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.
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 te 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.
Thanks for the reply.
Please can you recommend me changing circuit that can charge two 12volt 90AH car battery in some hours? (2) please can I use two NPN thus TIP41 to boost the output of the SG3525 by connecting the base of the NPNs to each line before connecting it to the MOSFET?
It is not recommended to charge lead acid batteries in less than 10 hours, still you can try the following circuit:
https://www.homemade-circuits.com/2014/03/fast-battery-charger-circuit.html
your second request is simply not required…
Thank you Hiram, sorry unfortunately your first request is not feasible on this planet, because no system can produce an output that may be even close to the input value.
2) If you are using a lead acid battery then you must charge it for at least 12 hours at C/10 rate in order to maintain good health of your battery…or you can opt for a Li-ion battery and get it charged within a couple of hours.
My inverter is not turning on my 95watt LG television. It works fine with other loads but not with the TV. When I first turn it on, it attempts to come on but draws the power down and it will go off, it keeps repeating itself. I'm using sg3524 oscillator with feedback using optocoupler. Could it be that my feedback response time is slow?
It could be because your battery is not rated to hold 95 watts, the battery should be at least 25AH rated and fully charged.
Hello,
I am designing a buck converter for a solar charge controller. I am using SG3525 and IR2110. I am experiencing a strange reaction:
– If I connect the MOSFETs directly to SG3525's outputs, then all is good;
– If I connect the IR2110 driver to the outputs of SG3525, I find the pulses in the outputs of IR2110 but when I connect the same MOSFETs, one of the SG3525 outputs stops. I only get the pulses on one of the channels. Why does it stop pulsing ? If I disconnect the MOSFETs from IR2110, both channels pulse again.
All this test is done with the feedback pin linked to ground, so SG3525 sends a 50+50 duty cycle.
Please give me an idea what is happening.
Thank you,
Mihai.
Hello,
that's strange, try connecting LEDs with 1K resistors across the IR2110 pinouts and check how the LEDs respond…..or try connecting a resistor right across the gate/source of each mosfet and see if that helps.
you can also check the issues using BJTs instead of mosfets to learn if there's any difference in the response
by the way there's an easier alternative in the form of the following design
https://www.homemade-circuits.com/2015/05/5v-pwm-solar-battery-charger-circuit.html
thank u sir……
thank u for quick response sir….im working on voltage mode feedback control for half bridge converter. i have selected ucc25600, but it requires a center tap transformer (isolation transformer between mosfet and ic )for driving power switches. it would be helpful if u suggest any other ic for feedback purpose without use of isolation transformer.
Thanks leela, the feedback control is a secondary issue, the primary issue is the half-bridge topology which can be implemented only through a specialized IC as suggested by me earlier. Other ICs like SG3525 will require a center tap transformer for the operations.
You can Google for "half bridge driver IC" and see if you can find other options also of your choice…
hi,
im working on half-bridge LLC resonant converter used to drive LEDs(40v and 1a). is sg3525 is suitable for this converter??? or any suitable ic for this converter.
Hi, I don't think SG3525 can be used for half-bridge driver application, you can try the following concept for your requirement
https://www.homemade-circuits.com/2013/09/half-bridge-mosfet-driver-ic-irs21531d.html
Hi, why did you have to replace the fets?
you might be using wrong fets or there could be some other reason….
It cannot be because of the IC, because the IC output can be configured with as many mofets as you may want
please make sure the fets are connected very close to the IC output pins.
You can read the following article for more help
https://www.homemade-circuits.com/2013/09/mosfet-protection-basics-explained-is.html
Hi there, can I have some advice from you? I am currently working on an inverter project. I have generated three SPWM, with each 120 degree phase shift from each other. I am wondering if I can use the SG3525 to generate the other three complemented PWM signals with dead time? Is there a direct PWM input to the SG3525 and by-passing the internal PWM generator block?
Are there any alternative solutions for my application?
Thanks!
Hi, sorry I am not quite sure about how the IC could be triggered with an external PWM….By the way the IC has only two outputs, so getting three outputs may not be possible.
Hello sir..iam adnan. and iam working on a project in which i need to built an inverter of output frequency of 1MHz. as mention that in sg3525 built in oscillator whose frequency range is 100KHz to 500KHz. so i have to ask that can i use this ic sg3525to produce pulses of this switching frequency if not then plz recoment me an ic that can work on this switching frequency so i can get pulses to operate mosfets with desired switching frequency.plz
Hello Adi, I think the best oscillator circuit for getting high frequencies without issues is a transistorized astable using BC547 or similar transistor.
