I previously posted a switching circuit using an IRFZ44N to switch about 12-14 vdc at 5 amps maximum. Thanks to several forum members, I have made some changes to the circuit and the result is attached. As you may note, the IRFZ44N has been changed to an IRLZ44N, the voltage requlator has been changed from a 7812 to a 7809, and a couple of ceramic caps have been added to the regulator to suppress transients.
As some of you know, I am a tinkerer and not an engineer; my math skills are poor. So today, after making the changes to the prototype, I decided to do some "shade tree" experimentation in an effort to determine what the cooling requirements would be on the MOSFET.
Gate voltage: 7.67v
Load voltage: 13.36v
Load current: 2.73a
Duty cycle: 2 seconds off, 8 seconds on for 1 hour
Ambient temperature: 24 deg. C
Max. tab temperature of IRLV44N: 33 deg. C (mostly still ambient air and no heat sink)
My hope is that even with a full load of 5a, no additional cooling will be required, but I don't know. I intend to build a 5a power supply and load, but I haven't done so yet. In the interim, what do you think? Will I be able to put this circuit in a small enclosure without a heat sink or a fan?
Thanks in advance for your help.
As some of you know, I am a tinkerer and not an engineer; my math skills are poor. So today, after making the changes to the prototype, I decided to do some "shade tree" experimentation in an effort to determine what the cooling requirements would be on the MOSFET.
Gate voltage: 7.67v
Load voltage: 13.36v
Load current: 2.73a
Duty cycle: 2 seconds off, 8 seconds on for 1 hour
Ambient temperature: 24 deg. C
Max. tab temperature of IRLV44N: 33 deg. C (mostly still ambient air and no heat sink)
My hope is that even with a full load of 5a, no additional cooling will be required, but I don't know. I intend to build a 5a power supply and load, but I haven't done so yet. In the interim, what do you think? Will I be able to put this circuit in a small enclosure without a heat sink or a fan?
Thanks in advance for your help.
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