What affects the Junction Temperature of LEDs?
1. Ambient Temperature 2. Power Dissipation (Forward current times forward voltage) 3. Thermal resistance, junction to cathode pin (This specification is listed in product data sheet.) 4. Thermal resistance, pin to air For more information review Application Brief AB A04 – LED Lamp Thermal Properties. What pitfalls are associated with LEDs connected in parallel? If two or more LEDs with different electrical characteristics (Forward Voltage (Vf) Vs. Forward Current (If)) are connected in parallel, then the resulting voltage across the LEDs connected in parallel will tend to take on the Vf of the LED with the lowest Vf. This is called ” current-hogging” and can cause noticeable brightness differences between LEDs. This issue is detailed in Application Brief AB D 007. What are the concerns when connecting LEDs in parallel? The forward voltage of LEDs varies from LED to LED. LED forward voltage increases with an increase in forward current. When LEDs are connected in parallel, the voltage
