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why pwm signal to half bridge rectifier

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I am trying very hard to understand this. I have seen one half bridge ic from TI or any other IC why it accepts a PWM signal alone. Based on the inputs INA and INB it switches the outputs OUTA and OUTB which are given to gate inputs. Now my doubt is why a pwm signal should be given as input to the IC. Please help. If i have not provided sufficient information please tell me. Other doubt is suppose if i switch on the inputs with pwms of 50% duty cycle what does it mean. The output of the half bride ic also will be a pwm? I am very confused.
 

ronsimpson

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1) Micro-computer with 3.3 volt power supply. It has a PWM output 0 to 99% and 0 to 3.3 volts with a maximum of 10mA.
2) Bridge driver with 15 volt supply and the bridge supply of 100 volts. It inputs the PWM signal and outputs two types of signals.
2a) For the bottom MOSFET, a 0 to 15V signal with a maximum of 2Amp.
2b) For the top MOSFET, a 0 to 115V signal with a maximum of 2 Amp.
3) Two MOSFETS. (150V, 10A)
 
Sorry for the basic question but what ever i am acheiving through can i acheive through output port. And also if i am using pwm how to know which duty cycle i have to give and what should be the ftequency. Please help.
 

MikeMl

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Unlike all the bad circuits on the Web, the correct way of driving any H-bridge is to have four non-overlapping drive signals such as from four port pins on a microprocessor where explict delays are programmed into the port pin sequence. If you try to do it with only two port pins (one for each side of the bridge), you invariably end up with huge shoot-through currents, destroyed FETs, current pulses that couple into other circuitry. With separate control of the upper and lower part of a half-bridge, you have the proper, separate control of each FET gate driver.
 

ronsimpson

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how to know which duty cycle i have to give and what should be the ftequency.
We need to know what you want to do. What is your project?

Frequency: The higher the frequency the smaller the inductors and capacitors needed.
Duty Cycle: I need to know what you are doing!
example: buck-PWM 50% = 12 volts in 6 volts out.
There are "boost-PWM" where the output voltage is larger then the input voltage.
 
Thank you for the reply. I am doing a project on rotating the motor using field oriented control which is absolutely knew to me. First step in a document suggested me to give a fixed stator voltage to the winding's so that the permanent magnet PMSM locks at a fixed position. Now my doubt is how can i provide this fixed voltage? Can I provide a pwm signal to all the H legs with certain duty cycle. please help. Any other suggestions can you provide? How to proceed?
 
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