OR BETTER..
What do u think about that?
What do u think about that?
An externally hosted image should be here but it was not working when we last tested it.
sure???
Q1 and Q4???
Are u sure? Q1 is connected to +12V... Maybe Q2/Q4???
Do u mean this?
Q1 and Q4???
Are u sure? Q1 is connected to +12V... Maybe Q2/Q4???
Do u mean this?
An externally hosted image should be here but it was not working when we last tested it.
The mosfets used should be IRFZ44E (very good switchers) or the originals on the schematic. The IRF540 are not able to switch very high inductive currents, and the on resistance is much higher in the IRF540 than the IRFZ44E. Also the Voltage imbalance is probably caused by improper number of secondary windings between the two windings.You could Also regulate this circuit by monitoring one or both of the dc output voltages with the on-chip comparators in the SG3524 against a reference voltage which is also on-chip.
Symx:
My supplyer have the IRFZ44N instead of IRFZ44E.
I gave a look at pdf (datasheet) and if i'm not wring they're a bit better than "E"..
N:
Vdss=55V
Rds(on)=17.5mOHM
Id=49A
Ultra Low On-Resistance
Dynamic dv/dt Rating
Fast Switching
E:
VDSS = 60V
RDS(on) = 0.023OHM
ID = 48A
Dynamic dv/dt Rating
Fast Switching
Am I wrong?
My supplyer have the IRFZ44N instead of IRFZ44E.
I gave a look at pdf (datasheet) and if i'm not wring they're a bit better than "E"..
N:
Vdss=55V
Rds(on)=17.5mOHM
Id=49A
Ultra Low On-Resistance
Dynamic dv/dt Rating
Fast Switching
E:
VDSS = 60V
RDS(on) = 0.023OHM
ID = 48A
Dynamic dv/dt Rating
Fast Switching
Am I wrong?
Sorry for delay was on vacation.
Yes the current looks good, but compare the two for switching energy and power dissipation.
Repetitive Avalanche Energy† 11 mJ for IRFZ44E
Repetitive Avalanche Energy† 9.4 mJ for IRFZ44N
PD @TC = 25°C Power Dissipation 110 W for IRFZ44E
PD @TC = 25°C Power Dissipation 94 W for IRFZ44N
And I believe the Z44N will be out of production soon,and the Z44E will supersede.
Yes the current looks good, but compare the two for switching energy and power dissipation.
Repetitive Avalanche Energy† 11 mJ for IRFZ44E
Repetitive Avalanche Energy† 9.4 mJ for IRFZ44N
PD @TC = 25°C Power Dissipation 110 W for IRFZ44E
PD @TC = 25°C Power Dissipation 94 W for IRFZ44N
And I believe the Z44N will be out of production soon,and the Z44E will supersede.
MaXiZ:
If the IC is running properly,You should have a low duty square wave at those pins. Of course the duty cycle will depend on the difference (voltage) between the on-chip
comparators input pins. Also the totem pole drivers are correct except the resistor to ground should be in series with the bases from the IC pin. This will permit you to place a very small capacitance to ground from the totem driver bases,this usually prevent ringing and subsequent
re-firing of the opposite phase power FET. Just a thaught.
If the IC is running properly,You should have a low duty square wave at those pins. Of course the duty cycle will depend on the difference (voltage) between the on-chip
comparators input pins. Also the totem pole drivers are correct except the resistor to ground should be in series with the bases from the IC pin. This will permit you to place a very small capacitance to ground from the totem driver bases,this usually prevent ringing and subsequent
re-firing of the opposite phase power FET. Just a thaught.
MaXiZ
If your meter can pick up DC readings from the pulses at those pins, they should be very low at no load on the power supply and increase with increasing load as the controller makes the mosfets turn on longer to drive the transformer harder.
If your meter can measure frequency, you should get a frequency reading somewhere around 50khz at ech pin, based on the RC time constant of R10 and C7, divided by two since each pin receives half of the full frequency. I can't be sure if that is the right frequency as the inside of the chip could contain frequency dividers.
jewilson
Thanks. It is probably true about the emitter resistors, but they could help in the dead-time between mosfet switchings.
If your meter can pick up DC readings from the pulses at those pins, they should be very low at no load on the power supply and increase with increasing load as the controller makes the mosfets turn on longer to drive the transformer harder.
If your meter can measure frequency, you should get a frequency reading somewhere around 50khz at ech pin, based on the RC time constant of R10 and C7, divided by two since each pin receives half of the full frequency. I can't be sure if that is the right frequency as the inside of the chip could contain frequency dividers.
jewilson
Thanks. It is probably true about the emitter resistors, but they could help in the dead-time between mosfet switchings.
Re: SO
MaXiZ,
Pins 11 and 14 should have a pulsed DC wave form on them. Therefore, they should provide both a DC reading and a frequency presence. The DC voltage reading should increase as the output of the supply is loaded down.
With no load on the output, you should still get DC reading on pins 11 and 14, but it should be small, maybe .1 or .2 volts.
MaXiZ,
Pins 11 and 14 should have a pulsed DC wave form on them. Therefore, they should provide both a DC reading and a frequency presence. The DC voltage reading should increase as the output of the supply is loaded down.
MaXiZ said:
With no load on the output, you should still get DC reading on pins 11 and 14, but it should be small, maybe .1 or .2 volts.
(Symx,
You might be thinking of the SG3425 when you say that the pull-down resistors which go from pins 11 and 14 to ground are not needed. On the SG3424, the open emitters at those pins need to be externally pulled down when those internal transistors are turned off.)
True enough the circuit would benifit with both the pulldown and lowpass resistors.That is correct, the SG3525 contains a totem pole output stage to directly drive higher capacitance loads.The SG3524 does not contain an active pulldown.But at this stage, and with the light capacitive load seen by the SG3524 in his current circuit a 1K resistor is sufficient for a pulldown.
External totem pole circuits are desirable so as to control the charge and discharge rates to prevent ringing and common mode conduction.But lets not confuse him anymore than need be, and get the basic circuit up and going.
You might be thinking of the SG3425 when you say that the pull-down resistors which go from pins 11 and 14 to ground are not needed. On the SG3424, the open emitters at those pins need to be externally pulled down when those internal transistors are turned off.)
True enough the circuit would benifit with both the pulldown and lowpass resistors.That is correct, the SG3525 contains a totem pole output stage to directly drive higher capacitance loads.The SG3524 does not contain an active pulldown.But at this stage, and with the light capacitive load seen by the SG3524 in his current circuit a 1K resistor is sufficient for a pulldown.
External totem pole circuits are desirable so as to control the charge and discharge rates to prevent ringing and common mode conduction.But lets not confuse him anymore than need be, and get the basic circuit up and going.
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