High side driving when full duty cycle & without transformer?

Thread Starter

Carbon Helium

Joined Sep 29, 2019
4
In general just boost capacitor with dedicated ICs like IR2110 will work, however it is not suitable for full duty cycle required application.

Apparently with transformer will cost more when isolation is not mandatory.

My idea:
1. build a step-up converter to make a voltage of VIN+12V and switch it between MOSFET's Gate by several PNP and NPN transistors
2. place a resistor between Source and Gate to keep MOSFET normally closed.
3. place a bidirectional Zener diode between Souce and Gate to ensure Vgs < Vgs max.
4. when opened, current flow through the resistor and Zener diode GS to make Vgs ≈ 10V
5. when closed, no current supply to Gate, Vgs = 0

I'm wondering using Boost or Ćuk converter circuit to generate a higher voltage as bridge high side MOSFET driving source, but I haven't seen any combination of them.
Is there any problem or better suggestion?
Please help me, thank you very much! ;)
 

Thread Starter

Carbon Helium

Joined Sep 29, 2019
4
It sounds like you are switching the high side. If you could switch the low side then you won't need the boosted voltage.
yes, but driving low side would make ground voltage differ from other parts of the circuit.
moreover, when designing synchronized SMPs and bridge topology this is unavoidable.
 

Alec_t

Joined Sep 17, 2013
10,384
Your outlined proposal for the high-side drive sounds ok, but couldn't you use P-MOSFETs for the high-side and avoid the need for the booster?
 

Thread Starter

Carbon Helium

Joined Sep 29, 2019
4
Your outlined proposal for the high-side drive sounds ok, but couldn't you use P-MOSFETs for the high-side and avoid the need for the booster?
but P-Channel MOSFET require higher voltage to close seems as same complexity as N-Channel ones.

I previously made a LED driver with P-Channel MOSFET, I just connect Gate and Source via a 10K resistor to keep it closed, when input voltage has ripple the LED light up slightly.
So if you want to design it reliable, a voltage higher than VIN is required too.
 
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