JP2013219921A - Dc power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a DC power supply device capable of being reduced in cost and size, causing no short-circuit accident and securing safety.SOLUTION: A bias power supply for applying positive and negative bias voltages to FETs 14 and 15 constituted using a wide bandgap semiconductor material so as to prevent the FETs from being improperly operated is realized not by using another power supply but by using a primary coil N1 having a transformer structure for a choke coil of a chopper circuit, and charging capacitors 21 and 22 (a, b) for positive and negative bias connected via diodes 26 and 27 to secondary coils N2 and N3 with intermediate taps corresponding to auxiliary coils added to the choke coil. Accordingly, there is obtained a DC power supply device capable of being reduced in cost and size, causing no short-circuit accident and securing safety.

Description

  The present invention relates to a DC power supply apparatus that receives AC power supplies of various voltages and frequencies.

  A DC power supply device that receives AC power supplies of various voltages and frequencies is used in various technical fields, for example, from household electronic devices to ground equipment, ship equipment, and power supply systems for aircraft.

  By the way, in an electronic device that uses a single-phase AC voltage of AC 100 V to AC 440 V as a primary power source and requires a relatively large DC power, a harmonic ripple current generated when the primary power source is full-wave rectified is generated by the primary power source or the primary power source. Therefore, there is a demand for a DC power supply device capable of AC / DC conversion with extremely low harmonic ripple, high power factor and high efficiency.

  Therefore, in recent years, an AC power input stage has a switching type power factor improvement circuit that improves the power factor while boosting the rectified voltage, and a predetermined voltage required by the load device is increased at the output stage of the power factor improvement circuit. 2. Description of the Related Art A DC power supply device is known in which a DC / DC converter that can output efficiently is connected to achieve high power factor and high efficiency.

  The switching type power factor correction circuit includes a full-wave rectifier circuit and a boost chopper circuit. The step-up chopper circuit includes a choke coil and a reverse current blocking diode connected in series with the positive terminal of the full wave rectifier circuit, a connection terminal between the choke coil and the reverse current blocking diode, and a negative terminal (circuit ground) of the full wave rectifier circuit. And an output capacitor arranged between the output terminal (cathode terminal) of the backflow blocking diode and the negative terminal (circuit ground) of the full-wave rectifier circuit.

  In the step-up chopper circuit, energy is stored in the choke coil while the switching element is on, and the stored energy charges the output capacitor via the backflow prevention diode while the switching element is off. In the switching type power factor correction circuit, the switching element is on / off controlled so that a DC voltage exceeding the input voltage (rectified voltage) is stored in the output capacitor of the boost chopper circuit, and the input voltage (full-wave rectified) is used. The waveform of the ripple voltage) and the envelope waveform of the feedback current (current flowing through the switching element and input current of the boost chopper circuit) fed back from the boost chopper circuit to the negative terminal of the full-wave rectifier circuit are in phase In addition, the on / off ratio of the switching element is controlled so as to obtain a similar waveform. Accordingly, the switching type power factor correction circuit can perform AC / DC conversion with a high power factor.

  Further, a DC / DC converter that converts a DC voltage boosted and output by the power factor correction circuit into a predetermined voltage required by the load device is generally a DC / DC converter based on a switching method using a switching element and a transformer. However, there is a demand for a compact, lightweight, low loss product.

  However, a switching element in a DC / DC converter by this switching method is generally composed of a power semiconductor material using silicon (silicon: Si), and reduction of on-resistance and saturation voltage are technical limits. As a result, the efficiency of DC / DC converters has reached its peak.

  Therefore, in recent years, as a result of research on wide band gap semiconductors, GaN (gallium nitride) and SiC (silicon carbide: silicon carbide) that have low on-resistance, high breakdown voltage, large current, and high-speed switching were used. Switching elements (hereinafter simply abbreviated as “FET”) are beginning to be used. In general, it is known that the use of FETs using GaN or SiC can significantly improve conduction loss, increase the switching frequency, and provide a small and highly efficient DC / DC converter. ing.

  However, FETs made of GaN or SiC, which are currently in practical use, have a low gate voltage threshold in order to reduce the on-resistance, so that the gate voltage is not applied between the drain and source. Most elements are turned on when a voltage is applied.

