TW201427212A - Over current protection circuit and power supply thereof - Google Patents

Abstract

An embodiment of the present invention discloses an over current protection circuit and a power supply thereof. The over current protection circuit includes a current transformer, a scale resistance, and an auxiliary switching unit. The current transformer is coupled to a current path of a primary switching unit, and the current transformer generates an auxiliary current according to a primary current within the current path. The scale resistance is electrically connected to the current transformer, and the scale resistance generates a first voltage signal according to the auxiliary current. The auxiliary switching unit is electrically connected to the scale resistance, and the auxiliary switching unit turns on or turns off the primary switching unit according to the control of the first voltage signal. Therefore, the present invention can turn off the primary switching unit in time to avoid damages to the primary switching unit.

Description

Overcurrent protection circuit and its power supply

The present invention relates to an overcurrent protection circuit and a power supply thereof, and more particularly to an overcurrent protection circuit applied to a power switching element and a power supply thereof.

Conventionally, a power supply unit usually has a plurality of power switching elements, and by controlling the power switching elements, it is possible to selectively output power of the power supply. Please refer to FIG. 1. FIG. 1 is a schematic diagram of a conventional power supply. As shown in FIG. 1, the power supply 9 of the bridge architecture may have four power switching elements SW1, SW2, SW3, SW4. The power supply 9 can switch on the power switching elements SW1 and SW4, or turn on the power switching elements SW2 and SW3 to supply power to the load R at the back end.

However, when a malfunction occurs, the power switching elements of the same arm (for example, the power switching elements SW1 and SW2, or the power switching elements SW3 and SW4) are simultaneously turned on. At this time, the resistance value between the voltage source Vin and the ground terminal is extremely small, and the current flowing through each power switching element is inevitably increased rapidly. Not only will the power switching components be damaged by overvoltage, overcurrent or overpower, but the load R or other components on the line will also be destroyed due to uncontrollable paths.

Accordingly, the industry needs an overcurrent protection circuit and its power supply, which can solve the damage caused by overcurrent of the power switching component and reduce the return rate of the product to the factory.

In view of this, the present invention is directed to an overcurrent protection circuit that can sample a current flowing through a power switching element and directly convert an abnormal current into a voltage signal to quickly turn off the power switching element to avoid damage of the power switching element.

Embodiments of the present invention provide an overcurrent protection circuit including a current comparator, a proportional resistance element, and an auxiliary switching element. The current transfer path of the main switch element coupled to the current transformer generates a slave current according to the main current in the current transfer path. The proportional resistance element is electrically connected to the current comparator, and generates a first voltage signal according to the current. The auxiliary switching element is electrically connected to the proportional resistance element and is controlled by the first voltage signal to selectively control the main switching element to be turned on or off.

In an exemplary embodiment of the invention, the main reclosing element and the auxiliary switching element are power transistors, and the control end of the auxiliary switching element is electrically connected to the proportional resistance element, and the 汲 terminal of the auxiliary switching element is electrically connected to the control end of the main switching element. The source terminal of the auxiliary switching element is electrically connected to the source terminal of the main switching element. In addition, when the first voltage signal exceeds the first threshold, the auxiliary switching element is turned on, and the control end of the main switching element is electrically connected to the source terminal of the main switching element via the auxiliary switching element.

The invention provides a power supply device with an overcurrent protection circuit, which can sample the current flowing through the power switching element and directly convert the abnormal current into a voltage signal, and quickly close the power shutoff component to avoid power. Damage to the switching element and the power supply.

Embodiments of the present invention provide a power supply including at least one main switching element and an overcurrent protection circuit, the overcurrent protection circuit including a current comparator, a proportional resistance element, and an auxiliary switching element. Current transformer The current transmission path of the main switching element is correspondingly generated according to the main current in the current transmission path. The proportional resistance element is electrically connected to the current comparator, and generates a first voltage signal according to the current. The auxiliary switching element is electrically connected to the proportional resistance element and is controlled by the first voltage signal to selectively control the main switching element to be turned on or off.

