JP6040433B2 - Power converter and overvoltage protection method in power converter - Google Patents

Description

  The present invention relates to a power conversion device such as a DC-DC converter, and more particularly to a power conversion device having an overvoltage protection function and an overvoltage protection method in the power conversion device.

  Conventionally, in a power conversion device that converts a DC input voltage to a desired DC output voltage, a function (hereinafter referred to as the following) that protects the components of the device and an external load from an overvoltage generated on the secondary side of a transformer included in the power conversion device. There is a device having an “overvoltage protection function”.

In FIG. 6, the structural example of the conventional power converter device 3 which has an overvoltage protection function is shown.
The power conversion device 3 basically converts the DC input voltage Vin into an output voltage Vout lower than the DC input voltage Vin, and the DC input voltage Vin is applied as a component relating to the power conversion. Input terminals TINH and TINL, input power source reverse connection prevention diode D1, input capacitor C1, high frequency current absorption coil L01 and capacitor C01, voltage conversion transformer T, switching n-type MOS transistor Q1, synchronization A rectifying n-type MOS transistor Q2, a freewheeling diode D2, a smoothing coil L02 and a capacitor C02, output terminals TOUTH and TOUTL to which an external load LD is connected, a control circuit CNT for switching control, and a voltage regulator VRG are provided.

  In addition, the power conversion device 3 includes a secondary side overvoltage detection circuit OVD and a primary side overvoltage latch stop circuit LTC as components related to the overvoltage protection function. Among these, the secondary side overvoltage detection circuit OVD is composed of resistance elements R201, R202, R203, a comparator CMP, and a light emitting diode P201. Here, the resistance elements R201 and R202 are connected in series between the output terminal TOUTH on the high voltage side and the output terminal TOUTL on the low voltage side. A node between the resistance element R201 and the resistance element R202 is connected to a positive input portion of the comparator CMP, and a reference voltage VREF is supplied to the negative input portion. A resistance element R203 and a light emitting diode P201 are connected in series between the output portion of the comparator CMP and the output terminal TOUTH.

  On the other hand, the primary side overvoltage latch stop circuit LTC is composed of a resistance element R301 and a light receiving transistor P301. The resistor element R301 and the light receiving transistor P301 are connected in series between the output portion of the voltage regulator VRG that supplies the operating power supply voltage VCC and the input portion of the latch circuit LT in the control circuit CNT. The latch circuit LT is for controlling the operation of the drive circuit DR in the control circuit CNT. When a high level signal is held in the latch circuit LT, the operation of the drive circuit DR is controlled to an inactive state. The switching operation of the n-type MOS transistor Q1 is stopped.

  The voltage regulator VRG is for generating the operating power supply voltage VCC of the control circuit CNT from the DC input voltage Vin, and details thereof will be described in the embodiments of the present invention described later. However, the voltage regulator VRG is not essential to the present invention.

  According to the power conversion device 3 configured as described above, the output voltage Vout is generated on the secondary side of the transformer T by controlling the switching of the n-type MOS transistor Q1 by the control circuit CNT. At this time, the output voltage Vout is detected by an output detection circuit (not shown), and the control circuit CNT performs feedback control of switching of the n-type MOS transistor Q1 so that the output voltage Vout becomes a desired voltage value.

  In such feedback control, for example, if the output detection circuit for detecting the output voltage Vout is opened due to some factor such as disconnection of the signal line, the above-described feedback control does not function. As a result, the output voltage Vout rises to a voltage given by (DC input voltage Vin) × (number of turns of the secondary coil L2 of the transformer T) / (number of turns of the primary side coil L1 of the transformer T). When the output voltage Vout increases in this way, an excessive voltage is applied to each component constituting the secondary side of the transformer T and the external load LD, which may be damaged.

  Therefore, in the conventional power conversion device 3, when the output voltage Vout rises and an overvoltage occurs, the power conversion operation is stopped by stopping the switching operation of the n-type MOS transistor Q1.

  Specifically, in the secondary overvoltage detection circuit OVD shown in FIG. 6, when the potential of the node between the resistance element R201 and the resistance element R202 exceeds the reference voltage VREF due to the increase of the output voltage Vout, the comparator CMP is activated. Output low level. Thereby, the light emitting diode P201 is energized to emit light.

  When the light emitting diode P201 emits light, the light receiving transistor P301 in the primary overvoltage latch stop circuit LTC optically coupled to the light emitting diode P201 is turned on. As a result, a high level signal is input to the latch circuit LT in the control circuit CNT via the resistance element R301 and the light receiving transistor P301, and the latch circuit LT holds this signal. When the latch circuit LT holds a high level signal, the drive circuit DR is deactivated, and as a result, the switching of the n-type MOS transistor Q1 is stopped.

  When the switching of the n-type MOS transistor Q1 is stopped, no alternating current is supplied to the primary winding L1 of the transformer T, so that no voltage is induced in the secondary winding L2 of the transformer T. Therefore, the power conversion operation in the power conversion device 3 is stopped, whereby the output voltage Vout is reduced and the overvoltage is suppressed.

