Apr 20, 2017 How can I fix my PC when Windows 10 won’t boot? That depends on Windows 10 counting boots correctly. It may bring up WinRE or the UEFI/Trusted Platform Module (TPM) screen –.
![]() Summary :
Windows 10 stuck on loading screen' is a very common issue nowadays, and this post introduces you several solutions to deal with this issue effectively. Please try them one by one and hope they are helpful in removing Windows 10 freezing on loading screen.
Quick Navigation :'Windows 10 Stuck on Loading Screen' Issue Occurs
Windows 10 is the latest Windows Operating System (OS) and it owns many great features which are available only on Windows 10. Many users choose to update their Windows OS to this version to enjoy its charming features. However, no Windows OS is perfect. Windows 10 is not an exception.
Here, it is said that many Windows 10 users have encountered this issue: 'Windows 10 stuck on loading screen'.
What is the truth? When you search this issue online, you will discover that quite a lot of Windows 10 users post this issue on different forums to seek an available solution.
Apparently, this is a very common issue. And when it appears, you will see the computer screen displays Windows 10 black screen with loading circle and cursor (see the following picture).
Don't worry if Windows stuck on welcome screen! Here, you can find 7 effective solutions to solve this issue.
Under what circumstance can this issue be triggered? You can read the next section to get the answer.
When 'Windows 10 Hangs at Loading Screen' Issue May Happen?
Windows 10 stuck on black screen with spinning dots may occur in different situations. Three common scenarios are here:
1. Windows Update Stuck on Loading Screen.
Some users say that they want to upgrade their Windows OS to the latest Windows 10, but finally, Windows 10 stuck on black loading screen without any process issue happens.
2. Windows 10 Stuck on Spinning Dots on Startup
A lot of users claim that they are unable to turn on Windows 10 normally because it has been getting stuck on the black screen with white spinning dots at the bottom just before the login screen.
3. Windows 10 Hangs at Loading Screen When Upgrading Nvidia Drivers
A few Windows 10 users post on the internet that when they try to update their Nvidia drivers, the computer screen becomes black suddenly. After doing a hard reset of the system, Windows 10 black screen spinning dots issue occurs.
Of course, there are also other circumstances which will not be listed in this post. However, the result is the same: Windows 10 stuck on black screen with spinning dots.
This is really an annoying thing because you are unable to boot your computer properly. Thus, to get your computer out of the Windows 10 freezing on loading screen issue is the highest priority. In this post, we collect several methods which receive some positive feedbacks on the internet. If you are facing the same issue, please try them one by one.
Method 1: Unplug USB Dongle
If Windows 10 stuck on loading screen occurs, please try to disconnect all the worked USB dongles. Here USB dongle means the device which is connected to your computer with a USB cable including blue tooth, SD card readers, flash drive, wireless mouse dongle, and more.
This method gains a lot of positive feedback online. And if you are lucky enough, the issue will be solved. If not, please continue to try the next method.
Method 2: Do Disk Surface Test
If the hard drive has bad sectors, the possibility of 'Windows 10 stuck on loading screen' issue is great. So, you need to do disk surface test and shield the bad sectors.
To achieve these aims, we recommend you to use a piece of professional partition magic manager. And MiniTool Partition Wizard is a good choice.
In this case, you can't boot your computer normally, thus you can use this software's 'Bootable Media' feature to build a bootable disc/flash drive and then set your computer to boot from this bootable device.
Here, you should know that this feature 'Bootable Media' is available in all registered MiniTool Partition Wizard. Here take MiniTool Partition Wizard Professional Edition as an example.
You can refer to these two posts to get the bootable media, and then boot your computer from it:
1. How to Build Boot CD/DVD Discs and Boot Flash Drive with Bootable Media Builder? 2. How to Boot from Burned MiniTool Bootable CD/DVD Discs or USB Flash Drive?
You need to select the target disk after entering the software's main interface, and then click on 'Surface Test' feature from the left action pane. Then, click on 'Start Now' button to start surface test process.
