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

Abstract

The invention relates to the technical field of power conversion, and discloses a DC-DC converter output voltage control circuit and method and a converter, and the DC-DC converter output voltage control circuit comprises a digital subtraction unit, an add-subtract counting unit, a decoding storage unit, a digital-to-analog conversion unit, a feedback control unit and a switch conversion unit. The digital subtraction unit can calculate a preset target output voltage value and a storage value of the decoding storage unit and control the counting state of the add-subtract counting unit according to a calculation result, and the decoding storage unit can store a counting result of the add-subtract counting unit; the digital-to-analog conversion unit can convert the storage value of the decoding storage unit into the reference voltage, and the feedback control unit can control the output voltage of the switch conversion unit according to the reference voltage and the output feedback voltage, so that the control flexibility of the output voltage can be improved; the soft start and soft close of the DC-DC converter and the soft regulation of the output voltage are realized.

Description

Technical Field

[0001] The present application relates to the field of power conversion technology, and in particular to a DC-DC converter output voltage control circuit. In addition, the present application also relates to a DC-DC converter output voltage control method and a DC-DC converter. Background Art

[0002] Electronic circuits are usually powered by DC power supplies, and different types of electronic circuits, or even different parts of electronic circuits, usually require DC power supplies of different voltages. For this reason, DC-DC converters are usually required in electronic circuits. The DC-DC converters in electronic circuits usually charge the inductor in the output circuit by switching the switch tube, and the voltage across the inductor increases as the energy is accumulated by the inductor, and the output voltage increases accordingly.

[0003] During the startup of the DC-DC converter, the switch tube quickly charges the inductor, causing the output voltage to rise rapidly. At this time, if the output load is small or unloaded, the energy in the inductor is discharged slowly, which can easily cause the output voltage to overshoot greatly during the power-on process, making the output voltage greater than the set output voltage in a short period of time, which can easily cause damage to the electronic circuit. During the shutdown of the DC-DC converter, if the output load is small or unloaded, the induced electromotive force generated by the inductor can easily cause the low-side current 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] In order to prevent the DC-DC converter from voltage overshoot or input voltage boost, the output voltage needs to be controlled to change slowly when the DC-DC converter is started, shut down and adjusts the output voltage, that is, to achieve soft start, soft shutdown and soft voltage adjustment of the DC-DC converter.

[0005] The Chinese invention patent application with publication number CN101741233A discloses a soft shutdown control module, which controls the first current source 204 to charge the capacitor Css through the first switch element 202 at startup to form a slowly rising variable reference signal Vss; controls the second current source 205 to discharge the capacitor Css through the second switch element 203 at shutdown to form a slowly falling variable reference signal Vss, and then uses the variable reference signal Vss to control the switch of the switch tube, so that the converter output voltage rises slowly at startup and falls slowly at shutdown, realizing the soft start and soft shutdown of the converter. However, this module needs to use a larger capacitor Css to realize the slow change of the variable reference signal Vss, and the larger capacitor is difficult to integrate into the chip, which increases the volume of the module and the complexity of the circuit, and the cost of use is high.

[0006] The invention patent application with publication number CN101741233A discloses a soft start circuit of a DC-DC switching power supply controlled by digital-to-analog conversion, which uses a counter to control the connection mode of the resistors in the weighted resistor network through an electronic switch, divides the reference voltage Vbg in different proportions, forms a step-shaped digital-to-analog conversion voltage V2, until the digital-to-analog conversion voltage V2 reaches the reference voltage Vbg, and uses the digital-to-analog conversion voltage V2 to control the switch of the switch tube, 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 the soft start circuit can only rise from zero to a fixed reference voltage Vbg after a fixed number of rises, and can only realize 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 rises, and cannot adjust the output voltage, nor can it adapt to the requirements for 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 realize 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 in this application adopts the following technical solution: A DC-DC converter output voltage control circuit comprises a digital subtraction unit, an addition and subtraction counting unit, a decoding storage unit, a digital-to-analog conversion unit, a feedback control unit and a switch conversion unit, wherein the digital subtraction unit has a first subtraction input terminal, a second subtraction input terminal and a subtraction output terminal, wherein the first subtraction input terminal is provided with a target output voltage value preset module, the second subtraction input terminal can receive a storage value of the decoding 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 storage unit is connected to the addition and subtraction counting unit to store the counting result of the addition and subtraction counting unit and transmit it to the second subtraction input terminal; the digital-to-analog conversion unit is connected to the decoding storage unit to convert the storage value of the decoding storage unit into a reference reference voltage, and the feedback control unit is connected to the digital-to-analog conversion unit and the switch conversion unit to control the output voltage of the switch conversion unit according to the reference reference voltage and the output feedback voltage from the switch conversion unit.

[0009] By adopting the above technical solution, the digital subtraction unit can be used to calculate the difference between the target output voltage value in the target output voltage value preset module and the voltage formed by the reference value stored in the decoding storage unit, and the addition and subtraction counting unit can be controlled according to the difference state to determine whether to perform addition and subtraction calculations, and the direction of addition and subtraction counting. The digital-to-analog conversion unit can be used to convert the voltage formed by the reference value stored in the decoding storage unit into a reference reference voltage in real time, and the real-time size of the reference reference voltage is used to control the size of the output voltage of the switch conversion unit, so that the output voltage of the switch conversion unit is adjusted to the set size at a set adjustment rate, and the output voltage of the DC-DC converter is accurately controlled to achieve soft start, soft shutdown and soft voltage adjustment of the DC-DC converter.

