CN111030207A

CN111030207A - Power supply circuit for maximizing use of battery electric quantity

Info

Publication number: CN111030207A
Application number: CN201911097401.2A
Authority: CN
Inventors: 余金存
Original assignee: Zhejiang Viewshine Intelligent Meter Co Ltd
Current assignee: Zhejiang Viewshine Intelligent Meter Co Ltd
Priority date: 2019-11-12
Filing date: 2019-11-12
Publication date: 2020-04-17

Abstract

The invention discloses a power supply circuit for maximizing the use of the electric quantity of a battery. The low dropout linear regulator comprises a low dropout linear regulator U1, a first feedback resistor R1, a first pull-up resistor R2, a second feedback resistor R3, a second current-limiting resistor R4, a first current-limiting resistor R5, a first voltage-dividing resistor R6, a second voltage-dividing resistor R7, a P-channel MOS transistor Q1, an NPN triode Q2, a first feedforward capacitor C1, a first energy-storage electrolytic capacitor C2, a second filtering tantalum capacitor C3, a first filtering capacitor C4, a third filtering capacitor C5, a fourth filtering capacitor C6 and a fifth filtering capacitor C7. On the basis of the existing mature and low-cost GPRS power supply circuit, the invention further extracts the service time of the battery by improving the LDO transient response, reduces the social cost, improves the environmental awareness of people, is beneficial to advocating a low-carbon life style, and simultaneously can save energy resources and protect the ecological environment.

Description

Power supply circuit for maximizing use of battery electric quantity

Technical Field

The invention belongs to the field of communication of the Internet of things, and relates to a circuit for improving transient response of an LDO (low dropout regulator) and accurately measuring an under-voltage point. The power supply circuit is applied to the field of communication of the Internet of things related to a gas meter, transient response of the power supply circuit is improved, and an undervoltage point is accurately measured, so that the electric quantity of the battery is used to the maximum.

Background

With the development of semiconductor technology and the popularization of digital control in recent years, the rapid development of the instrument industry is promoted. The instruments are various in types, and a large amount of manpower and material resources are needed for reading instrument data. The direct networking of table utensil, upload table utensil data, to the server like tolerance, valve state, battery voltage that consume, the backstage can directly calculate the consumption amount of money, to the gas company, the manpower of checking meter that had both practiced thrift, the service personnel in gas business office can know the table utensil trouble in advance, makes things convenient for maintenance personal to go to the door and maintains. For the public, the public does not need to go to a business hall to buy the gas in advance, and only needs to pay the gas fee on a household mobile phone or on the internet. The Internet of things meter is a mode benefiting the nation and the people in the civil gas industry.

At present, the Internet of things meter mainly comprises two types of GPRS and NB-IoT, wherein the GPRS is widely applied at present and has the widest signal coverage, but the power consumption is large, and relatively large current is consumed for reporting data through single emission. To address this deficiency, the mobile communications industry has introduced NB-IoT, which is about half of GPRS under the same conditions as the power consumption of normal transmissions. However, currently, the NB network signal coverage does not completely cover the whole country, and the price and the charge of the NB module are also higher. The power supply problem encountered when applying the GPRS module is solved, and the application technology of the NB is not involved. The gas meter is mainly powered by a battery due to the characteristics that the difference of installation environments is large, gas-electricity separation is required due to safety, monitoring is not needed in real time and the like. Since the GPRS module requires a current of about 1.6A instantaneously when transmitting the announcement data, an alkaline battery is used for cost reasons. Generally 4 alkaline batteries, which can be used by consumers for one year. When the battery voltage is too low, some gas meters can remind consumers of replacement by using an indicator lamp or a screen or a buzzer. The service time of the battery is further prolonged, the social cost can be reduced, the environmental awareness of people is improved, the low-carbon life style is promoted, meanwhile, the energy resource is saved, the ecological environment is protected, the contribution is made to building the resource-saving and environment-friendly society, the comprehensive, coordinated and sustainable development road of the economic society is promoted, and the significance is very great.

