ZHCSKB9Q December 1999 – October 2019 UCC1895 , UCC2895 , UCC3895
PRODUCTION DATA.
- 1 特性
- 2 应用
- 3 说明
- 4 修订历史记录
- 5 Pin Configuration and Functions
- 6 Specifications
-
7 Detailed Description
- 7.1 Overview
- 7.2 Functional Block Diagrams
- 7.3
Feature Description
- 7.3.1 ADS (Adaptive Delay Set)
- 7.3.2 CS (Current Sense)
- 7.3.3 CT (Oscillator Timing Capacitor)
- 7.3.4 DELAB and DELCD (Delay Programming Between Complementary Outputs)
- 7.3.5 EAOUT, EAP, and EAN (Error Amplifier)
- 7.3.6 OUTA, OUTB, OUTC, and OUTD (Output MOSFET Drivers)
- 7.3.7 PGND (Power Ground)
- 7.3.8 RAMP (Inverting Input of the PWM Comparator)
- 7.3.9 REF (Voltage Reference)
- 7.3.10 RT (Oscillator Timing Resistor)
- 7.3.11 GND (Analog Ground)
- 7.3.12 SS/DISB (Soft Start/Disable)
- 7.3.13 SYNC (Oscillator Synchronization)
- 7.3.14 VDD (Chip Supply)
- 7.4 Device Functional Modes
- 7.5 Programming
-
8 Application and Implementation
- 8.1 Application Information
- 8.2
Typical Application
- 8.2.1 Design Requirements
- 8.2.2
Detailed Design Procedure
- 8.2.2.1 Power Loss Budget
- 8.2.2.2 Preliminary Transformer Calculations (T1)
- 8.2.2.3 QA, QB, QC, QD FET Selection
- 8.2.2.4 Selecting LS
- 8.2.2.5 Selecting Diodes DB and DC
- 8.2.2.6 Output Inductor Selection (LOUT)
- 8.2.2.7 Output Capacitance (COUT)
- 8.2.2.8 Select Rectifier Diodes
- 8.2.2.9 Input Capacitance (CIN)
- 8.2.2.10 Current Sense Network (CT, RCS, RR, DA)
- 8.2.3 Application Curves
- 9 Power Supply Recommendations
- 10Layout
- 11器件和文档支持
- 12机械、封装和可订购信息
8.2.2.10.1 Output Voltage Setpoint
Peak current mode control is chosen for this design and a TL431 (U1) acts as the output voltage error amplifier. It has a 2.5-V internal reference and we want to regulate VOUT to 12 V. We set RB, the lower resistor of the output voltage divider chain to 10 kΩ. RA the upper resistor is given by:
It is possible, but not necessary, to add a small resistor, RLOOP, in series with the feedback network as a signal injection point for loop stability tests, RLOOP.
The output of U1 is transferred across the isolation barrier by the optocoupler U2 and fed into the EAP pin of the UCC3895 as a current demand signal. The UCC2895 internal error amplifier is configured as a voltage follower by connecting EAN to EAOUT.