York Gate Driver Board

[Theodora Andy]

Usingthe Automotive 1-kW 48-V BLDC Motor Drive Reference Design (TID-00281) as a reference, I have used the same circuit for the gate drivers and H-Bridge to design my own PCB for a 2 phase BLDC 48V motor.

Thank you for the interest in the UCC27201A half bridge driver. I am an AE supporting this product and will work to resolve your concerns. I do have some questions and will need more details to provide the best advice.

It sounds like from your description that there is possible damage to the driver output stage, and maybe relating to VDD. Can you comment on if the drivers that fail, is it the LO output that is affected or HO output, or maybe both.

Possible causes of driver output stage damage can be from driver output voltage overshoot or undershoot. Another possible cause may be VDD or HB-HS voltage transients exceeding the device rating. Also if there is excessive high frequency noise on the LI and HI inputs during power train switching, there may be false triggering of the driver output. Excessive driver output high frequency oscillations can stress the device.

During layout review I have a couple of comments. The component placement is close to the IC which is good compared to many motor drive designs. I see that the VDD bypassing routing can be improved considerably regarding the VSS trace connection. If the VDD caps can be moved to the left, the VSS connection could be made directly to the driver power pad and pin 7. There does look like a good (low inductance) ground plane on the bottom layer however. We usually recommend that the power train switch node trace have minimum overlap over the ground or DC input. This is to minimize the switch node parasitic capacitance. I see the switch node is a large plane. May be reduce the size to be a large trace width connection instead of the plane, and remove the ground plane on INNER1 in this area, as it does not seem to have any connections in that area.

Using scope probe connections with a short ground connection, probing as close to the IC pins as possible record the following. 1) LO, HO-HS (differential probe if possible), and HS. Record a time base to see the turn on and turn off switching edge details, and expand the voltage scale as much as possible. 2) LI, HI, HO-HS, and LO.

Ringing and voltage spikes are typically increased as the power device dV/dt increases. One way to reduce possible excessive ringing is to increase the gate resistance from 10 Ohms which will reduce the MOSFET Vds dV/dt. As an experiment you can try higher gate resistance values to see if there is any improvement.

I have had issues with other gate drivers (not TI) which didn't have RC filtering on the inputs. When I added an RC filter to the inputs it fixed the problem, so this is something to consider for this design.

The need for R/C filters on the driver inputs, is very much dependent on the layout. My general advice is to make provisions for an R/C filter, and if not needed a 0 ohm jumper can be installed as the resistor, and capacitor removed.

For test 1, the dyno spins the motor anti-clockwise and current is applied to the motor so that it spins in the same direction (anti-clockwise) by applying a positive current - these tests have been successful so far and we have tested up to 5000rpm 35A.

For test 2, the dyno spins the motor anti-clockwise and current is applied to the motor so that it spins in the opposite direction (clockwise) by applying a negative current - these tests cause the gate drivers to fail even at low currents e.g. 5A

When the back emf exceeds the DC link voltage (48V) a phase current can be seen as it flows through the parasitic diodes in the MOSFET. I can't remember the scaling of the current clamp but the magnitude of the current was not a concern.

I am trying to use an IGBT module (dual IGBTs in common-emitter arrangement) as a static switch for 120VAC. I've done as much reading as I can, and I understand there are issues with losses and turn-on/off challenges. I am building 3 different switches using different devices and comparing losses, transient response, etc.

Here is my issue. I ended up burning the input (control) side of my gate driver. I think gate current went through it and destroyed it. High current (presumably) went out the VCC1 pin and into the microcontroller, destroying it as well. Everything else seems fine. The DC-DC converter appears unscathed, as does the IGBT and snubber.

There are plenty of reasons that can cause IGBTs blowing.

Here are just some suspect points regarding IGBTs.

A) Your 2 IGBT connection look suspicious. PS-Collectro-Emitter-Emitter-Collector-Load?

