TWI869843B - Analog Digital Integrated System - Google Patents

Abstract

An analog-digital integration system includes a feedforward voltage input device, a voltage compensator and a multiplier. The multiplier is composed of a plurality of operational amplifiers and a decoder. The multiplier is used to perform analog-to-digital conversion and decoding on a first input potential analog signal input by the feedforward voltage input device and a second input potential analog signal input by the voltage compensator, obtain a potential adjustment ratio, and adjust the first input potential analog signal according to the potential adjustment ratio to generate a current command analog signal.

Description

Analog Digital Integrated System

The present invention relates to an analog digital integration system, in particular to an analog digital integration system that does not require the use of an MCU (or DSP) and does not require programming to execute digital functions.

Most common power converters are either analog or digital controllers, but both types have certain problems. The following describes the problems of analog and digital controllers respectively.

The circuit design of analog controllers may encounter the following problems: (1) Poor accuracy; (2) Too many functions and complex circuits; (3) Failure to provide sufficient application flexibility; (4) Engineering design application personnel need engineers with stronger professional capabilities.

The application and design issues of digital controllers are as follows: (1) High cost. Generally, to execute the actions of analog circuits, a high-speed computing core, such as DSP level, must be used; (2) Development assistance from firmware personnel is required, and the hardware personnel of analog applications need to coordinate the development; (3) The development process is long. Since MCU/DSP are both low-voltage components, if they are applied to high voltages greater than 5V, it becomes necessary to add voltage divider resistors. At the same time, to avoid interference problems, filter capacitors must also be added, resulting in a lot of additional resistors and capacitors.

Therefore, both analog and digital controllers have their shortcomings, but also their advantages. From the perspective of traditional PFC controllers, most are analog designs. From the perspective of design application, they are suitable for most engineers, especially in terms of adjusting the compensator, which is quite simple and easy. However, in recent years, due to the development of network communication related industries and the large-scale construction of servers, the requirements for power supply have become higher and higher. Well-known foreign companies have proposed digital PFC to meet the power supply requirements. Therefore, the role of power control has changed from analog to digital. Almost all design engineers must have an additional firmware engineer to assist in completing the setting of the compensator on the control, which cannot be completed by hardware engineers.

To further illustrate the characteristics and problems of the controller circuit, an active power factor corrector must control both the input current and the output voltage, and the command of the current control loop is determined by the rectified line voltage, so the input impedance of the converter can be made resistive. The output voltage is controlled by changing the average value of the current command.

The analog multiplier multiplies the rectified line voltage by the output of the voltage error amplifier to generate a current control command. Therefore, the current control command has the same shape as the input voltage, and its average value represents the output voltage control command size.

As shown in FIG. 1 , the basic controller circuit 3 required for the active power factor corrector (high power factor switching regulator 31) is used to output power to the load 35, wherein the output of the output current multiplier is called Imo, and the output of this multiplier 32 is the control command of the input current.

As shown in Figure 1, the input of the multiplier 32 (the voltage after the input voltage is rectified) is expressed in the form of current, because this is the basic concept commonly used in control ICs such as UC3854/ML4812/CM6502S.

In addition to the multiplier 32, it also includes a squarer 33 and a divider 34. The main function of these circuits is to divide the output of the voltage error amplifier by the average value of the input voltage and take the square of the value. The final value is multiplied by the rectified voltage signal Iac. The current Iac at the output of the rectifier is connected to the input of the multiplier via a resistor to track the input voltage waveform signal.

This additional circuit will keep the voltage loop gain constant. Without it, the voltage loop gain will be the square of the average input voltage. The average value of the input voltage is called the feedforward voltage signal or Vff. When the feedforward voltage signal is fed forward to the voltage loop gain, this value provides an open loop correction and this value needs to be squared and used as the divisor of the voltage error amplifier output voltage signal.

