The IRS2505 is a control IC for boost-type PFC circuits operating in critical-conduction mode. The IC incorporates a free-running frequency oscillator with on-time and off-time control of the boost power MOSFET without the need for a secondary winding. Also included in the design is over-voltage protection of the DC bus and cycle-by-cycle over-current protection of the power MOSFET. Micro-power start-up current and an internal 20.8 V zener clamp at VCC are provided to simplify the external VCC supply circuitry.

• Critical-conduction mode PFC control
• High PF and ultra-low THD
• Wide load and line range
• Regulated and programmable DC bus voltage
• No secondary winding required
• MOSFET cycle-by-cycle over-current protection
• DC bus over-voltage protection
• Low EMI gate drive
• Ultra-low start-up current
• 20.8 V internal zener clamp on VCC
• Excellent ESD and latch immunity
• RoHS compliant
• 5-pin SOT-23 package