In summary, the overcurrent protection circuit and the power supply thereof provided by the embodiments of the present invention have a simple circuit design and an immediate response speed, and can directly sample the current flowing through the power switching element, and directly an abnormality. The current is converted into a voltage signal such that the voltage signal can be quickly turned off by the voltage signal to avoid damage to the power switching element.

The detailed description of the present invention and the accompanying drawings are to be understood by the claims The scope is subject to any restrictions.

Referring to FIG. 2, FIG. 2 is a functional block diagram of an overcurrent protection circuit according to an exemplary embodiment of the present invention. As shown in FIG. 2, the overcurrent protection circuit 1 is configured to detect a current flowing through the main switching element Q1, and determine whether the current is abnormal by a simple circuit, thereby generating a corresponding feedback signal to control the main switching element Q1. Turn on or off. Here, the overcurrent protection circuit 1 includes at least a current transformer 10, a proportional resistance element 12, and an auxiliary switching element 14. In an example, between the proportional resistance element 12 and the auxiliary switching element 14, the first diode 16 and the first auxiliary are electrically connected. Resistance 18. In addition, between the main switching element Q1 and the auxiliary closing element 14, the second diode 20 and the second auxiliary resistor 22 are electrically connected.

The current transformer 10 couples the current transmission path of the main switching element Q1, and correspondingly generates a slave current according to the main current in the current transmission path. In practice, the primary reclosing element Q1 and the auxiliary switching element 14 can be power switches, power transistors. It will be apparent to those skilled in the art that the current transfer path of the main reclosing element Q1 refers to a line that receives current from the drain of the main switching element Q1 and then outputs current from the source. In the example of Fig. 2, the current transformer 10 can be placed on a line connected to the source terminal of the main switching element Q1. Of course, the present invention does not limit the arrangement position of the flow controller 10. For example, the flow controller 10 can also be disposed on a line connected to the 汲 terminal of the main switching element Q1. Thereby, the comparator 10 can couple the main current flowing through the main switching element Q1 at a specific ratio to generate a corresponding slave current, which can be designed by a person skilled in the art.

The proportional resistive element 12 is electrically connected to the flow comparator 10, for example, the proportional resistive element 12 can be connected in parallel with the flow comparator 10. In practice, the proportional resistance element 12 can be a passive component having a fixed resistance value, so that the proportional resistor element 12 generates a first voltage according to the relationship between the current value of the current output from the current transformer 10 and the resistance value. signal.

The first voltage signal is used as the control terminal voltage of the auxiliary switching element 14. Accordingly, the auxiliary switching element 14 is electrically connected to the proportional resistance element 12, controlled by the first voltage signal to selectively control the main closing element Q1 to be turned on or off. In practice, when the first voltage signal exceeds the first threshold, the auxiliary switching element 14 is controlled to conduct. The first A voltage signal may be a threshold voltage of the auxiliary switching element 14, and when the auxiliary switching element 14 is turned on, the voltage difference between the control terminal and the source terminal of the main switching element Q1 is pulled low, thereby turning off the main switching element Q1. Accordingly, the overcurrent protection circuit 1 proposed in the present embodiment has an extremely short reaction time. As long as the auxiliary switching element 14 is turned on because of the abnormality of the main current of the main switching element Q1, the main switching element Q1 is immediately turned off, thereby reducing the main The possibility that the switching element Q1 is damaged due to excessive current.

With continued reference to FIG. 2, the first diode 16 and the first auxiliary resistor 18 are designed to prevent abnormal operation of the auxiliary switching element 14 (eg, to avoid backflow). It will be apparent to those skilled in the art that under appropriate circuit design, the first diode 16 and the first auxiliary resistor 18 are not necessarily essential components. Similarly, the second diode 20 and the second auxiliary resistor 22 are also designed to prevent backflow. Under appropriate circuit design, the second diode 20 and the second auxiliary resistor 22 are not necessarily essential components.

