A starting control circuit and a switching power supply system

Abstract

The present invention discloses a startup control circuit and a switching power supply system. The circuit includes: a voltage detection and action unit, a hysteresis compensation and startup control unit, and a linear voltage regulation unit; in the present invention, the charge amount in the startup energy storage capacitor is stored through a high-voltage startup circuit. Even when the voltage at the startup energy storage capacitor terminal reaches the operating voltage threshold of the control chip, the control circuit will not supply power to the chip until the charge amount stored in the startup energy storage capacitor is sufficient to support the energy required at the moment of chip startup. And before the voltage at the startup energy storage capacitor terminal drops to the chip shutdown voltage threshold, the power supply voltage of the auxiliary power supply system can be established, and the auxiliary power supply system continues to supply power to the control chip to make the switching power supply system work normally.

Description

Technical Field

[0001] The present invention relates to the technical field of switching power supplies, and particularly to a startup control circuit and a switching power supply system. Background Art

[0002] Existing switching power supply systems generally include an auxiliary power supply system, a high-voltage startup circuit, a startup energy storage capacitor, and a control chip connected in sequence. The input end of the auxiliary power supply system is connected to the output end of the control chip, and the output end of the auxiliary power supply system is connected to the input end of the control chip; when the system input is established, the high-voltage startup circuit provides short-term power supply for the control chip to enable the switching power supply system to start normally. After the control chip is turned on, it will control the auxiliary power supply system to establish a supply voltage so that the supply voltage established by the auxiliary power supply system can support the stable operation of the control chip. The high-voltage startup circuit has the advantages of simple circuit structure and low cost. In a switching power supply system with a high-voltage startup circuit, no additional flyback power supply is required, effectively improving the overall efficiency of the system.

[0003] However, the startup current that a conventional high-voltage startup circuit can provide is small, and the capacitance of the startup energy storage capacitor cannot be taken too large to meet the startup time requirement. Once the voltage across the startup energy storage capacitor reaches the chip operating threshold voltage, the system control chip starts to work. At this time, the charge stored in the energy storage capacitor will be quickly discharged. Before the supply voltage of the auxiliary power supply system is established, the voltage at the startup energy storage capacitor terminal is lower than the control chip turn-off operating threshold, and the control chip turns off. Therefore, it is difficult for a conventional high-voltage startup circuit to meet the normal operation of a control chip with a large inrush current during startup. The system needs to be restarted multiple times before it can operate stably, indirectly resulting in an increase in the system startup time, and it is difficult to ensure a monotonic increase in the output voltage during startup. Summary of the Invention

[0004] In view of the above problems, the present invention provides a technical solution for a startup control circuit. This solution can store the charge in the startup energy storage capacitor through the high-voltage startup circuit. Even when the voltage at the startup energy storage capacitor terminal reaches the control chip operating voltage threshold, the control circuit will not supply power to the chip until the charge stored in the startup energy storage capacitor is sufficient to support the energy required by the chip during startup. Before the voltage at the startup energy storage capacitor terminal drops to the chip turn-off voltage threshold, the supply voltage of the auxiliary power supply system can be established, and the auxiliary power supply system continues to supply power to the control chip to enable the switching power supply system to operate normally.

[0005] The present invention is achieved through the following technical solutions:

[0006] In a first aspect, a startup control circuit is provided, which is applied to a switching power supply system, wherein the switching power supply system includes a high-voltage startup circuit, a startup energy storage capacitor C0, a control chip, and an auxiliary power supply system; the startup control circuit includes: a voltage detection and action unit, a hysteresis compensation and startup control unit, and a linear voltage stabilization unit;

[0007] The first input end of the voltage detection and action unit is used to be connected to the input end of the high-voltage startup circuit and the positive end of the startup energy storage capacitor C0, the second input end is connected to the first output end of the hysteresis compensation and startup control unit, and the output end is connected to the first input end of the hysteresis compensation and startup control unit;

[0008] The second input end of the hysteresis compensation and startup control unit is used to be connected to the input end of the high-voltage startup circuit and the positive end of the startup energy storage capacitor C0, the third input end is connected to the output end of the linear voltage stabilization unit, and the second output end is used to be connected to the control chip;

[0009] The input end of the linear voltage stabilizing unit is used to connect to the auxiliary power supply system;

[0010] The voltage detection and action unit is used to detect the voltage V at the positive end of the startup energy storage capacitor C0 in real time. CC1 , the voltage V CC1 is compared with the preset start threshold and the voltage V CC1 When it is greater than a preset start-up threshold, a conduction signal is sent to the hysteresis compensation and start-up control unit;

