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winny
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I want to design a Power Supplypower supply (Buck Converterbuck converter) which converts 9V9 V to 5V5 V and supplies it to the LED Stripstrip. The LED Stripstrip is a basic 1 meter long 70Leds70 LEDs/meter WS2812B Stripstrip. In my Projectproject, iI want to set the brightness around 5%.

Basic Schematic from my Problem

The Problemproblem: I am confused how to size the Buck Converterbuck converter. The total Currentcurrent at 100% Brightnessbrightness is around 4.2A2 A (60mA per LED) but the average is only about 210mA210 mA and the RMS about 900mA900 mA ( ImaxImax * sqrt(D)  ).

The LEDs change brightness by changing the PWM signal. This means, that the ideal current draw would be a 400Hz Square Wave400 Hz square wave with 5% dutycycleduty cycle. But if you look closer at the Stripstrip, every LED has a bypass capacitor. Also, the Buck Converterbuck converter has some Capacitancecapacitance (around 40 uF) and I want to place big bulky capacitors parallel to the output, over 1mF1 mF in total.

I want to simulate/calculate how much current gets drawn from the bulk capacitors by the led strip. This is crucial, because i wouldntI wouldn't need to design my converter for >4.2A2 A. For now, iI have this Buck Converterbuck converter from TI: LM60440, Datasheet

Could anyone help with these calculations or help me simulate it in LTSpiceLTspice? Also, does anyone have tips for selecting a buck converter for this application? Low EMI is important for me, frequency spreading is key here.

I want to design a Power Supply (Buck Converter) which converts 9V to 5V and supplies it to the LED Strip. The LED Strip is a basic 1 meter long 70Leds/meter WS2812B Strip. In my Project, i want to set the brightness around 5%.

Basic Schematic from my Problem

The Problem: I am confused how to size the Buck Converter. The total Current at 100% Brightness is around 4.2A (60mA per LED) but the average is only about 210mA and the RMS about 900mA ( Imax * sqrt(D)  ).

The LEDs change brightness by changing the PWM signal. This means, that the ideal current draw would be a 400Hz Square Wave with 5% dutycycle. But if you look closer at the Strip, every LED has a bypass capacitor. Also, the Buck Converter has some Capacitance (around 40 uF) and I want to place big bulky capacitors parallel to the output, over 1mF in total.

I want to simulate/calculate how much current gets drawn from the bulk capacitors by the led strip. This is crucial, because i wouldnt need to design my converter for >4.2A. For now, i have this Buck Converter from TI: LM60440, Datasheet

Could anyone help with these calculations or help me simulate it in LTSpice? Also, does anyone have tips for selecting a buck converter for this application? Low EMI is important for me, frequency spreading is key here.

I want to design a power supply (buck converter) which converts 9 V to 5 V and supplies it to the LED strip. The LED strip is a basic 1 meter long 70 LEDs/meter WS2812B strip. In my project, I want to set the brightness around 5%.

Basic Schematic from my Problem

The problem: I am confused how to size the buck converter. The total current at 100% brightness is around 4.2 A (60mA per LED) but the average is only about 210 mA and the RMS about 900 mA (Imax * sqrt(D)).

The LEDs change brightness by changing the PWM signal. This means, that the ideal current draw would be a 400 Hz square wave with 5% duty cycle. But if you look closer at the strip, every LED has a bypass capacitor. Also, the buck converter has some capacitance (around 40 uF) and I want to place big bulky capacitors parallel to the output, over 1 mF in total.

I want to simulate/calculate how much current gets drawn from the bulk capacitors by the led strip. This is crucial, because I wouldn't need to design my converter for >4.2 A. For now, I have this buck converter from TI: LM60440, Datasheet

Could anyone help with these calculations or help me simulate it in LTspice? Also, does anyone have tips for selecting a buck converter for this application? Low EMI is important for me, frequency spreading is key here.

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xdZapo
xdZapo
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Current Drawn from Bulk Capacitor at LED-Strip Output

I want to design a Power Supply (Buck Converter) which converts 9V to 5V and supplies it to the LED Strip. The LED Strip is a basic 1 meter long 70Leds/meter WS2812B Strip. In my Project, i want to set the brightness around 5%.

Basic Schematic from my Problem

The Problem: I am confused how to size the Buck Converter. The total Current at 100% Brightness is around 4.2A (60mA per LED) but the average is only about 210mA and the RMS about 900mA ( Imax * sqrt(D) ).

The LEDs change brightness by changing the PWM signal. This means, that the ideal current draw would be a 400Hz Square Wave with 5% dutycycle. But if you look closer at the Strip, every LED has a bypass capacitor. Also, the Buck Converter has some Capacitance (around 40 uF) and I want to place big bulky capacitors parallel to the output, over 1mF in total.

I want to simulate/calculate how much current gets drawn from the bulk capacitors by the led strip. This is crucial, because i wouldnt need to design my converter for >4.2A. For now, i have this Buck Converter from TI: LM60440, Datasheet

Could anyone help with these calculations or help me simulate it in LTSpice? Also, does anyone have tips for selecting a buck converter for this application? Low EMI is important for me, frequency spreading is key here.