TWI639285B - Surge protection circuit with timely switching off circuit - Google Patents

Abstract

The invention is a surge protection circuit with a timely switch-off circuit, comprising a first switch electrically connected between a power input end and a load connection end, and having a first control end; a capacitor electrically connected to a first resistor electrically connected between the first control terminal and a ground terminal; a second resistor electrically connected to the power input terminal and the ground Between the terminals; when an input power source electrically connected to the power input terminal generates a high voltage surge, both ends of the capacitor are equally short-circuited, so that the first switch is turned off in time to avoid the purpose of the high voltage surge entering the load circuit.

Description

Surge protection circuit with timely switching off circuit

A surge protection circuit, especially a surge protection circuit with a timely switch-off circuit.

The surge protection circuit is a circuit that is generally provided by the electronic device in order to avoid an abnormal high voltage when the input power of the electronic device 40 generates an abnormal high voltage, for example, a start surge, and the abnormal high voltage directly enters the electronic device. Cause damage. Generally, the surge protection circuit includes a switch Q and a driving circuit 30. The switch Q is electrically connected between the input power source VIN and the electronic device 40, and has a control terminal. The driving circuit 30 is electrically connected to the circuit. The input power source VIN and the control terminal of the switch Q receive an input voltage and drive the switch Q according to the input voltage. When the input power source VIN generates a normal operating voltage, the driving circuit 30 controls the switch Q to be turned on, so that the electronic device 40 accepts the input voltage to operate; when the input power source VIN generates an abnormal high voltage, for example, a start surge The driving circuit 30 controls the switch Q to form an open circuit to disconnect the electrical connection between the input power source VIN and the electronic device 40 to prevent abnormal high voltage of the input power source from entering the electronic device, so as to protect the electronic device 40. Subject to abnormal high voltage damage.

Since the driving circuit 30 is generally composed of a plurality of driving switches, that is, the operating mechanism of the surge protection circuit includes the interaction of a plurality of switches, and each of the driving switches has a respective reaction time, so from the input The power supply generates an abnormally high voltage. When the surge protection circuit operates and cuts off the input power supply VIN and the conduction of the load power 40, a specific total reaction time is required. When the number of the drive switches is increased, the total reaction time is obtained. It will be longer. During the total reaction time, the electronic device 40 may have been damaged by the entry of the abnormal voltage. Therefore, the existing surge protection circuit must be further improved.

In view of the fact that the existing driving circuit generates a high voltage surge at the input power source, it takes a long reaction time to turn off the switch, so that the load circuit connected to the input power source through the switch may have been subjected to the high voltage before the switch is turned off. The invention provides a surge protection circuit with a timely switch-off circuit, comprising a power input terminal, a load connection terminal, a first switch, a capacitor, a first resistor and a second resistor. The power input terminal is electrically connected to the input power source, and the load connection end is connected to the load circuit; the first switch is electrically connected between the power input end and the load connection end, and the switch has a first control terminal, the capacitor is electrically connected between the power input end and the first control end of the first switch, the first resistor is electrically connected between the control end of the first switch and a ground end, The second resistor is electrically connected between the power input end and the ground.

When the input power source generates a high voltage surge, the capacitor and the first resistor form a differential circuit. When the first control terminal of the first switch forms a voltage surge, the voltage across the capacitor is close to 0V, and the capacitor The two ends are equally short-circuited, so that the first switch is quickly turned off, so that the purpose of avoiding damage of the high-voltage surge wave entering the load circuit through the first switch is achieved.

Referring to FIG. 1 , the surge protection circuit with a timely switch-off circuit is connected between an input power supply VIN and a load circuit 20 , and the surge protection circuit with a timely switch-off circuit includes a power supply. The input terminal I/P, a load connection terminal O/P, a first switch Q1, a capacitor C, a first resistor R1, and a second resistor R2. The power input terminal I/P is connected to the input power source VIN, and the load connector O/P is connected to the load circuit 20.

