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 detection circuit, a short-circuit start control circuit, and first and second switch circuits. The energy storage circuit stores charges from the constant current source circuit to generate a soft-start signal when at least one of the first and second switch circuits stops working, and releases the stored charges when both the first and second switch circuits are working. The short-circuit detection circuit generates a short-circuit indication signal based on the feedback voltage and the short-circuit reference voltage of the DC-DC converter. The first switch circuit works when the short-circuit indication signal is at an effective level, and stops working otherwise. The short-circuit start control circuit generates a short-circuit start control signal based on the soft-start signal and the feedback voltage, and maintains the voltage difference between the soft-start signal and the feedback voltage at a preset value when the output terminal of the DC-DC converter is short-circuited so that the DC-DC converter continuously supplies current to its output terminal.

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 detection circuit, a first switch circuit, a short-circuit start control circuit, and a second switch 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 charges from the constant current to generate a soft-start signal when at least one of the first switch circuit and the second 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 first switch circuit and the second switch circuit are working. The short-circuit detection circuit is configured to generate a short-circuit indication signal based on the feedback voltage of the DC-DC converter and a short-circuit reference voltage from a short-circuit reference voltage terminal and provide the short-circuit indication signal to the first switch circuit via a second node. The short-circuit indication signal is used to indicate whether the output terminal of the DC-DC converter is short-circuited. The first switch circuit is coupled to the second switch circuit via a third node. The first switch circuit is configured to: operate when the short-circuit indication signal is at an effective level to connect the first node and the third node, and stop operating when the short-circuit indication signal is at an invalid level to disconnect the first node and the third node. The short-circuit start control circuit is configured to generate a short-circuit start control signal based on the soft-start signal and the feedback voltage of the DC-DC converter, provide the short-circuit start control signal to the second switch circuit via a fourth node, and maintain the voltage difference between the soft-start signal and the feedback voltage at a 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 second switch circuit is configured to: operate when the short-circuit start control signal is at an effective level to connect the third node and a second voltage terminal, and stop operating when the short-circuit start control signal is at an invalid level to disconnect the third node and the second voltage terminal.

[0006] In some embodiments of the present disclosure, the short-circuit start control circuit includes an amplifier. Among them, a first input terminal of the amplifier is coupled to the first node. The second input terminal of the amplifier is provided with the feedback voltage of the DC-DC converter. The output terminal of the amplifier is coupled to the fourth node. The first offset voltage of the first input terminal of the amplifier is greater than the second offset voltage of the first input terminal of the error amplifier in the DC-DC converter.

[0007] In some embodiments of the present disclosure, the short-circuit detection circuit includes a comparator. Among them, a first input terminal of the comparator is coupled to the short-circuit reference voltage terminal. The second input terminal of the comparator is provided with the feedback voltage of the DC-DC converter. The output terminal of the comparator is coupled to the second node.

[0008] In some embodiments of the present disclosure, the comparator is a hysteresis comparator.

[0009] In some embodiments of the present disclosure, the first switching circuit includes a first transistor. Wherein, the control electrode of the first transistor is coupled to the second node. The first electrode of the first transistor is coupled to the third node. The second electrode of the first transistor is coupled to the first node.

[0010] In some embodiments of the present disclosure, the second switching circuit includes a second transistor. Wherein, the control electrode of the second transistor is coupled to the fourth node. The first electrode of the second transistor is coupled to the second voltage terminal. The second electrode of the second transistor is coupled to the third node.

[0011] In some embodiments of the present disclosure, the energy storage circuit includes a capacitor. Wherein, the first end of the capacitor is coupled to the first node. The second end of the capacitor is coupled to the second voltage terminal.

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

[0013] 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 comparator, an amplifier, a first transistor, a second transistor, a third transistor, and a capacitor. Wherein, the first input terminal of the comparator is coupled to the short-circuit reference voltage terminal. The second input terminal of the comparator is supplied with the feedback voltage of the DC-DC converter. The output terminal of the comparator is coupled to the control electrode of the first transistor. The first input terminal of the amplifier is coupled to the first electrode of the third transistor and the first end of the capacitor. The second input terminal of the amplifier is coupled to the second input terminal of the comparator. The output terminal of the amplifier is coupled to the control electrode of the second transistor. The first offset voltage of the first input terminal of the amplifier is greater than the second offset voltage of the first input terminal of the error amplifier in the DC-DC converter. The first electrode of the first transistor is coupled to the second electrode of the second transistor. The second electrode of the first transistor is coupled to the first end of the capacitor. 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 bias voltage terminal. The first electrode of the third transistor is coupled to the first end of the capacitor. The second electrode of the third 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.

