TL494 magic chip

Posted on Feb 6, 2014

Everything is working with simple passive mosfet drive. But if we increase switching frequency or place powerful mosfet (or even several mosfets) There is no load in gate circuit, but there is gate capacitance. And if we need fast switching we must charge and discharge gate very quickly. With passive drive there are limitations. We can use active

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charge-discharge circuit. Also this circuit uses inverter transistor for proper signaling: Few comments about schematics. R5 is TL494 output load- anything about 1K. R1 is Q1 load, not critical- 1K. Q1 inverts signal from controller. R2 is used to prevent overload of totem pole bases. Q2 and Q3 are complementary pair. R3 are useful if are few mosfets on the output, only few ohms. Q1 and Q3- C945, Q3-A733. All transistors from old PC power supply. R4 load simulation. Connect pair of these totem poles and connect to transformer like in older post. You can notice small increase of the performance. Don`t overload. There are lots of parasitic oscillations in this circuit. These schematic dos not work, why because R1 activate Q3 so mosfet is fully ON hotttttt. Just remove R1, R5, Q1, and R2. Connect directly to pin 9&10 and pin 9, 10 need resistor 3. 9K to ground. Work nice trust me I spend to much time with this. i have built the circuit and have a great pulse on both c1 and c2 but when i connect this driver circuit i have no pulse at the gate of the mosfet. i have checked all connections about 40 times and they are accurate to your schematic here. any ideas michael: c1 and c2 are colector of q1 and q2 The circuilt is quite simple and consist of two stages: first- signal inverter on q1. Next stage is totem pole driver. Note, that transistors are different npn and pnp. It is so called complementary pair transistors. As structure...

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