CN102594141B - Digital switching power supply conversion device and method - Google Patents

Abstract

The invention discloses a digital switch power conversion device and method. The device includes an analog-to-digital conversion unit, three summation units and a drive unit. The method includes: comparing the digitized output voltage signal with the current reference voltage signal to obtain an error voltage signal; summing the error voltage signal and the difference between the current reference voltage signal and the previous reference voltage signal, and according to the calculated and result in generating a pulse frequency modulation signal with a corresponding duty ratio; the change of the output voltage signal of the switching power supply is controlled according to the duty ratio of the pulse frequency modulation signal. The invention adopts the digital-analog hybrid technology, can respond quickly to the output voltage and the reference voltage at the same time, and can adapt to the requirement of the current digital system on the change of the power supply voltage. And its circuit scale is small, has very good applicability.

Description

A digital switching power supply conversion device and method

technical field

The invention relates to the field of switching power supply conversion, in particular to a digital switching power supply conversion device and method.

Background technique

In order to achieve high efficiency of power supply, switching power supply is widely used now. Switching power supplies can be divided into Buck (step-down), Boost (step-up) and Buck/Boost (step-down/boost) types according to the relationship between the input and output voltages, among which the Buck type for step-down is the most commonly used. With the development of portable products, the power consumption requirements of the system are increased, and the output of the power supply is required to have the ability of self-adaptation or dynamic adjustment. However, the usual switching power supply circuits are implemented by analog circuits, and the switching power supply realized by analog circuits is not very convenient for applications that need to dynamically adjust the voltage. Therefore, it is necessary to digitize the switching power supply to facilitate the connection with digital circuits.

There are many ways to realize the digital switching power supply. The main method is to replace the error amplifier, comparator and other circuits in the analog switching power supply with digital circuits. ) signal controls the power switch to realize power conversion.

US patent US6005377 is a typical digital switching power supply. Its approach is to faithfully replace the comparator, error amplifier, ramp generation circuit, etc. in the analog switching power supply with digital circuits, and at the same time add an ADC and a DAC and other circuits. This method is simple and easy to implement. Its disadvantages It is realized by using the look-up table method, which does not give full play to the flexible characteristics of the digital circuit, and the structure of the digital circuit is complex.

US Patent No. 7,141,956 is another structure for realizing a digital switch circuit. It consists of two control loops, fast and slow. The fast loop realizes the fast tracking of the voltage, and the slow loop realizes the precise control of the voltage, achieving a better compromise between speed and precision. The disadvantage of this structure is that multiple analog circuits such as ADCs and DACs are used, and the circuit scale is large. In addition, this structure does not consider much in response to the requirements of digital systems for power changes.

US Patent US7710092 is an improvement of US Patent US7141956, which mainly simplifies the structure of the circuit, improves the response speed of the system loop, and uses self-tracking technology to achieve a rapid response to output voltage changes. The response speed is not considered much, and the circuit is supported by analog modules such as ADC and DAC at the same time, and the circuit scale is relatively large.

When the above-mentioned digital switching power supplies are used in digital systems, they cannot quickly respond to the requirements of digital systems for changes in output power supply voltage, and the circuit scale is relatively large, and they cannot meet the requirements of current digital systems for energy saving.

Contents of the invention

The invention provides a digital switching power supply conversion device and method to solve the problem in the prior art that the digital switching power supply cannot quickly respond to the requirements of the digital system for the change of the output power supply voltage.

Technical scheme of the present invention comprises:

A digital switching power conversion device, comprising:

An analog-to-digital conversion unit, configured to perform analog-to-digital conversion on the output voltage signal of the switching power supply and output it to the first summation unit;

The first summation unit is used to compare the digital voltage signal output by the analog-to-digital conversion unit with the current reference voltage signal to obtain an error voltage signal and output it to the second summation unit;

The third summing unit is used to determine the difference between the current reference voltage signal and the previous reference voltage signal, and output it to the second summing unit;

The second summation unit is used to sum the output signal of the first summation unit and the output signal of the third summation unit and then output to the pulse frequency modulation signal generation unit;

The drive unit is used to generate a pulse frequency modulation signal with a corresponding duty ratio according to the output signal of the second summation unit, and control the output voltage signal of the switching power supply to change according to the duty ratio of the pulse frequency modulation signal.

