7 ms·

GaN diodes have higher voltage drop (1.4-1.7) than Schottky (0.3) or even normal diodes (0.7). How can they be more efficient?

by dvh 2y ago

deleted 2y ago
[deleted]
connicpu 2y ago
Probably not for the diode properties, but the transistor properties. I'm not an expert in this field, but some quick googling says GaN transistors (compared to silicon) have faster switching speeds and lower on-state resistance. I'm sure there's other tradeoffs, but those are great properties for high power, high frequency circuits.
magicalhippo 2y ago
Here's what ST says[1]: The very high electron mobility of GaN material allows devices with very low on-resistance and exceptionally high switching frequencies, which are key advantages in the design of next generation power systems, especially those for electric vehicles and renewable energy applications. Regarding the band gap[2]: It has a wide bandgap of 3.4 eV and an electron mobility of 1,700 cm2/Vs. Comparatively, Silicon sits at 1.1 eV and 1,400 cm2/Vs. GaN’s inherent properties thus result in a higher breakdown voltage and lower on-state resistance, which means that the component can more efficiently handle greater loads compared to a similar-sized silicon device, which then leads to a lower bill of materials. [1]: https://www.st.com/content/st_com/en/about/innovation---technology/GaN.html https://www.st.com/content/st_com/en/about/innovation---tech... [2]: https://blog.st.com/powergan/ https://blog.st.com/powergan/
londons_explore 2y ago
You aim for no current to ever flow through the diode. Any time current might flow through the diode, you should either switch on the transistor (so the same current flows through the channel), or switch some other transistor in your circuit to block the current (ie. a series transistor with source and drain switched).
adrian_b 2y ago
They are more efficient at high switching frequencies, because they have very low switching losses. When a diode is not switched, or it is switched at very low frequencies, then the losses are given by the voltage drop when the diode is on and by the leakage current when the diode is off. These 2 parameters cannot be improved simultaneously, so some diodes are better when used at low voltages and high currents and others are better at high voltages and low currents. However when the switching frequency is increased, which is desirable in power supplies and in amplifiers because it allows the use of smaller inductors and capacitors, reducing the size of the equipment, the switching losses increase proportionally with the frequency and over some frequency they become higher than the static losses. When such high frequencies are reached, the most efficient diodes become those with the smallest switching losses, which currently are the gallium nitride diodes. The GaN diodes and field-effect transistors have enabled the much smaller chargers that exist now for laptops and smartphones, in comparison with the traditional bricks, which for many small computers were bigger and heavier than the computers. GaN diodes and transistors are the best for switching power supplies and switching amplifiers with working voltages from about 100 V up to 500 V or 600 V, which is enough for equipment powered by household voltages (the voltage supported by a device in a power supply is significantly higher than the nominal voltages like 120 V or 230 V, because what counts is the peak voltage not the effective voltage and also not the nominal value but the highest value within the permitted tolerances increased by some safety factor; thus a 500 V to 600 V device is needed for 230 V mains electric power). For the higher voltages that may be needed in industrial and automotive applications, silicon carbide diodes and transistors are the best. For voltages under 100 V, silicon diodes and transistors remain the best.

GaN diodes have higher voltage drop (1.4-1.7) than Schottky (0.3) or even normal diodes (0.7). How can they be more efficient?

by dvh 2y ago

GaN diodes have higher voltage drop (1.4-1.7) than Schottky (0.3) or even normal diodes (0.7). How can they be more efficient?

deleted 2y ago

[deleted]

connicpu 2y ago

Probably not for the diode properties, but the transistor properties. I'm not an expert in this field, but some quick googling says GaN transistors (compared to silicon) have faster switching speeds and lower on-state resistance. I'm sure there's other tradeoffs, but those are great properties for high power, high frequency circuits.

magicalhippo 2y ago

Here's what ST says[1]: The very high electron mobility of GaN material allows devices with very low on-resistance and exceptionally high switching frequencies, which are key advantages in the design of next generation power systems, especially those for electric vehicles and renewable energy applications. Regarding the band gap[2]: It has a wide bandgap of 3.4 eV and an electron mobility of 1,700 cm2/Vs. Comparatively, Silicon sits at 1.1 eV and 1,400 cm2/Vs. GaN’s inherent properties thus result in a higher breakdown voltage and lower on-state resistance, which means that the component can more efficiently handle greater loads compared to a similar-sized silicon device, which then leads to a lower bill of materials. [1]: https://www.st.com/content/st_com/en/about/innovation---technology/GaN.html https://www.st.com/content/st_com/en/about/innovation---tech... [2]: https://blog.st.com/powergan/ https://blog.st.com/powergan/

londons_explore 2y ago

You aim for no current to ever flow through the diode. Any time current might flow through the diode, you should either switch on the transistor (so the same current flows through the channel), or switch some other transistor in your circuit to block the current (ie. a series transistor with source and drain switched).

adrian_b 2y ago

They are more efficient at high switching frequencies, because they have very low switching losses. When a diode is not switched, or it is switched at very low frequencies, then the losses are given by the voltage drop when the diode is on and by the leakage current when the diode is off. These 2 parameters cannot be improved simultaneously, so some diodes are better when used at low voltages and high currents and others are better at high voltages and low currents. However when the switching frequency is increased, which is desirable in power supplies and in amplifiers because it allows the use of smaller inductors and capacitors, reducing the size of the equipment, the switching losses increase proportionally with the frequency and over some frequency they become higher than the static losses. When such high frequencies are reached, the most efficient diodes become those with the smallest switching losses, which currently are the gallium nitride diodes. The GaN diodes and field-effect transistors have enabled the much smaller chargers that exist now for laptops and smartphones, in comparison with the traditional bricks, which for many small computers were bigger and heavier than the computers. GaN diodes and transistors are the best for switching power supplies and switching amplifiers with working voltages from about 100 V up to 500 V or 600 V, which is enough for equipment powered by household voltages (the voltage supported by a device in a power supply is significantly higher than the nominal voltages like 120 V or 230 V, because what counts is the peak voltage not the effective voltage and also not the nominal value but the highest value within the permitted tolerances increased by some safety factor; thus a 500 V to 600 V device is needed for 230 V mains electric power). For the higher voltages that may be needed in industrial and automotive applications, silicon carbide diodes and transistors are the best. For voltages under 100 V, silicon diodes and transistors remain the best.