Hold-Up Capacitor: Calculations And Uses

1
3/3/23, 300 PM
Hold-Up Capacitor Value Calculations Uses

• What is a Hold-Up Capacitor When Do We Need It?
• What is Hold-Up Time?

Home(hH opwst/o/oCxealltceuclaht.deet/heen/V)alu
eCoafpHaoclidto-rUsp(hC appsac//iotoxer?ltech.de/
en/category/capacitors/)
Oxeltech

• References

Hold-Up Capacitor Calculations and (h
ps//oxeltech.de/en/hold-up-capacitor-calculations
-and-
Uses use/)
What Is A Hold-Up Capacitor When Do We
NHoeeld-UItp? Capacitor Calculations And Uses In
real-time critical applications such as avionics
and life-support systems, it is very important to
have an uninterruptable power supply supplying
adequate power to the system.
Share
Any sudden drop in power can jeopardize the
systems working, leading to fatalities in the
worst- case scenario. Here is a typical
switched-mode power supply block diagram
A capacitor is placed right after the recti
cation block to cater for this sudden drop
(usually from a main line power outage). In case
of a power drop, the capacitor can kick in and
maintain power levels for the load until the
power comes back.
What Is Hold-Up Time? Hold-Up is when the power
supply keeps supplying power to load before it
drops below the speci ed voltage level. This
voltage level and the corresponding hold-up time
di er for di erent power supplies. Generally,
linear supplies have very short hold-up times and
go to zero almost instantaneously. However, the
switched-mode supplies can hold up until the
power comes back on or the UPS gets
connected. This is because switched-mode power
supplies have hold-up capacitors after the recti
cation stage that keep the power within given
levels. How To Calculate The Value Of Hold-Up
Capacitor? It has been established earlier that
switched-mode power supplies use hold-up
capacitors to hold the power level above a speci
c level in case of power cuts. Now to calculate
the value of such a capacitor, the supplys
hold-up time is set rst. Secondly, the output
voltage and current values are to be known to
calculate power. This power value is to be used
later for capacitor value calculation. Using the
power relation, we can calculate the output power
that the circuit provides to load P W V . I
V,A We also calculate the energy stored in a
given capacitor
2
3/3/23, 300 PM
Hold-Up Capacitor Value Calculations Uses
E J ½ . C . ( V2U V2L ) Oxeltech Here VU
is the voltage at the beginning of discharge
time, i.e. the nominal output voltage, and VL
is the voltage at the end of cap discharge time,
i.e. the safe limit for hold-up time.
Share
We know that power is energy per unit of time, so
we can use this relation and write the energy
relation in terms of power and time. After that,
the equation can be rearranged to nd the
capacitance value
C F ( 2 . P W . ts ) / ( V2U V2L
) Lets do an example and use this relation to
nd the hold-up capacitor for a system Example
The hold-up time of a switched-mode power supply
is 10ms. The output voltage is set to 5V, and
the current is 1A. The safe voltage limit for the
hold-up is 4.8V. Find the value of the hold- up
capacitor. We can rst nd the power supplied by
the capacitor P W V . I V,A
P 5W The relation for energy is given here E
J ½ . C . ( V2U V2L ) Here VU is the
voltage at the beginning of discharge time, i.e.
5V, and VL is the voltage at the end of cap
discharge time, i.e. 4.8V. Now, we can rearrange
this to nd the capacitance value C F ( 2 .
P W . ts ) / ( V2U V2L )
Here P W E J /ts relation is used to replace
energy. The nal value for the capacitor comes
