A Constant On-time Controller for Switching Power Supply with External Compensation

Abstract

The invention relates to a switching power source fixed on-time controller with external compensation. A switching power source comprises an MOSFET switching tube. The fixed on-time controller comprises an RS trigger, a time delayer and a comparator. The time delayer is connected with the RS trigger, the output end of the RS trigger is connected with the MOSFET switching tube, the input end of the RS trigger is connected with the output end of the comparator, one input end of the comparator is connected with the output end of the switching power source, and the other input end of the comparator is connected with a direct current bias correcting circuit. The direct current bias correcting circuit comprises a subtracter, a digital processor and a reference voltage. One end of the subtracter is connected with the comparator, and the other end of the subtracter is connected with the digital processor and the reference voltage. The digital processor and the reference voltage are respectively grounded, and the digital processor outputs the voltage compensation amount to the subtracter. Compared with the prior art, the witching power source fixed on-time controller has the advantages of effectively eliminating direct current bias and being simple in structure.

Description

technical field [0001] The invention relates to a switching power supply, in particular to a constant conduction time controller of a switching power supply with external compensation. Background technique [0002] With the rapid development of mobile devices, DC-DC choppers as their power management systems, that is, switching power supplies, must meet the following technical requirements: (1) low output voltage; (2) high output voltage accuracy; (3) small size; (4) When the output load is transient, the transient overshoot of the output voltage is small. The above requirements put forward higher requirements on the steady-state and dynamic characteristics of the switching power supply, and pose new challenges to the control method of the switching power supply. Among them, the traditional fixed on-time control method is widely used in switching power supplies because it meets the basic requirements of stability, dynamic performance and simplicity. Traditional fixed on-tim...

AI Technical Summary

Problems solved by technology

However, this control method has a disadvantage that there is a DC bias problem. Because some electronic devices, such as computers, have high requirements on the accuracy of the power supply, and due to the characteristics of fixed on-time control, the output voltage must be greater than the reference voltage. This necessarily results in a DC offset between the average value of the output voltage and the reference voltage

Therefore, the traditional fixed on-time control method is difficult to meet the high-precision technical specifications of the output voltage

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