AVR-Chat

----- Original Message -----
From: "kc wong" <studioee03@yahoo.com>
To: "AVR-Chat" <avr-chat@yahoogroups.com>; "bascom"
<bascomlist@yahoogroups.com>; "hbridge"
<d200_h-bridge_motor_driver@yahoogroups.com>; "megabitty"
<megabitty@yahoogroups.com>
Sent: Tuesday, December 21, 2004 04:11
Subject: [AVR-Chat] mosfet driver IR2110/hbridge cct


> dear all,
>
> i build a full hbridge cct with 4 mosfet and 2 IR2110
mosfet driver and test it yesteday.
> i supply 5V to Vcc, 12V to Vcc and give signal with 5V to
Hin or Lin continuously to switching the 4 mosfet
continuously at 40Hz like usual.
> i connect Vb to Vs with cap 1uF, a diode FR103 from Vcc to
Vb, SD and Vss to GND, cap 22uF from Vdd to Vss,cap 22uF
from Vcc to com. HO to gate of high side mosfet through
22ohm and its Source to Vs. Lo to gate of mosfet low side
through 22ohm and its source to com.
>
> after that i supply 5V to Vdd and 12 V to Vcc and 0V to my
load. i found that Vbs=11.0V, and Vgate of high and low
mosfet or Vho and Vlo are around 4.0V.
> then i increase the load voltage (middle of hbridge like
usual) slowly.everthing looks find and the output is ok. but
when i keep increase the voltage, i found that the Vho or
gate voltage decrease and finally both high side mosfet turn
off when the load voltage exceed 3.0V but both low side
mosfet still on.
>
> then i increase the Vcc to 15V, the load output voltage
can reach only 6.0V. after that both the high side mosfet
off again. i check Vbs, it show more than 10V so i think it
is ok.
>
> (1) so what problem??    why Vgate of high side mosfet or
Vho keep decrease when i increase the load voltage? i need
to apply high voltage later, may be up to 200V and 10A to my
motor(load) so what can i do to my cct.
>
> thanks..
>
> from kim

From what I see, you are driving your upper MOSFETs with
just 15 volts relative to GROUND.  They are working like
voltage followers.

To fully turn on the upper MOSFETs, thier gate voltage has
to be a 6..12 volts higher than the voltage at thier source.

So you will need an isolated high-side driver for the two
upper MOSFETs.





erikc
firewevr@airmail.net