out to be C F 0 .0 510 20 40 81633
F OR CµF 510 20 .40 µF There you go!
3
Hold-Up Capacitor Value Calculations Uses Now
we can understand the usage of a hold-up
capacitor and incorporate it into our design
decisions for switched-mode power supplies.
Moreover, we can calculate the value of such a
capacitor according to our speci c
application. Oxeltech References
3/3/23, 300 PM
. h ps//en.cosel.co.jp/technical/qanda/a0066_1.h
tml (h ps//en.cosel.co.jp/technical/qanda/a0066_
1.html) If you are facing any di iculties with
your Hold-Up Capacitor calculations or any
general hardware design challenge, feel free to
Contact Us (h ps//oxeltech.de/en/contact-us/)
for our consultancy. You can check out our other
Technical Blogs (h ps//oxeltech.de/en/blog/) on
various topics or visit our new website
Oxeltech.de to nd all about our services (h
ps//oxeltech.de/en/services/) and products.
Share
Team Oxeltech November 6, 2022(h
ps//oxeltech.de/en/2022/11/06/) 717 am
No Commen ts
(h ps//oxeltech.de/en/hold-up-capacitor-
calculations-and-use/respond)
Did You Enjoy This Article?
Join Oxeltech community and get updated every
week We have a lot more just for you! Lets join
us now
Email
Subscribe Now
No charge
Unsubscribe anytime
Leave A Reply Your email address will not be
published. Required elds are marked Comment
Name
Email
4
3/3/23, 300 PM
Hold-Up Capacitor Value Calculations Uses
Website Oxeltech Save my name, email, and
website in this browser for the next time I
comment.
Post Comment Recent Post
Share
How To Write A Driver For Accelerometer LIS3DSH
In Zephyr? (Https//Oxeltech.De/En/How-To-Write-A
- Driver-For-Accelerometer-Lis3dsh-In-Zephyr/) Ja
nuary 16, 2023
(h ps//oxeltech.de/en/how- to-write-a-driver-for
- accelerometer-lis3dsh- in-zephyr/) SoC Vs SoM
System On Chip Vs System On Module
(Https//Oxeltech.De/En/System-On-Chip-Soc-Vs-
System-On-Module-Som/) December 23, 2022
(h ps//oxeltech.de/en/system-
on-chip-soc-vs-system- on-module-som/) ESD Best
Practices (Https//Oxeltech.De/En/Esd-Best-
Practices/) December 6, 2022
(h ps//oxeltech.de/en/esd- best-practices/) How
To Choose Between Microcontroller And FPGA For
Your Embedded Application? (Https//Oxeltech.De/E
n/Fpga-Vs-Microcontroller/) December 6, 2022
(h ps//oxeltech.de/en/fpga- vs-microcontroller/)
Hold-Up Capacitor Calculations And Uses
(Https//Oxeltech.De/En/Hold-Up-Capacitor-
Calculations-And-Use/) November 6, 2022
(h ps//oxeltech.de/en/hold- up-capacitor-
5
3/3/23, 300 PM
Hold-Up Capacitor Value Calculations Uses
MTBF Concept And Application (Https//Oxeltech.D
e/En/Mtbf-Concept-And- ApplicOatixone/)l
tech October 6, 2022
Share
(h ps//oxeltech.de/en/mtbf- concept-and- applica
tion/) All About LiDAR Technology Complete
Guide (Https//Oxeltech.De/En/Lidar-Technology/)
September 6, 2022
(h ps//oxeltech.de/en/lidar- technology/) How
To Choose The Right Flash Memory For Your
Embedded Application. (Https//Oxeltech.De/En/Flas
h- Memory-In-Embedded-System/) August 6, 2022
(h ps//oxeltech.de/en/ ash- memory-in-embedded-
system/) Altiums PCB Designer Tools Guide
(Https//Oxeltech.De/En/Altium-Pcb-Designer-Tools-
Guide/) July 6, 2022
(h ps//oxeltech.de/en/altium-
pcb-designer-tools- guide/) Altiums Amazing
Features Project Management Tools
(Https//Oxeltech.De/En/Altium-Project-Management/
) June 6, 2022
(h ps//oxeltech.de/en/altium-
project-management/) Ceramic Capacitors Which
Aspects To Consider When Using Them In Your
Design? (Https//Oxeltech.De/En/Ceramic-Capacitor
-Uses/) May 8, 2022
6
3/3/23, 300 PM
Hold-Up Capacitor Value Calculations Uses
How To Control DC Servo Motors?