[0011] The hysteresis compensation and startup control unit is used to generate a hysteresis voltage after receiving the conduction signal and transmit it to the voltage detection and action unit, and after charging its own power supply capacitor C5 through the startup energy storage capacitor C0, it supplies power to the control chip to turn on the control chip, so that the power supply voltage V CC2 Establish;

[0012] The voltage detection and action unit is also used to receive the hysteresis voltage and to CC1 is compared with the hysteresis voltage and the voltage V CC1 When the voltage is less than the hysteresis voltage, a shutdown signal is sent to the hysteresis compensation and startup control unit to control the hysteresis compensation and startup control unit to shut down;

[0013] The linear voltage regulator unit is used to provide a power supply voltage V CC2 After the hysteresis compensation and startup control unit are turned off, the supply voltage V CC2 The voltage is stabilized and the power supply capacitor C5 of the hysteresis compensation and startup control unit is charged, so that the power supply capacitor C5 is charged to supply power to the control chip.

[0014] Preferably, the voltage detection and action unit includes: a resistor R1, a resistor R2, a resistor R3, a resistor R6, a precision voltage regulator U1, and a capacitor C2. One end of the resistor R1 serves as the first input end of the voltage detection and action unit, and the other end of the resistor R1 is connected to one end of the resistor R2; after the other end of the resistor R2 is commonly connected to one end of the resistor R3, one end of the capacitor C2, and the first end of the precision voltage regulator U1, it serves as the second input end of the voltage detection and action unit; the second end of the precision voltage regulator U1 is connected to one end of the resistor R6, and the other end of the resistor R6 serves as the output end of the voltage detection and action unit; the other end of the resistor R3, the other end of the capacitor C2, and the third end of the precision voltage regulator U1 are connected to the reference ground.

[0015] Preferably, the hysteresis compensation and start control unit includes: a hysteresis compensation circuit, a main control circuit, a start control circuit, and a power supply capacitor C5; the first end of the hysteresis compensation circuit serves as the first output end of the hysteresis compensation and start control unit and is connected to the second input end of the voltage detection and action unit; the second end of the hysteresis compensation circuit is connected to the third end of the main control circuit and the second end of the start control; the first end of the main control circuit serves as the first input end of the hysteresis compensation and start control unit and is connected to the output end of the voltage detection and action unit; the second end of the main control circuit is connected to the first end of the start control circuit and then serves as the second input end of the hysteresis compensation and start control unit for connecting to the input end of the high-voltage start circuit and the positive end of the start energy storage capacitor C0; the third end of the start control circuit is connected to the positive end of the power supply capacitor C5 and simultaneously serves as the third input end and the second output end of the hysteresis compensation and start control unit, and is connected to the output end of the linear voltage regulator unit and the control chip; the negative end of the power supply capacitor C5 is connected to the reference ground;

[0016] The main control circuit is configured to receive the conduction signal and control the hysteresis compensation circuit to generate a hysteresis voltage and send a start signal to the start control circuit;

[0017] The hysteresis compensation circuit is configured to generate a hysteresis voltage to the voltage detection and action unit;

[0018] The start control circuit is configured to conduct after receiving the start signal, so that the start energy storage capacitor C0 and the power supply capacitor C5 form a path.

[0019] Preferably, the main control circuit includes: a resistor R4, a capacitor C1, and a triode Q1. One end of the resistor R4, one end of the capacitor C1, and the collector of the triode Q1 are commonly connected and used as the second end of the main control circuit. The other end of the resistor R4, the other end of the capacitor C1, and the base of the triode Q1 are commonly connected and used as the first end of the main control circuit. The emitter of the triode Q1 is used as the third end of the main control circuit.

[0020] Preferably, the hysteresis compensation circuit includes: a resistor R5 and a diode VD1. One end of the resistor R5 is used as the first end of the hysteresis compensation circuit. The other end of the resistor R5 is connected to the cathode of the diode VD1, and the anode of the diode VD1 is used as the second end of the hysteresis compensation circuit.

[0021] Preferably, the start control circuit includes: a resistor R7, a resistor R8, a resistor R9, a resistor R 10 , a capacitor C3, a triode Q2, and a triode Q3; One end of the resistor R7 is used as the second end of the start control circuit, and the other end is connected to one end of the resistor R8, one end of the capacitor C3, and the base of the triode Q3; The collector of the triode Q3 is connected to one end of the resistor R 10 ; The other end of the resistor R 10 is connected to one end of the resistor R9 and the base of the triode Q2; After the other end of the resistor R9 is connected to the emitter of the triode Q2, it is used as the first end of the start control circuit; The drain of the triode Q2 is used as the third end of the start control circuit; The other end of the resistor R8, the other end of the capacitor C3, and the emitter of the triode Q3 are connected to the reference ground.

