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Low Cost Green-Mode PWM Controller for Flyback Converters
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General Description
This highly integrated PWM controller provides several special enhancements designed to meet the low
standby-power needs of low-power SMPS. To minimize standby power consumption, the proprietary green-mode
function provides off-time modulation to linearly decrease the switching frequency under light-load conditions.
This green-mode function enables the power supply to easily meet even the strictest power conservation requirements.
The BiCMOS fabrication process enables reducing the start-up current to 9uA, and the operating current to 3mA.
To further improve power conservation, a large start-up resistance can be used. Built-in synchronized slope compensation
ensures the stability of peak current mode control. Proprietary internal compensation provides a constant output power limit
over a universal AC input range (90VAC to 264VAC). Pulse-by-pulse current limiting ensures safe operation even during short-circuits.
To protect the external power MOSFET from being damaged by supply over voltage, the SG6859’s output driver is
clamped at 17V. SG6859 controllers can be used to improve the performance and reduce the production cost of power supplies.
The SG6859 is the best choice for replacing linear and RCC-mode power adapters. It is available in 8-pin DIP and 6-pin SOT-26 packages.
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Features
- Green-Mode PWM
- Supports the “Blue Angel” Standard
- Low Start-up Current (9µA)
- Low Operating Current (3mA)
- Leading-Edge Blanking
- Constant Output Power Limit
- Universal Input
- Built-in Synchronized Slope Compensation
- Current-mode operation
- Cycle-by-cycle current limiting
- Under voltage lockout (UVLO)
- Programmable PWM Frequency with Frequency Hopping
- VDD Over-Voltage Protection (auto restart)
- Gate Output Voltage Clamped at 17V
- Low Cost
- Few External Components Required
- Small SOT-26 and DIP-8 Packages
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Applications
General-purpose, switching-mode power supplies and flyback power converters, such as:
- Battery chargers for cellular phones, cordless phones, PDAs, digital cameras, and power tools
- Power adapters for ink jet printers, video game consoles, and portable audio players
- Open-frame SMPS for TV/DVD standby and auxiliary supplies, home appliances, and consumer electronics
- Replacements for linear transformers and RCC SMPS
- PC 5V standby power
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