HVLED805 STMicroelectronics, HVLED805 Datasheet - Page 18

• Manufacturer Part Number: HVLED805
• Description: IC LED DRVR ACDC OFFLINE 16NSOIC
• Manufacturer: STMicroelectronics

Specifications of HVLED805

• Constant Current: Yes
• Constant Voltage: Yes
• Internal Driver: Yes
• Type - Primary: General Purpose
• Mounting Type: Surface Mount
• Topology: AC DC Offline Switcher, PWM
• Number Of Outputs: 1
• Voltage - Supply: 11.5 V ~ 23 V
• Package / Case: 16-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Frequency: -
• Voltage - Output: -
• Operating Temperature: -

Application information
5.5
18/29
Constant current operation
Figure 15
flyback converter.
The output voltage of the auxiliary winding is used by the demagnetization block to generate
the control signal for the mosfet switch Q1. A resistor R in series with it absorbs a current
V
The flip-flop’s output is high as long as the transformer delivers current on secondary side.
This is shown in
The capacitor C has to be chosen so that its voltage V
Since it is charged and discharged by currents in the range of some ten µA (I
typically 20 µA) at the switching frequency rate, a capacitance value in the range 4.7-10 nF
is suited for switching frequencies in the ten kHz.
The average output current can be expressed as:
Equation 2
Where I
side and T is the switching period.
Taking into account the transformer ratio n between primary and secondary side, I
be expressed is a function of the primary peak current I
Equation 3
As in steady state the average current I
Equation 4
Which can be solved for V
Equation 5
Where V
As V
C
/R, where V
C
is fed to the CC comparator, the primary peak current can be expressed as:
S
CLED
is the secondary peak current, T
presents the principle used for controlling the average output current of the
=R • I
C
is the voltage developed across the capacitor C.
Figure 16
LED
I
CLED
and is internally defined.
C
.
:
⋅
(
T
Doc ID 18077 Rev 1
−
T
ONSEC
I
V
OUT
C
=
C
=
:
)
V
I
+
ONSEC
S
I
CLED
2
S
⎛
⎜
⎝
=
I
⋅
CLED
⎛
⎜
⎝
n
T
⋅
⋅
I
ONSEC
T
P
is the conduction time of the secondary
ONSEC
T
−
T
V
R
C
C
⎞
⎟
⎠
P
⎞
⋅ ⎟
⎠
can be considered as a constant.
:
T
ONSEC
=
0
CLED
HVLED805
S
is
can also