Short-circuit recovery soft start circuit for DC-DC converter and DC-DC converter

Abstract

Embodiments of the present disclosure provide a short - circuit recovery soft - start circuit for a DC - DC converter, which includes: a constant - current source circuit, an energy - storage circuit, a short - circuit start - up control circuit, a pull - down circuit, a pull - up circuit, and a switching circuit. The energy - storage circuit stores the charge from the constant - current source circuit to generate a soft - start signal when at least one of the short - circuit start - up control circuit and the switching circuit stops working, and releases the stored charge conversely. The short - circuit start - up control circuit works when the voltage difference between the soft - start signal and the feedback voltage of the DC - DC converter is greater than or equal to a preset value, and stops working conversely, and maintains the voltage difference at the preset value when the output terminal of the DC - DC converter is short - circuited so that the DC - DC converter continuously provides current to the output terminal of the DC - DC converter. The pull - down circuit provides a pull - down signal to the switching circuit. The pull - up circuit provides a pull - up signal to the switching circuit. The switching circuit works when the pull - down signal is at an invalid level, and stops working conversely.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to the technical field of integrated circuits, and in particular, to a short-circuit recovery soft start circuit for a DC-DC converter, and a DC-DC converter. Background Art

[0002] With the rapid development of the integrated circuit industry and the increasing expansion of the analog integrated circuit market, DC-DC converters have also received widespread attention and rapid development. As a high-efficiency switching power supply technology, DC-DC converters have the advantages of fast dynamic response, simple control, and direct control of output current, and are widely used. However, there is a problem with typical DC-DC converters: a large surge current will be generated during its startup phase, making the DC-DC converter unable to work normally. In severe cases, the power switch tube in the DC-DC converter will burn out, causing losses. In order to solve this problem, a "soft start" circuit can be added to the DC-DC converter to eliminate its surge current when it is powered on.

[0003] In the actual use of the DC-DC converter, the output end of the DC-DC converter may be short-circuited. After the output short circuit is detected, if only the current at the output end is limited, it is difficult to detect the release of the output short circuit state in time and enable the DC-DC converter to re-establish a soft start recovery process. Therefore, it is easy to cause the output voltage of the DC-DC converter to overshoot, or it is impossible to distinguish between the soft start after the output short circuit recovery and the normal power-on soft start, which affects the normal power-on use of the DC-DC converter. Summary of the invention

[0004] The embodiments described herein provide a short-circuit recovery soft start circuit for a DC-DC converter, and a DC-DC converter.

[0005] According to a first aspect of the present disclosure, a short-circuit recovery soft-start circuit for a DC-DC converter is provided. The short-circuit recovery soft-start circuit includes: a constant current source circuit, an energy storage circuit, a short-circuit start control circuit, a pull-down circuit, a pull-up circuit, and a switching circuit. Among them, the constant current source circuit is configured to provide a constant current to the energy storage circuit via a first node. The energy storage circuit is configured to: store the charge from the constant current to generate a soft-start signal when at least one of the short-circuit start control circuit and the switching circuit stops working, output the soft-start signal to a first input terminal of an error amplifier in the DC-DC converter via the first node, and release the stored charge when both the short-circuit start control circuit and the switching circuit are working. The short-circuit start control circuit is configured to: work to connect the first node and the second node when the voltage difference between the soft-start signal and the feedback voltage of the DC-DC converter is greater than or equal to a preset value, stop working to disconnect the first node and the second node when the voltage difference between the soft-start signal and the feedback voltage is less than the preset value, and maintain the voltage difference at the preset value when the output terminal of the DC-DC converter is short-circuited so that the DC-DC converter continuously provides current to the output terminal of the DC-DC converter. The pull-down circuit is configured to generate a pull-down signal according to the feedback voltage of the DC-DC converter and provide the pull-down signal to the switching circuit via a third node. The pull-up circuit is configured to generate a pull-up signal and provide the pull-up signal to the switching circuit via the third node. Among them, when the pull-down signal is at an invalid level, the pull-up signal is at an effective level. The switching circuit is configured to: work to connect the second node and the second voltage terminal when the pull-down signal is at an invalid level, and stop working to disconnect the second node and the second voltage terminal when the pull-down signal is at an effective level.

