A high voltage starting circuit

Abstract

The application discloses a high-voltage starting circuit, comprising a logic module, a first capacitor C1, a starting module and a load in connection with each other; the starting module comprises an initial starting branch, one end of which is connected with the load and the other end of which is connected with the first end of the first capacitor C1, and the initial starting branch comprises a first MOS tube Q1, a first resistor R1 and a first switch K1; the initial starting branch is configured to be turned on when the voltage of a starting voltage source is greater than a starting threshold voltage, so as to provide an initial charging current for the first capacitor C1; a fast starting branch is connected between a first node A at the output end of the load and the first end of the first capacitor C1, and is configured to be turned on when the voltage of the first capacitor C1 is greater than a fast charging threshold voltage, so as to provide a fast charging current for the first capacitor C1; the initial starting branch and the fast starting branch are connected with the logic module, and the logic module is configured to make the initial starting branch and the fast starting branch both be turned off when the voltage of the first capacitor C1 is greater than an off threshold voltage.

Description

Technical Field

[0001] This application relates to the field of circuit design, and more specifically to a high-voltage starting circuit. Background Technology

[0002] In existing switching power supplies, the control chip is typically powered by a startup resistor placed between the input terminal and the VCC capacitor to ensure that the control chip can start up when the power supply is first powered on. Once the auxiliary winding output is established, the VCC voltage is maintained by the auxiliary winding. However, since the startup resistor is always connected to the high-voltage side, a current path remains continuously during normal system operation, resulting in additional power consumption and hindering energy efficiency.

[0003] To address the aforementioned power consumption issues, some solutions introduce controllable switching devices into the startup path. These devices disconnect the startup path once the VCC voltage reaches a set value, reducing no-load power consumption. However, in these solutions, the startup path often lacks a current control mechanism. Direct connection could lead to excessively rapid charging of the VCC capacitor, causing voltage overshoot or interference. Furthermore, under certain abnormal conditions, the chip enters a protection state, and the startup path reconnects after the VCC voltage drops, causing the system to repeatedly start up, making it difficult to pinpoint the source of the fault. Utility Model Content

[0004] The purpose of this application is to provide a high-voltage starting circuit to solve the problem that the starting branch in the prior art is difficult to effectively limit the starting current under abnormal conditions.

[0005] To achieve the above objectives, this application discloses the following technical solution:

[0006] This application provides a high-voltage starting circuit, including interconnected logic modules, a first capacitor C1, a starting module, and a power supply, wherein the power supply provides a starting voltage source for the starting module;

[0007] The startup module includes:

[0008] An initial startup branch is provided, with one end connected to the power dissipation device and the other end connected to the first terminal of the first capacitor C1. The initial startup branch includes a first MOSFET Q1, a first resistor R1, and a first switch K1. The first resistor R1 is connected between the current input terminal and the control terminal of the first MOSFET Q1, and the control terminal of the first MOSFET Q1 is also grounded through the first switch K1. The initial startup branch is configured to conduct when the voltage of the startup voltage source is greater than the startup threshold voltage, thereby providing an initial charging current to the first capacitor C1.

[0009] A fast-start branch is connected between the first node A of the power consumption output terminal and the first terminal of the first capacitor C1, and is configured to conduct when the voltage of the first capacitor C1 is greater than the fast-charging threshold voltage, so as to provide fast-charging current to the first capacitor C1.

[0010] The initial startup branch and the fast startup branch are both connected to the logic module. The logic module is configured to disconnect both the initial startup branch and the fast startup branch when the voltage of the first capacitor C1 is greater than the turn-off threshold voltage.

[0011] The first capacitor C1 is configured to provide operating voltage to the control chip in the switching power supply.

[0012] Optionally, it also includes a power transistor Q2;

[0013] The power supply is a GAN device, the output terminal of the power supply is connected to the input terminal of the power transistor Q2, and the control terminal of the power supply is connected to the startup module;

[0014] The output terminal of the power transistor Q2 is grounded, and the control terminal receives the signal SW from the logic module.

[0015] Optionally, the initial startup branch further includes a second resistor R2, a third resistor R3, a Zener diode Z, a first diode D1, and a fourth resistor R4;

[0016] In the initial startup branch, the first end of the second resistor R2 is connected to the first node A, and the second end is connected to the first end of the first capacitor C1 in sequence through the third resistor R3, the Zener diode Z, the first MOSFET Q1, the first diode D1 and the fourth resistor R4.