[0022] Preferably, the linear voltage regulator unit includes: a resistor R 11 , a capacitor C4, a voltage regulator diode ZD1, a diode VD2, and a triode Q4; The positive end of the capacitor C4, one end of the resistor R 11 , and the collector of the triode Q4 are commonly connected and used as the input end of the linear voltage regulator unit; The other end of the resistor R 11 is connected to the cathode of the voltage regulator diode ZD1 and the base of the triode Q4. The emitter-collector of the triode Q4 is connected to the anode of the diode VD2, and the cathode of the diode VD2 is used as the output end of the linear voltage regulator unit.

[0023] In a second aspect, a switching power supply system is provided, including a high-voltage start circuit, a start energy storage capacitor C0, a control chip, an auxiliary power supply system, and the start control circuit as described above; The output end of the high-voltage start circuit is connected to the positive end of the start energy storage capacitor C0 and the first input end of the start control circuit. The output end of the start control circuit is connected to the input end of the control chip. The output end of the control chip is connected to the input end of the auxiliary power supply system. The output end of the auxiliary power supply system is connected to the second input end of the start control circuit.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1) Even when the voltage at the terminal of the startup energy storage capacitor reaches the operating voltage threshold of the control chip, the control circuit of the present invention will not supply power to the chip until the charge stored in the startup energy storage capacitor is sufficient to support the energy required at the moment of chip startup. And before the voltage at the terminal of the startup energy storage capacitor drops to the chip shutdown voltage threshold, the power supply voltage of the auxiliary power supply system can be established, and the auxiliary power supply system continues to supply power to the control chip, enabling the switching power supply system to operate normally, improving the startup ability of the high-voltage startup circuit, and preventing the system from restarting repeatedly;

[0026] 2) The circuit structure is simple, and only a few analog devices are needed to achieve startup control, with relatively low cost;

[0027] 3) The preset startup threshold u th1 can be reasonably adjusted, or the energy stored in the startup energy storage capacitor C0 can be adjusted to meet the startup requirements of different systems, increasing the applicable range of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is the schematic diagram of the startup control circuit of the present invention;

[0029] Figure 2 is the working timing diagram of the startup control circuit of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0031] First Embodiment

[0032] Refer to Figure 1 , which is the schematic diagram of the startup control circuit described in this embodiment. In this embodiment, a startup control circuit is provided and applied to a switching power supply system. The switching power supply system includes a high-voltage startup circuit, a startup energy storage capacitor C0, a control chip, and an auxiliary power supply system; the startup control circuit includes: a voltage detection and action unit 100, a hysteresis compensation and startup control unit 200, and a linear voltage regulation unit 300;

[0033] The first input terminal of the voltage detection and action unit 100 is used to be connected to the input terminal of the high-voltage startup circuit and the positive terminal of the startup energy storage capacitor C0, the second input terminal is connected to the first output terminal of the hysteresis compensation and startup control unit 200, and the output terminal is connected to the first input terminal of the hysteresis compensation and startup control unit 200;

[0034] The second input terminal of the hysteresis compensation and startup control unit 200 is used to be connected to the input terminal of the high-voltage startup circuit and the positive terminal of the startup energy storage capacitor C0, the third input terminal is connected to the output terminal of the linear voltage stabilization unit 300, and the second output terminal is used to be connected to the control chip;

[0035] The input end of the linear voltage stabilizing unit 300 is used to connect to the auxiliary power supply system;

[0036] The voltage detection and action unit 100 is used to detect the voltage V at the positive terminal of the startup energy storage capacitor C0 in real time. CC1 , the voltage V CC1 is compared with the preset start threshold and the voltage V CC1 When it is greater than the preset start-up threshold, a conduction signal is sent to the hysteresis compensation and start-up control unit 200;

[0037] The hysteresis compensation and startup control unit 200 is used to generate a hysteresis voltage and transmit it to the voltage detection and action unit 100 after receiving the turn-on signal, and after charging its own power supply capacitor C5 through the startup energy storage capacitor C0, it supplies power to the control chip to turn on the control chip, so that the power supply voltage V CC2 Establish;

[0038] The voltage detection and action unit 100 is also used to receive the hysteresis voltage and to CC1 is compared with the hysteresis voltage and the voltage V CC1 When it is less than the hysteresis voltage, a shutdown signal is sent to the hysteresis compensation and startup control unit 200 to control the hysteresis compensation and startup control unit 200 to shut down;

[0039] The linear voltage regulator unit 300 is used to adjust the supply voltage V CC2 After the hysteresis compensation and startup control unit 200 is turned off, the power supply voltage V CC2 The voltage is stabilized and the power supply capacitor C5 of the hysteresis compensation and startup control unit 200 is charged, so that the power supply capacitor C5 is charged to supply power to the control chip.

