[introduction] climate calefacient, rich is rare be short of and be being polluted is the whole world is in the increasingly serious environment problem that face. Dynamoelectric bicycle is a kind of green that can replace car of traditional internal-combustion engine energy-saving tool, it is to alleviate one of solutions of environmental problem. China is the dynamoelectric bicycle market with the biggest whole world, sales volume reachs 49.8 million of 2021 by 30.5 million growth 2017, compound year of increase rate for 13.0% , 75.9% what held global total sales volume 2021.

How to cure angst of boat of dynamoelectric bicycle add? DC/DC converter technology has good plan

Climate calefacient, rich is rare be short of and be being polluted is the whole world is in the increasingly serious environment problem that face. Dynamoelectric bicycle is a kind of green that can replace car of traditional internal-combustion engine energy-saving tool, it is to alleviate one of solutions of environmental problem. China is the dynamoelectric bicycle market with the biggest whole world, sales volume reachs 49.8 million of 2021 by 30.5 million growth 2017, compound year of increase rate for 13.0% , 75.9% what held global total sales volume 2021.

Dc – dc (DC/DC) converter is a kind of dc (circuit of transformation of DC) power source. In configuration of different electric car power source, join batteries and line of dc transmit electricity need to use converter of a DC/DC at least. Input electric energy through storing temporarily, release electric energy in the output end of different voltage next, DC/DC converter can change volts d.c. value, from certain voltage value turns into another different numerical value. Store can parts of an apparatus is not magnetic field model store can parts of an apparatus (inductor, transformer) it is electric field model store can parts of an apparatus (capacitor) . Occupy sky comparing through adjusting (switch is in charge of / judge time specific value) control is inputted and can output the power between to flow. Such doing is to control output electric current of voltage, input, output electric current or keep constant power. On electric car, this converter basically is used at furnishing to assist laden device, for example lamp of horn, LED and other peripheral equipment.

Converter of ST advanced DC/DC develops an ode for dynamoelectric bicycle can

Want to alleviate the angst of add boat course of development of electric car user, use DC/DC converter is a good solution. Meaning law semiconductor rolled out new generation tall compositive L3751 of degree of DC/DC changeover controller, promoted the switch of schism power parts of an apparatus property. The controller chip of meaning law semiconductor uses high-powered grid driver, control the operation of high speed switch of MOSFET, reduce the dimension of Chu Nengyuan parts of an apparatus and radio radiate amount.

L3751 is 6V of limits of voltage of a job the general DC/DC synchronism to 75V changes controller, applied range is very wide. What new product can save applied circuit is exterior yuan of parts of an apparatus, simplify development process, at the same time cut PCB dimension. What L3751 has 40 accept second is the shortest guide a time, extremely tall voltage changeover is had to compare inside limits of frequency of switch of 100 KHz – 1 MHz. This controller uses pulse leap pattern, when light load, but utmost ground extracts high-energy effect, effective control outputs voltage ripple. Mode of compulsive PWM (FPWM) can maintain switch frequency inside laden limits constant, and utmost ground reduces output voltage ripple. Piece go up compositive grid driver is OK the amount that utmost ground reduces exterior component, and be standard VTH MOSFET only optimize a design. To ensure what the key such as dynamoelectric bicycle applies is safe, the safety with the overall buy inside controller protects a function, include output to shed monitoring of protection of protection, input voltage UVLO, internal tension, heat to close too.

     

L3751 function is described

L3751 is one is based on constant the former unripe step-down of framework of type of frequency voltage control changes controller. This chip cites feedback the base (the output voltage VOUT that FB) detects and in-house and referenced voltage (0.8V) is compared, bring in COMP next error signal is provided on the foot, be worth according to COMP voltage finally with interior but process designing frequency is toothed the comparison of wave result, control what outside power switch is in charge of to guide a time. If the graph is shown 2 times, in-house and main module includes:

? Manostat: For in-house circuit power supply, offer in-house and fixed referenced voltage. This module still realized voltage to monitor circuit (UVLO) , use at monitoring input voltage and internal tension;

? The driver of MOSFET of raceway groove of compositive and exterior N and lift capacitance circuit oneself: For power supply of driver of high margin switch

? Compositive and toothed wave makes circuit: The basis is in-house but signal adjustment occupies process designing oscillator or input synchronism to be compared for nothing; Answer function to circuit voltage transient to improve controller, realized way of the feed before input voltage

? Amplifier of voltage mode error

? PWM comparator and relevant imitate and digital circuit: Use at controlling the drive of in-house MOSFET

? The soft circuit that start and referenced voltage clamp implement: Move level to restrict surge electric current with Yu Zaiqi

? Adjustable without sensor or essence accurate cereal sheds limitative feeling to measure module and belch circuit; Handle overload and short circuit case

? The heat that prevents hot out of control shuts circuit

? Output voltage monitoring circuit: If output the 87% above that voltage measured value is worth in the target, can send PGOOD power supply good signal.                

     

The diode of controller emulates mode (DEM) can raise the application when light load can effect. When light load, DEM mode moves with DCM and pulse leap means, utmost land increases light load can effect, control output voltage ripple, reduce changeover loss with utmost ground. The mode of compulsive PWM (FPWM) inside laden limits can maintain switch frequency constant, and utmost ground reduces output voltage ripple, the proposal uses DEM pattern in the low noise application such as the power source in sensor or imitate circuit.

Referenced design

Meaning law semiconductor offers the referenced design that is based on L3751 for the user, if the graph is shown 3 times, apply to the DC-DC converter that inputs 12 VDC of voltage of voltage 36-72V DC, output, 10A.

        

 Graph 3: L3751 dc converter consults plan

 

     Graph 4: Reference board principle pursues

? Circuit description

Circuit of wave of the high capacity capacitor that input class component includes to form PI network, filter (C4, C5 and L1) , in order to reduce the radiate of high frequency radio that operation of high frequency switch causes. The VIN that inputs controller of join of voltage of dc bus line cites a base (the 20) that cite a base, there is series connection resistance in method. VIN is power supply of controller interior circuit, in-house LDO manostat furnishs in the meantime, output voltage in order to produce the Vcc of 7.5V. VIN still is the power source of in-house grid driver. Citing a base 20 on need joins a small MLCC electric capacity. Make can cite a base through inputting cent to press circuit to be in (bias voltage brings to bear on on the 1) that cite a base, so that controller is enabled when 40V, avoid batteries deepness to discharge. Once EN/UVLO brings crural voltage to exceed 1.2 V model to be worth, the soft phase that start can begin, SS/TRK brings crural voltage to rise, controller is started. To be in the controller when voltage of the smallest input can run 40V, the block of resistor R1 and R6 is worth individual choice 100K and 4.7K. To ensure control loop is stabilized absolutely, do not suffer the effect of capacitor type, controller realized III compensator, offerred two to was mixed at 0 o’clock for developer 3 the utmost, ensure phasic abundant spends enough to rise rank the function that jumps load.

? Function and test result

We checked circuit board below all sorts of laden conditions, got can effect and function test result.

                           

Graph 5: Input voltage is right can effect and laden change

Epilogue

Be in China, those who come from policy end, technology end, market end, demand end is new change to be aided together push dynamoelectric bicycle industry to accelerate development. Chinese day all two rounds give a frequency to exceed 1 billion, dynamoelectric bicycle is 80% countrymans give the option of travel. According to data of alliance of industry of network of 5G content couplet, increment market will amount to dimensions of market of predicting China dynamoelectric bicycle 2021 60 million. And the new technology such as efficient DC/DC converter can help system of electric car electron satisfy the demand with smaller, more efficient, better performance, promote market development thereby.

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