CN104426127B - A kind of load starting circuit - Google Patents

Abstract

The invention provides a kind of load starting circuit, including：Input, including input anode and input cathode, for receiving electric energy from power supply；Output end, including output head anode and negative pole of output end, for providing electric energy to load；Energy-storage units, it is connected between input anode and input cathode, and for providing electric energy to output head anode and negative pole of output end；Switch element, for control output end whether to load provide electric energy；And under-voltage detection and control unit, for detecting the energy in the energy-storage units, and according to the disconnection or conducting of the testing result control switch element.Load starting circuit provided by the invention, can proof load normal work, stepped starting need not be loaded again.

Description

A load starting circuit

technical field

The invention relates to a load starting circuit, in particular to a load starting circuit which does not require load classification starting.

Background technique

For a load connected to a DC voltage source, the maximum power of the load should be equal to or less than the maximum power of the power supply. However, the power of the startup process of some loads may exceed the maximum power of the power supply. In this way, the output voltage of the power supply will decrease. For some loads (such as digital chips), this voltage drop can cause component failure (such as failure to start) or even damage. In this case, the load cannot be started normally.

At present, a common load starting circuit includes a current limiting unit (as shown in Figure 1) to limit the load current exceeding a certain threshold, thereby avoiding a voltage drop. However, this circuit does not take into account the type of load whose starting current is greater than the normal operating current. If such a circuit is placed before a load of the type mentioned above, the load may not start properly due to current limitation. One solution is to use load classification to start different loads at different times. Figure 2 shows a comparison of power demand for an unstaged start-up (a) and a staged start-up (b). Among them, the starting time of the load classification starting will be longer, but the starting power demand will be smaller, thereby reducing the starting power demand at the moment of starting. However, the structure of the load classification starting circuit is relatively complicated, the cost is high, software control is also required, and the reliability is low.

Contents of the invention

The invention aims to provide a load starting circuit, which can ensure the normal operation of the load and does not need the load starting in stages.

The present invention provides a DC load starting circuit, comprising:

The input terminal, including the positive pole of the input terminal and the negative pole of the input terminal, is used to receive electric energy from the power supply;

The output terminal, including the positive pole of the output terminal and the negative pole of the output terminal, is used to provide electric energy to the load;

The energy storage unit is connected between the positive pole of the input terminal and the negative pole of the input terminal, and is used to provide electric energy to the positive pole of the output terminal and the negative pole of the output terminal;

a switch unit for controlling whether the output terminal provides electric energy; and

an undervoltage detection and control unit, configured to detect the energy in the energy storage unit, and control the switching unit to be turned off or on according to the detection result,

Wherein, when the energy of the energy storage unit is lower than a threshold, the undervoltage detection and control unit controls the switch unit to be in an off state; when the energy of the energy storage unit is greater than or equal to a threshold, the The undervoltage detection and control unit controls the switch unit to be in a conduction state. When the switch unit is turned on, the energy storage unit supplies power to the load together with the power supply. If the starting power of the load is greater than the maximum power of the power supply, the additional starting power required can be provided by the energy storage unit. Even if the starting power of the load is greater than the maximum power of the power supply, the voltage drop can be avoided and the load can be guaranteed large enough current.

According to the load starting circuit provided by the present invention, the energy stored in the energy storage unit is zero at the beginning of starting.

According to the load starting circuit provided by the present invention, the energy storage unit is composed of a capacitor.

According to the load starting circuit provided by the present invention, the switch unit is composed of an electronic switch or a mechanical switch.

The load starting circuit provided by the present invention further includes a current limiting unit, which is used to limit the current flowing into the input terminal.

According to the load starting circuit provided by the present invention, wherein the undervoltage detection and control unit includes a voltage divider and a hysteresis comparator, the voltage divider is connected in parallel to the energy storage unit, and provides the hysteresis comparator with Input voltage.

According to the load starting circuit provided by the present invention, the voltage divider is composed of two or more resistors connected in series.

According to the load starting circuit provided by the present invention, the current limiting unit includes a three-terminal voltage regulator and a resistor.

The present invention also provides a load starting device, comprising two or more load starting circuits as claimed in claim 1, each load starting circuit is connected in parallel with each other, and respectively starts the corresponding loads.

According to the load starting device provided by the present invention, the starting time of each switch unit in each load starting circuit is different.