[0014] In some embodiments of the present disclosure, the comparator is a hysteresis comparator.

[0015] According to a third aspect of the present disclosure, there is provided a DC-DC converter. The DC-DC converter includes the short-circuit recovery soft start circuit according to the first aspect or the second aspect of the present disclosure. Description of the Drawings

[0016] To more clearly illustrate the technical solutions of the embodiments of the present disclosure, the accompanying drawings of the embodiments will be briefly described below. It should be understood that the following-described accompanying drawings only relate to some embodiments of the present disclosure and do not limit the present disclosure, where:

[0017] Figure 1 is an exemplary circuit diagram of a soft start circuit and an error amplifier in a DC-DC converter;

[0018] 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

[0019] Figure 3 is Figure 2 an exemplary circuit diagram of the short-circuit recovery soft start circuit for a DC-DC converter of the illustrated embodiment.

[0020] In the accompanying drawings, marks with the same last two digits correspond to the same elements. It should be noted that the elements in the accompanying drawings are schematic and not drawn to scale. Detailed Embodiments

[0021] 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 in conjunction with the accompanying drawings. Obviously, the described embodiments are some, but not all, of the 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 also fall within the scope of protection of the present disclosure.

[0022] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the subject matter of the present disclosure belongs. Further, it will be understood that terms such as those defined in commonly used dictionaries should 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 expressly defined otherwise herein. As used herein, a statement that two or more parts are "connected" or "coupled" together shall mean that these parts are directly joined together or joined through one or more intermediate components.

[0023] 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).

[0024] Figure 1 The soft start circuit 120 and the error amplifier 110 in a DC-DC converter (the complete circuit structure is not shown) are illustrated. The error amplifier 110 includes: transistor MP1, transistor MP2, transistor MP3, transistor MN1, transistor MN2, and a first current source I1. The soft start circuit 120 includes a capacitor C and a second current source I2.

[0025] The gate of 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 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 the first reference voltage terminal V REF1 . The gate of 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 the feedback voltage FB. The feedback voltage FB is obtained by dividing the output voltage of the DC-DC converter. The drain of transistor MP2 is coupled to the output terminal EAOUT of the error amplifier 110. Transistors MN1 and MN2 form a current mirror.

[0026] 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 considered as the offset voltage introduced by transistor MP3, which can be referred to as the second offset voltage in the context. The value of this second offset voltage is Vos2.

[0027] During the soft start phase, the second current source I2 charges the upper plate of the capacitor C, thereby generating the soft start signal SS_REF. As the voltage V SS_REF of the upper plate of the capacitor C rises to Vos2, 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 SS_REFrises as the [voltage] rises. During this process, the voltage V of the soft start signal SS_REF SS_REF is always higher than the voltage value V of the feedback voltage FB FB by Vos2. 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 smoothly rises to the expected voltage during the soft start phase.

[0028] However, in the case of a short circuit occurring at the output of the DC-DC converter, the feedback voltage FB suddenly drops to 0V. When the short circuit state is removed, since the voltage differences between the first and second non-inverting input terminals of the error amplifier 110 and the inverting input terminal of the error amplifier 110 are both large, the DC-DC converter cannot soft start again, and the output voltage of the DC-DC converter will exhibit an overshoot phenomenon, thus affecting the normal operation of the load circuit of the DC-DC converter.

[0029] Embodiments of the present disclosure propose a short-circuit recovery soft start circuit for a DC-DC converter, aiming to expect that the DC-DC converter can still soft start again after the short circuit state at the output of the DC-DC converter is removed, and does not conflict with the soft start during normal power-on.

