CN106972848B - Voltage selection circuit - Google Patents
Voltage selection circuit Download PDFInfo
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- CN106972848B CN106972848B CN201610023706.9A CN201610023706A CN106972848B CN 106972848 B CN106972848 B CN 106972848B CN 201610023706 A CN201610023706 A CN 201610023706A CN 106972848 B CN106972848 B CN 106972848B
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
- H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
- H03K17/56—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices
- H03K17/687—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being field-effect transistors
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Abstract
The invention provides a voltage selection circuit, comprising: a first transistor, a first end of which is coupled to the first input end, and a second end of which is coupled to the voltage output end; a second transistor, a first end of which is coupled to the second input end and a second end of which is coupled to the voltage output end; the first resistor is positioned between the first input end and a control end of the second transistor; the second resistor is positioned between the second input end and a control end of the first transistor; a first current adjusting circuit coupled to the control terminal of the first transistor; the second current adjusting circuit is coupled to the control end of the second transistor; a comparison circuit for comparing voltages at the first input terminal and the second input terminal; and the control circuit is arranged to control the first current adjusting circuit and the second current adjusting circuit according to the comparison result of the comparison circuit.
Description
Technical Field
The present invention relates to a voltage selection circuit, and more particularly, to a voltage selection circuit capable of operating normally when the difference between input voltages is smaller than the threshold voltage of a transistor.
Background
The voltage selection circuit has a wide application range, and is mainly used for selecting the maximum or the minimum of a plurality of input voltages as an output voltage.
Conventional voltage selection circuits mostly employ transistors as voltage switching elements. Therefore, when the difference between the input voltages is smaller than the threshold voltage of the transistor, the transistor often fails to switch smoothly, thereby causing the voltage selection circuit to output an erroneous voltage signal.
Disclosure of Invention
Therefore, how to reduce or eliminate the above-mentioned drawbacks of the conventional voltage selection circuit is a problem to be solved in the industry.
The present specification provides embodiments of a voltage selection circuit, comprising: a first input terminal for receiving a first input voltage; a second input terminal for receiving a second input voltage; a voltage output terminal for providing an output voltage; a first transistor, wherein a first terminal of the first transistor is coupled to the first input terminal, and a second terminal of the first transistor is coupled to the voltage output terminal; a second transistor, wherein a first end of the second transistor is coupled to the second input end, and a second end of the second transistor is coupled to the voltage output end; a first resistor in a first signal path between the first input terminal and a control terminal of the second transistor; a second resistor in a second signal path between the second input terminal and a control terminal of the first transistor; a first current adjusting circuit coupled to the control terminal of the first transistor; a second current adjusting circuit coupled to the control terminal of the second transistor; a comparison circuit, coupled to the first input terminal and the second input terminal, configured to compare the first input voltage and the second input voltage; and a control circuit, coupled to the first current adjusting circuit, the second current adjusting circuit, and the comparing circuit, configured to control the first current adjusting circuit and the second current adjusting circuit according to a comparison result of the comparing circuit.
One of the advantages of the above embodiments is that the control circuit can control the first current adjusting circuit or the second current adjusting circuit to adjust the voltage at the control terminal of the first transistor or the second transistor according to the comparison result of the comparison circuit. Therefore, even under the condition that the difference between the input voltages is smaller than the threshold voltage of the transistor, the first transistor and the second transistor can be smoothly turned on or off, so that the voltage selection circuit can output correct voltage signals.
Other advantages of the present invention will be explained in more detail by the following description and the accompanying drawings.
Drawings
Fig. 1 is a simplified functional block diagram of a voltage selection circuit according to a first embodiment of the present invention.
Fig. 2 is a simplified functional block diagram of a voltage selection circuit according to a second embodiment of the present invention.
Description of reference numerals:
100. 200 voltage selection circuit
102 first input terminal
104 second input terminal
106 voltage output terminal
112. 212 first transistor
114. 214 second transistor
122 first resistance
124 second resistor
132. 232 first current regulating circuit
134. 234 second current regulating circuit
140 comparison circuit
150 control circuit
Detailed Description
Embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings, the same reference numbers indicate the same or similar elements or process flows.
