BUCK circuit, current sharing control method and switching power supply thereof

Abstract

The present invention relates to a BUCK circuit, a current sharing control method and a switching power supply thereof, which comprises a first buck module and a second buck module, wherein the power supply end of the first buck module is connected to a load interface, and the power supply end of the second buck module is connected to the load interface; a sampling module, wherein the first sampling input end of the sampling module is connected to the detection end of the first buck module, and the second sampling input end of the sampling module is connected to the detection end of the second buck module, and the sampling module is used to sample the output current of the first buck module and the second buck module; and a current sharing control module, comprising a sampling receiving end, a first switch control end and a second switch control end, wherein the sampling receiving end is connected to the sampling output end of the sampling module, the first switch control end is connected to the control end of the first buck module, and the second switch control end is connected to the control end of the second buck module, and the current sharing control module is used to adjust the duty cycle of the first buck module and the second buck module. The present invention has the effect of a simple control circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a BUCK circuit, a current sharing control method and a switching power supply thereof. Background Art

[0002] BUCK circuit, also known as step-down circuit, is a DC-DC conversion circuit with an output voltage lower than the input voltage. The input current is pulsating and the output current is continuous. In switching power supplies, in order to improve power density and reduce output voltage ripple, a multi-channel parallel BUCK circuit power supply method is often used. When multiple BUCK circuits are connected in parallel, the device parameters in each channel may be inconsistent and there may be deviations, resulting in inconsistent power and current borne by each channel, or even overload. Therefore, when the power supplies are connected in parallel, current sharing control must be designed to ensure reasonable power distribution between the power supplies, prevent one or more branch power supplies from operating in the current limit state, and ensure uniform distribution of electrical and thermal stress between the power supplies. Therefore, current sharing control has become the research focus of current power electronics technology.

[0003] In existing switching power supplies, a resistor is usually added to the output end of each BUCK circuit in parallel to sample the current of each path, and then the current is sent to the inside of each circuit for feedback control through the feedback circuit of each path, resulting in the need for an additional feedback circuit for each BUCK circuit. When there are more BUCK circuits in parallel, there are more feedback circuits, making the feedback control circuit more complicated and more expensive.

[0004] The above-mentioned related technologies have the defect that the control circuit is complicated. Summary of the invention

[0005] In order to improve the problem of complex control circuits, the present application provides a BUCK circuit, a current sharing control method and a switching power supply thereof.

[0006] In the first aspect, a BUCK circuit provided in the present application adopts the following technical solution:

[0007] A BUCK circuit comprises a first buck module and a second buck module, wherein the first buck module and the second buck module both comprise a power input terminal, a control terminal, a detection terminal and a power supply terminal, wherein the power supply terminal of the first buck module is connected to a load interface, and the power supply terminal of the second buck module is connected to the load interface; a sampling module, wherein the sampling module comprises a first sampling input terminal, a second sampling input terminal and a sampling output terminal, wherein the first sampling input terminal is connected to the detection terminal of the first buck module, and the second sampling input terminal is connected to the detection terminal of the second buck module, and the sampling module is used to sample the output currents of the first buck module and the second buck module. a current balancing control module, wherein the current balancing control module comprises a sampling receiving end, a first switch control end and a second switch control end, wherein the sampling receiving end is connected to the sampling output end of the sampling module, the first switch control end is connected to the control end of the first buck module, the second switch control end is connected to the control end of the second buck module, and the current balancing control module is used to adjust the duty cycle of the first buck module and the second buck module; a power supply module, wherein the power supply output end of the power supply module is respectively connected to the power supply input end of the first buck module and the second buck module, and the power supply module is used to provide power for the first buck module and the second buck module.

[0008] By adopting the above technical solution, the sampling module samples the output current in the first buck module and the second buck module, and provides a current signal for the current sharing control module. The current sharing control module can adjust the duty cycle of the first buck module and the second buck module according to the obtained current signal, so that the output current of the first buck module and the second buck module is the same. Compared with the related art, the current of the first buck module and the second buck module in the present application is controlled by the current sharing control module, and there is no need to add a feedback circuit to each buck circuit. The control circuit is simple, the cost is reduced, and the signal processing difficulty is small.

[0009] Optionally, the first buck module includes a field effect transistor Q1 and a first inductor L1, and the second buck module includes a field effect transistor Q2 and a second inductor L2, the source of the field effect transistor Q1 is connected to the power output end of the power module as the power input end of the first buck module, the drain of the field effect transistor Q1 is connected to one end of the first inductor L1, the gate of the field effect transistor Q1 is connected to the current sharing control module as the control end of the first buck module, and the other end of the first inductor L1 is connected to the input end of the load interface; the source of the field effect transistor Q2 is connected to the power output end of the power module as the power input end of the second buck module, the drain of the field effect transistor Q2 is connected to one end of the second inductor L2, the gate of the field effect transistor Q2 is connected to the current sharing control module as the control end of the second buck module, and the other end of the second inductor is connected to the input end of the load interface.

