Ripple suppression circuit and power supply device

Abstract

The invention discloses a ripple suppression circuit and a power supply device, and belongs to the technical field of switching power supplies, the ripple suppression circuit comprises a first operational amplifier and a first capacitor, and the second end of the first capacitor is connected with the output end of the first operational amplifier; and the second end of the second capacitor is connected with the reverse end of the first operational amplifier. According to the ripple suppression circuit and the power supply device, high-frequency oscillation of a system can be effectively suppressed, and stable operation of the circuit is ensured; a differential mode inductor with a low direct-current resistance DCR is adopted, output ripples are greatly attenuated, meanwhile, direct-current conduction loss is reduced, and the overall efficiency of the system is improved; and a high-capacity passive filter device is not needed, so that the circuit size is reduced, and the power density of the system is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of switching power supply, and particularly relates to a ripple suppression circuit and a power supply device. BACKGROUND

[0002] As a core power conversion device in the power electronics industry, switching power supply has penetrated into key fields such as industrial automation, communication infrastructure and consumer electronic terminal, and has built the energy transmission center of modern electronic system, due to its high efficiency conversion rate and compact structure. However, the high-frequency switching topology used by the technology will inevitably cause high-frequency harmonic noise while realizing the improvement of power density, which is manifested as periodic voltage fluctuation at the output end, which is equivalent to ripple effect.

[0003] Specifically, the high-frequency switching action of the switching power supply inevitably produces output ripple, which affects the output quality of the power supply, interferes with the load device, and affects the stability and reliability of the system. A first inductor-capacitor filter is usually connected in parallel at the output end to suppress the output voltage ripple and suppress the output ripple to the required value. However, the inductor-capacitor filter is large in size and high in cost, which limits the development of high power density and low cost of switching power supply. Parasitic parameters deteriorate high-frequency performance, and the self-resonant frequency of inductance and capacitance limits the high-frequency characteristics of the inductor-capacitor filter. Another method is to use a low dropout regulator (LDO) in the latter stage of the switching power supply to suppress the output voltage ripple. LDO has a large power supply rejection ratio (PSRR), and selecting a suitable LDO can effectively suppress the switching sub-ripple of the switching power supply. However, LDO needs to work in closed loop to have good ripple suppression effect, so LDO has a large voltage difference, especially in large current application scenarios, the loss is large, and the overall system efficiency is low.

[0004] Therefore, how to effectively suppress the output ripple of the switching power supply has become a key problem in the field of power supply design. SUMMARY

[0005] The present application aims to provide a ripple suppression circuit and a power supply device.

[0006] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows: A ripple suppression circuit, comprising, a first operational amplifier, a first capacitor, a second end of the first capacitor being connected to an output end of the first operational amplifier; a second capacitor, a second end of the second capacitor being connected to an opposite end of the first operational amplifier.

[0007] Further, the ripple suppression circuit further comprises, a first inductor, a first end of the first inductor being connected to a first voltage, a second end of the first inductor being connected to a first end of the first capacitor and a first end of the second capacitor.

[0008] Further, the ripple suppression circuit further comprises, a third capacitor, a first end of the third capacitor being connected to a second end of the first capacitor; a first resistor, a first end of the first resistor being connected to a second end of the third capacitor, a second end of the first resistor being connected to a second end of the second capacitor; a second resistor, a first end of the second resistor being connected to a first end of the third capacitor, a second end of the second resistor being connected to a second end of the first resistor.

[0009] Further, the first inductor is a differential mode inductor.

[0010] Further, the first capacitor is an injection capacitor.

[0011] Further, the second capacitor is a detection capacitor.

[0012] Further, the first voltage is connected to an output end of a switching power supply circuit, the second voltage is connected to a load.

[0013] Further, an equivalent impedance of the low on-impedance network is expressed as: , wherein, is a closed loop output impedance of the first operational amplifier, is an impedance of the first capacitor, is a voltage gain from a sampling point of the first operational amplifier to an output end of the first operational amplifier.

[0014] Further, a transfer function of the first voltage to the second voltage is expressed as: , wherein, is an impedance of the fourth capacitor, is a resistance value of the third resistor R3, is an equivalent impedance of the low on-impedance network, is a resistance value of the fourth resistor, is an impedance of the first inductor.

[0015] A power supply device, comprising a switching power supply circuit and a ripple suppression circuit according to any one of the above; the switching power supply circuit is used to convert an input DC voltage into a stable DC output voltage, the ripple suppression circuit is connected to an output end of the switching power supply circuit.