Fig. 1 is a simplified functional block diagram of a voltage selection circuit 100 according to a first embodiment of the present invention. As shown in fig. 1, the voltage selection circuit 100 includes a first input terminal 102, a second input terminal 104, a voltage output terminal 106, a first transistor 112, a second transistor 114, a first resistor 122, a second resistor 124, a first current adjusting circuit (current adjusting circuit)132, a second current adjusting circuit 134, a comparison circuit 140, and a control circuit 150.
In the voltage selection circuit 100, the first input terminal 102 is for receiving a first input voltage Vi1, the second input terminal 104 is for receiving a second input voltage Vi2, and the voltage output terminal 106 is for providing an output voltage Vout.
A first terminal of the first transistor 112 is coupled to the first input terminal 102, and a second terminal of the first transistor 112 is coupled to the voltage output terminal 106. Similarly, a first terminal of the second transistor 114 is coupled to the second input terminal 104, and a second terminal of the second transistor 114 is coupled to the voltage output terminal 106.
The first resistor 122 is located on a first signal path between the first input terminal 102 and a control terminal of the second transistor 114, and the second resistor 124 is located on a second signal path between the second input terminal 104 and a control terminal of the first transistor 112. For example, in the present embodiment, one end of the first resistor 122 is coupled to the first input terminal 102, and the other end is coupled to the control terminal of the second transistor 114. Similarly, one end of the second resistor 124 is coupled to the second input terminal 104, and the other end is coupled to the control terminal of the first transistor 112.
The first current adjusting circuit 132 is coupled to the control terminal of the first transistor 112, and the second current adjusting circuit 134 is coupled to the control terminal of the second transistor 114.
The comparison circuit 140 is coupled to the first input terminal 102 and the second input terminal 104, and configured to compare the first input voltage Vi1 with the second input voltage Vi 2.
The control circuit 150 is coupled to the first current adjusting circuit 132, the second current adjusting circuit 134, and the comparing circuit 140, and configured to control the first current adjusting circuit 132 and the second current adjusting circuit 134 according to a comparison result of the comparing circuit 140.
When the control circuit 150 turns on the first current adjustment circuit 132, the first current adjustment circuit 132 draws a first predetermined current I1 from the second signal path, and when the control circuit 150 turns on the second current adjustment circuit 134, the second current adjustment circuit 134 draws a second predetermined current I2 from the first signal path. In other words, the first current adjusting circuit 132 and the second current adjusting circuit 134 function as current sinks.
In the voltage selection circuit 100, a first predetermined voltage obtained by multiplying the magnitude of the second predetermined current I2 by a resistance of the first resistor 122 is greater than a threshold voltage of the second transistor 114, and a second predetermined voltage obtained by multiplying the magnitude of the first predetermined current I1 by a resistance of the second resistor 124 is greater than a threshold voltage of the first transistor 112.
In operation, the control circuit 150 may only turn on one of the first current adjusting circuit 132 and the second current adjusting circuit 134 at a time.
For example, in the embodiment of fig. 1, the first transistor 112 and the second transistor 114 are implemented by P-type metal oxide semiconductor field effect transistors (PMOS). When the comparison circuit 140 determines that the first input voltage Vi1 is greater than the second input voltage Vi2, the control circuit 150 may turn on the first current adjustment circuit 132 and turn off the second current adjustment circuit 134.
In this case, even if the difference between the first input voltage Vi1 and the second input voltage Vi2 is smaller than the threshold voltage of the first transistor 112, the voltage at the control terminal of the first transistor 112 is the result of subtracting the second predetermined voltage from the second input voltage Vi2, so that the first transistor 112 can be ensured to be turned on (turn on) smoothly, and the output voltage Vout is equal to the first input voltage Vi 1.
Conversely, when the comparison circuit 140 determines that the first input voltage Vi1 is less than the second input voltage Vi2, the control circuit 150 may turn on the second current adjustment circuit 134 and turn off the first current adjustment circuit 132.
