JP2010193590A - Power supply interruption countermeasure circuit, switching power unit, and method of controlling charge of capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply interruption countermeasure circuit which can improve the yield strength in power interruptions, without making the mounting area of a capacitor increase. <P>SOLUTION: A capacitor C2 is connected via a transistor Q1, between output power lines on the high-potential side and the low-potential side of a boosting circuit 12 included in a switching power unit. A detection circuit 31 switches off a transistor Q1, when that the output voltage of the boosting circuit 12 have reached its overshoot detection voltage is detected, in a state where the transistor Q1 is ON. By having the transistor Q1 turn off, charging of the capacitor is stopped. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power supply instantaneous interruption countermeasure circuit and a switching power supply apparatus, and more particularly to a power supply instantaneous interruption countermeasure circuit and a switching power supply apparatus having a capacitor for instantaneous interruption countermeasures. The present invention also relates to a method for controlling charging of a capacitor for measures against instantaneous interruption.

  There is a power supply device provided with a capacitor for countermeasures against instantaneous power interruption (for example, see Patent Documents 1 and 2). The capacitor for power supply interruption countermeasures is normally charged with a power supply voltage. The power supply interruption countermeasure capacitor releases the charged charge when the power input to the power supply unit is stopped. By supplying power from a capacitor for countermeasures against instantaneous power interruption for a while after the power supply is stopped, power supply to the subsequent circuit can be stabilized.

JP-A-6-30524 JP-A-9-74761

  In recent years, as the system becomes larger, the power supply capacity of the apparatus has increased. Along with this, the power supply device is also required to have a high momentary breaking strength. In order to improve the instantaneous interruption tolerance, the capacity of the instantaneous interruption countermeasure capacitor that releases energy at the moment of interruption may be increased. However, if the capacitance of the capacitor itself is increased or the number of capacitors is increased in order to increase the capacity of the instantaneous interruption countermeasure capacitor, the mounting area of the instantaneous interruption countermeasure capacitor increases. An increase in mounting area becomes an obstacle to miniaturization of the power supply device.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a power supply device capable of improving the instantaneous interruption strength without increasing the mounting area of a capacitor.

  In order to achieve the above object, a power supply interruption countermeasure circuit according to the present invention is connected via a switching element between output power lines on a high potential side and a low potential side of a booster circuit included in a switching power supply device. A capacitor and an overshoot detection unit that turns off the switching element and stops charging the capacitor when detecting that the output voltage of the booster circuit has reached the overshoot detection voltage in a state where the switching element is on; It is characterized by providing.

  The switching power supply device of the present invention includes a booster circuit, a capacitor connected via a switching element between the high-potential side and low-potential side output power supply lines of the booster circuit, and the switching element in an on state. And an overshoot detector that turns off the switching element and stops charging the capacitor when detecting that the output voltage of the booster circuit has reached an overshoot detection voltage.

  The capacitor charging control method of the present invention is characterized in that a capacitor charged with an output voltage of a booster circuit included in a switching power supply is charged with an overshoot voltage of the booster circuit.

  The instantaneous power failure countermeasure circuit, the switching power supply device, and the capacitor charging control method of the present invention can improve the instantaneous power failure resistance without increasing the mounting area of the capacitor.

The block diagram which shows the power supply device containing the power supply instantaneous interruption countermeasure circuit of 1st Embodiment of this invention. The block diagram which shows the specific circuit structure of a detection circuit. The figure which shows an operation | movement waveform. The block diagram which shows the power supply instantaneous interruption countermeasure circuit of 2nd Embodiment of this invention. The figure which shows the operation | movement waveform in 2nd Embodiment. The block diagram which shows the power supply instantaneous interruption countermeasure circuit of the modification of 1st Embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a power supply device according to a first embodiment of the present invention. The power supply apparatus includes a rectifying unit 11, a booster circuit 12, a power supply instantaneous interruption countermeasure circuit 13, and a D / D unit (voltage conversion unit) 14.

