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MB39C603 датащи(PDF) 11 Page - Cypress Semiconductor |
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MB39C603 датащи(HTML) 11 Page - Cypress Semiconductor |
11 / 30 page Document Number: 002-08450 Rev. *B Page 11 of 30 MB39C603 8.2 PFC (Power Factor Correction) Function Switching on time (TON) is generated by comparing VCOMP with an internal sawtooth waveform (refer to Figure 3-1). Since VCOMP is slow varying with connecting an external capacitor (CCOMP) from the COMP pin to the GND pin, TON is nearly constant within an AC line cycle. In this state, IP_PEAK is nearly proportional to the AC line voltage (VBULK). It can bring the phase differences between the input voltage and the input current close to zero, so that high Power Factor can be achieved. 8.3 Phase Dimming Function MB39C603 is compatible with both leading-edge dimmers (TRIAC dimming) and trailing-edge dimmers. To realize the phase dimming, this device has two functions, dimmer conduction angle detect function for LED current control and TRIAC dimmer hold current control function. Figure 8-2 shows how MB39C603 detects the conduction angle. VBULK is scaled via a resistor divider connected to the VAC pin. The conduction angle is detected by monitoring the voltage on the VAC pin (VVAC). MB39C603 measures a half of power cycle period (Tpow) as duration between negative crossings of VVAC and a Phase Comp threshold voltage (VPHTH2). Dimmer-ON period (Tdim) is measured as duration between a positive crossing of VVAC and another Phase Comp threshold voltage (VPHTH1) and the following negative crossing. Conduction angle is defined as Tdim/Tpow × 180°. Figure 8-2 Conduction Angle Detection Waveform Phase Comp output Tpow Tdim Conduction angle = Tdim / Tpow × 180° VVAC VBULK VPHTH1 VPHTH2 MB39C603 regulates LED current by changing a reference of Err Amp as a function of the conduction angle. Table 8-1 shows ILED dimming ratio based on the conduction angle. In addition, the initial ILED ratio in Power –On state is 5%. Table 8-1 ILED Ratio Based on Conduction Angles Conduction Angle ILED Ratio [%] θ < 45deg 5 45deg ≤ θ < 90deg (25/45) × θ -20 90deg ≤ θ < 135deg (70/45) × θ -110 135deg ≤ θ 100 |
Аналогичный номер детали - MB39C603 |
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Аналогичное описание - MB39C603 |
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