CN108566083A - A kind of DC current/current conversion circuit of width out-put dynamic range - Google Patents

Abstract

The invention discloses a DC current/current conversion circuit with a wide output dynamic range, which includes a positive bus bar, a negative bus bar, and an input terminal access capacitor connected in parallel between the positive bus bar and the negative bus bar, an energy storage and conversion inductance, an output storage Energy and filter capacitors, the positive busbar is located at the connection point of the input capacitor, energy storage and conversion inductor, and an electronic switch is connected in series. The positive busbar is located between the energy storage and conversion inductor, output energy storage and filter capacitor. The freewheeling and isolation diodes are connected in series between the connection points of the latter. For the input current of the constant current power supply mode, the ratio of the output current to the input current can be adjusted by adjusting the duty cycle of the switch to realize the current/current conversion function, and the output current can be greater than, equal to or less than the input current, and the duty cycle can be fixed Or sampling the output current and adjusting the duty cycle through the feedback circuit can stabilize the output current at a certain value, which has the advantages of simplicity, practicality, high efficiency, stability and reliability.

Description

A DC Current/Current Conversion Circuit with Wide Output Dynamic Range

technical field

The invention relates to power electronic conversion technology, in particular to a DC current/current conversion circuit with a wide output dynamic range.

Background technique

The existing daily DC power supply system usually adopts a constant voltage power supply method, and the power conversion method also adopts voltage/voltage conversion or voltage/current conversion. With the development of science and technology and the expansion of new power supply technology, especially in the future underwater information system and network, the constant current power supply system will show its unique advantages. In this type of power supply system, it is inevitable to use a conversion device that converts a certain current value into a current (current/current) of other values. This requires the design of a DC current/current conversion circuit to complete this function, but the output current range of the existing DC current/current conversion circuit cannot be adjusted, so how to achieve wide output dynamic range adjustment has become an urgent problem to be solved key technical issues.

Based on the above requirements, the Chinese patent document with application number 201410009977.X discloses a constant current constant voltage converter based on PWM modulation. The constant current constant voltage converter has a DC current/voltage conversion function and also has a current conversion function. However, this technical solution has the following disadvantages: ① the model of the circuit design of the technical solution limits its output current to be less than the input current; ② the circuit model of this patent does not have C and L in the circuit model of the present invention; ③ the technology In the scheme, the switch is connected in parallel with the output and input current. In addition, the Chinese patent document with the application number 201410009981.6 discloses an isolated high-frequency switching constant current converter, which also has the function of DC current/current conversion. However, this technical solution has the following disadvantages: ① The current change of this technical solution It cannot be adjusted by the pulse width of PWM, and its pulse width is fixed; ②The ratio of output current to input current in this technical solution is determined by the transformer, and does not have a feedback control function; ③The circuit model of this technical solution is more complicated.

Contents of the invention

The technical problem to be solved by the present invention: Aiming at the above-mentioned problems of the prior art, a DC current/current conversion circuit with a wide output dynamic range is provided. The present invention can adjust the duty cycle of the electronic switch for the input current of the constant current power supply mode. To adjust the ratio of the output current to the input current, set different duty ratios to output different current values (theoretically, it can be any value), and the current/current conversion function can be realized, and the output current can be greater than, equal to or less than the input Current, fixed duty cycle or sampling the output current and adjusting the duty cycle through the feedback circuit can stabilize the output current at a certain value, which has the advantages of simplicity, practicality, high efficiency, stability and reliability.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

The present invention provides a DC current/current conversion circuit with a wide output dynamic range, including a positive bus bar, a negative bus bar, and an input terminal access capacitor C _i , an energy storage and conversion inductance L , The output energy storage and filter capacitor Co , the positive busbar is located on the input end access capacitor C _i , the connection point of the energy storage and conversion inductance L is connected in series with an electronic switch Q , the positive busbar is located on the energy storage A freewheeling and isolation diode DT is connected in series between the connection points of the switching inductance L , the output energy storage and the filter capacitor Co , and the positive busbar and the negative busbar are connected to the side of _the capacitor C _i by the input terminal. As the input end of the DC current/current conversion circuit, the side close to the output energy storage and filter capacitor Co is used as the output end of the DC current/current conversion circuit.

Preferably, the electronic switch Q is a bipolar transistor, or a field effect transistor, or an IGBT.

Preferably, a pulse width modulation circuit PWM is also included, and the control terminal of the electronic switch Q is connected to the output terminal of the pulse width modulation circuit PWM.

