Voltage-controlled oscillation circuit and switching power supply

Abstract

The application relates to the technical field of switching power supplies, and particularly discloses a voltage-controlled oscillation circuit and a switching power supply, which comprise an oscillation current generating module, a voltage control module and a charge-discharge proportional current control module; the oscillation current generating module is electrically connected with the voltage control module; the voltage control module is electrically connected with the charge-discharge proportional current control module; the oscillation current generating module is used for generating corresponding oscillation current according to the external load of the voltage-controlled oscillation circuit; the voltage control module is used for performing voltage stabilization control according to the oscillation current to obtain a stable voltage control signal which does not follow external charge-discharge voltage fluctuation; 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 performing charge-discharge control on the external charge-discharge capacitor according to the charge-discharge current proportion. The voltage-controlled oscillation circuit can improve the precision and stability of the switching power supply control chip without changing the production process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of switching power supply, and particularly relates to a voltage-controlled oscillation circuit and a switching power supply. BACKGROUND

[0002] In the technical field of switching power supply, there is a very high requirement for the precision and stability of the duty cycle of the switching waveform of the switching power supply control chip, and the precision and stability of the switching waveform of the current control chip mainly depend on the stability of the production process, so it is difficult to adjust the precision of the duty cycle after the production of the control chip. In addition to the influence of the production process, the duty cycle of the control chip is also affected by the Eddy effect in the actual circuit work, such as Figure 3 As shown in FIG. 1, the existing switching power supply control chip is affected by the Eddy effect during work, which reduces the precision and stability of the duty cycle of the control chip.

[0003] Therefore, how to improve the precision and stability of the switching power supply control chip without changing the production process has become a technical problem to be solved by the person skilled in the art. SUMMARY

[0004] The present application provides a voltage-controlled oscillation circuit and a switching power supply, which solves the problem that the precision of the switching power supply control chip is affected by the Eddy effect under the condition that the production process cannot be changed in the related art, resulting in low precision and poor stability.

[0005] As a first aspect of the present application, a voltage-controlled oscillation circuit is provided, comprising: an oscillation current generation module, a voltage control module, and a charge-discharge proportional current control module, the oscillation current generation module being electrically connected to the voltage control module, and the voltage control module being electrically connected to the charge-discharge proportional current control module; the oscillation current generation module is configured to generate a corresponding oscillation current according to an external load of the voltage-controlled oscillation circuit; the voltage control module is configured to perform voltage stabilization control according to the oscillation current to obtain a stable voltage control signal that does not follow external charge-discharge voltage fluctuations; and the charge-discharge proportional current control module is configured to determine a charge-discharge current ratio according to the stable voltage control signal, and perform charge-discharge control on an external charge-discharge capacitor according to the charge-discharge current ratio; wherein the oscillation current generation module comprises: a mirror current generation unit and a mirror current output unit, the mirror current generation unit being connected to the mirror current output unit, the mirror current generation unit being configured to generate a matching oscillation current according to a resistance change of the external load; and the mirror current output unit being configured to mirror output the oscillation current; wherein the mirror current generation unit comprises a first comparator and a first N-type MOS tube, a non-inverting input terminal of the first comparator being configured 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 tube, an output terminal of the first comparator being connected to a gate terminal of the first N-type MOS tube, and the source terminal of the first N-type MOS tube being further configured to connect one end of an external load, the other end of the external load being connected to a signal ground, and a drain terminal of the first N-type MOS tube being connected to the mirror current output unit; the mirror current output unit comprises: 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, a collector of the first P-type transistor being connected to the drain terminal of the first N-type MOS tube, an emitter of the first P-type transistor being connected to the voltage control module, a base of the first P-type transistor being connected to a base of the second P-type transistor, and the collector of the first P-type transistor being a second voltage terminal; an emitter of the second P-type transistor being connected to the emitter of the first P-type transistor, and a collector of the second P-type transistor being a third voltage terminal; an emitter of the third P-type transistor being connected to the base of the first P-type transistor, a base of the third P-type transistor being connected to the collector of the first P-type transistor, and a collector of the third P-type transistor being connected to the signal ground; an emitter of the fourth P-type transistor being connected to the emitter of the first P-type transistor, a base of the fourth P-type transistor being connected to the base of the first P-type transistor, and a collector of the fourth P-type transistor being a fourth voltage terminal; an emitter of the fifth P-type transistor being connected to the emitter of the first P-type transistor, a base of the fifth P-type transistor being connected to the base of the first P-type transistor, and a collector of the fifth P-type transistor being a fifth voltage terminal.

