CN205490120U - Put short -circuit protection circuit based on two fortune - Google Patents

Abstract

The utility model relates to a short-circuit protection circuit based on a double operational amplifier, comprising a first operational amplifier circuit, a second operational amplifier circuit and a control circuit, the first operational amplifier circuit includes a first operational amplifier X1, a diode D1, a resistor R1, R5, R6, R7, capacitor C1, the anode of the diode D1 is externally connected to the sampling signal, and its cathode is connected to the non-inverting input terminal of the first operational amplifier X1 through the resistor R7, and the inverting input terminal of the first operational amplifier X1 is connected through the resistor R5 is connected to the power supply, the negative terminal of the power supply of the first operational amplifier X1 is respectively connected to its non-inverting input terminal through a resistor R1, and connected to its inverting input terminal through a resistor R6, and the capacitor C1 is connected in parallel to both ends of the resistor R1. The output terminal of the first operational amplifier X1 is connected with the second operational amplifier circuit. The utility model reduces the short-circuit power consumption of the switching power supply by controlling the hiccup time of the system, and improves the capacity of the switching power supply with capacitive load.

Description

A short-circuit protection circuit based on dual operational amplifiers

technical field

The utility model relates to a short-circuit protection circuit of a switching power supply, in particular to a short-circuit protection circuit based on a double operational amplifier.

Background technique

At present, the short-circuit protection circuit of switching power supply mainly adopts the short-circuit protection circuit of single operational amplifier, which has the advantages of simple circuit, saving volume and convenient debugging. However, when the system is short-circuited, the power consumption of the system is large, and it is easy to form heat accumulation, and long-term work will have a certain impact on the reliability of internal components. In addition, the short-circuit power consumption of the system and the ability to carry capacitive loads have a reverse trend. Therefore, the research on the short-circuit protection circuit of dual operational amplifiers can not only solve the problem of large short-circuit power consumption, but also solve the problem of poor capacitive load capacity of the system.

Utility model content

The purpose of the utility model is to provide a short-circuit protection circuit based on dual operational amplifiers, the circuit is reliable, the system power consumption is low when short-circuited, the debugging is convenient, and the capacitive load capacity is strong.

In order to achieve the above object, the utility model adopts the following technical solutions: comprising a first operational amplifier circuit, a second operational amplifier circuit and a control circuit, the output terminal of the first operational amplifier circuit is connected with the input terminal of the second operational amplifier circuit , the output terminal of the second operational amplifier circuit is connected with the input terminal of the control circuit, and the first operational amplifier circuit includes a first operational amplifier X1, a diode D1, resistors R1, R5, R6, R7, a capacitor C1, and the diode D1 The anode of the anode is externally connected to the sampling signal, and its cathode is connected to the non-inverting input terminal of the first operational amplifier X1 through the resistor R7, and the inverting input terminal of the first operational amplifier X1 is connected to the power supply through the resistor R5, and the first operational amplifier X1 The negative terminal of the power supply is respectively connected to its non-inverting input terminal via resistor R1, and its inverting input terminal via resistor R6. The capacitor C1 is connected in parallel to both ends of the resistor R1, and the output terminal of the first operational amplifier X1 is connected to the second operational amplifier. circuit connected.

The second operational amplifier circuit includes a second operational amplifier X2, a diode D2, resistors R2, R3, R4 and a capacitor C2, the non-inverting input terminal of the second operational amplifier X2 is connected to its positive power supply terminal through a resistor R2, and the diode The anode of D2 is connected to the output terminal of the first operational amplifier X1, and its cathode is connected to the non-inverting input terminal of the second operational amplifier X2. The capacitor C2 is connected in parallel to both ends of the resistor R2, and the inverting input terminal of the second amplifier X2 passes through the resistor R4 is connected to the negative terminal of its power supply, and connected to the inverting input terminal of the first operational amplifier X1 through the resistor R3.

The control circuit includes a triode Q1, a diode D3, a resistor R8 and a capacitor C4, the base of the diode Q1 is connected to the cathode of the diode D3 through the resistor R8, the anode of the diode D3 is connected to the second operational amplifier circuit, and the diode Q1 The collector of the diode Q1 is externally connected to the control terminal of the PWM, and the emitter of the diode Q1 is connected to its base through a capacitor C4.

It can be seen from the above technical solution that the short-circuit protection circuit of the dual op-amp described in the present invention can well control the hiccup time of the system during short-circuit by adjusting the threshold voltage of the second-stage op-amp circuit and the values of R2 and C2. Control the hiccup time of the system, reduce the short-circuit power consumption of the switching power supply, and improve the capability of the switching power supply with capacitive load.

Description of drawings

Fig. 1 is a block diagram of the utility model;

Fig. 2 is a circuit diagram of the utility model.

detailed description

Below in conjunction with accompanying drawing, the utility model is further described:

As shown in Figures 1 and 2, the short-circuit protection circuit based on dual operational amplifiers in this embodiment includes a first operational amplifier circuit 1, a second operational amplifier circuit 2 and a control circuit 3, and the output terminal of the first operational amplifier circuit 1 is connected to the second operational amplifier circuit. The input terminals of the second operational amplifier circuit 2 are connected, the output terminal of the second operational amplifier circuit 2 is connected with the input terminal of the control circuit 3, and the first operational amplifier circuit 1 includes the first operational amplifier X1, diode D1, resistors R1, R5, R6 , R7, capacitor C1, the anode of the diode D1 is externally connected to the sampling signal, its cathode is connected to the non-inverting input terminal of the first operational amplifier X1 through the resistor R7, and the inverting input terminal of the first operational amplifier X1 is connected to the power supply through the resistor R5, the first The negative terminal of the power supply of the operational amplifier X1 is connected to its non-inverting input terminal through the resistor R1, and its inverting input terminal through the resistor R6. The capacitor C1 is connected in parallel to both ends of the resistor R1. The output terminal of the first operational amplifier X1 is connected to the second operational amplifier. Circuit 2 is connected. The resistors R5 and R6 in this circuit provide a DC voltage to the negative input terminal of the first-stage operational amplifier X1 through voltage division, and the sampling point is the first-stage operational amplifier X1 after passing through the diode D1, resistor R7, resistor R1, and capacitor C1. The positive input of the provides a DC voltage.

