KR200412046Y1 - Switching mode power supply circuit for digital protective relays - Google Patents

Abstract

The present invention relates to an SMPS circuit for a digital protective relay.

The SMPS circuit for a digital protective relay according to the present invention includes a rectifying unit for rectifying and converting an AC power input from the outside into a DC power source, a switching circuit unit driven by a DC power source to generate a pulse signal having a specific frequency, and a pulse. In response to the switching of the DC power supply of the rectifying unit to induce an AC voltage having a plurality of potential levels, and a plurality of voltage output and rectifying units rectifying each of the plurality of AC voltages output from the transformer to output a desired output voltage. It characterized in that it comprises a switching control unit for sensing the output voltage to cut off the power applied to the switching circuit portion from the rectifier and the switching circuit according to the magnitude of the output voltage.

Digital Protection Relay, SMPS Circuit, Switching Control, Power Off

Description

Switching mode power supply circuit for digital protective relays

1 is a schematic block diagram of a conventional SMPS circuit for a digital protection relay,

FIG. 2 is a circuit diagram of the switching circuit unit shown in FIG. 1;

3 is a schematic block diagram of an SMPS circuit for a digital protective relay according to a preferred embodiment of the present invention;

4 is a circuit diagram of the switching circuit unit shown in FIG. 3;

5 is a circuit diagram of a first blocking unit according to a preferred embodiment of the present invention;

6 is a circuit diagram of a second blocking unit according to a preferred embodiment of the present invention, and

FIG. 7 is a diagram illustrating an operation of a switching controller using a second blocking unit according to another exemplary embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

110: noise filter 120: rectifier

140: switching circuit unit 150: switching control unit

152: first blocking unit 154, 200: second blocking unit

160: transformer

The present invention relates to a switching mode power supply (SMPS) circuit for a digital protection relay, and more particularly, to a SMPS circuit for a digital protection relay to supplement a switching characteristic of the SMPS to supply a stable power even in an unstable external power environment.

In general, the protection relay is intended to maintain the stability of the power system.When an accident such as a short circuit, overload, or ground fault occurs in an electric circuit, the protection part is immediately disconnected from the system to prevent the accident from spreading to other systems. This is to ensure that the device is as intact as possible.

These protective relays are developed from the inductive or stationary relay to the digital relay in the past, and the internal components are configured using digital circuits. It should be equipped with SMPS circuit to obtain.

1 is a schematic block diagram of a conventional SMPS circuit for a digital protective relay.

As shown in FIG. 1, a conventional SMPS circuit for a digital protection relay includes a noise filter unit 10 for removing noise input from the outside and an AC power output from the noise filter unit 10 to a DC power source. The rectifier 20, the low voltage detector 30 that detects whether or not the voltage rectified by the rectifier 20 is lower than or equal to a set voltage, and the pulse width modulated by the voltage rectified by the rectifier 20 PWM) and the switching circuit unit 40, the transformer 50 for changing the voltage output from the switching circuit unit 40 to the desired output voltage, and 5V AC power output from the transformer 50 to rectify 5V 5V voltage output unit 60 for outputting with DC voltage, 12V voltage output unit 70 for rectifying 12V AC power and outputting 12V DC voltage, 24V voltage for rectifying output 24V AC power and outputting 24V DC voltage Output part ( 80).

FIG. 2 is a circuit diagram of the switching circuit unit 40 shown in FIG. As illustrated in FIG. 2, the switching circuit unit 40 includes a switching IC 41, a bias unit 42 for driving the first transistor Q2 included in the switching IC 41, and the switching IC ( R-stsrt resistor 43 for applying current to the R-stsrt terminal of the 41 and the feedback (Feedback) structure and the resistance portion 44 to apply the current to the internal terminal (Q1, Q2) base terminal to turn on / off , 45).