[0006] Further, the voltage control module comprises a voltage stabilizing control unit and a voltage output unit, the voltage stabilizing control unit is connected with the voltage output unit, and the voltage stabilizing control unit is used to control the voltage of the fourth voltage terminal and the voltage of the fifth voltage terminal according to the oscillation current and the second reference voltage; the voltage output unit is used to control the voltage of the fourth voltage terminal and the voltage of the fifth voltage terminal in cooperation with the voltage stabilizing control unit so that the voltage of the fourth voltage terminal is equal to the voltage of the fifth voltage terminal, thereby obtaining a stable voltage control signal which does not follow the fluctuation of the external charging and discharging voltage.

[0007] Further, the voltage stabilizing control unit comprises 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 with the voltage output unit, and the non-inverting input terminal of the second comparator is the first voltage terminal, the output terminal of the second comparator is connected with the gate terminal of the first P-type MOS tube, the source terminal of the first P-type MOS tube is connected with the emitter of the first P-type transistor, the drain terminal of the first P-type MOS tube is connected with the non-inverting input terminal of the second comparator, one end of the first resistor is connected with the non-inverting input terminal of the second comparator, and the other end of the first resistor is connected with the signal ground.

[0008] Further, the voltage output unit comprises 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 with the base of the eighth P-type transistor, the collector of the first N-type transistor is connected with the emitter of the first P-type transistor, the emitter of the first N-type transistor is connected with the base of the second N-type transistor, the collector of the second N-type transistor is connected with the base of the eighth P-type transistor, the emitter of the second N-type transistor is connected with the signal ground, the base of the third N-type transistor is connected with the base of the second N-type transistor, the collector of the third N-type transistor is connected with the first voltage terminal, the base of the sixth P-type transistor is connected with the first voltage terminal, the emitter of the sixth P-type transistor is connected with the fourth voltage terminal, the collector of the sixth P-type transistor is connected with the charging and discharging proportion current control module, the base of the seventh P-type transistor is connected with the first voltage terminal, the emitter of the seventh P-type transistor is connected with the fifth voltage terminal, the collector of the seventh P-type transistor is connected with the charging and discharging proportion current control module, the collector of the seventh P-type transistor is also connected with one end of an external charging and discharging capacitor, the other end of the external charging and discharging capacitor is connected with the signal ground, and the emitter of the eighth P-type transistor is connected with the third voltage terminal, and the collector of the eighth P-type transistor is connected with the signal ground.

[0009] Further, the charging and discharging proportional current control module comprises a charging and discharging control unit and a switch signal output unit, the charging and discharging control unit is connected with the switch signal output unit, and the charging and discharging control unit and the switch signal output unit are both electrically connected with an external charging and discharging capacitor; the charging and discharging control unit is used for generating a charging control signal when a current switch signal is high, and generating a discharging control signal when the current switch signal is low, the charging control signal is used for charging control of the external charging and discharging capacitor, the discharging control signal is used for discharging control of the external charging and discharging capacitor, and a charging current of the external charging and discharging capacitor is equal to a discharging current; the switch signal output unit is used for outputting a low-level switch signal when a voltage value of the external charging and discharging capacitor is high, and outputting a high-level switch signal when the voltage value of the external charging and discharging capacitor is low.

[0010] Further, the charging and discharging control unit comprises a second N-type MOS tube, a fourth N-type transistor, a fifth N-type transistor and a sixth N-type transistor, a gate terminal of the second N-type MOS tube is connected with an output terminal of the switch signal output unit, a drain terminal of the second N-type MOS tube is connected with a base of the fourth N-type transistor, a source terminal of the second N-type MOS tube is connected with a signal ground, a collector of the fourth N-type transistor is connected with a source terminal of the first P-type MOS tube, a base of the fourth N-type transistor is connected with a base of the fifth N-type transistor, a collector of the fifth N-type transistor is connected with a collector of the sixth P-type transistor, an emitter of the fifth N-type transistor is connected with the signal ground, a base of the sixth N-type transistor is connected with the base of the fifth N-type transistor, a collector of the sixth N-type transistor is connected with a collector of the seventh P-type transistor, and an emitter of the sixth N-type transistor is connected with the signal ground.

