Low-loss peak absorption Buck circuit

Abstract

The utility model discloses a low-loss peak absorption Buck circuit, and relates to the technical field of power electronics. In order to solve the defects of high power consumption, large occupied space, inconvenience in model selection and poor reliability of the existing peak absorption circuit, the peak absorption circuit comprises a first switching tube Q1, an inductor L, an output capacitor Cout, an absorption circuit and a follow current circuit, the D pole of the first switch tube Q1 is connected with the voltage input end, the other end of the first switch tube Q1 is connected with the input end of the follow current circuit, the absorption circuit is connected between the D pole and the S pole of the first switch tube Q1 in parallel, and the inductor L is connected between the S pole of the first switch tube Q1 and the voltage output end in series. The follow current circuit is connected in series between the S pole of the first switch tube Q1 and the signal grounding end, and the output capacitor Cout is connected in series between the inductor L and the signal grounding end. The voltage spike optimization circuit is mainly used for optimizing the voltage spike of the parasitic inductance between the voltage input end and the switching tube Q1.

Description

TECHNICAL FIELD

[0001] The utility model relates to power electronics technical field especially relates to a low loss peak absorption's buck circuit. BACKGROUND

[0002] In the buck circuit, due to the parasitic inductance existing on the connecting line between the voltage input end and the switch tube Q1, when the switch tube is turned off, a great voltage peak will be generated due to the existence of the parasitic inductance L, and the greater the power and input current, the greater the voltage peak, which will increase the turn-off loss of the switch tube. The voltage peak and the input voltage are superimposed on both ends of the switch tube, in order to meet the voltage stress requirement of the switch tube and ensure the reliability of the circuit, a MOS tube with higher voltage resistance is often selected as the switch tube, and the on-resistance of the MOS tube with higher voltage resistance is greater, which will reduce the efficiency of the circuit and increase the cost. At the same time, the voltage peak will cause the output voltage ripple noise to be larger, which reduces the performance of the power supply.

[0003] In order to optimize the voltage peak of the switch tube of the buck circuit, an RCD absorption circuit (i.e. a circuit composed of a resistor R, a capacitor C and a diode D) is usually added at both ends of the switch tube, which has a good effect on absorbing the voltage peak at both ends of the switch tube Q1 (as shown in Figure 1 When the switch tube Q1 is turned off, the voltage peak at both ends of the switch tube Q1 charges the capacitor C through the diode D1, and when the switch tube Q1 is turned on, the capacitor C discharges through the resistor R and the switch tube Q1. According to the working principle of the RCD absorption circuit, the energy of the voltage peak at both ends of the switch tube Q1 is consumed on the resistor R, although this method can also improve the voltage peak, but the power consumption and temperature need to be considered in the selection of the device, and the space occupied is large.

[0004] Therefore, a low-loss peak absorption buck circuit with low loss, low device heating, easy selection, high reliability is needed. UTILITY MODEL CONTENTS

[0005] The utility model discloses in order to solve the defect that the existing peak absorption circuit is high in power consumption, occupies large space, is inconvenient to select and is poor in reliability, provides a low-loss peak absorption buck circuit with low loss, low device heating, easy selection and high reliability.

[0006] The utility model provides a kind of low-loss sharp peak absorption's Buck circuit, including one switch tube Q1, inductance L, output capacitor Cout, absorption circuit and freewheeling circuit;The D pole of one switch tube Q1 is connected with voltage input end, and the other end of one switch tube Q1 is connected with the input end of freewheeling circuit, and the absorption circuit is connected between the D pole and S pole of one switch tube Q1, and the inductance L is connected between the S pole of one switch tube Q1 and voltage output end, and the freewheeling circuit is connected between the S pole of one switch tube Q1 and signal ground end, and the output capacitor Cout is connected between inductance L and signal ground end.

[0007] Further: the absorption circuit includes capacitor C, one diode D1 and two diodes D2, one end of the capacitor C is connected between voltage input end and one switch tube Q1, the other end of the capacitor C is connected with the anode of one diode D1, the cathode of one diode D1 is connected with the S pole of one switch tube Q1, the cathode of two diodes D2 is connected between capacitor C and one diode D1, and the anode of two diodes D2 is connected with signal ground end.

[0008] Further: one diode D1 and two diodes D2 are selected from patch diode.

[0009] Further: the freewheeling circuit is synchronous circuit, and the synchronous circuit includes two switch tubes Q2, the D pole of two switch tubes Q2 is connected with the S pole of one switch tube Q1, and the S pole of two switch tubes Q2 is connected with signal ground end.

[0010] Further: the G pole of one switch tube Q1 and two switch tubes Q2 is provided with driving circuit.

[0011] Further: the driving circuit includes two protection resistors RGS2 and driving power supply, and the two protection resistors RGS2 are connected in parallel across driving power supply.