  Therefore, conventionally, a positive power source and a negative power source are prepared to drive an FET made of GaN or SiC. When turning on, a positive voltage is applied to the gate, and when turning off An FET driving circuit that can apply a negative voltage to the gate is required.

  When a FET made of GaN or SiC, which may be turned on when no gate voltage is applied, is used as a switching element of a DC / DC converter, the primary of the transformer of the DC / DC converter Since there is a risk that the voltage input to the winding is always short-circuited, a protection element for preventing a short circuit, a power relay circuit, and the like are required. For example, a protection method disclosed in Patent Document 1 is considered. There was also the problem of having to.

  From the above, when using FETs made of GaN or SiC that have low on-resistance, high breakdown voltage, large current, and high-speed switching as the switching element of the DC / DC converter, the DC / DC converter is in a stopped state. In this case, a separate power source is required for always applying a negative voltage to the gate of the FET.

  That is, in the single forward DC / DC converter, since there is one FET, one set of two types of positive and negative power supplies is required. In a half-bridge type DC / DC converter used in a power supply circuit with a large output power, two FETs are used, so two sets of two types of positive and negative power supplies are required. In the full bridge type DC / DC converter, two sets are required as power sources for driving the two FETs connected to the higher voltage, and also for the two FETs connected to the lower voltage. Since at least one set of power supplies that can output both positive and negative voltages is required, a total of three or more sets of power supplies are required. For this reason, the power supply circuit is complicated, and it is difficult to reduce the size of the DC power supply device.

  To solve this problem, a method has been proposed in which a separate power supply is prepared so that a negative gate voltage can be applied only to the low-voltage side FET even when the power supply is stopped (for example, Patent Documents 2 and 3).

Japanese Patent No. 2696270 JP 2004-242475 A JP 2007-252048 A

  However, the power supplies having the configurations shown in Patent Documents 2 and 3 require a separate negative power supply that needs to be started before the input voltage is applied, and a separate power supply for operating the control system, and are thus downsized. It is difficult to plan. In addition, there is a problem that the drive circuit becomes complicated and the scale of the power supply circuit becomes large.

  In addition, when the voltage used in power supply systems for ships and aircraft is boosted using a power factor correction circuit, the output voltage becomes extremely high, such as DC600V to DC800V or more, so the FET is driven. There is also a problem that the power source needs to have a high withstand voltage and the entire circuit becomes large.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a safe direct-current power supply apparatus that can be reduced in price and reduced in size and free from a short-circuit accident.

  In order to solve the above-described problems and achieve the object, the present invention provides a full-wave rectifier circuit to which AC power is input from an AC power supply, and an output DC voltage of the full-wave rectifier circuit using a choke coil and a first switching circuit. A DC power supply device comprising: a chopper circuit that boosts or lowers voltage by an element; and a DC / DC converter that converts a DC power generated by the chopper circuit to a DC power having a predetermined voltage by a second switching element and a transformer. The second switching element is an FET configured using a wide band gap semiconductor material, and first and second bias voltages for applying positive and negative bias voltages to the gate terminal of the FET in the drive circuit of the FET. The choke coil has a transformer structure including a primary winding and a secondary winding having an intermediate tap. That a primary winding, characterized in that connected between the one end and the center tap of the first and second capacitors respectively through diodes the secondary winding.

  According to the present invention, a bias power source that applies positive and negative bias voltages to an FET configured using a wide band gap semiconductor material so as not to perform inadvertent operation is not a separate power source, but a chopper circuit. A primary winding in a transformer structure is used as a choke coil, and a positive and negative bias capacitor is connected to a secondary winding with an intermediate tap corresponding to an auxiliary winding added to the choke coil via a diode. This is realized by connecting the second capacitor and charging the positive and negative bias capacitors based on the current flowing in the primary winding, so that the price can be reduced and the size can be reduced, and there is no short circuit accident. There is an effect that a safe DC power supply device can be realized.

FIG. 1 is a block diagram showing a configuration of a DC power supply device according to Embodiment 1 of the present invention. FIG. 2 is a waveform diagram for explaining the charging operation to the positive bias capacitor and the negative bias capacitor shown in FIG. FIG. 3 is a block diagram showing a configuration of a DC power supply device according to Embodiment 2 of the present invention.