During this process, the bad sectors will be marked as red, and the normal sectors will be marked as green.
If there are bad sectors on the hard disk, you need to shield them. Under this circumstance, you need to use CHKDSK of Window snap-in tool. Just go to the Safe Mode to run Command Prompt and type chkdsk c: /f to shield these bad sectors.
Tip: How to enter Safe Mode in this case? When Windows 10 stuck on loading screen issue happens, to enter safe mode, you should boot your computer from the bootable disk, or shut down your computer abnormally once or more times until your computer boot with 'Automatic Repair' screen. Then select Advance options > Troubleshoot > Advanced options > Startup Settings > Restart, after your computer restart, press 4 or F4 on the keyboard to start your PC in Safe Mode.
After that, you can restart your computer. If 'Windows 10 stuck on loading screen' problem happens again, the hard drive may be damaged. Under this situation, you should consider replacing the original hard disk.
However, you may want to clone the original data on the target hard drive in advance. Here, you can use 'Copy Disk' feature of MiniTool Partition Wizard Bootable Edition to clone data on the hard drive.
Step 1: to clone hard drive data, you should select the disk you want to copy and click on 'Copy Disk' from the left action pane. On the first pop-out window, you need to select the target disk which you want to use as the alternative disk and press 'Next' to continue.
Here, you should know that the content on the target disk will be deleted. So, please make sure that there is no important data on it.
Step 2: on the second pop-out window, please choose the copy options according to your own needs and click 'Next' to continue.
Step 3: after that, you will enter a window which tells you how to boot from the destination disk. Read the 'Note' and click on 'Finish' button to go back to the main interface. Then, click on 'Apply' to execute this copy operation.
In addition, MiniTool ShadowMaker, free PC backup software, also offers you a feature to clone a hard drive for backup with simple clicks. Just use it to back up your disk data when Windows 10 stuck on spinning dots issue occurs due to bad sectors.
After copying disk, your data on the source disk will be kept well on the destination disk. Then you will not be bothered by the risk of data loss caused by 'Windows 10 hangs at loading screen' issue.
Of course, 'Windows 10 freezing on loading screen' issue may be caused by other reasons. You can also try the following methods to solve this issue.
Method 3: Enter Safe Mode to Fix This Issue
Entering Safe Mode and doing something useful is another easy way to fix this issue. Here, there are four different operations for different situations after you enter the Safe Mode. You can select a proper operation according to your actual situation.
1. If you encounter this issue when you are trying to update Nvidia Derivers, you can enter the Safe Mode and make a roll back of the Nvidia drivers. Then try to restart your computer in normal mode.
2. In some cases, 'Windows stuck on loading screen' issue is caused by Windows update or other problems. At this time, you can enter the Safe Mode, do nothing and then reboot your computer.
3. Virus or malware may cause 'Windows stuck on loading screen' issue. Why not use a piece of antivirus software to scan your computer in Safe Mode, remove all the virus and malware from your computer, and then try to restart your computer.
4. It is possible that the installed antivirus software conflicts with the current Windows OS, and then 'Windows 10 stuck on spinning dots' issue happens when you want to start your computer. So, you can uninstall that antivirus software in Safe Mode, and then restart your computer to verify whether it is normal.
On condition that this method is unavailable for your case, we have the fourth way to be recommended. Please read on.
Method 4: Do System Repair
In case that there is something wrong with Windows 10 system, you can do system repair to fix it. Since you can't boot Windows 10 normally, you need to use a Windows 10 installation CD or enter the Safe Mode to open command prompt window and type 'bootrec.exe /fix' to do a system repair.
If system repair still doesn't work for you, try method 5.
Method 5: Do System Restore
If the above four methods can't fix 'Windows 10 freezing on loading screen' issue, you can also do a system restore which will take your computer back to an earlier point in time. However, you have to make sure that there is a full system backup on your computer, and the system protection is turned on.
