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LYT4313 Datasheet(PDF) 4 Page - Power Integrations, Inc. |
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LYT4313 Datasheet(HTML) 4 Page - Power Integrations, Inc. |
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4 / 20 page  Rev. B 02/13 4 LYT4211-4218/4311-4318 www.powerint.com Functional Description A LYTSwitch device monolithically combines a controller and high-voltage power FET into one package. The controller provides both high power factor and constant current output in a single-stage. The LYTSwitch controller consists of an oscillator, feedback (sense and logic) circuit, 5.9 V regulator, hysteretic over-temperature protection, frequency jittering, cycle-by-cycle current limit, auto-restart, inductance correction, power factor and constant current control. FEEDBACK Pin Current Control Characteristics The figure shown below illustrates the operating boundaries of the FEEDBACK pin current. Above I FB(SKIP) switching is disabled and below I FB(AR) the device enters into auto-restart. Figure 6. FEEDBACK Pin Current Characteristic. The FEEDBACK pin current is also used to clamp the maximum duty cycle to limit the available output power for overload and open-loop conditions. This duty cycle reduction characteristic also promotes a monotonic output current start-up characteristic and helps preventing over-shoot. REFERENCE Pin The REFERENCE pin is tied to ground (SOURCE) via an external resistor. The value selected sets the internal references, determining the operating mode for dimming (LYT4311-4318) and non-dimming (LYT4211-4218) operation and the line overvoltage thresholds of the VOLTAGE MONITOR pin. For non-dimming or PWM dimming applications with LYT4211-4218, the external resistor should be a 24.9 k W ±1%. For phase angle AC dimming with LYT4311-4318, the external resistor should be a 49.9 k W ±1%. One percent resistors are recommended as the resistor tolerance directly affects the output tolerance. Other resistor values should not be used. BYPASS Pin Capacitor Power Gain Selection LYTSwitch devices have the capability to tailor the internal gain to either full or a reduced output power setting. This allows selection of a larger device to minimize dissipation for both thermal and efficiency reasons. The power gain is selected with the value of the BYPASS pin capacitor. The full power setting is selected with a 4.7 µF capacitor and the reduced power setting (for higher efficiency) is selected with a 47 µF capacitor. The BYPASS pin capacitor sets both the internal power gain as well as the over-current protection (OCP) threshold. Unlike the larger devices, the LYT4x11 power gain is not programmable. Use a 47 µF capacitor for the LYT4x11. Switching Frequency The switching frequency is 132 kHz during normal operation. To further reduce the EMI level, the switching frequency is jittered (frequency modulated) by approximately 2.6 kHz. During start-up the frequency is 66 kHz to reduce start-up time when the AC input is phase angle dimmed. Jitter is disabled in deep dimming. Soft-Start The controller includes a soft-start timing feature which inhibits the auto-restart protection feature for the soft-start period (t SOFT) to distinguish start-up into a fault (short-circuit) from a large output capacitor. At start-up the LYTSwitch clamps the maximum duty cycle to reduce the output power. The total soft-start period is t SOFT. Remote ON/OFF and EcoSmart™ The VOLTAGE MONITOR pin has a 1 V threshold comparator connected at its input. This voltage threshold is used for remote ON/OFF control. When a signal is received at the VOLTAGE MONITOR pin to disable the output (VOLTAGE MONITOR pin tied to ground through an optocoupler photo- transistor) the LYTSwitch will complete its current switching cycle before the internal power FET is forced off. The remote ON/OFF feature can also be used as an eco-mode or power switch to turn off the LYTSwitch and keep it in a very low power consumption state for indefinite long periods. When the LYTSwitch is remotely turned on after entering this mode, it will initiate a normal start-up sequence with soft-start the next time the BYPASS pin reaches 5.9 V. In the worst case, the delay from remote on to start-up can be equal to the full discharge/charge cycle time of the BYPASS pin. This reduced consumption remote off mode can eliminate expensive and unreliable in-line mechanical switches. IFB(AR) IFB(DCMAXR) DC10 DCMAX IFB(SKIP) IFB PI-5433-060410 Skip-Cycle CC Control Region Soft-Start and CC Fold-Back Region Auto-Restart Maximum Duty Cycle |
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Similar Description - LYT4313 |
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