  Hereinafter, embodiments of a DC power supply device according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a configuration of a DC power supply device according to Embodiment 1 of the present invention. In the first embodiment, a wide bandgap semiconductor is used as a switching element in a DC / DC converter of a DC power supply device including a full-wave rectifier circuit, a boost chopper circuit, and a half-bridge switching DC / DC converter. A method of driving the FET when an FET made of a material (GaN or SiC) is used will be described.

  In FIG. 1, an AC power source 1 is a generator that is used as a primary power source in, for example, a commercial power source for home use or a power supply system for ships or aircraft. The voltage output from the generator used as the primary power source in the power system for ships or aircraft is a predetermined voltage within a range of AC 130 Vrms to AC 312 Vrms, for example.

  One end of the AC power supply 1 is connected to one input terminal of the diode bridge 3 constituting the full-wave rectifier circuit via the reactor 2 constituting the filter circuit, and the other end of the AC power supply 1 is connected via the power relay circuit 28. Are connected to the other input terminal of the diode bridge 3. In short, the AC power from the AC power supply 1 is input to the diode bridge 3 after removing or smoothing the superimposed noise component or pulsating current component.

  The output DC voltage (full-wave rectified pulsating voltage) of the diode bridge 3 is an input voltage of the step-up chopper circuit, and an input voltage detection provided between the positive terminal and the negative terminal (circuit ground) of the diode bridge 3. It is detected by the resistor 4 and sent to the PWM control circuit 25. The input voltage detection resistor 4 is a voltage dividing circuit using two resistors, and an input voltage detected from the voltage dividing output terminal is output.

  The step-up chopper circuit includes a primary winding N1 (corresponding to a choke coil) of a transformer 5, a first switching element (IGBT in the illustrated example) 6, a drive circuit 9, a backflow prevention diode 7, an output capacitor (electrolytic capacitor). ) 8. One end (winding start end in the illustrated example) of the primary winding N1 of the transformer 5 is connected to the positive end of the diode bridge 3, and the other end (winding end end in the illustrated example) of the primary winding N1 is a first switching element. One end (collector terminal in the illustrated example) of 6 and the anode terminal of the backflow prevention diode 7 are connected. The other end (emitter terminal in the illustrated example) of the first switching element 6 is connected to the negative end of the diode bridge 3 via the current detection resistor 10. The drive circuit 9 for the first switching element 6 is controlled by the PWM control circuit 25. The output capacitor 8 is connected between the cathode terminal of the backflow prevention diode 7 and the circuit ground to which the other end of the first switching element 6 is connected.

  The whole of the diode bridge 3 and the step-up chopper circuit is a power factor correction circuit. The current detection resistor 10 interposed in the circuit ground line connected to the negative electrode end of the diode bridge 3 uses the switching current flowing through the first switching element 6 which is a component of the power factor correction circuit as the input current of the boost chopper circuit. It is provided for detection. The input current of the boost chopper circuit detected by the current detection resistor 10 is sent to the PWM control circuit 25 and the abnormality detection circuit 29. The abnormality detection circuit 29 is controlled by the PWM control circuit 25.

  The output voltage detection resistor 11 connected in parallel with the output capacitor 8 detects the voltage between the terminals of the output capacitor 8 as the output voltage of the boost chopper circuit (that is, as the output voltage of the power factor correction circuit). The output voltage of the power factor correction circuit detected by the output voltage detection resistor 11 is sent to the PWM control circuit 25. The output voltage detection resistor 11 is a voltage dividing circuit using two resistors, and an output voltage detected from a voltage dividing output terminal is output.

  In the power factor correction circuit, the PWM control circuit 25 drives the first switching element 6 on / off through the drive circuit 9, whereby the boosting operation and the power factor correction operation are performed in parallel. First, the boosting operation is realized as follows.

  When the first switching element 6 is turned on, the input voltage is applied as it is to the primary winding N1 of the transformer 5, and a current proportional to the input voltage and the on-time of the first switching element 6 flows. Energy proportional to the square of the value is stored. When the first switching element 6 is turned off, the current that was flowing in the primary winding N1 immediately before due to the energy stored in the primary winding N1 in the primary winding N1 in the same direction after the turning off. As a result of continuing to flow as it is, charges are accumulated in the output capacitor 8 via the backflow blocking diode 7. When the first switching element 6 repeats the on / off operation, a predetermined output voltage boosted to the input voltage or higher is formed in the output capacitor 8.

