TI engineers share how to easily solve the overheating problem caused by overloading of power banks

alan000345

TI engineers share how to easily solve the overheating problem caused by overloading of power banks [Copy link]

If the power bank overheats while charging the mobile device, it can easily lead to safety problems such as fire and explosion. We often see such accidents in the media. Therefore, the designers of the power bank usually add overcurrent protection circuits and overheat protection circuits to increase the reliability of the product. The power bank industry is highly competitive and the cost pressure is great. Therefore, the simpler and more reliable these additional circuits are, the more competitive the product is. TI's reference design PMP9806 is designed to meet this customer demand. The input voltage of this reference design is 2.7-4.4V, and the output capacity is 18W (5V/3A, 9V/2A and 12V/1.5A). When the output current of the boost converter TPS61088 is greater than the set value, the output voltage will drop, effectively limiting the output power and output current, thereby avoiding the overheating problem caused by overload use of the power bank. Let's take a look at the specific circuit design. Figure 1 is the system block diagram of the TI reference design PMP9806. The sampling resistor RS converts the output current into a voltage signal VSENSE. The operational amplifier A1 amplifies VSENSE into VAMP1 and connects it to the input of the operational amplifier A2. VFB is the reference voltage of the TPS61088 FB pin, and VFB is 1.204V. When the output current is less than the current limit point, when VAMP1 is lower than 1.204V, the diode D is not conducting, the resistor RADJ is floating, and the voltage of the TPS61088 FB pin is only determined by the output voltage. When the output current is higher than the current limit point, when VAMP1 is higher than 1.204V, the diode D is conducting, VAMP2 directly follows the voltage of VAMP1, the voltage of the TPS61088 FB pin rises, and the output voltage drops. If the output current rises further, the output voltage will drop further. The drop in the output voltage is determined by the resistance value of RADJ. The smaller the resistance of RADJ, the greater the drop in output voltage. 102)]

Figure 1. PMP9806 block diagram

TI reference design PMP9806 design indicators

Table 1 gives the design indicators of PMP9806. The current limit value is set at 5% higher than the normal output. Once the output current is higher than the current limit, the output voltage drops immediately, thereby limiting the maximum output power and effectively preventing the overheating problem caused by overload use of the power bank.

Table 1. Design indicators

Input Voltage	Output Voltage/Output Current	Output Current Limit Point
3V- 4.2V	9V/2A	Io ≥ 2.1A
	5V/3A	Io ≥ 3.15A
	12V/1.5A	Io ≥ 1.575A

Parameter calculation of TI reference design PMP9806

Figure 2 shows the schematic diagram of the PMP9806 current limiting circuit. The two most critical parameters in this current limiting circuit are the selection of the amplification factor of the operational amplifier A1 and the selection of the parameters of the adjustment resistor RADJ.

Taking the output Vo=9V, Io=2A as an example, the current limit point is set at 2.1A. The sampling resistor is 25m ohm, so when the output current reaches the current limit point, the voltage VSENSE across the sampling resistor is: (1)

At this time, in order for the current limiting circuit to work, the output of operational amplifier A1 must reach the reference voltage value of TPS61088 FB pin 1.204V. Therefore, we can get the following equation:

(2) From this we can get the magnification of A1: 102)] (3) Therefore, R17 can be set to 232k ohm and R16 can be set to 10.5k ohm. 102)]

Figure 2. PMP9806 current limiting circuit When VAMP1 is higher than 1.204V, diode D is turned on and VAMP2 directly follows the voltage of VAMP1. Therefore, the following relationship can be derived: 102)] (4)

(5)

From the above formula (5), we can deduce the expression of RADJ:

(6)[/color ]

Where:

If you want to limit the output power to a smaller value, such as When the output current reaches 3A, the output voltage is 5.5V, then RADJ can be set to 121K. Figure 3 shows the test results of TI reference design PMP9806. The startup waveforms when the output current is 2A and 3A are shown. When the output current is 2A, the output voltage of the boost converter TPS61088 is 9V after the startup is completed. When the output current is 3A, the load current exceeds 2.1A current limit point, so the boost converter TPS61088 directly enters the current limiting state after startup, and the output voltage is only 6.2V. Figure 4 shows the dynamic waveform when the output current suddenly increases from 2A to 3A. We can see that the output voltage drops from 9V to 6.2V within 50us, quickly limiting the maximum output power. Within a certain range, it effectively prevents the overheating problem caused by overload during the use of the power bank. [/ url]

Figure 3. Startup waveform when the output current is 2A and 3A (VO=9V) (170, 102, 102)][url=http://e2echina.ti.com/cfs-file.ashx/__key/communityserver-blogs-components-weblogfiles/00-00-00-01-19/8345.2017_2D00_11_2D00_21_5F00_214443.png][/ url]

Figure 4. Dynamic current limiting waveform when the output current suddenly rises from 2A to 3A

TI reference design PMP9806 can help us easily solve the overheating problem caused by overload use of power bank. If used in conjunction with reference design PMP9779, The problem of output short circuit protection can be solved at the same time. The method provided by TI reference design PMP9806 is not only applicable to power banks, but also to products such as Bluetooth speakers, POS machines and electronic cigarettes. If you are interested, you can download the design documents from the TI website For reference.ashx/__key/communityserver-blogs-components-weblogfiles/00-00-00-01-19/3175.2017_2D00_11_2D00_21_5F 00_221047.png]

[align =left]If you want to limit the output power to a smaller value, for example, when the output current reaches 3A, the output voltage is 5.5V, then RADJ=121K.

