IR2125 - High Side Switching problem

[devura]

I am using the following circuit for high side driving of an IGBT. Details of the circuit are as follows:


+ HV is 110 V DC
IGBT = CT60AM18F (60Amps/900V Mitsubishi)
Rg = 39 Ohms / 0.25W
Rs = 0.1 Ohm / 2W NIWW

Instead of 100K (between HVRTN and pin-1 of 555 IC), I am using 56K/2W and instead of 11DF6 and 1N4148 diodes, I am using MUR160 diodes. My load is inductive and is a contactor coil of approximately 200 Ohms resistance

My problem is that, when I am applying short circuit, with system on load (fault under load) condition, my IGBT is sustaining the short-circuit and is protected. But if the load is short circuited first and then the supply is switched ON, there is no protection coming into picture and my IGBT is getting punctured (Gate – Emitter – Collector – ALL SHORTED).

already have a 4.7KOhm / 0.25W resistor connected
to Ground from IN pin. So is is guarenteed that the
IN pin is pulled to LOW during start-up.

I have sepearte power for 110 V DC at +HV and +8V at the
IN input. The exact circuit I am using is attached herewith
for your reference. My inductive load (Contactor coil) is
connected between O6 and SGND i.e, in parallel with the
100k/0.25W resitor in the circuit attached.

I am repeating my problem again:

When 110V DC is applied and when the input is applied, the
IGBT gets the gate pulses and the load is switched ON.
In this condition, When I short-circuit the load, the Gate
pulses to the IGBT are switched OFF and ERR pin goes HIGH.
Thus the IGBT gets protected from short-circuit.

If I switch OFF the 110V DC and the voltage at the IN pin,
and then short-circuit the load and if I now switch ON the
110V DC, followed by switching ON the IN voltage. My IGBT
is not protected. In this case, all Gate-Emitter_Collector
of the IGBT are shorted.

Again I have 16 such channels working in parallel on the
same 110V DC supply i.e., identical 16 circuits for 16 different
loads

 

[Papabravo]

A schematic diagram would really help.

 

[devura]

Circuit Details

I am using the following circuit (attached herewith) for high side driving of an IGBT. Details of the circuit are as follows:

1. + HV is 110 V DC from a battery bank.
2. High side Driver Used – IR 2125
3. IGBT Used – IXEH40N120D1 (60Amps/1200V - With HiperFRED )
4. Rg – 39 Ohms / 0.25W
5. Rs – 0.1 Ohm / 2W NIWW

Load is connected between O6 and SGND in the circuit attached – Load is inductive in nature (coil of a contactor with coil resistance approx 300 Ohms). The load i.e., the contactor is located at a distance of approximately 10 meters from this circuit and there is no provision for providing any protection mechanisms or components on the load side.

I have separate power for 110 V DC at +HV and +8V for the IN – input of IR 2125 is derived through a power supply, whose input is again the same 110V DC. I already have a 4.7KOhm/0.25W resistor connected to Ground from IN pin of IR2125, so it is guaranteed that the IN pin is pulled to LOW during start-up.

I am facing the following problem:

Case 1:

When 110V DC is applied first and when the input to IN pin of IR2125 is applied, the IGBT gets the gate pulses from the IR 2125 and the load is switched ON. In this condition, if I short-circuit the load (short the contactor coil), the Gate pulses to the IGBT are switched OFF and ERR pin of IR 2125 goes HIGH, thus indicating a fault and the IGBT gets protected from short-circuit.

Case 2:
If I switch OFF the 110V DC and the voltage at the IN pin,
and then short-circuit the load and if I now switch ON the
110V DC, followed by switching ON the IN voltage, my IGBT
is not getting protected. In this case, all Gate-Emitter-Collector of the IGBT are getting shorted. The tracks on the PCB are also getting damaged in this case.

Case 3:
If I change the load to resistive, i.e., if I connect a 300 Ohms resistance as load and repeat the test as described in the above two cases, the circuit works fine, i.e., the IGBT is protected from short circuit in both the cases 1 and 2.

I have 16 such circuits in one card on the same 110V DC supply i.e., identical 16 circuits for 16 different loads.

Kindly advise, what action to take and how to come out of this problem.

 

[em2006]

Maybe the Q of the coil is too high. Try to alterate the nature of the load by connecting a resistor across the coil of the contactor.
Or, try to connect a fast diode diode across the coil (inverse), and a series diode (direct).

 

[Hero999]

A resistor with a diode in series is the best way of doing it. If you omit the resistor current will decay at the diode's voltage drop * inductance, whilst adding a resistor will cause it to decay exponentially.

 

[devura]

IR2125 - High Side Switching

I have tried both of your suggestions, but still I am not able to come out of the problem.

Any new suggestions please ???