[0017] The second terminal of the first capacitor C1 is grounded.

[0018] Optionally, the fast-start branch includes a second resistor R2, a third switch Q3, a first diode D1, and a fourth resistor R4;

[0019] In the fast-start branch, the first end of the second resistor R2 is connected to the first node A, and the second end is connected to the first end of the first capacitor C1 in sequence through the third switch Q3, the first diode D1 and the fourth resistor R4.

[0020] Optionally, it also includes:

[0021] The current regulation module includes a fourth switch Q4 and a fifth resistor R5;

[0022] The first end of the fifth resistor R5 is connected to the second end of the second resistor R2, and the second end of the fifth resistor R5 is connected to the control terminal of the third switch Q3.

[0023] The current input terminal of the fourth switch Q4 is connected to the first node A, the current output terminal is connected to the second terminal of the fifth resistor R5, and the control terminal is connected between the fifth resistor R5 and the second resistor R2.

[0024] Optionally, the logic module includes a fifth switch Q5, a sixth resistor R6, and a second switch K2;

[0025] The current input terminal of the fifth switch Q5 is connected to the second terminal of the fifth resistor R5, the current output terminal is grounded through the sixth resistor R6, and the control terminal is grounded through the second switch K2.

[0026] Optionally, the logic module further includes:

[0027] The third switch K3 has one end connected to the control terminal of the power supply and the other end grounded.

[0028] The follower AMP has its non-inverting input connected to the first terminal of the first capacitor C1, its inverting input connected to the output terminal of the follower AMP, and its output terminal connected to the control terminal of the fifth switch Q5.

[0029] The comparator CMP has its non-inverting input connected to the first terminal of the first capacitor C1, and its inverting input connected to the first reference voltage Vref via the fourth switch K4. The inverting input of the comparator CMP is also connected to the second reference voltage Uvlo via the fifth switch K5. The output of the comparator CMP is connected to the control terminals of the first switch K1, the second switch K2, the third switch K3, and the fourth switch K4, and is also connected to the control terminal of the fifth switch K5 via a NOT gate.

[0030] Optionally, the fast charging current is greater than the initial charging current.

[0031] Optionally, the start-up threshold voltage is the sum of the regulated voltage of the Zener diode Z and the gate-source turn-on voltage of the first MOSFET Q1;

[0032] The fast charging threshold voltage is the turn-on voltage of the fifth switch Q5;

[0033] The shutdown threshold voltage is the second reference voltage Uvlo.

[0034] The high-voltage startup circuit provided in this application introduces a first MOSFET Q1, a first resistor R1, and a first switch K1 into the initial startup branch. This enables controlled pre-charging of the first capacitor C1 during the initial power-on phase of the switching power supply, reducing the initial inrush current and improving the stability of the startup process. As the voltage of the first capacitor C1 gradually rises to the fast-charging threshold voltage, the fast-start branch is continuously turned on, providing a larger charging current to accelerate the charging process and improve startup efficiency. When the voltage of the first capacitor C1 rises to the turn-off threshold voltage, the logic module automatically cuts off both startup branches to avoid continuous power consumption. The overall structure ensures chip startup reliability while reducing power consumption and improving system safety.

[0035] Furthermore, by introducing a current regulation module and a logic module, combined with depletion-mode devices and multiple discrete components, staged control and dynamic switching of the starting current are achieved, effectively improving the stability and response speed of the starting process. After startup, the system can promptly disconnect the starting branch to reduce power consumption. Simultaneously, by accurately detecting the voltage threshold through comparators and followers, when VCC experiences undervoltage protection, the high-voltage starting circuit can automatically restart, alerting to the abnormality and resuming normal operation after the abnormality is resolved, significantly improving the circuit's safety and reliability. Attached Figure Description

[0036] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this application and, together with the specification, serve to explain the principles of this application.

[0037] Figure 1 A structural block diagram of a high-voltage starting circuit according to an embodiment of this application is shown;

[0038] Figure 2 A high-voltage starting circuit topology diagram according to an embodiment of this application is shown;

[0039] Figure 3 An ideal waveform diagram of VCC voltage according to an embodiment of this application is shown. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0041] It should be noted that references to "an embodiment," "embodiment," "example embodiment," etc., in this specification refer to the described embodiment including specific features, structures, or characteristics; however, not every embodiment must include these specific features, structures, or characteristics. Furthermore, such expressions do not refer to the same embodiment. Moreover, when describing specific features, structures, or characteristics in conjunction with embodiments, whether or not explicitly described, it is indicated that incorporating such features, structures, or characteristics into other embodiments is within the knowledge of those skilled in the art.

