HVLED805TR STMicroelectronics, HVLED805TR Datasheet - Page 15

• 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
5.3
Secondary side demagnetization detection and triggering
block
The demagnetization detection (DMG) and Triggering blocks switch on the power MOSFET
if a negative-going edge falling below 50 mV is applied to the DMG pin. To do so, the
triggering block must be previously armed by a positive-going edge exceeding 100 mV.
This feature is used to detect transformer demagnetization for QR operation, where the
signal for the DMG input is obtained from the transformer’s auxiliary winding used also to
supply the IC.
Figure 12. DMG block, triggering block
The triggering block is blanked after MOSFET’s turn-off to prevent any negative-going edge
that follows leakage inductance demagnetization from triggering the DMG circuit
erroneously.
This blanking time is dependent on the voltage on COMP pin: it is T
= 0.9 V, and decreases almost linearly down to T
The voltage on the pin is both top and bottom limited by a double clamp, as illustrated in the
internal diagram of the DMG block of
V, while the lower clamp is located at -60mV. The interface between the pin and the auxiliary
winding will be a resistor divider. Its resistance ratio as well as the individual resistance
values will be properly chosen (see
and
Please note that the maximum I
in all the Vin range conditions. No capacitor is allowed between DMG pin and the auxiliary
transformer.
The switching frequency is top-limited below 166 kHz, as the converter’s operating
frequency tends to increase excessively at light load and high input voltage.
A Starter block is also used to start-up the system, that is, to turn on the MOSFET during
converter power-up, when no or a too small signal is available on the DMG pin.
The starter frequency is 2 kHz if COMP pin is below burst mode threshold, i.e. 1 V, while it
becomes 8 kHz if this voltage exceed this value.
“Section 5.6: Voltage feedforward block on page
Aux
R dmg
DMG
Rfb
110mV
60mV
CLAMP
D MG
Doc ID 18077 Rev 1
DMG
+
-
“Section 5.5: Constant current operation on page
sunk/sourced current has to not exceed ±2 mA (AMR)
Figure
BLAN KIN G
From CC/C V Block
TIME
12. The upper clamp is typically located at 3.3
BLANK
20”.
T UR N-ON
= 6 µs for V
LOGIC
LEB
From OCP
ST AR TER
S
R
Application information
BLANK
COMP
Q
= 1.3 V
= 30 µs for V
To Driver
18”
COMP
15/29