As shown in Figure 2, the second operational amplifier circuit 2 includes a second operational amplifier X2, a diode D2, resistors R2, R3, R4 and a capacitor C2, and the non-inverting input terminal of the second operational amplifier X2 is connected to the positive terminal of its power supply through a resistor R2 , the anode of the diode D2 is connected to the output terminal of the first operational amplifier X1, its cathode is connected to the non-inverting input terminal of the second operational amplifier X2, the capacitor C2 is connected in parallel to both ends of the resistor R2, and the inverting input terminal of the second amplifier X2 passes through the resistor R4 is connected to the negative terminal of its power supply, and connected to the inverting input terminal of the first operational amplifier X1 through the resistor R3. Resistors R3 and R4 in this circuit provide a DC voltage to the negative input terminal of the second-stage operational amplifier X2 through voltage division, and the output of the first-stage operational amplifier X1 is the positive input terminal of the operational amplifier X2 through the diode D2, resistor R2, and capacitor C2. A DC voltage is provided at the input.

As shown in Figure 2, the control circuit 3 includes a triode Q1, a diode D3, a resistor R8 and a capacitor C4, the base of the diode Q1 is connected to the cathode of the diode D3 through the resistor R8, and the anode of the diode D3 is connected to the second operational amplifier circuit 2 The output terminal of the second operational amplifier X2 is connected, the collector of the diode Q1 is externally connected to the control terminal of the PWM, and the emitter of the diode Q1 is connected to its base through a capacitor C4.

The utility model uses two op-amps in series and is divided into two stages. The first-stage op-amp circuit 1 is a threshold protection point circuit, and the second-stage op-amp circuit 2 is a hiccup circuit. The short-circuit protection is realized through the control circuit 3 Purpose. When the output is short-circuited, the current sampling signal will reach the positive input terminal of the first operational amplifier X1 through the diode D1, so that the output of X1 is at a high level, and the high level quickly charges the capacitor C2 to 5V-0.7V=4.3V , the level of the positive input terminal of the op amp X2 is higher than the level of the negative input terminal, so the output is high level, the transistor Q1 is turned on, and the voltage of the PWM control terminal is pulled to low level, so as to achieve the purpose of limiting the short-circuit current. Before the voltage on the capacitor C2 drops to the level of the negative input terminal of the second-stage operational amplifier X2, the operational amplifier X2 keeps outputting a high level, and the system is always in an idle state. This state is also called "hiccup". By adjusting R2 and C2, the hiccup time of the system during short circuit can be well controlled. By controlling the hiccup time of the system, the power consumption during the short circuit protection of the system can be further reduced.

The above-mentioned embodiments are only described to the preferred implementation of the utility model, and are not limited to the scope of the utility model. Various modifications and improvements made should fall within the scope of protection determined by the claims of the utility model.

Claims (3)

1. null1. one kind based on double operational short-circuit protection circuit，It is characterized in that: include the first discharge circuit、Second discharge circuit and control circuit，The outfan of described first discharge circuit and the input of the second discharge circuit are connected，The outfan of the second discharge circuit is connected with the input of control circuit，Described first discharge circuit includes the first operational amplifier X1，Diode D1,Resistance R1、R5、R6、R7，Electric capacity C1，The external sampled signal of anode of described diode D1，Its negative electrode is connected through the in-phase input end of resistance R7 and the first operational amplifier X1，The reverse input end of described first operational amplifier X1 is connected with power supply through resistance R5，The power cathode end of described first operational amplifier X1 is connected with its in-phase input end through resistance R1 respectively、It is connected with its reverse input end through resistance R6，Described electric capacity C1 is connected in parallel on the two ends of resistance R1，The outfan of described first operational amplifier X1 and the second discharge circuit are connected.
2. The most according to claim 1 based on double operational short-circuit protection circuit, it is characterized in that: described second discharge circuit includes the second operational amplifier X2, diode D2, resistance R2, R3, R4 and electric capacity C2, the in-phase input end of described second operational amplifier X2 is connected with its power positive end through resistance R2, the outfan of described diode D2 anode and the first operational amplifier X1 is connected, the in-phase input end of its negative electrode and the second operational amplifier X2 is connected, described electric capacity C2 is connected in parallel on the two ends of resistance R2, the reverse input end of the second amplifier X2 is connected with its power cathode end by resistance R4, and it is connected through the reverse input end of resistance R3 and the first operational amplifier X1.
3. The most according to claim 1 and 2 based on double operational short-circuit protection circuit; it is characterized in that: described control circuit includes audion Q1; diode D3; resistance R8 and electric capacity C4; the base stage of described diode Q1 is connected through the negative electrode of resistance R8 with diode D3; the anode of described diode D3 and the second discharge circuit are connected, and the control end of the external PWM of colelctor electrode of diode Q1, the emitter stage of described diode Q1 is connected with its base stage through electric capacity C4.