In this case, even if the difference between the first input voltage Vi1 and the second input voltage Vi2 is smaller than the threshold voltage of the second transistor 114, the voltage at the control terminal of the second transistor 114 is the result of subtracting the first predetermined voltage from the first input voltage Vi1, so that the second transistor 114 can be ensured to be turned on smoothly, and the output voltage Vout is equal to the second input voltage Vi 2.
As can be seen from the above description, the architecture of the voltage selection circuit 100 is well suited for use as a maximum voltage selector (maximum voltage selector).
Fig. 2 is a simplified functional block diagram of a voltage selection circuit 200 according to a second embodiment of the present invention. As shown in fig. 2, the voltage selection circuit 200 includes the first input terminal 102, the second input terminal 104, the voltage output terminal 106, a first transistor 212, a second transistor 214, a first resistor 122, a second resistor 124, a first current adjustment circuit 232, a second current adjustment circuit 234, the comparison circuit 140, and the control circuit 150.
The first input terminal 102, the second input terminal 104, the voltage output terminal 106, and the comparison circuit 140 of the voltage selection circuit 200 are connected and operate in the same manner as the embodiment of fig. 1.
In the voltage selection circuit 200, a first terminal of the first transistor 212 is coupled to the first input terminal 102, and a second terminal of the first transistor 212 is coupled to the voltage output terminal 106. Similarly, a first terminal of the second transistor 214 is coupled to the second input terminal 104, and a second terminal of the second transistor 214 is coupled to the voltage output terminal 106.
The first resistor 122 is located on a first signal path between the first input terminal 102 and a control terminal of the second transistor 214, and the second resistor 124 is located on a second signal path between the second input terminal 104 and a control terminal of the first transistor 212. For example, in the present embodiment, one end of the first resistor 122 is coupled to the first input terminal 102, and the other end is coupled to the control terminal of the second transistor 214. Similarly, one end of the second resistor 124 is coupled to the second input terminal 104, and the other end is coupled to the control terminal of the first transistor 212.
The first current adjusting circuit 232 is coupled to the control terminal of the first transistor 212, and the second current adjusting circuit 234 is coupled to the control terminal of the second transistor 214.
The control circuit 150 is coupled to the first current adjusting circuit 232, the second current adjusting circuit 234 and the comparing circuit 140, and configured to control the first current adjusting circuit 232 and the second current adjusting circuit 234 according to a comparison result of the comparing circuit 140.
When the control circuit 150 turns on the first current adjustment circuit 232, the first current adjustment circuit 232 provides a first predetermined current I1 to the second signal path, and when the control circuit 150 turns on the second current adjustment circuit 234, the second current adjustment circuit 234 provides a second predetermined current I2 to the first signal path. In other words, the first current adjusting circuit 232 and the second current adjusting circuit 234 function as current sources.
Similar to the voltage selection circuit 100, a first predetermined voltage obtained by multiplying the magnitude of the second predetermined current I2 by the resistance of the first resistor 122 in the voltage selection circuit 200 is greater than a threshold voltage of the second transistor 214, and a second predetermined voltage obtained by multiplying the magnitude of the first predetermined current I1 by the resistance of the second resistor 124 is greater than a threshold voltage of the first transistor 212.
In operation, the control circuit 150 may only turn on one of the first current adjusting circuit 232 and the second current adjusting circuit 234 at a time.
For example, in the embodiment of fig. 2, the first transistor 212 and the second transistor 214 are implemented by N-type metal oxide semiconductor field effect transistors (NMOS). When the comparing circuit 140 determines that the first input voltage Vi1 is greater than the second input voltage Vi2, the control circuit 150 may turn off the first current adjusting circuit 232 and turn on the second current adjusting circuit 234.
In this case, even if the difference between the first input voltage Vi1 and the second input voltage Vi2 is smaller than the threshold voltage of the second transistor 214, the voltage at the control terminal of the second transistor 214 is the sum of the first input voltage Vi1 and the first predetermined voltage, so that the second transistor 214 can be ensured to be turned on smoothly, and the output voltage Vout is equal to the second input voltage Vi 2.
Conversely, when the comparing circuit 140 determines that the first input voltage Vi1 is less than the second input voltage Vi2, the control circuit 150 may turn off the second current adjusting circuit 234 and turn on the first current adjusting circuit 232.