[0042] Furthermore, certain terms are used in the specification and subsequent claims to refer to specific components or parts. Those skilled in the art will understand that manufacturers may use different names or terms to refer to the same component or part. This specification and subsequent claims do not distinguish components or parts by differences in name, but rather by differences in function. The terms "comprising" and "including" used throughout the specification and subsequent claims are open-ended and should be interpreted as "including but not limited to." Additionally, the term "connection" here includes any direct and indirect electrical connection means. Indirect electrical connection means include connections made through other means.

[0043] Figure 1 A structural block diagram of a high-voltage starting circuit 100 according to an embodiment of this application is shown. Figure 2 A topology diagram of a high-voltage starting circuit 100 according to an embodiment of this application is shown. Figure 1 and Figure 2 As shown, the high-voltage start-up circuit 100 includes interconnected logic modules 110, a first capacitor C1, a start-up module 120, and a power supply, which provides a start-up voltage source for the start-up module 120. The start-up module 120 includes an initial start-up branch 121 and a fast start-up branch 122.

[0044] One end of the initial startup branch 121 is connected to the power supply, and the other end is connected to the first terminal of the first capacitor C1. The initial startup branch 121 includes a first MOSFET Q1, a first resistor R1, and a first switch K1. The first resistor R1 is connected between the current input terminal and the control terminal of the first MOSFET Q1, and the control terminal of the first MOSFET Q1 is also grounded through the first switch K1. The initial startup branch 121 is configured to conduct when the voltage of the startup voltage source is greater than the startup threshold voltage, thereby providing an initial charging current to the first capacitor C1. The fast startup branch 122 is connected between the first node A of the power supply output terminal and the first terminal of the first capacitor C1, and is configured to conduct when the voltage of the first capacitor C1 is greater than the fast charging threshold voltage, thereby providing a fast charging current to the first capacitor C1. Both the initial startup branch 121 and the fast startup branch 122 are connected to the logic module 110. The logic module 110 is configured to disconnect both the initial startup branch 121 and the fast startup branch 122 when the voltage of the first capacitor C1 is greater than the turn-off threshold voltage.

[0045] In this embodiment, the first capacitor C1 is the VCC power supply capacitor of the control chip in the switching power supply system, which is used to store energy and maintain the power supply voltage. Specifically, the first capacitor C1 is charged by the startup module 120 when the system is initially powered on. When the voltage across its terminals rises to a preset voltage value, the system begins to work normally and obtains continuous power from the auxiliary winding (not shown in the figure). The first capacitor C1 plays a key role in energy buffering and voltage support during this process.

[0046] According to the above embodiment, by introducing a first MOSFET Q1, a first resistor R1, and a first switch K1 into the initial startup branch 121, controlled pre-charging of the first capacitor C1 is achieved in the initial stage of power-on of the switching power supply, reducing the initial inrush current and improving the stability of the startup process. When the voltage of the first capacitor C1 gradually rises to the fast charging threshold voltage, the fast startup branch 122 is continuously turned on, providing a larger charging current to accelerate the charging process and improve startup efficiency. When the voltage of the first capacitor C1 rises to the turn-off threshold voltage, the logic module 110 automatically cuts off the two startup branches to avoid continuous power consumption. The overall structure ensures chip startup reliability while reducing power consumption and improving system safety.

[0047] In one embodiment, the first MOSFET Q1 is an NMOS transistor, and a first resistor R1 is connected in series between its drain and gate. The first resistor R1 is a high-value resistor, and a first switch K1 is connected between its gate and ground. Initially, the first switch K1 is open, and when there is no control voltage on the gate of the first MOSFET Q1 and the gate voltage is about 0.7V higher than the source voltage, the gate and source of the first MOSFET Q1 can be forward-biased as diodes.

[0048] In one embodiment, reference Figure 2 The high-voltage starting circuit 100 is connected to an external transformer 200, which includes a primary winding N1 and a secondary winding N2. The first terminal of the primary winding N1 is connected to the current input terminal of the power dissipation circuit, and the second terminal is connected to the voltage VIN. The high-voltage starting circuit 100 also includes a power transistor Q2. The current input terminal of the power transistor Q2 is connected to the current output terminal of the power dissipation circuit, and the control terminal of the power dissipation circuit is connected to the starting module 120. The output terminal of the power transistor Q2 is grounded, and the control terminal receives the signal SW from the logic module 110.

