A dc-dc converter and a control method thereof

Abstract

A DC-DC converter and a control method thereof, the converter comprising a logic module, a power tube, an inductor, an output capacitor, a voltage dividing resistor and an error amplifier, characterized in that the converter further comprises a first control unit, a second control unit and a third control unit; wherein the first control unit realizes the switching of the converter between a constant current starting mode and a closed loop starting mode based on an output voltage, and realizes the delay of the constant current starting mode based on the output of the second control unit; the second control unit and the third control unit control the switching state of the power tube of the converter in the closed loop starting mode based on the size of the inductor current and the output voltage. The method realizes the fast starting of the converter and the stability of the output voltage, avoids the back and forth switching of the converter between the two working modes, and ensures the normal starting of the circuit.

Description

Technical Field

[0001] This invention relates to the field of integrated circuits, and more specifically, to a DC-DC converter and its control method. Background Technology

[0002] DC-DC (Direct Current-Direct Current) converters are widely used in integrated circuits as voltage converters that can transform input voltage and effectively output a fixed voltage. DC-DC converters typically operate in two different modes: constant current startup mode and closed-loop startup mode.

[0003] Specifically, when a DC-DC converter first starts up, the output voltage Vout is too low. To ensure a fast startup, the converter typically uses a unique circuit to keep the circuit in a constant-current conduction state during the initial startup process, causing the output voltage to rise rapidly. Once the output voltage reaches a certain level, to prevent further increases and stabilize the output, the converter automatically switches to a closed-loop startup mode. This mode uses the feedback voltage to control the on / off state of the power transistors, ensuring relative stability of the output voltage.

[0004] However, this type of circuit may suffer from the problem of the converter oscillating between constant current conduction and closed-loop startup modes, thus failing to achieve full startup. To address this issue, a new DC-DC converter and its control method are urgently needed. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a DC-DC converter and its control method. This converter extends the time the circuit is in constant current startup mode through a delay unit, and directly jumps to the closed-loop startup mode after the closed-loop startup-related circuits have actually run normally, thereby achieving rapid startup of the converter and stable output voltage.

[0006] The present invention adopts the following technical solution.

[0007] In a first aspect, the present invention relates to a DC-DC converter, the converter including a logic module, a power transistor, an inductor, an output capacitor, a voltage divider resistor, and an error amplifier. The converter also includes a first control unit, a second control unit, and a third control unit. The first control unit switches the converter between a constant current start-up mode and a closed-loop start-up mode based on the output voltage, and delays the constant current start-up mode based on the output of the second control unit. The second and third control units control the switching state of the power transistor of the converter in the closed-loop start-up mode based on the inductor current and the magnitude of the output voltage.

[0008] Preferably, the first control unit includes a first comparator and a delay module; wherein, the positive input terminal of the first comparator is the output voltage Vout, the negative input terminal is the input voltage Vin, and the output terminal OUT1 is connected to the delay module; the delay module receives the output OUT2 of the second control unit and implements the delay based on the control of OUT2; the output OUT3 of the delay module is input to the logic module and controls the logic module to switch between constant current start mode and closed loop start mode.

[0009] Preferably, when OUT3 is in a low-level state, the converter operates in constant current start-up mode, with power transistor Mp0 always on and power transistor Mn0 always off; when OUT3 is in a high-level state, the converter operates in closed-loop start-up mode, with power transistors Mp0 and Mn0 switching between on and off states based on the outputs of the second control unit and the third control unit.

[0010] Preferably, in the converter, the device voltage terminal of the error amplifier EA is connected to the output terminal OUT1 of the first comparator in the first control unit; and when OUT1 is high, the error amplifier EA enables the second control unit and the third control unit to achieve closed-loop output; when OUT1 is low, the output of the error amplifier EA is always high, the output of the second control unit OUT2 is always high, and the output of the third control unit is always low.

[0011] Preferably, the second control unit includes a current detection module, a voltage control module, and a second comparator; wherein, the current detection module detects the inductor current and outputs the detection result to the voltage control module; the voltage control module receives the detection result and generates an inverse proportional voltage V1; the negative input terminal of the second comparator receives the inverse proportional voltage V1, the positive input terminal receives the output voltage Vea of ​​the error amplifier, and the output terminal generates OUT2 and is connected to the logic module.

