CN217769905U - Power supply capable of receiving AC input power and DC input power - Google Patents

Abstract

The present disclosure relates to power supplies. According to one embodiment of the present disclosure, the power supply is capable of receiving ac input power and dc input power. The power supply includes: a rectifier bridge having a positive output terminal and a negative output terminal; a first capacitor connected in parallel with the rectifier bridge between the positive output terminal and the negative output terminal; a capacitor unit connected in parallel with the rectifier bridge between the positive output terminal and the negative output terminal; the capacitor unit comprises a switch and a second capacitor connected with the switch in series; the first capacitor has a first nominal voltage and a first nominal capacitance; the second capacitor has a second voltage rating and a second nominal capacitance; the first nominal voltage is at least 1.5 times the second nominal voltage; and the first nominal capacitance is less than the second nominal capacitance. The technical solutions of the present disclosure have beneficial effects including at least one of the following: the reliability of the power supply is improved, the occupied area of a circuit board of the power supply circuit is reduced, and the cost is reduced.

Description

Power supply capable of receiving AC input power and DC input power

Technical Field

The present disclosure relates generally to power supplies, and in particular, to power supplies capable of receiving ac input power and dc input power.

Background

In general, a power supply is provided to a flowmeter, a thermometer, a pressure gauge, a densitometer, or the like. The power supply may be configured to output a direct current; the input power is alternating current or direct current.

SUMMERY OF THE UTILITY MODEL

A brief summary of the disclosure is provided below in order to provide a basic understanding of some aspects of the disclosure. It should be understood that this summary is not an exhaustive overview of the disclosure. The following summary is not intended to identify key or critical elements of the disclosure, nor is it intended to be limiting as to the scope of the disclosure. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.

According to an aspect of the present disclosure, there is provided a power supply capable of receiving an ac input power and a dc input power. The power supply includes: a rectifier bridge having a positive output terminal and a negative output terminal; a first capacitor connected in parallel with the rectifier bridge between the positive output terminal and the negative output terminal; a capacitor unit connected in parallel with the rectifier bridge between the positive output terminal and the negative output terminal; the capacitor unit comprises a switch and a second capacitor connected with the switch in series; the first capacitor has a first voltage rating and a first nominal capacitance; the second capacitor has a second voltage rating and a second nominal capacitance; the first rated voltage is at least 1.5 times the second rated voltage; and the first nominal capacitance is less than the second nominal capacitance.

The technical scheme of the present disclosure has the beneficial technical effects of at least one of the following: the reliability of the power supply is improved, the occupied area of a circuit board of the power supply circuit is reduced, and the cost is reduced.

Drawings

The disclosure may be better understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements. It should be understood that the drawings are not necessarily drawn to scale. In the drawings:

FIG. 1 shows a circuit diagram of a conventional power supply;

fig. 2 illustrates an exemplary circuit diagram of a power supply according to one embodiment of the present disclosure;

FIG. 3 illustrates an exemplary circuit diagram of a power supply according to one embodiment of the present disclosure;

FIG. 4 illustrates an exemplary circuit diagram of a power supply according to one embodiment of the present disclosure; and

fig. 5 illustrates an exemplary circuit diagram of a power supply according to one embodiment of the present disclosure.

Detailed Description

Exemplary embodiments of the present disclosure will be described hereinafter with reference to the accompanying drawings. In the interest of clarity and conciseness, not all features of an actual implementation are described in the specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions may be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another.

Here, it is also to be noted that, in order to avoid obscuring the present disclosure by unnecessary details, only the device structure closely related to the scheme according to the present disclosure is shown in the drawings, and other details not so much related to the present disclosure are omitted.

It is to be understood that the disclosure is not limited to the described embodiments, as described below with reference to the drawings. In this context, embodiments may be combined with each other, features may be replaced or borrowed between different embodiments, one or more features may be omitted in one embodiment, where feasible.

The present disclosure relates to power supply, and more particularly to power supplies. To illustrate the basic principles of the present disclosure, a conventional power supply will first be described.

