Assembly of the pulse charger with your own hands begins with the choice of the topology of the circuit, since it depends on this efficiency and dimensions of the future device. Unlike the classical transformer models, which work on reducing the network voltage at a frequency of 50 Hz, pulse converters use high-frequency switching of power keys. This allows you to reduce the weight of the structure several times and avoid the use of massive copper winding material.
The main task in the design is to correctly calculate the parameters of the throttle and select field transistors that can withstand the current load. Modern. pulse-chargers provide a more stable charge current and are less susceptible to overheating when properly assembled. Homemade design often surpasses factory budget counterparts in terms of repairability and the possibility of upgrading control units.
To implement the project, you will need not only a basic element base, but also an understanding of the principles of PWM controllers. They form the podity of pulses, regulating the average value of the output voltage. It is important to immediately determine the required power, since the choice of components of the inlet rectifier and the output filter depends on this.
The principle of operation and the advantages of the impulse scheme
The fundamental difference of pulse charging is the voltage conversion. First, the 220V network voltage is straightened and smoothed out by the capacitors, turning into a constant high voltage. It is then fed to keys that switch current at high frequency (usually 20 kHz to several MHz) through the primary winding of the high-frequency transformer.
This approach allows the use of transformers with a small ferrite core. High-frequency transformer It transmits energy more efficiently than iron at 50 Hertz. After the secondary winding, the current is straightened again, but with high-speed diodes, and is supplied to the battery.
- 🔋 High efficiency, reaching 90-95%, which reduces energy loss on heating.
- ⚖️ Compact and light weight of the structure due to the absence of heavy iron.
- ⚙️ The ability to automatically adjust the charge parameters and protect against overpole.
⚠️ Warning: Working with high voltage at the circuit input is deadly. All manipulations on settings are carried out only with power disconnected and discharged capacitors.
The use of modern components, such as MOSFET Transistors and Schottky diodes allow you to minimize switching losses. This is especially true for devices that are planned for long-term operation without supervision. Automation built into the controller monitors the temperature and current, preventing emergency situations.
Required components and tools for assembly
For high-quality manufacture of the charger, it is necessary to prepare proven components. The heart of the scheme will be a PWM controller that manages power keys. Popular chips series UC384x or specialized controllers for flyback-topology. They provide a stable frequency and have built-in protections.
Power requires the selection of transistors with low resistance of the open channel Rds(on). This is a critical parameter that affects the heating of the keys. For the output straightening, Shottky diodes are ideal, with low voltage drop and high speed.
List of rare components
Pulse circuits often require heat-resistant capacitors (105°C) and ferrite rings with specific magnetic permeability, which are not always available in conventional radio parts stores.
Don't forget the cooling system. Even at high efficiency, radiators are necessary to remove heat from the power elements. The fan can be controlled by the thermostat, turning on only when a certain temperature is reached, which reduces noise and wear of the mechanism.
| Component | Function | Requirements |
|---|---|---|
| PHIM controller | Pulse generation | Frequency 50-100 kHz |
| Power keys | Current switching | Voltage > 400V, Current > 10A |
| Straightener | AC/DC Transformation | Schottky diodes, speed. |
| Transformer. | The galvanic interchange | Ferrit, power > 150 W |
Step-by-step instructions for assembling the device
The assembly begins with the manufacture or reworking of the transformer. If a ready-made power supply is used (for example, from a computer), you need to make sure that it is serviceable and that you can work in the charger mode. In a homemade version, the windings are wound on the ferrite ring according to the calculated number of turns.
Then the power board is mounted. Place components so that the power circuits are as short as possible, which will reduce the level of electromagnetic interference. Printing board It shall be made of textolite of at least 1.5 mm thick to ensure mechanical strength and thermal conductivity.
☑️ Pre-insertion check
After soldering all the elements, the primary start is made through an incandescent lamp connected to the break of the mains wire. This will avoid cotton and failure of components in the presence of errors in installation. The lamp shall not burn at full strength when idling.