[0012] Preferably, when OUT2 is high, the control delay module implements the delay when the OUT1 signal switches from low to high; when OUT2 is low, it does not affect the output of the OUT1 signal.

[0013] Preferably, the third control unit includes a third comparator; and the negative input terminal of the third comparator is connected to the output Vea of ​​the error amplifier, the positive input terminal is connected to the detection result output by the current detection module, and the output terminal OUT4 is connected to the logic module.

[0014] Preferably, when the converter is in the delay process of the delay module, the converter uses OUT3 to shield the second control unit and the third control unit, and realizes that the output voltage Vout is equal to the input voltage Vin.

[0015] A second aspect of the present invention relates to a control method for a DC-DC converter, wherein the method is implemented using a DC-DC converter as described in the first aspect of the present invention.

[0016] The beneficial effect of the present invention is that, compared with the prior art, the DC-DC converter and its control method of the present invention can extend the time of the circuit in constant current start-up mode by delaying the unit, and directly jump to the closed-loop start-up mode after the closed-loop start-up related circuit is actually running normally, thereby realizing the rapid start-up of the converter and the stability of the output voltage, avoiding the converter switching back and forth between the two working modes, and ensuring the normal start-up of the circuit.

[0017] The beneficial effects of the present invention also include: 1. This method does not change the commonly used converter control circuit in existing technologies; it simply adds a delay module to achieve accurate switching of the operating state. Furthermore, this delay module cleverly employs control from a second control unit, preventing redundant delay logic and ensuring its accuracy.

[0018] 2. This invention utilizes a voltage control module to control the reference voltage V1, so that the reference voltage V1 is actually controlled by the inductor current and changes accordingly. This allows the control signals OUT2 and OUT3 to change synchronously, thus ensuring a smooth switch from constant current start-up mode to closed-loop mode under any load, guaranteeing a monotonically increasing vout. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the circuit structure of a DC-DC converter according to an embodiment of the present invention; Figure 2 This is a voltage timing diagram of each node during the startup process of a DC-DC converter according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the circuit structure of a DC-DC converter according to another embodiment of the present invention; Figure 4 This is a voltage timing diagram of each node during the startup process of a DC-DC converter according to another embodiment of the present invention. Detailed Implementation

[0020] The present application will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, and should not be construed as limiting the scope of protection of the present application.

[0021] Figure 1 This is a schematic diagram of the circuit structure of a DC-DC converter according to one embodiment of the present invention. Figure 2This is a voltage timing diagram of each node during the startup process of a DC-DC converter according to an embodiment of the present invention. Figures 1-2 As shown, this invention provides a DC-DC converter. Specifically, existing DC-DC converters typically implement closed-loop startup control, and in addition, to improve the initial startup speed, a constant current startup circuit may be included.

[0022] However, this circuit has certain problems. The present invention... Figure 1 and Figure 2 The circuit in the image is used to illustrate this problem. Figure 1 In this circuit, COMP1, acting as the first control unit, outputs the control signal OUT1 to the logic module, thereby controlling the circuit to operate in either constant current startup mode or closed-loop startup mode. If OUT1 can control the circuit to enter closed-loop startup mode, the error amplifier EA will also achieve a changing output Vea under the control of OUT1. Simultaneously, with the control of the inductor current and the magnitude of the reference voltage V1, the output voltages of the control signals OUT2 and COMP3 will change, thereby controlling the logic module to output changing PON and NON signals in real time. This causes the power transistors Mp0 and Mn0 to change their on or off states, ensuring that the output voltage remains relatively stable.

[0023] However, as Figure 2 As shown, this circuit may experience the following abnormal situations. When the converter is first started up, the output voltage is low. At this time, OUT1 will always be in a low level state. At this time, the OUT1 control logic module makes Mp0 always on and Mn0 always off, so that the inductor current IL remains constant and is output to the output terminal of the converter with constant current, so that the output voltage of the converter can continue to increase.

