CN110601309B - Circuit and method for realizing trickle charge in switch mode charger - Google Patents
Circuit and method for realizing trickle charge in switch mode charger Download PDFInfo
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- CN110601309B CN110601309B CN201910933514.5A CN201910933514A CN110601309B CN 110601309 B CN110601309 B CN 110601309B CN 201910933514 A CN201910933514 A CN 201910933514A CN 110601309 B CN110601309 B CN 110601309B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/44—Methods for charging or discharging
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
The invention discloses a circuit and a method for realizing trickle charge in a switch mode charger, which mainly solve the problem that the trickle charge current ICHG of the existing switch mode charger cannot be controlled and adjusted more accurately, so that the application scene is limited. The time-sharing timing is carried out by utilizing the time when the inductive current appears, the pause time is introduced between the time when the inductive current appears twice continuously, and the comparator and the RS trigger are utilized to realize the control of the average value of the charging current in the switch mode charger, so that the trickle charging current can be controlled accurately without adding extra MOSFET and heating, the cost is saved, and the service life of the charger can be effectively prolonged. Therefore, the method has high use value and popularization value.
Description
Technical Field
The present invention relates to a charging circuit, and more particularly, to a circuit and method for trickle charging in a switch mode charger.
Background
In a conventional switching mode charger (switching mode charger), the charging principle is that a DC-DC output is applied to a battery VBAT, and the charging current to the VBAT is controlled to be a constant value by an output current loop of the DC-DC, as shown in fig. 1; when the VBAT voltage is higher than a constant threshold (typically 3V), the current that can be directly charged is typically a large value above 1A. When the VBAT voltage is relatively low, below a threshold (typically 2V), the charging current must be controlled to a small value, called the trickle charge phase. The trickle-mode charging also varies according to the battery characteristics of different battery manufacturers, typically ranging from 100mA to 500 mA.
Fig. 2 is a trickle charge scheme commonly used at present, the principle of the trickle charge scheme is that a large-proportion current source composed of MP1 and MP2 is used to realize trickle charge instead of a DC-DC switching operation mode, MP2 operates in an LDO mode, and the source-drain voltage difference VDS thereof is VIN-VBAT, so when VBAT is at least 0V, the source-drain voltage difference of MP2 will reach VIN, so the power consumption P on MP2 is ICHG VIN. One result of this is that in some applications VIN voltage will reach 12V, ICHG current will have a power consumption P of 0.1A VIN 12V 1.2W even if only 100mA, which is a relatively large heat-generating power consumption for a MOSFET, and this also consumes a larger MOSFET area and increases chip cost.
In order to solve the above-mentioned problems, some improvement is proposed to the trickle charge method, based on the principle of fig. 1, the DC-DC is directly operated in the switching mode, and the VBAT is directly charged, so that the cost of the larger MOSFET operated in the LDO mode can be saved, and the charging process does not generate heat. However, this solution also has a problem that when the battery voltage is particularly low, limited by the minimum on-time of the DC-DC itself, the peak value of the inductor current will reach a relatively large value, and thus it is impossible to stably control the average current at a small trickle charge level. The formula of the inductor current ripple is as follows:
where L is the inductance value and TON is the high side MOS turn-on time of DC-DC, it has a minimum limit TON _ MIN, so that when the voltage of VBAT is low and VIN is highest, even though TON reaches its minimum TON _ MIN, the average value of the inductor current will exceed the trickle setting. As shown in fig. 3, after the peak value of the DC-DC inductor current is determined, half of IPEAK is the average current IAVG of the DC-DC output, but the average current IAVG may still be larger than the required trickle charge current ICHG, and if IPEAK cannot be further reduced, this may limit the application scenarios, and it may not be possible to control and adjust the magnitude of ICHG more accurately.