[0010] In a specific implementation scheme, 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 so as 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 maintenance.

[0011] By adopting the above technical solution, a latch connected to the digital subtraction unit at the input end 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 add-subtraction counter based on the latch, and control the add-subtraction counter to perform addition counting, subtraction counting or maintain the original counting result, and transmit it to the decoding storage unit to form a voltage reference value corresponding to the output voltage, which is stored in the decoding storage unit and used to adjust the output voltage, so that the output voltage is gradually adjusted with the counting reference as the adjustment unit.

[0012] In a specific feasible implementation scheme, 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 storage unit and can convert the storage value of the decoding 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 voltage at both ends of the resistance conversion module.

[0013] By adopting the above technical solution, the voltage forming reference value stored in the decoding storage unit can be decoded to form a multi-channel control signal by using the decoder module connected to the decoding storage unit, and the resistance value of the resistance conversion module can be controlled by using the multi-channel control signal, 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, a voltage drop of different magnitudes can be formed in the resistance conversion module, thereby forming a reference voltage corresponding to the voltage forming reference value, and using the reference voltage to control the magnitude of the converter output voltage, so as to conveniently and gradually perform soft adjustment on the converter output voltage.

[0014] In a specific implementation scheme, the decoder module includes a first temperature decoder and a second temperature decoder, the first temperature decoder can convert the low-bit data of the storage value of the decoding storage unit into a first multi-channel control signal, and the second temperature decoder can convert the high-bit data of the storage value of the decoding storage unit into a second multi-channel 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 with each other, the first resistance conversion array can change the equivalent resistance value under the control of the first multi-channel control signal, and the second resistance conversion array can change the equivalent resistance value under the control of the second multi-channel control signal.

[0015] By adopting the above technical solution, the first temperature decoder and the second temperature decoder can be used to decode the low-order data and the high-order data of the storage value of the decoding storage unit respectively, and form the first multi-channel control signal and the second multi-channel 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 modules, and on this basis, form a larger number of different reference voltages, thereby improving the convenience of adjusting the output voltage of the converter and improving the adjustment accuracy.

[0016] In a specific implementation scheme, the first resistance conversion array includes 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 includes 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.

[0017] By adopting the above technical solution, using multiple reference resistors connected in series, and an electronic switch connected between the same end of the series circuit and the connection point of the adjacent reference resistor 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 with the resistance value of the minimum reference resistor as the adjustment unit. 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 voltage forming the reference value, thereby ensuring the uniformity of the converter output voltage adjustment.

[0018] In a specific feasible implementation scheme, the feedback control unit includes a voltage comparison module, a waveform processing module and a logic driving 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 output feedback voltage with 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 driving 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.

[0019] By adopting the above technical solution, using the voltage comparison module connected to the switch conversion unit, the digital-to-analog conversion unit and the waveform processing module respectively, the output feedback voltage corresponding to the output voltage of the converter can be obtained through the switch conversion unit, and 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, and after being processed by the logic drive module, a drive signal for driving the switch conversion unit to operate is generated, and the output voltage of the switch conversion unit is controlled so that the output feedback voltage is equal to the reference voltage, so that the output voltage of the converter is stably maintained at the target output voltage.

[0020] In a specific feasible implementation scheme, the waveform processing module includes a comparator and an RS trigger, the input end of the comparator is respectively connected to the voltage comparison module and the sawtooth wave signal, the output end is connected to the R end of the RS trigger, the S end of the RS trigger is connected to the clock signal, and the Q end of the RS trigger is connected to the logic drive module; the logic drive module can generate two inverted drive signals under the control of the Q end output signal of the RS trigger; the switch conversion unit includes a first switch element, a second switch and a charging module, the first switch element and the second switch 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 drive signals, and the charging module is connected between the connection between the first switch element and the second switch element and the output end of the DC-DC converter.

[0021] By adopting the above technical solution, using a comparator whose input ends are respectively connected to the voltage comparison module and the sawtooth wave signal, and an RS trigger connected to the comparator, a pulsed output voltage adjustment signal can be generated according to the comparison result of the voltage comparison module, and a logic signal for switching control of the switch control element is formed after being processed by the logic drive module. The logic drive module can generate an anti-phase drive signal for controlling the two switch elements respectively, ensuring the coordinated operation of the two switch elements, and adjusting the output voltage in opposite directions by switching the two switch elements respectively. The charging module can ensure the relative stability of the output voltage of the converter.

[0022] The DC-DC converter output voltage control method provided in this application adopts the following technical solution: A DC-DC converter output voltage control method can control the output voltage of the DC-DC converter output voltage control circuit provided by the present application, comprising the following steps: S10, presetting a 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 switching circuit according to the voltage forming reference value, so that the converter output voltage is gradually adjusted to the target output voltage.

[0023] By adopting the above technical solution, by comparing the voltage forming reference value with the target output voltage value, the target output voltage and the current output voltage determined by the voltage forming reference value can be determined, so as to accurately adjust the voltage forming reference value, adjust the voltage forming reference value toward the target output voltage value, and adjust the current output voltage to the target value. In this way, the adjustment direction and adjustment amplitude of the output voltage can be freely determined by the method of presetting the target output voltage value, and the converter can be turned off by presetting the target output voltage value to zero, and the converter can be started by presetting the target output voltage value in the off state. By gradually adjusting the voltage forming reference value and controlling the converter switch circuit to gradually adjust the converter output voltage according to the voltage forming reference value, the output voltage can be controlled to be adjusted step by step and in small increments to the target output voltage, so as to realize the soft start, soft shutdown and soft adjustment of the output voltage of the converter, prevent overshoot and excessive increase of the input voltage in the output voltage adjustment process, and ensure the stable operation of the DC-DC converter.

