Power Management Integrated Circuit (PMIC) Guide

I Basic definition

Power Management Integrated Circuits (PMIC) is a chip that is responsible for the conversion, distribution, detection, and other power management of electrical energy in electronic equipment systems. It is mainly responsible for converting the source voltage and current into power that can be used by microprocessors, sensors, and other loads.

II PMIC Types

The relatively wide range of power management includes power conversion (DC-DC, AC-DC, and  DC -AC), power distribution and detection, and systems that combine power conversion and power management. Accordingly, the classification of power management integrated circuits includes these aspects, such as linear power supply chips, voltage reference chips, switching power supply chips.  LCD driver chips, LED driver chips, voltage detection chips, battery charging management chips, gate drivers, load switches, wide bandgap switches, etc.

(1) Voltage regulator chips 

1) Linear regulator chips

(I) Traditional linear regulator chip

Linear regulators convert the input voltage (VI) to different output voltages (VO) using a linear component (i.e. resistive component) to regulate the output voltage VO. Below are the application circuits for linear regulators.

Figure 1. application circuits for linear regulators

(II) low dropout linear regulator chip

For linear regulators, an important type is a low dropout (LDO) linear regulator. It can continuously output a stable voltage when the difference between the input voltage (VIN) and the output voltage (VOUT) is very small.

The four key elements of  LDO  are:

- Dropout

- Noise

- Power Supply Rejection Ratio (PSRR)

- Static current Iq

(III) Advantages and disadvantages of linear regulator chips

Linear regulators are called "linear regulators" because the relationship between input and output is linear during operation. Because the input and output are connected in series with the control element, sometimes also called "series regulator".

Figure 2. Linear Regulator Circuit

Linear regulator chips are generally bucked by the control element, so the greater the voltage difference between input and output (the degree of bucking), the greater the losses and the lower the efficiency. Therefore, it is suitable for low-power power supplies.

2) Switching regulator

Switching regulators convert VIN to a different VOUT through a switching element and use an external inductor and capacitor to stabilize the output voltage VOUT. Switching regulators are generally more efficient and support higher output currents than linear regulators. However, there is still ripple or switching noise after the output has been regulated, which remains even after filtering.

I) Types of switching regulator chips

a) Buck converter chips

Buck type step-down switching regulator is the one whose input voltage is higher than the output voltage, and the conversion principle is shown in the following figure.

Figure 3. Buck-type step-down switching regulator conversion principle

Figure 4

①Detect the output voltage and compare it with the reference voltage.

②When it is lower than the set output voltage, the switch is ON and the current direction flows according to the red arrow.

③The inductor stores magnetic energy.

④When the output voltage is higher than the set voltage, the switch is turned OFF and the current direction flows according to the green arrow.

⑤ The inductor converts the stored magnetic energy into the current for the load output and then returns it to the inductor.

⑥When the magnetic energy of the inductor disappears and the output voltage starts to drop, the switch turns ON again.

By controlling the turn-off and turn-on time of the switch, a stable output voltage can be obtained.

Example of buck converter circuit application:

Figure 5. Buck Converter Circuit Application Examples

 b) Boost converter chip

The boost circuit is one of the six basic chopper circuits, a switching  DC boost circuit, which can make the output voltage higher than the input voltage. It is mainly used in DC motor drives, single-phase power factor correction (PFC) circuits, and other AC/DC power supplies.

Figure 6. boost converter circuit

Boost converter circuit application examples:

Figure 7. Boost Converter Circuit Application Example

c) Buck-boost converter  chip

Buck-boost converter is a DC-DC  converter whose output voltage magnitude can be greater than the input voltage or less than the input voltage. Buck-boost converters are equivalent to revertant converters, but with a single inductor instead of a transformer.

Figure 8. buck-boost converter

Examples of buck-boost converter circuit applications.

Figure 9. Buck-Boost Converter Circuit Application Example

d) Negative voltage converter chips

Figure 10. Negative Voltage Converter Circuit

Negative voltage converter circuit application examples.

Figure 11. Negative Voltage Converter Circuit Application Example

II) Advantages and disadvantages of switching regulator chips

The switching regulator chip turns on the switching element (MOSFET) and supplies power from the input to the output until the output voltage reaches the desired voltage. Once the output voltage reaches the specified value, the switching element is turned off and no more input power is consumed. By repeating this action at high speed, the switching element regulates the output voltage to the specified value.

Figure 12. switching regulator circuit

(2) Voltage reference chip

Within the rated operating current range, the accuracy of the reference voltage source device (voltage value deviation, drift, current regulation rate, and other indicator parameters) is much better than the ordinary  Zener regulator diode or three-terminal regulator, so it is used in the need for high-precision reference voltage as a reference voltage. It is generally used for A/D, D / A, and high-precision voltage sources. Some voltage monitoring circuits also use the reference voltage source.

Commonly used TL431 voltage reference chip application examples.

Figure 13. TL431 voltage reference chip application example 

(3) Voltage detection chip

Voltage detection chip circuit application examples.

Figure 14. Application example of voltage detection chip circuit

(4) Driver chips

Commonly used LED driver chip circuit application examples.

Figure 15. Application example of LED driver chip circuit

Commonly used digital display driver chip circuit application examples.

Figure 16. Digital display driver chip circuit application example

Commonly used gate driver chip circuit application examples.

Figure 17. Application example of gate driver chip circuit

III Application scope

The application range of power management integrated circuits is very wide. The development of power management integrated circuits is important to improve the performance of the whole machine. The choice of a power management integrated circuit is directly related to the needs of the system, and the development of digital power management integrated circuit still needs to cross the cost barrier.

In today's world, people's life is a moment that can not be separated from electronic equipment. Power management integrated circuit in the electronic equipment system is responsible for the transformation of electrical energy, distribution, detection, and other electrical energy management responsibilities. Power management integrated circuit is indispensable to the electronic system, and their performance has a direct impact on the performance of the machine.

IV Future trends

Power management integrated circuit has a bright future. Through the development of new processes, packaging and circuit design technologies, there will be more outstanding performance of the device is born, they can improve power density, extend battery life, reduce electromagnetic interference, enhance power and signal integrity and improve system security, to help engineers around the world to achieve innovation.