JP 2000-184727 A

  However, according to the above-described conventional technology, there is a problem that it is not possible to suppress overvoltage caused by dielectric breakdown between the primary winding L1 and the secondary winding L2 of the transformer T.

This problem will be specifically described with reference to the waveform diagram of FIG.
Before the time t1 when the breakdown of the transformer T occurs, as shown in FIG. 7, the DC input voltage Vin appears on the cathode side of the diode D1 on the primary side as the voltage VC1, and the output voltage Vout at that time is A desired voltage value based on the feedback control described above is obtained. From this state, when dielectric breakdown of the transformer T occurs at time t1 due to some factor, the primary side winding L1 of the transformer T passes through the dielectric breakdown portion indicated by the resistor r having a small electrical resistance value shown in FIG. Is shorted to one end of the secondary winding L2. In this case, as shown in the waveform after time t1 in FIG. 7, the output voltage Vout on the secondary side is pulled up by the voltage VC1 on the primary side via the resistor r, and the electrical resistance value of the resistor r is sufficiently high. If it is smaller, the output voltage Vout is approximately equal to the voltage VC1. As a result, the output voltage Vout increases and an overvoltage is generated on the secondary side of the transformer T.

  Thus, when an overvoltage due to the dielectric breakdown of the transformer T occurs, even if the switching operation of the n-type MOS transistor Q1 is stopped by the above-described overvoltage protection function provided in the conventional power converter 3, the insulation of the transformer T Since the primary side voltage VC1 given by the DC input voltage Vin appears on the secondary side as the output voltage Vout through the destruction portion, the overvoltage does not disappear.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a power conversion device capable of suppressing an overvoltage caused by a dielectric breakdown of a transformer and an overvoltage protection method in the power conversion device. To do.

In order to solve the above problems, a power conversion device according to the present invention intermittently supplies a DC input applied between a first input terminal and a second input terminal to a primary winding of a transformer. A power conversion device that induces a voltage in the secondary winding of the transformer, rectifies the voltage induced in the secondary winding, and generates a desired DC output between the first output terminal and the second output terminal A first current path between one end of the secondary winding of the transformer and the first output terminal, and a second current between the other end of the secondary winding and the second output terminal. A detection unit that detects an overvoltage appearing between the path, a short circuit unit that short-circuits between the first current path and the second current path when the detection unit detects the overvoltage, and the detection unit When the overvoltage is detected, the supply of the DC input to the primary winding of the transformer is cut off. And a blocking portion, the blocking portion, the circuit element and a switching transistor for controlling the power conversion operation of the transformer primary winding and the power converter are connected in series to a series circuit connected in series A third current path between the first input terminal and one end of the primary winding of the transformer or a fourth current path between the second input terminal and the other end of the primary winding. The power conversion device includes a circuit element that is inserted on one of the current paths and that is controlled from a conduction state to a non-conduction state when the detection unit detects the overvoltage.

Moreover, the overvoltage protection method in the power converter device according to the present invention provides the transformer by intermittently supplying a DC input applied between the first input terminal and the second input terminal to the primary winding of the transformer. An overvoltage in a power converter that induces a voltage in the secondary winding of the power supply and rectifies the voltage induced in the secondary winding to generate a desired DC output between the first output terminal and the second output terminal A protection method comprising: a first current path between one end of a secondary winding of the transformer and the first output terminal; and a first current path between the other end of the secondary winding and the second output terminal. A step of detecting an overvoltage appearing between two current paths; a step of short-circuiting between the first current path and the second current path when the overvoltage is detected; and a case of detecting the overvoltage. , Cut off the supply of the DC input to the primary winding of the transformer And a step, the step of cutting off the supply of the DC input is connected in series with the series circuit and the switching transistors are connected in series to control the power conversion operation of the transformer primary winding and said power converter A circuit element that is configured to be a third current path between the first input terminal and one end of the primary winding of the transformer or between the second input terminal and the other end of the primary winding. Overvoltage protection in a power conversion device including a step of controlling a circuit element inserted on any one of the fourth current paths from a conductive state to a non-conductive state when the overvoltage is detected It has a method configuration.

  According to the above configuration, when the detection unit detects an overvoltage, the short-circuit unit includes the first current path between one end of the secondary winding of the transformer and the first output terminal, and the secondary winding of the transformer. The second current path between the end and the second output terminal is short-circuited. Moreover, the interruption | blocking part interrupts | blocks supply of the DC input to the primary winding of a transformer. As a result, the potential difference between the second current path and the first current path is reduced, and overvoltage is suppressed.

  According to the present invention, it is possible to suppress overvoltage caused by dielectric breakdown of the transformer.

