CN201149987Y - overvoltage protection device - Google Patents

Abstract

In order to solve the problems of surge voltage suppression and overvoltage protection, an overvoltage protection device is provided, which comprises a comparison module, a first switch, a second switch and an output switch. The comparison module compares the input voltage after the operation voltage division with a critical voltage, and outputs a control signal according to a comparison operation result. The control end of the first switch is coupled to the comparison module and controlled by the control signal. The control end of the second switch is coupled with the drain end of the first switch and is controlled by the output signal of the drain end of the first switch. The control end of the output switch is coupled with the drain end of the second switch, the drain end of the output switch is coupled with the voltage output end, the source end of the output switch is coupled with the voltage input end, and the output switch is controlled by the output signal of the drain end of the second switch to cut off the input voltage or transmit the input voltage to the voltage output end. The utility model discloses can reach the suppression of the protection of overvoltage and surge voltage.

Description

overvoltage protection device

technical field

The utility model provides an overvoltage protection device, in particular a circuit device with surge suppression and input overvoltage protection used in a power adapter (Power Adapter) or a palm-type device.

Background technique

Please refer to FIG. 1 , when an electrical device 20 using a DC power source (such as a notebook computer, a liquid crystal display, etc.) is to be powered by an AC power source, a power adapter 21 is required for power conversion. In FIG. 1 , the power converter 21 obtains AC power through an AC power plug 22 , and converts the AC power into a DC power output to supply power to the electrical equipment 20 . In the architecture of FIG. 1 , there is a common problem, that is, when the electrical equipment 20 is turned on (Tum On) or the AC power plug 22 of the power adapter 21 is inserted into the AC power outlet (not shown) in the initial state, very It is easy to cause an excessive surge voltage (Spike), resulting in excessive surge current (Inrush Current). Excessive inrush current often causes sparks in AC power sockets and switches or interferes with other electrical appliances in use, thereby affecting the power quality.

In addition, if the AC power received by the power adapter 21 is not stable enough (for example, the voltage is too high), the power adapter 21 will convert the overvoltage AC power into overvoltage DC power, and then send it to the electrical equipment 20 In this way, the overvoltage DC power supply will cause the electrical equipment 20 to burn out. Therefore, there is an urgent need for a surge voltage suppression circuit and an overvoltage protection circuit in the power adapter 21 to solve the aforementioned problems.

Utility model content

In order to solve the problem of suppressing surge voltage and protecting overvoltage, the utility model provides an overvoltage protection device, which is used in a power adapter (Power Adapter), and has the protection of suppressing surge and input overvoltage.

The overvoltage protection device of the first embodiment of the utility model has a voltage input terminal and a voltage output terminal, including a comparison module, a first switch, a second switch and an output switch. Wherein, the comparison module obtains the input voltage from the voltage input terminal, and the comparison module compares and calculates the input voltage and the critical voltage, and at the same time outputs a control signal according to the result of the comparison and calculation. The first control terminal of the first switch is coupled to the comparison module, the first drain terminal of the first switch is coupled to the voltage input terminal, and the first source terminal of the first switch is coupled to the ground terminal, wherein the first switch is controlled by the control signal. The second control terminal of the second switch is coupled to the first drain terminal, and the second source terminal of the second switch is coupled to the ground terminal, wherein the second switch is controlled by the output signal of the first drain terminal. The third control terminal of the output switch is coupled to the second drain terminal, the third drain terminal of the output switch is coupled to the voltage output terminal, and the third source terminal of the output switch is coupled to the voltage input terminal, wherein the output switch is controlled by the second drain terminal extreme output signal, while blocking the input voltage or passing the input voltage to the voltage output terminal.

In addition, the overvoltage protection device of the second embodiment of the present invention further includes a first surge suppressor and a second surge suppressor. Wherein, the first surge suppressor is coupled to the input voltage terminal and the second control terminal, and turns off the second switch according to the surge voltage. The second surge suppressor is coupled between the third control terminal and the third source terminal, and cuts off the output switch according to the surge voltage.

In the above overvoltage protection device, the comparison module may include: a shunt voltage regulator coupled to the voltage input terminal, the shunt voltage regulator generating the critical voltage value according to the input voltage; a voltage dividing unit coupled to the voltage input terminal , receiving the input voltage and generating a divided input voltage; and a comparator having a non-inverting input terminal, an inverting input terminal and an output terminal, the non-inverting input terminal receiving the divided input voltage, The inverting input terminal receives the critical voltage value, and the output terminal outputs the control signal.