[0040] Specifically, when the system input is established, the high-voltage startup circuit works to charge the startup energy storage capacitor C0 first, and the voltage V CC1 The voltage detection and action unit 100 detects the voltage V at the positive terminal of the startup energy storage capacitor C0 in real time. CC1 , when the voltage V CC1 Greater than the start threshold u th1, the voltage detection and action unit 100 sends a conduction signal to the hysteresis compensation and start control unit 200. After the hysteresis compensation and start control unit 200 is turned on, it forms a path between the start energy storage capacitor C0 and the power supply capacitor C5 of the hysteresis compensation and start control unit 200 itself, and the voltage V CC1 charges the power supply capacitor C5, and the voltage V CC3 at the positive terminal of the power supply capacitor C5 rises. When the voltage V CC3 rises to the control chip turn-on threshold voltage, the system starts to work, so that the charge stored in the start energy storage capacitor C0 is sufficient to support the energy required at the moment of starting the control chip; since after the switching power supply system starts to work, the voltage V CC1 and the voltage V CC3 will start to drop. After the hysteresis compensation and start control unit 200 is turned on, a hysteresis voltage u th4 is also generated and given to the voltage detection and action unit 100. Only when the voltage V CC1 is less than the hysteresis voltage u th4 , the voltage detection and action unit 100 will control the hysteresis compensation and start control unit 200 to turn off, so as to ensure that before the voltage V CC1 drops to the hysteresis voltage u th4 , and before the voltage V CC3 drops to the control chip turn-off threshold voltage, the power supply voltage V CC2 of the auxiliary power supply system is established, and the power supply capacitor C5 is powered by the linear voltage regulation unit 300 to complete the startup process of the system, solving the problem that the conventional high-voltage startup circuit is difficult to meet the normal operation of the control chip with a large inrush current at startup, and the system needs to be restarted multiple times before it can work stably, indirectly resulting in an increase in the system startup time, and the output voltage is difficult to ensure a monotonic rise during the startup process.

[0041] As a specific implementation manner of the voltage detection and action unit 100, the voltage detection and action unit 100 includes: a resistor R1, a resistor R2, a resistor R3, a resistor R6, a precision voltage regulator U1, and a capacitor C2. One end of the resistor R1 is used as the first input terminal of the resistor voltage detection and action unit 100, and the other end of the resistor R1 is connected to one end of the resistor R2; after the other end of the resistor R2 is commonly connected to one end of the resistor R3, one end of the capacitor C2, and the first end of the precision voltage regulator U1, it is used as the second input terminal of the voltage detection and action unit 100; the second end of the precision voltage regulator U1 is connected to one end of the resistor R6, and the other end of the resistor R6 is used as the output terminal of the voltage detection and action unit 100; the other end of the resistor R3, the other end of the capacitor C2, and the third end of the precision voltage regulator U1 are connected to the reference ground.

[0042] As a specific implementation of the hysteresis compensation and startup control unit 200, the hysteresis compensation and startup control unit 200 includes: a hysteresis compensation circuit, a main control circuit, a startup control circuit, and a power supply capacitor C5; the first end of the hysteresis compensation circuit serves as the first output end of the hysteresis compensation and startup control unit 200 and is connected to the second input end of the voltage detection and action unit 100; the second end of the hysteresis compensation circuit is connected to the third end of the main control circuit and the second end of the startup control; the first end of the main control circuit serves as the first input end of the hysteresis compensation and startup control unit 200 and is connected to the output end of the voltage detection and action unit 100; after the second end of the main control circuit is connected to the first end of the startup control circuit, it serves as the second input end of the hysteresis compensation and startup control unit 200 and is used to be connected to the input end of the high-voltage startup circuit and the positive end of the startup energy storage capacitor C0; the third end of the startup control circuit is connected to the positive end of the power supply capacitor C5 and simultaneously serves as the third input end and the second output end of the hysteresis compensation and startup control unit 200, and is connected to the output end of the linear voltage regulation unit 300 and the control chip; the negative end of the power supply capacitor C5 is connected to the reference ground;

[0043] The main control circuit is used to receive the conduction signal and control the hysteresis compensation circuit to generate a hysteresis voltage and send a startup signal to the startup control circuit;

[0044] The hysteresis compensation circuit is used to generate a hysteresis voltage to the voltage detection and action unit 100;

[0045] The startup control circuit is used to conduct after receiving the startup signal, so that the startup energy storage capacitor C0 and the power supply capacitor C5 form a path.

