H-Bridge MOSFET driver output issue. - Page 1
Forum section: electronics / beginners

author: kushal4269
author_rank: Newbie
timestamp: February 13, 2020, 11:09:52 am
content: Hello,I am working on H-bridge mosfet driver ckt. I am using 4 IRFP460 mosfet in H-bridge configuration,and giving trigger to them with one IR2110 half bridge driver IC(giving 1 o/p to two of same signal mosfet) as shown in fig-01(IR2110 ckt is also attached below). For generating PWM signal I am using TL494 in push-pull Configuration(I/P1 and I/P2 are outputs of TL494).Max tgigger voltage = 12v with 1kHz to 100kHz freq.(AS TL494 and IR211 are powered by same 15v regulated supply.)H-bridge Supply voltage = 30vload = 5K6 ohm.I can not figure out ,-> Why I am not getting exactly zero volts at zero trigger voltage(in orange).-> How can I reduce the spikes at the time of turning on the mosfet(in green).-> My o/p max voltage is in +ve is only 10v (Which is also not symmaetric in -ve side ) whereas my Supply is 30v (If cosider 5v drop across mosfet then also I am not getting 20v), I have already confirm that IRFP460 mosfet has around 5v voltage drop .thanks.

author: mvs
author_rank: Frequent Contributor
timestamp: February 13, 2020, 03:39:59 pm
content: Quote from: kushal4269 on February 13, 2020, 11:09:52 amIt will not work that way... You need two half bridge drivers to drive full bridge.

author: kushal4269
author_rank: Newbie
timestamp: February 13, 2020, 04:33:34 pm
content: Thanks for reply mvs. I will sure try that.Can you provide reason why it needs two driver when we can give trg with only one. (as two mosfet have same trg singal).

author: mvs
author_rank: Frequent Contributor
timestamp: February 13, 2020, 07:13:22 pm
content: Trg signal might be the same, but the signal level is not the same. To open a N-channel MOSFET you need to apply some positive voltage, say +10V, above its source. Since the source of fully opened high side MOSFET is tight to positive supply of the bridge, in your case +30V, you need to apply around +40V to the gate relative to ground. It is a way to high for your low side MOSFET, Vgs(max)=+/-20V. So you can not connect gates together.You need also create this +40V in your circuit. IR2110 is typically used in a bootstrap configuration, where a bootstrap capacitor (connected between Vb and Vs) is charged throught bootstrap diode (connected between Vcc and Vb, see fig. on the first page of IR2110 datasheet). This is the easy way of doing it, but you get some limits on max. duty cycle of the high side switch (see datasheet and/or appnote for bootstrap calculation).

author: kushal4269
author_rank: Newbie
timestamp: February 14, 2020, 12:06:31 pm
content: Thanks for your follow up,But still I am getting the same output(Previously uploaded scope image.)Low trg current cold be the reason but I am using IRFP460 mosfet, And my trg ckt has 1A limit (Max prg voltage = 15V) so that can not be the case.Do I have to Use Transformer at output stage to get smooth Waveform.

author: mvs
author_rank: Frequent Contributor
timestamp: February 14, 2020, 02:15:07 pm
content: Quote from: kushal4269 on February 14, 2020, 12:06:31 pmYour schematic is wrong... H-Bridge with IR2110 should look like this:

author: Dmeads
author_rank: Regular Contributor
timestamp: February 16, 2020, 08:08:14 am
content: Quotelook how the correct schematic has additional capacitors and other components in it. Your (talking to the OP) schematic only has 2kohm resistors. Your need these exeternal components to act as a bootstrap for the high side MOSFET.I struggled with this a couple months ago haha and blew up a few MOSFETs, it happens.This link is a great video on high and low side MOSFET switching.check it out, and it should make more sense to you.Also you shouldn't have a 5V drop across your MOSFET. Try the suggested schematic and see if it comes out better. Im not sure what RDSon (Drain to Source resistance is of the IRFP460 is, but realistically your signal should be able to at least swing +29 to -29V if not more).