Voltage conversion device and bootstrap control circuit thereof

Abstract

A bootstrap control circuit includes a regulator, a capacitor, a voltage detector, and a charging path controller. The regulator generates a first voltage. The capacitor is coupled between the regulator and the inductor of the DC-DC conversion circuit. The voltage detector detects a voltage difference between both ends of the capacitor to obtain a detection signal. The charging path controller turns on or off a connection path between the capacitor and the inductor of the DC-DC conversion circuit, and connects the capacitor to a reference voltage when the connection path of the capacitor and the inductor of the DC-DC conversion circuit is cut off.

Description

Technical Field

[0001] The present invention relates to a voltage conversion device and a bootstrap control circuit thereof, and more particularly to a voltage conversion device and a bootstrap control circuit thereof that can avoid output voltage disturbance and additional conduction loss. Background Art

[0002] In a bootstrap-controlled voltage conversion device, a voltage conversion operation can be performed by alternately switching two transistors. The bootstrap control circuit of the voltage conversion device provides a capacitor to store charge during the voltage conversion operation. If the voltage conversion device turns to a light load state, the charge in the capacitor may be lost, and the bootstrap control circuit needs to provide a charging path to recharge the capacitor. In the conventional technology, the bootstrap control circuit always provides a charging path through the inductor by turning on the lower bridge of the (direct current - direct current) DC - DC conversion circuit of the voltage conversion device. Since the inductor stores energy during the voltage conversion operation, and the energy can cause output voltage disturbance for the recharge operation of the capacitor. In addition, during the recharge operation, the energy of the inductor needs to be recycled to the input end of the voltage conversion device to avoid excessive output voltage. The on-resistance of the two transistors of the voltage conversion circuit can cause on-loss, and the two alternately switched transistors in the voltage conversion circuit may induce switching loss. Summary of the Invention

[0003] The present invention provides a voltage conversion device and a bootstrap control circuit thereof that can avoid output voltage disturbance and additional conduction loss, and reduce the switching loss of the DC - DC conversion circuit.

[0004] According to an embodiment of the present invention, the bootstrap control circuit is applicable to a DC - DC conversion circuit. The bootstrap control circuit includes a regulator, a capacitor, a voltage detector, and a charging path controller. The regulator generates a first voltage. The capacitor is coupled between the regulator and the inductor of the DC - DC conversion circuit. The voltage detector is coupled in parallel to the capacitor to detect the voltage difference between the two ends of the capacitor to obtain a detection signal. The charging path controller is coupled to the capacitor and the voltage detector. The charging path controller turns on or off the connection path between the capacitor and the inductor of the DC - DC conversion circuit, and when the connection path between the capacitor and the inductor of the DC - DC conversion circuit is cut off, the charging path controller connects the capacitor to a reference voltage.

[0005] According to an embodiment of the present invention, the voltage conversion device includes the DC - DC conversion circuit and the bootstrap control circuit as mentioned above. The DC - DC conversion circuit receives an input voltage and generates an output voltage.

[0006] Generally speaking, the bootstrap control circuit can determine whether to connect the capacitor to the reference voltage or the inductor according to the voltage difference between the two ends of the capacitor. In this way, in the light load state, the charging path of the capacitor can be isolated from the inductor. In this way, output voltage disturbances and additional conduction losses can be avoided, and the switching losses of the DC-DC conversion circuit can be reduced.

[0007] To make the above features and advantages of the present invention more understandable, embodiments accompanied by drawings are described in detail below. Description of the Drawings

[0008] The accompanying drawings are included to provide a further understanding of the present invention, and the drawings are incorporated into and constitute a part of this specification. The drawings illustrate embodiments of the present invention and, together with the description, are used to explain the principles of the present invention.

[0009] Figure 1 A schematic diagram showing a bootstrap control circuit according to an embodiment of the present disclosure.

[0010] Figure 2 A circuit diagram showing a voltage conversion device according to an embodiment of the present disclosure.

[0011] Figure 3 A waveform graph showing the voltage conversion device 200.

[0012] Figure 4 A circuit diagram showing a voltage conversion device according to an embodiment of the present disclosure.

[0013] Figure 5 A circuit diagram showing a voltage conversion device according to another embodiment of the present disclosure.