In the above overvoltage protection device, the shunt regulator may include a Zener diode, an input capacitor, and an input resistor, wherein the Zener diode is coupled in series to the input resistor and coupled in parallel to the input capacitor.

In the above-mentioned overvoltage protection device, the first surge suppressor may include a first resistor coupled in series with the first capacitor, the first end of the first resistor is coupled to the input voltage end, and the first end of the first resistor The second terminal is commonly coupled to the first drain terminal of the first switch, the second control terminal of the second switch and the first terminal of the first capacitor, and the second terminal of the first capacitor is coupled to the ground terminal.

In the above overvoltage protection device, the second surge suppressor may include a second resistor coupled in parallel to the second capacitor, the first terminal of the second capacitor is coupled to the input voltage terminal, and the second capacitor of the second capacitor terminal is commonly coupled to the drain terminal of the second switch and the third control terminal of the output switch.

In the above overvoltage protection device, the first switch may be an N-channel field effect transistor.

In the above overvoltage protection device, the second switch may be an N-channel field effect transistor.

In the above overvoltage protection device, the output switch may be a P-channel field effect transistor.

In the above overvoltage protection device, the second switch, the output switch and the second surge suppressor can form a standard slow start circuit.

To sum up, the utility model can control the cut-off of the output switch through the judgment of the comparison module when the overvoltage is input, so as to achieve overvoltage protection. At the same time, when the surge voltage occurs, the first surge suppressor used in the utility model will guide the surge voltage to the ground terminal, and the second surge suppressor will short-circuit the control terminal and the source terminal of the output switch, It makes the output of the cut-off voltage, so as to prevent the surge voltage. Therefore, the utility model can achieve overvoltage protection and surge voltage prevention and control.

Description of drawings

FIG. 1 is a functional block diagram of a conventional power converter;

2 is a schematic diagram of a voltage protection device of the present invention;

3 is a schematic circuit diagram of the voltage protection device of the first embodiment of the present invention;

4 is a schematic circuit diagram of a voltage protection device according to a second embodiment of the present invention;

Figure 5A is a schematic diagram of the waveform of the output voltage when the utility model works at a normal input voltage;

Figure 5B is a schematic diagram of the waveform of the output voltage when the utility model works at an input voltage; and

FIG. 5C is a schematic diagram of the waveform of the output voltage when the utility model works when the surge voltage occurs.

Wherein, the reference signs are explained as follows:

Tradition:

Electrical Equipment 20

Power Converter 21

AC power plug 22

The utility model:

Voltage protection device 1, 1'

Voltage input terminal T1

Voltage output terminal T2

Input voltage Vin

Output voltage Vout

Compare Module 10

Shunt Regulator 101

Voltage divider unit 102

Comparator 103

Zener diode D1

Input Capacitor C1

Input resistor R1

Resistor R2, R3

first switch Q1

Second switch Q2

Output switch Q3

Threshold voltage Vth

Input voltage V1 after voltage division

Ground terminal G

Control signal S1

First surge suppressor 12

Second surge suppressor 14

First capacitor C2

first resistor R4

Second capacitor C3

Second resistor R5

Output signal S2, S3

Detailed ways

Please refer to FIG. 2 , which is a schematic diagram of the overvoltage protection device of the present invention. The overvoltage protection device 1 has a voltage input terminal T1 and a voltage output terminal T2. The overvoltage protection device 1 obtains an input voltage Vin from the voltage input terminal T1 and outputs an output voltage Vout from the voltage output terminal T2. When the input voltage Vin is introduced into the overvoltage protection device 1, if the voltage value of the input voltage Vin is greater than the preset protection range of the overvoltage protection device 1, the overvoltage protection device 1 will cut off the excessively high input voltage Vin, so that It cannot pass. In addition, if an excessive surge voltage occurs, the overvoltage protection device 1 will also cut off the input voltage Vin so that it cannot pass through.

