DN05022D

DN05022/D Low-Cost LED Dimming with Output Capacitor http://onsemi.com DESIGN NOTE Table 1. DEVICE DETAILS Device NSIC2050B, NSI50010Y Application AC LED, Dimmable Input Voltage 100−127 Vac Topology Bridge + CCR and PWM Sensing I/O Isolation No Circuit Description This circuit can be thought of as having two separate portions. There is an LED management portion and a dimmer management/PWM Signal portion. The LED management portion charges the output capacitor to run the LEDs in a “DC” state. The dimmer management portion provides loading current for the TRIAC in a dimmer and provides a gate voltage to the series-pass MOSFET. The gate drive of the series MOSFET PWMs the LEDs at their peak current rating. The NSIC2050B Constant Current Regulators regulate the current through the LEDs. The NSI50010Y limits the power consumption of the dimmer management circuit. For optimal performance, the gate voltage of the MOSFET (driven by the voltage divider of the 11 kW and 1.5 kW resistors) needs to be equal to the threshold voltage when the input voltage to the circuit is at the dimmer’s minimum conduction angle. Also, some dimmers may require more than 10 mA of loading current, so the NSI50010Y may be replaced with another CCR such as the NSIC2020B (20 mA CCR), though power consumption will increase. 2 × NSIC2050B 2 × BAS21SL Vin 100 W 2W 3.3 mF 250 V 60 V 3 × Cree MX−6S NSI50010Y BAV23CL 1.5 kW 1/4 W 11 kW 1/2 W MTD6N20E BZX84C15L Figure 1. LED Lighting with CCRs, Dimmabl...