IC 555 can also be used for the same.
can you send me any link regarding to this issue so that i can make circuit arrangement for this frequency plz. because i dont have any idea about this circuit arrangment.
and one thing more sir g. can i use sg3525 for less than 500khz switching frequency mean for 300KHz inverter?????
yes that's possible.
here;s the link for the transistorized inverter:
https://www.homemade-circuits.com/2012/09/mini-50-watt-mosfet-inverter-circuit.html
you can decrease C1/C2 values for getting any desired high frequency depending on the T1/T2 MHz rating
Plss wat should be the voltage at pins 11 and 14 whn it hasnt been connected to mosfet?
Am designing a DC TO DC booster, anytime I connect the mosfet and high frequency switchin trafo only one mosfet get hot n destroyed. Plss wat could be the problem?
the peak voltages at these pinouts will be equal to the supply voltage, but their average voltage will be around 50% less than the supply voltage and will also depend on the PWM set through the pots at pin1/2
first confirm the frequency at these pins using a frequency meter, and this frequency should chnage as Rt or Ct is changed…., and the mosfet should be close to these pinouts for correct functioning….use a PCB for it, breadboard might not work
Hello
Actually, I am working with sg3525 to build inverter 12 DC to 240 AC with f 50 Hz
But I have problems that output is not 50 Hz nor 240 volt
I don't know what is my problem?
So can help with that ?
first check the frequency at the output pins of the IC….both pins must oscillate at the 50Hz rate
Hi i've a problem with sg3524 used in single ended mode in a buck converter. The problem is that the output freq seems to change (i don't mean the duty cycle but freq of output waveform between Collector and Emitter pin). How is it possible? it is set to have something like 60kHz, but i could see it is very lower, as 70 Hz. The circuit is the same of application note with only difference that i used p-mos and not p-darlington. Thank you
Hi, test the frequency at the base of the transistors and at the output of the transformer, if these are showing 60kHz then your IC is working normally,otherwise you can disconnect the BJTs from the IC outputs and the check the frequency on the output pins separately.
That is a modified sine wave inverter pls i need a circuit of a pure sine wave inverter
presently I do not have the exact circuit that you are requesting….If I find it I'll let you know
The waveform should look exactly like that of ac mains and that is pure sine wave
you can referring to the following article which shows the waveform images of a pwm based sine wave inverter
https://www.homemade-circuits.com/2013/10/modified-sine-wave-inverter-circuit.html
using pwm you cannot expect anything better than this.
Pls sir i was asked to construct a pure sine wave inverter(not modified sine wave) using sg3525 and 555 ic or 4047 ic as my final year project to be passed on march 24th pls can u help me with a circuit diagram and also if you have any schematic of a pure sine wave (not modified)inverter not modified sine wave you can also send me the link but the most important thing is that it must be pure sinewave and have pwm feature
victory, any inverter that uses PWM is a modified sine wave inverter…so better clarify the exact specs from your seniors, if possible get the waveform image which you are supposed to achieve.
Pin8 is connected to ground no cap i only have a 100nf cap on pin 7 and 100k resistor on pin6 it is sg3524 not 3525
pin8 capacitor is only responsible for any sort of soft start effect, if there's no capacitor at pin8 then the reason could something else….try keeping the pin8 open or disconnected with ground
Happy new year sir..this marks the 3weeks of my inverter functioning effectively pls can you tell me how i can eliminate soft start in my sg3524 inverter as it affects my appliance during automatic changeover when mains is unavailable as it trips off my tv and then on the tv whereas i want it to run automatically without switching off during changeover…i used 100uf cap for a relay power supply so the problem does not lie on the automatic changeover circuit and am 100% sure on that (2)what is the maximum power of an inverter with a single irf3205 in each oscillator of the ic?
Happy New Year to you Victory!
Do you have any capacitor connected across pin#8 and ground of the IC?
If yes then just remove it to eliminate the soft start effect.
mosfets don't decide the output wattage they are only rated to handle it….it's the battery and the trafo which are responsible for the power output ..
..IR3205 will easily handle upto 400 watts
What is the voltage supply at pin10 to shutdown the Ic
I replaced the ic and it works fine now but pls(1)how many hours or minuites will my 300watt inverter power a 220watt load using 12v 36amp battery(2)what's the positive voltage pin10 of the ic will receive before shutting down the inverter(3)i want to rectify a 15v transformer to charge battery but i know that the voltage will be up to 20vdc after rectification and so can i connect a 12v cooling fan at the output so as to reduce the voltage to 15v or should i use a 12v lamp
1) back up can be expected to be not more than 1 hour.
2)pin10 must receive a permanent high or positive from the battery to shut down.
3)a lamp in series will work better than in parallel with the output, although both the methods are crude and not much recommended.