The switch Q1 is electrically connected between the power input terminal I/P and the load connection terminal O/P, and has a first control terminal. The capacitor C is electrically connected to the power input terminal I/P and the first switch. The first resistor R1 is electrically connected between the first control terminal of the first switch Q1 and a ground terminal, and the second resistor R2 is electrically connected to the power input terminal I/P. And between the ground terminals.

When the input power supply VIN provides a stable voltage, for example, a stable operating voltage, the voltage across the second resistor R2 is equivalent to the voltage of the input VIN, and the capacitor C is equivalent to an open circuit, that is, the first resistor The voltage across R1 is zero, so that the capacitor C forms a stable voltage across the power input terminal I/P and the first control terminal of the first switch Q1, so that the first switch Q1 turns on the power input terminal I. /P and the load connection terminal O/P; when the voltage of the input power supply VIN rises rapidly, so that the power input terminal I/P rises rapidly in a short time, since the capacitor C cannot pass through the first resistor R1 in time Charging, the voltage on the capacitor C cannot produce a sudden change. At the moment when the input power source rises rapidly, the two ends of the capacitor C are equivalent to a short circuit, and the voltage across the capacitor C is zero, so that the first The switch Q1 is turned off in time when the voltage surge occurs, and an open circuit is formed between the power input terminal I/P and the load connection terminal O/P to prevent the voltage surge from entering the load circuit 20 in time. Further, the capacitor C forms a differential circuit with the first resistor R1. When the voltage of the power input terminal I/P rises rapidly, the connection between the capacitor C and the first resistor R1 is the first The first control terminal of the switch Q1 thus generates a voltage surge such that the voltage across the capacitor C approaches zero, thus causing the first switch Q1 to quickly and timely turn off when the power input I/P rises rapidly.

Referring to FIG. 2, in the first preferred embodiment of the present invention, the surge protection circuit with a timely switch-off circuit further includes a driving unit 10 electrically connected to the power input terminal I/P and the first The first control terminal of the first switch Q1 is electrically connected to the first control terminal of the switch Q1, and the first resistor R1 and the second resistor R2 are transmitted through the first resistor R1. The drive unit 10 is electrically connected to the ground.

The driving unit 10 receives the input power VIN through the power input terminal I/P, and controls the first switch Q1 according to the input power VIN. When the voltage supplied by the input power source VIN is greater than a first voltage, the driving unit 10 controls the first switch Q1 to be turned on, and when the voltage of the input power source VIN is greater than a second voltage, the driving unit 10 controls the first The switch Q1 is turned off, so that the first switch forms an open circuit between the power input terminal I/P pole and the load connection terminal O/P. Wherein the second voltage is greater than the first voltage.

Further, when the voltage of the power input terminal I/P is greater than the first voltage, for example, a normal operating voltage, the driving circuit turns on the first resistor R1 and the second resistor R2 and the ground terminal. The voltage across the capacitor C is equal to the voltage of the input power supply VIN. The first switch Q1 is thus turned on, and a path is formed between the load connection terminal O/P and the power input terminal I/P.

When the voltage of the power input terminal I/P is greater than the second voltage, the driving unit 10 forms an open circuit between the first resistor R1 and the second resistor R2 and the ground terminal, so that the two ends of the second resistor R2 The voltage is equal to the voltage of the input terminal I/P, the voltage across the second resistor R2 is zero, the voltage across the capacitor C is equal to the voltage of the input terminal I/P, and the voltage across the capacitor C is zero. Therefore, the first switch Q1 is turned off to prevent the input power source VIN from supplying the excessive voltage to the load connection terminal O/P.

Referring to FIG. 3, in a second preferred embodiment of the present invention, the surge protection circuit with a timely switch-off loop includes a first Zener diode ZD1, and the first Zener diode ZD1 has An anode and a cathode, the anode of the first Zener diode ZD is connected to the first control terminal, and a cathode thereof is electrically connected to the power input terminal I/P.

In the preferred embodiment, the first switch Q1 is a P-channel Metal-Oxide-Semiconductor-Field-Effect Transistor (PMOSFET) having a gate and a source. a drain, the source of which is electrically connected to the power input end, the drain of which is connected to the load connection end, and the gate thereof is the first control end.