The switching IC 41 controls the output voltage using a frequency. The object of which the frequency can be controlled by the switching IC 41 is a rising speed of the charging voltage of the capacitor C2. When the charging voltage of the capacitor C2 becomes a voltage 0.7V that can conduct the transistor Q2, the transistor Q2 is turned on and the transistor Q1 is turned off to increase the output voltage. In this case, the charging voltage of the capacitor C2 is increased to reduce the time for which the transistor Q2 is turned on. As the time for which the transistor Q2 is conducted decreases, the internal peak current decreases, and the time for turning off the transistor Q1 also decreases, thereby increasing the output frequency. When the output frequency is constant, the maximum power drops when the input voltage decreases, and the maximum power increases when the input voltage increases.

However, when a voltage below a predetermined voltage is applied from the outside for some reason, the switching circuit unit 40 malfunctions and thus fails to generate a 5V voltage required to drive the digital protection relay. In the case of a digital protective relay having a certain burden, when the 5V voltage required to maintain the burden is not applied, an overcurrent is applied to the ICs constituting the internal circuit, causing internal data to be burned out.

In particular, in the digital protection relay, when the above-mentioned phenomenon occurs, a reset circuit operates to reset the main circuit, thereby causing a defect in which internal relay element set values, RTC (Real Time Clock), and calibration data are initialized. Done.

Accordingly, an object of the present invention is to provide a SMPS circuit for a digital protection relay that can prevent the digital protection relay from operating unstable by cutting off the power applied to the switching circuit unit when an unstable power is applied from the outside.

In order to achieve the above object, the SMPS circuit for digital protection relay according to the present invention, the rectifier for rectifying the AC power input from the outside to convert the DC power; A switching circuit unit driven by the DC power supply and configured to generate a pulse signal having a specific frequency; A transformer configured to switch the DC power of the rectifying unit in response to the pulse to induce an AC voltage having a plurality of potential levels; A voltage output unit rectifying each of the plurality of AC voltages output from the transformer and outputting a desired output voltage; And a switching control unit which senses an output voltage of the rectifying unit and cuts power applied from the rectifying unit to the switching circuit unit and power applied to the transformer from the switching circuit unit according to the magnitude of the output voltage to control the operation of the switching circuit unit. Characterized in that comprises a.

The switching controller may include: a first blocking unit to cut off power applied from the rectifying unit to the switching circuit unit when an output voltage of the rectifying unit is equal to or less than a predetermined voltage; And a second blocking unit which cuts off power applied to the transformer from the switching circuit unit when the output voltage of the rectifying unit is equal to or lower than a predetermined voltage.

The switching controller may include: a first blocking unit to cut off power applied from the rectifying unit to the switching circuit unit when an output voltage of the rectifying unit is equal to or less than a predetermined voltage; And a second blocking unit to cut off power applied from the rectifying unit to the switching circuit unit in order to stop the operation of the switching circuit unit when the output voltage of the rectifying unit falls below a predetermined voltage while the switching circuit unit is operating. It is characterized by.

Hereinafter, with reference to the accompanying drawings will be described the present invention in more detail. However, in describing the present invention, when it is determined that the detailed description of the related known functions or configurations may unnecessarily obscure the subject matter of the present invention, detailed description thereof will be omitted.

3 is a schematic block diagram of an SMPS circuit for a digital protection relay according to a preferred embodiment of the present invention.

As shown in FIG. 3, the SMPS circuit 100 for a digital protection relay according to the present invention includes a noise filter unit 110, a rectifier unit 120, a low voltage detector unit 130, a switching circuit unit 140, and a switching controller. 150, a transformer 160, a 5V voltage output unit 170, a 12V voltage output unit 180, and a 24V voltage output unit 190 are configured.

The noise filter unit 110 removes a noise component included in a voltage applied from the outside and outputs the noise component to the rectifier 120.

The rectifier 120 rectifies AC power output from the noise filter unit 110, converts the AC power into DC power, and outputs the DC power to the switching circuit 140.

The low voltage detector 130 detects whether the voltage output from the rectifier 120 is lower than the set voltage.

