In this article I have explained the pinout functions of the IC SG3525 which is a regulating pulse width modulator IC. So I have explained in details:
Main Technical Features
The main features of the IC SG3525 may be understood with the following points:
- Operating voltage = 8 to 35V
- Error amp reference voltage internally regulated to 5.1V
- Oscillator frequency is variable through an external resistor within the range of 100Hz to 500 kHz.
- Facilitates a separate oscillator sync pinout.
- Dead time control is also variable as per intended specs.
- Has an internal soft start feature
- Shut down facility features a pulse by pulse shutdown enhancement.
- Input under voltage shut down feature also is included.
- PWM pulses are controlled through latching for inhibiting multiple pulse outputs or generation.
- Output supports a dual totem pole driver configuration.
Pinout Diagram of the IC
SG3525 PinOut Description
A practical implementation of the following pinout data may be understood through this inverter circuit
The IC SG3525 is a single package multi function PWM generator IC, the main operations of the respective pin outs are explained with the following points:
Pin#1 and #2 (EA inputs): These are inputs of the built-in error amplifier of the IC. Pin#1 is the inverting input while pin#2 is the complementary non-inverting input.
It's a simple op amp arrangement inside the IC which controls the PWM of the IC outputs at Pin#11 and Pin#14. Thus these EA pins 1 and 2 can be effectively configured for implementing an automatic the output voltage correction of a converter.
It is usually done by applying a feedback voltage from the output through a voltage divider network to the non-inverting input of the op amp (pin#1).
The feedback voltage should be adjusted to be just below the internal reference voltage value (5.1 V) when the output is normal.
Now, if the output voltage tends to increase above this set limit, the feedback voltage would also increase proportionately and at some point exceed the reference limit. This will prompt the IC to take necessary corrective measures by adjusting the output PWM, so that the voltage is restricted to the normal level.
Pin#3 (Sync): This pinout can be used for synchronizing the IC with an external oscillator frequency. This is generally done when more than a single IC is used and requires to be controlled with a common oscillator frequency.
Pin#4 (Osc. Out): It's the oscillator output of the IC, the frequency of the IC may be confirmed at this pin out.
Pin#5 and #6 (Ct, Rt): These are termed CT, RT respectively. Basically these pinouts are connected with an external resistor and a capacitor for setting up the frequency of the inbuilt oscillator stage or circuit. Ct must be attached with a calculated capacitor while the Rt pin with a resistor for optimizing the frequency of the IC.
The formula for calculating the frequency of IC SG3525 with respect to RT and CT is given below:
f = 1 / Ct(0.7RT + 3RD)
- Where, f = Frequency (in Hertz)
- CT = Timing Capacitor at pin#5 (in Farads)
- RT = Timing Resistor at pin#6 (in Ohms)
- RD = Deadtime resistor connected between pin#5 and pin#7 (in Ohms)
Pin#7 (discharge): This pinout can be used for determining the deadtime of the IC, meaning the time gap between the switching of the two outputs of the IC (A and B). A resistor connected across this pin#7 and pin#5 fixes the dead time of the IC.
Pin#8 (Soft Start): This pinout as the name suggests is used for initiating the operations of the IC softly instead of a sudden or an abrupt start. The capacitor connected across this pin and ground decides the level of soft initialization of the output of the IC.
Pin#9 (Compensation): This pinout is for compensating the error amplifier op amp. Mostly this pinout is connected to ground via a RC network. However, if required this pinout can be configured with an external transistor which can ground this pin during a critical situation, enabling a shutdown of the IC output.
Why Compensation Network is Required at pin#9
See, if you connect feedback directly without compensation then things do not stay calm, they start misbehaving.
The system can oscillate, like it keeps shaking instead of settling. Output voltage can go up and down.
If load changes then it may become unstable, especially under sudden load change and then you may see strange behavior.
We therefore do not leave it just open..
So we connect a resistor. We also connect a capacitor. Sometimes an RC network between Pin#9 and ground, but sometimes also to feedback pin, depends on how it is arranged.
This then forms what we call a compensation network for the SG3525 IC.
Pin#10 (Shutdown): As the name suggest this pinout may be used for shutting down the outputs of the IC in an event of a circuit malfunction or some drastic conditions.
A logic high at this pin out will instantly narrow down the PWM pulses to the maximum possible level making the output device's current go down to minimal levels.
However if the logic high persists for longer period of time, the IC prompts the slow start capacitor to discharge, initiating a slow turn ON and release. This pinout should not be kept unconnected for avoiding stray signal pick ups.
Pin#11 and #14 (output A and output B): These are the two outputs of the IC which operate in a totem pole configuration or simply in a flip flop or push pull manner.
