L6585D_07 STMICROELECTRONICS [STMicroelectronics], L6585D_07 Datasheet - Page 17

• Manufacturer Part Number: L6585D_07
• Description: Combo IC for PFC and ballast control
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

L6585D
7
Half-bridge current control
The information about the lamp current can be obtained by reading the voltage across a
sense resistor placed in series to the source of the half-bridge low side MOS.
This circuitry is enabled at the end of the pre-heating phase and it enriches the L6585D with
two features:
●
●
During run mode another protection is active: a second comparator (HBCSH) on the pin
HBCS detects anomalous current flow through the sense resistor such as the spikes
generated by the capacitive mode; the crossing of this second threshold latches the IC.
Controlled lamp voltage/current during ignition
sense resistor (such that the V
voltage higher than the ignition voltage) it is possible to limit the maximum lamp voltage
during ignition. In case of this occurrence, then the L6585D would react with a small
frequency increase that allows limiting the lamp voltage (V
risk of crossing the resonance frequency of the L
ignites before T
–
–
–
If instead that the lamp hasn’t ignited after a time equal to the pre-heat time
right) the oscillator stops, the chip enters low consumption mode and this condition is
latched until the mains supply voltage is removed or a re-lamp is detected.
Over-current protection during run mode: if the HBCSL threshold is crossed, the T
internal generator is turned on as well as the one at pin EOI causing a frequency
increase: this implements a current control structure.
EOI internal switch opens and its voltage moves asymptotically to 2V
The switching frequency reaches the operating one;
When T
CH
CH
reaches 1.52, it will be discharged
reaches 1.50V
HBCS
(Figure 5
level is crossed in correspondence of a lamp
left) that is EOI has exceeded 1.9V, then:
BALLAST
(Figure
-C
5): by properly setting the
+IGN
Half-bridge current control
RES
). This also prevents the
circuit. If the lamp
(Figure 5
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CH