Non-isolated bidirectional conversion circuit and control method thereof

Abstract

The invention discloses a non-isolated bidirectional conversion circuit and a control method thereof. The circuit comprises a first equivalent direct current power supply end, a second equivalent direct current power supply end, a first equivalent capacitor, a second equivalent capacitor, a first equivalent inductor, a second equivalent inductor, a first synchronous switch set, a second synchronous switch set, a driving circuit and a control circuit; the first synchronous switch set comprises a first switch tube and a fourth switch tube, the first switch tube is connected between the second end of the second equivalent inductor and the positive electrode of the first equivalent direct current power supply end, the fourth switch tube is connected between the negative electrode of the firstequivalent direct current power supply end and the second end of the first equivalent inductor; the second synchronous switch set comprises a second switch tube and a third switch tube; the second switch tube is connected between the second end of the first equivalent direct current power supply end and the positive electrode of the second equivalent direct current power supply end, and the thirdswitch tube is connected between the negative electrode of the second equivalent direct current power supply end and the second end of the second equivalent inductor. According to the invention, the problem of conversion of the input voltage and the output voltage of a large ratio is solved.

Description

technical field [0001] The invention relates to the technical field of conversion circuits, in particular to a non-isolated bidirectional conversion circuit and a control method thereof. Background technique [0002] With the rapid development of industries such as energy storage, there are more and more applications of batteries and similar products, so bidirectional conversion is required in the circuit. If there is no need for electrical isolation, the most common is to use a buck (boost) circuit, such as figure 1 As shown, the inherent characteristic of the circuit is V1=V2*D or V2=V1*1 / (1-D). When the difference between V1 and V2 is large, the duty cycle D is either extremely small or extremely large; In this case, the gain is not in a linear relationship, so the aforementioned ideal equation relationship cannot be realized; at the same time, the circuit loss is extremely large, so it is urgent to design a circuit that can expand the gain (or multiple relationship). ...

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Problems solved by technology

[0002] With the rapid development of industries such as energy storage, there are more and more applications of batteries and similar products, so bidirectional conversion is required in the circuit. If there is no need for electrical isolation, the most common is to use a buck (boost) circuit, such as figure 1 As shown, the inherent characteristic of the circuit is V1=V2*D or V2=V1*1 / (1-D). When the difference between V1 and V2 is large, the duty cycle D is either extremely small or extremely large; In this case, the gain is not in a linear relationship, so the aforementioned ideal equation relationship cannot be realized; at the same time, the circuit loss is extremely large, so it is urgent to design a circuit that can expand the gain (or multiple relationship)

[0003] In view of the above problems, in the prior art there will be figure 1 The inductance in is changed to the inductance of the two coils coupled to each other (or called a transformer), such as figure 2 As shown, after adding a coupling coil T1-2, the turn ratio of the inductance coil changes through the change of the path during conduction and freewheeling, so that the magnetic recovery slope of the corresponding inductance can be changed, or the gain can be changed. The specific principle is because The public knowledge will not be described in detail here; figure 1 The scheme of the middle circuit, in the same on-time, can change the step-up (or step-down) ratio, which solves the problem to some extent figure 1 Gain problem in the circuit, but then there will be another known problem, the stress of the switching tube in the circuit is compared with the conventional figure 1 The circuit will be more than 1 times higher. For example, when the low-voltage terminal V1 is raised to the high-voltage terminal V2, Q4 is turned on, and the coupling coil T1-2 is suspended. Since the coupling coil must have leakage inductance, and compared with the conventional multi-coil coupling pure The leakage inductance of the transformer is larger; this means that the leakage inductance at the moment of switching will generate a large voltage spike, and at the same time, the fixed coupling voltage V1 and V2 generated by the coil T1-2 and the coupling coil T1-1 form a series connection, which will make the first The voltage stress of the second switching tube Q2 increases, and in addition, when the second switching tube Q2 is turned off or the fourth switching tube Q4 is turned on (or turned off), the leakage inductance will also generate a higher oscillation voltage in the second switching tube Q2 peak; therefore, in actual use, it is necessary to select figure 1 Switching tubes with more than twice the stress margin of switching tubes in the medium circuit, resulting in uneconomical or difficult selection

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