JP6429231B2 - Power supply - Google Patents

Description

  The present invention relates to a power supply device that converts electric power from a commercial power supply that is alternating current into direct current power of a predetermined voltage and outputs the same.

  As such a power supply device, there is a so-called switching power supply device. In such a power supply device, the input AC power source is rectified on the primary side to be converted into DC power, and the DC power is applied to the secondary side coil by flowing the DC power in the form of pulses in the primary side coil of the transformer. Transformed AC power is generated. The AC power generated in the secondary coil is rectified to DC power and output.

  The primary coil is provided with a switching element for causing DC power to flow in a pulse form and an oscillation IC for turning on and off the switching element at a predetermined frequency. The switching element is turned on / off by a pulse signal having a predetermined frequency output from the oscillation IC.

  The oscillation IC is provided with a feedback terminal, and the feedback terminal is connected to the light receiving part side of the photocoupler. When the light receiving part side receives light, an oscillation stop signal is input to the feedback terminal, and the switching element On / off stops and the output of electric power from the secondary coil stops.

  The light emitting part paired with the light receiving part of the photocoupler is provided on the secondary side, and is connected to a detection circuit that monitors the output voltage on the secondary side. For example, if a short circuit occurs between the output terminals on the secondary side, a large current flows between the two terminals, and the primary side is damaged by the influence. Therefore, the detection circuit detects such a short-circuit failure and detects it. The light-emitting part of the photocoupler is caused to emit light and received by a light-receiving part that is a pair, and the switching element is turned on and off as described above (see, for example, Patent Document 1).

Japanese Patent Laying-Open No. 2012-235561 (FIG. 1)

  In the conventional power supply device described above, the secondary coil outputs only one type of voltage called a one-tap, and therefore, the driving power for the detection circuit is also supplied from the output power of the secondary coil.

  In such a configuration, when the secondary output terminals are short-circuited, the output voltage on the secondary side is drastically lowered, and the light emission of the light emitting portion of the photocoupler is stopped. Then, on / off of the switching element on the primary side resumes and power is generated on the secondary side. However, if the short circuit is not resolved, the light emitting portion of the photocoupler emits light again to stop the on / off of the switching element. As described above, the fact that the light emission of the light emitting portion stops immediately and the switching element is turned on and off again is repeated in a short cycle. For this reason, the integrated amount of the operation time on the primary side increases, and damage to the primary side due to overheating tends to occur.

  In order to solve such a problem, the number of turns of the secondary coil is increased and another tap is provided to generate power of different types of voltages, and the detection circuit uses power of voltage different from that for output. If the is driven, it is possible to extend the time until the detection circuit goes down. Therefore, it is conceivable to lengthen the repetition period and shorten the integrated amount of the operating time on the primary side. However, in order to configure in this way, the secondary coil of the transformer must be 2 taps or more, which increases the size of the transformer and increases the cost.

  Therefore, in view of the above problems, the present invention short-circuits the output terminals on the secondary side by shortening the integrated amount of the operation time on the primary side even if the secondary side coil of the transformer is one tap. However, it is an object to provide a power supply device in which the primary side is not easily damaged.

In order to solve the above-described problems, a power supply device according to the present invention is provided with an oscillation IC for passing an intermittent current to a primary coil on a primary side across a transformer, and a photocoupler is connected to a feedback terminal of the oscillation IC. When the terminals of the secondary coil of the transformer are short-circuited, the light emitting unit paired with the photocoupler is caused to emit light, and an oscillation prohibition signal is input to the feedback terminal. In the power supply apparatus provided with a protection circuit for stopping the generation of power to the secondary side, the secondary coil of the transformer transformer is configured to output only one type of voltage, and the light emitting portion of the photocoupler emits light by a comparator. And the operation power source of the comparator is charged from the charging unit charged with the electric power generated in the secondary coil of the transformer. When the terminals of the secondary coil of the transformer transformer are short-circuited, the voltage drop rate of the power supplied to the comparator is set to the voltage drop between the terminals of the secondary coil of the transformer transformer. It is configured to be slower than the speed.

  Since the operating power of the comparator is supplied from the charging unit instead of the power generated between the terminals of the secondary coil, the power is supplied to the comparator even if the voltage between the terminals of the secondary coil rapidly decreases due to a short circuit. Therefore, the period from when the oscillation on the primary side is stopped and then restarted and then stopped again can be extended.

  As is clear from the above description, the present invention can extend the cycle of the primary side oscillation stop and restart cycle when the secondary side is short-circuited, as described above, so that the short-circuit is eliminated. The cumulative amount of primary side operation time up to can be shortened, and the risk of damage on the primary side can be reduced.

The circuit diagram which shows the structure of one embodiment of this invention The figure for comparing the operation cycle of the primary side when the secondary side is short-circuited

  Referring to FIG. 1, reference numeral 1 denotes a circuit configuration of a power supply device according to the present invention. The left side is the primary side 11 and the right side is the secondary side 12 across the transformer 13 located in the center.

  On the primary side 11, AC power supplied from an external commercial power source is full-wave rectified and converted to DC power, and supplied to the primary coil of the transformer 13. Further, an oscillation IC 2 is provided on the primary side 11, and the switching element is turned on and off by the oscillation IC 2, and the current supplied to the primary side coil is intermittently transmitted at a predetermined frequency, whereby the transformer 13 AC power is induced in the secondary coil.

