Hello,
I plan to make a design with TL494. But here I could not understand the high wattage values of the resistors connected to the output pins. What is the reason for this?
Enes,
No, the two output pins in your switching converter application should not consume much power at all. Again, the circuit you referenced is a parametric test circuit intended to test the max continuous collector current. In a switching converter application, you are likely driving one or two external power MOSFETs switching the primary side of a transformer. The peak current required by the power MOSFET is high but short duration and the average current, determined by switching frequency, is comparatively small.
The internal bipolar transistors of the TL494 output stage are not intended to drive the external power MOSFETs directly. The TL494 provides the gate drive logic signals which are then used as input signals to an external gate drive circuit. The external gate drive circuit is providing the high peak source/sink current needed to efficiently drive the external power MOSFETs. The TL494 output current is rated for 200mA source/sink current but a gate drive peak source/sink current rating should be more like ±1Apk.
Below is an example of TL494 buck converter and you can see the external totem pole gate drive circuit (red box) used to drive MOSFET, Q1. If your prefer not to design the external gate drive circuit discretely, check out TI's extensive portfolio of integrated gate driver ICs here.
Regards,
Steve
