Philips Semiconductors

Product specification

NE/SE5560

Switched-mode power supply control circuit

1994 Aug 31

14

that it does not saturate, even under transient conditions, where the

max. inductance is determined by

the transformer. The function of

Pin 16 of the NE5560.

ON

ON

ON

T

T

T

δ1

δ1

δ2

δ2

δ3

δ3

(50)

SL00378

Figure 19. Output Stage Inhibit

Figure 20 shows the electrical realization. When the voltage at Pin

charging current for the timing capacitor on Pin 8.

The operating frequency is not affected, because the upper trip level

for sawtooth increases also. Note that the

effect on

these duty cycles have halved. The graph for

Figure 22.

NOTE:

APPLICATIONS

NE/SE5560 Push-Pull Regulator

This application describes the use of the Philips Semiconductors

NE/SE5560 adapted to function as a push-pull switched mode

regulator, as shown in Figures 23 and 24.

Input voltage range is +12V to +18V for a nominal output of +30V

and -30V at a maximum load current of 1A with an average

efficiency of 81%.

Features include feed-forward input compensation, cycle-to-cycle

drive current protection and other voltage sensing, line (to positive

output) regulation <1% for an input range of +13V to +18V and load

regulation to positive output of <3% for

The main pulse-width modulator operates to 48kHz with power

switching at 24kHz.

FEED-FORWARD

16

2

6

7

8

DO NOT EXCEED VCC

CSS

R1

R2

RT

CT

δMAX

INPUT

SL00379

Figure 20. External

δ Maximum Control

WORKING

δ LEVEL

δMAX

LEVEL

d

MAX

1

d

MAX

2

VZ

V16

2XVZ

T

T

SL00380

Figure 21. Feed-Forward Circuitry

100

90

80

70

60

50

40

30

20

10

1

1.5

2

2.5

V

16

V

Z

δ

SL00381

Figure 22. Feed-Forward Regulation