  In the process, the power factor correction operation is performed as follows. That is, the PWM control circuit 25 supplies the effective value (envelope waveform) of the input current to the boost chopper circuit detected by the current detection resistor 10 to the boost chopper circuit detected by the input voltage detection resistor 4. The on / off ratio of the first switching element 6 is controlled through the drive circuit 9 so as to be in phase with and similar to the pulsating waveform of the input voltage, and the power factor operates as close as possible to the value 1.

  Next, a series circuit of capacitors 12 and 13 and a series circuit of second switching elements 14 and 15 are connected in parallel between both ends of the output voltage detection resistor 11. The connection end of the capacitors 12 and 13 is connected to one end (the winding start end in the illustrated example) of the primary winding of the transformer 16, and the connection end of the second switching elements 14 and 15 is the primary end of the transformer 16. The other end of the winding (in the illustrated example, the end of winding) is connected. The second switching elements 14 and 15 are driven by driving circuits 23 and 24, respectively. The drive circuits 23 and 24 have the same configuration. Details will be described later.

  Here, the series circuit of the capacitors 12 and 13, the series circuit of the second switching elements 14 and 15, the transformer 16, and the drive circuits 23 and 24 constitute a half-bridge switching DC / DC converter. doing. In this half-bridge switching DC / DC converter, when the second switching elements 14 and 15 are turned on / off in a reverse phase relationship, an alternating voltage is applied to the primary winding of the transformer 16, which is the transformer 16. Are converted to a DC voltage, and an output voltage 30 of the DC / DC converter is generated.

  The PWM control circuit 25 monitors the output voltage 30 of the DC / DC converter, and the output capacitor 8 notified from the output voltage detection resistor 11 so that the output voltage 30 becomes a predetermined voltage required by the load device. The on / off ratio of the second switching elements 14 and 15 is controlled in accordance with the output voltage formed by.

  Next, when operating the DC power supply device, the PWM control circuit 25 causes the abnormality detection circuit 29 to operate when the input voltage notified from the input voltage detection resistor 4 and the internal circuit of the DC power supply device are normal. The normal activation is notified and the power relay circuit 28 is turned on.

  At the time of abnormality, the following protection operation is performed. First, when the PWM control circuit 25 operates the DC power supply device, if the input voltage notified from the input voltage detection resistor 4 and the internal circuit of the DC power supply device are abnormal, the PWM control circuit 25 causes the abnormality detection circuit 29 to malfunction. The activation is notified and the power relay circuit 28 is turned off. Thus, for example, when the power factor correction circuit is stopped, the second switching elements 14 and 15 connected in series in the DC / DC converter are made of a wide band gap semiconductor material (GaN or SiC). Even if the arm short circuit state assumed when using the FET occurs, an excessive short circuit current continues to flow to protect the circuit from being damaged.

  In addition, the abnormality detection circuit 29 generates an abnormality when there is a notification from the current detection resistor 10 that the current flowing through the first switching element 6 has become zero, or a notification that current has flowed more than necessary. When the current is detected, the power relay circuit 28 is turned off to protect the entire circuit. Since the current detection resistor 10 notifies the PWM control circuit 25 in a balanced manner, reliable protection is performed.

  In the first embodiment, a power factor correction circuit that converts an input AC voltage into a DC voltage while performing full-wave rectification and boosting while improving the power factor and, for example, two second power supplies connected in series. DC / DC of a half bridge system in which the connection ends of the two switching elements 14 and 15 as well as the connection ends of the two capacitors 12 and 13 connected in series are connected to different ends of the primary winding of the transformer 16. In a DC power supply device composed of a converter, the second switching elements 14 and 15 in a half-bridge DC / DC converter are made of a wide band gap semiconductor material (GaN or SiC) that can be switched at a high frequency with little conduction loss. The purpose is to realize a small and highly efficient DC power supply device. Hereinafter, the second switching elements 14 and 15 are referred to as FETs 14 and 15, and the drive circuits 23 and 24 are referred to as FET drive circuits 23 and 24.