[0011] Further, the switch signal output unit comprises a third comparator, a fourth comparator and a latch, a same-phase input terminal of the third comparator is connected with one end of the external charging and discharging capacitor, an opposite-phase input terminal of the third comparator is connected with a third reference voltage, an output terminal of the third comparator is connected with a first input terminal of the latch, a same-phase input terminal of the fourth comparator is connected with one end of the external charging and discharging capacitor, an opposite-phase input terminal of the fourth comparator is connected with a fourth reference voltage, an output terminal of the fourth comparator is connected with a second input terminal of the latch, and an output terminal of the latch is an output terminal of the switch signal output unit, wherein the third reference voltage is greater than the fourth reference voltage.

[0012] As another aspect of the present application, a switching power supply is provided, comprising: a switching power supply control chip and a switching tube, an output terminal of the switching power supply control chip being connected with a control terminal of the switching tube, the switching power supply control chip comprising a drive circuit and the voltage-controlled oscillation circuit as described above, an output terminal of the voltage-controlled oscillation circuit being connected with an input terminal of the drive circuit, and an output terminal of the drive circuit being the output terminal of the switching power supply control chip.

[0013] The voltage-controlled oscillation circuit provided by the present application can generate corresponding oscillation current according to external load through the oscillation current generation module, and the voltage control module can further perform voltage stabilization control according to the oscillation current to obtain a stable voltage control signal that does not follow external charging and discharging voltage fluctuation, and finally the charging and discharging proportion current control module performs charging and discharging control on the external charging and discharging 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. The voltage-controlled oscillation circuit can keep the current for charging the external charging and discharging capacitor stable due to the stable voltage control signal, thereby eliminating the problems of reduced duty cycle accuracy and poor stability caused by the Eyring effect in the prior art, thereby improving the accuracy and stability of the switching power supply control chip without changing the production process, and further improving the product performance of the switching power supply. BRIEF DESCRIPTION OF DRAWINGS

[0014] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, and are used together with the following detailed description to explain the present application, but do not constitute a limitation on the present application.

[0015] Figure 1 The circuit structure block diagram of the voltage-controlled oscillation circuit provided by the present application.

[0016] Figure 2 The circuit principle diagram of the voltage-controlled oscillation circuit provided by the present application.

[0017] Figure 3 The circuit schematic diagram of the voltage-controlled oscillation system of the prior art.

[0018] Figure 4 The output switching waveform of the voltage-controlled oscillation circuit provided by the present application and the voltage waveform of the external charging and discharging capacitor.

[0019] Figure 5 The structure block diagram of the switching power supply provided by the present application. DETAILED DESCRIPTION

[0020] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0021] In order to make the technical personnel better understand the present application, the following will be combined with the drawings in the embodiments of the present application, the technical solutions in the embodiments of the present application are described clearly and completely, obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by the ordinary skilled in the art without making creative labor should belong to the scope of protection of the present application.

[0022] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances to implement the embodiments of the application described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0023] In the present embodiment, a voltage-controlled oscillation circuit is provided, Figure 1 The circuit structure block diagram of the voltage-controlled oscillation circuit 100 provided according to the embodiment of the present application is shown as Figure 1 The voltage-controlled oscillation circuit 100 includes an oscillation current generating module 110, a voltage control module 120 and a charge-discharge proportional current control module 130, the oscillation current generating module 110 is electrically connected with the voltage control module 120, the voltage control module 120 is electrically connected with the charge-discharge proportional current control module 130; the oscillation current generating module 110 is used to generate corresponding oscillation current according to the external load of the voltage-controlled oscillation circuit; the voltage control module 120 is used to control the voltage stabilization according to the oscillation current to obtain a stable voltage control signal not following the external charge-discharge voltage fluctuation; the charge-discharge proportional current control module 130 is used to determine the charge-discharge current proportion according to the stable voltage control signal, and control the external charge-discharge capacitor according to the charge-discharge current proportion.

