DC-DC converter output voltage control circuit, method and converter

Abstract

The present application relates to the technical field of power conversion, and discloses a DC-DC converter output voltage control circuit, method and converter. The DC-DC converter output voltage control circuit includes a digital subtraction unit, an addition and subtraction counting unit, a decoding and storage unit, a digital-to-analog conversion unit, a feedback control unit and a switching conversion unit. The digital subtraction unit can calculate the magnitude of a preset target output voltage value and the stored value of the decoding and storage unit, and control the counting state of the addition and subtraction counting unit according to the calculation result. The decoding and storage unit can store the counting result of the addition and subtraction counting unit. The digital-to-analog conversion unit can convert the stored value of the decoding and storage unit into a reference voltage. The feedback control unit can control the output voltage of the switching conversion unit according to the reference voltage and the output feedback voltage, which can improve the flexibility of output voltage control and realize the soft start, soft shutdown and soft regulation of the output voltage of the DC-DC converter.

Description

Technical Field

[0001] This application relates to the technical field of power conversion, and in particular to a control circuit for the output voltage of a DC-DC converter. In addition, this application also relates to a method for controlling the output voltage of a DC-DC converter and a DC-DC converter. Background Art

[0002] Electronic circuits usually use DC power supplies. Different types of electronic circuits, or even different parts of an electronic circuit, usually require DC power supplies with different voltages. Therefore, DC-DC converters are usually required in electronic circuits. The DC-DC converter in an electronic circuit can usually charge the inductor on the output circuit by switching the switching transistor. The energy is accumulated by the inductor, causing the voltage across the inductor to rise, and the output voltage to rise accordingly.

[0003] During the startup process of a DC-DC converter, the switching transistor quickly charges the inductor, causing the output voltage to rise rapidly. At this time, if the output load is small or no-load, the electrical energy in the inductor is discharged relatively slowly, which easily causes a large overshoot in the output voltage during the power-on process, making the output voltage greater than the set output voltage for a short time, and this can easily cause damage to the electronic circuit. During the shutdown process of the DC-DC converter, if the output load is small or no-load, the induced electromotive force generated by the inductor easily causes the current on the low side of the switching circuit to become negative, and the input voltage increases through the charging effect of the capacitor, causing damage to the electronic circuit. The same is true when the output voltage of the DC-DC converter is adjusted significantly.

[0004] To prevent voltage overshoot or input voltage boost in the DC-DC converter, during startup, shutdown, and output voltage adjustment of the DC-DC converter, it is necessary to control the output voltage to change slowly, that is, to achieve soft startup, soft shutdown, and soft adjustment of the voltage of the DC-DC converter.

[0005] Chinese Patent Application Publication No. CN101741233A discloses a soft shutdown control module. During startup, the first current source 204 is controlled by the first switching element 202 to charge the capacitor Css, forming a variable reference signal Vss that rises slowly. During shutdown, the second current source 205 is controlled by the second switching element 203 to discharge the capacitor Css, forming a variable reference signal Vss that drops slowly. Then, the switching of the switching transistor is controlled by the variable reference signal Vss, so that the output voltage of the converter rises slowly during startup and drops slowly during shutdown, realizing soft startup and soft shutdown of the converter. However, this module requires a large capacitor Css to achieve the slow change of the variable reference signal Vss, and large capacitors are difficult to integrate into the chip, increasing the volume of the module and the complexity of the circuit, and the usage cost is relatively high.

[0006] The invention patent application with the publication number CN101741233A discloses a soft-start circuit for a DC-DC switching power supply with digital-to-analog conversion control. By using a counter to control the connection mode of resistors in a reference resistor network through an electronic switch, different ratios of voltage division are performed on the reference voltage Vbg to form a stepwise rising digital-to-analog conversion voltage V2 until the digital-to-analog conversion voltage V2 reaches the reference voltage Vbg, and the digital-to-analog conversion voltage V2 is used to control the switching of the switching transistor, so that the output voltage of the converter rises slowly, realizing the soft start of the converter. However, the digital-to-analog conversion voltage V2 of this soft-start circuit can only rise from zero to a fixed reference voltage Vbg after a fixed number of lifts, and can only achieve soft start but not soft shutdown. Moreover, its analog-to-digital conversion voltage V2 can only rise to a fixed value after a fixed number of lifts, unable to adjust the output voltage and unable to meet the requirements for the start-up time under different output voltages. Summary of the Invention

[0007] In order to improve the flexibility of controlling the output voltage of a DC-DC converter and achieve soft start, soft shutdown, and soft regulation of the output voltage of the DC-DC converter, the present application provides a DC-DC converter output voltage control circuit, method, and converter.

[0008] The DC-DC converter output voltage control circuit provided by the present application adopts the following technical solutions:

[0009] A DC-DC converter output voltage control circuit includes a digital subtraction unit, an addition and subtraction counting unit, a decoding and storage unit, a digital-to-analog conversion unit, a feedback control unit, and a switching conversion unit. The digital subtraction unit has a first subtraction input terminal, a second subtraction input terminal, and a subtraction output terminal. The first subtraction input terminal is provided with a target output voltage value preset module. The second subtraction input terminal can receive the stored value of the decoding and storage unit. The subtraction output terminal is connected to the addition and subtraction counting unit to control the counting state of the addition and subtraction counting unit. The decoding and storage unit is connected to the addition and subtraction counting unit to store the counting result of the addition and subtraction counting unit and send it to the second subtraction input terminal. The digital-to-analog conversion unit is connected to the decoding and storage unit to convert the stored value of the decoding and storage unit into a reference reference voltage. The feedback control unit is connected to the digital-to-analog conversion unit and the switching conversion unit to control the output voltage of the switching conversion unit according to the reference reference voltage and the output feedback voltage from the switching conversion unit.

[0010] By adopting the above technical solution, the digital subtraction unit can calculate the difference between the target output voltage value in the target output voltage value preset module and the voltage forming the reference value stored in the decoding and storage unit, and control whether the addition and subtraction counting unit performs addition and subtraction calculations and the direction of addition and subtraction counting according to the difference state. The digital-to-analog conversion unit can convert the voltage forming the reference value stored in the decoding and storage unit into a reference reference voltage in real time, and control the magnitude of the output voltage of the switch conversion unit by using the real-time magnitude of the reference reference voltage, so that the output voltage of the switch conversion unit is adjusted to a set magnitude at a set adjustment rate, and the output voltage of the DC-DC converter is accurately controlled, so as to realize the soft start, soft shutdown and soft adjustment of the voltage of the DC-DC converter.

[0011] In a specific implementable embodiment, the addition and subtraction counting unit includes a latch and an addition and subtraction counter. The input end of the latch is connected to the digital subtraction unit to generate different counting control signals according to the calculation result of the digital subtraction unit. The output end of the latch is connected to the addition and subtraction counter to control the addition and subtraction counter to perform addition counting, subtraction counting or holding.

[0012] By adopting the above technical solution, the latch with its input end connected to the digital subtraction unit can receive and store the calculation result of the digital subtraction unit, and generate a counting control signal for controlling the working state of the addition and subtraction counter accordingly, control the addition and subtraction counter to perform addition counting, subtraction counting or maintain the original counting result, and transmit it to the decoding and storage unit to form a voltage forming reference value corresponding to the output voltage, and store it in the decoding and storage unit for adjusting the output voltage, so that the output voltage is gradually adjusted with the counting reference as the adjustment unit.

[0013] In a specific implementable embodiment, the digital-to-analog conversion unit includes a decoder module, a constant current source and a resistance conversion module. The decoder module is connected to the decoding and storage unit and can convert the stored value of the decoding and storage unit into a multi-channel control signal. The resistance conversion module is connected to the constant current source and can change the equivalent resistance value under the control of the multi-channel control signal to form a reference reference voltage at both ends of the resistance conversion module.