[0014] Explanation of the Reference Numerals in the Drawings

[0015] 100, 220, 420, 520: Bootstrap control circuit;

[0016] 101, 210, 410, 510: DC-DC conversion circuit;

[0017] 110, 221, 421, 524: Regulator;

[0018] 120, 222, 422, 522: Voltage detector;

[0019] 130, 223, 423, 523: Charging path controller;

[0020] 200, 400, 500: Voltage conversion device;

[0021] 211, 511: High-side pre-driver;

[0022] 212, 512: Low-side pre-driver;

[0023] 424, 524: Reference voltage generator;

[0024] CBOOT: Capacitor;

[0025] D1: Diode;

[0026] DET: Detection signal;

[0027] DETB: Inverted detection signal;

[0028] DV1, DV2: Drive signal;

[0029] GND: Reference ground terminal;

[0030] HL: Heavy load state;

[0031] I1, IL: Current;

[0032] IREF: Reference current;

[0033] IS: Second current generator;

[0034] IV1: Inverter;

[0035] L1: Inductor;

[0036] LL: Light load state;

[0037] LX, V1: Voltage;

[0038] M1, M2, M3, M4, MNHS, MNLS: Transistor;

[0039] NDRV, NHDRV: Control signal;

[0040] R1: Resistor;

[0041] SW1, SW2: Switch;

[0042] V1: Voltage;

[0043] VA, VCBP: Power supply voltage;

[0044] VBOOT: Voltage difference;

[0045] VCBN, VREF: Reference voltage;

[0046] VDETH, VDETL: Threshold;

[0047] VGS: Gate-to-source voltage;

[0048] VIN: Input voltage;

[0049] VOUT: Output voltage. Detailed Implementation Manner

[0050] Throughout the specification (including the claims) of this application, the term "coupled (or connected)" is widely used and encompasses direct and indirect connection or coupling of components. For example, if this disclosure describes a first device being coupled (or connected) to a second device, it should be interpreted that the first device can be directly connected to the second device, or the first device can be indirectly connected to the second device through other devices or by specific coupling components. Additionally, terms such as "first" and "second" mentioned throughout the specification (including the claims) of this application are only used to name elements or distinguish different embodiments or scopes, and do not intend to limit the upper or lower limits of the number of elements, nor the order of the elements. Moreover, elements / components / steps with the same reference numerals represent the same or similar parts in the drawings and embodiments. Elements / components / symbols with the same reference numerals in different embodiments can be referred to the relevant descriptions.

[0051] Please refer to Figure 1 , which shows a schematic diagram of a bootstrap control circuit according to an embodiment of the present disclosure. The bootstrap control circuit 100 is applicable to the DC-DC conversion circuit 101. The bootstrap control circuit 100 includes a regulator 110, a capacitor CBOOT, a voltage detector 120, and a charge path controller 130. The regulator 110 receives the input voltage VIN or the output voltage of the DC-DC conversion circuit 101. The regulator 110 generates a voltage V1 according to the input voltage VIN or the output voltage VOUT. In this embodiment, the DC-DC conversion circuit 101 can be a DC-DC boost converter or a DC-DC buck converter. If the DC-DC conversion circuit 101 is a DC-DC boost converter, the regulator 110 can generate the voltage V1 according to the output voltage VOUT. If the DC-DC conversion circuit 101 is a DC-DC buck converter, the regulator 110 can generate the voltage V1 according to the input voltage VIN. The regulator 110 can be a low-dropout (LDO) voltage regulator.

[0052] On the other hand, the first end of the capacitor CBOOT is coupled to the regulator 110, and the second end of the capacitor CBOOT is coupled to the charge path controller 130. The second end of the capacitor CBOOT is further coupled to the inductor L1 of the DC-DC conversion circuit 101 through the charge path controller 130. The voltage detector 130 is coupled in parallel to the capacitor CBOOT. The voltage detector 130 is configured to detect the voltage difference VBOOT between the two ends of the capacitor CBOOT to obtain a detection signal DET. The voltage detector 130 further transmits the detection signal DET to the charge path controller 130. The charge path controller 130 can connect or disconnect the connection path between the capacitor CBOOT and the inductor L1 of the DC-DC conversion circuit according to the detection signal DET. Additionally, when the connection path between the capacitor CBOOT and the inductor L1 of the DC-DC conversion circuit 101 is disconnected, the charge path controller 130 can connect the capacitor CBOOT to the reference voltage VREF. Conversely, when the connection path between the capacitor CBOOT and the inductor L1 of the DC-DC conversion circuit 101 is connected, the charge path controller 130 can disconnect the connection between the capacitor CBOOT and the reference voltage VREF.

