KR20170009559A - Over voltage protection circuit - Google Patents

Abstract

An overvoltage protection circuit according to an embodiment of the present invention includes an AC voltage input section, a rectifying section for rectifying an output voltage of the AC input section, an overvoltage sensing section connected to an output terminal of the rectifying section, And a latch circuit for putting the signal of the control terminal to a low state based on the voltage of the overvoltage sensing section, thereby protecting the circuit and the circuit element from the AC overvoltage input and improving the stability.

Description

[0001] OVER VOLTAGE PROTECTION CIRCUIT [0002]

The present invention relates to an overvoltage protection circuit. And more particularly, to an overvoltage protection circuit capable of preventing the circuit from being burned down when an AC overvoltage is input.

An AC / DC converter for converting an AC voltage into a DC voltage is often used as a power supply for supplying power to an electronic device.

Generally, the AC / DC converter can rectify the commercial AC power of 220V to DC and convert the rectified DC voltage to the required DC operating voltage.

However, when an overvoltage occurs when the AC / DC converter is converted into a DC voltage, there is a limit in protecting the internal parts of the power supply by the overvoltage.

In addition, if a three-phase AC circuit is erroneously connected, a high voltage may be applied to the circuit, causing the circuit element to be burned out, and in some cases, there may be a risk of fire and explosion.

Therefore, there is an increasing number of researches on how to protect the circuit in the event of AC overvoltage.

.

It is an object of the present invention to provide an overvoltage protection circuit that can protect circuits and circuit elements from AC overvoltage inflow.

According to one aspect of the present invention, there is provided an overvoltage protection circuit comprising: an AC voltage input unit; a rectifying unit for rectifying an output voltage of the AC input unit; an overvoltage sensing unit connected to an output terminal of the rectifying unit; And a latch circuit for putting the signal of the control terminal to a low state based on the voltage of the overvoltage sensing part, thereby protecting the circuit and the circuit element from the AC overvoltage input, The stability can be improved.

According to at least one of the embodiments of the present invention, there is an advantage in that the circuit and circuit elements can be protected from AC overvoltage input.

In addition, according to at least one of the embodiments of the present invention, there is an advantage that the AC voltage can be stably converted to the DC voltage.

Meanwhile, various other effects will be directly or implicitly disclosed in the detailed description according to the embodiment of the present invention to be described later.

Figure 1 illustrates a simplified example of the voltage flow at the AC input.
Figure 2 is a diagram referred to illustrate the AC overvoltage type.
Figs. 3 to 5 are diagrams referred to in explaining the overvoltage protection circuit according to the embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it is needless to say that the present invention is not limited to these embodiments and can be modified into various forms.

In the drawings, the same reference numerals are used for the same or similar parts throughout the specification.

The suffix "module" and " part "for components used in the following description are given merely for convenience of description and do not give special significance or role in themselves. Accordingly, the terms "module" and "part" may be used interchangeably.

Figure 1 illustrates a simplified example of the voltage flow at the AC input.

A power supply device using a commercial AC power supply may be provided with an AC / DC converter circuit for obtaining a constant constant voltage output to a household appliance or an industrial electronic device.

Such a power supply device first receives an AC voltage from an AC power source.

The AC power source may be an AC power source having a voltage of 110V or 220V and having a different voltage.

Referring to FIG. 1, the AC filter 110 performs noise included in the input AC voltage. The frequency of the AC input power source is typically 50 Hz to 60 Hz, and the AC filter 110 removes lower or higher frequencies.

On the other hand, the rectifying / smoothing part converts the alternating current into direct current. The rectification / smoothing part can be implemented as a bridge diode circuit in which the alternating current is half-wave rectified and the diode is connected in bridge form.

For example, as shown in FIG. 1, the AC input voltage can be full-wave rectified by the bridge diode 120 to output a pulsating voltage.

And smoothed by a smoothing circuit (not shown) to convert the full-wave rectified AC input voltage into a DC voltage 130. [ The smoothing circuit may be composed of a smoothing capacitor, a low-frequency filter using elements of L and C, and other elements of R, L, and C.

On the other hand, when an instantaneous surge and an overvoltage are applied to an electronic device for various reasons such as AC power instability and lightning, there is a risk that the circuit element is burned. That is, the surge voltage can be directly applied to the rectifying circuit, the smoothing circuit, etc., and the circuit elements used in each circuit can be burned out.