Further, the device also includes:

A digital filter, configured to filter the error voltage signal output by the first summation unit and output it to the second summation unit.

Further, the digital filter provides at least two zeros to compensate the influence of the output double pole on the loop stability.

Further, the analog-to-digital conversion unit is implemented by a flash analog-to-digital converter or a pipelined analog-to-digital converter.

Further, the driving unit realizes the control of the change of the output voltage signal of the switching power supply by controlling the switching unit to be turned on and off according to the duty cycle of the pulse frequency modulation signal.

Further, the switch unit is a MOS double switch.

Further, the analog-to-digital conversion unit performs analog-to-digital conversion on the output voltage signal of the switching power supply after being divided by the resistance, and then outputs it to the first summing unit.

A digital switching power conversion method, comprising the steps of:

Perform analog-to-digital conversion on the output voltage signal of the switching power supply to obtain a digital output voltage signal;

Comparing the digitized output voltage signal with the current reference voltage signal to obtain the error voltage signal;

The error voltage signal, and the difference between the current reference voltage signal and the previous reference voltage signal are summed, and a pulse frequency modulation signal with a corresponding duty ratio is generated according to the summation result, and the duty ratio of the pulse frequency modulation signal is Control the change of the output voltage signal of the switching power supply.

Further, the analog-to-digital conversion of the output voltage signal of the switching power supply is implemented by using a flash analog-to-digital converter or a pipelined analog-to-digital converter.

Further, according to the duty cycle of the pulse frequency modulation signal, by controlling the switch unit to be turned on and off, the control of the change of the output voltage signal of the switching power supply is realized.

The beneficial effects of the present invention are as follows:

The technical scheme of the present invention overcomes the problem that the digital switching power supply in the prior art cannot quickly respond to the requirements of the digital system for the change of the output power supply voltage, adopts the digital-analog hybrid technology, and has a fast response to the output voltage and the reference voltage at the same time, It can adapt to the requirements of current digital systems for power supply voltage changes, and can realize fast and flexible output voltage control, and its circuit scale is small, which can be easily realized and has good applicability.

Description of drawings

Fig. 1 is the circuit schematic diagram of the digital switching power conversion device of the present invention;

FIG. 2 is a flow chart of the digital switching power supply conversion method of the present invention.

Detailed ways

The specific implementation process of the present invention will be further described in detail below in conjunction with each accompanying drawing.

Please refer to Fig. 1, which is a schematic circuit diagram of the digital switching power conversion device of the present invention, as can be seen from the figure, the digital switching power conversion device of the present invention mainly includes an analog-to-digital conversion (ADC) unit, three summation unit, a digital filter H(z), a digital delay unit Z-1, a drive unit and a switch unit, wherein the drive unit further includes a pulse frequency modulation (PWM) signal generation unit and a drive control unit.

The output voltage signal _V0 of the switching power supply enters the input terminal of the ADC unit after being divided by a resistor, and the output of the ADC unit is a digital signal of N bits, and the inversion of this digital signal and the digital reference signal digital Ref enters the first summing unit, The output of the first summing unit circuit is connected to the input of the digital filter H (z), the coefficient of the digital filter H (z) is stored in the corresponding register, and the output of the digital filter H (z) is connected to the second summing unit One input terminal of the second summation unit, the other input terminal of the second summation unit is connected to the output of the third summation unit; one input of the third summation unit is the digital reference signal digital Ref, and the other input is the digital reference signal digital Ref through The signal after the digital delay unit Z ^-1 ; the output of the second summation unit is connected to the PWM signal generating unit, the output of the PWM signal generating unit is connected to the input of the drive control unit, and the drive control unit controls the on and off of the switch unit, Then the output voltage signal V ₀ is formed after filtering.

