SLUUCI9A January   2022  – December 2022 UCC28781

 

  1.   Abstract
  2.   Trademarks
  3. 1 Introduction
  4. 2 General Texas Instruments High Voltage Evaluation (TI HV EVM) User Safety Guidelines
  5. 3 Description of EVM
  6. 4 Electrical Performance Specifications of EVM
  7. 5 Schematic Diagram of EVM
  8. 6 Operating the EVM from a DC or an AC Source
    1. 6.1 Typical Applications
    2. 6.2 Using the EVM with a DC Voltage Source
    3. 6.3 Using the EVM with an AC Voltage Source
  9. 7 Test Set-ups
    1. 7.1 Test Set-up Requirements
      1. 7.1.1 Test Set-up Requirements for DC Input
      2. 7.1.2 Test Set-up Requirements for AC Input
    2. 7.2 Test Set-up Diagrams
    3. 7.3 Terminals and Test Points
  10. 8 Performance Data and Typical Characteristic Curves
    1. 8.1 Table of Efficiency Measurements with DC Input
    2. 8.2 Table of Efficiency Measurements with AC Input
    3. 8.3 Efficiency Graphs with DC Input Voltage (Typical Results)
    4. 8.4 Switching Frequencies in Various Operating Modes
    5. 8.5 Key Switching Waveforms and Operating Mode Load Current
    6. 8.6 Thermal Images at Full Load (15 V, 4.0 A) with DC and AC Inputs
  11. 9 Transformer Details
  12. 10EVM Assembly and Layout
  13. 11List of Materials
  14. 12Revision History

6.3 Using the EVM with an AC Voltage Source

The UCC28781EVM-053 may also be powered from an isolated high-voltage AC source ranging from 264 VRMS down to 90 VRMS with line frequency ranging from 50 Hz to 60 Hz. In general, input voltage must be > 90 VRMS to start and output current should be limited to 2 A or less when starting with input voltage < 180 VRMS.

Full-rated output power (60 W) may be obtained for input voltages in the 180-VRMS to 264-VRMS range. Output power rating is reduced (30 W) for input voltages in the 90-VRMS to 180-VRMS range due to the high rms level of primary current at low input voltages.

The isolated AC source should be connected to the EVM at J1 (AC INPUT terminal block) using a low-impedance cable such as suitably-insulated 18AWG twisted-pair wire less than 1 meter in length. The EVM provides the traditional full-wave rectified and filtered bulk-voltage section to enable evaluation of ZVSF performance when powered by an AC line. The output of the AC section is connected to the DC input by jumpering terminal block J2 to block J3 with short insulated jumper wires, observing the proper polarities. See connections per Figure 7-2.

When using an AC line input, the X-Cap Discharge (XCD) feature of the UCC28781-Q1 may be evaluated by installing the XCD Jumper into the "XCD ENABLED" position at J5. Remember to reposition the XCD Jumper into the "XCD DISABLED" position any time the AC input is not being used to avoid the risk of component damage from DC operation. Turn off all input power before repositioning the XCD jumper. Do not change J5 position under power.

The output of the EVM (15 V) is taken from terminal block J4 which should be connected to a passive resistor load or to an active electronic load. An active load usually affords great flexibility in loading methods and perturbations.