Step-down Module
Introduction Step-down Module:
The starting voltage is 4.2V, when testing you should set the input voltage to 4.5V and the output voltage to 1.4V. IC Station Team test it on the digital oscilloscope and the result shows when the actual testing of the product is in accordance with the description.
In general, the performance of the LM2596 Step Down Power Module is very good. You had better set the output voltage to 3-4V lower than the input voltage, then the testing results will be more stable. The LM 2596 regulator is a monolithic integrated circuit ideally suited for the easy or convenient design of a step-down switching regulator (buck converter). It is capable of driving a 3.0 A load with excellent line or load regulation. It is internally compensated to minimize the number of external components to simplify the power of the supply design. Since the LM 2596 converter is a switch mode power supply, it is efficiency is significantly higher in comparison with popular 3 terminal linear regulators, especially with higher input voltages. The LM 2596 operates at a switching frequency of 150 kHz thus allowing smaller-sized filter components than what could be needed with lower-frequencycould switching regulators. Available in a standard 5−lead TO−220 package with several different lead bend options, and a D2PAK surface mount package. The other features include a guaranteed 4% tolerance on output voltage within specified input voltages and output load conditions and 15% on the oscillator frequency. External shutdown is included and features 80 A (typical) standby current. Self-protection features include a switch cycle−by−cycle current limit for the output switch, as well as thermal shutdown for complete protection under fault conditions.
Spceifications:
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Switching frequency: 150KHz
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Input voltage: 4.75-35V
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Output voltage: 1.25-26V
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Rated current is: 2A
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Maximum: 3A
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output power: 10W
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The starting voltage is: 4.2V
Circuit Operation:
The basic circuit diagram shown is of a diode-rectifier type (non-synchronous rectification) step-down of the circuit. In the case of synchronous rectification. D1 is replaced with a switching element current flow (transistor). which is turned on and off in operation opposite that of Q1, but the basics are the same. The diagrams below summarize the above, showing the voltage or current waveform at each major node. It is easy to see how, as Q1 is turned on and off, thedrain current ID, inductor current IL, as well as the output capacitor current ICO and input capacitor current ICIN change. With a firm understanding of the circuit operation, one could understand the jobs performed by the various components and the characteristics these components would have. Hereafter, with this operation or current flows in mind. we would process to explain inductor selection.
The TPS6420x controller is designed to operate from 1 to 3 series-connected cells or from a 3.3 V or 5 V supply obtained from a USB port. At its output, it could produce 3.3 V at 2 A, suitable for powering a microcontroller-based system. With a suitable choice of external components (inductor, P-channel MOSFET, or Schottky diode) the device could be operated over a wide range of possible output voltages or currents. A further advantage is it is extremely low quiescent current consumption in power-down mode (100 nA typical) or in no-load operation (20 mA).
Also, if the input voltage is less than and equal to the desired output voltage, the device could connect the output directly to the input. Using just a few external components the TPS6420x could cover an output of the voltage range from 1.2 V up to the input voltage at up to 3 A, as long as a suitable channel MOSFET or Schottky diode is used. The device is an asynchronous step-down converter that unlike the more widely-used PFM (pulse-frequency modulation) and PWM (pulse width modulation) types, involves a constant on-time and/or constant off-time.
Conventional controllers operate in PWM mode at medium to high loads, switching to PFM at lower loads in order to minimize switching losses. The control described here also adjusts it is switching frequency in accordance with the load to achieve a similar effect to the PFM/PWM controllers. The circuit diagram shows a classical step-down converter with an input voltage in the range of 3.3 V to 6 V and an output voltage of 3.3 V at a current of up to 2 A. The optional 33 m shunt resistor provides for the current limit. The TPS64202 offers a minimum on-time selectable for 1.6 ms, 0.8 ms, 0.4 ms, and 0.2 ms and a fixed off-time of 300 ns. A MOSFET in the supply voltage path is switched on the controller for as long as is necessary for the output voltage to reach it is nominal value, and until the maximum- permissible current as determined by the shunt resistor, is reached. If the current does exceed this limit the MOSFETs are switched off for 300 ns. If the nominal output voltage is reached, the MOSFETs are switched off and remain in the off state until the output voltage once again falls below the nominal value.
