With the development of power conversion technology, power MOSFETs have been widely used in switching converters. To this end, Silicon General Semiconductor Corporation of the United States introduced the SG3525 for driving N-channel power MOSFETs. SG3525 is a single-chip integrated PWM control chip with excellent performance, complete functions and versatility. It is simple, reliable and easy to use. The output driver is push-pull output form, which increases the driving capability. The internal contains undervoltage lockout circuit and soft start. Control circuit, PWM latch, overcurrent protection, adjustable frequency, and can limit the maximum duty cycle. Its performance characteristics are as follows: 1) Wide operating voltage range: 8 to 35V. 2) Built-in 5.1V ± 1.0% reference voltage source. 3) The on-chip oscillator operates at a frequency of 100 Hz to 400 kHz. 4) With oscillator external synchronization function. 5) The dead time is adjustable. In order to meet the needs of driving fast FETs, the final stage uses push-pull working circuits to make the switching speed more Shaanxi, and the final output or sink current can reach 400mA. 6) Built-in undervoltage lockout circuit. When the input voltage is less than 8V, the chip is internally locked and stops working (except the reference source and necessary circuit), so that the current consumption is reduced to less than 2mA. 7) There is a soft start circuit. The inverting input of the comparator is pin 8 of the soft-start control chip, which can be connected to a soft-start capacitor. The reference voltage Uref inside the capacitor is supplied by a constant current source, and the time to reach 2.5V is t=(2.5V/50μA)C, and the duty ratio changes from small to large (50%). 8) Built-in PWM (Pulse Width Modulation). The latch removes all jitter and oscillating signals from the comparator. The system can be reasserted only in the next clock cycle, and the reliability of the system is high. The SG3525 is a fixed-frequency PWM circuit in a standard 16-pin standard DIP package. Its pin functions are shown in Figure 1, and the internal block diagram is shown in Figure 2. The DC power supply Vs is divided into two paths after being connected from the pin 15, and one is added to the NOR gate; the other is sent to the input terminal of the reference voltage regulator to generate a stable component as a power source. The oscillator pin 5 must be connected to the external capacitor CT, and the pin 6 must be connected to the external resistor RT. The oscillator frequency factory is determined by the external resistor RT and the capacitance CT. The output of the oscillator is divided into two paths, one is sent to the flip-flop and the two NOR gates in the form of clock pulses; the other is sent to the comparison as a sawtooth wave. The non-inverting input of the comparator, the inverting input of the comparator is connected to the output of the error amplifier, the output of the error amplifier is compared with the sawtooth voltage in the comparator, and a square wave pulse which changes width according to the output voltage of the error amplifier is output. This square wave pulse is then sent to an input of the NOR gate. The other two inputs of the NOR gate are the flip-flop and the oscillator sawtooth. The two outputs of the flip-flop are complementary, alternately output high and low levels, and send the PwM pulse to the bases of the transistors VT1 and VT2. The role of the sawtooth wave is to add dead time to ensure that VT1 and VT2 are not turned on at the same time. Finally, VT1 and VT2 respectively output PWM waves having a phase difference of 180°. 1000 Portable Power Station,1000 Portable Power Station Price, 1000 Portable Power Station product Jiangsu Zhitai New Energy Technology Co.,Ltd , https://www.jszhitaienergy.com
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