What's the proper schematic for driving the IGBT (IRG4BC20UD) from a microcontroller (MSP430-g2553) pin through the optocoupler (FOD3148)? I am going to design a full bridge inverter to drive 9W CFLs (220V/50Hz)? PLEASE HELP!
Hi John,You should wire the LED with a single series resistor - I get about 90 ohms at 3Vdd and 10ma - so remove the 100 ohm nearest the uC. A '1' on the output port should source about 10ma at 2.7V. 2.7Vout-1.8Vfmax = .9V .9/10ma=90 ohms series resistance.
The NOTES part of the data sheet says to connect pins 1 and 4 to LED common (Item 9) but the pinout says NC - go figure.
You show no load on the IGBT so when it turns on, it will smoke maybe?
ronv pretty much sums up the rest.
Good Luck.
Sure.Can you kindly tell me how did you come up with the 10mA/2.7V at the output port? I find it very hard to understand datasheets. Please help! I also don't understand the datasheet note about pin 1 and 4 need to be connected to the led common as it shows no connection in the test circuit.
Agreed. To test one channel (not the H bridge) don't connect HV where you have it. Connect it to what you called Vo on the drawing. Vo then becomes the collector of the IGBT. Turn on the LED and the IGBT should turn on, pulling Vo to ground.The load goes in the center bar of the H made by the 4 IGBT's.
Hi John,A couple of things.
The NMK0515SC is rated for 15V at 250ma. The drawing in post #5 shows pins 3 and 4 reversed (hooked up backwards). Is the power supply for the IGBT separate?
Are you sure everything is hooked up according to the drawing? 13V through a 1K resistor is only 13ma, even if the IGBT is shorted/backwards so something is wrong there.
Hi John,The datasheet for the DC DC converter is a bit fuzzy on the 10% requirement. It does not specifically say (that I can find) that the min output current must be 10% of full load. It does use 10% as a minimum load for the various output specifications. I would therefore load it to 10% minimum for your tests. How about an LED running at 7ma as a power on indicator for now?
The extra LC on the output is not necessary. You can add them to reduce ripple but don't worry about that for now.
As far as the opto, why not test it by removing the IGBT stuff and just rigging another LED to the output? Use Fig 22 in the opto datasheet as a reference (for the output side) and put an LED and resistor to pull 20ma or so from pins 6+7 to ground, anode towards ground. When your processor turns on the opto, the LED should light, troubleshoot from there.
Good luck.
What are you measuring the voltage with? Be sure you are measuring from the pin to ground, not across the LED. Be aware that if you are driving the output as a PWM, the voltage measured with a DVM will be roughly the expected output voltage * the duty cycle i.e. 2.7V 50% duty cycle gives .5*2.7V=1.35V measured. Other than that, I don't know.Any observation on that? I am producing a spwm signal from the pin 1.2 of chip 2553.
Hi,Are you sure you have the 90 ohm resistor in series with the diode?
Check that pin at the output of the mico with the resistor disconnected.
by Jake Hertz
by Jake Hertz
by Jake Hertz
by Don Wilcher