[0053] Specifically, in the heavy load state of the DC-DC conversion circuit 101, the voltage detector 120 can generate a detection signal DET with a second logic value by detecting the voltage difference VBOOT between the two ends of the capacitor CBOOT. In this case, the charge path controller 130 can connect the connection path between the capacitor CBOOT and the inductor L1, and the capacitor CBOOT can be charged based on the input voltage VIN or the output voltage VOUT through the voltage bistate switching of the inductor L1.

[0054] When the DC-DC conversion circuit 101 transitions from the heavy load state to the light load state, the charge of the capacitor CBOOT can decrease. At this time, the voltage detector 130 can detect that the voltage value of the voltage difference VBOOT between the two ends of the capacitor CBOOT is lower than the threshold, and the voltage detector 130 can generate a detection signal DET with a first logic value. In response to the detection signal DET with the first logic value, the charge path controller 130 can disconnect the connection path between the inductor L1 and the capacitor CBOOT. On the other hand, the charge path controller 130 can connect the capacitor CBOOT to the reference voltage VREF to establish another charge path. In this way, the capacitor CBOOT can be charged based on the reference voltage VREF.

[0055] It can be seen that in the light load state, the capacitor CBOOT is disconnected from the inductor L1, and the capacitor CBOOT is charged based on the reference voltage VREF. In addition, in the light load state, the inductor L1 does not need to release charge to the capacitor CBOOT, and the DC-DC conversion circuit 101 can generate an output voltage VOUT with a stable voltage value. Conduction losses caused by the current of the inductor L1 during the charging process can be avoided, and the efficiency of the DC-DC conversion circuit 101 in the light load state can be improved.

[0056] It should be noted here that in this embodiment, the reference voltage VREF can be a reference ground voltage, or the reference voltage VREF can be generated according to the input voltage VIN or the output voltage VOUT of the DC-DC conversion circuit 101. For example, if the DC-DC conversion circuit 101 is a DC-DC boost converter, then the reference voltage VREF can be equal to the input voltage VIN minus the bias voltage. If the DC-DC conversion circuit 101 is a DC-DC buck converter, then the reference voltage VREF can be equal to the output voltage VOUT minus the bias voltage. Here, the voltage value of the bias voltage can be determined by the designer of the DC-DC conversion circuit 101, and there is no special limitation here.

[0057] Please refer to Figure 2 , which shows a circuit diagram of a voltage conversion device according to an embodiment of the present disclosure. The voltage conversion device 200 includes a DC-DC conversion circuit 210 and a bootstrap control circuit 220. The DC-DC conversion circuit 210 includes a high-side pre-driver 211, a low-side pre-driver 212, an inductor L1, and transistors MNHS and MNLS. The transistors MNHS and MNLS are serially coupled between the output voltage VOUT and the reference ground terminal GND. The transistors MNHS and MNLS can be N-type transistors. MNHS and MNLS are respectively driven by the high-side pre-driver 211 and the low-side pre-driver 212. The power supply terminal of the high-side pre-driver 211 receives the power supply voltage VCBP, and the reference ground terminal of the high-side pre-driver 211 receives the reference voltage VCBN. The high-side pre-driver 211 further receives a control signal NHDRV and generates a drive signal DV1 according to the control signal NHDRV. The drive signal DV1 is provided to the gate of the transistor MNHS, and the drive signal DV1 can transition between the power supply voltage VCBP and the reference voltage VCBN.

[0058] The power supply terminal of the low-side pre-driver 212 receives a power supply voltage VA, and the reference ground terminal of the low-side pre-driver 212 is coupled to the reference ground terminal GND. The low-side pre-driver 212 further receives a control signal NDRV and generates a drive signal DV2 according to the control signal NDRV. The drive signal DV2 is provided to the gate of the transistor MNLS, and the drive signal DV2 can transition between the power supply voltage VA and the voltage of the reference ground terminal GND.