 

[em2006]

I do not understood how you performed the shortcircui test, as you described. In my opinion the case 2 and case 3 are the same. If you shorted the load when has no voltage on the circuit, and, after this, you switched-on 110VDC and 8VDC, your load was a jumper (R=0, L=0) even if before the load was an inductor or a resistor. Or, you said

Case 2:
If I switch OFF the 110V DC and the voltage at the IN pin, and then short-circuit the load and if I now switch ON the 110V DC, followed by switching ON the IN voltage, my IGBT is not getting protected...
Case 3:
If I change the load to resistive, i.e., if I connect a 300 Ohms resistance as load and repeat the test as described in the above two cases, the circuit works fine, i.e., the IGBT is protected from short circuit...

Who tells to circuit what before was in place of the jumper, inductor or resistor?

Another obs:
If the load is shorted when is no voltage (switch-off), and after this you apply the supply voltages, the charge pump circuit using 555 and asociated components, can NOT start, because, in the normal working, the 555 take supply voltage from the LOAD (load voltage) via resistor R75(56K/1W), this voltage charges the 100nF capacitor C42 connected between pins 8 and 1 of the 555 generating minus 15V referenced to pin 5 of the IR2125, necessary to prepare the auxiliary voltage for the bootstrap circuit. During the load is shorted, this voltage is zero, and the 555 is not working.

Another question:
Why you choosed like this expensive IGBT, 1200V/60A, if the supply voltage is 110VDC only, and load is 300 OHM? Do you have another suplimentar loads instead of DC-contactor coil? Why not MOSFET? (usually rated voltage of the IGBT is 600V and over, I never used IGBTs rated under 600V, maybe they are not available, I looked for it..) In the shortcircuit conditions, the load is about 20m wire (cable), or not? (You said the contactor is located at 10m distance from the PCB containing IGBTs).

 

[devura]

First of all, thankyou for your detailed understanding of the circuit

As explained, I am also puzzled to see my system not-working in Case 2,
but working perfectly in Case 3, although both of them are similar in
nature. This is where I had to come into the forum, for your help.

Regarding your question " Who tells to circuit what before was in place
of the jumper, inductor or resistor?", I would like to say that my load
is actually the INDUCTOR. I have placed a RESISTOR, just to see how my
circuit responds to resitive load.

Regarding your another observation that if the load is shorted, the 555
will not work, then the IR2125 should go into shutdown mode, because of
Under Voltage Lockout - Basically this is what I understand - Correct me
if I am wrong.

I have only mentioned the 60Amps / 1200Volts IGBT in the circuit. I agree
that the actual load requirements do not demand this kind of device.
Moreover I have tried the same circuit, by using various MOSFETS also,
like 6N60 and IRF740 etc, but the problem still exists.

As you have pointed out, in the short circuit conditions, since the load is
located about 10mtrs away, the load is about 20mtrs wire cable.

Any new suggestions, please


By the way International Rectifier has given me this reply, for my problem
and I quote:

"Here is an Application Note "Using The Current Sensing IR212X Gate Drive ICs" with other possible configurations for the current sensing. May be it could be better to use the configuration like described on page 6 (Desat Detection Circuit Configuration) or page 4 Figure 3a.

In this circuit you use the IR2125 it's not possible to use the current sense
function. Therefore you need a MOSFET with current sense pin. What you have is a normal Transistor and you are measuring the current flowing through the 100kOhm resistor and not through the load. Please see the datasheet on page 1 typical connection... this MOSFET has 4 pins (drain, gate, source and current
sense).

 

[FRIED]

When the output is turned on the CS is blanked for a short period. This may be sufficient to destroy the switch. To limit the rate of rise put an inductor (with diode) in series with the switch.

 

[devura]

As per IR Technical Team's suggestion, where they have said that it's not possible to use the current sense function and therefore we need a MOSFET with current sense pin. We have now got the IRC740 Hexsense MOSFET with us and even after using this MOSFET with 5 pins (drain, gate, source, current sense, kelvin), in the circuit, we are still not able to solve the original problem, because we are faced with a new problem now. With this MOSFET, the GATE is not switching OFF, even when the INPUT is removed i.e., the GATE is always HIGH irrespective of the changes in the IN from LOW - to - HIGH - to - LOW.

Pls advise - Thanks in advance

 

[Blatman Bond]

What is your load?
I can't see any low side switch in your schematic, but diode and capacitor bootstrap applied, it will not work if the output voltage never reach the ground.
For only 110Vdc i better to use mosfet, 500V rated mosfet still low Rds-on.
IRFP460 only 0.2 ohm when switched on. I see that your current sense is 0.1 ohm, too big for high current.

 

[Blatman Bond]

Sorry, your load is 200 ohm contactor, low current. I think mosfet is better.

IGBT designed for high voltage high current switch, when drop voltage affect the efficiency.
10A 900V rated mosfet has typically 1.5 ohm Rds-on, but 10A 500V rated mosfet only 0.7 ohm.
Mosfets are bad switch on high voltage high current operation. IGBT always drop only 2.5V on Vce sat.