Highly-Integrated Green-Mode PWM ControllerGeneral DescriptionA highly integrated PWM controller, SG6846G provides several features to enhance the performance of flyback converters. To minimize standby power consumption, a proprietary green-mode function provides off-time modulation to continuously decrease the switching frequency under light-load conditions. Under zero-load conditions, the power supply enters burst-mode, which completely shuts off PWM output. Output restarts just before the supply voltage drops below the UVLO lower limit. This green-mode function enables power supplies to meet international power conservation requirements. The SG6846G is designed for SMPS with surge-current output, incorporated with a two-level OCP function. Besides the cycle-by-cycle current limiting; if the switching current is higher than OCP threshold and lasts for 500ms, SG6846G shuts down immediately. SG6846G also integrates a frequency-hopping function internally, which helps reduce EMI emission of a power supply with minimum line filters. The built-in synchronized slope compensation provides proprietary internal compensation for constant output power limit over a universal AC input range. The gate output is clamped at 18V to protect the external MOSFET from over-voltage damage. Other protection functions include AC input brownout protection with hysteresis and VDD over-voltage protection. For over-temperature protection, an external NTC thermistor can be applied to sense the ambient temperature. When OCP, VDD OVP, or OTP are activated, an internal latch circuit latches off the controller. The latch resets when VDD supply is removed. SG6846G is available in an 8-pin SOP package. Product Status/Pricing/Packing
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Features
■ Low Operating Current: 3.7mA ■ Peak-Current-Mode Operation with Cycle-by-Cycle Current Limiting ■ PWM Frequency Continuously Decreasing with Burst Mode at Light Loads ■ VDD Over-Voltage Protection (OVP) ■ AC Input Brownout Protection with Hysteresis ■ Constant Output Power Limit (Full AC Input Range) ■ Internal Latch Circuit for OVP, OTP, and OCP ■ Two-Level OCP Delay: 500ms ■ Programmable PWM Frequency with Frequency Hopping ■ OCP Threshold is Half Peak Current Limit ■ Feedback Open-loop Protection with 500ms Delay ■ Soft Startup Time: 5ms Applications
Application Notes |
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