[0012] Further: the freewheeling circuit is asynchronous circuit, and the asynchronous circuit includes freewheeling diode D and one resistor R1, the one resistor R1 is connected in series between two diodes D2 and signal ground end, the cathode of freewheeling diode D is connected with the S pole of switch tube Q1, and the anode of freewheeling diode D is connected with signal ground end.

[0013] Further: the freewheeling diode D is selected from power diode.

[0014] The utility model has the advantages that:

[0015] The low-loss peak absorption Buck circuit is composed of a capacitor and two diodes, and does not have loss type devices such as resistors, is extremely low in loss compared with a traditional RCD absorption circuit, is simple to select, and is small in occupied space. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a circuit diagram of a traditional RCD absorption circuit;

[0017] Figure 2 is a circuit diagram of a synchronous low-loss peak absorption Buck circuit;

[0018] Figure 3 is a circuit diagram of an asynchronous low-loss peak absorption Buck circuit. DETAILED DESCRIPTION

[0019] The following only for the preferred specific embodiments of the utility model, but the protection scope of the utility model is not limited to this, any skilled in the art person in the utility model disclosed technology range, can easily think of the change or replacement, all should be covered in the protection scope of the utility model. The following described embodiments are only used to explain the utility model, and cannot be explained as the limitation of the utility model, and the protection scope of the utility model should be the protection scope of claims. The following detailed description of the embodiments of the utility model, in order to facilitate the description of the utility model and simplify the description, the technical terms used in the specification of the utility model should be interpreted broadly, including but not limited to the conventional replacement scheme not mentioned in the application, and including direct implementation mode and indirect implementation mode.

[0020] Embodiment 1

[0021] Combined with Figure 2 and Figure 3 The embodiment discloses a low-loss peak absorption Buck circuit, which comprises a first switch tube Q1, an inductor L, an output capacitor Cout, an absorption circuit and a freewheeling circuit. The D pole of the first switch tube Q1 is connected with a voltage input end, another end of the first switch tube Q1 is connected with an input end of the freewheeling circuit, the absorption circuit is connected in parallel between the D pole and the S pole of the first switch tube Q1, the inductor L is connected in series between the S pole of the first switch tube Q1 and a voltage output end, the freewheeling circuit is connected in series between the S pole of the first switch tube Q1 and a signal ground end, and the output capacitor Cout is connected in series between the inductor L and the signal ground end.

[0022] The absorption circuit comprises a capacitor C, a first diode D1 and a second diode D2, one end of the capacitor C is connected between a voltage input end and a first switch tube Q1, the other end of the capacitor C is connected with the positive electrode of the first diode D1, the negative electrode of the first diode D1 is connected with the S pole of the first switch tube Q1, the negative electrode of the second diode D2 is connected between the capacitor C and the first diode D1, and the positive electrode of the second diode D2 is connected with a signal ground end. The first diode D1 and the second diode D2 are selected from patch diodes.

[0023] The low-loss peak absorption Buck circuit is only composed of the capacitor C and the two diodes D1 and D2. Since the capacitance of the capacitor C is much larger than the parasitic capacitance of the first switch tube Q1, when the first switch tube Q1 is turned off in the Buck circuit, the voltage peak generated by the parasitic inductance of the input connection line is mostly charged to the capacitor C through the first diode D1, thereby reducing the voltage peak between the two ends of the first switch tube Q1; when the first switch tube Q1 is turned on in the Buck circuit, the energy stored in the capacitor C is discharged to the input voltage through the second diode D2 until the voltage between the two ends of the capacitor C is approximately equal to the input voltage, and the energy of the voltage peak is returned to the input end for reuse.

[0024] According to the working principle of the absorption circuit, the energy of the voltage peak is stored in the capacitor C when the first switch tube Q1 is turned off. Different from the traditional RCD absorption circuit, the energy stored in the capacitor C can be released to the input voltage for reuse when the first switch tube Q1 is turned on, instead of being wasted on the resistor R, so that the voltage peak of the first switch tube Q1 is suppressed while the loss is almost not increased.

[0025] Embodiment 2

[0026] The difference between this embodiment and embodiment 1 is that, as shown in Figure 2 The freewheeling circuit is a synchronous circuit, the synchronous circuit further comprises a second switch tube Q2, the D pole of the second switch tube Q2 is connected with the S pole of the first switch tube Q1, and the S pole of the second switch tube Q2 is connected with a signal ground end. The G poles of the first switch tube Q1 and the second switch tube Q2 are both provided with a driving circuit. The driving circuit comprises a second protective resistor RGS2 and a driving power supply, and the second protective resistor RGS2 is connected in parallel across the driving power supply. The VG2 pin is connected with the G pole of the second switch tube Q2, and the SGND pin is connected with SGND.

