A voltage stabilizing circuit suitable for wide input voltage

Abstract

The present invention belongs to the field of aviation electrical, and specifically relates to a voltage stabilizing circuit adapted to wide input voltage. The voltage detection signal is positively input to one end of the first resistor R1, one end of the third resistor R3, one end of the fourth resistor R4, and one end of the fifth resistor R5; the voltage detection signal is negatively input to one end of the second resistor R2, the emitter of the first triode V1, and the negative end of the three-terminal voltage regulator WY1; the other end of the first resistor R1 is connected to the other end of the second resistor R2 and the base of the first triode V1; the other end of the third resistor R3 is connected to the collector of the first triode V1, the base of the second triode V2, and one end of the sixth resistor R1; the other end of the fourth resistor R4 is connected to the collector of the second triode V2; the other end of the fifth resistor R5 is connected to the positive input end of the three-terminal voltage regulator WY1, the negative electrode of the first diode V3, and the positive electrode of the second diode V4; the other end of the sixth resistor R1 is connected to the negative electrode of the second diode V4; the positive electrode of the first diode V3 is connected to the emitter of the second triode V2.

Description

Technical Field

[0001] The invention belongs to the field of aviation electrical engineering, and in particular relates to a voltage stabilizing circuit adaptable to a wide input voltage. Background Art

[0002] It is relatively easy to find domestic voltage stabilizers that meet the use conditions of aviation products and have an output voltage of 15V and an output current of not less than 300mA. However, the input DC voltage range is generally 18V~30V, and the maximum is 16V~40V or 9V~36V, which cannot meet the requirement of an input DC voltage range of not less than 18V~60V. Therefore, it is necessary to design a circuit to solve the voltage regulation problem under wide input voltage conditions. Summary of the invention

[0003] Purpose of the invention: To provide a voltage stabilizing circuit that is adaptable to a wide input voltage, so as to solve the voltage stabilization problem under wide input voltage conditions.

[0004] Technical solution:

[0005] A voltage stabilizing circuit adapted to wide input voltage includes: a three-terminal voltage stabilizer, 6 resistors, two triodes and two diodes, wherein:

[0006] The voltage detection signal is positively input to one end of the first resistor R1, one end of the third resistor R3, one end of the fourth resistor R4, and one end of the fifth resistor R5;

[0007] The voltage detection signal is negatively input to one end of the second resistor R2, the emitter of the first transistor V1, and the negative end of the three-terminal regulator WY1;

[0008] The other end of the first resistor R1 is connected to the other end of the second resistor R2 and the base of the first transistor V1;

[0009] The other end of the third resistor R3 is connected to the collector of the first transistor V1, the base of the second transistor V2, and one end of the sixth resistor R1;

[0010] The other end of the fourth resistor R4 is connected to the collector of the second transistor V2;

[0011] The other end of the fifth resistor R5 is connected to the positive input end of the three-terminal regulator WY1, the cathode of the first diode V3, and the anode of the second diode V4;

[0012] The other end of the sixth resistor R1 is connected to the cathode of the second diode V4;

[0013] The anode of the first diode V3 is connected to the emitter of the second transistor V2.

[0014] Further, R5 is the ratio of the difference between the minimum value of the voltage detection signal and the lower limit of the voltage at the positive input terminal of the three-terminal regulator WY1 to the input current of the three-terminal regulator WY1.

[0015] Furthermore, the transistors V1 and V2 are 3DK9D transistors.

[0016] Furthermore, diodes V3 and V4 are BZG05H diodes.

[0017] Furthermore, the three-terminal voltage regulator WY1 is a CW78M15K type voltage regulator.

[0018] Furthermore, when the voltage detection signal Ui exceeds a first predetermined value, the voltage division value corresponding to R2 makes the base voltage of the first transistor V1 greater than the turn-on voltage, and the first predetermined value makes the positive input terminal of the three-terminal regulator WY1 not exceed the upper limit.

