Sinrace Power Supply Technology (Shenzhen) Co., Ltd.
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Certifications
| The design based on LT3782 of high current boost circuit |
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LT3782 is two-phase stepper step-up DC / DC controller produced by American Linear Technology Corporation., 28-pin SSOP package chip, the switching frequency is programmable between 150 ~ 500 kHz, using two-phase BOOST topology. The output FET current and Schottky diode leakage current requirements are reduced by half, that is, phase difference of two output is 180 °, the two output are mutual inhibited to output ripple current , output ripple is 1 / 3 of single phase BOOST conversion circuit. Power efficiency, is high , the requirements for heat dissipation is small. Figure 1 is a map of LT3782, 29th pin is the cooling foot of bottom of the chip. 27 pin is connected to input power; 4 pin is connected to ground; 11 pins are used to set the switching frequency; 20 and 23BGATE pins are used to drive the FET gate; 8,9,1 2 and 13SENSE pin is used to feedback FET output current; 16 pin is the output voltage feedback pin, the pin voltage is 2.44 V, can set the output voltage value by the feedback resistor. 17 pin is low voltage shutdown pin, when the pin voltage is greater than 2.45 V, the device start working, when the pin voltage is less than 0.3 V, the device enters a low-voltage shutdown mode. 14 pin is the soft-start pin, when powering, the output voltage gradiently change from 0 V to the set output voltage, the typical start-up time can be calculated by the following formula: t＝2．44C／10 Circuit achievement Overall design of switching power supply Circuit shown in Figure 2, 12 V car battery voltage goes through the plug JP1 and R5 to supply LT3782, LT3782 generates a two-phase oscillating output to drive N-channel FET Q1 and Q2, the FET output respectively goes through Schottky diode D1 and D2 to rectifying, output by the output filter capacitor C7. Parameter setting of switching power supply the resistor R1 is used to set the switching frequency of LT3782, LT3782 switching frequency is programmable between 150 ~ 500 kHz. Here select the switching frequency of 250 kHz, with reference to Figure 3 take the resistance R1 = 75 kHz. Circuit test In order to verify the performance of the switching power supply, using the method shown in Figure 4 to verify. Because the power supply input current is large, the input DC power supply use the Agilent 6574A-J07. Its output current is up to 42 A, output voltage is adjustable in O ~ 50 V range, output load use Kenwood PEL102-201, through which you can visually see the output voltage and current situation. After verification, the circuit is completely satisfied with unit demand. Conclusion Based on the two-phase stepper boost DC / DC Controller LT3782 produced by Linear Technology Corporation, designed a high current output step-up DC / DC module. The module is in 12 V car battery power supply, according to the need to provide 24 V, 18.5 V and multiple outputs with up to 7 A current, using two-phase DC / DC technology, the power efficiency reach over 90%. Compared to convert to required voltage after going through AC 220 V, the power has been improved to be more high efficiency, comply with development direction to construct the conservation-oriented society currently ,it’s more practical. |