Here, you still need to do it in Safe Mode. Please follow these operations: press 'Start' button > select 'Control Panel' > search for 'Recovery' > click 'Open System Restore' > press 'Next' > choose the restore point you want to use > select 'Next' > choose 'Finish'.
Note: If you don't see any restore points and receive the warning 'System protection is turned off. To turn it back on so that you can use System Restore, configure system protection' after you click 'Open System Restore', this method will be unavailable because you can't turn on system protection in Safe Mode.
If this method doesn't work for you, please try the next method to fix Windows 10 stuck on spinning dots issue.
Method 6: Clear CMOS Memory
Misconfiguration of BIOS may be the cause of Windows 10 freezing on loading screen. So you can clear the BIOS memory on the computer motherboard which can return the BIOS settings to the factory settings.
Method 7: Replace CMOS Battery
If your computer has been used for more than three years, you should consider replacing the CMOS battery. There are real cases show that if CMOS battery is powered off for an extended amount of time, 'Windows 10 hangs at loading screen' issue may happen when you boot your computer.
Method 8: Check Computer RAM
'Windows 10 stuck on loading screen' issue may also happen if the computer RAM is loose. Under this circumstance, you should cut off the power of your computer, open the computer case, and reinstall the RAM. After that, you can restart your computer to check whether it can boot normally. Of course, you can try this method twice if this issue is not solved after the first try.
Method 9: Clean Reinstall Windows 10
If all of the above methods are unavailable to solve 'Windows hangs at loading screen' issue, you should try to do a clean reinstallation of Windows 10. Before reinstallation, you can use 'Copy Disk' function of MiniTool Partition Wizard Bootable Edition to back up all data on the computer, format your computer hard drive and then reinstall Windows 10 to fix Windows 10 stuck on black loading screen.
Method 10: Roll back to a Previous Version of Windows
Sometimes, this problem is solved with one of the above methods, but you feel regretful after installing Windows 10 or even days later you encounter this issue again, so you want to go back to a previous version of Windows.
However, you should first check whether you have the chance to do this. General speaking, you have 10 days to roll back to your previous Windows OS since Windows 10 Anniversary Update (Version 1607).
Then, you will be able to roll back to an earlier version in WinRE by going to Choose an option > Troubleshoot > Advanced options and choose the option Go back to the previous build or Go back to the previous version.
Tip: Sometimes, you may fail to perform Windows 10 rollback since the option is grayed out after 10 days. Here, this post - 3 Ways to Go Back to an Earlier Build Not Available Windows 10 shows you more solutions.
Bottom Line
When you are facing 'Windows 10 stuck on loading screen' issue, don't be panic and annoyed. Please try these 10 methods which are introduced in this post. There is always a way which can solve this problem.
In addition, you can leave your related questions on the comment bar. Meanwhile, if you have your own ideas and suggestions, you can also share with us or send an email to [email protected]. Thank you!
Abstract
Switching converters on applications demanding reduced output noise may encounter delayed startup, or may not startup at all, due to excessive output inrush. Output inrush current, attributed to inappropriate design of output filters and its impact, can be minimized by increasing the soft start time, increasing the switching frequency, or decreasing the output capacitance. In this article, practical design considerations toward preventing start-up issues due to excessive output inrush will be presented.
Introduction
Many switching converter designs are driven by stringent output noise requirements. The demand for low output noise has pushed designers to implement heavy output filtering, such as using several capacitors at the output. With increased capacitance across the output rail, excessive inrush current may become an issue during startup that can potentially lead to inductor saturation or damage of the power switch.
The power switch of a monolithic switching regulator is internal to the chip, as opposed to a switching controller. This is an ideal approach on point-of-load switching converter applications, because of advantages like smaller PCB footprint and better design of the gate-drive circuit. This means that protection against overcurrent becomes a necessity to avoid damaging not only the switch, but the regulator chip itself. The ADP5070 dual, high performance dc-to-dc monolithic switching regulator is an example, as illustrated in Figure 1.