[0014] By adopting the above technical solution, by using the decoder module connected to the decoding storage unit, it is possible to decode the voltage stored in the decoding storage unit to form a reference value and generate a multiplexed control signal, and use the multiplexed control signal to control the resistance value of the resistance conversion module, so that the resistance conversion module has different equivalent resistance values. By using the constant current source connected to the resistance conversion module, when the constant current provided by the constant current source passes through the resistance conversion module, different voltage drops can be formed in the resistance conversion module, thereby forming a reference reference voltage corresponding to the voltage formation reference value, and using the reference reference voltage to control the magnitude of the output voltage of the converter, so as to conveniently perform soft adjustment on the output voltage of the converter step by step.

[0015] In a specific feasible implementation, the decoder module includes a first temperature decoder and a second temperature decoder. The first temperature decoder can convert the low-order data of the stored value of the decoding storage unit into a first multiplexed control signal, and the second temperature decoder can convert the high-order data of the stored value of the decoding storage unit into a second multiplexed control signal. The resistance conversion module includes a first resistance conversion array and a second resistance conversion array. The first resistance conversion array, the second resistance conversion array and the constant current source are connected in series. The first resistance conversion array can change the equivalent resistance value under the control of the first multiplexed control signal, and the second resistance conversion array can change the equivalent resistance value under the control of the second multiplexed control signal.

[0016] By adopting the above technical solution, the first temperature decoder and the second temperature decoder can respectively decode the low-order data and high-order data of the stored value of the decoding storage unit, generate a first multiplexed control signal and a second multiplexed control signal respectively, and control the equivalent resistance values of the first resistance conversion array and the second resistance conversion array respectively. It is possible to use a smaller number of resistors in the first resistance conversion array and the second resistance conversion array to form a larger number of different equivalent resistance values of the resistance conversion module, and on this basis, form a larger number of different reference reference voltages, improve the convenience of adjusting the output voltage of the converter, and improve the adjustment accuracy.

[0017] In a specific feasible implementation, the first resistance conversion array includes a plurality of first electronic switches S0 and a plurality of first reference resistors R0 connected in series with each other. The plurality of first electronic switches S0 are respectively connected to both ends of the series circuit formed by connecting the plurality of first reference resistors R0, and the connection line between adjacent first reference resistors R0 and the same end of the series circuit formed by connecting the plurality of first reference resistors R0, and the plurality of first electronic switches S0 can be switched respectively under the control of one path of control signal in the first multi-path control signal; the second resistance conversion array includes a plurality of second electronic switches S0' and a plurality of second reference resistors R0' connected in series with each other. The plurality of second electronic switches S0' are respectively connected to both ends of the series circuit formed by connecting the plurality of second reference resistors R0', and the connection line between adjacent second reference resistors R0' and the same end of the series circuit formed by connecting the plurality of second reference resistors R0', and the plurality of second electronic switches S0' can be switched respectively under the control of one path of control signal in the second multi-path control signal; R0' = (n + 1)R0, where n is the number of the first reference resistors R0.

[0018] By adopting the above technical solution, by using a plurality of reference resistors connected in series with each other and an electronic switch connected between the connection point of adjacent reference resistors at the same end of the series circuit and the other end of the series circuit, the equivalent resistance value of the resistance conversion array can be conveniently adjusted, so that the equivalent resistance value of the resistance conversion array changes in units of the resistance value of the smallest reference resistor. By setting the relationship between the resistance value of the second reference resistor R0' and the resistance value of the first reference resistor R0, it can be ensured that the equivalent resistance of the resistance conversion module changes linearly in proportion to the reference value of the voltage, ensuring the uniformity of the adjustment of the output voltage of the converter.

[0019] In a specific feasible implementation, the feedback control unit includes a voltage comparison module, a waveform processing module, and a logic drive module. The voltage comparison module is respectively connected to the switch conversion unit, the digital-to-analog conversion unit, and the waveform processing module to be able to compare the magnitudes of the output feedback voltage and the reference reference voltage. The waveform processing module can generate an output voltage adjustment signal according to the comparison result of the voltage comparison module. The logic drive module is connected to the waveform processing module and the switch conversion unit and can control the working state of the switch conversion unit according to the output voltage adjustment signal, thereby controlling the output voltage of the switch conversion unit.

[0020] By adopting the above technical solution, by using a voltage comparison module respectively connected to a switching conversion unit, a digital-to-analog conversion unit, and a waveform processing module, an output feedback voltage corresponding to the output voltage of the converter can be obtained through the switching conversion unit, compared with the reference voltage formed by the digital-to-analog conversion unit, and the comparison result is transmitted to the waveform processing module. The waveform processing module can process the comparison result of the voltage comparison module to form an output voltage adjustment signal determined by the comparison result. After being processed by the logic driving module, a driving signal for driving the switching conversion unit to act is generated to control the output voltage of the switching conversion unit, so that the output feedback voltage is equal to the reference voltage, thereby stably maintaining the output voltage of the converter as the target output voltage.

[0021] In a specific implementable embodiment, the waveform processing module includes a comparator and an RS flip-flop. The input terminals of the comparator are respectively connected to the voltage comparison module and a sawtooth wave signal, the output terminal is connected to the R terminal of the RS flip-flop, the S terminal of the RS flip-flop is connected to a clock signal, and the Q terminal of the RS flip-flop is connected to the logic driving module; the logic driving module can generate two inverted driving signals under the control of the signal output from the Q terminal of the RS flip-flop; the switching conversion unit includes a first switching element, a second switch, and an energy storage module. The first switching element and the second switching element are connected in series at the input end of the DC-DC converter and can be switched respectively under the control of the two inverted driving signals. The energy storage module is connected between the connection point of the first switching element and the second switching element and the output end of the DC-DC converter.

[0022] By adopting the above technical solution, by using a comparator with input terminals respectively connected to a voltage comparison module and a sawtooth wave signal, and an RS flip-flop connected to the comparator, a pulsed output voltage adjustment signal can be generated according to the comparison result of the voltage comparison module. After being processed by the logic driving module, a logic signal for controlling the switching of the switching control element is formed. The logic driving module can generate inverted driving signals for controlling two switching elements respectively to ensure the coordinated operation of the two switching elements, and the output voltage is adjusted in opposite directions respectively through the switching of the two switching elements. The energy storage module can ensure the relative stability of the output voltage of the converter.

[0023] The technical solution adopted by the output voltage control method of the DC-DC converter provided in this application is as follows:

[0024] A method for controlling the output voltage of a DC-DC converter, which can control the output voltage of the DC-DC converter output voltage control circuit provided in this application, includes the following steps: S10. Preset the target output voltage value; S20. Compare the magnitude of the voltage formed reference value stored in the comparison circuit with the target output voltage value, and gradually adjust the voltage formed reference value according to the comparison result until the voltage formed reference value is equal to the target output voltage value; S30. Control the converter switch circuit according to the voltage formed reference value, so that the converter output voltage is gradually adjusted to the target output voltage.

[0025] By adopting the above technical solution, by using the method of comparing the magnitude of the voltage formed reference value with the target output voltage value, it is possible to determine the magnitude of the target output voltage and the current output voltage determined by the voltage formed reference value, so as to accurately determine the adjustment direction of the voltage formed reference value, adjust the voltage formed reference value in the direction of the target output voltage value, so as to adjust the current output voltage to the target value. In this way, it is possible to freely determine the adjustment direction and adjustment amplitude of the output voltage by presetting the target output voltage value, and to achieve the shutdown of the converter by presetting the target output voltage value to zero, and to achieve the startup of the converter by presetting the target output voltage value in the off state. By gradually adjusting the voltage formed reference value and controlling the converter switch circuit according to the voltage formed reference value to gradually adjust the converter output voltage, it is possible to control the step-by-step small-amplitude progressive adjustment of the output voltage to the target output voltage, realize the soft start, soft shutdown and soft adjustment of the output voltage of the converter, prevent overshoot in the process of output voltage adjustment and excessive increase of the input terminal voltage, and ensure the stable operation of the DC-DC converter.