[0019] Furthermore, when the voltage detection signal Ui is between the second predetermined value and the first predetermined value, the resistance of the third resistor R3 enables the second transistor V2 to be reliably turned on, and the second predetermined value is that the current flowing through the fifth resistor R5 is equal to the input current of the three-terminal regulator WY1.

[0020] Furthermore, the second predetermined value is greater than 18.5V.

[0021] Beneficial effects:

[0022] The invention is economical, practical, and easy to implement. It solves the voltage stabilization problem under a wide input voltage. First, a three-terminal voltage stabilizer WY1 with a low price and good versatility is selected as the voltage stabilization source, and a resistor R5 is connected in series at its input end to reduce the voltage and limit the current.

[0023] 1) In the range where the input voltage Ui is low, the voltage difference across the resistor R5 is small, so the current flowing through R5 is also small, which cannot meet the input current (or input power) requirement of WY1. By designing a branch consisting of resistor R4, the collector-emitter of transistor V2, and diode V3, and connecting it in parallel with the resistor R5 branch, the line voltage drop is reduced, and the required current can be provided to WY1, thus solving this problem;

[0024] 2) In the range where the input voltage Ui is high, the input voltage of WY1 also increases accordingly. In order to prevent the input voltage of WY1 from exceeding the specified value, a larger voltage difference is required across the resistor R5, which means that the current flowing through R5 must also increase accordingly. However, in this state, the input current required by WY1 is relatively small. In order to resolve this contradiction, the current flowing through R5 is shunted by designing the diode V4, resistor R6, and collector-emitter branch of the transistor V1, which solves this problem well.

[0025] 3) In the range of low input voltage Ui, the voltage divider circuit composed of resistors R1 and R2 makes transistor V1 in the cut-off state. In the range of high input voltage Ui, transistor V1 is turned on, and the reverse voltage formed between the collector of V1 and the input of WY1 cleverly achieves the goal of turning off V2. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the cross-linking signal of the "ground power monitoring unit";

[0027] Figure 2 It is a schematic diagram of a voltage stabilizing circuit adapted to a wide input voltage according to the present invention. DETAILED DESCRIPTION

[0028] 1Aircraft ground power supply

[0029] Ground power (also called external power) is the source of power for an aircraft when it is parked on the ground. Almost all aircraft use ground power. Ground power is introduced into the aircraft power grid through the ground power socket installed on the aircraft. Ground power is divided into:

[0030] a) AC ground power supply (rated phase voltage is 115V, 400Hz, three-phase four-wire);

[0031] b) DC ground power supply (rated voltage is 28V and rated voltage is 270V).

[0032] 2 DC ground power supply monitoring unit

[0033] In order to protect electrical equipment and isolate faults when the ground power supply is abnormal, aircraft are equipped with a "ground power monitoring unit", which is an electrical product composed of electronic components and has independent functions. According to the different types of monitored power supplies, the "ground power monitoring unit" is divided into "AC ground power monitoring unit" and "DC ground power monitoring unit". This patent mainly involves a "DC ground power monitoring unit" with a rated voltage of 28V.

[0034] The main function of the "DC ground power supply monitoring unit" is to control the DC ground power supply contactor to disconnect or not connect when overvoltage, undervoltage, short circuit, or reverse polarity fault is detected in the DC ground power supply. For the cross-linking signal relationship, refer to Figure 1 . Figure 1 On the left is a schematic diagram of an external DC working power supply for the "DC ground power supply monitoring unit". This power supply generally comes from a battery or the output of a ground power transformer rectifier (EPTRU); on the right is a schematic diagram of an external DC working power supply that is not provided. In this case, only the "voltage detection signal" can be used as the "working power supply", that is, the voltage signal of the monitored power supply is used as its own working power supply.

