A phase-shifted full-bridge periodic self-protection circuit and its control method

Abstract

The invention discloses a phase-shifted full-bridge cycle self-protection circuit and a control method thereof. The protection circuit comprises a DSP (Digital Signal Processor), a current sample and comparison circuit, an active oscillator circuit, a first falling edge-triggered D flip-flop, a second falling edge-triggered D flip-flop, a first dual input OR gate, a second dual input OR gate, a first NOT gate, a first dual input AND gate, a second dual input AND gate, a third dual input AND gate, a fourth dual input AND gate, a fifth dual input AND gate, a sixth dual input AND gate, a seventh dual input AND gate, and an eighth dual input AND gate. Four paths of input PWM (Pulse-Width Modulation) signals can be simultaneously turned to be low level when a circuit is overcurrent, so that total switch-off of a switch tube is realized, and the magnetic biasing phenomenon of a transformer cannot be generated when continuous overcurrent occurred; and meanwhile, the DSP only needs to output four paths of PWM signals, so that the utilization ratio of the DSP is improved. The cycle self-protection circuit is simple and practical, overcurrent protection is realized with least PWM signals, and the design cost is lowered.

Description

technical field [0001] The invention relates to the technical field of a phase-shifted full-bridge switching power supply, in particular to a phase-shifted full-bridge periodic self-protection circuit and a control method thereof. Background technique [0002] The phase-shifted full-bridge circuit is already a very mature soft-switching circuit, and it is often used as a circuit topology for medium and high-power power supplies. The four switching tubes on the bridge arm are often controlled by a TI2000 series DSP processor, through which the DSP processor can generate Time-zone PWM signal, to avoid the phenomenon of the same bridge arm straight-through on the circuit, but when there is an overcurrent, it is necessary to turn off all four switches, and the DSP processor always outputs 2 complementary PWM signals, which cannot be realized The switch tube is fully closed, which is contrary to the requirement in the case of overcurrent. In addition, the commonly used single-cy...

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Problems solved by technology

[0002] The phase-shifted full-bridge circuit is already a very mature soft-switching circuit, and it is often used as a circuit topology for medium and high-power power supplies. The four switching tubes on the bridge arm are often controlled by a TI2000 series DSP processor, through which the DSP processor can generate Time-zone PWM signal, to avoid the phenomenon of the same bridge arm straight-through on the circuit, but when there is an overcurrent, it is necessary to turn off all four switches, and the DSP processor always outputs 2 complementary PWM signals, which cannot be realized The switch tube is fully closed, which is contrary to the requirements in the case of overcurrent

In addition, the commonly used single-cycle protection control will cause transformer magnetic bias phenomenon when the system continuously over-current occurs. Although the half-cycle protection control can alleviate the magnetic bias phenomenon, it needs to add a PWM signal at the same time, which will undoubtedly increase the burden on the DSP processor. , especially for multi-machine parallel circuits, due to the limited PWM port of the DSP processor, if each single machine needs to add a PWM signal, only one DSP processor can be controlled originally, and two pieces may be needed at this time Even more, at a higher cost

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