The DC current/current conversion circuit with a wide output dynamic range of the present invention has the following advantages: the present invention includes a pulse width modulation circuit PWM, a positive bus bar, a negative bus bar, and an input terminal access capacitor C connected in parallel between the positive bus bar and the negative bus bar in sequence. _i , energy storage and conversion inductance L , output energy storage and filter capacitor Co , an electronic switch Q is connected in series between the connection points of the input capacitor C _i , energy storage and conversion inductance L on the positive busbar, and the electronic The control terminal of the switch Q is connected to the output terminal of the pulse width modulation circuit PWM, and the positive busbar is located between the connection points of the energy storage and conversion inductor L , the output energy storage and the filter capacitor Co , and a freewheeling and isolation diode D is connected in series. _T , for the input current of the constant current power supply mode, the ratio of the output current to the input current can be adjusted by adjusting the duty ratio of the electronic switch Q , and different current values can be output by setting different duty ratios (theoretically, it can be any value ), can realize the current/current conversion function, and the output current can be greater than, equal to or less than the input current, fixed duty cycle or sampling the output current and adjusting the duty cycle through the feedback circuit can stabilize the output current at a certain value, with Simple and practical, high efficiency, stable and reliable advantages.

Description of drawings

FIG. 1 is a schematic diagram of a basic topology structure of Embodiment 1 of the present invention.

FIG. 2 is a schematic diagram of waveforms of main parameters in Embodiment 1 of the present invention.

Detailed ways

Embodiment one:

As shown in Figure 1, the DC current/current conversion circuit with a wide output dynamic range in this embodiment includes a pulse width modulation circuit PWM, a positive bus bar, a negative bus bar, and an input capacitor connected in parallel between the positive bus bar and the negative bus bar. C _i , energy storage and conversion inductance L , output energy storage and filter capacitor Co , an electronic switch is connected in series between the connection points of input capacitor C _i , energy storage and conversion inductance L on the positive busbar Q , the control terminal of the electronic switch Q is connected to the output terminal of the pulse width modulation circuit PWM, and the positive bus is connected in series between the connection points of the energy storage and conversion inductance L , the output energy storage and the filter capacitor Co There is a freewheeling and isolation diode D _T , and the side of the positive busbar and the negative busbar that is connected to the capacitor C _i at the input end is used as the input end of the DC current/current conversion circuit, and one side of the positive busbar and the negative busbar is connected to the output capacitor Co The side is used as the output end of the DC current/current conversion circuit.

The input capacitor C _i is the core device of the DC current/current conversion circuit with a wide output dynamic range. The input capacitor C _i has the function of energy storage and energy conversion. When the electronic switch Q is off, the input current flows to The input terminal is connected to the capacitor C _i to charge, and the input terminal is connected to the capacitor C _i to store the electric energy; when the electronic switch Q is closed, the input terminal is connected to the capacitor C _i to discharge, and the electric energy is converted to the energy storage and converted to the inductance L. The energy storage and conversion inductor L has the function of energy storage and energy conversion. When the electronic switch Q is closed, the energy storage and conversion inductor L stores the electric energy from the input capacitor C _i and the input power supply; when the electronic switch Q is off During the on period, the energy storage and _conversion inductance L is discharged to the output energy storage and filter capacitor Co and _the load RL , and the electric energy is converted to the output energy storage and filter capacitor Co and the load RL . The freewheeling and isolation diode D _T is a freewheeling diode and has the function of isolation. When the electronic switch Q is closed, the voltage on the freewheeling and isolating diode D _T is - ( V _o +V _i ), and the freewheeling and isolating diode D _T Cut-off; during the period when the electronic switch Q is off, the freewheeling and isolation diode DT is turned on, providing a path for the energy storage and _switching inductance L to discharge. The output energy storage and filter capacitor Co has the function of output energy storage and filtering at the same time. When the electronic switch Q is off, the output energy storage and filter capacitor Co absorbs the electric energy from the energy storage and conversion inductance L ; when the electronic switch Q is closed, the output The energy storage and filter capacitor Co releases electric energy to _the load RL . RL is _the load. The electronic switch Q is an electronic switch controlled by a PWM pulse signal. Usually, when the control pulse is at a high level, the electronic switch Q is turned on; when the control pulse is at a low level, the electronic switch Q is turned off (disconnected). The pulse width modulation circuit PWM outputs a pulse signal with a duty cycle of D according to the relative value of v _ref and v _f , where v _ref is the reference voltage and v _f is the comparison voltage. In Figure 1, except that the electronic switch Q is a switch model, the rest of the components are common components. In practical applications, the switch model of the electronic switch Q can use bipolar transistors, field effect transistors, or IGBTs as required; pulse width modulation Circuit PWM can be implemented using various PWM integrated circuits.

