Overview
The UC3854BDW is an enhanced bipolar Continuous Conduction Mode (CCM) Power Factor Correction (PFC) controller produced by Texas Instruments. This component is designed to provide all the necessary functions for active power factor corrected preregulators. It achieves near-unity power factor by shaping the AC input line current waveform to correspond to the AC input line voltage using average current mode control. This approach maintains stable, low distortion sinusoidal line current without the need for slope compensation, unlike peak current mode control.
Key Specifications
| Parameter | Value | Unit |
|---|---|---|
| Package | SOIC (DW) | - |
| Pins | 16 | - |
| Operating Temperature Range | 0°C to 70°C | °C |
| VCC Turn-On Threshold | 14.5 to 17.5 | V |
| VCC Turn-Off Threshold | 9 to 11 | V |
| ENA Threshold, Rising | 2.4 to 2.7 | V |
| ENA Input Current | -5 to 5 | µA |
| Voltage Amplifier Offset Voltage | -8 to 8 | mV |
| Start-Up Supply Current | 300 µA | µA |
| Oscillator Frequency | 85 to 115 kHz | kHz |
Key Features
- Controls Boost PWM to Near-Unity Power Factor
- Limits Line Current Distortion To <3%
- World-Wide Operation Without Switches
- Accurate Power Limiting
- Fixed-Frequency Average Current-Mode Control
- High Bandwidth (5 MHz), Low-Offset Current Amplifier
- Integrated Current- and Voltage-Amplifier Output Clamps
- Multiplier Improvements: Linearity, 500 mV VAC Offset (Eliminates External Resistor), 0 V to 5 V Multout Common-Mode Range
- VREF GOOD Comparator
- Faster and Improved Accuracy ENABLE Comparator
- UVLO Options (16 V/10 V or 10.5 V/10 V)
- 300-µA Start-Up Supply Current
Applications
The UC3854BDW is suitable for a variety of power supply applications that require high power factor correction, including:
- Offline power supplies
- Active power factor corrected preregulators
- High-power DC-DC converters
- Avionics and industrial power systems
- Systems requiring low line current distortion and high efficiency
Q & A
- What is the primary function of the UC3854BDW?
The UC3854BDW is designed to provide active power factor correction, achieving near-unity power factor by shaping the AC input line current waveform to correspond to the AC input line voltage.
- What control method does the UC3854BDW use?
The UC3854BDW uses average current mode control, which maintains stable, low distortion sinusoidal line current without the need for slope compensation.
- What are the key features of the UC3854BDW's voltage amplifier?
The voltage amplifier has high bandwidth (5 MHz), low offset, and integrated output clamps. It also features improved current sinking capability and a low offset VAC pin.
- What are the UVLO options available for the UC3854BDW?
The UC3854BDW offers UVLO threshold options of 16 V/10 V for offline operation and 10.5 V/10 V for startup from an auxiliary 12-V regulator.
- What is the typical start-up supply current of the UC3854BDW?
The typical start-up supply current is 300 µA.
- In what packages is the UC3854BDW available?
The UC3854BDW is available in 16-pin N (PDIP), DW (SOIC Wide), J (CDIP), and 20-pin Q (PLCC) packages.
- What is the operating temperature range of the UC3854BDW?
The operating temperature range is 0°C to 70°C.
- How does the UC3854BDW improve power limiting during brownout conditions?
The UC3854BDW provides foldback power limiting during brownout and extreme low line conditions by clamping the maximum multiplier output current to 2 × IAC at all times.
- What is the purpose of the VREF GOOD comparator in the UC3854BDW?
The VREF GOOD comparator ensures that the MOSFET driver output remains low if the supply of the 7.5 V reference is not yet up.
- How does the UC3854BDW reduce external component count?
The UC3854BDW reduces the external component count through features like amplifier output clamps, improved amplifier current sinking capability, and a low offset VAC pin, among others.
