SLVT255 July   2026

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1Test Prerequisites
    1. 1.1 Voltage and Current Requirements
    2. 1.2 Safety Warning
    3. 1.3 Dimensions
    4. 1.4 Test Setup
  8. 2Testing and Results
    1. 2.1 Efficiency Graphs
    2. 2.2 Efficiency Data
    3. 2.3 Thermal Images
  9. 3Waveforms
    1. 3.1 Switching
    2. 3.2 Output Voltage Ripple
    3. 3.3 Start-Up Sequence
    4. 3.4 Dynamic Response
  10.   Trademarks

1.4 Test Setup

HV DC source connected to the VIN of the reference design board through power analyzer. The output connected to the electronic load for output current setting.

PMP41133 Test Setup Figure 1-1 Test Setup

The HV pin of UCC256612 starts to work at Vin is more than 20V, and charge VCCP pin. When VCCP ≥ VCCUVLOr (~7.5V), V5P provides 5V output. VCCP keeps charge to VCCStartSelf (~14V) and turn off the HV charging current until the VCCP = VCCStartExt (~ 10.9V).

The system brown in voltage is about 400V ~ 430V. We can check the voltage of VCCP, V5P and the gate voltage of external depletion mode N-Channel MOSFET (Q102) to confirm the start-up circuit works normally. Figure 1-2 shows the start-up waveform at VIN = 50V. V5P keeps at 5V, VCCP works in charging and discharging period. The image shows the voltage dip on the gate voltage which matches the charging period on VCCP. This means the HV sinks current and conducts Q102 by pulling low the source. The gate voltage of Q102 keeps in about half of VIN to provide the balance voltage stress between Q102 and HV pin.

PMP41133 Start-up Waveform at VIN = 50V. CH1: VIN, CH2: Gate of Q102, CH3: V5P, CH4: VCCP Figure 1-2 Start-up Waveform at VIN = 50V. CH1: VIN, CH2: Gate of Q102, CH3: V5P, CH4: VCCP