WO2015003541A1 - 一种外部电源和电池供电的电源切换电路及切换方法 - Google Patents
一种外部电源和电池供电的电源切换电路及切换方法 Download PDFInfo
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- WO2015003541A1 WO2015003541A1 PCT/CN2014/079775 CN2014079775W WO2015003541A1 WO 2015003541 A1 WO2015003541 A1 WO 2015003541A1 CN 2014079775 W CN2014079775 W CN 2014079775W WO 2015003541 A1 WO2015003541 A1 WO 2015003541A1
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- voltage
- power supply
- external power
- comparator
- battery
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- 238000000034 method Methods 0.000 title claims abstract description 14
- 239000000758 substrate Substances 0.000 claims description 23
- 239000003638 chemical reducing agent Substances 0.000 claims 22
- 102100036285 25-hydroxyvitamin D-1 alpha hydroxylase, mitochondrial Human genes 0.000 description 7
- 101000875403 Homo sapiens 25-hydroxyvitamin D-1 alpha hydroxylase, mitochondrial Proteins 0.000 description 7
- 238000010586 diagram Methods 0.000 description 5
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- IOYNQIMAUDJVEI-BMVIKAAMSA-N Tepraloxydim Chemical compound C1C(=O)C(C(=N/OC\C=C\Cl)/CC)=C(O)CC1C1CCOCC1 IOYNQIMAUDJVEI-BMVIKAAMSA-N 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J9/00—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting
- H02J9/04—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source
- H02J9/06—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems
Definitions
- the present invention relates to the field of electronic circuit technologies, and in particular, to an external power supply and a battery-powered power supply switching circuit and a switching method. Background technique
- the power switching circuit needs to control two sets of switches to control the connection and disconnection of the external power supply, as well as the connection and disconnection of the battery power. And use one of the power supplies to power the system based on the voltage relationship between the external power source and the battery power source. The status of the two sets of switches needs to be strictly guaranteed. Otherwise, if two power supplies are connected at the same time or disconnected at the same time, the system may be faulty. Summary of the invention
- the technical problem to be solved by the present invention is to provide an external power supply and a battery-powered power supply switching circuit and a switching method, so that only one set of switches can be used to realize the selection of the system power supply, thereby simplifying the circuit structure and improving the circuit. reliability.
- an external power supply and battery power supply switching circuit including: a switch, a first buck, a second buck, a third buck, a voltage reference module, a voltage divider, and a comparison And level shifting modules, where:
- the input of the first buck is connected to the external power supply, the output is connected to the voltage reference module and the comparator; the input of the second buck is connected to the battery power, and the output is connected to the voltage reference module and the comparator;
- the input of the buck is connected to the external power supply, and the output is connected to the load;
- the input of the voltage divider Connect an external power supply, the output is connected to one input of the comparator;
- the input of the voltage reference module is connected to the output of the first buck and the second buck, and the output is connected to one input of the comparator;
- the comparator is based on the voltage
- the comparison result of the reference module and the voltage divider outputs a logic signal to the input end of the level shifting module;
- the switch has one end connected to the battery power source, the other end is connected to the load, the control end is connected to the level shifting module; and the output terminal of the level shifting module is connected to the switch The control terminal controls the on and off of the switch through logic signals.
- the first buck is a diode, a triode or a MOSFET.
- the first buck when the first buck is a diode, the anode of the diode is connected to an external power source, and the cathode is connected to the voltage reference module and the comparator; when the first buck is an NPN transistor, the collector and the base of the NPN transistor are connected externally The power supply, the emitter is connected to the voltage reference module and the comparator; when the first buck is a PNP transistor, the emitter of the PNP transistor is connected to the external power source, the base and the collector are connected to the voltage reference module and the comparator; When the buck is a ⁇ OS tube, the drain terminal, the gate terminal and the substrate of the ⁇ OS tube are connected to an external power source, and the source terminal is connected to the voltage reference module and the comparator; when the first buck is a PM0S tube, the PM0S tube The source is connected to an external power supply, and the drain, gate, and substrate are connected to a voltage reference module and a comparator.
- the second buck is a diode, a triode or a MOSFET.
- the second buck when the second buck is a diode, the anode of the diode is connected to the battery power source, the cathode is connected to the voltage reference module and the comparator; when the second buck is an NPN transistor, the collector and the base of the NPN transistor are connected to the battery The power supply, the emitter is connected to the voltage reference module and the comparator; when the second buck is a PNP transistor, the emitter of the PNP transistor is connected to the battery power, the base and the collector are connected to the voltage reference module and the comparator; When the buck is a ⁇ OS tube, the drain terminal, the gate terminal and the substrate of the ⁇ OS tube are connected to the battery power source, and the source terminal is connected to the voltage reference module and the comparator; when the second step-down device is the PM0S tube, the PM0S tube The source is connected to an external power supply, and the drain, gate, and substrate are connected to a voltage reference module and a comparator.
- the third buck is a diode, a triode or a MOSFET.