In conjunction with FIG. 2 , please refer to FIG. 3 . FIG. 3 is a schematic circuit diagram of an overvoltage protection device according to a first embodiment of the present invention. The overvoltage protection device 1 includes a comparison module 10 , a first switch Q1 , a second switch Q2 and an output switch Q3 . Wherein, the comparison module 10 obtains the input voltage Vin from the voltage input terminal T1, and compares the input voltage Vin with the threshold voltage Vth, and outputs the control signal S1 according to the comparison result. Meanwhile, the first control terminal of the first switch Q1 is coupled to the comparison module 10, the first drain terminal of the first switch Q1 is coupled to the voltage input terminal T1, and the first source terminal of the first switch Q1 is coupled to a ground terminal G, Wherein, the first switch Q1 is controlled by the control signal S1.

With reference to FIG. 2, referring to FIG. 3, the second control terminal of the second switch Q2 is coupled to the first drain terminal of the first switch Q1, and the second source terminal of the second switch Q2 is coupled to the ground terminal G, wherein the second switch Q2 is controlled by the output signal S2 of the first drain terminal of the first switch Q1. In addition, the third control terminal of the output switch Q3 is coupled to the second drain terminal of the second switch Q2, the third drain terminal of the output switch Q3 is coupled to the voltage output terminal T2, and the third source terminal of the output switch Q3 is coupled to the voltage input terminal. T1, wherein the output switch Q3 is controlled by the output signal S3 of the second drain terminal of the second switch Q2 to cut off the input voltage Vin or transmit the input voltage Vin to the voltage output terminal T2.

Cooperating with Fig. 2, referring to Fig. 3, the aforementioned first switch Q1 is an N-channel field effect transistor (NMOS FET), the second switch Q2 is an N-channel field effect transistor (NMOS FET), and the output switch Q3 is a P-channel field effect transistor. Transistors (PMOS FETs).

With reference to FIG. 2 , referring to FIG. 3 , the comparison module 10 includes a shunt regulator 101 , a voltage dividing unit 102 and a comparator 103 . Wherein, the shunt regulator 101 includes a zener diode D1 , an input capacitor C1 and an input resistor R1 , wherein the zener diode D1 is coupled in series to the input resistor R1 and is coupled in parallel to the input capacitor C1 . The shunt regulator 101 is coupled to the voltage input terminal T1 to generate a threshold voltage Vth according to the input voltage Vin. Meanwhile, the voltage dividing unit 102 is coupled to the voltage input terminal T1, receives the input voltage Vin and generates a divided input voltage V1. In addition, the non-inverting input terminal (+) of the comparator 103 is used to receive the divided input voltage V1, while the inverting input terminal (-) of the comparator 103 receives the threshold voltage value Vth, and the comparator 103 The output end outputs the control signal S1.

With reference to Fig. 2 and Fig. 3, the designer can use Zener diode D1 with different working ranges to obtain the critical voltage value Vth, and can also design resistance values of resistors R2 and R3 in the voltage dividing unit 102 to set The required overvoltage protection range. When the input voltage Vin is introduced into the overvoltage protection device 1 , the zener diode D1 breaks down along with the input voltage Vin, thereby generating a stable threshold voltage Vth output. At the same time, the resistor R3 in the voltage dividing unit 102 generates a divided input voltage V1 according to the input voltage Vin.

When the input voltage Vin is normal, the divided input voltage V1 does not exceed the threshold voltage Vth, that is, it is lower than the preset protection range of the overvoltage protection device 1 . At this time, the comparator 103 outputs a control signal S1 with a low potential “LOW” to control the first switch Q1 to be turned off (OFF). Since the first switch Q1 enters the cut-off state, the input voltage Vin is sent to the second control terminal of the second switch Q2 through the first resistor R4 to control the second switch Q2 to conduct (ON). The turned-on second switch Q2 guides the third control terminal of the output switch Q3 to the ground terminal G, so that the output switch Q3 enters the conduction state. At this time, the input voltage Vin will be output from the voltage input terminal T1 of the overvoltage protection device 1 through the turned-on output switch Q3 to form the output voltage Vout. Please cooperate with FIG. 5A , which is a schematic diagram of the waveform of the output voltage Vout when the utility model works at a normal input voltage Vin. FIG. 5A shows that the output voltage Vout is 6V.

