High-precision starting circuit

Abstract

The invention discloses a high-precision starting circuit which comprises an input port, a switch control circuit, a constant current control circuit, a voltage stabilization control circuit and an output port. Wherein the switch control circuit is used for passively adjusting the impedance of the switch control circuit according to the requirements of constant current and voltage stabilization functions when a high voltage is input and accessed, so as to bear a relatively large voltage drop; the constant current control circuit dynamically adjusts the impedance of the switch control circuit according to the actual load current during constant current work so as to achieve the purpose of constant current. When the voltage stabilization control circuit is in a voltage stabilization state, the impedance of the switch control circuit is dynamically adjusted according to the actual load voltage so as to achieve the purpose of voltage stabilization. The invention can achieve the following effects: a constant current value and a voltage stabilization value can be set in a user-defined manner; the constant current value and the voltage stabilization value are high in precision and good in temperature characteristic; when the device works under constant current, the output can still be stable and is not influenced by the magnitude of load current; when the switching power supply starting circuit is used, switching-off can be realized without an external device.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power electronics, and particularly relates to a high-precision starting circuit. BACKGROUND

[0002] In daily life, switching power supplies are widely used due to their high efficiency and small size. With the development of the field of artificial intelligence, switching power supply products are becoming more and more complex in function and larger in power, and the requirement for efficiency is also getting higher and higher. Therefore, a multi-stage scheme is usually adopted for control, and a high-end power supply product adopts the control mode of MCU and DSP. Before the auxiliary power supply of the power supply product starts to work, power needs to be taken from an external power supply end to supply the controller. After the controller is powered, the power supply system can normally operate, and the auxiliary power supply can take over the power supply of the power supply system. This puts high requirements on the starting circuit. On the one hand, the starting current needs to be large, and it is best to be set according to the actual demand. On the other hand, the output voltage of a general constant current circuit cannot be stable when the load is loaded. Even if the constant current is not reached, the output voltage will be lower as the load current drawn by the load is larger. Therefore, the starting circuit is best set to a regulated state so that the supply voltage can stably rise to the set value to meet the power supply requirement. In addition, after the auxiliary power supply takes over the power supply of the system, the starting circuit needs to be reliably turned off to reduce the power consumption of the power supply system and improve the efficiency.

[0003] Generally, in order to solve the starting problem, some methods adopt the way of charging through an input end by using a resistor and a capacitor. The limitation of this way is great. On the one hand, the resistor loss is very large. The higher the requirement of the starting circuit is, the higher the power level requirement of the resistor is. On the other hand, the starting circuit cannot be automatically turned off after starting, and the loss continues to exist. Some other methods start through the self-starting circuit of a control chip. However, with the increasing complexity of the power supply system, the starting capacity of the chip-level self-starting circuit may not be enough, and there is also a power supply timing problem between chips.

[0004] In addition, the Chinese patent document with the publication number CN216356466U discloses a low-power high-voltage starting circuit. In this starting circuit, a resistor and a capacitor are used to charge through a high voltage. However, a MOSFET is connected in series below the resistor to turn off the resistor charging circuit to reduce the power consumption after the charging is completed.

[0005] But the above patent has obvious defects, specifically: due to the use of resistance current limiting way to start, the resistance needs to withstand a large starting moment power consumption, if the starting current is greater, the resistance of the bearing power consumption is greater, so the resistance volume will become very large, so the starting ability is limited, not conducive to the market electronic products more and more miniaturization and complex trend, and with the input voltage is different, its starting current will change, can not realize constant current charging, start time is indefinite, not conducive to complex timing control, and in low voltage input, the starting current is small, in high voltage input, the starting current is large, the loss on the resistance increases. In addition, this circuit needs to reduce the power consumption of normal operation, also need to increase the special control, to shut down the starting circuit, increase the complexity of control. And because it increases a active control of the shutdown circuit to shut down the starting circuit, and the starting circuit withstand high voltage, the MOSFET in the shutdown circuit also needs to withstand high voltage, its volume is generally large, increases the cost and volume, but only play the role of shutdown, is very uneconomical. SUMMARY

[0006] Therefore, the present application provides a high-precision starting circuit, compared with the conventional scheme, not only can reduce the number of devices, but also can realize high-precision, large current charging, the current can also be set according to the demand, the invention content is as follows: Compared with the prior art, the present application has the advantages of: A high-precision starting circuit, characterized in that the starting circuit comprises an input port, a switch control circuit, a constant current control circuit, a voltage stabilizing control circuit and an output port; The starting circuit is used to withstand the power consumption in the starting process by setting a transistor in the switch control circuit. In the starting process, the constant current control circuit dynamically adjusts the impedance of the transistor according to the actual load current to achieve constant current, and the voltage stabilizing control circuit dynamically adjusts the impedance of the transistor according to the actual load voltage to achieve voltage stabilization. After the starting is completed, the voltage stabilizing control circuit can automatically adjust the impedance of the transistor to automatically shut down the starting circuit.