In order to solve this problem, a surge protection circuit can be constructed by inserting a varistor.

A varistor is a semiconductor device whose resistance varies depending on the input voltage. Since the varistor acts as a nonconductor at a certain voltage or lower, it has no effect on the circuit.

However, when a certain amount or more of the voltage is applied to the varistor, it becomes a conductor.

Accordingly, the varistor can emit electricity to another place or absorb the self, thereby protecting the device from surge.

Typically, surge protection circuits are often designed to protect up to about 450V.

On the other hand, surge protection circuits can not protect the circuit elements in the power supply if overvoltage deviates from the design value of the surge protection circuit, or if constant overvoltage is applied instead of surge voltage.

For example, a continuous overvoltage may be introduced into a circuit during a phase mis-connection of a three-phase AC power source.

Fig. 2 is a diagram referred to explain the AC overvoltage type, illustrating the case of mis-miswiring of three-phase AC power.

When the phase voltage of the 3-phase AC power supply is 220V, the line voltage due to the phase-to-phase connection is 220V * √3 = 320V, and the phase voltage of the 3-phase AC power supply is 277V, the line voltage due to the phase-to-phase connection is 277V * √3 = 480V do.

Assuming that commercial AC power is 220V, it should be connected to Neutral in 3-phase 4-wire type, but in case of mis-wiring, phase-to-phase voltage may be 540V. Therefore, it is higher than the design value of a conventional surge protection circuit, so that other circuit elements can be burned out. Not only surge protection circuits can be destroyed.

In addition, the surge protection circuit can only cope with the surge voltage, and the circuit can not be protected when the overvoltage continues to flow due to the misalignment.

Therefore, the present invention proposes a corresponding overvoltage protection circuit for miswiring or for continuous overvoltage.

Figs. 3 to 5 are diagrams referred to in explaining the overvoltage protection circuit according to the embodiment of the present invention.

3, an overvoltage protection circuit according to an exemplary embodiment of the present invention includes an AC voltage input unit 310 to which an AC power is input, a rectification unit 320 to rectify an output voltage of the AC input unit 310, A control unit (Main IC) 450 for stopping the operation of the power supply unit based on the signal of the control terminal, and a control unit 350 for controlling the voltage of the overvoltage sensing unit 350 And a latch circuit 400 for turning the signal of the control terminal to a low level.

If the voltage sensed by the overvoltage sensing unit 350 is equal to or greater than a predetermined value, it can be determined that the overvoltage is flowing.

Therefore, if the voltage sensed by the overvoltage sensing unit 350 is equal to or greater than a predetermined value, the latch circuit 400 can switch the control terminal of the connected main IC 450, particularly the control unit, to the low state. have.

Accordingly, the control unit 450 can stop the operation of the power supply unit to prevent the overvoltage input.

Meanwhile, the AC voltage input unit 310 may include an AC filter for filtering noise introduced by an AC power source.

The AC filter eliminates the noise included in the input AC voltage, and the AC input power source has a frequency of 50 Hz to 60 Hz, so that the AC filter can remove the lower or higher frequency.

The AC filter may be implemented by a combination of a capacitor C and an inductor L to remove a noise component of an input electrical signal.

Meanwhile, the AC voltage input unit 310 further includes a transformer or a transformer circuit, so that the input voltage can be transformed as needed.

Meanwhile, the overvoltage protection circuit according to an embodiment of the present invention may further include a surge protection circuit 325. For example, the surge protection circuit 325 may comprise a varistor.

A varistor is a semiconductor device whose resistance varies depending on the input voltage. Since the varistor acts as a nonconductor at a certain voltage or lower, it has no effect on the circuit.

However, when a certain amount or more of the voltage is applied to the varistor, it becomes a conductor.

Accordingly, the varistor can emit electricity to another place or absorb the self, thereby protecting the device from surge.

When a predetermined AC voltage is applied from the outside, the rectifying unit 320 receives the AC voltage and rectifies it by half-wave rectification or full-wave rectification according to the circuit configuration. This rectifying action is generally accomplished through a rectifying diode.

When a single diode is used, only half-wave rectification is possible, but full-wave rectification can be performed by using a bridge diode having four diodes.

According to an embodiment, the rectifying unit 320 may be a bridge diode.

In the present invention, the overvoltage sensing unit 350 may be connected to the output terminal of the rectifying unit 320, particularly, the output terminal of the bridge diode.