[0046] As a specific implementation of the main control circuit, the main control circuit includes: a resistor R4, a capacitor C1, and a triode Q1. One end of the resistor R4, one end of the capacitor C1, and the collector of the triode Q1 are commonly connected and then serve as the second end of the main control circuit. The other end of the resistor R4, the other end of the capacitor C1, and the base of the triode Q1 are commonly connected and then serve as the first end of the main control circuit. The emitter of the triode Q1 serves as the third end of the main control circuit.

[0047] As a specific implementation of the hysteresis compensation circuit, the hysteresis compensation circuit includes: a resistor R5 and a diode VD1. One end of the resistor R5 serves as the first end of the hysteresis compensation circuit. The other end of the resistor R5 is connected to the cathode of the diode VD1. The anode of the diode VD1 serves as the second end of the hysteresis compensation circuit.

[0048] As a specific implementation of the startup control circuit, the startup control circuit includes: a resistor R7, a resistor R8, a resistor R9, a resistor R 10, capacitor C3, triode Q2 and triode Q3; one end of resistor R7 serves as the second end of the startup control circuit, and the other end is connected to one end of resistor R8, one end of capacitor C3, and the base of triode Q3; the collector of triode Q3 is connected to resistor R 10 one end; the other end of resistor R 10 is connected to one end of resistor R9 and the base of triode Q2; after the other end of resistor R9 is connected to the emitter of triode Q2, it serves as the first end of the startup control circuit; the drain of triode Q2 serves as the third end of the startup control circuit; the other end of resistor R8, the other end of capacitor C3, and the emitter of triode Q3 are connected to the reference ground.

[0049] As a specific embodiment of the linear voltage regulation unit 300, the linear voltage regulation unit 300 includes: resistor R 11 , capacitor C4, zener diode ZD1, diode VD2 and triode Q4; the positive end of capacitor C4 is connected to one end of resistor R 11 and the collector of triode Q4 together, and serves as the input end of the linear voltage regulation unit 300; the other end of resistor R 11 is connected to the cathode of zener diode ZD1 and the base of triode Q4, the emitter of triode Q4 is connected to the anode of diode VD2, and the cathode of diode VD2 serves as the output end of the linear voltage regulation unit 300.

[0050] Specifically, when the system input is established, the high-voltage startup circuit works first to charge the startup energy storage capacitor C0, and the voltage V CC1 at the startup energy storage capacitor C0 rises. Resistors R1, R2, and R3 sample the voltage V cc1 in real time. When the voltage V CC1 is greater than the startup threshold u th1 , that is, the voltage u1 between resistor R1 and resistor R2 is greater than the reference voltage value u ref of the precision voltage regulator U1, the precision voltage regulator U1 conducts, and its second end outputs a low level. After the second end of the precision voltage regulator U1 outputs a low level, the base of triode Q1 is at a high level after being divided by resistors R4 and R6, and triode Q1 conducts. After triode Q1 conducts, diode VD1 conducts, and then a voltage Δu, that is, the hysteresis voltage u th4 , is injected into the first end of chip U1 through resistor R5. Therefore, only when the voltage V CC1 drops below the hysteresis voltage u th4 will the precision voltage regulator U1 turn off. After triode Q1 conducts, the voltage V CC1 divides the voltage through resistors R7 and R8 to make the base of triode Q3 at a high level, and triode Q3 conducts. After triode Q3 conducts, it passes through resistor R 10Pull down the base of the triode Q2, and the triode Q2 conducts. After the triode Q2 conducts, the voltage V CC1 charges the power supply capacitor C5 through the triode Q2, and the voltage V CC3 rises. When the voltage V CC3 rises to the turn-on threshold voltage of the control chip, the system starts to work, and the voltage V CC1 and the voltage V CC3 start to decline. Before the voltage V CC1 drops to the hysteresis voltage u th4 , and before the voltage V CC3 drops to the turn-off threshold voltage of the control chip, the power supply voltage V CC2 of the auxiliary power supply system is established, and the voltage V CC3 is supplied through the first-stage linear voltage regulator unit 300, and the system completes the startup process.

