Loop-free digital control method for isolation Buck-Boost circuit

Abstract

The invention discloses a loop-free digital control method for an isolation Buck-Boost circuit. The circuit comprises an isolation Buck-Boost main circuit, an output voltage sampling circuit, an inputvoltage sampling circuit, a high voltage comparison circuit, a low voltage comparison circuit, an input voltage comparison circuit and a PWM controller. By introducing a loop-free digital control method, the isolation Buck-Boost circuit is in a loop-free control state, and when the input voltage is greater than or equal to the input threshold voltage Vth, the circuit works in a Buck mode; and when the input voltage is smaller than Vth, the circuit works in a Boost mode, and the duty ratio of the corresponding NPN type switching tube is adjusted according to the high-low threshold digital comparison signal of the output voltage signal, so that the output voltage is stable. The control method can broaden the input range, simplify the sampling and control circuit, improve the efficiency andpower density of the circuit, and meet the electrical isolation requirement.

Description

technical field [0001] The invention relates to the technical field of power supplies, in particular to a loop-free digital control method for an isolated Buck-Boost circuit. Background technique [0002] With the rapid development of computer, communication and network technology, how to integrate low-voltage and high-current DC / DC converters that can be applied to different occasions has become an important research topic at present. The isolated Buck-Boost circuit is a topology that can adapt to a wide range of input voltages, and can meet the requirements of brick power supplies for volume, reliability, efficiency, and power density. The isolated Buck-Boost circuit is integrated in a quarter brick (57.9*36.8*8.1mm), a DC / DC converter with high efficiency and high power density can be realized, but at the same time it also increases the complexity of the circuit; especially in the case of strict requirements on volume and speed, it can be The choice of control chips and ...

AI Technical Summary

Problems solved by technology

The isolated Buck-Boost circuit is a topology that can adapt to a wide range of input voltages, and can meet the requirements of brick power supplies for volume, reliability, efficiency, and power density. The isolated Buck-Boost circuit is integrated in a quarter brick (57.9*36.8*8.1mm), a DC / DC converter with high efficiency and high power density can be realized, but at the same time it also increases the complexity of the circuit; especially in the case of strict requirements on volume and speed, it can be The choice of control chips and the placement of control chips are relatively limited

If the ground of the control chip is connected to the ground of the input voltage of the primary side, the output voltage and current sampling of the secondary side will be led to the ADC pin of the primary side control chip through optocoupler isolation. The "pure delay" brought by the optocoupler when" caused trouble in controlling

If the ground of the control chip is connected to the ground of the output voltage of the secondary side, although this will make the loop control easy to realize, but the primary side needs to detect and monitor more power, and the introduction of the secondary side will make the circuit more complicated.

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