KR200444228Y1 - Switched-Mode Power Supplies with Overvoltage Protection - Google Patents

Abstract

The present invention relates to a switching mode power supply (SMPS), more specifically, to determine whether the overvoltage is applied by comparing the input voltage applied to the switching mode power supply with the reference voltage in the first comparator And a switching mode power supply having an overvoltage protection circuit which transmits its output value to a power switch from a cascaded second comparator and stops the operation of the switching mode power supply upon overvoltage input, thereby protecting the circuit even upon overvoltage input. It relates to a supply device.

Switching Mode Power Supplies, Overvoltage Protection, Comparators, Optocouplers

Description

Switching mode power supply with overvoltage protection circuit {SWITCHING MODE POWER SUPPLY HAVING OVER VOLTAGE PROTECTION CIRCUIT}

The present invention relates to a switching mode power supply (SMPS), more specifically, to determine whether the overvoltage is applied by comparing the input voltage applied to the switching mode power supply with the reference voltage in the first comparator And a switching mode power supply having an overvoltage protection circuit which transmits its output value to a power switch from a cascaded second comparator and stops the operation of the switching mode power supply upon overvoltage input, thereby protecting the circuit even upon overvoltage input. It relates to a supply device.

In general, a switching mode power supply (SMPS) uses a semiconductor device such as a power transistor (MOSFET) as a switch to convert an input voltage into a square wave voltage, and then converts a DC output voltage controlled through a filter into a home appliance. As a device for supplying a product, etc., a power supply is controlled using a switching processor of a semiconductor device, which is a stabilized power supply device that is highly efficient, strong in durability, and advantageous in miniaturization and light weight.

If the switching mode power supply (SMPS) has a small capacity, even if a voltage of 300 V or more is applied, if only the internal voltage of the switching element inside the switching mode power supply (SMPS) is secured, the problem does not occur even when used for a long time. When the capacity of the power supply device (SMPS) is increased and the circuit scheme is changed to a large capacity, there is a problem in that the circuit is damaged by the input overvoltage or the life of the home appliance is shortened.

Accordingly, in recent years, as described in Korean Patent No. 10-0735498, when an overvoltage occurs in the output terminal, a plurality of rated diodes are shorted to ground the overvoltage, or the controller and the output voltage distribution unit of the power factor correction circuit are provided. An overvoltage protection circuit configured to protect the power supply by controlling the controller and turning on the switching transistor in the event of an overvoltage is presented.

However, the overvoltage protection circuit composed of a plurality of rated diodes has a problem that the circuit of the power supply is stably protected when overvoltage is applied, but the reuse of the rated diode is impossible, and the overvoltage protection circuit that turns on the transistor by controlling the controller when an overvoltage occurs is specified. Reuse of the device is possible because there is no direct damage to the device, but there is a problem that the efficiency of circuit protection due to overvoltage is halved by controlling only the operation of the power factor correction circuit by turning on and off the transistor.

In addition, the conventional overvoltage protection circuit has a problem in that it is inconvenient to use by blocking the inflow of the overvoltage unconditionally without discriminating whether the overvoltage is temporary or if the overvoltage is immediately removed or it is a constant that causes circuit damage.

The technical problem to be solved by the present invention is to stop the power switch itself by stopping the power switch when the over-voltage flows into the switching mode power supply, to prevent direct damage to the device and to protect the circuit from overvoltage The present invention provides a switching mode power supply having an overvoltage protection circuit capable of increasing the voltage.

In addition, the present invention delays whether or not the overvoltage of the input voltage determined by the first comparator for a predetermined time, and then transfers it to the second comparator. When the input voltage is overvoltage, it is determined whether the overvoltage state is temporary or continuous, and the overvoltage is continuously The present invention provides a switching mode power supply having an overvoltage protection circuit which can stop the power supply only when it is input.