[0007] Preferably, the switch control circuit is connected with the input port Vin, the output end of the switch control circuit is connected with the first collection end of the constant current control circuit, the control end of the switch control circuit is connected with the output end of the constant current control circuit; the second collection end of the constant current control circuit is connected with the output port; the first collection end of the voltage stabilizing control circuit is connected with the output port; the second collection end of the voltage stabilizing control circuit is connected with the reference ground end GND, and the output end of the voltage stabilizing control circuit is connected with the control end of the switch control circuit. The switch control circuit comprises a transistor Q1, the source stage of the transistor Q1 corresponds to the output end of the switch control circuit, and the gate of the transistor Q1 corresponds to the control end of the switch control circuit.

[0008] Preferably, the switch control circuit further comprises a resistor R2 and a capacitor C3; the first end of the resistor R2 is connected with the input port Vin, and the second end is connected with the first end of the capacitor C3; the second end of the capacitor C3 is connected with the reference ground end GND; the drain of the transistor Q1 is connected with the first end of the resistor R2; and the gate of the transistor Q1 is connected with the second end of the resistor R2.

[0009] Preferably, the constant current control circuit comprises a reference source device.

[0010] Preferably, the constant current control circuit comprises a resistor R1, a capacitor C1 and a reference source U1; the first end of the resistor R1 corresponds to the first collection end of the constant current control circuit; the second end of the resistor R1 corresponds to the second collection end of the constant current control circuit; the first end of the resistor R1 is connected with the reference pole of the reference source U1, the first end of the capacitor C1 and the source stage of the transistor Q1; the second end of the resistor R1 is connected with the anode of the reference source U1; the second end of the capacitor C1 is connected with the cathode of the reference source U1; and the cathode of the reference source U1 corresponds to the output end of the constant current control circuit.

[0011] Preferably, the reference source U1 of the constant current control circuit is a 431 reference device.

[0012] Preferably, the constant voltage control circuit comprises a reference source device.

[0013] Preferably, the constant voltage control circuit comprises a resistor R3, a resistor R4, a resistor R5, a capacitor C2, a capacitor C4 and a reference source U2; the second end of the resistor R3 is connected with the first end of the resistor R4; the second end of the resistor R4 is connected with the reference ground end GND; the first end of the resistor R5 is connected with the cathode of the reference source U2, and the second end is connected with the first end of the capacitor C2; the cathode of the reference source U2 corresponds to the output end of the constant voltage control circuit; the second end of the capacitor C2 and the second end of the resistor R3 are connected with the reference pole of the reference source U2; the anode of the reference source U2 corresponds to the second collection end of the constant voltage control circuit, and is connected with the reference ground end GND; the first end of the capacitor C4 is connected with the first end of the resistor R3, and the second end is connected with the reference ground end GND; and the connection point of the capacitor C4 and the resistor R3 corresponds to the first collection end of the constant voltage control circuit.

[0014] Preferably, the reference source U2 of the constant voltage control circuit is a 431 reference device.

[0015] The technical solution provided by the application uses a reference source device as a charging current sampling, and has very high current accuracy, is not affected by external power supply voltage, and has very good temperature characteristics. Moreover, unlike general constant current circuits, the application also has a voltage stabilizing output function, overcoming the problem that the output voltage of a general constant current circuit decreases with an increase in load current before reaching a constant current. Since the reference source device is used as a voltage sampling of a voltage stabilizing circuit, the accuracy and temperature characteristics are very good. Moreover, before the load current reaches a constant current value, the output voltage can be normally established to a stable voltage value and continuously stabilized. If the load current reaches a constant current value, the circuit can automatically switch to a constant current state, and the circuit design is simple and ingenious. Compared with the prior art, the application has the following advantages: 1. Compared with the general prior art which uses a resistor to start, the application realizes high-precision, low-temperature-drift constant current charging by dynamically adjusting the impedance of a transistor. The problems of small starting current, change of starting current with input voltage, and large resistor loss of the traditional resistor starting method are solved.

