CN214586613U - Linear voltage-stabilized power supply with low voltage drop - Google Patents
Linear voltage-stabilized power supply with low voltage drop Download PDFInfo
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- CN214586613U CN214586613U CN202120538961.3U CN202120538961U CN214586613U CN 214586613 U CN214586613 U CN 214586613U CN 202120538961 U CN202120538961 U CN 202120538961U CN 214586613 U CN214586613 U CN 214586613U
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Abstract
The utility model discloses a low voltage drop linear voltage-stabilized power supply, which comprises an unstable power supply circuit, a filter circuit, a series adjusting tube circuit, an error amplifier circuit, a reference source circuit and a feedback resistance network circuit; the error amplifier circuit is composed of an IC1, the filter circuit is composed of an electrolytic capacitor C2, the negative electrode of an electrolytic capacitor C2 is connected with a working ground, an unstable power source Uin is simultaneously connected with the positive electrode of the capacitor C2, a pin 7 of the IC1 and the emitter of the series regulating tube circuit transistor T1, the base electrode of the T1 is connected with the output end of the IC1, the collector electrode of the T1 is sequentially connected with a resistor R1 and a reverse-connected voltage regulator D1 to work, the collector electrode of the T1 is simultaneously connected with the working ground sequentially through resistors R2 and R3, the connection point of the resistor R1 and the voltage regulator D1 is connected with the reverse-phase input end of the IC1, the connection point of the resistors R2 and R3 is connected with the non-phase input end of the IC1, and the collector electrode of the transistor T1 outputs stable voltage.
Description
Technical Field
The utility model relates to a linear constant voltage power supply technique, especially a linear constant voltage power supply that unstable input power and stable output power only have extremely low voltage difference.
Background
A voltage regulator circuit is a circuit that can maintain a constant output voltage even when an input voltage, a load, an ambient temperature, a circuit parameter, and the like are changed. The circuit can provide stable direct current power supply and is widely used in various electronic devices.
The process of stabilizing the output voltage by using the adjustment action of the circuit is called voltage stabilization, and the process is divided into a linear voltage-stabilized power supply and a switch voltage-stabilized power supply according to the working state of an adjusting tube, wherein the linear voltage-stabilized power supply is generally a series voltage-stabilized power supply.
The switching stabilized power supply adjusts the duty ratio or frequency of high-frequency alternating current pulse and adjusts output voltage through an energy storage element inductance capacitor, and has the advantages of high voltage conversion efficiency and large output ripple waves and sometimes generates high-frequency interference on a circuit.
Linear regulators are the best choice when the input and output voltages in the system are close, achieving high efficiency. Linear regulators are most often used in applications where the lithium ion battery voltage is converted to 3V, and although ten percent of the battery's final discharge energy may not be used, linear regulators can still provide longer battery life in a low noise configuration.
The linear series type voltage-stabilized source adjusts the output voltage by adjusting the dynamic resistance of the adjusting tube, and has the advantage of small output ripple.
However, the conventional linear voltage stabilizer has the serious defects that the voltage drop between input and output is overlarge, the conversion efficiency of the voltage stabilizer is very low under the condition of large input-output voltage difference, and the heat is serious, for example, the input voltage of a three-terminal voltage-stabilizing 78XX series chip is required to be at least 2V-3V higher than the output voltage, otherwise, the common linear voltage stabilizer cannot work normally. However, in some cases, such conditions are obviously too harsh, e.g. 5V to 3.3V, and the voltage difference between the input and the output is only 1.7V, which obviously does not satisfy the operating conditions of the conventional linear regulator.
A linear voltage-stabilized power supply with low voltage drop between input and output is designed, and the saturation voltage drop of a transistor with lower power can be as low as 0.3V, so that the unstable input voltage of the voltage-stabilized power supply designed by the people is only 0.35V higher than the required output voltage, and the power supply has higher conversion efficiency.
Disclosure of Invention
The utility model aims to solve the technical problem that a technique of the linear stable power of low pressure drop that simple structure, low in cost, use are reliable is provided.