[0006] In some embodiments of the present disclosure, the short-circuit start control circuit includes a first transistor. Among them, the control electrode of the first transistor is provided with the feedback voltage of the DC-DC converter. The first pole of the first transistor is coupled to the first node. The second pole of the first transistor is coupled to the second node.

[0007] In some embodiments of the present disclosure, the first transistor is a P-type low-threshold transistor. The threshold voltage of the first transistor is greater than the offset voltage of the first input terminal of the error amplifier in the DC-DC converter.

[0008] In some embodiments of the present disclosure, the switching circuit includes a second transistor. Among them, the control electrode of the second transistor is coupled to the third node. The first pole of the second transistor is coupled to the second voltage terminal. The second pole of the second transistor is coupled to the second node.

[0009] In some embodiments of the present disclosure, the second transistor is an N-type transistor.

[0010] In some embodiments of the present disclosure, the pull-down circuit includes a third transistor. Wherein, the control electrode of the third transistor is supplied with the feedback voltage of the DC-DC converter. The first electrode of the third transistor is coupled to the second voltage terminal. The second electrode of the third transistor is coupled to the third node.

[0011] In some embodiments of the present disclosure, the third transistor is an N-type low-threshold transistor.

[0012] In some embodiments of the present disclosure, the constant current source circuit includes a fourth transistor. Wherein, the control electrode of the fourth transistor is coupled to the first bias voltage terminal. The first electrode of the fourth transistor is coupled to the first node. The second electrode of the fourth transistor is coupled to the first voltage terminal.

[0013] In some embodiments of the present disclosure, the pull-up circuit includes a fifth transistor. Wherein, the control electrode of the fifth transistor is coupled to the second bias voltage terminal. The first electrode of the fifth transistor is coupled to the third node. The second electrode of the fifth transistor is coupled to the first voltage terminal.

[0014] In some embodiments of the present disclosure, the energy storage circuit includes a capacitor. Wherein, the first terminal of the capacitor is coupled to the first node. The second terminal of the capacitor is coupled to the second voltage terminal.

[0015] According to a second aspect of the present disclosure, there is provided a short-circuit recovery soft start circuit for a DC-DC converter. The short-circuit recovery soft start circuit includes: a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, and a capacitor. Wherein, the control electrode of the first transistor is supplied with the feedback voltage of the DC-DC converter. The first electrode of the first transistor is coupled to the first electrode of the fourth transistor and the first terminal of the capacitor. The second electrode of the first transistor is coupled to the second electrode of the second transistor. The control electrode of the second transistor is coupled to the second electrode of the third transistor and the first electrode of the fifth transistor. The first electrode of the second transistor is coupled to the second voltage terminal. The control electrode of the third transistor is coupled to the control electrode of the first transistor. The first electrode of the third transistor is coupled to the second voltage terminal. The control electrode of the fourth transistor is coupled to the first bias voltage terminal. The second electrode of the fourth transistor is coupled to the first voltage terminal. The control electrode of the fifth transistor is coupled to the second bias voltage terminal. The second electrode of the fifth transistor is coupled to the first voltage terminal. The first terminal of the capacitor is coupled to the first input terminal of the error amplifier in the DC-DC converter. The second terminal of the capacitor is coupled to the second voltage terminal.

[0016] In some embodiments of the present disclosure, the first transistor is a P-type low-threshold transistor.

[0017] In some embodiments of the present disclosure, the third transistor is an N-type low-threshold transistor.

[0018] In some embodiments of the present disclosure, the second transistor is an N-type transistor.

[0019] According to a third aspect of the present disclosure, a DC-DC converter is provided. The DC-DC converter includes a short-circuit recovery soft-start circuit according to the first aspect or the second aspect of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to illustrate the technical solutions of the embodiments of the present disclosure more clearly, the drawings of the embodiments will be briefly described below. It should be understood that the following described drawings only relate to some embodiments of the present disclosure and do not limit the present disclosure, where:

[0021] Figure 1 is an exemplary circuit diagram of a soft-start circuit and an error amplifier in a DC-DC converter;

[0022] Figure 2 is a schematic block diagram of a short-circuit recovery soft-start circuit for a DC-DC converter according to an embodiment of the present disclosure; and

[0023] Figure 3 is Figure 2 an exemplary circuit diagram of a short-circuit recovery soft-start circuit for a DC-DC converter of the illustrated embodiment.