When the voltage of the input power source VIN is at a breakdown voltage of the first Zener diode ZD1, for example, a normal operating voltage, the first Zener diode ZD1 is not turned on by a reverse voltage. The voltage across the Zener diode ZD1 is equal to the voltage across the capacitor C; when the input power supply VIN provides a voltage greater than the breakdown voltage of the first Zener diode ZD1, such as a peak of voltage chopping a voltage, the first Zener diode ZD1 collapses and conducts, and clamps a voltage across the source and the gate of the first switch Q1 to maintain a breakdown voltage of the first Zener diode ZD1, thereby avoiding The first switch Q1 is damaged by the voltage of the input VIN above its rated withstand voltage.

Referring to FIG. 4, in the third preferred embodiment of the present invention, the driving unit 10 includes: a second switch Q2, a third switch Q3, a second Zener diode ZD2, and a third base. The nano-diode ZD3, a third resistor R3, a fourth resistor R4, a fifth point resistor R5, and a sixth resistor R6. The second switch Q2 has a second control terminal, and the first resistor R1 is electrically connected to the ground through the second switch Q2, and the third switch Q3 is electrically connected to the second switch Q2. The control terminal and the ground terminal are connected to each other, and the third switch Q3 has a third control terminal.

The second Zener diode ZD2 has an anode and a cathode. The cathode of the second Zener diode ZD2 is connected to the power input terminal I/P, and the third resistor R3 is electrically connected to the second base. The anode of the polar body ZD2 and the second control end of the second switch Q2 are electrically connected between the anode of the second Zener diode ZD2 and the ground.

The third Zener diode ZD3 has an anode and a cathode, the third Zener diode ZD3 cathode is electrically connected to the power input terminal I/P, and the fifth resistor R5 is electrically connected to the third base The anode of the polar body ZD3 and the third control end of the second switch Q3 are electrically connected between the anode of the third Zener diode ZD3 and the ground.

In the preferred embodiment, the first voltage is a breakdown voltage of the second Zener diode ZD2, and the second voltage is a breakdown voltage of the third Zener diode ZD3.

In the preferred embodiment, the second switch Q2 and the third switch Q3 are respectively an npn-type Bipolar Junction Transistor (npn-type BJT), and each has a base, A set of poles, an emitter. The collector of the second switch Q2 is connected to the first resistor R1, the emitter of the second switch Q2 is connected to the ground, and the base of the second switch Q2 is the second control terminal; the third switch Q3 The collector is connected to the second control end of the second switch, the emitter of the third switch Q3 is connected to the ground, and the base of the third switch Q3 is the third control terminal.

When the voltage of the input power source VIN is greater than the first voltage and less than the second voltage, for example, a stable operating voltage, the voltage of the input power source VIN is less than the breakdown voltage of the third Zener diode ZD3, the third base The nano-diode ZD3 is not turned on by a reverse voltage, and the third switch Q3 is not turned on by a turn-on voltage, so the third switch Q3 is between the second control end of the second switch Q2 and the ground. Form an open circuit. Further, the voltage of the input power source VIN is greater than the breakdown voltage of the second Zener diode ZD2, and the second Zener diode ZD2 collapses and is turned on, so the input power source VIN passes through the turned-on second kinner The diode ZD2 and the third resistor R3 provide a second control terminal of the second switch Q2, such that the second switch Q2 is turned on, and the second switch Q2 is between the first resistor R1 and the ground. Form a path.

The capacitor C and the first resistor R1 are connected in series between the power input terminal I/P and the ground, and the capacitor C is connected in parallel with the first resistor R1 and the second resistor R2, that is, The voltage across the second resistor R2 is equivalent to the voltage across the capacitor C and the first resistor R1. Further, since the input power source VIN is a stable operating voltage, both ends of the capacitor C are equivalent to an open circuit, and the The first resistor R1 has no current passing through, so the voltage across the first resistor R1 is zero, the voltage across the capacitor C is equal to the voltage of the input power source VIN, and the gate of the first switch Q2 forms a conduction between the gate and the source. During the voltage across, the first switch Q1 is thus turned on, so that the voltage of the first power source VIN is supplied to the load connection terminal O/P through the first switch Q1.

