LYT4212E Power Integrations, LYT4212E Datasheet - Page 10

• Manufacturer Part Number: LYT4212E
• Description: LED Lighting Drivers HighPower LED Driver 15 W (85-132 VAC)
• Manufacturer: Power Integrations

Specifications of LYT4212E

• Rohs: yes
• Input Voltage: 85 V to 132 V
• Operating Frequency: 124 kHz to 140 kHz
• Maximum Supply Current: 1.2 mA
• Output Current: 1.17 A
• Maximum Operating Temperature: + 150 C
• Mounting Style: Through Hole
• Package / Case: eSIP-7C
• Minimum Operating Temperature: - 40 C

Figure 10b. Resultant Waveforms Following Rectification of TRIAC Dimmer Output.
Figure 11 shows undesired rectified bus voltage and current
with the TRIAC turning off prematurely and restarting.
If the TRIAC is turning off before the end of the half-cycle
erratically or alternate half AC cycles have different conduction
angles then flicker will be observed in the LED light due to
variations in the output current. This can be solved by including
a bleeder and damper circuit.
Dimmers will behave differently based on manufacturer and
power rating, for example a 300 W dimmer requires less
dampening and requires less power loss in the bleeder than a
600 W or 1000 W dimmer due to different drive circuits and
TRIAC holding current specifications. Multiple lamps in parallel
driven from the same dimmer can introduce more ringing due to
the increased capacitance of parallel units. Therefore, when
testing dimmer operation verify on a number of models,
different line voltages and with both a single driver and multiple
drivers in parallel.
Rev. B 02/13
Figure 11. Example of Phase Angle Dimmer Showing Erratic Firing.
LYT4211-4218/4311-4318
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350
300
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0
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Conduction Angle (°)
Conduction Angle (°)
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Voltage
Current
Voltage
Current
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PI-5984-060810
PI-5985-060810
350
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0.35
0.3
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0
Start by adding a bleeder circuit. Add a 0.44 µF capacitor and
510 W 1 W resistor (components in series) across the rectified
bus (C1 and R1 in Figure 8). If the results in satisfactory operation
reduce the capacitor value to the smallest that result in acceptable
performance to reduce losses and increase efficiency.
If the bleeder circuit does not maintain conduction in the TRIAC,
then add an active damper as shown in Figure 12. This consists
of components R6, C3, and Q1 in conjunction with R8. This
circuit limits the inrush current that flows to charge C4 when the
TRIAC turns on by placing R8 in series for the first 1 ms of the
TRIAC conduction. After approximately 1 ms, Q1 turns on and
shorts R8. This keeps the power dissipation on R8 low and
allows a larger value to be used during current limiting.
Increasing the delay before Q1 turns on by increasing the value
of resistor R6 will improve dimmer compatibility but cause more
power to be dissipated across R8. Monitor the AC line current
and voltage at the input of the power supply as you make the
adjustments. Increase the delay until the TRIAC operates
properly but keep the delay as short as possible for efficiency.
As a general rule the greater the power dissipated in the bleeder
and damper circuits, the more types of dimmers will work with
the driver.
Trailing Edge Phase Controlled Dimmers
Figure 11 shows the line voltage and current at the input of the
power supply with a trailing edge dimmer. In this example, the
dimmer conducts at 90 degrees. Many of these dimmers use
back-to-back connected power FETs rather than a TRIAC to
control the load. This eliminates the holding current issue of
TRIACs and since the conduction begins at the zero crossing,
high current surges and line ringing are minimized. Typically these
types of dimmers do not require damping and bleeder circuits.
Figure 12. Ideal Dimmer Output Voltage and Current Waveforms for a Trailing
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Edge Dimmer at 90° Conduction Angle.
50
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Conduction Angle (°)
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www.powerint.com
PI-5986-060810
Voltage
Current
350
0.35
0.25
0.15
0.05
-0.05
-0.15
-0.25
-0.35