The GPRS signal transmission is characterized in that:

taking the above marine remote GPRS module M72 as an example, since the transmission unit of GSM on the wireless path is a pulse train composed of GMSK modulated bits, which is called burst, GSM transmits burst in a cycle of 4.615ms, the duration of burst is 577us, the current consumption reaches 1.6A at most, and the current consumption of the rest of idle time is as low as ten milliamperes, thereby causing a rapid transient change in the load current of the GSM module, as shown in fig. 1. When the maximum current is 1.6A when the module transmits, VBAT has a transient drop in the process of recovering and lifting. The working voltage of the Shanghai moving away GPRS module M72 is 3.4-4.6V, and in order to ensure that the M72 can work normally, namely the valley of the power supply voltage drop is higher than 3.4V, the voltage value of the system voltage low-voltage alarm (namely informing a user to replace a battery) is 3.4V plus the amplitude delta t V of the drop. The falling amplitude delta t is shortened, and the replacement time of the battery can be prolonged on the premise of not influencing the function. The scheme shows how to shorten the falling amplitude delta t, namely, improve the transient response of the LDO.

Disclosure of Invention

The invention aims to provide a power supply circuit which maximizes the use of the electric quantity of a battery on the basis of the existing mature and low-cost GPRS power supply circuit. By improving the transient response of the LDO, the service time of the battery is further extracted.

The technical scheme adopted for solving the technical problems is as follows:

the circuit comprises a low dropout linear regulator U1, a first feedback resistor R1, a first pull-up resistor R2, a second feedback resistor R3, a second current-limiting resistor R4, a first current-limiting resistor R5, a first voltage-dividing resistor R6, a second voltage-dividing resistor R7, a P-channel MOS tube Q1, an NPN triode Q2, a first feed-forward capacitor C1, a first energy-storage electrolytic capacitor C2, a second filtering tantalum capacitor C3, a first filtering capacitor C4, a third filtering capacitor C5, a fourth filtering capacitor C6 and a fifth filtering capacitor C7.

One end of a first current limiting resistor R5 is connected with a control pin GPRS _ POWER _ JD of the singlechip, the other end of the first current limiting resistor R5 is connected with a base electrode of an NPN triode Q2, an emitting electrode of the NPN triode Q2 is connected with GND, a collector electrode of the NPN triode Q2 is connected with one end of a second current limiting resistor R4, the other end of the second current limiting resistor R4 is connected with one end of a first pull-up resistor R2 and a grid electrode of a P-channel MOS tube Q1, the other end of the first pull-up resistor R8 is connected with a source electrode of a P-channel MOS tube Q1 and an anode electrode VIN of an alkaline battery, a drain electrode of the P-channel MOS tube Q1 is connected with an anode electrode of a first energy-storage electrolytic capacitor C2, one end of the first filter capacitor C4, a 1 st pin and a 2 th pin of a low dropout regulator (SPX29302T5) U1, a cathode electrode of the first energy-storage electrolytic capacitor C2 is connected with a cathode electrode of the first filter capacitor C4, and a low dropout regulator (LDO) U24 and a GND pin 583 and GND 5733, the 4 th pin of the low dropout regulator LDO (SPX29302T5) U1 is connected with one end of a first feedback resistor R1, one end of a first feedforward capacitor C1, the anode of a second filter tantalum capacitor C3, one end of a third filter capacitor C5, one end of a fourth filter capacitor C6, one end of a fifth filter capacitor C7, one end of a first voltage-dividing resistor R6 and the power pin of the GPRS module are connected at 3.8V, the 5 th pin of the low dropout regulator (SPX29302T5) U1 is connected with the other end of a first feedback resistor R1, one end of a second feedback resistor R3 and the other end of a first feedforward capacitor C1, the other end of the second feedback resistor R3 is connected with the LDO, the cathode of a second filter tantalum capacitor C3, the other end of a third filter capacitor C5, the other end of a fourth filter capacitor C6, the other end of the fifth filter capacitor C7, the other end of the first voltage-dividing resistor R7 is connected with the GND of the first voltage-dividing resistor R6, The one-chip microcomputer is connected with a pin CMP with an internal comparator function, and the other end of one end of the second divider resistor R7 is connected with GND.

