A

8/97

TOP209/210

7

Figure 8. Schematic Diagram of a 12 V, 8 W 110/220 VAC Input Power Supply Using the TOP210.

The circuit shown in Figure 8 produces a 12 V, 8 W power

supply that operates from 85 to 132 VAC or 170 to 264 VAC

input voltage. The 12 V output voltage is determined by the

TOPSwitch CONTROL pin shunt regulator voltage, the voltage

drops of D2 and D3, and the turns ratio between the bias and

output windings of T1. Other output voltages are also possible

by adjusting the transformer turns ratios. R1 and C5 provide

filtering of the bias winding to improve line and load regulation.

AC power is rectified and filtered by BR1, C1 and C9 to create

the high voltage DC bus applied to the primary winding of T1.

The other side of the transformer primary is driven by the

integrated high-voltage MOSFET within the TOP210. JP1 is a

jumper used to select 110 VAC or 220 VAC operation. Installing

JP1 selects 110 VAC operation. Leaving JP1 open selects

220 VAC operation. RA and RB, which equalize voltage across

C1 and C9, are necessary only when JP1 is not installed. D1 and

VR1 clamp the leading-edge voltage spike caused by transformer

leakage inductance to a safe value and reduce ringing. The

power secondary winding is rectified and filtered by D2, C2,

L1, and C3 to create the 12 V output voltage. R2 provides a pre-

load on the 12 V output to improve load regulation at light loads.

The bias winding is rectified and filtered by D3, R1, and C5 to

create a bias voltage to the TOP210. L2 and Y1-capacitor C7

attenuate common-mode emission currents caused by high-

voltage switching waveforms on the DRAIN side of the primary

winding and the primary to secondary capacitance. L2 and C6

attenuate differential-mode emission currents caused by the

fundamental and harmonics of the trapezoidal primary current

waveform. C5 filters internal MOSFET gate drive charge

current spikes on the CONTROL pin, determines the auto-

restart frequency, and together with R1, compensates the control

loop.

PI-2046-052397

VR1

BZY97-C200

D1

UF4005

R1

6.8

Ω

3

µH

RA

470 k

Ω

RB

470 k

Ω

JP1*

JUMPER

BR1

DFO6M

C1

10

µF

200 V

R2

330

1W

L1

F1

2A

T1

T1RD2

1

4

+

-

2

3

8

D2

MBR360

5

L2

12 mH min.

0.2A

C6

47nF

250VAC

X2

C7

1nF

250 VAC

Y1

* JPI INSTALLED FOR 110 VAC INPUT

JPI OPEN FOR 220 VAC INPUT

C5

47

µF

10 V

D3

1N4148

C3

120

µF

16 V

C2

330

µF

16 V

C9

10

µF

200 V

12 V

RTN

CIRCUIT PERFORMANCE:

Line Regulation - –1%

(85-132 VAC) or

(170-265 VAC)

Load Regulation - –5%

(10-100%)

Ripple Voltage – 50 mV

Meets CISPR-22 Class B

J1

L

N

U1

TOP210

D

S

C

CONTROL

TOPSwitch