Voltage-controlled oscillation circuit and switching power supply

Abstract

The invention relates to the technical field of switching power supplies, and particularly discloses a voltage-controlled oscillation circuit and a switching power supply, the voltage-controlled oscillation circuit comprises an oscillation current generation module, a voltage control module and a charge-discharge proportional current control module, the oscillation current generation module is electrically connected with the voltage control module, and the voltage control module is electrically connected with the charge-discharge proportional current control module; the oscillation current generation module is used for generating corresponding oscillation current according to an external load of the voltage-controlled oscillation circuit; the voltage control module is used for performing voltage stabilization control according to the oscillating current to obtain a stable voltage control signal which does not fluctuate along with the external charging and discharging voltage; and the charge-discharge proportional current control module is used for determining a charge-discharge current proportion according to the stable voltage control signal and carrying out charge-discharge control on an external charge-discharge capacitor according to the charge-discharge current proportion. According to the voltage-controlled oscillation circuit provided by the invention, the precision and the stability of the switching power supply control chip can be improved under the condition that the production process is not changed.

Description

Technical Field

[0001] The present invention relates to the technical field of switching power supplies, and in particular to a voltage-controlled oscillator circuit and a switching power supply. Background Art

[0002] In the field of switching power supply technology, there are usually very high requirements for the accuracy and stability of the duty cycle of the switching waveform of the switching power supply control chip. However, the accuracy and stability of the duty cycle of the switching waveform of the current control chip mainly depend on the stability of the production process. Therefore, it is difficult to adjust the accuracy of the duty cycle after the control chip is produced. In addition to being affected by the production process, the duty cycle of the control chip will also be affected by the Early effect in actual circuit operation, such as Figure 3 As shown in FIG. 1 , the existing switching power supply control chip is affected by the Early effect during operation, resulting in reduced accuracy of the duty cycle of the control chip and poor stability.

[0003] Therefore, how to improve the accuracy and stability of the switching power supply control chip without changing the production process has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0004] The present invention provides a voltage-controlled oscillator circuit and a switching power supply, which solve the problem in the related art that the accuracy of the switching power supply control chip is affected by the Early effect when the production process cannot be changed, resulting in low accuracy and poor stability.

[0005] As a first aspect of the present invention, a voltage-controlled oscillation circuit is provided, which includes: an oscillating current generating module, a voltage control module and a charge-discharge proportional current control module, wherein the oscillating current generating module is electrically connected to the voltage control module, and the voltage control module is electrically connected to the charge-discharge proportional current control module; the oscillating current generating module is used to generate a corresponding oscillating current according to an external load of the voltage-controlled oscillation circuit; the voltage control module is used to perform voltage stabilization control according to the oscillating current to obtain a stable voltage control signal that does not follow the external charge and discharge voltage fluctuations; the charge and discharge proportional current control module is used to determine the charge and discharge current ratio according to the stable voltage control signal, and to control the external charge and discharge current according to the charge and discharge current ratio. The oscillating current generating module includes: a mirror current generating unit and a mirror current output unit, wherein the mirror current generating unit is connected to the mirror current output unit, and the mirror current generating unit is used to generate a matching oscillating current according to the resistance change of the external load; the mirror current output unit is used to output the oscillating current in a mirror image; wherein the mirror current generating unit includes a first comparator and a first N-type MOS transistor, the non-inverting input terminal of the first comparator is used to input a first reference voltage, the inverting input terminal of the first comparator is connected to the source terminal of the first N-type MOS transistor, the output terminal of the first comparator is connected to the gate terminal of the first N-type MOS transistor, and the first N-type MOS transistor is connected to the gate terminal of the first N-type MOS transistor. The source terminal of the transistor is also used to connect to one end of an external load, the other end of the external load is connected to a signal ground, and the drain terminal of the first N-type MOS transistor is connected to the mirror current output unit; the mirror current output unit includes: a first P-type transistor, a second P-type transistor, a third P-type transistor, a fourth P-type transistor and a fifth P-type transistor, the collector of the first P-type transistor is connected to the drain terminal of the first N-type MOS transistor, the emitter of the first P-type transistor is connected to the voltage control module, the base of the first P-type transistor is connected to the base of the second P-type transistor, and the collector of the first P-type transistor is a second voltage terminal; the emitter of the second P-type transistor is connected to the emitter of the first P-type transistor, The collector of the second P-type transistor is the third voltage terminal; the emitter of the third P-type transistor is connected to the base of the first P-type transistor, the base of the third P-type transistor is connected to the collector of the first P-type transistor, and the collector of the third P-type transistor is connected to the signal ground; the emitter of the fourth P-type transistor is connected to the emitter of the first P-type transistor, the base of the fourth P-type transistor is connected to the base of the first P-type transistor, and the collector of the fourth P-type transistor is the fourth voltage terminal; the emitter of the fifth P-type transistor is connected to the emitter of the first P-type transistor, the base of the fifth P-type transistor is connected to the base of the first P-type transistor, and the collector of the fifth P-type transistor is the fifth voltage terminal.

[0006] Furthermore, the voltage control module includes: a voltage stabilization control unit and a voltage output unit, the voltage stabilization control unit is connected to the voltage output unit, and the voltage stabilization control unit is used to control the voltage of the fourth voltage terminal and the voltage of the fifth voltage terminal according to the oscillating current and the second reference voltage; the voltage output unit is used to cooperate with the voltage stabilization control unit to control the voltage of the fourth voltage terminal and the voltage of the fifth voltage terminal so that the voltage of the fourth voltage terminal is equal to the voltage of the fifth voltage terminal, so as to obtain a stable voltage control signal that does not follow the fluctuations of the external charging and discharging voltage.

