# MC44603P ON Semiconductor, MC44603P Datasheet - Page 18

#### MC44603P

Manufacturer Part Number

MC44603P

Description

Other Power Management Voltage/Current PWM

Manufacturer

ON Semiconductor

Type

PWM Mode Controllerr

Datasheet

1.MC44603DWR2.pdf
(24 pages)

#### Specifications of MC44603P

Input Voltage Range

18 V

Mounting Style

Through Hole

Package / Case

PDIP-16

Lead Free Status / Rohs Status

Lead free / RoHS Compliant

#### Available stocks

Company

Part Number

Manufacturer

Quantity

Price

Company:

Part Number:

**MC44603P**2

Manufacturer:

ON

Quantity:

9 800

standby losses mainly consist of the energy waste due to:

Losses can be considered constant. This waste of energy

decreases when the standby losses are reduced.

increased (each switching requires some energy to turn on

the power switch).

frequency.

decreasing the switching frequency as much as possible.

frequency lower than the normal working one.

•

transformer during the on−time to be transferred to the

output during the off−time, is equal to:

where:

Input power is labelled P

where f

AC Line

In a classical flyback (as depicted in Figure 40), the

− the startup resistor R

− the consumption of the IC and the power

−

− the inrush current limitation resistor R

− the switching losses in the power switch → P

− the snubber and clamping network

P

P

P

P

Consequently, standby losses can be minimized by

The MC44603A was designed to operate at a standby

During a switching period, the energy drawn by the

− L is the transformer primary inductor,

− l

Standby Power Calculations with MC44603A

startup

ICL

control

SW

switch control

pk

R

ICL

only depends on the current drawn from the mains.

is the inductor peak current.

S

and P

Figure 40. Power Losses in a Classical

is the normal working switching frequency.

is nearly constant and is equal to:

increases when the oscillator frequency is

V

in

SN−CLN

P in + 0.5 x L x I pk 2 x f S

+

(V in –V CC ) 2 R startup

MC44603A

Flyback Structure

E + 1

V

R

CC

startup

are proportional to the switching

startup

in

2

:

x L x I pk 2

Clamping

Network

R

Snubber

S

ICL

→ P

→ P

→ P

→ P

+

control

SW

SN−CLN

startup

ICL

http://onsemi.com

18

Also,

where R

current.

the internal current sense comparator input).

a V

the threshold level by connecting a resistor to Pin 12.

noninverting input voltage is typically equal to (3.0 x V

V

[(V

labelled P

And as:

V

x (V

an oscillator discharge current reduction in order to increase

the oscillator period and to diminish the switching

frequency. As it is represented in Figure 41, the (0.8 x I

current source is disconnected and is replaced by a lower

value one (0.25 x I

Where: I

ER

F

CS

R

Thus, the input power is proportional to V

That is why the standby detection is performed by creating

As depicted in Figure 41, the standby comparator

The V

Thus, when the power drawn by the converter decreases,

) while the inverter input value is (V

P Stby

CS

12

13

R P Stby

AmpOut

R P Stby

decreases and when V

threshold. An internal current source (0.4 x I

R P Stby +

0.4 I

S

P thL + 0.5 x L x

F Stby

thL

is the resistor used to measure the power switch

CS

V R P Stby + R P Stby x 0.4 x I ref

)/3] and if the corresponding power threshold is

ref

)/3], the standby mode is activated. This results in

V

:

ref

= V

threshold level is typically equal to

0

V

ref

ref

F Stby

0.6 I

Figure 41. Standby

1

2R

1R

/R

10.6 x R S x R ref

+ R R P Stby x 0.4 x

ref

C

F Stby

Stby

I pk +

).

C. S. Comparator

V ref

CS

0.8 I

V R P Stby

V CS

3.0 R S

becomes lower than [V

ref

R S

1

V

ref

I

Discharge/2

V

ref

0

0.25

I

x

F Stby

R P Stby

2

Current Mirror X2

x f S

R ref

V ref

L x f S

CS

P thL

V

I

2

ref

Discharge

0.2 I

+ V

(V

Discharge

Oscillator

ref

Current

CS

F

ref

).

being

) sets

CS−th

CS

ref

+

)