TWI763057B - Boost converter for eliminating start-up overshoot - Google Patents

Abstract

A boost converter for eliminating start-up overshoot includes a bridge rectifier, a boost inductor, a power switch element, a PWM (Pulse Width Modulation) IC (Integrated Circuit), an output stage circuit, a first start-up circuit, and a second start-up circuit. The bridge rectifier generates a rectified voltage according to a first input voltage and a second input voltage. The boost inductor receives the rectified voltage. The power switch element selectively couples the boost inductor to a ground voltage according to a PWM voltage. The PWM IC is suppled by a supply voltage. The output stage circuit generates an output voltage. In a cold mode, the supply voltage is generated by the first start-up circuit. Next, in a hot mode, the supply voltage is generated by the second start-up circuit.

Description

Boost Converter to Eliminate Startup Overshoot

The present invention relates to a boost converter, in particular to a boost converter capable of eliminating start-up overshoot.

In order to achieve the effect of fast start-up of a conventional boost converter, the output potential of the conventional boost converter usually rises quickly, which may easily cause the problem of start-up overshoot and cause damage to the corresponding output capacitor. In view of this, it is necessary to propose a new solution to overcome the difficulties faced by the previous technology.

In a preferred embodiment, the present invention provides a boost converter for eliminating startup overshoot, comprising: a bridge rectifier that generates a rectified potential according to a first input potential and a second input potential; a boost inductor , receives the rectified potential; a power switch selectively couples the boost inductor to a ground potential according to a PWM potential; a PWM integrated circuit generates the pulse PWM potential, wherein the PWM integrated circuit is supplied by a supply potential electricity; an output stage circuit, coupled to the boost inductor, and generating an output potential; a first startup circuit, coupled to the output stage circuit, wherein the first startup circuit includes a positive temperature coefficient resistor; and a second start-up circuit coupled to the boost inductor, wherein the second start-up circuit includes a coupling coil set; wherein in a cold mode, the supply potential of the PWM integrated circuit is determined by The first start-up circuit is generated, and then in a warm-up mode, the supply potential of the PWM integrated circuit is generated by the second start-up circuit.

100,200: Boost Converter

110, 210: Bridge Rectifiers

120,220: Power switch

130, 230: Pulse Width Modulation Integrated Circuits

140, 240: Output stage circuit

150,250: First start circuit

160,260: Second start circuit

162, 262: Coupling coil set

263: First Coil

264: Second coil

265: Third Coil

C1: first capacitor

C2: Second capacitor

C3: Third capacitor

D1: first diode

D2: Second diode

D3: Third diode

D4: Fourth diode

D5: Fifth diode

D6: sixth diode

D7: seventh diode

D8: Eighth diode

DZ: Zener Diode

M1: first transistor

N1: the first node

N2: second node

N3: The third node

N4: Fourth Node

N5: Fifth node

N6: sixth node

N7: seventh node

N8: Eighth Node

N9: ninth node

N10: The tenth node

N11: Eleventh node

N12: Twelfth Node

L1: first inductor

L2: Second Inductor

LU: boost inductor

Q2: Second transistor

R1: first resistor

R2: Second resistor

R3: Third resistor

R4: Fourth resistor

RPTC: Positive Temperature Coefficient Resistor

VCC: Supply potential

VIN1: the first input potential

VIN2: The second input potential

VM: PWM potential

VOUT: output potential

VR: rectified potential

VSS: ground potential

FIG. 1 shows a schematic diagram of a boost converter according to an embodiment of the present invention.

FIG. 2 shows a schematic diagram of a boost converter according to an embodiment of the present invention.

FIG. 3 is a waveform diagram showing the output potential of a conventional boost converter.

FIG. 4 is a waveform diagram showing the output potential of the boost converter according to an embodiment of the present invention.

In order to make the objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are given in the following, and are described in detail as follows in conjunction with the accompanying drawings.

Certain terms are used in the description and the scope of the patent application to refer to called a specific element. It should be understood by those skilled in the art that hardware manufacturers may refer to the same element by different nouns. This specification and the scope of the patent application do not use the difference in name as a way to distinguish elements, but use the difference in function of the elements as a criterion for distinguishing. The words "including" and "including" mentioned in the entire specification and the scope of the patent application are open-ended terms, so they should be interpreted as "including but not limited to". The word "substantially" means that within an acceptable error range, those skilled in the art can solve the technical problem within a certain error range and achieve the basic technical effect. Furthermore, the term "coupled" in this specification includes any direct and indirect electrical connection means. Therefore, if a first device is described as being coupled to a second device, it means that the first device can be directly electrically connected to the second device, or indirectly electrically connected to the second device through other devices or connecting means. Second device.