(Https//Oxeltech.De/En/Dc-Servo-Motor-Controller/
) April 21, O202x2 eltech
Share
(h ps//oxeltech.de/en/dc- servo-motor-controller
/) Your Ultimate Guide To Designing Analog
Filters (Https//Oxeltech.De/En/Analog-Filters-De
sign-Guide/) April 9, 2022
(h ps//oxeltech.de/en/analog-
lters-design-guide/) Consumer Electronics,
Industrial Electronics And Industrial Standards
(Https//Oxeltech.De/En/Consumer-
And-Industrial-Electronics-Standards/) April 1,
2022
(h ps//oxeltech.de/en/consumer-
and-industrial- electronics-standards/) Design
Guide On USB-C PD Charge-Through Feature With
Data Role Swap (Https//Oxeltech.De/En/Usb-C-
Design-Guide/) March 23, 2022
(h ps//oxeltech.de/en/usb- c-design-guide/) Alti
ums Team Collaboration Features In PCB Design
(Https//Oxeltech.De/En/Altium-365-Team-
Collaboration/) March 6, 2022
(h ps//oxeltech.de/en/altium-
365-team- collaboration/) Using Zephyr OS For
Interfacing An IMU Sensor With NRF52 Over SPI
(Https//Oxeltech.De/En/Using-Zephyr-
Os-For-Interfacing-An-Imu-Sensor-With-Nrf52-Over-
Spi/) July 25, 2021
(h ps//oxeltech.de/en/using- zephyr-os-for-
7
3/3/23, 300 PM
Hold-Up Capacitor Value Calculations Uses
interfacing-an-imu- sensor-with-nrf52-over-
spi/)
Use OOf Gxroeunl dtiengcThechniques In PCB Design
To Prevent Electromagnetic Interference (EMI)
(Https//Oxeltech.De/En/Pcb-Grounding-Techniques/)
June 29, 2021
Share
(h ps//oxeltech.de/en/pcb- grounding-techniques/
) PCB Design Guidelines For Reduced
Electromagnetic Interference (EMI)
(Https//Oxeltech.De/En/Pcb-Design-
Guidelines-For-Reduced-Electromagnetic-Interferenc
e- Emi/) May 5, 2021
(h ps//oxeltech.de/en/pcb- design-guidelines-for
- reduced- electromagnetic- interference-emi/) E
MC Vs EMI Compatibility, Principles Mechanism
Comparisons (Https//Oxeltech.De/En/Emc-And-Emi/)
April 18, 2021
(h ps//oxeltech.de/en/emc- and-emi/)
Continue Reading
8
Hold-Up Capacitor Value Calculations Uses (h
ps//oxeltech.de/en/how-to-write-a-driver-for-acce
lerometer-lis3dsh-in-zephyr/)
3/3/23, 300 PM
Oxeltech How To Write A Driver For Accelerometer
LIS3DSH In Zephyr? (Https//Oxeltech.De/En/How-To-
Write-A-Driver-For-Accelerometer-
Lis3dsh-In-Zephyr/) Team Oxeltech January 16,
2023
Share
In our previous Zephyr blog, we looked at how to
interface a simple IMU Accelerometer sensor
with Zephyr RTOS running on NRF52832. Knowing
how Read More (H ps//Oxeltech.De/En/How-To-Write-
A Driver-For-Accelerometer-Lis3dsh-In- Zephyr/)
(h ps//oxeltech.de/en/system-on-chip-soc-vs-syste
m-on-module-som/) SoC Vs SoM System On Chip Vs
System On Module (Https//Oxeltech.De/En/System-O
n-Chip-Soc-Vs-System-On- Module-Som/) Team
Oxeltech December 23, 2022 What is System on
Chip, SoC? A System on Chip or SoC is a key
component in Embedded Systems today. An SoC
refers to a Read More (H ps//Oxeltech.De/En/Syste
m-On-Chip-Soc-Vs-System-On-Module-Som/)
Would You Like Some Info?
Name Name Email Email Message
9
3/3/23, 300 PM
Hold-Up Capacitor Value Calculations Uses
Message
Oxeltech
Send Lets Discuss
Share
Contact Us for any Queries
info_at_oxeltech.de (mailtoinfo_at_oxeltech.de)
(mailtoinfo_at_oxeltech.de)
49176 64738476 (Tel[phone])
(h p s//w
(tel[phone]
ww.li
nkedi n.co m/co mpan y/oxe ltech /)
Hardware Design Simulation(h ps//oxeltech.de/en
/hardware-design-simulation/) PCB Layout
Assembly(h ps//oxeltech.de/en/pcb-layout-assembly
/) Firmware Development(h ps//oxeltech.de/en/
rmware-development/)
Imprint(h ps//oxeltech.de/en/imprint/)
Contact Us(h ps//oxeltech.de/en/contact-us/)
Blog(h ps//oxeltech.de/en/blog/) Member Of IHK
(Https//Www.Ihk.De/)