  The rectification unit 11 rectifies an AC power supply and outputs a DC voltage. The booster circuit 12 boosts the output voltage of the rectifying unit 11. The voltage converter 14 converts the input DC voltage into an output DC voltage. The capacitor C1 is a capacitor for stabilizing the output of the booster circuit 12. The plus side is connected to the high potential output power line of the boost circuit 12, and the minus side is connected to the low potential output power line. The rectification unit 11, the booster circuit 12, and the voltage conversion unit 14 are the same as those used for a normal switching power supply.

  The power supply interruption countermeasure circuit 13 includes a detection circuit 31, a capacitor C2, and a transistor Q1. The detection circuit 31 is connected between the output power supply lines of the booster circuit 12, that is, between the output power supply line on the high potential side and the output power supply line on the low potential side. The capacitor C2 is an electrolytic capacitor for measures against instantaneous interruption. The transistor Q1 is a switching element. The gate of the transistor Q1 is connected to the output of the detection circuit 31. The transistor Q1 is controlled to be turned on / off based on the output of the detection circuit 31.

  The capacitor C2 is connected between the high-potential side output power supply line and the low-potential side output power supply line of the booster circuit 12 via the transistor Q1. That is, the positive side of the capacitor C2 is connected to the output power supply line on the high potential side of the booster circuit 12, and the negative side is connected to the source of the transistor Q1. The drain of the transistor Q1 is connected to the output power line on the low potential side of the booster circuit 12.

  The detection circuit 31 includes an overshoot detection unit that detects that the output voltage of the booster circuit 12 has exceeded the set voltage (overshoot voltage), and an instantaneous interruption detection unit that detects output stop of the booster circuit 12. Doubles as The detection circuit 31 detects that the output of the booster circuit 12 has stopped when the output voltage of the booster circuit 12 becomes equal to or less than the instantaneous interruption voltage (power failure voltage). The detection circuit 31 functions as an overshoot detection unit when the transistor Q1 is on, and functions as an instantaneous voltage detection circuit when the transistor Q1 is off.

  At the start of power generation, the detection circuit 31 sets the signal output to the gate of the transistor Q1 to High and turns on the transistor Q1. When the transistor Q1 is turned on, the capacitor C2 is charged with the output voltage of the booster circuit 12. When detecting that the output voltage of the booster circuit 12 has reached the overshoot detection voltage while the transistor Q1 is on, the detection circuit 31 changes the signal output to the gate of the transistor Q1 to Low. The transistor Q1 is turned off when the signal input to the gate becomes Low. The capacitor C2 stops charging when the transistor Q1 is turned off, and holds the charged electric charge.

  When the detection circuit 31 detects an instantaneous interruption voltage while the transistor Q1 is off, the detection circuit 31 sets the signal output to the gate of the transistor Q1 to High and turns on the transistor Q1. When the transistor Q1 is turned on, the capacitor C2 discharges the stored charge. When the power failure state is resolved and the output voltage of the booster circuit 12 increases, the capacitor C2 is charged with the output voltage of the booster circuit 12 via the transistor Q1 in the on state. When the output voltage of the booster circuit 12 reaches the overshoot detection voltage, the detection circuit 31 sets the signal input to the gate of the transistor Q1 to Low and turns off the transistor Q1.

  FIG. 2 shows a specific circuit configuration of the detection circuit 31. The detection circuit 31 includes resistors R1 to R6 and a comparator Z1. The resistors R5 and R6 are connected in series with each other and are inserted between the output power supply lines of the booster circuit 12. The resistors R1 and R2 are connected in series with each other and inserted between the Vcc power supply and the output power supply line on the low potential side of the booster circuit 12. The negative input terminal of the comparator Z1 is connected to the connection node of the resistors R5 and R6, and the positive input terminal is connected to the connection node of the resistors R1 and R2. The resistor R3 is connected between the output terminal of the comparator Z1 and the Vcc power supply. The resistor R4 is connected between the output terminal of the comparator Z1 and a connection node between the resistors R1 and R2. The output terminal of the comparator Z1 is connected to the gate of the transistor Q1.