Disclosure of Invention
The invention aims to provide a circuit and a method for realizing trickle charge in a switch mode charger, which mainly solve the problem that the trickle charge scheme of the existing switch mode charger cannot accurately control and adjust the magnitude of the trickle charge current ICHG so that the application scene is limited.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a circuit for realizing trickle charge in a switch mode charger comprises current sources I1 and I2, a capacitor C1 with one end connected with a current source I1 and the other end grounded, a Clamp tube Clamp connected with the connection end of the current source I1 and the capacitor C1, MOS tubes Q1 and Q2 with a drain D connected with the connection end of the current source I1 and the capacitor C1, a current source I3 with one end connected with a source S of the MOS tube Q2 and the other end grounded, a comparator COMP1 with a negative electrode connected with the connection end of the current source I1 and the capacitor C1, a capacitor C2 with one end connected with the positive electrodes of the current source I2 and the comparator COMP1 and the other end grounded, and an RS trigger with an S port connected with the output end of the comparator COMP 1; the gate G of the MOS tube Q2 is connected with the QZ port of the RS trigger, the gate G of the MOS tube Q3 is connected with the Q port of the RS trigger, the R port of the RS trigger is externally connected with a ZCD _ COMP comparator which outputs a detection signal ZCD in the switch mode charger, and the gate G of the MOS tube Q1 is connected with the output end of the comparator COMP 1; the output end of the comparator COMP1 and the R port of the RS trigger are connected with a main logic control module in the switch mode charger.
Based on the above mentioned circuit for realizing trickle charge in the switch mode charger, the present invention also provides a method for realizing trickle charge in the switch mode charger, comprising the following steps:
(1) enabling two current sources I1 and I2 to respectively provide currents with the magnitude of I, I/n, and timing a complete switching period comprising two periods of time with inductive current and two periods of time without inductive current;
(2) the comparator COMP1 outputs a T _ TRIK pulse signal to turn on a high-end MOS tube Q4 in the switch mode charger, and an inductor L charges; the current source I1 starts to charge the capacitor C1;
(3) when the inductor current is 0 after the inductor freewheeling is finished, the inductor current appears through a 0 detection signal ZCD pulse, a MOS tube Q5 in the switch mode charger is closed, meanwhile, the output Q1Z of the RS trigger becomes high, and the voltage TW stops rising and keeps stable;
(4) the current source I2 charges the capacitor C2 until the positive VRAMP voltage of the comparator COMP1 is higher than the negative TSW voltage of the comparator COMP1, the comparator COMP1 turns over, and the process goes to step (1) again for the next cycle.
Further, in step (1), the charging time can be obtained from the capacitance charging formula as follows:
wherein n is constant, voltage and capacitance are equal, and current I has a difference of n times, so that the obtained charging time T has a difference of n times, that is, the time T with inductive current in trickle charging in the circuit of the switch mode charger is realizedWAnd time T of no inductive currentDThe relationship between: n x TW＝TD。
Further, in the step (1), the timing mode adopts RC timing or a current source to time charging and discharging of the capacitor.
Compared with the prior art, the invention has the following beneficial effects:
the invention realizes the control of the average value of the charging current in the switch mode charger by utilizing the comparator and the RS trigger, thus achieving the purposes of not increasing additional MOSFET and heating, and simultaneously more accurately controlling the magnitude of the trickle charging current, saving the cost and effectively prolonging the service life of the charger.
Drawings
Fig. 1 is a schematic diagram of a charging circuit for a switch mode charger.
Fig. 2 is a schematic diagram of a trickle charge circuit of a prior art switch mode charger.
Fig. 3 is a conventional trickle charge current waveform diagram.
FIG. 4 is a schematic diagram of a trickle charge circuit for a switch mode charger in accordance with the present invention.
FIG. 5 is a schematic diagram of the trickle charge circuit and the switch mode charger of the present invention
FIG. 6 is a trickle charge current waveform diagram according to the present invention.
Detailed Description
The present invention will be further described with reference to the following description and examples, which include but are not limited to the following examples.
Examples
As shown in fig. 4 and 5, the trickle charge circuit for use in a switch mode charger disclosed in the present invention comprises current sources I1, I2, a capacitor C1 with one end connected to current source I1 and the other end grounded, a Clamp tube damp connected to the connection end of current source I1 and capacitor C1, MOS transistors Q1, Q2 with drain D connected to the connection end of current source I1 and capacitor C1, a current source I3 with one end connected to the source S of MOS transistor Q2 and the other end grounded, a comparator COMP1 with its negative electrode connected to the connection end of current source I1 and capacitor C1, a capacitor C2 with one end connected to the positive electrodes of current source I2 and comparator COMP1 and the other end grounded, and an RS flip-flop with its S port connected to the output end of comparator COMP 1; the gate G of the MOS tube Q2 is connected with the QZ port of the RS trigger, the gate G of the MOS tube Q3 is connected with the Q port of the RS trigger, the R port of the RS trigger is externally connected with a ZCD _ COMP comparator which outputs a detection signal ZCD in the switch mode charger, and the gate G of the MOS tube Q1 is connected with the output end of the comparator COMP 1; the output end of the comparator COMP1 and the R port of the RS trigger are connected with a main logic control module in the switch mode charger.