[0007] Furthermore, the voltage stabilization control unit includes: a second comparator, a first resistor and a first P-type MOS transistor, the inverting input terminal of the second comparator is used to input a second reference voltage, the non-inverting input terminal of the second comparator is connected to the voltage output unit, and the non-inverting input terminal of the second comparator is a first voltage terminal, the output terminal of the second comparator is connected to the gate terminal of the first P-type MOS transistor, the source terminal of the first P-type MOS transistor is connected to the emitter of the first P-type transistor, the drain terminal of the first P-type MOS transistor is connected to the non-inverting input terminal of the second comparator, one end of the first resistor is connected to the non-inverting input terminal of the second comparator, and the other end of the first resistor is connected to the signal ground.

[0008] Further, the voltage output unit includes: a first N-type transistor, a second N-type transistor, a third N-type transistor, a sixth P-type transistor, a seventh P-type transistor and an eighth P-type transistor, the base of the first N-type transistor is connected to the base of the eighth P-type transistor, the collector of the first N-type transistor is connected to the emitter of the first P-type transistor, the emitter of the first N-type transistor is connected to the base of the second N-type transistor, the collector of the second N-type transistor is connected to the base of the eighth P-type transistor, the emitter of the second N-type transistor is connected to the signal ground, the base of the third N-type transistor is connected to the base of the second N-type transistor, and the collector of the third N-type transistor is connected to the emitter of the first P-type transistor. A voltage end, the base of the sixth P-type transistor is connected to the first voltage end, the emitter of the sixth P-type transistor is connected to the fourth voltage end, the collector of the sixth P-type transistor is connected to the charge and discharge proportional current control module, the base of the seventh P-type transistor is connected to the first voltage end, the emitter of the seventh P-type transistor is connected to the fifth voltage end, the collector of the seventh P-type transistor is connected to the charge and discharge proportional current control module, the collector of the seventh P-type transistor is also connected to one end of the external charge and discharge capacitor, the other end of the external charge and discharge capacitor is connected to the signal ground, the emitter of the eighth P-type transistor is connected to the third voltage end, and the collector of the eighth P-type transistor is connected to the signal ground.

[0009] Furthermore, the charge and discharge proportional current control module includes: a charge and discharge control unit and a switch signal output unit, the charge and discharge control unit is connected to the switch signal output unit, and the charge and discharge control unit and the switch signal output unit are both electrically connected to an external charge and discharge capacitor; the charge and discharge control unit is used to generate a charging control signal when the current switch signal is high, and to generate a discharge control signal when the current switch signal is low, the charging control signal is used to control the charging of the external charge and discharge capacitor, and the discharge control signal is used to control the discharge of the external charge and discharge capacitor, and the charging current and discharge current of the external charge and discharge capacitor are equal; the switch signal output unit is used to output a low-level switch signal when the voltage value of the external charge and discharge capacitor is high, and to output a high-level switch signal when the voltage value of the external charge and discharge capacitor is low.

[0010] Furthermore, the charge and discharge control unit includes: a second N-type MOS transistor, a fourth N-type transistor, a fifth N-type transistor, and a sixth N-type transistor, wherein the gate terminal of the second N-type MOS transistor is connected to the output terminal of the switch signal output unit, the drain terminal of the second N-type MOS transistor is connected to the base terminal of the fourth N-type transistor, the source terminal of the second N-type MOS transistor is connected to the signal ground, the collector of the fourth N-type transistor is connected to the source terminal of the first P-type MOS transistor, the emitter of the fourth N-type transistor is connected to the base terminal of the fifth N-type transistor, the collector of the fifth N-type transistor is connected to the collector terminal of the sixth P-type transistor, the emitter of the fifth N-type transistor is connected to the signal ground, the base terminal of the sixth N-type transistor is connected to the base terminal of the fifth N-type transistor, the collector terminal of the sixth N-type transistor is connected to the collector terminal of the seventh P-type transistor, and the emitter terminal of the sixth N-type transistor is connected to the signal ground.

[0011] Furthermore, the switching signal output unit includes: a third comparator, a fourth comparator and a latch, the non-inverting input of the third comparator is connected to one end of the external charging and discharging capacitor, the inverting input of the third comparator is connected to a third reference voltage, the output of the third comparator is connected to the first input of the latch, the non-inverting input of the fourth comparator is connected to one end of the external charging and discharging capacitor, the inverting input of the fourth comparator is connected to a fourth reference voltage, the output of the fourth comparator is connected to the second input of the latch, and the output of the latch is the output of the switching signal output unit, wherein the third reference voltage is greater than the fourth reference voltage.

[0012] As another aspect of the present invention, a switching power supply is provided, comprising: a switching power supply control chip and a switching tube, wherein the output end of the switching power supply control chip is connected to the control end of the switching tube, the switching power supply control chip comprises a drive circuit and the voltage-controlled oscillation circuit described above, the output end of the voltage-controlled oscillation circuit is connected to the input end of the drive circuit, and the output end of the drive circuit is the output end of the switching power supply control chip.