  In that case, the problem is that in order to drive the FETs 14 and 15 made of GaN or SiC, two types of positive and negative power supplies are required, and the FET 14 connected to the high voltage side is connected to the GND. Since it is used in a state floating from the potential, a power supply different from that of the FET 15 connected to the low voltage side is required, and a plurality of power supply circuits must be provided in the FET drive circuits 23 and 24. It was difficult to reduce the size.

  With respect to this problem, in the first embodiment, as shown in FIG. 1, instead of providing positive and negative power supply circuits in the FET drive circuits 23 and 24, positive bias capacitors 21a and 21b and negative bias capacitors are provided. Capacitors 22a and 22b are arranged. The primary of transformer 5 is configured by adding two auxiliary windings (secondary windings N2, N3 with intermediate taps) to the choke coil (primary winding N1) to the choke coil used in the boost chopper circuit. The winding N1 is used, and through the two secondary windings N2 and N3 and the diodes 26 and 27 based on the current flowing through the primary winding N1 as the first switching element 6 is turned on / off. The positive bias capacitors 21a and 21b and the negative bias capacitors 22a and 22b are charged, and the FETs 14 and 15 made of GaN or SiC are charged by the charging voltages of the positive bias capacitors 21a and 21b and the negative bias capacitors 22a and 22b. A positive or negative bias voltage can be applied to the gate terminal.

  This will be specifically described. As shown in FIG. 1, the FET drive circuit 23 that drives the high-voltage side FET 14 and the FET drive circuit 24 that drives the low-voltage side FET 15 have the same configuration, and are each connected in series with an NPN transistor 17a. 17b and PNP transistors 18a and 18b, current limiting resistors 19a and 19b, drive circuits 20a and 20b, and positive bias capacitors 21a and 21b and negative bias capacitors 22a and 22b connected in series. ing.

  The drive circuits 20a and 20b are controlled by the PWM control circuit 25. The commonly connected base terminals of the NPN transistor 17a and the PNP transistor 18a connected in series are connected to the output terminal of the drive circuit 20a, and the commonly connected emitter terminals are connected via the current limiting resistor 19a. Connected to the gate terminal of the FET 14. In addition, the commonly connected base terminals of the NPN transistor 17b and the PNP transistor 18b connected in series are connected to the output terminal of the drive circuit 20b, and the emitter terminals connected in common are connected to the current limiting resistor 19b. To the gate terminal of the FET 15.

  Both ends of the secondary winding N2 of the transformer 5 are connected to the power supply terminal of the drive circuit 20a in the FET drive circuit 23 through the diode 26, and a series circuit of an NPN transistor 17a and a PNP transistor 18a. Both ends are connected to both ends of a series circuit of a positive bias capacitor 21a and a negative bias capacitor 22a. The intermediate tap provided in the secondary winding N2 of the transformer 5 is connected to the connection terminal between the positive bias capacitor 21a and the negative bias capacitor 22a in the FET drive circuit 23 and the drain terminal of the FET 14. .

  Further, both ends of the secondary winding N3 of the transformer 5 are connected to the power supply terminal of the drive circuit 20b in the FET drive circuit 24 via the diode 26, and a series circuit of the NPN transistor 17b and the PNP transistor 18b. And both ends of a series circuit of a positive bias capacitor 21b and a negative bias capacitor 22b. The intermediate tap provided in the secondary winding N3 of the transformer 5 is connected to the connection end of the positive bias capacitor 21b and the negative bias capacitor 22b in the FET drive circuit 24 and the drain terminal of the FET 15. .

  In the above configuration, the FET drive circuits 23 and 24 perform the same operation. The FET drive circuit 23 drives and controls the high-voltage side FET 14 as follows. For example, when the drive signal output from the drive circuit 20a becomes a high level, the PNP transistor 18a is turned off and the NPN transistor 17a is turned on, and the voltage of the positive bias capacitor 21a passes through the current limiting resistor 19a to the gate of the FET 14. The FET 14 is turned on. When the drive signal output from the drive circuit 20a becomes low level, the NPN transistor 17a is turned off and the PNP transistor 18a is turned on at the same time, and the charge stored in the gate of the FET 14 through the current limiting resistor 19a is rapidly increased. The gate voltage of the FET 14 is lowered to the negative voltage stored in the negative bias capacitor 22a to turn off the FET 14 and maintain the off state. The FET drive circuit 24 performs the same operation for the FET 15 on the low voltage side.