In order to improve the power factor, the current command must closely follow the input voltage. If the voltage loop bandwidth is too large, the input current will be severely distorted in order to maintain the output voltage at a constant value. Therefore, the voltage loop bandwidth must be less than the input power frequency. Based on transient response considerations, the voltage loop bandwidth should be as large as possible. Therefore, the closer the bandwidth is to the power frequency, the better. The purpose of adding the square of the average input voltage is to keep the voltage loop constant without changing with the average input voltage. This characteristic controls the power delivered to the load by the voltage error amplifier.

This type of traditional PFC control circuit will produce the following problems: 1. Large distortion, generally caused by excessive ripple in the multiplier input feedforward voltage and voltage loop compensation for dynamic response. 2. When the system is turned on and off quickly, the signal change of the multiplier input feedforward voltage cannot be synchronized, resulting in incorrect multiplier output signal and causing the current loop to follow the wrong current, which can easily cause damage or explosion of the PFC main switch. 3. When the system is in a fast high or low voltage change, the signal change at the input of the multiplier cannot be synchronized, resulting in an incorrect output signal of the multiplier, which in turn causes the current loop to follow the wrong current command, which can easily cause damage or explosion of the PFC main switch. 4. When the load changes, the signal of the voltage loop has a very small bandwidth due to current distortion, causing the output voltage to change with a delay before the multiplier input is changed when the load changes. Therefore, the output voltage will drop too low, making it impossible for the downstream circuit to regulate the voltage. 5. During system verification, the current overshoot and oscillation caused by the feedback circuit following the wrong current command change during SAGING may cause the PFC main switch to explode.

Compared with the traditional PFC control circuit, this case develops an analog-digital hybrid PFC controller, which uses a digital ADC to read the input voltage signal and the voltage loop output signal to determine the size of the current command, so the entire digital core can be regarded as a digital multiplier. This case uses the advantages of digital high-speed calculation to immediately generate an almost distortion-free current command and compare it with CS, and then compare the DAC output with the internal RAMP to generate the required PWM, so that the overall loop can achieve low-distortion high power factor correction. Therefore, this case should be an optimal solution.

The analog-digital integration system of the present invention at least comprises: a feedforward voltage input device for generating a first input potential analog signal; a voltage compensator for generating a second input potential analog signal; a multiplier at least comprising a first input conversion unit electrically connected to the feedforward voltage input device for converting the first input potential analog signal into a first input potential digital signal; a second input conversion unit electrically connected to the voltage compensator for converting the second input potential analog signal into a first input potential digital signal. Two input potential digital signals; a digital signal decoding unit electrically connected to the first input conversion unit and the second input conversion unit, for generating a potential adjustment ratio according to the first input potential analog signal and the second input potential analog signal; and an output potential adjustment unit electrically connected to the digital signal decoding unit and the forward feed voltage input device, for adjusting the first input potential analog signal according to the potential adjustment ratio generated by the digital signal decoding unit to generate a current command analog signal.

More specifically, the first input conversion unit, the second input conversion unit and the output potential adjustment unit are an operational amplifier.

More specifically, the digital signal decoding unit is a decoder.

More specifically, the first input potential analog signal is a reference voltage, and the second input potential analog signal is an adjustment voltage. The adjustment voltage changes according to an output power, and the change in the reference voltage is used to define the potential adjustment ratio.

Other technical contents, features and effects of the present invention will be clearly presented in the following detailed description of the preferred embodiments with reference to the drawings.

Please refer to FIG. 2 , which is a schematic diagram of the structure of the analog digital integration system of the present invention, wherein the analog digital integration system at least includes a feedforward voltage input device 11 , a voltage compensator 12 and a multiplier 13 .

The analog-digital integration system of the present invention is used to connect in series a power conversion circuit 2 (such as a power factor correction circuit (PFC) or other types of power conversion circuits), and can change the structure of the analog-digital integration system according to the type of the power conversion circuit.

The feedforward voltage input device 11 is electrically connected to the power conversion circuit 2 to generate a first input potential analog signal.

The voltage compensator 12 is electrically connected to the power conversion circuit 2 to generate a second input potential analog signal.