[0051] Reference Figure 2 , for the working timing diagram, the working process of the startup control circuit of this embodiment will be described in detail below in combination with Figure 2 :

[0052] [t0 - t1] process: At time t0, the input end of the switching power supply system starts to supply power, and the high-voltage startup circuit starts to work, charging the startup energy storage capacitor C0, and the voltage V cc1 starts to rise. The resistors R1, R2, and R3 perform voltage division sampling on the voltage V cc1 . When the voltage V cc1 ≥ the turn-on threshold u th1 , the voltage u1 at the resistor R3 end ≥ u ref (reference voltage of the precision voltage regulator U 1的 ).

[0053] [t1 - t2] process: At time t1, the voltage u1 at the resistor R3 end ≥ u ref . At this time, the second end of the precision voltage regulator U1 outputs a low level. After the base voltage of the triode Q1 is divided by the resistors R4 and R6 and is lower than the voltage V cc1 - 0.7V, the triode Q1 conducts. After the triode Q1 conducts, the diode VD1 conducts, and a hysteresis voltage is given to the precision voltage regulator U1 through the resistor R5. Only when the voltage V cc1 ≤ the hysteresis voltage u th4 , the precision voltage regulator U1 turns off. At the same time, the base of the triode Q3 is made high level, the triode Q3 conducts, and the triode Q2 thus conducts. The voltage V cc1 charges the power supply capacitor C5 through the triode Q2, and the voltage V cc3 starts to rise, and the voltage V cc1 starts to decline.

[0054] [t2 - t3] Process: At time t2, voltage V cc3 reaches u th2 , and the control chip of the system starts to work. Since the control chip consumes a large amount of current at the moment of startup (especially for systems including digital control chips), voltage V cc1 and voltage V cc3 begin to drop. Since the startup energy storage capacitor C0 has stored a relatively large amount of charge before startup, it is sufficient to support the power supply voltage V CC2 of the auxiliary power supply system to be established to the steady-state operating voltage u th3 of the control chip. Therefore, the system can start normally and quickly.

[0055] Specifically, during the actual debugging process, if it is found that the startup energy is insufficient, the startup threshold u th1 can be appropriately increased to increase the energy storage capacity of the startup energy storage capacitor C0, ensure the successful startup of the system at one time, and avoid multiple restarts.

[0056] At time t3, if there is no startup control circuit of this embodiment, it is difficult for a general high-voltage startup circuit to provide sufficient working current. Before the power supply voltage V CC2 of the auxiliary power supply system is established at u th3 , voltage V cc1 and voltage V cc3 have already dropped to the turn-off voltage of the control chip, resulting in startup failure. It is necessary to go through multiple restarts until the charge of the startup energy storage capacitor C0 is stored enough to start normally.

[0057] Second Embodiment

[0058] A switching power supply system is provided, including a high-voltage startup circuit, a startup energy storage capacitor C0, a control chip, an auxiliary power supply system, and the startup control circuit of the first embodiment; the output end of the high-voltage startup circuit is connected to the positive end of the startup energy storage capacitor C0 and the first input end of the startup control circuit, the output end of the startup control circuit is connected to the input end of the control chip, the output end of the control chip is connected to the input end of the auxiliary power supply system, and the output end of the auxiliary power supply system is connected to the second input end of the startup control circuit.

[0059] Specifically, when the system input is established, the high-voltage startup circuit first works to charge the startup energy storage capacitor C0, and the voltage V CC1 at the positive end of the startup energy storage capacitor C0 rises. The voltage detection and action unit 100 detects the voltage V CC1 at the positive end of the startup energy storage capacitor C0 in real time. When the voltage V CC1 is greater than the startup threshold u th1, the voltage detection and action unit 100 sends a conduction signal to the hysteresis compensation and start control unit 200. After the hysteresis compensation and start control unit 200 is turned on, it forms a path between the start energy storage capacitor C0 and the power supply capacitor C5 of the hysteresis compensation and start control unit 200 itself, and the voltage V CC1 charges the power supply capacitor C5, and the voltage V at the positive terminal of the power supply capacitor C5 CC3 rises. When the voltage V CC3 rises to the control chip turn-on threshold voltage, the system starts to work, so that the charge stored in the start energy storage capacitor C0 is sufficient to support the energy required at the moment of starting the control chip; since after the switching power supply system starts to work, the voltage V CC1 and the voltage V CC3 will start to drop. After the hysteresis compensation and start control unit 200 is turned on, a hysteresis voltage u th4 is also generated and given to the voltage detection and action unit 100. Only when the voltage V CC1 is less than the hysteresis voltage u th4 , the voltage detection and action unit 100 will control the hysteresis compensation and start control unit 200 to turn off, so as to ensure that before the voltage V CC1 drops to the hysteresis voltage u th4 , and before the voltage V CC3 drops to the control chip turn-off threshold voltage, the power supply voltage V CC2 of the auxiliary power supply system is established, and the power supply capacitor C5 is powered by the linear voltage regulation unit 300, so that the system completes the start-up process, solving the problem that the conventional high-voltage start-up circuit is difficult to meet the normal operation of the control chip with a large inrush current at startup, and the system needs to be restarted multiple times before it can work stably, indirectly resulting in an increase in the system start-up time, and the output voltage is difficult to ensure a monotonic rise during the startup process.