In addition, when the input voltage Vin is too high, the divided input voltage V1 exceeds the threshold voltage Vth, that is, exceeds the preset protection range of the voltage protection device 1 . At this time, the comparator 103 outputs a control signal S1 with a high potential “HIGH” to control the first switch Q1 to be turned on. The turned-on first switch Q1 guides the second control terminal of the second switch Q2 to the ground terminal G, thus causing the second switch Q2 to be turned off. The turned-off second switch Q2 makes the third control terminal of the output switch Q3 into a floating state, so that the output switch Q3 is turned off. The cut-off output switch Q3 will cut off the over-high input voltage Vin, so that the over-high input voltage Vin cannot pass through the voltage protection device 1, thereby achieving overvoltage protection. Please cooperate with FIG. 5B , which is a schematic diagram of the waveform of the output voltage Vout when the utility model works when the input voltage Vin is exceeded. FIG. 5B shows that the output voltage Vout is cut off to 0V after the transient time t1.

In conjunction with FIG. 2 , please refer to FIG. 4 , which is a schematic circuit diagram of an overvoltage protection device according to a second embodiment of the present invention. In the second embodiment of the present invention, the same elements as those of the first embodiment are shown with the same symbols. The principle of circuit action and the achieved functions and effects of the second embodiment and the first embodiment are the same, the main difference is that: the overvoltage protection device 1' of the second embodiment adds a first surge suppressor 12 and a second surge suppressor. Two surge suppressors 14. Wherein, the first surge suppressor 12 is coupled to the input voltage terminal T1 and the second control terminal of the second switch Q2, and turns off the second switch Q2 according to the inrush voltage (Inrush Voltage). The second surge suppressor 14 is coupled between the third control terminal and the third source terminal of the output switch Q3, and turns off the output switch Q3 according to the surge voltage.

With reference to FIG. 2 , referring to FIG. 4 , the first surge suppressor 12 includes a first resistor R4 serially coupled to the first capacitor C2, wherein the first end of the first resistor R4 is coupled to the input voltage terminal T1, and the first The second terminal of the resistor R4 is coupled to the first drain terminal of the first switch Q1, the second control terminal of the second switch Q2 and the first terminal of the first capacitor C2, and the second terminal of the first capacitor C2 is coupled to ground End G. In addition, the second surge suppressor 14 includes a second resistor R5 coupled in parallel to the second capacitor C3, the first terminal of the second capacitor C3 is coupled to the input voltage terminal T1, and the second terminal of the second capacitor C3 is commonly coupled to The second drain terminal of the second switch Q2 is connected to the third control terminal of the output switch Q3.

In conjunction with Figure 2, please refer to Figure 4. The surge voltage is high-frequency AC noise. Therefore, according to formula (1), when the surge voltage occurs, the first capacitor C2 and the second capacitor C3 will be affected by the high-frequency AC noise. A short circuit is formed due to the surge voltage (capacitive reactance is equal to 0).

$\mathrm{Xc}=-\mathrm{<figure-callout\; id="1"\; label="j"\; filenames="Y20082000125100131.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{1}{\mathrm{\&omega;c}}$ …Formula 1)

In formula (1), Xc is the capacitive reactance value of the capacitor, ω is the frequency value, and C is the capacitance value of the capacitor. When high-frequency AC noise occurs, the capacitive reactance value Xc of the capacitor is approximately equal to 0, so the capacitor A short circuit condition will be formed.

According to the aforementioned formula (1), when a surge voltage occurs, the first capacitor C2 in the first surge suppressor 12 will be short-circuited immediately, and the surge voltage will be guided to the ground terminal G. At this time, the short-circuited first capacitor C2 is connected between the second control terminal and the second source terminal of the second switch Q2 to control the second switch Q2 to enter a cut-off state. The disabled second switch Q2 allows the third control terminal of the output switch Q3 to form a floating state, so that the output switch Q3 is turned off. In addition, when the surge voltage occurs, the second capacitor C3 in the second surge suppressor 14 will also be short-circuited immediately. At this time, the short-circuited second capacitor C3 is connected across the third control terminal of the output switch Q3 and the third between the source terminals to control the output switch Q3 to enter the cut-off state. The cut-off output switch Q3 will cut off the input voltage Vin, so that the input voltage Vin cannot pass through the voltage protection device 1, so as to prevent the surge voltage. Please refer to FIG. 5C , which is a schematic diagram of the waveform of the output voltage Vout when the utility model works when the surge voltage occurs. FIG. 5C shows that when the surge voltage occurs, the output voltage Vout is immediately cut off to 0V.