To prevent damage during output overload condition or startup when high current flows through the internal switch, switching regulator manufacturers employ different current-limiting techniques on monolithic switching regulators. Despite the existence of current-limit protection, the switching regulator may not properly operate as intended, especially during startup. For instance, with hiccup mode as the current-limit protection, at initial power-up when the output capacitor is still fully discharged, the switching regulator may enter hiccup mode, causing a longer start-up time or potentially not starting up at all. The output capacitor may pull excessive inrush current that, in addition to the load, causes the inductor current to go high and hit the hiccup mode current-limit threshold.
Overcurrent Protection Schemes
Integrating the power switch inside switching converters makes the current-limiting protection a basic function. Three commonly used current-limiting schemes are: constant current-limiting, foldback current-limiting, and hiccup mode current-limiting.
Constant Current-Limiting
For a constant current-limiting scheme, the output current is held constant to a specific value (ILIMIT) when an overload condition occurs. As a result, the output voltage drops. This scheme is implemented by using cycle-by-cycle current-limiting that utilizes the peak inductor current information through the power switch to detect the overload condition.
Figure 2 shows a typical inductor current of a buck converter during normal and overload conditions for the peak current-limiting scheme. During overload condition, as illustrated by ILIMIT, the switching cycle is terminated when the peak current detected is greater than the predetermined threshold.
In the constant current-limiting scheme, the output current is maintained at ILIMIT, resulting in high power dissipated in the regulator. This power dissipation causes the junction temperature to increase, which may exceed thermal limits.
Foldback Current-Limiting
The foldback current-limiting scheme partially solves the issue with constant current-limiting, helping to keep the transistor in its safe operating area under fault or overload conditions. Figure 3 shows the comparison of the VOUT vs. IOUT response curves between the constant and foldback current-limiting schemes. The reduction in output current (IOUT), as opposed to constant current-limiting, reduces power dissipation, thus reducing the thermal stress on the switching converter.
The disadvantage of this scheme is that it is not fully self-recoverable. Due to its foldback nature and depending on the nature of the load, the operating point could fall into the foldback region toward the short circuit operating point once the current-limit threshold was reached or exceeded. This would require power cycling the part or re-enabling the part to get back to the normal operating condition.
Hiccup Mode Current-Limiting
In a hiccup mode current-limiting scheme, the converter switching goes into a series of short burst of pulses followed by sleep time--hence the name hiccup. Once an overload condition occurs, the switching converter enters hiccup mode, where sleep time refers to the switch being turned off for a predefined period of time. At the end of the sleep time, the switching converter attempts to start again from soft start. If the current limit fault is cleared, the device resumes normal operation—otherwise, it re-enters hiccup mode.
The hiccup mode current-limiting scheme overcomes the drawbacks of the two overcurrent protections discussed. Firstly, it solves the thermal dissipation problem, as the sleep time reduces the average load current that allows the converter to cool down. Secondly, it allows smooth autorecovery once the overload condition is removed.
However, some issues may arise if the hiccup mode detector is active during startup. Excessive inrush current, in addition to the load current, may cause the inductor current to go beyond the current limit threshold, which triggers hiccup mode and prevents the converter from starting up. For example, the negative output of the inverting regulator of ADP5071, configured to have an output voltage of –15 V and 100 mA output current with around 63 μF of total output capacitance, is not starting up after powering from a 3.3 V power supply. The negative rail is under hiccup mode, as shown in Figure 4, which is triggered by the large output inrush current. Inductor current peak goes to around 1.5 A, exceeding the typical current-limit threshold of around 1.32 A.
Also, if there’s excessive inrush due to large output capacitance, the converter may get unexpected longer start-up time, as shown in Figure 5.
Inductor Current in Switching ConvertersInductor Current Average
In nonisolated switching converters, the location of the inductor defines the converter topology. With a common ground reference between input and output, there are just three distinct rails possible for the position of the inductor: the input, the output, and the ground rails.