- the third buck when the third buck is a diode, the anode of the diode is connected to an external power source, and the cathode is connected Load; when the third buck is an NPN transistor, the collector and base of the NPN transistor are connected to an external power source, and the emitter is connected to the load; when the third buck is a PNP transistor, the emitter of the PNP transistor is connected to an external power source, The base and the collector are connected to the load; when the third step-down device is the ⁇ OS tube, the drain terminal, the gate terminal and the substrate of the ⁇ OS tube are connected to the external power source, the source end is connected to the load; when the third step-down device is connected For the PM0S tube, the source of the PM0S tube is connected to an external power supply, and the drain terminal, the gate terminal, and the substrate are connected to the load.
- the switch comprises: two PM0S tubes MP1 and MP2 connected in series, the source end of the MP1 and the substrate are connected to the battery power supply, the drain end is connected to the drain end of the MP2, the gate end is connected with the control signal; the source end of the MP2 and the substrate are connected to the load The gate terminal is connected to the control signal.
- an external power supply and battery power supply switching method provided includes: controlling a switch to cut off a battery-to-load path when detecting that an external power supply voltage is not lower than a preset voltage threshold; When the voltage to the external power source is lower than the preset voltage threshold, the control switch connects the battery to the load path.
- the preset voltage threshold is less than the sum of the lowest battery operating voltage and the buck value of the third buck.
- the predetermined voltage threshold is achieved by the relative relationship between the output voltage of the voltage reference module and the output voltage of the voltage divider output.
- the power switching circuit and the switching method provided by the invention remove the battery power to the outside when the external power source is dead, by introducing a step-down device between the external power source and the output voltage.
- the risk of power supply back-up so only one switch is needed to control the battery power; when the battery power supplies the load, the threshold voltage of the control switch SW1 is set to avoid the generation of charging current from the external power source to the battery power source. Therefore, the selection of the system power supply can be realized by using only one set of switches, which simplifies the structure of the control circuit and improves the circuit reliability.
- FIG. 1 is a schematic structural diagram of a power switching circuit according to an embodiment of the present invention.
- 2 is a schematic structural diagram of a power switching circuit according to a preferred embodiment of the present invention.
- FIG. 3 is a schematic structural diagram of another power switching circuit according to a preferred embodiment of the present invention. detailed description
- Embodiment 1 is shown in FIG. 1 as an external power supply and a battery power supply switching circuit.
- the power switching circuit includes: a switch SW1, a first buck 10, a second buck 20, and a third buck 30.
- Voltage reference module 40, voltage divider 50, comparator 60 and level shifting module 70 wherein:
- the input of the first buck 10 is connected to an external power supply, the output is connected to the voltage reference module 40 and the comparator 60; the input of the second buck 20 is connected to the battery power, and the output is connected to the voltage reference module 40 and Comparator 60; the input end of the third buck 30 is connected to an external power supply, and the output is connected to the load; the input of the voltage divider 50 is connected to an external power supply, and the output is connected to an input of the comparator 60;
- the input terminal is connected to the output terminals of the first buck 10 and the second buck 20, and the output terminal is connected to one input terminal of the comparator 60; the comparator 60 outputs a logic signal according to the comparison result of the voltage reference module 40 and the voltage divider 50.
- the switch SW1 To the input of the level shifting module 70; the switch SW1, the end is connected to the battery power, the other end is connected to the load, the control end is connected to the level shifting module 70; the output of the level shifting module 70 is connected to the control end of the switch SW1, through the logic The signal controls the on and off of the switch SW1.
- the comparator 60 when the voltage of the external power source is not lower than the threshold voltage set by the circuit, the comparator 60 generates a logic signal net03 for outputting to the level shifting module 70, and the level shifting module 70 performs level shifting of the logic signal net03.
- the logic signal net04 controls the switch SW1 to turn off, turns off the path between the battery power supply and the load, and the external power supply supplies power to the load through the third buck 30.
- the comparator 60 When the voltage of the external power source is lower than the threshold voltage set by the circuit, the comparator 60 generates a logic signal net03 output to the level shift.
- the module 70, the level shifting module 70 performs level shifting of the logic signal net03 to generate a logic signal net04 to control the switch SW1 to be turned on, and the battery power source supplies power to the load through the switch SW1.
- the circuit needs to set an appropriate threshold voltage VTM according to the operating voltage range of the battery, assuming that the operating voltage of the battery is at least VBAT MIN and the step-down value of the buck is V d .
- the threshold voltage VTM can be determined by the following formula:
- the setting of the threshold voltage VTM is realized by the relative relationship between the output reference voltage netO1 of the voltage reference module 40 and the output divided voltage net02 of the voltage divider 50.
- the reference voltage netOl is a relatively constant voltage; and the divided voltage net02 is the linear divided voltage of the external power supply.
- the threshold voltage VTM can be calculated by the following formula:
- the first buck 10, the second buck 20, and the third buck 30 include, but are not limited to, diodes, transistors, or MOSFETs.
