ZHCS779C March 2012 – July 2025 UCC28070 , UCC28070A
PRODUCTION DATA
- 1
- 1 特性
- 2 應用
- 3 說明
- 4 Pin Configuration and Functions
- 5 Specifications
-
6 Detailed Description
- 6.1 Overview
- 6.2 Functional Block Diagram
- 6.3
Feature Description
- 6.3.1 Interleaving
- 6.3.2 Programming the PWM Frequency and Maximum Duty-Cycle Clamp
- 6.3.3 Frequency Dithering (Magnitude and Rate)
- 6.3.4 External Clock Synchronization
- 6.3.5 Multi-phase Operation
- 6.3.6 VSENSE and VINAC Resistor Configuration
- 6.3.7 VSENSE and VINAC Open-Circuit Protection
- 6.3.8 Current Synthesizer
- 6.3.9 Programmable Peak Current Limit
- 6.3.10 Linear Multiplier and Quantized Voltage Feed Forward
- 6.3.11 Enhanced Transient Response (VA Slew-Rate Correction)
- 6.3.12 Bias Voltages (VCC and VREF)
- 6.3.13 PFC Enable and Disable
- 6.3.14 Adaptive Soft-Start
- 6.3.15 PFC Start-Up Hold Off
- 6.3.16 Output Overvoltage Protection (OVP)
- 6.3.17 Zero-Power Detection
- 6.3.18 Thermal Shutdown
- 6.3.19 Current Loop Compensation
- 6.3.20 Voltage Loop Compensation
- 6.4 Device Functional Modes
-
7 Application and Implementation
- 7.1 Application Information
- 7.2
Typical Application
- 7.2.1 Design Requirements
- 7.2.2
Detailed Design Procedure
- 7.2.2.1 Output Current Calculation
- 7.2.2.2 Bridge Rectifier
- 7.2.2.3 PFC Inductor (L1 and L2)
- 7.2.2.4 PFC MOSFETs (M1 and M2)
- 7.2.2.5 PFC Diode
- 7.2.2.6 PFC Output Capacitor
- 7.2.2.7 Current-Loop Feedback Configuration (Sizing of the Current-Transformer Turns-Ratio NCT and Current-Sense Resistor RS)
- 7.2.2.8 Current-Sense Offset and PWM Ramp for Improved Noise Immunity
- 7.2.3 Application Curves
- 7.3 Power Supply Recommendations
- 7.4 Layout
- 8 器件和文檔支持
- 9 Revision History
- 10Mechanical, Packaging, and Orderable Information
7.2.2.4 PFC MOSFETs (M1 and M2)
The main specifications for the PFC MOSFETs are:
- BVDSS, drain source breakdown voltage: ≥650V
- RDS(on), ON-state drain source resistance: 520mΩ at 25 °C, estimate 1Ω at 125°C
- COSS, output capacitance: 32pF at ~400V
- tr, devise rise time: 12ns
- tf, device fall time: 16ns
The losses in the device are calculated by Equation 45 and Equation 46. These calculations are approximations because the losses are dependent on parameters which are not well controlled. For example, the RDS(on) of a MOSFET may increase by a factor of 2 from 25°C to 125°C. Therefore several iterations may be needed to choose an optimum device for an application different than the one discussed here.
Each phase carries half the load power so the conduction losses are estimated by:
The switching losses in each MOSFET are estimated by:
The total losses in each MOSFET are then:
