I would like to use the 5206-2G H-bridge for my wireless power transfer circuit, but i can't find the switching frequency which the FET's can tolerate. I have looked several times at the datasheet, but i can't seem to find it.
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i can't find the switching frequency which the FET's can tolerate
From the data sheet: -
The worst case is going from Source OFF to Source ON to Source OFF = 30 us + 5 us = 35 us. Given that you want a decent level of switching efficiency the switching time of 35 us ought to be no more (open to debate) that 5% of the cycle time. That makes the cycle time 700 us or, a switching frequency of 1430 Hz.
It might work at a higher frequency quite effectively (lighter loads) but there's nothing in the data sheet to underpin this. Note that in the table above it says: -
(Device Active for > 1 ms)
And that should inform us that they are recommending a switching frequency of 500 Hz.
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\$\begingroup\$ Can you elaborate on the 5% switching of the cycle time? \$\endgroup\$ Commented Feb 24, 2020 at 9:16
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\$\begingroup\$ While a MOSFET is "switching states" it is dissipating excessive power and this produces heat and, of course, losses. To maintain those losses at reasonable levels and give the circuit a chance of operating at decent levels of power efficiency, a general rule of thumb is to consider that the total switching time is 5% of the overall cycle time. You are at liberty to choose 10% of course but the device may warm too much and this may affect the lifetime of the device. \$\endgroup\$– Andy akaCommented Feb 24, 2020 at 9:20
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\$\begingroup\$ Just to be sure, when you're saying switching time, it's the time it takes the FET to go from on to off, right? It has nothing to do with the duty cycle of the input? \$\endgroup\$ Commented Feb 24, 2020 at 9:27
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\$\begingroup\$ To go from off --> on --> off. Maximum and minimum duty cycles are restricted by the times given if the cycle time is short. You have to think along the lines that if the pulse time to do off/on/off is 35 us and the cycle time is 700 us, then minimum effective duty cycle is 5%. If you operated it lower than this duty cycle you can't really predict how much energy is pushed into your load because at least 50% is dissipated as heat..... \$\endgroup\$– Andy akaCommented Feb 24, 2020 at 9:37
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\$\begingroup\$ .... I'm not saying you can't operate at 1% duty cycle if the cycle time is 700 us but, if you did, would that be an effective thing to do given that you'll be barely putting anything into the load and what energy you do use will be mainly warming the H-bridge. \$\endgroup\$– Andy akaCommented Feb 24, 2020 at 9:37