DC-DC circuit with low ripple noise and adjustable output voltage

Abstract

The utility model discloses a DC-DC circuit with low ripple noise and adjustable output voltage, comprising a chip U1, an inductor L1, a diode D1, a resistor R1 and a resistor R2, one end of the inductor L1 is connected with a fuse F1 and a cathode of the diode D1, the other end of the inductor L1 is connected with a capacitor C2, a capacitor C3 and a pin 1 of the chip U1, and a pin 2 of the chip U1 is connected with a cathode of a diode D2 and an inductor L2. According to the utility model, the circuit is simple, and can be converted into different voltages by DC / DC in many occasions, such as MCU power supply, protection circuit power supply, operational amplifier circuit power supply and the like, and certainly can be used for supplying power to small and medium power equipment. And the frequency is not high, so that the ripple noise can be greatly reduced by slightly adding some filter circuits, and the cost of used devices is relatively low.

Description

TECHNICAL FIELD

[0001] The utility model relates to power supply technical field especially relates to a low ripple noise output voltage adjustable DC-DC circuit. BACKGROUND

[0002] With the development of AC / DC power supply to a certain extent, the market for different voltage requirements of DC more and more, such as 3.3V, 5V, 9V, 12V, etc., we can not output every voltage AC / DC mode, this will design power supply many times, use many EMI filter circuit, rectifier circuit, switching power supply etc., these not only the volume of circuit occupies big, and ripple noise generated by each other will affect the back-end equipment, comprehensive cost is high. SUMMARY

[0003] In order to make up for the deficiencies of the prior art, the application provides a low ripple noise output voltage adjustable DC-DC circuit to solve the problems in the prior art.

[0004] In order to solve the above technical problems, the utility model provides the following technical scheme:

[0005] A low ripple noise output voltage adjustable DC-DC circuit, including chip U1, inductance L1, diode D1, resistance R1 and resistance R2, one end of inductance L1 connects fuse F1 and the negative pole of diode D1, the other end of inductance L1 connects capacitor C2, capacitor C3 and the pin 1 of chip U1, the pin 2 of chip U1 connects the negative pole of diode D2 and inductance L2, the other end of inductance L2 connects capacitor C6, capacitor C9, capacitor C10, resistance R1, capacitor C1, capacitor C4, capacitor C7 and inductance L3, the other end of inductance L3 connects capacitor C5 and capacitor C8, the other end of capacitor C2 connects the other end of capacitor C3, the positive pole of diode D2, the other end of capacitor C6, the other end of capacitor C9, the other end of capacitor C10, the other end of capacitor C4, the other end of capacitor C7, the other end of capacitor C8, the other end of resistance R2 and ground terminal.

[0006] As a further technical scheme of the utility model: the model of chip U1 is XL2576S-ADJE1.

[0007] As a further technical scheme of the utility model: diode D1 is TVS diode.

[0008] As a further technical scheme of the utility model: diode D1 is freewheeling diode.

[0009] As a further technical scheme of the utility model: capacitor C2, capacitor C4 and capacitor C6 are electrolytic capacitors.

[0010] The one or more technical solutions provided in the embodiments of the application have at least the following technical effects or advantages:

[0011] The utility model discloses a circuit is simple, can use DC / DC conversion into different voltage in many occasions, such as MCU power supply, protection circuit power supply, operational amplifier circuit power supply etc., of course can also power supply for small and medium power equipment. Plus, the frequency is not high, slightly adds some filter circuit, can greatly reduce ripple noise, and the device cost of use is also relatively lower. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 It is the circuit diagram of low ripple noise output voltage adjustable DC-DC circuit.

[0013] Figure 2 It is the pin diagram of XL2576S-ADJE1 chip. DETAILED DESCRIPTION

[0014] The technical solutions in the embodiments of the utility model will be described clearly and completely below, obviously, the described embodiments are only part of the embodiments of the utility model, not all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by the person skilled in the art without creative labor belong to the protection scope of the utility model.

[0015] As Figure 1 Indicated, a kind of low ripple noise output voltage adjustable DC-DC circuit, including input protection circuit, input filter circuit, output filter circuit, output voltage regulating circuit.

[0016] Wherein, input protection circuit includes input VIN+, fuse F1, TVS diode D1. Wherein input VIN+ is connected to external power supply, VIN+ is connected with one end of fuse F1, the other end of F1 is connected with the negative pole of TVS diode D1, and the positive pole of TVS diode D1 is connected with ground.

[0017] It is worth mentioning in the utility model, if input appears large current, F1 will disconnect the front and rear circuit in time. If input high voltage appears, D1 rapidly changes from high resistance state to low impedance, and overvoltage is rapidly discharged to ground, so as to protect circuit, when overvoltage disappears, TVS diode automatically restores to high resistance state.

[0018] The specific input filter circuit includes inductor L1, electrolytic capacitor C2, ceramic capacitor C3. Wherein the other end of fuse F1 is connected with one end of inductor L1, the other end of inductor L1 is connected with one end of C2, C3, the other end of C2, C3 is connected with the ground. When the external power input, some interference may be introduced, inductor L1 can filter out part of the noise interference, in order to prevent large transient voltage, must be selected for the maximum RMS current requirements of low ESR (equivalent series resistance) input capacitor. For most applications, a few hundred uF input capacitor is enough, its placement position as close as possible to the position of XL2576, such as C2, also suggests that the input capacitor on the increase of 0.1uF to 1uF ceramic capacitor for high frequency decoupling, such as C3.

