SBAA549 April   2022 AMC23C11 , AMC23C12 , AMC23C14

 

  1.   Trademarks
  2. 1Background
  3. 2Overcurrent Protection on DC+
  4. 3DC+ Power Supply Solution
    1. 3.1 Selection of Charge Pump Capacitor
    2. 3.2 Simulation in PSpice for TI
    3. 3.3 Hardware Test
    4. 3.4 Low-Cost Power Supply Solution
  5. 4Power-On Short-Circuit Risk and Solution
  6. 5Reference

3 DC+ Power Supply Solution

Figure 3-1 shows the implementation of a DC+ power supply.


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Figure 3-1 DC+ Power Supply Solution

The DC+ power supply solution consists of two parts. The first part is a bootstrap circuit consisting of a high-voltage diode D1, a capacitor C7 and current-limiting resistor R6. C7 is charged by the low-side gate driver power supply. The second part is a charge pump consisting of a high-voltage diode D2, a capacitor C2 and current-limiting resistor R4. When the half bridge starts to operate there are three operating states as follows:

  • When the low-side IGBT turns on, C7 is charged by the power supply of the low-side gate driver and D2 is turned off.
  • When the high-side IGBT turns on, D2 conducts, C7 charges the isolated comparator and capacitor C2.
  • When the low-side IGBT turns on again, C7 is charged by the low-side power supply and C2 continues to supply power to the isolated comparator.

In summary, this charge-pump based bootstrap circuit provides power to the isolated comparators with the help of energy stored in capacitors C7 and C2 during the IGBT switch phases.