阅读说明：本技术 一种宽输出acdc变换电路及控制方法 (Wide-output ACDC conversion circuit and control method ) 是由 陈世杰 程宇 于 2021-08-06 设计创作，主要内容包括：本发明提供一种宽输出ACDC变换电路,包括：AC/DC变换器和DC/DC变换器,所述AC/DC变换器输出直流母线电压,所述DC/DC变换器调节所述直流母线电压并提供输出电压给负载,所述直流母线电压经过变压器传输至二次侧与所述输出电压进行比较调节产生调节信号后再传输至一次侧,所述AC/DC变换器根据所述调节信号调节所述直流母线电压。本发明的所述直流母线电压跟随所述输出电压变化,ACDC变换电路输出电压能够在很宽的范围内调节,且可以保证DC/DC变换器工作于最高效率。(The invention provides a wide output ACDC conversion circuit, comprising: the DC/DC converter is used for regulating the DC bus voltage and providing the output voltage to a load, the DC bus voltage is transmitted to the secondary side through a transformer and is compared with the output voltage to regulate to generate a regulating signal and then is transmitted to the primary side, and the AC/DC converter is used for regulating the DC bus voltage according to the regulating signal. The voltage of the direct current bus of the invention changes along with the output voltage, the output voltage of the ACDC conversion circuit can be adjusted in a wide range, and the DC/DC converter can be ensured to work at the highest efficiency.)

1. A wide output ACDC conversion circuit, comprising:

an AC/DC converter for inputting AC power and rectifying the AC power into DC bus voltage;

a DC/DC converter including a first isolation transformer and converting a DC bus voltage on a primary side into a secondary output voltage,

a second isolation transformer for sampling the DC bus voltage from the primary side and converting the DC bus voltage into a sampling voltage on the secondary side,

the signal isolation transmitter generates a first signal after the output voltage and the sampling voltage are compared and adjusted, and transmits the first signal to the primary side through the signal isolation transmitter in an isolation way,

and a controller for generating a driving signal for driving the switch in the AC/DC converter according to the first signal.

2. A wide output ACDC conversion circuit as claimed in claim 1, wherein: the signal isolation transmitter includes a first signal isolation transmitter,

the PWM conversion module is used for comparing and adjusting the output voltage serving as a reference with the sampling voltage to generate a first signal, the first signal is converted into a second signal, and the second signal is a PWM signal;

the isolation transmission module receives the second signal and transmits the second signal from the secondary side to the primary side to generate a third signal;

and the signal rectification module is used for rectifying and regulating the third signal and then transmitting the third signal to the controller.

3. A wide output ACDC conversion circuit as claimed in claim 2, wherein: the duty cycle of the second signal varies following the amplitude of the first signal.

4. A wide output ACDC conversion circuit as claimed in claim 3, wherein: and the third signal is converted into a fourth signal after being rectified and converted and then superposed with the voltage of the direct current bus, and the fourth signal is transmitted to the controller.

5. A wide output ACDC conversion circuit as claimed in claim 4, wherein: the AC/DC converter includes a DC/DC converter,

a rectification module that rectifies the alternating current into direct current,

and the power factor correction module receives the direct current input to carry out power factor correction control, and regulates the direct current input into the direct current bus voltage to ensure that the amplitude of the direct current bus voltage changes along with the output voltage.

6. A wide output ACDC conversion circuit as claimed in claim 5, wherein: the controller comprises a control unit for controlling the operation of the motor,

the first adjusting unit is used for comparing and adjusting the fourth signal with a reference voltage and multiplying the fourth signal with direct current to generate a current reference signal,

and the second adjusting unit is used for comparing and adjusting the current reference signal with the input current of the power factor correction module and then generating a driving signal through the second PWM generating unit, wherein the driving signal drives a switch in the power factor correction module.

7. A wide output ACDC conversion circuit as claimed in claim 6, wherein: the wide-output ACDC conversion circuit comprises an auxiliary power supply, wherein the auxiliary power supply is of a topological structure comprising a second isolation transformer, the second isolation transformer comprises an auxiliary winding, and the auxiliary winding is arranged on the secondary side of the second transformer and outputs sampling voltage.

8. A control method of wide output ACDC conversion circuit is characterized in that,

step S1, collecting the intermediate DC bus voltage to the secondary side by a transformer setting winding in an auxiliary power supply in the ACDC conversion circuit;

step S2, sampling the output voltage of the ACDC conversion circuit, taking the output voltage as a reference, and comparing the output voltage with the collected intermediate DC bus voltage to generate a feedback error signal;

step S3 converts the feedback error signal into a PWM duty signal;

s4, transmitting the PWM duty ratio signal to a primary side through an isolation optocoupler or an isolation transformer;

step S5 rectifies the feedback error signal into a dc voltage signal on the primary side;

step S6 injects a dc voltage signal into the PFC control feedback to adjust the intermediate dc bus voltage.