- the logic signal net04 controls the switch SW1 to be turned off, and the path between the battery power and the load is turned off.
- the external power supply supplies the output voltage VDD2 to the load through the third buck. Due to the reverse-cut characteristic of the third buck, the voltage from the output voltage VDD2 to the external power supply does not overflow, and at the same time, as long as the preset voltage threshold It is less than the sum of the lowest battery operating voltage and the buck value of the third buck, and the external power supply does not charge the battery through the switch SW1.
- FIG. 2 is a schematic structural diagram of a power switching circuit according to a preferred embodiment of the present invention.
- three diodes are used to implement the functions of the buck, specifically including: a switch SW1, three diodes D l, D2, D3, a voltage reference module 40, a voltage divider 50, a comparator 60, and a level shifting module. 70, where:
- the control signal net04 is from the level shifting module 70;
- the anode of the diode D1 is connected to the external power supply, the cathode is connected to the internal step-down voltage VDD1;
- the anode of the diode D2 is connected to the battery power supply, the cathode Connect the internal step-down voltage VDD 1 ;
- the anode of the diode D3 is connected to the external power supply, the cathode is connected to the output voltage VDD2;
- the input of the voltage divider 50 is connected to the external power supply, and the output divided voltage net02 is connected to one input of the comparator 60;
- the operating power of 40 is the internal step-down voltage VDD1, and the output reference voltage netO l is connected to the other input terminal of the comparator 60;
- the lithium battery is taken as an example.
- the typical lithium battery operating voltage is about 3V ⁇ 4. 2V, assuming that the step-down value of the diode is 0. 7V, then by the formula VTM ⁇ VBATMTM + V, :: It can be seen that the threshold voltage setting range is VTM ⁇ 3. 7V.
- the logic signal net04 controls the switch SW1 to be turned off, the path between VBAT and the load is turned off, and the external power supply passes through the diode.
- D3 output voltage VDD2 supplies power to the load.
- the output voltage VDD2 is equal to the difference between the external power supply voltage and the diode D3. For example, when the external power supply voltage is 3.7V, the output voltage is 3V.
- the logic signal net04 controls the switch SW1 to be turned on, and the battery power supplies the voltage to the load through the output voltage VDD2 of the switch SW1. Due to the reverse cut-off characteristic of the diode D3, the VDD2 is inverted to the voltage of the external power supply. However, due to the bi-directional characteristics of the switch SW1, the threshold voltage required to meet the above formula (1) is required to avoid the external power supply charging the battery through the switch SW1.
- the voltage of the internal step-down voltage VDD1 is equal to (V BUS - 0.7 V) or (V BAT - 0. 7V) The one with the higher voltage. Therefore, any of the external power source and the battery power source can be powered, and the voltage reference module 40 and the comparator 60 can be powered.
- the minimum voltage of VDD1 is only VBAT MIN - 0.7V when the system is only powered by the battery. Therefore, it is ensured that the control function of the power switch can be realized.
- the minimum operating voltage of the voltage reference module 40 and the comparator 60 must be lower than VDD1. Minimum voltage.
- the minimum operating voltage of the voltage reference module 40 and the comparator 60 must be lower than 2. 3V.
- step-down value of the diode in this embodiment is merely an example, and other types of diodes may be selected in practice, and a triode and a MOS tube may be used instead.
- the collector and the base of the NPN transistor are connected to an external power source, and the emitter is connected to the voltage reference module 40 and the comparator 60;
- the PNP transistor when a PNP transistor is used instead of the diode D1, the PNP transistor The emitter is connected to the external power source, the base and the collector are connected to the voltage reference module 40 and the comparator 60;
- the ⁇ OS tube is used instead of the diode D1, the drain terminal, the gate terminal and the substrate of the ⁇ OS tube are connected to the external power source, the source The terminal is connected to the voltage reference module 40 and the comparator 60;
- the PMOS transistor when the PMOS transistor is used instead of the diode D1, the source of the PM0S transistor is connected to an external power supply, and the drain terminal, the gate terminal and the substrate are both connected to the voltage reference module 40 and the comparator 60.
- the NPN transistor When the NPN transistor is used instead of the diode D2, the anode of the diode is connected to the battery power source, and the cathode is connected to the voltage reference module 40 and the comparator 60.
- the NPN transistor When the NPN transistor is used instead of the diode D2, the collector and the base of the NPN transistor are connected to the battery power source, and the emission is performed.
- the pole is connected to the voltage reference module 40 and the comparator 60; when the PNP transistor is used instead of the diode D2, the emitter of the PNP transistor is connected to the battery power source, and the base and the collector are connected to the voltage reference module 40 and the comparator 60; When the diode replaces the diode D2, the drain terminal, the gate terminal and the substrate of the ⁇ OS tube are connected to the battery power source, and the source terminal is connected to the voltage reference module 40 and the comparator 60; when the PM0S tube is used instead of the diode D2, the source end of the PM0S tube An external power supply is connected, and the drain terminal, the gate terminal and the substrate are both connected to the voltage reference module 40 and the comparator 60.