The specific functions of each component in the above-mentioned digital switching power conversion device are as follows:

The ADC unit is used to perform analog-to-digital conversion on the output voltage signal of the switching power supply after the resistor divider and output it to the first summation unit. Considering the needs of the loop response speed, the ADC unit here must have a fast conversion speed;

The first summation unit is used to compare the digital voltage signal output by the ADC unit with the current reference voltage signal to obtain an error voltage signal, which is filtered by the digital filter H(z) and then output to the second summation unit ;The digital filter H(z) is also used to compensate the response of the loop and increase the stability of the loop;

The third summing unit is used to determine the difference between the current reference voltage signal and the previous reference voltage signal, and output it to the second summing unit;

The second summing unit is used for summing the output signal of the first summing unit and the output signal of the third summing unit and then outputting to the PWM signal generating unit;

The PWM signal generation unit is used to generate a PWM signal with a corresponding duty ratio according to the output signal of the second summation unit and output it to the drive control unit;

The drive control unit is used to control the switching unit on and off according to the duty cycle of the received PWM signal to control the change of the output voltage signal of the switching power supply. The switching unit is a MOS double switch.

Wherein, the specific process of the drive control unit controlling the change of the output voltage signal of the switching power supply according to the duty cycle of the received PWM signal is as follows:

The drive control unit receives the PWM signal, and generates two non-overlapping PWM signals according to the duty cycle of the received PWM signal to drive the upper and lower MOS switches of the MOS double switch respectively, and the driving of the upper MOS switch and the input PWM signal In the same phase, the drive of the lower MOS switch and the input PWM signal have an opposite phase, that is, when the upper MOS switch is turned on, the lower MOS switch is not turned on, and vice versa. When the upper MOS switch is turned on and the lower MOS switch is not turned on, the power supply charges the inductor L and outputs at the same time; when the upper MOS switch is turned off and the lower MOS switch is turned on, since the current of the inductor cannot change suddenly, L generates counter electromotive force, which freewheels through the MOS switch below. The filter composed of inductor L and capacitor C provides a stable output voltage for the output.

The specific working process of the above-mentioned digital switching power conversion device is as follows:

The output voltage V ₀ is converted into a digital signal of N bits after being divided by resistors and sampled by the ADC. Here, the ADC unit can use flashADC (flash analog-to-digital converter) to achieve fast analog-to-digital conversion, and other high-speed ADCs can also be used. , such as high-speed pipeline ADC (pipeline analog-to-digital converter) to achieve fast analog-to-digital conversion. Compare the digitized output voltage sampling signal with the expected reference voltage digital Ref of the system to obtain an error voltage. If the error voltage is used to directly generate a PWM signal proportional to the error voltage, the double pole generated by the LC of the output stage makes There will be stability problems in the loop, so a digital filter H(Z) must be added here to compensate. The digital filter H(Z) here must provide at least two zeros to compensate the output double pole for loop stability. Impact. Here the transfer function of the digital filter H(Z) can be expressed as:

$\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; A</span>}\underset{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; \&Pi;</span>}}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; z</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; z</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; z</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; z</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}}}$

Among them, α _1k , α _2k , β _1k , β _2k and other coefficients can be stored in registers, and different values can be set according to different application environments to meet the characteristics of the entire switching power supply loop as a low-pass filter and meet the stability requirements of the system That's it.

In digital systems, especially in portable devices, the power consumption of the system is very high, and the output voltage needs to be controlled in real time. When high-speed, high-frequency operation is required, the output voltage will be increased, and when standby or low-power operation is required, the output voltage will be decreased. At this time, it is necessary to adjust the reference voltage digitalRef of the switching power supply. The requirement for the switching power supply is that the switching power supply has the ability to respond quickly to the reference voltage. In the digital switching power supply conversion device of the present invention, when the value of the reference voltage digital Ref changes, the difference between the previous reference voltage value and the pre-adjusted reference voltage value will be calculated to determine the adjustment direction of the output voltage, that is The adjustment direction of the duty cycle of the PWM signal directly affects the adjustment of the PWM duty cycle together with the output of the digital filter H(Z). For example, if the output is to be increased, that is, the reference voltage digital Ref is increased, the difference of the reference voltage is positive, and the input signal input to the PWM signal generating unit will be directly increased to increase the duty cycle, thereby increasing the output voltage. In this way, it quickly responds to the change of the reference voltage, and the loop will make the output voltage quickly stabilize at the set value.

