TL494 Multiphase Buck Converter

1 year ago

Open source license: Public Domain

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Description

This is a Two-Phase Multiphase Buck Converter that I built using the TL494 PWM control IC. The TL494 has a Push-Pull output mode, which is essentially two alternating PWM signals with a maximum duty-cycle close to 50%, which I have used to drive two P-Chennel MOSFETs (IRF4905) in two phases.

The switching frequency is around 63KHz, which gives an effective output ripple frequency of 126KHz, which is one of the advantages of a Multiphase DC-DC Converter: the effective frequency is equal to 'n' times the switching frequency of a phase, where 'n' is the number of phases. This allows the use of 'slower' MOSFETs and diodes in multiple low frequency (relatively) phases, but the output ripple frequency is a much higher value equal to 'n' time the actual switching frequency. Due to this effectively higher output ripple frequency, the value of output capacitance (and even input capacitance) is lower that what it would be in a single phase system. In addition, the output current is shared between all the phases, resulting in lower phase currents. This is why high power, high current DC-DC converters are of the multiphase type.

This circuit, however, is only experimental and is not representative of the benefits that come with a multiphase Buck Converter.

IMG_20200729_183206661.jpgIMG_20200729_183232182.jpgDrain Waveforms.pngGate Waveforms.png

Documents

BOM

ID Name Designator Footprint Quantity
1 10u C1,C2 CASE-A_3216 2
2 100u C3,C4 CASE-A_3216 2
3 0.1u C5,C6 C0201 2
4 1n C7,C8 C0201 2
5 1N5819 D1,D3 DO-41_BD2.4-L4.7-P8.70-D0.9-FD 2
6 1N4148 D2 DO-35_BD2.0-L4.0-P8.00-D0.5-FD 1
7 33u L1,L2 L0402 2
8 IRF4905PBF_C558142 Q1,Q8 TO-220-3_L10.0-W4.5-P2.54-L 2
9 2N3904 Q2,Q5 TO-92-3_L5.1-W4.1-P1.27-L 2
10 2N3906 Q3,Q4,Q6,Q7 TO-92-3_L4.9-W3.7-P1.27-L 4
11 5k R1 R0201 1
12 2.2k R2,R4 R0201 2
13 100R R3,R5 R0201 2
14 4.7R R6,R13 R0201 2
15 100R x10p R8 R0201 1
16 10k R7,R9,R10,R11 R0201 4
17 0.33R R12 R0201 1
18 TL494G-D16-T U1 DIP-16_L19.7-W6.6-P2.54-LS10.9-BL 1
19 1N4744A ZD1*,ZD2* DO-41_BD2.8-L4.2-P8.00-D0.7-FD 2

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