Car chargers that are routinely used to power car batteries (car 12V, truck 24V) are widely used in lithium battery charging in a variety of portable and handheld devices, such as: mobile phones, PDAs, GPS, etc.; car chargers must consider lithium batteries The actual demand for charging (constant voltage CV, constant current CC, overvoltage protection OVP), but also take into account the harsh environment of the vehicle battery (transient spike voltage, system switching noise interference, EMI, etc.); therefore, the power management selected by the car charger program The IC must meet the requirements of: high-voltage, high-efficiency, high-reliability, low-frequency (favorable EMI design) switching power supply chip; popularly speaking, it requires "skin".
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A brief introduction to the common car charger scheme is as follows:
[1] Schematic diagram of low-end car charging solution realized by single piece 34063
Advantages: low cost;
Disadvantages: (1) Poor reliability, single function; no over temperature protection, short circuit protection and other safety measures;
(2) Although the output is DC voltage, the way to control the output constant current charging current is the maximum switching power.
Flow peak limit, accuracy is not high enough;
(3) Since 34063 is 1.5A switching current PWM+PFM mode (no error amplifier inside),
Its car charging scheme output DC voltage and current ripple is relatively large, not pure enough; output current capability is also very
Limit; (common in low-end car chargers between 300ma and 600ma)
[2] Schematic diagram of car charging scheme for 34063+NPN (NMOS) to achieve current expansion
Advantages: The flow is expanded on the basis of the [1] scheme to meet the growing demand for charging current capability;
Disadvantages: There are similar deficiencies in the [1] scheme;
[3] Schematic diagram of the 2576+358+ voltage regulator
Advantages: (1) Due to 2576 built-in overcurrent protection, over temperature protection and other safety measures, combined with 358 (double op amp) to achieve output constant voltage CV, constant current CC, overvoltage protection OVP and other functions; achieve reliable, safe, Complete lithium battery charging solution;
(2) Since the 2576 is a fixed 52K PWM converter, the EMI design of the car charger is relatively easy;
(3) Since both 2576 and 358 are manufactured by 40V high-voltage bipolar process, they are more “skinnyâ€;
(4) This kind of scheme is commonly used in car chargers of 0.8A ~ 1.5A; Disadvantages: (1) The system is relatively complicated and the cost is high;
(2) Constant current CC and overvoltage protection OVP are realized by controlling the output of 358 to control the EN of 2576. Therefore, the charging current has a large ripple, and the response speed of CC and OVP is not fast enough (by switching 2576 whether Work to achieve);
[4] Schematic diagram of XLSEMI design single-chip car charger IC XL4002
Based on the system requirements in the field of car chargers, Shanghai Xinlong Semiconductor Co., Ltd. provides a series of single-chip ICs dedicated to car charging solutions; in addition to conventional overcurrent protection, over temperature protection, output short circuit protection, and built-in dedicated lithium battery Charging CV, CC, OVP; equivalent to integrating all functional modules such as 2576+358+ voltage regulator in [3] scheme into one IC;
Advantages: In addition to the corresponding advantages of the [3] scheme, there are:
(1) A fully integrated solution for car chargers with low system cost and high reliability;
(2) The internal CV, CC, and OVP of the IC are realized by controlling the PWM; therefore, the output voltage, the output current, the output overvoltage protection are more accurate, and the response speed is fast;
(3) Core Dragon provides a series of cost-effective products with charging current between 0A ~ 3A;
[5] XLSEMI car charger series product quick selection table
Model XL4001 XL4002 XL4101 XL4102
Switching frequency 150KHZ 52KHZ 150KHZ 52KHZ
Output current 2A 2A 3A 3A
Package SOP8-EP SOP8-EP TO263-5L TO263
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