How to “Increase” Your PWM Voltage (Effectively)
3. Adjusting the Duty Cycle
The most direct way to influence the effective PWM voltage is by tweaking the duty cycle. Remember, the duty cycle is the percentage of time the signal is “on.” A higher duty cycle means a higher average voltage. Most microcontrollers and PWM controllers allow you to adjust the duty cycle through software or hardware settings. The higher the duty cycle, the closer the average voltage is to the peak voltage.
For example, if you’re using an Arduino, you’d typically use the `analogWrite()` function. This function takes a value between 0 and 255, which corresponds to a duty cycle from 0% to 100%. So, `analogWrite(127)` would give you approximately a 50% duty cycle, and `analogWrite(255)` would give you a 100% duty cycle. Experiment with different values to see how they affect the voltage.
Keep in mind the limitations of your device. Some devices may not respond linearly to changes in duty cycle. For example, an LED might appear very dim at a low duty cycle and then suddenly jump in brightness as you increase it. Also, the frequency of the PWM signal can influence how the device responds. Too low a frequency might cause flickering, while too high a frequency might cause the device to not respond at all.
So, the first step in “increasing” your PWM voltage is to simply increase the duty cycle. It’s the most fundamental and straightforward way to control the effective voltage.
4. Using a Different Power Supply
As previously mentioned, the supply voltage dictates the maximum voltage achievable with PWM. If you need an effective voltage higher than your current supply voltage, you’ll need to switch to a higher voltage power supply.
Before you run off and grab the highest voltage supply you can find, there are a few crucial things to consider. First, make sure all your components are rated for the higher voltage. Applying too much voltage to a component can damage it, potentially causing it to fail catastrophically (and maybe even dramatically, with sparks and smoke!). Check the datasheets for all your components to ensure they can handle the increased voltage.
Second, consider the current requirements of your circuit. A higher voltage power supply might also be capable of delivering more current than your circuit needs. Make sure you have appropriate current limiting resistors or other protection measures in place to prevent damage.
Third, if you are using any type of logic device, such as a microcontroller, you must be very careful with the voltages that are applied to them. Applying the wrong voltages to these parts will almost certainly damage them beyond repair. Always look at the specifications.
5. Amplifying the PWM Signal (Driver Circuits)
Sometimes, you need more current than your PWM controller can provide, or you need to switch a higher voltage than your controller is designed for. That’s where driver circuits come in. A driver circuit acts as an intermediary between your PWM controller and the device you’re trying to control. It amplifies the current or voltage (or both) of the PWM signal, allowing you to control devices that would otherwise be beyond the capabilities of your controller.
A common example is using a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) as a switch. The PWM signal from your microcontroller controls the gate of the MOSFET, which then switches a higher voltage and current to your load. The MOSFET acts like a valve, allowing you to control a large flow of water (current) with a small turn of a tap (PWM signal).
When selecting a driver circuit, make sure it’s compatible with your PWM signal and the voltage and current requirements of your load. You’ll also need to consider the switching speed of the driver circuit. If it’s too slow, it might distort the PWM signal and reduce its effectiveness. Another component is a relay, which are great for high current devices. Just keep in mind that relays are mechanical devices, and they have a limited lifespan. They are also not as fast as transistors. Relays also consume additional power.
A well-designed driver circuit can significantly extend the capabilities of your PWM controller, allowing you to control a wider range of devices and achieve higher effective voltages and currents.