The circuit of the invention is realized in the following steps:

the invention is improved on the basis of a GPRS POWER supply circuit, a P-channel MOS tube Q1 is added at the front end of the original GPRS POWER supply circuit, when most of GPRS does not work, a single chip microcomputer GPRS _ POWER _ JD pin is pulled down to be in a low level, an NPN triode Q2 is not conducted, and the grid electrode of the P-channel MOS tube Q1 is connected with VIN through a first pull-up resistor R2 to keep a high level; the P-channel MOS transistor Q1 is non-conductive and the circuit does not consume any current. The significance of adding a first-level control circuit (an NPN triode Q2 controls a P-channel MOS tube Q1) is that the gas meter is generally externally connected with 4 sections of alkaline electricity, VIN can reach 6V voltage according to 1.5V calculation, if the grid electrode of the P-channel MOS tube Q1 is directly connected with a control pin of a single chip microcomputer, the voltage resistance value of the pin of the single chip microcomputer is exceeded, and the single chip microcomputer can be damaged. 1000uf is selected as the first energy storage electrolytic capacitor C2, and the value of the first energy storage electrolytic capacitor C2 is continuously increased or a plurality of energy storage electrolytic capacitors are connected in parallel, so that the transient response of the LDO is not greatly facilitated. The filtering tantalum capacitor C3 selects 220uf, and the value of the filtering tantalum capacitor is continuously increased or a plurality of energy storage electrolytic capacitors are connected in parallel, so that the transient response of the LDO is not greatly facilitated.

When the pin GPRS _ POWER _ JD is at a low level, Q2 is turned off; the gate voltage of the Q1 gate is equal to VIN under the action of the R2 pull-up, Q1 is turned off, and the whole circuit is in an unpowered forbidden state.

When the pin GPRS _ POWER _ JD is at a high level, Q2 is turned on, the gate voltage of Q1 is (VIN-0.7V)/2 after resistance voltage division by R2 and R4, the gate voltage of Q1 is lower than the gate voltage Q1 of Q1, and POWER is supplied to the back-end circuit; at this time, the voltage differential negative feedback circuit formed by the low-dropout linear voltage-stabilized power supply chip U1 and the R1, R3 and C1 starts to work, and the decoupling capacitors C2 and C3 and the filter capacitors C4, C5, C6, C7 and U1 are charged. Starting up after 1 second, sending data, wherein the maximum emission current is 1.7A (the U1 outputs a voltage transient voltage drop of 420mV under the condition of no voltage differential negative feedback circuit); at the moment, a voltage differential negative feedback circuit formed by R1, R3 and C1 reflects the tiny variation of voltage to an operational amplifier in U1 in advance by utilizing the advance effect of capacitance current, so that the system reacts faster to the tiny variation, the overshoot at the final regulation stage of U1 is avoided, and the transient voltage drop of U1 is reduced to 155mV, so that a front-end battery can use lower voltage to release more energy, and the battery can be used for a longer time under the condition of ensuring the normal work of a rear-end module.

The power pin of the GPRS module is 3.8V, is connected with the comparator pin of the singlechip with the internal comparator after being divided by the first voltage dividing resistor R6 and the second voltage dividing resistor R7, and realizes the monitoring of the drop voltage.

The invention has the following beneficial effects:

the invention reduces the lowest working voltage of the system by improving the transient response capability of the LDO, achieves the comprehensive social benefits of fully utilizing the energy of the battery, reducing the system cost, saving resources and reducing pollution, and responds to the requirements and calls of the nation for building an energy-saving and environment-friendly society.

