1.SSL2101: SO16封裝, 集成mosfet和泄放開關
2.SSL2102: SO20封裝, 集成mosfet和泄放開關
3.SSL2103: SO14封裝，外部MOSFET和泄放開關

1.1 The application requirement

When designing an application that can support a wide output voltage range and a constant current, it is important to dimension all components for the maximum output power. The basic application is optimized for a 30 W output and it can be scaled down relatively easily. The application described here, is a retro-fit application using a lamp within an existing infrastructure. The application targets the lower end of the market(commercial, domestic) and has the following specifications:

• Output power of 30 W
• Power factor of 0.7 or larger
• 150 mA peak-to-peak output current ripple ( 10 %)
• Efficiency of 72 %
• The lamp is compatible with a triac dimmers, without noticeable flicker or jumps on the output
• The input voltage is 230 V, 50 Hz
• The output voltage is 42 V, 700mA

1.2 The design choices

The SSL2102 is rated for a maximum output power of 25 W. A higher output power might cause life time issues due to improper cooling. This must be taken into account when the PCB is designed and an extra heatsink might be required.The output power is important for the selection of the transformer. For outputs above 26 W, an E30 or an EFD30 core must be used. The transformer will take up a large part of the required space.The design is optimized for a 230 V (AC) input.

Almost all component values will change when the design is modified for 120 V (AC).Because the input voltage is halved, the input current must be doubled to have the same output power. The buffer capacitance must be doubled, the turns ratio must be changed,the damper resistor can be halved, etc. The brightness control circuit is also optimized for 230 V (AC), which determines the dimmer duty factor by averaging the rectified input voltage.

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