[0024] In the embodiment of the present application, the oscillation current generating module 110 can generate corresponding oscillation current according to the change of the external load, that is, when the switch power supply connected with the voltage-controlled oscillation circuit connects different external loads, the oscillation current generating module 110 in the voltage-controlled oscillation circuit can generate corresponding oscillation current according to the change of the load, so as to subsequently adjust the corresponding switch duty cycle based on the oscillation current.

[0025] The voltage control module 120 can perform voltage stabilization control based on the oscillation current, and the stable voltage control signal obtained through the voltage stabilization control does not follow the external charging and discharging voltage fluctuation, so that the current for charging the external charging and discharging capacitor remains stable, thereby eliminating the problems of reduced duty cycle accuracy and poor stability caused by the Eyring effect in the prior art.

[0026] The charging and discharging proportional current control module 130 can perform charging and discharging control on the external charging and discharging capacitor according to the stable voltage control signal, so that the duty cycle of the output switch signal can be maintained in a stable state. The specific duty cycle can also be adjusted as needed.

[0027] Therefore, the voltage-controlled oscillator provided by the present application generates corresponding oscillation current according to the external load through the oscillation current generation module, and the voltage control module can further perform voltage stabilization control according to the oscillation current to obtain a stable voltage control signal that does not follow the external charging and discharging voltage fluctuation. Finally, the charging and discharging proportional current control module performs charging and discharging control on the external charging and discharging capacitor based on the stable voltage control signal, so that the duty cycle of the output switch signal can be maintained in a stable state. The voltage-controlled oscillator can eliminate the problems of reduced duty cycle accuracy and poor stability caused by the Eyring effect in the prior art, so as to improve the accuracy and stability of the switching power supply control chip without changing the production process, and further improve the product performance of the switching power supply.

[0028] In the embodiment of the present application, the oscillation current generation module 110 includes a mirror current generation unit and a mirror current output unit, the mirror current generation unit is connected with the mirror current output unit, the mirror current generation unit is used to generate matched oscillation current according to the resistance change of the external load; and the mirror current output unit is used to mirror output the oscillation current.

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

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

[0031] In the oscillation 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 constitute a mirror current source, according to ideal triode collector current I E : , the I ES is proportional to the area of the triode, the V T are all the same, so under ideal conditions, the V BE of the same triode current is proportional to the area. Due to the existence of Early effect in practical application, the triode current is also affected by the CE terminal voltage difference, the greater the CE terminal voltage difference, the greater the current. In the embodiment of the present application, the base end and the emitter end 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, the V BE are the same. Since the area of the fourth P-type transistor PNP4 and the fifth P-type transistor PNP5 is 1:1, if V4 = V5, then I E(PNP4) = I E(PNP5) , that is, in the embodiment of the present application, under the condition that the voltage of the fourth voltage terminal V4 and the voltage of the fifth voltage terminal V5 are the same, the emitter current of the fourth P-type transistor PNP4 and the emitter current of the fifth P-type transistor PNP5 are the same.

[0032] In the embodiment of the present application, the voltage control module 120 comprises: a voltage stabilizing control unit and a voltage output unit, the voltage stabilizing control unit is connected with the voltage output unit, the voltage stabilizing control unit is used for controlling the voltage of the fourth voltage terminal and the voltage of the fifth voltage terminal according to the oscillation current and the second reference voltage; the voltage output unit is used for controlling the voltage of the fourth voltage terminal and the voltage of the fifth voltage terminal in cooperation with the voltage stabilizing control unit to make the voltage of the fourth voltage terminal equal to the voltage of the fifth voltage terminal, so as to obtain a stable voltage control signal which does not follow the fluctuation of external charging and discharging voltage.

