5-21

HV-2405E

For applications requiring 30mA or less and not directly off

line (i.e. filter network preceding supply), the external tran-

sistor and associated resistors in Figure 1 can be replaced

with a single 1/4W resistor R2 and capacitor C3 (Figure 7) if:

(1) The filter network reduces the input dv/dt to less than

10V/

Source resistor R1 equals 150

current) and (3) Inhibit Capacitor C3 equals 150pF (turns off

the HV-2405E during large voltage transients).

For applications where EMI (conductive interference) is a

design requirement, the circuit shown in Figure 8 is the rec-

ommended application circuit. This circuit delivers an output

voltage of 5V to 24V with an output current from 0 to 30mA

and passes VDE 0871 class “B” test requirements for con-

ductive interference with a resistive load.

Basic Operation

When power is initially applied the filter network reduces the

magnitude of any transient noise spikes that might result in

operation outside the SOA of the HV-2405E (see Start-up in

section titled “How the HV-2405E Works” for and explanation

of the SOA). When the voltage on pin 8 goes positive an

internal switch connects pin 8 to pin 2 and C2 starts to

charge through R1 and R2. When the voltage on pin 2

reaches a predetermined voltage the switch opens and the

charging of C2 stops. R1 limits the input current and along

with C1 provides a snubber for the internal switch. R2 also

has the effect of limiting the input current by increasing the

voltage on pin 2 sooner in the cycle. A linear regulator takes

current from C2 and provides a DC voltage at pin 6. The volt-

provides protection from large input voltage transients by

turning off the HV-2405E and the output capacitor C4 pro-

vides stabilization of the output stage.

HV-2405E

C2

330

µF

C3

150pF

C4

10

µF

C0

0.33

µF

+

-

R2

2.7

Ω

COMPONENT LIST

FUSE = 1/ 4A

R1 = 150

Ω, 3W

R2 = 2.7

Ω, 1/4W

C1 = 0.1

µF, AC RATED

C2 = 330

µF, 15V + V

C3 = 150pF, CERAMIC

C4 = 10

µF, V

C0 = 0.33

µF, AC RATED

L1 = 2.2mh,

µ = 2000

ELECTROLYTIC

ELECTROLYTIC

R1

150

Ω

C1

0.1

µF

L1

2.2mh

FUSE

AC RETURN

Z1

AC HIGH

FILTER

NETWORK

Operation

The operation of the imbedded supply is illustrated in Figure 9

and Figure 10. Figure 9 shows operation with a 30mA load

and Figure 10 with the output short circuited. Notice that In

both cases, the inhibit function of the HV-2405E prevents the

circuit from turning on when the input voltage was applied

near the peak line voltage. Also notice the initial current pulse

(Figure 9) is approximately 1.6A and decreased to 1A within

40ms. This decrease in the input current results when the

charging current required to maintain the voltage on C2

decreased. The effect of the series resistor (R2) is illustrated

by the small voltage spike on the Vpin 2 trace. This voltage

spike increases the voltage on pin 2 to the 10V trip point

sooner in the cycle, thereby limiting the input current.

FIGURE 9. START UP OPERATION

FIGURE 10. SHORT CIRCUIT OPERATION

(500V/DIV) (PIN 8)

INPUT CURRENT

(1A/DIV)

(10V/DIV)

(5V/DIV)

TIME (20ms/DIV)

IMBEDDED SUPPLY

OUTPUT SHORT CIRCUITED

(500V/DIV) (PIN 8)

INPUT CURRENT

(1A/DIV)

(10V/DIV)

(5V/DIV)

TIME (20ms/DIV)

IMBEDDED SUPPLY