555 timer for pre-made H-bridge "IMS-2b"

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youdontknowme

Joined May 30, 2017
7
Hi,

I came across this pre-built H-bridge "IMS-2B" that claims to be able to support up to 200khz. I have attached the specs.
"IN1" and "IN2" pins will be supplied by 555 timer (2 outputs of 100khz square-wave that are inverse to each other).
"V+" pin will be connected to +12V dc supply and "GND" pin will be connected to -12V dc supply.
The 2 output pins of this H-bridge that is supposedly for motor will go to the transmitter coil instead (for wireless power transfer).

just wondering if there will be any problem with this setup ?? Also, the inverted square-wave has lesser amplitude than the other, will this be an issue ?

Thankyou
 

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crutschow

Joined Mar 14, 2008
23,152
just wondering if there will be any problem with this setup ??
Unless the briged circuitry is designed to specifically prevent it, you will need non-overlap input signals so that both inputs are not momentarily high at the same time, which will cause large shoot-through currents in the bridge, generating high dissipation and possible bridge failure.

The LTspice simulation of such a circuit is shown below:
The inverter outputs are paralleled to better drive the load stray capacitance (bridge input terminals).
Notice that each output is completely low before the other output starts to go high.
This insures that only one side of the bridge is on at a time.

upload_2019-10-12_9-8-30.png
 
Last edited:

crutschow

Joined Mar 14, 2008
23,152
That applies to a resistive load only, so not a coil load.
I don't see how that affects the bridge operating frequency.
A bridge can normally drive an inductive load, even if the coil current doesn't return to zero at end of each pulse.
The MOSFET bridge substrate diodes carry any inductive current current during that time
 

KeithWalker

Joined Jul 10, 2017
390
Hi,
just wondering if there will be any problem with this setup ?? Also, the inverted square-wave has lesser amplitude than the other, will this be an issue ?

Thankyou
Your displayed waveforms do not indicate the amplitude or reference level. As long as the inputs go lower then 0.5 volts and higher than 2.5 volts with respect to circuit common (TTL logic levels) it should work correctly. The truth-table for the inputs indicates that if both inputs are high or both inputs are low at the same time, the outputs will be off. You should not get any problem with overlap signals.
 
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