[0033] Specifically, the voltage output unit comprises a first NPN transistor NPN1, a second NPN transistor NPN2, a third NPN transistor NPN3, a sixth PNP transistor PNP6, a seventh PNP transistor PNP7 and an eighth PNP transistor PNP8, a base of the first NPN transistor NPN1 is connected to a base of the eighth PNP transistor PNP8, a collector of the first NPN transistor NPN1 is connected to an emitter of the first PNP transistor PNP1, an emitter of the first NPN transistor NPN1 is connected to a base of the second NPN transistor NPN2, a collector of the second NPN transistor NPN2 is connected to a base of the eighth PNP transistor PNP8, an emitter of the second NPN transistor NPN2 is connected to a signal ground, a base of the third NPN transistor NPN3 is connected to a base of the second NPN transistor NPN2, a collector of the third NPN transistor NPN3 is connected to the first voltage terminal V1, a base of the sixth PNP transistor PNP6 is connected to the first voltage terminal V1, an emitter of the sixth PNP transistor PNP6 is connected to the fourth voltage terminal V4, a collector of the sixth PNP transistor PNP6 is connected to the charge-discharge proportional current control module 130, a base of the seventh PNP transistor PNP7 is connected to the first voltage terminal V1, an emitter of the seventh PNP transistor PNP7 is connected to the fifth voltage terminal V5, a collector of the seventh PNP transistor PNP7 is connected to the charge-discharge proportional current control module 130, the collector of the seventh PNP transistor PNP7 is also connected to one end of an external charge-discharge capacitor C0, the other end of the external charge-discharge capacitor C0 is connected to the signal ground, an emitter of the eighth PNP transistor PNP8 is connected to the third voltage terminal V3, a collector of the eighth PNP transistor PNP8 is connected to the signal ground.

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

[0035] In this embodiment of the invention, based on 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 formula for the collector current of an ideal transistor, the collector current is related to V... BE The relationship is exponential, so a large current difference will only result in a slight increase in V. BE The gap. If V4 is not equal to V5, due to the Earlley effect, I E(PNP4) with I E(PNP5) There are minor differences. Because the area ratio of the sixth P-type transistor PNP6 to the seventh P-type transistor PNP7 is 1:1, therefore I... E(PNP4) with I E(PNP5) A small difference in current becomes V BE(PNP6) With V BE(PNP7) A 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 proximity of voltages at the fourth voltage terminal V4 and the fifth voltage terminal V5 will result in similar voltages at both terminals, leading to I... c(PNP4) with I c(PNP5) Similarity, I c(PNP4) with I c(PNP5) The similarity will promote V BE(PNP6) With V BE(PNP7) Since they are similar, the voltages at the fourth voltage terminal V4 and the fifth voltage terminal V5 will eventually be equal, i.e., V4 = V5. E(PNP4) = I E(PNP5) I c(PNP4) = I c(PNP5) This eliminates the Early effect in PNP transistors. It should be understood that, as... Figure 3 The image shows a typical voltage-controlled oscillator system in the prior art. Figure 3 The collector terminal of the PNP5 shown fluctuates continuously due to the influence of the external charging and discharging voltage CF, which in turn leads to... Figure 3 The emitter current of the PNP5 capacitor fluctuates continuously, which in turn affects the fluctuation of the charging and discharging current of the external charging and discharging capacitor, ultimately affecting the duty cycle fluctuation of the output switching waveform. Therefore, the Earlley effect further impacts the accuracy of the duty cycle on top of the manufacturing process. In contrast, embodiments of this invention, for example... Figure 2As shown, through the setting of the first P-type MOS tube and the second comparator COMP2, the final voltage of the fourth voltage terminal V4 and the fifth voltage terminal V5 can be equal, and a stable voltage control signal not following the external charging and discharging voltage fluctuation is finally obtained, which can make the emitter current PNP5 of the fifth P-type transistor equal to the emitter current of the fourth P-type transistor PNP4, so as to accurately control the charging and discharging process of the external charging and discharging capacitor, and finally obtain a stable duty cycle. Therefore, the voltage-controlled oscillation circuit of the embodiment of the present application can obtain a stable duty cycle on the basis of eliminating the Early effect.

[0036] In the embodiment of the present application, 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 constitute a mirror current source. According to the relationship among the emitter, collector and base currents of the transistor, it is known that: , ; when is large 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 of the fourth P-type transistor PNP4 and 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, then . Therefore . In this way, when R0 changes in a large range, the current of the first P-type MOS tube P1 is basically maintained at: , so that the same operational amplifier can adapt to different load changes.