The switching circuit 140 is driven by a DC power output from the rectifier 120, and generates a pulse signal having a specific frequency and outputs the pulse signal to the transformer 160. As illustrated in FIG. 4, the switching circuit unit 140 includes a switching IC 143, a bias unit 142 for driving the transistor Q1 included in the switching IC 141, and the transistor Q1. Has a R-start resistor 143 and a feedback structure for applying a current to a base terminal of the transistor, and applies a current to a base terminal of the transistors Q1 and Q2 of the switching IC 141. It includes a resistance unit (144, 145) to turn on / off.

The transformer 160 generates an AC voltage having a plurality of potential levels by switching the DC power of the rectifier 120 in response to a pulse output from the switching circuit unit 140, thereby generating the AC voltage having a plurality of potential levels. The 12V voltage output unit 180 and the 24V voltage output unit 190 are respectively induced.

The 5V voltage output unit 170 rectifies the 5V AC power output from the transformer 160 and converts the 5V DC power to a 5V DC voltage for driving a digital protection relay (not shown).

The 12V voltage output unit 180 rectifies and regulates the 12V AC power output from the transformer 160 to convert the 12V DC voltage into a 12V DC voltage.

The 24V voltage output unit 190 rectifies and adjusts the 24V AC power output from the transformer 160 to convert the 24V DC voltage to output.

The switching controller 150 detects the output voltage of the rectifier 120 and cuts off power applied from the rectifier 120 to the switching circuit unit 140 according to the magnitude of the output voltage, or the switching circuit unit 140. ) To block the output signal.

The switching controller 150 includes a first blocking unit 152 that cuts off power applied to the switching circuit unit 140 and a second blocking unit 154 that blocks an output signal of the switching circuit unit 140. .

As shown in FIG. 5, the first blocking unit 152 includes a resistor R25 and a zener diode D13, and the power input terminal V-IN and fast on of the switching circuit unit 140 are provided. It is connected between the (FAST-ON) terminals.

The second blocking unit 154 detects a voltage applied from the outside to cut off the power applied to the switching circuit unit 140 when the external applied voltage is less than or equal to a predetermined voltage.

In more detail, the first blocking unit 152 switches only when the voltage applied from the power input terminal V-IN is greater than a Zener voltage (eg, 70 V) set in the Zener diode D13. Current is applied to the R-start terminal of the IC 141. In addition, when the voltage applied from the power input terminal V-IN is smaller than the zener voltage set in the zener diode D13, the first blocking unit 152 may have a voltage R− of the switching IC 141. Cut off the current applied to the start terminal.

Meanwhile, as illustrated in FIG. 6, the second blocking unit 154 includes a plurality of zener diodes ZD1 and ZD2, transistors Q1 and Q2, a diode D1, and a plurality of resistors R1 to R2. ) Is connected to the fast off (FAST_OFF) terminal of the switching circuit 140.

The second blocking unit 154 detects a voltage applied from the outside and blocks the output signal of the switching IC 141 when it is determined that the external applied voltage is less than or equal to a predetermined voltage.

The operation of the second blocking unit 154 will be briefly described. First, when a normal voltage is applied from the outside, the node A is applied to a voltage larger than the zener voltage VZD1 (for example, 18V) of the zener diode ZD1, and the zener diode ZD1 is turned on. Accordingly, a conduction current is applied from the zener diode ZD1 to the transistor Q2 so that the transistor Q2 is turned on. Then, the current applied to the base terminal of the transistor Q1 is cut off and the transistor Q1 is turned off. Accordingly, the fast off (FAST_OFF) terminal of the second blocking unit 154 is in a floating state, and the output signal of the switching IC 141 is output to the transformer 160.

On the other hand, when the voltage applied from the outside decreases and a voltage smaller than the zener voltage VZD1 of the zener diode ZD1 is applied to the node A, the current flowing in the zener diode ZD1 is cut off. As a result, the current applied from the zener diode ZD1 to the transistor Q2 is cut off and the transistor Q2 is turned off. On the other hand, transistor Q1 is turned on by the conduction current applied from zener diode ZD2. Accordingly, since the currents output from the switching IC 141 are all applied to the ground terminal GND through the transistor Q1, the voltage applied from the switching IC 141 to the transformer 160 is completely blocked.