[0035] 3. Power supply circuit in DC ground power supply monitoring unit

[0036] In order to make the "DC ground power supply monitoring unit" work stably and reliably, the working power supply is generally selected at 15V. Figure 1 In the case on the left, since the external DC working voltage is generally in the range of 22V to 29V, most 15V voltage regulators can be used. Figure 1 The situation on the right is not acceptable, because according to the relevant standards, the normal voltage range of the DC ground power supply at the detection point is 24V~29V, and in emergency state it is 18V~29V, and the overvoltage protection action point is around 31.4V. In actual assessment, the overvoltage protection function test voltage is generally selected at multiple points within the range of 31.4V~60V for testing. This means that the "DC ground power supply monitoring unit" must work normally when the input DC voltage is within the range of 18V~60V.

[0037] It is difficult to find domestically produced voltage stabilizing devices that meet the use conditions of aviation products, have an input DC voltage range of not less than 18V to 60V, an output voltage of 15V, and an output current of not less than 300mA.

[0038] In order to meet the requirements of input voltage Ui=18V~60V, output voltage Uo=15V±0.7V, output current Io≈300mA, the circuit designed by this patent is shown in Figure 2 , which consists of resistors R1 to R6, transistors V1 and V2, diodes V3 and V4, and a three-terminal regulator WY1 (input voltage range is 18V to 30V, and the output voltage is typically 15V). The technical concept is briefly described as follows:

[0039] 1) During the entire operation of the "DC ground power supply monitoring unit", the output power of the voltage regulator WY1 does not change much, so the input power demand of WY1 is basically constant, that is, the product of the input voltage and the input current is basically constant. For this reason, the input voltage is divided into two sections, 18V~U1 is the low input voltage area (indicated by UL), and U1~60V is the high input voltage area (indicated by UH);

[0040] 2) In the UL area, in order to control the input voltage of the voltage regulator WY1 within the specified range and provide the required input current for WY1, a branch consisting of resistor R4, the collector-emitter of transistor V2, and diode V3 is used to provide the required input for WY1, and the voltage drop of the branch should be relatively small;

[0041] 3) In the UH region, in order to ensure that the input voltage of the voltage regulator WY1 does not exceed 30V, the resistor R5 branch is used to reduce the voltage. However, since Ui is relatively high in this state, the current flowing through the R5 branch is relatively large, which exceeds the input current requirement of WY1, so the diode V4, resistor R6, and the collector-emitter branch of the transistor V1 are designed for shunting. At the same time, the branch composed of the resistor R4, the collector-emitter of the transistor V2, and the diode V3 is closed.

[0042] Figure 2 The working principle of the circuit is briefly described as follows:

[0043] 1) In the UL region, the input voltage Ui is less than U1, and the voltage divider circuit composed of resistors R1 and R2 makes the base voltage of transistor V1 lower than its turn-on voltage. Transistor V1 is in the cut-off state, and no current flows through resistor R6 and diode V4. The voltage difference across resistor R5 enables resistor R3 to provide the required base voltage and current for turning on transistor V2, and V2 turns on. The R5 branch and the branch composed of R4, the collector-emitter of V2, and V3 simultaneously supply power to WY1;

[0044] 2) In the UH region, the input voltage Ui>U1, the voltage divider circuit composed of R1 and R2 makes the base voltage of V1 higher than its turn-on voltage, V1 is turned on, and the current flowing through the R5 branch is shunted through the collector-emitter branch of V4, R6, and V1. At the same time, because the collector voltage of V1 is lower than the input voltage of WY1, the base-emitter junction of the transistor V2 is subjected to reverse voltage and is cut off, V2 is turned off, and no current flows through the branch composed of R4, the collector-emitter of V2, and V3.

[0045] The invention is economical, practical and easy to implement. The purpose is to solve the voltage stabilization problem under wide input voltage. First, a three-terminal voltage stabilizer WY1 with low price and good versatility is selected as the voltage stabilization source, and a resistor R5 is connected in series at its input end to reduce the voltage and limit the current. However:

[0046] 1. In the range of low input voltage Ui, the voltage difference across resistor R5 is small, so the current flowing through R5 is also small, which cannot meet the input current (or input power) requirement of WY1. By designing a branch consisting of resistor R4, collector-emitter of transistor V2, and diode V3, and connecting it in parallel with the resistor R5 branch, the line voltage drop is reduced and the required current can be provided to WY1, thus solving this problem.

