Self-adaptive current limiting control circuit

Abstract

The utility model discloses a self-adaptive current-limiting control circuit, which belongs to the technical field of current-limiting control circuits, accurately controls the conduction of a P-type MOS (Metal Oxide Semiconductor) tube by monitoring the charging voltage of a C3, and simultaneously introduces a self-locking control method of a Q4 and a Q8, so that the Q1 does not repeatedly act due to the fluctuation of the input voltage, and the self-adaptive current-limiting control circuit has the advantages of simple structure and low cost. And a circuit formed by the D8, the D13, the D14, the divider resistors R20, R19 and Q6 can also protect the Q1 from being impacted by the surge to the greatest extent, so that the reliability of the circuit is improved, and compared with the prior art, the circuit can obviously reduce the loss generated by the current-limiting resistor, and can not be influenced by the environment temperature.

Description

Technical Field

[0001] This utility model relates to a current limiting control circuit, and more particularly to an adaptive current limiting control circuit, belonging to the technical field of current limiting control circuits. Background Technology

[0002] In the rectifier circuit of a switching power supply system, a large-capacity electrolytic capacitor typically provides energy to the subsequent conversion circuit to ensure sufficient sustainment time and minimal ripple voltage after power failure. However, due to the presence of this large-capacity electrolytic capacitor, the voltage across it cannot change abruptly during startup, effectively creating a short circuit. This results in a very large inrush current, which could potentially burn out the input fuse or trigger the input circuit breaker. To mitigate the impact of this inrush current, a power resistor (or NTC / PTC resistor) is typically connected in series in the input power circuit of a switching power supply to limit the startup current.

[0003] Common control methods currently include Figure 1 As shown, a power resistor (or NTC or PTC resistor) with a large resistance value is connected in series in the input circuit to suppress the inrush current generated at the moment of startup.

[0004] The shortcomings of existing technologies:

[0005] 1) If a regular power resistor is connected in series in the power circuit to suppress inrush current, due to the presence of this resistor, the circuit will always have a fixed loss once it is working, P = I. 2 The magnitude of loss depends on the resistor value, input voltage, and output power. Lower input voltage results in greater loss; higher output power or higher resistance also leads to greater loss. Therefore, this reduces system efficiency and, at low input voltages, affects the system's load-carrying capacity.

[0006] 2) While inserting an NTC (negative temperature coefficient) or PTC (positive temperature coefficient) thermistor in series in the circuit can suppress inrush current, the resistance of an NTC resistor is several times higher at low temperatures than at room temperature. The system can generally operate normally at 0℃ or -20℃, but at -40℃, the resistance increases dramatically, posing a risk that the system will not be able to start under load. Similarly, the resistance of a PTC resistor increases with temperature; at 70℃ or 85℃, its resistance increases sharply, significantly affecting the system's load-carrying capacity. Therefore, this solution has limited applicability to certain temperature environments.

[0007] 3) Medium-power switching power supplies (hundred-watt level) typically have a common resistor connected in series in the power circuit. After the power supply starts up, a relay short-circuits this resistor (e.g., ...).Figure 2 The scheme can play a current limiting role and does not affect system efficiency and load capacity, but the relay needs a special chip drive and is large in size and high in cost, and in addition, a large "attracting" sound is generated when the contact is operated, and the contact resistance between the contacts is increased with the increase of the number of contact operations, thereby affecting reliability. Practical new type content

[0008] The main purpose of the utility model is to provide a self-adaptive current limiting control circuit.

[0009] The purpose of the utility model can be achieved by adopting the following technical scheme:

[0010] A self-adaptive current limiting control circuit, comprising a rectifier bridge, one end of R2, 3 feet of Q1, the cathode of Z1, one end of R5, the cathode of D8 are connected to the rectifier bridge;

[0011] The anode of Z1 is connected to the other end of R5, 1 foot of Q1 and one end of R8;

[0012] 2 feet of Q1 are connected to one end of R11, the anode of C3 and a switching power supply converter.

[0013] Preferably, the anode of D8 is connected to the cathode of D13, the anode of D13 is connected to the cathode of D14, the anode of D14 is connected to one end of R26, the other end of R26 is connected to one end of R19 and one end of C8, and 1 foot of Q6.

[0014] Preferably, the other end of R15 is connected to the cathode of D15 and one end of R18, and the anode of D15 is connected to one end of R12 and 1 foot of Q4.

[0015] Preferably, 3 feet of Q4 are connected to the anode of D16, 1 foot of Q5 is connected to the other end of R13 and one end of R17, 3 feet of Q5 are connected to one end of R23 and one end of C6, the other end of R17 is connected to 2 feet of U1, one end of R20 and one end of R25 are connected to 1 foot of U1.