No.what is a freewheeling diode and what type of diode should i use and also the connection details.
connect each 1N5408 diode across each of the mosfets…cathode to drain, and anode to source pin of the mosfet
I've tried the bjt stage yet the same thing happens what could be the problem
disconnect the transformer from the mosfets and connect 12V car headlamps across drain and positive of each mosfet, if it still burns then definitely the fault could be assumed to be with the IC output…
by the way did you connect freewheeling diodes across drain and source of each mosfets???
We don't have any voltage regulator apart from lm7812 here in nigeria.pls sir can u pls tell me why my sg3524 inverter keeps burning the mosfet after some minuites of operation despite being placed on heatsink and not overloaded i'm only running a 100watt load on it.the mosfet is irf3205..could it be the ic?
Victory, please try connecting the mosfets through BJT drivers as shown in the following example, and see the response:
https://www.homemade-circuits.com/2015/05/simplest-pwm-modified-sine-wave.html
Pls sir for a 12v transformer to output 15v after rectification that will be at peak voltage but when there is lower voltage it gives 12v dc so it's advisable to use a 14-15v transformer
In that case you can use a 24V or 18V trafo and regulate it to 14.4V through a LM338 circuit…this will take care of any low voltage situation and give a perfectly constant output for your battery
Thanks sir for the explanation
I want to control pwm duty factor from 0-100% is this possible? i shorted pin 9 & 1 and pin 2 is shorted with 16 and i am using vdr from pin 16 to vary the voltage of pin 1 to control duty factor….
I don't think the connections are correct, it should be as shown in the following article:
https://www.homemade-circuits.com/2013/01/modified-sine-wave-inverter-circuit.html
ignoring the D5 connection, P2 can be used for controlling the duty cycle.
And almost everything here is kinda fake
We don't have any high amp voltage regulator here in nigeria although i'm a Biafran
you can try making the simple high amp regulator as explained in the following article:
https://www.homemade-circuits.com/2015/03/100-amp-variable-voltage-power-supply.html
The 15v is it on no load also i want to charge the battery with 14.4v not 15v as 15v will damage
I think I just forgot to tell you that the input current for your 36AH battery should not be more than 5amps…so I think 9amp is way too high….or probably you could use a LM338 current limiter circuit in the middle for correcting the issue.
after connecting the input voltage must drop to your discharged battery's voltage level….if it's 11.5V then initially the connected supply should drop to 11.5V and then gradually rise as the batt begins charging….
15V input will not damage the battery if you use an overcharge cut off circuit or manually switch OFF as soon as the battery reaches 14.4V…
Sir can u please suggest what the problem might be i rectified a 12vac and it producer 13,8v with 9amp current and my battery voltage is now 11,4volt and so i NEEDED to charge it but when i connect my multimeter in series with the battery when connected I discovered that the battery is only drawing 0,4 amp whereas the current of my charger is 9amp pls what could be the problem or is that normal? I really need to charge the battery 12v 36amp (2)i also constructed ur automatic changeover circuit using relay but when i connect the load to the pole and initiate mains power to the nc the bulb lights well and once i apply dc to the relay coil it offs the light but i see some sparks inside the relay which makes the light to flicker what could be the pro,
victory,
what did you use for the filter capacitor? make sure it's rated at at least 20,000uF/25V…because after rectification the output from your power supply is supposed to be above 15V, and not 13.8V
for the relay problem, just connect a 220uF/25V capacitor parallel with the relay coil, and check the response
Please explain the frequency calculation
Pls what will be the dc voltage of a 15vac transformer after rectification and is their anything wrong with connecting the dc voltage directly to my 12v 36amp battery Will reversed current from the battery destroy the bridge diodes,,also pls tell me the time that my 12v 36amp batt. Be fully charged when charging with a current of 2amp 3,adding a diode to the positive line after rectification will it reduce the voltage
after smoothing it could be well over 20V, you can use it if the current rating of the trafo is not over 4 amp
No, diodes of the bridge will never get destroyed by the battery power.
yes, after 10 hour of charging at 3 amp rate your battery should fully charged…..a series diode will reduce only 0.7V so that's fine if your trafo is already 15V rated.
sorry, the charging rate should be at least 4 amps…3 amp could take around 20 hours for full charging
The inverter is faulty i replaced the mosfet with original one as i was deceived with a fake irf3205 mosfet the new one powered a 200watt load very normal and my tv works without noised
The inverter is faulty i replaced the mosfet with original one as i was deceived with a fake irf3205 mosfet the new one powered a 200watt load very normal and my tv works without noise as if it's a pure sinewave
Thank you sir, I checked and is correct.
