DC converter circuit

Abstract

The utility model discloses a DC converter circuit, and the DC converter circuit comprises a first switching tube which is used for controlling a primary winding of the DC converter circuit; the auxiliary circuit provides power supply voltage; the starting circuit receives the power supply voltage and the starting signal and provides starting voltage according to the starting signal; the control circuit is coupled to the starting circuit and provides a driving signal according to the starting voltage; at the first moment, the starting circuit receives a starting signal and provides starting voltage to the control circuit under the control of the starting signal, the control circuit outputs a driving signal to control the first switching tube after receiving the starting voltage, so that the first switching tube is conducted, the primary winding is electrified, and the auxiliary circuit outputs power supply voltage to the starting circuit; at the second moment, the starting signal disappears, the starting circuit provides the starting voltage to the first input end of the control circuit, and the second moment is after the first moment. Through the starting circuit, quick starting and stable power supply of the converter circuit with low power consumption and high performance are realized.

Description

Technical Field

[0001] This application relates to the field of DC-DC converter circuit technology, and more particularly to a DC-DC converter circuit. Background Technology

[0002] In traditional vehicle-mounted DC-DC converter designs, the auxiliary power source is drawn from the battery (KL30) on the low-voltage output side, such as... Figure 1 As shown, after receiving the power-on enable signal EN from the vehicle control unit, the auxiliary power source starts working, supplying power to the DC-DC converter's control unit and MCU. When the DC-DC converter receives the work command Communication from the vehicle control unit, it starts working, outputting power to the low-voltage battery and simultaneously powering its own auxiliary power source. However, in this traditional vehicle DC-DC converter design, starting the auxiliary power source requires a low-voltage battery with the battery voltage within its normal operating range. If the low-voltage battery experiences undervoltage, poor connection, short circuit, or other faults, the auxiliary power source will not start normally, and similarly, the DC-DC converter will not be able to report fault information to the vehicle's main unit. Utility Model Content

[0003] The technical objective of this application is to provide a DC-DC converter circuit to solve the problem that the auxiliary source cannot start working properly, thus affecting the performance of the DC-DC converter circuit.

[0004] To achieve the above technical objectives, this application adopts the following technical solution.

[0005] According to a first aspect of the present application, the embodiments of the present application provide a direct current converter circuit, comprising: a first high-voltage input end configured to receive a positive high voltage; a second high-voltage input end configured to receive a negative high voltage; an output voltage end configured to provide an output voltage; a first primary winding having a first end and a second end, wherein the first end is coupled to the first high-voltage input end; a second primary winding having a first end and a second end, wherein the second end is coupled to a reference ground; a first secondary winding having a first end and a second end, wherein the first end is coupled to the output voltage end and the second end is coupled to the reference ground; a first switch tube having a first end coupled to the second end of the first primary winding, a second end coupled to the reference ground, and a third end configured to receive a driving signal, the first switch tube being turned on or turned off under the control of the driving signal; an auxiliary circuit having an input end and an output end, wherein the input end is coupled to the first end of the second primary winding and the output end is configured to provide a supply voltage; a starting circuit having a first input end, a second input end, a control end, and an output end, wherein the first input end is coupled to the first high-voltage input end, the second input end is coupled to the output end of the auxiliary circuit to receive the supply voltage, the control end is configured to receive a starting signal, and the output end is configured to provide a starting voltage; and a control circuit having a first input end VCC and an output end DR, wherein the first input end is coupled to the output end of the starting circuit and the output end is configured to provide the driving signal; at a first time, the starting circuit receives the starting signal and provides the starting voltage to the first input end of the control circuit based on the positive high voltage under the control of the starting signal, the control circuit is configured to output the driving signal to control the first switch tube after receiving the starting voltage, so that the first switch tube is turned on, the first primary winding is powered on, the first secondary winding generates electricity by induction, the second primary winding generates electricity by induction, and the auxiliary circuit outputs the supply voltage to the starting circuit; at a second time, the starting signal disappears, and the starting circuit provides the starting voltage to the first input end of the control circuit based on the supply voltage, wherein the second time is after the first time.