[0049] In one embodiment, reference Figure 2 The transformer 200 includes a second diode D2 and a second capacitor C2. The first terminal of the secondary winding N2 is grounded via the second diode D2 and the second capacitor C2, and the second terminal is also grounded. The output voltage VOUT is across the second capacitor C2.

[0050] According to the above embodiment, the primary winding N1 of transformer 200 is connected to the power dissipation transistor and the input voltage, and is responsible for converting and transmitting the input electrical energy to the secondary winding. The power dissipation transistor and the power transistor Q2 work in coordination through the startup module 120 and the logic module 110 to achieve effective control of the switching power supply and management of switching actions.

[0051] In one embodiment, although the depletion type is a gallium nitride (GaN) transistor, in practical applications, other types of depletion type field-effect transistors can be selected according to design requirements, and the specific device type is not limited to this.

[0052] In one embodiment, reference Figure 2 The initial startup branch 121 also includes a second resistor R2, a third resistor R3, a Zener diode Z, a first diode D1, and a fourth resistor R4. In the initial startup branch 121, the first end of the second resistor R2 is connected to the first node A, and the second end is connected to the first end of the first capacitor C1 in sequence through the third resistor R3, the Zener diode Z, the first MOSFET Q1, the first diode D1, and the fourth resistor R4. The second end of the first capacitor C1 is grounded.

[0053] In one embodiment, reference Figure 2 The fast-start branch 122 includes a second resistor R2, a third switch Q3, a first diode D1, and a fourth resistor R4. In the fast-start branch 122, the first end of the second resistor R2 is connected to the first node A, and the second end is connected to the first end of the first capacitor C1 in sequence through the third switch Q3, the first diode D1, and the fourth resistor R4.

[0054] According to the above embodiments, both the initial start-up branch 121 and the fast start-up branch 122 include a second resistor R2, a first diode D1 and a fourth resistor R4, that is, these three are devices shared by the two start-up branches.

[0055] In one embodiment, when the initial startup branch 121 is turned on, it provides an initial charging current to the first capacitor C1, and when the fast startup branch 122 is turned on, it provides a fast charging current to the first capacitor C1, wherein the fast charging current is greater than the initial charging current. This design allows for slow charging with a smaller current in the early stages of circuit startup, which helps suppress surges and improve the smoothness of the startup process. In the subsequent stages, a larger current is used to accelerate the charging speed, which helps the high-voltage startup circuit 100 quickly enter the normal operating state and improves the overall startup efficiency.

[0056] In one embodiment, reference Figure 2 The high-voltage starting circuit 100 also includes a current regulation module 130. This current regulation module 130 includes a fourth switch Q4 and a fifth resistor R5. The first terminal of the fifth resistor R5 is connected to the second terminal of the second resistor R2, and the second terminal of the fifth resistor R5 is connected to the control terminal of the third switch Q3. The current input terminal of the fourth switch Q4 is connected to the first node A, the current output terminal is connected to the second terminal of the fifth resistor R5, and the control terminal is connected between the fifth resistor R5 and the second resistor R2.

[0057] In one embodiment, reference Figure 2 The control chip also includes a seventh resistor R7, one end of which is connected to the control terminal of the power dissipator, and the other end is connected to the first terminal of the first capacitor C1. In this embodiment, during normal operation, the first capacitor C1 provides a stable reference voltage to the gate of the power dissipator, which, together with the seventh resistor R7, forms a certain RC buffer effect, effectively suppressing voltage spikes and interference, and improving the reliability of the power dissipator control process and the overall anti-interference capability of the circuit.

[0058] In one embodiment, reference Figure 2 The logic module 110 includes a fifth switch Q5, a sixth resistor R6, and a second switch K2. The current input terminal of the fifth switch Q5 is connected to the second terminal of the fifth resistor R5, the current output terminal is grounded through the sixth resistor R6, and the control terminal is grounded through the second switch K2.

[0059] In one embodiment, reference Figure 2The logic module 110 also includes a third switch K3, a follower AMP, and a comparator CMP. The third switch K3 has one end connected to the control terminal of the power supply and the other end grounded. The follower AMP has its non-inverting input connected to the first terminal of the first capacitor C1, its inverting input connected to the output terminal of the follower AMP, and its output connected to the control terminal of the fifth switch Q5. The comparator CMP has its non-inverting input connected to the first terminal of the first capacitor C1, its inverting input connected to the first reference voltage Vref via the fourth switch K4, and its inverting input also connected to the second reference voltage Uvlo via the fifth switch K5. The output terminal of the comparator CMP is connected to the control terminals of the first switch K1, the second switch K2, the third switch K3, and the fourth switch K4, and is also connected to the control terminal of the fifth switch K5 via a NOT gate.