The multiplier 13 at least includes a first input conversion unit 131 , a second input conversion unit 132 , a digital signal decoding unit 133 , and an output potential adjustment unit 134 .

The first input conversion unit 131 is an operational amplifier (Analog-to-Digital Converter, ADC). The first input conversion unit 131 is electrically connected to the feedforward voltage input device 11 to convert the first input potential analog signal into a first input potential digital signal.

The second input conversion unit 132 is an operational amplifier (Analog to Digital Converter, ADC). The second input conversion unit 132 is electrically connected to the voltage compensator 12 to convert the second input potential analog signal into a second input potential digital signal.

The digital signal decoding unit 133 is a decoder. The digital signal decoding unit 133 is electrically connected to the first input conversion unit 131 and the second input conversion unit 132. The digital signal decoding unit 133 is used to generate a potential adjustment ratio according to the first input potential analog signal and the second input potential analog signal.

The output potential adjustment unit 134 is an operational amplifier (Digital to Analog Converter, DAC), and the output potential adjustment unit 134 is electrically connected to the digital signal decoding unit 133 and the forward feed voltage input device 11, and is used to adjust the first input potential analog signal according to the potential adjustment ratio generated by the digital signal decoding unit 133 to generate a current command analog signal.

The first input potential analog signal is a reference voltage, and the second input potential analog signal is an adjustment voltage. The adjustment voltage changes according to an output power, and the change of the reference voltage is used to define the potential adjustment ratio.

As shown in FIG. 3A, it is a schematic diagram of a power conversion circuit of a power factor correction (PFC) circuit. This case uses the PFC circuit as an example, and FIGS. 3B-1, 3B-2, 3B-3 and 3B-4 are schematic diagrams of the circuit implementation of the analog digital integration system of this case.

As shown in FIG. 3A , the framed point A is connected in series to the voltage divider circuit of the feedforward voltage input 11. The feedforward voltage input 11 can be used as a buffer through an operational amplifier to solve the load effect. However, the present invention can also not use a buffer and directly divide the voltage at point A for input, and the first input conversion unit 131 can perform sampling to obtain a first input potential analog signal.

As shown in FIG. 3A , the boxed point B is connected in series to the voltage divider circuit of the voltage compensator 12 and then used as a voltage compensator through an operational amplifier to determine the output power for power regulation. The second input conversion unit 132 can perform sampling to obtain and output a second input potential analog signal.

As shown in FIG. 3A , the boxed point C is connected in series to the current compensator 14 , and the current command analog signal output by the output potential adjustment unit 134 is used to control the current compensator 14 , and is output to the PWM generator to output a PWM signal to the PWM contact of the power conversion circuit 2 .

As shown in FIG. 3B-3 , the timing controller 15 is used to generate the timing required by the first input conversion unit 131 (ADC1), the second input conversion unit 132 (ADC2), the digital signal decoding unit 133 (DECODER1), the protection logic 16 (DECODER2) and the PWM generator 17.

As shown in FIG. 3B-3, the protection logic 16 is a decoder used to protect logic and judge abnormalities.

As shown in Figure 1 and [0010], the traditional controller circuit divides the output of the amplifier (the second input potential analog signal) by the square of the average value of the input voltage (the average value of the input voltage is called the feedforward voltage signal or Vff), and then multiplies the final value by the rectified voltage signal Iac. The current Iac (the first input potential analog signal) at the output of the rectifier is connected to the input of the multiplier via a resistor to track the input voltage waveform signal.

Since the rectified voltage signal and the value obtained by taking the square of the average value of the input voltage have a certain correlation, the "rectified voltage signal" divided by the "value obtained by taking the square of the average value of the input voltage" is defined as an X value.

Therefore, if you want to obtain the current command analog signal (Imo), the traditional method is as described above, as shown in Figure 1. For example, when point a (the rectified voltage signal) is 100V, point b (the output of the amplifier) is 5V, and point c (the average value of the input voltage) is (100 ² ), the final current obtained is 0.05 (0.01x5).