Drawings

FIG. 1 is a graph of voltage characteristics of a GPRS power supply circuit simulating reporting of GPRS data in the present invention;

FIG. 2 is the whole circuit of the GPRS power supply circuit of the present invention;

FIG. 3 is a graph of voltage characteristics when a GPRS power supply circuit simulates reporting of GPRS data without introducing a feed-forward capacitor in the invention;

FIG. 4 is a voltage characteristic curve diagram of simulated GPRS data reporting time without introducing a feedforward capacitor, reducing a feedback resistor, in the GPRS power supply circuit of the present invention;

FIG. 5 is a graph showing voltage characteristics of simulated GPRS data reporting without reducing feedback resistance after a feed-forward capacitor is introduced into a GPRS power supply circuit of the present invention;

Detailed Description

In order to explain technical contents, structural features, and effects of the present invention in detail, the following detailed description is made with reference to the accompanying drawings in conjunction with the embodiments.

For example, in a sleep mode of power saving, the current of the shanghai mobile GPRS module M72 is 1.2mA, which is unacceptable for a gas meter, and the general standby quiescent current of the gas meter industry needs to be less than 50 uA. The data can be reported once a day. Therefore, a P-channel MOS tube is added at the front end of the GPRS POWER supply circuit, when most of GPRS does not work, the pin of the singlechip GPRS _ POWER _ JD is pulled down to be at a low level, the NPN triode is not conducted, and the grid electrode of the P-channel MOS tube is connected with VIN through a first pull-up resistor R2 to keep at a high level; the P-channel MOS tube is not conducted, and the circuit does not consume any current. The significance of adding a level triode to control the MOS tube is that the gas meter is generally externally connected with 4 sections of alkaline electricity, the VIN can reach 6V voltage according to 1.5V calculation, if the grid of the P-channel MOS tube is directly connected with the control pin of the singlechip, the voltage resistance value of the pin of the singlechip is exceeded, and the singlechip can be damaged. The energy storage electrolytic capacitor C2 is selected to be 1000uf, the value of C2 is increased continuously or a plurality of energy storage electrolytic capacitors are connected in parallel, and the transient response of the LDO is not greatly facilitated. The filtering tantalum capacitor C3 selects 220uf, and the value of C3 is continuously increased or a plurality of energy storage electrolytic capacitors are connected in parallel, so that the transient response of the LDO is not greatly facilitated.

As shown in FIG. 3, the maximum drop was-420 mV. If the values of the feedback resistors R1 and R3 are reduced, the original 22K of R1 is reduced to 530 ohms, and the original 10K of R3 is reduced to 200 ohms, so that the maximum drop-out of-230 mV (shown in FIG. 3) is achieved, the transient response of the LDO is remarkably improved, but compared with the original scheme, the current of 8mA is increased, and the power consumption is increased. In order not to increase the power consumption and have fast response, a feed-forward capacitor C1 is introduced, and when the value of 0.1uf is selected, as shown in FIG. 5, the maximum drop is-155 mV, so that the transient response of the LDO is remarkably improved and the power consumption is not increased.

When the feedforward capacitor C1 is not introduced, the low-voltage alarm value needs to be set to be 3.4V plus 0.42V, namely 3.84V, of the normal operating voltage of the module. After the feed-forward capacitor C1 is introduced, the value of the low-voltage alarm is 3.4V plus 0.155V, namely 3.555V, of the normal operating voltage of the module. The voltage is lower than the original proposal by 0.285V, and the service life of the battery is further extracted.

In the above, it is mentioned that the normal operating voltage of the module is 3.4V, we need to sample the input voltage (LDO output voltage) of the module, the sampling time for completing an AD once is about 10 microseconds, and it needs to acquire a correct voltage value many times, and the whole GPRS transmission period needs to acquire in real time, and acquisition needs to be suspended when other tasks with higher priority are executed, and the moment of dropping is possibly missed, so that the use of AD acquisition is not recommended. A comparator may be used to implement this function. The power supply pin 3.8V is connected with the comparator pin of the single chip microcomputer with the internal comparator after being subjected to voltage division by R6 and R7, so that the drop voltage is monitored.