Refer to the three basic switching topologies shown in Figure 6. When the inductor is at the output rail, the topology is a buck. When it is at the input rail, the topology is a boost. And when the inductor is at the ground rail, the topology is an inverting buck-boost.
During steady-state condition, the average current (IOUTRAIL) on the output rail must be equal to the output current since the average current on the capacitor is zero. For a buck topology, IL-AVE = IOUT. However, for the boost and the inverting buck-boost topologies, ID-AVE = IOUT.
For boost and inverting buck-boost topologies, it is only during switch-off time that current flows through the diode. Therefore, ID-AVE = IL-AVE during switch turn off. Refer to Figure 7 in deriving the average inductor current with respect to the output current. The rectangular area in green during switch-off time is the average diode current ID-AVE, with height equal to IL-AVE, and width equal to TOFF. This current all goes to the output and, therefore, can be translated into a rectangular area averaged to a width of T and with height IOUT.
Table 1 shows a summary of the average inductor current IL-AVE and switching duty cycle D. Based on the equations, the inductor current will be at its maximum when the input voltage is at its minimum providing maximum duty cycle and when the output current is at its maximum.
Inductor Current Peak
Figure 8 shows inductor voltage and current waveforms of a buck-boost inverter in a steady-state condition in continuous conduction mode of operation. As to any switching topology, the amount of inductor current ripple (∆IL) can be derived according to the ideal inductor Equation 2.
In switching converter applications where the inductor current is triangular and exhibits a constant rate of change, and therefore constant induced voltage, (∆IL/∆t) can be used in the inductor equation, as found in the rearranged Equation 3. Inductor current ripple is determined by the applied voltseconds to the inductor and the inductance.
Switch turn-on time can be easily related to duty cycle and switching frequency as in Equation 4. It is therefore more convenient to use voltsecond products during switch turn-on than switch turn-off in the succeeding formula.
Table 2 shows a summary of the inductor current ripple in the three different topologies. The voltseconds product term tON, based on Equation 3, is replaced by Equation 4, and the term VL-ON is replaced by the induced voltage across the inductor according to topology.
Looking back at the steady-state inductor current in Figure 8, it will be observed that the inductor current average simply lies at the geometrical center of the ramp or the swinging of waveform at the point ∆IL/2. Therefore, the inductor current peak is the sum of inductor current average and half of the inductor current ripple, as shown in Equation 5.
Capacitor Inrush Current
The charging current or displacement current equation of the capacitor is defined in Equation 6. It states that current flows through a capacitor in correspondence to a rate of change of voltage across it.
The capacitor charging current should be considered when choosing output capacitor values for switching converters. At startup, assuming that the capacitor voltage is equal to zero or no capacitor charge, the output capacitor will begin to charge and draw as much current depending on the total capacitance and rate of change of the capacitor voltage, until the capacitor voltage reaches steady-state.
The rising of the output voltage in switching converters is a controlled ramp with constant slope so the rate of change equation can be simplified, as shown in Equation 7. Change in output voltage (∆V) corresponds to the output voltage at steady-state and ∆t corresponds to the time it takes for the output to reach its final value during startup, or what is commonly called soft start time.
If there is too much output capacitance (COUT) or if the soft start time is small, the current demanded from the regulator ICAP may be too high, which may cause problems with the converter operation. This large amount of current impulse is referred to as the inrush current. Figure 9 shows capacitor inrush current and output voltage during the startup of an inverting buck-boost converter with an output of 15 V, 10 µF output capacitor, and 4 ms soft start time.
Inductor Current Peak at Startup
A simple boost converter circuit is shown on Figure 10. When the transistor switch is on close switch, current flows through the inductor while no current flows through the output rail. It is the discharging phase of COUT where the discharging current (ICAP) goes to the output while none goes through the reverse-biased diode. When the transistor's open switch is off, current ID flows through the diode.