FIG. 1 shows a schematic diagram of a boost converter 100 according to an embodiment of the present invention. For example, the boost converter 100 may be applied to a desktop computer, a notebook computer, or an all-in-one computer. As shown in FIG. 1, the boost converter 100 includes: a bridge rectifier 110, a boost inductor LU, a power switch 120, a pulse width modulation integrated circuit 130, an output stage circuit 140, a A first start-up circuit 150 and a second start-up circuit 160 . It should be noted that, although not shown in FIG. 1, the boost converter 100 may further include other components, such as a voltage regulator or/and a negative feedback circuit.

The bridge rectifier 110 can generate a rectified potential VR according to a first input potential VIN1 and a second input potential VIN2. Both the first input potential VIN1 and the second input potential VIN2 can come from an external input power supply, wherein the first input potential An alternating voltage having an arbitrary frequency and an arbitrary amplitude can be formed between VIN1 and the second input potential VIN2. For example, the frequency of the AC voltage can be about 50Hz or 60Hz, and the RMS value of the AC voltage can be from 90V to 264V, but it is not limited thereto. The boost inductor LU can receive the rectified potential VR. The power switch 120 can selectively couple the boost inductor LU to a ground potential VSS (eg, 0V) according to a PWM potential VM. For example, if the PWM potential VM is at a high logic level, the power switch 120 couples the boost inductor LU to the ground potential VSS (ie, the power switch 120 can approximate a short circuit path) ); on the contrary, if the PWM potential VM is at a low logic level, the power switch 120 will not couple the boost inductor LU to the ground potential VSS (that is, the power switch 120 can be approximately a open path). The PWM integrated circuit 130 can generate the PWM potential VM. The PWM integrated circuit 130 can be powered by a supply potential VCC. The output stage circuit 140 is coupled to the boost inductor LU, wherein the output stage circuit 140 can generate an output potential VOUT. For example, the output potential VOUT may be approximately a DC potential, and its level may be approximately 400V, but it is not limited thereto. The first start-up circuit 150 is coupled to the output stage circuit 140 , wherein the first start-up circuit 150 includes a positive temperature coefficient resistor RPTC. The second startup circuit 160 is coupled to the boost inductor LU, wherein the second startup circuit 160 includes a coupling coil set 162 . It must be noted that in a cold mode, the supply potential VCC of the PWM integrated circuit 130 is generated by the first start-up circuit 150, and then in a warm-up mode, the PWM integrated circuit The supply potential VCC of 130 is generated by the second start-up circuit 160 instead. In this design, the positive temperature coefficient resistor RPTC can form a damping circuit together with the output stage circuit 140, and the first start-up circuit 150 and the second start-up circuit 160 can respectively provide power to the PWM integrated circuit 130 . According to the actual measurement results, the design method proposed in the present invention can almost completely eliminate the start-up overshoot of the boost converter 100 .

The following embodiments will introduce the detailed structure and operation of the boost converter 100 . It must be understood that these drawings and descriptions are only examples and are not intended to limit the scope of the present invention.

FIG. 2 shows a schematic diagram of a boost converter 200 according to an embodiment of the present invention. In the embodiment of FIG. 2, the boost converter 200 has a first input node NIN1, a second input node NIN2, and an output node NOUT, and includes a bridge rectifier 210, a boost inductor LU, A power switch 220 , a PWM integrated circuit 230 , an output stage circuit 240 , a first start-up circuit 250 , and a second start-up circuit 260 . The first input node NIN1 and the second input node NIN2 of the boost converter 200 can respectively receive a first input potential VIN1 and a second input potential VIN2 from an external input power source, and the output node NOUT of the boost converter 200 It can be used to output an output potential VOUT to an electronic device (not shown).

The bridge rectifier 210 includes a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4. The anode of the first diode D1 is coupled to the first input node NIN1, and the cathode of the first diode D1 is coupled to a first node N1 to output a rectified potential VR. The anode of the second diode D2 is coupled to the second input node NIN2, and the cathode of the second diode D2 is coupled to the first node N1. The anode of the third diode D3 is coupled to a second node N2, and the third two The cathode of the pole body D3 is coupled to the first input node NIN1. The anode of the fourth diode D4 is coupled to the second node N2, and the cathode of the fourth diode D4 is coupled to the second input node NIN2.