[0024] In the drawings, labels with the same last two digits correspond to the same elements. It should be noted that the elements in the drawings are schematic and not drawn to scale. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] In order to make the objectives, technical solutions, and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below with reference to the drawings. Obviously, the described embodiments are some, but not all, embodiments of the present disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of the present disclosure without creative efforts shall also fall within the scope of protection of the present disclosure.

[0026] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which the subject matter of the present disclosure belongs. It will be further understood that terms such as those defined in commonly used dictionaries shall be interpreted as having a meaning consistent with their meaning in the context of the specification and the relevant art, and will not be interpreted in an idealized or overly formal form unless clearly defined herein. As used herein, the statement of connecting or coupling two or more parts together shall mean that these parts are directly combined together or combined through one or more intermediate components.

[0027] In all embodiments of the present disclosure, since the source and drain (emitter and collector) of a transistor are symmetric, and the conduction current directions between the source and drain (emitter and collector) of an N-type transistor and a P-type transistor are opposite, in the embodiments of the present disclosure, the controlled intermediate terminal of the transistor is referred to as the control electrode, and the remaining two terminals of the transistor are respectively referred to as the first electrode and the second electrode. The transistors employed in the embodiments of the present disclosure are mainly switching transistors. Additionally, terms such as "first" and "second" are only used to distinguish one component (or a part of a component) from another component (or another part of a component).

[0028] Figure 1 Illustrated are a soft start circuit 120 and an error amplifier 110 in a DC-DC converter (the complete circuit structure is not shown). The error amplifier 110 includes: a transistor MP1, a transistor MP2, a transistor MP3, a transistor MN1, a transistor MN2, and a first current source I1. The soft start circuit 120 includes a capacitor C and a second current source I2.

[0029] The gate of the transistor MP3 serves as the first non-inverting input terminal (which can be referred to as the first input terminal in the context) of the error amplifier 110. The first non-inverting input terminal of the error amplifier 110 is coupled to the upper plate of the capacitor C. The gate of the transistor MP1 serves as the second non-inverting input terminal of the error amplifier 110. The second non-inverting input terminal of the error amplifier 110 is coupled to a first reference voltage terminal V REF1 . The gate of the transistor MP2 serves as the inverting input terminal of the error amplifier 110. The inverting input terminal of the error amplifier 110 is coupled to the feedback voltage terminal of the DC-DC converter, and thus can be provided with a feedback voltage FB. The feedback voltage FB is obtained by dividing the output voltage of the DC-DC converter. The drain of the transistor MP2 is coupled to the output terminal EAOUT of the error amplifier 110. The transistors MN1 and MN2 form a current mirror.

[0030] There is an offset voltage between the first non-inverting input terminal and the inverting input terminal of the error amplifier 110. This offset voltage can be regarded as the offset voltage of the first input terminal of the transistor MP3. The value of this offset voltage is Vos.

[0031] During the soft start phase, the second current source I2 charges the upper plate of the capacitor C, thereby generating a soft start signal SS_REF. As the voltage V of the upper plate of the capacitor C SS_REF rises to Vos, the voltage output from the output terminal EAOUT of the error amplifier 110 flips to a high level. This prompts the output voltage of the DC-DC converter to start rising, so that the feedback voltage FB follows the voltage V of the soft start signal SS_REF SS_REFIn this process, the voltage V SS_REF Always higher than the feedback voltage FB voltage value V FB High Vos. When the voltage value of the feedback voltage FB is V FB Increase to V REF1 The soft start process ends when the DC-DC converter output voltage rises smoothly to the expected voltage during the soft start phase.

[0032] However, in the case of a short circuit at the output end of the DC-DC converter, the feedback voltage FB suddenly drops to 0 V. When the short circuit state is released, since the voltage difference between the first and second non-inverting input ends of the error amplifier 110 and the inverting input end of the error amplifier 110 is large, the DC-DC converter cannot be soft-started again, and the output voltage of the DC-DC converter will overshoot, thereby affecting the normal operation of the load circuit of the DC-DC converter.

[0033] The embodiments of the present disclosure propose a short-circuit recovery soft start circuit for a DC-DC converter, aiming to enable the DC-DC converter to soft start again after the short-circuit state at the output end of the DC-DC converter is released, and not conflicting with the soft start during normal power-on.