[0060] In summary, the start control circuit described in this embodiment effectively improves the start-up time of the switching power supply system, solves the problems such as insufficient start energy of the conventional high-voltage start-up circuit leading to multiple restarts, etc. In practical applications, this solution can be slightly improved according to the actual situation to achieve the purpose.

[0061] The above-mentioned embodiments of the present invention are only examples for explaining the present invention, and are not intended to limit the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes and modifications can be made based on the above description. It is impossible to list all the implementation manners here. Any obvious changes or modifications derived from the technical solutions of the present invention still fall within the protection scope of the present invention.

Claims

1. A startup control circuit is applied to a switching power supply system, and the switching power supply system includes a high-voltage startup circuit, a startup energy storage capacitor C0, a control chip, and an auxiliary power supply system; characterized in that, The startup control circuit includes: a voltage detection and action unit, a hysteresis compensation and startup control unit, and a linear voltage regulator unit; The first input terminal of the voltage detection and action unit is used to be connected to the input terminal of the high-voltage startup circuit and the positive terminal of the startup energy storage capacitor C0. The second input terminal is connected to the first output terminal of the hysteresis compensation and startup control unit, and the output terminal is connected to the first input terminal of the hysteresis compensation and startup control unit; The second input terminal of the hysteresis compensation and startup control unit is used to be connected to the input terminal of the high-voltage startup circuit and the positive terminal of the startup energy storage capacitor C0. The third input terminal is connected to the output terminal of the linear voltage regulator unit, and the second output terminal is used to be connected to the control chip; The input terminal of the linear voltage regulator unit is used to be connected to the auxiliary power supply system; The voltage detection and action unit is used to detect the voltage V at the positive terminal of the starting energy storage capacitor C0 in real time CC1 , compare the voltage V CC1 with a preset starting threshold, and when the voltage V CC1 is greater than the preset starting threshold, send a conduction signal to the hysteresis compensation and starting control unit; The hysteresis compensation and startup control unit is used to generate a hysteresis voltage and transmit it to the voltage detection and action unit after receiving a conduction signal to conduct. After charging the power supply capacitor C5 of itself through the startup energy storage capacitor C0, it powers the control chip to turn on the control chip, so that the power supply voltage V of the auxiliary power supply system CC2 Establish; The voltage detection and action unit is further configured to, after receiving the hysteresis voltage, compare the voltage V CC1 with the hysteresis voltage in real time, and when the voltage V CC1 is less than the hysteresis voltage, send a turn-off signal to the hysteresis compensation and start control unit to control the turn-off of the hysteresis compensation and start control unit; The linear voltage regulator unit is used to regulate the power supply voltage V of the auxiliary power supply system CC2 After the establishment and hysteresis compensation and the start control unit are turned off, the power supply voltage V input to the auxiliary power supply system CC2 is regulated, and the power supply capacitor C5 of the hysteresis compensation and start control unit is charged so that the power supply capacitor C5 is charged to supply power to the control chip.

2. The startup control circuit according to claim 1, wherein The voltage detection and action unit includes: resistor R1, resistor R2, resistor R3, resistor R6, precision voltage regulator U1, and capacitor C2. One end of resistor R1 serves as the first input terminal of the voltage detection and action unit, and the other end of resistor R1 is connected to one end of resistor R2. After the other end of resistor R2 is commonly connected to one end of resistor R3, one end of capacitor C2, and the first terminal of precision voltage regulator U1, it serves as the second input terminal of the voltage detection and action unit. The second terminal of precision voltage regulator U1 is connected to one end of resistor R6, and the other end of resistor R6 serves as the output terminal of the voltage detection and action unit. The other end of resistor R3, the other end of capacitor C2, and the third terminal of precision voltage regulator U1 are connected to the reference ground.

