Over-voltage and under-voltage protection circuit for medical instrument

Abstract

The utility model discloses an overvoltage and undervoltage protection circuit for a medical instrument. The overvoltage and undervoltage protection circuit consists of an overvoltage detection circuit and an undervoltage detection circuit, wherein the overvoltage detection circuit consists of a PMOS (P-channel Metal Oxide Semiconductor) tube (Q3), a triode (Q1), resistors (R1, R2, R9 and R10) and a voltage stabilizing diode D2; the under-voltage detection circuit is composed of triodes (Q5 and Q6), a capacitor (C1), a diode (D1) and resistors (R3, R4, R5, R6, R7 and R8). The circuit has the advantages that the voltage stabilizing performance of the voltage stabilizing diode triggers the switch-on and switch-off of the Q1, overvoltage automatic power-off is achieved, the switch-on and switch-off of the triode Q6 are controlled through charging and discharging of the C1, early warning information is sent to the MCU when the voltage is low, data are automatically stored, and the situation that expensive medical equipment runs under the overvoltage or undervoltage condition, and unnecessary loss is caused is prevented.

Description

Technical Field

[0001] The utility model belongs to the electronic industry, and particularly relates to an overvoltage and undervoltage protection circuit for medical devices. Background Art

[0002] In medical devices, overvoltage can cause electronic devices to overheat and even burn out, and undervoltage may also cause equipment damage. For example, the motor is a key component in medical devices. If the voltage of the motor is too low by more than 10%, the motor current will increase, the winding temperature will rise, and in severe cases, the mechanical equipment will stop running or cannot start, and even burn out the motor.

[0003] The main function of the overvoltage and undervoltage protection circuit is to cut off the power after saving data when the power supply voltage is higher than the overvoltage set value, and to give an alarm when the power supply voltage is lower than the undervoltage set value, so as to extend the service life of medical device equipment. Summary of the Invention

[0004] The purpose of the utility model is to provide a novel overvoltage and undervoltage protection circuit, which ensures an alarm when the power supply voltage is lower than the undervoltage set value; cuts off the power when the power supply voltage is higher than the overvoltage set value, and saves important data before power-off; and at the same time increases the reliability of the equipment.

[0005] The technical solution of the utility model consists of an overvoltage detection circuit and an undervoltage detection circuit.

[0006] The overvoltage detection circuit consists of a PMOS transistor (Q3), a triode (Q1), resistors (R1, R2, R9, R10), and a zener diode D2.

[0007] When the power supply input increases, the voltage of D2 is stabilized near the stable value, a voltage difference appears between the b-pole and the e-pole of Q1, and finally Q1 conducts, pulling up the gate of Q3, and Q3 cuts off, and the voltage at NET1 disappears.

[0008] The threshold value of overvoltage detection can be set by adjusting R10 and R9.

[0009] The undervoltage detection circuit consists of triodes (Q5, Q6), a capacitor (C1), a diode (D1), and resistors (R3, R4, R5, R6, R7, R8).

[0010] When the voltage at NET1 is normal, the capacitor C1 is charged through the resistor R4 and the diode D1. After the power supply is stabilized, the b-pole of Q6 is the power supply voltage. Since the voltage of the b-pole is higher than that of the e-pole, the triode Q6 does not conduct. If Q6 does not conduct, the b-pole of Q5 has no voltage, and Q5 does not conduct either.

[0011] When the voltage is too low, C1 discharges, and the e-pole voltage of Q6 remains at U NET1*R3 / (R3 + R4) - 0.7V, and the base voltage of Q6 decreases. At a certain moment, the voltage difference between the emitter and base voltages of Q6 is greater than the conduction voltage U of Q6 eb When this occurs, Q6 conducts, Q5 conducts, and the undervoltage alarm voltage changes from 3.3V to 0V.

[0012] The voltage threshold is set by adjusting the ratio of R1 to R2.

[0013] Advantages of the present utility model:

[0014] The voltage regulation performance of the voltage stabilizing diode triggers the conduction and cut-off of Q1, realizing automatic power-off under overvoltage. The charging and discharging of C1 control the switching of the triode Q6. At low voltages, a warning message is sent to the MCU, and data is automatically saved to prevent unnecessary losses caused by the operation of expensive medical device equipment under overvoltage or undervoltage conditions. Description of the Drawings

[0015] Figure 1 This is the circuit diagram of the present utility model. Detailed Embodiment

[0016] To enable those skilled in the art to better understand the solution of the present utility model and make the above-mentioned objects, features, and advantages more obvious and understandable, the present utility model will be further described in detail below in conjunction with embodiments.

[0017] As Figure 1 shown, the technical solution of the present utility model consists of an overvoltage detection circuit and an undervoltage detection circuit.

[0018] The overvoltage detection circuit consists of a PMOS transistor (Q3), a triode (Q1), resistors (R1, R2, R9, R10), and a voltage stabilizing diode D2.

[0019] Working principle of the overvoltage detection circuit: Select a voltage stabilizing diode with a voltage regulation value equal to or not much different from the power supply voltage. When the power supply input is normal, the voltage drop of the voltage stabilizing diode is equal to the power supply input voltage, the voltage difference between the base and emitter of Q1 is not large, Q1 is cut off, the gate of Q3 is grounded, Q3 conducts, and the voltage at NET1 is equal to the power supply input voltage.

[0020] When the power supply input increases, the voltage of D2 stabilizes near the stable value, a voltage difference appears between the base and emitter of Q1, and finally Q1 conducts, pulling up the gate of Q3, Q3 is cut off, and the voltage at NET1 disappears.