[0016] Preferably, 3 feet of U1 are connected to one end of R23, one end of R24, one end of C7, 2 feet of Q8, 2 feet of Q6, the other end of C8 and the other end of R19;

[0017] The other end of C7 is connected to 1 foot of Q8 and one end of R22, the other end of R22 is connected to the cathode of D16, one end of C6 and one end of R24, the other end of C6 is connected to one end of R23 and 3 feet of Q5.

[0018] Preferably, the other end of R11 is connected to one end of R16, the other end of R16 is connected to one end of R20, and one end of R20 is connected to the 1-pin of U1.

[0019] The utility model discloses the beneficial technical effects:

[0020] The self-adapting current-limiting control circuit provided by the utility model can accurately control the conduction of the P-type MOS tube by monitoring the charging voltage of C3, and the self-locking control method of Q4 and Q8 is introduced, so that Q1 will not repeatedly act due to the fluctuation of input voltage. The circuit composed of D8, D13, D14, voltage dividing resistor R26, R19 and Q6 can also protect Q1 from the impact of surge to the maximum, thereby improving the reliability of the circuit.

[0021] Compared with the prior art, the circuit can significantly reduce the loss caused by the current-limiting resistor, and can not be affected by the environment temperature on the circuit. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a prior art circuit diagram;

[0023] Figure 2 It is a prior art circuit diagram;

[0024] Figure 3 It is a circuit diagram of a preferred embodiment one of a self-adapting current-limiting control circuit according to the utility model;

[0025] Figure 4 It is a circuit diagram of a preferred embodiment two of a self-adapting current-limiting control circuit according to the utility model;

[0026] Figure 5 It is a circuit diagram of a preferred embodiment three of a self-adapting current-limiting control circuit according to the utility model;

[0027] Figure 6 It is a circuit diagram of a preferred embodiment four of a self-adapting current-limiting control circuit according to the utility model;

[0028] Figure 7 It is a circuit diagram of a preferred embodiment five of a self-adapting current-limiting control circuit according to the utility model DETAILED DESCRIPTION

[0029] In order to make the skilled person in the art more clear and explicit technical scheme of the utility model, the utility model is described in further detail below in combination with embodiments and drawings, but the embodiment of the utility model is not limited thereto.

[0030] The adaptive current limiting control circuit provided by the embodiment comprises a rectifier bridge, one end of R2, pin 3 of Q1, the cathode of Z1, one end of R5, the cathode of D8 are connected to the rectifier bridge;

[0031] The anode of Z1 is connected to the other end of R5, pin 1 of Q1 and one end of R8;

[0032] Pin 2 of Q1 is connected to one end of R11, the anode of C3 and a switching power converter.

[0033] In the embodiment, the anode of D8 is connected to the cathode of D13, the anode of D13 is connected to the cathode of D14, the anode of D14 is connected to one end of R26, the other end of R26 is connected to one end of R19 and one end of C8, pin 1 of Q6.

[0034] In the embodiment, the other end of R15 is connected to the cathode of D15 and one end of R18, the anode of D15 is connected to one end of R12 and pin 1 of Q4.

[0035] In the embodiment, pin 3 of Q4 is connected to the anode of D16, pin 1 of Q5 is connected to the other end of R13 and one end of R17, pin 3 of Q5 is connected to one end of R23 and one end of C6, the other end of R17 is connected to pin 2 of U1, pin 1 of U1 is connected to one end of R20 and one end of R25.

[0036] In the embodiment, pin 3 of U1 is connected to one end of R23, one end of R24, one end of C7, pin 2 of Q8, pin 2 of Q6, the other end of C8 and the other end of R19.

[0037] The other end of C7 is connected to pin 1 of Q8 and one end of R22, the other end of R22 is connected to the cathode of D16, one end of C6 and one end of R24, the other end of C6 is connected to one end of R23 and pin 3 of Q5.

[0038] In the embodiment, the other end of R11 is connected to one end of R16, the other end of R16 is connected to one end of R20, and one end of R20 is connected to pin 1 of U1.

[0039] The resistance R2 in the main power loop is a current limiting resistance, and a P-channel MOS tube is connected to both ends of R2, which replaces R2 after the capacitor charging is completed; the electrolytic capacitor C3 is an energy storage capacitor after rectification. The circuit in the red box is the schematic diagram of the present application, and the detailed working process is as follows:

[0040] When the AC power rectifier bridge rectifies and charges C3 through the current-limiting resistor R2. Because the voltage on the capacitor cannot be changed suddenly, the voltage across C3 is 0 at the moment when the AC power is connected, at this time the voltage sampling circuit composed of R11, R16, R20, R25 and U1 is in the cut-off state, U1 is cut off, so Q5 is also cut off, and the rear Q4 and Q8 are also in the off state, and the P-type MOS tube Q1 is cut off. The current charges C3 through R2, and when the voltage across C3 rises to a set value, the circuit considers that the charging is completed.

