This circuit implements zero-current switched boost conversion, producing

sinusoidal input currents with a minimum of external components, while keeping

peak current substantially below that of fully-discontinuous converters.

•

Low-Cost Power Factor

Correction

•

Power Factor Greater Than 0.99

Few External Parts Required

Controlled On-Time Boost PWM

Zero-Current Switching

The UC1852 provides controlled switch on-time to regulate the output bulk DC

voltage, an off-time defined by the boost inductor, and a zero-current sensing

circuit to reactivate the switch cycle. Even though switching frequency varies with

both load and instantaneous line voltage, it can be maintained within a reasonable

range to minimize noise generation.

Limited Peak Current

Min and Max Frequency Limits

Starting Current Less Than 1mA

High-Current FET Drive Output

Under-Voltage Lockout

While allowing higher peak switch currents than continuous PFCs such as the

UC1854, this device offers less external circuitry and smaller inductors, yet better

performance and easier line-noise filtering than discontinuous current PFCs with

no sacrifice in complexity or cost. The ability to obtain a power factor in excess of

0.99 makes the UC1852 an optimum choice for low-cost applications in the 50 to

500 watt power range. Protection features of these devices include under-voltage

lockout, output clamping, peak-current limiting, and maximum-frequency

clamping.

The UC1852 family is available in 8-pin plastic and ceramic dual in-line packages,

and in the 8-pin small outline IC package (SOIC). The UC1852 is specified for

operation from -55°C to +125°C, the UC2852 is specified for operation from -40°C

to +85°C, and the UC3852 is specified for operation from 0°C to +70°C.

TYPICAL APPLICATION

UDG-92001

10/94

UC1852

UC2852

UC3852

ABSOLUTE MAXIMUM RATINGS

CONNECTION DIAGRAM

Supply Voltage (Low-impedance Source)..........................30.0V

Supply Current (High-impedance Source) ......................30.0mA

OUT Current, Peak.............................................................±1.0A

OUT Energy, Capacitive Load............................................ 5.0µJ

Input Voltage, ISNS ............................................................±5.0V

Input Voltage, VFB............................................. –0.3V to +10.0V

COMP Current...............................................................±10.0mA

ISET Current..................................................................–10.0mA

Power Dissipation at Ta≤25°C (Note 3) ..............................1.0W

Storage Temperature .......................................–65°C to +150°C

Lead Temperature (Soldering, 10 Seconds)................... +300°C

Note 1: All voltages with respect to GND (Pin 1).

DIL–8 (TOP VIEW)

J or N Package

SOIC–8 (TOP VIEW)

D Package

Note 2: All currents are positive into the specified terminal.

Note 3: Refers to DIL-8 Package. Consult Packaging Section of

Unitrode Integrated Circuits databook for thermal limitations and

considerations of package.

UDG-92002

Unless otherwise stated, VCC=24V, ISET=50kΩ to GND, RAMP=1nF to GND, ISNS=

–0.1V, VFB connected to COMP, no load on OUT, –55°C<Ta<+125°C for the UC1852,

–40°C<Ta<+85°C for the UC2852, and 0°C<Ta<+70°C for the UC3852, and Ta=Tj.

ELECTRICAL CHARACTERISTICS

PARAMETER

Timer Section

TEST CONDITIONS

MIN.

TYP.