It is a circuit diagram which shows the structure of the power converter device by 1st Embodiment of this invention. It is a wave form diagram for demonstrating operation | movement of the power converter device by 1st Embodiment of this invention. It is a circuit diagram which shows the 1st modification of the power converter device by 1st Embodiment of this invention. It is a circuit diagram which shows the 2nd modification of the power converter device by 1st Embodiment of this invention. It is a circuit diagram which shows the structure of the power converter device by 2nd Embodiment of this invention. It is a circuit diagram which shows the structural example of the power converter device by a prior art. It is a wave form diagram for demonstrating operation | movement of the power converter device by a prior art.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
In addition, in each figure, the same code | symbol is attached | subjected to the element which is common in the component shown in above-mentioned FIG.

(First embodiment)
In FIG. 1, the structure of the power converter device 1 by 1st Embodiment of this invention is shown. This power converter 1 converts a DC input voltage Vin applied between a high voltage side input terminal TINH and a low voltage side input terminal VINL to a desired output voltage Vout lower than the DC input voltage Vin. A DC input voltage Vin is intermittently supplied to the primary winding L1 of the transformer T to induce a voltage in the secondary winding L2 of the transformer T, and the secondary winding L2 By rectifying the induced voltage, a desired output voltage Vout is generated between the output terminal TOUTH on the high voltage side and the output terminal TOUTL on the low voltage side.

That is, the power conversion device 1 includes, as components related to power conversion, input terminals TINH and TINL to which a DC input voltage Vin is applied, a diode D1 for preventing reverse connection of an input power source, an input capacitor C1, and a coil L01 for absorbing high-frequency current. And a capacitor C01, a voltage converting transformer T, a switching n-type MOS transistor Q1, a synchronous rectifying n-type MOS transistor Q2, a freewheeling diode D2, a smoothing coil L02 and a capacitor C02, and an external load LD are connected. Output terminals TOUTH and TOUTL and a voltage regulator 30 are provided. The input terminal TINL and the output terminal TOUTL are electrically connected outside the power conversion device 1. In addition to the above configuration, the power conversion device 1 includes a detection unit 10, a short-circuit unit 20, and a cutoff unit 30 as components related to the overvoltage protection function.
Although omitted in FIG. 1, the power conversion device 1 further includes the control circuit CNT shown in FIG. 6 for controlling the switching of the n-type MOS transistors Q1 and Q2, and the operation of the control circuit CNT. The power supply voltage VCC is supplied from the voltage regulator 30.

The configuration of the power conversion device 1 will be described in more detail.
A DC input voltage Vin is applied between the input terminal TINH and the input terminal TINL, and the anode of the input power source reverse connection prevention diode D1 is connected to the input terminal TINH. The diode D1 is an optional component and is not an essential element for the power conversion device 1. The cathode of the diode D1 is connected to one end of the fuse F, and the other end of the fuse F is connected to one end of the coil L01. An input capacitor C1 is connected between the other end of the fuse F and the input terminal TINL, and a capacitor C01 is connected between the other end of the coil L01 and the input terminal TINL. The other end of the coil L01 is connected to one end of the primary winding L1 of the transformer T. The other end of the primary winding L1 is connected to the drain of the n-type MOS transistor Q1, and the source of the n-type MOS transistor Q1 Is connected to the input terminal TINL.

  One end of the secondary winding L2 of the transformer T is connected to one end of a coil L02 constituting a smoothing circuit, and the other end of the coil L02 is connected to an output terminal TOUTH. The other end of the secondary winding L2 of the transformer T is connected to the drain of the synchronous rectification n-type MOS transistor Q2, and the source of the n-type MOS transistor Q2 is connected to the output terminal TOUTL. One end of the secondary winding L2 of the transformer T is connected to the cathode of the circulating diode D2, and the anode of the diode D2 is connected to the output terminal TOUTL. A capacitor C02 that forms a smoothing circuit together with the coil L02 is connected between the other end of the coil L02 and the output terminal TOUTL, and an external load LD is connected between the output terminal TOUTH and the output terminal TOUTL.

  Hereinafter, a current path between one end (high voltage terminal) of the secondary winding L2 of the transformer T and the output terminal TOUTH, that is, a current from one end of the secondary winding L2 to the output terminal TOUTH via the coil L02. The path is referred to as a “first current path”, and the current path between the other end (low voltage terminal) of the secondary winding L2 of the transformer T and the output terminal TOUTL, that is, the other end of the secondary winding L2 is n A current path that reaches the output terminal TOUTL via the type MOS transistor Q2 is referred to as a “second current path”. Further, the current winding between the input terminal TINH and one end (high voltage terminal) of the primary winding L1 of the transformer T, that is, the primary winding from the input terminal TINH through the diode D1, the fuse F, and the coil L01. A current path that reaches one end of L1 is referred to as a “third current path”, and the current path between the input terminal TINL and the other end (low voltage terminal) of the primary winding L1 of the transformer T, that is, from the input terminal TINH. The current path that reaches the other end of the primary winding L1 through the n-type MOS transistor Q1 is referred to as a “fourth current path”.