TI reference design Figure 3 shows the startup waveforms when the output current is 2A and 3A. When the output current is 2A, the output voltage of the boost converter TPS61088 is Normal output is 9V. When the output current is 3A, since the load current exceeds the 2.1A current limit, the boost converter TPS61088 directly enters the current limit state after startup, and the output voltage is only 6.2V. Figure 4 shows the dynamic waveform when the output current suddenly increases from 2A to 3A. We can see that the output voltage drops from 9V to 6.2V within 50us, quickly limiting the maximum output power to a range, thus effectively preventing The overheating problem caused by overloading during the use of the power bank. color=rgb(170, 102, 102)]

Figure 3. Startup waveform when the output current is 2A and 3A (VO=9V) (170, 102, 102)]

Figure 4. Dynamic current limiting waveform when the output current suddenly rises from 2A to 3A

TI reference design PMP9806 can help us easily solve the overheating problem caused by overload use of power bank. If used in conjunction with reference design PMP9779, The problem of output short circuit protection can be solved at the same time. The method provided by TI reference design PMP9806 is not only applicable to power banks, but also to products such as Bluetooth speakers, POS machines and electronic cigarettes. If you are interested, you can download the design documents from the TI website For reference.ashx/__key/communityserver-blogs-components-weblogfiles/00-00-00-01-19/3175.2017_2D00_11_2D00_21_5F 00_221047.png][/url]

[align =left]If you want to limit the output power to a smaller value, for example, when the output current reaches 3A, the output voltage is 5.5V, then RADJ=121K.

TI reference design Figure 3 shows the startup waveforms when the output current is 2A and 3A. When the output current is 2A, the output voltage of the boost converter TPS61088 is Normal output is 9V. When the output current is 3A, since the load current exceeds the 2.1A current limit, the boost converter TPS61088 directly enters the current limit state after startup, and the output voltage is only 6.2V. Figure 4 shows the dynamic waveform when the output current suddenly increases from 2A to 3A. We can see that the output voltage drops from 9V to 6.2V within 50us, quickly limiting the maximum output power to a range, thus effectively preventing The overheating problem caused by overloading during the use of the power bank. color=rgb(170, 102, 102)]

Figure 3. Startup waveform when the output current is 2A and 3A (VO=9V) (170, 102, 102)]

Figure 4. Dynamic current limiting waveform when the output current suddenly rises from 2A to 3A

TI reference design PMP9806 can help us easily solve the overheating problem caused by overload use of power bank. If used in conjunction with reference design PMP9779, The problem of output short circuit protection can be solved at the same time. The method provided by TI reference design PMP9806 is not only applicable to power banks, but also to products such as Bluetooth speakers, POS machines and electronic cigarettes. If you are interested, you can download the design documents from the TI website For reference.Figure 3. Startup waveforms at output currents of 2A and 3A (VO = 9V) 102)]

Figure 4. Dynamic current limiting waveform when the output current suddenly rises from 2A to 3A

TI reference design PMP9806 can help us easily solve the overheating problem caused by overload of power bank. If used in conjunction with reference design PMP9779, it can also solve the problem of output short-circuit protection. The method provided by TI reference design PMP9806 is not only applicable to power banks, but also to products such as Bluetooth speakers, POS machines and e-cigarettes. If you are interested, you can download the design document from the TI website for reference.

Figure 3. Startup waveforms at output currents of 2A and 3A (VO = 9V) 102)]

Figure 4. Dynamic current limiting waveform when the output current suddenly rises from 2A to 3A

TI reference design PMP9806 can help us easily solve the overheating problem caused by overload of power bank. If used in conjunction with reference design PMP9779, it can also solve the problem of output short-circuit protection. The method provided by TI reference design PMP9806 is not only applicable to power banks, but also to products such as Bluetooth speakers, POS machines and e-cigarettes. If you are interested, you can download the design document from the TI website for reference.

电容器

What a powerful information sharing, there are also formulas. Please share more of this kind of information. It is a well-founded design. Heat dissipation power bank is really important. If not handled properly, it will explode.

qwqwqw2088

The test result of PMP9806 shows that the voltage dropped from 9V to 6.2V within 50us. I don't know how this was tested.

alan000345

qwqwqw2088 posted on 2018-11-30 10:15 The test result of PMP9806, it dropped from 9V to 6.2V within 50us, I don't know how this was tested

Oscilloscope, is it a high-end one? It is indeed difficult to measure, in such a short time, I feel that ti is still very strong.

szjrft

Yes, very good.

alan000345

szjrft posted on 2018-12-1 09:07 Yes, very good

Thank you