[0024] In a specific feasible implementation scheme, step S20 includes the following steps: S21, obtain the difference between the target output voltage value and the current voltage forming a 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 forming a reference value to increase by 1 adjustment reference, and then execute step S21; S23, control the voltage forming a reference value to decrease by 1 adjustment reference, and then execute step S21; S24, maintain the voltage forming a reference value; step S30 includes the following steps: S31, generate a reference reference voltage according to the voltage forming a reference value, and obtain the output feedback voltage according to the converter output voltage; S32, compare the reference reference voltage with the output feedback voltage, and generate a switching circuit control signal according to the comparison result; S33, control the converter switching circuit according to the switching circuit control signal, so that the converter output voltage gradually changes to the target output voltage.

[0025] By adopting the above technical solution, the voltage forming reference value is adjusted step by step by gradually increasing or decreasing the voltage forming reference value by 1 adjustment reference, so that the voltage forming reference value can be gradually changed to the target output voltage value in a small amount, and slowly adjusted to the target output voltage value, and the time when the converter output voltage reaches the target output voltage can be accurately determined according to the size of the difference between the target output voltage value and the current output voltage value, so as to achieve precise control of the converter. The method of generating a reference reference voltage by a voltage forming reference value can obtain a reference reference voltage that changes slowly in a step-by-step manner with a certain slope, and the change slope of the reference reference voltage can be conveniently controlled by controlling the corresponding relationship between the voltage forming reference value and the reference reference voltage.

[0026] The DC-DC converter of the present application uses the AC-DC contactor control circuit provided in the present application, and can realize soft start, soft shutdown and soft regulation of the output voltage of the DC-DC converter.

[0027] In summary, the present application includes at least one of the following beneficial technical effects: By comparing the voltage in the circuit to form a reference value and a preset target output voltage value, the converter can be soft-started by presetting a target output value when the converter is in an off state, the converter can be soft-shut down by presetting the target output value to zero when the converter is in an on state, and the converter output voltage can be soft-regulated by setting a different target output value when the converter is in an on state, and the time of soft start, soft shutdown and soft regulation can be accurately controlled, thereby improving the flexibility of the DC-DC converter output voltage control of the present application; By controlling the voltage forming reference value to be cyclically increased by 1 when the target output voltage value is greater than the voltage forming reference value, and controlling the voltage forming reference value to be cyclically decreased by 1 when the target output voltage value is less than the voltage forming reference value, the voltage forming reference value can be bidirectionally and gradually adjusted, thereby bidirectionally and gradually softly adjusting the output voltage of the DC-DC converter, thereby preventing the over-adjustment of the output voltage of the DC-DC converter; By setting the digital subtraction unit, the addition and subtraction counting unit and the decoding storage unit, the digital subtraction unit can be used to compare the preset target output voltage value with the voltage forming reference value stored in the decoding storage unit, and the addition and subtraction counter is controlled to perform addition and subtraction counting or maintain the counting result according to the comparison result, and the new voltage forming reference value is stored after decoding by the decoding storage unit, so that the voltage forming reference value can be conveniently adjusted step by step, thereby realizing the step-by-step soft adjustment of the converter output voltage; By setting the first temperature decoder and the second temperature decoder to respectively decode the low-order data and the high-order data of the voltage forming a reference value, and adjusting the equivalent resistance values ​​of the first resistance conversion array and the second resistance conversion array respectively according to the decoding results, a smaller number of reference resistors can be used to form a larger number of different equivalent resistance values ​​of the resistance conversion module, and a constant current source can be used to form a larger number of different reference reference voltage values, thereby improving the regulation accuracy of the converter output voltage through a relatively simple circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a structural principle diagram of an embodiment of a DC-DC converter output voltage control circuit of the present application.

[0029] Figure 2 This is a structural schematic diagram of the digital logic part in one embodiment of the DC-DC converter output voltage control circuit of the present application.

[0030] Figure 3 This is a schematic diagram of the control flow of the digital logic part in one embodiment of the DC-DC converter output voltage control circuit of the present application.

[0031] Figure 4 This is a structural schematic diagram of a digital-to-analog conversion unit in an embodiment of a DC-DC converter output voltage control circuit of the present application.

[0032] Figure 5 This is a structural schematic diagram of a feedback control unit and a switch conversion unit in one embodiment of a DC-DC converter output voltage control circuit of the present application.

[0033] Figure 6 The diagram is a schematic diagram of a reference voltage variation waveform during a soft start process of an output voltage control circuit of a DC-DC converter according to an embodiment of the present application.

[0034] Figure 7 The diagram is a schematic diagram of a waveform of a reference voltage change during a soft shutdown process of an output voltage control circuit of a DC-DC converter according to an embodiment of the present application.

[0035] Figure 8 This is a schematic diagram of a reference voltage variation waveform during the output voltage soft regulation process of an output voltage control circuit of a DC-DC converter according to an embodiment of the present application.

[0036] Fig. 9 This is a flowchart of an embodiment of a DC-DC converter output voltage control method of the present application.

[0037] Fig.10 1 is a flowchart of step S20 in one embodiment of the DC-DC converter output voltage control method of the present application.