[0034] Figure 2 A schematic block diagram of a short-circuit recovery soft start circuit 220 for a DC-DC converter according to an embodiment of the present disclosure is shown. The short-circuit recovery soft start circuit 220 may include: a constant current source circuit 221, an energy storage circuit 222, a short-circuit start control circuit 223, a pull-down circuit 224, a pull-up circuit 225, and a switch circuit 226. Among them, the constant current source circuit 221 may be coupled to the energy storage circuit 222 and the short-circuit start control circuit 223 via a first node N1. The constant current source circuit 221 may also be coupled to a first voltage terminal V1. The constant current source circuit 221 may be configured to provide a constant current I2 to the energy storage circuit 222 via the first node N1.

[0035] The energy storage circuit 222 can be coupled to the constant current source circuit 221 and the short-circuit start-up control circuit 223 via the first node N1. The energy storage circuit 222 can also be coupled to the second voltage terminal V2. The energy storage circuit 222 can be configured to: store the charge from the constant current I2 to generate a soft start signal SS_REF when at least one of the short-circuit start-up control circuit 223 and the switch circuit 226 stops working, and to send the charge to the error amplifier (which has, for example, a configuration such as Figure 1 The first input terminal of the controller 220 outputs the soft start signal SS_REF, and releases the stored charge when both the short circuit start control circuit 223 and the switch circuit 226 are working.

[0036] The short - circuit start - up control circuit 223 can be coupled to the constant - current source circuit 221 and the energy - storage circuit 222 via the first node N1. The short - circuit start - up control circuit 223 can also be coupled to the feedback voltage terminal of the DC - DC converter. The short - circuit start - up control circuit 223 can be configured to operate when the voltage difference between the soft - start signal SS_REF and the feedback voltage FB of the DC - DC converter is greater than or equal to a preset value, so that the first node N1 and the second node N2 are connected, and to stop operating when the voltage difference between the soft - start signal SS_REF and the feedback voltage FB is less than the preset value, so that the first node N1 and the second node N2 are disconnected.

[0037] The short - circuit start - up control circuit 223 can also be configured to maintain the voltage difference between the soft - start signal SS_REF and the feedback voltage FB at the above - mentioned preset value when the output terminal of the DC - DC converter is short - circuited, so that the DC - DC converter continuously supplies current to the output terminal of the DC - DC converter. In some embodiments of the present disclosure, the short - circuit start - up control circuit 223 maintains the voltage difference between the soft - start signal SS_REF and the feedback voltage FB at a value greater than the offset voltage of the first input terminal of the error amplifier in the DC - DC converter. Briefly, (V SS_REF -V FB )>Vos, where V SS_REF represents the voltage value of the soft - start signal SS_REF, V FB represents the voltage value of the feedback voltage FB, and Vos represents the voltage value of the offset voltage. In other words, the above - mentioned preset value is greater than Vos.

[0038] The pull - down circuit 224 can be coupled to the pull - up circuit 225 and the switch circuit 226 via the third node N3. The pull - down circuit 224 can also be coupled to the feedback voltage terminal of the DC - DC converter and the second voltage terminal V2. The pull - down circuit 224 can be configured to generate a pull - down signal according to the feedback voltage of the DC - DC converter and provide the pull - down signal to the switch circuit 226 via the third node N3. In some embodiments of the present disclosure, when the feedback voltage FB of the DC - DC converter is at a low level, the pull - down signal is at an invalid level (e.g., high level). When the feedback voltage FB of the DC - DC converter is at a high level, the pull - down signal is at an effective level (e.g., low level).

[0039] The pull - up circuit 225 can be coupled to the pull - down circuit 224 and the switch circuit 226 via the third node N3. The pull - up circuit 225 can also be coupled to the first voltage terminal V1. The pull - up circuit 225 can be configured to generate a pull - up signal and provide the pull - up signal to the switch circuit 226 via the third node N3. Wherein, when the pull - down signal is at an invalid level, the pull - up signal is at an effective level. When the pull - down signal is at an effective level, the pull - up signal is at an invalid level.

[0040] The switch circuit 226 can be coupled to the pull - down circuit 224 and the pull - up circuit 225 via a third node N3. The switch circuit 226 can also be coupled to a second voltage terminal V2. The switch circuit 226 can be configured to operate when the pull - down signal is at an invalid level, such that the second node N2 is connected to the second voltage terminal V2, and to stop operating when the pull - down signal is at an active level, such that the second node N2 is disconnected from the second voltage terminal V2.

