What Do You Know about Power Management ICs?

A power management chip refers to an integrated circuit chip that converts or controls the power supply and provides a suitable voltage or current for the normal operation of the load. In electronics, it is a very important type of chip in the analog integrated circuit.

Technical Parameters

The core structure of the power management chips is a PWM controller and MOSFET. The specific selections are based on the input/output voltage and current. The following criteria mainly reflect the manufacturer's chip technology level.

PMIC (Power Management ICs)

A PMIC is a small, multifunctional integrated circuit that implements voltage conversion, voltage regulation, and battery management. It controls and manages all aspects of the power system as follows:

Power conversion is to convert the voltage meet different power requirements.

Power management refers to ways to control power switches, adjust power supply voltage and current, etc.

Power monitoring is the real-time monitoring and feedback of parameters such as voltage, current, temperature, and power consumption to ensure system stability and safety.

The advantage of a PMIC is that it can integrate multiple power management functions into one chip, reducing system complexity and cost. In addition, it improves system efficiency and lifetime as it dynamically adjusts supply voltage and current based on system demand to minimize power dissipation and heat loss.

DC-DC Regulators

Depending on the method of voltage conversion used, DC regulators are divided into two categories: linear regulators and switching regulators. These are the two basic types of voltage regulators used in electronics such as cameras, cell phones, wearable devices, and computers. Designers will select the appropriate DC regulator for their systems based on input voltage, output voltage, and required current load.

1.Linear Regulator

A linear regulator converts an input voltage (VIN) to a different output voltage (VOUT), using a resistive component to regulate the output voltage VOUT.

General characteristics:

1) Dissipate power

2) For low current and low power rails

3) Not very efficient

4) For low-noise power supply

5) Low ripple and low noise make it suitable for sensitive analog integrated circuits, such as sensors, phase-locked loops, etc.

Linear regulators cannot store large amounts of unused energy, and if the dropout voltage is too large, the free power to the load will be dissipated as heat. They are working in the linear region, their function is to maintain a stable output voltage even when the input voltage or load current changes. Further more, they are primarily low drop-out regulators (LDO regulators). They have the following features:

LDO is the most widely used power chip in IoT electronic products.

Basic structure: Include four modules of voltage reference source, error amplifier, adjustment tube, and feedback resistor.

Working principles: The error amplifier, adjustment tube, and feedback resistor form the LDO control loop. When the input voltage or load current changes, the LDO can suppress the change of the output voltage through the negative feedback adjustment function.

2.DC-DC Switching Regulator

A switching regulator converts VIN to a different VOUT through a switching element and uses 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, but there is still ripple or switching noise after the output is regulated, even after filtering.

According to the relationship between input and output voltage, the following table is the classification, main functions, key parameters and application scenarios of DC-DC switching regulators.

Power Conversion Chips

The power supply of the vehicle system usually comes from the battery. For the specific power-consuming chips in the vehicle system, the battery voltage cannot be used directly, and a power conversion chip is needed to convert the meet voltage to the requirement. In addition, due to the special working conditions of the vehicle system, the voltage has a certain fluctuation range. The following two types of DC-DC switching power supply and LDO power supply are analyzed.

1）DC-DC Switching Regulator

The power tube of the DC-DC chip works in a high-frequency switching state, and uses inductors and capacitors for energy storage and filtering to achieve the function of voltage conversion.

According to whether the power tube is externally or internally integrated, the DC-DC chip can be further divided into a DC conversion controller and a DC switching converter. Usually, the DC conversion controller architecture is used for large current output scenarios, and the applications with small current output uses DC switching converter with integrated power transistor. According to the relationship between the output voltage and the input voltage, it can be divided into Buck, Boost, Buck/Boost types, except them, there also has Sepic, Cuk, Zeta and other topologies.

2）LDO Linear Regulator

LDO regulator is also widely used in voltage conversion of vehicle systems. Unlike the DC-DC switching regulator, the power tube of it does not work in a high-frequency switching state, but works at a specific point of the output characteristic curve. Compared with DC-DC chips, LDO has the advantages of lower noise, less external passive components, simple circuit, and less EMC interference. However, its power conversion efficiency is low, especially when the input-output voltage difference is large, the heat generation is significantly higher than that of DC-DC regulators, so it is not suitable for high-current output scenarios, and the output current is usually within hundreds of mA to several A.

For LDO, according to the adjustment method of the output voltage, it can be divided into general-purpose LDO and follow-up LDO.

General-purpose LDOs are the most widely used, and almost every vehicle-mounted system will have applications. The follower LDO has a specific application scenario, and the output voltage of the LDO needs to follow the change of the another LDO or the reference voltage.

BMIC (Battery Management Integrated Circuit)

1.Basic

BMIC mainly includes battery fuel gauges, battery safety chip, charging management chip. It can convert the external power supply into the charging voltage and current suitable for the battery cell, and monitors the charging state of the battery cell in real time during the charging process, adjusts and controls the charging voltage and current to ensure safe and efficient charging of the battery cell. According to the characteristics of the lithium battery, the BMIC chips automatically perform pre-charging, constant-current charging, and constant-voltage charging to effectively control the charging status of each stage.

BMIC can be divided into switch mode, linear mode and switched capacitor mode according to the working mode.