  The comparator Z1 compares the voltage obtained by dividing the output voltage of the booster circuit 12 by the resistor R5 and the resistor R6 with the voltage (reference voltage) at the positive input terminal. The reference voltage is a voltage obtained by dividing the control voltage Vcc by the resistors R1, R3, R4, and R2 when the output of the comparator Z1 is High. This voltage is referred to as a reference voltage VH. The reference voltage is a voltage obtained by dividing the control voltage Vcc by the resistors R1, R4, and R2 when the output of the comparator Z1 is Low. This voltage is referred to as a reference voltage VL.

  The reference voltage VH is a voltage corresponding to a voltage obtained by dividing the overshoot detection voltage by the resistor R5 and the resistor R6. The reference voltage VL is a voltage corresponding to a voltage obtained by dividing the power failure detection voltage by the resistor R5 and the resistor R6. The overshoot detection voltage is higher than the output voltage (rated voltage) of the booster circuit 12 in a steady state. Further, the power failure detection voltage is a voltage lower than the output voltage of the booster circuit 12 in a steady state. The relationship between the reference voltage VH and the reference voltage VL is VH> VL.

  The transistor Q1 operates in synchronization with the output of the comparator Z1. That is, the transistor Q1 is turned on when the output of the comparator Z1 is High, and is turned off when the output of the comparator Z1 is Low.

  FIG. 3 shows operation waveforms. When AC power is input to the rectification unit 11, the rectification unit 11 starts rectification. The booster circuit 12 starts boosting, and the output voltage of the booster circuit 12 (the voltage VC1 across the capacitor C1) gradually increases (a). Along with this, the voltage Vdiv obtained by dividing the output voltage VC1 of the booster circuit 12 by the resistors R5 and R6 also increases (b). The output voltage Vout of the comparator Z1 becomes High while the voltage Vdiv is lower than the reference voltage VH (c). Since the output voltage Vout is High, the transistor Q1 is turned on (d), and the capacitor C2 is charged with the output voltage VC1 of the booster circuit 12.

  When the output voltage VC1 of the booster circuit 12 reaches the overshoot detection voltage at time t1, the voltage Vdiv obtained by dividing the voltage VC1 by the resistors R5 and R6 becomes higher than the reference voltage VH, and the output of the comparator Z1 is Low. To change. As a result, the transistor Q1 is turned off, and charging of the capacitor C2 is stopped. After the charging is stopped, the capacitor C2 holds the charged electric charge. The voltage at the time of stopping the charging of the capacitor C2 is an overshoot detection voltage, which is higher than the output voltage of the booster circuit 12 at the steady state. Therefore, the capacitor C2 retains more charge than when charged with the output voltage at the steady state of the booster circuit 12.

  The output voltage VC1 of the booster circuit 12 settles to a steady voltage (set voltage) after overshoot. The voltage at the positive input terminal of the comparator Z1 changes from the reference voltage VH to the reference voltage VL after the output of the comparator Z1 changes to Low. Since the steady-state output voltage VC1 of the booster circuit 12 is higher than the instantaneous interruption detection voltage, the voltage obtained by dividing the output voltage VC1 of the booster circuit 12 by the resistors R5 and R6 is higher than the reference voltage VL. Therefore, the output of the comparator Z1 remains low and the transistor Q1 remains off.

  When the AC power input to the rectifying unit 11 is stopped for some reason, the output voltage VC1 of the booster circuit 12 decreases due to the absence of power input. When the output voltage VC1 of the booster circuit 12 drops to the voltage for detecting instantaneous interruption at time t2, the voltage Vdiv obtained by dividing the voltage VC1 by the resistors R5 and R6 becomes lower than the reference voltage VL. When the voltage Vdiv becomes lower than the reference voltage VL, the comparator Z1 changes the output to High, and the transistor Q1 is turned on. When the transistor Q1 is turned on, the capacitor C2 discharges the held charge to the voltage conversion unit 14.