[0016] 2. The application differs from the resistor current-limiting starting method of the general prior art in that the power consumption in the starting process is added to the transistor instead of the resistor. Since the transistor is used in the starting circuit, it is usually a high-voltage transistor, so its wafer area is generally larger, and the instantaneous power it can withstand is much larger than that of a surface mount resistor, and its volume is smaller than that of a plug-in resistor. Therefore, another obvious advantage of the application is that it can bear a larger starting current and can be applied to digital chip starting.

[0017] 3. In the starting process, the application differs from the general constant current starting scheme. After completion of starting, the general constant current starting scheme needs to increase an active control circuit to turn off the starting circuit to reduce loss. Since the application has a voltage stabilizing control circuit, as long as the output voltage of the auxiliary power supply is greater than the set value of the voltage stabilizing control circuit after completion of starting, the voltage stabilizing control circuit will automatically adjust the impedance of the transistor so that it no longer obtains current from the input end, thereby avoiding additional loss after completion of starting, without the need to increase an additional control circuit for control, greatly reducing the complexity of the circuit.

[0018] 4. The application has high-precision constant current and voltage stabilizing functions, good temperature characteristics, and can be used not only as a starting circuit of a switching power supply but also in battery charging and other occasions. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is an embodiment schematic diagram of the application used as a starting circuit of a switching power supply; DETAILED DESCRIPTION For a better understanding of the present application, it will now be described in detail in accordance with the following drawings which are provided simply as examples of embodiments of the application and in which:

[0020] Throughout this specification the use of "embodiment" or "exemplary embodiment" denotes the described feature, structure, or characteristic as being a desirable configuration, but that the feature, structure, or characteristic can not be necessary to implementation of the applications in its broadest form. Also, when introducing elements of aspects of the present applications, the articles "a," "an," "the" and "said" are intended to mean that there are one or more of the elements. The articles are not to be construed as excluding particular embodiments or configurations of the present applications recited in the claims.

[0021] As shown in Figure 1 The application provides a high-precision starting circuit, comprising an input port Vin, a switch control circuit 101, a constant current control circuit 102, a voltage stabilizing control circuit 103 and an output port Vout; the switch control circuit 101 is connected with the input port Vin, the output end of the switch control circuit 101 is connected with the first collecting end of the constant current control circuit, the control end of the switch control circuit 101 is connected with the output end of the constant current control circuit; the second collecting end of the constant current control circuit is connected with the output port Vout; the first collecting end of the voltage stabilizing control circuit is connected with the output port Vout; the second collecting end of the voltage stabilizing control circuit is connected with a reference ground end GND, and the output end of the voltage stabilizing control circuit is connected with the control end of the switch control circuit 101. The switch control circuit 101 is used for passively adjusting its own impedance according to the needs of constant current and voltage stabilizing functions when high voltage is input, and bears a large voltage drop. The switch control circuit 101 comprises a resistor R2, a capacitor C3 and a transistor Q1. The source stage of the transistor Q1 corresponds to the output end of the switch control circuit 101; the gate of the transistor Q1 corresponds to the control end of the switch control circuit 101. The first end of the resistor R2 is connected with the input port Vin, and the second end is connected with the first end of the capacitor C3; the second end of the capacitor C1 is connected with the reference ground end GND; the drain (D in the figure) of the transistor Q1 is connected with the first end of the resistor R2, the source stage (S in the figure) of the transistor Q1 is connected with the first end of the resistor R1 of the constant current control circuit, and the gate (G in the figure) of the transistor Q1 is connected with the second end of the resistor R2. The input port Vin is reduced in voltage through RC buffering to turn on the transistor Q1, and after the transistor Q1 is turned on, current will flow between the drain and the source of the transistor Q1.

[0022] Since the power consumption in the starting process is added to the transistor instead of the resistor, the transistor can use high-performance transistors according to the use scene, thereby meeting the on-demand requirement of large starting current; in addition, compared with the resistor, the transient power tolerance level of the transistor is higher than that of the resistor, and the volume is smaller than that of the resistor.

[0023] The constant current control circuit 102 comprises a resistor R1, a capacitor C1 and a reference source U1. The first end of the resistor R1 corresponds to the first collection end of the constant current control circuit 102; the second end of the resistor R1 corresponds to the second collection end of the constant current control circuit 102. The first end of the resistor R1 is connected with the reference pole of the reference source U1, and the second end of the resistor R1 is connected with the cathode of the reference source U1; the first end of the capacitor C1 is connected with the first end of the resistor R1, and the second end is connected with the anode of the reference source; the anode of the reference source U1 corresponds to the output end of the constant current control circuit.