  In the transformer 5, when the winding ratio of the primary winding N1 and the secondary windings N2 and N3 is Vin, and the voltage required to drive the FETs 14 and 15 is ± Vg, The configuration is such that Vin / 2Vg = N1 / N2 = N1 / N3.

  Here, when the first switching element 6 is turned on, electric charges are stored in the positive bias capacitor 21a and the negative bias capacitor 22a of the FET drive circuit 23 through the diode 26 by the voltage generated in the secondary winding N2. . The amount of charge stored in each is determined by the position of the intermediate tap. For example, if the position of the intermediate tap is just in the middle of the secondary winding N2, the potentials of the positive bias capacitor 21a and the negative bias capacitor 22a are charged to Vg, respectively. Similarly, when the first switching element 6 is turned on, the potentials of the positive bias capacitor 21b and the negative bias capacitor 22b of the FET drive circuit 24 via the diode 27 by the voltage generated in the other secondary winding N3. Are charged to Vg respectively.

  Next, with reference to FIGS. 1 and 2, the operation of the portion related to the first embodiment, that is, the operation of charging the positive and negative bias capacitors will be described. FIG. 2 is a waveform diagram for explaining the charging operation to the positive bias capacitor and the negative bias capacitor shown in FIG. 2A shows the waveforms of the input voltage 35 and the input current 36 whose power factor has been improved. In FIG. 2A, the charging current 37 and the charging voltage 38 for the positive bias capacitors 21a and 21b are shown. Each waveform is shown.

  In FIG. 2A, an input voltage 35 is a voltage that is input to the step-up chopper circuit from the diode bridge 3 that performs full-wave rectification of the AC voltage, and has a pulsating waveform. The PWM control circuit 25 controls the on / off ratio of the first switching element 6 so that the waveform of the input voltage 35 and the waveform of the current flowing through the first switching element 6 have the same and similar waveforms. Therefore, the input current 36 flowing through the primary winding N1 of the transformer 5 is a sawtooth current, but the envelope waveform is in-phase and similar to the waveform of the input voltage 35. Note that the maximum value of the input voltage 35 is 321 · √2 V in the illustrated example.

  At this time, voltages corresponding to the winding ratios N2 / N1 and N3 / N1 are generated in the secondary windings N2 and N3 of the transformer 5, but the positive bias capacitors 21a and 21b have a voltage higher than the stored voltage. Since the charging current flows only when a large voltage is generated, the sawtooth charging current 37 shown in FIG. 2 (a) flows, and the charging voltage 38 of the positive bias voltage Vg necessary for driving the FETs 14 and 15 is obtained. Is charged. The charging current and charging voltage for the negative bias capacitors 22a and 22b can be similarly shown. With the above operation, a bias voltage necessary to drive the FETs 14 and 15 made of GaN or SiC can be obtained without using positive and negative power supply circuits.

  As described above, according to the first embodiment, in a DC power supply device including a switching power factor correction circuit and a half-bridge switching DC / DC converter, 2 in the half-bridge DC / DC converter. In the case where a FET made of a wide band gap semiconductor material (GaN or SiC) is used for one switching element, a positive and negative bias capacitor is connected in series to the FET drive circuit, and A choke coil in a step-up chopper circuit constituting a rate improvement circuit is realized by a primary winding in a transformer structure including a primary winding and a secondary winding having an intermediate tap, for positive and negative biases connected in series. Connect the both ends of the capacitor and the corresponding ends of the secondary winding via diodes respectively. The connecting end of the connected positive and negative bias capacitors and the intermediate tap of the secondary winding are directly connected. In the step-up chopper circuit, the switching element is turned on / off and the boost operation is performed. By charging the positive and negative bias capacitors via the secondary winding and diode based on the current flowing through a certain primary winding, the FET made of GaN or SiC can be used for the positive and negative bias capacitors. It is possible to store and generate positive and negative bias voltages to be applied so as not to cause an inadvertent operation.