[0010] By adopting the above technical solution, the field effect transistor Q1 and the field effect transistor Q2 are used to control the opening and closing of the first buck module and the second buck module, and the current sharing control module controls the opening and closing of the field effect transistor Q1 and the field effect transistor Q2 respectively to adjust the duty cycle of the first buck module and the second buck module so that the output current of the first buck module and the second buck module are the same.

[0011] Optionally, the current equalization control module includes a first control module and a second control module, the first control module includes a first control chip U1, the second control module includes a second control chip U2, the first control chip U1 and the second control chip U2 both include an output end, a reference voltage end and a compensation end, the output end of the first control chip U1 is connected to the gate of the field effect transistor Q1; the output end of the second control chip U2 is connected to the gate of the field effect transistor Q2, the reference voltage end of the first control chip U1 is connected to the output end of the second control chip U2, the reference voltage end of the second control chip U2 is grounded, and the compensation end of the second control chip U2 is connected to the sampling output end of the sampling module.

[0012] By adopting the above technical solution, the second control chip U2 in the second control module receives the current signal of the sampling module to control the first control module and the opening and closing of the field effect tube Q2 of the second buck module. The first control chip U1 in the first control module receives the voltage signal of the second control chip U2 to control the opening and closing of the field effect tube Q1 of the first buck module. The voltage signal output by the second control chip U2 is input into the first control chip U1, so that the first control chip U1 generates a suitable PWM signal to drive the field effect tube Q1, thereby stabilizing the output voltage and making the output current flowing through the first buck module and the second buck module the same.

[0013] Optionally, the sampling module includes a first current detection module for sampling the output current of the first buck module, a second current detection module for sampling the output current of the second buck module, and a differential amplification module, the first current detection module includes a first current sampling end and a first current output end, the second current detection module includes a second current sampling end and a second current output end, the differential amplification module includes a first current receiving end, a second current receiving end and a signal output end, the first current sampling end is connected to the detection end of the first buck module as the first sampling input end of the sampling module, the second current sampling end is connected to the detection end of the second buck module as the second sampling input end of the sampling module, the first current output end is connected to the first current receiving end, the second current output end is connected to the second current receiving end, and the signal output end is connected to the sampling receiving end as the sampling output end of the sampling module.

[0014] By adopting the above technical solution, the first current detection module samples the output current of the first buck module, the second current module samples the output current of the second buck module, the output current of the first buck module and the second buck module are passed through the differential amplifier module to form a differential current signal, and the current sharing control module receives the differential current signal to control the current sharing in the circuit.

[0015] Optionally, the differential amplification module includes a differential amplifier, which includes a positive power supply terminal, a negative power supply terminal and an amplified output terminal, the positive power supply terminal is connected to the second current output terminal of the second current detection module, the negative power supply terminal is connected to the first current output terminal of the first current detection module, and the amplified output terminal is connected to the compensation terminal of the second control chip U2 as the sampling output terminal of the sampling module.

[0016] By adopting the above technical solution, the differential amplifier forms a differential current signal from the output current of the first buck module and the second buck module, and outputs the differential current signal to the compensation end of the second control chip U2. The second control chip U2 controls the current sharing in the first buck module and the second buck module according to the differential current signal.

[0017] Optionally, a field effect transistor Q3 is connected between the drain of the field effect transistor Q1 and the first inductor L1, the source of the field effect transistor Q3 is connected to the drain of the field effect transistor Q1, the drain of the field effect transistor Q3 is grounded, and the gate of the field effect transistor Q3 is connected to the current balancing control module; a field effect transistor Q4 is connected between the drain of the field effect transistor Q2 and the first inductor L2, the source of the field effect transistor Q4 is connected to the drain of the field effect transistor Q2, the drain of the field effect transistor Q4 is grounded, and the gate of the field effect transistor Q4 is connected to the current balancing control module.

[0018] By adopting the above technical solution, when the output voltage is low and the output current is small, the power conversion efficiency is low. The setting of the field effect transistor Q3 and the field effect transistor Q4 reduces the rectification loss of the first buck module and the second buck module, and the conduction voltage drop is proportional to the conduction circuit, so that the power consumption is also low when the circuit output current is small.

[0019] Optionally, the current equalization control module also includes a first driving module connected between the first control module and the first buck module and a second driving module connected between the second control module and the second buck module, the voltage input end of the first driving module is connected to the output end of the first control module, the voltage input end of the second driving module is connected to the output end of the second control module, the voltage output end of the first driving module is connected to the control end of the first buck module, and the voltage output end of the second driving module is connected to the control end of the second buck module.