External devices which are intended for controlling the converter transformers are integrated with these pinouts for implementing the final operations.
Pin#12 (ground): It's the ground pin of the IV or the Vss.
Pin#13 (Vcc): The output to A and B are switched via the supply applied to pin#13. This is normally done via a resistor connected to the main DC supply. Thus this resistor decides the magnitude of trigger current to the output devices.
Pin#15 (Vi): It's the Vcc of the IC, that is the supply input pin.
Pin#16: The internal 5.1V reference is terminated through this pinout and can be used for external reference purposes. Example, you can use this 5.1V for setting up a fixed reference for a low battery cut-off op amp circuit, etc. If it's not used then this pin must be grounded with a low value capacitor.
Questions & Answers
Thank you for putting this information out. I was reading the comments and you have the patience of a saint. Everyone asking you to design some idea they have without doing any reading and research. I would’ve shut down comments long ago. Most of it you can’t even understand…….
Thanks for your time in helping others.
Thanks for your honest feedback, sometimes I do find it difficult to handle some of these comments but still I make sure to answer them because I believe that’s what makes my blog unique compared to other online websites..
Pin 8 ter ukur 0 volt. Bagian mana yng bermasalah?
Why do you ant to measure pin#8 voltage? It is for applying soft start only. Is your inverter working normally?
Tidak. Inverter saya bermasalah frekwensi out tidak keluar. Pin 8 soft star 0 volt. Dimana letak masalahnya?
If your inverter is not working, it may be due to some other reasons, pin#8 is not where it needs to be diagnosed. You can just leave the pin#8 connected to ground through a 1uF capacitor, and check other points like Rt/Ct pins, check whether you are getting a frequency across the Ct capacitor or not…
Jadi yang menyebabkan pin 8 soft start 0 volt apa? Seharusnya ada tegangan 4,7 volt di pin 8.
Are you getting a frequency at the output pins of the IC, or across the pin#5 capacitor? If not, then your IC may be faulty. Please build it in the following way and check again:
please apart from pin 11 and 14, how can I generate pwm output from another pin if I want a single output.
You can try the following configuration:
Thanks for this. please recommended values? I don’t understand “to output filter”?
Please ignore the “filter” word….you can use the output as the ON/OFF single ended oscillator.
Yes sir, thanks, please value for R1, please how can I use npn transistor instead of PNP?
Both the resistors can be 10k, and the transistor can be BC557…
hello sir
whit thankfully for useful explanation
I have a MMA inverter welder use sg3525 card control and I turned it for TIG welder and I need to shot down while weldering for this option i used a key for connecting pin 10 to 16 after a few times TIG weldering the Igbt went to die (😂)so pls tell me why and if help me to understand how I should
thank you
shahab
podes probar las mediciones del IC 3525 16 pines porque tengo uno y no se si mide bien los pines gracias
Hello Shahab,
Connecting pin#10 to pin#16 or the positive supply should shut down the IC output, so that should not cause the IGBTs to burn, but maybe due to the sudden voltage spikes the IGBTs are getting affected.
Make sure to use resistor across gate/emitter of the IGBTs, connect reverse diodes across the collector/emitter of the IGBTs, and consider using an IGBT rated to handle 2X power than the load power.
UC3525 Half bridge converter output voltage increases 2V, to 3V from set voltage
sir please can you help me out with the formula solving
sir i want laminating transformer full data.
You can refer to the following article:
https://www.homemade-circuits.com/how-to-make-transformers/
swagatam sir i want 7amp18vdc to 14vdc regulating power supply for lead acid battery charging
You can try any LM338 based power supply. Use two LM338 in parallel.
ckt diagram pls sir
Please refer to the LM317 based circuit, replace the LM317 with LM196 or use two LM338 in parallel:
https://www.homemade-circuits.com/how-to-make-current-controlled-12-volt/
hai sir i have one drought ,sir can run 24v operating voltage inverter transformer, to 12v.
sreenivasulu, I cannot understand your question.
24v operating inverter , can run 12v operating supply, in case 24v inverter secondary side winding modification , i mean 12 0 12v,
24V inverter cannot run on a 12V battery, for modification, rewind the DC side winding to 9-0-9V
it will runs 12v sir
I have tried this IC synchronization many times but the output results remain unstable
if you run a 24V transformer with 12V then the output will be 50% lower.
swagtam sir if 1000w inverter trasnsformer priymariside turns reduced i mean 230v turns data ,reduced 60v will increase amps. can i give e bike operating voltage 60v, 18amp.
