Ultrafast recovery diodes are indispensable in diodes. With a reverse recovery time of only tens of nanoseconds and the ability to withstand reverse high voltages of hundreds or even thousands of volts, they have been widely used in medium and high power switching rectification applications. This article introduces the secrets of the 5th generation FRED Pt® ultrafast recovery diodes. See
There is an Easter egg at the end of the article
.
Ultrafast recovery diodes are indispensable in diodes. Since they have a reverse recovery time of only tens of nanoseconds and can withstand reverse high voltages of hundreds or even thousands of volts, they have been widely used in medium and high power switching rectification applications.
As we all know, for a typical PN structure diode, when the voltage switches from forward to reverse, due to the charge storage effect, a large instantaneous reverse recovery current will be generated on the diode, and then this current will decrease and enter the reverse cut-off state. This is the reverse recovery process.
Qrr
(which represents the recovery charge required to switch from a specified forward current to a reverse cut-off state) and trr
(
which represents the recovery time required from a specified forward current to a specified reverse current) are two important parameters that describe the reverse recovery process of the diode. If you want the diode to "act" faster, you need to find a way to reduce Qrr
and
shorten
trr
.
Figure 1: Vishay's 5th generation FRED Pt
®
ultrafast recovery diode
To achieve this goal, people have found that doping precious metals in diodes is a feasible method. By adopting a unique platinum (Pt) doping process, Vishay has launched
the
FRED Pt
®
(Fast Recovery Epitaxial Diodes) ultra-fast recovery diode series with low t
rr
and high reverse withstand voltage characteristics
. After years of development, FRED Pt
®
has evolved to the fifth generation.
The newly launched 5th generation FRED Pt®
includes
6 models of devices, which can achieve the fastest reverse recovery time of 26nS (T
J
= 25℃, I
F
= 1A, dI
F
/dt = 100A/μs, VR
=
30V), the minimum recovery charge is only 1550nC (T
J
= 125℃, I
F
= 40A, VR
=
400V, dI
F
/dt = 600A/ms), the reverse cut-off voltage is 1200V, the rated current can reach 30A to 60A, and the maximum operating junction temperature is 175℃……
If we carefully check the datasheet of the latest generation of FRED Pt
®
, we will definitely find more beautiful and eye-catching performance parameters. However, to summarize its characteristics and advantages in the most concise words, only seven words are needed, that is -
fast, gentle, low consumption, and high efficiency
. Let's interpret these keywords one by one.
01
quick
Since it is called "ultrafast recovery diode", "fast" must be its basic skill. The 6 products of the 5th generation FRED Pt
®
include two types of devices, X-type Hyperfast and H-type Ultrafast, whose reverse recovery time is between 26nS and 38nS, which is a very good result for high-power switching diodes with 30A - 60A and 1200V reverse voltage.
02
soft
The 5th generation FRED Pt
®
series devices have a unique feature, that is, compared with other diode rectification technologies, their reverse recovery process is more "gentle". As shown in Figure 2, in the reverse recovery process of the entire diode, compared with the performance of other green and yellow competitors, the 5th generation FRED Pt
®
represented by the black curve
has a lower maximum reverse recovery current I
RRM
peak, and a more stable waveform without "burrs". For the entire system, this "gentle" low oscillation and low reverse voltage spike characteristics mean lower EMI and switching power loss, and its value is self-evident.
Figure 2, 5th generation FRED Pt®
ultrafast
recovery diode
Reverse recovery characteristic curve
03
Low consumption
The power loss of a diode mainly includes three parts: switching loss, forward (conduction) loss and reverse loss. The 5th generation FRED Pt®
has
made a series of optimizations to reduce the loss. To be honest, this is not a simple "system engineering".
-
Switching loss:
For high-frequency devices, the impact of switching loss on total power loss is more prominent. As mentioned earlier, the 5th generation FRED Pt® has a
shorter
reverse recovery time trr
,
and the reverse recovery current waveform has a small peak and small oscillation, which effectively reduces the switching loss.
-
Forward loss
:
The important parameter that affects forward loss is the forward voltage drop V
F
. The smaller
the V
F
is, the lower the forward loss is. However, from the perspective of manufacturing process principles,
it is difficult to achieve
higher t
rr
switching speed and lower V
F
at the same time. Often, measures to reduce t
rr
will increase V
F.
The 5th generation FRED Pt
®
has achieved a good balance between the two, maintaining a low V
F
while being "fast"
. For example, compared with similar rectifier solutions, the H-type rectifier in the 5th generation FRED Pt
®
has a 40% lower switching loss under the same forward voltage drop, thereby reducing the overall power loss.
