How does an optocoupler limit the gate voltage?
You can limit the gate voltage by having a resistor in series with the optocoupler’s transistor. If the transistor to ground is 4k7 you can pick 10k for this. If the optocoupler’s LED is on the transistor will conduct and make the gate high, switching the MOSFET on.
Can a microcontroller drive a MOSFET with an optocoupler?
Anything up to about 10 kHz should work OK./ For faster PWM a properly designed driver is required. As far as the MOSFET is concerned, an optocoupler is just a transistor. As far as the microcontroller is concerned, an optocoupler is just an LED.
How to calculate optocoupler efficiency in a circuit?
The most convenient way of specifying optocoupling efficiency is to quote the output-to-input current transfer ratio (CTR) of the device, i.e., the ratio of the output collector current (I C) of the phototransistor, to the forward current (I F) of the LED. Thus, CTR = I C /I F.
Which is the output side of the optocoupler?
So Q2 is the output side of the opto-couper. R2 would be replaced by the input LED side of the opto-coupler and it’s current limiting resistor. The optocoupler’s isolation gives you the advantage that you can place its output transistor anywhere you like, independent of the microcontroller’s supply voltage.
Do you need a transistor to drive a MOSFET?
So, all you need is a normal transistor-driven MOSFET circuit, and a normal microcontroller-driven LED circuit. Here’s an example of driving a MOSFET with a transistor: So Q2 is the output side of the opto-couper. R2 would be replaced by the input LED side of the opto-coupler and it’s current limiting resistor.
How does an optocoupler work on a microcontroller?
R2 would be replaced by the input LED side of the opto-coupler and it’s current limiting resistor. The optocoupler’s isolation gives you the advantage that you can place its output transistor anywhere you like, independent of the microcontroller’s supply voltage. Driving the opto-coupler means driving its LED.
How does a phototransistor work in an optocoupler?
Phototransistor Optocoupler. Current from the source signal passes through the input LED which emits an infra-red light whose intensity is proportional to the electrical signal. This emitted light falls upon the base of the photo-transistor, causing it to switch-ON and conduct in a similar way to a normal bipolar transistor.
How many types of optocouplers are there in the market?
Since there is no direct electrical connection between the input and output of an optocoupler, electrical isolation up to 10kV is achieved. Optocouplers are available in four general types, each one having an infra-red LED source but with different photo-sensitive devices.