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10
The HIP5600 provides an efficient and economical solution
as a start-up supply for applications operating from either AC
(50V
RMS
to 280V
RMS
) or DC (50V
DC
to 400V
DC
).
FIGURE 14. START UP CIRCUIT
The HIP5600 has on chip thermal protection and output cur-
rent limiting circuitry. These features eliminate the need for
an in-line fuse and a large heat sink.
The HIP5600 can provide up to 40mA for short periods of time
to enable start up of a switch mode power supply‘s control cir-
cuit. The length of time that the HIP5600 will be on, prior to
thermal shutdown, is a function of the power dissipation in the
part, the amount of heat sinking (if any) and the ambient tem-
perature. For example; at 400V
DC
with no heat sink, it will pro-
vide 20mA for about 8s, see Figure 8.
Power supply efficiency is improved by turning off the
HIP5600 when the SMPS is up and running. In this applica-
tion the output of the HIP5600 would be set via RF1 and RF2
to be about 9V. The tickler winding would be adjusted to about
12V to insure that the HIP5600 is kept off during normal oper-
ating conditions.The input current under these conditions is
approximately equal to I
BIAS
. (See Figure 27)
.
The HIP5600 can supply a 450
μ
A (
±
20%) constant current.
(See Figure 15). It makes use of the internal bias network.
See Figure 27 for bias current versus input voltage.
With the addition of a potentiometer and a 10
μ
F capacitor the
HIP5600 will provide a constant current source. I
OUT
is given
by Equation 13 in Figure 16.
The HIP5600 can control a P-channel MOSFET or IGPT in a
self-oscillating buck regulator. The circuit shown (Figure 17)
shows the self-oscillating concept with a P-IGBT driving a
dedicated fan load. The output voltage is set by the resistor
combination of RF1, RF2, and RF3. Components C3 and
RF3 impresses the output ripple voltage across RF1 causing
the HIP5600 to oscillate and control the conduction of the
P-IGBT. The start-up protection components limit the initial
surge current in the P-IGBT by forcing this device into its
active region. The snubber circuit is recommended to reduce
the power dissipation of the P-IGBT.
V
OUT
+ 50V
DC
TO 400V
DC
BUS
A
V
O
V
I
RF1
RF2
HIP5600
10
μ
F
PWM
+12V
±
FIGURE 15. CONSTANT 450
μ
A CURRENT SOURCE
FIGURE 16. ADJUSTABLE CURRENT SOURCE
+20V
DC
TO +400V
DC
I
OUT
A
V
O
V
I
HIP5600
LOAD
±
NOTES:
1. V
OUT
Floating
2. Fixed 500
μ
A Current Source
A
V
O
V
I
I
OUT
0.02
μ
F
HIP5600
10
μ
F
I
OUT
=1.21V
R1
(EQ. 13)
R1
+50V
DC
TO +400V
DC
±
HIP5600