The combined effect of the above measures ultimately results in an overall power loss of the 5th generation FRED Pt
®
that is 10% lower than similar silicon wafer solutions.
Figure 3, 5th generation FRED Pt®
ultrafast
recovery diode
Has lower power loss
04
Efficient
Directly related to low loss is the higher efficiency of the device. The conversion rate of the 5th generation FRED Pt®
can
reach 98.3%, while the best efficiency performance among competing products is 98.15%. Although the difference is only 0.15% in terms of value, imagine that in a 15KW power supply, this difference means a reduction of 22.5W of additional heat. With low heat, the heat sink required by the power supply system is small, so the seemingly "subtle" efficiency improvement cannot be underestimated in terms of improving the overall performance of the power supply system.
Moreover, we can clearly see from Figure 4 that after the efficiency improvement, the 5th generation FRED Pt®
is
closer to the efficiency performance of SiC devices. That is to say, in the 50kHz frequency application range, the FRED Pt® silicon device can completely
replace
the expensive SiC diode to achieve a higher cost-effectiveness!
Figure 4, 5th generation FRED Pt®
ultrafast
recovery diode
Power loss comparison with other solutions
05
Market positioning and roadmap
It can be seen that
the outstanding advantages of
the 5th generation FRED Pt® ultrafast recovery diodes, such as
fast
, gentle, low consumption and high efficiency,
are hard to resist. However, in practical applications, if you want to make accurate selections, you still need
to have a clear understanding
of the characteristics of different material numbers and the overall development path of FRED Pt®
.
Figure 5, Performance overview of 6 types
of 5th generation FRED Pt
®
ultrafast recovery diodes
Let's first look at
the entire development history of the
FRED Pt
®
series. The first generation of FRED Pt
®
was acquired from IR. On this basis, Vishay developed the classic second generation product, which established the "keynote" of high speed, low power consumption, and softness for the entire product series. The wide product line from 200V to 1200V can basically cover the needs of most low-power application scenarios. The automotive-grade devices developed on this basis are the favorite of automotive applications.
Starting from the 4th generation of products, FRED Pt®
began
to focus on creating more "personalized" products for different application markets. For example, the 600V/650V 4th generation FRED Pt®
emphasizes
the "softness" of reverse recovery and the characteristics of low forward conduction voltage drop, making it a good "companion" for IGBT.
The fifth generation FRED Pt®
targets
applications with high power, high switching frequency and low switching loss. The fifth generation devices have different characteristics and positioning. For example, X-type devices have lower Q
rr
and shorter t
rr
,
while
H-type devices have better forward voltage drop. Developers can choose more suitable devices to meet the needs of specific applications, such as electric vehicle charging piles (X-type), solar energy (H-type), high-voltage DC power supply (H-type), etc.
Figure 6, Comparison of characteristics
of
2nd, 4th and 5th generation FRED Pt®
ultrafast
recovery diodes
Figure 7, FRED Pt
®
ultrafast recovery diode development roadmap
In the future,
the fifth generation of FRED Pt®
will
evolve in two directions. First, develop automotive-grade devices, which is obviously Vishay's strength, to tackle such high-threshold applications (FRED Pt®
AEC
-Q101 certified products have passed the Part Average Test (PAT) and Statistical Yield Limit (SYL) analysis to ensure that the electrical parameters meet the high quality level requirements of automotive applications); second, launch low-voltage products (600V/650V), enrich the product line, and expand the application coverage.
By then, I hope that the seven-word formula of the 5th generation FRED Pt®
can
be transformed into various "magic skills" in the hands of developers and benefit more users.
Readers have prizes for interaction
After reading the above content, I believe you have a better understanding of the 5th generation FRED
Pt
®
. Please
write
the answers to the following questions
in the message area before 17:00 on August 9.
We will select the first 10 fans who answer all the questions correctly and send them fan gifts (Thermos thermos cups).
1. Which of the following options are characteristics of the 5th generation FRED Pt
®
ultra-fast recovery diode:
A. High efficiency and low power consumption B. Gentle C. Fast D. All of the above
2. Which of the following products is suitable for the 5th generation FRED Pt
®
X-type device?
A. Electric vehicle charging station B. Solar energy C. High voltage DC power supply D. All of the above
3. Which of the following voltage options is suitable for the 5th generation FRED
Pt®
products
to be launched in the future:
A. 1200V B. 1000V C. 600V/650V D.200V
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