[0059] The first end of the inductor L1 receives an input voltage VIN, and the second end of the inductor L1 is coupled to the coupled end of the transistor MNHS and the transistor MNLS.

[0060] The transistors MNHS and MNLS can be alternately switched according to the drive signal DV1 and the drive signal DV2 to convert the input voltage VIN through the inductor L1 to generate an output voltage VOUT. In this embodiment, the DC-DC conversion circuit 210 is a DC-DC boost converter, and the output voltage VOUT can be greater than the input voltage VIN.

[0061] The bootstrap control circuit 220 includes a regulator 221, a capacitor CBOOT, a voltage detector 222, and a charge path controller 223. The regulator 221 can receive the output voltage VOUT through the diode D1. The regulator 221 can generate a power supply voltage VCBP according to the output voltage VOUT. In this embodiment, the regulator 221 can be a low-dropout (LDO) voltage regulator. One end of the capacitor CBOOT is coupled to the regulator 221 to receive the power supply voltage VCBP. The other end of the capacitor CBOOT receives a reference voltage VCBN and is coupled to the voltage detector 222 and the charge path controller 223.

[0062] The voltage detector 222 is coupled to both ends of the capacitor CBOOT and receives the power supply voltage VCBP and the reference voltage VCBN. The voltage detector 222 is used to detect the voltage difference VBOOT between both ends of the capacitor CBOOT. In this embodiment, the voltage detector 222 can include a resistor R1 and transistors M1 and M2. The resistor R1 and the transistors M1 and M2 are serially coupled and form a first current generator. The transistor M1 is connected in a diode configuration. In Figure 2 it, the resistor R1 is coupled to the anode of the diode formed by the transistor M1, the first end of the transistor M2 is coupled to the cathode of the diode formed by the transistor M1, and the control end of the transistor M2 is coupled to the lower end of the capacitor CBOOT. The first current generator formed by the resistor R1 and the transistors M1 and M2 can generate a current I1 according to the voltage difference VBOOT through the second end of the transistor M2.

[0063] The voltage detector 222 further includes a second current generator IS formed by transistors M3 and M4 and a current comparator. The control terminal and the first terminal of transistor M4 are coupled together to receive current I1. The control terminal of transistor M3 and the control terminal of transistor M4 are coupled together, and the first terminal of transistor M3 receives a reference current IREF generated by the second current generator IS. Transistors M3 and M4 form a current mirror circuit and mirror current I1 to the first terminal of transistor M3. Thus, the reference current IREF can be compared with current I1. If the reference current IREF is greater than current I1, then the detection signal DET can be pulled up to a high logic value (the first logic value); and if the reference current IREF is less than current I1, then the detection signal DET can be pulled down to a low logic value (the second logic value). Additionally, the second terminal of transistor M3 and the second terminal of transistor M4 are coupled to the reference ground terminal GND.

[0064] In addition, the charge path controller 223 includes a switch SW1, a switch SW2, and an inverter IV1. The inverter IV1 receives the detection signal to generate an inverted detection signal DETB by inverting the detection signal DET. The switch SW1 and the switch SW2 are controlled by the inverted detection signal DETB and the detection signal DET, respectively.

[0065] In this embodiment, if the detection signal DET is at a high logic value, then the switch SW1 can be turned off and the switch SW2 can be turned on. That is, in this way, the connection path between the inductor L1 and the capacitor CBOOT is cut off by the switch SW1. The capacitor CBOOT is coupled to the reference ground terminal GND through the switch SW2 to receive a reference voltage. On the other hand, if the detection signal DET is at a low logic value, then the switch SW1 can be turned on and the switch SW2 can be turned off. That is, in this way, the connection path between the inductor L1 and the capacitor CBOOT is turned on through the switch SW1, and the capacitor CBOOT can be isolated from the reference ground GND through the switch SW2.

[0066] Please refer jointly to Figure 2 and Figure 3 where Figure 3 shows a waveform graph of the voltage conversion device 200. At Figure 3During the heavy load state HL, transistors MNHS and MNLS are alternately switched according to control signal NHDRV and control signal NDRV. Control signal NHDRV and control signal NDRV are complementary to each other. The voltage LX at the coupling end between inductor L1 and transistors MNHS and MNLS transitions between two voltage values, and the highest voltage value of voltage LX can be equal to output voltage VOUT. In the heavy load state HL, the voltage difference VBOOT across the two ends of capacitor CBOOT can be higher than threshold VDETL, and the detection signal DET generated by voltage detector 222 can be maintained at a low logic value.