Then, each structure of the detection part 10, the short circuit part 20, and the interruption | blocking part 30 regarding the overvoltage protection function which the power converter device 1 has is demonstrated.
The detection unit 10 is for detecting an overvoltage appearing between the first current path and the two current paths, and a light emitting diode P11 connected in series between the first current path and the two current paths, A Zener diode Z11 and resistance elements R11 and R12 are included. Here, one end of the resistance element R11 is connected to the output terminal TOUTH located on the first current path, and the other end of the resistance element R11 is connected to one end (anode) of the light emitting diode P11. The other end (cathode) of the light emitting diode P11 is connected to the cathode of the Zener diode Z11, and the anode of the Zener diode Z11 is connected to one end of the resistor element R12. The other end of the resistance element R12 is connected to the output terminal TOUTL located on the second current path.
Note that the connection order of the light emitting diode P11, the Zener diode Z11, and the resistance elements R11 and R12 is not limited to this example, and may be arbitrarily changed.

The short-circuit unit 20 is controlled to be in a conductive state when the detection unit 10 detects an overvoltage, and short-circuits between the first current path and the second current path. It is composed of a thyristor TH21 (switching element) connected between the current path and a stabilizing capacitor C21. Here, the anode of the thyristor TH21 is connected to the output terminal TOUTH located on the first current path, and the cathode thereof is connected to the output terminal TOUTL located on the second current path. The control electrode of the thyristor TH21 is connected between the anode of the Zener diode Z11 constituting the detection unit 10 and one end of the resistance element R12.
In this example, the control electrode of the thyristor TH21 is connected to a node between the anode of the Zener diode Z11 and one end of the resistor element R12. However, the present invention is not limited to this example, and the resistor element R11 and the resistor element R12. Any node between the nodes may be connected to any node.

  The shut-off unit 30 is controlled to be open when the detecting unit 10 detects an overvoltage, and shuts off the supply of the DC input voltage Vin to the primary winding of the transformer T. (Circuit element). The fuse F is inserted on a third current path between the input terminal TINH and one end of the primary winding L1 of the transformer. In the present embodiment, one end of the fuse F is connected to the cathode of the diode D1, and the other end of the fuse F is connected to one end of the coil L01. However, the present invention is not limited to this example, and the fuse F can be inserted at any position on the third current path as long as the supply of the DC input voltage Vin to the primary winding of the transformer T can be cut off. Good.

  In the present embodiment, in order to cope with overvoltage caused by dielectric breakdown between one end on the high voltage side of the primary winding L1 of the transformer T and one end on the high voltage side of the secondary winding L2, The fuse F is inserted on the three current paths, but the insulation breakdown between the other end of the primary winding L1 of the transformer T on the low voltage side and the other end of the secondary winding L2 on the low voltage side When dealing with an overvoltage caused by the above, the fuse F is inserted on the fourth current path. That is, the fuse F is inserted in either the third current path or the fourth current path so as to be connected in series with the dielectric breakdown part according to the part of the dielectric breakdown part that causes overvoltage.

  The interruption unit 30 further includes thyristor TH31 (switch element), capacitor C32, resistance elements R31 and R32, light receiving transistor P31, pnp type as components for blowing the fuse F when the detection unit 10 detects an overvoltage. A bipolar transistor Q31 and resistance elements R33, R34, R35, and R36 are provided.

  More specifically, the thyristor TH31 is connected between the third current path and the fourth current path so as to be connected in series with the fuse F between the input terminal TINH and the input terminal TINL. That is, the anode of the thyristor TH31 is connected to the other end of the fuse F located on the third current path, and the cathode is connected to the input terminal TINL located on the fourth current path.

  Further, resistance elements R31 and R32 and a light receiving transistor P31 are connected in series between the output portion of the voltage regulator VRG and the input terminal TINL. That is, one end of the resistor element R31 is connected to the output portion of the voltage regulator VRG, one end of the resistor element R32 is connected to the other end of the resistor element R31, and the other end of the resistor element R32 is one end of the light receiving transistor P31. The other end (emitter) of the light receiving transistor P31 is connected to the input terminal TINL. The light-receiving transistor P31 is optically coupled to the light-emitting transistor P11 that constitutes the above-described detection unit 10 to constitute a photocoupler.

  The emitter of the pnp bipolar transistor Q31 is connected to the output part of the voltage regulator VRG, and the base of the pnp bipolar transistor Q31 is connected to a node between the resistor element R31 and the resistor element R32. Resistance elements R33, R34, and R35 are connected in series between the collector of the pnp bipolar transistor Q31 and the control electrode of the thyristor TH31, and the resistance element is connected between the control electrode of the thyristor TH31 and the input terminal TINL. R36 is connected.

  A capacitor C32 is connected between the control electrode of the thyristor TH31 and the input terminal TINL, and a capacitor C31 is connected between the emitter and base of the pnp bipolar transistor Q31. These capacitors C31 and C32 are for stabilization. That is, the capacitor C31 is for maintaining the pnp bipolar transistor Q31 in the off state when the power is turned on, and the capacitor C32 is for maintaining the thyristor TH31 in the off state when the power is turned on. Therefore, the fuse F is prevented from being erroneously blown in a transient state.