[0026] In a specific feasible implementation, step S20 includes the following steps: S21. Obtain the difference between the target output voltage value and the current voltage formed reference value. If the difference is greater than zero, execute step S22. If the difference is less than zero, execute step S23. Otherwise, execute step S24; S22. Control the voltage formed reference value to increase by 1 adjustment reference, and then execute step S21; S23. Control the voltage formed reference value to decrease by 1 adjustment reference, and then execute step S21; S24. Keep the voltage formed reference value; step S30 includes the following steps: S31. Generate a reference reference voltage according to the voltage formed reference value, and obtain an output feedback voltage according to the converter output voltage; S32. Compare the magnitude of the reference reference voltage and the output feedback voltage, and generate a switch circuit control signal according to the comparison result; S33. Control the converter switch circuit according to the switch circuit control signal, so that the converter output voltage gradually changes to the target output voltage.

[0027] By adopting the above technical solution, the method of gradually increasing or decreasing the voltage formation reference value by one adjustment reference is used to perform step-by-step adjustment on the voltage formation reference value, which can make the voltage formation reference value gradually change towards the target output voltage value in small steps, slowly adjust to the target output voltage value, and can accurately determine the time when the converter output voltage reaches the target output voltage according to the magnitude of the difference between the target output voltage value and the current output voltage value, realizing precise control of the converter. Through the method of generating a reference reference voltage from the voltage formation reference value, a reference reference voltage that changes slowly in a stepped manner with a certain slope can be obtained, and the change slope of the reference reference voltage can be conveniently controlled by controlling the corresponding relationship between the voltage formation reference value and the reference reference voltage.

[0028] The DC-DC converter of the present application uses the AC-DC contactor control circuit provided by the present application, and can realize soft start, soft shutdown and soft adjustment of the output voltage of the DC-DC converter.

[0029] In summary, the present application includes at least one of the following beneficial technical effects:

[0030] By comparing the magnitude of the voltage formation reference value in the circuit with the preset target output voltage value, the converter can be softly started by presetting a target output value in the off state of the converter, softly shut down by presetting the target output value to zero in the working state of the converter, and softly adjusted the output voltage of the converter by setting a different target output value in the working state of the converter, and can accurately control the time of soft start, soft shutdown and soft adjustment, improving the flexibility of the output voltage control of the DC-DC converter of the present application;

[0031] By controlling the voltage formation reference value to cycle increment by 1 when the target output voltage value is greater than the voltage formation reference value, and controlling the voltage formation reference value to cycle decrement by 1 when the target output voltage value is less than the voltage formation reference value, the voltage formation reference value can be adjusted step by step in both directions, thereby performing two-way step-by-step soft adjustment on the output voltage of the DC-DC converter to prevent overshoot of the output voltage of the DC-DC converter;

[0032] By setting up a digital subtraction unit, an addition and subtraction counting unit and a decoding and storage unit, the digital subtraction unit can be used to compare the preset target output voltage value with the voltage formation reference value stored in the decoding and storage unit, and control the addition and subtraction counter to perform addition and subtraction counting or maintain the counting result according to the comparison result, and store it as a new voltage formation reference value after decoding by the decoding and storage unit, which is convenient for step-by-step adjustment of the voltage formation reference value and realizes step-by-step soft adjustment of the converter output voltage;

[0033] By setting a first temperature decoder and a second temperature decoder to decode the low-order data and high-order data of the voltage to form a reference value respectively, and adjusting the equivalent resistance values of the first resistance conversion array and the second resistance conversion array according to the decoding results respectively, it is possible to form more different equivalent resistance values of resistance conversion modules with a smaller number of reference resistors, and form more different reference reference voltage values with a constant current source, thereby improving the adjustment accuracy of the output voltage of the converter through a relatively simple circuit. Description of the Drawings

[0034] Figure 1 FIG. is a schematic structural diagram of an embodiment of the output voltage control circuit of the DC-DC converter of the present application.

[0035] Figure 2 FIG. is a schematic structural diagram of the digital logic part in an embodiment of the output voltage control circuit of the DC-DC converter of the present application.

[0036] Figure 3 FIG. is a schematic diagram of the control flow of the digital logic part in an embodiment of the output voltage control circuit of the DC-DC converter of the present application.

[0037] Figure 4 FIG. is a schematic structural diagram of the digital-to-analog conversion unit in an embodiment of the output voltage control circuit of the DC-DC converter of the present application.

[0038] Figure 5 FIG. is a schematic structural diagram of the feedback control unit and the switch conversion unit in an embodiment of the output voltage control circuit of the DC-DC converter of the present application.

[0039] Figure 6 FIG. is a schematic diagram of the waveform change of the reference reference voltage during the soft start process of an embodiment of the output voltage control circuit of the DC-DC converter of the present application.

[0040] Figure 7 FIG. is a schematic diagram of the waveform change of the reference reference voltage during the soft shutdown process of an embodiment of the output voltage control circuit of the DC-DC converter of the present application.

[0041] Figure 8 FIG. is a schematic diagram of the waveform change of the reference reference voltage during the soft adjustment process of the output voltage of an embodiment of the output voltage control circuit of the DC-DC converter of the present application.

[0042] Figure 9 FIG. is a flowchart of an embodiment of the output voltage control method of the DC-DC converter of the present application.

[0043] Figure 10 FIG. is a flowchart of step S20 in an embodiment of the output voltage control method of the DC-DC converter of the present application.

[0044] Figure 11 This is a flowchart of step S30 in an embodiment of the output voltage control method for the DC-DC converter of the present application.

[0045] Description of reference numerals: 1. Digital subtraction unit; 11. Target output voltage value preset module; 2. Addition and subtraction counting unit; 21. Latch; 22. Addition and subtraction counter; 3. Decoding and storage unit; 4. Digital-to-analog conversion unit; 41. Decoder module; 411. First temperature decoder; 412. Second temperature decoder; 42. Constant current source; 43. Resistance conversion module; 431. First resistance conversion array; 432. Second resistance conversion array; 5. Feedback control unit; 51. Voltage comparison module; 52. Waveform processing module; 521. Comparator; 522. RS flip-flop; 53. Logic drive module; 6. Switch conversion unit; 61. First switch element; 62. Second switch element; 63. Energy storage module. Detailed implementation manners

[0046] The following will describe the detailed implementation manners of the present application with reference to the accompanying drawings. It should be understood that the detailed implementation manners described herein are only for the purpose of illustration and explanation of the present application, and are not used to limit the present application.

[0047] In the description of the present application, it should be noted that unless otherwise clearly defined and limited, the terms "set" and "connect" 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 direct connection, or an indirect connection through an intermediate medium, and can be the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0048] In this specification, the terms "first" and "second" are only used for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Therefore, the features defined with "first" and "second" may explicitly or implicitly include one or more of the described features.

[0049] An embodiment of the output voltage control circuit of the DC-DC converter of the present application is as Figures 1 to 5As shown in the figure, it includes a digital subtraction unit 1, an addition and subtraction counting unit 2, a decoding and storage unit 3, a digital-to-analog conversion unit 4, a feedback control unit 5, and a switch conversion unit 6. Among them, the digital subtraction unit 1 has a first subtraction input terminal, a second subtraction input terminal, and a subtraction output terminal. A target output voltage value preset module 11 is provided at the first subtraction input terminal, and a target output voltage value can be input and stored in the target output voltage value preset module 11. In this embodiment, an eight-bit binary number LEVEL<7:0> representing the target output voltage can be stored in the target output voltage value preset module 11. The eight-bit binary number LEVEL<7:0> has 256 different values, so 256 different output voltages evenly distributed can be preset. According to the different rated output voltages of the DC-DC converter, each value can represent 1V, or a set voltage unit greater than 1V or less than 1V. The second subtraction input terminal is connected to the decoding and storage unit 3 and can receive the stored value of the decoding and storage unit 3, that is, the voltage formation reference value. In this embodiment, the voltage formation reference value is also an eight-bit binary number D<7:0>.

[0050] The digital subtraction unit 1 can perform a subtraction operation on the target output voltage value input at the first subtraction input terminal and the voltage formation reference value input at the second subtraction input terminal, calculate the difference between LEVEL<7:0> - D<7:0>, and output the calculation result through the subtraction output terminal.