In order to achieve the above object, the present invention provides a low voltage drop linear voltage-stabilized power supply, which comprises an unstable power circuit, a filter circuit, a series regulating transistor circuit, an error amplifier circuit, a reference voltage source circuit, and a feedback resistance network circuit; the error amplifier circuit is composed of an IC1, the filter circuit is composed of an electrolytic capacitor C2, the negative electrode of an electrolytic capacitor C2 is connected with a working ground, an unstable power source Uin is simultaneously connected with the positive electrode of the capacitor C2, a pin 7 of the IC1 and the emitter of the transistor T1 of the series adjusting tube circuit, the base electrode of the transistor T1 is connected with the output end of the IC1, the reference voltage source circuit is composed of a resistor R1 and a voltage stabilizing diode D1, the feedback resistor network circuit is composed of a resistor R2 and a resistor R3, the collector of the T1 is sequentially connected with the working ground through a resistor R1 and a reverse voltage stabilizing tube D1, the collector of the T1 is simultaneously sequentially connected with the working ground through resistors R2 and R3, the connection point of the resistor R1 and the voltage stabilizing tube D1 is connected with the reverse phase input end of the IC1, the connection point of the resistors R2 and R3 is connected with the non-phase input end of the IC1, and the collector of the transistor T1 outputs a stable voltage.
In the error amplifier circuit, pin 1 of the IC1 is connected with pin 8 of the IC1 through a capacitor C1.
Drawings
Fig. 1, 2 and 3 are included to provide a further understanding of the present invention and form a part of the present application, and fig. 1 is a schematic diagram of a conventional linear series regulator; FIG. 2 shows the maximum efficiency and U of a conventional linear regulatorOThe relation of the ratio of/Uin; FIG. 3 is an electrical schematic of a low voltage drop linear regulated power supply.
Detailed Description
Structure of traditional linear series voltage-stabilized power supply
Since the voltage regulator designed herein is also a linear voltage regulator, it is necessary to first describe the structure of the conventional linear series regulator, for comparison, the circuit structure of the conventional linear voltage regulator is shown in fig. 1.
FIG. 1 is a very mature conventional linear regulator circuit, whose operation principle is not described in detail, and whose maximum efficiency and U are the same as those of the conventional linear regulatorO/UINThe ratio is proportional, as shown in fig. 2.
As can be seen from fig. 2, the efficiency of the conventional linear regulator is only 27.5% when the input is 12V and the output is 3.3V, in which case 82.5% of the input power is completely wasted and heat is generated in the regulator. This means that the transistor must be provided in the worst case (maximum U)inAnd full load) the thermal capability to handle its power/heat dissipation. Therefore, the size of the conventional linear regulator and its heat sink may be large, especially in UOFar below UinWhen the user wants to use the device.
Alternatively, the linear regulator may be in UOIs close to UinHas very high efficiency, however, the general linear regulator has another limitation that U isinAnd UOThe minimum voltage difference between them requires that the transistor T must operate in its linear mode, as shown in fig. 1.
It then requires a certain minimum voltage drop across the collector to emitter of a bipolar transistor or across the drain to source of an FET. When U is turnedOToo close to UinConventional linear regulators may no longer be able to regulate the output voltage.
It is also apparent that linear regulators, including the regulated power supply designed herein, can only provide step-down DC/DC conversion. In those requiring UOThe voltage is higher than UinVoltage, or need to be derived from a positive UinVoltage generating negative UOIn voltage applications, linear regulators are obviously inoperative.
Low-voltage drop linear stabilized power supply electrical principle
The electrical principle of the low-voltage drop linear voltage-stabilized power supply is shown in fig. 3, and the low-voltage drop linear voltage-stabilized power supply comprises a series adjusting tube circuit, an error amplifier circuit, a reference source circuit and a feedback resistance network circuit, wherein an emitter of an adjusting tube is connected with an input power supply, a collector of the adjusting tube is connected with the feedback resistance network circuit, and feedback voltages formed by reference source voltage and the feedback resistance network are respectively connected with an inverting terminal and a non-inverting terminal of the error amplifier.