In this case, even if the difference between the first input voltage Vi1 and the second input voltage Vi2 is smaller than the threshold voltage of the first transistor 212, the voltage at the control terminal of the first transistor 212 is the sum of the second input voltage Vi2 and the second predetermined voltage, so that the first transistor 212 can be ensured to be turned on smoothly, and the output voltage Vout is equal to the first input voltage Vi 1.
As can be seen from the above description, the architecture of the voltage selection circuit 200 is well suited for use as a minimum voltage selector (minimum voltage selector).
In fact, the first predetermined current I1 and the second predetermined current I2 in the above embodiments can be substantially equal in magnitude, and both the first resistor 122 and the second resistor 124 can be designed to have substantially equal resistance values, so as to simplify the complexity of circuit control.
The above are only preferred embodiments of the present invention, and all equivalent changes and modifications made in the claims of the present invention should be covered by the present invention.
Claims (10)
1. A voltage selection circuit (100; 200) comprising:
a first input terminal (102) for receiving a first input voltage (Vi 1);
a second input (104) for receiving a second input voltage (Vi 2);
a voltage output terminal (106) for providing an output voltage (Vout);
a first transistor (112; 212), wherein a first terminal of the first transistor (112; 212) is coupled to the first input terminal (102) and a second terminal of the first transistor (112; 212) is coupled to the voltage output terminal (106);
a second transistor (114; 214), wherein a first terminal of the second transistor (114; 214) is coupled to the second input terminal (104) and a second terminal of the second transistor (114; 214) is coupled to the voltage output terminal (106);
a first resistor (122) in a first signal path between the first input terminal (102) and a control terminal of the second transistor (114; 214);
a second resistor (124) in a second signal path between the second input terminal (104) and a control terminal of the first transistor (112; 212);
a first current regulation circuit (132; 232) coupled to the control terminal of the first transistor (112; 212);
a second current regulation circuit (134; 234) coupled to the control terminal of the second transistor (114; 214);
a comparison circuit (140), coupled to the first input terminal (102) and the second input terminal (104), configured to compare the first input voltage (Vi1) and the second input voltage (Vi 2); and
a control circuit (150) is coupled to the first current adjustment circuit (132; 232), the second current adjustment circuit (134; 234), and the comparison circuit (140) and configured to control the first current adjustment circuit (132; 232) and the second current adjustment circuit (134; 234) according to a comparison result of the comparison circuit (140).
2. The voltage selection circuit (100; 200) of claim 1, wherein the control circuit (150) turns on only one of the first current regulation circuit (132; 232) and the second current regulation circuit (134; 234) at a time.
3. The voltage selection circuit (100) of claim 2, wherein the first current adjustment circuit (132) draws a first predetermined current (I1) from the second signal path when the control circuit (150) turns on the first current adjustment circuit (132), and the second current adjustment circuit (134) draws a second predetermined current (I2) from the first signal path when the control circuit (150) turns on the second current adjustment circuit (134).
4. The voltage selection circuit (100) of claim 3, wherein the control circuit (150) turns on the first current adjustment circuit (132) and turns off the second current adjustment circuit (134) when the comparison circuit (140) determines that the first input voltage (Vi1) is greater than the second input voltage (Vi 2).
5. The voltage selection circuit (100) of claim 4, wherein a first predetermined voltage obtained by multiplying the magnitude of the second predetermined current (I2) by a resistance of the first resistor (122) is greater than a threshold voltage of the second transistor (114), and a second predetermined voltage obtained by multiplying the magnitude of the first predetermined current (I1) by a resistance of the second resistor (124) is greater than a threshold voltage of the first transistor (112).
6. The voltage selection circuit (100) of claim 5, wherein the first predetermined current (I1) and the second predetermined current (I2) are substantially equal in magnitude, and the first resistor (122) and the second resistor (124) have substantially equal resistance values.
7. The voltage selection circuit (200) of claim 2, wherein the first current adjustment circuit (232) provides a first predetermined current (I1) to the second signal path when the control circuit (150) turns on the first current adjustment circuit (232), and the second current adjustment circuit (234) provides a second predetermined current (I2) to the first signal path when the control circuit (150) turns on the second current adjustment circuit (234).