[0038] Fig.11 1 is a flowchart of step S30 in one embodiment of the DC-DC converter output voltage control method of the present application.

[0039] Explanation of the accompanying drawings: 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 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 trigger; 53. Logic drive module; 6. Switch conversion unit; 61. First switch element; 62. Second switch element; 63. Charging module. DETAILED DESCRIPTION

[0040] The specific implementation of the present application is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present application, and is not used to limit the present application.

[0041] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "disposed" 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 direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0042] In this specification, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or suggesting relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the said features.

[0043] An embodiment of the DC-DC converter output voltage control circuit of the present application is as follows: Figures 1 to 5As shown, it includes 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. Among them, the digital subtraction unit 1 has a first subtraction input terminal, a second subtraction input terminal and a subtraction output terminal, and 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, and the eight-bit binary number LEVEL<7:0> has 256 different values, so 256 uniformly distributed different output voltages 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 storage unit 3 and can receive the storage value of the decoding storage unit 3, that is, the voltage forming reference value. In this embodiment, the voltage forming reference value is also an eight-bit binary number D<7:0>.

[0044] The digital subtraction unit 1 can perform subtraction operation on the target output voltage value inputted from the first subtraction input terminal and the voltage inputted from the second subtraction input terminal to form a reference value, calculate the difference between LEVEL<7:0> and D<7:0>, and output the calculation result through the subtraction output terminal.

[0045] 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 by the subtraction output terminal. Specifically, when the calculation result is greater than zero, that is, the target output voltage value is greater than the voltage forming reference value, addition counting 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, the target output voltage value is less than the voltage forming reference value, subtraction counting 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, the target output voltage value is equal to the voltage forming reference value, counting is stopped, 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>.

[0046] 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 forming reference value D<7:0>, and store the new voltage forming reference value D<7:0> in the decoding storage unit 3, replacing the original voltage forming reference value D<7:0>, and at the same time, the new voltage forming reference value D<7:0> is transmitted to the second subtraction input terminal of the digital subtraction unit 1, and the target output voltage value LEVEL<7:0> is re-subtracted. This cycle is repeated until the voltage forming reference value D<7:0> is equal to the target output voltage value LEVEL<7:0>, realizing the step-by-step step-by-step change of the voltage forming reference value D<7:0> from the original value to the target output voltage value LEVEL<7:0>.

[0047] 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 forming reference value D<7:0> stored in the decoding storage unit 3 to obtain a reference voltage Vref corresponding to the voltage forming reference value D<7:0>. Specifically, the proportional relationship between the reference voltage Vref and the voltage forming reference value D<7:0> can be determined according to the rated output voltage of the DC-DC converter, the adjustment range of the output voltage, and the change rate of the output voltage.

[0048] 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.

[0049] Specifically, when the output feedback voltage Vfb is greater than the reference voltage Vref, it means that the output voltage of the switch conversion unit 6 is too high, and 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 means that the output voltage of the switch conversion unit 6 is too low, and 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 equal to the reference voltage Vref, and the output voltage of the DC-DC converter is adjusted to a set voltage level.

[0050] 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 being provided to the output end through the switch conversion unit 6, thereby adjusting the output end voltage of the switch conversion unit 6. Through the feedback adjustment of the feedback control unit 5, the output end voltage of the switch conversion unit 6 can be controlled in real time at a level corresponding to the reference reference voltage Vref. The reference reference voltage Vref corresponds to the voltage forming reference value D<7:0>, and the voltage forming reference value D<7:0> can be gradually changed in steps to the preset target output voltage value LEVEL<7:0>. In this way, by presetting different target output voltage values ​​LEVEL<7:0>, the output voltage of the DC-DC converter can be adjusted in steps to different target output voltages, and the soft adjustment of the output voltage of the DC-DC converter can be conveniently realized. By presetting a non-zero target output voltage value LEVEL<7:0> when the DC-DC converter is in the off state, the output voltage of the DC-DC converter can be gradually increased from zero to the target output voltage, thereby realizing the soft start of the DC-DC converter; by presetting the target output voltage value LEVEL<7:0> to zero when the DC-DC converter is in the working state, the output voltage of the DC-DC converter can be gradually reduced to zero, thereby realizing the soft shutdown of the DC-DC converter.

[0051] In some embodiments of the DC-DC converter output voltage control circuit of the present application, as Figure 2 As 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, and the calculation result of the digital subtraction unit 1 equal to zero is directly transmitted to the latch 21 for latching, and 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 by the logic signal latched in the latch 21. Specifically, if the latch 21 latches a logic signal converted according to a calculation result of the digital subtraction unit 1 that is greater than zero, the add-subtract counter 22 performs addition counting based on the voltage forming the reference value D<7:0>, so that the counting result Q<7:0> increases by 1; if the latch 21 latches a logic signal converted according to a calculation result of the digital subtraction unit 1 that is less than zero, the add-subtract counter 22 performs subtraction counting based on the voltage forming the reference value D<7:0>, so that the counting result Q<7:0> decreases by 1; if the latch 21 latches a logic signal of the calculation result of the digital subtraction unit 1 that is equal to zero, the add-subtract counter 22 keeps the original counting result Q<7:0> unchanged.