- the collector and the base of the NPN transistor are connected to the external power source, and the emitter is connected to the load.
- the PNP transistor is used instead of the diode D3
- the emitter of the PNP transistor is connected to the external power source, the base and the collector are connected.
- the source end is connected to the load; when the PM0S tube is used instead of the diode D3, the source end of the PM0S tube is connected to the external power source, the drain end, the gate end and the lining The bottom is connected to the load.
- FIG. 3 is a schematic structural diagram of a power switching circuit according to a preferred embodiment of the present invention.
- This embodiment further exemplifies the scheme of the switch SW1 on the basis of the second embodiment, and the same part as the second embodiment is not heavy here.
- the switch SW1 comprises: two series connected PM0S tubes MP1 and MP2, the source end of the MP1 and the substrate are connected to the battery power supply, the drain end is connected to the drain end of the MP2, and the gate end is connected to the control signal net04a of the level shifting module 70 ; the source end of the MP2
- the load is connected to the substrate, and the gate terminal is connected to the control signal net04b of the level shifting module 70.
- level shifting must be performed by level shifting module 70 to move MP4 control signal net 04a to The battery power supply is in the same voltage domain, and the MP2 control signal net04b is moved to the same voltage domain as the load power supply VDD2.
- the power switching circuit and the switching method provided by the invention remove the battery power to the outside when the external power source is dead, by introducing a step-down device between the external power source and the output voltage.
- the risk of power supply back-up so only one switch is needed to control the battery power; when the battery power supplies the load, the threshold voltage of the control switch SW1 is set to avoid the generation of charging current from the external power source to the battery power source. Therefore, the selection of the system power supply can be realized by using only one set of switches, which simplifies the structure of the control circuit and improves the circuit reliability.