According to the load starting device provided by the present invention, the switch unit corresponding to the load with relatively high priority is turned on before the switch unit corresponding to the load with relatively low priority. Therefore, start the load with high priority first, and then start the load with low priority, so that the power is not greater than the power of the power supply

According to the load starting device provided by the present invention, the energy thresholds of the energy storage units in each load starting circuit are different.

According to the load starting device provided by the present invention, the threshold value of the energy storage unit corresponding to the load with relatively high priority is lower than the threshold value of the energy storage unit corresponding to the load with relatively low priority. Therefore, the energy storage unit corresponding to the load with relatively high priority reaches the threshold earlier, and then the switch unit corresponding to the load with relatively higher priority is turned on earlier.

The load start-up circuit provided by the invention can provide more start-up current to the load during start-up without overloading the power supply, and loads with start-up power greater than the normal power and the power supply can be perfectly started. This can not only ensure the normal operation of the load, but also does not require load classification. At the same time, the included under-voltage detection circuit can not only control the start-up process, but also prevent the load from working under abnormal voltage conditions. In addition, compared with load classification starting, the load starting circuit provided by the present invention has simple structure, low cost, does not need software control, and has high reliability.

Description of drawings

The following drawings are only intended to illustrate and explain the present invention schematically, and do not limit the scope of the present invention. in,

Fig. 1 is a load starting circuit including a current limiting unit in the prior art;

Fig. 2 is the power demand of ungraded startup (a) and graded startup (b) in the prior art;

Fig. 3 is a schematic structural diagram of a load starting circuit according to the present invention;

4 is a schematic structural diagram of a load starting circuit according to Embodiment 1;

5 is a schematic structural diagram of a load starting circuit according to Embodiment 2;

Fig. 6 is a schematic structural diagram of a plurality of load starting circuits according to an embodiment of the present invention.

List of reference signs

Power supply P; load L; current limiting unit 1, 11, 31, 41; switching unit 2, 12, 22, 32, 42; energy storage unit 3, 13, 23, 33, 43; undervoltage detection and control unit 4, 14, 24, 34, 44; resistors R1, R2, R3, R4; three-terminal regulators 11a, 21a, hysteresis comparator HC

detailed description

The invention provides a DC load starting circuit for starting a load L under the action of a power supply P. The structure of the load starting circuit is shown in FIG. 3 , including a current limiting unit 1 , a switching unit 2 , an energy storage unit 3 and an undervoltage detection and control unit 4 . The positive pole I+ and the negative pole I− of the input terminal of the load starting circuit are connected to a power source P to receive power from the power source P. The positive pole O+ and the negative pole O− of the output terminal of the load start-up circuit are connected to the load L for supplying electric energy to the load. When the load L is connected between the positive pole O+ and the negative pole O- of the output terminal, the energy storage unit 3 is connected in parallel with the load L, and after parallel connection, it is connected in series with the current limiting unit 1 between the positive pole I+ and the negative pole I- of the input terminal of the power supply P . The disconnection or conduction of the switch unit 2 determines whether the output end supplies electric energy to the load L. The undervoltage detection and control unit 4 is used to detect the energy of the energy storage unit 3. When the energy of the energy storage unit 3 does not reach a certain energy threshold, the undervoltage detection and control unit 4 controls the switch unit 2 to be in the disconnected state. When the energy of the energy unit 3 reaches the energy threshold, the undervoltage detection and control unit 4 controls the switch unit 2 to be in a conduction state.

At the start, the energy stored in the energy storage unit 3 is zero, and the undervoltage detection and control unit 4 will turn off the switch unit 2 so that the output terminal does not provide electric energy to the load L. Then, the energy storage unit 3 will be charged by the power source P and finally reach a certain energy threshold. When the energy storage unit reaches the energy threshold, the undervoltage detection and control unit 4 will turn the switch unit 2 into a conduction state, so that the output terminal provides electric energy to the load L. At this time, the energy storage unit 3 and the power supply P supply power to the output terminal powered by. In this way, if the start-up power of the load L is greater than the maximum power of the power supply P, the additional start-up power required by it can be provided by the energy storage unit 3 (instead of all being directly provided by the power supply P). Since the energy storage unit 3 provides additional power to complete the process of starting the load L, even if the starting power of the load L is greater than the maximum power of the power supply P, the voltage drop can be avoided and the load L can be guaranteed to receive a large enough current.

In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation manners of the present invention will now be described with reference to the accompanying drawings.