[0041] In Figure 2 the example of, a high - voltage signal is input from the first voltage terminal V1, and the second voltage terminal V2 is grounded. In context, the active level of a certain signal indicates that the event represented by the signal occurs. In Figure 2 the example of, the active level of the pull - down signal is a low level, and the invalid level of the pull - down signal is a high level. For other signals except the pull - down signal, the active level can be a high level, and the invalid level can be a low level.

[0042] In the normal power - on soft - start phase, the initial energy storage of the energy - storage circuit 222 is zero. The constant - current source circuit 221 supplies a constant current I2 to the energy - storage circuit 222. Therefore, the voltage of the soft - start signal SS_REF starts to rise from 0V. As described above with reference to Figure 1 when the voltage V SS_REF of the soft - start signal SS_REF rises to Vos, the voltage output from the output terminal EAOUT of the error amplifier 110 flips to a high level. This prompts the output voltage of the DC - DC converter to start rising, so that the feedback voltage FB rises as the voltage V SS_REF of the soft - start signal SS_REF rises. After the output voltage of the DC - DC converter starts to rise, the voltage V SS_REF of the soft - start signal SS_REF is always higher than the voltage value V FB of the feedback voltage FB by Vos. When the voltage value V FB of the feedback voltage FB rises to V REF1 , the soft - start process ends. The output voltage of the DC - DC converter rises smoothly to the expected voltage during the soft - start phase.

[0043] In the normal power - on soft - start phase, (V SS_REF - V FB ) = Vos. As described above, in V SS_REF - V FBWhen the voltage is less than the preset value, the short-circuit start control circuit 223 stops working, so that the first node N1 and the second node N2 are disconnected. The preset value is greater than Vos. Therefore, in the normal power-on soft start stage, the short-circuit start control circuit 223 always stops working, and the first node N1 and the second node N2 are always disconnected. In this way, the energy storage circuit 222 can normally store the charge from the constant current I2, so that the normal power-on soft start stage is not affected.

[0044] When the output of the DC-DC converter is short-circuited, the feedback voltage FB is pulled down to 0V. (V SS_REF -V FB ) is greater than the above-mentioned preset value, therefore, the short-circuit start control circuit 223 operates so that the first node N1 is connected to the second node N2. When the feedback voltage FB is at a low level, the pull-down signal is at an invalid level. The switch circuit 226 operates when the pull-down signal is at an invalid level so that the second node N2 is connected to the second voltage terminal V2. When both the short-circuit start control circuit 223 and the switch circuit 226 are working, the energy storage circuit 222 begins to release the stored charge. Since the short-circuit start control circuit 223 can maintain the voltage difference between the soft start signal SS_REF and the feedback voltage FB as a preset value, the voltage value of the soft start signal SS_REF is maintained as the preset value. Since the preset value is greater than Vos, the voltage outputted by the output terminal EAOUT of the error amplifier remains at a high level, so that the DC-DC converter continues to provide current to the output terminal of the DC-DC converter.

[0045] Since the DC-DC converter continues to provide current to the output end of the DC-DC converter, after the short-circuit state is released, the output voltage of the DC-DC converter begins to rise, thereby driving the feedback voltage FB to rise. When the voltage difference between the soft start signal SS_REF and the feedback voltage FB is less than the above-mentioned preset value, the short-circuit start control circuit 223 stops working, thereby disconnecting the first node N1 and the second node N2. At this time, the energy storage circuit 222 can store the constant current I2 provided by the constant current source circuit 221, so that the soft start signal SS_REF begins to rise. Afterwards, the voltage difference between the soft start signal SS_REF and the feedback voltage FB maintains the offset voltage until the voltage value V of the feedback voltage FB reaches 0. FB Exceed V REF1 , the soft start process ends. The output voltage of the DC-DC converter rises smoothly to the expected voltage during the soft start phase.

[0046] Figure 3 Show Figure 2 The illustrated embodiment is an exemplary circuit diagram of a short-circuit recovery soft-start circuit 220 for a DC-DC converter.