8. The voltage selection circuit (200) of claim 7, wherein the control circuit (150) turns off the first current adjustment circuit (232) and turns on the second current adjustment circuit (234) when the comparison circuit (140) determines that the first input voltage (Vi1) is greater than the second input voltage (Vi 2).
9. The voltage selection circuit (200) of claim 8, wherein a first predetermined voltage obtained by multiplying a magnitude of the second predetermined current (I2) by a resistance of the first resistor (122) is greater than a threshold voltage of the second transistor (214), and a second predetermined voltage obtained by multiplying a magnitude of the first predetermined current (I1) by a resistance of the second resistor (124) is greater than a threshold voltage of the first transistor (212).
10. The voltage selection circuit (200) of claim 9, wherein the first predetermined current (I1) and the second predetermined current (I2) are substantially equal in magnitude, and the first resistor (122) and the second resistor (124) have substantially equal resistance values.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201610023706.9A CN106972848B (en) | 2016-01-14 | 2016-01-14 | Voltage selection circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201610023706.9A CN106972848B (en) | 2016-01-14 | 2016-01-14 | Voltage selection circuit |
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| Publication Number | Publication Date |
|---|---|
| CN106972848A CN106972848A (en) | 2017-07-21 |
| CN106972848B true CN106972848B (en) | 2020-04-28 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201610023706.9A Active CN106972848B (en) | 2016-01-14 | 2016-01-14 | Voltage selection circuit |
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Citations (7)
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| CN1717858A (en) * | 2002-12-24 | 2006-01-04 | 照明技术电子工业有限公司 | Energy saving startup circuit for power supply |
| CN101175346A (en) * | 2006-11-02 | 2008-05-07 | 立锜科技股份有限公司 | Backlight control circuit capable of automatically adjusting voltage and control method for luminous element |
| US7443199B2 (en) * | 2005-12-07 | 2008-10-28 | Infineon Technologies Ag | Circuit arrangement for voltage selection, and method for operating a circuit arrangement for voltage selection |
| CN103259520A (en) * | 2012-02-16 | 2013-08-21 | 赛普拉斯半导体公司 | Systems and methods for switching between voltages |
| CN103490758A (en) * | 2012-06-12 | 2014-01-01 | 英飞凌科技股份有限公司 | Circuit and a method for selecting a power supply |
| CN103582230A (en) * | 2012-08-10 | 2014-02-12 | 聚积科技股份有限公司 | Light emitting diode driving device |
| CN103997324A (en) * | 2013-02-19 | 2014-08-20 | 美国亚德诺半导体公司 | Analog minimum or maximum voltage selector circuit |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7893560B2 (en) * | 2008-09-12 | 2011-02-22 | Nellcor Puritan Bennett Llc | Low power isolation design for a multiple sourced power bus |
-
2016
- 2016-01-14 CN CN201610023706.9A patent/CN106972848B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1717858A (en) * | 2002-12-24 | 2006-01-04 | 照明技术电子工业有限公司 | Energy saving startup circuit for power supply |
| US7443199B2 (en) * | 2005-12-07 | 2008-10-28 | Infineon Technologies Ag | Circuit arrangement for voltage selection, and method for operating a circuit arrangement for voltage selection |
| CN101175346A (en) * | 2006-11-02 | 2008-05-07 | 立锜科技股份有限公司 | Backlight control circuit capable of automatically adjusting voltage and control method for luminous element |
| CN103259520A (en) * | 2012-02-16 | 2013-08-21 | 赛普拉斯半导体公司 | Systems and methods for switching between voltages |
| CN103490758A (en) * | 2012-06-12 | 2014-01-01 | 英飞凌科技股份有限公司 | Circuit and a method for selecting a power supply |
| CN103582230A (en) * | 2012-08-10 | 2014-02-12 | 聚积科技股份有限公司 | Light emitting diode driving device |
| CN103997324A (en) * | 2013-02-19 | 2014-08-20 | 美国亚德诺半导体公司 | Analog minimum or maximum voltage selector circuit |
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| CN106972848A (en) | 2017-07-21 |
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