By Kirchhoff’s current law, the current through the output rail (ID) must be equal to the sum of the current flowing through the output capacitor (ICAP) and output load (IOUT). This is described by Equation 8.
This equation applies during every charging phase or when voltage is rising across the capacitor. Therefore, it is also applicable during the startup of a switching converter when the initial state of the output capacitor is discharged or when the output voltage is not yet in the steady-state value.
The inductor current peak during startup can be defined using Equation 5 and includes the impact of inrush current due to output capacitor. Equation 8 will be applied into the IL-AVE equations in Table 1, replacing IOUT with IOUT + ICAP. Inductor current peak equations during startup are summarized in Table 3.
For any of the three topologies, the inductor current peak is proportional to IOUT. In terms of output current, the output capacitor must be designed at full load conditions.
Most applications require operation within a range of input voltage. So against input voltage, there is a difference between the buck and the other two topologies in terms of the magnitude of the dc and ac components voltage of the inductor current. This can be understood better through Figure 11. For the buck, as input voltage goes up, ac component voltage goes up. Average current is equal to output current, so the dc component voltage remains constant. Inductor current peak is therefore maximum at maximum input voltage.
For the boost and buck-boost inverter, as input voltage goes up, ac component voltage goes up--but dc component voltage goes down because of the impact to the average current by the duty cycle, as shown in Table 1. The dc component voltage dominates, so the inductor peak current is at its maximum rating at minimum input voltage. In terms of input voltage, design of the output capacitor must be done at the maximum input voltage for buck and at minimum input voltage for boost and buck-boost inverter.
Mitigating Impact of InrushOutput Capacitor Filter
As shown in previous sections, too much capacitance at the output causes high inrush current that may cause the inductor current peak to reach the current-limit threshold during startup. Therefore, the right amount of capacitance is necessary to achieve smallest output voltage ripple, while maintaining good converter start-up performance.
For buck converters, the relationship between COUT and the peak-to-peak voltage ripple is defined by Equation 9.
For boost and inverting buck-boost converters, the relationship between COUT and the peak-to-peak ripple is defined by Equation 10.
Note that these equations neglect the effect of parasitic elements on the capacitors and inductors. These, in line with the rated specifications of the converter, can help the designer in limiting the capacitors added to the output. A good balance of filtering level and output inrush current are key considerations.
Second-Stage LC Filter
In certain cases, switching transients occur on the output voltage, as shown in Figure 12. If the magnitude is significant, it becomes an issue to the output load. The switching spikes are primarily caused by the switching transitions of the current on the output rail, which is the diode current for boost and buck-boost inverters. They can be magnified due to the stray inductance on the PCB copper traces. Because the spikes are in much higher frequency than the switching frequency of the converter, the peak-to-peak ripple cannot be reduced by the output filter capacitor alone—additional filtering is needed.
Figure 12 shows the periodic switching action of the inductor in a boost converter represented by the blue trace, and the output voltage ripple represented by the yellow trace. High frequency transients are observed within the ripple voltage upon the switching transitions of the inductor current.
A great article on analog.com that provides more insight on how to reduce the high frequency transients by second-stage LC filtering is “Designing Second Stage Output Filters for Switching Power Supplies” by Kevin Tompsett.
Ripple Measurement
The right measurement method is also important when getting the output voltage ripple. Incorrect measurement setup can result in inaccurate and high voltage ripple readings, potentially leading to over-design of the output capacitor. It is easy to make the mistake of putting too much capacitance at the output in the hopes of reducing voltage ripple without realizing the tradeoffs.
An application note done by Aldrick Limjoco entitled “Measuring Output Ripple and Switching Transients in Switching Regulators” should be of help. See the references for details.
Soft Start Feature
For boost and inverting buck-boost, a bigger impact is dictated by the increase of the dc component voltage of the inductor current. At lower input voltage, the increase in the duty cycle causes a big increase in the inductor current average as shown in the (1-D) factor in equations in Table 3—this is also illustrated in Figure 11. This means that the inrush current of the output capacitor has to be significantly reduced. It is achieved by increasing the soft start time (tSS) in Equation 7.
