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LED Driver ICs Forum Discussions

User20590
Level 1
First question asked
Level 1
Can your H-bridge drivers be operated with less than four MOSFETs in pure buck mode?
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1 Solution
j_oehmen
Moderator
Moderator 10 replies posted 5 replies posted 10 questions asked
Moderator
In order to save BOM cost it is possible to use our H-Bridge drivers with 2 MOSFETs only.

TLD5190QV, TLD5190QU, TLD5542-1QV and TLD5542-1QU will turn on the low side gate drivers in error conditions. Then the following fault behaviors have to be considered:

* Short-to-battery: battery is getting discharged via the low side MOSFET M2 without current limitation (destructive for the discharge path)
* Overvoltage or open load: Output capacitor is getting discharged via lows side MOSFET M2 without current limitation

In order to avoid such discharge currents without current limitation the highside MOSFET M4 of the H-bridge may also be replaced by a power diode instead of a short-circuit.

When using the diode please consider the voltage drop for the duty cycle calculation (D = (Vout+Vdiode)/Vin).

Please also connect BST2 to IVCC and SWN2 to GND in order to avoid triggering undervoltage on BST2.

During input transients the device could go in buck-boost or boost mode and behave similar to normal buck controllers stopping to regulate at the maximum duty cycle.

E.g. see the product pages of TLD5190QV and TLD5542-1QV

View solution in original post

0 Likes
1 Reply
j_oehmen
Moderator
Moderator 10 replies posted 5 replies posted 10 questions asked
Moderator
In order to save BOM cost it is possible to use our H-Bridge drivers with 2 MOSFETs only.

TLD5190QV, TLD5190QU, TLD5542-1QV and TLD5542-1QU will turn on the low side gate drivers in error conditions. Then the following fault behaviors have to be considered:

* Short-to-battery: battery is getting discharged via the low side MOSFET M2 without current limitation (destructive for the discharge path)
* Overvoltage or open load: Output capacitor is getting discharged via lows side MOSFET M2 without current limitation

In order to avoid such discharge currents without current limitation the highside MOSFET M4 of the H-bridge may also be replaced by a power diode instead of a short-circuit.

When using the diode please consider the voltage drop for the duty cycle calculation (D = (Vout+Vdiode)/Vin).

Please also connect BST2 to IVCC and SWN2 to GND in order to avoid triggering undervoltage on BST2.

During input transients the device could go in buck-boost or boost mode and behave similar to normal buck controllers stopping to regulate at the maximum duty cycle.

E.g. see the product pages of TLD5190QV and TLD5542-1QV
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