[0051] The addition and subtraction counting unit 2 is connected to the subtraction output terminal of the digital subtraction unit 1, and the addition and subtraction counting unit 2 can change the counting state under the control of the calculation result output at the subtraction output terminal. Specifically, when the calculation result is greater than zero, that is, when the target output voltage value is greater than the voltage formation reference value, an addition count is performed, so that the counting result of the addition and subtraction counting unit 2 gradually increases; when the calculation result is less than zero, that is, when the target output voltage value is less than the voltage formation reference value, a subtraction count is performed, so that the counting result of the addition and subtraction counting unit 2 gradually decreases; and when the calculation result is equal to zero, that is, when the target output voltage value is equal to the voltage formation reference value, the counting stops, so that the counting result of the addition and subtraction counting unit 2 remains unchanged. In this embodiment, the counting result of the addition and subtraction counting unit 2 is also an eight-bit binary number Q<7:0>.

[0052] The decoding storage unit 3 is connected to the addition and subtraction counting unit 2, and can decode the counting result Q<7:0> of the addition and subtraction counting unit 2 to obtain a new voltage formation reference value D<7:0>, and store the new voltage formation reference value D<7:0> in the decoding storage unit 3, replacing the original voltage formation reference value D<7:0>. At the same time, the new voltage formation reference value D<7:0> is sent to the second subtraction input terminal of the digital subtraction unit 1 to perform a new subtraction calculation with the target output voltage value LEVEL<7:0>. This cycle continues until the voltage formation reference value D<7:0> is equal to the target output voltage value LEVEL<7:0>, realizing a step-by-step and ladder-like change of the voltage formation reference value D<7:0> from the original value to the target output voltage value LEVEL<7:0>.

[0053] The digital-to-analog conversion unit 4 is connected to the decoding storage unit 3, and can perform digital-to-analog conversion on the voltage formation reference value D<7:0> stored in the decoding storage unit 3 to obtain a reference voltage Vref corresponding to the voltage formation reference value D<7:0>. Specifically, the proportional relationship between the reference voltage Vref and the voltage formation reference value D<7:0> can be determined according to the rated output voltage, the adjustment range of the output voltage, and the change rate of the output voltage of the DC-DC converter.

[0054] The feedback control unit 5 is connected to the digital-to-analog conversion unit 4 and the switch conversion unit 6. The feedback control unit 5 can compare the reference voltage Vref from the digital-to-analog conversion unit 4 with the output feedback voltage Vfb generated according to the output voltage on the output loop of the switch conversion unit 6, and control the working state of the switch conversion unit 6 according to the comparison result, thereby controlling the output voltage of the switch conversion unit 6, that is, the output voltage of the DC-DC converter.

[0055] Specifically, when the output feedback voltage Vfb is greater than the reference voltage Vref, it indicates that the output voltage of the switch conversion unit 6 is too high. At this time, the feedback control unit 5 outputs a control signal to control the switch conversion unit 6 to reduce the output voltage; when the output feedback voltage Vfb is less than the reference voltage Vref, it indicates that the output voltage of the switch conversion unit 6 is too low. At this time, the feedback control unit 5 outputs a control signal to control the switch conversion unit 6 to increase the output voltage. In this way, the output feedback voltage Vfb can be made equal to the reference voltage Vref, and the output voltage of the DC-DC converter can be adjusted to the set voltage level.

[0056] The switch conversion unit 6 is arranged between the input end and the output end of the DC-DC converter. The switch conversion unit 6 can control the rhythm of the energy of the DC power supply at the input end to be provided to the output end through the switch conversion unit 6, so as to adjust the voltage at the output end of the switch conversion unit 6. Through the feedback regulation of the feedback control unit 5, the voltage at the output end of the switch conversion unit 6 can be controlled in real time at a level corresponding to the reference voltage Vref. The reference voltage Vref corresponds to the voltage formation reference value D<7:0>, and the voltage formation reference value D<7:0> can also change step by step in a stepped manner towards the preset target output voltage value LEVEL<7:0>. In this way, by presetting different target output voltage values LEVEL<7:0>, a stepped adjustment of the output voltage of the DC-DC converter towards different target output voltages can be realized, and the soft adjustment of the output voltage of the DC-DC converter can be conveniently realized. When a non-zero target output voltage value LEVEL<7:0> is preset in the off state of the DC-DC converter, the output voltage of the DC-DC converter can be gradually increased from zero to the target output voltage, realizing the soft start of the DC-DC converter; when the target output voltage value LEVEL<7:0> is preset to zero in the working state of the DC-DC converter, the output voltage of the DC-DC converter can be gradually reduced to zero, realizing the soft shutdown of the DC-DC converter.

[0057] In some embodiments of the output voltage control circuit of the DC-DC converter of the present application, such as Figure 2 shown, the addition and subtraction counting unit 2 includes a latch 21 and an addition and subtraction counter 22. The input end of the latch 21 is connected to the digital subtraction unit 1. The calculation result of the digital subtraction unit 1 equal to zero is directly transmitted to the latch 21 for latching. The calculation results of the digital subtraction unit 1 greater than zero and less than zero are respectively converted into standard logic signals through a logic gate and transmitted to the latch 21 for latching. The output end of the latch 21 is connected to the addition and subtraction counter 22, and the counting state of the addition and subtraction counter 22 can be controlled through the logic signal latched in the latch 21. Specifically, if the logic signal latched in the latch 21 is converted from the calculation result of the digital subtraction unit 1 greater than zero, the addition and subtraction counter 22 performs an addition count on the basis of the voltage formation reference value D<7:0>, so that the counting result Q<7:0> increases by 1; if the logic signal latched in the latch 21 is converted from the calculation result of the digital subtraction unit 1 less than zero, the addition and subtraction counter 22 performs a subtraction count on the basis of the voltage formation reference value D<7:0>, so that the counting result Q<7:0> decreases by 1; if the logic signal latched in the latch 21 is the calculation result of the digital subtraction unit 1 equal to zero, the addition and subtraction counter 22 keeps the original counting result Q<7:0> unchanged.

[0058] The counting result Q<7:0> of the addition and subtraction counter 22 is stored after being decoded by the decoding storage unit 3, forming a new voltage formation reference value D<7:0>. The new voltage formation reference value D<7:0> is sent to the digital subtraction unit 1 for subtraction operation on the one hand, serves as the basis for the new addition and subtraction counting of the addition and subtraction counter 22 on the other hand, and is also output to the digital-to-analog conversion unit 4 to generate the reference voltage Vref.

[0059] The setting of the latch 21 enables the addition and subtraction counter 22 and the digital subtraction unit 1 to work under the control of different clock pulses. By controlling the frequency ratio of the clock pulses of the addition and subtraction counter 22 and the digital subtraction unit 1, the counting times of the addition and subtraction calculator 22 within one calculation period of the digital subtraction unit 1 can also be changed, thereby changing the change rate of the reference voltage Vref.

[0060] In some embodiments of the output voltage control circuit of the DC-DC converter of the present application, such as Figure 4 shown, the digital-to-analog conversion unit 4 includes a decoder module 41, a constant current source 42, and a resistor conversion module 43. The input end of the decoder module 41 is connected to the decoding storage unit 3, and is used to convert the voltage formation reference value D<7:0> stored in the decoding storage unit 3 into a multiplexed control signal. The resistor conversion module 43 generally includes a resistor array composed of multiple resistors. Multiple electronic switches are arranged in the resistor array, and the multiple electronic switches can be opened and closed respectively under the control of the multiplexed control signals generated by the decoding storage unit 3. Through the combination of different opening and closing states of the multiple electronic switches, the resistor array forms different equivalent resistance values.

[0061] The resistor conversion module 43 is connected to the constant current source 42. The constant current source 42 generates a constant current flowing through the resistor conversion module 43, forming a voltage drop across the resistor conversion module 43. The constant current forms different voltage drops at different equivalent resistance values of the resistor conversion module 43, and a reference voltage Vref is formed across the resistor conversion module 43.

