HVLED805TR STMicroelectronics, HVLED805TR Datasheet - Page 17

• Manufacturer Part Number: HVLED805TR
• Description: IC LED DRVR ACDC OFFLINE 16NSOIC
• Manufacturer: STMicroelectronics
• Type: General Purposer

Specifications of HVLED805TR

• Constant Current: Yes
• Constant Voltage: Yes
• Topology: AC DC Offline Switcher, PWM
• Number Of Outputs: 1
• Internal Driver: Yes
• Type - Primary: General Purpose
• Voltage - Supply: 11.5 V ~ 23 V
• Mounting Type: Surface Mount
• Package / Case: *
• Internal Switch(s): Yes
• Efficiency: *
• Operating Supply Voltage: 11.5 V to 23 V
• Maximum Supply Current: 1.4 mA
• Maximum Power Dissipation: 0.9 W
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Frequency: -
• Operating Temperature: -
• Current - Output / Channel: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 497-10810-2

HVLED805
Figure 14. Voltage control principle: internal schematic
Due to the parasitic wires resistance, the auxiliary voltage is representative of the output just
when the secondary current becomes zero. For this purpose, the signal on DMG pin is
sampled-and-held at the end of transformer’s demagnetization to get an accurate image of
the output voltage and it is compared with the error amplifier internal reference.
During the MOSFET’s OFF-time the leakage inductance resonates with the drain
capacitance and a damped oscillation is superimposed on the reflected voltage. The S/H
logic is able to discriminate such oscillations from the real transformer’s demagnetization.
When the DMG logic detects the transformer’s demagnetization, the sampling process
stops, the information is frozen and compared with the error amplifier internal reference.
The internal error amplifier is a transconductance type and delivers an output current
proportional to the voltage unbalance of the two outputs: the output generates the control
voltage that is compared with the voltage across the sense resistor, thus modulating the
cycle-by-cycle peak drain current.
The COMP pin is used for the frequency compensation: usually, an RC network, which
stabilizes the overall voltage control loop, is connected between this pin and ground.
The output voltage can be defined according the formula:
Equation 1
Where n
The R
Voltage feedforward block on page
DMG
SEC
Aux
value can be defined depending on the application parameters (see
Rdmg
and n
AUX
DMG
Rfb
are the secondary and auxiliary turn’s number respectively.
R
Doc ID 18077 Rev 1
FB
=
DEMAG
20” section).
LOGIC
S/H
n
n
AUX
SEC
⋅
V
V
2.5V
OUT
REF
−
+
-
V
EA
COMP
REF
⋅
R
DMG
R
C
Application information
F rom Rsense
+
-
CV
To PWM Logic
“Section 5.6:
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