[0030] Figure 2 FIG. shows 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. The short-circuit recovery soft start circuit 220 may include: a constant current source circuit 221, an energy storage circuit 222, a short-circuit detection circuit 223, a first switch circuit 224, a short-circuit start control circuit 225, and a second switch circuit 226. Among them, the constant current source circuit 221 may be coupled to the energy storage circuit 222, the first switch circuit 224, and the short-circuit start control circuit 225 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 supply a constant current I2 to the energy storage circuit 222 via the first node N1.

[0031] The energy storage circuit 222 may be coupled to the constant current source circuit 221, the first switch circuit 224, and the short-circuit start control circuit 225 via the first node N1. The energy storage circuit 222 may also be coupled to a second voltage terminal V2. The energy storage circuit 222 may 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 first switch circuit 224 and the second switch circuit 226 stops working, and supply it to an error amplifier in the DC-DC converter via the first node N1 (which, for example, has Figure 1The first input terminal of the switch circuit 220 outputs the soft start signal SS_REF, and releases the stored charge when both the first switch circuit 224 and the second switch circuit 226 are in operation.

[0032] The short circuit detection circuit 223 can be coupled to the first switch circuit 224 via the second node N2. The short circuit detection circuit 223 can also be coupled to the short circuit reference voltage terminal V REF2 The short-circuit detection circuit 223 can be configured to detect the feedback voltage FB of the DC-DC converter and the short-circuit reference voltage terminal V REF2 The short-circuit reference voltage V REF2 To generate a short circuit indication signal and provide the short circuit indication signal to the first switch circuit 224 via the second node N2. The short circuit indication signal is used to indicate whether the output terminal of the DC-DC converter is short-circuited. In some embodiments of the present disclosure, the effective level (e.g., high level) of the short circuit indication signal indicates that the output terminal of the DC-DC converter is short-circuited. The invalid level (e.g., low level) of the short circuit indication signal indicates that the output terminal of the DC-DC converter is not short-circuited. In some embodiments of the present disclosure, when the feedback voltage FB is lower than the short circuit reference voltage V REF2 In the case of the short circuit indication signal flipping to the effective level. When the feedback voltage FB is higher than or equal to the short circuit reference voltage V REF2 In the case of , the short circuit indication signal flips to an invalid level. In some alternative embodiments of the present disclosure, when the feedback voltage FB is lower than the short circuit reference voltage V REF2 In the case of the short circuit indication signal flipped to the effective level. FB Higher than or equal to V REF2 In the case of +ΔV, the short circuit indication signal turns to the effective level, and ΔV represents the hysteresis voltage. ΔV>0V.

[0033] The first switch circuit 224 may be coupled to the second switch circuit 226 via the third node N3. The first switch circuit 224 may be coupled to the short circuit detection circuit 223 via the second node N2. The first switch circuit 224 may be coupled to the constant current source circuit 221, the energy storage circuit 222, and the short circuit start control circuit 225 via the first node N1. The first switch circuit 224 may be configured to work when the short circuit indication signal is at an effective level, so that the first node N1 and the third node N3 are connected. The first switch circuit 224 may also be configured to stop working when the short circuit indication signal is at an invalid level, so that the first node N1 and the third node N3 are disconnected.

[0034] The short - circuit start - up control circuit 225 can be coupled to the feedback voltage terminal of the DC - DC converter. The short - circuit start - up control circuit 225 can be coupled to the constant current source circuit 221, the energy storage circuit 222, and the first switch circuit 224 via the first node N1. The short - circuit start - up control circuit 225 can be coupled to the second switch circuit 226 via the fourth node N4. The short - circuit start - up control circuit 225 can be configured to generate a short - circuit start - up control signal according to the soft - start signal SS_REF and the feedback voltage FB of the DC - DC converter, and provide the short - circuit start - up control signal to the second switch circuit 226 via the fourth node N4.

[0035] The short - circuit start - up control circuit 225 can also be configured to: when the output terminal of the DC - DC converter is short - circuited, maintain the voltage difference between the soft - start signal SS_REF and the feedback voltage FB at a preset value so that the DC - DC converter continuously provides current to the output terminal of the DC - DC converter. In some embodiments of the present disclosure, the short - circuit start - up control circuit 225 maintains the voltage difference between the soft - start signal SS_REF and the feedback voltage FB at a value greater than the second offset voltage introduced at the first input terminal of the error amplifier in the DC - DC converter. Briefly, (V SS_REF -V FB )>Vos2, 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 Vos2 represents the voltage value of the second offset voltage. In other words, the above - mentioned preset value is greater than Vos2.