Based on the above mentioned circuit for realizing trickle charge in the switch mode charger, the present invention also provides a method for realizing trickle charge in the switch mode charger, comprising the following steps:
(1) enabling two current sources I1 and I2 to respectively provide currents with the magnitude of I, I/n, and timing a complete switching period comprising two periods of time with inductive current and two periods of time without inductive current; the charging time can be obtained by the capacitance charging formula as follows:
wherein n is constant, voltage and capacitance are equal, and current I has a difference of n times, so that the obtained charging time T has a difference of n times, that is, the time T with inductive current in trickle charging in the circuit of the switch mode charger is realizedWAnd time T of no inductive currentDThe relationship between: n x TW＝TD. The timing mode adopts RC timing or a current source to time the charging and discharging of the capacitor.
(2) The comparator COMP1 outputs a T _ TRIK pulse signal to turn on a high-end MOS tube Q4 in the switch mode charger, and an inductor L charges; the current source I1 starts to charge the capacitor C1;
(3) when the inductor current is 0 after the inductor freewheeling is finished, a 0 detection signal ZCD pulse appears in the inductor current, a MOS transistor Q5 in the switch mode charger is closed, meanwhile, the output Q1Z of the RS trigger becomes high, and the voltage TW stops rising and keeps stable;
(4) the current source I2 charges the capacitor C2 until the positive VRAMP voltage of the comparator COMP1 is higher than the negative TSW voltage of the comparator COMP1, the comparator COMP1 turns over, and the process goes to step (1) again for the next cycle.
The time of the occurrence of the inductive current is utilized to time-share time counting, the pause time is introduced between the occurrence of the inductive current of two continuous times, and then the goal of controlling the average value can be achieved by controlling the pause time. As shown in FIG. 6, the time of occurrence of the inductor current is denoted as TWThe time when no inductive current appears in the intermediate pause time machine is recorded as TDAnd satisfies the relationship:
n*TW＝TD；
the average current IAVG at this time is no longer IPEAK/2, but rather:
therefore, once IPEAK is determined and n is determined, the value of IAVG is determined.
Through the design, the trickle charger does not need to be additionally provided with an additional MOSFET (metal oxide semiconductor field effect transistor) and does not generate heat, and meanwhile, the trickle charging current can be accurately controlled, so that the cost is saved, and the service life of the charger can be effectively prolonged. Therefore, the method has high use value and popularization value.
The above-mentioned embodiment is only one of the preferred embodiments of the present invention, and should not be used to limit the scope of the present invention, but all the insubstantial modifications or changes made within the spirit and scope of the main design of the present invention, which still solve the technical problems consistent with the present invention, should be included in the scope of the present invention.
Claims (4)
1. A circuit for realizing trickle charge in a switch mode charger is characterized in that the switch mode charger comprises a main logic control module, NMOS tubes Q4 and Q5, an inductor L, a comparator ZCD _ COMP, a comparator COMP and a trigger; the drain electrode of the NMOS tube Q4 is connected with a power supply VIN, the source electrode of the NMOS tube Q4 is connected with the drain electrode of the NMOS tube Q5, one end of an inductor L is connected with the source electrode of the NMOS tube Q4, the other end of the inductor L is connected with the anode of the battery, the negative input end of a comparator ZCD _ COMP obtains a signal from the source electrode of the NMOS tube Q5 and is used for sending an inductor current zero-crossing detection signal ZCD, the negative input end of the comparator COMP obtains a signal from the drain electrode of the NMOS tube Q4, and the NMOS tubes Q4, Q5 and the trigger are controlled by a main logic control module; the trickle charging circuit comprises current sources I1 and I2, a capacitor C1, a Clamp tube Clamp connected with the connection end of the current source I1 and the capacitor C1, NMOS tubes Q1 and Q2, a current source I3, a comparator COMP1, a capacitor C2 and an RS trigger, wherein one end of the capacitor C1 is connected with the current source I1, the other end of the capacitor C1 is connected with the connection end of the drain D and the current source I1, one end of the current source I3 is connected with the source S of the NMOS tube Q2, the other end of the current source I1 is connected with the connection end of the capacitor C1, one end of the capacitor C2 is connected with the anodes of the current source I2 and the comparator COMP1, and the other end of the capacitor C2 is connected with the ground, and the RS trigger, the S port of the RS trigger is connected with the output end of the comparator COMP 1; the gate G of the NMOS tube Q2 is connected with the QZ port of the RS trigger, the gate G of the NMOS tube Q3 is connected with the Q port of the RS trigger, the R port of the RS trigger is externally connected with a ZCD _ COMP comparator which outputs a detection signal ZCD in the switch mode charger, and the gate G of the NMOS tube Q1 is connected with the output end of the comparator COMP 1; the output end of the comparator COMP1 and the R port of the RS trigger are connected with a main logic control module in the switch mode charger; the capacitance values of the capacitor C1 and the capacitor C2 are equal.
