The stabilizer module is based on the integrated circuit L4960, which contains all the active elements of the pulse converter. Thanks to pulsed operation, the efficiency reaches 70 ... 85%. The output voltage is user-defined. Recommendations: The device is especially recommended for practitioners and designers of electronics to reduce voltage and power supply where high system efficiency is required.Specifications
Efficiency: 70 ... 85%,
input voltage range: 8 ... 50 V DC
output voltage range: 5 ... 40 V DC
maximum load current: 2.5 A
switching frequency: 100 kHz
thermal fuse tripping temperature : 150ºC
Device description
Good performance was achieved through the use of the L4960 switching regulator. In its composition, this chip contains all the elements important for the correct and reliable operation. These include a soft start system, an output transistor clock generator, a power terminal, thermal protection, and a PWM controller controlled by an error amplifier. Thus, the L4960 does not require the use of too many external components. The parameters of the power supply depend on two components - the inductor L1 and the pulse diode D1.
Components R1, C2 determine the operation of the reference frequency generator. Capacitor C3 together with resistor R2 serve as an error compensation circuit. Capacitor C4 sets the initial speed of the inverter after turning on the power. This capacitor provides a rather slow increase in the pulse duration at the output of the system, which prevents the possibility of transients at the output of the power supply. The task of the diode D1 is to create a path for the reverse current to flow, which is induced by the energy stored in the core of the inductor L1. The lower the resistance, the higher the resulting power supply efficiency. Since the stabilizer operates in a pulsed mode with the order of tens or even hundreds of kHz, the elements of the output filter should have optimal parameters for this frequency range. At the output of the stabilizer, filtering capacitors with a capacity of 150 ... 470 uF can be used. In the presented device, a capacitance of about 200 μF is used, which is divided into two capacitors of 100 μF each (C5 + C6). The use of two capacitors instead of one with a larger capacity is due to very poor capacitor parameters in the higher frequency range, which reduces the quality of filtration and the efficiency of the power source.Resistors R3 and R4 are a feedback divider that sets the value of the output voltage. This voltage is easiest to adjust by changing the resistance of R3. In the elements of the calculation of the divider, it is necessary to take into account that the internal reference voltage is 5.1V. Table 1 shows the values of R3 for the most typical output voltages, LED D2 indicates a stabilizer, and resistor R5 limits the current flowing through it.
The resistance value R5 shown in the diagram allows the diode to operate in the range of the output voltage 5 ... 15V. If the output voltage increases above 15 V, it is worth increasing the value of the resistance R5, which will prevent damage to the diode D2.The circuit board and the arrangement of the elements are shown in Figure 2.
The correct assembly procedure when applying generally accepted principles will ensure immediate and trouble-free activation of the power source. The US1 chip together with the D1 diode must be screwed to the radiator, while it is necessary to isolate the radiator from the diode radiator. To fasten the screws, use mica insulators and plastic bushings.