I want to work with two IC SG3525, both working at 50 kHz but one commanding the other, so that the waves are synchronized outputs A, also the output waveforms B also synchronized.
Please send me a sample schema, my email is jmimbelac@yahoo.es
Thank you
connect the pin4 of the IC which has Rt, Ct configured at 50kHz, with pin3 of the other IC without Rt, Ct….that's all ….now both will be synchronized at 50kHz
Also this is what i observed the drain voltage of the fet on no load at pin 11 of ic is 10.5v and at pin14 is 8v but when i connect the load to it drain voltage becomes 0 which makes the transformer to stop humming is that a clear indication that it's the battery cos i don't want to buy another battery and end up having the same result and since the inverter is producing the desired voltage i don't see anything wrong with it.
just connect a voltmeter across the battery terminal while the inverter is loaded, if the voltage drops to zero will indicate a faulty battery…you can also try attaching an ammeter in series with the battery positive and check the current while the inverter is loaded…if the current reading is too high then your inverter is faulty.
Hello sir i have constructed an inverter based on sg3524 with 2 irf3205 mosfet which is supposed to deliver 300watt and at the output i get 300vac and adjust it to 220vac using the preset and my transformer is 9-0-9 300va but when i connect a 20watt cfl bulb it works fine but if i connect a 60watt load the output becomes 0v and transformer stops humming but once i remove the 60watt load inverter comes on immediately and after sometime it starts to on itself and off itself at a period of about 3seconds…pls where could the problem come from as i'm using a 12v 36amp battery could this be as a result of faulty battery? Because when i bought the batt. I checked the voltage with a dmm and it reads 21v and then decreases fast to 13volt also i didn't charge it when i bought it before using is anything wrong with the battery? If yes can i still power the inverter with an 18amp bactery as i will buy new one if the new battery i bought would be faulty..thanks in advance
Hello victory,
a good 12V battery of any kind can NEVER show 21V at any cost…so definitely your battery could be severely faulty…and using a battery for an inverter application without charging is another grave fault that one can make…so both ways it's the battery that looks defective.
you can use any AH rated battery, that will not harm your inverter in any manner…but just make sure it's 12v rated for your 9-0-9v trafo inverter
If I'm getting no output from A and B and shutdown pin is low, what is causing outputs to stop? Thanks!
shutdown pin should be at "low" to enable the A/B pins functioning….there could be some other fault in your circuit
Dear Swagatam Sir,
Can I use this IC to synchronise 2 sine waves with a phase difference?
Thanks in advance.
Dear Faris,
please read the pin#3 explanation given in the above article, here sync feature becomes relevant only when more than one IC is involved and all the ICs need to work with a single oscillator frequency, secondly the IC is not designed to respond to sine waves, it'll ultimately convert all frequencies to square waves…
Sir,
can you please suggest me any method by which I can synchronise two sine waves of high voltage?
Faris, you'll have to explain me the whole application that you are trying to implement, only then i'll be able to suggest you something…
Can use XR2203 ,PLL and zero crossing circuit .go through these the ic datasheet to get the idea .
how do we calculate dead time? whats the formula for Rd
please check the datasheet of the IC, it might be there
I really benefit from your aticle.i wish you all the best
Thanks and Glad you found the article useful!
Dear Sir
I want know how to calculate RT AND CT
Dear Rashabtha,
f = 1.3/Rt.Ct
Rt in kHz, Ct in uF and f in kHz
Hello Nomi, It indicates that your SMPS is wrongly designed or constructed, a bridge will never heat up without load or under correct loads
Hello sir .i have built a car smps based on sg3525.on off load my dc rectifier heat up gaudily,i am using 12v 1.5 AH power supply.when i attach a car battery my rectifier blows with in seconds and in result my mosfets also blows.i cannot figurout where is the problam.please help me with that.
check the supply voltage, it may be too high or there could be soem other incorrect connections.
I have the same issue.
Hi
i need help about the sg3524 i build an inverter with it but my problem is that i only get 1.5vac form pin 11 and pin 14 and i know it should be at least 2.5 volt so my inverter is not working please help
check the peak voltage at those pinouts with a peak voltage detector, it should be equal to the battery voltage, or adjust the PWM pin preset for correcting the output to the desired limit.
In any case the mosfets will conduct, albeit with different RMS levels.
sir if i want to use pin10 of the sg3524 as shutdown in my inverter how do i make the circuit to sense my battery low voltage and trigger the shutdown
beelal, pls refer to this example for the connection details:
https://www.homemade-circuits.com/2013/01/modified-sine-wave-inverter-circuit.html
I have no idea about it, you may take the help of a professional trafo designer.
Just use a 7812 IC for limiting the voltage to 12V for the ICs, rest everything will remain as is.