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Abstract
一种外部电源和电池供电电源切换电路及切换方法,该电源切换电路包括:开关、第一降压器、第二降压器、第三降压器、电压基准模块、分压器、比较器和电平转移模块,其中,当外部电源的电压不低于预设的电压阈值时,电平转移模块控制开关截止电池到负载的通路;当外部电源的电压低于预设的电压阈值时,电平转移模块控制开关连通电池到负载的通路。采用所述电源切换电路及切换方法,仅使用1组开关即可实现对***供电电源的选择,简化了控制电路的结构并提高了电路可靠性。
Description
说 明 书 一种外部电源和电池供电的电源切换电路及切换方法 技术领域
本发明涉及电子电路技术领域, 尤其涉及一种外部电源和电池供电的电源 切换电路及切换方法。 背景技术
在既有外部电源供电又有电池供电的电子***中, 电源切换电路需要控制 两组开关, 分别控制外部电源的连通和断开, 以及电池电源的连通和断开。 并 且根据外部电源和电池电源的电压大小关系来控制使用其中一个电源给***供 电。 两组开关的状态需要严格保障, 否则一旦出现两个电源同时连接入或者同 时断开的状态, 都可能导致***出错。 发明内容
有鉴于此, 本发明要解决的技术问题是提供一种外部电源和电池供电的电 源切换电路及切换方法, 以仅使用一组开关来实现对***供电电源的选择, 达 到简化电路结构并提高电路可靠性。
本发明解决上述技术问题所采用的技术方案如下:
根据本发明的一个方面, 提供的一种外部电源和电池供电电源切换电路包 括: 开关、 第一降压器、 第二降压器、 第三降压器、 电压基准模块、 分压器、 比较器和电平转移模块, 其中:
第一降压器的输入端连接到外部电源, 输出端连接到电压基准模块和比较 器; 第二降压器的输入端连接到电池电源, 输出端连接到电压基准模块和比较 器; 第三降压器的输入端连接到外部电源, 输出端连接负载; 分压器的输入端
连接外部电源, 输出端连接比较器的一个输入端; 电压基准模块的输入端连接 第一降压器和第二降压器的输出端, 输出端连接比较器的一个输入端; 比较器 根据电压基准模块和分压器的比较结果输出逻辑信号到电平转移模块的输入 端; 开关, 一端连接电池电源, 另一端连接负载, 控制端连接电平转移模块; 电平转移模块的输出端连接开关的控制端, 通过逻辑信号控制开关的导通和截 止。
优选地, 第一降压器为二极管、 三极管或 M0S管。
其中, 当第一降压器为二极管时, 二极管的阳极连接外部电源, 阴极连接 到电压基准模块和比较器; 当第一降压器为 NPN三极管时, NPN三极管的集电极 和基极连接外部电源, 发射极连接到电压基准模块和比较器; 当第一降压器为 PNP三极管时, PNP三极管的发射极连接外部电源, 基极和集电极连接到电压基 准模块和比较器; 当第一降压器为匪 OS管时, 匪 OS管的漏端、 栅端和衬底均 连接外部电源,源端连接到电压基准模块和比较器;当第一降压器为 PM0S管时, PM0S管的源端连接外部电源, 漏端、 栅端和衬底均连接到电压基准模块和比较 器。
优选地, 第二降压器为二极管、 三极管或 M0S管。
其中, 当第二降压器为二极管时, 二极管的阳极连接电池电源, 阴极连接 到电压基准模块和比较器; 当第二降压器为 NPN三极管时, NPN三极管的集电极 和基极连接电池电源, 发射极连接到电压基准模块和比较器; 当第二降压器为 PNP三极管时, PNP三极管的发射极连接电池电源, 基极和集电极连接到电压基 准模块和比较器; 当第二降压器为匪 OS管时, 匪 OS管的漏端、 栅端和衬底均连 接电池电源, 源端连接到电压基准模块和比较器; 当第二降压器为 PM0S管时, PM0S管的源端连接外部电源, 漏端、 栅端和衬底均连接到电压基准模块和比较 器。
优选地, 第三降压器为二极管、 三极管或 M0S管。
其中, 当第三降压器为二极管时, 二极管的阳极连接外部电源, 阴极连接
负载;当第三降压器为 NPN三极管时, NPN三极管的集电极和基极连接外部电源, 发射极连接负载; 当第三降压器为 PNP三极管时, PNP三极管的发射极连接外部 电源, 基极和集电极连接到负载; 当第三降压器为匪 OS管时, 匪 OS管的漏端、 栅端和衬底均连接外部电源,源端连接到负载;当第三降压器为 PM0S管时, PM0S 管的源端连接外部电源, 漏端、 栅端和衬底均连接到负载。
优选地, 开关包括: 两个串联的 PM0S管 MP1和 MP2, MP1的源端和衬底连 接电池电源, 漏端连接 MP2的漏端, 栅端连接控制信号; MP2的源端和衬底连接 负载, 栅端连接控制信号。 根据本发明的另一个方面, 提供的一种外部电源和电池供电电源切换方法 包括: 当检测到外部电源的电压不低于预设的电压阈值时, 控制开关截止电池 到负载的通路; 当检测到外部电源的电压低于预设的电压阈值时, 控制开关连 通电池到负载的通路。
优选地, 预设的电压阈值小于电池工作电压最低值与第三降压器的降压值 的和。
优选地, 预设的电压阈值通过电压基准模块的输出电压和分压器输出的输 出电压的相对关系来实现。
本发明提供的电源切换电路及切换方法, 通过在外部电源到输出电压之间 引入一个降压器, 利用降压器反向不导通的特性消除了当外部电源没电时, 电 池电源向外部电源反灌的风险, 因此仅需一个开关实现对电池电源的控制; 在 电池电源对负载供电时, 通过设置控制开关 SW1 的阈值电压来避免由外部电源 可能向电池电源的充电电流的产生。 从而仅使用一组开关即可实现对***供电 电源的选择, 简化了控制电路的结构并提高了电路可靠性。 附图说明