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

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

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

[0041] Further specifically, the latch can specifically comprise two NOT gates and two NOR gates, and the specific connection relationship is as shown in Figure 2

[0042] It should be understood that when the voltage of one end CF of the external charge-discharge capacitor C0 is at a low level, i.e. 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 switch signal SW output by the output terminal of the switch signal output unit is at a high level, then the second N-type MOS transistor N2 is turned on, and the fourth P-type transistor PNP4 is pulled low, 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 PNP5 and the sixth P-type transistor NPN6 is turned off, at this time the external charge-discharge capacitor C0 is charged by the fifth P-type transistor PNP5. When the charge reaches CF greater than V_H, SW is at a low level, at this time the second N-type MOS transistor N2 is turned off, the base of the fourth P-type transistor NPN4 is at a high level, then the mirror current source composed of the fifth P-type transistor PNP5 and the sixth P-type transistor NPN6 is turned on, since the area ratio of the fifth P-type transistor PNP5 and the sixth P-type transistor NPN6 is 1:2, the current of the sixth P-type transistor NPN6 is twice that of the fifth P-type transistor PNP5, at this time the external charge-discharge capacitor C0 needs to discharge the sixth P-type transistor NPN6 to meet the current demand of the sixth P-type transistor NPN6, i.e. through discharging to make the current of the sixth P-type transistor NPN6 twice that of the fifth P-type transistor PNP5, the discharging process ends when CF is lower than V_L, i.e. SW is at a high level. Since the charging current and the discharging current are equal in the charging and discharging process, the duty cycle of the SW switch signal can reach fifty percent.

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

[0044] As shown in Figure 2 , when SW is low, the second N-type MOS tube N2 is cut off, and NPN4, NPN5 and NPN6 work normally, since the areas of NPN5 and NPN6 are 1:2, the current of NPN5 is twice that of NPN6. Because the currents of the same branch are equal, the current of NPN4 is Ic(PNP4), and since Ic(PNP4) = Ic(PNP5), at this time the external charge-discharge capacitor C0 is discharged, and the current is ; when SW is high, the second N-type MOS tube N2 is turned on, and the current flows to N2, NPN4, NPN5 and NPN6 are cut off, at this time the external charge-discharge capacitor C0 is charged, and the current is , thus forming a SW waveform diagram with a duty cycle of 50%, and the specific waveform diagram is shown in Figure 4 As shown in Figure 4 , CF oscillates between V_H and V_L, and in a general voltage-controlled oscillator as shown in Figure 3 , since V4 is not equal to CF, and CF is always changing, the charge-discharge current of CF is affected by the Eley effect of PNP triode, and cannot be completely consistent, so that the duty cycle deviates, and the embodiment of the present application eliminates the influence of the Eley 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-discharge process of the external charge-discharge capacitor, and finally obtaining a stable duty cycle.

[0045] Therefore, the voltage-controlled oscillation circuit provided by the present application can generate different oscillation currents according to different external loads; the voltage control module can control the base voltages of the sixth P-type triode and the seventh P-type triode to make the voltages of the fourth voltage terminal and the fifth voltage terminal eventually equal; the charge-discharge proportional current control module can control the charge-discharge current proportion and control whether to charge or discharge the external charge-discharge capacitor according to the voltage of the external charge-discharge capacitor, and the voltage-controlled oscillation circuit can eliminate the Eley effect of PNP triode, has the advantages of low dependence on production process stability and high stability.

[0046] As another embodiment of the present application, a switching power supply 10 is provided, wherein, as shown in Figure 5As shown, it comprises: a switching power control chip 11 and a switching tube 12, the output end of the switching power control chip 11 is connected with the control end of the switching tube 12, the switching power control chip 11 comprises a drive circuit 200 and the voltage-controlled oscillation circuit 100 described above, the output end of the voltage-controlled oscillation circuit 100 is connected with the input end of the drive circuit 200, and the output end of the drive circuit 200 is the output end of the switching power control chip 11.

[0047] In the embodiment of the present application, when the switching power is connected with an external load, the voltage-controlled oscillation circuit 100 in the switching power control chip 11 can generate a corresponding oscillation current according to different external loads, and then obtain a stable voltage control signal based on the oscillation current, and finally realize the control of the charging and discharging current ratio and the charging and discharging of the external charging and discharging capacitor based on the stable voltage control signal, so as to obtain a stable switching signal, which can be output to the drive circuit 200, the drive circuit 200 can generate a drive signal according to the stable switching signal, and the drive signal can effectively drive the switching action of the switching tube 12, so as to realize the working of the switching power.