  The oscillation IC 2 is provided with a feedback terminal 21, and the feedback terminal 21 is connected to a light receiving portion 3 a of a photocoupler. When the light receiving unit 3a of the photocoupler receives light, an oscillation stop signal is input to the feedback terminal 21, and the switching element is turned off and on. Then, since the pulsed current is not supplied to the primary side coil of the transformer 13, the induction of power to the secondary side coil is stopped. When the light receiving unit 3a stops receiving light, the switching element is turned on and off again, so that the primary side coil of the transformer 13 is resumed in the form of pulses. As a result, the induction of power to the secondary side coil is resumed. Resumed.

  The AC power induced in the secondary coil is rectified, smoothed by the capacitor 6, and supplied to the output terminal. In this embodiment, the voltage of the output DC power is set to 16 volts, and the V16 power supply 61 is used.

  When a short-circuit fault occurs in the load connected to the output terminal or in the middle of wiring, a large current flows through the resistor 51, and the potential difference between both ends of the resistor 51 changes greatly. Then, the vertical relationship between the voltages at the two voltage dividing points 52 and 53 is inverted, the output of the comparator 4 is inverted, and the transistor 54 is turned on. Then, the light emitting part 3b of the photocoupler emits light by the V16 power supply 61. As described above, when the light emitting unit 3b emits light, the light is received by the light receiving unit 3a, and thus the oscillation IC 2 stops turning on and off the switching element. As a result, the power supply device 1 stops operating and no power is output from the secondary side 12.

  However, when a short circuit failure occurs, the electric charge stored in the capacitor 6 is immediately released, so that the voltage of the V16 power supply 61 decreases rapidly, and the light emitting unit 3b emitting light by the V16 power supply 61 is turned off. Further, when the power of the comparator 4 is supplied from the V16 power supply 61, the inverted state of the output is reset, so that the transistor 54 is turned off and the light emitting unit 3b is not emitting light. The operation on the primary side 11 resumes immediately.

  However, if the short circuit failure has not been resolved, the primary side operation stop and the operation restart are repeated in a short cycle as described above, and the state shown in FIG.

  Therefore, in this embodiment, the operating power of the comparator 4 is supplied from the V16A power supply 71 instead of the V16 power supply 61. Returning to FIG. 1, the comparator 4a is shown in the lower part of the secondary side 12. This is described to facilitate understanding of the power supply circuit of the comparator 4, and is the same as the comparator 4 described in the upper part thereof. It is.

  The capacitor 7 shown on the right side of the comparator 4a is provided as a charging unit, and the capacitor 7 is charged by the V16 power supply 61 in a normally operating state. However, since the diode 8 is interposed in the forward direction between the V16 power supply 61 and the capacitor 7, even if the output terminal of the secondary side 12 is short-circuited and the voltage of the V16 power supply 61 is lowered, the V16A power supply 71 The voltage is kept higher than that. The inverted state of the output of the comparator 4 is held by the V16A power supply 71 that holds the high voltage, and the on state of the transistor 54 is also held by the V16A power supply 71. For this reason, even if the light emission part 3b is light-extinguished and the primary side 11 starts operation | movement, since the light emission part 3b light-emits immediately, the primary side 11 cannot restart operation | movement.

  This state continues until the electric charge of the capacitor 7 is released. When the electric charge of the capacitor 7 is released, the primary side 11 resumes the operation, but at the same time, the capacitor 7 is charged again, so that the operation of the primary side 11 until the short-circuit fault is resolved is shown in FIG. As shown in (b), it is repeated at a longer cycle than the conventional one. As a result, the cumulative amount of operation time on the primary side 11 until the short-circuit failure is eliminated is shortened, and heat generation on the primary side 11 is reduced.

  In addition, this invention is not limited to an above-described form, You may add a various change in the range which does not deviate from the summary of this invention.

DESCRIPTION OF SYMBOLS 1 Power supply device 11 Primary side 12 Secondary side 13 Transformer transformer 2 Oscillation IC
3a light receiving unit 3b light emitting unit 4 (4a) comparator 7 capacitor (charging unit)
8 Diode

Claims (1)

An oscillation IC is provided on the primary side across the transformer, and the intermittent current flows through the primary coil. The light receiving side of the photocoupler is connected to the feedback terminal of the oscillation IC, and the secondary side of the transformer Provided with a protection circuit that stops the generation of power to the secondary side by causing the light emitting part paired with the photocoupler to emit light and inputting an oscillation inhibition signal to the feedback terminal when the coil terminals are short-circuited In the power supply apparatus, the secondary coil of the transformer transformer is configured to output only one type of voltage, and the light emitting portion of the photocoupler is configured to emit light by a comparator, and the operation power source of the comparator is used as the power supply for the comparator. It is configured to be supplied from a charging unit that is charged with electric power generated in the secondary coil of the transformer, and the secondary side of the transformer The power supply is configured such that the voltage drop rate of the power supplied to the comparator is slower than the voltage drop rate between the secondary coil terminals of the transformer transformer when the terminals of the coil are short-circuited. apparatus.

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