[0006] Through one of the above-mentioned embodiments or multiple embodiments of the present application, at least the following technical effects can be achieved: In the embodiments of the present application, the starting circuit is configured to receive the starting signal and provide the starting voltage to the control circuit under the control of the starting signal, so that the primary winding of the direct current converter can be started based on the starting signal, the static current between the first high-voltage input end and the voltage end of the control circuit is avoided, the overall power consumption of the system is reduced, and the stability of the power supply to the primary control circuit is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0007] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0008] Figure 1 A structure diagram of a DC converter circuit is given;

[0009] Figure 2 A structure diagram of a DC converter circuit according to an embodiment of the present application is given;

[0010] Figure 3 A structure diagram of a DC converter circuit according to an embodiment of the present application is given;

[0011] Figure 4 A structure diagram of a DC converter circuit according to an embodiment of the present application is given;

[0012] Figure 5 A structure diagram of a start-up circuit according to an embodiment of the present application is given. DETAILED DESCRIPTION

[0013] The technical solutions in the embodiments of the present application will be clearly and completely described in connection with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0014] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms “connected”, “connected” should be understood in a broad sense, for example, can be fixedly connected, can be detachably connected, or integrally connected; can be mechanically connected, or electrically connected or can communicate with each other; can be directly connected, or indirectly connected through an intermediate medium, can be the internal connection of two elements or the interaction relationship between two elements. For a person of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. In the description of the present application, the meaning of “multiple” is two or more than two, unless otherwise explicitly specified and limited. In addition, the terms “first”, “second” are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by “first”, “second” can explicitly or implicitly include one or more features.

[0015] Figure 1 A structure diagram of a DC converter circuit is given. In the traditional design scheme of the vehicle-mounted DC converter, the power of the auxiliary source comes from the battery KL30 on the low-voltage side of the output, such as Figure 1As shown, after the auxiliary source receives the start-up enable signal of the vehicle-mounted control unit, the auxiliary source starts to work, and supplies power to the control unit and MCU of the DC converter. When the DC converter receives the working instruction of the vehicle-mounted control unit, the DC converter starts to work, and outputs to the low-voltage battery and simultaneously supplies power to the auxiliary source of the DC converter. However, if the auxiliary source of the DC converter is to be started, the prerequisite is that the low-voltage battery supplies power, and the battery voltage is within the normal working voltage range. If the low-voltage battery has faults such as under-voltage, poor connection, and short circuit, the auxiliary source of the DC converter cannot work normally, and the DC converter cannot report fault information to the vehicle-mounted host unit.

[0016] Figure 2 The structure schematic diagram of the DC converter circuit according to an embodiment of the present application is given. The auxiliary source takes power from the primary high-voltage input side. After the auxiliary source receives the start-up enable signal EN of the vehicle-mounted control unit, the auxiliary source starts to work, and supplies power to the control unit and MCU of the DC converter. When the DC converter receives the working instruction of the vehicle-mounted control unit, the DC converter starts to work, and outputs to the low-voltage battery, and does not need to supply power to the auxiliary source of the DC converter.

[0017] Figure 3 The circuit structure schematic diagram of the DC converter circuit according to an embodiment of the present application is given. The DC converter circuit includes a first high-voltage input end, a second high-voltage input end, an output voltage end, a first primary winding N1, a second primary winding N3, a first secondary winding N2, a first switch tube Q1, an auxiliary circuit 10, a starting circuit 20, and a control circuit 30.

[0018] The first high-voltage input end receives the positive high voltage HV+, the second high-voltage input end receives the negative high voltage HV-, and the output voltage Vout end provides the output voltage Vout. The first primary winding N1 has a first end and a second end, wherein the first end is coupled to the first high-voltage input end.

[0019] The second primary winding N3 has a first end and a second end, wherein the second end is coupled to a reference ground. The first secondary winding N2 has a first end and a second end, wherein the first end is coupled to an output voltage Vout terminal and the second end is coupled to the reference ground. The first switch Q1 has a first end coupled to the second end of the first primary winding N1, a second end coupled to the reference ground, and a third end receiving a driving signal VDR, wherein the first switch Q1 is turned on or turned off under the control of the driving signal VDR. The auxiliary circuit 10 has an input terminal and an output terminal, wherein the input terminal is coupled to the first end of the second primary winding N3 and the output terminal provides a supply voltage VCC. The start-up circuit 20 has a first input terminal, a second input terminal, a control terminal, and an output terminal, wherein the first input terminal is coupled to the first high voltage input terminal, the second input terminal is coupled to the output terminal of the auxiliary circuit 10 to receive the supply voltage VCC, the control terminal receives a start-up signal DCDC_Wakeup, and the output terminal provides a start-up voltage. The control circuit 30 has a first input terminal and an output terminal DR, wherein the first input terminal VCC is coupled to the output terminal of the start-up circuit 20 and the output terminal DR provides the driving signal VDR.