  The power supply instantaneous interruption countermeasure circuit 13 of the present embodiment includes a detection circuit 31 and an instantaneous interruption countermeasure capacitor C2 as a minimum configuration. The capacitor C2 is inserted between the high-potential-side output power supply line and the low-potential-side output power supply line of the booster circuit 12 via the transistor Q1. When the detection circuit 31 detects that the output voltage of the booster circuit 12 has reached the overshoot detection voltage while the transistor Q1 is on, the detection circuit 31 turns off the transistor Q1 and stops charging the capacitor C2. In general, the amount Q of charge stored in a capacitor is represented by the product (Q = C · V) of the capacitance C of the capacitor and the applied voltage V. In the present embodiment, since the charging voltage is the overshoot detection voltage, more charge can be charged in the capacitor C2 than when the capacitor is charged with the steady-state voltage of the booster circuit 12.

  In order to improve the instantaneous power failure resistance in the switching power supply device, it is only necessary to charge a larger amount of electric charge with the capacitor for countermeasure against instantaneous power loss and increase the electrical energy stored in the capacitor. However, if the capacitance of the capacitor is increased in order to increase the charge charge, the mounting area of the capacitor is increased, which hinders downsizing of the power supply device. In the present embodiment, attention is paid to the occurrence of an overshoot detection voltage in the booster circuit 12, and the overshoot detection voltage is used to charge a capacitor for measures against instantaneous interruption. By doing so, the amount of electric charge stored in the capacitor is increased even if the capacitance remains the same. Therefore, the instantaneous interruption resistance can be improved without increasing the mounting area of the capacitor.

  FIG. 4 shows a power supply interruption countermeasure circuit according to the second embodiment of the present invention. The power supply instantaneous interruption countermeasure circuit 13a of the present embodiment includes an overshoot detection unit 32, an instantaneous interruption detection unit 33, a capacitor C2 for countermeasure against instantaneous interruption, and a transistor Q1. In the power supply interruption countermeasure circuit 13 of the first embodiment shown in FIG. 1, the detection circuit 31 serves as both an overshoot detection unit and an instantaneous interruption detection unit. In the power supply instantaneous interruption countermeasure circuit 13a of this embodiment, the overshoot detection unit 32 and the instantaneous interruption detection unit 33 are separated. In the present embodiment, the instantaneous interruption detection unit 33 detects the output stop of the booster circuit when a current interruption occurs in the output current of the booster circuit 12.

  The overshoot detection unit 32 includes resistors R7 to R9 and a comparator Z2. The resistors R7 and R8 are connected in series with each other, and are connected between the high-potential-side output power supply line and the low-potential-side output power supply line of the booster circuit 12. The negative input terminal of the comparator Z2 is connected to a connection node between the resistors R7 and R8, and a predetermined reference voltage Vref is input to the positive input terminal. The output of the comparator Z2 is connected to the gate of the transistor Q1. The resistor R9 is connected between the control voltage Vcc and the output of the comparator Z2.

  The comparator Z2 compares the voltage obtained by dividing the output voltage of the booster circuit 12 with the resistor R7 and the resistor R8 with the reference voltage Vref. The reference voltage Vref is a voltage corresponding to a voltage obtained by dividing the overshoot detection voltage by the resistor R7 and the resistor R8. The comparator Z2 changes the output from High to Low when the output voltage of the booster circuit 12 becomes the overshoot detection voltage. The output of the comparator Z2 is input to the gate of the transistor Q1. The transistor Q1 is turned off when the output of the comparator Z2 becomes Low.

  The instantaneous interruption detection unit 33 includes resistors R10 to R14, capacitors C3 and C4, and a comparator Z3. The booster circuit 12 includes a diode D1 inserted in series with the output power line on the high potential side. The resistors R10 and R11 are connected in series with each other and then connected to the output side of the diode on the anode side and the low potential side. The resistors R12 and R13 are connected in series with each other and then connected to the output side of the diode on the anode side and the low potential side. Capacitor C3 is connected in parallel with resistor R11. Capacitor C4 is connected in parallel with resistor R13.

