I want to use your isolated half bridge gate driver, the ADuM5230, which has an isolated internal supply, but it only powers one driver, not both. How can I do this without getting a separate isolated supply?
The ADuM5230 isolated supply powers the isolated A side output. The B side, which is fully isolated from the A side, can be bootstrapped with a switching diode from the isolated 15V supply to charge the bypass capacitor on the B supply to be 15V above the switchnode voltage. This assumes the switchnode is switching regularly at a rate to keep the bypass charged. A 1uF bypass capacitor on the B channel and a 10uF bypass on the A channel may provide enough charge for most applications that the ADuM5230 can be used in. This circuit uses the A channel as the low side and the B channel as the high side. See the attached schematic for details.
I have a question. Can I use ADuM5230 for driving a half-bridge, which connects a load to ground from +350V and from -350V? You can see this schematic in the attachment.
The boost diode should conduct when the half bridge output voltage is at the lowest voltage (-350V) to charge the VDDx 1uF capacitor, which would be when the low side MOSFET is on, so you need VISO to power the low side MOSFET with VOA. Then the boost diode anode should connect to VISO and cathode to VDDB to charge VDDB when VOA is on - see attached circuit.
The pulse width and frequency of the signal at VIB will determine if the VISO capacitor has enough time to charge the VDDB capacitor. The MOSFETs are 7nC at 10V or 0.7nF, which should charge from the ADuM5230 in less than 100ns for 100mA charging current.
I need to design a full bridge MOSFET gate driver using 2 unit of ADuM5230, the structure above is sweet for my design because of saving voltage supply at the output level.
My question is this: how may I use this structure with buffer on both chanel of output as mentionned in "Typical application usage" in the datasheet.
Typical application usage circuit
I have attached a circuit with the ADuM5230 with external buffer and a bootstrap diode to power the high side in a Half Bridge configuration. For a full bridge, you will need 2 of these circuits.
As stated before, this circuit works if the the switchnode is switching regularly at a rate to keep the bypass capacitor charged.
Thank you for the answers Brian
As I'm making up the circuit as showed above( the last with bootstrap diode), I'm testing it step by step. After maked the circuit as here after:
when I measured, the voltage at Viso and VoA was correct, but the voltage between VddB and GNDB was always being 0V. The same thing happened between VoB and GNDB. My questions are: Is this results normal or do I have something wrong with my chip or circuit. If it is normal, Is that means I need to make up all of the circuit (as showed in your response above) included the bipolar totem drivers and MOSFETs to get the channel B voltage worked
Yes, this is normal. For the VDDB and VOB to operate, the rest of the circuit needs to be completed to get the VDDB to GNDB capacitor to charge up to the VISO to GNDA voltage through the boost diode. If desired, you could start with a lower voltages at +V and -V and increase gradually to see that your circuit wiring is OK before going to higher voltages.
Thanks again Brian, I appreciate your explanation
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