Technical Field

The invention belongs to the technical field of electric energy conversion, and relates to a method for adjusting the voltage of an intermediate direct current bus.

Background

In the high-power switching power supply in the ACDC, the mainstream architecture is AC/DC converter + DC/DC, and the converter DC/DC converter can realize the highest efficiency by using an LLC resonant converter. The LLC resonant converter can achieve higher efficiency, and is therefore commonly used in some medium-and high-power switching power supplies, but when the LLC resonant converter is applied to a scene of wide voltage range output, the LLC resonant converter cannot work at a resonance point in the whole output voltage range, but the efficiency is highest when the LLC resonant circuit works at a resonance frequency, which results in that when the LLC resonant converter is applied to wide voltage range output, its efficiency can be significantly reduced.

Disclosure of Invention

In order to solve the problem, the DC bus voltage between the AC/DC converter and the DC/DC converter needs to change along with the output voltage, so that the LLC operates at the resonance point in the entire output voltage range, thereby achieving high efficiency in the entire output voltage range.

To achieve the above and other related objects, the present invention provides a wide output ACDC conversion circuit, comprising:

an AC/DC converter for inputting AC power and rectifying the AC power into DC bus voltage;

a DC/DC converter including a first isolation transformer and converting a DC bus voltage on a primary side into a secondary output voltage,

a second isolation transformer for sampling the DC bus voltage from the primary side and converting it into a sampling voltage on the secondary side, a signal isolation transmitter for generating a first signal after comparing and adjusting the output voltage and the sampling voltage and transmitting the first signal to the primary side via the signal isolation transmitter,

and a controller for generating a driving signal for driving the switch in the AC/DC converter according to the first signal.

In an embodiment of the present invention, the signal isolation transmitter includes,

the PWM conversion module is used for comparing and adjusting the output voltage serving as a reference with the sampling voltage to generate a first signal, the first signal is converted into a second signal, and the second signal is a PWM signal;

the isolation transmission module receives the second signal and transmits the second signal from the secondary side to the primary side to generate a third signal;

and the signal rectification module is used for rectifying and regulating the third signal and then transmitting the third signal to the controller.

In an embodiment of the invention, a duty ratio of the second signal varies with an amplitude of the first signal.

In an embodiment of the invention, the third signal is converted into a fourth signal after being rectified and converted, and the fourth signal is transmitted to the controller.

In an embodiment of the present invention, the AC/DC converter includes,

a rectification module that rectifies the alternating current into direct current,

and the power factor correction module receives the direct current input to carry out power factor correction control, and regulates the direct current input into the direct current bus voltage to ensure that the amplitude of the direct current bus voltage changes along with the output voltage.

In an embodiment of the present invention, the controller includes,

the first adjusting unit is used for comparing and adjusting the fourth signal with a reference voltage and multiplying the fourth signal with direct current to generate a current reference signal,

and the second adjusting unit is used for comparing and adjusting the current reference signal with the input current of the power factor correction module and then generating a driving signal through the second PWM generating unit, wherein the driving signal drives a switch in the power factor correction module.

In an embodiment of the present invention, the wide-output ACDC conversion circuit includes an auxiliary power supply, the auxiliary power supply is a topology structure including a second isolation transformer, the second isolation transformer includes an auxiliary winding, and the auxiliary winding is disposed on a secondary side of the second transformer and outputs a sampling voltage.

The invention also provides a control method of the wide-output ACDC conversion circuit, which comprises the following steps,

step S1, collecting the intermediate DC bus voltage to the secondary side by a transformer setting winding in an auxiliary power supply in the ACDC conversion circuit;

step S2, sampling the output voltage of the ACDC conversion circuit, taking the output voltage as a reference, and comparing the output voltage with the collected intermediate DC bus voltage to generate a feedback error signal;

step S3 converts the feedback error signal into a PWM duty signal;

s4, transmitting the PWM duty ratio signal to a primary side through an isolation optocoupler or an isolation transformer;

step S5 rectifies the feedback error signal into a dc voltage signal on the primary side;

step S6 injects a dc voltage signal into the PFC control feedback to adjust the intermediate dc bus voltage.

According to the technical scheme, the direct-current bus voltage and the output voltage are used as feedback, the direct-current bus voltage is accurately adjusted, the large error caused in batch production is avoided, the deviation of the working point of the actual LLC resonant circuit is avoided, and the efficiency consistency in batch production is good.

Drawings

Fig. 1 is a block diagram of an ACDC conversion circuit according to the present invention.

FIG. 2 shows an embodiment of the present invention.

Fig. 3 is a waveform diagram of key signals in fig. 2.