[0013] The voltage-controlled oscillator circuit provided by the present invention generates an oscillating current corresponding to an external load through an oscillating current generating module. The voltage control module can then perform voltage stabilization control based on the oscillating current to obtain a stable voltage control signal that does not follow the fluctuations of the external charge and discharge voltage. Finally, the charge and discharge proportional current control module controls the charge and discharge of the external charge and discharge capacitor based on the stable voltage control signal, thereby maintaining the duty cycle of the output switching signal in a stable state. Due to the stable voltage control signal, the voltage-controlled oscillator circuit can maintain a stable current for charging the external charge and discharge capacitor, thereby eliminating the problems of reduced duty cycle accuracy and poor stability caused by the Early effect in the prior art. This improves the accuracy and stability of the switching power supply control chip without changing the production process, thereby improving the product performance of the switching power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention, but do not constitute a limitation of the present invention.

[0015] Figure 1 This is a circuit structure block diagram of the voltage-controlled oscillator circuit provided by the present invention.

[0016] Figure 2 This is a circuit schematic diagram of the voltage-controlled oscillator circuit provided by the present invention.

[0017] Figure 3 FIG. 1 is a circuit diagram of a voltage-controlled oscillator system in the prior art.

[0018] Figure 4 This is a schematic diagram of the output switching waveform of the voltage-controlled oscillator circuit provided by the present invention and the voltage waveform of the external charging and discharging capacitor.

[0019] Figure 5 This is a structural block diagram of the switching power supply provided by the present invention. DETAILED DESCRIPTION

[0020] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0021] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0022] It should be noted that the terms "first," "second," and the like in the specification and claims of the present invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate for the embodiments of the present invention described herein. In addition, the terms "including," "having," and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to these processes, methods, products, or apparatuses.

[0023] In this embodiment, a voltage-controlled oscillator circuit is provided. Figure 1 FIG. 1 is a circuit structure block diagram of a voltage-controlled oscillator circuit 100 according to an embodiment of the present invention. Figure 1 As shown, it includes: an oscillating current generating module 110, a voltage control module 120 and a charge-discharge proportional current control module 130, the oscillating current generating module 110 is electrically connected to the voltage control module 120, and the voltage control module 120 is electrically connected to the charge-discharge proportional current control module 130; the oscillating current generating module 110 is used to generate a corresponding oscillating current according to the external load of the voltage-controlled oscillation circuit; the voltage control module 120 is used to perform voltage stabilization control according to the oscillating current to obtain a stable voltage control signal that does not follow the external charge and discharge voltage fluctuations; the charge and discharge proportional current control module 130 is used to determine the charge and discharge current ratio according to the stable voltage control signal, and control the charge and discharge of the external charge and discharge capacitor according to the charge and discharge current ratio.

[0024] In an embodiment of the present invention, the oscillating current generating module 110 can generate a corresponding oscillating current according to changes in the external load. That is, when the switching power supply in which the voltage-controlled oscillation circuit is located is connected to different external loads, the oscillating current generating module 110 in the voltage-controlled oscillation circuit can generate a corresponding oscillating current according to changes in the load, so as to facilitate subsequent adjustment of the corresponding switching duty cycle based on the oscillating current.

[0025] The voltage control module 120 can perform voltage stabilization control based on the oscillating current. Specifically, through voltage stabilization control, a stable voltage control signal that does not follow the fluctuations of the external charging and discharging voltage can be obtained. The stable voltage control signal can keep the current for charging the external charging and discharging capacitor stable, thereby eliminating the problems of reduced duty cycle accuracy and poor stability caused by the Early effect in the prior art.

[0026] The charge-discharge ratio current control module 130 can control the charge and discharge of the external charge and discharge capacitor according to the stable voltage control signal, so that the duty cycle of the output switching signal can be maintained in a stable state. The specific duty cycle can also be adjusted as needed.

[0027] Therefore, the voltage-controlled oscillator circuit provided by the present invention generates a corresponding oscillating current according to an external load through an oscillating current generating module, and the voltage control module can then perform voltage stabilization control based on the oscillating current to obtain a stable voltage control signal that does not follow the fluctuations of the external charge and discharge voltage. Finally, the charge and discharge proportional current control module controls the charge and discharge of the external charge and discharge capacitor based on the stable voltage control signal, so that the duty cycle of the output switching signal can be maintained in a stable state. Due to the stable voltage control signal, the voltage-controlled oscillator circuit can keep the current used to charge the external charge and discharge capacitor stable, thereby eliminating the problems of reduced duty cycle accuracy and poor stability caused by the Early effect in the prior art, thereby achieving the goal of improving the accuracy and stability of the switching power supply control chip without changing the production process, thereby improving the product performance of the switching power supply.

[0028] In an embodiment of the present invention, the oscillating current generating module 110 includes: a mirror current generating unit and a mirror current output unit, wherein the mirror current generating unit is connected to the mirror current output unit, and the mirror current generating unit is used to generate a matching oscillating current according to the resistance change of the external load; the mirror current output unit is used to mirror and output the oscillating current.