Switching mode power supply provided with an overvoltage protection circuit for achieving the above object, AC input filter having a bridge diode to receive the AC power to remove noise, and rectified to a DC power; A power factor correction circuit including a booster for raising a DC voltage rectified by the bridge diode, a first diode and a second diode connected to one terminal of the booster, and a switching transistor for switching by a pulse width control signal; A main converter having a transformer connected to an output terminal of the first diode to convert an output voltage of the power factor correction circuit; A secondary rectifier filter connected to the secondary coil of the transformer to rectify and output the output of the main converter; A pulse width control unit having a power switch connected to the primary coil of the transformer and controlling a current supply time to the primary coil while switching; And an input voltage sensing unit for dividing a DC voltage at an output terminal of the power factor correction circuit to recognize a magnitude of an input voltage, a reference voltage unit for generating a reference voltage for determining whether the input voltage is overvoltage, and detecting the input voltage. A first comparator for comparing an input voltage recognized by a negative voltage with a reference voltage, and a second comparator connected to an output terminal of the first comparator and having an output terminal connected to the power switch to stop the operation of the power supply when an overvoltage is input. It is characterized by including an overvoltage protection circuit provided.

The present invention can significantly improve the protection efficiency of the switching mode power supply from overvoltage by stopping the operation of the power supply itself when the overvoltage is introduced, and whether the state persists if the input voltage is overvoltage. After the determination, the switching mode power supply can be stopped only when the overvoltage is continuously applied.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a switching mode power supply with an overvoltage protection circuit according to the present invention, Figure 2 is a circuit diagram of a switching mode power supply with an overvoltage protection circuit according to the present invention, Figure 3 It is a block diagram of an overvoltage protection circuit according to the present invention.

1 and 2, the switching mode power supply provided with an overvoltage protection circuit according to an embodiment of the present invention, the AC input filter 100 for receiving and rectifying the AC power and outputting the DC power; The power factor correction circuit 200 boosts the rectified DC power, the main converter 300 converting the boosted DC power into a constant AC power, and converts the converted AC power again into a DC power supply. Converted from the main converter by the secondary rectifier filter 400 for supplying to the lower end, the voltage feedback unit 500 for feeding back the DC power rectified and output to the load stage, and the DC power of the secondary rectifier filter to be fed back A pulse width control unit 600 for adjusting the pulse width, and an overvoltage protection circuit 700 for controlling the operation of the switching mode power supply itself by sensing that an overvoltage is applied to the AC input terminal. It is configured to include.

The AC input filter 100 removes noise of an AC voltage input through AC input terminals ACL and ACN, and absorbs a surge current to supply a stable AC voltage from which noise is removed. ZN2, ZN3, ZN4, and ZN5, and capacitors C2, C3, C4, and C22, bridge diode BD1 for smoothing and rectifying the stably filtered AC voltage to DC voltage, and the bridge diode. Both terminals are connected to the two output terminals of and comprises a capacitor (C7) for supplying a rectified DC voltage to the power factor correction circuit.

The power factor correction circuit (PFC) 200 increases the rectified DC voltage to DC 400V to supply the converter and improves the power factor regardless of the magnitude of the AC voltage input to the AC input terminal. A booster L1 connected to an output terminal of the bridge diode, a first diode D1 and a second diode D2 connected to one terminal connected to the booster, and a pulse width control signal to switch the second diode D2. It comprises a switching transistor (Q1) for controlling the conduction by supplying a current to the anode terminal.

In this case, the power factor correction circuit 200 may turn on or turn off the switching transistor Q1 at a time point where the current flowing from the inductor, which is the booster L1, is detected. And a PFC controller U1 for generating and outputting a driving signal. The switching transistor Q1 for switching on / off by this driving signal is connected to a terminal of the PFC controller U1.

Here, the current sensing unit includes a resistor (R4) connected between one terminal of the booster (L1) and the zero current detection terminal (ZCD) of the PFC controller, the current flow state in the booster PFC controller (U1) To pass.

