A digital power supply input voltage feedforward control circuit and control method

Abstract

The present invention discloses a digital power input voltage feedforward control circuit and a control method in the field of digital power. A first sampling circuit and a second sampling circuit are respectively used for voltage division sampling of the input voltage and the output voltage. A main power primary switch tube driving circuit and a main power secondary switch tube circuit are respectively used for driving the power tubes on the primary side and the secondary side of the transformer. The output end of the first sampling circuit is connected to a feedforward function module through an error analog-to-digital conversion module, and the output end of the second sampling circuit is connected to a digital loop compensation module through an error analog-to-digital conversion module. A group of digital pulse width modulation signal generating modules are connected to the main power primary switch tube driving circuit, and another digital pulse width modulation signal generating module is connected to the main power secondary switch tube driving circuit. When the input voltage undergoes a large transient change, the present invention can quickly respond and adjust the duty cycle of the power tube signal to stabilize the output voltage as soon as possible, so as not to generate a large overshoot or undershoot and protect the normal operation of the load device.

Description

Technical Field

[0001] The present invention relates to the field of digital power supplies, and specifically to a digital power supply input voltage feedforward control circuit and a control method. Background Art

[0002] With the development of power electronics technology, digital power supplies have been widely used, and at the same time, higher requirements are put forward for the performance of digital power supplies, especially for the input voltage transient response characteristics of digital power supplies. The current design goal of digital power supplies is generally to achieve an output voltage disturbance of less than 10% under the condition of the maximum input voltage transient. A large overshoot of the output voltage may damage the load device, and a large undershoot of the output voltage may cause the load device to stop or reset. Summary of the Invention

[0003] The purpose of the present invention is to provide a digital power supply input voltage feedforward control circuit and a control method. Based on the input voltage feedforward control composed of an external sampling circuit and a feedforward function module inside the controller, it can stabilize the output voltage as soon as possible when the input voltage of the power supply undergoes a large transient change, so as not to generate a large overshoot or undershoot, and protect the normal operation of the load device.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A digital power supply input voltage feedforward control circuit includes a first sampling circuit and a second sampling circuit, which are respectively used for voltage division sampling of the input voltage on the primary side of the transformer and the output voltage on the secondary side; a main power primary switch tube driving circuit and a main power secondary switch tube circuit, which are respectively used for driving the power tubes on the primary side and the secondary side of the transformer; a controller, including a plurality of error analog-to-digital conversion modules, a digital loop compensation module, a feedforward function module, and a digital pulse width modulation signal generation module. The output end of the first sampling circuit is connected to the feedforward function module through an error analog-to-digital conversion module, and the output end of the second sampling circuit is connected to the digital loop compensation module through another error analog-to-digital conversion module. One group of digital pulse width modulation signal generation modules is connected to the main power primary switch tube driving circuit, and another group of digital pulse width modulation signal generation modules is connected to the main power secondary switch tube driving circuit.

[0006] As an improved scheme of the present invention, the first sampling circuit includes voltage division resistors R1 and R2, the voltage division resistors R1 and R2 are connected in series, one end of which is connected to the input voltage Vin and the other end is grounded, and the connection common end of the voltage division resistors R1 and R2 outputs a first sampling voltage to an error analog-to-digital conversion module in the controller.

[0007] As an improved scheme of the present invention, a filtering resistor R3 is connected to the connection common end of the voltage division resistors R1 and R2, and a filtering capacitor C1 is connected between the filtering resistor R3 and the ground.

[0008] As an improvement of the present invention, the second sampling circuit includes voltage dividing resistors R4 and R5. The voltage dividing resistors R4 and R5 are connected in series, one end of which is connected to the output voltage Vo and the other end is grounded. The common connection end of the voltage dividing resistors R4 and R5 outputs a second sampling voltage to another error analog-to-digital conversion module in the controller.

[0009] As an improvement of the present invention, the main power primary switch tube driving circuit includes a digital isolator and at least one primary driver. One end of the digital isolator is connected to the digital pulse width modulation signal generating module, and the other end is connected to the primary driver. The primary driver is connected to the driving end of the power tube on the primary side of the transformer; the main power secondary switch tube driving circuit includes at least one secondary driver. One end of the secondary driver is connected to the digital pulse width modulation signal generating module, and the other end is connected to the driving end of the power tube on the secondary side of the transformer.

[0010] As an improvement of the present invention, the model of the controller is UCD3138.

