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Translating a FET drive signal up in voltage

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treez

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Hi
We need to switch some PWM dimming FETs on and off. These FETs sit on top of a 100V rail and the driving micro sits at 0V…therefore we need to translate the drive signal up in voltage.
We can either use a SI8710 digital isolator, or a IRS25752 bootstrap driver. The IRS25752 looks a hands down winner as its cheaper, smaller, and uses less bias current.

Can you think of any disadvantages of the IRS25752?

IRS25752
https://www.infineon.com/dgdl/irs25752lpbf.pdf?fileId=5546d462533600a40153567b388b2839

SI8710
https://media.digikey.com/pdf/Data Sheets/Silicon Laboratories PDFs/Si87xx.pdf
 

The bootstrap device won't work for static voltages, if that's a concern...
 
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Both drivers need a power supply on top of the 100V rail in this circuit, thus IRS25752 is the cheaper solution.
 
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Hi,

Optocoupler, photoMOS, relais...
Or some kind of switched capacitor circuit...this may avoid extra power supply.

Klaus
 

We should know pwm frequency and load current to decide about appropriate driver circuit.
 

pwm frequency is 500Hz. Load is just 2 little sot23 fets being driven on/off
 

Simple charge pump creates 107V on top of 100V supply rail. Switched by NPN transistor biased by 5V clock signal at 500 Hz. This results in the load getting 7V DC pulses.

charge pump clk NPN cap applies 107V to load ref'd to 100V supply rail.png

Duty cycle and component values can be adjusted to produce a wide range of volt levels. The simulation has the resistors carrying a few mA.
 
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