MR2900

Application

TVs, displays, printers, VTR, DVD, STB, air-conditioners, refrigerators, and other electrical appliances, and office equipment.


Specifications

Model	Absolute maximum ratings		Maximum output capacity Po[W]
	Peak input voltage	Peak input current	Input voltage range
	Vin[V]	Iin[A]	90V to 276VAC	180V to 276VAC
MR2920	900	7	100	150
MR2940		10	150	225

Maximum output capacity and input voltage range differ with design conditions.


Description

In conventional start-up circuits employing a start-up resistor, current continues to flow following power supply start-up, thus wasting power and reducing efficiency, particularly during standby. See Fig.3.1 Comparison of Start-up Circuits - Conventional Start-up Circuit.

In the MR2000 Series start-up circuit the start-up current is supplied from the input voltage at power supply start-up, and is shut-off when the power supply is in operation.

The start-up circuit supplies a current of 12mA (typical) from the IC internal constant current source until the voltage at the Vcc pin reaches 14V (typical). This current is consumed internally in the IC as well as being used as the charging current for the condenser connected externally between the Vcc pin and GND.

This design allows a stable start-up only minimally dependent upon input voltage. When the voltage at the Vcc pin reaches 14V (typical) the start-up circuit is disconnected, the start-up current no longer flows and oscillation begins simultaneously. The current consumed in the IC is then supplied from the control coil. See Fig.3.1 Comparison of Start-up Circuits - MR2000 Start-up Circuit.

In the case of an instantaneous power failure or a load short, oscillation is stopped when the voltage at the Vcc pin reaches 8.5V, and when this voltage drops to 7.6V the start-up circuit operates again and the voltage at the Vcc pin then begins rising. See Fig.3.2.

Incorporation of the functions described above improve efficiency, particularly during standby, and reduces the number of start-up resistors required, thus reducing the overall number of components.