[0024] When the output voltage Vout increases to a certain level, such as when it increases to be exactly the same as the input voltage Vin, the output level OUT1 of the first comparator COMP1 will be reversed. At this time, OUT1 will control the logic module to no longer be in constant current start mode, but to switch to closed loop start mode.

[0025] In closed-loop startup mode, the control signal OUT1 acts as the device voltage for the error amplifier EA, affecting its output. Specifically, when the output voltage OUT1 is low, the error amplifier's output signal Vea remains high, and the logic module, controlled by OUT1, also masks the output signals of OUT2 and COMP3. When OUT1 transitions to a high level, its output signal causes the MOSFET in the error amplifier EA to fully conduct, allowing the error amplifier's output signal to potentially be both high and low. At this point, as the reference signal Vref1 gradually increases, when the feedback voltage is approximately equal to R1... When Vin / (R1+R2), the output signal Vea of ​​the error amplifier will gradually decrease.

[0026] However, if the rate of decrease of Vea is slow, Vea may not decrease to a level lower than the reference voltage V1. In this case, the state of the OUT2 signal will not change, and the OUT2 signal will remain high. This will simultaneously turn off Mn0 and Mp0, resulting in IL=0A.

[0027] Therefore, during this period, if a load is connected to the converter and consumes a certain amount of load current, the output voltage Vout will actually decrease slowly and fall below Vin. This causes the OUT1 signal to invert before the OUT2 signal inverts, meaning the circuit returns to the constant current startup mode before truly entering the closed-loop startup mode, thus raising the output voltage Vout again. This cycle repeats, causing the circuit to switch between the two different startup modes multiple times, and the circuit can never truly start up completely.

[0028] To address this problem, the present invention provides a novel DC-DC converter. Figure 3 This is a schematic diagram of the circuit structure of a DC-DC converter according to another embodiment of the present invention. Figure 4 This is a voltage timing diagram of each node during the startup process of a DC-DC converter according to another embodiment of the present invention. Figure 3 and Figure 4 As shown, the present invention provides a DC-DC converter, which includes a logic module, a power transistor, an inductor, an output capacitor, a voltage divider resistor, and an error amplifier. The converter also includes a first control unit, a second control unit, and a third control unit. The first control unit switches the converter between a constant current startup mode and a closed-loop startup mode based on the output voltage, and delays the constant current startup mode based on the output of the second control unit. The second and third control units control the switching state of the power transistor of the converter in the closed-loop startup mode based on the inductor current and the output voltage.

[0029] It is understood that in the circuit of the present invention, a delay module is added to achieve accurate switching between the two startup modes. This allows a certain amount of time for the actual startup process of the closed-loop startup circuit during the switching to closed-loop startup. When the closed-loop startup circuit has actually finished starting and truly entered the startup state, the delay module outputs a control signal to make the converter switch to closed loop, so that the closed-loop signal can control the state of the power transistor, thereby achieving a smooth switching of startup modes.

[0030] Preferably, the first control unit includes a first comparator and a delay module; wherein, the positive input terminal of the first comparator is the output voltage Vout, the negative input terminal is the input voltage Vin, and the output terminal OUT1 is connected to the delay module; the delay module receives the output OUT2 of the second control unit and implements the delay based on the control of OUT2; the output OUT3 of the delay module is input to the logic module and controls the logic module to switch between constant current start mode and closed loop start mode.

[0031] It is understood that in this invention, a delay module is added to the first control unit, and this delay module implements the actual delay based on the output voltage of the second control unit OUT2. In other words, when the state of the second control unit changes, the delay module is also triggered to delay, thereby delaying the switching time from constant current start mode to closed-loop start mode, so that OUT2 and OUT3 can truly enter the closed-loop start mode only after the state change has been fully completed.

[0032] Preferably, when OUT3 is in a low-level state, the converter operates in constant current start-up mode, with power transistor Mp0 always on and power transistor Mn0 always off; when OUT3 is in a high-level state, the converter operates in closed-loop start-up mode, with power transistors Mp0 and Mn0 switching between on and off states based on the outputs of the second control unit and the third control unit.