When the voltage of the input power source VIN is greater than the second voltage, that is, greater than the breakdown voltage of the third Zener diode ZD3, the third Zener diode ZD3 collapses and conducts, and the input power source VIN passes through The third Zener diode ZD3 and the fifth resistor R5 provide a third control terminal-on voltage of the third switch Q3, and the third switch Q3 is therefore at the second control end of the second switch Q2 and the ground. The second control terminal of the second switch Q2 is electrically connected to the ground, and the second switch Q2 is thus turned off, thereby forming an open circuit between the first resistor R1 and the ground. The voltage at both ends is equal to the voltage of the input power source VIN, that is, the voltage across the capacitor C is zero between the source and the gate of the first switch Q1, and the first switch Q1 is thus turned off and not turned on. The first switch Q1 forms an open circuit between the power input terminal I/P and the load connection terminal O/P, thereby preventing the voltage of the input power source VIN greater than the second voltage from entering the load circuit 20.

In summary, when the input power supply VIN provides a stable operating voltage greater than the first voltage, the driving unit turns on the first resistor R1 and the ground, so that the capacitor C provides the first switch. The first switch Q1 is turned on when the voltage of the input power source VIN is greater than the second voltage, and the driving unit 10 forms a gap between the first resistor R1 and the ground terminal. In the open circuit, the voltage across the capacitor C is equal to the voltage of the input power source VIN, and the first switch Q1 is thus turned off. When the voltage of the input power source VIN suddenly rises, even if the reaction time of the driving unit 10 cannot turn off the first switch Q1 in time, the capacitance C is in the first stage due to the differential effect of the capacitor C and the first resistor R1. The first control terminal of a switch Q1 generates a voltage surge, and the voltage across the capacitor C instantaneously drops to zero, so that the first switch Q1 is quickly turned off in time to avoid the sudden rise of the input voltage in the driving unit. The load circuit 20 is entered through the first switch Q1 that has not been turned off before the operation is performed.

Referring to FIG. 5, in a fourth preferred embodiment of the present invention, an output capacitor Cout is electrically connected between the load connection terminal O/P and the ground terminal to suppress the The high frequency voltage of the load connection O/P.

In the preferred embodiment, the surge protection circuit with a timely switch-off loop further includes an input diode Din, wherein the first switch Q1, the capacitor C, and the second resistor R2 pass through the input diode Din is electrically connected to the power input terminal I/P, and the input diode Din has an anode and a cathode, wherein an anode of the input diode Din is electrically connected to the power input terminal I/P, the input diode The cathode of the body Din is electrically connected to the first switch Q1, the capacitor C, and the second resistor R2.

The input diode Din provides a rectification protection. When the load circuit 20 generates a chopping voltage, the peak voltage of the chopping voltage is prevented from entering the input power source VIN, or the capacitor C is prevented from generating a discharge. Reverse the power supply VIN, thus avoiding damage to the input power supply VIN.

The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Although the present invention has been disclosed in the above preferred embodiments, it is not intended to limit the present invention. A person skilled in the art can make some modifications or modifications to equivalent embodiments by using the above-disclosed technical contents without departing from the technical scope of the present invention, but without departing from the technical solution of the present invention, according to the present invention. Technical Substantials Any simple modifications, equivalent changes and modifications made to the above embodiments are still within the scope of the technical solutions of the present invention.

