Bidirectional constant current source circuit and control method thereof

Abstract

The present application relates to a kind of bidirectional constant current source circuit and its control method, high-precision sampling unit acquires load real-time current and sends into control unit, control unit receives constant current source output current given value, control unit outputs constant current source output current given value with positive and negative direction and converted digital load real-time current value into linear unit, linear unit adjusts output constant current value to load, while control unit outputs the given voltage value required by rectification unit and enters rectification unit.The high-frequency rectification switching power supply circuit is combined with the three-stage tube linear power supply circuit, and noise filtering technology is used simultaneously.Under the condition of high-power and wide-range current output, the current error precision can reach e ‑5 magnitude, and the ripple noise can be reduced to milliamper level.The combined circuit has higher power density and smaller size under the same power condition compared with the traditional three-stage tube linear power supply circuit alone, and the output current precision and stability are improved by nearly 100 times compared with the high-frequency switching power supply circuit alone, and the output current ripple is reduced by more than 5 times.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of power electronics, especially a kind of high-power high-precision low-noise bidirectional constant current source circuit and its control method. BACKGROUND

[0002] The existing high-precision bidirectional constant current source circuit is mainly high-frequency switching power supply circuit and triode linear power supply circuit at present.Power density is high in high-frequency switching power supply circuit, and it is suitable for high-power occasions, but it is relatively difficult to realize high precision and low noise due to its inherent high switching frequency characteristic;Triode linear power supply circuit is beneficial to high precision and low noise realization due to its triode characteristics, but the number of triodes increases in high-power occasions, which leads to large power supply volume and low power density. SUMMARY

[0003] In view of the above problems, a bidirectional constant current source circuit and its control method are proposed, which combines high-frequency rectifier switching power supply circuit with triode linear power supply circuit, and uses noise filtering technology to meet the output requirements of high-precision low-noise bidirectional constant current source in high-power occasions.

[0004] The technical solution of the present application is: a bidirectional constant current source circuit, including rectifier unit, noise filter unit, linear unit, high-precision sampling unit, auxiliary power supply unit and control unit, AC 380V input rectifier unit for high-frequency rectification, rectifier unit outputs DC high voltage into noise filter unit, noise filter unit filters high-frequency noise in DC high voltage and outputs to linear unit; Two-phase AC 220V input auxiliary power supply unit, AC / DC conversion in auxiliary power supply unit, auxiliary power supply unit outputs two DC, respectively for control unit and high-precision sampling unit power supply; High-precision sampling unit collects real-time current of load and sends it to control unit, control unit receives constant current source output current given value, control unit outputs constant current source output current given value with positive and negative direction and converted digital load real-time current value into linear unit, linear unit adjusts output constant current value to load, and control unit outputs rectifier unit required output given voltage value into rectifier unit.

[0005] Preferably, the linear unit includes a plurality of parallel triodes with internal digital control and communication function, and two groups of contactors for current commutation control, which controls the accuracy of each triode working in linear amplification area small current, and ensures the overall high-precision current output of triode group.

[0006] Preferably, the linear unit is internally composed of an anti-reverse diode D, a forward transistor group connected in parallel, a negative transistor group connected in parallel, a positive contactor KZ, a negative contactor KF, a controller and a drive unit. The positive input end is connected to the positive electrode of the anti-reverse diode D, the negative electrode of the anti-reverse diode D is connected to the negative input end via a DC voltage support capacitor C, the positive transistor group and the negative contactor KF normally open switch are connected in series between the negative electrode of the anti-reverse diode D and the negative input end, and the positive transistor group and the negative contactor KF normally open switch are connected in series. The connection point is connected to the positive end of the load; the negative triode group and the positive contactor KZ normally open switch are connected in series between the negative electrode of the anti-reverse diode D and the negative input terminal, and the connection point of the negative triode group and the positive contactor KZ normally open switch in series is connected to the negative end of the load. The controller and the drive unit receive the digital load real-time current value and the output current set value output by the control unit through 485B, and the controller and the drive unit output drive signals of the positive triode group and the negative triode group as well as control signals of the positive contactor KZ and the negative contactor KF.

[0007] Preferably, the structures and numbers of the positive transistor group and the negative transistor group are the same, and each transistor group includes several transistors and a corresponding number of current-sharing resistors, and the transistors are connected in series with the current-sharing resistors and then in parallel.