[0062] Since the reference voltage Vref is generated across the resistor conversion module 43 and does not rely on a large-capacity capacitor, it is easier to be integrated into the chip, greatly reducing the volume of the device for forming the reference voltage Vref. At the same time, compared with capacitors, the manufacturing accuracy of resistors is higher, and it is more convenient and flexible to control the equivalent resistance of the resistor array through electronic switches. Therefore, the control accuracy of the reference voltage Vref is also higher, and the control is more convenient and flexible.

[0063] In a preferred embodiment of the output voltage control circuit of the DC-DC converter of the present application, such as Figure 4As shown, the decoder module 41 includes a first temperature decoder 411 and a second temperature decoder 412. The first temperature decoder 411 is connected to the low-order data output terminal of the decoding storage unit 3, and can decode the low-order data of the voltage forming the reference value D<7:0> stored in the decoding storage unit 3 to form a corresponding thermometer code, and use this thermometer code as the first multiplexed control signal for controlling the electronic switches in the control resistance array. The DNL (differential nonlinearity) performance of the thermometer code is excellent, and the differential nonlinearity error of the output signal is small, which can provide a more accurate analog signal.

[0064] The second temperature decoder 412 is connected to the high-order data output terminal of the decoding storage unit 3, and can decode the high-order data of the voltage forming the reference value D<7:0> stored in the decoding storage unit 3 to form a corresponding thermometer code, and use this thermometer code as the second multiplexed control signal for controlling the electronic switches in the control resistance array.

[0065] By separately decoding the low-order data and high-order data of the voltage forming the reference value D<7:0> through the first temperature decoder 411 and the second temperature decoder 412, the number of data bits of the thermometer code obtained by decoding the voltage forming the reference value D<7:0> can be reduced, and the structural complexity of the digital-to-analog conversion unit 4 can be reduced.

[0066] The resistance conversion module 43 includes a first resistance conversion array 431 and a second resistance conversion array 432. After the first resistance conversion array 431 and the second resistance conversion array 432 are connected in series with each other, they are connected in series in the power supply circuit of the constant current source 42. Both the first resistance conversion array 431 and the second resistance conversion array 432 are formed by connecting multiple resistors. A plurality of electronic switches are connected in different resistor connection circuits. By controlling the on-off states of different electronic switches or combinations of electronic switches, the resistance conversion array can be controlled to form different equivalent resistances.

[0067] The multiple electronic switches in the first resistance conversion array 431 can change their on-off states respectively under the control of the first multiplexed control signal, thereby changing the equivalent resistance value of the first resistance conversion array 431; the multiple electronic switches in the second resistance conversion array 432 can change their on-off states respectively under the control of the second multiplexed control signal, thereby changing the equivalent resistance value of the second resistance conversion array 432. Through the combination of the equivalent resistance of the first resistance conversion array 431 and the equivalent resistance of the second resistance conversion array 432, more different equivalent resistance values can be formed.

[0068] As a specific implementation manner of the output voltage control circuit of the DC-DC converter of the present application, as Figure 4As shown, the first resistor conversion array 431 includes a plurality of first electronic switches S0 and a plurality of first reference resistors R0. The plurality of first reference resistors R0 are connected in series with each other. The plurality of first electronic switches S0 are respectively connected between one end of the series circuit formed by connecting the plurality of first reference resistors R0 and the other ends of the plurality of first reference resistors R0 connected in sequence, and the plurality of first electronic switches S0 can be switched respectively under the control of the control signal corresponding to one of the first multiplex control signals.

[0069] The second resistor conversion array 432 includes a plurality of second electronic switches S0' and a plurality of second reference resistors R0'. The plurality of second reference resistors R0' are connected in series with each other. The plurality of second electronic switches S0' are respectively connected between one end of the series circuit formed by connecting the plurality of second reference resistors R0' and the other ends of the plurality of second reference resistors R0' connected in sequence, and the plurality of second electronic switches S0' can be switched respectively under the control of the control signal corresponding to one of the second multiplex control signals.

[0070] In a specific embodiment, the first temperature decoder 411 is a three-input, seven-output temperature decoder. The input end of the first temperature decoder 411 is connected to the three low-order data output ends of the decoding storage unit 3, and can decode the three low-order data D<2:0> forming the reference value D<7:0> of the voltage into a seven-bit thermometer code LSB<6:0>. The first resistor conversion array 431 includes seven first reference resistors R0 connected in series with each other, and seven first electronic switches S0 connected between one end of the series circuit composed of all the first reference resistors R0 and the other ends of each first reference resistor R0. Each first electronic switch S0 can be closed when one bit in the seven-bit thermometer code is 0, so that the first reference resistor R0 connected in series between the two ends of the first electronic switch S0 is short-circuited; and when a certain bit in the seven-bit thermometer code is 1, the corresponding first electronic switch S0 is disconnected, without affecting the connection state of the first reference resistor R0 connected between the two ends of the first electronic switch S0. For example, when D<2:0> is 000, the seven-bit thermometer code LSB<6:0> is decoded into 0000000, and all seven first electronic switches S0 are closed, and the equivalent resistance of the first resistor conversion array 431 is zero; when D<2:0> is 001, the seven-bit thermometer code LSB<6:0> is decoded into 0000001, Figure 4 the leftmost first electronic switch S0 on the left is disconnected, and the other first electronic switches S0 are all closed, and the equivalent resistance of the first resistor conversion array 431 is R0; and so on.

[0071] The second temperature decoder 412 is a five-bit input and thirty-one-bit output temperature decoder. The input end of the second temperature decoder 412 is connected to the five high-order data output ends of the decoding storage unit 3, and can decode the five high-order data D<7:3> of the voltage forming the reference value D<7:0> into a thirty-one-bit thermometer code MSB<30:0>. The second resistance conversion array 432 includes thirty-one second reference resistors R0' connected in series with each other, and thirty-one second electronic switches S0' connected between one end of the series circuit composed of all the second reference resistors R0' and the other end of each second reference resistor R0'. Each second electronic switch S0' can be closed when one bit in the thirty-one-bit thermometer code is 0, so that the second reference resistor R0' connected in series between the two ends of the second electronic switch S0' is short-circuited; when a certain bit in the thirty-one-bit thermometer code is 1, the corresponding second electronic switch S0' is disconnected, and does not affect the connection state of the second reference resistor R0 connected between the two ends of the second electronic switch S0'. For example, when D<7:3> is 00000, the decoded thirty-one-bit thermometer code MSB<30:0> is 0…0 (a total of 31 0s), and all thirty-one second electronic switches S0' are closed, and the equivalent resistance of the second resistance conversion array 432 is zero; when D<7:3> is 00001, the decoded thirty-one-bit thermometer code MSB<30:0> is 0…01 (a total of 30 0s), Figure 4 the leftmost first second electronic switch S0' on the left is disconnected, and the other second electronic switches S0' are all closed, and the equivalent resistance of the second resistance conversion array 432 is R0'; and so on.

[0072] The resistance value of each second reference resistor R0' is equal to R0'=(n + 1)R0, where n is the number of first reference resistors R0 connected in series in the first resistance conversion array 431. In this embodiment, R0' = 8R0. In this way, during the change process of the voltage forming the reference value D<7:0>, when D<2:0> carries over to D<7:3>, or D<2:0> borrows from D<7:3>, the uniformity of the change of the equivalent resistance value of the resistance conversion module 43 formed by the series connection of the first resistance conversion array 431 and the second resistance conversion array 432 can be ensured.

[0073] The first temperature decoder 411 has seven output bits and can decode the three low-order data D<2:0> of the voltage reference value D<7:0> to form eight output bit states as shown in Table 1. Similarly, the second temperature decoder 412 has thirty-one output bits and can decode the five high-order data D<7:3> of the voltage reference value D<7:0> to form thirty-two output bit states. The combination of the two can decode the voltage reference value D<7:0> represented by an eight-bit binary number to form 8×32 = 256 states corresponding to the voltage reference value D<7:0> represented by an eight-bit binary number. In this way, through 7 + 31 = 38 output bits, 256 output states can be formed, greatly simplifying the decoding circuit and improving the output accuracy of the voltage reference value D<7:0>.