It can be seen that the conventional linear regulator shown in fig. 3 is very similar in structure to the conventional linear regulator shown in fig. 1, but when carefully observed, the two are still different, and the tube is adjusted (e.g. T in fig. 3)1) The type and connection structure of (1) are different from those of (1). The common voltage stabilizer generally uses an NPN tube or an NPN composite adjusting tube as an adjusting tube, and the low dropout voltage stabilizer designed by the invention uses a PMOS transistor or a PNP transistor as the adjusting tube.
For a given supply voltage, a bipolar transistor can provide the maximum output current, with a PNP transistor being preferred over an NPN transistor because the base of the PNP transistor can be connected to ground, allowing the transistor to fully saturate if necessary, and the saturation voltage drop for lower power transistors can be as low as 0.3V. The base of the NPN transistor can only be connected with the highest possible power voltage, so that the minimum voltage drop is limited to one UbeJunction voltage drop (in this case U)cb= 0). Therefore, the NPN transistor and the composite tuning tube cannot provide a voltage difference of less than 1 v.
The PMOS transistor and the PNP transistor can quickly reach saturation, thereby minimizing the voltage loss and power consumption of the regulator tube, and allowing the regulator tube to be used as a low dropout, low power consumption voltage regulator. The PMOS regulator tube may provide the lowest possible voltage drop that allows the lowest quiescent current to be achieved. The main disadvantage of PMOS transistors is that MOS transistors are usually used as external devices, especially when controlling large currents, so that the error amplifier IC constitutes a controller and cannot constitute a complete regulator itself.
Low voltage drop linear regulated power supply start-up procedure
At the moment of system power-up, due to input capacitance C2The characteristic that the voltage cannot change suddenly, and the power supply of the whole circuit is still zero, including the emitter of the adjusting tube and the operational amplifier IC1A reference voltage source,The feedback voltage formed by the feedback resistor is zero.
With the capacitance C2Rapid charging of (U) input voltageinContinuously rising, adjusting the tube T1The emitter of the power amplifier is firstly electrified, because the adjusting tube is still in a cut-off state, feedback voltage and reference voltage are not formed, the output of the error amplifier is still zero, and the adjusting tube T is1Starting with the formation of a starting current, which follows the capacitor voltage (i.e. the input voltage U)in) Constantly rising, adjusting the tube T1The collector voltage of (2) continuously rises with the input voltage.
With adjustment of the tube T1And when the output is about to reach a specified value, the output feedback voltage obtained by the feedback network is also close to the reference voltage value, so that the start of the stabilized voltage supply is finished.
Linear regulated power supply voltage stabilization process
The core of the circuit is a CA3130 type operational amplifier and a PNP type transistor T1CA3130 is an amplifier combining the advantages of CMOS and bipolar transistors, with gate protected P-channel mosfet (pmos) transistors in the input circuit for providing very high input impedance, very low input current.
Reference voltage UrefIs formed by a resistor R1And a voltage regulator diode D1The voltage is divided from the output end, so that the voltage is very stable; the feedback voltage is formed by a feedback resistance network R2、 R3Forming a feedback voltage, integrating the operational amplifier CA3130 with peripheral elements to form an error amplifier, outputting the feedback voltage and a reference voltage UrefThe small error signals are amplified and then amplified to be output through the adjusting tube, so that negative feedback is formed, and the output voltage is ensured to be stabilized on a specified value; similarly, if the input voltage changes or the output current changes, the closed loop will keep the output voltage constant.
It is noted that the operational amplifier and the regulating tube are operated in a linear state, so the design still belongs to a linear voltage-stabilized power supply.
The voltage-stabilizing process of the circuit is simple, e.g.Fruit output voltage UoHas an increasing tendency, R2/R3The voltage at the node (i.e., the feedback voltage, connected to the non-inverting input of the operational amplifier) will rise, while the non-inverting input of the error amplifier CA3130 is higher than the inverting input because the inverting input (i.e., the reference voltage) is generated by the zener diode D1Is constant at UrefTherefore, the output of the error amplifier will increase, which will result in the tuning tube T1The operating point shifts down and even shuts down, eventually resulting in a reduction in the output voltage of the regulator.
