ZHCSC62D March 2014 – December 2017 UCC28630 , UCC28631 , UCC28632 , UCC28633 , UCC28634
PRODUCTION DATA.
- 1 特性
- 2 应用
- 3 说明
- 4 修订历史记录
- 5 Device Comparison Table
- 6 Pin Configuration and Functions
- 7 Specifications
-
8 Detailed Description
- 8.1 Overview
- 8.2 Functional Block Diagram
- 8.3
Feature Description
- 8.3.1 High-Voltage Current Source Start-Up Operation
- 8.3.2 AC Input UVLO / Brownout Protection
- 8.3.3 Active X-Capacitor Discharge (UCC28630 and UCC28633 only)
- 8.3.4 Magnetic Input and Output Voltage Sensing
- 8.3.5 Fixed-Point Magnetic Sense Sampling Error Sources
- 8.3.6 Magnetic Sense Resistor Network Calculations
- 8.3.7 Magnetic Sensing: Power Stage Design Constraints
- 8.3.8 Magnetic Sense Voltage Control Loop
- 8.3.9 Peak Current Mode Control
- 8.3.10 IPEAK Adjust vs. Line
- 8.3.11 Primary-Side Constant-Current Limit (CC Mode)
- 8.3.12 Primary-Side Overload Timer (UCC28630 only)
- 8.3.13 Overload Timer Adjustment (UCC28630 only)
- 8.3.14 CC-Mode IOUT(lim) Adjustment
- 8.3.15 Fault Protections
- 8.3.16 Pin-Fault Detection and Protection
- 8.3.17 Over-Temperature Protection
- 8.3.18 External Fault Input
- 8.3.19 External SD Pin Wake Input (except UCC28633)
- 8.3.20 External Wake Input at VSENSE Pin (UCC28633 Only)
- 8.3.21 Mode Control and Switching Frequency Modulation
- 8.3.22 Frequency Dither For EMI (except UCC28632)
- 8.4 Device Functional Modes
-
9 Applications and Implementation
- 9.1 Application Information
- 9.2
Typical Application
- 9.2.1 Notebook Adapter, 19.5 V, 65 W
- 9.2.2 UCC28630 Application Schematic
- 9.2.3 Design Requirements
- 9.2.4
Detailed Design Procedure
- 9.2.4.1 Custom Design With WEBENCH® Tools
- 9.2.4.2 Input Bulk Capacitance and Minimum Bulk Voltage
- 9.2.4.3 Transformer Turn Ratio
- 9.2.4.4 Transformer Magnetizing Inductance
- 9.2.4.5 Current Sense Resistor RCS
- 9.2.4.6 Transformer Constraint Verification
- 9.2.4.7 Transformer Selection and Design
- 9.2.4.8 Slope Compensation Verification
- 9.2.4.9 Power MOSFET and Output Rectifier Selection
- 9.2.4.10 Output Capacitor Selection
- 9.2.4.11 Calculation of CC Mode Limit Point
- 9.2.4.12 VDD Capacitor Selection
- 9.2.4.13 Magnetic Sense Resistor Network Selection
- 9.2.4.14 Output LED Pre-Load Resistor Calculation
- 9.2.5 External Wake Pulse Calculation at VSENSE Pin (UCC28633 Only)
- 9.2.6 Energy Star Average Efficiency and Standby Power
- 9.2.7 Application Performance Plots
- 9.3 Dos and Don'ts
- 10Power Supply Recommendations
- 11Layout
- 12器件和文档支持
- 13机械、封装和可订购信息
9.2.4.8 Slope Compensation Verification
After choosing the current sense resistor, transformer inductance and transformer turns ratio, verify the required slope compensation against the fixed internal slope compensation. The worst case slope compensation requirement always occurs at the highest duty cycle operating point (at minimum bulk voltage level).
For stability, the slope compensation should be at least 50% of the difference between the inductor up-slope and down-slope. [reference Bob Mammano TI Power Supply Design Seminar paper, 2001, SLUP173]. For a flyback converter, the difference in slopes in CCM is equal the operating duty cycle multiplied by the inductor current down-slope value. For example, for 50% dBULK(min) at minimum bulk capacitor voltage, the required slope compensation ramp is 25% of the inductor current down-slope.
As listed in Table 8, the specified peak-load transient is 130 W for 2 ms. In a worst case, peak transient timing with respect to the AC phase, the VBULK minimum level dips to 65 V. This corresponds to a duty cycle of approximately 63.5% according to Equation 50.
The required slope compensation ramp is calculated at 63.5% duty cycle.
This value is within the 30 mV/μs of internal slope compensation provided by the controller.