[0060] In one embodiment, power transistor Q2 and fifth switch transistor Q5 are NMOS transistors, and third switch transistor Q3 and fourth switch transistor Q4 are PMOS transistors.

[0061] In one embodiment, the aforementioned start-up threshold voltage is the sum of the regulated voltage of Zener diode Z and the voltage difference from the current input terminal to the current output terminal of the first MOSFET Q1 in the on-state, i.e., the sum of the voltage of Zener diode Z and the gate-source on-state voltage of the first MOSFET Q1. The fast-charging threshold voltage is the turn-on voltage of the fifth switch Q5. The turn-off threshold voltage is the second reference voltage Uvlo.

[0062] According to the above embodiments, the working principle of the high-voltage startup circuit 100 provided in this application is as follows: When the switching power supply system is powered on, the depletion-type gallium nitride device (GaN) is in a conducting state because it is a normally conducting device, causing its source voltage to rise, that is, the voltage VA of the first node A begins to rise. When the voltage VA rises to the startup threshold voltage, that is, when it rises to the sum of the voltage regulation value of the Zener diode Z and the gate-source conduction voltage of the first MOSFET Q1, the first switch K1 is opened, the initial startup branch 121 is turned on, and the current flows sequentially through the second resistor R2, the third resistor R3, the Zener diode Z, the first MOSFET Q1, the first diode D1 and the fourth resistor R4, providing a small current to charge the first capacitor C1, and the startup process begins. As the voltage across the first capacitor C1 rises, when the voltage across C1 (i.e., VCC voltage) reaches the turn-on threshold of the fifth switch Q5, the follower AMP turns on the fifth switch Q5, thereby pulling down the gate voltage of the third switch Q3. Since the source potential of the third switch Q3 is close to VA, the third switch Q3 turns on. At this time, the fast-start branch 122 starts and forms a loop. Current flows through the second resistor R2, the third switch Q3, the first diode D1, and the fourth resistor R4 to charge the first capacitor C1. Compared to the initial start-up branch 121, the fast-start branch 122 has a larger current and can quickly increase the VCC voltage. At the same time, because the third switch Q3 turns on, it pulls down the voltage at one end of the third resistor R3, causing the initial start-up branch 121 to be short-circuited and thus disconnected. The start-up module 120 only retains the fast-start branch 122 to continuously charge C1. As the VCC voltage rises further, the gate-source voltage difference of the fifth switch Q5 gradually increases, enhancing its conduction capability. The current Iq5 flowing through the fifth switch Q5 rises rapidly, leading to an increase in the current Ir5 across the fifth resistor R5. This results in a larger gate-source voltage difference for the third switch Q3, enhancing its conduction capability. Simultaneously, the current Ir2 further increases, increasing the voltage difference across the second resistor R2, thus increasing the gate-source voltage difference for the fourth switch Q4. When the gate-source voltage difference of the fourth switch Q4 exceeds its turn-on threshold, Q4 begins to conduct, and its drain-source current Iq4 increases. Since current Iq5 equals the sum of current Iq4 and current Ir5, the increase in current Iq4 conversely suppresses current Ir5, reducing the gate-source voltage difference of the third switch Q3, weakening its conduction capability, and correspondingly decreasing current I2. Thus, a closed-loop negative feedback regulation mechanism is formed between the fifth switch Q5, the third switch Q3, the fourth switch Q4, the second resistor R2, and the fifth resistor R5, which dynamically stabilizes the charging current of the fast start-up branch 122 and avoids current overshoot and VCC voltage oscillation.

[0063] During this process, the comparator CMP initially outputs a low level. After being inverted by the NOT gate, it drives switch K5 to conduct, allowing the undervoltage protection voltage (UVLO) of VCC to be connected to the inverting input of the comparator CMP. As the first capacitor C1 (i.e., the VCC capacitor) continues to charge, the VCC voltage gradually rises. When the VCC voltage exceeds the turn-off threshold voltage UVLO, the comparator CMP output signal S1 flips from low to high, causing switches K1, K2, K3, and K4 to close. Specifically, switch K2 pulls the gate of the fifth switch Q5 low, turning it off and cutting off the fast-start branch 122; switch K1 turns off the first MOSFET Q1, thereby shutting down the initial startup branch 121. At this point, both the initial startup branch 121 and the fast-start branch 122 are completely disconnected, the VCC startup charging process is complete, and the system enters the normal operation phase.