The overvoltage sensing unit 350 includes voltage dividing resistors R1 and R2 for dividing the output voltage of the rectifying unit 320 and a voltage detecting unit 320 connected to the first node A between the voltage dividing resistors R1 and R2 And a delay capacitor C1.

Although the two voltage dividing resistors R1 and R2 are illustrated in FIG. 3, the present invention is not limited thereto. For example, voltage division may be performed using three or more resistors or a circuit element replacing the resistor to divide the output voltage of the rectifying unit 320 up to an appropriate value.

Meanwhile, when the surge is applied to the circuit, the delay capacitor C1 can prevent the latch circuit 400 and the like from performing the overvoltage protection operation.

When the momentary surge voltage is applied, the surge voltage is divided by the voltage dividing resistors R1 and R2, and a certain type of charging operation is performed from the delay capacitor C1 to a predetermined value to delay the operation of the latch circuit 400 .

On the other hand, the surge protection circuit 325 performs a corresponding operation to the surge voltage, thereby protecting the circuit.

The overvoltage sensing unit 350 may further include a first diode D1 having one end connected to the first node A and the other end connected to the latch circuit 400. [

In this case, the first diode D1 may be turned on at an overvoltage input higher than a predetermined voltage. That is, the first diode D1 may be turned on when the voltage value of the first node A becomes higher than a predetermined voltage.

Meanwhile, the latch circuit 400 may pass the control terminal to the ground (GND) based on the sensing voltage of the overvoltage sensing unit 350.

That is, if the voltage value of the first node A becomes higher than a preset voltage, the latch circuit 400 can switch the control terminal of the controller 450 to the ground (GND) to switch to the low state.

Meanwhile, according to an embodiment, a capacitor (X-cap) may be connected in series to the front end of the rectifying circuit 320 to increase the internal pressure.

Typically, the power supply of an electronic device may include a capacitor for the purpose of EMI suppression. In particular, a line-to-line arrangement for filtering differential mode noise is referred to as an X-cap.

When the X-cap is connected in series to the front end of the rectifier circuit 320, the internal pressure can be increased.

4, the latch circuit 400 includes first and second transistors Q1 and Q2 which are turned on and off by the voltage of the overvoltage sensing unit 350, .

In this case, when the first and second transistors Q1 and Q2 are turned on, the signal of the control terminal of the controller 450 may be changed from a high state to a low state.

That is, when an overvoltage flows from the outside, the overvoltage sensing unit 350 connected to the output terminal of the bridge diode 320 senses this, and the latch circuit 400 implements a latch mode to stop the operation of the power supply .

The overvoltage sensing unit 350 may sense the voltage value of a predetermined node, for example, the first node A, and configure the latch circuit 400 to operate when the voltage value is greater than a predetermined value. To this end, the overvoltage sensing unit 350 may include a switching element such as a diode D1 and a transistor.

Meanwhile, the latch circuit 400 may include first and second transistors Q1 and Q2. In addition to the first and second transistors Q1 and Q2, the latch circuit 400 further includes circuit elements for forming a path, .

The base of the second transistor Q2 may be connected to the collector of the first transistor Q1.

The collector terminal of the second transistor Q2 may be connected to a resistor connected in parallel with one end of the capacitor and a base end of the first transistor Q1.

At this time, the resistor connected in parallel and the other end of the capacitor may be connected to a ground (GND).

The time constant of the resistor and the capacitor connected in parallel can be changed according to the device value, and the time when the first transistor Q1 is turned on can be adjusted by adjusting the time constant.

4, a resistor connected in parallel with the emitter terminal of the second transistor Q2 may be connected to one end of the capacitor.

4, the control terminal of the controller 450, particularly, the controller 450 may be connected to the collector terminal of the first transistor Q1 and the base terminal of the second transistor Q2.

A diode or a switching element may be disposed between the base end of the first transistor Q1 and the control terminal of the control unit 450, and the second transistor Q2.

On the other hand, when an overvoltage is input to the circuit, that is, the first diode D1 is turned on and applied to the base end of the first transistor Q1, the first transistor Q1 is turned on.

Accordingly, the second transistor Q2 may be turned on, and the collector terminal of the first transistor Q1 and the base terminal of the second transistor Q2 may be grounded.

The diode is turned on between the base end of the first transistor Q1 and the control terminal of the controller 450 and the control terminal of the controller 450 is grounded GND) to switch to the low state.

Meanwhile, when the electric signal of the control terminal is changed to the low state, the controller 450 stops the operation of the power supply device to prevent the overvoltage input.