The PFC controller U1 receives a zero current detection terminal (ZCD: Zero Current Detection) for detecting a zero crossing point of a switching current by receiving a current flow state of a circuit transmitted from the current sensing unit, and the switching. Inverting input terminal INV of the error amplifier receiving the output voltage from the output terminal (B + node) of the power factor correction circuit due to the switching action of the transistor Q1 as a feedback signal, and on / off of the switching transistor Q1. It comprises a drive terminal (GD) for outputting a drive signal for controlling the. In this case, the drive terminal GD applies a driving signal to the gate of the switching transistor Q1 through the diode D4 and the resistor R8 connected in parallel.

In addition, the switching transistor Q1 supplies a current to the second diode D2 while switching by a drive signal output from the drive terminal GD of the PFC controller U1, so that a gate is provided to the drive terminal GD. The drain terminal is connected to the second diode D2.

At this time, the signal transmission between the booster and the power factor correction circuit such as the first diode, the second diode, and the switching transistor, and the PFC controller U1 supplying a control signal to the power factor correction circuit are electrically connected to each other. (SUB1-1 to SUB1-6, CN3-1 to CN3-6).

The main converter 300 is a transformer (T1) for converting a voltage output from a constant DC voltage of DC 400V from the power factor correction circuit is connected to the primary coil is connected to the output terminal (B +) of the first diode (D1). It is configured to include.

At this time, the pulse width (PWM: Pulse Width Modulation) control unit (PWM) consisting of a power switch (U2) connected to the primary coil of the transformer (T1) and switching by a constant pulse width to control the current supply time to the primary coil 600) is further included. The power switch U2 is composed of a switching IC having a transistor that is switched by a pulse width controlled by a pulse width controller and whose output is adjusted.

In addition, the pulse width controller 600 controls the operation of the power switch (U2) by receiving a feedback of the operation signal from the voltage and the overvoltage protection circuit in the secondary rectification filter to be described later, for this purpose, the voltage feedback unit 500 Is electrically connected).

At this time, the voltage feedback unit 500 feeds back the value of the voltage finally output from the secondary rectifier filter to control the operation of the main converter, the pulse width for controlling the output terminal of the secondary rectifier filter and the main converter. A feedback input terminal CN2-1 to CN2-5 connected to the control unit and connected to the rectifier feedback terminals SUB3-1 to SUB3-5 connected to the secondary rectifier filter to receive the output voltage value; It includes a feedback output terminal (CN1-4, CN1-5, CN1-6) for transmitting the feedback voltage input from the feedback input terminal to the main converter.

The secondary rectifier filter 400 is connected to the secondary coil of the transformer (T1) to supply a constant DC voltage to home appliances by smoothing the AC voltage converted to a constant voltage to be output from the main converter, the inductor (L2) Rectifier feedback terminals SUB3-1, SUB3-2, and SUB3-3 including capacitors connected to one end, capacitors and resistors connected to the other end of the inductor L2, and feeding back a smoothed DC voltage. , SUB3-4, SUB3-5).

As illustrated in FIG. 3, the overvoltage protection circuit 700 includes an input voltage detector 710 that recognizes a voltage input to the main converter, and a reference voltage that provides a constant reference voltage for determining whether an overvoltage is input. And a first comparator 720 for comparing the input voltage detected by the input voltage detector with a reference voltage and an output terminal of the first comparator, and comparing the output value with the reference voltage to determine whether an overvoltage is input. It is configured to include a second comparator 730 to determine.

In this case, the input voltage detecting unit 710 recognizes a value obtained by dividing the DC voltage at an output ratio (B + terminal) of the power factor correction circuit by a plurality of resistors R35, R36, and R37 at a constant ratio. The divided voltage value is configured to apply to the non-inverting terminal (pin 3) of the first comparator U8-A. That is, some resistors R35 and R36 are connected to the output terminal B + terminal of the power factor correction circuit, and the non-inverting terminal of the first comparator U8-A is connected through the connection terminals SUB2-1 and CN1-1. (Pin 3) and resistor (R37). By applying the voltages distributed by the plurality of resistors to the first comparator as described above, the magnitude of the high input voltage can be easily compared with the magnitude of the stable low reference voltage.