[0008] Preferably, the rectifier unit is composed of multiple modules connected in parallel using existing internal digitally controlled rectifier modules with communication functions. The number of parallel modules is selected according to the overall output rated power requirement of the circuit, and the power on / off and output voltage instructions are transmitted by the control unit 485A communication. At the same time, the standby, running, and fault states are also transmitted to the control unit in real time through 485A communication. The AC energy of the power grid is converted into DC voltage and stored according to the control instructions of the control unit to provide DC voltage for the linear unit.

[0009] A bidirectional constant current source circuit control method is provided. The bidirectional constant current source circuit is constructed. The control unit receives a high-precision output current analog signal i transmitted by a high-precision sampling unit, and converts it into a digital high-precision output current value i after internal high-precision A / D conversion. o When the control unit receives the output current given value I command, it uses 485B to convert the output current given value I and the digital high-precision output current value i o The linear unit first controls the corresponding direction contactor inside the closed linear unit according to the positive or negative value of the output current given value I, and then controls the corresponding direction contactor inside the closed linear unit according to the received real-time digital high-precision output current value i oAfter the closed-loop control of the output current given value I is carried out, the positive or negative transistor group is driven to amplify the power of the circuit, and the accuracy of the corresponding current output of each transistor is controlled to ensure the high-precision output of the entire linear unit; at the same time, in order to ensure that the internal transistors of the linear unit operate in the linear amplification area, the control unit uses 485A to real-timely set the given voltage value U ref Transmitted to the rectifier unit, the rectifier unit is internally regulated according to the given voltage value U ref Real-time control of its own voltage follower output realizes the control of the voltage inner loop, ensuring the stability of the voltage drop of the triode group inside the linear unit. The linear unit operates in the linear amplification area, where the given voltage value U ref as follows:

[0010] U ref =i o *R+U p

[0011] Where i o is the real-time high-precision output current value of the load side; R is the load resistance parameter; U p is the required pipe pressure drop for the linear unit.

[0012] The beneficial effects of the present invention are as follows: the bidirectional constant current source circuit and its control method of the present invention combine the high-frequency rectifier switch power supply circuit with the three-stage linear power supply circuit, and at the same time utilize the noise filtering technology, under the condition of high power and wide range current output, the current error accuracy can reach e -5 The ripple noise can be reduced to the milliampere level; compared with a single traditional three-stage linear power supply circuit, the combined circuit has higher power density and smaller size under the same power conditions. Compared with a single high-frequency switching power supply circuit, the output current accuracy and stability are improved by nearly 100 times, and the output current ripple is reduced by more than 5 times. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a circuit diagram of a high-power, high-precision, low-noise, bidirectional constant current source according to the present invention;

[0014] Figure 2 This is the internal circuit diagram of the linear unit;

[0015] Figure 3 This is a numerical diagram of the actual output current value of the bidirectional constant current source circuit in an embodiment of the present invention measured by high-precision measuring equipment. DETAILED DESCRIPTION

[0016] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0017] The high-power, high-precision, low-noise bidirectional constant current source circuit proposed in the present invention includes a rectifier unit 1, a noise filter unit 2, a linear unit 3, a high-precision sampling unit 4, an auxiliary power supply unit 5 and a control unit 6. The AC380V grid inputs the rectifier unit 1, and the rectifier unit 1 outputs a DC high voltage that enters the noise filter unit 2. The noise filter unit 2 performs high-frequency noise filtering on the DC high voltage and then outputs the output to the linear unit 3; a two-phase AC220V input is provided to the auxiliary power supply unit 5. After AC / DC conversion is performed in the auxiliary power supply unit 5, the auxiliary power supply unit 5 outputs two DC powers, wherein the output DC24V is used to power the control unit 6, and the output DC±15V is used to power the high-precision sampling unit 4; the high-precision sampling unit 4 collects the real-time current of the load and sends it to the control unit 6. The control unit 6 receives the constant current source output current set value, and the control unit 6 outputs the constant current source output current set value with positive and negative directions and the converted digital load real-time current value to the linear unit 3. The linear unit adjusts the output constant current value to the load. At the same time, the control unit 6 outputs the output set voltage value required by the rectifier unit and enters the rectifier unit 1.