[0020] By adopting the above technical solution, the setting of the first driving module and the second driving module facilitates the current sharing control module to control the first buck module and the second buck module, thereby improving efficiency.

[0021] In a second aspect, the present application provides a switching power supply, which adopts the following technical solution:

[0022] A switching power supply comprises the BUCK circuit described above.

[0023] By adopting the above technical solution, the BUCK circuit does not need to add a resistor at the output end of each parallel path, samples the current of each path, and then performs feedback control on the current of each path. The structure is simple, the cost is low, the signal processing difficulty is small, and the power density is improved, and the ripple of the output voltage of the switching power supply is reduced.

[0024] In a third aspect, the present application provides a BUCK circuit current sharing control method, which adopts the following technical solution:

[0025] A BUCK circuit current sharing control method, comprising:

[0026] The sampling module samples the output current of the first buck module and the second buck module respectively, and converts them into differential current signals;

[0027] Obtaining a first relational expression between the duty cycle of the first buck module and the differential current signal, obtaining a second relational expression between the duty cycle of the second buck module and the differential current signal, and obtaining a calculation formula for the duty cycle difference according to the first and second relational expressions;

[0028] Based on the calculation formula of the duty cycle difference, obtaining the duty cycle difference between the first buck module and the second buck module;

[0029] According to the duty cycle difference, the current sharing control module adjusts the output current of the first buck module to be equal to the output current of the second buck module.

[0030] By adopting the above technical solution, the sampling module will sample the output current of the first buck module and the second buck module respectively, and convert it into a differential current signal and then output it to the current sharing control module. The current sharing control module calculates the duty cycle difference according to the differential current signal and the impedance of the first inductor L1 and the second inductor L2. The current sharing control module adjusts the duty cycle of the first buck module and the second buck module respectively according to the duty cycle difference, so that the output current of the first buck module and the second buck module is the same.

[0031] Optionally, the duty cycle of the first buck module (100) and the differential current signal are expressed by equation 1:

[0032] d1*Vin=1 / 2*Iout*r1+Vout;

[0033] The second relationship between the duty cycle of the second buck module (100) and the differential current signal is:

[0034] d2*Vin=1 / 2*Iout*r2+Vout;

[0035] Wherein Vin is the input voltage, Vout is the output voltage, Iout is the differential current signal, r1 is the impedance of the first inductor L1, r2 is the impedance of the second inductor L2, d1 is the duty cycle of the first buck module (100), and d2 is the duty cycle of the second buck module (200);

[0036] According to equation 1 and equation 2, the calculation formula of duty cycle difference can be obtained:

[0037] (d2-d1)*Vin=1 / 2*Iout* (r2-r1).

[0038] By adopting the above technical solution, after combining Relationship 1 and Relationship 2, a calculation formula for the duty cycle difference is obtained. The duty cycle difference can be obtained by only knowing the differential current signal, the input voltage, and the impedance of the first inductor L1 and the second inductor L2. The signal processing difficulty is small, and the difficulty of current sharing control of the buck circuit is reduced.

[0039] In summary, the present invention includes at least one of the following beneficial technical effects:

[0040] 1. The output current of the first buck module and the second buck module is sampled by the sampling module, and a current signal is provided to the current sharing control module. The current sharing control module can adjust the duty cycle of the first buck module and the second buck module according to the obtained current signal, so that the output current of the first buck module and the second buck module is the same. Compared with the related art, the current of the first buck module and the second buck module in the present application is controlled by the current sharing control module, and there is no need to add a feedback circuit to each buck circuit. The control structure is simple, the cost is reduced, and the signal processing difficulty is small;

[0041] 2. The second control chip U2 in the second control module receives the current signal of the sampling module to control the first control module and the opening and closing of the field effect tube Q2 of the second buck module. The first control chip U1 in the first control module receives the voltage signal of the second control chip U2 to control the opening and closing of the field effect tube Q1 of the first buck module. The voltage signal output by the second control chip U2 is input into the first control chip U1, so that the first control chip U1 generates a suitable PWM signal to drive the field effect tube Q1, thereby stabilizing the output voltage and making the output current flowing through the first buck module and the second buck module the same. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a structural block diagram of the BUCK circuit of an embodiment of the present application.

[0043] Figure 2This is a structural block diagram of the relationship between the current sharing control module and the sampling module of the BUCK circuit of the embodiment of the present application.

[0044] Figure 3 It is a circuit schematic diagram of the first buck module, the second buck module and the sampling module of the first embodiment of the present application.

[0045] Figure 4 This is a circuit schematic diagram of the current sharing control module of the first embodiment of the present application.

