KR200285758Y1 - Apparatus for protection of SMPS - Google Patents

Abstract

The present invention relates to a protection device of the SMPS, detects the input voltage of the DC / DC converter, and cuts off any voltage other than the upper and lower limits of the input allowable voltage range, and removes the mounting or power on / off of the SMPS. The purpose is to protect the devices inside the SMPS by minimizing the effects of inrush current generated during the circuit.

The present invention is a protection device for protecting the internal element of the switching power supply using the inrush current prevention unit for blocking the inrush current of the SMPS, a high voltage sensing unit for detecting a high voltage from the input voltage input to the SMPS, A low voltage sensing unit for detecting a low voltage from the input voltage, a voltage blocking unit for driving the high voltage sensing unit and a low voltage sensing unit to cut off the input voltage, and a sensing voltage of the high voltage sensing unit and the low voltage sensing unit is normal And a hysteresis unit for returning to a normal input state.

Description

Protection device of switching power supply {Apparatus for protection of SMPS}

The present invention relates to a device for protecting a switching mode power supply (hereinafter, abbreviated as 'SMPS'), and more particularly, by detecting an input voltage of a DC / DC converter. The present invention relates to a SMPS protection device that protects the SMPS internal devices from inrush current or from inrush current to prevent failure.

1 is a circuit diagram for preventing inrush current according to the related art. As shown in FIG. 1, when an input power is applied, the circuit is applied to the zener diode ZD3 through a resistor R8 to maintain a constant voltage. It is charged to the capacitor C2. When the capacitor C2 is charged for a predetermined time, the field effect transistor FET is turned on to output the input power and is supplied to the SMPS input circuit.

When the input power is applied, the inrush current is suppressed by a soft start function that delays the input and output during the time that the capacitor C2 is charged.

The characteristic of SMPS is that the input current decreases as the input voltage increases, and the input current increases as the input voltage decreases. Accordingly, when the input voltage is high, the voltage stress of each device increases, and when the input voltage decreases, the current stress of each device increases, causing a failure when the input voltage increases above the allowable voltage range or the input voltage decreases below the allowable voltage range. In addition, when the input voltage decreases below the allowable voltage range, a device error occurs.

The present invention is to solve the above-mentioned problems of the prior art, the purpose is to detect the input voltage of the DC / DC converter to cut off the input voltage other than the upper limit and the lower limit of the input allowable voltage range, SMPS The present invention provides a protection device for an SMPS that protects devices inside the SMPS while minimizing the influence of inrush current generated during demounting or power on / off.

1 is a block diagram of an inrush current prevention circuit of the SMPS according to the prior art,

2 is a circuit diagram of a protection device of an SMPS according to an embodiment of the present invention.

<Description of Symbols for Major Parts of Drawings>

10: high voltage detection unit 20: low voltage detection unit

30: voltage cut off part 40: hysteresis part

50: inrush current prevention unit

The protection device of the SMPS according to the present invention for achieving the object of the present invention is a protection device for protecting the internal elements of the switching power supply using an inrush current blocking unit for blocking the inrush current of the SMPS, which is input to the SMPS A high voltage sensing unit for sensing a high voltage at an input voltage, a low voltage sensing unit for detecting a low voltage at the input voltage, a voltage blocking unit for driving the high voltage sensing unit and a low voltage sensing unit by a bias voltage, and blocking the input voltage; And a hysteresis unit for returning to a normal input state when the detected voltages of the high voltage detector and the low voltage detector are normal.

The present invention made as described above will be described in detail with reference to the accompanying drawings.

2 is a circuit diagram of a protection device of an SMPS according to an embodiment of the present invention, a high voltage sensing unit 10 for detecting a high voltage from a voltage input to the SMPS, and a low voltage sensing unit for sensing a low voltage at the input voltage ( 20), a voltage blocking unit 30 for driving an input voltage by blocking the input voltage by driving the bias voltages of the high voltage detecting unit 10 and the low voltage detecting unit 20, and the high voltage detecting unit 10 and the low voltage detecting unit ( 20 is composed of a hysteresis unit 40 for returning to a normal input state when the sensed voltage is normal, and an inrush current prevention unit 50 for detecting and blocking an inrush current instantaneously input when the input voltage is input.