[0047] exist Figure 3In the example, the constant current source circuit 221 may include a fourth transistor M4. Among them, the control electrode of the fourth transistor M4 is coupled to the first bias voltage terminal Vb1. The first electrode of the fourth transistor M4 is coupled to the first node N1. The second electrode of the fourth transistor M4 is coupled to the first voltage terminal V1. By setting the first bias voltage value of the first bias voltage terminal Vb1, the magnitude of the constant current I2 generated by the constant current source circuit 221 can be controlled. Those skilled in the art should understand that Figure 3 the internal structure of the constant current source circuit 221 in is exemplary, and the constant current source circuit 221 can also be implemented by other circuits. The embodiments of the present disclosure do not limit the specific implementation manners of the constant current source circuit 221.

[0048] The energy storage circuit 222 may include a capacitor C. Among them, the first end of the capacitor C is coupled to the first node N1. The second end of the capacitor is coupled to the second voltage terminal V2.

[0049] The short-circuit start control circuit 223 may include a first transistor M1. Among them, the control electrode of the first transistor M1 is provided with the feedback voltage FB of the DC-DC converter. The first electrode of the first transistor M1 is coupled to the first node N1. The second electrode of the first transistor M1 is coupled to the second node N2. In Figure 3 the example, the first transistor M1 is a P-type low-threshold transistor (LVT). The threshold voltage Vth1 of the first transistor is greater than the offset voltage of the first input terminal of the error amplifier in the DC-DC converter. That is, Vth1 > Vos.

[0050] The pull-down circuit 224 may include a third transistor M3. Among them, the control electrode of the third transistor M3 is provided with the feedback voltage FB of the DC-DC converter. The first electrode of the third transistor M3 is coupled to the second voltage terminal V2. The second electrode of the third transistor M3 is coupled to the third node N3. In Figure 3 the example, the third transistor M3 is an N-type low-threshold transistor.

[0051] The pull-up circuit 225 may be a third current source, which is capable of outputting a third current I3. In some embodiments of the present disclosure, the pull-up circuit 225 may include a fifth transistor M5. Among them, the control electrode of the fifth transistor M5 is coupled to the second bias voltage terminal Vb2. The first electrode of the fifth transistor M5 is coupled to the third node N3. The second electrode of the fifth transistor M5 is coupled to the first voltage terminal V1. By setting the second bias voltage value of the second bias voltage terminal Vb2, the magnitude of the third current I3 generated by the pull-up circuit 225 can be controlled. Those skilled in the art should understand that Figure 3 the internal structure of the pull-up circuit 225 in is exemplary, and the pull-up circuit 225 can also be implemented by other circuits. The embodiments of the present disclosure do not limit the specific implementation manners of the pull-up circuit 225.

[0052] The switching circuit 226 may include a second transistor M2. Wherein, the control electrode of the second transistor M2 is coupled to the third node N3. The first electrode of the second transistor M2 is coupled to the second voltage terminal V2. The second electrode of the second transistor M2 is coupled to the second node N2.

[0053] In Figure 3 the example, a high voltage signal is input from the first voltage terminal V1, and the second voltage terminal V2 is grounded. The first transistor M1 is a P-type transistor. The second transistor M2 to the fifth transistor M5 are all N-type transistors.

[0054] In the normal power-on soft start stage, the initial voltage value of the capacitor C is zero. The fourth transistor M4 supplies a constant current I2 to the capacitor C. Therefore, the voltage of the soft start signal SS_REF starts to rise from 0V. As described above with reference to Figure 1 when the voltage V of the soft start signal SS_REF SS_REF rises to Vos, the voltage output from the output terminal EAOUT of the error amplifier 110 flips to a high level. This causes the output voltage of the DC-DC converter to start rising, so that the feedback voltage FB rises as the voltage V of the soft start signal SS_REF SS_REF rises. After the output voltage of the DC-DC converter starts to rise, the voltage V of the soft start signal SS_REF SS_REF is always higher than the feedback voltage FB by Vos. When the voltage value V of the feedback voltage FB FB rises to V REF1 , the soft start process ends. The output voltage of the DC-DC converter rises smoothly to the expected voltage during the soft start stage.

[0055] In the normal power-on soft start stage, (V SS_REF - V FB ) = Vos. When V SS_REF - V FB is lower than the threshold voltage Vth1 of the first transistor M1, the first transistor M1 is turned off. And Vth1 is greater than Vos. Therefore, in the normal power-on soft start stage, the first transistor M1 is always turned off. In this way, the capacitor C can be normally charged, so that the normal power-on soft start stage is not affected.