B) Driver output resistors according DS - top one 3 times bigger than bottom one. In your circuit they are both 20R.

C) Wires that goes to Gate should be as short as possible (avoiding parasitic inductance).

D) Parameters of Driver and IGBTs must match each other. Double check things like Driver output voltage and current, IGBT gate charge, threshold voltage, switching frequency.

Most time these kind of circuits require very detail design and step by step debugging with oscilloscope. For your and others better understanding SCH design must be done properly not just draft on paper with pen. Your time learning any free available CAD tolls will definitely worth it considering possible losses.

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A gate driver is a power amplifier that accepts a low-power input from a controller IC and produces a high-current drive input for the gate of a high-power transistor such as an IGBT or power MOSFET. Gate drivers can be provided either on-chip or as a discrete module. In essence, a gate driver consists of a level shifter in combination with an amplifier. A gate driver IC serves as the interface between control signals (digital or analog controllers) and power switches (IGBTs, MOSFETs, SiC MOSFETs, and GaN HEMTs). An integrated gate-driver solution reduces design complexity, development time, bill of materials (BOM), and board space while improving reliability over discretely-implemented gate-drive solutions.[1]

In 1989, International Rectifier (IR) introduced the first monolithic HVIC gate driver product, the high-voltage integrated circuit (HVIC) technology uses patented and proprietary monolithic structures integrating bipolar, CMOS, and lateral DMOS devices with breakdown voltages above 700 V and 1400 V for operating offset voltages of 600 V and 1200 V.[2]

In contrast to bipolar transistors, MOSFETs do not require constant power input, as long as they are not being switched on or off. The isolated gate-electrode of the MOSFET forms a capacitor (gate capacitor), which must be charged or discharged each time the MOSFET is switched on or off. As a transistor requires a particular gate voltage in order to switch on, the gate capacitor must be charged to at least the required gate voltage for the transistor to be switched on. Similarly, to switch the transistor off, this charge must be dissipated, i.e. the gate capacitor must be discharged.

When a transistor is switched on or off, it does not immediately switch from a non-conducting to a conducting state; and may transiently support both a high voltage and conduct a high current. Consequently, when gate current is applied to a transistor to cause it to switch, a certain amount of heat is generated which can, in some cases, be enough to destroy the transistor. Therefore, it is necessary to keep the switching time as short as possible, so as to minimize switching loss [de]. Typical switching times are in the range of microseconds. The switching time of a transistor is inversely proportional to the amount of current used to charge the gate. Therefore, switching currents are often required in the range of several hundred milliamperes, or even in the range of amperes. For typical gate voltages of approximately 10-15V, several watts of power may be required to drive the switch. When large currents are switched at high frequencies, e.g. in DC-to-DC converters or large electric motors, multiple transistors are sometimes provided in parallel, so as to provide sufficiently high switching currents and switching power.

The switching signal for a transistor is usually generated by a logic circuit or a microcontroller, which provides an output signal that typically is limited to a few milliamperes of current. Consequently, a transistor which is directly driven by such a signal would switch very slowly, with correspondingly high power loss. During switching, the gate capacitor of the transistor may draw current so quickly that it causes a current overdraw in the logic circuit or microcontroller, causing overheating which leads to permanent damage or even complete destruction of the chip. To prevent this from happening, a gate driver is provided between the microcontroller output signal and the power transistor.

Charge pumps are often used in H-Bridges in high side drivers for gate driving the high side n-channel power MOSFETs and IGBTs. These devices are used because of their good performance, but require a gate drive voltage a few volts above the power rail. When the centre of a half bridge goes low the capacitor is charged via a diode, and this charge is used to later drive the gate of the high side FET gate a few volts above the source or emitter pin's voltage so as to switch it on. This strategy works well provided the bridge is regularly switched and avoids the complexity of having to run a separate power supply and permits the more efficient n-channel devices to be used for both high and low switches.

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