TL494 boost with load

lz15229

TL494 boost with load [Copy link]

 

In the boost circuit of tl494, the chip power supply and the boost part power supply are provided separately. The boost part input is 12V, 2A. The circuit is as follows. The VCC and VDD of IR2110 are both 12V, which is shared with the chip power supply voltage of tl494. Because the square wave high level from tl494 is 11.5V, the logic voltage of IR2110 must be 12V for IR2110 to work. When no-load, adjust the sampling resistor to make the output voltage 37V, then connect a 100Ω high-power load. The given input of the boost part is 12V, 2A (the no-load digital power input shows 12V, 0.1A), then the input voltage is shown on the digital power supply as 9V, 2A. IRF540 heats up, the output voltage is 22V, but the waveform of the drive output is still a square wave. The picture is as follows. The inductor in the circuit is wound by itself, and the specific size is still unknown. Why can't the circuit carry the load? How to improve the load-carrying capacity?

maychang

TL494 drives IRF540 via IR2110? What do you want to do? The power control chip can directly drive the MOS tube.

lz15229

maychang posted on 2017-12-6 21:10 TL494 drives IRF540 via IR2110? What do you want to do? The power control chip can directly drive the MOS tube.

It can drive directly, but the effect is not good, but this is not the main problem, why is the circuit so poor in load capacity

qwqwqw2088

"The inductor in the circuit is wound by myself, and the specific size is unknown." This is hard to say... In the boost circuit, if the inductor is too small, the ripple is large, and the constant voltage output is unstable. If the inductor is too large, the load capacity is poor... This is just a suspicion of the inductor. As for the original poster's circuit, it seems incomplete.

maychang

lz15229 posted on 2017-12-6 21:37 It can be driven directly, but the effect is not good. However, this is not the main problem. Why is the circuit so poor in load capacity?

The first reason: "Then the input voltage digital power supply shows 9V, 2A, IRF540 heats up, the output voltage is 22V, but the waveform of the drive output is still a square wave." Your "input voltage digital power supply shows 9V", which means that your "digital power supply" has entered the current limiting state (the current is greater than 2A) and cannot output enough power. The second reason: "The inductor in the circuit is wound by itself, and the specific size is not known yet."

lz15229

qwqwqw2088 posted on 2017-12-6 22:17 "The inductor in the circuit is wound by myself, and the specific size is not known yet." This is hard to say. In the boost circuit, the inductor is too small, the ripple is large, and the constant voltage...

OK, thank you. Only the IR2110 driver part and the dead zone voltage DTC control part are omitted in the picture. The rest are the same as soldered.

lz15229

maychang posted on 2017-12-7 07:57 The first reason: "Then the input voltage digital power supply shows 9V, 2A, IRF540 heats up, the output voltage is 22V, but the drive output waveform is still...

When the load is not loaded, the input current is only a few hundred mA. When the load is connected, the input current seems to be set to a certain value, and it can reach that value.

maychang

lz15229 posted on 2017-12-7 13:00 When no-load, the input current is only a few hundred mA. When a load is connected, the input current seems to be set to the same value as the setting.

When a load is connected, the input current seems to be set to the same value as the setting. This is a sign that your Boost circuit consumes too much current so that your digital power supply has entered current limiting state.

lz15229

maychang posted on 2017-12-7 14:12 How to input current when connected to load? It seems that it can reach the maximum value set by the setting. It is exactly what your Boost circuit consumes...

The no-load output is 37V, and the load is 100 ohms, then the output drops to 22V, so the load current is only 0.22A, how can the input current of the digital power supply be so large

maychang

lz15229 posted on 2017-12-7 15:40 The no-load output is 37V, connected to a load of 100 ohms, and then the output drops to 22V. In this way, the load current is only 0.22A. Why is the input current of the digital power supply so large?

That is because most of the power provided by your digital power supply is consumed in your MOS tube IRF540. It is precisely because a considerable part of the power is dissipated in the MOS tube that your MOS tube will heat up.

lz15229

maychang posted on 2017-12-7 16:25 That is because most of the power provided by your digital power supply is consumed in your MOS tube IRF540. It is precisely because a considerable part of the power is dissipated in the MOS ...

Well, I just measured it, the current flowing through the MOS tube is 1.66A, and the current flowing through the load is 0.3A. How to solve the problem? Change the inductor?

maychang

lz15229 posted on 2017-12-7 16:56 Well, I just measured it. The current flowing through the MOS tube is 1.66A, and the current flowing through the load is 0.3A. How should the problem be solved? Should I change the inductor?

"How should the problem be solved" The information you provided is too little. The first post didn't even say how high the voltage and current you required the boost part to output. I can't say how to solve it.

lz15229

maychang posted on 2017-12-7 17:30 "How to solve the problem" You provided too little information. The first post didn't even say how high the voltage and current you required the boost part to output. I can't...

12V to 36V, the maximum load current is 0.5A

maychang

lz15229 posted on 2017-12-7 18:13 12V to 36V, maximum load current 0.5A

When I say "too little information", I don't mean that 36V 0.5A is not a lot. The PWM frequency of your TL494 output is about 44kHz from the oscilloscope. I guess the waveform on the IRF540 gate is on the oscilloscope. But there is no waveform on the drain of the MOS tube.

maychang

lz15229 posted on 2017-12-7 18:13 12V to 36V, maximum load current 0.5A

When I say "too little information", I don't mean that 36V 0.5A is not a lot. The PWM frequency of your TL494 output is about 44kHz from the oscilloscope. I guess the waveform on the IRF540 gate is on the oscilloscope. But there is no waveform on the drain of the MOS tube.

lz15229

maychang posted on 2017-12-7 18:23 When I say "too little information", I don't mean that 36V0.5A is not a lot. The PWM frequency of your TL494 output is about 44kHz from the oscilloscope. I estimate from the oscilloscope...

Well, maybe there are some parameters that I don't understand and haven't measured. If the inductor is saturated, what effect will it have on the circuit?

lz15229

maychang posted on 2017-12-7 18:23 When I say "too little information", I don't mean that 36V 0.5A is not a lot. The PWM frequency of your TL494 output is about 44kHz from the oscilloscope. I estimate from the oscilloscope...

Another question, if the load current is 0.5A, is it normal for the current flowing through the MOS tube to be 2A?

maychang

lz15229 posted on 2017-12-7 18:55 Well, maybe there are some parameters that I don’t understand or measure. If the inductor is saturated, what impact will it have on the circuit?

When the inductor core enters magnetic saturation, the current of the power tube will increase sharply. Of course, the loss on the power tube will also increase.

maychang

lz15229 posted on 2017-12-7 19:06 Another question, if the load current is 0.5A, is it normal for the current flowing through the MOS tube to be 2A?

The current in the load is 0.5A, and the voltage across the load is 36V, so the power obtained by the load is 18W. The output current of the 12V power supply is 1.5A, and the power is 18W.

lz15229

maychang posted on 2017-12-7 19:44 When the inductor core enters magnetic saturation, the power tube current will increase sharply, and of course the power tube loss will also increase.

Then the power tube current is so large here, is it because the inductor is magnetically saturated?