[0052] The counting result Q<7:0> of the add-subtract counter 22 is decoded and stored by the decoding storage unit 3 to form a new voltage forming reference value D<7:0>. The new voltage forming reference value D<7:0> is transmitted to the digital subtraction unit 1 for subtraction operation on the one hand, and serves as the basis for the new addition and subtraction count of the add-subtract counter 22 on the other hand. It is also output to the digital-to-analog conversion unit 4 for generating a reference voltage Vref.

[0053] The setting of the latch 21 enables the add-subtract counter 22 and the digital subtraction unit 1 to operate under different clock pulse controls. By controlling the frequency ratio of the clock pulses of the add-subtract counter 22 and the digital subtraction unit 1, the number of counts of the add-subtract counter 22 within a calculation cycle of the digital subtraction unit 1 can also be changed, thereby changing the change rate of the reference voltage Vref.

[0054] In some embodiments of the DC-DC converter output voltage control circuit of the present application, as Figure 4 As shown, the digital-to-analog conversion unit 4 includes a decoder module 41, a constant current source 42 and a resistance 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 stored in the decoding storage unit 3 into a reference value D<7:0> into a multi-channel control signal. The resistance conversion module 43 generally includes a resistor array composed of a plurality of resistors, and a plurality of electronic switches are arranged in the resistor array. The plurality of electronic switches can be opened and closed respectively under the control of the multi-channel control signal generated by the decoding storage unit 3, and the resistor array forms different equivalent resistance values ​​through the combination of different opening and closing states of the plurality of electronic switches.

[0055] The resistance conversion module 43 is connected to the constant current source 42, and the constant current source 42 generates a constant current flowing through the resistance conversion module 43, forming a voltage drop at both ends of the resistance conversion module 43. The constant current forms different voltage drops under different equivalent resistance values ​​of the resistance conversion module 43, and a reference voltage Vref is formed at both ends of the resistance conversion module 43.

[0056] Since the reference voltage Vref is generated at both ends of the resistance conversion module 43, it does not need to rely on a capacitor with a large capacity, so it is easier to integrate into the chip, greatly reducing the volume of the device 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, so the control accuracy of the reference voltage Vref is also higher, and the control is more flexible and convenient.

[0057] In a preferred embodiment of the DC-DC converter output voltage control circuit of the present application, 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 reference value D<7:0> stored in the decoding storage unit 3 to form a corresponding thermometer code, and the thermometer code is used as the first multi-channel control signal for controlling the electronic switch in the control resistor array. The thermometer code has excellent DNL (differential nonlinearity) performance, and the differential nonlinearity error of the output signal is small, which can provide a more accurate analog signal.

[0058] 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 the thermometer code as the second multi-channel control signal to control the electronic switch in the control resistor array.

[0059] By using the first temperature decoder 411 and the second temperature decoder 412 to respectively decode the low-order data and the high-order data of the voltage forming reference value D<7:0>, the number of data bits of the thermometer code obtained by decoding the voltage forming reference value D<7:0> can be reduced, thereby reducing the structural complexity of the digital-to-analog conversion unit 4.

[0060] The resistance conversion module 43 includes a first resistance conversion array 431 and a second resistance conversion array 432. The first resistance conversion array 431 and the second resistance conversion array 432 are connected in series with each other and then connected in series in the power supply circuit of the constant current source 42. The first resistance conversion array 431 and the second resistance conversion array 432 are both formed by connecting a plurality of resistors to each other, and a plurality of electronic switches are connected in different resistance connection circuits. By controlling different electronic switches or the opening and closing states of electronic switch combinations, the resistance conversion arrays can be controlled to form different equivalent resistances.

[0061] The multiple electronic switches in the first resistance conversion array 431 can change the open and close states under the control of the first multi-channel 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 the open and close states under the control of the second multi-channel control signal, thereby changing the equivalent resistance value of the second resistance conversion array 432. More different equivalent resistance values ​​can be formed by combining the equivalent resistance of the first resistance conversion array 431 with the equivalent resistance of the second resistance conversion array 432.

[0062] As a specific implementation of the DC-DC converter output voltage control circuit of the present application, Figure 4As shown, the first resistance conversion array 431 includes multiple first electronic switches S0 and multiple first reference resistors R0, the multiple first reference resistors R0 are connected in series with each other, the multiple first electronic switches S0 are respectively connected between one end of the series circuit formed by connecting the multiple first reference resistors R0 and the other end of the multiple first reference resistors R0 connected in sequence, and the multiple first electronic switches S0 can be switched respectively under the control of a control signal corresponding to one of the first multiple control signals.

[0063] The second resistance conversion array 432 includes multiple second electronic switches S0' and multiple second reference resistors R0'. The multiple second reference resistors R0' are connected in series with each other. The multiple second electronic switches S0' are respectively connected between one end of the series circuit formed by connecting the multiple second reference resistors R0' and the other end of the multiple second reference resistors R0' connected in sequence, and the multiple second electronic switches S0' can be switched under the control of a control signal corresponding to one of the second multi-path control signals.

[0064] In a specific embodiment, the first temperature decoder 411 is a three-bit input and seven-bit output temperature decoder. The input end of the first temperature decoder 411 is connected to the three low-bit data output ends of the decoding storage unit 3, and can decode the three low-bit data D<2:0> of the voltage forming the reference value D<7:0> into the 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 end 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, which does not affect the connection state of the first reference resistor R0 connected at both 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 to be 0000000, the seven first electronic switches S0 are all closed, and the equivalent resistance of the first resistance conversion array 431 is zero; when D<2:0> is 001, the seven-bit thermometer code LSB<6:0> is decoded to be 0000001, Figure 4 The first first electronic switch S0 on the left side is disconnected, and the other first electronic switches S0 are all closed, and the equivalent resistance of the first resistance conversion array 431 is R0; and so on.

