CN211830566U - Power supply circuit and electronic equipment for improving LDO (Low dropout regulator) ripple rejection ratio - Google Patents
Power supply circuit and electronic equipment for improving LDO (Low dropout regulator) ripple rejection ratio Download PDFInfo
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- CN211830566U CN211830566U CN202020437221.6U CN202020437221U CN211830566U CN 211830566 U CN211830566 U CN 211830566U CN 202020437221 U CN202020437221 U CN 202020437221U CN 211830566 U CN211830566 U CN 211830566U
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Abstract
The utility model belongs to the technical field of power supply design, there is the rejection performance influence or the technical problem with high costs of not considering the power ripple in order to solve among the prior art LDO power supply, the utility model provides an improve the power supply circuit of LDO ripple rejection ratio and including this power supply circuit's electronic equipment, improve the power supply circuit of LDO ripple rejection ratio and include: the low dropout linear regulator is connected with a power supply, and the filter circuit is connected with the low dropout linear regulator; wherein the attenuation ratio of the filter circuit is designed in conjunction with a ripple rejection ratio that satisfies a predetermined requirement. Therefore, by adding a filter circuit between the LDO and the object to be powered, the suppression performance of the power supply ripple can be improved by using a low-cost scheme.
Description
Technical Field
The utility model relates to a power design technical field especially relates to power supply circuit for LDO, and more specifically relates to a power supply circuit who improves LDO ripple rejection ratio reaches electronic equipment including this power supply circuit.
Background
With the development of the internet of things, more and more equipment terminals with sensors are provided, and in order to improve the detection sensitivity and improve the user experience, the power supply noise of partial circuits of the sensors needs to be reduced as much as possible, and the influence of the equipment on the performance of the sensors is reduced.
An LDO (low dropout regulator) is a low dropout regulator, which utilizes a power tube working in a linear region to generate regulated output voltage, and has the advantages of small static current, low cost and simple application; therefore, the use of LDO power supply is a common solution, but the ripple rejection ratio (PSSR) of the LDO gradually decreases with the increase of the frequency, so that the LDO cannot suppress the high-frequency noise at the input end well. At present, in practical use, improvement is mainly performed between an LDO output and a device to be powered, and there are two main types in specific implementation: 1. DC-DC and LDO cascades are used, and 2, a plurality of LDO cascades are used.
Therefore, the application scheme of the existing LDO has at least the following problems:
when the LDO is directly connected to the Power input of the device, there is a problem that the Power Supply Rejection Ratio (PSRR) of the LDO does not sufficiently consider the Rejection performance of the Power Supply Rejection Ratio) of the Power Supply ripple input at different frequencies.
And 2, in the cascade use process of the DC-DC and the LDO, the noise suppression effect of the external passive filter circuit of the power supply is not considered.
3. In the cascade use process of a plurality of LDOs, the noise caused by a power supply is not quantitatively analyzed, transition configuration may exist in cascade use, not only the cost is increased, but also the LDOs can generate noise in use.
SUMMERY OF THE UTILITY MODEL
In order to solve the LDO power supply among the prior art and have the rejection performance influence of not considering the power ripple or have with high costs technical problem, the utility model provides an improve the power supply circuit of LDO ripple rejection ratio and including this power supply circuit's electronic equipment through increasing filter circuit between LDO and waiting to supply power the object, can use low-cost scheme to improve the rejection performance of power ripple like this.
In order to achieve the above object, the present invention provides a technical solution comprising:
an aspect of the utility model provides an improve power supply circuit of LDO ripple rejection ratio, a serial communication port, include:
a low dropout regulator connected to a power supply, and
the filter circuit is connected with the low dropout linear regulator;
wherein the attenuation rate of the filter circuit is AfilterThe ripple rejection ratio of the power supply circuit is PSSRfA relationship between the attenuation rate and the ripple rejection ratio is configured to satisfy the following relationship:
wherein, VpRepresents the supply voltage, γ represents the supply voltage fluctuation percentage; fft represents that Fourier transform is carried out, the ripple signal is transformed from a time domain to a frequency domain, and the amplitude of different frequency components of the ripple voltage is obtained; vfsIs the amplitude of the different frequency components of the signal and n is the signal-to-noise ratio.
