Phase-shifting control method of a boost converter and implementing circuit

Abstract

The present invention relates to a phase-shifting control method of a boost converter and an implementing circuit, wherein the boost converter is provided with a main energy storing loop and at least one second energy storing loop connected with the main energy storing loop in parallel; a main loop current passing through the main energy storing loop has main loop charging time distance and main loop discharging time distance; and a second loop current passing through the second energy storing loop has second loop charging time distance and second loop discharging time distance. An ideal switching time sequence of judging value when the second loop current decreases to zero current is calculated, an actual switching time sequence of the second loop charging time distance is started, break-over error time distance of the phase differences of the ideal switching time sequence and the actual switching time sequence is obtained, and the second loop charging time distance is decided by thebreak-over error time distance and the main loop charging time sequence. Thus, the break-over error time distance of the nest period is avoided to enlarge, and further, a problem that the second loopcurrent generates subharmonic oscillation is avoided.

Description

technical field [0001] The invention relates to a phase shift control method and implementation circuit of a boost converter, in particular to a control method for driving a parallel boost converter to ensure that it works in a critical mode. Background technique [0002] Most of today's power supplies or power adapters provide the function of adjusting voltage through switching converters, and the most common one is boost converters, whose purpose is not only to adjust voltage It can also be seen in the power factor correction circuit, and the power factor of the input power is adjusted by step-up; see figure 1 , figure 1 Shown is the basic structure of the circuit of the parallel boost converter. After the rectification unit 1 is connected to the input terminal 101 to obtain the input power and modulate it into DC, the boost converter 2 modulates the modulated power output to A power conversion unit 3, and the power conversion unit 3 converts the modulated power into the...

AI Technical Summary

Problems solved by technology

[0004] The current and driving signal waveforms of the correlation shift method can be seen in image 3 , image 3 The upper half of shows the main loop current (I) flowing through the main energy storage coil 21 master ) and the secondary loop current (I) flowing through the secondary energy storage coil 22 slave ), image 3 The lower part shows the first drive signal and the second drive signal corresponding to the main loop current and the secondary loop current. The output timing of the first drive signal is the same as that of the phase shift conduction method, but the control unit 25 judges The zero current time point of the secondary energy storage coil 22 is used as the timing of outputting the second drive signal, and the cut-off timing of the second drive signal is obtained by adding a time difference to the cut-off timing of the first drive signal; It can ensure that the converter works in a critical state, but the conduction sequence of the secondary energy storage circuit is determined based on the detection of the current drop of the secondary circuit to zero current, and is not directly controlled. When the converter is connected to the load to make the main circuit When the current fluctuates or the input power fluctuates and causes the power to float, there is a conduction error time distance ΔT between the actual cut-off timing of the auxiliary energy storage circuit and the ideal cut-off timing (such as Figure 4 shown), this will lead to the phenomenon of sub-harmonic oscillation in the current output by the boost converter 2. After theoretical derivation and experimental data verification, when the duty ratio D (Duty ratio) is less than 0.5, sub-harmonic oscillation will occur, and in Figure 4 It can be seen that the secondary loop current will fluctuate from large to small, and in severe cases, it will cause the secondary loop current to be completely out of order, making the converter inefficient or unable to operate

[0005] Since the phase-shift conduction method is difficult to control its operation in the critical mode, the shortcomings of the sub-harmonic oscillation generated by the phase-shift off-state method must be improved to improve the efficiency of the parallel boost converter.

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