  The negative input terminal of the comparator Z3 is connected to the connection node (node A) of the resistors R10 and R11, and the positive input terminal is connected to the connection node (node B) of the resistors R12 and R13. The output terminal of the comparator Z3 is connected to the gate of the transistor Q1 through the diode D2. The resistor R14 is connected between the control voltage Vcc and the output terminal of the comparator Z3.

  The voltage at the node A is a voltage obtained by dividing the voltage at the anode of the diode D1 by the resistor R10 and the resistor R11. The voltage at the node B is a voltage obtained by dividing the voltage at the cathode of the diode D1 by the resistors R12 and R13. When a current flows through the diode D1, if R10 = R12 and R11 = R13, the potential difference between the node A and the node B becomes a voltage corresponding to the forward voltage of the diode D1. The resistance values of the resistors R10 to R14 are set such that the voltage at the node A is higher than the voltage at the node B in a state where a current flows through the diode D1.

  The comparator Z3 compares the voltage at the node A with the voltage at the node B. When a current is flowing through the diode D1, that is, when the booster circuit 12 is outputting a current, the voltage at the node A is higher than the voltage at the node B. When the output current is stopped in the booster circuit 12, the voltage at the node A becomes lower than the voltage at the node B. The comparator Z3 changes the output from Low to High when the voltage at the node B becomes higher than the voltage at the node A. That is, when a current interruption occurs in the output of the booster circuit 12, the output of the comparator Z3 changes to High. When the output of the comparator Z3 becomes High, the transistor Q1 is turned on.

  When the transistor Q2 in the booster circuit 12 is turned on, the voltage at the anode of the diode D1 may instantaneously approach 0V. The capacitor C3 connected in parallel with the resistor R11 has a role of preventing the voltage at the node A from being lowered in such a case. A capacitor C4 connected in parallel with the resistor R13 is provided to remove noise.

  FIG. 5 shows operation waveforms. When the output voltage of the booster circuit 12 (the voltage VC1 across the capacitor C1) reaches the overshoot detection voltage at time t1 (a), the voltage obtained by dividing the voltage VC1 by the resistor R7 and the resistor R8 is the reference voltage Vref. (B), the output Vout2 of the comparator Z2 changes from High to Low (d). Along with this, the transistor Q1 changes from on to off, and charging of the capacitor C2 stops (f). At this time, since the booster circuit 12 performs current output, the voltage at the node A is higher than the voltage at the node B (c), and the output Vout3 of the comparator Z3 is low (e).

  When the output of the booster circuit 12 stops for some reason at time t2, the current flowing through the diode D1 stops, and the voltage at the node A becomes lower than the voltage at the node B. For this reason, the output Vout3 of the comparator Z3 changes to High. When the output Vout3 of the comparator Z3 becomes High, the transistor Q1 is turned on. When the transistor Q1 is turned on, the capacitor C2 discharges the stored charge to the voltage conversion unit 14.

  In the present embodiment, the instantaneous interruption detection unit 33 detects the output stop of the booster circuit 12 based on the output current interruption of the booster circuit 12. Also in this case, when the output from the booster circuit 12 is stopped, the electrical energy stored in the capacitor C2 can be supplied to the voltage converter 14 at the subsequent stage. Other effects, that is, the effect that the capacitor C2 can store more electric charge and the instantaneous breakdown strength can be improved without increasing the mounting area of the capacitor, are the same as in the first embodiment.

  In each of the above embodiments, the transistor Q1 is used as the switching element, but the switching element is not limited to the transistor. FIG. 6 shows a power supply interruption countermeasure circuit according to a modification of the first embodiment. In FIG. 6, a relay RE1 is used instead of the transistor Q1. An effect similar to that of the first embodiment can also be obtained by controlling on / off of the relay RE1 based on the output of the comparator Z1.