Accordingly, it is possible to provide a protection function that cuts off the power supply when an abnormal condition such as an overvoltage input occurs.

On the other hand, the power supply must be turned off and on again or reset to operate again.

Meanwhile, the overvoltage sensing unit 350 and the latch circuit 400 may be referred to as an overvoltage protection circuit unit.

5, an overvoltage protection circuit according to an embodiment of the present invention includes an AC voltage input unit 510 to which an AC power is input, a bridge diode 520 to rectify an output voltage of the AC input unit 510, An overvoltage protection circuit unit 530 connected to the output terminal of the power supply unit 520, and a control unit (Main IC) 450 for stopping the operation of the power supply unit based on the signal of the control terminal.

In this case, the overvoltage protection circuit unit 530 may include the overvoltage sensing unit 350 and the latch circuit 400 described above.

The overvoltage protection circuit according to an embodiment of the present invention may further include a smoothing circuit unit 525 for smoothing the voltage rectified through the bridge diode 520 and converting the smoothed voltage into a predetermined DC voltage.

On the other hand, a full-wave rectifier circuit can be implemented using an intermediate tap transformer and two diodes without using the bridge diode 520. [

However, since the power supply voltage is reduced by half in comparison with the case of using the intermediate tap, and the magnitude of the voltage applied to the non-conducting diode in the opposite direction is also reduced by half, so that the method using the bridge diode composed of four diodes Is more preferable.

5, the smoothing circuit 525 may smoothly convert the ripple voltage rectified through the rectifier circuit such as the bridge diode 520 and convert the rectified ripple voltage into a direct current. The smoothing circuit 525 may be a capacitor.

Alternatively, the smoothing circuit 525 can be configured by combining a capacitor and a resistor.

Alternatively, the smoothing circuit 525 may be constituted by a circuit in which a capacitor and an inductor are combined to realize a more stable operation.

That is, the configurations of the bridge diode 520 and the smoothing circuit 525 shown in FIG. 5 are illustrative, and the present invention is not limited thereto and can be replaced with any type of circuit capable of performing the rectifying and smoothing functions have.

On the other hand, the DC voltage converted in the smoothing circuit 525 is applied to the inside of the circuit and used as a power source.

On the other hand, if the DC voltage is converted into a predetermined DC voltage through the smoothing circuit 525, it can be converted into a DC voltage of a size suitable for use by using the transformer circuit 540, and then supplied to the load LOAD.

The voltage required by the components in the electronic equipment and the electronic equipment varies, so that the transformer circuit 540 can transform the voltage to an appropriate voltage and supply it to the load LOAD.

Meanwhile, in some embodiments, the overvoltage protection circuit may further include a power factor correction circuit for generating a power factor correction voltage.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It should be understood that various modifications may be made by those skilled in the art without departing from the spirit and scope of the present invention.

AC Inputs: 310
Rectification part: 320
Overvoltage sensing part: 350
Latch circuit: 400
Control section: 450

Claims (9)

An AC voltage input unit;
A rectifier for rectifying an output voltage of the AC input unit;
An overvoltage sensing unit connected to an output terminal of the rectifying unit;
A control unit for stopping the operation of the power supply unit based on the signal of the control terminal; And
And a latch circuit that turns a signal of the control terminal to a low state based on a voltage of the overvoltage sensing portion. The method according to claim 1,
Wherein the rectifying unit is a bridge diode. The method according to claim 1,
The overvoltage sensing unit includes:
Voltage dividing resistors for dividing an output voltage of the rectifying unit, and a delay capacitor connected to a first node between the voltage dividing resistors. The method of claim 3,
The overvoltage sensing unit includes:
Further comprising a first diode having one end connected to the first node and the other end connected to the latch circuit. 5. The method of claim 4,
Wherein the first diode is turned on when the overvoltage is higher than a predetermined voltage. The method according to claim 1,
Wherein the latch circuit passes the control terminal to ground (GND) based on a voltage of the overvoltage sensing unit. The method according to claim 1,
Wherein the latch circuit includes first and second transistors whose on and off states are determined by a voltage of the overvoltage sensing unit. 8. The method of claim 7,
Wherein when the first and second transistors are turned on, the signal of the control terminal is switched from a high state to a low state. The method according to claim 1,
Wherein the AC voltage input unit includes an AC filter for filtering noise introduced by an AC power source.

Images