[0046] Figure 5 It is a circuit schematic diagram of the first buck module, the second buck module and the sampling module of the second embodiment of the present application.

[0047] Figure 6 It is a flow chart of the BUCK circuit current sharing control method according to an embodiment of the present application.

[0048] Figure 7 It is a schematic diagram of a calculation formula for obtaining a duty cycle difference in the BUCK circuit current sharing control method according to an embodiment of the present application.

[0049] Explanation of the reference numerals: 100, first buck module; 200, second buck module; 300, current sharing control module; 310, first control module; 320, second control module; 330, first driving module; 340, second driving module; 400, sampling module; 410, first current detection module; 420, second current detection module; 430, differential amplifier module; 500, power supply module; 600, load interface. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions and advantages of this application more clear, the following Figure 1-7 It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0051] An embodiment of the present invention provides a BUCK circuit.

[0052] Embodiment 1;

[0053] Reference Figure 1 and Figure 2The BUCK circuit includes a first buck module 100, a second buck module 200, a current sharing control module 300, a sampling module 400 and a power module 500. The power module 500 is used to provide power to the first buck module 100 and the second buck module 200, the sampling module 400 is used to sample the output current of the first buck module 100 and the second buck module 200, and the current sharing control module 300 controls the output current of the first buck module 100 and the second buck module 200 by receiving the current signal output by the sampling module 400, so that the output currents of the first buck module 100 and the second buck module 200 are the same.

[0054] Reference Figure 3 In this embodiment, the first buck module 100 and the second buck module 200 both include a power input terminal, a control terminal, a detection terminal and a power supply terminal. The power supply terminal of the first buck module 100 is connected to the load interface, and the power supply terminal of the second buck module 200 is connected to the load interface; the first buck module 100 includes a field effect transistor Q1 and a first inductor L1, the source of the field effect transistor Q1 is connected to the power output terminal of the power module 500, the drain of the field effect transistor Q1 is connected to one end of the first inductor L1, and the other end of the first inductor L1 is connected to the input terminal of the load interface; the second buck module 200 includes a field effect transistor Q2 and a second inductor L2, the source of the field effect transistor Q2 is connected to the power output terminal of the power module 500, the drain of the field effect transistor Q2 is connected to one end of the second inductor L2, and the other end of the second inductor L2 is connected to the input terminal of the load interface.

[0055] A freewheeling diode D1 is connected between the drain of the field effect tube Q1 and the first inductor L1, the anode of the freewheeling diode D1 is grounded, and the cathode of the freewheeling diode D1 is connected to the drain of the field effect tube Q1; a freewheeling diode D2 is connected between the drain of the field effect tube Q2 and the first inductor L2, the anode of the freewheeling diode D2 is grounded, and the cathode of the freewheeling diode D2 is connected to the drain of the field effect tube Q2. The freewheeling diode D1 and the freewheeling diode D2 provide a continuous current to the load, which plays a role in smoothing the current and preventing sudden changes in the load current.

[0056] The sampling module 400 includes a first current detection module 410, a second current detection module 420 and a differential amplification module 430. The first current detection module 410 includes a first resistor R1 and a first capacitor C1 connected in series. The first resistor R1 is connected between the cathode of the freewheeling diode D1 and the first inductor L1, and one end of the first capacitor C1 is connected between the load interface and the first inductor L1. The first current detection module 410 can sample the current in the first inductor L1; the second current detection module 420 includes a second resistor R2 and a second capacitor C2 connected in series. The second resistor R2 is connected between the cathode of the freewheeling diode D2 and the second inductor L2, and one end of the second capacitor C2 is connected between the load interface and the second inductor L2. The second current detection module 420 can sample the current in the second inductor L2. Generally speaking, the first current detection module 410 and the second current detection module 420 are low-pass filters, which have a filtering function and can attenuate high-frequency signals. In the embodiment of the present application, the spectrum in the resistance of the first inductor L1 and the second inductor L2 is extracted by the low-pass filter, thereby obtaining the impedance of the first inductor L1 and the second inductor L2.

[0057] The differential amplifier module 430 includes a differential amplifier, which includes a positive power supply terminal, a negative power supply terminal, a non-inverting input terminal, an inverting input terminal and a signal output terminal, wherein the non-inverting input terminal is connected to a power supply and the inverting input terminal is grounded; the negative power supply terminal is connected between the first resistor R1 and the first capacitor C1 through a third resistor R3, and the positive power supply terminal is connected between the second resistor R2 and the second capacitor C2 through a fourth resistor R4; a fifth resistor R5 is connected in parallel between the negative power supply terminal and the signal output terminal, and a third capacitor C3 is connected in parallel between the two ends of the fifth resistor R5; a sixth resistor R6 is connected between the positive power supply terminal and the fourth resistor R4, one end of the sixth resistor R6 is connected to the positive power supply terminal, and the other end of the sixth resistor R6 is grounded; and a fourth capacitor C4 is connected in parallel between the two ends of the sixth resistor R6. The differential amplifier forms a differential current signal from the current sampled by the first current detection module 410 and the second current detection module 420.