[0020] At a first time, the start-up circuit 20 receives the start-up signal DCDC_Wakeup and provides a start-up voltage to the first input terminal of the control circuit 30 based on the positive high voltage HV+ under the control of the start-up signal DCDC_Wakeup, wherein the control circuit 30 is configured to output the driving signal VDR to control the first switch Q1 to turn on when the start-up voltage is received, so that the first primary winding N1 is energized, the first secondary winding N2 induces electricity, the second primary winding N3 induces electricity, and the auxiliary circuit 10 outputs the supply voltage VCC to the start-up circuit 20. At a second time, the start-up signal DCDC_Wakeup disappears, and the start-up circuit 20 provides the start-up voltage to the first input terminal of the control circuit 30 based on the supply voltage VCC, wherein the second time is after the first time.

[0021] In the embodiment of the present application, the starting circuit 20 has two power supply voltage sources, the first high-voltage input end and the supply voltage VCC provided by the auxiliary circuit 10, and switching is completed through the starting signal DCDC_Wakeup. At the first moment when the DC converter starts to work, the starting signal DCDC_Wakeup appears, the starting circuit 20 is controlled to provide a starting voltage to the first input end of the control circuit 30 based on the positive high voltage HV+, and the control circuit 30 normally starts after receiving the starting voltage, outputs the drive signal VDR to control the first switch tube Q1 to be turned on. When the first switch tube Q1 is turned on, the loop between the first high-voltage input end, the first primary winding, and the reference ground is turned on, the first primary winding N1 is powered, the first secondary winding N2 generates electricity by induction, and the output end provides the output voltage Vout. The second secondary winding N2 is powered to make the second primary winding N3 generate electricity to supply power to the auxiliary circuit 10, and the output end of the auxiliary circuit 10 outputs the supply voltage VCC to the starting circuit 20. At the second moment, the starting signal DCDC_Wakeup disappears, and the starting circuit 20 is switched from being powered by the first high-voltage input end to being powered by the supply voltage VCC, which provides a starting voltage to the first input end of the control circuit 30. The second moment is after the first moment, and the interval between the second moment and the first moment is determined according to the specific parameters of the circuit.

[0022] When the power supply sources of the first high-voltage input end and the second high-voltage input end are high-voltage battery packs, since the starting signal DCDC_Wakeup is used for starting, when the DC converter circuit is not working, the starting signal DCDC_Wakeup does not exist, and the static current between the first high-voltage input end and the control circuit is almost zero, which does not consume current from the high-voltage battery pack, and has extremely low system power consumption. The starting signal DCDC_Wakeup comes from the vehicle control unit, which is arranged on the secondary side of the circuit, and wakes up the DC converter circuit through the starting circuit 20 from the secondary side of the circuit. Only a starting signal with a very small current / voltage value is needed. After the DC converter circuit is started, the auxiliary circuit 10 provides the supply voltage VCC to the starting circuit, and the starting circuit no longer needs the starting signal to provide the starting voltage to the control circuit 30, forming a self-locking power supply of the DC converter circuit. At this time, the starting signal DCDC_Wakeup no longer exists, reducing the power consumption of the starting signal DCDC_Wakeup.

[0023] In some embodiments, the first switch tube Q1 can adopt a SIC transistor with a withstand voltage of 1700V, which can support a high voltage input of 1000V or above. Compared with a conventional non-SIC transistor, the SIC transistor has a high voltage input performance, and does not need an additional MOS tube or an IC in series with a built-in MOS to improve the withstand voltage of the first switch tube Q1 in the primary side loop of the direct current converter. The series connection of the additional MOS tube causes the phenomenon that the on and off of the MOS are not synchronized, resulting in a decrease in the reliability of the direct current converter circuit. In the present application, the SIC transistor with high voltage is used, and does not need to be connected in series with the additional MOS tube, avoiding the reliability problem caused by the unsynchronized on and off of the multiple MOS tubes in series.