[0036] In some embodiments of the present disclosure, when the voltage value V SS_REF of the soft - start signal SS_REF minus the voltage value V FB of the feedback voltage FB is higher than or equal to the above - mentioned preset value, the short - circuit start - up control signal is at an effective level. When the voltage value V SS_REF of the soft - start signal SS_REF minus the voltage value V FB of the feedback voltage FB is lower than the above - mentioned preset value, the short - circuit start - up control signal is at an invalid level.

[0037] The second switch circuit 226 can be coupled to the first switch circuit 224 via the third node N3. The second switch circuit 226 can be coupled to the short - circuit start - up control circuit 225 via the fourth node N4. The second switch circuit 226 can also be coupled to the second voltage terminal V2. The second switch circuit 226 can be configured to: operate when the short - circuit start - up control signal is at an effective level, so that the third node N3 and the second voltage terminal V2 are connected. The second switch circuit 226 can also be configured to: stop operating when the short - circuit start - up control signal is at an invalid level, so that the third node N3 and the second voltage terminal V2 are disconnected.

[0038] InFigure 2 In the example, a high-voltage signal is input from the first voltage terminal V1, and the second voltage terminal V2 is grounded. In the context, the valid level of a certain signal indicates that the event represented by the signal occurs. In Figure 2 the example, the valid level can be a high level, and the invalid level can be a low level.

[0039] In the normal power-on soft-start stage, the initial energy storage of the energy storage circuit 222 is zero. The constant current source circuit 221 provides 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 referred to above Figure 1 When the voltage V of the soft-start signal SS_REF SS_REF rises to Vos2, 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 voltage value V of the feedback voltage FB FB by Vos2. 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.

[0040] In the normal power-on soft-start stage, (V SS_REF - V FB ) = Vos2. As described above, when (V SS_REF - V FB ) is lower than the above preset value, the short-circuit start control signal is at an invalid level. And the above preset value is greater than Vos2. Therefore, in the normal power-on soft-start stage, the short-circuit start control signal is always at an invalid level. The second switch circuit 226 stops working when the short-circuit start control signal is at an invalid level. Therefore, 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.

[0041] When the output terminal of the DC-DC converter is short-circuited, the feedback voltage FB is pulled down to 0V. The short-circuit detection circuit 223 outputs a short-circuit indication signal at an active level, so that the first switch circuit 224 starts to operate. The short-circuit start control circuit 225 outputs a short-circuit start control signal at an active level, so that the second switch circuit 226 starts to operate. When both the first switch circuit 224 and the second switch circuit 226 are operating, the energy storage circuit 222 starts to release the stored charge. Since the short-circuit start control circuit 225 can maintain the voltage difference between the soft start signal SS_REF and the feedback voltage FB at a preset value, the voltage value of the soft start signal SS_REF is maintained at this preset value. Since this preset value is greater than Vos2, the voltage output at the output terminal EAOUT of the error amplifier remains high, so that the DC-DC converter continuously supplies current to the output terminal of the DC-DC converter.

[0042] Since the DC-DC converter continuously supplies 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 starts to rise, thus 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 preset value, the short-circuit start control circuit 225 outputs a short-circuit start control signal at an inactive level, so that the second switch circuit 226 stops operating. 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 starts to rise. After that, the voltage difference between the soft start signal SS_REF and the feedback voltage FB maintains the second offset voltage until the voltage value V of the feedback voltage FB FB exceeds V REF1 , and the soft start process ends. The output voltage of the DC-DC converter smoothly rises to the expected voltage during the soft start stage.

[0043] Figure 3 Shows Figure 2 An exemplary circuit diagram of the short-circuit recovery soft start circuit 220 for a DC-DC converter according to the illustrated embodiment.

[0044] In Figure 3 the example, the constant current source circuit 221 may include a third transistor M3. Wherein, the control electrode of the third transistor M3 is coupled to the bias voltage terminal Vb. The first electrode of the third transistor M3 is coupled to the first node N1. The second electrode of the third transistor M3 is coupled to the first voltage terminal V1. By setting the bias voltage value of the bias voltage terminal Vb, 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 3The internal structure of the constant current source circuit 221 therein is exemplary, and the constant current source circuit 221 can also be implemented by other circuits. Embodiments of the present disclosure do not limit the specific implementation manners of the constant current source circuit 221.