[0067] When voltage conversion device 200 transitions from the heavy load state HL to the light load state LL, the switching frequency of control signal NHDRV and control signal NDRV decreases. The current IL on the inductor decreases correspondingly. The voltage difference VBOOT across the two ends of capacitor CBOOT can drop below threshold VDETH and reach threshold VDETL. When the voltage difference VBOOT across the two ends of capacitor CBOOT reaches threshold VDETL, voltage detector 222 can generate a detection signal DET with a high logic value. Charge path controller 223 can switch capacitor CBOOT to be coupled from inductor L1 to reference ground terminal GND, and pull reference voltage VCBN to the reference ground voltage when detection signal DET is at a high logic value.

[0068] On the other hand, if the voltage difference VBOOT across the two ends of capacitor CBOOT is charged to be higher than threshold VDETH, then voltage detector 222 can pull down detection signal DET to a low logic value. Charge path controller 223 can reconnect capacitor CBOOT to inductor L1, and cut off the connection path between capacitor CBOOT and reference ground terminal GND.

[0069] In addition, in the light load state LL, voltage LX can be equal to input voltage VIN. Furthermore, threshold VDETH and threshold VDETL can be set by adjusting at least one of the resistance of resistor R1, the turn-on voltage of the diode formed by transistor M1, the threshold voltage of transistor M2, the current value of reference current IREF, and the mirror ratio of the current mirror formed by transistors M3 and M4.

[0070] Please refer to Figure 4 which shows the circuit diagram of a voltage conversion device according to an embodiment of the present disclosure. Voltage conversion device 400 includes a DC-DC conversion circuit 410 and a bootstrap control circuit 420. The details of DC-DC conversion circuit 410 are similar to Figure 2 the DC-DC conversion circuit 210 in the embodiment of

[0071] The bootstrap control circuit 420 includes a regulator 421, a capacitor CBOOT, a voltage detector 422, a charging path controller 423, and a reference voltage generator 424. Figure 2 In the embodiment of the present invention, the bootstrap control circuit 420 further includes a reference voltage generator 424. The reference voltage generator 424 is coupled to the switch SW2 and provides the reference voltage VREF to the switch SW2. If the switch SW2 is turned on, the capacitor CBOOT can be charged based on the reference voltage VREF.

[0072] If one embodiment, the reference voltage generator 424 may provide a reference ground voltage as the reference voltage VREF. In other embodiments, the reference voltage generator 424 may generate the reference voltage VREF according to the input voltage VIN of the DC-DC conversion circuit 410. The reference voltage generator 424 may be a low dropout (LDO) regulator, and the reference voltage generator 424 may generate the reference voltage VREF by subtracting the input voltage VIN of the DC-DC conversion circuit 410 from the bias voltage.

[0073] It should be noted here that in a light load state, transistor MNHS and transistor MNLS are cut off. The voltage LX at the coupling terminal between inductor L1 and transistor MNHS and transistor MNLS is equal to the input voltage VIN. When capacitor CBOOT is charged by charging path controller 423, if reference voltage VREF is 0 volts, then when switch SW2 is turned on, reference voltage VCBN will be pulled to 0 volts. In this way, the gate-to-source voltage VGS of transistor MNHS can be equal to -VIN. In this embodiment, since the absolute value of gate-to-source voltage VGS needs to be less than a certain voltage value (i.e., 5 volts), the input voltage VIN may be limited.

[0074] For the reasons discussed above, in this embodiment, the reference voltage generator 424 can generate the reference voltage VREF by subtracting the input voltage VIN of the DC-DC conversion circuit 410 from the bias voltage, wherein the bias voltage can have a specific voltage value. That is, the input voltage VIN is not limited in this embodiment.