[0011] A control method for a digital power input voltage feedforward control circuit includes: the first sampling circuit samples the input voltage and outputs a first sampling voltage. An error analog-to-digital conversion module in the controller converts the first sampling voltage into a digitized first error signal and outputs it to the feedforward function module. The feedforward function module outputs a gain amplification value of the input voltage;

[0012] The second sampling circuit samples the output voltage and outputs a second sampling voltage. Another error analog-to-digital conversion module in the controller converts the second sampling voltage into a digitized second sampling voltage and outputs it to the digital loop compensation module to obtain a control signal. The control signal is multiplied by the gain amplification value and output to the digital pulse width modulation signal generating module. The digital pulse width modulation signal generating module adjusts the duty cycle of the pulse width modulation signal PWM of the power tubes on the primary side and the secondary side of the transformer respectively through the main power primary switch tube driving circuit and the main power secondary switch tube driving circuit to achieve stable output of the output voltage.

[0013] As an improvement of the present invention, the error analog-to-digital conversion module continuously compares the error value of the currently collected input voltage with the error value of the previously collected input voltage at a fixed frequency. When the error value △Vin is greater than the preset reference value Vref, the error analog-to-digital conversion module resets the current reference value Vref so that the error value △Vin is always not greater than the preset reference value Vref. Then the feedforward function module starts and non-linearly amplifies the error value △Vin; when the error value △Vin is not greater than the preset reference value Vref, the feedforward function module starts and non-linearly amplifies the error value △Vin

[0014] As an improvement of the present invention, the non-linear gain amplification formula is: Gain = Kc + Kp * △Vin, where Kp is the amplification factor of the input voltage error value △Vin; Kc is a constant, which is configured in the feed-forward function module to gradually decrease to a value adapted to the current output voltage through a cyclic function.

[0015] Beneficial effects: The input voltage feed-forward control of the present invention is composed of the first sampling circuit based on the external input voltage and the feed-forward function module inside the controller. When the input voltage undergoes a large transient change, it can quickly respond and adjust the duty cycle of the main power switch tube signals on the primary and secondary sides of the drive transformer to quickly stabilize the output voltage, so as not to generate a large overshoot or undershoot, and protect the normal operation of the load device. Brief Description of the Drawings

[0016] Figure 1 is the structural block diagram of the present invention;

[0017] Figure 2 is the specific implementation schematic diagram of the present invention. Detailed Implementation Manner

[0018] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0019] Embodiment 1, see Figure 1-2 , a digital power input voltage feed-forward control circuit, including a first sampling circuit and a second sampling circuit, which are respectively used for voltage division sampling of the input voltage Vin on the primary side of the transformer and the output voltage Vo on the secondary side.

[0020] Optionally, the first sampling circuit includes voltage division resistors R1 and R2. The voltage division resistors R1 and R2 are connected in series, one end of which is connected to the input voltage Vin and the other end is grounded. The connection common end of the voltage division resistors R1 and R2 is connected to the controller and outputs a first sampling voltage Vin_sen. Among them, the relationship between the first sampling voltage Vin_sen and the input voltage Vin is: Vin_sen = Vin * R2 / (R1 + R2).

[0021] Preferably, a filter resistor R3 is further connected to the connection common end of the voltage division resistors R1 and R2. The filter resistor R3 is connected to the ground with a filter capacitor C1, both of which are used to filter out high-frequency interference signals, and its cut-off frequency fc is: fc = 1 / (2 * π * R3 * C1).

[0022] Optionally, similar to the first sampling circuit, the second sampling circuit includes voltage-dividing resistors R4 and R5. The voltage-dividing resistors R4 and R5 are connected in series, with one end connected to the output voltage Vo and the other end grounded. The common connection end of the voltage-dividing resistors R4 and R5 outputs the second sampling voltage to the controller.

[0023] In this embodiment, the main power of the digital power supply is a full-bridge synchronous rectification topology. The main power primary switch tube driving circuit is used to drive the power tubes on the primary side of the transformer T1, such as Figure 2 shown. There are 4 power tubes on the primary side of the transformer T1, namely Q1, Q2, Q3, and Q4. Among them, the drains of the power tubes Q1 and Q2 are connected to the input voltage Vin. The source of the power tube Q1 is connected to the drain of the power tube Q4 and the same-name end of the primary winding of the transformer T1. The source of the power tube Q2 is connected to the drain of the power tube Q3 and the different-name end of the primary winding of the transformer T1. The sources of the power tubes Q3 and Q4 are grounded.

[0024] The main power secondary switch tube circuit is used to drive the power tubes on the secondary side of the transformer T1. The transformer T1 has 2 secondary windings and 2 power tubes. The secondary windings include the first secondary winding and the second secondary winding. The power tubes include Q5 and Q6. Among them, the drain of the power tube Q5 is connected to the same-name end of the first secondary winding. The drain of the power tube Q6 is connected to the different-name end of the second secondary winding. The drains of the power tubes Q5 and Q6 are connected and also connected to the ground at the same time. The same-name end of the second winding outputs the voltage Vo to the second sampling circuit through the inductor L1.