Yes it will increase the amps proportionately.
swagatam sir how can convert 200w , to 500w inverter ckt board.
sir pls say high amp mosfet number and transformer rating that means amps rating, can i use same ckt board
sreenivasulu, please tell me the power (watts) of the inverter that you want to build and which circuit diagram?
i have 10v 0v 10v transformer 18amp . it can useful sir,further upgrading 5oow .convertion.
i am purchased amazon 200w kit irf 44n, pulsmodular ic sg3524 using ,for amlification boosting bc547 npn used thats kit.
First try the board and check whether you get 200 watt power output or not….if the boards works correctly, then you can upgrade the MOSFETs by replacing them with IRF3205 (3 in parallel). The battery must be also upgraded to 200 Ah….
18 amp transformer will produce only 10 x 18 = 180 watts….so it will not work for a 1000 watt output
can runs atx transformer, 3 atx transformers , 3 nos 200w boards,and individual for 100ah 12v battery.
If you want to use ferrite transformers then its winding will need to be calculated.
sir can i use 200amp inverter welding machine ferrite core transformer.
Without calculating the winding and matching the circuit frequency you cannot use any ferrite transformer.
winding cliculation formula need sir, can generate 70v,12 amp with help of ferrite core transformer. then connect 3sets connect o/p voltages in parllel 70v,36amp.can get using e bike operating voltage .
You can refer the following article, but i cannot help with the calculations, you will have to do it yourself:
https://www.homemade-circuits.com/how-to-design-and-calculate-ferrite-core-transformers-for-inverters/
which amp rating transformer suitable sir
For 1000 watt inverter, divide 1000 by the battery voltage that will give you amp rating of the transformer.
You can do it by upgrading the mosfets, battery and the transformer.
swagatam sir sg3524 and sg3525 both are same or not,
Yes, both are same with their basic functions, but please refer to their datasheets to confirm the pinouts
What is Maximum output current of sg3525.can I drive directly irfp250 MOSFET.
You can drive the MOSFETs directly from the SG3525 outputs, MOSFET gates do not require high current to operate.
Hi swagatam
Please sir which this, is the real formula “1/CT(0.7RT+3RD)” or “(1/CT(0.7RT+3RD))(0.5)” in calculating the frequency in this IC SG3525
Hi Emmanuel,
The formula is
f = 1 / Ct(0.7Rt + 3RD)
The PWM frequency relies on the timing capacitance and resistance, with the timing capacitor (CT) linked to ground through pin 5 and the timing resistor (RT) connected to ground through pin 6. Additionally, the deadtime is determined by the resistance between pins 5 and 7 (RD) and to a lesser extent, this value also affects the frequency.
i know all those connections but I’m confused with the formula because I find out that the IC can only oscillate from 100Hz to 100KHz and if needed for 50Hz on the output of a transformer one need to calculate for 100Hz and multiply it with 0.5 which is 50%. So I need clarification on this please.
Yes, what you have learned is correct, but since the IC can oscillate at a minimum 100 Hz, it cannot go down to 50 Hz. You will have to use a divide by two stage for getting 50 Hz.
Thanks for your quick response.
I would have like to see your prototype for the SPWM chopping aspects of your SG3525 inverter so to see the output waves form of the design.
No problem, If I happen to build a prototype I will surely let you know and show you the waveform.
Thanks you very much and keep up the good work.
You are welcome Emmanuel!
Swagatam,
I am trying to get a smooth control of PWM using the SG3525 especially when using an optocoupler which only has a small adjustment range on its input. Most of the circuits I have tried give me either no output i.e. PWM too narrow or normal output i.e. no PWM control with nothing in between.
What am I doing wrong? Is there a circuit which I could use which allows me experiment with the range of control?
Hello Paul, please explain the schematic that you have used, without understanding the schematic it can be difficult me to suggest.
please someone help me to know more about compensation in sg3525
Hello again, for a push pull transformer would I have to reduce the oscillator frequency in half for transformer calculations?
The oscillator frequencies at pin#11 or pin#14 should be 50 Hz, if 50 Hz is required at the transformer output, or 60 Hz if 60 Hz is required at the transformer output.
Thank you! On the datasheet I do not see suggested values for soft start capacitors or a max/min value. Would 1 pf work?
In some schematics I have seen pin#8 connected directly to ground when not used. I would prefer connecting a small value capacitor instead…yes a pF will work.
Hello, to disable soft start can I leave pin 8 floating?
Thanks,
Jon
Hi, I am not very sure about it, it is better to keep a very small value capacitor connected, such as a 0.001uF or similar.
Hi,
Please i will like to know the pin of sg3525 that is called PWM feed or the pin that two diode in sine wave can be fed to when using sg3525 as PWM oscillator in design a pure sine wave for inverter.
Regards,
Sina.