Here, the high voltage detector 10 may include a second resistor for dividing the fourth zener diode ZD4 connected in series with the first resistor R1 and a base (Anode) of the fourth zener diode ZD4. A third and twelfth resistors R3 and R12 connected in series to a fourth transistor Q4 connected to a base terminal and turned on at an input high voltage, and connected to a collector terminal of the fourth transistor Q4 in series; And a third transistor Q3 connected between the third and twelfth resistors R3 and R4 and driven by the fourth transistor Q4.

In addition, the low voltage detecting unit 20 divides the ninth and tenth resistors R9 and R10 and the ninth and tenth resistors R9 and R10 connected in series with the output terminal of the voltage cutoff unit 30. Connected to the fifth transistor Q5 connected to the collector terminal of the fifth transistor Q5 to be turned off when the input low voltage is connected to the second zener diode ZD2 and the sixth resistor R6 connected in series. The connection is made up.

In addition, the voltage cut-off unit 30 is connected in series to the collector terminal of the second transistor Q2 which is connected to an input power source and operates when an abnormal voltage and a normal voltage are applied, and thus the field effect transistor of the inrush current preventing unit 50 is formed. The seventh and eighth resistors R7 and R8 driving the FET and the second capacitor C2 for delaying the gate time of the field effect transistor FET of the inrush current preventing unit 50. It is connected to the dedicated first diode D1.

In addition, the hysteresis unit 40 is connected to an input power source and is connected to a first zener diode ZD1 that is turned on when an input voltage is applied, and fourth and fifth resistors connected in series to the first zener diode ZD1 to divide the voltage. R4 and R5 and the fourth and fifth resistors R4 and R5 are connected to the base terminal of the second transistor Q2 of the voltage blocking unit 30.

In addition, the inrush current preventing unit 50 is connected in parallel to the third zener diode ZD3 for stabilizing the gate voltage of the field effect transistor FET for turning on / off the input power and the third zener diode ZD3 in parallel. And a second capacitor C2 for delaying the conduction time, and an eleventh resistor R11 for discharging the second capacitor C2.

When described in more detail with reference to Figure 2 attached to the operation according to the embodiment of the present invention is configured as follows.

First, the present invention blocks the inrush current and the high voltage and the low voltage outside the allowable range of the power supplied to the SMPS, so that the SMPS operates in a stable power region.

FIG. 2 is a circuit diagram of a protection device of an SMPS according to an embodiment of the present invention. First, the high voltage sensing unit 10 includes the input voltage distribution resistors R1 and R2 and a fourth zener diode ZD4 with respect to the input voltage. To distribute). That is, the first resistor R1 and the fourth zener diode ZD4 are connected in series, are divided with the second resistor R2, are connected to the base terminal of the fourth transistor Q4, and the input voltage rises above the allowable range. When the zener diode ZD4 is turned on, the fourth transistor Q4 is turned on, and the third transistor Q3 is connected to the third and twelfth resistors R3 and R12 by being turned on by the fourth transistor Q4. The positive bias voltage is applied to the base to turn on the third transistor Q3, and the reverse bias voltage is applied to the base of the second transistor Q2 of the voltage cutoff unit 30 to turn off the transistor Q2. .

Here, when the second transistor Q2 of the voltage blocking unit 30 maintains the turn-off state due to the input high voltage, the gate operation voltage of the field effect transistor FET of the inrush current preventing unit 30 is cut off to prevent the main SMPS. The input power is cut off to protect the voltage stress of internal SMPS devices from the input high voltage.

