High-Voltage Half-Bridge Driver Simplifies Lamp Ballast Design

Designed for electronic lamp ballast and electronic transformer applications, the SGS-THOMSON L6569 integrated circuit includes all of the circuits needed to drive two power MOSFETs in half-bridge push-pull arrangement, eliminating the external oscillator and external bootstrap diode. Moreover, the base drive transformer is eliminated, making design less critical.

A 50% duty cycle square wave is generated by the internal oscillator at a frequency set by an external RC network. Internal logic assures a minimum dead time to avoid cross conduction. Moreover, an innovative functional block (patent pending) on the chip performs the bootstrap diode function, improving dead time accuracy. The elimination of the external diode is particularly helpful in surface mounting applications.

Produced using the high voltage BCD-Offline mixed bipolarCMOS-DMOS technology, the L6569 operates on supplies up to 600V and provides driver current up to 270mA (sink), 170mA (source). Startup current is less than 150uA and operating current is less than 2mA. Dead time accuracy is typically 1.2us.

Two versions of the integrated circuit are available, differing in the startup method. Aimed at Compact Florescent Lamp (CFL) applications, type L6569 drives the lower external MOSFET ON before the undervoltage threshold is reached. In contrast the L6569A version drives the lower external MOSEFT OFF before the undervoltage threshold is reached; this type is for tube lamp and electronic transformer applications. Both types are available in Minidip or SO-8 packages.

BCD-Offline technology combines on a single chip low voltage CMOS and bipolar control circuits with high-voltage groundedsource lateral double-diffused MOS transistors (HV LDMOS) and grounded-source lateral insulated-gate bipolar transistors (HV LIGBT). In source-follower configuration the source can float up to 20V. Designed for operating voltages in the 500V-700V range, this technology is aimed at important growth markets like electronic fluorescent lamp drivers, appliance motor control and power supplies. Needing just 16 masks, it is a simple, cost-effective process for high-volume, consumer applications.

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