1

00:00:00,400 --> 00:00:05,733

Hello everyone, today we are going to learn the switching power supply mode composed of MOS tubes

2

00:00:07,900 --> 00:00:12,266

Switching power supply mode is to use the conduction and cutoff of MOS tube

3

00:00:12,366 --> 00:00:15,566

to control the opening and closing of power supply

4

00:00:17,633 --> 00:00:23,433

For example, switching the standby voltage to the boot voltage, or switch the voltage,

5

00:00:24,100 --> 00:00:28,100

such as switch the S3 voltage to the S0 voltage

6

00:00:29,066 --> 00:00:34,033

We can also call this type of power supply DC to DC, or flat to flat

7

00:00:35,166 --> 00:00:38,666

In other words, its power supply is flat conversion,

8

00:00:39,000 --> 00:00:42,000

no voltage drop, and the loss is small

9

00:00:44,966 --> 00:00:49,300

But there is a condition that it must meet the conduction condition of MOS tube

10

00:00:50,266 --> 00:00:53,366

For example, this is a P-channel MOS tube

11

00:00:53,866 --> 00:00:58,866

The G-pole voltage of the P-channel MOS tube must be more than 4.5 volts

12

00:00:58,866 --> 00:01:02,500

less than the S-pole of it to be fully conductive

13

00:01:03,766 --> 00:01:08,900

In order for its G-pole voltage to be less than 4.5V at the S-pole,

14

00:01:09,300 --> 00:01:16,000

the G-pole must be low, that is, below 0.5V, because the S-pole is 5V

15

00:01:16,833 --> 00:01:23,766

Only when the G-pole voltage is below 0.5V, will it be 4.5V smaller than S

16

00:01:24,766 --> 00:01:29,233

So how does this G-pole voltage get below 0.5V?

17

00:01:31,400 --> 00:01:36,700

We have to get this MOS tube down here on, pull this G pole down

18

00:01:40,066 --> 00:01:44,566

After pulling down, the low level can control its conduction

19

00:01:45,966 --> 00:01:53,000

In this diagram, when G pole is 4.5V below the S pole, the D and S poles are on,

20

00:01:56,633 --> 00:02:00,266

and it has an internal resistor of 18 milliohms,

21

00:02:00,433 --> 00:02:02,766

which is called the internal resistor

22

00:02:16,066 --> 00:02:17,966

Okay, this is a MOS tube

23

00:02:18,900 --> 00:02:23,866

G is less than 4.5V above the S pole, fully conductive,

24

00:02:24,400 --> 00:02:29,133

and has a resistor of 18 milliohms between the D and S poles

25

00:02:33,766 --> 00:02:36,233

Ok, this is the switching power supply mode,

26

00:02:36,833 --> 00:02:41,900

control 5V to 5V, 3.3V to 3.3V