[0016] Beneficial effects: The ripple suppression circuit and power supply device of this invention can effectively suppress high-frequency oscillations of the system and ensure stable circuit operation; the use of a differential mode inductor with low DC resistance (DCR) can significantly attenuate output ripple while reducing DC conduction loss and improving the overall system efficiency; and there is no need to use large-capacity passive filter devices, which is beneficial to reduce circuit size and increase system power density.

[0017] To make the above-mentioned features and advantages of the invention more apparent and understandable, specific embodiments are described below, and detailed descriptions are provided in conjunction with the accompanying drawings. Attached Figure Description

[0018] Figure 1 This is a circuit diagram of a ripple suppression circuit according to the present invention.

[0019] Figure 2 This is a structural diagram of a power supply device according to the present invention.

[0020] Figure 3 This is a circuit diagram of a power supply device according to the present invention.

[0021] Figure 4 for Figure 3 The simulation waveform diagram.

[0022] Figure 5 This is a graph of the output transfer function.

[0023] Figure 6 This is a comparison chart showing the PCB area occupied by the inductor-capacitor filter and the ripple suppression circuit of this invention. Detailed Implementation

[0024] To make the objectives and technical solutions of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0025] Figure 1 This is a circuit diagram of a ripple suppression circuit according to the present invention. Figure 1As shown in the figure, a kind of ripple suppression circuit 2, including, inductance L1, the first end of inductance L1 is connected voltage Vo, the second end of inductance L1 is connected the first end of capacitor C1, the first end of capacitor C2 and voltage Vo1, the second end of capacitor C1 is connected the first end of capacitor C3, the first end of resistance R2 and the output end of operational amplifier U1, the second end of capacitor C3 is connected the first end of resistance R1, the second end of capacitor C2 is connected the second end of resistance R1, the second end of resistance R2 and the opposite end of operational amplifier U1, the opposite end voltage of operational amplifier U1 is voltage V - , the positive end voltage of operational amplifier U1 is voltage V + .

[0026] The working principle of the ripple suppression circuit of the present application will be introduced below Figure 1 . When the circuit works, capacitor C2 collects the ripple current of voltage Vo, and through the negative feedback compensation network composed of resistance R1, resistance R2 and capacitor C3, compares and amplifies the ripple signal with the constant voltage source without ripple in operational amplifier U1, generates compensation current in the opposite direction and approximately equal size, and then injects the compensation current into the original circuit through capacitor C1 to superimpose and offset the original ripple current, while inductance L1 suppresses the high-frequency ripple current that has not been offset to the load, finally realizes the substantial reduction of output ripple. Optionally, inductance L1 is a differential mode inductance for suppressing differential mode ripple.

[0027] Optionally, capacitor C1 is an injection capacitor for injecting high-frequency compensation current.

[0028] Optionally, capacitor C2 is a detection capacitor for detecting the ripple current at the output end.

[0029] Further, voltage Vo is connected to the output end of the switching power supply circuit, and voltage Vo1 is connected to the load.

[0030] Figure 2 The structural diagram of the power supply device of the present application is shown in the figure Figure 2 . As shown in the figure, a kind of power supply device, including switching power supply circuit 1, ripple suppression circuit 2;The switching power supply circuit 1 is used to convert input DC voltage into stable DC output voltage, and the ripple suppression circuit 2 is connected to the output end of the switching power supply circuit 1.

[0031] The first end of the switching power supply circuit 1 is connected to the input power VIN, and the second end of the switching power supply circuit 1 is grounded. The first end of inductance L1 is connected to the third end of the switching power supply circuit 1, and the fourth end of the switching power supply circuit 1 is grounded.

[0032] Further, voltage Vo1 is connected to the load.

[0033] Optionally, the switching power supply circuit 1 can be a DC-DC converter.

[0034] The working principle of the ripple suppression circuit of the present application will be introduced belowFigure 2 The working principle of the power supply device is introduced. When the circuit works, the capacitor C2 collects the ripple current at the output end of the switching power supply circuit 1, and through the negative feedback compensation network composed of the resistor R1, the resistor R2 and the capacitor C3 and the operational amplifier U1, the ripple signal is compared and amplified with the ripple-free constant voltage source, a compensation current with opposite direction and approximately equal size is generated, and then the compensation current is injected into the original circuit through the capacitor C1 to superimpose and offset the original ripple current. At the same time, the inductor L1 suppresses the high-frequency ripple current that has not been offset to the load, and finally the output ripple is greatly reduced.