If the output voltage U isoAnd when the temperature is reduced to be below the specified value, the working process is opposite.
Since the PNP transistor is used as the adjusting tube, the circuit has the advantage that the voltage drop between the input and the output is very small, which is mainly determined by the adjusting tube T1The saturation voltage drop of the transistor with lower power can be as low as 0.3V, so that the unstable input voltage of the design is only 0.35V higher than the required output voltage, and the conversion efficiency is higher.
Design of circuit parameters
Since the ideal operational amplifier CA3130 can provide very high input impedance and very low input current, it has "virtual off" and "virtual short" characteristics, i.e. U+=U--，I+= I--=0, the calculation of the respective parameters of the circuit is also relatively simple.
Suppose passing through R2/R3Is 1mA and the current through the zener diode is 5 mA, the parameters of each element can be calculated from the following simple formula.
R1=0.2R2(kΩ)
R2=（Uo-Uref）*1 kΩ
R3= Uref*1 KΩ
In the formula of UoThe required stable output voltage is obtained; reference voltage Uref=UD1Erbi UoSlightly lower.
For example: if a stable output of 8V is required,the calculation result is Uref=6.8V，R1=220Ω，R2=1.2k，R3=6.8k。
The design provides another novel type of linear voltage-stabilized power supply, if the input voltage and the required output voltage have higher voltage drop and the output current is not too large, a common linear voltage-stabilized power supply can be adopted; if the input voltage is very small compared to the desired output voltage and a high conversion efficiency is desired, a low dropout regulator as described herein must be used. The design is subjected to simulation test of a simulation circuit, the circuit structure is perfect, and the element parameters are accurate.
Claims (2)
1. A linear voltage-stabilized power supply with low voltage drop is characterized in that: the stabilized voltage supply comprises an unstable power supply circuit, a filter circuit, a series regulating tube circuit, an error amplifier circuit, a reference voltage source circuit and a feedback resistance network circuit; the error amplifier circuit is composed of an IC1, the filter circuit is composed of an electrolytic capacitor C2, the negative electrode of an electrolytic capacitor C2 is connected with a working ground, an unstable power source Uin is simultaneously connected with the positive electrode of the capacitor C2, a pin 7 of the IC1 and the emitter of the transistor T1 of the series adjusting tube circuit, the base electrode of the transistor T1 is connected with the output end of the IC1, the reference voltage source circuit is composed of a resistor R1 and a voltage stabilizing diode D1, the feedback resistor network circuit is composed of a resistor R2 and a resistor R3, the collector of the T1 is sequentially connected with the working ground through a resistor R1 and a reverse voltage stabilizing tube D1, the collector of the T1 is simultaneously sequentially connected with the working ground through resistors R2 and R3, the connection point of the resistor R1 and the voltage stabilizing tube D1 is connected with the reverse phase input end of the IC1, the connection point of the resistors R2 and R3 is connected with the non-phase input end of the IC1, and the collector of the transistor T1 outputs a stable voltage.
2. A low voltage drop linear regulated power supply according to claim 1 wherein: in the error amplifier circuit, pin 1 of the IC1 is connected with pin 8 of the IC1 through a capacitor C1.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202120538961.3U CN214586613U (en) | 2021-03-16 | 2021-03-16 | Linear voltage-stabilized power supply with low voltage drop |
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| CN202120538961.3U CN214586613U (en) | 2021-03-16 | 2021-03-16 | Linear voltage-stabilized power supply with low voltage drop |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114995570A (en) * | 2022-06-10 | 2022-09-02 | 西安奥华电子仪器股份有限公司 | High-precision low-temperature-drift reference voltage circuit and debugging method thereof |
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2021
- 2021-03-16 CN CN202120538961.3U patent/CN214586613U/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114995570A (en) * | 2022-06-10 | 2022-09-02 | 西安奥华电子仪器股份有限公司 | High-precision low-temperature-drift reference voltage circuit and debugging method thereof |
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Granted publication date: 20211102 |