Example 1

This embodiment provides a load starting circuit for starting a load L under the action of a power supply P. The structure of the load starting circuit is shown in FIG. 4 , including a current limiting unit 11 , a switching unit 12 , an energy storage unit 13 and an undervoltage detection and control unit 14 .

The energy storage unit 13 is connected in parallel with the load L, and is connected in series with the current limiting unit 11 between the positive and negative poles of the power supply P after the parallel connection. The energy storage unit 13 is composed of a capacitor.

The switch unit 12 is located between the load L and the current limiting unit 11, and includes a PMOS transistor and a resistor R4. The source and drain of the PMOS transistor are respectively connected to the current limiting unit 11 and the load L, for connecting the load L to the current limiting The unit 11 is disconnected or disconnected from the current limiting unit 11 , ie for connecting or disconnecting the load L to or from the power supply P. The resistor R4 is connected in parallel between the source and the gate of the PMOS transistor.

The undervoltage detection and control unit 14 includes a voltage divider composed of a resistor R2 and a resistor R3 and a hysteresis comparator HC. The resistor R2 and the resistor R3 are connected in parallel to the energy storage unit 13 after being connected in series. The hysteresis comparator HC consists of an integrated operational amplifier, the first input of which is connected between the resistors R2 and R3, and the second input is connected to the reference voltage V _ref to compare the voltage between the resistors R2 and R3 with the reference Voltage V _ref , the output end of the hysteresis comparator HC is connected to the gate of the PMOS transistor of the switch unit 12 . Wherein the reference voltage V _ref is set as: when the voltage between the resistor R2 and the resistor R3 is lower than a certain voltage threshold V _th , the voltage output from the comparator HC to the gate of the PMOS transistor turns off the switch unit 12; when When the voltage between the resistor R2 and the resistor R3 is greater than or equal to a certain voltage threshold V _th , the voltage output from the comparator HC to the gate of the PMOS transistor turns on the switch unit 12 .

The current limiting unit 11 includes a three-terminal regulator 11a (in this embodiment a three-terminal regulator of the type LM317L) and a resistor R1, the voltage difference between _Vout and GND of the three-terminal regulator will not exceed a certain threshold (For example, for the three-terminal voltage regulator of the LM317L model, the threshold value is 1.2V), using this characteristic, the current flowing through the resistor R1 connected between V _out and GND is limited, for example, in this embodiment will not exceed 1.2V/R1.

At the beginning of starting, the energy of the capacitor in the energy storage unit 13 is zero, at this moment, the hysteresis comparator HC in the undervoltage detection and control unit 14 will make the switch unit 12 open, so that the load L and the external The circuit is disconnected. Then, the energy storage unit 13 will be charged by the power supply P, so that the voltage applied between the resistor R2 and the resistor R3 will gradually increase. When it reaches the voltage threshold _Vth , the comparator in the undervoltage detection and control unit 14 will The HC will turn on the switch unit 12 to connect the load L to an external circuit, thereby being activated. In this way, if the start-up power of the load L is greater than the maximum power of the power supply P, the additional start-up power required by it can be provided by the energy storage unit 13 (instead of all being directly provided by the power supply P). Since the energy storage unit 13 provides additional power to complete the process of starting the load L, even if the starting power of the load L is greater than the maximum power of the power supply P, the voltage drop can be avoided and the load L can be guaranteed to receive a large enough current.

Example 2

The load starting circuit provided by the present invention may also not have a current limiting unit. For example, for some power supplies, in order to avoid voltage drop, a current limiting unit is integrated inside the power supply. For this kind of power supply, the current limiting unit can be omitted in the load starting circuit provided by the present invention. For another example, for some power supplies, it exhibits the characteristic of "current limit" to the outside, that is, when the current reaches a certain upper threshold, the current is limited to prevent voltage drop. For this kind of power supply, the current limiting unit can also be omitted in the load starting circuit provided by the present invention.

Therefore, for this kind of power supply, the present embodiment provides a load starting circuit without a current limiting unit, which can avoid the situation that the load cannot be started due to insufficient current. The structure of the load starting circuit is shown in FIG. 5 , including a switch unit 22 , an energy storage unit 23 and an undervoltage detection and control unit 24 .

Wherein the energy storage unit 23 and the load L are connected in parallel between the positive and negative poles of the power supply P, and the energy storage unit 23 is composed of a capacitor.