[0024] Figure 4 A circuit structure schematic diagram of a direct current converter circuit according to an embodiment of the present application is given. Figure 5 A circuit structure schematic diagram of a start-up circuit 20 according to an embodiment of the present application is given.

[0025] In Figure 5 In the example shown, the start-up circuit 20 includes a wake-up circuit 21 and a power supply circuit 22, the wake-up circuit 21 includes an input end, an output end and a control end, the input end is coupled to the first high voltage input end to receive the positive high voltage HV+, the output end is coupled to the first input end of the control circuit 30, and the control end receives a start-up signal DCDC_Wakeup. At a first time, the wake-up circuit 21 generates a start-up voltage to the first input end of the control circuit 30 based on the positive high voltage HV+ after receiving the start-up signal DCDC_Wakeup.

[0026] The power supply circuit 22 includes an input end and an output end, the input end receives a power supply voltage VCC, and the output end is coupled to the first output end of the control circuit 30. At a second time, the power supply circuit 22 generates a start-up voltage to the first input end of the control circuit 30 based on the power supply voltage VCC.

[0027] In some embodiments, the wake-up circuit 21 includes at least one switch tube, the at least one switch tube is coupled in series between the input end and the output end of the wake-up circuit 21, and the at least one switch tube is turned on or turned off under the control of the start-up signal DCDC_Wakeup. When the switch tube is turned on, the start-up voltage is the positive high voltage HV+.

[0028] In Figure 5In the shown embodiment, the power supply circuit 22 includes a third diode D3 and a fourth capacitor C4. The positive terminal of the third diode D3 receives the power supply voltage VCC, and the negative terminal is coupled to the first output terminal of the control circuit 30. The first terminal of the fourth capacitor C4 is coupled to the first output terminal of the control circuit 30, and the second terminal is coupled to the reference ground. The wake-up circuit 21 includes a first resistor R1, two photo-transistors in series, a light-emitting diode, and a second resistor R2. The first resistor R1 is coupled between the first high-voltage input terminal and the first input terminal of the control circuit 30, and the light-emitting diode is disposed opposite the photo-transistors. The positive terminal of the light-emitting diode receives the start signal through the second resistor R2, and the negative terminal is coupled to the reference ground. When the start signal appears, the light-emitting diode emits light, the photo-transistors are optically coupled to the light-emitting diode and are turned on, the positive high voltage HV+ charges the fourth capacitor C4 through the first resistor R1 as a current-limiting resistor, and the voltage at the first input terminal of the control circuit 30 gradually rises from 0V. When the working threshold of the start voltage is reached, the start voltage is clamped by the voltage stabilizing circuit inside the control circuit 30 and no longer rises, and the DC converter circuit starts to work. Exemplarily, the working threshold of the start voltage is about 21V.

[0029] In some embodiments, the capacitance of the fourth capacitor C4 ranges from 0.1uF to 4.7uF.

[0030] In Figure 4 In the shown embodiment, the auxiliary circuit 10 includes a fifth diode D5 and a sixth capacitor C6. The fifth diode D5 has a positive terminal coupled to the first end of the second primary winding N3N3 and a negative terminal providing the power supply voltage VCC. The sixth capacitor C6 has a first terminal coupled to the power supply voltage VCC and a second terminal coupled to the reference ground.

[0031] When the second primary winding N3 generates electricity, the first end of the second primary winding N3 charges the sixth capacitor C6 through the fifth diode, and when the sixth capacitor C6 is fully charged, the power supply voltage VCC is output from the first end of the sixth capacitor C6.

[0032] In some embodiments, the capacitance of the sixth capacitor C6 ranges from 1uF to 10uF. The capacitance of the fourth capacitor C4 needs to be smaller than that of the sixth capacitor C6. When the circuit starts, it needs to be quickly charged to start the circuit to work. The first high-voltage input terminal charges the fourth capacitor C4 to quickly provide the start voltage. After the DC converter circuit starts, the second primary winding N3 charges the sixth capacitor C6, and after the charge is stable, the start circuit 20 switches to be powered by the power supply voltage VCC of the auxiliary circuit 10.

[0033] In Figure 4In the embodiment shown, the direct current converter circuit further comprises a shutdown circuit 40, the shutdown circuit 40 has a first end coupled to the first end of the second primary winding N3, and has a control end receiving a shutdown signal, when the shutdown circuit 40 receives the shutdown signal, the shutdown circuit 40 pulls the potential of the first end of the second primary winding N3 to low.