[0025] In this embodiment, the controller includes several error analog-to-digital conversion modules EADC, a digital loop compensation module CLA, a feed-forward function module FF, and a digital pulse width modulation signal generation module DPWM. Preferably, the controller model is UCD3138. The digital pulse width modulation signal generation module DPWM has a pulse width resolution of 250 ps.

[0026] The output end of the first sampling circuit is connected to the feed-forward function module FF through the error analog-to-digital conversion module EADC2. The output end of the second sampling circuit is connected to the digital loop compensation module CLA0 through the error analog-to-digital conversion module EADC0. The output value Vin_ff of the feed-forward function module FF and the output voltage feedback control signal Vo_fb of the digital loop compensation module CLA0 are multiplied to determine the duty cycle of the digital pulse width modulation signal generation module, realizing the feed-forward control of the input voltage of the digital power supply.

[0027] The digital pulse width modulation signal generation modules DPWM0A and DPWM1A are connected to the main power primary switch tube driving circuit. The digital pulse width modulation signal generation modules DPWM0B and DPWM1B are connected to the main power secondary switch tube driving circuit.

[0028] The main power primary switch tube drive circuit includes a digital isolator and at least one primary driver. Preferably, there are two primary drivers, and the model can be selected as UCC27211; the model of the digital isolator can be selected as ISO7240. One end of the digital isolator is connected to the digital pulse width modulation signal generation modules DPWM0A and DPWM1A, and the other end is connected to the primary driver. The primary driver is connected to the gates of the power tubes Q1, Q2, Q3, and Q4 on the primary side of the transformer. The main power secondary switch tube drive circuit includes at least one secondary driver. Preferably, the number of secondary drivers is one, and the model can be selected as UCC27324. One end of the secondary driver is connected to the digital pulse width modulation signal generation modules DPWM0B and DPWM1B, and the other end is connected to the gates of the power tubes Q5 and Q6 on the secondary side of the transformer.

[0029] The control method of the digital power input voltage feedforward control circuit includes:

[0030] The first sampling circuit samples the input voltage and outputs the first sampling voltage Vin_sen. The error analog-to-digital conversion module EADC2 conversion channel performs error comparison and analog-to-digital conversion, and then outputs the digitized first error signal to the feedforward function module FF. The feedforward function module FF outputs the gain amplified value of the input voltage.

[0031] The second sampling circuit samples the output voltage and outputs the second sampling voltage. The error analog-to-digital conversion module EADC0 conversion channel performs error comparison and analog-to-digital conversion, and then inputs the digitized error signal into the digital loop compensator module CLA0 to obtain a control signal. After the control signal is multiplied by the gain amplified value, it enters the pulse width modulation signal generation modules DPWM0A, DPWM1A, DPWM0B, and DPWM, and then generates a PWM drive signal to complete the conversion from digital quantity to analog quantity. The PWM drive signal is amplified by the main power primary switch tube drive circuit composed of the digital isolator ISO7240 and the driver UCC27211 and the main power secondary switch tube drive circuit composed of the driver UCC27324 to control the operation of the power tubes, and completes the control of the output voltage Vo of the digital power supply.

[0032] In this embodiment, by appropriately selecting the values of the voltage dividing resistors R1 and R2, the sampling value of the input voltage Vin can be scaled between 0 and 3.3V to facilitate the controller to read the voltage. Considering the compromise between the requirements of the controller pin for the input current value and the power consumption, the voltage dividing resistor R2 can be set to 1k, the filtering resistor R3 can be set to 1k, and the voltage dividing resistor R1 is determined according to a suitable scaling ratio. In order to filter out high-frequency signal interference above 10MHz, the filtering capacitor C1 can be set to about 10pF.

[0033] In this embodiment, the controller controls the first sampled voltage Vin_sen in a programmatic manner to implement the feedforward function. The error analog-to-digital conversion module EADC2 continuously compares the error value between the currently acquired input voltage and the previously acquired input voltage at a fixed frequency. When the error value △Vin is greater than the preset reference value Vref, the error analog-to-digital conversion module resets the current reference value Vref so that the error value △Vin is always not greater than the preset reference value Vref. Then, the feedforward function module is activated and non-linearly gains and amplifies the error value △Vin.