[0045] The energy storage circuit 222 may include a capacitor C. Wherein, a first end of the capacitor C is coupled to the first node N1. A second end of the capacitor is coupled to the second voltage terminal V2.

[0046] The short-circuit detection circuit 223 may include a comparator COMP. Wherein, a first input terminal of the comparator COMP is coupled to the short-circuit reference voltage terminal V REF2 . A second input terminal of the comparator COMP is supplied with the feedback voltage FB of the DC-DC converter. An output terminal of the comparator COMP is coupled to the second node N2. When the feedback voltage FB is lower than the short-circuit reference voltage V REF2 from the short-circuit reference voltage terminal V REF2 , the comparator COMP may output a high-level signal. When the feedback voltage FB is higher than or equal to the short-circuit reference voltage V REF2 , the comparator COMP may output a low-level signal. In some embodiments of the present disclosure, the comparator COMP is a hysteresis comparator. When the feedback voltage FB is lower than the short-circuit reference voltage V REF2 , the comparator COMP may output a high-level signal. When the voltage value V FB of the feedback voltage FB increases, the flip threshold of the comparator COMP becomes V REF2 + ΔV, where ΔV represents the hysteresis voltage. ΔV > 0V. In other words, when the voltage value V FB of the feedback voltage FB is higher than or equal to V REF2 + ΔV, the comparator COMP may output a low-level signal. This can prevent the output result of the comparator COMP from oscillating.

[0047] The first switch circuit 224 may include a first transistor M1. Wherein, a control electrode of the first transistor M1 is coupled to the second node N2. A first pole of the first transistor M1 is coupled to the third node N3. A second pole of the first transistor M1 is coupled to the first node N1.

[0048] The short-circuit start control circuit 225 may include an amplifier A. Wherein, a first input terminal of the amplifier A is coupled to the first node N1, so as to be supplied with the soft start signal SS_REF. A second input terminal of the amplifier A is supplied with the feedback voltage FB of the DC-DC converter. An output terminal of the amplifier A is coupled to the fourth node N4. There is a first offset voltage at the first input terminal of the amplifier A. The voltage value of the first offset voltage is Vos1. When the voltage value V SS_REF of the soft start signal SS_REF minus the voltage value V FB of the feedback voltage FBWhen the voltage value Vos1 is lower than the first offset voltage, the short - circuit start - up control signal is at a low level. At the voltage value V of the soft - start signal SS_REF SS_REF subtracting the voltage value V of the feedback voltage FB FB When the voltage value Vos1 is higher than or equal to the first offset voltage, the short - circuit start - up control signal is at a high level. The first offset voltage of the first input terminal of the amplifier A is greater than the second offset voltage of the first input terminal of the error amplifier in the DC - DC converter. The voltage value of the second offset voltage is Vos2. In short, Vos1 > Vos2.

[0049] The second switching circuit 226 may include a second transistor M2. Wherein, the control electrode of the second transistor M2 is coupled to the fourth node N4. 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 third node N3.

[0050] At Figure 3 In 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, the second transistor M2, and the third transistor M3 are all N - type transistors. The first input terminal of the comparator COMP is the non - inverting input terminal. The second input terminal of the comparator COMP is the inverting input terminal. The first input terminal of the amplifier A is the non - inverting input terminal. The second input terminal of the amplifier A is the inverting input terminal.

[0051] In the normal power - on soft - start stage, the initial voltage value of the capacitor C is zero. The third transistor M3 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 Vos2, 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 Vos2. 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.

[0052] In the normal power - on soft - start stage, (V SS_REF - V FB ) = Vos2. As described above, at V SS_REF - V FBWhen it is lower than Vos1, the short - circuit start control signal is at a low level. And Vos1 is greater than Vos2. Therefore, during the normal power - on soft - start phase, the short - circuit start control signal is always at a low level. The second transistor M2 is cut off when the short - circuit start control signal is at a low level. Thus, the capacitor C can be normally charged, so that the normal power - on soft - start phase is not affected.

