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1W with MR16LED alternative to 5WLED drive

In Electronic Infomation Category: 1 | on April 15,2011

Test circuit. This reference design block diagram shown in Figure 1.


Figure 1: Semiconductor MR16 LED replacement for the application of 1 W to 5 W LED Driver GreenPoint? Reference design block diagram.

Basic power topology

Buck - boost converter principle is very simple. Conduction state, the input voltage source directly connected to the inductor (L), and HD6415108F10 datasheet and thus the accumulation of energy in the inductor. At this stage, the output load capacitance C to provide energy. Off, the inductor through the output diode and HD6415108F10 price and capacitor connected to the output load, which transfers energy to the load.


Figure 2: Without Vin Vin compensation and HD6415108F10 suppliers and compensation with the average LED current vs. Vin curve.

Therefore, using the input voltage feed-forward compensation network to reduce the Iout vs. Vin nonlinear response curve due to errors. By the resistor R3, R5 and R4 addition resistance divider network comprising resistor (see Figure 5) is used to increase the ratio of voltage to the FB pin Vin, Vin increases, resulting in lower load current. Which serve to Figure 2a the effect of curve flattening, and reduces the overall current error (see Figure 2b).

Resistor R9 and capacitor C6 to limit the high-voltage external switch input source voltage of the gate extreme. R9 and R2 formed by the resistor divider network is used to set the maximum extreme gate source voltage (Vgs):


pulse feedback resistance

Resistor R7 and diode D5 to reduce jump pulse (pulse skipping) possibilities. Burst mode control as a feedback voltage and involved only a week of cross-testing, does not include using the window comparator, a pulse may have skipped (skipped pulse), it will not affect the DC skip adjust the pulse, but if the pulse have low frequency components, the application may be presented in the LED flashes.

R7 and D5 increased the flow of timing capacitor C2 to the current Ct. This effectively limits the NCP3065 offers a maximum duty cycle. When conditions allow low duty cycle, R7 and D5 values ??higher than necessary to make the duty cycle does not appear. In the off period, the need to D7 to block voltage, because this is buck - boost topology. More information about pulse feedback compensation ON Semiconductors NCP3065 see the data sheet.

Exchange Vs. Dc

Due to half-sine input to the buck - boost section, compared with the pure DC input, the operating point will be different. Due to the small size is an objective of this design, so after the full-bridge rectifier using the small input capacitance.

Therefore, this way, according to the selected input capacitance, line voltage can drop as low as 3 V. Therefore, the converter input is full wave rectified sine wave. Since the voltage regulator is lower than about 4 V does not work (non-functional), so there is regulation blind (dead spot). Therefore, our final regulation is 120 Hz line cycle, about 80% of the limited part of the remaining 20% ??is not regulated. AC input work, which will reduce the average current of about 20%.

When using more than 12 Vac voltage work, should consider the heat. In most applications, this module will increase the heat dissipation. Input voltage compensation for extra compensation network communication to deal with different working points.

protection

Zener diode Z1 and resistor R1, and the NCP3065 current limiting function is used to open circuit protection. Open event in the event of load, the loop will attempt to increase the output voltage to meet the current demand for zero-current feedback. If (Vin + Vout) than Z1 voltage, current will flow through R1, triggering NCP3065 current limiting function.

Input short circuit protection by fuse F1 to deal with. Inductive load surge protection must also be carefully considered, especially in the transformer feeder systems, such systems carry large amounts of source inductance, landscape lighting applications such as magnetic transformer is. Need to select the appropriate voltage surge protection device, the voltage can not exceed the extreme power FET gate-source voltage and the voltage with a reasonable margin. This may require selection by trial and error, because the need to absorb energy under different clamping voltage may be extended.

Increase in output current

This reference design is configured for the average LED current of 350 mA. This reference board to increase the current regulation is very simple, just current sensing resistor R8 to the value of the half, from 250 m reduced to 125 m. In addition, the input fuses must be increased to accommodate the increased input current consumption. When turned to the design of higher power, according to housing component (housing) of different environmental parameters that may require heat sinks.

Test results

This reference design in different AC input voltage and output current under DC voltage conditions at different energy efficiency of the test results are shown in Figure 3a and 3b. Which, as shown in Figure 3b, this reference design at 11 to 17 Vdc range of energy efficiency higher than 0.75, the energy efficiency of data in these low-power applications, brisk performance.


Figure 3: a) Iout vs. Vac b) energy efficiency vs. Vdc

reference design schematic
reference design board that kind shown in Figure 4, the complete circuit is shown in Figure 5.



Figure 4: Reference Design physical map. (Size 11 mm x 29 mm).



Figure 5: ON Semiconductor MR16 LED replacement for the application of 1 W to 5 W LED driver reference design schematic.

Summary:

This paper analyzes the challenge of driving high-brightness LED, Semiconductor introduced MR16 LED replacement for the application of 1 W to 5 W LED driver reference design, including the basic circuit topology, providing smooth output current burst mode control, pulse feedback compensation, AC and DC characteristics comparison of the work, protection features, and how to modify this reference design to provide more output current. The results show that AC voltage reference design in different conditions to provide a more smooth output current, and DC in different conditions provide excellent energy efficiency.

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