SMPS Based Power Supply Design Output 24V DC ,Input 130-240V DC

In this design I'm going to make Switched mode power supply with an output of 24V DC and input ranging from 140 to 240 V DC.

The current output is rated to 200 Watt.

The circuit uses IC TL494 as control IC. Pulse transformer is used to fire the power IGBTs.

The entire circuit is explained in next steps.

Bill of materials

C1 22PF

C2 2200UF/50V

C3 2200UF/50V

C4 820UF/250V

C4 1000UF/25V

C5 820UF/250V

D1 MUR3060PT

D2 1N4007 BRIGBE

D2 30A Bridge

J1

J2

J3

L1 CHOKE

Q1 IRF840

Q2 IRF840

Q3 25N120

Q4 25N120

R1 100K

R2 100K

R3 100K

R4 100K

R5 10K

R6 10K

R7 330E 1W

R8 330E 1W

R9 100E 1W

R10 100E 1W

R11 10K

R12 100K

R13 5.6K 5W

R14 4.7K

R15 10K

R16 1 MEG

R17 10K

R18 10 E 1 W

R19 10K

R20 10E 1 W

R21 10K

T1 PULSE TRANSFORMER

T2 MAIN TRANSFORMER

T3 220 TO 12 V TRANSFORMER

U1 TL494

IC TL494 is used to control the whole system.

TL494 collector pin 11 and 8 are pulled up to 12V DC with resistor R7 and R8. Both are 330 ohms 1 Watt.

PWM output is taken from pin 9 and 10 and used to fire the pulse transformer T1. Primary and secondary windings are bifilar windings with 5 turns each. Mosfet Q1 and Q2 are used to fire the pulse transformer. Output of pulse transformer is fed to IGBT Q3 and Q4 gates. These IGBTs are driving the main transformer T2. Output of T2 is rectified with a Schottky rectifier D1 (MUR3060PT). Output of this rectifier is filtered by capacitor C2 and C3 and here comes 24v Dc output at connector J2.

The circuit output is 24 V DC constant voltage.

The 24 V DC output is fed to the voltage divider R12 and R21. It is a 100k/10k voltage divider. The Voltage across 10k to GND is 24*(10/100) = 2.4 V DC.

This voltage is fed to Pin 1 of IC TL494. This is the output voltage.

Now we know that IC TL494 has 5 V reference voltage source for the PWM control reference. This 5V is taken from Pin 13 and pin14. Here in this circuit we are shorting pin 13 and 14 as we need the push pull mode of IC.

So, from Pin 13 a +5V DC signal is fed to 10K and 4.7K network. R14 and R15 network.

5*4.7/14.7 = 1.59 V.

This voltage is fed to R17 (10k). The output of R17 is fed to pin 2 and it is fed to pin 16 through 1Meg resistor R16. Here the circuit gain is 100. 1 Meg/10 K = 100.

Pin 1, 2 and 3 has an OPAMP that controls the PWM output and the circuit output voltage is locked as a constant voltage condition.

When Pin 1 output is greater than Pin 2, The Circuit controls the PWM.

The power transformer T2 is designed as follows.

Primary voltage = 480 V AC. (240 V AC center tapped)

The winding is center tapped push pull configuration.

So, Vin = 480/2 = 240V AC

No. of primary turns = (480*10^10)/(4*65000*228*1500) = 54 turns.

Core area = 228 sq. mm

Bmax = 1500 Gauss

Freq. = 65000 hz.

Vout = 35V AC. Voltage at two terminals

The winding is center tapped. So Vout = 35/2 = 17.5 V AC

Output voltage = 17.5 *1.414 = 24.745 V DC

No. of secondary turns = (35/480)*54 = 4 turns

Power handling = 200 Watt.

Primary current = 200/480 = 0.416 A

23 SWG wire is used with max. current capacity 0.548 A

So, 1 conductor for primary.

Secondary current = 200/35 = 5.71A

For secondary = 5.71/0.548 = 10 conductors.

The SMPS works on line voltage. Care must be taken to ensure the insulation for high voltage parts.

This is a tested circuit.