The reference voltage unit provides a voltage that is a criterion for comparing with an input voltage divided by the input voltage sensing unit to determine whether the input voltage is overvoltage, and to the inverting terminal (pin 2) of the first comparator. The first reference voltage generator (U8-C) 740 for supplying a constant voltage and the second reference voltage generator (U9) 750 for supplying a constant voltage to the non-inverting terminal (pin 5) of the second comparator. It is configured to include).

The reference voltage unit is preferably formed using a regulator that always generates a constant voltage regardless of the voltage state of the peripheral circuit. In this case, the reference voltage applied to the first and second comparators in the first and second reference voltage generators is preferably composed of a relatively low voltage of 2.5V so that the reference voltage can be easily and stably generated. .

In addition, the first comparator U8-A 720 divides the input voltage to be compared, that is, the voltage at the output terminal (B + terminal) of the power factor correction circuit by a plurality of resistors (V1). ) Is applied to the non-inverting terminal (pin 3), and the reference voltage V _Ref generated by the first reference voltage generator U8-C is applied to the inverting terminal (pin 2). It consists of an op amp that compares the input voltage V1 and the reference voltage V _Ref and outputs the result V2. In this case, the output terminal (pin 1) of the first comparator is configured by being connected to the inverting terminal (pin 6) of the second comparator.

The second comparator (U8-B) 730 is applied to the output voltage (V2) of the first comparator to the inverting terminal (pin 6), the reference voltage generated by the second reference voltage generator (U9) (V _Ref), the inverting input terminal is applied to the (pin 5), comparing the output voltage (V2) with a reference voltage (V _Ref) of the first comparator is applied as described above and as a result the output (V3) OP amplifier It consists of. At this time, the output terminal (pin 7) of the second comparator B8-B is connected to the pulse width controller through the connection terminals CN1-5 and SUB2-5. Accordingly, it is configured to determine whether to operate the power switch provided in the main converter based on the determination result of the overvoltage protection circuit, and to stop the operation of the switching mode power supply when the overvoltage is applied.

The output terminal of the second comparator U8-B further includes an opto coupler U3-A and U3-B whose operation is controlled by the output value V3. The optocoupler operates normally when the output value of the second comparator is high. When the output value is low, the optocoupler stops and the operation of the power switch U2 connected to the output terminal of the second comparator is stopped. The operation of the power supply (SMPS) is configured to be stopped.

In addition, the overvoltage protection circuit 700 prevents the operation of the switching mode power supply from being stopped by an instantaneous overvoltage such as lightning or lightning, and the switching only when the overvoltage is continuously supplied due to an abnormal AC input power supply. It is preferably configured to be able to stop the operation of the mode power supply.

Accordingly, when the first comparator recognizes that the input voltage is applied by the input voltage detector, the result value is not immediately transferred to the second comparator, but is temporarily stored to delay the transfer of the result value to the second comparator. The time delay unit 760 is further included.

When the output signal of the first comparator is in a HIGH state due to an overvoltage input, the time delay unit 760 delays a predetermined time and transmits the result value to the second comparator. A resistor R39 and a capacitor C36 are connected between the output terminal (pin 1) of the U8-A) and the inverting terminal of the second comparator U8-B. Therefore, when the output signal of the first comparator maintains a high state even after the delayed time, the time delay unit transmits the value to the second comparator to stop the operation of the switching mode power supply, When the output signal of the first comparator is changed to a low state after a time when the instantaneous overvoltage is removed from the surge circuit and delayed, a low signal is transmitted to the inverting terminal of the second comparator to supply switching mode power. Maintain the operation of the device.

Next, the operation of the switching mode power supply having the overvoltage protection circuit according to the present invention configured as described above will be described.

According to the present invention, a switching mode power supply having an overvoltage protection circuit determines whether an overvoltage is input by using a cascaded dual comparator when overvoltage is applied to an input voltage, and switching mode power supply when a high voltage is input. By stopping the operation of the power supply to prevent damage.

Therefore, the AC input filter, the power factor correction circuit, the main converter, the secondary rectifier filter, the voltage feedback unit, and the pulse width control unit except for determining whether the input voltage is overvoltage and determining whether the switching mode power supply is turned off accordingly. The operation of is similar to that of a conventional switching mode power supply, and the following description will focus on the operation in the overvoltage protection circuit.