The utility model discloses in preferred embodiment, low dropout linear regulator's model is SGM2032, low dropout linear regulator's input power supply ripple rejection ratio PSSRfGradually decaying with increasing frequency.
In a further preferred embodiment of the present invention, when the power supply is 5V, the accuracy requirement is ± 10%, the operating frequency of the unit to be powered is 0-1MHz, and the noise input from the power supply end in the operating frequency band is not more than 0.1 mV; when the power supply circuit works at 1KHz, 10KHz or 100KHz, the ripple rejection ratio of the low dropout linear regulator is 70dB, 50dB and 30dB respectively; the filter circuit has an attenuation ratio greater than 74dB at different frequencies.
In a preferred embodiment of the present invention, the filter circuit includes: the low dropout linear regulator comprises a first capacitor connected with the low dropout linear regulator, a second capacitor connected with a unit to be supplied with power, a first inductor positioned between the first capacitor and the low dropout linear regulator, and a second inductor positioned between the first capacitor and the second capacitor.
The embodiment of the utility model provides an in the preferred implementation mode, filter circuit includes: the low dropout regulator comprises a resistor connected with the low dropout regulator and a capacitor connected with the resistor, wherein the capacitor is connected with a unit to be powered.
The embodiment of the utility model provides an in the preferred implementation mode, filter circuit includes two at least different wave filters, two at least different wave filters are connected through cascaded mode, and two at least different wave filters are the wave filters of different classification, different characteristics respectively.
The utility model discloses in the preferred embodiment, power supply circuit includes a plurality of filter circuit to and input power detection module, with the selection module that input power detection module connects, the selection module detects input power's characteristic according to input power detection module, follow select one among a plurality of filter circuit with the linear stabiliser of low dropout connects.
The utility model discloses in the preferred embodiment, still include: the input power supply detection module is connected with the adjustment module; the parameter of at least one filtering element in the filtering circuit is set to be adjustable, and the adjusting module adjusts the parameter of the at least one filtering element to be a preset value according to the characteristic of the input power detected by the input power detecting module.
The utility model discloses another aspect still provides an electronic equipment, a serial communication port, include:
the power circuit for improving the LDO ripple rejection ratio as provided in any one of the first aspect, and a unit to be powered connected to the power circuit for improving the LDO ripple rejection ratio.
The utility model discloses in the preferred embodiment, treat that power supply unit is infrared induction lamp, moving object detection, sensor for the range finding, or weak signal detection module.
Adopt the above-mentioned technical scheme provided by the utility model, at low dropout linear regulator and treat to increase low-cost filter circuit between the power supply unit, use filter circuit decay power noise, filter circuit's parameter characteristic is according to input power supply's error behavior and the SNR requirement of treating that the power supply unit needs to satisfy moreover, sets up in advance, can satisfy the requirement of ripple rejection ratio so better.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure and/or process particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
Fig. 1 is a block diagram of a power circuit for improving the LDO ripple rejection ratio according to an embodiment of the present invention.
Fig. 2 is a graph showing the relationship between the frequency and the rejection ratio in the power circuit for improving the LDO ripple rejection ratio according to the embodiment of the present invention.
Fig. 3 is a first circuit diagram of a filter circuit in a power circuit for improving LDO ripple rejection ratio according to an embodiment of the present invention.
Fig. 4 is a circuit diagram of a filter circuit in a power circuit according to an embodiment of the present invention, which provides an improved LDO ripple rejection ratio.
Fig. 5 is a third circuit diagram of a filter circuit in a power circuit for improving the LDO ripple rejection ratio according to an embodiment of the present invention.
Fig. 6 is a block diagram of a power circuit according to a second embodiment of the present invention, which improves LDO ripple rejection ratio.
Fig. 7 is a block diagram of a power circuit according to a third embodiment of the present invention, which improves LDO ripple rejection ratio.
Fig. 8 is a block diagram of an electronic device according to a fourth embodiment of the present invention.