[0074] Table 1 Truth Table of the First Temperature Decoder

[0075] Input bit 000 001 010 011 100 101 110 111 Output bit 0000000 0000001 0000011 0000111 0001111 0011111 0111111 1111111

[0076] The first resistor conversion array 431 includes seven first reference resistors R0 and seven first electronic switches S0, and can be combined into eight equivalent resistor states of the first resistor conversion array 431; the second resistor conversion array 432 includes thirty-one second reference resistors R0' and thirty-one second electronic switches S0', and can be combined into thirty-two equivalent resistor states of the second resistor conversion array 432. By connecting the first resistor conversion array 431 and the second resistor conversion array 432 in series to form a resistor conversion module 43, 8×32 = 256 different equivalent resistance values of the resistor conversion module 43 can be formed. In this way, 256 different equivalent resistance values can be formed through the mutual combination of 7 + 31 = 38 resistors. After being converted by the constant current source 42, 256 different linearly varying reference voltages Vref are formed. Through a more concise resistor array structure, more precise control of the reference voltage Vref is achieved, improving the control accuracy of the output voltage of the DC-DC converter.

[0077] In some embodiments of the output voltage control circuit of the DC-DC converter of the present application, as Figure 5 shown, the feedback control unit 5 includes a voltage comparison module 51, a waveform processing module 52, and a logic drive module 53. The voltage comparison module 51 usually uses an error amplifier. The negative input terminal of the voltage comparison module 51 is connected to the switch conversion unit 6, the positive input terminal is connected to the digital-to-analog conversion unit 4, and the output terminal is connected to the waveform processing module 52. It can compare the output feedback voltage Vfb extracted from the switch conversion unit 6 with the reference voltage Vref from the digital-to-analog conversion unit 4 and send the comparison result to the waveform processing module 52.

[0078] The waveform processing module 52 can process the comparison result of the voltage comparison module 51 to generate an output voltage adjustment signal corresponding to the comparison result. The logic driving module 53 is connected to the waveform processing module 52 and the switch conversion unit 6, and can perform power amplification and logic processing on the output voltage adjustment signal output by the waveform processing module 52 to obtain a driving signal for controlling the working state of the switch conversion unit 6. When the output feedback voltage Vfb is greater than the reference voltage Vref, the output voltage of the switch conversion unit 6 is decreased; when the output feedback voltage Vfb is less than the reference voltage Vref, the output voltage of the switch conversion unit 6 is increased, so that the value of the output feedback voltage Vfb is finally equal to the value of the reference voltage Vref, and thus the output voltage of the switch conversion unit 6 is equal to the target output voltage.

[0079] As Figure 6 shown, when the DC-DC converter starts up, since the target output voltage LEVEL<7:0> is greater than the voltage formation reference value D<7:0>, the addition and subtraction counter 22 performs addition counting, and the voltage formation reference value D<7:0> is continuously incremented by 1 as the number of counting pulses N of the addition and subtraction counter 22 increases. The equivalent resistance value N×R0 of the resistance conversion module 43 also continuously increases, and the reference voltage Vref generated by the constant current source 42 flowing through the resistance conversion module 43 also continuously increases. Every time a counting pulse period Tclk passes, the voltage formation reference value D<7:0> increases by 1, and the reference voltage Vref increases by a step voltage Step = Iref×R0. After N counts, the voltage formation reference value D<7:0> is equal to the target output voltage value LEVEL<7:0>, the reference voltage Vref = Iref×N×R0, the output voltage of the DC-DC converter is stabilized at the target output voltage, the soft start of the DC-DC converter is completed, and the start-up time ton of the DC-DC converter = N×Tclk.

[0080] Similarly, as Figure 7As shown, when the DC-DC converter is turned off, the target output voltage LEVEL<7:0> is preset to zero, which is less than the voltage formation reference value D<7:0>. The addition and subtraction counter 22 performs subtraction counting. The voltage formation reference value D<7:0> is continuously decremented by 1 as the number of counting pulses N of the addition and subtraction counter 22 increases. The equivalent resistance value N×R0 of the resistance conversion module 43 also continuously decreases. The reference reference voltage Vref generated by the constant current source 42 flowing through the resistance conversion module 43 also continuously decreases. Every time a counting pulse period Tclk passes, when the voltage formation reference value D<7:0> decreases by 1, the reference reference voltage Vref decreases by a step voltage Step = Iref×R0. After N counts, the voltage formation reference value D<7:0> is equal to the target output voltage value LEVEL<7:0> which is equal to zero. The value of the reference reference voltage Vref decreases from Iref×N×R0 to zero, and the output voltage of the DC-DC converter decreases to zero, completing the soft turn-off of the DC-DC converter. The turn-off time toff of the DC-DC converter is toff = N×Tclk. Additionally, by setting EN of the target output voltage value preset module 11 to 0, the target output voltage value LEVEL<7:0> is also set to 0, and the soft turn-off of the DC-DC converter can also be performed.

[0081] By controlling the counting pulse period Tclk of the addition and subtraction counter 22, the step period during the soft start of the DC-DC converter can be controlled, thereby precisely controlling the soft start time ton and the soft turn-off time toff of the DC-DC converter. By presetting different target output voltage values LEVEL<7:0>, controlling the current value Iref output by the constant current source 42, and controlling the counting pulse period Tclk of the addition and subtraction counter 22, the magnitude of the reference reference voltage Vref can be flexibly controlled. When the output current Iref of the constant current source 42 and the counting pulse period Tclk of the addition and subtraction counter 22 are determined, only by setting the target output voltage value LEVEL<7:0>, an accurate reference reference voltage Vref can be obtained, as well as a determined rising or falling time of the reference reference voltage Vref.

[0082] As Figure 8 shown, when the DC-DC converter is in the working state, the reference reference voltage Vref can also be adjusted by presetting different target output voltage values LEVEL<7:0>, and then the output voltage of the DC-DC converter can be adjusted, which is also more convenient for adjusting the output voltage of the DC-DC converter. And the adjustment process of the output voltage is also a gradual soft adjustment process, without generating surge current and overshoot voltage, ensuring the safety and stability of the adjustment process.

[0083] In a preferred embodiment of the output voltage control circuit of the DC-DC converter in the present application, as Figure 5As shown in the figure, the waveform processing module 52 includes a comparator 521 and an RS flip-flop 522. The negative input terminal of the comparator 521 is connected to the voltage comparison module 51, the positive input terminal is connected to a sawtooth wave signal, and the output terminal is connected to the R terminal of the RS flip-flop 522, which can convert the output level of the voltage comparison module 51 into a pulse level signal. The S terminal of the RS flip-flop 522 is connected to a clock signal, which can modulate the pulse level signal to form a PWM signal and send it to the logic drive module 53 through the Q terminal of the RS flip-flop 522. The logic drive module 53 amplifies the power and performs logic processing on the PWM signal to generate two PWM pulse drive signals SH and SL with opposite phases.

[0084] The switch conversion unit 6 includes a first switch element 61, a second switch element 62, and an energy storage module 63. The first switch element 61 and the second switch element 62 are connected in series at the input terminal of the DC-DC converter. The first switch element 61 and the second switch element 62 can be turned on and off respectively under the control of two inverted PWM pulse drive signals. The energy storage module 63 includes an inductor L0 and a capacitor C0. One end of the inductor L0 is connected between the first switch element 61 and the second switch element 62, and the other end is connected to the output terminal of the DC-DC converter. The capacitor C0 is connected between the output terminal of the switch conversion unit 6 and the ground.

[0085] The PWM pulse drive signal SH of the logic drive module 53 is connected to the control terminal of the first switch element 61, and the PWM pulse drive signal SL is connected to the control terminal of the second switch element 62. The first switch element 61 is connected to the positive pole of the input terminal of the switch conversion unit 6. When the first switch element 61 is turned on, the input power supply of the DC-DC converter charges the energy storage module 63, and the energy stored in the inductor L0 and the capacitor C0 increases, and the output terminal voltage of the switch conversion unit 6 increases; when the second switch element 62 is turned on, in addition to being consumed on the load RL, the energy stored in the inductor L0 and the capacitor C0 also discharges through the second switch element 62, and the energy stored in the inductor L0 and the capacitor C0 decreases, and the output terminal voltage of the switch conversion unit 6 decreases.