Fig. 4 shows an embodiment of the power circuit of fig. 2.

Fig. 5 shows an embodiment of the PWM conversion module of fig. 2.

FIG. 6 shows an embodiment of the controller of FIG. 2 according to the present invention.

Fig. 7 shows an embodiment of the adjusting unit 251 in fig. 6 according to the present invention.

Fig. 8 is a flowchart illustrating steps of the ACDC conversion control method according to the present invention.

Detailed Description

The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.

It should be understood that the drawings attached hereto are only for the purpose of illustration and description, and are not intended to limit the scope of the present invention, which is defined by the claims, so as not to limit the scope of the present invention.

As shown in fig. 1, the ACDC converter circuit 10 includes a front-stage AC/DC converter 11 and a rear-stage DC/DC converter 12, where the AC/DC converter 11 rectifies and power factor corrects an input AC power vin to output a DC bus voltage Vbus, and the DC/DC converter 12 receives the DC bus voltage Vbus, adjusts the voltage, and performs isolation conversion to output an output voltage Vout. The direct current bus voltage Vbus is collected through an isolation transformer 13 and a sampling voltage Vf is output, the sampling voltage Vf and the output voltage Vout are compared through a signal isolation transmitter 14 and then output to a controller 15, and the controller 15 controls the AC/DC converter 11 to enable the direct current bus voltage Vbus output by the AC/DC converter to follow the output voltage Vout to change. The high-voltage safety problem is involved between the output voltage Vout and the direct-current bus voltage Vbus, so that isolation is needed, and the isolation transformer 13 isolates the output voltage Vout from the direct-current bus voltage Vbus, so that safety is guaranteed. The output direct-current bus voltage Vbus is made to change along with the output voltage Vout, and when the DC/DC converter 12 is an LLC resonant converter, the DC/DC converter can operate at a resonant point within the entire output voltage range, thereby achieving wide-range output and high efficiency within the entire output voltage range.

In an embodiment of the present invention, as shown in fig. 2, the AC/DC converter 21 includes a rectifying module 211 receiving the AC power Vin and outputting a DC power Vin, and a power factor correction module 212 receiving the DC power Vin, performing power factor correction and voltage regulation, and outputting a DC bus voltage Vbus. The DC/DC converter 12 receives the DC bus voltage Vbus and outputs an output voltage Vout, and the DC/DC converter 12 is an isolated converter including a transformer T1, such as an LLC resonant converter, and has high conversion efficiency.

The ACDC conversion circuit 20 further includes an auxiliary power supply 26, which receives the dc bus voltage Vbus, and after the dc bus voltage Vbus is isolated and converted, the auxiliary power supply 26 provides an auxiliary voltage Vaux, and the auxiliary power supply 26 includes a transformer T2. In the embodiment of the invention, a winding N3 is disposed on the secondary side of the transformer T2, and the output of the winding N3 is the sampled voltage Vf. The signal isolation transmitter 24 receives the sampled voltage Vf and the output voltage Vout, as shown in fig. 2, the signal isolation transmitter 24 includes a PWM conversion unit 241, an optical coupler 242, and a signal rectification module 243, and in combination with fig. 3, the PWM conversion unit 241 receives the sampled voltage Vf and the output voltage Vout, and converts the sampled voltage Vf and the output voltage Vout into a signal Ve1, which is a PWM wave containing information of the duty ratio D. For example, the difference between the output voltage Vout and the sampling voltage Vf becomes larger, the duty ratio of the signal Ve1 becomes smaller, the signal Ve1 is transmitted to the primary side through the optical coupler 242 to obtain a signal Ve2, the signal Ve2 is rectified by the signal rectification module 243 to obtain a signal Ve3, the signal Ve3 is input to the controller 25 as a voltage feedback signal of the voltage control loop, and is compared and adjusted with the voltage reference signal Vref to output a current reference signal Iref of the current control loop, the controller simultaneously samples the input current Iin of the power factor correction module, and the current Iin and the current reference signal Iref generate a driving signal Vd of the switching device in the power factor correction module 212 after comparison and adjustment.

In this embodiment, the optical coupler 242 is used as an exemplary embodiment of a signal isolation transmission device, but the present invention is not limited thereto, and any device capable of achieving the signal isolation transmission function may be used as an alternative to the embodiment of the present invention.

In fig. 3, when Vf is equal to Vout, the duty ratio of Ve1 is 0.5, Vout becomes larger and larger than Vf, and the duty ratio becomes smaller; vout becomes smaller than Vf, and the duty ratio becomes large.