[0029] Specifically, if Figure 2As shown, the mirror current generating unit includes a first comparator COMP1 and a first N-type MOS transistor N1, the non-inverting input terminal of the first comparator COMP1 is used to input a first reference voltage VREF1, the inverting input terminal of the first comparator COMP1 is connected to the source terminal of the first N-type MOS transistor N1, the output terminal of the first comparator COMP1 is connected to the gate terminal of the first N-type MOS transistor N1, the source terminal of the first N-type MOS transistor N1 is also used to connect one end of the external load R0, and the other end of the external load R0 is connected to the signal ground. The drain end of the first N-type MOS transistor N1 is connected to the mirror current output unit; the mirror current output unit includes: a first P-type transistor PNP1, a second P-type transistor PNP2, a third P-type transistor PNP3, a fourth P-type transistor PNP4 and a fifth P-type transistor PNP5, the collector of the first P-type transistor PNP1 is connected to the drain end of the first N-type MOS transistor N1, the emitter of the first P-type transistor PNP1 is connected to the voltage control module, and the base of the first P-type transistor PNP1 is connected to the second P-type transistor PNP2. NP2, and the collector of the first P-type transistor PNP1 is the second voltage terminal V2; the emitter of the second P-type transistor PNP2 is connected to the emitter of the first P-type transistor PNP1, and the collector of the second P-type transistor PNP2 is the third voltage terminal V3; the emitter of the third P-type transistor PNP3 is connected to the base of the first P-type transistor PNP1, the base of the third P-type transistor PNP3 is connected to the collector of the first P-type transistor PNP1, and the collector of the third P-type transistor PNP3 is connected to the signal ground; The emitter of the fourth P-type transistor PNP4 is connected to the emitter of the first P-type transistor PNP1, the base of the fourth P-type transistor PNP4 is connected to the base of the first P-type transistor PNP1, and the collector of the fourth P-type transistor PNP4 is the fourth voltage terminal V4; the emitter of the fifth P-type transistor PNP5 is connected to the emitter of the first P-type transistor PNP1, the base of the fifth P-type transistor PNP5 is connected to the base of the first P-type transistor PNP1, and the collector of the fifth P-type transistor PNP5 is the fifth voltage terminal V5.

[0030] In the embodiment of the present invention, the oscillating current generating module is used to generate different oscillating currents according to different external loads. According to the virtual short principle of the operational amplifier, the voltage V0 of the inverting input terminal of the first comparator COMP1 is equal to the first reference voltage VREF1 of its non-inverting input terminal. Therefore, the current I0 flowing through the external load R0 is: .

[0031] In the oscillating current generating module, the first P-type transistor PNP1, the second P-type transistor PNP2, the third P-type transistor PNP3, the fourth P-type transistor PNP4 and the fifth P-type transistor PNP5 form a mirror current source. E : , under the same production process, I ES Proportional to the transistor area, V T are all the same, so under ideal conditions, V BE The current ratio of the same transistor is proportional to the area. Due to the existence of the Early effect in actual applications, the transistor current is also affected by the voltage difference at the CE terminal. The greater the voltage difference at the CE terminal, the greater the current. In the embodiment of the present invention, the base terminal and emitter terminal of the first P-type transistor PNP1, the second P-type transistor PNP2, the third P-type transistor PNP3, the fourth P-type transistor PNP4 and the fifth P-type transistor PNP5 are connected together, V BE Since the areas of the fourth P-type transistor PNP4 and the fifth P-type transistor PNP5 are 1:1, if V4 = V5, then I E(PNP4) = I E(PNP5) That is to say, in the embodiment of the present invention, when the voltage of the fourth voltage terminal V4 can be made the same as the voltage of the fifth voltage terminal V5, the emitter current of the fourth P-type transistor PNP4 can be made the same as the emitter current of the fifth P-type transistor PNP5.

[0032] In an embodiment of the present invention, the voltage control module 120 includes: a voltage stabilization control unit and a voltage output unit, the voltage stabilization control unit is connected to the voltage output unit, the voltage stabilization control unit is used to control the voltage of the fourth voltage terminal and the voltage of the fifth voltage terminal according to the oscillating current and the second reference voltage; the voltage output unit is used to cooperate with the voltage stabilization control unit to control the voltage of the fourth voltage terminal and the voltage of the fifth voltage terminal so that the voltage of the fourth voltage terminal is equal to the voltage of the fifth voltage terminal, so as to obtain a stable voltage control signal that does not follow the external charge and discharge voltage fluctuations.

[0033] Specifically, the voltage stabilization control unit includes: a second comparator COMP2, a first resistor R1 and a first P-type MOS transistor P1, the inverting input terminal of the second comparator COMP2 is used to input the second reference voltage VREF2, the non-inverting input terminal of the second comparator COMP2 is connected to the voltage output unit, and the non-inverting input terminal of the second comparator COMP2 is the first voltage terminal V1, the output terminal of the second comparator COMP2 is connected to the gate terminal of the first P-type MOS transistor P1, the source terminal of the first P-type MOS transistor P1 is connected to the emitter terminal of the first P-type transistor PNP1, the drain terminal of the first P-type MOS transistor P1 is connected to the non-inverting input terminal of the second comparator COMP2, one end of the first resistor R1 is connected to the non-inverting input terminal of the second comparator COMP2, and the other end of the first resistor R1 is connected to the signal ground.

[0034] Specifically, the voltage output unit includes: a first N-type transistor NPN1, a second N-type transistor NPN2, a third N-type transistor NPN3, a sixth P-type transistor PNP6, a seventh P-type transistor PNP7 and an eighth P-type transistor PNP8, the base of the first N-type transistor NPN1 is connected to the base of the eighth P-type transistor PNP8, the collector of the first N-type transistor NPN1 is connected to the emitter of the first P-type transistor PNP1, the emitter of the first N-type transistor NPN1 is connected to the base of the second N-type transistor NPN2, the collector of the second N-type transistor NPN2 is connected to the base of the eighth P-type transistor PNP8, the emitter of the second N-type transistor NPN2 is connected to the signal ground, the base of the third N-type transistor NPN3 is connected to the base of the second N-type transistor NPN2, and the collector of the third N-type transistor NPN3 is connected to the emitter of the first P-type transistor PNP1. The base of the sixth P-type transistor PNP6 is connected to the first voltage terminal V1, the emitter of the sixth P-type transistor PNP6 is connected to the fourth voltage terminal V4, the collector of the sixth P-type transistor PNP6 is connected to the charge and discharge proportional current control module 130, the base of the seventh P-type transistor PNP7 is connected to the first voltage terminal V1, the emitter of the seventh P-type transistor PNP7 is connected to the fifth voltage terminal V5, the collector of the seventh P-type transistor PNP7 is connected to the charge and discharge proportional current control module 130, the collector of the seventh P-type transistor PNP7 is also connected to one end of the external charge and discharge capacitor C0, the other end of the external charge and discharge capacitor C0 is connected to the signal ground, the emitter of the eighth P-type transistor PNP8 is connected to the third voltage terminal V3, and the collector of the eighth P-type transistor PNP8 is connected to the signal ground.

