L6574D DATASHEET PDF

L6574D DATASHEET PDF

LD Cfl/tl Ballast Driver Preheat And Dimming. HIGH VOLTAGE RAIL TO V dV/dt IMMUNITY ± 50 V/ns IN FULL TEMPERATURE RANGE DRIVER. LD IC BALLAST DRIVER CFL/TL SO STMicroelectronics datasheet pdf data sheet FREE from Datasheet (data sheet) search for. LD datasheet, LD circuit, LD data sheet: STMICROELECTRONICS – CFL/TL BALLAST DRIVER PREHEAT AND DIMMING,alldatasheet.

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Compared to the formal CFL solution, this solution not only provides energy savings, but also higher reliability and a much longer operating life.

Typical dimmer Figure 2. Dimming CFL ballast solution Figure 3. Typical dimming system consisting of incandescent lamp and triac dimmer Figure 4. Block diagram of formal CFL ballast Figure 5. The half AC line cycle of sinuous wave and firing angle Figure 6. Schematic of the reference design board Figure 7. Main circuit Figure 8. L1 current per switching period Figure 9.

AN Application note – PDF

L1 current shape Figure PCB top-side view Figure PCB bottom-side view Figure Full load efficiency vs. AC line input Figure Triac turn-on time vs. Adtasheet input voltage and current Figure L1 voltage and current Figure Power factor in operating range Figure The dimmer consists of the triac and a few components, see Figure 1.

Dimmers of this type are appropriate for incandescent lamps and are very popular in the market. Typical dimming system consisting of incandescent lamp and triac dimmer The triac conducts once it has been triggered and holds latching current. The triac shuts down when the current is less than the holding current.

The dimmer works fine with a resistive load. The triac can be triggered at any timing of the sinuous voltage AC line inputand can be kept in conduction state until reaching zero line voltage. If the incandescent lamp Tungsten filament light bulb is replaced by a formal CFL Compact Florescent Lamp directly, the CFL cannot fully illuminate and may have intermittant blinking or no light at all.

Figure 4 shows the block diagram of a formal CFL. Block diagram of formal CFL ballast The formal CFL ballast consists of a rectifier, storage capacitor, ballast driver circuit, half bridge and resonant circuit.

The source energy stored only to the storage capacitor from the AC input at the timing nears its peak voltage per half cycle. When the formal CFL ballast is connected to the triac dimmer see Figure 1the triac conducts only after having been triggered, that is, when the rectified voltage is higher than the voltage across the storage capacitor. It is impossible to adjust the DC voltage across the storage capacitor and then extend triac firing angle less than However the lamp may continue to flicker and remain unstable if the DC voltage is not well managed.

With the implementation of the PFC solution, the lamp power can be adjusted by switching the frequency of the driver circuit that corresponds to the illumination level set by the triac dimmer.

The triac can be triggered at every point during the half cycle and conducts continuously until the end of the half cycle In addition, a circuit detects the firing angle of the triac and adjusts lamp power by adjusting the switching frequency of the half bridge to control lamp power depending on the position of the triac dimmer. Please note that while the triac dimmer is connected to the capacitive load CFLthe triac will not be fired if trigger angle is set lower than Because bus voltage the voltage across the storage capacitor falls, the system stops operating at an angle less than For this reason, the dimmable ballast cannot be operated in full dimming range.

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A hysteretic range per half AC cycle was turned on at 50 and turned off at Figure 5 shows us the Gate pulse trigger and firing angle per half cycle. It includes an LC filter, bridge rectifier, single stage PFC with high frequency ballast driver and resonant circuit. In this solution, the dimming function is obtained using two methods: When the trigger angle of the triac changes from 0 to 90, only frequency modulation works.

When the angle changes from 90 toboth of them work, and voltage modulation dominates.

Frequency modulation depends on the operational amplifier in LD. When the angle changes from 0 tothe voltage across C10 which is the positive input of the amplifier Pin 7, here pin number is for LDdecreases accordingly. The output Pin 5 of the amplifier decreases with Pin 7, and the negative input Pin 6 of the amplifier automatically decreases. The equivalent resistance between Pin 4 and GND of the IC decreases, so the switching frequency increases, hence lamp power decreases.

If the angle changes from tolamp power increases. Voltage modulation means that the voltage across C1 see Figure 6 decreases when the firing angle of the triac changes from 90 to This makes the lamp power decrease. There are two independent circuits, power factor correction PFC circuit and half bridge resonant circuit.

The other one is a half bridge resonant xatasheet, which is labeled as B solid line. Thus the voltage across C1 is always higher than the line peak.

In Figure 8 per switching cycle shows the model of a four stage current flow through L1. At t0, S1 is already turned on and S2 is off.

Assume the current through L1 il1 is zero, then il1 increases linearly by the voltage across Cf1, and the current flows through Cf1, Db1, S1 and L1. At t1, S1 is turned off and S2 is turned on. At the moment il1 reaches the positive peak that forces Ds2 to turn on, negative voltage Vc1-Vcf1 is applied to L1, causing il1 to decrease linearly.

At t2, il1 reaches zero, and il1 linearly increases to the negative peak by the voltage across Cf2. The current flows through Cf2, L1, S2 and Db2. At t3, S1 is turned on and S2 is turned off. When il1 reaches the negative peak that forces Ds1 to turn on, voltage Vc1-Vcf2 is applied to L1, causing il1 to decrease linearly.

At t4, il1 reaches zero, where the new switching cycle begins. L1 current shape The overall current flow shape in L1 during one half AC line cycle is shown in Figure 9. It is clear that the boost inductor current flows in two directions l657d4 the PFC circuit p6574d at boundary conduction mode.

For the resonant circuit, Lr and Cr are the main parameters. The calculation steps are given as follows: The input power Pin is determined by, Equation 5 Where Vac is the input voltage. For the half bridge resonant circuit, the equivalent resistance of the lamp is given by: In a compact application, the thermal issue becomes very critical. Electrical specifications of evaluation board 1 Parameter Value Min.

LD Data Sheet | STMicroelectronics OEMSecrets

AC line input The triac turn on time per half cycle relates to the power dissipation of l6574 lamp. Hence the maximum half cycle time is 10 ms. Theoretically, the range of Ton is 10 ms to 0ms corresponding to the firing angle 0 to But under real conditions the range of Ton is about 9 ms to 2 ms, see Figure A glitch circled on the waveform always vatasheet at each half cycle of the input voltage.

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A current spike circled on the waveform occurs at each half cycle when line voltage reaches the peak. Although it is not good for the power factor, it is suitable for this application as it ensures that the voltage on C1 is not higher than the peak of the input voltage.

L1 voltage and current Figure 15 shows the voltage and current waveform of the boost inductor L1. The glitch could happen while L1 works in two directions at critical conduction dahasheet. Although the glitch was there, due to the limitation of maximum Ton, the power factor is always higher than 0. Please refer to Figure 16 below. Power factor in operating range L6574c different Ton to triac in the dimming control circuit provides the different power dissipation to the lamp.

L6574D Datasheet

The figures also show the negative resistance characteristics of the lamp, such as when the lamp current decreases, the voltage increases accordingly. Figure 17, shows us the voltage and current measurement at Ton equal to 9 ms. Figure 18, shows us the voltage and current measurement at Ton equal to 5 ms. Figure 19 shows us the voltage and current measurement at Ton equal to 3 ms. CFLs can completely replace incandescent lamps in dimming systems. Information in this document is provided solely in connection with ST products.

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