Playing with circuits (4) - UC3843 floating buck, 60W efficiency 93%

PowerAnts

Playing with circuits (4) - UC3843 floating buck, 60W efficiency 93% [Copy link]

 

Today I played with the UC3843 floating buck, replacing the LM5116. The efficiency of 36V to 12V is 93%, and the efficiency of 48V to 12V is 91.5%. It has Schottky freewheeling and no optocoupler.

Pictures speak louder than words!

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PowerAnts

Today I set up a synchronous freewheeling, output 12V, 5A, input 24V/36V\48V, efficiency is 96.2%, 95.2%, 94.1% respectively

PowerAnts

Current progress: UC2843 is used only as a PWM generator, and the internal error amplifier and external NTC resistor are used as over-temperature protection to directly detect the temperature of the MOSFET pad with the highest temperature in the system. Another LM358 is used as an error amplifier and current processing to achieve a limited range of constant power control, and has CV/CC, input over-voltage and under-voltage protection, output over-voltage protection (to prevent the main switch from physically short-circuiting and causing disasters to electrical equipment), and achieves 300mS soft start, short-circuit self-recovery and lock options.

Without further ado, here is a waveform chart.

Efficiency comparison

Cost comparison: UC2843+LM358+a bunch of RC, diodes and triodes, about 2.5 yuan, LM5116 chip alone costs 8 yuan

伟林电源

Very good, looking forward to sharing.

PowerAnts

Efficiency test on the 3rd floor, both input and output are equipped with 20cm 1.5mm2 wires

伟林电源

Without the wire, it is estimated that the efficiency can be improved by a few tenths.

PowerAnts

This board has been put into production for 6K. Next, another pair of half bridges will be added on this basis to achieve 4-switch buck-boost. The target full-load efficiency is not less than 94% within the range of double the voltage difference (such as 12~48V input and 24V output).

whuer

It is totally unnecessary, just use an integrated chip

PowerAnts

whuer posted on 2019-10-20 08:45 It is totally unnecessary, just use an integrated chip

Please recommend some device models and original manufacturers that have been verified and adopted in large quantities by well-known customers, thank you!

苏正武

Didn't see the schematic

gh_nathan

Could you please tell me how you handle the current sampling part? And if there is no driver chip, what kind of driving method is used?