Power Factor Controllers
The MC34261/MC33261 are active power factor controllers specifically designed for use as a preconverter in electronic ballast and in off−line power converter applications. These integrated circuits feature an internal startup timer, a one quadrant multiplier for near unity power factor, zero current detector to ensure critical conduction operation, high gain error amplifier, trimmed internal bandgap reference, current sensing comparator, and a totem pole output ideally suited for driving a power MOSFET.
Also included are protective features consisting of input undervoltage lockout with hysteresis, cycle−by−cycle current limiting, and a latch for single pulse metering. These devices are available in dual−in−line and surface mount plastic packages.

• Internal Startup Timer
• One Quadrant Multiplier
• Zero Current Detector
• Trimmed 2% Internal Bandgap Reference
• Totem Pole Output
• Undervoltage Lockout with Hysteresis
• Low Startup and Operating Current
• Pinout Equivalent to the SG3561
• Functional Equivalent to the TDA4817