[0035] Further, the active compensation network 21 in the ripple suppression circuit 2 can be equivalent to a low-conductance impedance network. Figure 2 The low-conductance impedance network in the active compensation network 21 in the ripple suppression circuit 2 can be equivalent to a low-conductance impedance network.

[0036] Further, the equivalent impedance of the low-conductance impedance network is The expression of the equivalent impedance of the low-conductance impedance network is: , Among them, is the closed-loop output impedance of the operational amplifier U1, is the impedance of the capacitor C1, is the voltage gain from the sampling point a of the operational amplifier U1 to the output end of the operational amplifier.

[0037] Further, the voltage gain from the sampling point a of the operational amplifier U1 to the output end of the operational amplifier is The expression of the voltage gain from the sampling point a of the operational amplifier U1 to the output end of the operational amplifier is: , Among them, is the impedance of the capacitor C2, is the impedance of the capacitor C3, is the resistance of the resistor R1, is the resistance of the resistor R2.

[0038] Further, the closed-loop output impedance of the operational amplifier U1 is The expression of the closed-loop output impedance of the operational amplifier U1 is: , Among them, is the open-loop output impedance of the operational amplifier U1.

[0039] Further, the transfer function from the voltage Vo to the voltage Vo1 is The expression of the transfer function from the voltage Vo to the voltage Vo1 is: , Among them, is the impedance of the capacitor C4, is the resistance of the resistor R3, is the equivalent impedance of the low-conductance impedance network, The resistance of the resistor RL, The impedance of the inductor L1.

[0040] Further, when The impedance of the resistor RL and The impedance of the inductor L1 is much smaller than The impedance of the resistor RL, the expression of the transmission function can be approximately equal to , The resistor RL can be regarded as an active capacitor, and the circuit can be regarded as a second-order active filter.

[0041] The high-frequency ripple signal will preferentially flow through this low-conductivity impedance network, reducing the high-frequency ripple signal flowing to the load end, thereby reducing the ripple interference at the load end.

[0042] Figure 3 The circuit schematic diagram of the power supply device of the present application is shown in FIG. 1. Figure 3 As shown in the figure, the switching power supply circuit can be any DC-DC switching power supply, and here a step-down converter is taken as an example. A power supply device includes a transistor M1, the drain of the transistor M1 is connected to the positive electrode of a voltage V IN , the source of the transistor M1 is connected to the first end of an inductor L2 and the negative electrode of a diode D1, the second end of the inductor L2 is connected to the first end of an inductor L1 and the first end of a capacitor C4, the positive electrode of the diode D1 is connected to the second end of the capacitor C4, the second end of a resistor R3, the second end of a resistor RL and the ground, the second end of the inductor L1 is connected to the first end of a capacitor C5 and the first end of a capacitor C1, the first end of a capacitor C2 and the first end of the resistor RL, the second end of the capacitor C5 is connected to the first end of the resistor R3, the second end of the capacitor C1 is connected to the first end of a capacitor C3, the first end of a resistor R2 and the output end of an operational amplifier U1, the second end of the capacitor C3 is connected to the first end of a resistor R1, the second end of the resistor R1 is connected to the second end of the capacitor C2, the second end of the resistor R2 and the negative end of the operational amplifier U1, the voltage at the negative end of the operational amplifier U1 is a voltage V - , and the voltage at the positive end of the operational amplifier U1 is a voltage V + .

[0043] Figure 4 The simulation waveform diagram of Figure 3 is shown in FIG. 2. Figure 4As shown, I(L1) is the current ripple of inductor L1, i.e., the original output current ripple of the buck converter, with an amplitude of 65.37mA. I(C1) is the current of capacitor C1, with a current ripple amplitude of 63.61mA. I(Rl) is the current of resistor RL, with a current ripple amplitude of 1.44mA. I(C2) is the current of capacitor C2. It can be seen that the current I(C1) of capacitor C1 is almost equal in magnitude and opposite in direction to the current I(L1) of inductor L1. Before adding the ripple suppression circuit, the output voltage V(Vo) ripple amplitude was 102mV. After adding the ripple suppression circuit, the output voltage V(Vo1) ripple amplitude was only 1.44mV, a 70-fold reduction, and the power supply rejection ratio was approximately 37dB. The simulation results show that the ripple suppression circuit has a good ripple suppression effect, consistent with the theoretical analysis.

[0044] The output transfer function of the output ripple suppression circuit can be calculated in MathCAD as follows: Figure 5 As shown, at a frequency of 500kHz, the power supply rejection ratio is approximately 39dB, which is consistent with the trend of the simulation results.