[0035] In the embodiment of the present invention, according to the virtual short principle of the operational amplifier, the base voltage V1 of the sixth P-type transistor PNP6 and the seventh P-type transistor PNP7 is equal to the second reference voltage VREF2. According to the ideal transistor collector current formula, the collector current is proportional to V BE The relationship is exponential, so a larger current difference will only result in a small V BE If V4 is not equal to V5, due to the Early effect, I E(PNP4) with I E(PNP5) There is a small difference. Since the area ratio of the sixth P-type transistor PNP6 and the seventh P-type transistor PNP7 is 1:1, I E(PNP4) with I E(PNP5) The smaller current difference becomes V BE(PNP6) With V BE(PNP7) Smaller voltage difference. Because the base voltages of the sixth P-type transistor PNP6 and the seventh P-type transistor PNP7 are equal, V BE(PNP6) With V BE(PNP7) The similarity between the voltages of the fourth voltage terminal V4 and the fifth voltage terminal V5 will cause the voltages of the fourth voltage terminal V4 and the fifth voltage terminal V5 to be similar, and the similarity between the voltages of the fourth voltage terminal V4 and the fifth voltage terminal V5 will cause I c(PNP4) with I c(PNP5) Similar to I c(PNP4) with I c(PNP5) The proximity will promote V BE(PNP6) With V BE(PNP7) Therefore, the voltage of the fourth voltage terminal V4 is equal to the voltage of the fifth voltage terminal V5, that is, V4=V5, I E(PNP4) = I E(PNP5) , I c(PNP4) = I c(PNP5) , thereby eliminating the Early effect of the PNP transistor. It should be understood that if Figure 3 The figure shows a general voltage controlled oscillator system in the prior art. Figure 3 The collector terminal of PNP5 shown in the figure fluctuates continuously due to the influence of the external charge and discharge voltage CF. Figure 3 The emitter current of PNP5 fluctuates continuously, and the fluctuation of the emitter current further affects the fluctuation of the charge and discharge current of the external charge and discharge capacitor, which ultimately affects the fluctuation of the duty cycle of the output switch waveform. Therefore, the accuracy of the duty cycle is further affected by the Early effect on the basis of the production process; and the embodiment of the present invention is as follows. Figure 2As shown, by setting the first P-type MOS tube and the second comparator COMP2, the final voltage of the fourth voltage terminal V4 can be equal to the final voltage of the fifth voltage terminal V5, and finally a stable voltage control signal that does not follow the external charge and discharge voltage fluctuation is obtained. The stable voltage signal can make the emitter current PNP5 of the fifth P-type transistor equal to the emitter current of the fourth P-type transistor PNP4, thereby accurately controlling the charge and discharge process of the external charge and discharge capacitor, and finally obtaining a stable duty cycle. Therefore, the voltage-controlled oscillation circuit of the embodiment of the present invention can obtain a stable duty cycle on the basis of eliminating the Early effect.

[0036] In the embodiment of the present invention, the first N-type transistor NPN1, the second N-type transistor NPN2, the third N-type transistor NPN3, the sixth P-type transistor PNP6, the seventh P-type transistor PNP7, and the eighth P-type transistor PNP8 form a mirror current source. According to the relationship between the transistor emitter, collector, and base currents, it can be seen that: , ;when When it is big enough, If the area ratio of the fourth P-type transistor PNP4 to the second P-type transistor PNP2 is K, then , since the area ratio of the fourth P-type transistor PNP4 to the fifth P-type transistor PNP5 is 1:1, ,so .

[0037] The area ratio of the third N-type transistor NPN3 to the second N-type transistor NPN2 is twice the area ratio of the fourth P-type transistor PNP4 to the second P-type transistor PNP2. .so Thus, when R0 varies in a wide range, the current of the first P-type MOS transistor P1 is basically maintained at: , so that the same op amp can adapt to different load changes.

[0038] In the embodiment of the present invention, Figure 2As shown, the charge-discharge proportional current control module 130 includes: a charge-discharge control unit and a switch signal output unit, the charge-discharge control unit is connected to the switch signal output unit, and the charge-discharge control unit and the switch signal output unit are both electrically connected to the external charge-discharge capacitor C0; the charge-discharge control unit is used to generate a charge control signal when the current switch signal is high, and to generate a discharge control signal when the current switch signal is low, the charge control signal is used to control the charging of the external charge-discharge capacitor, and the discharge control signal is used to control the discharge of the external charge-discharge capacitor, and the charging current and the discharge current of the external charge-discharge capacitor are equal; the switch signal output unit is used to output a low-level switch signal when the voltage value of the external charge-discharge capacitor is high, and to output a high-level switch signal when the voltage value of the external charge-discharge capacitor is low.