Fig. 1 shows a circuit diagram of a conventional power supply 100 as a comparative example. The power supply 100 includes a rectifier bridge Rf, a capacitor Cp. The rectifier bridge Rf comprises diodes D1, D2, D3 and D4. Two input terminals of the rectifier bridge Rf receive the input power Pin of the power supply 100. The voltage of the input power Pin is denoted by Vin. The power supply 100 is capable of receiving ac input power and dc input power and outputting dc power, and the voltage of the output power Pout is represented by a voltage Vout between a pair of output terminals, including output terminals Toutp, toutn, of the power supply 100. In this way, the power supply 100 may use ac power as input power in the case where ac power is available, and select dc power as input power in the case where ac power is not available. As shown in fig. 1, the rectifier bridge Rf has a positive output Tp and a negative output Tn. The capacitor Cp is connected in parallel with the rectifier bridge Rf between the positive output terminal Tp and the negative output terminal Tn. The capacitor Cp has a nominal voltage Vr and a nominal capacitance cn. The capacitor Cp may function as a storage capacitor. After the input of power to the power supply 100 is stopped, the capacitor Cp stores a certain amount of power, and thus discharges to the outside; therefore, the power supply 100 can still provide output power to the outside for a certain time. This can be characterized as an output voltage hold time t _ h of the power supply with respect to the output voltage. In order to meet the voltage withstanding requirements and the requirements of the droop clauses in the standard, it is generally necessary to select a high-voltage large capacitance as the capacitor Cp, i.e., the rated voltage Vr of the capacitor Cp is sufficiently high and, at the same time, the nominal capacitance cn is sufficiently large. For example, in IEC 61000-4-29, it is required that: after the input power is turned off, the output voltage needs to have a holding time of more than 20mS (milliseconds).

The inventors have conducted studies on the power supply 100, and have recognized that: when the input power is 220V alternating current for example, the energy storage filtering can be realized by using a high-voltage small capacitor (the rated voltage is high, and the capacitance is small); however, when the input power is switched to a direct current of, for example, 24V, the high voltage small capacitor stores too little energy and may not meet the requirements of the fall terms. In addition, if a high-voltage large capacitor is selected as the capacitor Cp of the power supply 100, the capacitor is bulky, which inevitably increases the cost, increases the circuit board occupation area of the power supply circuit, increases the occupation space, and also causes a large inrush current at the time of high-voltage start (an additional control circuit may be required to limit the inrush current). This increases the complexity of the circuit if the own switching circuit and control circuit are chosen in order to solve the aforementioned problems. Based on the foregoing considerations, the inventors conceived the technical solution of the present disclosure based on experiments and analysis. The high-voltage input is matched with a small capacitor, and the low-voltage input is matched with a large capacitor, so that the design is simple, easy to realize and more reasonable.

One aspect of the present disclosure discloses a power supply capable of receiving ac input power and dc input power. This power supply is described below by way of example with reference to fig. 2.

Fig. 2 illustrates an exemplary circuit diagram of a power supply 200 according to one embodiment of the present disclosure. The power supply 200 is capable of receiving ac input power and dc input power, and is a power supply capable of receiving a wide range of ac and dc power. The power supply 200 includes: a rectifier bridge Rf, a first capacitor C1 and a capacitor unit Uc. The rectifier bridge Rf has a positive output Tp and a negative output Tn. The first capacitor C1 is connected in parallel with the rectifier bridge Rf between the positive output terminal Tp and the negative output terminal Tn. The capacitor unit Uc is connected in parallel with the rectifier bridge Rf between the positive output terminal Tp and the negative output terminal Tn. The capacitor unit Uc includes a switch Q and a second capacitor C2 connected in series with the switch Q. In fig. 2, the positive electrode of the capacitor is shown by the symbol "+". As shown in fig. 2, the first capacitor C1 has a first rated voltage Vr1 and a first nominal capacitance cn1; the second capacitor C2 has a second voltage rating Vr2 and a second nominal capacitance cn2. The first rated voltage Vr1 is at least 1.5 times the second rated voltage Vr2 (e.g., vr1/Vr2=1.5,1.8,2,3,4,5,8, 10 or higher); and the first nominal capacitance cn1 is less than the second nominal capacitance cn2 (i.e., cn1/cn2<1, e.g., cn1/cn2=0.5,0.2,0.1,0.05 or less). The voltage of the output power Pout of the power supply 200 is represented by a voltage Vout between the pair of output terminals of the power supply 200 including the output terminals ToutP, toutn. The output voltage Vout may be applied to a load of the power supply 200. In contrast, the first capacitor C1 may be referred to as a "high-voltage small capacitance", and the second capacitor C2 may be referred to as a "low-voltage large capacitance". When the input voltage Vin is a high voltage (e.g., 220V ac or 110V ac), the switch Q is configured to be in an off state, so that when the input power is stopped, the energy storage capacitor, the first capacitor C1, can provide enough power to keep the output voltage for a time t _ h long enough, e.g., longer than a predetermined threshold time. The predetermined threshold time may be a predetermined time greater than or equal to 20 milliseconds; configuring the switch Q to an on state when the input voltage Vin is low (e.g., 24 vdc or 12 vdc), such that when the input power is stopped, the energy storage capacitors, the first capacitor C1 and the second capacitor C2, can together provide power, greatly increasing the output voltage holding time, which ensures that even at low input voltages, the stored power is sufficient so that the output voltage holding time t _ h is sufficiently long, e.g., greater than a predetermined threshold time. The predetermined threshold time may be a predetermined time greater than or equal to 20 milliseconds. The switch Q is configured in an off state at high input voltages to prevent the high voltage from damaging the second capacitor C2. The high voltage and the low voltage in the present embodiment are relative terms, and are not limited to the case where the former is ac and the latter is dc. For example, power supply 200 may be configured to: in the case of inputting high-voltage alternating current (for example, 220V alternating current), only the first capacitor C1 is connected as an energy storage capacitor; in the case of inputting low-voltage alternating current (e.g., 110V alternating current), the first capacitor C1 and the second capacitor C2 are connected as energy storage capacitors, so that the power supply has a wide applicable scene.