Since the primary rectified DC voltage in the bridge diode provided in the AC input filter changes according to the AC input voltage applied to the AC input terminal (ACL, ACN), the DC voltage increases as the AC input voltage increases. In order to determine, first, the input voltage detection unit provided in the overvoltage protection circuit is rectified by the bridge diode and then divided by a plurality of resistors (R35, R36, R37) the DC voltage output from the power factor correction circuit (PFC), The divided value is applied to the non-inverting terminal (pin 3) of the first comparator U8-A as the input voltage V1.

In this case, the reference voltage V _Ref generated by the first reference voltage generator U8-C is applied to the inverting terminal (pin 2) of the first comparator U8-A and the second comparator U8-A. The reference voltage V _Ref generated by the second reference voltage generator U9 is applied to the non-inverting terminal (pin 5) of B).

When the AC input voltage is normal, since the input voltage V1 input to the non-inverting terminal is smaller than the reference voltage V _Ref , the output value V2 of the first comparator becomes low. The output value V2 of the first comparator is applied to the inverting terminal (pin 6) of the second comparator through the output terminal (pin 1), and to the non-inverting terminal (pin 5) of the second comparator. The reference voltage V _Ref generated by the reference voltage generator U9 is applied.

When the voltage inputted to the second comparator is compared, the voltage of the non-inverting terminal is applied because the voltage V2 applied to the inverting terminal is low and the voltage applied to the non-inverting terminal is a reference voltage of 2.5V. This higher value causes the output value of the second comparator to go high.

Therefore, the opto-couplers U3-A and U3-B which feed back the output voltage of the switching mode power supply SMPS operate normally and the rectified DC voltage while the switching mode power supply operates normally. Is output to a load such as a home appliance.

However, when an overvoltage is input and the AC input voltage is increased, the reference voltage input to the inverting terminal (pin 2) is increased while the input voltage V1 applied to the non-inverting terminal (pin 3) of the first comparator increases. It becomes larger than V _Ref , and accordingly, the output voltage V2 of the first comparator becomes HIGH.

The output voltage V2 of the first comparator is applied to the inverting terminal of the second comparator, a reference voltage is applied to the non-inverting terminal (pin 5) of the second comparator, and the inverting terminal ( Since the voltage applied to the pin 6) is high, the output value of the second comparator becomes a low state. Accordingly, the operation of the opto couplers U3-A and U3-B having one end connected to the output terminal (pin 7) of the second comparator is stopped, and thus the operation of the opto coupler is stopped. The power switch U2 of the switching mode power supply SMPS connected through the connection terminals CN1-5 and SUB2-5 stops operation to protect the switching mode power supply SMPS from AC overvoltage. .

4 is a switching waveform diagram of a power switch (U2) output terminal (pin 2) in a normal input power supply, and FIG. 5 is a power switch (U2) output terminal (pin 2) during an overvoltage protection circuit according to the present invention. Is a switching waveform diagram.

4 and 5, when the normal power is input, the power switch switches at regular intervals and supplies power to a load such as a home appliance, but when an overvoltage is applied to an AC input terminal, the first comparator and the second comparator The circuit is protected by stopping the operation of the optocoupler, stopping the operation of the power switch, and stopping the operation of the entire switching mode power supply.

Accordingly, when a high voltage of 380 V is applied to the AC input terminal while the steady state voltage is set to 280 V and 2.5 V is set to the reference voltage V _{Ref thereof} , the input voltage V1 constantly divided by the first comparator is applied. ) Is compared with the reference voltage (V _Ref ) and the output voltage (V2) of the first comparator is compared with the reference voltage (V _Ref ) again and outputted, and the resultant value (V3) stops the operation of the optocoupler. As a result, the entire operation of the switched-mode power supply stops, protecting the circuit.

At this time, can set the normal voltage to 300V, and to set a reference voltage (V _Ref), and to be set to 2.5V, the reference voltage (V _Ref) thereof to a different value is also available as a matter of course.