  In this way, a bias power supply that applies positive and negative bias voltages to prevent the FET made of GaN or SiC from being inadvertently operated is not a separate power supply, but a choke coil in the boost chopper circuit is a transformer structure. This is realized by charging positive and negative bias capacitors connected via a diode to a secondary winding with an intermediate tap corresponding to the auxiliary winding added to the choke coil. Therefore, it is possible to realize a safe direct-current power supply apparatus that can be reduced in price and reduced in size and free from a short circuit accident.

Embodiment 2. FIG.
FIG. 3 is a block diagram showing a configuration of a DC power supply device according to Embodiment 2 of the present invention. In the second embodiment, a wide band gap semiconductor material (as a switching element in a DC / DC converter of a DC power supply device including a full-wave rectifier circuit, a step-down chopper circuit, and a half-bridge switching DC / DC converter) A method of driving the FET when an FET made of GaN or SiC) is used will be described.

  That is, FIG. 3 shows a DC power supply device using a step-down chopper circuit in place of the switching type power factor correction circuit in the DC power supply device shown in FIG. 1 (Embodiment 1). Other configurations are the same as those in FIG. The PWM control circuit 25 is different only in that the power factor correction control operation described in FIG. 1 is not performed. When the FETs 14 and 15 made of GaN or SiC are used, the configuration for driving the FETs 14 and 15 is the same as that in FIG. 1, and here, the same reference numerals as those in FIG. Most of the components of the step-down chopper circuit overlap with those of the step-up chopper circuit, but in FIG. 3, the reference numerals are different.

  3, the step-down chopper circuit includes an input capacitor 40, a first switching element (IGBT in the illustrated example) 41, a drive circuit 42, a reverse current blocking diode 43, a primary winding N1 of a transformer 44, and an output capacitor. 45.

  One end of the input capacitor 40 and one signal terminal (collector terminal in the illustrated example) of the first switching element 41 are connected to the positive terminal of the diode bridge 3. The other end of the input capacitor 40, the anode terminal of the backflow prevention diode 43, and the negative end of the output capacitor (electrolytic capacitor) 45 are connected to the negative end (circuit ground) of the diode bridge 3. In the illustrated example, the current detection resistor 10 is provided in a connection line between the anode terminal of the backflow prevention diode 43 and the negative terminal of the output capacitor (electrolytic capacitor) 45.

  The other signal terminal (the emitter terminal in the illustrated example) of the first switching element 41 is connected to the cathode terminal of the reverse current blocking diode 43 and one end (the winding start end in the illustrated example) of the primary winding N1 of the transformer 44. ing. A positive terminal (+) of an output capacitor (electrolytic capacitor) 45 is connected to the other end of the primary winding N1 of the transformer 44 (winding end in the illustrated example).

  In the above configuration, the input capacitor 40 smoothes the DC voltage having a pulsating waveform output from the diode bridge 3 after full-wave rectification to generate the input voltage of the step-down chopper circuit. When the first switching element 41 is on, the current from the input capacitor 40 continues to flow into the output capacitor 45 through the primary winding N1 of the transformer 44, and current is supplied to the primary winding N1 of the transformer 44. Energy that continues to flow in the direction of the output capacitor 45 is accumulated. In this process, the output capacitor 45 is charged in the direction of boosting the input voltage generated by the input capacitor 40.

  After that, when the switching element 41 is turned off, the winding start of the primary winding N1 of the transformer 44 is performed by the energy accumulated in the primary winding N1 of the transformer 44 and continuing to flow the current from the winding start end to the winding end end. The reverse current blocking diode 43 having the cathode terminal connected to the end is turned on, negative charges are sent to the output capacitor 45, and the output capacitor 45 is charged in a direction to step down the input voltage generated by the input capacitor 40. The

  Eventually, in the PWM control circuit 25, the ratio of the ON time to the switching frequency of the first switching element 41 is such that a predetermined output voltage is generated by stepping down the input voltage generated by the input capacitor 40 in the output capacitor 45. In addition, the first switching element 41 is driven and controlled through the driving circuit 42 based on the charging voltage of the output capacitor 45.

  Here, the winding ratios “N1 / N2” and “N1 / N3” of the transformer 44 will be described. When the voltage across the input capacitor 40 is Vin, the voltage across the output capacitor 45 is Vo, and the voltage required to drive the FETs 14 and 15 is ± Vg, the winding ratios “N1 / N2” “N1 / N3” Is configured such that (Vin−Vo) / 2Vg = N1 / N2 = N1 / N3.