[0056] When the output terminal of the DC-DC converter is short-circuited, the feedback voltage FB is pulled down to 0V. (V SS_REF - V FB) is higher than the threshold voltage Vth1 of the first transistor M1, so that the first transistor M1 is turned on. Since the feedback voltage FB is pulled down to 0V, the third transistor M3 is turned off, and the third current I3 from the fifth transistor M5 turns on the second transistor M2. When both the first transistor M1 and the second transistor M2 are turned on, the capacitor C starts to discharge. The voltage value of the soft start signal SS_REF is maintained at Vth1 after it drops to Vth1. Since Vth1 is greater than Vos, the voltage output by the output terminal EAOUT of the error amplifier remains at a high level, so that the DC-DC converter continues to provide current to the output terminal of the DC-DC converter.

[0057] Since the DC-DC converter continues to provide current to the output terminal of the DC-DC converter, after the short circuit state is released, the output voltage of the DC-DC converter begins to rise, thereby driving the feedback voltage FB to rise. When the voltage difference between the soft start signal SS_REF and the feedback voltage FB is less than Vth1, the first transistor M1 is turned off. At this time, the capacitor C begins to charge, so that the soft start signal SS_REF begins to rise. Afterwards, the voltage difference between the soft start signal SS_REF and the feedback voltage FB maintains the offset voltage until the voltage value V of the feedback voltage FB reaches Vth1. FB Exceed V REF1 , the soft start process ends. The output voltage of the DC-DC converter rises smoothly to the expected voltage during the soft start phase.

[0058] The voltage value of the feedback voltage FB is V FB After exceeding the threshold voltage Vth3 of the third transistor M3, the third transistor M3 is turned on, thereby pulling down the voltage of the control electrode of the second transistor M2. Therefore, the second transistor M2 is turned off. In this way, the soft start signal SS_REF is increased to V REF1 Afterwards, it will not be clamped by the threshold voltage of the first transistor M1 and thus can continue to rise to the first voltage V1.

[0059] Those skilled in the art should understand that based on the above-mentioned inventive concept Figure 3 The variation of the circuit shown should also fall within the protection scope of the present disclosure. In this variation, other components can be added or the type of transistor can be changed.

[0060] In summary, the short-circuit recovery soft start circuit for a DC-DC converter according to an embodiment of the present disclosure can be used for soft start during normal power-on, and after the short-circuit state at the output end of the DC-DC converter is released, the DC-DC converter can still be soft-started again without conflicting with the soft start during normal power-on.

[0061] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of devices and methods according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagram may represent a module, a segment of a program, or a portion of an instruction, which contains one or more executable instructions for implementing the specified logical function. In some alternative implementations, the functions noted in the blocks may occur in a different order than that noted in the accompanying drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented by a dedicated hardware-based system that performs the specified functions or actions, or can be implemented by a combination of dedicated hardware and computer instructions.

[0062] Unless the context clearly indicates otherwise, the singular forms of the words used in this specification and the appended claims include the plural, and vice versa. Thus, when referring to the singular, it generally includes the plural of the corresponding term. Similarly, the terms "comprising" and "including" shall be interpreted as inclusive rather than exclusive. Likewise, the term "or" shall be interpreted as inclusive, unless such an interpretation is explicitly prohibited herein. Where the term "exemplary" is used herein, particularly when it is placed after a list of terms, the "exemplary" is merely illustrative and explanatory and should not be considered exclusive or extensive.

[0063] Further aspects and scopes of adaptability become apparent from the description provided herein. It should be understood that the various aspects of the present application can be implemented individually or in combination with one or more other aspects. It should also be understood that the description herein and the specific embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0064] The above has described in detail several embodiments of the present disclosure. However, it is obvious that those skilled in the art can make various modifications and variations to the embodiments of the present disclosure without departing from the spirit and scope of the present disclosure. The scope of protection of the present disclosure is defined by the appended claims.