There is a switch unit 22 between the load L and the power supply P, and the switch unit 22 is composed of two PMOS transistors and a resistor R4 for connecting the load L to the power supply P or disconnecting it from the power supply P.

The undervoltage detection and control unit 24 includes a voltage divider composed of resistors R2 and R3 and a hysteresis comparator HC. The resistor R2 and the resistor R3 are connected in parallel to the energy storage unit 23 after being connected in series. The comparator HC is formed by an integrated operational amplifier, its first input terminal is connected between the resistor R2 and the resistor R3, and its second input terminal is connected to the reference voltage V _ref to compare the voltage between the resistor R2 and the resistor R3 with the reference voltage V _ref , the output terminal of the hysteresis comparator HC is connected to the switching unit 22 . Wherein the reference voltage V _ref is set as: when the voltage between the resistor R2 and the resistor R3 is lower than a certain voltage threshold _Vth , the voltage output from the comparator HC to the switch unit 12 makes the switch unit 22 open; when the resistor R2 When the voltage between the resistor R3 and the resistor R3 is greater than or equal to a certain voltage threshold V _th , the voltage output from the comparator HC to the switch unit 22 turns on the switch unit 22 .

At the beginning of starting, the energy of the capacitor in the energy storage unit 23 is zero, at this moment, the comparator HC in the undervoltage detection and control unit 24 will make the switch unit 22 be in the disconnected state, thereby disconnecting the load L from its external circuit. Open the connection. Then, the energy storage unit 23 will be charged by the power supply P, so that the voltage applied between the resistor R2 and the resistor R3 will gradually increase, and when it reaches the voltage threshold _Vth , the hysteresis in the undervoltage detection and control unit 24 The comparator HC turns on the switch unit 22 to connect the load L to an external circuit, thereby being activated. In this way, if the start-up power of the load L is greater than the maximum power of the power supply P, the additional start-up power required by it can be provided by the energy storage unit 23 (instead of all being directly provided by the power supply P). Since the energy storage unit 23 provides additional power to complete the process of starting the load L, even if the starting power of the load L is greater than the maximum power of the power supply P, the voltage drop can be avoided and the load L can be guaranteed to receive a large enough current.

According to other embodiments of the present invention, the current limiting unit is not limited to the structures in the above embodiments, and may also be other circuit components known in the art that function to limit the current.

According to other embodiments of the present invention, the switch unit is not limited to the structure in the above-mentioned embodiments, except for the electronic switches composed of electronic components such as transistors used in the above-mentioned embodiments, known in the art can also be used Other switch configurations, such as mechanical switch configurations. The connection manner of the switch unit in the circuit is not limited to the manner described in the above embodiments. The present invention can be realized as long as it is a switch unit arranged to be able to switch the load L between the power-on state and the power-off state under the control of the undervoltage detection and control unit.

According to other embodiments of the present invention, the energy storage unit is not limited to the capacitor described in the above embodiments, and may also be other circuit components known in the art capable of storing energy.

According to other embodiments of the present invention, the undervoltage detection and control unit is not limited to the structure described in the above embodiments, for example, the voltage divider may include 3 or more resistors, and the hysteresis comparator The first end is connected between two of the resistors. The undervoltage detection and control unit can also be other components known in the prior art that can realize undervoltage detection and control. The undervoltage detection and control unit is not limited to the connection method described in the above-mentioned embodiments, for example, in addition to being powered by the power supply P in the above-mentioned embodiment, the undervoltage detection and control unit can also be powered by an external power source other than the power supply P Mains powered. The present invention can be implemented as long as the undervoltage detection and control unit is arranged to be triggered after the energy of the energy storage unit reaches a certain threshold and controls the switch unit to conduct.

The load starting circuit provided by the present invention can also be applied in the case of multiple loads to solve the problem of starting multiple loads. For example, as shown in FIG. 6, the power supply P can respectively start two loads L1 and L2 by using two load starting circuits C1 and C2, wherein the load starting circuit C1 includes a current limiting unit 31, a switching unit 32, an energy storage unit 33 and an undervoltage The detection and control unit 34 , the load starting circuit C2 includes a current limiting unit 41 , a switch unit 42 , an energy storage unit 43 and an undervoltage detection and control unit 44 .