MAX. UNITS

ISET Voltage

4.5

88

12

5.0

98

5.5

108

50

V

µA

mA

V

RAMP Charge Current

RAMP Discharge Current

RAMP Saturation Voltage

RAMP Threshold - Maximum Frequency

RAMP Threshold - PWM Comparator

Current Sense Comparator

ISNS Restart Threshold

ISNS Fault Threshold

RAMP=2.5V

ISNS= –1.0V, RAMP=1.0V

ISNS= –1.0V, IRAMP=100µA

VFB=10V, COMP open

28

0.006

1.02

4.3

0.200

1.12

4.8

0.92

3.9

V

–18

–550

–100

–10

–450

–30

–4

mV

µA

–350

100

ISNS Input Current

Error Amplifier Section

VFB Input Voltage

4.6

–5.00

10

5.0

5.3

V

µA

mA

µA

V

VFB Input Bias Current

COMP Sink Current

–0.03

5.00

COMP=7.5V

COMP Source Current

COMP Clamp Voltage

OUT Output

COMP=2.5V

–300

9.2

–175

10.0

–100

10.6

VFB=0.0V, COMP open

OUT Saturation Voltage High

OUT Saturation Voltage Low

OUT Saturation Voltage Low @ 10mA

OUT Clamp Voltage

VCC=13V, IOUT= –200mA, RAMP=2V

IOUT=200mA, ISNS= –1.0V

IOUT=10mA, ISNS= –1.0V

IOUT= –200mA, RAMP=2V

IOUT=100mA, VCC=0V

0.5

1.7

1.6

2.5

2.2

V

0.05

12.0

1.0

0.40

14.5

2.2

10.0

0.5

OUT Voltage during UVLO

Overall Section

Inactive Supply Current

Active Supply Current

VCC=10V

ICC=25mA

0.2

3.0

30

0.4

6.0

33

1.0

10.0

36

mA

V

VCC Clamp Voltage

VCC Turn-On Threshold

VCC Turn-Off Threshold

VCC Threshold Hysteresis

14.5

10.5

3

16.3

11.5

5

17.5

13.0

7

V

2

UC1852

UC2852

UC3852

DETAILED BLOCK DIAGRAM

UDG-92003

PIN DESCRIPTIONS

COMP: COMP is the output of the error amplifier and the accuracy, ISNS should be connected to a current sense

input of the PWM comparator. To limit PWM on-time, this resistor through no more than 200 ohms.

pin is clamped to approximately 10V. To implement soft

OUT: The output of a high-current power driver capable of

start, the COMP pin can be pulled low and ramped up with

driving the gate of a power MOSFET with peak currents

a PNP transistor, a capacitor, and a resistor.

exceeding ±500mA. To prevent damage to the power

GND: Ground for all functions is through this pin.

MOSFET, the OUT pin is internally driven by a 12V supply.

However, lead inductance between the OUT pin and the

load can cause overshoot and ringing. External current

boost transistors will increase this overshoot and ringing. If

there is any significant distance between the IC and the

MOSFET, external clamp diodes and/or series damping

resistors may be required. OUT is actively held low when

the VCC is below the UVLO threshold.

ISET: The dominant function is of this pin is to program

RAMP charging current. RAMP charging current is

approximately 5V divided by the external resistor placed

from ISET to ground. Resistors in the range of 10kΩ to

50kΩ are recommended, producing currents in the range

of 100µA to 500µA.

A second function of ISET is as reference output. The ISET

pin is normally regulated to 5V ±10%. It is critical that this

pin onlysee the loading of the RAMP programmingresistor,

but a high input-impedance comparator or amplifier may be

connected to this pin or to a tap on the RAMP programming

resistor if required.

RAMP: A controlled on-time PWM requires a timer whose

time can be modulated by an external voltage. The timer

current is programmed by a resistor from ISET to GND. A

capacitor from RAMP to GND sets the on time in

conjunction with the voltage on COMP. Recommended

valuesfor thetimer capacitors are between100pFand1nF.

The third function of the ISET pin is as a FAULT output. In

the event of an over-current fault, the ISET pin is forced to

approximately 9V by the fault comparator. Thiscan beused

to trip an external protection circuit which can disable the

load or start a fault restart cycle.

VCC: VCC isthe logic andcontrol power connection for this

device. VCC current is the sum of active device supply

current and the average OUT current. Knowing the

maximum operating frequency and the MOSFET gate

charge (Qg), average OUT current can be estimated by:

ISNS: This input to the zero and over current comparators

is specially built to allow operation over a ±5V dynamic

range. In noisy systems or systems with very high Q

inductors, it is desirable tofilterthe signal entering the ISNS

input to prevent premature restart or fault cycles. For best

I_OUT= Q _g× F

To prevent noise problems, bypass VCC to GND with both

a ceramic and an electrolytic capacitor.

