Join Barron Stone for an in-depth discussion in this video ✓ Solution: Circuit protection, part of Electronics Foundations: Semiconductor Devices.
- [Instructor] Lets take a look at my solution for the challenge to protect my thermostat from a short circuiting power supply. If one of the supplies failed and turns into a short circuit current from the other supply would flow backwards through it. That's a reverse current which I can easily stop with a diode. If I place a reverse current protection diode between the two power supplies like this, it'll block that reverse current coming from the right supply, from flowing through the short circuit on the left to keep my thermostat running.
However, if it was the power supply on the right that failed instead of the one on the left, that diode wouldn't help. Because current from the working supply on the left would flow straight through the broken supply on the right. To fully protect this system from short circuiting power supplies, I need two diodes to protect against reverse current, one for each supply. When the supplies are functioning correctly, both of these diodes will be forward biased, so current will flow from the power supplies to my device more or less freely.
If either one of the supplies fails and internally short circuits, the diode protecting it will become reverse biased and block current from flowing backwards through the short. The other power supply can fully support the thermostat, so the system continues to function. Since I'm placing these protection diodes in series with the power sources, I want to minimize the amount of supply voltage that I loose to the forward voltage drop across the diode. Which makes this a good time to use Schottcky diodes, which have a low forward voltage and a large reverse breakdown voltage.
- Semiconductor materials
- Diode applications
- Rectifying a signal
- Detecting the signal peak
- Protecting against large signals, reverse current, and flyback voltage
- Special purpose zener diodes, Schottky diodes, and photodiodes
- NPN and PNP bipolar junction transistors
- Using a BJT as a switch
- Field effect transistors
- Differences between BJTs and MOSFETs
- Operational amplifiers
- Op-amp applications
- Comparing signals
- Buffering signals
- Amplifying signals
- Filtering signals
- Combining signals