Introduction to common solutions for portable notebook car adapters

With the rapid development and popularization of consumer electronic products, portable notebooks represented by knockoff notebooks, netbooks, EPCs, etc. have become the preferred devices for mobile office or entertainment computers that focus on mobility and portability. Portable notebooks are gaining wider popularity and application in the fields of office, life entertainment, portable electronic equipment, etc., with their high cost performance, high entertainment, wireless Internet access, mobile office, outdoor operation and other excellent performance.

Considering the mobility of portable notebooks, when used for a long time in special environments such as outdoor and field, in addition to improving the battery life of portable notebooks, a suitable external power supply is also required; with the popularity of household cars, car batteries have become an ideal power supply for portable notebooks to power outdoor; since the input power supply voltage of conventional portable notebooks is not completely consistent (copycat notebooks, EPC, conventional notebooks are mostly between 16V and 20V, and most netbooks are 12V, with differences between different brands and manufacturers), but the conventional car battery voltage is 12V for cars and 24V for trucks. Considering the factors of full and low power of car batteries, the battery voltage of cars is generally between 10V and 14.5V, and the battery voltage of trucks is between 20V and 28V; therefore, the car battery cannot directly power the portable notebook through the cigarette lighter plug, and must undergo voltage conversion, which requires a DC voltage conversion solution with high conversion efficiency, high output power (mostly between 30W and 90W), high reliability, environmental protection and energy saving, high cost performance, and small size, that is, a portable notebook car adapter solution.

Portable laptop car adapters must take into account voltage matching (depending on the actual laptop power supply requirements and the different car battery voltages, voltage conversion may require different topologies such as boost, buck, and buck-boost), and must also take into account the harsh environment of the car battery (transient spike voltage, engine noise interference, EMI, etc.). At the same time, it must also ensure sufficient output power (generally, the input power of a portable laptop with a 7-10 inch screen is about 30W-50W, and the input power of a 10-15 inch screen is about 50W-90W).

The following is a brief introduction to the conventional portable notebook car adapter solution:

[1] Inverter DC/AC + AC/DC Adapter

Advantages: This solution is a last resort when there is no other better solution. Since the AC/DC part is the standard AC adapter of a portable notebook, it can be directly connected to the 220V AC output of a regular car inverter;

Disadvantages: The system is relatively complex and costly overall; because of the two-stage power conversion, the overall system conversion efficiency is very low (the total maximum efficiency does not exceed 60%), the fuel economy is very poor, and there is a huge waste of energy, which is not cost-effective.

In the DC/AC part, the output power of the most popular and most common car inverter on the market is between 70W and 150W. The inverter circuit mainly uses a pulse width modulation circuit based on TL494 or KA7500 chips. The main implementation method of this solution is to directly convert the voltage of the car battery from DC12V or DC24V to AC220V, and then power the laptop through the AC/DC Adapter. Car inverters can be divided into two types: sine wave output and square wave output.

The advantages of sine wave output are: it can provide uninterrupted high-quality AC power and can be applied to any load. The disadvantages are: its technical requirements and circuit structure are relatively complex and the cost is high. The advantages of square wave output are: its technical requirements are low, the size is small, the circuit is simple, and the price is low.

[2] Adapter implemented using a flyback switching power supply topology

Figure 1 Schematic diagram of PWM controller + MOSFET to achieve FLYBACK

Advantages: Through simple system design, it is easy to achieve voltage reduction, voltage increase, and voltage-boost/voltage-reduction conversion.

Disadvantages: Since the system requires external power switching tubes and switching transformers, the switching frequency is relatively low (generally between 30Khz and 65K). Relatively speaking, the entire system has a relatively complex circuit, a relatively large volume, a low degree of integration (more discrete components are required on the periphery), and a low conversion efficiency (generally when the output power is around 50W, the efficiency is up to about 80%). In general, the system has a low power density, a large volume that is not conducive to portability, and a low cost-performance ratio.

[3] Boost PWM Controller + MOSFET Car Adapter

Figure 2 Schematic diagram of PWM Controller + MOSFET to achieve BOOST function

Advantages: Depending on the peripheral connection method, the application of boost topology and buck-boost topology can be easily realized.

Disadvantages: Since the voltage, current and temperature of the external power tube are not controlled and it works in a high temperature and high current state, there are many factors that affect the long-term reliability of the system. To ensure the safety and reliability of the system, additional auxiliary circuits are required to achieve this; for example: overvoltage protection OVP, overcurrent protection OCP, overheating protection OTP, etc., which will result in complex circuits, increased system costs, reduced efficiency and other unfavorable factors.

[4] XLSEMI portable notebook car power supply series solutions:

Shanghai Xinlong Semiconductor Co., Ltd. has long been focusing on the research and development of high-voltage, high-efficiency, high-current, high-reliability, and cost-effective monolithic switching power supply integrated circuits. For portable notebook car adapter solutions, XLSEMI provides a series of mature, high-efficiency, high-cost-effective, high-power density, and high-reliability monolithic high-power integrated circuit solutions with industry-leading technology levels.

1. Boost topology:

This topology can directly boost the 12V power supply of a car to the 16V~20V voltage required by a laptop, with an output current capacity of 2A~5A. The reference diagram is as follows:

Figure 3 Schematic diagram of XL6010/XL6011 implementing BOOST function

Features: (1) The system has a simple structure, convenient and flexible design, and can achieve very high efficiency (up to 93% at 50W output).

(2) Since the high-power switch tube is built-in, the voltage, current and temperature of the power tube are all controlled; at the same time, the chip has built-in soft start circuit, loop frequency compensation capacitor, internal fixed frequency, fully built-in overvoltage protection, overcurrent protection, overheating protection and other circuits. The reliability and safety of the chip are greatly improved, there are very few peripheral devices, the system size is small, the power density is high, and the cost performance is high.

2. Buck-Boost topology (SEPIC):

When a car battery (10V~14.5V) is needed to power a 12V portable notebook; or when the portable notebook's power supply requirement is around 16V~20V, but it is required to be compatible with both 12V and 24V batteries, a buck-boost topology must be used.

Figure 3 Schematic diagram of XL6010/XL6011 implementing SEPIC Buck-Boost function

Features: (1) The system has a simple structure, convenient and flexible design, and can achieve high efficiency (up to 90% at 50W output).

(2) The simplest, most efficient, and smallest monolithic, fully integrated buck-boost solution with high power density and high cost performance.

3. Buck topology

When it is required to power a portable notebook or other on-board electronic equipment only by using the truck's 24V battery, it is only necessary to simply step down the voltage; XL4005/4012 step-down application circuit (VIN=20V~30V, VOUT=12V/16V/19V)

Figure 4 XL4005/4012 BUCK function diagram

Features: (1) Fully built-in single-chip high voltage, high frequency, high efficiency, high current, high reliability, and high cost performance integrated circuit.

(2) The system design is simple, convenient and flexible, with high power density.

(3) Conventional over-current protection, over-temperature protection, and output short-circuit protection are all built-in.

(4) High efficiency, with an efficiency of over 90% when the input voltage is 20V-30V and the output power is 50W.

[5] XLSEMI Notebook Car Adapter Solution Quick Selection Table