Pwm dimming offline led driver

So we can apply the same concept to binary in order to convert a decimal number to binary. All we need to do is replace the ones, tens and hundreds etc.

You can use this handy online converter to do the maths for you! The number of binary numbers that we can use in this system can also be referred to the number of bits. For example the number of digits in our example for is 8 bits. We call the bit to the far left the most significant bit and the bit to the far right the least significant bit.

We need to take into account that we can also represent zero with all 0s, therefore we can represent a total of decimal numbers in an 8-bit system. To represent the number in our second example we need 12 bits. Therefore the maximum decimal number that a digital system can represent is limited by the number of bits in the system. We can refer to 8 bits as one byte of data. Therefore to represent a number greater than in an 8-bit system, we would need to use two bytes of data.

So what does this all mean? We need to represent the value of our duty cycle in binary in order to make it compatible with a digital system. This means that we can have steps of brightness. More steps of brightness mean we can have a smoother fade of brightness and we can also represent more colours if we are controlling an RGB LED. If we were to use a 4-bit system, we could only have 4 steps in brightness.

This would not produce a smooth fade! A 4-bit system would give us 16 steps of brightness, which would be better but still not smooth. An 8-bit system is usually thought of as a good compromise between cost and performance, although a bit or even bit system would give noticeably better results. So the higher the number of bits, the better the resolution that we can achieve.

The effect also applies exponentially for each bit we add. An 8-bit system can represent up to steps but a bit system does not represent steps, it represents 65, steps! We know the maximum number of steps is so we can calculate the duty cycle for step We can see here that 1 step in an 8-bit system makes a 0. We can also calculate this directly. We know that a bit system can represent up to steps, so we can apply this to the formula above.

That is a huge difference! In a bit system there are a little over 16 steps for every single step in an 8-bit system. This means a bit system has a resolution 16 times finer than an 8-bit system. This makes a very noticeable difference to how smoothly we can fade brightness. The answer lies in the hardware limitation. It is just not feasible to cram this many wires inside a tiny little chip.

It is also more costly to produce a chip with more bits, therefore there is a tradeoff between cost and performance. For many digital dimming systems an 8-bit resolution provides a good balance between cost and performance.

Most 8-bit microcontrollers provide the ability to implement a PWM system with more than 8-bits, however this can be at the expense of performance or resources available within the chip.

Some microcontrollers feature dedicated hardware to produce a PWM output that we can use for dimming. It is also possible to implement it with software. We will take a look at manually implementing an 8-bit system in order to gain an understanding of how it works.

Another factor that we did not discuss yet is cycle time. This is the time that it takes our PWM to complete one cycle. We can say that the unit of time for our graph is milliseconds. There are milliseconds in 1 second. We already know that one cycle of the PWM signal takes 10 units of time, therefore we can say that the cycle time for this PWM is 10ms. The speed in which a PWM signal repeats over and over is usually expressed as frequency. Now that we know the cycle time, we can calculate the frequency f.

The frequency of the PWM signal in our example graph is Hz, or we can say that the cycle repeats times per second. On the other hand, the driver detects the PWM duty cycle to determine the output current.

But it is best to know that there are two methods to realize PWM dimming drivers. The fake dimming method is a concept that converts the PWM inputs into an analog control signal. There is a resistor-capacitor RC filter inside the driver. One advantage of fake PWM dimming is that it is noise-free. It is noise-free since the LED current is constantly continuous at the output.

On the other hand, the drawback with this method is that the peak value of the PWM must be 10V; otherwise, the accuracy is terrible. There is a microcontroller MCU inside the driver. It also permits a high level of the reference voltage, which is above offset errors. Upowertek is a renowned and trusted manufacturer of dimmable LED drivers. With an increasing reputation, highly experienced workforce, and updated methods, Upowertek provides the best dimmable LED drivers.

LED lighting penetrates everybody's life, becoming more intelligent and more sophisticated. When designing high quality and excellent luminaire, the It is a trend in the lighting industry to replace traditional incandescent and fluorescent lamps with more efficient and Now more and more high power luminaires are utilized for horticultural or industrial lighting applciations to realize better control Hence dimmable LED drivers Choosing a power supply for your project can be challenging and tough because there are so many options and Basically you will need a driver per LED.

Some drivers can also use a seperate dimming signals. I looked at Constant Current and building hardware for it, but because of the driver per LED you need, it quickly becomes expensive. Constant voltage means that voltage instead of the amperage the LED sees always stays constant. Most LED strips work this way.

As I mentioned above, although lowering voltage can lower the light output this comes with undesired effects. For this they invented something called PWM dimming. PWM has a frequency and a duty cycle. The Frequency determines how many times the LED is pulsed a second and the duty cycle determines how long this pulse will be.