Output power detection circuit

Abstract

The utility model discloses an output power detection circuit capable of accurately judging the output power of a power supply. The output power detection circuit comprises an input end positive electrode, an input end negative electrode, an output end positive electrode, an output end negative electrode, an operational amplifier and a reference voltage circuit, the input end positive electrode is connected with the output end positive electrode, the input end negative electrode is connected with the output end negative electrode through a current detection resistor R1, and the input end negative electrode is grounded; the reference voltage circuit outputs a reference voltage to the inverted input end of the operational amplifier, the positive input end of the operational amplifier is connected with the negative electrode of the output end through a resistor R2, and the positive input end of the operational amplifier is connected with the positive electrode of the output end through a resistor R3. And the operational amplifier outputs a corresponding control signal according to a comparison result of the normal-phase input end voltage and the inverted-phase input end voltage of the operational amplifier.

Description

Technical Field

[0001] The utility model relates to the technical field of power supplies, in particular to an output power detection circuit. Background Art

[0002] Existing output power detection circuits generally determine the output power by sampling the output voltage or output current. However, the output voltage and output current of a power supply are constantly changing. It is difficult to accurately determine the output power of a power supply by simply sampling the output voltage or the output current. Summary of the Invention

[0003] The technical problem to be solved by the utility model is to provide an output power detection circuit which can accurately judge the output power of a power supply.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] An output power detection circuit includes an input positive electrode, an input negative electrode, an output positive electrode, an output negative electrode, an operational amplifier, and a reference voltage circuit, wherein the input positive electrode is connected to the output positive electrode, the input negative electrode is connected to the output negative electrode via a current detection resistor R1, and the input negative electrode is grounded, the reference voltage circuit outputs a reference voltage to the inverting input of the operational amplifier, the operational amplifier's non-inverting input is connected to the output negative electrode via a resistor R2, and the operational amplifier's non-inverting input is connected to the output positive electrode via a resistor R3, and the operational amplifier outputs a corresponding control signal based on a comparison result between its non-inverting input voltage and its inverting input voltage.

[0006] Preferably, the reference voltage circuit includes a three-terminal regulator U2 and a resistor R4, the anode of the three-terminal regulator U2 is grounded, the reference terminal of the three-terminal regulator U2 is short-circuited with the cathode of the three-terminal regulator U2, the cathode of the three-terminal regulator U2 is respectively connected to the inverting input terminal of the operational amplifier and one end of the resistor R4, and the other end of the resistor R4 is input with the supply voltage.

[0007] Preferably, the other end of the resistor R4 is connected to an external power supply.

[0008] Preferably, the other end of the resistor R4 is connected to the positive electrode of the output end, or is connected to the positive electrode of the output end through a DC-DC circuit.

[0009] Preferably, the reference voltage circuit also includes a resistor R5 and a resistor R6, the resistor R5 is connected between the cathode of the three-terminal regulator U2 and the inverting input terminal of the operational amplifier, one end of the resistor R6 is connected to the inverting input terminal of the operational amplifier, and the other end of the resistor R6 is grounded.

[0010] Preferably, the reference voltage circuit further includes a capacitor C2, and the capacitor C2 is connected in parallel with the resistor R6.

[0011] Preferably, the reference voltage circuit further includes a capacitor C3, one end of the capacitor C3 is connected to the cathode of the three-terminal regulator U2, and the other end of the capacitor C3 is grounded.

[0012] Preferably, the model of the three-terminal voltage regulator U2 is TL431.

[0013] Preferably, the output power detection circuit further includes a capacitor C1 , one end of the capacitor C1 is connected to the non-inverting input terminal of the operational amplifier, and the other end is grounded.

[0014] Preferably, when the voltage at the positive input terminal of the operational amplifier is greater than the voltage at the inverting input terminal of the operational amplifier, the operational amplifier outputs a high-level signal; when the voltage at the positive input terminal of the operational amplifier is less than the voltage at the inverting input terminal of the operational amplifier, the operational amplifier outputs a low-level signal.