In addition, when the application is in the case of multiple loads, multiple loads can be divided into different startup priorities according to the importance of the loads: the priority of critical loads is high, such as L1; the priority of non-critical loads is low, such as L2. For a load with high priority, such as L1, its corresponding load start circuit C1 is set to start the load earlier than the load circuit C2, that is, the switch unit 32 is turned on earlier than the switch unit 31 . For example, the threshold of the energy storage unit 33 can be lower than the threshold of the energy storage unit 43 , so that the threshold of the energy storage unit 33 reaches earlier, and then the switch unit 32 is turned on earlier than the switch unit 31 . In this case, when starting, the switch unit 32 that supplies power to the critical load L1 is turned on first, and the switch unit 42 that supplies power to the non-critical load L2 is turned on later, so that the load with a higher priority is started first, and the load with a higher priority is started later. Low load, so that the power is not greater than the power of the power supply.

The load start-up circuit provided by the invention can provide more start-up current to the load during start-up without overloading the power supply, and loads with start-up power greater than the normal power and the power supply can be perfectly started. This can not only ensure the normal operation of the load, but also does not require load classification. At the same time, the included under-voltage detection circuit can not only control the start-up process, but also prevent the load from working under abnormal voltage conditions. In addition, compared with load classification starting, the load starting circuit provided by the present invention has simple structure, low cost, does not need software control, and has high reliability.

It should be understood that although this description is described according to various embodiments, not each embodiment only includes an independent technical solution, and this description of the description is only for clarity, and those skilled in the art should take the description as a whole , the technical solutions in the various embodiments can also be properly combined to form other implementations that can be understood by those skilled in the art.

The above descriptions are only illustrative specific implementations of the present invention, and are not intended to limit the scope of the present invention. Any equivalent changes, modifications and combinations made by those skilled in the art without departing from the concept and principle of the present invention shall fall within the protection scope of the present invention.

Claims (13)

1. A dc load start-up circuit comprising:

an input terminal comprising an input terminal anode and an input terminal cathode for receiving electrical energy from a power source;

the output end comprises an output end anode and an output end cathode and is used for supplying electric energy to the load;

the energy storage unit (3, 13, 23, 33, 43) is connected between the positive pole of the input end and the negative pole of the input end and is used for supplying electric energy to the positive pole of the output end and the negative pole of the output end;

a switching unit (2, 12, 22, 32, 42) for controlling whether the output terminal supplies the power to the load; and

the undervoltage detection and control unit (4, 14, 24, 34, 44) is used for detecting the energy in the energy storage unit and controlling the switch-off or switch-on of the switch unit according to the detection result;

when the energy of the energy storage unit is lower than a threshold value, the undervoltage detection and control unit controls the switch unit to be in an off state, and when the energy of the energy storage unit is larger than or equal to the threshold value, the undervoltage detection and control unit controls the switch unit to be in an on state, an

Wherein the under-voltage detection and control unit comprises a voltage divider and a hysteresis comparator, the voltage divider is connected in parallel to the energy storage unit and provides an input voltage to the hysteresis comparator.

2. A load starting circuit according to claim 1, wherein the energy stored in the energy storage unit is zero at the start of starting.

3. The load start-up circuit of claim 1, wherein the energy storage unit comprises a capacitor.

4. The load start-up circuit of claim 1, wherein the switching unit comprises an electronic switch.

5. The load startup circuit of claim 1, wherein the switching unit comprises a mechanical switch.

6. The load start-up circuit of claim 1, further comprising a current limiting unit for limiting the current flowing in the input terminal.

7. The load startup circuit of claim 1 wherein the voltage divider is comprised of two or more resistors connected together in series.

8. The load start-up circuit of claim 6, wherein the current limiting unit comprises a three-terminal regulator and a resistor.

9. A load starting apparatus comprising two or more load starting circuits according to claim 1, each load starting circuit being connected in parallel with each other to start a respective corresponding load.

10. The load starting apparatus of claim 9, wherein the start times of the respective switching elements in the respective load starting circuits are different.

11. The load starting apparatus of claim 10, wherein the switch unit corresponding to the load with the relatively high priority is turned on before the switch unit corresponding to the load with the relatively low priority.

12. The load starting apparatus of claim 9, wherein the threshold of energy of the energy storage unit in each load starting circuit is different.

13. A load starting apparatus as claimed in claim 12, wherein the threshold of the energy storage unit corresponding to a load of relatively high priority is lower than the threshold of the energy storage unit corresponding to a load of relatively low priority.