Claims

1. A short-circuit recovery soft-start circuit for a DC-DC converter, comprising: A constant current source circuit, an energy storage circuit, a short-circuit start control circuit, a pull-down circuit, a pull-up circuit, and a switch circuit Wherein, the constant current source circuit is configured to provide a constant current to the energy storage circuit via a first node The energy storage circuit is configured to: store charges from the constant current to generate a soft start signal when at least one of the short-circuit start control circuit and the switch circuit stops working, output the soft start signal to a first input terminal of an error amplifier in the DC-DC converter via the first node, and release the stored charges when both the short-circuit start control circuit and the switch circuit are working The short-circuit start control circuit is configured to: work when a voltage difference between the soft start signal and a feedback voltage of the DC-DC converter is greater than or equal to a preset value to connect the first node and a second node, stop working when the voltage difference between the soft start signal and the feedback voltage is less than the preset value to disconnect the first node and the second node, and maintain the voltage difference at the preset value when an output terminal of the DC-DC converter is short-circuited to enable the DC-DC converter to continuously provide current to the output terminal of the DC-DC converter The pull-down circuit is configured to generate a pull-down signal according to the feedback voltage of the DC-DC converter and provide the pull-down signal to the switch circuit via a third node The pull-up circuit is configured to generate a pull-up signal and provide the pull-up signal to the switch circuit via the third node, wherein when the pull-down signal is at an invalid level, the pull-up signal is at a valid level The switch circuit is configured to: work when the pull-down signal is at the invalid level to connect the second node and a second voltage terminal, and stop working when the pull-down signal is at a valid level to disconnect the second node and the second voltage terminal 2. The short-circuit recovery soft start circuit according to claim 1, wherein, The short-circuit start control circuit includes a first transistor Wherein, the control electrode of the first transistor is provided with the feedback voltage of the DC-DC converter, the first electrode of the first transistor is coupled to the first node, and the second electrode of the first transistor is coupled to the second node 3. The short-circuit recovery soft start circuit according to claim 2, wherein, The first transistor is a P-type low-threshold transistor, and the threshold voltage of the first transistor is greater than the offset voltage of the first input terminal of the error amplifier in the DC-DC converter 4. The short-circuit recovery soft-start circuit according to claim 1, wherein, The switch circuit includes a second transistor Wherein, the control electrode of the second transistor is coupled to the third node, the first electrode of the second transistor is coupled to the second voltage terminal, and the second electrode of the second transistor is coupled to the second node 5. The short-circuit recovery soft start circuit according to claim 1, wherein, The pull-down circuit includes a third transistor Wherein, the control electrode of the third transistor is provided with the feedback voltage of the DC-DC converter, the first electrode of the third transistor is coupled to the second voltage terminal, and the second electrode of the third transistor is coupled to the third node 6. The short-circuit recovery soft start circuit according to claim 5, wherein, The third transistor is an N-type low-threshold transistor 7. The short-circuit recovery soft start circuit according to claim 1, wherein, The constant current source circuit includes a fourth transistor Among them, the control electrode of the fourth transistor is coupled to the first bias voltage terminal, the first electrode of the fourth transistor is coupled to the first node, and the second electrode of the fourth transistor is coupled to the first voltage terminal.

8. The short-circuit recovery soft-start circuit according to claim 1, wherein, The pull-up circuit includes a fifth transistor. Among them, the control electrode of the fifth transistor is coupled to the second bias voltage terminal, the first electrode of the fifth transistor is coupled to the third node, and the second electrode of the fifth transistor is coupled to the first voltage terminal.

9. A short-circuit recovery soft-start circuit for a DC-DC converter, comprising: A first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, and a capacitor. Among them, the control electrode of the first transistor is supplied with the feedback voltage of the DC-DC converter. The first electrode of the first transistor is coupled to the first electrode of the fourth transistor and the first end of the capacitor. The second electrode of the first transistor is coupled to the second electrode of the second transistor. The control electrode of the second transistor is coupled to the second electrode of the third transistor and the first electrode of the fifth transistor. The first electrode of the second transistor is coupled to the second voltage terminal. The control electrode of the third transistor is coupled to the control electrode of the first transistor. The first electrode of the third transistor is coupled to the second voltage terminal. The control electrode of the fourth transistor is coupled to the first bias voltage terminal. The second electrode of the fourth transistor is coupled to the first voltage terminal. The control electrode of the fifth transistor is coupled to the second bias voltage terminal. The second electrode of the fifth transistor is coupled to the first voltage terminal. The first end of the capacitor is coupled to the first input terminal of the error amplifier in the DC-DC converter. The second end of the capacitor is coupled to the second voltage terminal.

10. A DC-DC converter, comprising: The short-circuit recovery soft-start circuit according to any one of claims 1 to 9.

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