Switching power supply output driving device

Abstract

The invention relates to a switching power supply output driving device, which comprises a multi-stage step driving unit, and is characterized in that the multi-stage step driving unit can charge a grid electrode of a first NMOS (N-channel Metal Oxide Semiconductor) tube and open the first NMOS tube according to the grid electrode voltage of the first NMOS tube of a switching power supply; each stage of step driving unit comprises a driving circuit and a digital logic unit, the output end of the driving circuit is connected with the grid electrode of the first NMOS tube, the output end of the digital logic unit is connected with the control end of the driving circuit, and the input end of the digital logic unit receives a signal for controlling the step driving unit. The power consumption can be effectively reduced, and the working reliability is improved.

Description

technical field [0001] The invention relates to an output driving device of a switching power supply. Background technique [0002] Switching power supplies have been widely used in the fields of electronic and electrical equipment and home appliances. The development of new power devices has promoted the high frequency of switching power supplies. The benefits of high frequency are the unprecedented miniaturization of switching power supply devices and the application of switching power supplies in a wider range of fields, especially in high-tech fields. It has promoted the miniaturization and portability of high-tech products, and the development and application of switching power supplies have far-reaching significance in saving resources and protecting the environment. Power MOS tubes and IGBTs can make the operating frequency of small and medium-sized switching power supplies reach 400kHz (AC / DC), 1MHz (DC / DC), coupled with the development of control technology and the...

AI Technical Summary

Problems solved by technology

[0005] At present, there are mainly four types of switching power supply output drive devices: the first one is the direct drive device of the power chip, because different chips have different driving capabilities, if the power chip does not have a relatively large driving peak current, then the tube conduction speed will be slow. If it is relatively slow, it will lead to a sharp increase in the switching loss of the switching power supply and reduce the output efficiency.

The second type is a push-pull output drive device. The advantage of this drive device is that it can provide sufficient current drive capability, quickly complete the charging process for the input capacitance of the MOS power tube gate, and increase the switching speed, but it cannot match the NMOS tube gate. Therefore, it usually occurs that the instantaneous rise slope of the gate drive voltage of the MOS transistor is too large, causing overshoot and oscillation of the output waveform, which greatly reduces the reliability of the switching power supply and increases the EMI problem.

The third type is the accelerated turn-off drive device. The drive circuit can provide a low-impedance path for the fast discharge of the capacitance charge between the gate and source of the MOS power tube when the power tube is turned off. A resistor is often connected in parallel with the drive resistor. and a diode, so this device is only good for the fast turn-off of the MOS power tube, but cannot effectively control the on-state of the MOS power tube, and cannot substantially improve the output efficiency of the switching power supply

The fourth is the isolated drive device, which is used to drive a very small number of high-end MOS tubes. It needs to be driven by a transformer. This device can separate DC and pass AC, but the device is often prone to magnetic core saturation. The inductance and capacitance on the PCB board are matched, and the cost is high, so this device is rarely used in the market

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