Figure 2 is a schematic diagram of waveforms of relevant nodes in the circuit of Figure 1, where: I _i is the input current, V _i is the input voltage, V _g is the control voltage applied to the control electrode of the electronic switch Q , and I _Q is the energy storage and the current of the conversion inductor L , V _L is the voltage across the energy storage and conversion inductor L , V _D is the voltage of the freewheeling and isolation diode DT , I _o is the output current, and V _{o is} the output voltage. The electronic switch Q is controlled by a pulse with a certain frequency (period T ), and the switch is closed during the high-level period of the pulse ( t _on ). During the pulse low-level period ( t _off ), the switch is turned off, and the relationship between the output current I _o and the input current I _i is shown in formula (1);

I _o =( t _off / t _on )/ I _i (1)

In formula (1), I _o represents the output current of the electronic switch Q , t _off represents the pulse low level period, t _on represents the pulse high level period, and I _i represents the input current of the electronic switch Q.

If the duty cycle is set as D= t _on / T , where T represents the period, and t _on represents the high-level period of the pulse, then the formula (1) can be transformed into the form shown in the following formula (2):

I _o =(( 1-D) / D )/ I _i (2)

It can be seen from formula (1) and formula (2) that as long as the duty cycle D of the control pulse is adjusted, the ratio of output to input current can be changed. If the input current I _i is a constant current, then the output is also a constant current of different values. As long as different duty cycle D is set, different constant current values can be output. Theoretically, when the duty ratio D is between 0 and 1, the output current can be any value. In practice, when the value of D is between 0.1~0.9 [ I _o ≈ (0.1~10) I _i ], there is a more accurate transformation value. Experiments have proved that the conversion efficiency of this circuit can reach more than 90% under the condition of rated working power. For example: Assuming that the input current I _i of the input constant current source current is 1A, and to make the converter output 2A, then t _off / t _on =22, so that the duty cycle D=33% can be deduced, that is, as long as the v _f , the duty cycle D of the PWM output pulse of the pulse width modulation circuit is 0.33. Similarly, if you want to output a current of 0.5A, you can adjust v _f so that the duty ratio D is 0.67.

Compared with the Chinese patent document with application number 201410009977.X which discloses a constant current constant voltage converter based on PWM modulation, the output current of the circuit in this embodiment can be either smaller than the input current or larger than the input current, and the electronic switch Q is It is connected in series between the input and output, and the input capacitor C _i , the energy storage and conversion inductance L , the output energy storage and filter capacitor Co are added. Compared with the Chinese patent document with application number 201410009981.6 which discloses an isolated high-frequency switching constant current converter, the current change of the circuit in this embodiment can be adjusted by the pulse width of PWM, the pulse width is adjustable, and no transformer is needed and With feedback control function, the circuit structure is simpler and the equipment cost is lower.

To sum up, the DC current/current conversion circuit with a wide output dynamic range of this embodiment can adjust the ratio of the output current to the input current by adjusting the duty cycle of the electronic switch Q for the input current of the constant current power supply mode, and set Different duty ratios can output different current values (theoretically any value), can realize current/current conversion function, and the output current can be greater than, equal to or less than the input current, fixed duty ratio or sample the output current and The output current can be stabilized at a certain value by adjusting the duty cycle through the feedback circuit, which has the advantages of simplicity, practicality, high efficiency, stability and reliability.

Embodiment two:

This embodiment is basically the same as Embodiment 1, and the main difference is that in this embodiment, the DC current/current conversion circuit with a wide output dynamic range of this embodiment does not include an integrated pulse width modulation circuit PWM, and the control of the electronic switch Q The terminal is connected with the output terminal of the external PWM output device.

The above descriptions are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions under the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those skilled in the art, some improvements and modifications without departing from the principles of the present invention should also be regarded as the protection scope of the present invention.

Claims (3)

1. A DC current/current conversion circuit with a wide output dynamic range, characterized in that: it includes a positive busbar, a negative busbar, and an input terminal connected in parallel between the positive busbar and the negative busbar in turn to connect capacitor C _i , energy storage and conversion The inductance L , the output energy storage and filter capacitor Co , the positive busbar is located between the connection point of the input capacitor Ci , the energy storage and the conversion inductance L , and an electronic switch Q _is connected in series, and the positive busbar A freewheeling and isolation diode D _T is connected in series between the connection points of the energy storage and conversion inductance L , the output energy storage and the filter capacitor Co , and the positive busbar and the negative busbar are connected to the capacitor C _i by the input terminal One side is used as the input terminal of the DC current/current conversion circuit, and the side close to the output energy storage and filter capacitor Co is used as the output terminal of the DC current/current conversion circuit. 2. The DC current/current conversion circuit with wide output dynamic range according to claim 1, characterized in that: the electronic switch Q is a bipolar transistor, or a field effect transistor, or an IGBT. 3. The direct current/current conversion circuit of wide output dynamic range according to claim 1 or 2, characterized in that: it also includes a pulse width modulation circuit PWM, the control terminal of the electronic switch Q is connected with the pulse width modulation circuit PWM connected to the output.