Such a power supply with a switched capacitor configuration may have at least one of the following benefits: output voltage hold times are long, e.g., meeting the requirements of the sag provision, or hold times of at least 20 milliseconds, while ensuring that a wide range of input power can be received; since the second capacitor C2 is connected at a low input voltage, the first capacitor C1 with a higher capacitance is not needed, that is, the capacitance of the first capacitor C1 can be relatively smaller (compared with the capacitor Cp in the power supply 100), so that a capacitor with a smaller volume and a smaller circuit board occupation area can be selected to serve as the first capacitor C1, thereby reducing the circuit board occupation area of the power supply circuit, reducing the occupation space, reducing the cost, reducing the inrush current when starting at a high voltage, and eliminating the need to configure a circuit for limiting the inrush current.

Preferably, the energy storage capacitance of the power supply 200 may be only two, i.e., the first capacitor C1 and the second capacitor C2. This can simplify the circuit and substantially reduce the circuit board footprint of the power supply circuit.

In one example, the switch Q may be a mechanical switch. The user may, for example, manually select the operating state of the switch Q, including an on state and an off state, depending on the parameters of the input power to be accessed. For example, the switch Q is configured to be in an off state when the input voltage Vin is a high voltage (e.g., 220V ac or 110V ac), and configured to be in an on state when the input voltage Vin is a low voltage (e.g., 24V dc or 12V dc).

In one example, the switch Q may be a relay type switch or a MOS transistor. The operating state of the switch Q may be controlled using a switch control unit.

In one example, the first capacitor and the second capacitor are electrolytic capacitors. Two electrodes of an electrolytic capacitor need to be distinguished between positive and negative electrodes. Although in fig. 2, both capacitors are shown with their positive poles, the storage capacitor used by the power supply of the present disclosure is not limited to capacitors that require distinguishing the positive and negative poles.

In one example, the amount of capacitance of the storage capacitor may be determined based on the output voltage holding time. For example, the ratio of cn2 to cn1 is greater than or equal to 20. The ratio of the second nominal capacitance cn2 to the first nominal capacitance cn1 may be between 5 and 10, taking into account the regulation of the secondary output capacitance.

In one embodiment, the power supply of the present disclosure may include a switch control unit. The switch control unit is configured to monitor an input voltage of the power supply and control an operating state of the switch based on the monitored input voltage, enabling automatic switching of an access state of an energy storage capacitor of the power supply. An exemplary description is provided below with reference to fig. 3.