FIG. 7 is a view illustrating an operation of the switching controller 150 to which the second blocking unit 200 according to another embodiment of the present invention is applied.

Referring to FIG. 7, as described with reference to FIG. 5, the first blocking unit 152 may switch the IC only when the voltage applied from the power input terminal V-IN is greater than the zener voltage set in the zener diode D13. When a current is applied to the R-start terminal of 141 and the voltage applied from the power input terminal V- IN is smaller than the zener voltage set in the zener diode D13, the R-start of the switching IC 141 is applied. It blocks the current applied to the terminal.

Meanwhile, unlike the second blocking unit 154 illustrated in FIG. 6, the second blocking unit 200 is connected to a fast on terminal of the switching circuit unit 140. The operation of the second blocking unit 200 will be described briefly as follows. First, when a normal voltage is applied from the outside, the zener diode D30 is turned on, a conduction current is applied from the zener diode D30 to the transistor Q1, and the transistor Q1 is turned on. Then, the current applied to the base terminal of the transistor Q2 is cut off and the transistor Q2 is turned off. In this case, the FAST OFF terminal of the second blocking unit 200 is in a floating state, and does not affect the operation of the switching IC 141.

On the other hand, when a normal voltage is applied from the outside and the switching IC 141 is operating, the voltage applied from the outside gradually decreases to form a low voltage below the zener voltage of the zener diode D30. The current flowing through the diode D30 is cut off. Accordingly, the current applied from the zener diode D30 to the transistor Q1 is cut off so that the transistor Q1 is turned off while the transistor Q2 is turned on. In this case, since the current applied to the FAST ON terminal is applied to the ground terminal GND through the transistor Q2 of the second blocking unit 200, the current is applied to the R-start terminal of the switching IC 141. The current is completely cut off. As a result, the operation of the switching IC 141 is stopped.

As described above, according to the present invention, when the voltage applied from the outside is sensed, and when the voltage applied from the outside is below a certain voltage, the power applied to the switching circuit unit is cut off, thereby causing the switching circuit unit to malfunction due to an external low voltage. Can be prevented.

Further, according to the present invention, when the voltage applied from the outside gradually decreases below a certain voltage while the switching circuit unit is operating, the power applied to the switching circuit unit is cut off to stop the operation of the switching circuit unit, or the switching By shutting off the output from the circuit, it is possible to prevent the digital protection relay from operating unstable due to the external low voltage failing to obtain a stable output power.

Claims (3)

Rectifier for rectifying the AC power input from the outside to convert to DC power; A switching circuit unit driven by the DC power supply and configured to generate a pulse signal having a specific frequency; A transformer configured to switch the DC power of the rectifying unit in response to the pulse to induce an AC voltage having a plurality of potential levels; A voltage output unit rectifying each of the plurality of AC voltages output from the transformer and outputting a desired output voltage; And A switching control unit which senses an output voltage of the rectifying unit and cuts power applied to the switching circuit unit from the rectifying unit and power applied to the transformer from the switching circuit unit according to the magnitude of the output voltage to control an operation of the switching circuit unit; SMPS circuit for the digital protective relay made, including. The method of claim 1, The switching control unit, A first blocking unit to cut off power applied from the rectifying unit to the switching circuit unit when the output voltage of the rectifying unit is lower than or equal to a predetermined voltage; And And a second breaker that cuts off the power applied to the transformer from the switching circuit unit when the output voltage of the rectifier unit is equal to or lower than a predetermined voltage. The method of claim 1, The switching control unit, A first blocking unit to cut off power applied from the rectifying unit to the switching circuit unit when the output voltage of the rectifying unit is lower than or equal to a predetermined voltage; And And a second blocking unit to cut off power applied from the rectifying unit to the switching circuit unit to stop the operation of the switching circuit unit when the output voltage of the rectifying unit falls below a predetermined voltage while the switching circuit unit is operating. SMPS circuit for digital protection relay, characterized in that.

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