[0039] Specifically, the charge and discharge control unit includes: a second N-type MOS transistor N2, a fourth N-type transistor NPN4, a fifth N-type transistor NPN5, and a sixth N-type transistor NPN6. The gate terminal of the second N-type MOS transistor N2 is connected to the output terminal of the switch signal output unit, the drain terminal of the second N-type MOS transistor N2 is connected to the base terminal of the fourth N-type transistor NPN4, the source terminal of the second N-type MOS transistor N2 is connected to the signal ground, and the collector of the fourth N-type transistor NPN4 is connected to the source terminal of the first P-type MOS transistor P1. The emitter of the fourth N-type transistor NPN4 is connected to the base of the fifth N-type transistor NPN5, the collector of the fifth N-type transistor NPN5 is connected to the collector of the sixth P-type transistor PNP6, the emitter of the fifth N-type transistor NPN5 is connected to the signal ground, the base of the sixth N-type transistor NPN6 is connected to the base of the fifth N-type transistor NPN5, the collector of the sixth N-type transistor NPN6 is connected to the collector of the seventh P-type transistor PNP7, and the emitter of the sixth N-type transistor NPN6 is connected to the signal ground.

[0040] Specifically, the switching signal output unit includes: a third comparator COMP3, a fourth comparator COMP4 and a latch, the non-inverting input of the third comparator COMP3 is connected to one end of the external charging and discharging capacitor C0, the inverting input of the third comparator COMP3 is connected to the third reference voltage V_H, the output of the third comparator COMP3 is connected to the first input of the latch, the non-inverting input of the fourth comparator COMP4 is connected to one end of the external charging and discharging capacitor C0, the inverting input of the fourth comparator COMP4 is connected to the fourth reference voltage V_L, the output of the fourth comparator COMP4 is connected to the second input of the latch, and the output of the latch is the output of the switching signal output unit, wherein the third reference voltage V_H is greater than the fourth reference voltage V_L.

[0041] More specifically, the latch may include two NOT gates and two NOR gates, and the specific connection relationship is as follows: Figure 2 shown.

[0042] It should be understood that when the voltage at one end CF of the external charge and discharge capacitor C0 is at a low level, that is, CF is less than V_H, and CF is less than V_L, the third comparator COMP3 and the fourth comparator COMP4 both output a low level. At this time, the switching signal SW output by the output end of the switching signal output unit is at a high level, and the second N-type MOS transistor N2 is turned on, thereby pulling down the fourth P-type transistor PNP4. At this time, the base of the fourth P-type transistor NPN4 is at a low level, so the mirror current source composed of the fifth P-type transistor NPN5 and the sixth P-type transistor NPN6 is turned off. At this time, the external charge and discharge capacitor C0 is charged by the fifth P-type transistor PNP5. When CF is charged to a level greater than V_H, SW is at a low level. At this time, the second N-type MOS transistor N2 is turned off, and the base of the fourth N-type transistor NPN4 is at a high level. The mirror current source formed by the fifth P-type transistor NPN5 and the sixth N-type transistor NPN6 is turned on. Since the area ratio of the fifth N-type transistor NPN5 to the sixth N-type transistor NPN6 is 1:2, the current of the sixth N-type transistor NPN6 is twice that of the fifth N-type transistor NPN5. Since the currents of the fourth P-type transistor PNP4 and the fifth P-type transistor PNP5 are equal, the external charge-discharge capacitor C0 is required to discharge the sixth N-type transistor NPN6 to meet the current demand of the sixth N-type transistor NPN6. That is, through discharge, the current of the sixth N-type transistor NPN6 is twice the current of the fifth N-type transistor PNP5. This discharge process ends when CF falls below V_L, that is, when SW is at a high level. Since the charging current is equal to the discharging current during the charging and discharging process, the duty cycle of the SW switch signal can reach 50%.

[0043] Specifically, in the charge and discharge proportional current control module, since V_H is greater than V_L, when CF is greater than V_H, the output of the third comparator COMP3 is high, the output of the fourth comparator COMP4 is high, and the output switch signal SW is low; when CF is less than V_L, the output of the fourth comparator COMP4 is low, and the output switch signal SW is high.

[0044] like Figure 2 As shown, when SW is low, the second N-type MOS tube N2 is cut off, and NPN4, NPN5 and NPN6 work normally. Since the area of ​​NPN5 and NPN6 is 1:2, , because the currents in the same branch are equal, so = Ic(PNP4), and because Ic(PNP4) = Ic(PNP5), the external charge and discharge capacitor C0 is discharging at this time, and the current is When SW is high, the second N-type MOS tube N2 is turned on, and all the current flows to N2. NPN4, NPN5 and NPN6 are cut off. At this time, the external charge and discharge capacitor C0 is charging, and the current is , thus forming a SW waveform with a duty cycle of 50%, the specific waveform is as follows Figure 4 As shown. Figure 4 As shown, CF oscillates back and forth between V_H and V_L, and Figure 3 In the conventional voltage-controlled oscillator shown, since V4 is not equal to CF and CF is constantly changing, the charge and discharge currents of CF are affected by the Early effect of the PNP transistor and cannot be completely consistent, resulting in a deviation in the duty cycle. However, the embodiment of the present invention eliminates the influence of the Early effect, so that the final voltages of the fourth voltage terminal V4 and the fifth voltage terminal V5 are equal, thereby accurately controlling the charge and discharge process of the external charge and discharge capacitor and ultimately obtaining a stable duty cycle.

