Power supply switching circuit

Abstract

The utility model belongs to the technical field of medical power supplies, and particularly relates to a power supply switching circuit, which comprises an external direct-current power supply, a battery power supply, a voltage comparison circuit, a power supply control circuit and a power supply output, an external direct-current power supply is connected with the voltage comparison circuit and directly connected with power output; one end of the voltage comparison circuit is connected with an external direct-current power supply; and one end of the power supply control circuit is connected with the battery power supply. According to the circuit, when the voltage of the external direct-current power supply is lower than the voltage of the internal battery in a wide range, the external direct-current power supply can be automatically switched for power supply.

Description

Technical Field

[0001] The utility model belongs to the technical field of medical power supplies, in particular to a power supply switching circuit. Background Art

[0002] At present, most emergency equipment is used in the field or in emergency transport vehicles, and the working environment is relatively complex. The equipment itself has internal battery power supply, but the external DC power supply is not uniform, and the equipment needs to have a wide range of voltage power supply capabilities. However, most of the existing equipment on the market can only accept power supply with a voltage higher than the battery itself. When using a power supply with a lower voltage than the battery, it can only be powered by internal boosting first, and the work process is relatively complicated. Utility Model Content

[0003] The utility model aims to provide a power supply switching circuit, which can realize automatic switching of external DC power supply when the external DC power supply voltage is lower than the internal battery voltage in a relatively wide range.

[0004] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0005] A power supply switching circuit, the switching circuit comprising: an external DC power supply, a battery power supply, a voltage comparison circuit, a power supply control circuit and a power supply output;

[0006] The external DC power supply is connected to the voltage comparison circuit and directly connected to the power output; one end of the voltage comparison circuit is connected to the external DC power supply and the other end is connected to the power control circuit; one end of the power control circuit is connected to the battery power supply and the other end is connected to the power output.

[0007] Preferably, the voltage comparison circuit comprises a first resistor, a second resistor, a fourth resistor, a fifth resistor, an amplifier, and a capacitor;

[0008] The external DC power supply is connected to the 2nd pin of the amplifier through the fourth resistor, and the 2nd pin of the amplifier is grounded through the fifth resistor; the reference voltage source is connected to the 3rd pin of the amplifier through the second resistor, and the 3rd pin of the amplifier is connected to the 1st pin of the amplifier through the first resistor, and the 1st pin of the amplifier is the output terminal;

[0009] One end of the capacitor is connected to pin 11 of the amplifier and grounded, and the other end is connected to pin 4 of the amplifier and connected to the power supply of the amplifier to provide filtering for the power supply of the amplifier.

[0010] Preferably, the power control circuit includes a second PMOS transistor, a third PMOS transistor, a fourth NMOS transistor, a voltage stabilizing diode, a sixth resistor, an eighth resistor, a ninth resistor and a tenth resistor;

[0011] The drain of the second PMOS tube is connected to the power output, and the drain of the third PMOS tube is connected to the battery power supply; the source of the second PMOS tube and the source of the third PMOS tube are connected to the cathode of the voltage-stabilizing diode, and the gate of the second PMOS tube and the gate of the third PMOS tube are connected to the anode of the voltage-stabilizing diode;

[0012] The source of the second PMOS tube and the source of the third PMOS tube are connected to one end of the sixth resistor, and the gate of the second PMOS tube and the gate of the third PMOS tube are connected to the other end of the sixth resistor;

[0013] The sixth resistor is connected in parallel with the voltage stabilizing diode;

[0014] The gate of the second PMOS tube and the gate of the third PMOS tube are connected to the drain of the fourth NMOS tube through the eighth resistor after the connection point with the sixth resistor and the positive electrode of the voltage regulator diode; the source of the fourth NMOS tube is grounded, the gate of the fourth NMOS tube is grounded through the tenth resistor, and the connection point between the gate of the fourth NMOS tube and the tenth resistor is connected to the output end of the voltage comparison circuit through the ninth resistor.

[0015] Preferably, the voltage of the external DC power supply is 9V to 48V, and the voltage of the battery power supply is 12V to 16V.