[0058] Reference Figure 4 The current sharing control module 300 includes a first control module 310 and a second control module 320. The first control module 310 includes a first control chip U1, and the second control module 320 includes a second control chip U2. Both the first control chip U1 and the second control chip U2 are chips with an optional model of UC3842. The first control chip U1 and the second control chip U2 both include a power supply pin 1, a reference voltage pin 2, an oscillation pin 3, a negative feedback pin 4, a compensation pin 5, a current feedback pin 6, a ground pin 7, and an output pin 8.

[0059] The power supply voltage VCC is input to the power supply end pin 1 of the first control chip U1 and the second control chip U2, a seventh resistor R7, a fifth capacitor C5 and a sixth capacitor C6 are connected in series between the reference voltage end pin 2 of the first control chip U1 and the output end pin 8 of the second control chip U2, an oscillation end pin 3 of the first control chip U1 is connected between the seventh resistor R7 and the fifth capacitor C5, a transistor T1 and an eighth resistor R8 are connected in series between the oscillation end pin 3 of the first control chip U1 and the current feedback end pin 6 of the first control chip U1, a collector of the transistor T1 is connected to the reference voltage end pin 2, a base of the transistor T1 is connected to the oscillation end pin 3 of the first control chip U1, an emitter of the transistor T1 is connected to one end of the eighth resistor R8, a ninth resistor R9 is connected between the eighth resistor R8 and the current feedback end pin 6 of the first control chip U1, one end of the ninth resistor R9 is connected to the current feedback end pin 6 of the first control chip U1, and the other end of the ninth resistor R9 is grounded. By inputting the voltage signal output by the second control chip U2 into the first control chip U1, the first control chip U1 generates a suitable PWM signal to drive the field effect transistor Q1, thereby stabilizing the output voltage.

[0060] The first control module 310 also includes a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12, a thirteenth resistor R13, a fourteenth resistor R14 and a seventh capacitor C7; one end of the twelfth resistor R12 is used as a voltage output end, for outputting voltage sampling and inputting to an external control unit, the tenth resistor R10, the eleventh resistor R11 and the twelfth resistor R12 are sequentially connected in series between the compensation end pin 5 of the first control chip U1 and the voltage output end, the seventh capacitor C7 is connected in parallel at both ends of the tenth resistor R10, the thirteenth resistor R13 is connected between the fifth capacitor C5 and the sixth capacitor C6, and one end of the thirteenth resistor R13 is connected to the analog ground; the fourteenth resistor R14 is connected between the eleventh resistor R11 and the twelfth resistor R12, and one end of the fourteenth resistor R14 is connected to the analog ground. The power supply voltage VCC of the first control chip U1 and one end of the thirteenth resistor R13 connected to the ground are connected to an auxiliary DC power supply. Through the above arrangement, it is used for voltage sampling to form a voltage feedback loop, so as to better control the output voltage.

[0061] In order to better drive and control the first buck module 100 and the second buck module 200, the current sharing control module 300 also includes a first driving module 330 and a second driving module 340. The first driving module 330 includes a first amplifier and an eighteenth resistor R18. One end of the eighteenth resistor R18 is connected to the gate of the field effect tube Q1, and the other end of the eighteenth resistor R18 is connected to the non-inverting input end of the first amplifier. The output end of the first control chip U1 is connected to the positive power supply end of the first amplifier, the negative power supply end of the first amplifier is grounded, and the inverting input end of the first amplifier is connected between the drain of the field effect tube Q1 and the freewheeling diode D1; the second driving module 340 includes a second amplifier and a nineteenth resistor R19. One end of the nineteenth resistor R19 is connected to the gate of the field effect tube Q2, and the other end of the nineteenth resistor R19 is connected to the non-inverting input end of the second amplifier. The output end of the second control chip U2 is connected to the positive power supply end of the second amplifier, the negative power supply end of the second amplifier is grounded, and the inverting input end of the second amplifier is connected between the drain of the field effect tube Q2 and the freewheeling diode D2.

