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Hello everyone, today we will learn about the introduction of the standby power supply circuit

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during the startup process of the laptop

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First, let's take a look at the workflow of the standby chip

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The first step in the standby chip workflow, first it needs to get the main power supply

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After the common point voltage is normal, provide a main power supply to the standby chip

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At the same time, a linear turn-on signal is generated by voltage division or other methods

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to provide the turn-on signal for the LDO module

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Then after the chip gets the main power supply and the linear turn-on signal,

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it will control to generate 3.3V linear and 5V linear output

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Among them, the 3.3V LDO linear power supply will provide standby power to the EC

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Then the internal clock of the EC starts to work

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The standby power supply will delay to generate the EC standby reset,

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or the reset is generated internally by EC

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Then EC will read the program and configure its own pins

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After the conditions are met, the EC will send an open signal to open the PWM

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This 5V linear powers the PWM core

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Because when the PWM is working in the future,

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its boot pin bootstrap boost needs this 5V as the bootstrap base voltage

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The 5V pulse output by the lower tube driver also needs this 5V linear power supply

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There are still many modules inside the chip that need to use this 5V linear power supply

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Then after the EC sends the open signal,

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it will control and generate two PWM outputs.

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Among them, the PWM output voltage of 3.3V will provide power

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for the deep sleep standby or main standby of the bridge

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Most of the 5V PWM output voltage is to provide power to some power supply chips,

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such as USB power supply, CPU power supply, memory power supply, etc.

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These power supply chips need to use this 5V PWM to provide the main power supply

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Well, overall speaking,

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the working process of the standby chip is to have the main power supply first,

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and then have a linear turn-on signal

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After that, there will be a linear output,

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and then supply power to the PWM core after the linear output.

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After the chip gets the open signal, it will control the generation of PWM power supply output,

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and finally generate the PG signal

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This is the workflow of the standby chip

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The whole LDO and PWM part are integrated in one chip

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Next, we take the TPS51125 standby chip as an example to introduce its working process

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First briefly introduce the definition of the pin

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The first pin ENTRIP1 and the sixth pin ENTRIP2

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These two pins are open pins,

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which are the opening of the PWM and the limit current setting of the two PWMs

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Because it controls a PWM power supply output on the left

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and controls a PWM power supply output on the right

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which is called dual PWM controller,

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which is a very common 3.3V and 5V standby power supply chip in laptops

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The second and fifth pins are PWM feedback pins FB

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The third pin, VREF, is a reference voltage and a linear output

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The fourth pin is TON frequency setting

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The 24th pin and the 7th pin are VO pins, which are the voltage detection input pins of two PWMs

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The 8th pin VREG3 is a 3.3V linear output

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The 9th pin VBOOT2 and the 22nd pin VBOOT1, two bootstrap boost pins

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DRVH is the upper tube drive, DRVL is the lower tube drive, LL is the phase pin

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Here is the same

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DRVH and DRVL are upper and lower tube drivers, phase pins, etc.

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The above PG is PGOOD, which is generally an open-drain output

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The bottom EN0 is linear open

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SKIPSEL is the working mode setting

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GND is the ground, VIN is the main power supply of this chip

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VREG5 is a linear output of 5V

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VCLK is the clock, its clock is equivalent to the drive of the lower tube,

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and the output is used for external bootstrap boost

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Well, let's take a look at it

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To work, a chip must first get the main power supply,

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and the power supply input from 5V to 28V is provided externally

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Then it needs to get an open signal

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This is a linear open signal, usually from an external voltage division

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With the linear open signal, it will first generate a 2V reference,

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and then generate a 5V linear and a 3.3V linear

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Among them, the 3.3V linear voltage will provide standby power supply to EC,

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and provide standby conditions for EC

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Most of the 5V linear voltage is used inside the chip

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Then, after receiving the open signal sent from the outside,

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it controls the generation of two PWM outputs

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The open signal is like this

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The ENTRIP1 and ENTRIP2 are externally grounded through resistors,

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and are also connected to two N-channel MOS tubes

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If the two MOS tubes are turned on and grounded,

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then these two pins will become 0V, and the PWM output will be turned off

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Therefore, the two MOS tubes connected externally must be cut off

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This is generally controlled by the high level sent by the EC,

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which pulls down the G poles of the two MOS tubes and makes the MOS tubes cut off

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ENTRIP1 and ENTRIP2, the first pin and the sixth pin are pulled up by 5V linear voltage inside the chip,

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and then form a series voltage divider with an external pull-down resistor to turn on the two PWM outputs

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Usually the voltage of these two pins is around 2V,

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After the two-way PWM output,

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it will pass through the VO pin and the FB pin to be detected whether the two output voltages are normal

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When the two power supply outputs are stable, the PG signal is output from the PGOOD pin open drain

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Ok, this is the workflow of the standby chip