The first end of the boost inductor LU is coupled to the first node N1 to receive the rectified potential VR, and the second end of the boost inductor LU is coupled to a third node N3.

The power switch 220 includes a first transistor M1. For example, the first transistor M1 can be an N-type MOSFET. The control terminal of the first transistor M1 is used for receiving a pulse width modulation potential VM, the first terminal of the first transistor M1 is coupled to the ground potential VSS, and the second terminal of the first transistor M1 is is coupled to the third node N3. The PWM potential VM can be used to adjust the duty cycle of the power switch 220 . For example, if the PWM potential VM is at a high logic level, the first transistor M1 will be enabled; on the contrary, if the PWM potential VM is at a low logic level, the first transistor M1 will be enabled M1 will be disabled.

The PWM integrated circuit 230 can generate the PWM potential VM. For example, the PWM potential VM can be maintained at a fixed potential when the boost converter 200 is initialized, and a periodic clock waveform can be provided after the boost converter 200 enters a normal use stage. In addition, the PWM integrated circuit 230 is powered by a supply potential VCC.

The output stage circuit 240 includes a fifth diode D5, a first capacitor C1, a first resistor R1, and a second resistor R2. The anode of the fifth diode D5 is coupled to the third node N3, and the cathode of the fifth diode D5 is coupled to the output Node NOUT. The first capacitor C1 has a first end and a second end, wherein the first end of the first capacitor C1 is coupled to the output node NOUT, and the second end of the first capacitor C1 is coupled to the ground potential VSS. The first end of the first resistor R1 is coupled to the output node NOUT, and the second end of the first resistor R1 is coupled to a fourth node N4. The first end of the second resistor R2 is coupled to the fourth node N4, and the second end of the second resistor R2 is coupled to the ground potential VSS.

The first start-up circuit 250 includes a positive temperature coefficient resistor RPTC, a first inductor L1, a second inductor L2, a sixth diode D6, a third resistor R3, a Zener diode DZ, A second transistor Q2, and a second capacitor C2. The first terminal of the positive temperature coefficient resistor RPTC is coupled to the second node N2, and the second terminal of the positive temperature coefficient resistor RPTC is coupled to the ground potential VSS. When the temperature of the boost converter 200 increases, the resistance value of the positive temperature coefficient resistor RPTC will increase; conversely, when the temperature of the boost converter 200 decreases, the resistance value of the positive temperature coefficient resistor RPTC will increase Small. The first end of the first inductor L1 is coupled to the second node N2, and the second end of the first inductor L1 is coupled to the ground potential VSS. The first end of the second inductor L2 is coupled to a fifth node N5, and the second end of the second inductor L2 is coupled to a sixth node N6. In some embodiments, the fifth node N5 is further coupled to a ground pin of the PWM IC 230 . It must be noted that the first inductor L1 and the second inductor L2 are coupled to each other (eg, the first inductor L1 can be on one side and the second inductor L2 can be on the opposite side).

The anode of the sixth diode D6 is coupled to the fifth node N5, and the cathode of the sixth diode D6 is coupled to a seventh node N7. The first end of the third resistor R3 is coupled to the seventh node N7, and the second end of the third resistor R3 is coupled to the sixth node N6. The anode of the Zener diode DZ is coupled to the fifth node N5, and the cathode of the Zener diode DZ is coupled to an eighth node N8 to selectively output the supply potential VCC to the PWM product Body circuit 230 . For example, the second transistor Q2 may be an NPN type bipolar junction transistor. The control terminal of the second transistor Q2 is coupled to the seventh node N7, the first terminal of the second transistor Q2 is coupled to the eighth node N8, and the second terminal of the second transistor Q2 is coupled to the seventh node N8. Four nodes N4. The second capacitor C2 has a first end and a second end, wherein the first end of the second capacitor C2 is coupled to the fifth node N5, and the second end of the second capacitor C2 is coupled to the eighth node N8 .