[0062] The reference voltage pin 2 of the second control chip U2 is connected in series with a transistor T2, a sixteenth resistor R16 and a seventeenth resistor R17 in sequence, the collector of the transistor T2 is connected to the reference voltage pin 2 of the second control chip U2, the emitter of the transistor T2 is connected to one end of the sixteenth resistor R16, one end of the seventeenth resistor R17 is grounded, the reference voltage pin 2 of the second control chip U2 is also connected in series with a fifteenth resistor R15 and an eighth capacitor C8, the eighth capacitor C8 is connected to the ground end of the seventeenth resistor R17, and the base of the transistor T2 is connected between the fifteenth resistor R15 and the eighth capacitor C8. The oscillation end pin 3 of the second control chip U2 is connected between the base of the transistor T2 and the fifteenth resistor R15; the negative feedback end pin 4 of the second control chip U2 is grounded; the compensation end pin 5 of the second control chip U2 is connected to the signal output end of the differential amplifier; the current feedback end pin 6 of the second control chip U2 is connected between the sixteenth resistor R16 and the seventeenth resistor R17.

[0063] Reference Figure 3 The load interface is connected in parallel with a ninth capacitor C9 for protecting the load, making the load less prone to overload and improving the safety of the circuit. One end of the ninth capacitor C9 is connected to the power supply end of the first buck module 100, and the other end of the ninth capacitor C9 is grounded.

[0064] The implementation principle of Example 1 of the present application is as follows: the first current detection module 410 samples the current of the first inductor L1, the second current detection module 420 samples the current of the second inductor L2, and the differential amplifier module 430 controls the PWM signal output by the second control chip U2 in the second control module 320 by converting the currents sampled by the first current detection module 410 and the second current detection module 420 into differential current signals. The second control chip U2 controls the field effect transistor Q2 of the second buck module 200 and outputs a voltage signal to the first control chip U1, so that the first control chip U1 generates a suitable PWM signal to drive the field effect transistor Q1, thereby adjusting the duty cycle of the first buck module 100 and the second buck module 200, so that the currents flowing through the first inductor and the second inductor are evenly distributed.

[0065] Embodiment 2;

[0066] Reference Figure 5 The difference between this embodiment and the first embodiment is that the freewheeling diode D1 in the first buck module 100 is changed to a field effect transistor Q3, and the freewheeling diode D2 in the second buck module 200 is changed to a field effect transistor Q4, the source of the field effect transistor Q3 is connected between the drain of the field effect transistor Q1 and the first inductor L1, the drain of the field effect transistor Q3 is grounded, and the gate of the field effect transistor Q3 is connected to the current sharing control module 300; the source of the field effect transistor Q4 is connected between the drain of the field effect transistor Q2 and the second inductor L2, the drain of the field effect transistor Q4 is grounded, and the gate of the field effect transistor Q4 is connected to the current sharing control module 300. The arrangement of the field effect transistor Q3 and the field effect transistor Q4, when the output voltage is low and the output current is small, the power conversion efficiency is low, the rectification loss of the first buck module 100 and the second buck module 200 is reduced, and the conduction voltage drop is proportional to the conduction circuit, so that the power consumption is also low when the output current of the circuit is small, synchronous rectification is achieved, and the efficiency is improved.

[0067] The implementation principle of Example 2 of the present application is: the freewheeling diode D1 and the freewheeling diode D2 in the circuit are respectively replaced with the field effect transistor Q3 and the field effect transistor Q4, so as to reduce the rectification loss of the first buck module 100 and the second buck module 200, and the conduction voltage drop is proportional to the conduction circuit, so that the power consumption is low when the output current of the circuit is small, synchronous rectification is realized, and the efficiency is improved.

[0068] The present application also discloses a switching power supply. The switching power supply includes the BUCK circuit of the above embodiment. With the BUCK circuit, it is not necessary to add a resistor at the output end of each parallel path, sample the current of each path, and then perform feedback control on the current of each path. The structure is simple, the cost is low, the signal processing difficulty is small, and the power density is improved, and the ripple of the output voltage of the switching power supply is reduced.

[0069] The embodiment of the present application also discloses a BUCK circuit current sharing control method using the BUCK circuit of the above embodiment.

[0070] Reference Figure 6 and Figure 7 The BUCK circuit current sharing control method mainly includes the following steps:

[0071] In step S710 , the sampling module 400 samples the output currents of the first buck module 100 and the second buck module 200 respectively, and converts them into differential current signals.

[0072] Specifically, in the embodiment of the present application, the first current detection module 410 in the sampling module 400 samples the output current of the first buck module 100 through the resistor in the first inductor L1, and the second current detection module 420 samples the output current of the second buck module 200 through the resistor in the second inductor L2. The output current of the first buck module 100 and the output current of the second buck module 200 are converted into differential current signals through the differential amplifier module 430; the first current detection module 410 and the second current detection module 420 are low-pass filters, which can extract the frequency spectrum of the resistance in the inductor and obtain the impedance of the first inductor L1 and the second inductor L2.