[0018] Taking the rated output power of 30kW as an example, when using a high-precision, low-noise, bidirectional constant current source circuit and control method, the circuit structure is as follows Figure 1 As shown, the connection relationship of the circuit is as follows: the AC380V three-phase four-wire A, B, C, and N of the power grid are respectively connected to the rectifier unit, and the two-phase AC220V of C and N are connected to the input end of the auxiliary power supply unit, the DC24V output end of the auxiliary power supply unit is connected to one of the input ends of the control unit, and the DC±15V output end of the auxiliary power supply unit is connected to the input end of the high-precision sampling unit. At the same time, the control unit receives the current analog signal i output from the high-precision sampling unit, the rectifier unit communication signal 485A, the linear unit communication signal 485B, and the external output current set value I. The DC high voltage output of the rectifier unit main circuit is connected to the input end of the noise filter unit, the output end of the noise filter unit is connected to the input end of the linear unit, and the output end of the linear unit is connected to the load, wherein the negative output line connected to the load passes through the high-precision sampling unit.

[0019] The rectifier unit 1 can be implemented by connecting multiple modules in parallel using existing internal digitally controlled rectifier modules with communication functions. The number of parallel modules is selected according to the overall output rated power requirements of the circuit. Taking a 30kW rated output as an example, three 15kW rectifier modules with RS485 functions are connected in parallel considering the redundant design in case of faults. The modules output power according to the power on / off and output voltage instructions transmitted by the control unit 485A communication. At the same time, the 485A communication also transmits its own status such as standby, operation, and fault to the control unit in real time, so as to facilitate the overall control of the control unit. The control instructions of the control unit are used to convert the AC energy of the power grid into DC voltage and then store it to provide DC voltage for the subsequent linear units.

[0020] The noise filtering unit 2 can adopt an LC filtering circuit, a multi-stage filtering circuit, etc. For example, an LC filtering circuit is selected in which L=40μH and C=10000μF to filter the high-frequency noise generated by the rectifier unit. In actual use, the parameters are fine-tuned according to the noise frequency point.

[0021] The linear unit 3 can be realized by connecting multiple transistors in parallel with internal digital control and communication functions. At the same time, the output current is commutated by controlling two sets of contactors KZ and KF. By controlling the accuracy of the small current of each transistor working in the linear amplification area, the overall high-precision current output of the transistor group is guaranteed. Figure 2The linear unit is composed of an anti-reverse diode D, a forward transistor group Z1-Z4 connected in parallel, a negative transistor group F1-F4 connected in parallel, a positive contactor KZ, a negative contactor KF, a controller and a drive unit. The positive input terminal is connected to the positive electrode of the anti-reverse diode D, and the DC voltage support capacitor C is connected between the negative electrode of the anti-reverse diode D and the negative input terminal. The positive transistor group Z1-Z4 and the negative contactor KF normally open switch are connected in series between the negative electrode of the anti-reverse diode D and the negative input terminal. The positive transistor group Z1-Z4 and the negative contactor KF normally open switch are connected in series. The negative transistor group F1-F4 and the forward contactor KZ normally open switch are connected in series between the negative electrode of the anti-reverse diode D and the negative input terminal. The negative transistor group F1-F4 and the forward contactor KZ normally open switch are connected in series and connected to the negative end of the load. The controller and the drive unit receive the digital load real-time current value and the output current set value output by the control unit 6 through 485B. The controller and the drive unit output the drive signals of the forward transistor group Z1-Z4 and the negative transistor group F1-F4 and the control signals of the positive contactor KZ and the negative contactor KF. The 8 transistor groups are all connected in series with current-sharing resistors and then connected in parallel to output current. There are 4 groups in the positive direction and 4 groups in the negative direction. Taking this embodiment as an example, the 8 transistor groups have the same structure. Each transistor group includes 17 transistors and 17 current-sharing resistors. The transistors are connected in series with current-sharing resistors and then connected in parallel. The 17 transistors output 50A current. After the 4 positive groups are connected in parallel, a maximum constant current output of 200A can be achieved. When the controller inside the linear unit receives the forward output current value instruction from the control unit through 485B, the controller and the drive unit generate the contactor closing signal K1 to control the forward contactor KZ to close first. The controller and the drive unit generate the G1-G68 drive signals to amplify the power of the transistors S1-S68 in the forward transistor group Z1-Z4. By controlling the small current accuracy of each transistor working in the linear amplification area, the small current reaches the given current value after being connected in parallel. Then the current flows from the positive input end of the linear unit 3 through the positive 4 transistor groups Z1-Z4, the positive end of the load, the negative end of the load, and the forward contactor KZ back to the negative input end of the linear unit. When When the linear unit's internal controller receives a negative output current command from the control unit via 485B, the controller and drive unit generate contactor closure signal K2 to first close the negative contactor KF. The controller and drive unit then generate drive signals G69-G136 to amplify the power of transistors S69-S137 in the negative transistor group F1-F4. By controlling the low-current precision of each transistor operating in the linear amplification region, the low-currents, when connected in parallel, reach the specified current value. Current then flows from the linear unit's positive input terminal through the four negative transistor groups F1-F4, the negative terminal of the load, the positive terminal of the load, and the negative contactor KF, returning to the linear unit's negative input terminal. Simultaneously, the linear unit transmits its operating and fault status to the control unit in real time via 485B communication, facilitating overall control.