Fig. 3 illustrates an exemplary circuit diagram of a power supply 300 according to one embodiment of the present disclosure. The power supply 300 is capable of receiving both ac input power and dc input power and is a power supply that can receive a wide range of ac and dc power. The power supply 300 includes: a rectifier bridge Rf, a first capacitor C1, a capacitor unit Uc and a switch control unit Uqc. The rectifier bridge Rf has a positive output terminal Tp and a negative output terminal Tn. The first capacitor C1 is connected in parallel with the rectifier bridge Rf between the positive output terminal Tp and the negative output terminal Tn. The capacitor unit Uc is connected in parallel with the rectifier bridge Rf between the positive output terminal Tp and the negative output terminal Tn. The capacitor unit Uc includes a switch Q and a second capacitor C2 connected in series with the switch Q. As shown in fig. 3, the first capacitor C1 has a first rated voltage Vr1 and a first nominal capacitance cn1; the second capacitor C2 has a second rated voltage Vr2 and a second nominal capacitance cn2. The first rated voltage Vr1 is at least 1.5 times of the second rated voltage Vr 2; and the first nominal capacitance cn1 is smaller than the second nominal capacitance cn2. The voltage of the output power Pout of the power supply 300 is represented by a voltage Vout between a pair of output terminals of the power supply 300 including the output terminals Toutp, toutn. The power supply 300 applies the output voltage Vout to the load. In contrast, the first capacitor C1 may be referred to as a "high-voltage small capacitance", and the second capacitor C2 may be referred to as a "low-voltage large capacitance". When the input voltage Vin is a high voltage (e.g., 220V ac or 110V ac), the switch Q is configured to be in an off state, so that when the input power is stopped, the energy storage capacitor, the first capacitor C1, can provide enough power to keep the output voltage for a time t _ h long enough, e.g., longer than a predetermined threshold time. The predetermined threshold time may be a predetermined time greater than or equal to 20 milliseconds; when the input voltage Vin is low (e.g., 24V dc or 12V dc), the switch Q is configured to be on, so that the energy storage capacitors, the first capacitor C1 and the second capacitor C2, can together provide energy when the input power ceases, which ensures that the stored energy is sufficient to cause the output voltage holding time t _ h to be sufficiently long, e.g., greater than a predetermined threshold time, even at low input voltages. The predetermined threshold time may be a predetermined time greater than or equal to 20 milliseconds. The switch Q is configured in an off state at high input voltages to prevent the high voltage from damaging the second capacitor C2. As shown in fig. 3, the switch control unit Uqc is connected with the switch Q to control the operating state of the switch Q. The switch control unit Uqc may be coupled to the rectifier bridge Rf such that, in case the switch control unit Uqc determines that the input voltage Vin of the rectifier bridge Rf is lower than a first predetermined threshold voltage, the switch control unit Uqc outputs a switch-on signal to the switch Q, thereby automatically switching in the second capacitor C2 in case of a low input voltage, and in case of a high input voltage, the switch control unit Uqc outputs a switch-off signal to the switch Q, thereby putting the switch Q in a switch-off state, thereby switching in only one energy storage capacitor, the first capacitor C1. In one example, the switch control unit Uqc may be implemented using a comparison circuit. The value of the first predetermined threshold voltage may be determined according to actual needs. In one example, the first predetermined threshold voltage is above 36 volts, for example, the first predetermined threshold voltage is 100 volts or 120 volts. In one example, the switch Q is a MOS transistor (metal oxide semiconductor transistor). In one example, the power required for the operation of the switch control unit Uqc may be a part of the output power Pout of the power supply 300. For example, two voltage dividing resistors are connected between the output terminals Toutp, toutn, and the switch control unit Uqc is electrically connected to a node between the two voltage dividing resistors to apply a desired operating voltage to the switch control unit Uqc.

Although the power supply 300 shown in fig. 3 includes only two storage capacitors. The power supply of the present disclosure may also include more storage capacitors to equalize, for example, performance, cost, size.

It will be appreciated that for the power supply 300, the first capacitor may be replaced by two capacitors connected in parallel, wherein each replacement capacitor has a nominal capacitance of one half that of the first capacitor and each replacement capacitor has a voltage rating equal to the voltage rating of the first capacitor; the second capacitor may be replaced by two capacitors connected in parallel, wherein each replacement capacitor has a nominal capacitance of half that of the first capacitor and each replacement capacitor has a voltage rating equal to the voltage rating of the first capacitor.

