Overview
The UC3854DWTR is a high-power factor preregulator integrated circuit designed by Texas Instruments. This device is specifically engineered to provide active power factor correction (PFC) for power systems, ensuring that the current drawn from sinusoidal power lines is sinusoidal and in phase with the voltage. The UC3854DWTR is part of the UCx854 family and is particularly suited for applications requiring high power factor and efficiency across a wide range of line frequencies (50 Hz to 400 Hz) and voltages (75 V to 275 V).
The IC implements all necessary control functions to build a power supply that optimally uses available power-line current while minimizing line-current distortion. It features average current-mode control, which maintains sinusoidal line current without slope compensation and with minimal response to noise transients.
Key Specifications
| Parameter | Value | Units |
|---|---|---|
| Package | SOIC (DW) | - |
| Pins | 16 | - |
| Operating Temperature Range | 0°C to 70°C | °C |
| Supply Current, Off | 1.5 to 2.0 | mA |
| Supply Current, On | 10 to 16 | mA |
| VCC Turn-On Threshold | 14.5 to 17.5 | V |
| VCC Turn-Off Threshold | 9 to 11 | V |
| PWM Frequency | Up to 200 kHz | Hz |
| Current Amplifier Bandwidth | 1 MHz typical | Hz |
| Multiplier Output Voltage (High) | 2.5 V typical | V |
Key Features
- Control Boost PWM to achieve a power factor of up to 0.99
- Limit line-current distortion to less than 5%
- World-wide operation without switches
- Feedforward line regulation
- Average current-mode control for fixed-frequency current control with stability and low distortion
- Low noise sensitivity
- Low startup supply current
- Fixed-frequency PWM drive
- Low-offset analog multiplier and divider
- 1-A totem-pole gate driver
- Precision voltage reference (7.5 V)
- Power MOSFET-compatible gate driver
- Line anticipator, load-enable comparator, low-supply detector, and overcurrent comparator
Applications
The UC3854DWTR is generally applicable to the control of AC-DC power supplies that require active power factor correction (PFC) off universal AC lines. It is particularly useful in single-phase and three-phase systems with line voltages ranging from 75 V to 275 V and line frequencies from 50 Hz to 400 Hz.
Typical applications include:
- High-power factor preregulators
- AC-DC power supplies
- Boost converters operating in continuous mode
- Equipment meeting Class D input current harmonics standards per EN61000-3-2
Q & A
- What is the primary function of the UC3854DWTR?
The primary function of the UC3854DWTR is to provide active power factor correction (PFC) for power systems, ensuring that the current drawn from sinusoidal power lines is sinusoidal and in phase with the voltage.
- What is the operating temperature range of the UC3854DWTR?
The operating temperature range of the UC3854DWTR is 0°C to 70°C.
- What is the typical PWM frequency of the UC3854DWTR?
The UC3854DWTR can operate at PWM frequencies up to 200 kHz.
- What type of control mode does the UC3854DWTR use?
The UC3854DWTR uses average current-mode control to maintain sinusoidal line current with stability and low distortion.
- What are the key components included in the UC3854DWTR?
The UC3854DWTR includes a voltage amplifier, an analog multiplier and divider, a current amplifier, a fixed-frequency PWM, a power MOSFET-compatible gate driver, a 7.5-V reference, a line anticipator, a load-enable comparator, a low-supply detector, and an overcurrent comparator.
- How does the UC3854DWTR handle noise sensitivity?
The UC3854DWTR has low noise sensitivity due to its high reference voltage and high oscillator amplitude, which minimize the impact of noise transients.
- What is the purpose of the soft-start function in the UC3854DWTR?
The soft-start function in the UC3854DWTR allows the voltage control loop to begin operation before the output voltage has reached its operating point, eliminating turn-on overshoot.
- Can the UC3854DWTR be used in both single-phase and three-phase systems?
Yes, the UC3854DWTR can be used in both single-phase and three-phase systems with line voltages ranging from 75 V to 275 V and line frequencies from 50 Hz to 400 Hz.
- What standards does the UC3854DWTR meet in terms of input current harmonics?
The UC3854DWTR meets the Class D equipment input current harmonics standards per EN61000-3-2.
- How does the UC3854DWTR protect the power MOSFETs?
The UC3854DWTR protects the power MOSFETs through an emergency peak current limit and by clamping the output voltage internally to prevent gate overdrive.