[0034] The configuration of the reference value Vref (DAC) updates the value of Vref (DAC) according to the magnitude of v_input_error in the following function. v_input_error is the difference between the currently acquired input voltage and the previously acquired input voltage. This function is included in a state machine and is executed once every 100 us for a total of 300 times to ensure that Vref (DAC) is approximately equal to the current input voltage before enabling the feedforward function module FF.

[0035] if(v_input_error>10)

[0036] {

[0037] if(FeCtrl2Regs.EADCDAC.bit.DAC_VALUE>N1) / / N1 corresponds to the minimum value of the input voltage Vin

[0038] {FeCtrl2Regs.EADCDAC.bit.DAC_VALUE = FeCtrl2Regs.EADCDAC.bit.DAC_VALUE - 1;}

[0039] }

[0040] else if(v_input_error < -10)

[0041] {

[0042] if(FeCtrl2Regs.EADCDAC.bit.DAC_VALUE < N2) / / N2 corresponds to the maximum value of the input voltage Vin

[0043] {FeCtrl2Regs.EADCDAC.bit.DAC_VALUE = FeCtrl2Regs.EADCDAC.bit.DAC_VALUE + 1;}

[0044] }

[0045] When the error value △Vin is not greater than the preset reference value Vref, that is, the input voltage has stabilized, the feedforward function module FF is activated and non-linearly gains and amplifies the error value △Vin, and then enters the state machine for normal operation.

[0046] if(abs(v_input_error)<10) / / The deviation value of the input voltage Vin is very small

[0047] {

[0048] supply_state = STATE_REGULATED;

[0049] Filter0Regs.FILTERCTRL.bit.OUTPUT_MULT_SEL = 2; / / Enable the feedforward function

[0050] }

[0051] The non-linear gain amplification formula is: Gain = Kc + Kp * △Vin, where Kp is the amplification factor of the input voltage error value △Vin, and this value is non-linear, that is, the greater the error, the greater the gain value. When the error is small, this value is 0; Kc is a constant, which is configured in the feedforward function module to gradually decrease to a value suitable for the current output voltage through a loop function, and is used to adjust the duty cycle in both large and small directions.

[0052] When the input voltage is stable, if Kc is directly configured to a value between 0.5 and 0.7, enabling the feedforward function at this time will affect the output of the normal loop, causing the output voltage to drop. The reason for the drop is that the normal output of the loop is suddenly multiplied by Kc = 0.5 - 0.7 at this time, so the duty cycle will be immediately limited and the output voltage will drop. It is not until the digital loop compensation module CLA expands the duty cycle to the normal size after multiple cycles that the output voltage returns to the normal value. Therefore, in actual applications, Kc needs to be slowly reduced from 1 to the required value.

[0053] This embodiment is a hard-switching full-bridge main power topology, and Kc is selected as 0.7. In actual design, Filter2 is used to implement the setting of non-linear gain and Kc, so the software configuration is as follows:

[0054] Uint32 filter2_kc;

[0055] int filter2_kc_step = 0x200;

[0056] inline void handle_regulated_state(void)

[0057] {

[0058] filter2_kc = Filter2Regs.FILTERPRESET.bit.PRESET_VALUE; / / Kc value

[0059] if (Filter2Regs.FILTERPRESET.bit.PRESET_VALUE > 0x5A0000)

[0060] {

[0061] Filter2Regs.FILTERPRESET.bit.PRESET_VALUE = filter2_kc - filter2_kc_step;

[0062] Filter2Regs.FILTERPRESET.bit.PRESET_EN = 1;

[0063] }

[0064] }

[0065] Here, handle_regulated_state is a state in the software state machine and is executed every 100 us. Through such a loop function, it can be ensured that Kc is configured from 1 to 0.7 (0x5A0000 / 0x7FFFFF = 0.7) in steps, preventing the output voltage from dropping.

[0066] After the above - mentioned perfect pre - configuration, the feed - forward function module FF can be enabled. After enabling, Kc starts to decrease slowly from 1. The startup setting is implemented through the following code:

[0067] Filter0Regs.FILTERCTRL.bit.OUTPUT_MULT_SEL = 2;

[0068] The "OUTPUT_MULT_SEL" bit is used to select the value multiplied by the loop output to determine the final duty cycle. When set to 2, the output of the feed - forward is selected to be multiplied by the loop output, that is, the feed - forward is enabled.

[0069] Although this specification is described according to the implementation manners, not every implementation manner only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other implementation manners understandable by those skilled in the art.

[0070] In the description of the present invention, it should be noted that relative terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variant thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the phrase "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising said element.

[0071] In the description of the present invention, it should also be noted that the orientation or positional relationship indicated by terms such as "upper", "lower", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the inventive product is customarily placed during use. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention.