VIN‧‧‧ input power

20‧‧‧Load circuit

I/P‧‧‧ power input

O/P‧‧‧ load connection

Q1‧‧‧First switch

R1‧‧‧first resistance

R2‧‧‧second resistance

C‧‧‧ capacitor

ZD1‧‧‧First Kina diode

ZD2‧‧‧Second Kina diode

ZD3‧‧‧ third Kina diode

R3‧‧‧ third resistor

R4‧‧‧fourth resistor

R5‧‧‧ fifth resistor

R6‧‧‧ sixth resistor

Q2‧‧‧Second switch

Q3‧‧‧third switch

Cout‧‧‧ output capacitor

Din‧‧‧ input diode

30‧‧‧Drive unit

40‧‧‧Electronic devices

Q‧‧‧ switch

1 is a circuit diagram of an embodiment of a surge protection circuit with a timely switch-off circuit of the present invention. 2 is a circuit diagram of a first preferred embodiment of the surge protection circuit of the present invention having a timely switch-off circuit. 3 is a circuit diagram of a second preferred embodiment of the surge protection circuit of the present invention having a timely switch-off circuit. 4 is a circuit diagram showing a third preferred embodiment of the surge protection circuit of the present invention having a timely switch-off circuit. FIG. 5 is a schematic circuit diagram of a fourth preferred embodiment of the surge protection circuit of the present invention with a timely switch-off circuit. Figure 6 is a circuit diagram of a prior art surge protection circuit.

Claims (8)

A surge protection circuit with a timely switch-off circuit is connected between an input power supply and a load circuit, and includes: a power input end, the power supply is connected to the input power; and a load connection end, the power supply is connected to the a load circuit; a first switch electrically connected between the power input end and the load connection end, and the switch has a first control end; a capacitor electrically connected to the power input end and the first switch A first resistor is electrically connected between the control terminal of the first switch and a ground terminal; a second resistor is electrically connected between the power input terminal and the ground terminal. The hop protection circuit with a timely switch-off loop as described in claim 1, further comprising: a driving unit electrically connected to the power input terminal, wherein: when the voltage of the input power source is greater than a first voltage and less than one When the voltage is two, the driving circuit controls the first switch to be turned on; when the voltage of the input power source is less than the first voltage or greater than the second voltage, the driving circuit controls the first switch to be non-conductive. The surge protection circuit with a timely switch-off circuit according to claim 1, further comprising: a first Zener diode having an anode and a cathode, the anode of which is connected to the control end of the first switch, and the cathode thereof Connect the power input. The surge protection circuit of claim 2, wherein the driving unit further comprises: a second switch having a second control end; wherein the first resistor is electrically connected to the ground through the second switch; a third switch electrically connected to the second control end of the second switch Between the grounding ends and having a third control end; a second Zener diode having an anode and a cathode, the cathode of which is connected to the power input end; and a third resistor electrically connected to the second base a cathode between the anode and the second control end of the second switch; a fourth resistor electrically connected between the anode of the second base and the ground; and a third Zener diode The body has an anode and a cathode, the cathode of which is connected to the input power source; a fifth resistor is electrically connected between the anode of the third Zener diode and the third control end of the third switch; And a sixth resistor electrically connected between the anode of the third Zener diode and the ground; wherein a breakdown voltage of the second Zener diode is less than a breakdown voltage of the third Zener diode. The surge protection circuit with a switch-off loop as described in claim 4, wherein: the second open relationship is an npn-type bipolar junction transistor having a base, a collector, and an emitter, wherein The collector of the second switch is connected to the first resistor, the emitter of the second switch is connected to the ground, and the base of the second switch is the second control terminal; the third open relationship is an npn-type bipolar connection The surface transistor has a collector, an emitter, and a base, wherein the collector of the third switch is connected to the second control end of the second switch, and the emitter of the third switch is connected to the ground. And the base of the third switch is the third control end. The surge protection circuit of claim 1, wherein the first open relationship-p-type metal oxide semiconductor field effect transistor has a gate, a source, and a drain; , The source is electrically connected to the power input end; the drain is connected to the load connection end; the gate is the first control end. The surge protection circuit of claim 1, wherein the output protection capacitor is electrically connected between the load circuit and the ground. The surge protection circuit of the present invention as claimed in claim 1, further comprising: an input diode; wherein the first switch, the capacitor, and the second resistor are electrically connected through the input diode Up to the power input end, the input diode has an anode and a cathode; wherein the anode is electrically connected to the power input end, and the cathode electrically connects the first switch, the capacitor, and the second resistor.