Hi,
It never works.For driving the MOSFET you need an isolated voltage or a bootstrap circuit.
The base of the pre-driver transistor inside the MC34063 has a drive signal which is related to ground and not to the SW_E pin.
Regards,
Florin
It never works.For driving the MOSFET you need an isolated voltage or a bootstrap circuit.
The base of the pre-driver transistor inside the MC34063 has a drive signal which is related to ground and not to the SW_E pin.
Regards,
Florin
Do I need a level shifter?
The diode "D", and the capacitor "C" isn't enough for a bootstrap-circuit?
The diode "D", and the capacitor "C" isn't enough for a bootstrap-circuit?
OK, if we take a closer look over the push-pull driving circuit we will see that in the off state of the internal MC34063's transistor, the pnp's base is floating.So you have a lot of chances to keep the pnp off and no signal for the gate of the mosfet.
The D and C looks indeed like a level shifter circuit, but you need an alternating signal for shifting.In the present configuration you didn't have that signal.
Watch out for the maximum gate to source voltage rating.I think you need something to limit the voltage level.
Florin
The D and C looks indeed like a level shifter circuit, but you need an alternating signal for shifting.In the present configuration you didn't have that signal.
Watch out for the maximum gate to source voltage rating.I think you need something to limit the voltage level.
Florin
I draw somathing in TINA (this is a simulator-prg), it seems to work.
T4 transistor is the MC34063's internal transistor, and that R3 is also the integrated resistor, inside MC34063.
On the T4, there's 37V, which is quite high. Accourding to the datasheet of MC34063, the max. V_emitter_collector is 40V. I think, I gonna have to use a dedicated powersupply for the MC34063.
What do you think of this?
T4 transistor is the MC34063's internal transistor, and that R3 is also the integrated resistor, inside MC34063.
On the T4, there's 37V, which is quite high. Accourding to the datasheet of MC34063, the max. V_emitter_collector is 40V. I think, I gonna have to use a dedicated powersupply for the MC34063.
What do you think of this?
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You made at least one mistake in the simulation.The emitter of internal transistor isn't conected to the ground of input voltage.It is a floating point. At least this is what I see from the first schematic.
Repeate the simulation with the circuit like you draw at first time and see if it's working.
Repeate the simulation with the circuit like you draw at first time and see if it's working.
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