Most switching regulators (tss) have a soft start feature that refers to its capability, in order to give designers option to adjust the rise time of output voltage during startup. Changing the value of a single resistor is often the convenient method of adjusting the soft start time. Figure 13 shows the start-up waveforms of a buck-boost inverter. A significant 25% decrease in inductor current peak can be seen by a change in soft start time from 4 ms to 16 ms.
Increasing the Switching Frequency
Figure 14 illustrates the impact to inductor current by change switching frequency (fSW). Assuming that duty cycle D and output current are constant, the ac component voltage of the inductor current or ∆ IL/2 is affected by change in fSW, while the dc component voltage is not. Inductor current peak being inversely proportional is therefore lower at higher switching frequencies.
![]() ADP5070: An ExampleHow Large Can the Output Capacitance Be?
ADP5070 is a monolithic, dual-boost and inverting buck-boost regulator with hiccup mode current-limiting scheme as the overcurrent protection. Some customers forgot to consider the trade-off of putting too much capacitance at the output, especially at high duty cycle operating condition or at the minimum input voltage. This usually has led to start-up issues at the inverting output, because the inverting buck-boost regulator is designed with lower current-limit threshold than the boost regulator.
Figure 15 can be used as aid for application engineers as to how much capacitance is allowed at the output of ADP5070 to avoid start-up issues. Max COUT is shown vs. max IOUT on different input and output voltage combinations, using the direct relationship of inductor peak current to output current, including inrush in Table 3’s equation. It will help in the design limits of the output capacitor values after having considered the optimum VOUT ripple performance using either Equation 9 or Equation 10.
Both graphs were computed based on the shortest tSS and the current-limit threshold of the regulator. External components were chosen to be of much higher current handling capability than the regulator. In other words, the numbers in these graphs will definitely increase in magnitude if the tSS were increased.
For applications requiring higher output load current, ADP5071 should be considered. ADP5071 is designed with higher current-limit threshold than ADP5070 for both boost and inverting buck-boost regulators.
Computed vs. Measured Data
Figure 16 shows the start-up waveforms of the inductor induced voltage and current of the inverting regulator, while the data that follows in Figure 17 show the inductor current data both by computation using equation in Table 3 and measured bench data.
The data proves that inrush current is greatly reduced if tSS is increased, thereby lowering inductor peak current. At 4 ms tSS, the inverting regulator is already hitting the current-limit threshold of 0.6 A and has a tendency of having start-up issues. The remedy is to increase tSS to 16 ms to give enough inductor peak current margin.
Conclusion
This article has shown that careful design of the output filter capacitor is important in designing switching converters. Good knowledge of the factors influencing the inductor peak current during startup helps avoid start-up issues. Boost and inverting buck-boost converters are more prone to these issues, especially those using the hiccup mode current-limiting scheme.
A direct relationship between the inductor peak current and output inrush current has been provided. It will prove to be useful when designing the output capacitors while keeping track of the inductor peak current against current-limit threshold. For the same output conditions, output inrush current can be minimized by increasing the soft start time or the converter switching frequency.
This article comes as a reference material when designing a dc-to-dc switching converter using the ADP5070/ADP5071/ADP5073/ADP5074/ADP5075 series of monolithic switching regulators of Analog Devices.
References
Erickson, R.B. and D. Maksimovic. Fundamentals of Power Electronics, Second Edition. Springer, 2001.
Kirchhoff, Gustav. “Kirchoff’s Current Law.” Electronic Tutorials.
Limjoco, Aldrick S. Application Note AN-1144 Measuring Output Ripple and Switching Transients in Switching Regulators. Analog Devices, Inc., January, 2013.
Tompsett, Kevin. “Designing Second Stage Output Filters for Switching Power Supplies.” Analog Devices, Inc., February, 2016.
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