The second start-up circuit 260 includes a coupling coil set 262, a seventh diode D7, an eighth diode D8, a third capacitor C3, and a fourth resistor R4. The coupling coil set 262 includes a first coil 263 , a second coil 264 , and a third coil 265 . The first coil 263 has a first end and a second end, wherein the first end of the first coil 263 is coupled to the first node N1, and the second end of the first coil 263 is coupled to the third node N3 . The first end of the second coil 264 is coupled to a ninth node N9, and the second end of the second coil 264 is coupled to a tenth node N10. The first end of the third coil 265 is coupled to the tenth node N10, and the second end of the third coil 265 is coupled to the eleventh node N11. It must be noted that the first coil 263, the second coil 264, and the third coil 265 are coupled to each other (eg, the second coil 264 and the third coil 265 can be on the same side, while the first coil 263 can be on the opposite side side).

The anode of the seventh diode D7 is coupled to the fifth node N5, and the cathode of the seventh diode D7 is coupled to the ninth node N9. Anode coupling of the eighth diode D8 Connected to the fifth node N5, and the cathode of the eighth diode D8 is coupled to the eleventh node N11. The first end of the third capacitor C3 is coupled to the tenth node N10, and the second end of the third capacitor C3 is coupled to a twelfth node N12. The first end of the fourth resistor R4 is coupled to the twelfth node N12, and the second end of the fourth resistor R4 is coupled to the eighth node N8 to selectively output the supply potential VCC to the PWM Variable integrated circuit 230 . That is, the first start-up circuit 250 or the second start-up circuit 260 can alternatively generate the aforementioned supply potential VCC.

In some embodiments, the boost converter 200 may operate in a first stage, a second stage, a third stage, and a fourth stage in sequence, and the operation principle may be described below.

During the first phase, the boost converter 200 begins to receive the first input potential VIN1 and the second input potential VIN2. At this time, the input energy is transferred to the first capacitor C1 via the boost inductor LU and the fifth diode D5, so that the output potential VOUT gradually rises. It must be noted that the positive temperature coefficient resistor RPTC, the first inductor L1, and the first capacitor C1 can together form an RLC damping circuit, which can fine-tune the output potential VOUT and effectively eliminate the startup of the boost converter 200. overshoot.

During the second phase (ie, the aforementioned cooling mode), since the first inductor L1 and the second inductor L2 are coupled to each other, the energy stored in the first inductor L1 is transferred to the second inductor L2, Thus, the potential at the seventh node N7 is pulled up. At this time, the second transistor Q2 is enabled, and the reverse collapse of the Zener diode DZ occurs. Therefore, the Zener diode DZ can provide a stable supply potential VCC to the PWM integrated circuit 230, wherein the second capacitor C2 can filter out high frequency noise in the supply potential VCC. exist After the PWM IC 230 is powered by the supply potential VCC, it can operate the power switch 220 and the boost inductor LU at a high frequency, and the output potential VOUT will gradually approach a constant value (for example: 400V ).

During the third stage, the temperature of the boost converter 200 has risen to a critical value (eg, 85 degrees Celsius), and the resistance value of the positive temperature coefficient resistor RPTC will become so large that it can almost be regarded as an open circuit. According to the cold order law, the voltage inversion of the first inductor L1 and the second inductor L2 will occur simultaneously to disable the second transistor Q2. At this time, the first start-up circuit 250 stops outputting the supply potential VCC to the PWM integrated circuit 230 . The energy stored in the second inductor L2 is dissipated by the sixth diode D6 and the third resistor R3.

During the fourth stage (ie, the aforementioned warm-up mode), the second start-up circuit 260 may then replace the first start-up circuit 250 to output the supply potential VCC to the PWM integrated circuit 230 . Regardless of whether the boosting inductor LU is in the energy storage state or the energy releasing state, either the seventh transistor D7 or the eighth transistor D8 can be selected for transferring the energy of the boosting inductor LU. In addition, the third capacitor C3 and the fourth resistor R4 can form a delay protection circuit to prevent the second coil 264 and the third coil 265 from being accidentally short-circuited and burned.

FIG. 3 is a waveform diagram showing the output potential VOUT of the conventional boost converter, wherein the horizontal axis represents time and the vertical axis represents the potential level. According to the measurement results in Fig. 3, conventional boost converters usually face the problem of start-up overshoot (ie, the initial oscillation waveform of the output potential VOUT), which tends to reduce the lifetime of the entire circuit.

FIG. 4 is a waveform diagram showing the output potential VOUT of the boost converter 200 according to an embodiment of the present invention, wherein the horizontal axis represents time, and the vertical axis represents time table potential level. According to the measurement results in FIG. 4 , by using the first start-up circuit 250 and the second start-up circuit 260 , the boost converter 200 of the present invention can almost completely eliminate the non-ideal start-up overshoot, so that the boost voltage can be greatly increased Reliability and service life of converter 200 .