[0024] When the voltage drop generated by the drain-source current flowing through the resistor R1 is greater than the reference voltage Vref1 of the reference source U1, the cathode of the reference source will pull down the gate of the transistor, so that the drain-source impedance of the transistor increases, thereby reducing the drain-source current, so as to maintain the voltage across the resistor R1 equal to the reference voltage Vref1, thereby realizing the constant current starting function. The constant current size is: I=Vref1 / R1 For example, the reference source U1 of the constant current control circuit is a 431 reference device, and the reference voltage Vref1 is 1.25V.

[0025] In the present application, the constant current control circuit 101 uses a reference source device as a charging current sampling, which has very high current accuracy and is not affected by external supply voltage, and has very good temperature characteristics.

[0026] The voltage stabilizing control circuit 103 comprises a resistor R3, a resistor R4, a resistor R5, a capacitor C2, a capacitor C4 and a reference source U2. The first end of the resistor R3 is connected with the second end of the resistor R1 of the constant current control circuit, and the second end of the resistor R3 is connected with the first end of the resistor R4; the second end of the resistor R4 is connected with the reference ground end GND; the first end of the resistor R5 is connected with the cathode of the reference source U2, and the second end is connected with the first end of the capacitor C2; the cathode of the reference source U2 corresponds to the output end of the voltage stabilizing control circuit; the second end of the capacitor C2 is connected with the reference pole of the reference source U2; the reference end of the reference source U2 is connected with the second end of the resistor R3, the cathode is connected with the gate of the transistor Q1, the anode of the reference source U2 is connected with the reference ground end GND; the anode of the reference source U2 corresponds to the second collection end of the voltage stabilizing control circuit; the first end of the capacitor C4 is connected with the first end of the resistor R3, and the output port Vout, the second end of the capacitor C4 is connected with the reference ground end GND; wherein the connection point of the capacitor C4 and the resistor R3 corresponds to the first collection end of the voltage stabilizing control circuit.

[0027] When the constant current control circuit 101 controls capacitor C4 to be charged with a constant current, the voltage of capacitor C4 gradually rises until the voltage at the output port Vout rises to the set voltage value Vout. Vout is divided by resistors R3 and R4. When the divided voltage is greater than the reference voltage Vref2 of the reference source U2, the cathode of the reference source U2 will pull down the gate of transistor Q1, increasing its drain-source impedance and thus reducing the drain-source current, thereby maintaining the voltage Vout of capacitor C4 unchanged. The regulated voltage is: Vout = (R3 / R4 + 1) × Vref2 Preferably, the reference source U2 of the constant current control circuit is a 431 reference device, and the reference voltage Vref2 is 1.25V.

[0028] Unlike typical startup circuits, the voltage regulation control circuit 103 in this application overcomes the defect that the output voltage of a typical startup circuit changes with the magnitude of the current before reaching a constant current. Its regulated voltage value can also be set. Similarly, since a reference source device is used as the regulated voltage sampler, its accuracy and temperature characteristics are very good.

[0029] Furthermore, after the voltage regulator control circuit 103 completes startup, when the output voltage of the external auxiliary power supply is greater than the set value of the voltage regulator control circuit (i.e., greater than the set voltage value Vout), the voltage division of resistor R4 will inevitably be greater than the reference voltage Vref2 of the reference source U2. At this time, the cathode of the reference source U2 will pull down the gate voltage of transistor Q1 until the transistor switches off. Therefore, there is no need to set up a separate switching circuit to turn off the startup circuit after startup, thereby reducing losses.

[0030] In the voltage regulation output circuit of this application, the switch control circuit 101 passively adjusts its own impedance to bear a large voltage drop when a high voltage is input, according to the needs of constant current and voltage regulation functions. The constant current control circuit 102 dynamically adjusts the impedance of the switch control circuit according to the actual load current during constant current operation to achieve constant current. The voltage regulation control circuit 103 dynamically adjusts the impedance of the switch control circuit according to the actual load voltage during voltage regulation to achieve voltage regulation. The specific working principle is as follows: When a voltage is applied to the input terminal Vin, the switch control circuit 101 buffers the voltage through resistor R2 and capacitor C3 and provides a driving voltage to the gate of transistor Q1. Q1 then conducts, and Vin charges the load capacitor C4 through transistor Q1 and resistor R1, causing the Vout voltage to rise. The charging current from Vin to Vout is determined by the constant current control circuit 102. When the Vout voltage rises to the target voltage, the voltage regulation control circuit 103 pulls down the gate of transistor Q1, forming a closed loop to achieve voltage regulation.