Fig. 4 illustrates an exemplary circuit diagram of a power supply 400 according to one embodiment of the present disclosure. The power supply 400 is capable of receiving both ac input power and dc input power and is a power supply that can receive a wide range of ac and dc power. The power supply 400 includes: a rectifier bridge Rf, a first capacitor C1, a capacitor unit Uc, a third capacitor C3 and a switch control unit Uqc. The rectifier bridge Rf has a positive output terminal Tp and a negative output terminal Tn. The first capacitor C1 is connected in parallel with the rectifier bridge Rf between the positive output terminal Tp and the negative output terminal Tn. The capacitor unit Uc is connected in parallel with the rectifier bridge Rf between the positive output terminal Tp and the negative output terminal Tn. The capacitor unit Uc includes a switch Q and a second capacitor C2 connected in series with the switch Q. The first capacitor C1 has a first rated voltage Vr1 and a first nominal capacitance cn1; the second capacitor C2 has a second rated voltage Vr2 and a second nominal capacitance cn2. The first rated voltage Vr1 is at least 1.5 times of the second rated voltage Vr 2; and the first nominal capacitance cn1 is smaller than the second nominal capacitance cn2. The third capacitor C3 is connected in parallel with the rectifier bridge Rf between the positive output terminal Tp and the negative output terminal Tn. The third capacitor C3 has a third rated voltage Vr3 and a third nominal capacitance cn3. The third rated voltage Vr3 is at least 1.5 times the second rated voltage Vr 2; and the third nominal capacitance cn3 is smaller than the second nominal capacitance cn2. The voltage of the output power Pout of the power supply 400 is represented by a voltage Vout between the pair of output terminals of the power supply 400 including the output terminals Toutp, toutn. The power supply 400 applies an output voltage Vout to a load. In contrast, the first and third capacitors C1 and C3 may be referred to as "high-voltage small capacitance", and the second capacitor C2 may be referred to as "low-voltage large capacitance". When the input voltage Vin is a high voltage (e.g., 220V ac or 110V ac), the switch Q is configured to be in an off state, so that when the input power stops, the energy storage capacitors, i.e., the first capacitor C1 and the third capacitor C3, can provide enough power to make the output voltage holding time t _ h long enough, e.g., longer than a predetermined threshold time. The predetermined threshold time may be a predetermined time greater than or equal to 20 milliseconds; when the input voltage Vin is low (e.g., 24 vdc or 12 vdc), the switch Q is configured to an on state so that the energy storage capacitors-the first capacitor C1, the second capacitor C2 and the third capacitor C3-can together provide energy when the input power is stopped, which ensures that even at low input voltages the energy is stored sufficiently so that the output voltage holding time t _ h is sufficiently long, e.g., greater than a predetermined threshold time. The predetermined threshold time may be a predetermined time greater than or equal to 20 milliseconds. The switch Q is configured in an off state at high input voltages to prevent the high voltage from damaging the second capacitor C2. As shown in fig. 4, the switch control unit Uqc is connected to the switch Q to control the operating state of the switch Q. The switch control unit Uqc may be coupled to the rectifier bridge Rf such that, in case the switch control unit Uqc determines that the input voltage Vin of the rectifier bridge Rf is lower than a first predetermined threshold voltage, the switch control unit Uqc outputs a switch-on signal to the switch Q, thereby automatically switching in the second capacitor C2 in case of low input voltage, and a switch control unit Uqc outputs a switch-off signal to the switch Q, thereby putting the switch Q in a switch-off state in case of high input voltage. In one example, the switch control unit Uqc may be implemented using a comparison circuit. In one example, the first predetermined threshold voltage is above 36 volts, for example, the first predetermined threshold voltage is 100 volts. In one example, the switch Q is a MOS transistor (metal oxide semiconductor transistor). In one example, the power required for the operation of the switch control unit Uqc may be a part of the output power Pout of the power supply 400. For example, two voltage dividing resistors are connected between the output terminals Toutp, toutn, and the switch control unit Uqc is electrically connected to a node between the two voltage dividing resistors to apply a desired operating voltage to the switch control unit Uqc. Each of the first and third capacitors of power supply 400 in fig. 4 may have a smaller nominal capacitance than the first capacitor of power supply 300 in fig. 3, e.g., half the nominal capacitance of the first capacitor of power supply 300 in fig. 3. It can be appreciated that the switch control unit Uqc is not necessary for the power supply of the present disclosure configured with the stored energy third capacitor. For example, without a switch control unit, the switch Q may be manually controlled.