图 1是本发明实施例提供的一种电源切换电路的结构示意图。
图 2是本发明优选实施例提供的一种电源切换电路的结构示意图。
图 3是本发明优选实施例提供的另一种电源切换电路的结构示意图。 具体实施方式
为了使本发明所要解决的技术问题、 技术方案及有益效果更加清楚、 明白, 以下结合附图和实施例, 对本发明进行进一歩详细说明。 应当理解, 此处所描 述的具体实施例仅仅用以解释本发明, 并不用于限定本发明。 实施例一 如图 1 所示为一种外部电源和电池供电电源切换电路, 该电源切换电路包 括: 开关 SW1、 第一降压器 10、 第二降压器 20、 第三降压器 30、 电压基准模块 40、 分压器 50、 比较器 60和电平转移模块 70, 其中:
第一降压器 10 的输入端连接到外部电源, 输出端连接到电压基准模块 40 和比较器 60 ; 第二降压器 20的输入端连接到电池电源, 输出端连接到电压基准 模块 40和比较器 60; 第三降压器 30的输入端连接到外部电源, 输出端连接负 载; 分压器 50的输入端连接外部电源, 输出端连接比较器 60的一个输入端; 电压基准模块 40的输入端连接第一降压器 10和第二降压器 20的输出端, 输出 端连接比较器 60的一个输入端; 比较器 60根据电压基准模块 40和分压器 50 的比较结果输出逻辑信号到电平转移模块 70的输入端; 开关 SW1 , —端连接电 池电源, 另一端连接负载, 控制端连接电平转移模块 70 ; 电平转移模块 70的输 出端连接开关 SW1的控制端, 通过逻辑信号控制开关 SW1的导通和截止。
具体来说, 当外部电源的电压不低于电路设定的阈值电压时, 则比较器 60 产生逻辑信号 net03输出给电平转移模块 70,电平转移模块 70将逻辑信号 net03 进行电平转移产生逻辑信号 net04控制开关 SW1截止, 关断电池电源到负载的 之间的通路, 外部电源经过第三降压器 30对负载进行供电。 当外部电源的电压 低于电路设定的阈值电压时, 则比较器 60产生逻辑信号 net03输出给电平转移
模块 70, 电平转移模块 70将逻辑信号 net03进行电平转移产生逻辑信号 net04 控制开关 SW1导通, 电池电源通过开关 SW1对负载进行供电。
本实施例中, 由于第三降压器的反向截止特性, 不会出现由输出电压 VDD2 向外部电源的电压倒灌。 但由于开关 SW1 的双相导通特性, 如果此时电池电压 小于外部电源的电压与第三降压器的电压的差, 则存在外部电源通过第三降压 器和开关 SW1 向电池充电的风险。 因此, 电路需要根据电池的工作电压范围设 定合适的阈值电压 V™, 假设电池的工作电压最低为 VBATMIN, 降压器的降压值为 Vd。wn则阈值电压 V™可以由以下式确定:
V™ < VBATMIN + VD, ( 1 )
本实施例中, 阈值电压 V™的设定是通过电压基准模块 40 的输出基准电压 netOl和分压器 50的输出分压电压 net02的相对关系来实现的。基准电压 netOl 是一个相对恒定的电压; 而分压电压 net02 是外部电源的线性分压, 假设外部 电源的电压为 VBUS, 分压系数为 l/k, 即 net02 = (l/k) *VBUS, 则阈值电压 V™ 可通过以下公式计算:
VTH = (net01/net02) *VBUS = k*net01 ( 2 )
作为本实施例的优选方案, 第一降压器 10、 第二降压器 20、 第三降压器 30 包括但不限于采用二极管、 三极管或 M0S管来实现。
综上所述, 无论电池电源的电压为多少, 只要外部电源的电压不低于电路 设定的阈值电压 V™, 则逻辑信号 net04控制开关 SW1截止, 关断电池电源到负 载之间的通路, 外部电源经过第三降压器提供输出电压 VDD2对负载供电, 由于 第三降压器的反向截止特性,不会出现由输出电压 VDD2向外部电源的电压倒灌, 同时, 只要预设的电压阈值小于电池工作电压最低值与第三降压器的降压值的 和, 也不会出现外部电源通过开关 SW1对电池充电。 实施例二
如图 2 所示是本发明优选实施例提供的一种电源切换电路的结构示意图,
本实施例中采用三个二极管来实现降压器的功能, 具体包括: 开关 SW1 , 3个二 极管 D l、 D2、 D3, 电压基准模块 40、 分压器 50、 比较器 60和电平转移模块 70, 其中:
开关 SW1的一端连接电池电源,另一端连接输出电压 VDD2 ,控制信号 net04 来自电平转移模块 70 ; 二极管 D1的阳极连接外部电源, 阴极连接内部降压电压 VDD1 ; 二极管 D2 的阳极连接电池电源, 阴极连接内部降压电压 VDD 1 ; 二极管 D3的阳极连接外部电源, 阴极连接输出电压 VDD2 ; 分压器 50的输入端连接外 部电源, 输出分压电压 net02连接比较器 60的一个输入端; 电压基准模块 40 的工作电源为内部降压电压 VDD1 ,输出基准电压 netO l连接比较器 60的另一个 输入端; 比较器 60的工作电源为内部降压电压 VDD1 , 输出逻辑信号 net03连接 电平转移模块 70的输入端; 电平转移模块 70输出逻辑信号 net03经过电平转 移后的逻辑信号 net04, 逻辑信号 net04控制开关 SW1的导通和截止。