  The voltage regulator VRG is the same as that shown in FIG. 6 described above, and is essentially for supplying the operation power supply voltage VCC of the control circuit CNT (not shown) for controlling the switching of the n-type MOS transistor Q1. Is provided. In the present embodiment, the voltage VCC generated by the voltage regulator VRG is also used as an operation power supply for the cutoff unit 30. However, the present invention is not limited to this example, and it is also possible to use a voltage (for example, DC input voltage Vin or voltage VC1) appearing on the third current path as the operation power supply of the interrupting unit 30.

  The voltage regulator VRG includes resistance elements R101, R102, and R103, an npn bipolar transistor Q101, Zener diodes Z101 and Z102, and a capacitor C101. One end of the resistance element R101 is connected to one end of the primary winding L1 of the transformer T, and the other end of the resistance element R101 is connected to one end of the resistance element R102. The other end of resistance element R102 is connected to the base of npn bipolar transistor Q101 and the cathode of Zener diode Z101. The anode of the Zener diode Z101 is connected to the cathode of the Zener diode Z102, and the anode of the Zener diode Z102 is connected to the input terminal TINL.

  A node between the resistance element R101 and the resistance element R102 is connected to one end of the resistance element R103, and the other end of the resistance element R103 is connected to a collector of the npn-type bipolar transistor Q101. A stabilizing capacitor C101 is connected between the emitter of the npn-type bipolar transistor Q101 and the input terminal TINL, and the emitter of the npn-type bipolar transistor Q101 serves as an output portion of the voltage regulator VRG.

  According to the voltage regulator VRG having such a configuration, a constant reference voltage obtained by a series circuit of the resistor elements R101 and R102 and the Zener diodes Z101 and Z102 appears at a node between the resistor element R102 and the Zener diode Z101. . By applying this reference voltage to the base of the npn bipolar transistor Q101, a voltage obtained by subtracting the base-emitter voltage Vbe from the base voltage of the npn bipolar transistor Q101 is obtained as the operating power supply voltage VCC. Therefore, according to the voltage regulator VRG, a control circuit (not shown) for controlling the switching of the n-type MOS transistor Q1 and an operation power supply voltage VCC suitable for the cutoff unit 30 are generated from the high DC input voltage Vin. be able to.

  The resistor r shown in FIG. 1 is the same element as the resistor r shown in FIG. 6 described above, and is between the one end of the primary side winding L1 and the one end of the secondary side winding L2 of the transformer T. The dielectric breakdown part when a dielectric breakdown occurs is shown, and is not a component that the power conversion device 1 originally has.

Next, the case where dielectric breakdown occurs between one end on the high voltage side of the primary side winding L1 of the transformer T and one end on the high voltage side of the secondary side winding L2 will be described as an example. The operation (overvoltage protection method) will be described focusing on the overvoltage protection function with reference to the waveform diagram shown in FIG.
For convenience of explanation, it is assumed that the input terminal TINL and the output terminal TOUTL are fixed to the ground potential (0 V), but the present invention is not limited to this example.

  First, in a state before time t1 when the dielectric breakdown of the transformer T occurs, a desired output voltage Vout lower than the DC input voltage Vin is output from the DC input voltage Vin by normal operation.

  When a breakdown of the transformer T occurs at time t1, a current path indicated by a resistance r is formed in a breakdown portion between one end of the primary side winding L1 and one end of the secondary winding L2 of the transformer T. . As a result, a current flows from the primary side to the secondary side through the resistor r due to a potential difference between the primary side voltage VC1 (voltage between the terminals of the input capacitor C1) and the secondary side output voltage Vout. The output voltage Vout is raised by the current and starts to rise. At time t2, when the output voltage Vout reaches a predetermined threshold value Vth defined by the electrical characteristics of the Zener diode Z11 constituting the detection unit 10, the Zener diode Z11 is turned on. As a result, the light emitting diode P11 is energized to emit light, and the voltage at the node between the Zener diode Z11 and the resistance element R12 increases.

  The above-mentioned predetermined threshold value Vth defined by the electrical characteristics of the Zener diode Z11 is a value for determining the occurrence of overvoltage, and is used to protect the secondary side components of the device and the external load LD. Appropriately selected from the viewpoint.

  When the voltage at the node between the Zener diode Z11 of the detection unit 10 and the resistance element R12 rises, the thyristor TH21 of the short-circuit unit 20 to which this voltage is input to the control electrode is turned on, and the thyristor TH21 causes the first current to be turned on. The output terminal TOUTH located on the path and the output terminal TOUTL located on the second current path are short-circuited. As a result, the current flowing from the primary side to the secondary side via the resistance r of the dielectric breakdown portion is discharged to the output terminal VOUTL through the thyristor TH21, and as shown in the lower waveform of FIG. Then, the output voltage Vout decreases to approximately 0V. Therefore, the overvoltage resulting from the dielectric breakdown of the transformer T is suppressed, and the components constituting the secondary side of the power converter 1 and the external load LD are protected from the overvoltage.