[0045] Therefore, in the voltage-controlled oscillation circuit provided by the present invention, the oscillation current generating module can generate different oscillation currents according to different external loads; the voltage control module can control the base voltages of the sixth P-type transistor and the seventh P-type transistor so that the voltages of the fourth voltage terminal and the fifth voltage terminal are ultimately equal; the charge-discharge ratio current control module can control the charge-discharge current ratio and control whether to charge or discharge the external charge-discharge capacitor according to the voltage of the external charge-discharge capacitor. The voltage-controlled oscillation circuit can eliminate the Early effect of the PNP transistor and has the advantages of low dependence on the stability of the production process and high stability.

[0046] As another embodiment of the present invention, a switching power supply 10 is provided, wherein Figure 5As shown, it includes: a switching power supply control chip 11 and a switching tube 12, the output end of the switching power supply control chip 11 is connected to the control end of the switching tube 12, the switching power supply control chip 11 includes a driving circuit 200 and the voltage-controlled oscillation circuit 100 mentioned above, the output end of the voltage-controlled oscillation circuit 100 is connected to the input end of the driving circuit 200, and the output end of the driving circuit 200 is the output end of the switching power supply control chip 11.

[0047] In an embodiment of the present invention, when the switching power supply is connected to an external load, the voltage-controlled oscillator circuit 100 in the switching power supply control chip 11 can generate a corresponding oscillating current according to different external loads, and then obtain a stable voltage control signal based on the oscillating current. Finally, based on the stable voltage control signal, the charging and discharging current ratio and charging and discharging of the external charging and discharging capacitor are controlled, thereby obtaining a stable switching signal. The stable switching signal can be output to the driving circuit 200, and the driving circuit 200 can generate a driving signal based on the stable switching signal. The driving signal can effectively drive the switching action of the switching tube 12, thereby realizing the operation of the switching power supply.

[0048] Specifically, the driving circuit 200 may include a driving circuit structure composed of an inverter, a NOR gate, a NAND gate, and a level shift structure to realize the function of the driving circuit, which is well known to those skilled in the art and will not be described in detail here.

[0049] In summary, the switching power supply provided by the present invention can eliminate the problems of reduced duty cycle accuracy and poor stability caused by the Early effect in the prior art because the switching power supply control chip adopts the voltage-controlled oscillation circuit mentioned above, thereby achieving the goal of improving the accuracy and stability of the switching power supply control chip without changing the production process, thereby improving the product performance of the switching power supply.

[0050] It will be understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present invention, and the present invention is not limited thereto. Those skilled in the art will appreciate that various modifications and improvements can be made without departing from the spirit and substance of the present invention, and such modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A voltage-controlled oscillator circuit, characterized in that: include: An oscillating current generating module, a voltage control module and a charge-discharge proportional current control module, wherein the oscillating current generating module is electrically connected to the voltage control module, and the voltage control module is electrically connected to the charge-discharge proportional current control module; The oscillating current generating module is used to generate a corresponding oscillating current according to an external load of the voltage-controlled oscillating circuit; The voltage control module is used to perform voltage stabilization control according to the oscillating current to obtain a stable voltage control signal that does not follow the fluctuation of the external charge and discharge voltage; The charge-discharge ratio current control module is used to determine the charge-discharge current ratio according to the stable voltage control signal, and to control the charge and discharge of the external charge-discharge capacitor according to the charge-discharge current ratio; The oscillating current generating module includes: a mirror current generating unit and a mirror current output unit, wherein the mirror current generating unit is connected to the mirror current output unit. The mirror current generating unit is used to generate a matching oscillating current according to a resistance change of an external load; The mirror current output unit is used to output the oscillation current in a mirror image; The mirror current generation unit includes a first comparator and a first N-type MOS transistor, a non-inverting input terminal of the first comparator being used to input a first reference voltage, an inverting input terminal of the first comparator being connected to a source terminal of the first N-type MOS transistor, an output terminal of the first comparator being connected to a gate terminal of the first N-type MOS transistor, a source terminal of the first N-type MOS transistor being further used to connect to one terminal of an external load, the other terminal of the external load being connected to a signal ground, and a drain terminal of the first N-type MOS transistor being connected to the mirror current output unit; The mirror current output unit includes: a first P-type transistor, a second P-type transistor, a third P-type transistor, a fourth P-type transistor and a fifth P-type transistor, The collector of the first P-type transistor is connected to the drain terminal of the first N-type MOS transistor, the emitter of the first P-type transistor is connected to the voltage control module, the base of the first P-type transistor is connected to the base of the second P-type transistor, and the collector of the first P-type transistor is a second voltage terminal; The emitter of the second P-type transistor is connected to the emitter of the first P-type transistor, and the collector of the second P-type transistor is a third voltage terminal; The emitter of the third P-type transistor is connected to the base of the first P-type transistor, the base of the third P-type transistor is connected to the collector of the first P-type transistor, and the collector of the third P-type transistor is connected to the signal ground; The emitter of the fourth P-type transistor is connected to the emitter of the first P-type transistor, the base of the fourth P-type transistor is connected to the base of the first P-type transistor, and the collector of the fourth P-type transistor is a fourth voltage terminal; The emitter of the fifth P-type transistor is connected to the emitter of the first P-type transistor, the base of the fifth P-type transistor is connected to the base of the first P-type transistor, and the collector of the fifth P-type transistor is a fifth voltage terminal.

2. The voltage-controlled oscillator circuit according to claim 1, wherein: The voltage control module includes: a voltage stabilization control unit and a voltage output unit, wherein the voltage stabilization control unit is connected to the voltage output unit. The voltage stabilization control unit is used to control the voltage of the fourth voltage terminal and the voltage of the fifth voltage terminal according to the oscillating current and the second reference voltage; The voltage output unit is used to cooperate with the voltage stabilization control unit to control the voltage of the fourth voltage terminal and the voltage of the fifth voltage terminal so that the voltage of the fourth voltage terminal is equal to the voltage of the fifth voltage terminal, so as to obtain a stable voltage control signal that does not follow the fluctuations of the external charging and discharging voltage.