Setup of output parameters and calibration
The setup begins with checking the output voltage without load. Using multimeterMake sure the voltage matches the calculated value for the charge of a 12-volt battery (usually 14.4–14.8V). Adjustment is carried out by selecting the denominations of resistors in the feedback chain.
The current restriction is then checked. Having connected the equivalent of the load, make sure that when short circuit or connecting the discharged battery, the current does not exceed the specified value. It's a function. current-protectionThis saves the device and battery from overload.
- 🔧 Precisely set the cut-off threshold at full charge.
- 🌡️ Calibration of the temperature sensor for the fan.
- ⚡ Check the stability of the voltage during network surges.
⚠️ Note: Do not connect the battery until all load equivalent modes are fully checked. An error in the setting can lead to boiling of the electrolyte.
For fine tuning, an oscilloscope may be needed to see the shape of the pulses on the transistor gates. The absence of emissions and the “ring” indicates the correct installation and the absence of parasitic fluctuations.
Improvement of the protection and security system
Safety is a priority when working with batteries. Be sure to implement protection against overpole so that if the terminals are not connected correctly, the device does not fail. To do this, diode assemblies or circuits on the relay are used, breaking the chain if an error occurs.
Thermal protection is also critical. The temperature sensor installed on the radiator should turn off the device or reduce the charge current during overheating. It extends the service life. electronics It prevents fire.
Use a thermal paste when installing transistors on radiators to improve heat removal.
Additionally, you can install a fuse at the input 220V and the output of direct current. This will create a double barrier in case of insulation failure or short circuit within the circuit.
Testing and first battery run
The final stage is the connection of a real car battery. Before that, measure the voltage at the battery terminals. If it is below 10V, some smart charges may not start, requiring pre-activation with low current.
During the charge, monitor the temperature of the device and the battery itself. A moderate heat is considered normal, but not a hot state. Pulsations of the output voltage should not exceed 5-10% of the average value.
It is critical to monitor the current at the end of the charge: it should be smoothly reduced to a minimum, signaling the full capacity of the battery.A properly assembled pulsed device charges faster and more carefully than a transformer, thanks to precise control of parameters.
If all parameters are normal, the device can be considered ready for operation. Check the reliability of terminal contacts regularly, as vibration during transportation can weaken the connections.
Possible malfunctions and methods of their elimination
During operation, typical problems may arise. If the device goes into protection immediately after turning on, check the feedback circuit and the serviceability of the sensors. Often the reason lies in a cliff wire or poor contact.
Strong heating of the keys indicates insufficient cooling or operation of transistors in a suboptimal mode (under-open state). Check the signals on the shutters with an oscilloscope. Also, the cause may be high-frequency ringing, eliminated by the supply chains.
- 🔌 No voltage at the exit: check the inlet fuse and diode bridge.
- 📉 Unstable current: check the filter capacitors and PWM controller.
- 🔊 Whistling of the transformer: poor impregnation or violation of the operating mode.
How to calculate the number of transformers?
For the calculation, use the formula: N = (U) 10000) / (B S * f), where U is voltage, B is ferrite saturation induction, S is core cross-sectional area, f is frequency. For standard N87 ferrites at 50kHz, 1 volt is usually taken per 1-2 turn depending on the cross-section.
Can I charge LiFePO4 with this device?
Yes, but only if you change the algorithm of the controller. Lithium batteries require strict voltage control (3.65V per can) and do not tolerate overcharging. The standard lead mode (14.4V) can be dangerous for 4S builds of LiFePO4 without reconfiguration.
Why is the transformer buzzing when working?
The buzz is caused by magnetostriction of the core. If the hum is strong, it is possible that the halves of the core are not glued together or the gap is too large. Also, the reason may be work on the resonant frequency of mechanical oscillations of the windings.