Product category:
Power Supply ICs and Controllers
News Release from: National Semiconductor | Subject: LM5021
Edited by the Electronicstalk Editorial
Team on 09 June 2005
PWM controller is efficient at light
loads
A new high-performance AC/DC pulsewidth-modulation (PWM) current-mode controller is designed to save energy in power supplies.
National Semiconductor has introduced a high-performance AC/DC pulsewidth-modulation (PWM) current-mode controller that is designed to save energy in power supplies This device contains all the features needed to design energy-efficient single-ended flyback and forward AC/DC convertors for telecommunications, networking equipment power systems, and high-end industrial and consumer power supplies
This article was originally published on Electronicstalk on 5 Jan 2001 at 8.00am (UK)
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The LM5021 PWM controller is energy-efficient at light loads, satisfying energy conservation standards being implemented worldwide.
It also uses a cycle-skipping burst mode during standby or light-load operations to reduce power losses.
The low 25uA startup mode also minimises power loss and saves space, allowing the designer to use a small, low-power resistor.
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"Energy efficiency is more important today than ever, with legislation or advisory standards on standby power developing worldwide".
"National's integrated LM5021 PWM controller offers designers of AC/DC power convertors the right combination of performance, space savings, comprehensive protection and lower heat dissipation to reliably meet the new energy standards", said Paul Greenland, Director of Product Marketing for National Semiconductor's Power Management Group.
"The LM5021 also complements National's LM5000 family of high-voltage isolated DC/DC PWM controllers and drivers, enabling our customers to design complete power systems from the AC line cord to the point of load".
The chip integrates a high-frequency current-mode PWM controller with internal slope compensation, as well as a user-programmable soft-start and a 0.7A peak MOSFET driver.
The undervoltage lockout's wide hysteresis allows designers to select a smaller bias supply filter capacitor, saving money and board space.
The LM5021 has cycle-by-cycle current limiting and hiccup-mode overload protection, protecting against secondary short circuits and sustained operation above the power limit.
The built-in soft-start timer allows the designer to minimise startup surge currents that can stress components or saturate the power transformer.
The LM5021 is available in two versions, distinguished by the maximum duty cycle of the pulsewidth modulator - 80 and 50% - catering for flyback and forward convertors, respectively.
Available now in MSOP-8 and MDIP-8 packages, the LM5021 is priced at $0.45 each in 1000-unit quantities.
All packages are available lead-free.
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