[0053] When the output terminal of the DC - DC converter is short - circuited, the feedback voltage FB is pulled down to 0V. The voltage at the non - inverting input terminal of the comparator COMP is higher than that at the inverting input terminal. Therefore, the comparator COMP outputs a short - circuit indication signal at a high level, which makes the first transistor M1 conduct. The voltage at the non - inverting input terminal of the amplifier A is higher than that at the inverting input terminal. Therefore, the amplifier A outputs a short - circuit start control signal at a high level, which makes the second transistor M2 conduct. When both the first transistor M1 and the second transistor M2 are conducting, the capacitor C starts to discharge. Since there is a first offset voltage Vos1 at the non - inverting input terminal of the amplifier A, the voltage value of the soft - start signal SS_REF is maintained at Vos1 after it drops to Vos1. Since Vos1 is greater than Vos2, the voltage output at the output terminal EAOUT of the error amplifier remains at a high level, so that the DC - DC converter continuously provides current to the output terminal of the DC - DC converter.

[0054] Since the DC - DC converter continuously provides 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 starts to rise, which drives 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 Vos1, the amplifier A outputs a short - circuit start control signal at a low level, which makes the second transistor M2 cut off. At this time, the capacitor C starts to charge, and thus the soft - start signal SS_REF starts to rise. After that, the voltage difference between the soft - start signal SS_REF and the feedback voltage FB maintains the second offset voltage until the voltage value V FB exceeds V REF1 , the soft - start process ends. The output voltage of the DC - DC converter smoothly rises to the expected voltage during the soft - start phase.

[0055] When the voltage value V FB of the feedback voltage FB exceeds V REF2 +ΔV, the comparator COMP outputs a short - circuit indication signal at a low level, which makes the first transistor M1 cut off. In this way, after the soft - start signal SS_REF rises to V REF1 , it will not be clamped by the offset voltage of the amplifier A, so it can continue to rise to the first voltage V1.

[0056] Those skilled in the art should understand that variations made to the Figure 3 circuit shown should also fall within the scope of protection of this disclosure. In this variation, the first transistor M1, the second transistor M2, and the third transistor M3 may be P-type transistors. The first input terminal of the comparator COMP may be an inverting input terminal. The second input terminal of the comparator COMP may be a non-inverting input terminal. The first input terminal of the amplifier A may be an inverting input terminal. The second input terminal of the amplifier A may be a non-inverting input terminal.

[0057] In summary, the short-circuit recovery soft-start circuit for a DC-DC converter according to an embodiment of this disclosure can be used for soft-start during normal power-on, and enables the DC-DC converter to perform soft-start again after the short-circuit state at the output terminal of the DC-DC converter is removed, without conflicting with the soft-start during normal power-on.

[0058] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architectures, functions, and operations of devices and methods according to multiple embodiments of this disclosure. In this regard, each block in the flowchart or block diagram may represent a module, a segment of a program, or a part of an instruction, and the module, the segment of a program, or the part of an instruction contains one or more executable instructions for implementing the specified logical function. In some alternative implementations, the functions marked in the blocks may occur in a different order from that marked 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 diagram and / or flowchart, and combinations of blocks in the block diagram and / or flowchart, can be implemented by a dedicated hardware-based system for performing the specified functions or actions, or can be implemented by a combination of dedicated hardware and computer instructions.

[0059] Unless otherwise explicitly stated in the context, the singular forms of words used in this text and the appended claims include the plural, and vice versa. Thus, when referring to the singular, the corresponding plural terms are generally included. Similarly, the terms "comprising" and "including" shall be interpreted as inclusive rather than exclusive. Likewise, the term "including" and "or" shall be interpreted as inclusive, unless such an interpretation is explicitly prohibited in this text. Where the term "example" is used in this text, especially when it is located after a group of terms, the "example" is merely exemplary and illustrative, and should not be considered exclusive or extensive.

[0060] Further aspects and scopes of adaptability will become apparent from the description provided herein. It should be understood that the various aspects of the present application can be implemented alone 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.