[0034] In Figure 3 In the embodiment shown, the shutdown circuit 40 comprises a ninth resistor R9, a second transistor Q2, a tenth resistor R10, a third transistor Q3 and a twelfth resistor R12, the ninth resistor R9 has a first end and a second end, wherein the first end is coupled to the second end of the second primary winding N3. The second transistor Q2 has a first end, a second end and a third end, wherein the first end is coupled to the second end of the ninth resistor R9, and the second end is coupled to the first end of the ninth resistor R9. The tenth resistor R10 has a first end and a second end, wherein the first end is coupled to the third end of the second transistor Q2. The third transistor Q3 has a first end, a second end and a third end, wherein the first end is coupled to the second end of the tenth resistor R10, the second end is coupled to the reference ground, and the third end is coupled to the second end of the ninth resistor R9. The twelfth resistor R12 has a first end and a second end, wherein the first end is coupled to the second end of the tenth resistor R10, and the second end is coupled to the reference ground.

[0035] The second transistor Q2 and the third transistor Q3 are both crystal triodes, the first end is the base, the second end is the emitter, and the third end is the collector, the second transistor Q2 is a PNP type crystal triode, and the third transistor Q3 is an NPN type crystal triode, the shutdown signal is a logic high level pulse signal, the base of the third transistor Q3 is turned on after receiving the high level, the potential of the collector is pulled low, the collector of the third transistor Q3 is coupled to the base of the second transistor Q2, the potential of the base of the second transistor Q2 is pulled low, the second transistor Q2 is turned on, after the second transistor Q2 is turned on, the tenth resistor R10 and the twelfth resistor R12 are coupled in series at the first end of the second primary winding N3, the voltage division node at the connection of the tenth resistor R10 and the twelfth resistor R12 provides a high level for the third transistor Q3, and the second transistor Q2 and the third transistor Q3 are both self-locked on. Since the voltage drop of the crystal triode is very low when it is turned on, the voltage of the first end of the second primary winding N3 is pulled low. The auxiliary circuit 10 can no longer provide the supply voltage VCC, the control circuit 30 is turned off, and the first switch tube Q1 is no longer driven to open by the drive signal VDR, and the circuit is shut down.

[0036] Through the shutdown circuit 40 composed of the ninth resistor R9, the second transistor Q2, the tenth resistor R10, the third transistor Q3 and the twelfth resistor R12, the auxiliary MCU sends a shutdown signal in the form of a pulse level to the first end of the third transistor Q3 through the digital isolator, realizing the self-locked shutdown function of the direct current converter circuit.

[0037] In Figure 4 In the embodiment shown, the control circuit 30 further comprises a second input terminal, and the DC converter circuit further comprises a feedback circuit 50, the feedback circuit 50 having a first terminal coupled to the first terminal of the second primary winding N3 and a second terminal outputting a feedback signal to the second input terminal of the control circuit 30, the feedback circuit 50 generating the feedback signal according to the voltage of the first terminal of the second primary winding N3.

[0038] In Figure 4 In the embodiment shown, the feedback circuit comprises a seventh resistor R7 and an eighth resistor R8, the first terminal of the seventh resistor R7 being coupled to the first terminal of the second primary winding N3 and the second terminal being coupled to the second input terminal of the control circuit, and the first terminal of the eighth resistor R8 being coupled to the second input terminal of the control circuit and the second terminal being coupled to the reference ground.

[0039] The feedback circuit 50 is coupled to the second primary winding N3 of the circuit primary side, and the loss of the secondary feedback circuit 50 is not considered when the primary feedback is used, so that the feedback circuit 50 is simple and reliable.

[0040] The above is only the preferred embodiment of the present application, it should be noted that for those skilled in the art, without departing from the technical principles of the present application, can make a number of improvements and substitutions, these improvements and substitutions should also be considered as the protection scope of the present application.