[0073] Step S720, obtain a first relationship between the duty cycle of the first buck module 100 and the differential current signal, obtain a second relationship between the duty cycle of the second buck module 200 and the differential current signal, and obtain a calculation formula for the duty cycle difference according to the first and second relationship formulas.

[0074] Specifically, the calculation formula for the duty cycle difference is obtained from the first and second relationship.

[0075] The first relationship between the duty cycle of the first buck module 100 and the differential current signal is:

[0076] d1*Vin=1 / 2*Iout*r1+Vout;

[0077] The second relationship between the duty cycle of the second buck module 100 and the differential current signal is:

[0078] d2*Vin=1 / 2*Iout*r2+Vout;

[0079] Wherein Vin is the input voltage, Vout is the output voltage, Iout is the differential current signal, r1 is the impedance of the first inductor L1, r2 is the impedance of the second inductor L2, d1 is the duty cycle of the first buck module 100, and d2 is the duty cycle of the second buck module 200.

[0080] According to equation 1 and equation 2, the calculation formula of duty cycle difference can be obtained:

[0081] (d2-d1)*Vin=1 / 2*Iout* (r2-r1).

[0082] After combining equation 1 and equation 2, the calculation formula for the duty cycle difference is obtained. The duty cycle difference can be obtained by only knowing the differential current signal, the input voltage, and the impedance of the first inductor L1 and the second inductor L2. The signal processing difficulty is small, which reduces the difficulty of current sharing control of the buck circuit.

[0083] Step S730: Based on the calculation formula of the duty cycle difference, obtain the duty cycle difference between the first buck module 100 and the second buck module 200.

[0084] Step S740: According to the duty cycle difference, the current sharing control module 300 adjusts the output current of the first buck module 100 to be equal to the output current of the second buck module 200.

[0085] Specifically, the duty cycle difference is obtained by substituting the input voltage, the differential current signal, the impedance of the first inductor L1 and the impedance of the second inductor L2 into the calculation formula; the current sharing control module 300 adjusts the duty cycle of the first buck module 100 and the duty cycle of the second buck module 200 according to the duty cycle difference, so that the output current of the first buck circuit is the same as that of the second buck circuit.

[0086] The above are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. Any feature disclosed in this specification (including the abstract and drawings), unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

Claims

1. A BUCK circuit, characterized in that: include: A first buck module (100) and a second buck module (200), wherein the first buck module (100) and the second buck module (200) both comprise a power input terminal, a control terminal, a detection terminal and a power supply terminal, the power supply terminal of the first buck module (100) being connected to a load interface (600), and the power supply terminal of the second buck module (200) being connected to the load interface (600); A sampling module (400), the sampling module (400) comprising a first sampling input end, a second sampling input end and a sampling output end, the first sampling input end being connected to a detection end of the first buck module (100), the second sampling input end being connected to a detection end of the second buck module (200), the sampling module (400) being used to sample output currents of the first buck module (100) and the second buck module (200); A current balancing control module (300), the current balancing control module (300) comprising a sampling receiving end, a first switch control end and a second switch control end, the sampling receiving end being connected to the sampling output end of the sampling module (400), the first switch control end being connected to the control end of the first buck module (100), the second switch control end being connected to the control end of the second buck module (200), the current balancing control module (300) being used to adjust the duty cycle of the first buck module (100) and the second buck module (200); A power module (500), wherein a power output end of the power module (500) is respectively connected to the first buck module (100) and the power input end of the first buck module (100), and the power module (500) is used to provide power for the first buck module (100) and the first buck module (100); The first buck module (100) comprises a field effect tube Q1 and a first inductor L1, and the second buck module (200) comprises a field effect tube Q2 and a second inductor L2, the source of the field effect tube Q1 being connected to the power output end of the power module (500) as the power input end of the first buck module (100), the drain of the field effect tube Q1 being connected to one end of the first inductor L1, the gate of the field effect tube Q1 being connected to the current sharing control module (300) as the control end of the first buck module (100), and the other end of the first inductor L1 being connected to the input end of the load interface (600); The source of the field effect tube Q2 is connected to the power output end of the power module (500) as the power input end of the second buck module (200), the drain of the field effect tube Q2 is connected to one end of the second inductor L2, the gate of the field effect tube Q2 is connected to the current sharing control module (300) as the control end of the second buck module (200), and the other end of the second inductor is connected to the input end of the load interface (600); The current sharing control module (300) comprises a first control module (310) and a second control module (320), the first control module (310) comprises a first control chip U1, the second control module (320) comprises a second control chip U2, the first control chip U1 and the second control chip U2 both comprise an output terminal, a reference voltage terminal and a compensation terminal, the output terminal of the first control chip U1 is connected to the gate of the field effect transistor Q1; the output terminal of the second control chip U2 is connected to the gate of the field effect transistor Q2, the reference voltage terminal of the first control chip U1 is connected to the output terminal of the second control chip U2, the reference voltage terminal of the second control chip U2 is grounded, and the compensation terminal of the second control chip U2 is connected to the sampling output terminal of the sampling module (400); The sampling module (400) comprises a first current detection module (410) for sampling the output current of the first buck module (100), a second current detection module (420) for sampling the output current of the second buck module (200), and a differential amplification module (430); the first current detection module (410) comprises a first current sampling end and a first current output end; the second current detection module (420) comprises a second current sampling end and a second current output end; the differential amplification module (430) comprises a first current receiving end, a second current receiving end, and a signal output end; the first current sampling end is connected to the detection end of the first buck module (100) as a first sampling input end of the sampling module (400); the second current sampling end is connected to the detection end of the second buck module (200) as a second sampling input end of the sampling module (400); the first current output end is connected to the first current receiving end; the second current output end is connected to the second current receiving end; and the signal output end is connected to the sampling receiving end as a sampling output end of the sampling module (400); The current sharing control module (300) further comprises a first driving module (330) connected between the first control module (310) and the first buck module (100), and a second driving module (340) connected between the second control module (320) and the second buck module (200), wherein a voltage input end of the first driving module (330) is connected to an output end of the first control module (310), a voltage input end of the second driving module (340) is connected to an output end of the second control module (320), a voltage output end of the first driving module (330) is connected to a control end of the first buck module (100), and a voltage output end of the second driving module (340) is connected to a control end of the second buck module (200).