[0016] The utility model mainly solves the problem that when the external voltage is less than the battery voltage, the device cannot automatically switch to the external voltage for power supply. When the circuit is used, when the device has no external power supply, it is powered by the internal battery. When there is power input at the external DC power supply end, the voltage of the input power supply will be divided first, and then compared by the voltage comparison circuit. If the input voltage is less than the reference voltage after the voltage division, the comparator always outputs a high-level signal to control the NMOS tube Q4 of the power switching circuit to turn on, so that the PMOS tubes Q2 and Q3 of the power switching circuit remain in the on state, and the device continues to be powered by the internal battery. If the input power voltage is greater than the reference voltage after the voltage division, the comparator outputs a low-level signal to control the NMOS tube Q4 of the power switching circuit to turn off, so that the PMOS tubes Q2 and Q3 of the power switching circuit remain in the off state. At this time, even if the external DC power supply voltage is less than the battery voltage, the device is powered by the external DC power supply.

[0017] Compared with the prior art, the utility model has the following beneficial effects:

[0018] The DC power supply range is relatively wide and can provide power that is lower than the battery voltage. It can automatically switch from the battery to the DC power supply to simplify the complexity of the circuit. When the external input voltage of the circuit is lower than the battery voltage, it does not require a boost circuit or an additional MCU to control it, and can automatically switch to an external DC power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is an overall schematic diagram of the power supply switching circuit of the utility model;

[0020] Figure 2 It is a schematic diagram of the power supply comparison circuit of the utility model;

[0021] Figure 3 It is a schematic diagram of the power supply control circuit of the utility model;

[0022] In the attached figure:

[0023] EXDC_VAL is the output of the voltage comparison circuit; BATT_POWER is the battery power supply; POWER_BUS is the power output; GND is the ground; D3V3 is the power supply for amplifier U1. DETAILED DESCRIPTION

[0024] The technical solution of the utility model is described in detail below with reference to the accompanying drawings and embodiments.

[0025] Example 1

[0026] like Figure 1-3 As shown, a power supply switching circuit, the switching circuit includes: an external DC power supply, a battery power supply, a voltage comparison circuit, a power supply control circuit and a power supply output;

[0027] The external DC power supply is connected to the voltage comparison circuit and directly connected to the power output; one end of the voltage comparison circuit is connected to the external DC power supply, and the other end is connected to the power control circuit; the other two ends of the power control circuit, one end is connected to the battery power supply, and the other end is connected to the power output.

[0028] The voltage comparison circuit includes a first resistor R1, a second resistor R2, a fourth resistor R4, a fifth resistor R5, an amplifier U1, and a capacitor C1;

[0029] The external DC power supply is connected to the pin 2 of the amplifier U1 through the fourth resistor R4, and the pin 2 of the amplifier U1 is grounded through the fifth resistor R5; the reference voltage source is connected to the pin 3 of the amplifier U1 through the second resistor R2, and the pin 3 of the amplifier U1 is connected to the pin 1 of the amplifier U1 through the first resistor R1, and the pin 1 of the amplifier U1 is the output end;

[0030] One end of the capacitor C1 is connected to pin 11 of the amplifier U1 and to the ground, and the other end is connected to pin 4 of the amplifier U1 and to the power supply D3V3 of the amplifier, thereby providing filtering for the power supply of the amplifier U1.

[0031] The power control circuit includes a second PMOS transistor Q2, a third PMOS transistor Q3, a fourth NMOS transistor Q4, a voltage stabilizing diode D3, a sixth resistor R6, an eighth resistor R8, a ninth resistor R9 and a tenth resistor R10;

[0032] The drain of the second PMOS tube is connected to the power output, and the drain of the third PMOS tube is connected to the battery power supply; the source of the second PMOS tube and the source of the third PMOS tube are connected to the cathode of the voltage-stabilizing diode, and the gate of the second PMOS tube and the gate of the third PMOS tube are connected to the anode of the voltage-stabilizing diode;

[0033] The source of the second PMOS tube and the source of the third PMOS tube are connected to one end of the sixth resistor, and the gate of the second PMOS tube and the gate of the third PMOS tube are connected to the other end of the sixth resistor;

[0034] The sixth resistor is connected in parallel with the voltage stabilizing diode;

[0035] The gate of the second PMOS tube and the gate of the third PMOS tube are connected to the drain of the fourth NMOS tube through the eighth resistor after the connection point with the sixth resistor and the positive electrode of the voltage regulator diode; the source of the fourth NMOS tube is grounded, the gate of the fourth NMOS tube is grounded through the tenth resistor, and the connection point between the gate of the fourth NMOS tube and the tenth resistor is connected to the output end of the voltage comparison circuit through the ninth resistor.

[0036] The voltage of the external DC power supply is 9V to 48V, and the voltage of the battery power supply is 12V to 16V.

