Dear TI:
My customer need a solution to monitor IGBT current, they want to keep the time from detecting the current to turning off IGBT within 5us. The purpose is when detect IGBT short, the circuit can quickly respond and turn off the IGBT.
What kind of OPA can meet the requirement of customer? Or is there another solution for the customer's application. Can you provide the solution reference schematic?
Thanks!
Dear Ronald:
Thanks for your reply!
Questions answered for you:
What is the supply voltage value? 280V-460V
Is the sense low side (near ground)? Low side, near ground.
What is the normal sense voltage range? 0A-80A
What is the threshold voltage for over current / short? Threshold: over voltage 30A, short 60A
Do you have a amplifier gain in mind? no idea, help to design.
Customer system block for you:
Eric,
By supply voltage, I meant supply voltage for op amp which can be same as supply for microcontroller. perhaps, 1.8V, 3.3V, 5V?
I see your sense current ranges but Rs is unknown. Sense voltage should be greater than 10X offset error in op amp. 10 * 1.65mV = 16.5mV. 16.5mV / 30A = 0.55m-ohm. round up to 0.001 ohm or more for Rs.
Kelvin sense at sense resistor is critical. For micro control input : is this a ADC input or comparator input? Two resistors on non-inverting input so that zero current runs about 100mV at op amp output.
I'll chose a gain once op amp supply voltage is known.
Eric,
Here is a solution with fastest response time, well under 5us. It also amplifies transient noise so the 0pF caps can be increased if needed.
VF1 (out) = 0.1V + 48.47*(IG1)* Rs ; 0.1V = 3.063% of Vs
DC simulation.
AC response time