[0015] The beneficial technical effect of the present utility model is that: in the above-mentioned output power detection circuit, the positive electrode of the output terminal, resistor R3, resistor R2, current detection resistor R1 and ground form a closed loop, and the non-inverting input terminal of the operational amplifier is connected to the connection point between resistor R3 and resistor R2. Therefore, the voltage at the non-inverting input terminal of the operational amplifier changes with the changes in the output voltage and the output current. At the same time, a reference voltage is input to the inverting input terminal of the operational amplifier. The operational amplifier can accurately determine the output power of the power supply based on the comparison result of the voltage at its non-inverting input terminal and the voltage at its inverting input terminal. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a circuit principle diagram of the output power detection circuit of the utility model. DETAILED DESCRIPTION

[0017] In order to enable those skilled in the art to more clearly understand the purpose, technical solutions and advantages of the present invention, the present invention is further described below with reference to the accompanying drawings and embodiments.

[0018] The utility model provides an output power detection circuit.

[0019] like Figure 1As shown, in one embodiment of the present invention, the output power detection circuit includes an input positive terminal Input+, an input negative terminal Input-, an output positive terminal Output+, an output negative terminal Output-, an operational amplifier U1 and a reference voltage circuit 10, wherein the input positive terminal Input+ is connected to the output positive terminal Output+, the input negative terminal Input- is connected to the output negative terminal Output- through a current detection resistor R1, and the input negative terminal Input- is grounded, the reference voltage circuit 10 outputs a reference voltage to the inverting input terminal of the operational amplifier U1, the non-inverting input terminal of the operational amplifier U1 is connected to the output negative terminal Output- through a resistor R2, the non-inverting input terminal of the operational amplifier U1 is connected to the output positive terminal Output+ through a resistor R3, and the operational amplifier U1 outputs a corresponding control signal Signal according to the comparison result of its non-inverting input terminal voltage and the inverting input terminal voltage.

[0020] The reference voltage circuit 10 includes a TL431 three-terminal voltage regulator U2 and a resistor R4. The anode of the three-terminal voltage regulator U2 is grounded, the reference terminal of the three-terminal voltage regulator U2 is short-circuited with the cathode of the three-terminal voltage regulator U2, and the cathode of the three-terminal voltage regulator U2 is respectively connected to the inverting input terminal of the operational amplifier U1 and one end of the resistor R4. The other end of the resistor R4 is input with the supply voltage VCC. In some embodiments, the other end of the resistor R4 can be connected to the positive output terminal Output+, or connected to the positive output terminal Output+ via a DC-DC circuit, with the output voltage Vout providing the supply voltage VCC. In other embodiments, the other end of the resistor R4 can also be connected to an external power supply, with the external power supply providing the supply voltage VCC.

[0021] The reference voltage circuit 10 also includes resistors R5 and R6. Resistor R5 is connected between the cathode of the three-terminal voltage regulator U2 and the inverting input of the operational amplifier U1. One end of resistor R6 is connected to the inverting input of the operational amplifier U1, and the other end of resistor R6 is grounded. The regulated voltage output by the three-terminal voltage regulator U2 is divided by resistors R5 and R6 to reduce the voltage at the inverting input of the operational amplifier U1.

[0022] The reference voltage circuit further includes a capacitor C2 and a capacitor C3. The capacitor C2 is connected in parallel with the resistor R6. One end of the capacitor C3 is connected to the cathode of the three-terminal voltage regulator U2, and the other end of the capacitor C3 is grounded. The output power detection circuit further includes a capacitor C1. One end of the capacitor C1 is connected to the non-inverting input terminal of the operational amplifier U1, and the other end is grounded. The capacitors C1, C2, and C3 are all filter capacitors. After filtering, the signal can be made more stable.

[0023] It should be noted that the reference voltage circuit 10 is mainly used to output a reference voltage to the inverting input terminal of the operational amplifier U1. Therefore, in some embodiments of the present invention, some existing LDO circuits can also be used to provide the reference voltage. For example, an LDO circuit based on the three-terminal voltage regulator integrated circuit LM7805.

[0024] The working principle of the output power detection circuit of the present invention is as follows:

[0025] 1. When there is an output current I, the voltage drop V1 generated by flowing through the resistor R1 is V1 = R1 * I. V+ is divided by the resistors R2 and R3, so:

[0026]

[0027]

[0028] 2. Reference voltage setting: After short-circuiting the R pin and the K pin of the three-terminal voltage regulator U2 (TL431), a stable voltage Vref = 2.5V is obtained, and then it is divided by the resistors R5 and R6 to obtain V-, so:

[0029]

[0030] 3. When V+ > V-, the operational amplifier U1 outputs a control signal Signal as a high level; when V+ < V-, the operational amplifier U1 outputs a control signal Signal as a low level. The control signal Signal is output to the subsequent control circuit, and the control circuit performs corresponding control according to the control signal Signal. For example, adjusting the output power.