[0037] Figure 1 This is the overall diagram of the circuit. The two power supplies are an external DC power supply (9V to 48V) and a battery power supply (12V to 16V). The external DC power supply is connected to the voltage comparison circuit and directly connected to the power output; one end of the voltage comparison circuit is connected to the external power supply, and the other end is connected to the power control circuit; one end of the power control circuit is connected to the battery power supply, and the other end is connected to the power output.

[0038] Figure 2 It is a voltage comparison circuit. The external power supply is connected to the 2nd pin of the amplifier U1 after being divided by resistors R4 and R5. The 3rd pin of U1 is connected to the reference voltage source through resistor R2 and to the 1st pin of U1 through resistor R1, forming a hysteresis comparison circuit. The capacitor C1 is connected to the power supply of the amplifier U1 at both ends to provide filtering.

[0039] Figure 3It is a power control circuit. The P-channel MOS tubes Q2 and Q3 are connected to the battery power supply and the output power supply respectively, and are used to control the output of the battery power supply. The voltage regulator diode D3 is connected to the 1st and 4th pins of the P-channel MOS tube respectively to protect the MOS tube; the resistors R6 and R8 have the function of voltage division; the gate of the N-channel MOS tube is connected to the voltage comparison circuit through the resistor R9 to control the switching of the MOS tubes Q2 and Q3.

[0040] The components in this embodiment can all be purchased.

[0041] The above embodiments are only preferred embodiments of the present utility model and are not used to limit the present utility model. What is important is to protect the entire control process. Any modifications, equivalent substitutions, improvements, etc. made should be included in the protection scope of the present utility model.

[0042] Any content not described in detail in the present invention can be based on the conventional technical knowledge in the field.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model and are not intended to limit it. Although the utility model is described in detail with reference to the embodiments, a person skilled in the art should understand that any modification or equivalent replacement of the technical solution of the utility model does not deviate from the spirit and scope of the technical solution of the utility model, and should be included in the scope of the claims of the utility model.

Claims

1. A power supply switching circuit, characterized in that: The switching circuit includes: an external DC power supply, a battery power supply, a voltage comparison circuit, a power control circuit and a power output; The external DC power supply is connected to the voltage comparison circuit and directly connected to the power output; one end of the voltage comparison circuit is connected to the external DC power supply and the other end is connected to the power control circuit; one end of the power control circuit is connected to the battery power supply and the other end is connected to the power output.

2. The power supply switching circuit according to claim 1, characterized in that: The voltage comparison circuit includes a first resistor, a second resistor, a fourth resistor, a fifth resistor, an amplifier, and a capacitor; The external DC power supply is connected to the pin 2 of the amplifier via the fourth resistor, and the pin 2 of the amplifier is grounded via the fifth resistor; The reference voltage source is connected to the 3rd pin of the amplifier via the second resistor, the 3rd pin of the amplifier is connected to the 1st pin of the amplifier via the first resistor, and the 1st pin of the amplifier is the output terminal; One end of the capacitor is connected to pin 11 of the amplifier and grounded, and the other end is connected to pin 4 of the amplifier and connected to the power supply of the amplifier to provide filtering for the power supply of the amplifier.

3. The power supply switching circuit according to claim 1, characterized in that: The power control circuit includes a second PMOS tube, a third PMOS tube, a fourth NMOS tube, a voltage stabilizing diode, a sixth resistor, an eighth resistor, a ninth resistor and a tenth resistor; The drain of the second PMOS tube is connected to the power output, and the drain of the third PMOS tube is connected to the battery power supply; the source of the second PMOS tube and the source of the third PMOS tube are connected to the cathode of the voltage-stabilizing diode, and the gate of the second PMOS tube and the gate of the third PMOS tube are connected to the anode of the voltage-stabilizing diode; The source of the second PMOS tube and the source of the third PMOS tube are connected to one end of the sixth resistor, and the gate of the second PMOS tube and the gate of the third PMOS tube are connected to the other end of the sixth resistor; The sixth resistor is connected in parallel with the voltage stabilizing diode; The gate of the second PMOS tube and the gate of the third PMOS tube are connected to the drain of the fourth NMOS tube through the eighth resistor after the connection point with the sixth resistor and the positive electrode of the voltage regulator diode; the source of the fourth NMOS tube is grounded, the gate of the fourth NMOS tube is grounded through the tenth resistor, and the connection point between the gate of the fourth NMOS tube and the tenth resistor is connected to the output end of the voltage comparison circuit through the ninth resistor.

4. The power supply switching circuit according to claim 1, characterized in that: The voltage of the external DC power supply is 9V to 48V, and the voltage of the battery power supply is 12V to 16V.

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