[0033] Understandably, after the delay unit, the output signal OUT1 is converted to OUT3. The different high and low states of OUT3 can be used to control the different startup modes of the converter. In this invention, when OUT3 is low, the converter is still in constant current startup mode. At this time, although OUT1 may have changed to high, due to the effect of the delay module, OUT3 has not had time to change. Therefore, during this period, the circuits containing COMP2 and COMP3 cannot actually control the states of Mp0 and Mn0.

[0034] However, after the delay time has elapsed, the outputs of COMP2 and COMP3 can actually affect the operating state of the circuit. At this time, if the signal states of COMP2 and COMP3 happen to change, that is, the delay time is just enough to cancel out the time required before the level change of COMP2 and COMP3.

[0035] Therefore, the circuit will not switch back and forth between the two different startup modes.

[0036] Preferably, in the converter, the device voltage terminal of the error amplifier EA is connected to the output terminal OUT1 of the first comparator in the first control unit; and when OUT1 is high, the error amplifier EA enables the second control unit and the third control unit to achieve closed-loop output; when OUT1 is low, the output of the error amplifier EA is always high, the output of the second control unit OUT2 is always high, and the output of the third control unit is always low.

[0037] It is understood that in this invention, the device voltage of the error amplifier is controlled by OUT1. This method ensures that the signal change of the error amplifier occurs at the same time as the delay unit's start delay. Therefore, the delay time can be set more accurately.

[0038] Preferably, the second control unit includes a current detection module, a voltage control module, and a second comparator; wherein, the current detection module detects the inductor current and outputs the detection result to the voltage control module; the voltage control module receives the detection result and generates an inverse proportional voltage V1; the negative input terminal of the second comparator receives the inverse proportional voltage V1, the positive input terminal receives the output voltage Vea of ​​the error amplifier, and the output terminal generates OUT2 and is connected to the logic module.

[0039] Understandably, the second control unit can inversely convert the detection result obtained by the current detection module and generate an inversely proportional voltage V1. Specifically, the higher the inductor current, the lower V1. Conversely, the lower the inductor current, the higher V1. In this case, if the reference voltage V1 is controlled by the inductor current, then the output of OUT2 is actually determined based on the relationship between the output voltage Vout and the inductor current IL.

[0040] Therefore, this comparison actually takes into account that the level transition time of OUT2 varies depending on the power required by the downstream load connected to the converter, and thus the actual delay time for OUT1 also varies. This method effectively controls the delay time of OUT1 and reasonably controls the output level transition time of OUT3.

[0041] Preferably, when OUT2 is high, the control delay module implements the delay when the OUT1 signal switches from low to high; when OUT2 is low, it does not affect the output of the OUT1 signal.

[0042] It is understandable that when OUT2 is high or low, the delay module will have different functions, thereby achieving a reasonable delay.

[0043] Preferably, the third control unit includes a third comparator; and the negative input terminal of the third comparator is connected to the output Vea of ​​the error amplifier, the positive input terminal is connected to the detection result output by the current detection module, and the output terminal OUT4 is connected to the logic module.

[0044] The specific logic of the control logic unit for the output signal OUT4 of the third control unit can be implemented with reference to the existing technology, and will not be elaborated in this invention.

[0045] When the converter is in the delay period of the delay module, the converter disables the second and third control units. For example... Figure 4 As shown, Vout will not decrease at this time, but will always remain at the input voltage Vin. Only after the second and third control units switch their working states will the actual switching control be realized, thereby effectively preventing the back-and-forth switching between the two startup states and enabling the circuit to accurately enter the closed-loop startup mode.

[0046] A second aspect of the present invention relates to a control method for a DC-DC converter, which is implemented using a DC-DC converter described in the first aspect of the present invention.

[0047] Although this application has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made thereto without departing from the spirit and scope of this application. Accordingly, this specification and drawings are merely exemplary illustrations of this application as defined by the appended claims, and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of this application. Clearly, those skilled in the art can make various alterations and modifications to this application without departing from the spirit and scope of this application. Thus, if such modifications and modifications of this application fall within the scope of the claims of this application and their equivalents, this application is also intended to include such modifications and modifications.