From a practical point of view, the main switching element Q1 is generally controlled by a signal fed from the external feed terminal A, and the external feed terminal A can be substantially regarded as a control terminal connected to the main switching element Q1 via the resistor R1. When the auxiliary switching element 14 is off, the main switching element Q1 is controlled by a signal fed from the external feed terminal A. Note that the current comparator 10 should be coupled to the main current flowing through the main switching element Q1 at any time, thereby outputting the secondary current. However, when the current is within the normal range, the proportional resistance element 12 correspondingly generates the first voltage signal that does not exceed the first threshold (ie, does not exceed the threshold voltage of the auxiliary switching element 14), and thus the auxiliary switching element 14 is turned off.

Conversely, if the main current flowing through the main switching element Q1 suddenly increases abnormally, the proportional resistance element 12 generates a first voltage signal which will synchronously exceed the first threshold value, so that the auxiliary switching element 14 is turned on instantaneously. As can be seen from FIG. 2, when the auxiliary switching element 14 is turned on, the control terminal of the main switching element Q1, the second diode 20, the second auxiliary resistor 22, and the auxiliary switching element 14 form an on current path, and the main closing element Q1 The control terminal and the source terminal will have substantially similar voltages. Thereby, in the case where the voltage difference between the control terminal and the source terminal of the main reclosing element Q1 is less than the threshold voltage, the main switching element Q1 can be quickly turned off.

It should be noted that the main switching element Q1 described in this embodiment is not limited to an n-type power transistor. For example, the n-type power transistor shown in this embodiment can be replaced with a p-type power transistor. Those skilled in the art should be able to appropriately change the circuit connection relationship to display the circuit shown in this embodiment. Replace with other circuits with equivalent functions.

In order to more clearly illustrate the application mode of the present invention, please refer to FIG. 2 and FIG. 3 together. FIG. 3 is a functional block diagram of a power supply according to an exemplary embodiment of the present invention. As shown, the power supply 3 has a plurality of power shutoff elements SW1 SWSW4 and an overcurrent protection circuit 1 as illustrated in FIG. This embodiment selects one of the switching elements SW4 as the main switching element in the previous embodiment, and the overcurrent protection circuit 1 is coupled to the current transmission path of the closing element SW4. The ground symbol shown in FIG. 3 is not intended to limit the source terminal of the auxiliary switching element 14 to be grounded. As long as the auxiliary switching element 14 is turned on, the switching element SW4 can be directly controlled to be turned off, which should be disclosed in this embodiment. According to this, Figure 3 The source terminal of the auxiliary switching element 14 is shown not only to be grounded, but also to be connected to a contact having a specific voltage level.

As described in the previous embodiment, the overcurrent protection circuit 1 is for detecting whether the current (main current) flowing through the power switching element SW4 is abnormal, and can quickly cut off the power switching element SW4 that is subjected to excessive current. In general, the abnormality of the current flowing through the power switching element SW4 is mostly caused by noise, so that the power switching elements SW3 and SW4 of the same arm are simultaneously turned on, and the resistance value between the voltage source Vin and the ground terminal is instantaneously increased. Near zero, causing excessive current. If the load R on the line (for example, other electronic devices) does not have an overcurrent protection circuit or other protection circuit, the power switching elements SW3, SW4 and the load R are likely to be damaged when a malfunction occurs. Here, the overcurrent protection circuit 1 of the present embodiment is the same as the overcurrent protection circuit 1 illustrated in FIG. 2, and the embodiment is not described herein.

In summary, the overcurrent protection circuit and the power supply thereof provided by the embodiments of the present invention have a simple circuit design and an immediate response speed, and can directly sample the current flowing through the power switching element, and directly an abnormality. The current is converted into a voltage signal such that the voltage signal can be quickly turned off by the voltage signal to avoid damage to the power switching element.

The features and spirit of the present invention will be more apparent from the detailed description of the preferred embodiments. On the contrary, the intention is to cover various modifications and equivalents within the scope of the invention as claimed.