At very low output current the controller therefore operates in ‘discontinuous mode’ (DCM). Each switching cycle begins with the current at zero. It rises to the threshold or maximum value and then falls again back to zero. At the moment of switch-off, the Schottky diode causes the residual energy in the inductor to appear as a quickly decaying oscillation at the resonant for the frequency of the output filter. This low-energy oscillation in discontinuous mode is normal or has no adverse effect on the efficiency of the converter. It could be damped using the (optional) RC series network. At higher output current the switch-down converter operates in continuous conduction mode (CCM). In this mode, the inductor of the current never falls to zero. The output voltage is directly proportional to the switch mark-space ratio in this mode. If the Si2323 P-channel MOSFET from Vishay-Siliconix is not available, the IRLML6401 (12 V type) and IRLML6402 (20 V type) from IRF could be used instead.
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How the Step-down Module Work:
The LM2596 is a voltage regulator that uses pulse-width modulation (PWM) to control the switching of an inductor in a step-down switching regulator topology. When an input voltage is applied to the LM2596, it controls the switch of the inductor by turning on or off a switch at a high frequency. The switching action stores energy in the inductor during the on-time, or then releases it during the off-time, allowing it to transfer the energy to the output capacitor and load. The LM2596's PWM control adjusts the on-time of the switch to regulate the output of the voltage. The longer the on-time, the more energy is stored in the inductor, or the higher the output voltage. Conversely, the shorter the on-time, the less energy is stored in the inductor, and the lower the output voltage. The LM2596 also includes feedback control, that compares the output voltage to a reference voltage or adjusts the PWM duty cycle to maintain a stable output voltage. This allows the LM2596 to provide stable and reliable output voltage even when the input voltage and load conditions vary.
A ceramic and electrolytic capacitor is connected between the Vin pin and the GND pin of the LM2596 IC. This capacitor helps to smooth out any voltage spikes or transients on the input of the voltage or also helps to reduce noise in the circuit. Another ceramic or electrolytic capacitor is connected between the Vout pin or the GND pin of the LM2596 IC. This capacitor helps to stabilize the output of the voltage or reduce any ripple or noise in the output. An inductor is connected to the SW pin and the Vout pin of the LM2596 IC. The inductor helps to store or release energy to regulate the output voltage and also acts as a filter to reduce ripple in the output. A Schottky diode is connected in parallel with the inductor with the cathode connected to the Vout pin or the anode connected to the SW pin. The diode helps to conduct current from the inductor when the LM2596 switches off, preventing any voltage spikes that could damage the IC. Feedback Circuit: A voltage divider consisting of two resistors is connected between the Vout pin and the Adjust pin of the LM2596 IC. The feedback circuit provides a reference voltage to the IC, which it compares to the output voltage to regulate the output.
Converting a higher DC voltage to a lower one is a common requirement found in most an electronic circuit. This may be something like converting the 12V from a battery down to 5V in order to power an electronic board. A portion of when 5V may be further converted down to 3.3V to drive a lower voltage portion of the circuit. For many years linear regulators were the standard for converting higher DC voltages to lower DC voltages. They work well or are still widely used today but they do have some limitations. The main one is when a linear regulator converts the higher input voltage down to a lower output voltage by dissipating the excess voltage as heat. This is because the linear regulator uses a large power transistor that is throttled back in order to drop the voltage on the output and so it is basically acting like a large power resistor could to drop the voltage. As with a power resistor, the more voltage it needs to drop given the same amount of current, the more heat would be generated.
Frequently Asked Questions
What is the use of a step-down module?
A buck converter or step-down converter is a DC-to-DC converter that decreases voltage while increasing current, from its input (supply) to it is output (load). It is a class of switch mode power supply.
What is the principle of step-down operation?
A step-down transformer operates primarily on the basis of an electromagnetic induction. A conductor in a fluctuating electromagnetic field would see an induced current dependent on the rate at which the flux changes, according to Faraday's 1 law of electromagnetic induction.
Why is it called a buck converter?
The buck converter is so named because the inductor always “bucks” and acts against the input voltage. The output voltage of an ideal buck converter is equal to the product of the switching duty cycle or the supply voltage.
What is step-down voltage?
A Step-down transformer decreases the voltage incoming to the site by increasing the electrical current. It does this by converting the high incoming to the voltage in the primary winding to the necessary lower voltage in the secondary windings.
What is the input voltage of a step-down module?
This LM2596 step-down module has a wide input voltage range from 4.5V to 35V. The LM2596 also has internal thermal shutdown or current limit protection.