In some embodiments, the component parameters of the boost converter 200 may be as follows. The capacitance value of the first capacitor C1 can be between 1200 μF and 1800 μF, preferably 1500 μF. The capacitance value of the second capacitor C2 may be between 90nF and 110nF, preferably 100nF. The capacitance value of the third capacitor C3 may be between 80nF and 120nF, preferably 100nF. The inductance value of the boost inductor LU can be between 240 μH and 360 μH, preferably 300 μH. The inductance value of the first inductor L1 may be between 0.9 μH and 1.1 μH, preferably 1 μH. The inductance value of the second inductor L2 can be between 10 μH and 15 μH, preferably 12.5 μH. The resistance value of the first resistor R1 may be between 65.45KΩ and 88.55KΩ, preferably 77KΩ. The resistance value of the second resistor R2 can be between 2.55KΩ and 3.45KΩ, preferably 3KΩ. The resistance value of the third resistor R3 can be between 0.85KΩ and 1.15KΩ, preferably 1KΩ. The resistance value of the fourth resistor R4 may be between 0.85KΩ and 1.15KΩ, preferably 1KΩ. When the temperature of the boost converter 200 is 25 degrees Celsius, the resistance value of the positive temperature coefficient resistor RPTC may be about 100KΩ. When the temperature of the boost converter 200 is 85 degrees Celsius, the resistance value of the positive temperature coefficient resistor RPTC may be about 10 MΩ. The turns ratio of the first coil 263 to the second coil 264 may be between 1 and 10, preferably about 4.5. The turns ratio of the first coil 263 to the third coil 265 may be between 1 and 10, preferably about 4.5. The reverse breakdown voltage of the Zener diode DZ may be about 20V. The above parameter ranges are based on multiple experimental results and help maximize the boost converter 200 reliability and service life.

The present invention provides a novel boost converter, which simultaneously includes a first start-up circuit and a second start-up circuit to respectively provide power to the PWM integrated circuit. According to the actual measurement results, using the boost converter of the above design can almost completely eliminate the non-ideal start-up overshoot, so it is very suitable for use in various devices.

It should be noted that the potential, current, resistance value, inductance value, capacitance value and other component parameters mentioned above are not limitations of the present invention. Designers can adjust these settings according to different needs. The boost converter of the present invention is not limited to the states illustrated in FIGS. 1-4. The present invention may include only any one or more features of any one or more of the embodiments of Figures 1-4. In other words, not all of the features shown must be simultaneously implemented in the boost converter of the present invention.

Although the present invention is disclosed above with preferred embodiments, it is not intended to limit the scope of the present invention. Anyone skilled in the art can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, The protection scope of the present invention shall be determined by the scope of the appended patent application.

100: Boost Converter

110: Bridge Rectifier

120: Power switch

130: Pulse width modulation integrated circuit

140: Output stage circuit

150: First start circuit

160: Second start circuit

162: Coupling coil set

LU: boost inductor

RPTC: Positive Temperature Coefficient Resistor

VCC: Supply potential

VIN1: the first input potential

VIN2: The second input potential

VM: PWM potential

VOUT: output potential

VR: rectifier potential

VSS: ground potential

Claims (10)

