Switch electric power circuit with wide inputting range

Abstract

The invention relates to a wide input range switching power circuit comprising a transformer. A secondary coil of the transformer can be connected with various common output-rectifier filter circuits; a primary coil of the transformer comprises a first winding and a second winding which are different in turn number; the turn number of the first winding is greater than that of the second winding; the first winding is connected in series with a counterpressure-resistant diode; each winding is connected with a switching tube; the two switching tubes are controlled by a control circuit unit connected with a power supply; and a PWM signal is input in an input terminal of the control circuit unit; the switching-on and the switching-off of the two switching tubes are controlled by different input signals. Another winding is added in the wide input range switching power circuit, the two windings work in different voltage segments respectively within the whole input voltage range; when the input voltage is low, the winding with less turn number works, a transformation ratio N becomes larger, and the dutyfactor is reduced; and when the input voltage is high, the winding with more turn number begins to work, the dutyfactor D becomes larger, and the problem of undersize dutyfactor is solved. The wide input range switching power circuit has better performance under the wide input range.

Description

technical field [0001] The invention relates to a power supply circuit, in particular to a switching power supply topology for realizing wide-range input voltage. Background technique [0002] Traditional forward converters such as figure 1 as shown, [0003] Turn ratio of primary winding N2 to secondary winding N3: [0004] N=N3 / N2 (1) [0005] According to the relationship between the voltage and current on the inductor L1 and the two conditions that the current change on the inductor L1 is equal when the switch tube Q2 is turned on and off, the relationship between the input voltage Vin and the output voltage Vo can be obtained: [0006] Vo=N*D1*Vin / (D1+D2) (2) [0007] D1——MOS tube Q2 open duty ratio. [0008] D2 - Diode D3 conduction duty ratio. [0009] When the circuit works in continuous mode, D1+D2=1, so: [0010] Vo=N*D*Vin (3) [0011] D——MOS tube Q2 open duty cycle. [0012] It can be seen from the relationship between the input and output voltages in fo...

AI Technical Summary

Problems solved by technology

[0014] The technical problem to be solved by the present invention is to provide a wide input range switching power supply circuit that can effectively solve the problems of large duty cycle changes and improve system oscillation and device stress caused by excessive duty cycle

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