3. The startup control circuit according to claim 1, wherein The hysteresis compensation and startup control unit includes: a hysteresis compensation circuit, a main control circuit, a startup control circuit, and a power supply capacitor C5; the first terminal of the hysteresis compensation circuit serves as the first output terminal of the hysteresis compensation and startup control unit and is connected to the second input terminal of the voltage detection and action unit. The second terminal of the hysteresis compensation circuit is connected to the third terminal of the main control circuit and the second terminal of the startup control. The first terminal of the main control circuit serves as the first input terminal of the hysteresis compensation and startup control unit and is connected to the output terminal of the voltage detection and action unit. The second terminal of the main control circuit is connected to the first terminal of the startup control circuit and then serves as the second input terminal of the hysteresis compensation and startup control unit, which is used to be connected to the input terminal of the high-voltage startup circuit and the positive terminal of the startup energy storage capacitor C0. The third terminal of the startup control circuit is connected to the positive terminal of power supply capacitor C5 and then serves as both the third input terminal and the second output terminal of the hysteresis compensation and startup control unit, and is connected to the output terminal of the linear voltage regulator unit and the control chip; the negative terminal of power supply capacitor C5 is connected to the reference ground; The main control circuit is used to receive the conduction signal and control the hysteresis compensation circuit to generate a hysteresis voltage and send a startup signal to the startup control circuit; The hysteresis compensation circuit is used to generate a hysteresis voltage to the voltage detection and action unit; The startup control circuit is used to conduct after receiving the startup signal, so that the startup energy storage capacitor C0 and the power supply capacitor C5 form a path.

4. The startup control circuit according to claim 3, characterized in that The main control circuit includes: a resistor R4, a capacitor C1, and a triode Q1. One end of the resistor R4, one end of the capacitor C1, and the collector of the triode Q1 are commonly connected and used as the second end of the main control circuit. The other end of the resistor R4, the other end of the capacitor C1, and the base of the triode Q1 are commonly connected and used as the first end of the main control circuit. The emitter of the triode Q1 is used as the third end of the main control circuit.

5. The startup control circuit according to claim 3, wherein, The hysteresis compensation circuit includes: a resistor R5 and a diode VD1. One end of the resistor R5 is used as the first end of the hysteresis compensation circuit. The other end of the resistor R5 is connected to the cathode of the diode VD1. The anode of the diode VD1 is used as the second end of the hysteresis compensation circuit.

6. The startup control circuit according to claim 3, characterized in that, The starting control circuit includes: resistor R7, resistor R8, resistor R9, resistor R 10 , capacitor C3, triode Q2 and triode Q3; one end of resistor R7 serves as the second end of the starting control circuit, and the other end is connected to one end of resistor R8, one end of capacitor C3, and the base of triode Q3; the collector of triode Q3 is connected to one end of resistor R 10 ; the other end of resistor R 10 is connected to one end of resistor R9 and the base of triode Q2; after the other end of resistor R9 is connected to the emitter of triode Q2, it serves as the first end of the starting control circuit; the collector of triode Q2 serves as the third end of the starting control circuit; the other end of resistor R8, the other end of capacitor C3, and the emitter of triode Q3 are connected to the reference ground.

7. The startup control circuit according to claim 1, wherein The linear voltage regulator unit includes: resistor R 11 , capacitor C4, voltage regulator diode ZD1, diode VD2, and triode Q4; the positive terminal of capacitor C4 is connected to one end of resistor R 11 and the collector of triode Q4 together, and serves as the input terminal of the linear voltage regulator unit; the other end of resistor R 11 is connected to the cathode of voltage regulator diode ZD1 and the base of triode Q4, the emitter of triode Q4 is connected to the anode of diode VD2, and the cathode of diode VD2 serves as the output terminal of the linear voltage regulator unit.

8. A switching power supply system, characterized in that, It includes a high-voltage startup circuit, a startup energy storage capacitor C0, a control chip, an auxiliary power supply system, and a startup control circuit as described in any one of claims 1-7; the output end of the high-voltage startup circuit is connected to the positive end of the startup energy storage capacitor C0 and the first input end of the startup control circuit, the output end of the startup control circuit is connected to the input end of the control chip, the output end of the control chip is connected to the input end of the auxiliary power supply system, and the output end of the auxiliary power supply system is connected to the second input end of the startup control circuit.

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