[0047] 2. In the range where the input voltage Ui is high, the input voltage of WY1 also increases accordingly. In order to prevent the input voltage of WY1 from exceeding the specified value, a larger voltage difference is required across the resistor R5, which means that the current flowing through R5 must also increase accordingly. However, in this state, the input current required by WY1 is relatively small. In order to resolve this contradiction, the current flowing through R5 is shunted by designing the diode V4, resistor R6, and collector-emitter branch of the transistor V1, which solves this problem well.

[0048] 3. In the range of low input voltage Ui, the voltage divider circuit composed of resistors R1 and R2 makes transistor V1 in the cut-off state. In the range of high input voltage Ui, transistor V1 is turned on, and the reverse voltage formed between the collector of V1 and the input of WY1 cleverly achieves the goal of turning off V2.

[0049] Device parameter selection principles:

[0050] The resistance values ​​of resistors R1 and R2 should be determined according to the voltage division ratio corresponding to the determined voltage value of U1;

[0051] The resistor R3 should be determined according to the current value required for V2 to conduct reliably;

[0052] The resistor R4 should be considered according to the input current required by WY1 when V2 is turned on, as well as the voltage drop of the R4, V2, and V3 branches, and the effect of parallel connection with R5 should also be considered;

[0053] The determination of the resistance value of resistor R5 should mainly consider the voltage drop of R5 when the input voltage Ui>U1, and the influence of parallel connection with R4, V2, and V3 branches when V2 is turned on;

[0054] The resistance value of resistor R6 should be determined by considering the collector current that V1 can withstand when it is in the on state, and the current value that should be shunted from the R5 branch in this state;

[0055] Transistors V1 and V2 can use 3DK9D;

[0056] Diodes V3 and V4 can be made of BZG05H;

[0057] The model of the three-terminal regulator WY1 is CW78M15K.

[0058] Implementation Examples

[0059] Figure 2 The circuit has been successfully used in the "external power monitor" of a certain type of military aircraft. Hundreds of units have been produced and have been in service for several years with good results.

Claims

1. A voltage stabilizing circuit adapted to a wide input voltage, characterized in that: include: Three-terminal voltage regulator, 6 resistors, two transistors and two diodes, among which, The voltage detection signal is positively input to one end of the first resistor R1, one end of the third resistor R3, one end of the fourth resistor R4, and one end of the fifth resistor R5; The voltage detection signal is negatively input to one end of the second resistor R2, the emitter of the first transistor V1, and the negative end of the three-terminal regulator WY1; The other end of the first resistor R1 is connected to the other end of the second resistor R2 and the base of the first transistor V1; The other end of the third resistor R3 is connected to the collector of the first transistor V1, the base of the second transistor V2, and one end of the sixth resistor R6; The other end of the fourth resistor R4 is connected to the collector of the second transistor V2; The other end of the fifth resistor R5 is connected to the positive input end of the three-terminal regulator WY1, the cathode of the first diode V3, and the anode of the second diode V4; The other end of the sixth resistor R6 is connected to the cathode of the second diode V4; The anode of the first diode V3 is connected to the emitter of the second transistor V2.

2. The voltage stabilizing circuit according to claim 1, characterized in that: R5 is the ratio of the difference between the minimum value of the voltage detection signal and the lower limit of the voltage at the positive input terminal of the three-terminal regulator WY1 to the input current of the three-terminal regulator WY1.

3. The voltage stabilizing circuit according to claim 1, characterized in that: Transistors V1 and V2 are 3DK9D transistors.

4. The voltage stabilizing circuit according to claim 1, characterized in that: Diodes V3 and V4 are BZG05H diodes.

5. The voltage stabilizing circuit according to claim 1, characterized in that: The three-terminal voltage regulator WY1 is a CW78M15K type voltage regulator.

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