[0045] A domestically produced low-dropout linear regulator is used for output ripple suppression. With an input voltage of 2.5-5.5V and a load current of 5A, the typical input dropout voltage (Vdrop) at 5A is 0.18V, with a maximum of 0.36V. The power supply rejection ratio (PSRR) at 500kHz is approximately 38dB, comparable to the ripple suppression circuit. For the inductor L1 in this invention, an SPM4020-R47M can be used at 5A current. This inductor has an inductance of 0.47uH, a rated current of 6.8A, and a rated DC resistance (DCR) of 11.2mΩ, with a maximum of 14mΩ. The typical dropout voltage is 0.056V, which is 31% of the input dropout voltage (Vdrop) of the low-dropout linear regulator, resulting in a 2.37% efficiency improvement. The maximum dropout voltage is 0.07V, which is 19.4% of the input dropout voltage (Vdrop) of the low-dropout linear regulator, resulting in a 5.34% efficiency improvement. The overall system efficiency is significantly improved.

[0046] Under the same suppression effect, the inductor-capacitor filter uses an SPM7030-1R0M filter inductor with an inductance of 1uH and a filter capacitor of 1206 / 10uF / 25V. A comparison is made with the PCB area occupied by the ripple suppression circuit in this invention. Figure 6 As shown, the ripple suppression circuit 2 of this invention occupies only about 60% of the PCB area of ​​a traditional inductor-capacitor filter 3, effectively saving wiring space. Furthermore, the components used in this invention are all miniaturized and easy to integrate; when combined with three-dimensional stacking technology, the circuit size can be further significantly reduced, thereby significantly improving the system's power density.

[0047] The ripple suppression circuit and the power supply device can effectively suppress system high-frequency oscillation and ensure stable operation of the circuit; the differential mode inductor with low direct current resistance DCR can greatly attenuate output ripple and reduce direct current conduction loss, thereby improving overall efficiency of the system; and large-capacity passive filter devices are not needed, which is conducive to reducing the size of the circuit and improving the power density of the system.

[0048] Although the present application has been disclosed with the above-mentioned embodiments, it is not intended to limit the present application, and anyone skilled in the art can make some changes and modifications without departing from the spirit and scope of the present application. Therefore, the protection scope of the present application shall be defined by the appended patent claims.

Claims

1. A ripple suppression circuit, characterized in that, include, First operational amplifier, A first capacitor, the second end of which is connected to the output terminal of the first operational amplifier; The second capacitor has its second terminal connected to the inverting terminal of the first operational amplifier.

2. The ripple suppression circuit as described in claim 1, characterized in that, The ripple suppression circuit further includes a first inductor, a first end of which is connected to a first voltage, and a second end of which is connected to the first end of the first capacitor and the first end of the second capacitor.

3. The ripple suppression circuit as described in claim 2, characterized in that, The ripple suppression circuit also includes, A third capacitor, wherein the first terminal of the third capacitor is connected to the second terminal of the first capacitor; A first resistor, the first end of which is connected to the second end of the third capacitor, and the second end of which is connected to the second end of the second capacitor; The second resistor has its first end connected to the first end of the third capacitor, and its second end connected to the second end of the first resistor.

4. The ripple suppression circuit as described in claim 3, characterized in that, The first inductor is a differential mode inductor.

5. The ripple suppression circuit as described in claim 4, characterized in that, The first capacitor is an injection capacitor.

6. The ripple suppression circuit as described in claim 5, characterized in that, The second capacitor is a detection capacitor.

7. The ripple suppression circuit as described in claim 6, characterized in that, The first voltage is connected to the output terminal of the switching power supply circuit, and the second voltage is connected to the load.

8. The ripple suppression circuit as described in claim 7, characterized in that, Equivalent impedance of low on-resistance networks The expression is: ， in, The closed-loop output impedance of the first operational amplifier is . Let be the impedance of the first capacitor. This is the voltage gain from the sampling point of the first operational amplifier to the output of the operational amplifier.

9. The ripple suppression circuit as described in claim 8, characterized in that, Transfer function from the first voltage to the second voltage The expression is: ， in, The impedance of the fourth capacitor is... This is the resistance value of the third resistor. This is the equivalent impedance of a low on-resistance network. This is the resistance value of the fourth resistor. The impedance of the first inductor is given.

10. A power supply device, characterized in that, It includes a switching power supply circuit and a ripple suppression circuit as described in any one of claims 1-9; the switching power supply circuit is used to convert an input DC voltage into a stable DC output voltage, and the ripple suppression circuit is connected to the output terminal of the switching power supply circuit.

Images