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UCC21550: Low secondary current isolated mosfet gate drivers (UCC21550, ...)

Jean-Marc Lucchini
Prodigy 20 points
Part Number: UCC21550
Other Parts Discussed in Thread: UCC21551

Tool/software:

Dear all,

I must develop an AC high voltage function generator with maximum 600Vrms @ 400Hz, i.e. 1700Vpp sine, with a 3Mohm load (0.2mArms).

I have already a programmable DC voltage source up to 2kV and max. 2mA.

The best way to do that I think is to generate the output signal with a Mosfet push-pull stage, and a PWM signal from our CPU to make the sine wave.

 I’m looking for an isolated dual channel Mosfet gate driver with those properties:

  • 1700V channel-to channel isolation
  • Max. 1mA Ivdd secondary current (supply), that I have some margin for the load current.
  • 100kHz PWM

 I was looking at drivers like the UCC21550, 21551, 21540, etc… But all of them need about 3mA on VDD, which overloads my HV DC generator.

 Unfortunately there is no parameter filter on the TI website for quiescent current and for channel-to-channel isolation, it makes the research difficult.

Do you have something which fits?

Thank you, best regards.

  • +1
    TI__Mastermind 23196 points

    Hi Jean-Marc,

    You are describing a Class-D output. You will need an inductor to convert the PWM into an analog current. At 2000V and 400Hz, you will need a large inductance and a high switching frequency. 

    UCC21551 sounds like a good start to approach this idea. It is rated for a 2121Vdc working voltage:

    It does not require 3mA of VDD quiescent current; Iq is closer to 1.2mA with a 15V supply. 2.7mA is only when you are running a 500kHz switching frequency, and this does not come from your high voltage! This is 15V supply current, and you will need a 15V isolated supply or a bootstrap capacitor to power the gate driver. 

    If the output can be floating, you can reduce the required switch voltages by 1/2 using an H-bridge (see example below).

     

    You can couple this with a 1:10 transformer to reduce the switching voltage required further. You will have higher of switching losses at high-voltage, and it will be much more efficient to switch fast at low voltage, and let a transformer boost the amplitude. The parasitic capacitances of the switches themselves will likely exceed the 2mA budget if you switch them at a respectable frequency. 

    We have piezo-electric drivers that may be of interest up to 200V: https://www.ti.com/motor-drivers/actuator-drivers/piezo-drivers/products.html 

    Best regards,

    Sean