The low voltage detection unit 20 is connected to the fourth and fifth resistors R4 and R5, which are the starting resistors of the input voltage level hysteresis unit 40, and the starting zener diode ZD1 when the input voltage is applied to the input voltage. The transistor Q2 is turned on by being connected to the base terminal of the second transistor Q2 of the voltage cutoff unit 30 so that an operating voltage is applied to the gate of the field effect transistor FET of the inrush current preventing unit 50, thereby providing a normal voltage. When the input voltage decreases below the allowable range, the bias voltage is lowered on the base of the fifth transistor Q5 connected to the ninth and tenth resistors R9 and R10, which are the input voltage distribution resistors, to thereby reduce the fifth transistor Q5. ) Is turned off and when the fifth transistor Q5 is turned off, the bias voltage is cut off from the second zener diode ZD2 and the sixth resistor R6 connected to the base of the transistor Q2 of the voltage blocking unit 30. The second transistor Q2 of the voltage cutoff unit 30 It is turned off.

When the second transistor Q2 of the voltage cutoff unit 30 maintains the turn-off state due to an input undervoltage, the operation voltage of the gate of the field effect transistor FET of the inrush current preventing unit 50 is cut off, thereby The input power is cut off to protect the current stress of SMPS internal devices from the input undervoltage.

In addition, the input low voltage lowers the output voltage of the SMPS to prevent malfunction of circuits connected to the output terminal of the SMPS.

The voltage cut-off unit 30 may be configured to include a high voltage sensing unit 10 at the base of the second transistor Q2 that blocks the gate operating voltage of the field effect transistor FET of the inrush current preventing unit 50 when an input high voltage is applied. When the three transistors Q3 are connected, the reverse bias voltage is applied, and the second transistor Q2 is turned off, and when the low voltage is applied, the bias voltage for driving the base of the second transistor Q2 is a hysteresis unit. A seventh agent connected to the collector terminal of the second transistor Q2 by turning off the second transistor Q2 by turning off the fifth resistor R5 connected in series with the first control diode ZD1 of The gate operating voltage of the field effect transistor (FET) of the inrush current prevention unit 50 is blocked through the resistors R7 and R8 to cut off the input power, thereby protecting the SMPS.

When the supply power is applied, the hysteresis unit 40 has a fifth resistor R5 connected in series with the first zener diode ZD1 for voltage level setting connected to the base of the second transistor Q2 of the voltage blocking unit 30. As the first zener diode ZD1 conducts, the second transistor Q2 is turned on.

The electric field effect of the inrush current preventing unit 50 is applied by the seventh and eighth resistors R7 and R8 connected to the collector of the second transistor Q2 by turning on the second transistor Q2 of the voltage blocking unit 30. The field effect transistor FET of the inrush current preventing unit 50 is turned on to be connected to the gate of the transistor FET, thereby supplying input power to the SMPS.

Distribution resistors R9 and R10 of the low voltage sensing unit 20 are connected in series to the collector terminal of the second transistor Q2 of the voltage blocking unit 30 and connected to the base of the fifth transistor of the low voltage sensing unit 20. When the input voltage falls below the allowable range, the fifth transistor Q5 of the low voltage sensing unit 20 is turned off.

When the fifth transistor Q5 is turned off, the sixth resistor R6 connected in series with the second zener diode ZD2 connected to the collector terminal of the fifth transistor Q5 of the low voltage sensing unit 20 is the low voltage blocking unit. The base driving bias voltage of the second transistor Q2 is cut off by being connected to the base terminal of the second transistor Q2 of 30 so that the second transistor Q2 is turned off so that the electric field of the inrush current preventing unit 50 is reduced. The gate operation voltage of the effect transistor (FET) is cut off to cut off the input power supply of the SMPS, and the normal return is increased to the conduction voltage value of the first zener diode ZD1 for setting the voltage level of the hysteresis unit 40, so that the first zener When the diode ZD1 is turned on, the second transistor Q2 of the voltage blocking unit 30 is turned on to supply the input power of the SMPS.