In addition, the output voltage V2 of the first comparator is not immediately applied to the second comparator, but is temporarily delayed in the time delay circuit, thereby providing an instantaneous overvoltage such as a lightning strike to be removed by a protection means such as a surge circuit. As a result, the operation of the switching mode power supply (SMPS) is prevented from being frequently stopped, and the operation of the switching mode power supply (SMPS) is stopped for the protection of the circuit only at the time of continuous overvoltage input to the AC input terminal.

In the above description, the technical idea of the present invention has been described together with the accompanying drawings, which describes exemplary embodiments of the present invention by way of example, and does not limit the present invention. In addition, it is obvious that any person having ordinary knowledge in the technical field to which the present invention belongs may make various modifications and imitations without departing from the scope of the technical idea of the present invention.

1 is a block diagram of a switching mode power supply having an overvoltage protection circuit according to the present invention;

2 is a circuit diagram of a switching mode power supply having an overvoltage protection circuit according to the present invention;

3 is a block diagram of an overvoltage protection circuit according to the present invention;

4 is a switching waveform diagram of a power switch output terminal in a normal input power source;

5 is a switching waveform diagram of a power switch output terminal during an overvoltage protection circuit.

<Explanation of symbols for the main parts of the drawings>

100-AC input filter 200-Power factor correction circuit

300-Main Converter 400-Secondary Rectifier Filter

500-voltage feedback unit 600-pulse width control unit

700-Overvoltage Protection Circuit 710-Input Voltage Detector

720-Comparators 730-Comparators 2

740-First reference voltage generator 750-Second reference voltage generator

760-Time Delay

Claims (5)

delete delete delete In a switched mode power supply, An AC input filter having a bridge diode that receives AC power, removes noise, and rectifies the DC power; A power factor correction circuit including a booster for raising a DC voltage rectified by the bridge diode, a first diode and a second diode connected to one terminal of the booster, and a switching transistor for switching by a pulse width control signal; A main converter having a transformer connected to an output terminal of the first diode to convert an output voltage of the power factor correction circuit; A secondary rectifier filter connected to the secondary coil of the transformer to rectify and output the output of the main converter; A pulse width control unit having a power switch connected to the primary coil of the transformer and controlling a current supply time to the primary coil while switching; And an input voltage sensing unit for dividing a DC voltage at an output terminal of the power factor correction circuit to recognize a magnitude of an input voltage, a reference voltage unit for generating a reference voltage for determining whether the input voltage is overvoltage, and detecting the input voltage. A first comparator for comparing an input voltage recognized by a negative voltage with a reference voltage, and a second comparator connected to an output terminal of the first comparator and having an output terminal connected to the power switch to stop the operation of the power supply when an overvoltage is input. An overvoltage protection circuit provided; A resistor (R39) and a capacitor (C36) having one terminal connected between the output terminal of the first comparator and the inverting terminal of the second comparator, respectively, the time that the output value from the first comparator is transferred to the second comparator Further comprising a time delay unit for delaying; The overvoltage protection circuit is provided with an overvoltage protection circuit further comprises an opto-coupler configured to stop the operation when one terminal is connected to the output terminal of the second comparator, the output value of the second comparator low state Switched-mode power supplies. The method of claim 4, wherein The input voltage detector includes a plurality of resistors connected to an output terminal (B + terminal) of the power factor correction circuit to apply the divided input voltage V1 to the non-inverting terminal of the first comparator. The reference voltage unit includes a first reference voltage generator supplying a reference voltage V _Ref to the inverting terminal of the first comparator, and a second supplying reference voltage V _Ref to the non-inverting terminal of the second comparator. It includes a reference voltage generator, The first comparator comprises an OP amplifier comparing the input voltage (V1) and the reference voltage (V _Ref ), the output terminal is connected to the inverting terminal of the second comparator and delivers the output value (V2) of the first comparator, The second comparator is configured to compare the output value (V2) and the reference voltage (V _Ref ) of the first comparator and stop the operation of the power switch and the power supply by the output value is characterized in that Switched mode power supply.

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