  Although the overvoltage is suppressed by the above-described operation, the input terminal TINH which is the primary high voltage side input terminal to the output terminal TOUTL which is the secondary low voltage terminal through the thyristor TH21 constituting the short circuit unit 20. When this state continues, the thyristor TH21 generates heat. Therefore, in the present embodiment, the supply of the primary side DC input voltage Vin is blocked by the blocking unit 30.

  Specifically, as described above, when the output voltage Vout increases and exceeds a predetermined threshold value Vth, the Zener diode Z11 becomes conductive and the light emitting diode P11 emits light. When the light emitting diode P11 emits light, the light receiving transistor P31 constituting the blocking unit 30 optically coupled to the light emitting diode P11 is turned on. When the light receiving transistor P31 is turned on, the potential of the node between the resistor element R31 and the resistor element R32 is lowered, and the pnp bipolar transistor Q31 that is input to the base is turned on.

  When the pnp bipolar transistor Q31 becomes conductive, the potential of the node between the resistance element R35 and the resistance element R36 rises, and the thyristor TH31 that inputs this to the control electrode is turned on. As a result, the fuse F is electrically connected between the input terminal TINH to which the DC input voltage Vin is applied and the input terminal TINL. At this time, the fuse F is blown by the current flowing through the fuse F. As a result, as shown in the upper part of FIG. 2, the voltage VC1 on the primary side decreases to 0V after time t2.

  When the fuse F is blown, the third current path between the input terminal TINH and the primary winding L1 is cut off, and the supply of the DC input voltage Vin to the primary winding L1 is cut off. As a result, the current flowing from the primary side to the secondary side via the resistance r of the dielectric breakdown portion between the primary side and the secondary side of the transformer T is cut off, and the thyristor TH21 constituting the short-circuit portion 20 is No longer flows. Accordingly, heat generation at the thyristor TH21 is suppressed.

  As described above, according to the first embodiment, the short-circuit portion 20 shorts between the first current path and the second current path, and the cut-off portion 30 cuts off the third current path, thereby the short-circuit portion. While suppressing the heat generation at 20, the overvoltage caused by the dielectric breakdown of the transformer T can be suppressed.

-1st modification of 1st Embodiment Next, with reference to FIG. 3, the 1st modification of 1st Embodiment is demonstrated.
A power conversion device 1A according to the first modification shown in FIG. 3 includes a detection unit 10A and a cutoff unit 30A instead of the detection unit 10 and the cutoff unit 30 in the configuration of the power conversion device 1 shown in FIG. Among these, the detection unit 10A is different in configuration from the detection unit 10 in that it does not include the light emitting diode P11, and the cutoff unit 30A is different in configuration from the cutoff unit 30 in that it includes a thyristor TH311 as a fuse blowing circuit.

  Here, the anode of the thyristor TH311 is connected to the other end of the fuse F located on the third current path, and the cathode is connected to the output terminal TOUTL on the low voltage side located on the second current path. The control electrode of thyristor TH311 is connected to a node between zener diode Z11 and resistance element R12. That is, the same signal as that given to the control electrode of the thyristor TH21 constituting the short-circuit portion 20 is given to the control electrode of the thyristor TH311. Other configurations are the same as those of the power conversion apparatus 1 of FIG.

  According to the first modified example having the above-described configuration, when the output voltage Vout increases and reaches the predetermined threshold value Vth, the potential of the node between the Zener diode Z11 and the resistance element R12 configuring the detection unit 10A. Rises, and the thyristor TH21 of the short-circuit unit 20 that inputs this potential to the control electrode is turned on, and the thyristor TH311 of the blocking unit 30A is turned on. Here, when the thyristor TH21 of the short-circuit portion 20 is turned on, as described in the first embodiment, the output terminal TOUTH and the output terminal TOUTL are short-circuited, thereby suppressing overvoltage. Further, when the thyristor TH311 of the interrupting section 30A is turned on, the other end of the fuse F is electrically connected to the output terminal TOUTL on the low voltage side via the thyristor TH311. This is necessary for blowing the fuse F. Sufficient current flows through the fuse F. Therefore, according to the first modification, the fuse F can be blown with a simple configuration, and the supply of the DC input voltage Vin can be cut off.

  In the first modification, the cathode of the thyristor TH311 is connected to the output terminal TOUTL on the low voltage side located on the second current path. However, the high voltage side located on the first current path is used. May be connected to the output terminal TOUTH. In this case, if the thyristor TH21 of the short-circuit portion 20 is turned on, the cathode of the thyristor TH311 of the cutoff portion 30A is electrically connected to the output terminal TOUTL on the low voltage side via the thyristor TH21 of the short-circuit portion 20. Therefore, a current for blowing the fuse F can be generated in the same manner as in the first modified example.