[0031] The high-precision startup circuit proposed in this application utilizes a circuit composed of transistors and reference devices to achieve controllable current charging, enable shutdown without additional components, and consume almost no power after charging is complete. Furthermore, the circuit composed of transistors and reference devices ensures the accuracy of constant current and voltage regulation while achieving these properties. It can be used not only as a startup circuit for switching power supplies but also for other applicable scenarios readily apparent to those skilled in the art, such as battery charging.

[0032] The above description of the embodiments is only for the purpose of helping to understand the inventive concept of this application and is not intended to limit this application. For those skilled in the art, any modifications, equivalent substitutions, improvements, etc., made without departing from the principle of this application should be included within the protection scope of this application.

Claims

1. A high-precision start-up circuit, characterized in that, The startup circuit includes an input port, a switch control circuit, a constant current control circuit, a voltage regulation control circuit, and an output port. The startup circuit uses transistors located in the switch control circuit to absorb the power consumption during startup. During startup, the constant current control circuit dynamically adjusts the transistor impedance according to the actual load current to achieve constant current; the voltage regulation control circuit dynamically adjusts the transistor impedance according to the actual load voltage to achieve voltage regulation. After startup is complete, the voltage regulation control circuit can automatically adjust the impedance of the transistor so that the startup circuit can be automatically shut off.

2. The starting circuit according to claim 1, characterized in that: The switch control circuit is connected to the input port Vin, the output terminal of the switch control circuit is connected to the first acquisition terminal of the constant current control circuit, and the control terminal of the switch control circuit is connected to the output terminal of the constant current control circuit; the second acquisition terminal of the constant current control circuit is connected to the output port; the first acquisition terminal of the voltage regulation control circuit is connected to the output port; the second acquisition terminal of the voltage regulation control circuit is connected to the reference ground GND, and the output terminal of the voltage regulation control circuit is connected to the control terminal of the switch control circuit. The switching control circuit includes a transistor Q1, the source of which corresponds to the output terminal of the switching control circuit, and the gate of which corresponds to the control terminal of the switching control circuit.

3. The startup circuit according to claim 2, characterized in that: The switch control circuit also includes a resistor R2 and a capacitor C3; the first end of the resistor R2 is connected to the input port Vin, and the second end is connected to the first end of the capacitor C3; the second end of the capacitor C3 is connected to the reference ground GND; the drain of the transistor Q1 is connected to the first end of the resistor R2; and the gate of the transistor Q1 is connected to the second end of the resistor R2.

4. The starting circuit according to claim 2, characterized in that: The constant current control circuit includes a reference source device.

5. The startup circuit according to claim 4, characterized in that: The constant current control circuit includes a resistor R1, a capacitor C1, and a reference source U1; the first end of the resistor R1 corresponds to the first acquisition terminal of the constant current control circuit; the second end of the resistor R1 corresponds to the second acquisition terminal of the constant current control circuit; the first end of the resistor R1 is simultaneously connected to the reference terminal of the reference source U1, the first end of the capacitor C1, and the source terminal of the transistor Q1; the second end of the resistor R1 is connected to the anode of the reference source U1; the second end of the capacitor C1 is connected to the cathode of the reference source U1; the cathode of the reference source U1 corresponds to the output terminal of the constant current control circuit.

6. The startup circuit according to claim 5, characterized in that: The reference source U1 of the constant current control circuit is a 431 reference device.

7. The starting circuit according to claim 2, characterized in that: The voltage regulation control circuit includes a reference source device.

8. The startup circuit according to claim 7, characterized in that: The voltage regulation control circuit includes resistors R3, R4, and R5, capacitors C2 and C4, and a reference source U2. The second end of resistor R3 is connected to the first end of resistor R4. The second end of resistor R4 is connected to the reference ground (GND). The first end of resistor R5 is connected to the cathode of the reference source U2, and the second end is connected to the first end of capacitor C2. The cathode of the reference source U2 corresponds to the output terminal of the voltage regulation control circuit. The second ends of capacitor C2 and resistor R3 are connected to the reference electrode of the reference source U2. The anode of the reference source U2 corresponds to the second acquisition terminal of the voltage regulation control circuit and is connected to the reference ground (GND). The first end of capacitor C4 is connected to the first end of resistor R3, and the second end is connected to the reference ground (GND). The connection point between capacitor C4 and resistor R3 corresponds to the first acquisition terminal of the voltage regulation control circuit.

9. The startup circuit according to claim 8, characterized in that: The reference source U2 of the voltage regulation control circuit is a 431 reference device.

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