3550已经停止支持了。官网上面也没有太多的相关资料
就个人理解来看，直流输入应该是恒压的，可能会有零点几的上下波动，但一般来说都会是一个固定值，比如 +12V +48V等等。交流一般是一个电压范围如 100~220V AC
你可以参考下3560设备的电源输入要求
AC Input Voltage and Current
● 100-240 VAC (autoranging), 2.5-1.3A, 50-60 Hz (Cisco Catalyst 3560-8PC)
● 100-240 VAC (autoranging), 2.5-1.3A, 50-60 Hz (Cisco Catalyst 3560-12PC)
• 100-240 VAC (autoranging), 450-190mA, 50-60 Hz (Cisco Catalyst 3560-24TS)
● 100-240 VAC (autoranging), 650-270mA, 50-60 Hz (Cisco Catalyst 3560-48TS)
● 100-240 VAC (autoranging), 5.5-2.8A, 50-60 Hz (Cisco Catalyst 3560-24PS and Catalyst 3560-48PS)
● 100-240 VAC (autoranging), 3.0-1.5A, 50-60Hz (Cisco Catalyst 3560G-24TS and Catalyst 3560G-48TS)
● 100-240 VAC (autoranging), 8.0-4.0A, 50-60Hz (Cisco Catalyst 3560G-24PS and Catalyst 3560G-48PS)
DC Input Voltages
(RPS Input)
● +12V at 5A (Cisco Catalyst 3560-24TS and Catalyst 3560-48TS); 7.5A (Cisco Catalyst 3560-24PS and Catalyst 3560-48PS); 10.5A (Cisco Catalyst 3560G-24TS); 17.5A (Cisco Catalyst 3560G-48TS); 14A (Cisco Catalyst 3560G-24PS and Catalyst 3560G-48PS)
● -48V at 7.8A (PoE switches)
参考链接：http://www.cisco.com/c/en/us/products/collateral/switches/catalyst-3560-series-switches/product_data_sheet09186a00801f3d7d.html
