12V Sabit Güç Devresi Tasarımı

Thought for 4 mins 51 sec

Tam net hesap için, IPB110P06LMATMA1 datasheet’indeki RθJA / RθJC, güç dağıtımı, ve özellikle PCB bakır alanına bağlı termal eğriler lazım. Bu tür değerler datasheet’ten alınmalı; iş akışı da datasheet’i tek doğruluk kaynağı olarak kullanmayı söylüyor ve termal özellikler için hedefli datasheet sorgusu yapılmasını öneriyor .

Elimizdeki verilere göre yine de iyi bir ilk tahmin yapabiliriz:

Yaklaşık iletim kaybı

Daha önce konuştuğumuz RDS(on) ≈ 10-11 mΩ kabulüyle, 5 A akımda:

P = I² x R
5² x 0.010 = 0.25 W
kötüleşmiş durumda 5² x 0.011 = 0.275 W

Yani IPB110P06LMATMA1 için 25 C civarında yaklaşık 0.25-0.28 W iletim kaybı beklerim.

Termal marj yorumu

Bu güç seviyesi, D2PAK / TO-263 sınıfı bir MOSFET için genelde rahat taraftadır. Pratikte:

geniş bakırla sıcaklık artışı genelde düşük olur
dar bakır adasıyla sıcaklık belirgin artabilir
sıcaklık arttıkça RDS(on) da artacağı için gerçek kayıp 0.25 W’ın üstüne çıkar

Bu yüzden tasarım marjı açısından:

5 A sürekli akımda kullanılabilir
ama “çok rahat” diyebilmem için datasheet’teki PCB alanına göre termal direnç grafiğini görmem gerekir

Bakır alan ihtiyacı için pratik başlangıç

Datasheet eğrisi olmadan güvenli başlangıç önerim:

Table

Hedef	Öneri
Minimum çalışır yaklaşım	MOSFET tab pad’i altında ve çevresinde en az 1-2 cm² bakır
Daha rahat termal marj	2-4 cm² toplam bakır alan
Daha iyi ısı yayılımı	alt katmana çoklu termal via ile yayılım

Sonuç

IPB110P06LMATMA1 için 5 A’de yaklaşık iletim kaybı: 0.25-0.28 W
Bu, giriş koruma bloğu için mantıklı ve düşük kayıplı bir seviye
Ama kesin termal marj ve gereken bakır alan için datasheet’teki termal grafik şart

İstersen bir sonraki adımda bunu daha mühendislik seviyesinde yapayım:

40 C / 60 C ortam için sıcaklık artışı tahmini
1 oz bakır varsayımıyla daha somut alan hesabı
gate zener ve TVS ile birlikte tam giriş koruma bloğu değerlendirmesi

Datasheet ile hesapla

60C ortam varsay

Sürekli akım marjı

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