Hi, according to me there’s no such pinout which can be used to convert the IC SG3525 into a pure sine wave inverter.
I am ANURA SENANAYAKE. From sriLanka. I am a goverment nursing officer. But Iam an electronics hobbiiest. I always follow you. I preferred your articles. Wish you a bright future.
Thank you so much Anura! I appreciate your kind feedback!
Hi swag..
I build an smps inverter using the sg3525
When I power on the upper fet is very hot and the lower fet is cool and without load at the output of transformer. so I swaped the drain pin of the transformer but no changes then I return the connections back at it was then I swaped the gate the upper MOSFET which was at pin 14 that was heating to I swap it to pin 11 then the lower which was cool to from pin 11 to pin 14 then I power it on again so the lower MOSFET which was cool began to hot then the upper MOSFET which was hot before is now cool and if i leave it for long MOSFET get damaged.my ferrite transformer is 3+3 turns primary ,please help me I have Been trying for long but still same issues pls how do I tackle this fault what might be the solution I will be grateful in advance..
Okay I will try it again and give u feedback..
Hi David,
It seems something might not be correct with your ferrite core transformer and that might be causing the asymmetrical switching and heating of the MOSFET.
You can try increasing the turn number to 5+5 and check the response.
Hello,
I tried with pin 10 to use as shutdown for voltage regulation. I use TVS diodes to shut down the IC once a certain voltage has been hit (in this case 390 volts) it works fine however I am wondering how much current I should send to pin 10? I cannot find this anywhere in a datasheet.
Thanks,
Jon
Hi,
As per the internal diagram of the IC, the pin#10 has an integrated 5K series resistor, so this pinout is protected internally. The current is thus immaterial and can be of any value….however the voltage to pin#10 should be restricted below 12V.
Hi Swagatam, for operating a parallel resonant hi Q resonant inverter single leg I need to adjust the delay time in such a way, so to have a little overlap in opening of MOFSETS 1 and two. If I don’t use dead time resistor between legs 7-5 will I have some overelap in openeing the MOSFETS (shorting them). The circuite is here on page 5 figure 18.2 c : personal.strath.ac.uk/barry.williams/Book/Chapter%2018X.pdf
Thank you in advance
Regards
Emil
Hi Emil, I think SG3525 provides a minimum degree of dead time by default, so even if you don’t connect the dead time resistor across pin#7 and pin#5 still it won’t cause a shorting of the MOSFETs.
Hi Swagatam, thank you for your reply.What if I make a circuit with adjustable duty cycle and use the HI output twice: once directly to MOSFET 1 and second inverted through BC547 to MOSFET 2. Does the inverted signal keep the adjusted duty cycle of 50.01 or the inverted signal will be with duty cycle 49.99 which I don’t like it to be?
Hi Emil, I think the inverted duty cycle will be 49.99.
Hi Swagatam, thank you once agin. Verry kind of you. Meanwhile I solved the problem via a transformer driving the inverter leg trough the secondory. Ot works wonderfully. Thank you once again.
Thank you Emil, Glad you could solve it quickly.
Hie Chief
Have a question regarding pin 9, I have seen some Chinese welding inverters using Sg3525 as pmw control IC. What I only know about duty cycle is I use pin 1 as feedback pin but in these machine they ground pin 1 and use pin 9 to control duty cycle. How is that possible. Please explain .
Hi Francis, yes pin1 can be used as the feedback, since pin1 is the input of the one of the error amplifier. Pin9 can be used with an external PWM to control the output duty cycle.
You can refer to the following posts to learn about these pinouts
https://www.homemade-circuits.com/lm3524-datasheet-pinout-function-how-to-use/
https://www.homemade-circuits.com/inverter-circuit-with-feedback-control/
Dear Sir, would you be kind enough to post a SG3525 Test Circuit ?
(How to test working of SG3525)
Thank you very much in anticipation.
Hello Imsa, you can get the test circuit in the following datasheet of the IC. Please see the Figure.2 in the datasheet.
https://www.onsemi.com/pdf/datasheet/sg3525a-d.pdf
Hello Swagatam
I have built an inverter and its working well except that it is giving me 375ACV at the transformer output instead of 220/240ACV when the DC input voltage to the inverter is between 22 – 25.5VDC.
Could please assist me with a feedback output circuit for controlling 375VAC to 220/240ACV?
Your assistance will be appreciated.
Thanks
Aaron
Hello Aaron, The output voltage depends on the difference between the battery voltage and the transformer primary voltage rating. If the battery voltage is higher that will cause the output to be higher proportionately. You can refer to the following post, the first 3 designs have an automatic output voltage regulator facility
3 High Power SG3525 Pure Sinewave Inverter Circuits