TDK-Lambda has introduced its next generation of digitally controlled, AC-DC power supplies – the single-output CFE400M, which is available in convection-and fan-cooled versions.
When convection cooled, the power supply is rated at 300 W for operating temperatures up to 40°C (250 W at 50°C); when fan cooled – either integral quiet fan or customer air (1,5 m/s) – the power supply is rated at 400 W up to 50°C. The CFE400M also has a 450 W peak power for up to 10 seconds, for both cooling options.
Available in field adjustable 12 V, 24 V and 48 V d.c. versions with a 12 V d.c./0,25 A fan supply, the CFE400M has a 5 V/100 mA standby power output or a 5 V/2 A option. The 100 mA option meets the ErP Directive with less than 0,5 W standby power consumption and all models meet or exceed Climate Savers Silver level. Other features include high efficiency (94%), remote ON/OFF and remote sense.
The interleaved boundary mode boost converter, where the two converters operate at 180° to each other, halves the current through each PFC choke and reduces the ripple current in the boost capacitor; this in turn reduces the temperature of the boost capacitor and increases its life. Below half-load, one converter is disabled, reducing losses and increasing efficiency. At really low loads (around 50 W), the PFC burst mode function operates, which increases the low load efficiency of the CFE400M still further. The zero-voltage switching (ZVS) resonant converter on the output reduces noise, improves EMC and reduces the amount of filtering required on the output. Since there are lower switching losses due to the use of ZVS, overall efficiency is further increased.
The microprocessor on the CFE400M controls the output of the resonant converter and looks after the remote ON/OFF function. It also controls the current limit and peak current operation, which enables the power supply to power inductive and capacitive loads without malfunction. As with the previous generation of digitally controlled power supplies, the EFE series, the microprocessor also looks after housekeeping routines, such as controlling the timing to turn power on and off, and looking after the PFC, thereby reducing the overall control circuit component count by 25%.
Combining a 4 kV a.c. reinforced input-to-output isolation with dual fusing and an output-to-ground isolation of 1500 V a.c., the power supply meets IEN/EN/UL/CSA 60601-1 Ed 2 & 3 safety approvals for medical equipment, suitable for BF (body floating) type medical applications. Their 178 x 100 x 40 mm size also makes them applicable to other high-integrity applications such as ATE, automation, broadcast, instrumentation, routers, servers and security networks.
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