[0022] This power supply design aims to achieve high precision and low noise at high power levels, maximizing power density. Taking a 30kW power supply as an example, using a linear circuit alone would likely require five linear units connected in series to achieve high voltage and power, resulting in a volume approaching 2000*1000*1800mm. Using a high-frequency switching power supply alone would require a volume approaching 800*800*1000mm. While compact, achieving high precision and low noise is difficult. Therefore, a rectifier unit (a high-frequency switching power supply circuit) is used to convert the energy into DC after filtering. The linear units' inherent high precision and low noise characteristics are then leveraged for control at the output. This combined circuit achieves high-precision, low-noise current output while reducing the size by more than half compared to a linear circuit alone.

[0023] The high-precision sampling unit may adopt a high-precision DC current sensor based on the zero-flux principle. For example, a high-precision DC current sensor with a measuring range of 150A may be selected to transmit the analog signal i to the control unit.

[0024] The auxiliary power supply unit can use an industrial-grade low-power power supply component with an AC220V input and a DC24V and a DC±15V output. For example, select a 300W DC24V output power supply component and a 300W DC±15V output power supply component and use them in parallel at the AC220V input end.

[0025] The control unit can be implemented using existing circuits with data communication, data acquisition, and data processing functions, such as a digital signal processor (DSP) or a single-chip microcomputer supplemented by corresponding peripheral circuits, and at the same time using high-precision A / D conversion. The control unit receives the high-precision output current analog signal i transmitted by the high-precision sampling unit, and after internal high-precision A / D conversion, it is converted into a digital high-precision output current value i o When the control unit receives the output current given value I (positive current value is positive output, negative current value is negative current output) instruction, it uses 485B to output the digital high-precision current value i in real time. o , the output current given value I is transmitted to the linear unit. The linear unit first controls the corresponding direction contactor inside the closed linear unit according to the positive or negative of the output current given value I, and then controls the corresponding direction contactor inside the closed linear unit according to the real-time high-precision output current value i received. o After closed-loop control of the output current given value I, the four groups of transistors in the positive or negative direction are driven to amplify the circuit power, and the accuracy of the corresponding current output of each transistor is controlled to ensure the high-precision output of the entire linear unit. At the same time, in order to ensure that the transistors inside the linear unit operate in the linear amplification area, the tube voltage drop of the transistor group needs to be stable at 8V-10V, so the output voltage of the rectifier unit needs to be controlled. Taking 10V as an example, the control unit uses 485A to real-timely set the given voltage value Uref Transmitted to the rectifier unit, the rectifier unit is internally regulated according to the given voltage value U ref Real-time control of its own voltage follower output realizes the control of the voltage inner loop, ensuring that the voltage drop of the triode group inside the linear unit is stable at 10V, and the linear unit operates in the linear amplification area, where the given voltage value U ref as follows:

[0026] U ref =i o *R+U p

[0027] Where i o is the real-time high-precision output current value of the load side; R is the load resistance parameter; U p The voltage drop required by the linear unit is generally 8-10V. This embodiment takes 10V as an example.

[0028] In summary, the control unit uses the high-precision output current analog signal i transmitted by the high-precision sampling unit, and after internal high-precision A / D conversion, it communicates with the rectifier unit and the linear unit to complete the current outer loop and voltage inner loop control of the overall circuit group, thereby achieving high-power, high-precision, low-noise bidirectional constant current output to the load.

[0029] The circuit can output current with an error accuracy of e through the test platform. -5 Bidirectional constant current of magnitude, see Figure 3 , the ripple noise can be reduced to milliampere level.