  The driving method of the FETs 14 and 15 made of GaN or SiC in the second embodiment is realized by the same principle as described in the first embodiment. That is, when the switching element 41 is turned on, the voltages generated in the secondary windings N2 and N3 through the primary winding N1 and the negative bias capacitors 21a and 21b of the FET drive circuits 23 and 24 via the diodes 26 and 27 are negative. Electric charges are stored in the bias capacitors 22a and 22b. The amount of charge stored in each is determined by the position of the intermediate tap provided in the secondary windings N2 and N3. For example, if the position of the intermediate tap is exactly in the middle of the secondary windings N2 and N3, the potentials of the positive bias capacitors 21a and 21b and the negative bias capacitors 22a and 22b are necessary to drive the FETs 14 and 15, respectively. The battery is charged so as to have a stable voltage Vg.

  As described above, according to the second embodiment, in the DC power supply device including the full-wave rectifier circuit, the step-down chopper circuit, and the half-bridge switching DC / DC converter, the two DC / DC converters When the switching element is configured to use an FET made of a wide bandgap semiconductor material (GaN or SiC), the FET made of GaN or SiC is inadvertently operated as in the first embodiment. A bias power supply for applying positive and negative bias voltages is not a separate power supply, but a transformer-structure primary winding is used for the choke coil of the step-down chopper circuit, and an auxiliary winding added to the choke coil is used. Charging positive and negative bias capacitors connected via a diode to a secondary winding with an intermediate tap equivalent to Having realized and, can be low cost and downsizing, it is possible to realize a safe direct-current power supply without short circuit.

  As described above, the DC power supply according to the present invention can be reduced in price and reduced in size, and is useful as a safe DC power supply without a short-circuit accident. Suitable for DC power supply used in the system.

1 AC power (commercial power or generator)
2 Reactor 3 Full-wave rectifier circuit (diode bridge)
4 Input voltage detection resistor 5,44 Transformer N1 Primary winding (choke coil)
N2, N3 Secondary winding (auxiliary winding)
6, 41 First switching element 7, 43 Backflow blocking diode 8, 45 Output capacitor 9, 42 Drive circuit 10 Current detection resistor 11 Output voltage detection resistor 12, 13 Capacitor 14, 15 Made of wide band gap semiconductor material FET (second switching element)
16 Transformer constituting DC / DC converter 17a, 17b NPN type transistor 18a, 18b PNP type transistor 19a, 19b Current limiting resistor 20a, 20b Drive circuit 21a, 21b Positive bias capacitor 22a, 22b Negative bias capacitor 23, 24 FET drive circuit 25 PWM control circuit 26, 27 Diode 28 Power relay circuit 29 Abnormality detection circuit 30 Output voltage of DC / DC converter 36 Input voltage 36 Input current 37 Charging current 38 Charging voltage 40 Input capacitor

Claims (3)

A full-wave rectifier circuit to which AC power is input from an AC power source, a chopper circuit that steps up or down the output DC voltage of the full-wave rectifier circuit by a choke coil and a first switching element, and a direct current generated by the chopper circuit In a DC power supply device including a DC / DC converter that converts a power supply to a DC power supply having a predetermined voltage by a second switching element and a transformer,
The second switching element is an FET configured using a wide band gap semiconductor material, and first and second bias voltages for applying positive and negative bias voltages to the gate terminal of the FET in the drive circuit of the FET. With two capacitors,
The choke coil is a primary winding in a transformer structure including a primary winding and a secondary winding having an intermediate tap, and the first and second capacitors are respectively connected to the secondary winding via a diode. A direct current power supply device connected between one end of the power supply and the intermediate tap.   When the chopper circuit is a step-up chopper circuit, the on / off ratio of the first switching element is determined by the envelope waveform of the input current flowing through the first switching element in the process of generating and outputting a predetermined boosted voltage. 2. The DC power supply device according to claim 1, wherein the DC power supply device is controlled so as to be in phase and similar to a waveform of an output DC voltage of the full-wave rectifier circuit that is an input voltage. The abnormality detection circuit which turns off the power relay circuit which turns on / off the electric power input from the said alternating current power supply when the abnormal current flows into the 1st switching element of the said chopper circuit is provided. Or the direct-current power supply device of 2.

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