If point a is 200V and point b is 5V, Vff is (200 ² ), so the final current is 0.025 (0.005x5).

However, as mentioned above, the traditional method has a big problem. In order to respond in time, this case proposes to replace the traditional control mechanism with the concept of potential adjustment ratio logic. Since the mains electricity will always change, the ratio of point a to the square of the average value of the input voltage will change. However, since point a is related to the square of the average value of the input voltage, point a will also be related to the X value ("point a" divided by "the square of the average value of the input voltage"). Therefore, the relationship between point a and the X value can be tabulated and used as a potential adjustment ratio logic table.

The potential adjustment ratio logic table is built into the digital signal decoding unit 133, so when the voltage at point a changes, the ratio to be changed can be obtained by looking up the table based on the signal at point a.

In addition, after obtaining the relationship between point a and the X value, point b can be added to expand the potential adjustment ratio logic table to list multiple possible combinations. Therefore, after obtaining point a and point b, the corresponding potential adjustment ratio can be found according to point a and point b, and then the output potential adjustment unit 134 adjusts the first input potential analog signal according to the potential adjustment ratio to generate a current command analog signal.

The analog-digital integration system provided by the present invention has the following advantages when compared with other conventional technologies: 1. The present invention uses multiple operational amplifiers and a decoder to form a multiplier, wherein the decoder determines the requirements of the control mechanism based on the analog signals of the two operational amplifiers at the input end, and controls the subsequent loop through the operational amplifier at the output end. 2. The architecture of the present invention can reduce the complexity of digital control. As long as the content of the decoder is modified according to the design requirements, an analog and digital hybrid control architecture can be completed. 3. Compared with using a high-end MCU and designing its operation program, the present invention directly designs the decoding logic in the decoder, so its design is very simple and can greatly save costs. 4. The present invention can be applied to different power conversion circuits by simply changing the decoding logic inside the decoder. Therefore, the structure of the present invention can be applied to different types of power conversion circuits. 5. This case uses the advantages of digital control to solve the common problems of traditional PFC. The advantages of digitization are as follows: (1) High-speed sampling, reducing current THD, and improving dynamic response. (2) Accurate logic judgment: fast system startup and shutdown, fast high and low voltage changes of the mains. (3) Stable time and timing control: solve SAGING. 6. This solution has the advantages of analog control. Since the analog compensator is adopted by using simple hardware engineering settings, no firmware personnel assistance is required. At the same time, it achieves better characteristics, better costs and shorter development time than digital PFC. 7. The distortion sources of traditional PFC include the bridge rectifier at the input, the output of the multiplication circuit, and the ripples in the output and the forward feed voltage. Compared with the known technology, this case uses high-speed digital processing, the output of the multiplication circuit and the ripples in the output, which can reduce the output distortion of the multiplier caused by the continuous wave to the minimum. At the same time, the amplifier of the current loop uses a transconductance amplifier with a voltage lower than +/-1mV, which further reduces the distortion to 2%, making the characteristics of this case surpass the control DSP commonly used in PFC (such as: UCD3138, etc.). 8. The distortion sources of traditional PFC generally include the bridge rectifier at the input, the output of the multiplication circuit, and the ripples in the output and feedforward voltage. To solve the distortion problem, the output voltage and feedforward voltage loop can only be slowed down, which causes the input voltage and output voltage to fail to respond in dynamic response. Compared with the known technology, this case adopts the high-speed characteristics of digital processing and combines a multi-stage transconductance amplifier, so the multiplier output can be generated without the traditional feedforward voltage, and digital sampling can be used at the output voltage to achieve fast dynamic response. 9. The distortion sources of traditional PFC generally include the bridge rectifier at the input, the output of the multiplication circuit, and the ripples in the output and the feedforward voltage. To solve the distortion problem, the output voltage and the feedforward voltage loop can only be slowed down, which causes the input voltage and the output voltage to fail to respond in a dynamic response. Compared with the known technology, this case adopts the high-speed characteristics of digital processing and combines a multi-stage transconductance amplifier, so the multiplier output can be generated without the traditional feedforward voltage. This means that since high-speed digital sampling can immediately respond to changes in the input voltage and then immediately change the multiplier output, it avoids the input current being abnormal due to the multiplier output error, which in turn causes the PFC. MOSFET burns out. 10. There are two conventional PFC control methods (CRM (PEAK CURRENT MODE + FM) and CCM (AVERAGE CURRENT MODE + FIX FREQUENCY)). Compared with conventional PFC control methods, this case combines the two control methods. As long as the PFC inductor is properly designed, the efficiency can be improved while taking into account the current distortion. The use of multi-mode operation can change the traditional use of SIC DIODE and foreign COOLMOSFET to general PFC diodes and Taiwan-made MOSFETs to achieve high efficiency and low cost design.