When the power input is cut off by the low voltage, in order to supply power normally again, the power input is cut off at the cut-off voltage value of the second zener diode ZD2 of the low voltage sensing unit 20, and the normal return is performed by the first zener diode of the hysteresis unit 40. At the conduction voltage value of (ZD1), there is a hysteresis between two values that are conducted and return normally.

The inrush current preventing unit 50 is a field effect transistor (FET) which is turned on / off with respect to an input voltage condition of the third diode ZD3 for constant voltage, the capacitor C2 for time delay, and the eleventh resistor R11 for discharge. When the input power is applied, the second capacitor for time delay is maintained by maintaining the constant voltage by the third zener diode ZD3 connected in series with the seventh and eighth resistors R7 and R8 of the power cut-off unit 30. C2) and the gate of the field effect transistor Q1 are connected to the gate of the second capacitor C2 to start charging for a predetermined time, the field effect transistor (FET) is turned on to supply the input power to the SMPS.

In addition, if the normal input voltage is applied when the field effect transistor (FET) is turned off due to the input power off or high voltage or low voltage application, the input and output during the charging time of the time delay capacitor C2 as described above. Soft-start delay function reduces delay of inrush current.

Although the preferred embodiment according to the present invention has been described above, it can be modified in various shapes, and those skilled in the art have various modifications and modifications without departing from the utility model registration claims of the present invention. It is understood that examples may be practiced.

As described above, the protection device of the SMPS according to the present invention can add a circuit for blocking the input high voltage and the low voltage to the inrush current prevention circuit to enable the SMPS to operate stably in the voltage input allowable region, There is an effect that can be effectively prevented against the inrush current that is instantaneously applied. In addition, since the power cut function is implemented by one field effect transistor without the need for a separate switch, not only the additional circuit can be simplified, but also there is an economic effect.

Claims (5)

A protective device for protecting an internal element of a switching power supply by using an inrush current prevention unit for blocking inrush current to the switching power supply, A high voltage detecting unit detecting a high voltage from an input voltage input to the switching power supply device; A low voltage detecting unit detecting a low voltage from the input voltage; A voltage blocking unit which is driven by a bias voltage of the high voltage detecting unit and the low voltage detecting unit to block an input voltage; And And a hysteresis unit for returning to a normal input state when the detected voltages of the high voltage detection unit and the low voltage detection unit are normal. 2. The display device of claim 1, wherein the high voltage detector comprises a second resistor for dividing a fourth zener diode connected in series with a first resistor R1, and a base connected to an anode terminal of the fourth zener diode and turned on at an input high voltage. A fourth transistor, third and twelfth resistors connected in series to the collector of the fourth transistor and divided by the third transistor, and a third transistor connected between the third and twelfth resistors and driven by the fourth transistor; Protective device for a switching power supply, characterized in that the connection is configured. The semiconductor device of claim 1, wherein the low voltage detection unit comprises a ninth and tenth resistor connected in series to an output terminal of the voltage cutoff unit, and a fifth transistor connected to the ninth and tenth resistors by being divided to turn off at an input low voltage; And a second zener diode connected in series and connected to the collector terminal of the fifth transistor and a sixth resistor. The seventh circuit of claim 1, wherein the voltage blocking unit is connected to an input power source and connected in series to a collector terminal of a second transistor that operates when an input abnormal voltage and an input normal voltage are applied to drive the field effect transistor of the inrush current preventing unit. And an eighth resistor and a first diode for discharging a second capacitor for delaying the gate time of the field effect transistor of the inrush current preventing unit. The method of claim 1, wherein the hysteresis unit is connected to an input power source, the first zener diode to be turned on when the input voltage is applied, and the fourth and fifth resistors connected in series to the first zener diode to divide the voltage; And a fifth resistor connected to the base end of the second transistor of the voltage interrupter.