-2nd modification of 1st Embodiment Next, with reference to FIG. 4, the 2nd modification of 1st Embodiment is demonstrated.
The power conversion device 1B according to the second modification shown in FIG. 4 includes a fuse F and a thyristor TH312 in place of the blocking unit 30A in the configuration of the power conversion device 1A according to the first modification shown in FIG. The interruption | blocking part 30B is provided. Here, the anode of the thyristor TH312 is connected to the other end of the fuse F located on the third current path, and the cathode is connected to the input terminal TINL on the low voltage side located on the fourth current path. The The control electrode of thyristor TH312 is connected to a node between Zener diode Z11 and resistance element R12. That is, the same signal as that given to the control electrode of the thyristor TH21 of the short circuit unit 20 is given to the control electrode of the thyristor TH312 of the blocking unit 30B. Other configurations are the same as those of the first modification.

  According to the second modified example having the above-described configuration, when the output voltage Vout increases and reaches the predetermined threshold value Vth, the thyristor TH312 of the interrupting unit 30B is turned on, so that the other end of the fuse F is connected to the thyristor. It is electrically connected to the input terminal TINL via TH312. As a result, the fuse F is electrically connected between the input terminal TINH and the input terminal TINL. Therefore, since the DC input voltage Vin is applied to the fuse F, a sufficient current can flow through the fuse F, and the fuse F can be blown quickly with a simple configuration.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.
In FIG. 5, the structure of the power converter device 2 by 2nd Embodiment is shown.
The power conversion device 2 includes a blocking unit 40 instead of the blocking unit 30 in the configuration of the power conversion device 1 shown in FIG. 1 according to the first embodiment described above. Other configurations are the same as those of the power conversion apparatus 1 shown in FIG.

  The blocking unit 40 according to the second embodiment is configured to turn off the p-type MOS transistor Q41 (second circuit element) corresponding to the fuse F in FIG. 1 and the p-type MOS transistor Q41 when the detection unit 10 detects an overvoltage. And a control circuit CNT41 for controlling the operation. Here, the source of the p-type MOS transistor Q41 is connected to the other end of the coil L01, and its drain is connected to one end of the primary winding L1 of the transformer T.

  The control circuit CNT41 includes a latch circuit LT41, a light receiving transistor P41, and resistance elements R41 and R42. One end of the light receiving transistor P41 is supplied with the operating power supply voltage VCC from the voltage regulator VRG, and the other end of the light receiving transistor P41 is connected to one end of the resistor element R41. The other end of the resistor element R41 is connected to the input portion of the latch circuit LT41 and one end of the resistor element R42, and the other end of the resistor element R42 is connected to the input terminal TINL. The output portion of latch circuit LT41 is connected to the gate of p-type MOS transistor Q41.

  The operation power supply voltage VCC is supplied from the voltage regulator VRG to the latch circuit LT41. The latch circuit LT41 corresponds to the voltage VC1 higher than the operation power supply voltage VCC by incorporating a level shifter circuit or a charge pump circuit, for example. It is configured to be able to output a signal having a certain amplitude. That is, the latch circuit LT41 outputs 0V as a low level signal and outputs a voltage corresponding to the voltage VC1 as a high level signal, thereby controlling the p-type MOS transistor Q41 in a conductive state or a nonconductive state.

  The voltage regulator VRG has the same configuration as that shown in FIG. 1 according to the first embodiment described above, but in the second embodiment, one end of the resistance element R101 constituting the voltage regulator VRG is connected to the third current path. It is connected to a node closer to the input terminal TINH than the p-type MOS transistor Q41, and is connected to a node between the diode D1 and the coil L01 in the example of FIG. The reason for this is to ensure the operation of the blocking unit 40 after the supply of the DC input voltage Vin is blocked by the p-type MOS transistor Q41 constituting the blocking unit 40. However, one end of the resistance element R101 constituting the voltage regulator VRG may be connected anywhere between the input terminal TINH and the p-type MOS transistor Q41, and is not limited to the example of FIG.

  Next, taking as an example the case where dielectric breakdown occurs between one end of the primary side winding L1 and one end of the secondary side winding L2 of the transformer T, the operation of the power conversion device 2 according to the second embodiment will be described. Description will be made by paying attention to the overvoltage protection function.

  According to the power conversion device 2 according to the second embodiment, as in the first embodiment described above, when the dielectric breakdown of the transformer T occurs, the output voltage Vout increases, and the output voltage Vout becomes equal to the predetermined threshold value Vth described above. , The thyristor TH21 constituting the short circuit unit 20 is turned on. When the thyristor TH21 is turned on, the thyristor TH21 shorts between the output terminal TOUTH located on the first current path and the output terminal TOUTL located on the second current path. As a result, the output voltage Vout becomes approximately 0V. Accordingly, the occurrence of overvoltage due to the dielectric breakdown of the transformer T is suppressed.