The switch mode has high efficiency and is suitable for high-current applications with higher flexibility. It can be designed as a buck, boost or buck-boost architecture according to needs. The commonly used fast charging scheme usually chooses it.

The linear mode is suitable for low-power portable electronic products. It does not have high requirements for charging current and efficiency, usually not higher than 1A, but it has higher requirements for volume and cost.

The switched capacitor mode can achieve an efficiency of more than 97%, but due to the structure, its output voltage and input voltage usually form a fixed proportional relationship, and it is usually used in conjunction with a switch-type charging management chip in practical applications.

Battery fuel gauge ICs are mainly used to collect battery voltage, temperature, current and other information, calculate battery power, health and other information through Coulomb integration and battery modeling, and communicate through communication ports such as I2C/SMBUS/HDQ with external hosts. They can be discrete or integrated with battery protection ICs.

The first-level protection ICs can control the charge and discharge MOSFETs, and the protection action is recoverable, that is, when safety events such as overcharge, overdischarge, overcurrent, and short circuit occur, the corresponding charge and discharge switches will be disconnected. Then the closed switch will be restored again, and the battery can continue to be used.

They are digital-analog mixed-signal chips, involving metering algorithms, AFE/ADC and computing circuits, etc. The core technology is reflected in metering accuracy, battery string management, platform voltage, power consumption level, etc. Among them, AFE has its own ADC, which can perform analog-to-digital conversion, but it needs to cooperate with an embedded MCU to realize the fuel gauge function.

2. Features

1) Battery status monitoring

BMIC can monitor battery status in real time, including power, temperature, voltage and other parameters. Under this, users can clearly understand the battery status of their own devices, so as to better plan the use time and method.

2) Charge control

BMIC can control battery charging to ensure battery life health and prolong it. In other words, it can achieve the best charging effect while keeping charging safe.

3) Discharge protection

BMIC can monitor the discharge rate of the battery, and when it is close to the critical point, it can automatically shut down the power supply to protect the battery from excessive discharge damage.

4) Charging protection

BMIC can protect the battery from overcharge damage during charging, including overvoltage, overcurrent, etc., to ensure the safe use of the battery.

5) Performance optimization

BMIC can improve the overall performance of the device with functions above mentioned.

3. Applications

They are used in the consumer electronics market, for example, mobile phones, PCs, PADs, watches, earphones and other products are mainly products with low strings (1-4 strings), in which BMS performs functions such as calculation, security, and charging management, and the majority of hardware products are SoC.

In the industrial control market, the terminal applications of battery management chips mainly include power tools, drones, industrial robots, and energy storage. They have the characteristics of large number of battery strings, high working voltage, and strong current, so they have high technical requirements for power supply and battery management chips. From the perspective of hardware product form, the battery management system (BMS) of electric tools is mainly based on the combination of AFE+MCU+active equalization+isolation/communication/protection chips, while the BMS in the energy storage field is mainly based on AFE+ protection chip solutions.

In the new energy vehicle market, the cost and performance of the battery itself have become the key points for the success of the OEM, and the life, fast charging, and cost of the battery are closely related to the optimization of the BMS.

Application Examples

1. Automotive Electronics

Power chips are widely used in automotive electronic systems, and different types chips are used in automotive electronic components according to application requirements. With the development of automobiles towards electrification, networking and intelligence, more and more power chips are used in bicycles, and the number of power chips used in new energy vehicles will exceed 100.

Introduce a typical power supply chip application case. The application of power chips in automotive motor controllers, and they are mainly used to generate various secondary power supplies, such as main control chips, related sampling circuits, logic circuits, and power device drive circuits to provide operating power or reference levels .

Figure 1 shows the power supply scheme of a traditional automotive motor controller. It is not enough to meet the functional safety requirements of the product.

Figure 2 is based on the scheme shown in Figure 1, and the SBC chip with monitoring and diagnostic functions is used instead, which improves the weak power supply, that is, the architecture has a certain functional safety level (such as ASIL B).

Figure 3 shows that on the basis of the first two, the monitoring and diagnosis of the low-voltage power supply are more complete, and at the same time, a high-voltage/low-voltage DC-DC backup power supply is added to meet the requirements of the highest safety level (ASIL D). Remarks in the dotted line box show the power topology constructed by using the power chips.

(Note, it is only a general solution for research within a certain range, not for all applications in the motor controller of the car).

2. 5G Development

Benefiting from the rapid development and popularization of 5G, power management chips have a huge market.

3. Consumer Electronics

Mobile phones, computers, Bluetooth headsets, fast charging, etc.

Development Trends

Power management chips are widely used in mobile phones, consumer electronics, industrial control, medical equipment, automotive electronics and other application fields. This means that it has a huge market with the development.

1. High Efficiency and Low Energy

1) High power conversion rate

2) Low standby power consumption

2. High Integration

1) The thinness and shortness of the power supply is the focus of optimizing the user experience.

2) Integration makes the chip smaller and has fewer peripheral devices.

3. Kernel Digitization

1) Used for low-voltage and high-current loads with precise voltage regulation.

2) Meet high load transient requirements

4. Intelligent

1)Adapt to the needs of continuous upgrading of the main chip functions.

2) Meet the needs of diagnosing voltage supply, flexible parameter setting, real-time interactive communication, etc.

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