Power-conversion IC enables average parts to provide above-average power
By Margery Conner, Technical Editor -- EDN, March 21, 2006
Some applications have peak-power requirements that significantly differ from their average-power requirements. Printers are a prime example: The system need for power is much higher when the paper-feed motor and components are running, compared with when the print head alone is purring along. A typical ink-jet printer that operates at a continuous level of 30W during printing can require a burst of almost three times normal power when the paper advances. Designing the power system for such applications has its challenges, because, if you design for peak-power needs, then you may overspecify by using an oversized MOSFET, output diode, and transformer that increase system size, weight, and cost. However, if you design for the average-system-power requirements, then you risk overstressing the components and reducing system reliability.
Enter PeakSwitch, a monolithic power-converter switching IC that can provide a burst of power for several milliseconds by increasing the switching frequency of the IC's integrated 770V MOSFET as much as 277 kHz. When the system-power requirement returns to the baseline need, the switching frequency automatically drops to the normal frequency and drops to less than 1 kHz at no load. With this variable-switching frequency, the transformerf and MOSFETfs sizes suit average-power needs yet can also deliver peak power. The device also features on/off control, which provides low standby power, as well as constant-active-mode efficiency and enables compliance with current energy-efficiency standards, including the proposed Energy Star efficiency standard for printers.
PeakSwitch is available in lead-free, plastic-through-hole DIP-8 and higher-power-standard TO-220 packages. Price for the PKS604PN, a 16W-continuous, 44W-peak part in a DIP-8 package is 91 cents (1000). The PKS606YN, a 45W-continuous, 86W-peak part in a TO-220 package sells for $1.65.