[0064] When switch K4 is closed, the low-voltage reference voltage Vref is connected to the inverting input of comparator CMP. The voltage value of Vref is much lower than the VCC undervoltage protection threshold UVLO, used to set the restart voltage of startup module 120. At this time, the voltage at the inverting input of comparator CMP is significantly lower than the VCC voltage at the non-inverting input, therefore the output of comparator CMP remains at a high level, and the system maintains normal operation. Simultaneously, the closing of switch K3 pulls the gate of the GaN power supply to ground, ensuring that its gate voltage is not affected by VCC voltage fluctuations. The switching power supply chip enters normal operating mode and begins outputting signal SW to drive the power transistor Q2 to turn on and off. Since the GaN power supply is connected in series with the power transistor Q2, signal SW can synchronously control the conduction state of the GaN power supply, thereby achieving effective switching of the main power circuit. When power transistor Q2 is turned on, the voltage VA at the first node A is quickly pulled down to near ground potential. At this time, the first diode D1 plays a protective role, blocking the current path of VCC to ground through the fourth resistor R4, the first diode D1, the third resistor R3, the second resistor R2, and the second diode Q2, thus preventing the voltage of the first capacitor C1 from being discharged.

[0065] After the switching power supply starts up, the first capacitor C1 (i.e., the VCC capacitor) no longer relies on the startup branch for power supply. Instead, it is maintained by the auxiliary winding of transformer 200 (not shown in the figure) or other steady-state power supply paths to ensure the continuous stability of the VCC voltage. If an abnormality occurs during system operation, such as output overvoltage, overcurrent, or load short circuit, the logic module 110 will enter a protection state, stop outputting the signal SW, and the auxiliary coil will stop supplying power. At this time, the VCC voltage will gradually decrease. When the VCC voltage drops below the reference voltage Vref, the output signal S1 of comparator CMP flips to a low level, switches K1 and K2 open, and the initial startup branch 121 and the fast startup branch 122 are connected in sequence to recharge the first capacitor C1, and the startup process is re-executed. Through this mechanism, the high-voltage startup circuit 100 can automatically restart under abnormal conditions, reminding the user to troubleshoot and resolve the fault. After the abnormality is eliminated, the system can return to normal operation. This design significantly enhances the system's fault tolerance and operational safety, avoiding problems such as power lock-up or continuous power loss due to abnormalities.

[0066] According to the above embodiments, by introducing a current regulation module 130 and a logic module 110, combined with a transformer 200, depletion-type devices, and multiple discrete components, staged control and dynamic switching of the starting current are achieved, effectively improving the stability and response speed of the starting process. After startup, the system can promptly disconnect the starting branch to reduce power consumption. Simultaneously, by accurately detecting the voltage threshold through comparators and followers, when VCC experiences undervoltage protection, the high-voltage starting circuit 100 can automatically restart, alerting to the abnormality and resuming normal operation after the abnormality is resolved, significantly improving the circuit's safety and reliability.

[0067] The technical solution of this application will be further described below with reference to specific embodiments.

[0068] In one specific embodiment, the pinch-off voltage of the GaN device is set to 20V. Key device parameters include: R2 = 3kΩ, R5 = 100kΩ, R3 = 130kΩ, R4 = 1kΩ, R6 = 100kΩ, R1 = 4MΩ, the Zener diode Z has a regulated voltage of 5V, the turn-on voltage of the fifth switch Q5 and the first MOSFET Q1 are both 0.7V, the VCC capacitor C1 has a capacitance of 4.7μF, the UVLO undervoltage lockout threshold is 15V, the Vref reference voltage is 0.5V, and the normal operating voltage range of VCC is 9V to 19V. After the system is powered on, the voltage at the source VA of the GaN device gradually increases from 0V. When the voltage VA rises to approximately 5.7V (i.e., 5V + 0.7V) or higher, the initial startup branch 121 is activated, and a small current I1 begins to charge the VCC capacitor C1. The current can be approximated as I1≈(VA-5-0.7-VCC)÷(R2+R3+R4)≈100μA. As the voltage VA continues to rise, the current I1 increases synchronously, the voltage across capacitor C1 (VCC) gradually increases, and VCC rises accordingly.