3. The voltage-controlled oscillator circuit according to claim 2, wherein: The voltage stabilization control unit includes: a second comparator, a first resistor and a first P-type MOS tube, The inverting input terminal of the second comparator is used to input the second reference voltage, the non-inverting input terminal of the second comparator is connected to the voltage output unit, and the non-inverting input terminal of the second comparator is the first voltage terminal, and the output terminal of the second comparator is connected to the gate terminal of the first P-type MOS transistor. The source terminal of the first P-type MOS transistor is connected to the emitter terminal of the first P-type transistor, and the drain terminal of the first P-type MOS transistor is connected to the non-inverting input terminal of the second comparator. One end of the first resistor is connected to the non-inverting input terminal of the second comparator, and the other end of the first resistor is connected to the signal ground.

4. The voltage-controlled oscillator circuit according to claim 3, wherein: The voltage output unit includes: a first N-type transistor, a second N-type transistor, a third N-type transistor, a sixth P-type transistor, a seventh P-type transistor and an eighth P-type transistor, The base of the first N-type transistor is connected to the base of the eighth P-type transistor, the collector of the first N-type transistor is connected to the emitter of the first P-type transistor, and the emitter of the first N-type transistor is connected to the base of the second N-type transistor. The collector of the second N-type transistor is connected to the base of the eighth P-type transistor, and the emitter of the second N-type transistor is connected to the signal ground. The base of the third N-type transistor is connected to the base of the second N-type transistor, and the collector of the third N-type transistor is connected to the first voltage terminal. The base of the sixth P-type transistor is connected to the first voltage terminal, the emitter of the sixth P-type transistor is connected to the fourth voltage terminal, and the collector of the sixth P-type transistor is connected to the charge-discharge proportional current control module. The base of the seventh P-type transistor is connected to the first voltage terminal, the emitter of the seventh P-type transistor is connected to the fifth voltage terminal, the collector of the seventh P-type transistor is connected to the charge-discharge proportional current control module, the collector of the seventh P-type transistor is also connected to one end of an external charge-discharge capacitor, and the other end of the external charge-discharge capacitor is connected to a signal ground. The emitter of the eighth P-type transistor is connected to the third voltage terminal, and the collector of the eighth P-type transistor is connected to the signal ground.

5. The voltage-controlled oscillator circuit according to claim 4, wherein: The charge and discharge proportional current control module includes: a charge and discharge control unit and a switch signal output unit, wherein the charge and discharge control unit is connected to the switch signal output unit, and the charge and discharge control unit and the switch signal output unit are both electrically connected to an external charge and discharge capacitor; The charge and discharge control unit is used to generate a charge control signal when the current switch signal is at a high level, and to generate a discharge control signal when the current switch signal is at a low level, wherein the charge control signal is used to control the charging of the external charge and discharge capacitor, and the discharge control signal is used to control the discharging of the external charge and discharge capacitor, and the charging current and the discharging current of the external charge and discharge capacitor are equal; The switch signal output unit is configured to output a low-level switch signal when the voltage value of the external charge and discharge capacitor is at a high level, and output a high-level switch signal when the voltage value of the external charge and discharge capacitor is at a low level.

6. The voltage-controlled oscillator circuit according to claim 5, wherein: The charge and discharge control unit includes: a second N-type MOS transistor, a fourth N-type transistor, a fifth N-type transistor and a sixth N-type transistor. The gate terminal of the second N-type MOS transistor is connected to the output terminal of the switch signal output unit, the drain terminal of the second N-type MOS transistor is connected to the base terminal of the fourth N-type transistor, and the source terminal of the second N-type MOS transistor is connected to the signal ground. The collector of the fourth N-type transistor is connected to the source of the first P-type MOS transistor, and the emitter of the fourth N-type transistor is connected to the base of the fifth N-type transistor. The collector of the fifth N-type transistor is connected to the collector of the sixth P-type transistor, and the emitter of the fifth N-type transistor is connected to the signal ground. The base of the sixth N-type transistor is connected to the base of the fifth N-type transistor, the collector of the sixth N-type transistor is connected to the collector of the seventh P-type transistor, and the emitter of the sixth N-type transistor is connected to the signal ground.

7. The voltage-controlled oscillator circuit according to claim 6, wherein: The switch signal output unit includes: a third comparator, a fourth comparator and a latch, The non-inverting input terminal of the third comparator is connected to one end of the external charge and discharge capacitor, the inverting input terminal of the third comparator is connected to the third reference voltage, and the output terminal of the third comparator is connected to the first input terminal of the latch. The non-inverting input terminal of the fourth comparator is connected to one end of the external charge and discharge capacitor, the inverting input terminal of the fourth comparator is connected to the fourth reference voltage, and the output terminal of the fourth comparator is connected to the second input terminal of the latch. The output end of the latch is the output end of the switch signal output unit, The third reference voltage is greater than the fourth reference voltage.

8. A switching power supply, characterized in that: include: A switching power supply control chip and a switching tube, wherein the output end of the switching power supply control chip is connected to the control end of the switching tube, the switching power supply control chip comprises a drive circuit and the voltage-controlled oscillation circuit according to any one of claims 1 to 7, the output end of the voltage-controlled oscillation circuit is connected to the input end of the drive circuit, and the output end of the drive circuit is the output end of the switching power supply control chip.

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