The dc bus voltage Vbus is collected to the secondary side by means of winding coupling of the auxiliary power supply 26. The sampled output voltage Vout is used as a reference, the sampled output voltage Vout is compared with the sampled voltage Vf to generate a feedback error signal, the feedback error signal is converted into a PWM duty ratio signal Ve1, the signal Ve1 is transmitted to the primary side through an isolation optocoupler or an isolation transformer, and the signal rectifying module 243 rectifies the signal Ve2 into a direct-current voltage signal Ve 3. The dc voltage signal Ve3 is injected into the controller to regulate the intermediate dc bus voltage Vbus.

Fig. 4 shows an embodiment of the power circuit of the present invention, where the AC/DC converter 41 includes a rectifying module 411 and a power factor correction module 412, the rectifying module 411 is a full-bridge rectifying circuit formed by diodes D1-D4, the power factor correction module 412 is a boost converting module formed by an inductor L1, a switch S5 and a diode D9, the DC/DC converter is an LLC resonant converter, which includes a full-bridge module formed by switches S1-S4, a resonant module formed by a capacitor C2, an inductor L2 and a transformer T1, and a rectifying module formed by diodes D5-D8, and the capacitor Co performs output filtering rectification. The auxiliary power supply 46 is a flyback converter and comprises a transformer T2 and a switch S6, the switch S6 is connected in series with a primary winding N1 of the transformer T2, the transformer T2 comprises secondary windings N2 and N3, the winding N2 outputs an auxiliary voltage Vaux after being rectified and filtered by a diode D10 and a capacitor C3, and the winding N3 outputs a sampling voltage Vf after being rectified and filtered by a diode D11 and a capacitor C4, namely, the dc bus voltage is collected to the secondary side by the winding coupling mode of the auxiliary power supply 46.

Fig. 5 is a diagram of an embodiment of the PWM conversion module 241 in fig. 2, which includes a regulating unit 2411, where the regulating unit 2411 receives the output voltage Vout and the sampled voltage Vf, makes the difference between the output voltage Vout and the sampled voltage Vf, and generates a signal Ve0 after being regulated by a regulating manner such as PI and PID, and the PWM generating unit 2412 generates a PWM signal Ve1 according to the signal Ve0, and a duty ratio of the signal Ve1 represents a difference between the output voltage Vout and the sampled voltage Vf. For example, the output voltage Vout becomes large so that the difference between the output voltage Vout and the sampling voltage Vf becomes large in the forward direction, the duty ratio is decreased from 0.5, for example, to 0.3, as shown in fig. 3, the output voltage Vout becomes small and smaller than the sampling voltage Vf so that the difference between the output voltage Vout and the sampling voltage Vf becomes large in the reverse direction, and the duty ratio becomes large from 0.5, for example, to 0.7.

Fig. 6 shows an embodiment of the controller 25 in fig. 2, in which the adjusting unit 251 receives a difference value between a voltage reference signal Vref and a signal Ve3, outputs a regulated signal Vcom, and multiplies the signal Vcom by a direct current Vin to output a current reference signal Iref, the adjusting unit 252 receives the difference value between the current reference signal Iref and a current Iin, and outputs the regulated difference value to the PWM generating unit 253, the PWM generating unit 253 outputs a driving signal Vd, and controls a switching device in the power factor correction module 212, such as the switch S5 in fig. 4.

Fig. 7 is a specific embodiment of the signal rectifying module 243 in fig. 2 and the adjusting unit 251 in fig. 6, where the signal rectifying module 243 includes a resistor R1, a diode D12, a resistor R2, a resistor R3, and a capacitor C5, the resistor R1 limits current, the resistors R2 and R3 divide the voltage Vbus, and the capacitor C5 stabilizes voltage. And rectifying the signal Ve2 and then superposing the rectified signal Ve2 with the voltage Vbus to obtain a signal Ve 3. The adjusting unit 251 receives the signal Ve3 and the voltage reference signal Vref, compares and adjusts the signal Ve3 and outputs a current reference signal Iref. The adjusting unit 251 is a proportional-integral adjuster.

Fig. 8 is a control method of the wide output ACDC converter circuit according to the present invention, in step S1, a transformer setting winding in an auxiliary power supply in the ACDC converter circuit collects an intermediate dc bus voltage to a secondary side; step S2, sampling the output voltage of the ACDC conversion circuit, taking the output voltage as a reference, and comparing the output voltage with the collected intermediate DC bus voltage to generate a feedback error signal; step S3 converts the feedback error signal into a PWM duty signal; s4, transmitting the PWM duty ratio signal to a primary side through an isolation optocoupler or an isolation transformer; step S5 rectifies the feedback error signal into a dc voltage signal on the primary side; step S6 injects a dc voltage signal into the PFC control feedback to adjust the intermediate dc bus voltage.

In summary, the invention precisely adjusts the intermediate DC bus voltage to follow the output voltage, so that the DC/DC converter can operate in the state of highest efficiency, and the output voltage can be adjusted in the largest range.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.