[0065] The second temperature decoder 412 is a 5-bit input and 31-bit output temperature decoder. The input end of the second temperature decoder 412 is connected to the five high-bit data output ends of the decoding storage unit 3, and can decode the five high-bit data D<7:3> of the voltage forming the reference value D<7:0> into the 31-bit thermometer code MSB<30:0>. The second resistance conversion array 432 includes 31 second reference resistors R0' connected in series with each other, and 31 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 31-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; and when a bit in the 31-bit thermometer code is 1, the corresponding second electronic switch S0' is disconnected, which does not affect the connection state of the second reference resistor R0 connected at both ends of the second electronic switch S0'. For example, when D<7:3> is 00000, the decoded 31-bit thermometer code MSB<30:0> is 0…0 (31 zeros in total), and the 31 second electronic switches S0' are all closed, and the equivalent resistance of the second resistance conversion array 432 is zero; when D<7:3> is 00001, the decoded 31-bit thermometer code MSB<30:0> is 0…01 (30 zeros in total), Figure 4 The first second electronic switch S0 ′ on the left side 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.

[0066] 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, in the process of voltage forming the reference value D<7:0>, when D<2:0> carries to D<7:3>, or D<2:0> borrows to D<7:3>, the uniformity of the change of the equivalent resistance value of the resistance conversion module 43 formed by the first resistance conversion array 431 and the second resistance conversion array 432 connected in series can be ensured.

[0067] The first temperature decoder 411 has seven output bits, which can decode the three low-order data D<2:0> of the voltage forming 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, which can decode the five high-order data D<7:3> of the voltage forming reference value D<7:0> to form thirty-two output bit states. The combination of the two can decode the voltage forming reference value D<7:0> represented by an eight-bit binary number to form 8×32 = 256 states corresponding to the voltage forming reference value D<7:0> represented by the eight-bit binary number. In this way, 256 output states can be formed through 7 + 31 = 38 output bits, which greatly simplifies the decoding circuit and improves the output accuracy of the voltage forming reference value D<7:0>.

[0068] Table 1 Truth table of the first temperature decoder Input Bit 000 001 010 011 100 101 110 111 Output bits 0000000 0000001 0000011 0000111 0001111 0011111 0111111 1111111 The first resistance conversion array 431 includes seven first reference resistors R0 and seven first electronic switches S0, which can be combined into eight equivalent resistance states of the first resistance conversion array 431; the second resistance conversion array 432 includes thirty-one second reference resistors R0' and thirty-one second electronic switches S0', which can be combined into thirty-two equivalent resistance states of the second resistance conversion array 432. The first resistance conversion array 431 and the second resistance conversion array 432 are connected in series to form a resistance conversion module 43, which can form 8×32 = 256 different equivalent resistance values ​​of the resistance conversion module 43. In this way, 256 different equivalent resistance values ​​can be formed by combining 7 + 31 = 38 resistors, and 256 different linearly changing reference voltages Vref are formed after conversion by the constant current source 42. Through a simpler resistance array structure, a more accurate control of the reference voltage Vref is formed, and the control accuracy of the output voltage of the DC-DC converter is improved.

[0069] In some embodiments of the DC-DC converter output voltage control circuit of the present application, as Figure 5 As shown, the feedback control unit 5 includes a voltage comparison module 51, a waveform processing module 52 and a logic driving 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 transmit the comparison result to the waveform processing module 52.

[0070] The waveform processing module 52 can process the comparison result of the voltage comparison module 51 and 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, and reduce the output voltage of the switch conversion unit 6 when the output feedback voltage Vfb is greater than the reference reference voltage Vref, and increase the output voltage of the switch conversion unit 6 when the output feedback voltage Vfb is less than the reference reference voltage Vref, and finally make the value range of the output feedback voltage Vfb equal to the reference reference voltage Vref, so that the output voltage of the switch conversion unit 6 is equal to the target output voltage.

[0071] like Figure 6 As shown, when the DC-DC converter is started, since the target output voltage LEVEL<7:0> is greater than the voltage forming reference value D<7:0>, the up-down counter 22 performs addition counting, and the voltage forming reference value D<7:0> is continuously increased by 1 as the number of count pulses N of the up-down counter 22 increases, and the equivalent resistance value N×R0 of the resistance conversion module 43 is also continuously increased, and the current Iref generated by the constant current source 42 flows through the resistance conversion module 43. The reference reference voltage Vref generated by the reference voltage conversion module 43 is also continuously increased. After each counting pulse cycle Tclk, the voltage forming reference value D<7:0> increases by 1, and the reference reference voltage Vref increases by a step voltage Step = Iref×R0. After N counts, the voltage forming reference value D<7:0> is equal to the target output voltage value LEVEL<7:0>, the reference reference voltage Vref = Iref×N×R0, the output voltage of the DC-DC converter is stabilized to the target output voltage, and the soft start of the DC-DC converter is completed. The start-up time ton of the DC-DC converter is = N×Tclk.