[0072] In the description of the present invention, it should also be noted that unless otherwise clearly specified and limited, the terms "arranged" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0073] Therefore, the above description is only a preferred embodiment of the present application, and is not used to limit the scope of implementation of the present application; that is, all equivalent transformations made according to the scope of the claims of the present application are within the protection scope of the claims of the present application.

Claims

1. A digital power supply input voltage feedforward control circuit, comprising a first sampling circuit and a second sampling circuit, each for sampling a transformer primary-side input voltage and a transformer secondary-side output voltage; The main power primary switch tube driving circuit and the main power secondary switch tube circuit are used to drive the power tubes on the primary side and secondary side of the transformer respectively; the characteristics are: A controller comprising several error analog-to-digital conversion modules, a digital loop compensation module, a feedforward function module, and a digital pulse-width modulation signal generation module. The output end of the first sampling circuit is connected to the feedforward function module via one error analog-to-digital conversion module, and the output end of the second sampling circuit is connected to the digital loop compensation module via another error analog-to-digital conversion module. One set of digital pulse-width modulation signal generation modules is connected to the main power primary switch tube drive circuit, and another set of digital pulse-width modulation signal generation modules is connected to the main power secondary switch tube drive circuit. The first sampling circuit includes voltage-dividing resistors R1 and R2, which are connected in series, one end of which is connected to the input voltage Vin and the other end is grounded, and the common end of the voltage-dividing resistors R1 and R2 outputs the first sampling voltage to an error analog-to-digital conversion module in the controller; the common end of the voltage-dividing resistors R1 and R2 is connected to a filter resistor R3, and the filter resistor R3 is connected to the ground with a filter capacitor C1; the second sampling circuit includes voltage-dividing resistors R4 and R5, which are connected in series, one end of which is connected to the output voltage Vo and the other end is grounded, and the voltage-dividing resistors R4 and R5 are connected in series. The common end connected to resistors R4 and R5 outputs the second sampling voltage to another error analog-to-digital conversion module in the controller; the main power primary switch tube drive circuit includes a digital isolator and at least one primary driver, one end of the digital isolator is connected to the digital pulse width modulation signal generating module, and the other end is connected to the primary driver, and the primary driver is connected to the driving end of the power tube on the primary side of the transformer; the main power secondary switch tube drive circuit includes at least one secondary driver, one end of the secondary driver is connected to the digital pulse width modulation signal generating module, and the other end is connected to the driving end of the power tube on the secondary side of the transformer.

2. The digital power supply input voltage feedforward control circuit according to claim 1, characterized in that: The controller model is UCD3138.

3. The control method of a digital power supply input voltage feedforward control circuit according to claim 1, characterized in that: include: The first sampling circuit samples the input voltage and outputs a first sampled voltage. An error analog-to-digital conversion module in the controller converts the first sampled voltage into a digitized first error signal and outputs the signal to the feedforward function module. The feedforward function module outputs a gain amplified value of the input voltage. The second sampling circuit samples the output voltage and outputs the second sampled voltage. Another error analog-to-digital conversion module in the controller converts the second sampled voltage into a digitized second sampled voltage and outputs it to the digital loop compensation module to obtain a control signal. The control signal is multiplied by the gain amplification value and output to the digital pulse width modulation signal generation module. The digital pulse width modulation signal generation module adjusts the duty cycle of the pulse width modulation signal PWM of the power tubes on the primary side and the secondary side of the transformer through the main power primary switch tube drive circuit and the main power secondary switch tube drive circuit, respectively, to achieve stable output of the output voltage.

4. The control method of a digital power supply input voltage feedforward control circuit according to claim 3, characterized in that: The error analog-to-digital conversion module continuously compares the error value of the currently collected input voltage with the error value of the previously collected input voltage at a fixed frequency. When the error value ΔVin is greater than a preset reference value Vref, the error analog-to-digital conversion module resets the current reference value Vref so that the error value ΔVin is always no greater than the preset reference value Vref. Then, the feedforward function module starts and amplifies the nonlinear gain of the error value ΔVin. When the error value ΔVin is not greater than the preset reference value Vref, the feedforward function module is activated and performs a nonlinear gain amplification on the error value ΔVin.

5. The control method of a digital power supply input voltage feedforward control circuit according to claim 4, characterized in that: The nonlinear gain amplification formula is: Gain=Kc+Kp*△Vin, where Kp is the amplification factor of the input voltage error value △Vin; Kc is a constant, which is configured in the feedforward function module to gradually decrease through a loop function to a value suitable for the current output voltage.

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