When the voltage at the drop point is 3.4V, the voltage at the CMP after the voltage division by R6(20K) and R7(27K) is 3.4 × 20/(20+27) is equal to 1.45V, and the single-chip microcomputer Rysa R7F0C004 is configured to use the internal reference voltage of 1.45V. When the drop point is small and 3.4V, the interior of the single chip microcomputer is interrupted, the system knows that the battery is replaced according to the basis that the voltage can not maintain the GPRS notice any more.

Claims

1. A power supply circuit for maximally using the electric quantity of a battery is characterized by comprising a low dropout linear regulator U1, a first feedback resistor R1, a first pull-up resistor R2, a second feedback resistor R3, a second current-limiting resistor R4, a first current-limiting resistor R5, a first divider resistor R6, a second divider resistor R7, a P-channel MOS transistor Q1, an NPN triode Q2, a first feed-forward capacitor C1, a first energy-storage electrolytic capacitor C2, a second filtering tantalum capacitor C3, a first filtering capacitor C4, a third filtering capacitor C5, a fourth filtering capacitor C6 and a fifth filtering capacitor C7;

one end of a first current-limiting resistor R5 is connected with a control pin GPRS _ POWER _ JD of the singlechip, the other end of the first current-limiting resistor R5 is connected with a base electrode of an NPN triode Q2, an emitter of the NPN triode Q2 is connected with GND, a collector of the NPN triode Q2 is connected with one end of a second current-limiting resistor R4, the other end of the second current-limiting resistor R4 is connected with one end of a first pull-up resistor R2 and a grid electrode of a P-channel MOS tube Q1, the other end of the first pull-up resistor R2 is connected with a source electrode of the P-channel MOS tube Q1 and a positive electrode VIN of the alkaline battery, a drain electrode of the P-channel MOS tube Q1 is connected with a positive electrode of a first energy-storing electrolytic capacitor C2, one end of a first filter capacitor C4, a 1 st pin and a 2 nd pin of a low-voltage-difference linear regulator U1, a negative electrode of the first energy-storing electrolytic capacitor C2 is connected with a negative electrode of the first filter capacitor C4, a second end of the low-voltage difference, a 4 th pin of a low dropout linear regulator U1, one end of a first feedback resistor R1, one end of a first feedforward capacitor C1, the anode of a second filter tantalum capacitor C3, one end of a third filter capacitor C5, one end of a fourth filter capacitor C6, one end of a fifth filter capacitor C7, one end of a first divider resistor R6 and a power pin of a GPRS module are connected, a 5 th pin of the low dropout linear regulator U1 is connected with the other end of a first feedback resistor R1, one end of a second feedback resistor R3 and the other end of a first feedforward capacitor C1, the other end of the second feedback resistor R3 is connected with GND, the cathode of the second filter tantalum capacitor C3, the other end of the third filter capacitor C5, the other end of a fourth filter capacitor C6 and the other end of the fifth filter capacitor C7 are connected with GND, the other end of the first divider R6 is connected with one end of the second divider resistor R7 and one end of a voltage band comparator pin of a single chip voltage band, the other end of one end of the second voltage-dividing resistor R7 is connected to GND.

2. The power supply circuit according to claim 1, wherein the low dropout linear regulator is U1 model SPX29302T 5; the model of the P-channel MOS transistor Q1 is UT3401ZG, and the model of the NPN triode Q2 is 9013.

3. The POWER supply circuit according to claim 1 or 2, wherein when the pin GPRS _ POWER _ JD of the single chip microcomputer is pulled low, the NPN transistor Q2 is not turned on, and the gate of the P-channel MOS transistor Q1 is connected to VIN via a first pull-up resistor R2 to maintain a high level; the P-channel MOS tube Q1 is not conducted, and the circuit does not consume any current; an NPN triode Q2 is added to control a P-channel MOS transistor Q1, so that the voltage of up to 6V of VIN is prevented from damaging the single chip microcomputer.