Many compact fluorescent lamp (CFL) triac dimmer solutions currently use a simple ‘PI’ circuit to control the lamp’s voltage and current. The circuit consists of a proportional (P) part and an integrating (I) part. However, stability issues at deep dimming levels can cause the lamp to flicker, so these solutions typically limit dimming to about 20-30%. Adding a differential element to the PI circuit can keep the circuit stable and hence avoid flickering even at much lower dimming levels. By combining these elements to create a complete ‘PID’ controller network, NXP’s GreenChip UBA2027x family of CFL drivers enable flicker-free deep dimming down to 2%.