Overview
The UC3854DWTRG4, produced by Texas Instruments, is a high-power factor preregulator integrated circuit designed to provide active power factor correction (PFC) for power systems. This device ensures that the power supply draws sinusoidal current from the sinusoidal power lines, minimizing line current distortion. The UC3854 implements all necessary control functions to optimize the use of available power-line current, making it suitable for various high-power applications.
Key Specifications
| Parameter | Minimum | Typical | Maximum | Unit |
|---|---|---|---|---|
| Supply Current (OFF) | 1.5 | 2 | - | mA |
| Supply Current (ON) | 10 | 16 | - | mA |
| VCC Turn-on Threshold | 14.5 | 16 | 17.5 | V |
| VCC Turn-off Threshold | 9 | 10 | 11 | V |
| ENA Threshold, Rising | 2.4 | 2.55 | 2.7 | V |
| ENA Input Current | -5 | -0.2 | 5 | µA |
| VREF Output Voltage | 7.4 | 7.5 | 7.6 | V |
| Current Amplifier Gain-Bandwidth Product | 400 | 800 | - | kHz |
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 7.5-V voltage reference
- Power MOSFET-compatible gate driver
- Line anticipator, load-enable comparator, low-supply detector, and overcurrent comparator
Applications
- Offline AC-to-DC converters
- Medical, industrial, telecom, and IT power supplies
- Uninterruptible Power Supplies (UPS)
- Appliances and white goods
- High-power applications requiring active power factor correction
The UC3854 is particularly useful in systems that need to comply with Class D equipment input current harmonics standards per EN61000-3-2, especially for equipment with rated powers higher than 75 W.
Q & A
- What is the primary function of the UC3854?
The UC3854 provides active power factor correction for power systems, ensuring that the power supply draws sinusoidal current from sinusoidal power lines.
- What is the typical power factor achieved by the UC3854?
The UC3854 can achieve a power factor of up to 0.99.
- What is the operating temperature range for the UC3854?
The operating temperature range for the UC3854 is 0°C to 70°C.
- What type of control method does the UC3854 use?
The UC3854 uses average current-mode control for fixed-frequency current control.
- What are some of the key features of the UC3854?
Key features include a precision 7.5-V voltage reference, low-offset analog multiplier and divider, 1-A totem-pole gate driver, and power MOSFET-compatible gate driver.
- What are the typical applications of the UC3854?
Typical applications include offline AC-to-DC converters, medical and industrial power supplies, UPS, and appliances requiring high power factor correction.
- How does the UC3854 handle line current distortion?
The UC3854 limits line-current distortion to less than 5%.
- What is the role of the feedforward line regulation in the UC3854?
The feedforward line regulation helps in maintaining stable output voltage by compensating for changes in the input line voltage.
- What is the significance of the 7.5-V reference output in the UC3854?
The 7.5-V reference output is used as a precise voltage reference for the control circuits within the UC3854.
- How does the UC3854 handle overcurrent conditions?
The UC3854 includes an overcurrent comparator that shuts off the output pulse when an overcurrent condition is detected.