Referring to FIG. 4 again, the second switch Q2, the output switch Q3 and the second surge suppressor 14 form a standard soft-start circuit. If a surge current occurs, the surge current will charge the second capacitor C3 in the slow start circuit, so that the current flowing through the output switch Q3 will not be so sharp, thereby achieving the prevention of the surge current .

In summary, the overvoltage protection device of the present invention has the function of suppressing surge and input overvoltage protection. When overvoltage is input, it can control the output switch to be cut off through the judgment of the comparison module, so as to achieve overvoltage protection. . At the same time, when a surge voltage occurs, the first surge suppressor can be used to guide the surge voltage to the ground terminal, and the second surge suppressor can be used to short-circuit the control terminal and the source terminal of the output switch, so that the output of the cut-off voltage , so as to achieve the prevention and control of surge voltage.

However, the above is only a detailed description and illustration of one of the best specific embodiments of the present utility model, and any changes or modifications that can be easily conceived by those skilled in the art within the scope of the present utility model can be included in this utility model. within the scope of utility models.

Claims (9)

1. an overvoltage protection is characterized in that, has voltage input end and voltage output end, comprising:

Comparison module is obtained input voltage from this voltage input end, this this input voltage of comparison module comparison operation and critical voltage, and export control signal according to the comparison operation result;

First switch, first control end of this first switch couples this comparison module, and first drain electrode end couples this voltage input end, and first source terminal is couple to earth terminal, and this first switch is controlled by this control signal;

Second switch, second control end of this second switch couples this first drain electrode end, and second source terminal couples this earth terminal, and this second switch is controlled by the output signal of this first drain electrode end;

The output switch, the 3rd control end of this output switch couples this second drain electrode end, the 3rd drain electrode end couples this voltage output end, the 3rd source terminal couples this voltage input end, this output switch is controlled by the output signal of this second drain electrode end, is used for maybe this input voltage being sent to this voltage output end by this input voltage;

First surge suppressor, this first surge suppressor couple this Input voltage terminal and this second control end, and this first surge suppressor comes by this second switch according to surge voltage; And

Second surge suppressor, this second surge suppressor couple between the 3rd control end and the 3rd source terminal, and this second surge suppressor comes by this output switch according to this surge voltage.

2. overvoltage protection as claimed in claim 1 is characterized in that, this comparison module comprises:

Shunt regulator couples this voltage input end, and this shunt regulator produces this critical voltage value according to this input voltage;

Partial pressure unit couples this voltage input end, receives this input voltage, and produces the input voltage after the dividing potential drop; And

Comparator, it has non-inverting input, reverse input end and output, and this non-inverting input receives the input voltage after this dividing potential drop, and this reverse input end receives this critical voltage value, and this output is exported this control signal.

3. overvoltage protection as claimed in claim 2 is characterized in that this shunt regulator comprises Zener diode, input capacitor and input resistor, wherein this this input resistor of Zener diode coupled in series and this input capacitor of coupled in parallel.

4. overvoltage protection as claimed in claim 1; it is characterized in that; this first surge suppressor comprises first resistor of coupled in series first capacitor; first end of this first resistor couples this Input voltage terminal; second end of this first resistor couples first drain electrode end of this first switch, second control end of this second switch and first end of this first capacitor jointly, and second end of this first capacitor couples this earth terminal.

5. overvoltage protection as claimed in claim 1; it is characterized in that; this second surge suppressor comprises second resistor of coupled in parallel second capacitor; first end of this second capacitor couples this Input voltage terminal, and second end of this second capacitor couples the drain electrode end of this second switch and the 3rd control end of this output switch jointly.

6. overvoltage protection as claimed in claim 1 is characterized in that, this first switch is the N slot field-effect transistor.

7. overvoltage protection as claimed in claim 1 is characterized in that, this second switch is the N slot field-effect transistor.

8. overvoltage protection as claimed in claim 1 is characterized in that, this output switch is the P-channel field-effect transistor (PEFT) transistor.

9. overvoltage protection as claimed in claim 1 is characterized in that, this second switch, this output switch and this second surge suppressor are formed the slow-start circuit of a standard.

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