  When the output voltage Vout reaches the predetermined threshold value Vth, the light emitting diode P11 of the detecting unit 10 emits light, and the light receiving transistor P41 of the blocking unit 40 optically coupled to the light emitting diode P11 is turned on. As a result, a high level signal is applied to the input portion of the latch circuit LT41, and this signal level is held in the latch circuit LT41.

  When the latch circuit LT41 holds the high level signal, the latch circuit LT41 supplies a high level signal corresponding to the voltage VC1 to the gate of the p-type MOS transistor Q41, thereby controlling the p-type MOS transistor Q41 in a non-conductive state. When the p-type MOS transistor Q41 is controlled to be in a non-conductive state, the supply of the DC input voltage Vin is cut off as in the first embodiment described above, and no current flows through the thyristor TH21 of the short-circuit portion 20.

  According to the second embodiment, since the p-type MOS transistor Q41 is provided instead of the fuse, in addition to the effect of the first embodiment described above, the DC input voltage Vin can be reduced without requiring power for blowing the fuse. Supply can be cut off.

Although the embodiments and modifications of the present invention have been described above, the present invention is not limited to the above-described examples, and various modifications can be made without departing from the scope of the present invention.
For example, in the above-described first embodiment, the power conversion device 1 includes both the short-circuit unit 20 and the blocking unit 30, but may be configured to include only one of them. The same applies to the second embodiment.

  In the first embodiment described above, the current for blowing the fuse F is generated by short-circuiting the third current path and the fourth current path by the thyristor TH31. When the resistance r is sufficiently small, the fuse F can be blown by the current flowing through the resistance r and the thyristor TH21. In an application that assumes such a dielectric breakdown, the interrupting section 30 may be configured only from the fuse F.

  In the first embodiment described above, the detection unit 10 and the blocking unit 30 are optically coupled by a photocoupler including the light emitting diode P11 and the light receiving transistor P31, and the detection result of the overvoltage is detected from the detection unit 10. It is assumed that the light is transmitted to the blocking unit 30 by an optical signal. However, it is also possible to transmit the light by wired or wireless. The same applies to the second embodiment.

  DESCRIPTION OF SYMBOLS 1,1A, 1B, 2,3 ... Power converter device, 10, 10A ... Detection part, 20 ... Short-circuit part, 30, 30A, 30B, 40 ... Blocking part.

Claims (5)

A DC input applied between the first input terminal and the second input terminal is intermittently supplied to the primary winding of the transformer, thereby inducing a voltage in the secondary winding of the transformer, and the secondary winding. A power converter that rectifies a voltage induced in a line and generates a desired DC output between a first output terminal and a second output terminal,
Between a first current path between one end of the secondary winding of the transformer and the first output terminal, and a second current path between the other end of the secondary winding and the second output terminal. A detection unit for detecting an overvoltage appearing in
A short circuit that short-circuits between the first current path and the second current path when the detection unit detects the overvoltage;
A shut-off unit that shuts off the supply of the DC input to the primary winding of the transformer when the detection unit detects the overvoltage;
The blocking part is
A circuit element connected in series to a series circuit in which a primary winding of the transformer and a switching transistor that controls a power conversion operation of the power converter are connected in series, the first input terminal and the transformer Is interposed on one of the third current path between one end of the primary winding and the fourth current path between the second input terminal and the other end of the primary winding. And a power conversion device including a circuit element that is controlled from a conductive state to a non-conductive state when the detection unit detects the overvoltage. The short-circuit part is
The power conversion device according to claim 1, further comprising a switch element that is connected between the first current path and the second current path and that is turned on when the detection unit detects the overvoltage.   The power converter according to claim 1, wherein the circuit element is a fuse. The blocking part is
The fuse is connected in series with the fuse between the first input terminal and the second input terminal, and is connected between the third current path and the fourth current path. The power conversion device according to claim 3, further comprising a switch element that is turned on when detecting. A DC input applied between the first input terminal and the second input terminal is intermittently supplied to the primary winding of the transformer, thereby inducing a voltage in the secondary winding of the transformer, and the secondary winding. An overvoltage protection method in a power converter that rectifies a voltage induced in a line and generates a desired DC output between a first output terminal and a second output terminal,
Between a first current path between one end of the secondary winding of the transformer and the first output terminal, and a second current path between the other end of the secondary winding and the second output terminal. Detecting an overvoltage appearing in
If the overvoltage is detected, short-circuiting between the first current path and the second current path;
Cutting off the supply of the DC input to the primary winding of the transformer if the overvoltage is detected;
Shutting off the supply of the DC input comprises:
A circuit element connected in series to a series circuit in which a primary winding of the transformer and a switching transistor that controls a power conversion operation of the power converter are connected in series, the first input terminal and the transformer Is interposed on one of the third current path between one end of the primary winding and the fourth current path between the second input terminal and the other end of the primary winding. Controlling a circuit element that has been switched from a conductive state to a non-conductive state when the overvoltage is detected ,
An overvoltage protection method for a power converter.

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