A boost converter for eliminating startup overshoot, comprising: a bridge rectifier for generating a rectified potential according to a first input potential and a second input potential; a boost inductor for receiving the rectified potential; a power switch , selectively coupling the boost inductor to a ground potential according to a pulse width modulation potential; a pulse width modulation integrated circuit generates the pulse width modulation potential, wherein the pulse width modulation potential is The wave width modulation integrated circuit is powered by a supply potential; an output stage circuit is coupled to the boost inductor and generates an output potential; a first start-up circuit is coupled to the output stage circuit, The first start-up circuit includes a positive temperature coefficient resistor; and a second start-up circuit is coupled to the boost inductor, wherein the second start-up circuit includes a coupling coil set. The boost converter of claim 1, wherein the bridge rectifier comprises: a first diode having an anode and a cathode, wherein the anode of the first diode is coupled to a first diode an input node to receive the first input potential, and the cathode of the first diode is coupled to a first node to output the rectified potential; a second diode has an anode and a cathode, wherein the The anode of the second diode is coupled to a second input node to receive the second input potential, and the cathode of the second diode is coupled to the first node; a third diode having an anode and a cathode, wherein the anode of the third diode is coupled to a second node, and the cathode of the third diode is coupled to the first node an input node; and a fourth diode having an anode and a cathode, wherein the anode of the fourth diode is coupled to the second node and the cathode of the fourth diode is coupled to the second input node; wherein the boost inductor has a first end and a second end, the first end of the boost inductor is coupled to the first node to receive the rectified potential, and the boost The second end of the piezoelectric inductor is coupled to a third node. The boost converter of claim 2, wherein the power switch comprises: a first transistor having a control end, a first end, and a second end, wherein the control of the first transistor The terminal is used for receiving the PWM potential, the first terminal of the first transistor is coupled to the ground potential, and the second terminal of the first transistor is coupled to the third node. The boost converter of claim 2, wherein the output stage circuit comprises: a fifth diode having an anode and a cathode, wherein the anode of the fifth diode is coupled to the third diode node, and the cathode of the fifth diode is coupled to an output node to output the output potential; a first capacitor has a first terminal and a second terminal, wherein the first capacitor of the first capacitor The terminal is coupled to the output node, and the second terminal of the first capacitor is coupled connected to the ground potential; a first resistor having a first end and a second end, wherein the first end of the first resistor is coupled to the output node, and the first end of the first resistor The second end is coupled to a fourth node; and a second resistor has a first end and a second end, wherein the first end of the second resistor is coupled to the fourth node, And the second end of the second resistor is coupled to the ground potential. The boost converter of claim 4, wherein the first start-up circuit comprises: a first inductor having a first end and a second end, wherein the first end of the first inductor is coupled connected to the second node, and the second end of the first inductor is coupled to the ground potential; and a second inductor having a first end and a second end, wherein the second inductor the first terminal is coupled to a fifth node, and the second terminal of the second inductor is coupled to a sixth node; wherein the first inductor and the second inductor are coupled to each other; The PTC resistor has a first end and a second end, the first end of the PTC resistor is coupled to the second node, and the second end of the PTC resistor is coupled to the ground potential. The boost converter of claim 5, wherein the first start-up circuit further comprises: a sixth diode having an anode and a cathode, wherein the sixth diode has the The anode is coupled to the fifth node, and the cathode of the sixth diode is coupled to a seventh node; and a third resistor has a first end and a second end, wherein the first The first end of the three resistors is coupled to the seventh node, and the second end of the third resistor is coupled to the sixth node. The boost converter of claim 6, wherein the first startup circuit further comprises: a Zener diode having an anode and a cathode, wherein the anode of the Zener diode is coupled to the first Five nodes, and the cathode of the Zener diode is coupled to an eighth node to selectively output the supply potential; a second transistor having a control terminal, a first terminal, and a second terminal, wherein the control terminal of the second transistor is coupled to the seventh node, the first terminal of the second transistor is coupled to the eighth node, and the second terminal of the second transistor a terminal coupled to the fourth node; and a second capacitor having a first terminal and a second terminal, wherein the first terminal of the second capacitor is coupled to the fifth node, and the second capacitor The second end of the capacitor is coupled to the eighth node. The boost converter of claim 7, wherein the coupling coil set of the second start-up circuit comprises: a first coil having a first end and a second end, wherein the first coil of the first coil an end is coupled to the first node, and the second end of the first coil is coupled to the third node; A second coil has a first end and a second end, wherein the first end of the second coil is coupled to a ninth node, and the second end of the second coil is coupled to a a tenth node; and a third coil having a first end and a second end, wherein the first end of the third coil is coupled to the tenth node, and the second end of the third coil is coupled to an eleventh node; wherein the first coil, the second coil, and the third coil are coupled to each other. The boost converter of claim 8, wherein the second startup circuit further comprises: a seventh diode having an anode and a cathode, wherein the anode of the seventh diode is coupled to the a fifth node with the cathode of the seventh diode coupled to the ninth node; and an eighth diode with an anode and a cathode, wherein the anode of the eighth diode is coupled connected to the fifth node, and the cathode of the eighth diode is coupled to the eleventh node. The boost converter of claim 9, wherein the second start-up circuit further comprises: a third capacitor having a first end and a second end, wherein the first end of the third capacitor is coupled to to the tenth node, and the second end of the third capacitor is coupled to a twelfth node; and a fourth resistor having a first end and a second end, wherein the fourth resistor The first terminal of the resistor is coupled to the twelfth node, and the second terminal of the fourth resistor is coupled to the eighth node to selectively output the supply potential.

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