[0075] Please refer to Figure 5 , which shows a circuit diagram of a voltage conversion device according to another embodiment of the present disclosure. The voltage conversion device 500 includes a DC-DC conversion circuit 510 and a bootstrap control circuit 520. The DC-DC conversion circuit 510 is a DC-DC buck converter. The DC-DC conversion circuit 510 includes a transistor MNHS, a transistor MNLS, a high-side pre-driver 511, a low-side pre-driver 512, and an inductor L1. Different from Figure 2The DC-DC conversion circuit 210 therein. In the presented embodiment, the DC-DC conversion circuit 510 receives an input voltage VIN through the first end of the transistor MNHS, and the DC-DC conversion circuit 510 generates an output voltage VOUT through one end of the inductor L1. Wherein, the other end of the inductor L1 is coupled to the coupling end between the transistor MNHS and the transistor MNLS.

[0076] On the other hand, the bootstrap control circuit 520 includes a capacitor CBOOT, a regulator 521, a voltage detector 522, a charge path controller 523, and a reference voltage generator 524. In this embodiment, the regulator 521 receives the input voltage VIN and generates a power supply voltage VCBP according to the input voltage VIN. One end of the capacitor CBOOT receives the power supply voltage VCBP, and the other end of the capacitor CBOOT receives a reference voltage VCBN. The voltage detector 522 generates a detection signal DET by detecting the voltage difference VBOOT between both ends of the capacitor CBOOT. The charge path controller 523 receives the detection signal DET and determines to connect the lower end of the capacitor CBOOT to the inductor L1 or the reference voltage generator 524 according to the detection signal DET. The reference voltage generator 524 can receive the output voltage VOUT, generate a reference voltage VREF, and provide the reference voltage VREF to the capacitor CBOOT. In this embodiment, the reference voltage VREF can be equal to the output voltage VOUT minus a bias voltage, where the bias voltage can have a specific voltage value.

[0077] If the reference voltage VREF is 0 volts, then when the capacitor CBOOT is charged through the charge path controller 523, the voltage VCBN can be pulled to the reference voltage VREF (=0 volts). At this time, the gate-to-source voltage VGS of the transistor MNHS can be equal to -VOUT. When the gate-to-source voltage VGS is limited to less than 5 volts, the operating range of the output voltage VOUT is limited.

[0078] In this embodiment, the reference voltage generator 524 can generate the reference voltage VREF by subtracting the output voltage VOUT of the DC-DC conversion circuit 510 from the bias voltage. Thus, when the output voltage VOUT is greater than 5 volts, the absolute value of the gate-to-source voltage VGS of the transistor MNHS can be maintained at 5 volts, and the value of the output voltage VOUT is not limited.

[0079] It should be noted here that since the DC-DC conversion circuit 510 is a DC-DC buck converter, the input voltage VIN is greater than the output voltage VOUT.

[0080] It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the disclosed embodiments without departing from the scope or spirit of the present disclosure. In view of the foregoing, it is intended that the present disclosure cover modifications and variations of the present disclosure provided they come within the scope of the appended claims and their equivalents.

Claims

1. A bootstrap control circuit, applicable to a DC-DC conversion circuit, comprising: A regulator for generating a first voltage; A capacitor coupled between the regulator and an inductor of the DC-DC conversion circuit; A voltage detector coupled in parallel to the capacitor to detect a voltage difference between two ends of the capacitor to obtain a detection signal; And A charge path controller coupled to the capacitor and the voltage detector, Wherein the charge path controller turns on or off a connection path between the capacitor and the inductor of the DC-DC conversion circuit, and when the connection path between the capacitor and the inductor of the DC-DC conversion circuit is cut off, the charge path controller connects the capacitor to a reference voltage.

2. The bootstrap control circuit according to claim 1, wherein the charge path controller comprises: A first switch coupled between the capacitor and the inductor of the DC-DC conversion circuit, wherein the first switch is controlled by the detection signal; And A second switch coupled between the capacitor and the reference voltage, wherein the second switch is controlled by the detection signal.

3. The bootstrap control circuit according to claim 2, wherein the charge path controller further comprises: An inverter coupled to the voltage detector and the first switch, and generating an inverted detection signal according to the detection signal, Wherein the inverter transmits the inverted detection signal to the first switch, and the on / off states of the first switch and the second switch are different.

4. The bootstrap control circuit according to claim 1, wherein the voltage detector generates a first current according to the voltage difference between two ends of the capacitor, and generates the detection signal by comparing the first current with a reference current.

5. The bootstrap control circuit according to claim 4, wherein when the first current is less than the reference current, the voltage detector generates the detection signal having a first logic value; when the first current is greater than the reference current, the voltage detector generates the detection signal having a second logic value, Wherein the first logic value is different from the second logic value.