[0069] At this point, the comparator CMP initially outputs a low level, and switches K1, K2, K3, and K4 are all in the off state. The follower AMP applies the VCC voltage to the gate of the fifth switch Q5. When VCC exceeds the turn-on voltage of the fifth switch Q5 by 0.7V, the fifth switch Q5 turns on, forming a current Iq5, approximately Iq5 = VA ÷ (R2 + R5 + R6). The current Iq5 forms a voltage across the fifth resistor R5, which in turn drives the third switch Q3 to turn on, connecting the fast-start branch 122. At this time, the VCC capacitor C1 is charged with a large current I2, which is much larger than I1, increasing the charging speed. Meanwhile, the initial start-up branch 121 is short-circuited and automatically shuts down due to the conduction of the third switch Q3. To avoid excessive charging current in the fast-start branch 122, the system constructs a dynamic negative feedback mechanism through the fifth switch Q5, the third switch Q3, the fourth switch Q4, the second resistor R2, and the fifth resistor R5 to limit and regulate I2, ensuring a stable and reliable VCC charging process.

[0070] As the VCC voltage continues to rise, when it exceeds the UVLO threshold (15V), the comparator CMP output signal S1 flips to a high level, and switches K1, K2, K3, and K4 close successively, ending the startup process. Switch K2 closes, pulling down the gate of the fifth switch Q5, turning Q5 off and cutting off the fast startup branch 122; switch K1 closes, pulling down the gate of the first MOSFET Q1, turning Q1 off and simultaneously interrupting the initial startup branch 121; switch K3 closes, clamping the GaN gate to ground potential to ensure it is not affected by VCC fluctuations during subsequent operation; switch K4 closes, connecting the low-voltage reference Vref (0.5V) to the CMP inverting input. Since it is much lower than the UVLO voltage, the CMP output will remain high, ensuring stable system operation.

[0071] After startup, logic module 110 enters normal operating mode, outputting signal SW to drive power transistor Q2 to turn on and off, indirectly controlling the conduction of the series-connected GaN devices. When signal SW is high, power transistor Q2 is on, primary winding N1 stores energy, and the voltage VA at the first node A is pulled down to near 0V, with no current flowing through the first resistor R1. When signal SW is low, power transistor Q2 is off, the voltage VA at the first node A rises to 20V, and the current in the first resistor R1 is approximately IR1 = (20-5) ÷ (R3 + R2 + R1) ≈ 3.6μA, which is extremely small and negligible. Afterward, the VCC voltage no longer depends on the startup branch but is continuously maintained by the auxiliary winding or other power supply methods, ensuring stable operation of the power supply chip.

[0072] If an abnormality occurs during system operation (such as overvoltage, undervoltage, short circuit, etc.), logic module 110 enters protection mode, stops outputting signal SW, and VCC capacitor C1 is no longer powered. Its voltage is continuously consumed by the internal circuit, causing VCC to drop. When VCC drops below Vref (0.5V), the comparator CMP output flips to a low level, reconnecting the start-up branch to replenish voltage to VCC. At this time, the high-voltage start-up circuit 100 performs a restart function, prompting the user to troubleshoot the system abnormality. After the fault is cleared, the system can automatically resume normal operation, ensuring the overall reliability and safety of operation.

[0073] Figure 3 An ideal waveform diagram of the VCC voltage according to an embodiment of this application is shown. Figure 3 As shown, the initial startup period is from 0 to t1. During the initial startup period, the VCC capacitor C1 is slowly charged by the initial startup branch 121, and the VCC rises slowly. The rapid startup period is from t1 to t2. The rapid startup branch 122 is connected, and the VCC rises rapidly. After t2, the auxiliary winding maintains the VCC stability. If the system malfunctions at t3, the VCC begins to drop. At t4, the VCC drops below Vref, the startup branch is reactivated, and the system automatically restarts and replenishes power, completing the abnormal response closed loop.

[0074] The above parameter configurations can be flexibly adjusted according to specific application requirements to adapt to different startup speeds, charging current characteristics, and system reliability requirements.