The present invention has been disclosed through the above-mentioned embodiments, but they are not used to limit the present invention. Anyone familiar with this technical field and having common knowledge can make some changes and modifications without departing from the spirit and scope of the present invention after understanding the above-mentioned technical features and embodiments of the present invention. Therefore, the scope of patent protection of the present invention shall be determined by the claim items attached to this specification.

11: Feedforward voltage input 12: Voltage compensator 13: Multiplier 131: First input conversion unit 132: Second input conversion unit 133: Digital signal decoding unit 134: Output potential adjustment unit 14: Current compensator 15: Timing controller 16: Protection logic 17: PWM generator 2: Power conversion circuit 3: Basic controller circuit 31: High power factor switching regulator 32: Multiplier 33: Squarer 34: Divider 35: Load

[Figure 1] is a circuit diagram of a basic controller circuit for conventional PFC. [Figure 2] is a schematic diagram of the architecture of the analog-digital integration system of the present invention. [Figure 3A] is a schematic diagram of the PFC circuit of the analog-digital integration system of the present invention. [Figure 3B-1] is a schematic diagram of a partial circuit implementation of the analog-digital integration system of the present invention. [Figure 3B-2] is a schematic diagram of a partial circuit implementation of the analog-digital integration system of the present invention. [Figure 3B-3] is a schematic diagram of a partial circuit implementation of the analog-digital integration system of the present invention. [Figure 3B-4] is a schematic diagram of a partial circuit implementation of the analog-digital integration system of the present invention.

11: Feedforward voltage input 12: Voltage compensator 13: Multiplier 131: First input conversion unit 132: Second input conversion unit 133: Digital signal decoding unit 134: Output potential adjustment unit 2: Power conversion circuit

Claims (4)

An analog-digital integration system at least comprises: A feedforward voltage input device for generating a first input potential analog signal; A voltage compensator for generating a second input potential analog signal; A multiplier at least comprises: A first input conversion unit electrically connected to the feedforward voltage input device for converting the first input potential analog signal into a first input potential digital signal; A second input conversion unit electrically connected to the voltage compensator for converting the second input potential analog signal into a second input potential digital signal; A digital signal decoding unit is electrically connected to the first input conversion unit and the second input conversion unit to generate a potential adjustment ratio according to the first input potential analog signal and the second input potential analog signal; and an output potential adjustment unit is electrically connected to the digital signal decoding unit and the feedforward voltage input device to adjust the first input potential analog signal according to the potential adjustment ratio generated by the digital signal decoding unit to generate a current command analog signal. The analog-digital integration system as described in claim 1, wherein the first input conversion unit, the second input conversion unit and the output potential adjustment unit are an operational amplifier. An analog-digital integration system as described in claim 1, wherein the digital signal decoding unit is a decoder. An analog-digital integration system as described in claim 1, wherein the first input potential analog signal is a reference voltage, the second input potential analog signal is an adjustment voltage, the adjustment voltage changes according to an output power, and the change in the reference voltage is used to define the potential adjustment ratio.

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