Detailed Description
The following detailed description will be made with reference to the accompanying drawings and examples, so as to solve the technical problems by applying technical means to the present invention, and to fully understand and implement the technical effects of the present invention. It should be noted that the specific description is only for the purpose of making the present invention easier and clearer for those skilled in the art to understand, and is not a limiting explanation of the present invention; and as long as no conflict is formed, the embodiments and the features in the embodiments of the present invention can be combined with each other, and the technical solutions formed are all within the scope of the present invention.
Additionally, the steps illustrated in the flow charts of the drawings may be performed in a control system such as a set of controller-executable instructions and, although a logical ordering is illustrated in the flow charts, in some cases, the steps illustrated or described may be performed in an order different than that illustrated herein.
The technical solution of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments:
example one
As shown in fig. 1, the present embodiment provides a power supply circuit for improving LDO ripple rejection ratio, the power supply circuit including:
a low dropout regulator connected to a power supply, and
the filter circuit is connected with the low dropout linear regulator;
wherein the attenuation rate of the filter circuit is AfilterThe ripple rejection ratio of the power circuit is PSSRfThe relationship between the attenuation rate and the ripple rejection ratio is configured to satisfy the following relationship:
wherein, VpRepresents the supply voltage, γ represents the supply voltage fluctuation percentage; fft represents that Fourier transform is carried out, the ripple signal is transformed from a time domain to a frequency domain, and the amplitude of different frequency components of the ripple voltage is obtained; vfsIs the amplitude of the different frequency components of the signal and n is the signal-to-noise ratio.
Specifically, in the present embodiment, a filter circuit is used to improve a ripple rejection ratio of an LDO (low dropout regulator) in consideration of not increasing cost, and in consideration of how to improve the ripple rejection ratio PSRR, a structural relationship that the filter circuit needs to satisfy is analyzed, where the structural relationship includes:
1. the ripple amplitude and period of the external power supply is determined, the power supply output voltage fluctuation, typically expressed as a percentage of its nominal voltage, is converted to a specific amplitude, i.e. the amplitude
Vrp＝VpX gamma (formula 2)
VrpRepresenting ripple voltage, VpRepresenting the supply voltage and gamma representing the percentage of supply voltage fluctuation.
2. Fourier transform is carried out on the ripple wave determined based on the formula 2, the ripple wave signal is transformed from a time domain to a frequency domain, and the amplitudes of different frequency components of the ripple wave voltage, namely V, are obtainedfrp。
Vfrp＝fft(Vrp) (formula 3)
3. Obtaining the allowable amplitude V of different frequency components of the power supply noise according to the requirement of the circuit to be supplied on the power supply qualityfn。
4. According to the power supply ripple VfrpAnd allowable power supply noise VfnObtaining the amplitude A of the power supply ripple wave with different frequency components needing to be attenuatedf：AfIn dB
5. The attenuation rates of the filter at different frequencies are determined according to the following equation 6:
Afiler+PSSRf>Af(formula 6)
AfilterFor the attenuation ratio of the filter at different frequencies, PSSRfThe ripple rejection ratio of the LDO in different frequency bands is obtained; the LDO can restrain noises with different frequencies, and the requirements of a circuit to be powered on the power supply quality can be met after the suppression of the filter on the different noises is superposed.
The above equation 1 can be calculated by combining the above equations 2 to 6.
By adopting the technical scheme provided by the embodiment, the low-cost filter circuit is added between the low dropout linear regulator and the unit to be supplied with power, the filter circuit is used for attenuating the noise of the power supply, and the parameter characteristic of the filter circuit is set in advance according to the error performance of the input power supply and the signal-to-noise ratio requirement required to be met by the unit to be supplied with power, so that the requirement of the ripple rejection ratio can be better met.
In a preferred embodiment of this embodiment, the low dropout regulator is SGM2032, and the input power supply ripple rejection ratio PSSR of the low dropout regulatorfGradually decaying with increasing frequency. Specifically, as shown in fig. 2, the inventors found that the corresponding rejection ratio PSRR decreases with increasing frequency for a capacitance of 1 μ F in the filter circuit, and that there is a peak in the process of decreasing for a capacitance of 10 μ F in the filter circuit.
