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UPSL101 Datasheet(PDF) 6 Page - Unisonic Technologies |
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UPSL101 Datasheet(HTML) 6 Page - Unisonic Technologies |
6 / 8 page UPSL101 Preliminary LINEAR INTEGRATED CIRCUIT UNISONICTECHNOLOGIESCO.,LTD 6 of 8 www.unisonic.com.tw QW-R125-027.b FUNCTION DESCRIPTION The UTC UPSL101 is a primary side control offline LED lighting controller which can achieve high power factor and accurate LED current for an isolate lighting application in a single converter. The UTC UPSL101 can control the LED current accurately from the primary side information. It can significantly simplify the LED lighting system design by eliminating the secondary side feedback components and the opto-coupler. And it integrates power factor correction function and works in transition mode for reducing the MOSFET switching losses. The principle of operation can be understood by referring to the block diagram. Startup The VCC pin of UTC UPSL101 is connected to the line input through a resistor. A large value startup resistor can be used to minimize the power loss in application because the start current of UTC UPSL101 is very low. When the VCC voltage reaches UVLO(OFF), the internal startup circuit is disabled and the IC turns on. Operating Current The operating current of UTC UPSL101 is as low as 1.5mA. Good efficiency and very low standby power can be achieved. Transition Mode Operation During the external MOSFET on time, the rectified input voltage is applied across the primary side inductor and the primary current increases linearly from zero to the peak value. When the external MOSFET turns off, the energy stored in the inductor forces the secondary side diode to be turn on, and the current of the inductor begins to decrease linearly from the peak value to zero, this decreasing is also reflected on the auxiliary winding. UTC UPSL101 performs zero current detection (ZCD) through ZCD pin by monitoring the voltage activity on the auxiliary windings in series with external resistors. When ZCD pin voltage falls below 0.3V, an internal ZCD comparator is triggered and generates the turn on signal of the external MOSFET. LED Constant Current Regulation The proprietary real current control method allows the UTC UPSL101 controlling the secondary side LED current from the primary side information. The LED mean current can be calculated approximately as: CS LED R f re V * 2 N ≈ I N-Turn ratio of primary side to secondary side VREF-The reference voltage (typical 0.4V) RCS-The sensing resistor connected between the MOSFET source and GND. Current Sensing and Leading Edge Blanking Cycle-by-cycle current limiting is offered in UTC UPSL101. The switch current is detected by a sense resistor into the CS pin. When the power switch is turned on, a turn-on spike will occur on this resistor. A leading-edge blanking is built in to avoid false-termination of the switching pulse so that the external RC filtering is no longer needed. PWM duty cycle is determined by the current sense voltage and the voltage at pin COMP. Threshold of OCP Selection The threshold voltage level of OCP is selected by the voltage of OCP_TH pin. The UTC UPSL101 provides the source current equal to approximately 28μA through OCP_TH pin. So the proper resistor can be connected with the OCP_TH pin to GND in order to generate the voltage needed. If OCP_TH pin is connected with 33K resistor, the threshold voltage of OCP is about 1.8V; If OCP_TH pin is connected with 110K resistor, the threshold voltage of OCP is about 1.5V; If OCP_TH pin is connected with GND directly, the threshold voltage of OCP is about 2.1V. Voltage of OCP_TH Pin Connecting State of OCP_TH Threshold Voltage of OCP 3V 110K 1.5V 0.9V 33K 1.8V 0V GND 2.1V Maximum and Minimum On-Time The minimum on-time of the system is determined by the LEB time. The IC limits the on-time to a maximum time of approximately 50μs. |
Similar Part No. - UPSL101_15 |
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Similar Description - UPSL101_15 |
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