[0031] It should be noted that in actual application, the output power detection circuit of the present invention can adapt to power supplies with different input voltages by setting the resistance values of the resistors R1, R2, R3, R5, and R6.

[0032] The beneficial effects of the present utility model are as follows: in the output power detection circuit of the present utility model, the positive electrode of the output terminal, the resistor R3, the resistor R2, the current detection resistor R1 and the ground form a closed loop, and the non-inverting input terminal of the operational amplifier is connected to the connection point between the resistor R3 and the resistor R2. Therefore, the voltage of the non-inverting input terminal of the operational amplifier changes with the changes of the output voltage and the output current. At the same time, a reference voltage is input to the inverting input terminal of the operational amplifier. The operational amplifier can accurately determine the output power of the power supply based on the comparison result of the voltage of its non-inverting input terminal and the voltage of its inverting input terminal.

[0033] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Those skilled in the art may make various equivalent changes and improvements based on the above embodiment. Any equivalent changes or modifications made within the scope of the claims shall fall within the scope of protection of the present invention.

Claims

1. An output power detection circuit, characterized in that: The invention comprises a positive input terminal, a negative input terminal, a positive output terminal, a negative output terminal, an operational amplifier and a reference voltage circuit. The positive input terminal is connected to the positive output terminal, the negative input terminal is connected to the negative output terminal via a current detection resistor R1, and the negative input terminal is grounded. The reference voltage circuit outputs a reference voltage to the inverting input terminal of the operational amplifier. The positive input terminal of the operational amplifier is connected to the negative output terminal via a resistor R2, and the positive input terminal of the operational amplifier is connected to the positive output terminal via a resistor R3. The operational amplifier outputs a corresponding control signal according to the comparison result between the positive input terminal voltage and the inverting input terminal voltage.

2. The output power detection circuit according to claim 1, wherein: The reference voltage circuit includes a three-terminal regulator U2 and a resistor R4, the anode of the three-terminal regulator U2 is grounded, the reference terminal of the three-terminal regulator U2 is short-circuited with the cathode of the three-terminal regulator U2, the cathode of the three-terminal regulator U2 is respectively connected to the inverting input terminal of the operational amplifier and one end of the resistor R4, and the other end of the resistor R4 is input with the supply voltage.

3. The output power detection circuit according to claim 2, wherein: The other end of the resistor R4 is connected to an external power supply.

4. The output power detection circuit according to claim 2, wherein: The other end of the resistor R4 is connected to the positive electrode of the output terminal, or is connected to the positive electrode of the output terminal through a DC-DC circuit.

5. The output power detection circuit according to claim 2, wherein: The reference voltage circuit also includes a resistor R5 and a resistor R6. The resistor R5 is connected between the cathode of the three-terminal regulator U2 and the inverting input terminal of the operational amplifier. One end of the resistor R6 is connected to the inverting input terminal of the operational amplifier, and the other end of the resistor R6 is grounded.

6. The output power detection circuit according to claim 5, wherein: The reference voltage circuit further includes a capacitor C2, and the capacitor C2 is connected in parallel with the resistor R6.

7. The output power detection circuit according to claim 6, wherein: The reference voltage circuit further includes a capacitor C3 , one end of the capacitor C3 is connected to the cathode of the three-terminal regulator U2 , and the other end of the capacitor C3 is grounded.

8. The output power detection circuit according to any one of claims 2 to 7, wherein: The model of the three-terminal voltage regulator U2 is TL431.

9. The output power detection circuit according to claim 1, wherein: The output power detection circuit further includes a capacitor C1 , one end of the capacitor C1 is connected to the non-inverting input terminal of the operational amplifier, and the other end is grounded.

10. The output power detection circuit according to claim 1, wherein: When the voltage at the positive input terminal of the operational amplifier is greater than the voltage at the inverting input terminal of the operational amplifier, the operational amplifier outputs a high-level signal; when the voltage at the positive input terminal of the operational amplifier is less than the voltage at the inverting input terminal of the operational amplifier, the operational amplifier outputs a low-level signal.

Images