本实施例中, 以锂电池为例, 典型的锂电池工作电压约为 3V〜4. 2V, 假设 二极管的降压值为 0. 7V, 那么由公式 V™ < VBATM™ + V,::, 可知, 阈值电压设定 范围为 V™ < 3. 7V。
无论电池电源的电压为多少, 只要外部电源的电压不低于电路设定的阈值 电压 3. 7V时, 则逻辑信号 net04控制开关 SW1截止, 关断 VBAT到负载之间的 通路,外部电源经过二极管 D3输出电压 VDD2对负载进行供电,其输出电压 VDD2 的电压值等于外部电源电压与二极管 D3 降压值的差,比如, 外部电源的电压为 3. 7V时, 其输出电压为 3V。
当外部电源的电压低于电路设定的阈值电压时, 则逻辑信号 net04控制开 关 SW1导通, 电池电源通过开关 SW1输出电压 VDD2对负载供电, 由于二极管 D3 的反向截止特性, 不会出现由 VDD2向外部电源的电压倒灌。 但由于开关 SW1的 双向导通特性, 此时要求设定的阈值电压满足上述公式 (1 ) 才能避免出现外部 电源通过开关 SW1对电池充电。
在本实施例中, 内部降压电压 VDD1 的电压大小等于(VBUS - 0. 7V)或(VBAT -
0. 7V)中电压较大的那一个。 因此外部电源和电池电源中的任一个电源有电, 即 可对电压基准模块 40和比较器 60供电。 ***在仅有电池供电时 VDD1的最低电 压约为 VBATMIN - 0. 7V, 因此确保能够实现对电源开关的控制功能的前提是电压 基准模块 40和比较器 60的最低工作电压必须低于 VDD1的最低电压。 以锂电池 为例, VDD1的最低电压约为 2. 3V, 那么电压基准模块 40和比较器 60的最低工 作电压必须低于 2. 3V。
当然, 本实施例中二极管的降压值仅仅是举例说明, 实际中可以选择其他 类型的二极管来实现, 还可以采用三极管和 M0S管来替代。
具体来说, 当采用 NPN三极管替代二极管 D1时, NPN三极管的集电极和基 极连接外部电源, 发射极连接到电压基准模块 40和比较器 60; 当采用 PNP三极 管替代二极管 D1时, PNP三极管的发射极连接外部电源, 基极和集电极连接到 电压基准模块 40和比较器 60; 当采用匪 OS管替代二极管 D1时, 匪 OS管的漏 端、栅端和衬底均连接外部电源, 源端连接到电压基准模块 40和比较器 60; 当 采用 PM0S管替代二极管 D1时, PM0S管的源端连接外部电源, 漏端、 栅端和衬 底均连接到电压基准模块 40和比较器 60。
当采用 NPN三极管替代二极管 D2时, 二极管的阳极连接电池电源, 阴极连 接到电压基准模块 40和比较器 60; 当采用 NPN三极管替代二极管 D2时, NPN 三极管的集电极和基极连接电池电源, 发射极连接到电压基准模块 40和比较器 60; 当采用 PNP三极管替代二极管 D2时, PNP三极管的发射极连接电池电源, 基极和集电极连接到电压基准模块 40和比较器 60; 当采用匪 OS管替代二极管 D2时, 匪 OS管的漏端、 栅端和衬底均连接电池电源, 源端连接到电压基准模块 40和比较器 60 ;当采用 PM0S管替代二极管 D2时, PM0S管的源端连接外部电源, 漏端、 栅端和衬底均连接到电压基准模块 40和比较器 60。
当采用 NPN三极管替代二极管 D3时, NPN三极管的集电极和基极连接外部 电源, 发射极连接负载; 当采用 PNP三极管替代二极管 D3时, PNP三极管的发 射极连接外部电源, 基极和集电极连接到负载; 当采用匪 0S管替代二极管 D3
时,匪 OS管的漏端、栅端和衬底均连接外部电源,源端连接到负载; 当采用 PM0S 管替代二极管 D3时, PM0S管的源端连接外部电源, 漏端、栅端和衬底均连接到 负载。 实施例三
如图 3 所示是本发明优选实施例提供的一种电源切换电路的结构示意图, 本实施例在实施例二的基础上进一歩举例说明开关 SW1 的方案, 与实施例二相 同部分这里不再重述。 开关 SW1包括: 两个串联的 PM0S管 MP1和 MP2, MP1的 源端和衬底连接电池电源, 漏端连接 MP2的漏端, 栅端连接电平转移模块 70的 控制信号 net04a; MP2的源端和衬底连接负载, 栅端连接电平转移模块 70的控 制信号 net04b。 图 2中的控制信号 net04在图 3中被拆分为两个同相的控制信 号 net04a与 net04b。 当外部电源的电压低于阈值电压时, 控制信号 net04a和 net04b均为 0V电压的低电平, 开关 SW1导通, 电池电源通过开关 SW1对负载进 行供电。 当外部电源的电压不低于阈值电压时, net04a为 VBAT电压的高电平, net04b为 VDD2电压的高电平, 开关 SW1截止, 关断电池电源到负载的之间的通 路, 外部电源经过二极管 D3对负载进行供电。
需要说明地是, 本实施例中由于采用 PM0S管构成开关, 所以是高电平截止 和低电平导通。 当采用 PM0S管时, 由于 net03所属电压域为 VDD1 , 则 net03的 高电平不一定能够关断开关, 所以必须通过电平转移模块 70进行电平转移, 将 MP1的控制信号 net 04a移至与电池电源同一个电压域,而 MP2的控制信号 net04b 移至与负载电源 VDD2同一个电压域。