[0061] The above has described several embodiments of the present disclosure in detail. 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 protection scope 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 detection circuit, a first switch circuit, a short-circuit start control circuit, and a second 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 first switch circuit and the second 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 first switch circuit and the second switch circuit are working; The short-circuit detection circuit is configured to generate a short-circuit indication signal based on a feedback voltage of the DC-DC converter and a short-circuit reference voltage from a short-circuit reference voltage terminal and provide the short-circuit indication signal to the first switch circuit via a second node, and the short-circuit indication signal is used to indicate whether an output terminal of the DC-DC converter is short-circuited; The first switch circuit is coupled to the second switch circuit via a third node and is configured to: operate when the short-circuit indication signal is at an effective level to connect the first node and the third node, and stop operating when the short-circuit indication signal is at an invalid level to disconnect the first node and the third node; The short-circuit start control circuit is configured to generate a short-circuit start control signal based on the soft start signal and the feedback voltage of the DC-DC converter, provide the short-circuit start control signal to the second switch circuit via a fourth node, and maintain a voltage difference between the soft start signal and the feedback voltage at a 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 second switch circuit is configured to: operate when the short-circuit start control signal is at an effective level to connect the third node and a second voltage terminal, and stop operating when the short-circuit start control signal is at an invalid level to disconnect the third 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 an amplifier, Wherein, a first input terminal of the amplifier is coupled to the first node, a second input terminal of the amplifier is provided with the feedback voltage of the DC-DC converter, and an output terminal of the amplifier is coupled to the fourth node; Wherein, a first offset voltage of the first input terminal of the amplifier is greater than a second offset voltage of the first input terminal of the error amplifier in the DC-DC converter.

3. The short-circuit recovery soft start circuit according to claim 1, wherein, The short-circuit detection circuit includes a comparator, Wherein, a first input terminal of the comparator is coupled to the short-circuit reference voltage terminal, a second input terminal of the comparator is provided with the feedback voltage of the DC-DC converter, and an output terminal of the comparator is coupled to the second node.

4. The short-circuit recovery soft start circuit according to claim 3, wherein, The comparator is a hysteresis comparator.

5. The short-circuit recovery soft start circuit according to claim 1, wherein, The first switch circuit includes a first transistor Wherein, the control electrode of the first transistor is coupled to the second node, the first pole of the first transistor is coupled to the third node, and the second pole of the first transistor is coupled to the first node.

6. The short-circuit recovery soft-start circuit according to claim 1, wherein, The second switching circuit includes a second transistor. Wherein, the control electrode of the second transistor is coupled to the fourth node, the first pole of the second transistor is coupled to the second voltage terminal, and the second pole of the second transistor is coupled to the third node.

7. The short-circuit recovery soft start circuit according to claim 1, wherein, The energy storage circuit includes a capacitor. Wherein, the first terminal of the capacitor is coupled to the first node, and the second terminal of the capacitor is coupled to the second voltage terminal.

8. The short-circuit recovery soft-start circuit according to claim 1, wherein, The constant current source circuit includes a third transistor. Wherein, the control electrode of the third transistor is coupled to the bias voltage terminal, the first pole of the third transistor is coupled to the first node, and the second pole of the third transistor is coupled to the first voltage terminal.

9. A short-circuit recovery soft-start circuit for a DC-DC converter, comprising: A comparator, an amplifier, a first transistor, a second transistor, a third transistor, and a capacitor. Wherein, the first input terminal of the comparator is coupled to the short - circuit reference voltage terminal, the second input terminal of the comparator is supplied with the feedback voltage of the DC - DC converter, and the output terminal of the comparator is coupled to the control electrode of the first transistor. The first input terminal of the amplifier is coupled to the first pole of the third transistor and the first terminal of the capacitor, the second input terminal of the amplifier is coupled to the second input terminal of the comparator, the output terminal of the amplifier is coupled to the control electrode of the second transistor, and the first offset voltage of the first input terminal of the amplifier is greater than the second offset voltage of the first input terminal of the error amplifier in the DC - DC converter. The first pole of the first transistor is coupled to the second pole of the second transistor, and the second pole of the first transistor is coupled to the first terminal of the capacitor. The first pole of the second transistor is coupled to the second voltage terminal. The control electrode of the third transistor is coupled to the bias voltage terminal, the first pole of the third transistor is coupled to the first terminal of the capacitor, and the second pole of the third 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, and the second terminal 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.

Images