January 2011

Doc ID16539 Rev 1

1/29

AN3093

Application note

ALTAIR05T-800 5 W wide range CV-CC

optoless adapter demonstration board

1

Introduction

This application note describes the demonstration board of the all primary-sensing switching

regulator ALTAIR05T-800 and presents the results of its bench evaluation. The board

implements a 5 W (5 V / 1 A) wide range mains battery charger with constant

voltage/constant current.

The ALTAIR05T-800 combines a high-performance low-voltage PWM controller chip and

an 800 V, avalanche rugged power MOSFET in the same package.

The PWM chip is a quasi-resonant (QR) current mode controller IC specifically designed for

QR ZVS (zero-voltage switching at switch turn-on) flyback converters.

The device is capable of providing constant output voltage (CV) and constant output current

(CC) regulation using primary sensing feedback. This eliminates the need for the

optocoupler, the secondary voltage reference, as well as the current sensor, while

maintaining very accurate regulation.

Additionally, it is possible to compensate the voltage drop of the output cable, so as to

improve CV regulation on the externally accessible terminals.

Extremely low consumption under no-load conditions is ensured thanks to a controlled burst

mode operation that, along with the built-in high-voltage startup circuit and the low operating

current of the device, helps minimize residual input consumption. Although an auxiliary

winding is required in the transformer to correctly perform CV/CC regulation, the chip is

capable of powering itself directly from the rectified mains. This is useful especially during

CC regulation, where the flyback voltage generated by the winding drops. However, if ultra

low no-load input consumption is required to comply with the most stringent energy saving

recommendations, then the device needs to be powered via the auxiliary winding.

Figure 1.

Demonstration board picture

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