Fig. 5 illustrates an exemplary circuit diagram of a power supply 500 according to one embodiment of the present disclosure. The power supply 500 is capable of receiving both ac input power and dc input power and is a power supply that can receive a wide range of ac and dc power. The power supply 500 includes: a rectifier bridge Rf, a first capacitor C1, a capacitor unit Uc, an additional capacitor Ca and a switch control unit Uqc. The rectifier bridge Rf has a positive output Tp and a negative output Tn. The first capacitor C1 is connected in parallel with the rectifier bridge Rf between the positive output terminal Tp and the negative output terminal Tn. The capacitor unit Uc is connected in parallel with the rectifier bridge Rf between the positive output terminal Tp and the negative output terminal Tn. The capacitor unit Uc includes a switch Q and a second capacitor C2 connected in series with the switch Q. The first capacitor C1 has a first rated voltage Vr1 and a first nominal capacitance cn1; the second capacitor C2 has a second rated voltage Vr2 and a second nominal capacitance cn2. The first rated voltage Vr1 is at least 1.5 times of the second rated voltage Vr 2; and the first nominal capacitance cn1 is smaller than the second nominal capacitance cn2. The additional capacitor Ca is connected in parallel with the second capacitor C2. The additional capacitor Ca has a fourth nominal voltage Vr4 and a fourth nominal capacitance cn4. The first rated voltage Vr1 is at least 1.5 times of the fourth rated voltage Vr 4; and the first nominal capacitance cn1 is smaller than the fourth nominal capacitance cn4. The voltage of the output power Pout of the power supply 500 is represented by a voltage Vout between the pair of output terminals of the power supply 500 including the output terminals Toutp, toutn. The power supply 500 applies the output voltage Vout to the load. In contrast, the first capacitor C1 may be referred to as a "high-voltage small capacitance", and the second capacitor C2 and the additional capacitor C4 may be referred to as a "low-voltage large capacitance". When the input voltage Vin is a high voltage (e.g., 220V ac or 110V ac), the switch Q is configured to be in an off state, so that when the input power is stopped, the energy storage capacitor, the first capacitor C1, can provide enough power to keep the output voltage for a time t _ h long enough, e.g., longer than a predetermined threshold time. The predetermined threshold time may be a predetermined time greater than or equal to 20 milliseconds; when the input voltage Vin is low (e.g. 24V dc or 12V dc), the switch Q is configured to be on, so that the energy storage capacitors-the first capacitor C1, the second capacitor C2 and the additional capacitor Ca-are able to supply energy together when the input power stops, which ensures that even in case of low input voltage the stored energy is sufficient so that the output voltage holding time t _ h is sufficiently long, e.g. greater than a predetermined threshold time. The predetermined threshold time may be a predetermined time greater than or equal to 20 milliseconds. The switch Q is configured in an off state at high input voltage to prevent the high voltage from damaging the second capacitor C2, the additional capacitor Ca. As shown in fig. 5, the switch control unit Uqc is connected with the switch Q to control the operating state of the switch Q. The switch control unit Uqc may be coupled to the rectifier bridge Rf such that, in case the switch control unit Uqc determines that the input voltage Vin of the rectifier bridge Rf is lower than a first predetermined threshold voltage, the switch control unit Uqc outputs a switch-on signal to the switch Q, thereby automatically switching in the second capacitor C2 and the additional capacitor Ca in case of a low input voltage, and a switch-off signal to the switch Q, thereby putting the switch Q in a switched-off state in case of a high input voltage. In one example, the switch control unit Uqc may be implemented using a comparison circuit. In one example, the first predetermined threshold voltage is above 36 volts, for example, the first predetermined threshold voltage is 100 volts. In one example, the switch Q is a MOS transistor (metal oxide semiconductor transistor).

In one example, the power required for the operation of the switch control unit Uqc may be a part of the output power Pout of the power supply 500. For example, two voltage-dividing resistors are connected between the output terminals Toutp, toutn, and the switch control unit Uqc is electrically connected to a node between the two voltage-dividing resistors to apply a desired operating voltage to the switch control unit Uqc. Each of the second capacitor and the additional capacitor of the power supply 500 in fig. 5 may have a smaller nominal capacitance than the second capacitor of the power supply 300 in fig. 3, for example, half the nominal capacitance of the second capacitor of the power supply 300 in fig. 3. It will be appreciated that the switch control unit Uqc is not necessary for the power supply of the present disclosure to be configured with an additional capacitor. For example, without a switch control unit, the switch Q may be manually controlled.