[0041] With the completion of the charging of C3, the 2 and 3 pins of U1 begin to conduct, pull down the 1 pin potential of Q5, so that Q5 is turned on, and Vcc charges C6 through R9, Q5 and R24. The charging current will generate a voltage on R24 to trigger Q8 to turn on. Because Q8 is turned on, it pulls down the 1 pin potential of Q1 to make Q1 conduct at 2 and 3, and R2 is shorted by Q1. R2 no longer consumes energy, thereby reducing the loss.

[0042] At the same time, due to the conduction of Q8, the 1 pin potential of Q4 is also pulled down, so that Q4 is also turned on. Vcc will also pass through Q4, D16 and R24 to provide a conduction condition for Q8, so that Q4 and Q8 are in a self-locking state.

[0043] When the power input port is subjected to an abnormal surge impact, in order to protect Q1 from being damaged, the surge signal will pass through D8, D13, D14 and voltage dividing resistors R26 and R19 to make Q6 conduct, causing Vcc to pass through R9 and Q6 to ground, so that Q4 and Q8 are cut off, Q1 is closed, and the surge energy is applied to R2, thereby protecting Q1. After the surge signal disappears, Q6 is cut off, and the control circuit will work again.

[0044] Example Two

[0045] As shown in Figure 4 , the current-limiting resistor R2 is placed at the "ground" end of the power circuit, and Q1 is replaced by an N-channel MOS tube. The control circuit is basically the same, and the circuit working process is also the same. All the functions of the present application can be realized.

[0046] Example Three

[0047] As shown in Figure 5 , the current-limiting resistor R2 is placed at the "ground" end of the power circuit, and Q1 is replaced by a thyristor. The control circuit is basically the same, and the circuit working process is also the same. All the functions of the present application can be realized.

[0048] Example Four

[0049] As shown in Figure 6As shown, by placing the current-limiting resistor R2 at the "ground" terminal of the power circuit and replacing Q1 with an NPN transistor, the control circuit is basically the same, and the circuit operation process is also the same, which can achieve all the functions of this invention.

[0050] Example 5

[0051] like Figure 7 As shown, by placing the current-limiting resistor R2 at the "positive" terminal of the power circuit and replacing Q1 with a PNP transistor, the control circuit is basically the same, and the circuit operation process is also the same, so all the functions of this invention can be achieved.

[0052] The above description is only a further embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the scope disclosed by the present utility model, based on the technical solution and concept of the present utility model, shall fall within the protection scope of the present utility model.

Claims

1. An adaptive current limit control circuit, characterized by: The anode of Z1 is connected to the other end of R5, the 1-pin of Q1 and the one end of R8. The 2-pin of Q1 is connected to the one end of R11, the anode of C3 and the switching power converter. The anode of D8 is connected to the cathode of D13, the anode of D13 is connected to the cathode of D14, the anode of D14 is connected to the one end of R26, the other end of R26 is connected to the one end of R19 and the one end of C8, the 1-pin of Q6.

2. The adaptive current limit control circuit of claim 1, wherein: The other end of R15 is connected to the cathode of D15 and the one end of R18, the anode of D15 is connected to the one end of R12 and the 1-pin of Q4.

3. The adaptive current limit control circuit of claim 2, wherein: The 3-pin of Q4 is connected to the anode of D16, the 1-pin of Q5 is connected to the other end of R13 and the one end of R17, the 3-pin of Q5 is connected to the one end of R23 and the one end of C6, the other end of R17 is connected to the 2-pin of U1, the 1-pin of U1 is connected to the one end of R20 and the one end of R25.

4. The adaptive current limit control circuit of claim 3, wherein: The 3-pin of U1 is connected to the one end of R23, the one end of R24, the one end of C7, the 2-pin of Q8, the 2-pin of Q6, the other end of C8 and the other end of R19.

5. The adaptive current limit control circuit of claim 4, wherein: The other end of C7 is connected to the 1-pin of Q8 and the one end of R22, the other end of R22 is connected to the cathode of D16, the one end of C6 and the one end of R24, the other end of C6 is connected to the one end of R23 and the 3-pin of Q5. The other end of R11 is connected to the one end of R16, the other end of R16 is connected to the one end of R20, the one end of R20 is connected to the 1-pin of U1, and R25 is also connected to the 1-pin of U1.

6. The adaptive current limit control circuit of claim 5, wherein: ​

Images