In a further preferred embodiment of this embodiment, when the power supply is 5V, the accuracy requirement is ± 10%, the operating frequency of the unit to be powered is 0-1MHz, and the noise input from the power supply end in the operating frequency band is not greater than 0.1 mV; when the power supply circuit works at 1KHz, 10KHz or 100KHz, the ripple rejection ratio of the low dropout linear regulator is 70dB, 50dB and 30dB respectively; the attenuation rates of the filter circuit at different frequencies are all greater than 74 dB.
Assuming that a power supply is 5V, the precision is +/-10%, the working frequency of a unit to be powered is 0-1MHz, the noise input by a power supply end in a working frequency band is not more than 0.1mV, and a device to be powered is powered by 3.3 VLDO.
1. Determining the fluctuation amplitude of the power supply:
Vrp＝5×0.1V＝500mV
2. calculating the attenuation rate A of the power supply to the equipment to be powered at different frequenciesfIn order to simplify the calculation process, it is assumed that the noise attenuation rate requirements of the power supply device to be supplied to different frequency bands are consistent, that is:
3. calculating the attenuation rate of the filter in different frequency bands, namely:
Af>74dB-PSSRf
PSSRfdetermined by the selected LDO characteristics.
For example, the DO model is the SGM2032, the input power supply ripple rejection ratio PSSR of the LDO gradually attenuates as the frequency increases, and the PSSR of the SGM2032 changes with the frequency as shown in fig. 2. The ripple rejection ratio of the LDO is 70dB at 1KHz, 50dB at 10KHz and 30dB at 100KHz, so that the attenuation rate at different frequencies is greater than 74dB, the turning frequency is 1KHz, the attenuation rate at the turning frequency is greater than 4dB, the attenuation rate of a transition band is greater than 20dB, and the designed filter and the frequency response thereof are shown in figures 2 and 3, so that the power supply noise after the filter is added meets the requirement of the attenuation rate greater than 74 dB.
For the more specific design of the filter circuit, as shown in fig. 3, in a preferred implementation of this embodiment, the first filter circuit is provided and includes: the low dropout linear regulator comprises a first capacitor C1 connected with the low dropout linear regulator, a second capacitor C2 connected with a unit to be powered, a first inductor L1 positioned between the first capacitor C1 and the low dropout linear regulator, and a second inductor L2 positioned between the first capacitor C1 and the second capacitor C2.
As shown in fig. 4, in a preferred embodiment of this embodiment, the second filtering circuit includes: the low dropout regulator comprises a resistor connected with the low dropout regulator and a capacitor connected with the resistor, wherein the capacitor is connected with a unit to be powered.
As shown in fig. 5, in a preferred embodiment of this embodiment, the second filtering circuit includes: at least two different filters (first filter, second filter), which are connected in a cascade, and which are respectively of different classes and different characteristics.
Example two
On the basis of the first embodiment, in order to adapt the power supply circuit to different scenes, the market popularization of the power supply circuit is improved; an input power supply detection module is added, the direct current component of the input power supply value after sampling is removed, fft conversion is carried out on the alternating current component, the amplitude of ripples at different frequencies is obtained, and filter circuits with different characteristics are dynamically selected according to different requirements, so that the power supply quality meets the requirements of a circuit to be supplied with power. As shown in fig. 6, in a preferred embodiment of this embodiment, on the basis of the embodiment, the power circuit includes a plurality of filter circuits, an input power detection module, and a selection module connected to the input power detection module, where the selection module selects one of the plurality of filter circuits to connect to the low dropout linear regulator according to the characteristic of the input power detected by the input power detection module.
EXAMPLE III
On the basis of the first embodiment, the present embodiment is also intended to adapt the power supply circuit to different scenes, thereby improving the market popularization of the power supply circuit; and the parameters of the filter elements in the filter circuit are dynamically adjusted according to different application scenes, so that the power supply circuit can better adapt to more application requirements. Specifically, as shown in fig. 7, the preferred embodiment of this embodiment further includes, on the basis of the embodiment: the input power supply detection module is used for removing a direct current component from a sampled input power supply value, performing fft conversion on an alternating current component to obtain amplitudes of ripples at different frequencies, and the adjustment module is connected with the input power supply detection module and used for outputting different voltage amplitudes and adjusting parameters of the filter circuit; the parameter of at least one filtering element in the filtering circuit is set to be adjustable, and the adjusting module adjusts the attenuation rate of the filter to different frequency noises to be a preset value according to the characteristic that the input power detection module detects the input power.