[0075] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0076] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A high voltage start circuit, characterized by It includes interconnected logic modules, a first capacitor C1, a startup module, and a power supply, wherein the power supply provides a startup voltage source for the startup module; The startup module includes: An initial startup branch is provided, with one end connected to the power dissipation device and the other end connected to the first terminal of the first capacitor C1. The initial startup branch includes a first MOSFET Q1, a first resistor R1, and a first switch K1. The first resistor R1 is connected between the current input terminal and the control terminal of the first MOSFET Q1, and the control terminal of the first MOSFET Q1 is also grounded through the first switch K1. The initial startup branch is configured to conduct when the voltage of the startup voltage source is greater than the startup threshold voltage, thereby providing an initial charging current to the first capacitor C1. A fast-start branch is connected between the first node A of the power consumption output terminal and the first terminal of the first capacitor C1, and is configured to conduct when the voltage of the first capacitor C1 is greater than the fast-charging threshold voltage, so as to provide fast-charging current to the first capacitor C1. The initial startup branch and the fast startup branch are both connected to the logic module. The logic module is configured to disconnect both the initial startup branch and the fast startup branch when the voltage of the first capacitor C1 is greater than the turn-off threshold voltage. The first capacitor C1 is configured to provide operating voltage to the control chip in the switching power supply.

2. The high-voltage starting circuit according to claim 1, characterized in that, It also includes power transistor Q2; The power supply is a GAN device, the output terminal of the power supply is connected to the input terminal of the power transistor Q2 and serves as the first node A, and the control terminal of the power supply is connected to the startup module; The output terminal of the power transistor Q2 is grounded, and the control terminal receives the signal SW from the logic module.

3. The high-voltage starting circuit according to claim 2, characterized in that, The initial startup branch also includes a second resistor R2, a third resistor R3, a Zener diode Z, a first diode D1, and a fourth resistor R4; In the initial startup branch, the first end of the second resistor R2 is connected to the first node A, and the second end is connected to the first end of the first capacitor C1 in sequence through the third resistor R3, the Zener diode Z, the first MOSFET Q1, the first diode D1 and the fourth resistor R4. The second terminal of the first capacitor C1 is grounded.

4. The high-voltage starting circuit according to claim 3, characterized in that, The fast-start branch includes a second resistor R2, a third switch Q3, a first diode D1, and a fourth resistor R4; In the fast-start branch, the first end of the second resistor R2 is connected to the first node A, and the second end is connected to the first end of the first capacitor C1 in sequence through the third switch Q3, the first diode D1 and the fourth resistor R4.

5. The high-voltage starting circuit according to claim 4, characterized in that, Also includes: The current regulation module includes a fourth switch Q4 and a fifth resistor R5; The first end of the fifth resistor R5 is connected to the second end of the second resistor R2, and the second end of the fifth resistor R5 is connected to the control terminal of the third switch Q3. The current input terminal of the fourth switch Q4 is connected to the first node A, the current output terminal is connected to the second terminal of the fifth resistor R5, and the control terminal is connected between the fifth resistor R5 and the second resistor R2.

6. The high-voltage starting circuit according to claim 5, characterized in that, The logic module includes a fifth switch Q5, a sixth resistor R6, and a second switch K2; The current input terminal of the fifth switch Q5 is connected to the second terminal of the fifth resistor R5, the current output terminal is grounded through the sixth resistor R6, and the control terminal is grounded through the second switch K2.

7. The high-voltage starting circuit according to claim 6, characterized in that, The logic module also includes: The third switch K3 has one end connected to the control terminal of the power supply and the other end grounded. The follower AMP has its non-inverting input connected to the first terminal of the first capacitor C1, its inverting input connected to the output terminal of the follower AMP, and its output terminal connected to the control terminal of the fifth switch Q5. The comparator CMP has its non-inverting input connected to the first terminal of the first capacitor C1, and its inverting input connected to the first reference voltage Vref via the fourth switch K4. The inverting input of the comparator CMP is also connected to the second reference voltage Uvlo via the fifth switch K5. The output of the comparator CMP is connected to the control terminals of the first switch K1, the second switch K2, the third switch K3, and the fourth switch K4, and is also connected to the control terminal of the fifth switch K5 via a NOT gate.

8. The high-voltage starting circuit according to claim 1, characterized in that, The fast charging current is greater than the initial charging current.

9. The high-voltage starting circuit according to claim 7, characterized in that, The start-up threshold voltage is the sum of the Zener voltage of the Zener diode Z and the gate-source turn-on voltage of the first MOSFET Q1; The fast charging threshold voltage is the turn-on voltage of the fifth switch Q5; The shutdown threshold voltage is the second reference voltage Uvlo.

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