2. A BUCK circuit according to claim 1, characterized in that: The differential amplifier module (430) comprises a differential amplifier, and the differential amplifier comprises a positive power supply terminal, a negative power supply terminal and an amplified output terminal, the positive power supply terminal is connected to the second current output terminal of the second current detection module (420), the negative power supply terminal is connected to the first current output terminal of the first current detection module (410), and the amplified output terminal is connected to the compensation terminal of the second control chip U2 as the sampling output terminal of the sampling module (400).

3. A BUCK circuit according to claim 1, characterized in that: A field effect tube Q3 is connected between the drain of the field effect tube Q1 and the first inductor L1, the source of the field effect tube Q3 is connected to the drain of the field effect tube Q1, the drain of the field effect tube Q3 is grounded, and the gate of the field effect tube Q3 is connected to the current balancing control module (300); a field effect tube Q4 is connected between the drain of the field effect tube Q2 and the second inductor L2, the source of the field effect tube Q4 is connected to the drain of the field effect tube Q2, the drain of the field effect tube Q4 is grounded, and the gate of the field effect tube Q4 is connected to the current balancing control module (300).

4. A switching power supply, characterized in that: It comprises a BUCK circuit as described in any one of claims 1-3.

5. A method for controlling current sharing of a BUCK circuit using the BUCK circuit according to any one of claims 1 to 3, characterized in that: include: The sampling module (400) samples the output current of the first buck module (100) and the second buck module (200) respectively, and converts them into differential current signals; Obtaining a first relational expression between the duty cycle of the first buck module (100) and the differential current signal, obtaining a second relational expression between the duty cycle of the second buck module (200) and the differential current signal, and obtaining a calculation formula for the duty cycle difference according to the first and second relational expressions; Based on the calculation formula of the duty cycle difference, obtaining the duty cycle difference between the first buck module (100) and the second buck module (200); According to the duty cycle difference, the current sharing control module (300) adjusts the output current of the first buck module (100) to be equal to the output current of the second buck module (200).

6. A BUCK circuit current sharing control method according to claim 5, characterized in that: The steps of obtaining a first relational expression between the duty cycle of the first buck module (100) and the differential current signal, obtaining a second relational expression between the duty cycle of the second buck module (200) and the differential current signal, and obtaining a calculation formula for the duty cycle difference according to the first relational expression and the second relational expression include: The first relationship between the duty cycle of the first buck module (100) and the differential current signal is: d1*Vin=1 / 2*Iout*r1+Vout; The second relationship between the duty cycle of the second buck module (200) and the differential current signal is: d2*Vin=1 / 2*Iout*r2+Vout; Wherein Vin is the input voltage, Vout is the output voltage, Iout is the differential current signal, r1 is the impedance of the first inductor L1, r2 is the impedance of the second inductor L2, d1 is the duty cycle of the first buck module (100), and d2 is the duty cycle of the second buck module (200); According to equation 1 and equation 2, the calculation formula of duty cycle difference can be obtained: (d2-d1)*Vin=1 / 2*Iout* (r2-r1).

Images