1‧‧‧Overcurrent protection circuit

10‧‧‧ current comparator

12‧‧‧Proportional resistance element

14‧‧‧Auxiliary switching elements

16‧‧‧First Diode

18‧‧‧First auxiliary resistor

20‧‧‧second diode

22‧‧‧Second auxiliary resistor

3‧‧‧Power supply

9‧‧‧Power supply

Q1‧‧‧Main reclosed components

R1‧‧‧ resistance

A‧‧‧External feed end

SW1~SW4‧‧‧Power Switching Components

R‧‧‧ load

Vin‧‧‧voltage source

Figure 1 is a schematic diagram of a conventional power supply.

2 is a functional block diagram of an overcurrent protection circuit in accordance with an exemplary embodiment of the present invention.

3 is a functional block diagram of a power supply in accordance with an exemplary embodiment of the present invention.

1‧‧‧Overcurrent protection circuit

10‧‧‧ current comparator

12‧‧‧Proportional resistance element

14‧‧‧Auxiliary switching elements

16‧‧‧First Diode

18‧‧‧First auxiliary resistor

20‧‧‧second diode

22‧‧‧Second auxiliary resistor

Q1‧‧‧Main reclosed components

R1‧‧‧ resistance

A‧‧‧External feed end

Claims (10)

An overcurrent protection circuit comprising: a current transformer coupled to a current transmission path of a main switching element, corresponding to generating a slave current according to a main current in the current transmission path; a proportional resistance element electrically connected to The current comparator generates a first voltage signal according to the slave current; and an auxiliary shut-off element electrically connected to the proportional resistor element, controlled by the first voltage signal, to selectively control the main switch element to be turned on Or deadline. The overcurrent protection circuit of claim 1, wherein the main switching element and the auxiliary switching element are power transistors, and the control end of the auxiliary switching element is electrically connected to the proportional resistance element, the auxiliary switching element The 汲 is electrically connected to the control terminal of the main switching element, and the source terminal of the auxiliary switching element is electrically connected to the source terminal of the main switching element. The overcurrent protection circuit of claim 2, wherein when the first voltage signal exceeds a first threshold, the auxiliary switching element is turned on, and the control end of the main switching element passes the auxiliary switching element The source terminal of the main switching element is electrically connected. The overcurrent protection circuit of claim 2, wherein the first end of the current transformer is electrically connected to the first end of the proportional resistance element and the control end of the auxiliary switching element, the comparator The second end, the second end of the proportional resistance element and the source terminal of the auxiliary switching element are electrically connected to the source terminal of the main switching element. For example, the overcurrent protection circuit described in claim 4 of the patent scope further includes a first a diode body, the anode end of the first diode is electrically connected to the first end of the proportional resistance element, and the cathode end of the first diode is electrically connected to the control end of the auxiliary switching element. The overcurrent protection circuit of claim 5, further comprising a second diode, the anode end of the second diode being electrically connected to the control end of the main switching element, the second diode The cathode end is electrically connected to the 汲 terminal of the auxiliary switching element. The overcurrent protection circuit of claim 6, further comprising a first auxiliary resistor and a second auxiliary resistor, the first auxiliary resistor being electrically connected to the cathode end of the first diode and the auxiliary The second auxiliary resistor is electrically connected between the cathode end of the second diode and the cathode terminal of the auxiliary switching element. A power supply comprising: at least one main switching element; and an overcurrent protection circuit comprising: a current transformer, a current transmission path coupling the main switching element, according to a main current in the current transmission path, corresponding to Generating a slave current; a proportional resistor element electrically connected to the current transformer, generating a first voltage signal according to the slave current; and an auxiliary switching component electrically connected to the proportional resistor component, controlled by the first A voltage signal to selectively control the main switching element to be turned on or off. The power supply device of claim 8, wherein the main switch element And the auxiliary switching element is a power transistor, and the control end of the auxiliary switching element is electrically connected to the proportional resistance element, and the 汲 terminal of the auxiliary switching element is electrically connected to the control end of the main switching element, and the auxiliary switching element The source is electrically connected to the source terminal of the main switching element. The power supply device of claim 9, wherein when the first voltage signal exceeds a first threshold, the auxiliary switching element is turned on, and the control end of the main switching element is electrically connected to the auxiliary switching element. The source terminal of the main switching element is connected.