[0072] Similarly, if 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 forming reference value D<7:0>. The up-down counter 22 performs subtraction counting, and the voltage forming reference value D<7:0> is continuously reduced by 1 as the number of count pulses N of the up-down counter 22 increases, and the equivalent resistance value N×R0 of the resistance conversion module 43 is also continuously reduced, and the current Iref generated by the constant current source 42 flows through the resistance conversion module 43 to generate the reference voltage Vref. The reference voltage Vref is also continuously reduced. After each counting pulse cycle Tclk, the voltage forming reference value D<7:0> is reduced by 1, and the reference voltage Vref is reduced by a step voltage Step = Iref×R0. After N counts, the voltage forming 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 voltage Vref is reduced from Iref×N×R0 to zero, and the output voltage of the DC-DC converter is reduced to zero, completing the soft shutdown of the DC-DC converter. The shutdown time of the DC-DC converter is toff = N×Tclk. In addition, by setting EN of the target output voltage value preset module 11 to 0, the target output voltage value LEVEL<7:0> will also be set to 0, and the DC-DC converter can also be soft-closed.

[0073] By controlling the count pulse period Tclk of the up-and-down counter 22, the step period of the soft start of the DC-DC converter can be controlled, thereby accurately controlling the soft start time ton and the soft shut-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 count pulse period Tclk of the up-and-down counter 22, the size of the reference voltage Vref can be flexibly controlled. When the output current Iref of the constant current source 42 and the count pulse period Tclk of the up-and-down counter 22 are determined, it is only necessary to set the target output voltage value LEVEL<7:0> to obtain an accurate reference voltage Vref and a determined rise or fall time of the reference voltage Vref.

[0074] like Figure 8 As shown in the figure, when the DC-DC converter is in operation, the reference voltage Vref can be adjusted by presetting different target output voltage values ​​LEVEL<7:0>, thereby adjusting the output voltage of the DC-DC converter, which makes it more convenient to adjust the output voltage of the DC-DC converter. In addition, the output voltage adjustment process is also a gradual and soft adjustment process, which does not generate surge current and overshoot voltage, ensuring the safety and stability of the adjustment process.

[0075] In a preferred embodiment of the DC-DC converter output voltage control circuit of the present application, as Figure 5As shown, the waveform processing module 52 includes a comparator 521 and an RS trigger 522. The negative input terminal of the comparator 521 is connected to the voltage comparison module 51, the positive input terminal is connected to the sawtooth wave signal, and the output terminal is connected to the R terminal of the RS trigger 522, which can convert the output level of the voltage comparison module 51 into a pulse level signal. The S terminal of the RS trigger 522 is connected to the clock signal, which can modulate the pulse level signal to form a PWM signal, which is transmitted to the logic drive module 53 through the Q terminal of the RS trigger 522. The logic drive module 53 performs power amplification and logic processing on the PWM signal to generate two PWM pulse drive signals SH and SL with opposite phases.

[0076] The switch conversion unit 6 includes 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. The first switch element 61 and the second switch element 62 can be turned on and off respectively under the control of two inverse PWM pulse drive signals. The charging 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 end of the DC-DC converter. The capacitor C0 is connected between the output end of the switch conversion unit 6 and the ground.

[0077] The PWM pulse drive signal SH of the logic drive module 53 is connected to the control end of the first switch element 61, and the PWM pulse drive signal SL is connected to the control end of the second switch element 62. The first switch element 61 is connected to the positive electrode of the input end 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 charging module 63, the energy stored in the inductor L0 and the capacitor C0 increases, and the output voltage of the switch conversion unit 6 increases; when the second switch element 62 is turned on, the energy stored in the inductor L0 and the capacitor C0 is not only consumed on the load RL, but also released through the second switch element 62, the energy stored in the inductor L0 and the capacitor C0 is reduced, and the output voltage of the switch conversion unit 6 is reduced.

[0078] 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 end of the switch conversion unit 6 from being short-circuited. By controlling the on-time ratio of the first switch element 61 and the second switch element 62, the output 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.

[0079] The DC-DC converter output voltage control circuit of the present application can be used to implement the DC-DC converter output voltage control method of the present application.

[0080] An embodiment of the DC-DC converter output voltage control method of the present application is as follows: Fig. 9 As shown, the following steps are included: S10, preset a target output voltage value. By presetting the target output voltage value, the adjustment direction of the DC-DC converter output voltage can be flexibly controlled: when the DC-DC converter is turned off, 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; when the DC-DC converter is in operation, a zero value is preset for the target output voltage value, and the DC-DC converter can be controlled to be turned off; when the DC-DC converter is in operation, any reasonable target output voltage value is preset, and the output voltage of the DC-DC converter can be adjusted to a voltage corresponding to the target output voltage value.

[0081] S20, compare the preset target output voltage value with the voltage forming reference value stored in the circuit. A data storage unit is provided in the circuit, and the voltage forming reference value is stored in the data storage unit, and the voltage forming reference value is used as a reference for controlling the output voltage of the DC-DC converter. The difference between the voltage forming reference value and the target output voltage value is calculated, and when the difference is greater than zero, the voltage forming reference value is gradually reduced in a certain step until the voltage forming reference value is equal to the target output voltage value; when the difference is less than zero, the voltage forming reference value is gradually increased in a certain step until the voltage forming reference value is equal to the target output voltage value; when the difference is equal to zero, the voltage forming reference value is maintained.

[0082] When the DC-DC converter is powered off, the voltage forming reference value stored in the data storage unit is cleared. When the DC-DC converter is powered on, the voltage forming reference value stored in the data storage unit is automatically reset to zero, the DC-DC converter is in the off state, and its output voltage is zero, ensuring the safety of the DC output circuit.