Example four
As shown in fig. 8, the present embodiment provides an electronic apparatus including:
the power circuit for improving the LDO ripple rejection ratio and the unit to be powered connected with the power circuit for improving the LDO ripple rejection ratio are provided in any of the embodiments described above. In combination with different application scenarios, the units to be powered may be different, for example, when the electronic device is a display device requiring infrared control, the units to be powered may be infrared induction lamps, and when the electronic device is a radar ranging device, the units to be powered may be ranging sensors; the unit to be powered can also be a moving object detection module or other weak signal detection modules.
Finally, it should be understood that the above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way. The above disclosed embodiments and technical content can be utilized by any person skilled in the art to make many possible variations, simple substitutions and the like without departing from the scope of the present invention, which is within the protection scope of the present invention.
Claims (10)
1. A power circuit for improving LDO ripple rejection ratio, comprising:
a low dropout regulator connected to a power supply, and
the filter circuit is connected with the low dropout linear regulator;
wherein the attenuation rate of the filter circuit is AfilterThe ripple rejection ratio of the power supply circuit is PSSRfA relationship between the attenuation rate and the ripple rejection ratio is configured to satisfy the following relationship:
wherein, VpRepresents the supply voltage, γ represents the supply voltage fluctuation percentage; fft represents that Fourier transform is carried out, the ripple signal is transformed from a time domain to a frequency domain, and the amplitude of different frequency components of the ripple voltage is obtained; vfsIs the amplitude of the different frequency components of the signal and n is the signal-to-noise ratio.
2. The power supply circuit of claim 1, wherein the low dropout regulator is model number SGM2032, and an input power supply ripple rejection ratio PSSR of the low dropout regulatorfGradually decaying with increasing frequency.
3. The power supply circuit of claim 2, wherein when the power supply is 5V, the accuracy requirement is ± 10%, the operating frequency of the unit to be powered is 0-1MHz, and the noise input from the power supply end in the operating frequency band is not more than 0.1 mV; when the power supply circuit works at 1KHz, 10KHz or 100KHz, the ripple rejection ratio of the low dropout linear regulator is 70dB, 50dB and 30dB respectively; the filter circuit has an attenuation ratio greater than 74dB at different frequencies.
4. The power supply circuit according to any one of claims 1 to 3, wherein the filter circuit includes: the low dropout linear regulator comprises a first capacitor connected with the low dropout linear regulator, a second capacitor connected with a unit to be supplied with power, a first inductor positioned between the first capacitor and the low dropout linear regulator, and a second inductor positioned between the first capacitor and the second capacitor.
5. The power supply circuit according to claim 1, wherein the filter circuit comprises: the low dropout regulator comprises a resistor connected with the low dropout regulator and a capacitor connected with the resistor, wherein the capacitor is connected with a unit to be powered.
6. The power supply circuit according to claim 1, wherein the filter circuit comprises at least two different filters, the at least two different filters are connected in a cascade, and the at least two different filters are different types of filters with different characteristics.
7. The power circuit of claim 1, wherein the power circuit comprises a plurality of filter circuits, and an input power detection module, a selection module coupled to the input power detection module, the selection module selecting one of the plurality of filter circuits to couple to the low dropout regulator based on the input power detection module detecting the characteristic of the input power.
8. The power supply circuit according to claim 1, further comprising: the input power supply detection module is connected with the adjustment module; the parameter of at least one filtering element in the filtering circuit is set to be adjustable, and the adjusting module adjusts the parameter of the at least one filtering element to be a preset value according to the characteristic of the input power detected by the input power detecting module.
9. An electronic device, comprising:
the power circuit for improving the LDO ripple rejection ratio of any one of claims 1 to 8, and a unit to be powered connected to the power circuit for improving the LDO ripple rejection ratio.
10. The electronic device of claim 9, wherein the unit to be powered is an infrared sensor lamp, a moving object detection, a distance measurement sensor, or a weak signal detection module.
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