[0086] Since the phases of the PWM pulse drive signal SH and the PWM pulse drive signal SL are opposite, only one of the first switch element 61 and the second switch element 62 can be turned on at the same time, which can prevent the input terminal of the switch conversion unit 6 from being short-circuited. By controlling the conduction time ratio of the first switch element 61 and the second switch element 62, the output terminal voltage of the switch conversion unit 6 can be stabilized near the target output voltage, ensuring that the output voltage of the DC-DC converter is the target output voltage.

[0087] Using the output voltage control circuit of the DC-DC converter of the present application, the output voltage control method of the DC-DC converter of the present application can be realized.

[0088] An embodiment of the output voltage control method for the DC-DC converter of the present application is as follows Figure 9 shown, and includes the following steps:

[0089] S10. Preset a target output voltage value. By presetting the target output voltage value, the adjustment direction of the output voltage of the DC-DC converter can be flexibly controlled: in the off state of the DC-DC converter, by presetting a non-zero target output voltage value, the DC-DC converter can be controlled to start and output a DC voltage corresponding to the target output voltage; in the working state of the DC-DC converter, presetting a zero value for the target output voltage value can control the DC-DC converter to turn off; in the working state of the DC-DC converter, presetting any reasonable target output voltage value can adjust the output voltage of the DC-DC converter to the voltage corresponding to the target output voltage value.

[0090] S20. Compare the preset target output voltage value with the voltage formation reference value stored in the circuit. A data storage unit is provided in the circuit, and the voltage formation reference value is stored in the data storage unit, and the voltage formation reference value is used as the reference for controlling the output voltage of the DC-DC converter. Calculate the difference between the voltage formation reference value and the target output voltage value. When the difference is greater than zero, gradually reduce the voltage formation reference value at a certain step until the voltage formation reference value is equal to the target output voltage value; when the difference is less than zero, gradually increase the voltage formation reference value at a certain step until the voltage formation reference value is equal to the target output voltage value; when the difference is equal to zero, keep the voltage formation reference value.

[0091] In the power-off state of the DC-DC converter, the voltage formation reference value stored in the data storage unit is cleared. When the DC-DC converter is powered on, the voltage formation reference value stored in the data storage unit is automatically set to zero, and the DC-DC converter is in the off state, and its output voltage is zero, ensuring the safety of the DC output loop.

[0092] S30. Control the converter switch circuit according to the voltage formation reference value, so that the converter output voltage is gradually adjusted to the target output voltage. The DC-DC converter controls the output voltage through the switch circuit. Usually, a switch element for charging the output loop and a switch element for releasing the energy in the output loop are provided in the switch circuit. The conduction of the charging switch element will cause the output voltage of the output loop to rise, while the conduction of the energy-releasing switch element will cause the output voltage of the output loop to drop rapidly. Therefore, by controlling the working state of the switch circuit, the output voltage of the DC-DC converter can be easily controlled. Using different voltage formation reference values as control conditions to control the working state of the converter switch circuit, so that the DC-DC converter outputs different output voltages, and an output voltage corresponding to the voltage formation reference value can be formed.

[0093] Since the adjustment of the voltage formation reference value is a gradual adjustment based on a certain step, after setting a new target output voltage value, the voltage formation reference value will be gradually adjusted from the original stored value to the target output voltage value respectively, and the output voltage of the DC-DC converter will also gradually approach the target output voltage step by step. This can avoid overshoot caused by rapid adjustment of the output voltage of the DC-DC converter, realize soft adjustment of the output voltage, and improve the safety of using the DC-DC converter.

[0094] By presetting a non-zero target output voltage value in the off state of the DC-DC converter, or presetting a zero value as the target output voltage value in the working state, soft shutdown and soft start of the DC-DC converter can be realized. By arbitrarily presetting a reasonable target output voltage value in the working state, soft adjustment of the output voltage of the DC-DC converter in any direction can be realized, making the output voltage control method of the DC-DC converter of the present application have great flexibility in output voltage control.

[0095] Using the output voltage control method of the DC-DC converter of the present application, the output voltage of the output voltage control circuit of the DC-DC converter of any embodiment of the present application can be adjusted.

[0096] In some embodiments of the output voltage control method of the DC-DC converter of the present application, such as Figure 10 and Figure 11 shown, the method for adjusting the voltage formation reference value in step S20 includes the following steps:

[0097] S21. Compare the target output voltage value with the current voltage formation reference value to obtain the difference between the target output voltage value and the current voltage formation reference value. Specifically, a subtractor can be used to perform a subtraction operation on the target output voltage value and the current voltage formation reference value, and the calculation result is the difference between the two.

[0098] If the calculation result is greater than zero, that is, the target output voltage value is greater than the reference value formed by the current voltage, continue to perform the operations in step S22; if the calculation result is less than zero, that is, the target output voltage value is less than the reference value formed by the current voltage, then jump to step S23 and perform the operations in step S23; if the calculation result is equal to zero, that is, the target output voltage value is equal to the reference value formed by the current voltage, then jump to step S24 and perform the operations in step S24.

[0099] S22. Control the reference value of the voltage formation to increase by one adjustment reference. The adjustment reference can be the least significant bit of the memory, or can be freely determined according to the time requirements of the soft start and soft shutdown of the DC-DC converter. After the adjustment is completed, jump back to step S21, and re-compare the difference between the target output voltage value and the adjusted voltage formation reference value, forming a step-by-step cyclic adjustment of the voltage formation reference value, so that the voltage formation reference value gradually increases at a certain slope and gradually approaches the target output voltage value.

[0100] S23. Control the reference value of the voltage formation to decrease by one adjustment reference. After the adjustment is completed, jump back to step S21, and re-compare the difference between the target output voltage value and the adjusted voltage formation reference value, forming a step-by-step cyclic adjustment of the voltage formation reference value, so that the voltage formation reference value gradually decreases at a certain slope and gradually approaches the target output voltage value.

[0101] S24. Keep the reference value of the voltage formation. At this time, the voltage output by the DC-DC converter is the target output voltage. Keeping the reference value of the voltage formation can make the output voltage of the DC-DC converter remain the target output voltage.

[0102] The method for controlling the converter switch circuit in step S30 includes the following steps:

[0103] S31. Convert the reference value of the voltage formation into a reference reference voltage, which is usually carried out by means of digital-to-analog conversion. By converting the digital value used to adjust the output voltage of the converter into an analog voltage value through a certain standard, the corresponding relationship between the digital and the actual voltage can be established, and the precise adjustment of the output voltage of the converter can be realized.

[0104] Extract the output feedback voltage from the output loop of the converter. Usually, a voltage dividing circuit is set in the output loop of the converter, and an output feedback voltage proportional to the actual output voltage is extracted through the voltage dividing circuit.

[0105] Converting the reference reference voltage and extracting the output feedback voltage are usually carried out in parallel.

[0106] S32. Compare the magnitudes of the reference voltage and the output feedback voltage through a comparator circuit, and generate a control signal for the switching circuit based on the comparison result. When the output feedback voltage is less than the reference voltage, it indicates that the output voltage of the DC-DC converter is too low. At this time, generate a control signal to control the switching circuit to charge the output loop. When the output feedback voltage is greater than the reference voltage, it indicates that the output voltage of the DC-DC converter is too high. At this time, generate a control signal to control the switching circuit to discharge the output loop. When the output feedback voltage is equal to the reference voltage, no control signal is output to interfere with the switching circuit.

[0107] S33. Control the converter switching circuit according to the switching circuit control signal, specifically control the on and off of the charging switch element and the discharging switch element, and make the output voltage of the converter gradually change towards the target output voltage by controlling the charging and discharging of the converter output loop, and stably output the target output voltage.