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

[0049] In summary, the switching power provided by the present application can eliminate the problems of reduced duty cycle accuracy and poor stability caused by the Ehrlich effect in the prior art due to the use of the voltage-controlled oscillation circuit in the switching power control chip, so as to improve the accuracy and stability of the switching power control chip without changing the production process, and further improve the product performance of the switching power.

[0050] It can be understood that the above embodiments are only exemplary embodiments adopted for illustrating the principles of the present application, but the present application is not limited thereto. Those skilled in the art can make various modifications and improvements without departing from the spirit and essence of the present application, and these modifications and improvements are also regarded as the protection scope of the present application.

Claims

1. A voltage-controlled oscillator circuit, characterized in that, include: The system includes an oscillating current generation module, a voltage control module, and a charge / discharge proportional current control module. The oscillating current generation 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 oscillation current generation module is used to generate a corresponding oscillation current according to the external load of the voltage-controlled oscillator circuit. The voltage control module is used to perform voltage regulation control based on the oscillation current to obtain a stable voltage control signal that does not follow external charging and discharging voltage fluctuations. 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 / discharge of the external charge / discharge capacitor according to the charge / discharge current ratio. The oscillating current generation module includes a mirror current generation unit and a mirror current output unit, wherein the mirror current generation unit is connected to the mirror current output unit. The mirror current generation unit is used to generate a matching oscillating current based on the resistance change of the external load. The mirror current output unit is used to mirror the oscillating current output. The mirror current generation unit includes a first comparator and a first N-type MOSFET. The non-inverting input of the first comparator is used to input a first reference voltage. The inverting input of the first comparator is connected to the source terminal of the first N-type MOSFET. The output terminal of the first comparator is connected to the gate terminal of the first N-type MOSFET. The source terminal of the first N-type MOSFET is also used to connect to one end of an external load. The other end of the external load is connected to signal ground. The drain terminal of the first N-type MOSFET 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 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 the 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 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 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.

2. The voltage-controlled oscillator circuit according to claim 1, characterized in that, The voltage control module includes a voltage regulation control unit and a voltage output unit, wherein the voltage regulation control unit is connected to the voltage output unit. The voltage regulation and control unit is used to control the voltage of the fourth voltage terminal and the voltage of the fifth voltage terminal according to the oscillation current and the second reference voltage. The voltage output unit is used in conjunction with the voltage regulation 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, thereby obtaining a stable voltage control signal that does not follow the fluctuation of the external charging and discharging voltage.

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

4. The voltage-controlled oscillator circuit according to claim 3, characterized in that, 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 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, and the collector of the seventh P-type transistor is also connected to one end of an external charge / discharge capacitor, the other end of which is connected to 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 signal ground.

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

6. The voltage-controlled oscillator circuit according to claim 5, characterized in that, The charge / discharge control unit includes: a second N-type MOSFET, a fourth N-type transistor, a fifth N-type transistor, and a sixth N-type transistor. The gate terminal of the second N-type MOSFET is connected to the output terminal of the switching signal output unit, the drain terminal of the second N-type MOSFET is connected to the base terminal of the fourth N-type transistor, and the source terminal of the second N-type MOSFET is connected to signal ground. The collector of the fourth N-type transistor is connected to the source terminal 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 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 signal ground.

7. The voltage-controlled oscillator circuit according to claim 6, characterized in that, The switch 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 an external charging / discharging capacitor, the inverting input of the third comparator is connected to a third reference voltage, and 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 an external charging / discharging capacitor, the inverting input of the fourth comparator is connected to a fourth reference voltage, and the output of the fourth comparator is connected to the second input of the latch. The output terminal of the latch is the output terminal 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: The power supply control chip and the switching transistor are provided. The output terminal of the power supply control chip is connected to the control terminal of the switching transistor. The power supply control chip includes a driving circuit and a voltage-controlled oscillator circuit as described in any one of claims 1 to 7. The output terminal of the voltage-controlled oscillator circuit is connected to the input terminal of the driving circuit. The output terminal of the driving circuit is the output terminal of the power supply control chip.

Images