[0048] The beneficial effect of the present invention is that, compared with the prior art, the DC-DC converter and its control method of the present invention can extend the time of the circuit in constant current start-up mode by delaying the unit, and directly jump to the closed-loop start-up mode after the closed-loop start-up related circuit is actually running normally, thereby realizing the rapid start-up of the converter and the stability of the output voltage, avoiding the converter switching back and forth between the two working modes, and ensuring the normal start-up of the circuit.

[0049] The applicant of this invention has provided a detailed description of the embodiments of the invention in conjunction with the accompanying drawings. However, those skilled in the art should understand that the above embodiments are merely preferred embodiments of the invention. The detailed description is only intended to help readers better understand the spirit of the invention and is not intended to limit the scope of protection of the invention. On the contrary, any improvements or modifications made based on the inventive spirit of the invention should fall within the scope of protection of the invention.

Claims

1. A DC-DC converter, the converter comprising a logic module, a power transistor, an inductor, an output capacitor, a voltage divider resistor, and an error amplifier, characterized in that: The converter further includes a first control unit, a second control unit, and a third control unit; wherein, The first control unit includes a first comparator and a delay module; wherein, the non-inverting input terminal of the first comparator is the output voltage Vout, the negative input terminal is the input voltage Vin, and the output terminal OUT1 is connected to the delay module; the device voltage terminal of the error amplifier EA is connected to the output terminal OUT1 of the first comparator in the first control unit; the delay module receives the output OUT2 of the second control unit and implements a delay for the constant current start mode based on the control of OUT2, including delaying the switching of the OUT1 signal from low to high when OUT2 is high; when OUT2 is low, it does not affect the output of the OUT1 signal; the output OUT3 of the delay module is input to the logic module and controls the logic module to switch between constant current start mode and closed-loop start mode; The second and third control units control the switching state of the power transistors of the converter in closed-loop startup mode based on the magnitude of the inductor current and the output voltage. The second control unit includes a current detection module, a voltage control module, and a second comparator. The current detection module detects the inductor current and outputs the detection result to the voltage control module. The voltage control module receives the detection result and generates an inverse proportional voltage V1. The negative input of the second comparator receives the inverse proportional voltage V1, the positive input receives the output voltage Vea of ​​the error amplifier, and the output generates OUT2, which is connected to the logic module. The third control unit includes a third comparator. The negative input of the third comparator is connected to the output Vea of ​​the error amplifier, the positive input is connected to the detection result output by the current detection module, and the output OUT4 is connected to the logic module.

2. A DC-DC converter according to claim 1, characterized in that: The power transistors include power transistor Mp0 and power transistor Mn0; The gates of power transistors Mp0 and Mn0 are both controlled by the output signals of the logic module; the drain of power transistor Mp0 is connected to the drain of power transistor Mn0 and is connected to the input voltage Vin through inductor L; the source of power transistor Mp0 is connected to the output voltage Vout; the source of power transistor Mp0 is grounded to GND. When OUT3 is in a low-level state, the converter operates in constant current start mode, the power transistor Mp0 is always on, and the power transistor Mn0 is always off; When OUT3 is in a high-level state, the converter operates in closed-loop startup mode, and the power transistors Mp0 and Mn0 switch between on and off states based on the outputs of the second control unit and the third control unit.

3. A DC-DC converter according to claim 2, characterized in that: In the converter, when OUT1 is high, the error amplifier EA enables the second control unit and the third control unit to achieve closed-loop output; When OUT1 is low, the output of the error amplifier EA is always high, the output of the second control unit OUT2 is always high, and the output of the third control unit is always low.

4. A DC-DC converter according to claim 1, characterized in that: When the converter is in the delay process of the delay module, The converter, based on the control of OUT3, shields the second and third control units and achieves an output voltage Vout equal to the input voltage Vin.

5. A control method for a DC-DC converter, characterized in that: The method is implemented using a DC-DC converter as described in any one of claims 1-4.

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