[0019] The specific output filter circuit includes inductor L2, ceramic capacitor C6, electrolytic capacitor C9, solid electrolytic C10. Wherein L2 one end is connected with U1 Pin2 (SW) and D2 negative, D2 positive is connected with the ground, the other end of L2 is connected with one end of C6, C9, C10, the other end of C6, C9, C10 is connected with the ground. D2 is a freewheeling diode, it is recommended to use Schottky diode (current 5A, voltage 45-60V, according to the input voltage to select), L2 has a direct impact on the ripple current, inductance ripple current decreases with the increase of inductance value, and increases with the increase of VIN and VOUT. A reasonable starting point for setting the ripple current is △IL = 0.3*Im, wherein Im is the peak switching current limit. In order to ensure that the ripple current is below a specified maximum value, the inductance value should be selected as follows: (VOUT is the output voltage, F is the switching frequency, VIN(MAX) is the maximum input voltage). Generally speaking, once the capacitor ESR is satisfied, the capacitor is sufficient to meet the demand. The ESR of any capacitor along with its own capacity will generate a zero point for the system, the larger the ESR value, the lower the frequency band where the zero point is located, and the zero point of the ceramic capacitor is at a higher frequency, which is usually negligible, and is a good choice, but compared with the electrolytic capacitor, the large capacity and high voltage ceramic capacitor will be larger in size and higher in cost, so it is a good choice to use 0.1uF to 1uF ceramic capacitor (C6) combined with low ESR electrolytic capacitor (C9), in order to achieve lower ESR, an increase of a solid capacitor C10, the output ripple voltage is relatively small. Assuming that the output is 5V / 2A, the ripple noise is about 30-40mV. However, the present application considers that the high and low temperature working environment may increase the ripple noise, so a Π type filter is added, including electrolytic capacitor C4, ceramic capacitor C7, inductor L3, electrolytic capacitor C5, CBB capacitor C8, wherein one end of C4 and C7 is connected with one end of L3, the other end of C4 and C7 is connected with ground, the other end of L3 is connected with one end of C5 and C8, the other end of C5 and C8 is connected with ground, through such combination, the output ripple noise is further reduced, which can be reduced by 10-20mV.

[0020] The specific output voltage regulating circuit includes: resistor R1, resistor R2, ceramic capacitor C1, wherein one end of R1 is connected with one end of C10 and one end of C1, the other end of R1 is connected with Pin4(FB) of U1 and the other end of C1, the other end of C1 is connected with one end of R2, the other end of R2 is connected with ground. Pin4(FB) of U1 is a feedback pin, which detects the output voltage for adjustment through an external resistance dividing network, and the reference voltage is 1.23V. The output voltage VOUT=1.23*(1+R1 / R2), R1 and R2 are selected as high precision as possible. In order to improve stability and reduce input power line noise, compensation capacitor C1 is needed, the typical value of compensation capacitor C1 is between 100pF to 33nF, and is connected in parallel with output voltage setting resistor R1. For high output voltage, low input voltage or low output voltage or with extremely low ESR output capacitor (such as solid tantalum capacitor), etc., the compensation capacitor provides additional stability for the system. This capacitor can be ceramic capacitor, film capacitor or silver mica capacitor, etc. (since Z5U ceramic capacitor is unstable in performance, it is not recommended to use).

[0021] The main chip used is XL2576S-ADJE1 of Chip Dragon, a switching step-down DC-DC conversion chip; the fixed switching frequency is 52KHz, which can reduce the size of external components and facilitate EMC design. The chip has excellent linear regulation rate and load regulation rate, the input is 4.5-40V, the output voltage supports any adjustment between 1.23V and 37V, and the maximum output current is 3A. The chip has high integration, few peripheral devices, and flexible application. The pin configuration is as follows Figure 2 .

[0022] It is obvious for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be regarded as exemplary and non-limiting, and the scope of the present application is defined by the appended claims rather than the above description, and all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application.

[0023] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment have been properly combined to form other embodiments easily understood by those skilled in the art.

Claims

1. A low-ripple-noise output voltage adjustable DC-DC circuit, comprising a chip U1, an inductor L1, a diode D1, a resistor R1 and a resistor R2, characterized in that: One end of the inductor L1 is connected with the negative pole of the fuse F1 and the diode D1, the other end of the inductor L1 is connected with the capacitor C2, the capacitor C3 and the pin 1 of the chip U1, the pin 2 of the chip U1 is connected with the negative pole of the diode D2 and the inductor L2, the other end of the inductor L2 is connected with the capacitor C6, the capacitor C9, the capacitor C10, the resistor R1, the capacitor C1, the capacitor C4, the capacitor C7 and the inductor L3, the other end of the inductor L3 is connected with the capacitor C5 and the capacitor C8, the other end of the capacitor C2 is connected with the other end of the capacitor C3, the positive pole of the diode D2, the other end of the capacitor C6, the other end of the capacitor C9, the other end of the capacitor C10, the other end of the capacitor C4, the other end of the capacitor C7, the other end of the capacitor C8, the other end of the resistor R2 and the ground.

2. The low-ripple-noise output-voltage-adjustable DC-DC circuit according to claim 1, characterized in that, The model of the chip U1 is XL2576S-ADJE1.

3. The low-ripple-noise output-voltage-adjustable DC-DC circuit according to claim 1, characterized in that, The diode D1 is a TVS diode.

4. The low-ripple-noise output-voltage-adjustable DC-DC circuit according to claim 1, characterized by, The diode D1 is a freewheeling diode.

5. The low-ripple-noise output-voltage-adjustable DC-DC circuit according to claim 1, wherein The capacitor C2, the capacitor C4 and the capacitor C6 are electrolytic capacitors.

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