Claims

1. A direct current converter circuit, characterized by The direct current converter circuit comprises: a first high-voltage input end configured to receive a positive high voltage; a second high-voltage input end configured to receive a negative high voltage; an output voltage end configured to provide an output voltage; a first primary winding having a first end and a second end, wherein the first end is coupled to the first high-voltage input end; a second primary winding having a first end and a second end, wherein the second end is coupled to a reference ground; a first secondary winding having a first end and a second end, wherein the first end is coupled to the output voltage end and the second end is coupled to the reference ground; a first switch having a first end coupled to the second end of the first primary winding, a second end coupled to the reference ground, and a third end configured to receive a driving signal, the first switch being turned on or turned off under the control of the driving signal; an auxiliary circuit having an input end and an output end, wherein the input end is coupled to the first end of the second primary winding and the output end is configured to provide a supply voltage; a start-up circuit having a first input end, a second input end, a control end, and an output end, wherein the first input end is coupled to the first high-voltage input end, the second input end is coupled to the output end of the auxiliary circuit to receive the supply voltage, the control end is configured to receive a start-up signal, and the output end is configured to provide a start-up voltage; and a control circuit having a first input end and an output end, wherein the first input end is coupled to the output end of the start-up circuit and the output end is configured to provide the driving signal. The start-up circuit comprises a wake-up circuit and a supply circuit, the wake-up circuit comprises an input end, an output end, and a control end, wherein the input end is coupled to the first high-voltage input end to receive the positive high voltage, the output end is coupled to the first input end of the control circuit, and the control end is configured to receive the start-up signal, the wake-up circuit being configured to generate the start-up voltage to the first input end of the control circuit based on the positive high voltage at a first time after receiving the start-up signal; 2. The dc-to-dc converter circuit of claim 1, wherein, the supply circuit comprises an input end and an output end, wherein the input end is configured to receive the supply voltage and the output end is coupled to the first output end of the control circuit, the supply circuit being configured to generate the start-up voltage to the first input end of the control circuit based on the supply voltage at a second time after the first time. The wake-up circuit comprises at least one switch, the at least one switch being coupled in series between the input end and the output end of the wake-up circuit, the at least one switch being turned on or turned off under the control of the start-up signal, and when the switch is turned on, the voltage value of the first input end of the control circuit gradually increases.

3. The dc to dc converter circuit of claim 2, wherein, The supply circuit comprises a third diode and a fourth capacitor, the positive end of the third diode is configured to receive the supply voltage and the negative end is coupled to the first output end of the control circuit, the first end of the fourth capacitor is coupled to the first output end of the control circuit, and the second end is coupled to the reference ground.

4. The dc to dc converter circuit of claim 2, wherein, The capacitance value of the fourth capacitor ranges from 0.1uF to 4.7uF.

5. The dc to dc converter circuit of claim 4, wherein, The direct current converter circuit further comprises:

6. The dc-to-dc converter circuit of claim 1, wherein, a shutdown circuit having an input end coupled to the first end of the second primary winding and a control end configured to receive a shutdown signal, the shutdown circuit being configured to pull down the potential of the first end of the second primary winding when the shutdown signal is received. The shutdown circuit comprises:

7. The dc to dc converter circuit of claim 6, wherein, a ninth resistor having a first end and a second end, wherein the first end is coupled to the second end of the second primary winding. ​ a second transistor having a first terminal, a second terminal and a third terminal, wherein the first terminal is coupled to the second terminal of the ninth resistor, the second terminal is coupled to the first terminal of the ninth resistor; a tenth resistor having a first terminal and a second terminal, wherein the first terminal is coupled to the third terminal of the second transistor; a third transistor having a first terminal, a second terminal and a third terminal, wherein the first terminal is coupled to the second terminal of the tenth resistor, the second terminal is coupled to the reference ground, the third terminal is coupled to the second terminal of the ninth resistor; and a twelfth resistor having a first terminal and a second terminal, wherein the first terminal is coupled to the second terminal of the tenth resistor, the second terminal is coupled to the reference ground.

8. The dc to dc converter circuit of claim 1, wherein, The auxiliary circuit comprises: a fifth diode having a positive terminal coupled to the first terminal of the second primary winding and having a negative terminal providing a supply voltage; a sixth capacitor having a first terminal coupled to the supply voltage and a second terminal coupled to the reference ground.

9. The dc to dc converter circuit of claim 8, wherein, The sixth capacitor has a capacitance ranging from 1uF to 10uF.

10. The dc-to-dc converter circuit of claim 1, wherein, The control circuit further comprises a second input terminal, and the direct current converter circuit further comprises a feedback circuit having a first terminal coupled to the first terminal of the second primary winding and a second terminal outputting a feedback signal, the feedback circuit being configured to generate the feedback signal according to a voltage of the first terminal of the second primary winding.

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