AN3032

Ballast design

Doc ID 16165 Rev 2

7/26

3

Ballast design

This section describes the main components of the circuit.

3.1

L6585DE pin-by-pin biasing circuitry

Designed in a high-voltage BCD offline technology, the L6585DE embeds a PFC controller,

a half-bridge controller, the relevant drivers and the logic necessary to build an electronic

ballast.

●

Pin1 OSC is one of the two oscillator inputs. The value of the capacitor connected to

1 nF.

●

Pin2 RF: the choice of component and oscillator capacitance defines the half-bridge

the run frequency, while during the preheating phase the switching frequency is set by

and EOI pins (the EOI pin is pulled to ground during preheating).

With the following frequencies and ignition time:

Equation 1

Equation 2

●

Pin3 EOI is a multi-function pin. During preheating, the pin is internally shorted to

ground by the logic, so the resistor (Rpre//Rrun) connected between the RF pin and

ground sets the preheating switching frequency. During ignition it goes into a high

impedance state: the ignition time is the time necessary for the pin voltage to -

Equation 3

Three capacitors in parallel have been mounted to obtain this value

kHz

40

kHz

65

f

ms

60

.

0

5

C

33

.

1

1

e

−

=

.

0

5

3

C

10

6

.

499

k

⋅

=

Ω

=

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

=

k

33

f

k

R

e

/

1

run

14

Ω

=

⇒

⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

=

k

51

R

f

k

R

//

R

13

e

/

1

pre

14

13

nF

392

R

3

t

C

13

ign

6

=

⋅

=