In one embodiment, the power supply of the present disclosure is configured to be suitable for use with a flow meter, a thermometer, a pressure gauge, or a densitometer.

Although the switch is connected to the negative side of the capacitor in fig. 2 to 5, it may alternatively be connected to the positive side of the capacitor.

According to the scheme disclosed by the disclosure, when alternating current and direct current input power is supported, high-voltage starting is realized by using the second capacitor which can be selectively connected, the small capacitor is distributed, low-voltage starting is distributed with the large capacitor, and the connected capacitor is switched according to the input voltage. The beneficial technical effects comprise at least one of the following: the power supply has the advantages of improving the reliability of the power supply, reducing the occupied area of a circuit board of the power supply circuit, reducing the cost, easily designing the circuit and ensuring the output voltage retention time. When the power supply disclosed by the disclosure is used for the transmitter, the size of the transmitter can be reduced, and the cost is reduced.

It should be emphasized that the term "comprises/comprising" when used herein, is taken to specify the presence of stated features, elements or components, but does not preclude the presence or addition of one or more other features, elements or components.

While the disclosure has been disclosed by the description of the specific embodiments thereof, it will be appreciated that those skilled in the art will be able to devise various modifications, improvements, or equivalents of the disclosure within the spirit and scope of the appended claims. Such modifications, improvements and equivalents are also intended to be included within the scope of this disclosure.

Claims (12)

1. A power supply capable of receiving ac input power and dc input power, the power supply comprising:

a rectifier bridge having a positive output terminal and a negative output terminal;

a first capacitor connected in parallel with the rectifier bridge between the positive output terminal and the negative output terminal;

a capacitor unit connected in parallel with the rectifier bridge between the positive output terminal and the negative output terminal;

wherein the capacitor unit includes a switch and a second capacitor connected in series with the switch;

the first capacitor has a first voltage rating and a first nominal capacitance;

the second capacitor has a second voltage rating and a second nominal capacitance;

the first nominal voltage is at least 1.5 times the second nominal voltage; and is

The first nominal capacitance is less than the second nominal capacitance.

2. The power supply of claim 1, further comprising a switch control unit;

the switch control unit is connected with the switch to control the working state of the switch.

3. The power supply of claim 2, wherein the switch control unit is coupled with the rectifier bridge such that the switch control unit outputs an on signal to the switch if the switch control unit determines that the input voltage of the rectifier bridge is below a first predetermined threshold voltage.

4. The power supply of claim 3, wherein the first predetermined threshold voltage is above 36 volts.

5. The power supply of claim 1, wherein a ratio of said second nominal capacitance to said first nominal capacitance is between 5 and 10.

6. The power supply of claim 1, wherein the first capacitor and the second capacitor cause the power supply to have an output voltage hold time greater than a predetermined threshold time; and is provided with

The output voltage holding time is a holding time of the power supply with respect to the output voltage after the input of the power to the power supply is stopped.

7. The power supply of claim 6, wherein the predetermined threshold time is greater than or equal to 20 milliseconds.

8. The power supply of claim 1, wherein the first and second capacitors are electrolytic capacitors.

9. The power supply of claim 1, wherein the switch is a relay type switch, a mechanical switch, or a MOS transistor.

10. The power supply of claim 1, further comprising a third capacitor connected in parallel with the rectifier bridge between the positive output terminal and the negative output terminal;

wherein the third capacitor has a third voltage rating and a third nominal capacitance;

the third nominal voltage is at least 1.5 times the second nominal voltage; and is

The third nominal capacitance is less than the second nominal capacitance.

11. The power supply of claim 1, further comprising an additional capacitor;

wherein the additional capacitor is connected in parallel with the second capacitor;

said additional capacitor having a fourth voltage rating and a fourth nominal capacitance;

the first nominal voltage is at least 1.5 times the fourth nominal voltage; and is

The first nominal capacitance is less than the fourth nominal capacitance.

12. The power supply of claim 1, wherein the power supply is configured to be suitable for use with a flow meter, a thermometer, a pressure gauge, or a densitometer.

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