6. The bootstrap control circuit according to claim 4, wherein the voltage detector comprises: A first current generator coupled in parallel to the capacitor, generating the first current according to the voltage difference between two ends of the capacitor; A second current generator for generating the reference current; And A current comparator coupled to the first current generator and the second current generator, receiving and comparing the first current and the second current to generate the detection signal.

7. The bootstrap control circuit according to claim 6, wherein the current comparator comprises: A first transistor having a first end coupled to the first current generator to receive the first current, a second end of the first transistor coupled to a reference ground terminal, and a control end of the first transistor coupled to the first end of the first transistor; And A second transistor having a first end coupled to the second current generator to receive the reference current, a second end of the second transistor coupled to the reference ground terminal, and a control end of the second transistor coupled to the control end of the first transistor, wherein the detection signal is generated at the first end of the second transistor.

8. The bootstrap control circuit according to claim 6, wherein the first current generator comprises: A resistor, a diode, and a transistor connected in series, wherein the resistor and the diode are connected between a first end of the capacitor and a first end of the transistor, a control end of the transistor is coupled to a second end of the capacitor, and a second end of the transistor generates the first current.

9. The bootstrap control circuit according to claim 1, wherein the reference voltage is a ground voltage.

10. The bootstrap control circuit according to claim 1, wherein the reference voltage is generated according to an input voltage or an output voltage of the DC-DC conversion circuit.

11. The bootstrap control circuit according to claim 10, further comprising: A reference voltage generator, coupled to the charge path controller, and providing the reference voltage by subtracting the input voltage or the output voltage of the DC-DC conversion circuit from a bias voltage.

12. A voltage conversion device, comprising: A DC-DC conversion circuit that receives an input voltage and generates an output voltage; and A bootstrap control circuit, coupled to the DC-DC conversion circuit, wherein the bootstrap control circuit comprises: A regulator that generates a first voltage; A capacitor, coupled between the regulator and an inductor of the DC-DC conversion circuit; A voltage detector, coupled in parallel to the capacitor to detect a voltage difference between two ends of the capacitor to obtain a detection signal; and A charge path controller, coupled to the capacitor and the voltage detector, wherein the charge path controller turns on or off a connection path between the capacitor and the inductor of the DC-DC conversion circuit, and when the connection path between the capacitor and the inductor of the DC-DC conversion circuit is turned off, the charge path controller connects the capacitor to a reference voltage.

13. The voltage conversion device according to claim 12, wherein the charge path controller comprises: A first switch, coupled between the capacitor and the inductor of the DC-DC conversion circuit, wherein the first switch is controlled by the detection signal; and A second switch, coupled between the capacitor and the reference voltage, wherein the second switch is controlled by the detection signal.

14. The voltage conversion device according to claim 13, wherein the charge path controller further comprises: An inverter, coupled to the voltage detector and the first switch, and generating an inverted detection signal according to the detection signal, wherein the inverter transmits the inverted detection signal to the first switch, and the on / off states of the first switch and the second switch are different.

15. The voltage conversion device according to claim 12, wherein the voltage detector generates a first current based on the voltage difference between the two ends of the capacitor, and generates the detection signal by comparing the first current with a reference current.

16. The voltage conversion device according to claim 15, wherein when the first current is less than the reference current, the voltage detector generates the detection signal having a first logic value; when the first current is greater than the reference current, the voltage detector generates the detection signal having a second logic value, wherein the first logic value is different from the second logic value.

17. The voltage conversion device according to claim 15, wherein the voltage detector includes: a first current generator, coupled in parallel to the capacitor, generating the first current based on the voltage difference between the two ends of the capacitor; a second current generator, generating the reference current; and a current comparator, coupled to the first current generator and the second current generator, receiving and comparing the first current and the second current to generate the detection signal.

18. The voltage conversion device according to claim 12, wherein the reference voltage is a ground voltage.

19. The voltage conversion device according to claim 12, wherein the bootstrap control circuit further includes: a reference voltage generator, coupled to the charge path controller, providing the reference voltage by subtracting the input voltage or the output voltage of the DC-DC conversion circuit from a bias voltage.

20. The voltage conversion device according to claim 12, wherein the DC-DC conversion circuit is a boost converter or a buck converter.

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