[0027] It can be known from the above-mentioned synchronous circuit that the circuit can realize the absorption of voltage peak at both ends of the first switch tube by only an absorption circuit composed of one capacitor and two diodes and the second switch tube Q1, reduce the loss, and almost achieve no loss after selecting appropriate devices, and the device has less heat, is easy to select, is more reliable, and occupies less space. The synchronous circuit does not need to set a resistance to absorb and lose the voltage peak at both ends of the first switch tube Q1, and greatly improves the efficiency of the circuit.

[0028] Embodiment 3

[0029] The difference between the embodiment and the embodiment 1 is that, as shown in the figure, Figure 3 the freewheeling circuit is an asynchronous circuit, the asynchronous circuit further comprises a freewheeling diode D and a first resistance R1, the first resistance R1 is connected in series between the second diode D2 and a signal ground end, a negative electrode of the freewheeling diode D is connected with an S pole of the switch tube Q1, and a positive electrode of the freewheeling diode D is connected with the signal ground end. The freewheeling diode D is selected to be a power diode; at the same time, a VG1 pin is connected with a G pole of the first switch tube Q1, and a VS1 pin is connected with an S pole of the first switch tube Q1.

[0030] As shown in the figure, Figure 3 in the embodiment, the freewheeling diode D can be selected to be a plug-in diode, which has a larger VF value than a patch diode, so as to avoid that, after the first switch tube Q1 is turned off, the freewheeling current does not flow through the freewheeling diode D to cause damage to the second diode D2, when the freewheeling diode D is used for freewheeling, a small resistance value of the first resistance R1 needs to be connected in series in the second diode D2 to increase the impedance of the second diode D2 branch, so as to avoid that the freewheeling current flows through the second diode D2 to cause damage.

[0031] Different from the resistance R in the traditional RCD absorption circuit, the first resistance R1 can play a role in increasing the impedance, instead of being used for consuming the peak energy, at the same time, a voltage I*R1 obtained by multiplying the first resistance R1 and a certain current is only required to be larger than a VF value of the freewheeling diode D under the current I, thereby reducing the loss and improving the circuit efficiency.

[0032] The above is only a preferred embodiment of the present application, and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A low-loss spike absorption Buck circuit, characterized in that, It includes a first switching transistor Q1, an inductor L, an output capacitor Cout, a snubber circuit, and a freewheeling circuit. The drain (D) of the first switching transistor Q1 is connected to the voltage input terminal, and the other end of the first switching transistor Q1 is connected to the input terminal of the freewheeling circuit. The snubber circuit is connected in parallel between the drain (D) and source (S) of the first switching transistor Q1. The inductor L is connected in series between the source (S) of the first switching transistor Q1 and the voltage output terminal. The freewheeling circuit is connected in series between the source (S) of the first switching transistor Q1 and the signal ground terminal. The output capacitor Cout is connected in series between the inductor L and the signal ground terminal.

2. The low-loss spike absorption Buck circuit according to claim 1, characterized in that, The absorption circuit includes a capacitor C, a first diode D1, and a second diode D2. One end of the capacitor C is connected between the voltage input terminal and the first switch Q1, and the other end of the capacitor C is connected to the positive terminal of the first diode D1. The negative terminal of the first diode D1 is connected to the source terminal (S) of the first switch Q1. The negative terminal of the second diode D2 is connected between the capacitor C and the first diode D1, and the positive terminal of the second diode D2 is connected to the signal ground terminal.

3. The low-loss spike absorption Buck circuit according to claim 2, characterized in that, The first diode D1 and the second diode D2 are surface mount diodes.

4. The low-loss spike absorption Buck circuit according to claim 1, characterized in that, The freewheeling circuit is a synchronous circuit, which includes a second switch Q2. The drain (D) of the second switch Q2 is connected to the source (S) of the first switch Q1, and the source (S) of the second switch Q2 is connected to the signal ground terminal.

5. The low-loss spike absorption Buck circuit according to claim 4, characterized in that, Both the gate (G) terminals of the first switch Q1 and the second switch Q2 are equipped with driving circuits.

6. The low-loss spike absorption Buck circuit according to claim 5, characterized in that, The driving circuit includes a second protection resistor RGS2 and a driving power supply, wherein the second protection resistor RGS2 is connected in parallel across the driving power supply.

7. The low-loss spike absorption Buck circuit according to claim 1, characterized in that, The freewheeling circuit is an asynchronous circuit, which includes a freewheeling diode D and a first resistor R1. The first resistor R1 is connected in series between the second diode D2 and the signal ground terminal. The cathode of the freewheeling diode D is connected to the source terminal of the switching transistor Q1, and the anode of the freewheeling diode D is connected to the signal ground terminal.

8. The low-loss spike absorption Buck circuit according to claim 7, characterized in that, The freewheeling diode D is selected as a power diode.

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