[0083] S30, control 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. The DC-DC converter controls the output voltage through the switch circuit. Usually, a switch element for charging the output circuit and a switch element for releasing the energy in the output circuit are provided in the switch circuit. The conduction of the charging switch element will cause the output voltage of the output circuit to rise, and the conduction of the discharging switch element will cause the output voltage of the output circuit to drop rapidly. Therefore, the output voltage of the DC-DC converter can be conveniently controlled by controlling the working state of the switch circuit. Different voltage forming reference values ​​are used 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 forming reference value can be formed.

[0084] Since the voltage forming reference value is adjusted gradually based on a certain step size, after setting the new target output voltage value, the voltage forming reference value will be gradually adjusted from the original storage value to the target output voltage value, and the output voltage of the DC-DC converter will also gradually approach the target output voltage in steps. This can avoid overregulation caused by rapid adjustment of the output voltage of the DC-DC converter, realize soft regulation of the output voltage, and improve the safety of the use of the DC-DC converter.

[0085] By presetting a non-zero target output voltage value when the DC-DC converter is in the off state, or presetting a zero value as the target output voltage value in the working state, the soft shutdown and soft start of the DC-DC converter can be achieved. By arbitrarily presetting a reasonable target output voltage value in the working state, soft regulation of the DC-DC converter output voltage in any direction can be achieved, so that the DC-DC converter output voltage control method of the present application has great output voltage control flexibility.

[0086] By using the DC-DC converter output voltage control method of the present application, the output voltage of the DC-DC converter output voltage control circuit of any embodiment of the present application can be adjusted.

[0087] In some embodiments of the DC-DC converter output voltage control method of the present application, as Fig.10 and Fig.11 As shown, the method of adjusting the voltage to form a reference value in step S20 includes the following steps: S21, compare the target output voltage value with the current voltage forming a reference value to obtain the difference between the target output voltage value and the current voltage forming a reference value. Specifically, a subtractor can be used to perform a subtraction operation on the target output voltage value and the current voltage forming a reference value, and the calculation result is the difference between the two.

[0088] If the calculation result is greater than zero, that is, the target output voltage value is greater than the current voltage forming a reference value, continue to execute the operation in step S22; if the calculation result is less than zero, that is, the target output voltage value is less than the current voltage forming a reference value, then jump to step S23 and execute the operation in step S23; if the calculation result is equal to zero, that is, the target output voltage value is equal to the current voltage forming a reference value, then jump to step S24 and execute the operation in step S24.

[0089] S22, control the voltage to form a reference value to increase by 1 adjustment reference. The adjustment reference can be the minimum data 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, re-compare the difference between the target output voltage value and the adjusted voltage forming reference value, and form a step-by-step cyclic adjustment of the voltage forming reference value, so that the voltage forming reference value gradually increases with a certain slope and gradually approaches the target output voltage value.

[0090] S23, control the voltage to form a reference value reduced by 1 adjustment reference, jump back to step S21 after the adjustment is completed, re-compare the difference between the target output voltage value and the adjusted voltage to form a reference value, and form a step-by-step cyclic adjustment of the voltage to form a reference value, so that the voltage to form a reference value gradually decreases with a certain slope and gradually approaches the target output voltage value.

[0091] S24, maintaining the voltage to form a reference value. At this time, the voltage output by the DC-DC converter is the target output voltage, and maintaining the voltage to form a reference value can keep the output voltage of the DC-DC converter at the target output voltage.

[0092] Step S30: The method for controlling the converter switch circuit comprises the following steps: S31, converting the voltage forming reference value into a reference reference voltage, which is usually performed by a digital-to-analog conversion method. By converting the digital value used to adjust the output voltage of the converter into an analog voltage value according to a certain standard, a corresponding relationship between the digital value and the actual voltage can be established, thereby achieving accurate adjustment of the output voltage of the converter.

[0093] The output feedback voltage is extracted from the converter output loop. Usually, a voltage divider circuit is set in the converter output loop to extract an output feedback voltage that is proportional to the actual output voltage through the voltage divider circuit.

[0094] Converting the reference voltage and extracting the output feedback voltage are usually performed in parallel.

[0095] S32, compare the reference voltage and the output feedback voltage through a comparator circuit, and generate a switch circuit control signal according to the comparison result. When the output feedback voltage is less than the reference voltage, it means that the output voltage of the DC-DC converter is low, and a control signal is generated to control the switch circuit to charge the output circuit; when the output feedback voltage is greater than the reference voltage, it means that the output voltage of the DC-DC converter is high, and a control signal is generated to control the switch circuit to discharge the output circuit; when the output feedback voltage is equal to the reference voltage, no control signal is output to intervene in the switch circuit.

[0096] S33. The converter switching circuit is controlled according to the switching circuit control signal, specifically controlling the on and off of the charging switching element and the discharging switching element, and by controlling the charging and discharging of the converter output circuit, the converter output voltage gradually changes toward the target output voltage, and stably outputs the target output voltage.

[0097] An embodiment of a DC-DC converter of the present application uses the DC-DC converter output voltage control circuit of any embodiment of the present application, which can easily realize soft start, soft shutdown and soft adjustment of the output voltage of the DC-DC converter, greatly expanding the use scenarios of the DC-DC converter of the present application, and the flexibility, convenience and safety of use are also higher.

[0098] In the description of the present invention, the description with reference to the terms "one embodiment", "specific embodiment", "preferred embodiment" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In the present invention, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0099] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in 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-formed 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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