2. A method for trickle charge in a switched mode charger, using a circuit as claimed in claim 1 for trickle charge in a switched mode charger, comprising the steps of:
(1) enabling two current sources I1 and I2 to respectively provide currents with the magnitude of I, I/n, and timing a complete switching period comprising two periods of time with inductive current and without inductive current, wherein n is a constant;
(2) the comparator COMP1 outputs a T _ TRIK pulse signal to turn on an NMOS (N-channel metal oxide semiconductor) tube Q4 connected with a power supply VIN in the switch mode charger, and an inductor L charges; the current source I1 starts to charge the capacitor C1;
(3) when the inductor current is 0 after the inductor freewheeling is finished, the inductor current appears through a 0 detection signal ZCD pulse, an NMOS tube Q5 in the switch mode charger is closed, meanwhile, the output Q1Z of the RS trigger becomes high, and the voltage T _ SW of the upper electrode plate of the capacitor C1 stops rising and keeps stable;
(4) the current source I2 charges the capacitor C2 until the positive VRAMP voltage of the comparator COMP1 is higher than the negative T _ SW voltage of the comparator COMP1, the comparator COMP1 turns over, and the process goes to step (1) again for the next cycle.
3. A method for trickle charge in a switch mode charger as claimed in claim 2 wherein in step (1) the charging time is derived from the capacitance charging equation:
since the capacitance values of C1 and C2 are equal, when C1 and C2 are charged to the same voltage, i.e. the time T of inductive current is realized when trickle charge is performed in the switch mode charger circuitWAnd time T of no inductive currentDThe relationship between: n x TW=TD。
4. A method for implementing trickle charge in a switch mode charger according to claim 3, wherein in step (1), the timing manner uses RC timing or current source timing for capacitor charge and discharge.
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| CN201910933514.5A CN110601309B (en) | 2019-09-29 | 2019-09-29 | Circuit and method for realizing trickle charge in switch mode charger |
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| CN201910933514.5A CN110601309B (en) | 2019-09-29 | 2019-09-29 | Circuit and method for realizing trickle charge in switch mode charger |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101039070A (en) * | 2006-03-15 | 2007-09-19 | 麦奎尔有限公司 | Switching voltage regulator with low current trickle mode |
| CN102386659A (en) * | 2011-12-01 | 2012-03-21 | 无锡中星微电子有限公司 | Charging management circuit |
| CN109599925A (en) * | 2019-01-24 | 2019-04-09 | 沈建良 | Novel storage battery intelligent charger |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5372602B2 (en) * | 2009-05-26 | 2013-12-18 | フリースケール セミコンダクター インコーポレイテッド | Battery charging circuit and battery charger |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101039070A (en) * | 2006-03-15 | 2007-09-19 | 麦奎尔有限公司 | Switching voltage regulator with low current trickle mode |
| CN102386659A (en) * | 2011-12-01 | 2012-03-21 | 无锡中星微电子有限公司 | Charging management circuit |
| CN109599925A (en) * | 2019-01-24 | 2019-04-09 | 沈建良 | Novel storage battery intelligent charger |
Non-Patent Citations (1)
| Title |
|---|
| "恒流-恒压模式控制的锂电池充电器的设计";徐静萍;《半导体技术》;20110403;第36卷(第4期);第291-295页 * |
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