[0030] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A bidirectional constant current source circuit, characterized in that: It includes a rectifier unit, a noise filter unit, a linear unit, a high-precision sampling unit, an auxiliary power supply unit, and a control unit. The rectifier unit receives AC380V from the power grid for high-frequency rectification. The rectifier unit outputs a high-voltage DC power supply that enters the noise filter unit. The noise filter unit filters the high-frequency noise in the high-voltage DC power supply and then outputs it to the linear unit. The auxiliary power supply unit receives two-phase AC220V input. After AC / DC conversion, the auxiliary power supply unit outputs two DC currents, which power the control unit and the high-precision sampling unit respectively. The high-precision sampling unit collects the real-time current of the load and sends it to the control unit. The control unit receives the given output current value of the constant current source. The control unit outputs the given output current value of the constant current source with positive and negative directions and the converted digital real-time current value of the load into the linear unit. The linear unit adjusts the output constant current value to the load. At the same time, the control unit outputs the given output voltage value required by the rectifier unit into the rectifier unit. The linear unit includes multiple sets of parallel triodes with internal digital control and communication functions, and two sets of contactors for current commutation control, which control the accuracy of the small current of each triode working in the linear amplification region to ensure the high-precision current output of the entire triode group; The linear unit is internally composed of an anti-reverse diode D, a forward transistor group connected in parallel, a negative transistor group connected in parallel, a positive contactor KZ, a negative contactor KF, a controller and a drive unit. The positive input end is connected to the positive electrode of the anti-reverse diode D, the negative electrode of the anti-reverse diode D is connected to the negative input end via a DC voltage support capacitor C, the positive transistor group and the negative contactor KF normally open switch are connected in series between the negative electrode of the anti-reverse diode D and the negative input end, and the positive transistor group and the negative contactor KF normally open switch are connected in series. The contact is connected to the positive end of the load; the negative transistor group and the positive contactor KZ normally open switch are connected in series between the negative electrode of the anti-reverse diode D and the negative input terminal, and the connection point of the negative transistor group and the positive contactor KZ normally open switch in series is connected to the negative end of the load. The controller and the drive unit receive the digital load real-time current value and the output current set value output by the control unit through 485B. The controller and the drive unit output the drive signals of the positive transistor group and the negative transistor group and the control signals of the positive contactor KZ and the negative contactor KF.

2. The bidirectional constant current source circuit according to claim 1, characterized in that: The positive transistor group and the negative transistor group have the same structure and number of groups. Each transistor group includes several transistors and a corresponding number of current-sharing resistors. The transistors are connected in series with the current-sharing resistors and then in parallel.

3. The bidirectional constant current source circuit according to claim 1 or 2, characterized in that: The rectifier unit is composed of multiple modules in parallel using existing internal digitally controlled rectifier modules with communication functions. The number of parallel modules is selected according to the overall output rated power requirement of the circuit, and the output is performed according to the power on / off and output voltage instructions transmitted by the control unit 485A communication. At the same time, the standby, running, and fault states are also transmitted to the control unit in real time through 485A communication. The AC energy of the power grid is converted into DC voltage and stored according to the control instructions of the control unit to provide DC voltage for the linear unit.

4. A bidirectional constant current source circuit control method, characterized in that: Build the bidirectional constant current source circuit described in claim 3, and the control unit receives the high-precision output current analog signal transmitted by the high-precision sampling unit i After internal high-precision A / D conversion, it is converted into a digital high-precision output current value. i o , when the control unit receives the output current given value I After the instruction, use 485B to set the output current to a given value I And digital high-precision output current value i o Transmitted to the linear unit, the linear unit first gives the value according to the output current I The positive and negative of the linear unit controls the corresponding direction contactor inside the closed linear unit, and then outputs the current value with high precision according to the real-time digital quantity received. i o And the output current set value I After the internal closed-loop control, the positive or negative transistor group is driven to amplify the power of the circuit, and the accuracy of the corresponding current output of each transistor is controlled to ensure the high-precision output of the entire linear unit. At the same time, in order to ensure that the internal transistors of the linear unit operate in the linear amplification area, the control unit uses 485A to set the given voltage value in real time. U ref Transmitted to the rectifier unit, the rectifier unit internally adjusts the voltage according to the given value. U ref Real-time control of its own voltage follower output realizes the control of the voltage inner loop, ensuring the stability of the voltage drop of the triode group inside the linear unit, and the linear unit operates in the linear amplification area, where the given voltage value U ref as follows: U ref = i o × R + U p Where, i o Provides real-time high-precision output current value for the load side; R is the load resistance parameter; U p is the required pipe pressure drop for the linear unit.

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