  As described above, the present invention has been described based on the preferred embodiments. However, the power supply interruption countermeasure circuit, the switching power supply device, and the capacitor charging control method of the present invention are not limited to the above embodiments. Those modified and changed from the configuration of the above embodiment are also included in the scope of the present invention.

11: Rectifier 12: Booster circuit 13: Power supply interruption countermeasure circuit 14: Voltage converter (D / D unit)
31: detection circuit 32: overshoot detection unit 33: instantaneous interruption detection unit C1 to C4: capacitors D1, D2: diodes Q1, Q2: transistors R1 to R14: resistors RE1: relays Z1 to Z3: comparators

Claims (11)

A capacitor connected via a switching element between the high-potential side and low-potential side output power lines of the booster circuit included in the switching power supply device;
A power supply comprising an overshoot detection unit that turns off the switching element and stops charging the capacitor when detecting that the output voltage of the booster circuit has reached the overshoot detection voltage in a state where the switching element is on Instantaneous disconnection countermeasure circuit.   The overshoot detection unit compares a voltage obtained by dividing the output voltage of the booster circuit by a predetermined resistance ratio with a voltage corresponding to the overshoot detection voltage, and the divided voltage is the overshoot detection voltage. The power supply instantaneous interruption countermeasure circuit according to claim 1, further comprising a comparator that changes an output when the voltage exceeds a voltage corresponding to 1 and turns off the switching element.   3. The apparatus according to claim 1, further comprising an instantaneous interruption detecting unit that turns on the switching element when the output stop of the booster circuit is detected in a state where the switching element is off, and discharges the electric charge charged in the capacitor. Power supply interruption countermeasure circuit.   The power supply according to claim 3, wherein the instantaneous interruption detection unit detects the output stop when the output voltage of the booster circuit decreases to a power failure detection voltage in a state where the switching element is off, and turns on the switching element. Instantaneous disconnection countermeasure circuit.   The instantaneous interruption detection unit compares a voltage obtained by dividing the output voltage of the booster circuit by a predetermined resistance ratio with a voltage corresponding to the power failure detection voltage when the switching element is in an off state, 5. The instantaneous power failure countermeasure circuit according to claim 4, further comprising: a comparator that changes an output when the reduced voltage becomes equal to or lower than a voltage corresponding to the power failure detection voltage and turns on the switching element.   The power supply interruption countermeasure circuit according to claim 4 or 5, wherein the overshoot detection unit also serves as the instantaneous interruption detection unit.   The power supply instantaneously detecting unit according to claim 3, wherein the instantaneous interruption detecting unit detects the output stop when the current interruption occurs in the output current of the booster circuit in a state where the switching element is off, and turns on the switching element. Disconnection countermeasure circuit.   The instantaneous interruption detecting unit compares the voltage on the cathode side and the voltage on the anode side of the diode inserted in series in the output power supply line in the booster circuit, and when the voltage on the anode side becomes lower than the voltage on the cathode side The power supply interruption countermeasure circuit according to claim 7, which detects an output stop.   The instantaneous interruption detection unit compares a voltage obtained by dividing the voltage on the cathode side of the diode by a predetermined resistance ratio with a voltage obtained by dividing the voltage on the anode side of the diode by a predetermined resistance ratio, A comparator that changes the output when the voltage obtained by dividing the voltage on the side by a predetermined resistance ratio becomes lower than the voltage obtained by dividing the voltage on the cathode side by a predetermined resistance ratio, and starts discharging from the capacitor The power supply interruption countermeasure circuit according to claim 8. A booster circuit;
A capacitor connected via a switching element between the high-potential side and low-potential side output power lines of the booster circuit;
A switching device comprising: an overshoot detection unit configured to turn off the switching element and stop charging the capacitor when detecting that the output voltage of the booster circuit has reached an overshoot detection voltage while the switching element is on; Power supply.   A capacitor charging control method for charging a capacitor charged with an output voltage of a booster circuit included in a switching power supply device with an overshoot voltage of the booster circuit.

Images