Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Common ended LC filter for 100 watts inverter

Status
Not open for further replies.
F

fadhel93

Newbie level 4
Joined
May 19, 2015
Messages
7
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
59
Hello

I am working on a project of a 100 watts pure sine wave inverter, using DC to DC converter (push-Pull topology) as a supply for the H bridge (from 24 to 80 V ), the H bridge is controlled using mbed microcontroller. everything works fine till I connect the LC filter it draws large amount current without any load.
switching frequency=16KHz

Can anyone help me please.

123.JPG

321.JPG

schematic circuit for the H-bridge and mbed
 

Your LC arrangement could be called a second order butterworth filter. It should be designed to resonate at a higher frequency than your switching frequency. However it is possible the two frequencies are close together.

It is essential that a load be present across the capacitor. With no load, you may expect it to draw enormous current.

A similar problem comes up with audio amplifiers, if you were to install a similar type of 2nd-order low-pass filter. Suppose you disconnect the speaker. Then play a sound which is the resonant frequency for your series LC. It will draw extreme current, with the risk of burning up components in the power amplifier.
 

thank you,
"It should be designed to resonate at a higher frequency than your switching frequency." why?

The cutoff frequency for the filter is -1/2pisqrt(LC)- about 300Hz.

If I connect ceramic capacitors rather than non-polorized Electrolytic Capacitor , it did not draw current .
 

fadhel93 said:
thank you,
"It should be designed to resonate at a higher frequency than your switching frequency." why?
Click to expand...

Apologies for my error. I meant to say fundamental frequency.

Assuming your fundamental is 50 or 60 Hz, then you wish to filter out all higher frequencies. It is reasonable to set a rolloff frequency for 80-100 Hz.

The LC values need to be custom selected, to pass sufficient current for your load, while shaping the waveform into a sine.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top