[0108] An embodiment of the DC-DC converter of the present application uses the output voltage control circuit of the DC-DC converter of any embodiment of the present application, which can conveniently implement the soft start, soft shutdown and soft regulation of the output voltage of the DC-DC converter, greatly expanding the usage scenarios of the DC-DC converter of the present application, and the flexibility, convenience and safety of use are also higher.

[0109] In the description of the present invention, the descriptions referring to terms such as "one embodiment", "specific embodiment", "preferred embodiment", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In the present invention, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0110] The above are all the preferred embodiments of the present application. The protection scope of the present application is not limited by this. Therefore, all equivalent changes made according to the structure, shape and principle of the present application should be covered within the protection scope of the present application.

Claims

1. A DC-DC converter output voltage control circuit, characterized in that: The invention comprises a digital subtraction unit (1), an addition and subtraction counting unit (2), a decoding storage unit (3), a digital-to-analog conversion unit (4), a feedback control unit (5) and a switch conversion unit (6), wherein the digital subtraction unit (1) has a first subtraction input terminal, a second subtraction input terminal and a subtraction output terminal, the first subtraction input terminal is provided with a target output voltage value preset module (11), the second subtraction input terminal is capable of receiving a storage value of the decoding storage unit (3), the subtraction output terminal is connected to the addition and subtraction counting unit (2) so as to be able to control the counting state of the addition and subtraction counting unit (2), and the decoding storage unit (3) is capable of controlling the counting state of the addition and subtraction counting unit (2). The storage unit (3) is connected to the addition and subtraction counting unit (2) so as to store the counting result of the addition and subtraction counting unit (2) and transmit it to the second subtraction input terminal; the digital-to-analog conversion unit (4) is connected to the decoding storage unit (3) so as to convert the storage value of the decoding storage unit (3) into a reference reference voltage; the feedback control unit (5) is connected to the digital-to-analog conversion unit (4) and the switch conversion unit (6) so as to control the output voltage of the switch conversion unit (6) according to the reference reference voltage and the output feedback voltage from the switch conversion unit (6).

2. The DC-DC converter output voltage control circuit according to claim 1, characterized in that: The addition and subtraction counting unit (2) comprises a latch (21) and an addition and subtraction counter (22); the input end of the latch (21) is connected to the digital subtraction unit (1) so as to generate different counting control signals according to the calculation result of the digital subtraction unit (1); and the output end of the latch (21) is connected to the addition and subtraction counter (22) so as to control the addition and subtraction counter (22) to perform addition counting, subtraction counting or holding.

3. The DC-DC converter output voltage control circuit according to claim 1, characterized in that: The digital-to-analog conversion unit (4) comprises a decoder module (41), a constant current source (42) and a resistance conversion module (43); the decoder module (41) is connected to the decoding storage unit (3) and is capable of converting the storage value of the decoding storage unit (3) into a multi-channel control signal; the resistance conversion module (43) is connected to the constant current source (42) and is capable of changing the equivalent resistance value under the control of the multi-channel control signal, thereby forming a reference voltage at both ends of the resistance conversion module (43).

4. The DC-DC converter output voltage control circuit according to claim 3, characterized in that: The decoder module (41) comprises a first temperature decoder (411) and a second temperature decoder (412); the first temperature decoder (411) is capable of converting low-order data of a storage value of the decoding storage unit (3) into a first multi-channel control signal; the second temperature decoder (412) is capable of converting high-order data of a storage value of the decoding storage unit (3) into a second multi-channel control signal; the resistance conversion module (43) comprises a first resistance conversion array (431) and a second resistance conversion array (432); the first resistance conversion array (431), the second resistance conversion array (432) and the constant current source (42) are connected in series with each other; the first resistance conversion array (431) is capable of changing an equivalent resistance value under the control of the first multi-channel control signal; and the second resistance conversion array (432) is capable of changing an equivalent resistance value under the control of the second multi-channel control signal.

5. The DC-DC converter output voltage control circuit according to claim 4, characterized in that: The first resistance conversion array (431) comprises a plurality of first electronic switches S0 and a plurality of first reference resistors R0 connected in series, the plurality of first electronic switches S0 are respectively connected to the two ends of a series circuit formed by connecting the plurality of first reference resistors R0, and the same end of a series circuit formed by connecting a connection line between adjacent first reference resistors R0 and the plurality of first reference resistors R0, and the plurality of first electronic switches S0 can be respectively switched under the control of one control signal in the first multi-path control signal; the second resistance conversion array (432) comprises a plurality of second electronic switches S0' and a plurality of second reference resistors R0' connected in series, the plurality of second electronic switches S0' are respectively connected to the two ends of a series circuit formed by connecting the plurality of second reference resistors R0', and the same end of a series circuit formed by connecting a connection line between adjacent second reference resistors R0' and the plurality of second reference resistors R0', and the plurality of second electronic switches S0' can be respectively switched under the control of one control signal in the second multi-path control signal; R0'=(n+1)R0, where n is the number of the first reference resistors R0.

6. The DC-DC converter output voltage control circuit according to claim 1, characterized in that: The feedback control unit (5) comprises a voltage comparison module (51), a waveform processing module (52) and a logic drive module (53); the voltage comparison module (51) is respectively connected to the switch conversion unit (6), the digital-to-analog conversion unit (4) and the waveform processing module (52) so as to be able to compare the magnitude of the output feedback voltage with the reference reference voltage; the waveform processing module (52) is able to generate an output voltage adjustment signal according to the comparison result of the voltage comparison module (51); the logic drive module (53) is connected to the waveform processing module (52) and the switch conversion unit (6) so as to be able to control the working state of the switch conversion unit (6) according to the output voltage adjustment signal, thereby controlling the output voltage of the switch conversion unit (6).

7. The DC-DC converter output voltage control circuit according to claim 6, characterized in that: The waveform processing module (52) comprises a comparator (521) and an RS trigger (522); the input end of the comparator (521) is respectively connected to the voltage comparison module (51) and the sawtooth wave signal, the output end is connected to the R end of the RS trigger (522), the S end of the RS trigger (522) is connected to the clock signal, and the Q end of the RS trigger (522) is connected to the logic driving module (53); the logic driving module (53) is capable of generating two inverse driving signals under the control of the Q end output signal of the RS trigger (522); the switch conversion unit (6) comprises a first switch element (61), a second switch element (62) and a charging module (63); the first switch element (61) and the second switch element (62) are connected in series at the input end of the DC-DC converter and are capable of switching under the control of the two inverse driving signals respectively; the charging module (63) is connected between the connection between the first switch element (61) and the second switch element (62) and the output end of the DC-DC converter.

8. A DC-DC converter output voltage control method, capable of controlling the output voltage of a DC-DC converter output voltage control circuit according to any one of claims 1 to 7, characterized in that: The steps include: S10, preset target output voltage value; S20, comparing the voltage forming reference value stored in the circuit with the target output voltage value, and gradually adjusting the voltage forming reference value according to the comparison result until the voltage forming reference value is equal to the target output voltage value; S30 , controlling the converter switch circuit according to the voltage forming reference value, so that the converter output voltage is gradually adjusted to the target output voltage.

9. The DC-DC converter output voltage control method according to claim 8, characterized in that: Step S20 includes the following steps: S21, obtaining the difference between the target output voltage value and the reference value formed by the current voltage, if the difference is greater than zero, executing step S22, if the difference is less than zero, executing step S23, otherwise executing step S24; S22, the control voltage forms a reference value which is increased by 1 adjustment reference, and then executes step S21; S23, the control voltage forms a reference value which is reduced by 1 adjustment reference, and then executes step S21; S24, maintaining the voltage to form a reference value; Step S30 includes the following steps: S31, generating a reference voltage according to a voltage forming reference value, and obtaining an output feedback voltage according to a converter output voltage; S32, comparing the reference voltage with the output feedback voltage, and generating a switch circuit control signal according to the comparison result; S33. The converter switch circuit is controlled according to the switch circuit control signal, so that the converter output voltage gradually changes to the target output voltage.

10. A DC-DC converter, characterized in that: The DC-DC converter output voltage control circuit according to any one of claims 1 to 7 can realize soft start, soft shutdown and soft regulation of the output voltage of the DC-DC converter.

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