[0021] The overvoltage detection threshold can be set by adjusting R10 and R9. When R10 / (R9 + R10) * (U 电源输入 -U D2 ) is greater than the conduction voltage between the base and emitter of Q1, the subsequent power supply is turned off.

[0022] The undervoltage detection circuit consists of transistors (Q5, Q6), a capacitor (C1), a diode (D1), and resistors (R3, R4, R5, R6, R7, R8).

[0023] Operating principle of the undervoltage detection circuit:

[0024] When the voltage at NET1 is normal, the capacitor C1 is charged through the resistors R4 and the diode D1. After stabilization, through the voltage division of R3 and R4, the voltage on the left side of D1 is U NET1 *R3 / (R3 + R4). After passing through D1, the voltage drops by one diode voltage drop, i.e., 0.7V. Finally, the voltage of the capacitor C1 is charged to U NET1 *R3 / (R3 + R4) - 0.7V.

[0025] After the power supply stabilizes, the base of Q6 is the supply voltage. Since the voltage of the base is higher than that of the emitter, the transistor Q6 is not conducting. If Q6 is not conducting, then the base of Q5 has no voltage and Q5 is also not conducting.

[0026] When the voltage is too low, C1 discharges. The voltage of the emitter of Q6 remains at U NET1 *R3 / (R3 + R4) - 0.7V, while the voltage of the base of Q6 decreases. At a certain moment, the voltage difference between the emitter and base of Q6 is greater than the conduction voltage U eb of Q6, then Q6 conducts, Q5 conducts, and the undervoltage alarm voltage changes from 3.3V to 0V.

[0027] The voltage threshold is set by adjusting the ratio of R1 and R2. The duration of the low - power signal output by the circuit is adjusted by changing the capacitance value of C1 and the resistance values of resistors R5, R6, R8. For example, increasing the values of C1, R5, R6, R8 can extend the discharge time of C1, which also extends the time that Q2 continuously pulls down, and ultimately extends the duration of the low - power signal output by the circuit.

[0028] Appendix Figure 1 The circuit shown below is a case when the power supply input is 12V. The voltage at NET1 is used as the power supply voltage for the subsequent circuit. When the power supply input voltage is normal, the voltage drop of the zener diode is 12V. There is no voltage difference between the base and emitter of Q1, so Q1 is cut off. The gate of Q3 is grounded, so Q3 conducts. The voltage at NET1 is equal to the power supply voltage. The capacitor C1 is charged through the resistors R4 and the diode D1. After stabilization, through the voltage division of R3 and R4, the voltage on the left side of D1 is U NET1 *R3 / (R3 + R4). After passing through D1, the voltage drops by one diode voltage drop, i.e., 0.7V. Finally, the voltage of the capacitor C1 is charged to U NET1*When the power supply is stable after being powered by R3 / (R3 + R4) - 0.7V, the base of Q6 is the supply voltage. Since the voltage of the base is higher than that of the emitter, the triode Q6 is not conducting. If Q6 is not conducting, there is no voltage at the base of Q5, and Q5 is also not conducting.

[0029] When the input voltage of the power supply increases, the voltage drop across the zener diode remains 12V, the base voltage of Q1 is 12V, and the emitter voltage of Q1 increases with the increase of the power supply voltage. When R10 / (R9 + R10)*(U 电源输入 - UD2) is greater than 0.4V, Q1 conducts, the gate of Q3 is pulled high, Q3 turns off, and the voltage at NET1 disappears.

[0030] When the voltage at NET1 drops to the undervoltage threshold or a power failure occurs, C1 discharges, and the emitter voltage of Q6 remains at U NET1 *R3 / (R3 + R4) - 0.7V, while the base voltage of Q6 decreases. At a certain moment, when the voltage difference between the emitter voltage and the base voltage of Q6 is greater than the conduction voltage U eb of Q6, Q6 conducts, Q5 conducts, the undervoltage alarm signal changes from 3.3V to 0V, the MCU detects this low level, issues an alarm signal and saves important data.

Claims

1. An overvoltage and undervoltage protection circuit for medical equipment, consisting of an overvoltage detection circuit and an undervoltage detection circuit, characterized in that: The overvoltage detection circuit is composed of a PMOS tube (Q3), a triode (Q1), resistors (R1, R2, R9, R10), and a voltage stabilizing diode D2. When the power input increases, the voltage of D2 is near the stable value, a voltage difference appears between the b pole and the e pole of Q1, and finally Q1 is turned on, the gate of Q3 is pulled up, Q3 is turned off, and the voltage at NET1 disappears; the undervoltage detection circuit is composed of a triode (Q5, Q6), a capacitor (C1), a diode (D1), and resistors (R3, R4, R5, R6, R7, R8). When the voltage at NET1 is normal, the capacitor C1 is charged through the resistor R4 and the diode D1; after the power supply is stable, the b pole of Q6 is the power supply voltage; since the b pole voltage is higher than the e pole voltage, the triode Q6 is not turned on; when Q6 is not turned on, there is no voltage at the b pole of Q5, and Q5 is also not turned on; when the voltage is too low, C1 is discharged, and the e pole voltage of Q6 is maintained at U NET1 *R3 / (R3+R4)-0.7V, and the voltage at the b pole of Q6 decreases. At a certain moment, when the voltage difference between the e pole voltage and the b pole voltage of Q6 is greater than the on-state voltage Ueb of Q6, Q6 is turned on, Q5 is turned on, and the undervoltage alarm voltage changes from 3.3V to 0V.

2. The overvoltage and undervoltage protection circuit for medical equipment according to claim 1, characterized in that: The overvoltage detection threshold is set by adjusting R10 and R9.

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