以上参照附图说明了本发明的优选实施例, 并非因此局限本发明的权利范 围。 本领域技术人员不脱离本发明的范围和实质, 可以有多种变型方案实现本 发明, 比如作为一个实施例的特征可用于另一实施例而得到又一实施例。 凡在 运用本发明的技术构思之内所作的任何修改、 等同替换和改进, 均应在本发明 的权利范围之内。
工业实用性
本发明提供的电源切换电路及切换方法, 通过在外部电源到输出电压之间 引入一个降压器, 利用降压器反向不导通的特性消除了当外部电源没电时, 电 池电源向外部电源反灌的风险, 因此仅需一个开关实现对电池电源的控制; 在 电池电源对负载供电时, 通过设置控制开关 SW1 的阈值电压来避免由外部电源 可能向电池电源的充电电流的产生。 从而仅使用一组开关即可实现对***供电 电源的选择, 简化了控制电路的结构并提高了电路可靠性。
Claims
1、 一种外部电源和电池供电电源切换电路, 包括: 开关、 第一降压器、 第 二降压器、 第三降压器、 电压基准模块、 分压器、 比较器和电平转移模块, 其 中:
所述第一降压器的输入端连接到外部电源, 输出端连接到电压基准模块和 比较器; 所述第二降压器的输入端连接到电池电源, 输出端连接到电压基准模 块和比较器; 所述第三降压器的输入端连接到外部电源, 输出端连接负载; 所 述分压器的输入端连接外部电源, 输出端连接所述比较器的一个输入端; 所述 电压基准模块的输入端连接第一降压器和第二降压器的输出端, 输出端连接所 述比较器的一个输入端; 所述比较器根据电压基准模块和所述分压器的比较结 果输出逻辑信号到所述电平转移模块的输入端; 所述开关, 一端连接电池电源, 另一端连接负载, 控制端连接所述电平转移模块; 所述电平转移模块的输出端 连接所述开关的控制端, 通过逻辑信号控制所述开关的导通和截止。
2、 根据权利要求 1所述的电源切换电路, 其特征在于, 所述第一降压器为 二极管、 三极管或 M0S管。
3、 根据权利要求 2所述的电源切换电路, 其中,
当所述第一降压器为二极管时, 所述二极管的阳极连接外部电源, 阴极连 接到所述电压基准模块和所述比较器;
当所述第一降压器为 NPN三极管时, 所述 NPN三极管的集电极和基极连接 外部电源, 发射极连接到所述电压基准模块和所述比较器;
当所述第一降压器为 PNP三极管时, PNP三极管的发射极连接外部电源, 基 极和集电极连接到所述电压基准模块和所述比较器;
当所述第一降压器为匪 OS管时, 所述匪 OS管的漏端、 栅端和衬底均连接 外部电源, 源端连接到所述电压基准模块和所述比较器;
当所述第一降压器为 PM0S管时, 所述 PM0S管的源端连接外部电源, 漏端、
栅端和衬底均连接到所述电压基准模块和所述比较器。
4、根据权利要求 1所述的电源切换电路, 其中,所述第二降压器为二极管、 三极管或 M0S管。
5、 根据权利要求 4所述的电源切换电路, 其中,
当所述第二降压器为二极管时, 所述二极管的阳极连接电池电源, 阴极连 接到所述电压基准模块和所述比较器;
当所述第二降压器为 NPN三极管时, 所述 NPN三极管的集电极和基极连接 电池电源, 发射极连接到所述电压基准模块和所述比较器;
当所述第二降压器为 PNP三极管时, PNP三极管的发射极连接电池电源, 基 极和集电极连接到所述电压基准模块和所述比较器;
当所述第二降压器为匪 OS管时, 所述匪 OS管的漏端、 栅端和衬底均连接 电池电源, 源端连接到所述电压基准模块和所述比较器;
当所述第二降压器为 PM0S管时, 所述 PM0S管的源端连接外部电源, 漏端、 栅端和衬底均连接到所述电压基准模块和所述比较器。
6、根据权利要求 1所述的电源切换电路, 其中,所述第三降压器为二极管、 三极管或 M0S管。
7、 根据权利要求 6所述的电源切换电路, 其中,
当所述第三降压器为二极管时, 所述二极管的阳极连接外部电源, 阴极连 接负载;
当所述第三降压器为 NPN三极管时, 所述 NPN三极管的集电极和基极连接 外部电源, 发射极连接负载;
当所述第三降压器为 PNP三极管时, PNP三极管的发射极连接外部电源, 基 极和集电极连接到负载;
当所述第三降压器为匪 OS管时, 所述匪 OS管的漏端、 栅端和衬底均连接 外部电源, 源端连接到负载;
当所述第三降压器为 PM0S管时, 所述 PM0S管的源端连接外部电源, 漏端、
栅端和衬底均连接到负载。
8、 根据权利要求 1-7任意一项权利要求所述的电源切换电路, 其中, 所 述开关包括: 两个串联的 PM0S管 MP1和 MP2, MP1的源端和衬底连接电池电源, 漏端连接 MP2的漏端, 栅端连接控制信号; MP2的源端和衬底连接负载, 栅端连 接控制信号。
9、 一种外部电源和电池供电电源切换方法, 该方法包括:
当检测到外部电源的电压不低于预设的电压阈值时, 控制开关截止电池到 负载的通路; 当检测到外部电源的电压低于预设的电压阈值时, 控制开关连通 电池到负载的通路。
10、 根据权利要求 9所述的电源切换方法, 其中, 所述预设的电压阈值小于 电池工作电压最低值与第三降压器的降压值的和。
11、 根据权利要求 9或 10所述的电源切换方法, 其中, 所述预设的电压阈值 通过电压基准模块的输出电压和分压器输出的输出电压的相对关系来实现。
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