Corresponding to the above-mentioned device of the present invention, the present invention also provides a digital switching power supply conversion method, please refer to Figure 2, which is a flow chart of the digital switching power supply conversion method of the present invention, which mainly includes the following steps:

Step S21, performing analog-to-digital conversion on the output voltage signal of the switching power supply after the resistance division to obtain a digital output voltage signal;

In this step, the analog-to-digital conversion of the output voltage signal of the switching power supply is realized by flash ADC or pipeline ADC.

Step S22, comparing the digitized output voltage signal with the current reference voltage signal to obtain an error voltage signal, and filtering the error voltage signal;

Step S23, summing the filtered error voltage signal and the difference between the current reference voltage signal and the previous reference voltage signal, and generating a PWM signal with a corresponding duty cycle according to the summation result;

Step S24, controlling the change of the output voltage signal of the switching power supply according to the duty cycle of the PWM signal.

In this step, according to the duty cycle of the pulse frequency modulation signal, the control of the change of the output voltage signal of the switching power supply is realized by controlling the switching unit to be turned on and off.

For other specific implementation details of the method of the present invention, please refer to the description of the corresponding part in the above-mentioned device of the present invention, and no more details are given here.

In summary, the digital switching power supply conversion device and method proposed by the present invention overcomes the problem that the digital switching power supply in the prior art cannot quickly respond to the requirements of the digital system for output power voltage changes, and adopts digital-analog hybrid technology. Both the output voltage and the reference voltage have a fast response, which can adapt to the requirements of the current digital system for the change of the power supply voltage, and can realize fast and flexible output voltage control, and its circuit scale is small, which can be easily realized and has a good applicability.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (9)

1. a digital switch power supply change-over device, is characterized in that, comprising:

AD conversion unit, exports to the first sum unit for the output voltage signal of Switching Power Supply is carried out after analog-to-digital conversion;

The first sum unit, for digital voltage signal and the current reference voltage signal of AD conversion unit output are compared, obtains error voltage signal and exports to the second sum unit;

The 3rd sum unit, for determining the difference of current reference voltage signal and a upper reference voltage signal, outputs it to the second sum unit, to determine the adjustment direction of described output voltage signal;

The second sum unit, for the output signal of the output signal to the first sum unit and the 3rd sum unit sue for peace process after export to pulse frequency modulated signal generation unit;

Driver element, for produce the pulse frequency modulated signal of corresponding duty ratio according to the output signal of the second sum unit, changes according to the output voltage signal of the Duty ratio control Switching Power Supply of described pulse frequency modulated signal;

Digital filter, for carrying out the error voltage signal of described the first sum unit output to export to the second sum unit after filtering processing.

2. device as claimed in claim 1, is characterized in that, described digital filter provides and compensates the impact of output duopole on loop stability at least two zero points.

3. device as claimed in claim 1, is characterized in that, described AD conversion unit adopts flash type analog to digital converter or production line analog-digital converter to realize.

4. device as claimed in claim 1, is characterized in that, described driver element is according to the duty ratio of described pulse frequency modulated signal, and the conducting by control switch unit and closing realizes the control to switch power source output voltage signal intensity.

5. device as claimed in claim 4, is characterized in that, described switch element is MOS biswitch.

6. device as claimed in claim 1, is characterized in that, described AD conversion unit carries out exporting to the first sum unit after analog-to-digital conversion to the output voltage signal of the Switching Power Supply after electric resistance partial pressure.

7. a digital switch power conversion method, is characterized in that, comprises step:

The output voltage signal of Switching Power Supply is carried out to analog-to-digital conversion and obtain digitized output voltage signal;

Digitized output voltage signal and current reference voltage signal are compared, obtain error voltage signal to determine the adjustment direction of described output voltage signal;

To filtering error voltage signal after treatment, and the difference of current reference voltage signal and the upper reference voltage signal processing of suing for peace, produce the pulse frequency modulated signal of corresponding duty ratio according to summed result, according to the duty ratio of described pulse frequency modulated signal, the output voltage signal of Switching Power Supply is changed and controlled.

8. method as claimed in claim 7, describedly carries out analog-to-digital conversion to the output voltage signal of Switching Power Supply and adopts flash type analog to digital converter or production line analog-digital converter to realize.

9. method as claimed in claim 7, according to the duty ratio of described pulse frequency modulated signal, the conducting by control switch unit and closing, realizes the control to switch power source output voltage signal intensity.