VFB: VFB is the error amplifier inverting input. This input

serves as both the voltage sense input to the error amplifier

3

UC1852

UC2852

UC3852

TYPICAL CHARACTERISTICS

Error Amplifier Gain and Phase

Max Frequency vs. Rset and Ct

100

80

60

40

20

0

1000

100pF

500pF

1nF

Phase

3nF

Gain

(dB)

Phase

(deg)

Maximum

Frequency,

Gain

100

kHz

10

-20

1

10

100

10

100

1000

10000

Rset, k

Ω

Frequency, kHz

UDG-92005

UDG-92006

Max On-Time vs. Rset and Ct

OUT Rise and Fall Time

1000

100

10

200

150

Fall Time

Maximum

On-Time

10nF

ns 100

50

µs

3nF

1nF

Rise Time

300pF

100pF

1

0

1

10

100

5

10

Rset, kΩ

Load Capacitance, nF

UDG-92007

UDG-92008

4

UC1852

UC2852

UC3852

APPLICATION INFORMATION: A 100 Watt Power Factor Preregulator

UDG-92004

This circuit demonstrates a complete power factor preregulator based on the UC3852. This preregulatorwill supply

up to 100 watts at 400VDC and exhibit power factor greater than 0.995 with less than 10% total harmonic distortion.

Operating input range is 90V to 160V RMS at 50Hz to 60Hz.

This design is intentionally simple, yet fully functional. The UC3852 can also be used in designs featuringsoft start,

over-voltage protection, wide power-line voltage operation, and fault latching. For more information on applying

the UC3852, refer to Unitrode Application Note U–132.

PARTS LIST

C1

C2

C3

C4

C5

C6

D1

0.47µF/250VAC X2 Class Polyester

1nF/16V Ceramic

Q1

L1

IRF830 4.5A/500V 1.5Ω Power FET

680µH (Renco RL3792 with

10 Turn 24 AWG Secondary)

68µF/35V Aluminum Electrolytic

180pF/16V Ceramic

R1

R2

R3

R4

R5

R6

R7

R8

150kΩ, ¹⁄ W

4

0.2Ω, ¹⁄ W Carbon Composition

2

0.1µF/16V Polyester or Ceramic

82µF/450V Aluminum Electrolytic

10Ω, ¹⁄ W

4

13.3kΩ, ¹⁄ W

4

2A/500V Bridge Rectifier (Collmer

KBPC106 or Powertex MB11A02V60)

1MΩ, ¹⁄ W

4

D2

D3

100mA/50V Switching Diode (1N4148)

20kΩ, ¹⁄ W

4

2A/500V 250ns Recovery-Time Rectifier

(Motorola MR856)

200kΩ, ¹⁄ W

2

200kΩ, ¹⁄ W

2

IC1 UC3852N Power Factor Controller IC

UNITRODE INTEGRATED CIRCUITS

7 CONTINENTAL BLVD. • MERRIMACK, NH 03054

TEL. (603) 424-2410 • FAX (603) 424-3460

5

IMPORTANT NOTICE

Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue

any product or service without notice, and advise customers to obtain the latest version of relevant information

to verify, before placing orders, that information being relied on is current and complete. All products are sold

subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those

pertaining to warranty, patent infringement, and limitation of liability.

TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in

accordance with TI’s standard warranty. Testing and other quality control techniques are utilized to the extent

TI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily

performed, except those mandated by government requirements.

CERTAIN APPLICATIONS USING SEMICONDUCTOR PRODUCTS MAY INVOLVE POTENTIAL RISKS OF

DEATH, PERSONAL INJURY, OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE (“CRITICAL

APPLICATIONS”). TI SEMICONDUCTOR PRODUCTS ARE NOT DESIGNED, AUTHORIZED, OR

WARRANTED TO BE SUITABLE FOR USE IN LIFE-SUPPORT DEVICES OR SYSTEMS OR OTHER

CRITICAL APPLICATIONS. INCLUSION OF TI PRODUCTS IN SUCH APPLICATIONS IS UNDERSTOOD TO

BE FULLY AT THE CUSTOMER’S RISK.

In order to minimize risks associated with the customer’s applications, adequate design and operating

safeguards must be provided by the customer to minimize inherent or procedural hazards.

TI assumes no liability for applications assistance or customer product design. TI does not warrant or represent

that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other

intellectual property right of TI covering or relating to any combination, machine, or process in which such

semiconductor products or services might be or are used. TI’s publication of information regarding any third

party’s products or services does not constitute TI’s approval, warranty or endorsement thereof.


型号：	UC1852N
厂家：	ETC
描述：	Power Factor Controller 功率因数控制器\n 光电二极管控制器
文件：	总6页 (文件大小：235K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

UC1852N [ETC]

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