JP3205881B2 - DC-DC converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC-DC converter, and more particularly to a DC-DC converter suitable for stepping up or stepping down a DC power supply by means of a resonance switch combining a switching element and a resonance circuit. About.

[0002]

2. Description of the Related Art Conventionally, as a resonance type switching power supply device, a boosting type as shown in FIG. 2 and a step-down type as shown in FIG. 3 are known. 2 and 3, 1 is a DC power supply, 2 is a reactor, 3 is a resonance reactor, 4 is a switching element, 5 is a resonance capacitor, 6 and 7 are diodes, 8 is a capacitor, Reference numeral 9 indicates a load.

In a boost type switching power supply,
Turning on the switching element 4, the resonant reactor 3, sinusoidal as shown in FIG. 4 current I
L flows. That is, the charge charged in the resonance capacitor 5 is discharged via the switching element 4, and the resonance capacitor 5 is charged in the opposite direction. Then, the charge of the resonance capacitor 5 charged in the reverse direction is discharged in the reverse direction via the diode 7. By turning off the switching element 4 when a current is flowing through the diode 7, zero current switching becomes possible.

[0004]

However, in the above-described conventional switching power supply, it is difficult to control the output voltage to be constant when the output voltage changes due to the fluctuation of the load 9. That is, the output voltage of the switching power supply device is determined by the time of the current flowing through the switching element 4, and the pulse width of the pulse signal for driving the switching element 4 is determined by the resonance width of the resonance It is determined by the resonance frequency of the circuit. Therefore, when the resonance frequency is fixed, the switching frequency must be variable in order to control the conduction ratio of the current flowing through the switching element 4 to control the output voltage. On the other hand, when the switching frequency is fixed, the resonance frequency must be changed by changing the value of the reactor 3 or the capacitor 5 constituting the resonance circuit, or a magnetic amplifier or an iron resonance circuit must be coupled to the output side. .

However, in the method in which the switching frequency is made variable, the switching period becomes twice the resonance frequency. Further, if the switching frequency is simply made variable, the zero-current switching operation becomes impossible and the switching loss may increase. Further, in the method of changing the resonance frequency, a control circuit for changing the resonance frequency may be complicated, and the loss of the saturable core constituting the magnetic amplifier or the iron resonance circuit may increase. Therefore, the resonance frequency and the switching frequency are fixed, and the auxiliary switching element and the auxiliary diode are connected in series with the resonance capacitor,
The output voltage can be controlled by controlling the resonance operation and controlling the conduction ratio of each switching element. But,
Even if the resonance operation is executed by controlling the conduction ratio of each switching element, the efficiency may decrease depending on the state of the load due to the resonance current.

An object of the present invention is to provide a DC-DC converter capable of executing a resonance operation and a non-resonance operation in accordance with the state of a load.

[0007]

In order to achieve the above object, the present invention provides a main reactor connected in series to a DC power supply.
And a parallel connection to the DC power supply via the main reactor.
Via the connected reactor for resonance and the main reactor
Connected to the DC power supply in parallel
And a resonance capacitor that forms a resonance circuit with the resonance capacitor.
Main switching element connected in series with the transfer reactor
And the main switch connected in parallel to the main switching element.
Pass only the current in the opposite direction to the current flowing through the switching element.
Main rectifier element, connected in series with the resonance capacitor
Auxiliary switching element, and the auxiliary switching element
Connected in parallel to the auxiliary switching element.
An auxiliary rectifier that passes only the current in the opposite direction to the
Rectifier circuit that rectifies the signal from the reactor and leads it to the load
And a voltage detection circuit for detecting an output voltage of the rectifier circuit
Between the detection voltage of the voltage detection circuit and the output voltage command value.
Calculate the deviation and generate a pulse signal to suppress this deviation to zero.
A duty ratio creation circuit to be generated, and generation of the duty ratio creation circuit
To start resonance operation according to the pulse signal by
Pulse signal and auxiliary pulse signal for restarting resonance operation
A switch timing circuit for generating
The main switch according to the main pulse signal generated by the
A main drive circuit for driving the switching element;
Current detection means for detecting a power supply current, and the current detection means
The resonance operation command is issued when the detected value of
The resonance operation command means to be output and the resonance operation command means
The switch on condition that the resonance operation command is received from the
According to the auxiliary pulse signal generated by the timing circuit
Driving the auxiliary switching element
An auxiliary driving circuit for stopping the driving of the auxiliary switching element
And a DC-DC converter having the following.

In configuring the DC-DC converter, the following elements can be added.

(1) The conduction ratio creation circuit is adapted to perform the voltage detection
Calculate the deviation between the detection voltage of the output circuit and the output voltage command value.
A pulse signal for suppressing the deviation to zero is generated .

(2) The switch timing circuit is
The main switching element is triggered by the main pulse signal.
The turn-off timing is determined according to the auxiliary pulse signal.
Set after the auxiliary switching element is turned on
It becomes.

(3) Parallel to both ends of the resonance reactor
A connected switching element for impedance change,
The resonance operation command is output from the resonance operation command means.
The switching element for impedance change when
Turn off and at other non-resonances
Turn on the switching element for changing the
A driver for short-circuiting both ends of the reactor .

[0012]

According to the above means, when the main switching element is turned on in response to the main pulse signal, the resonance operation is opened.
The charge stored in the resonance capacitor flows as a resonance current through the resonance reactor, the main switching element, and the auxiliary rectifying element, and the resonance capacitor is reversely charged when the main switching element is in an ON state. . At this time, the auxiliary switching element is in the OFF state, and the charge reversely charged in the resonance capacitor is prevented from being discharged by the auxiliary rectifying element. Therefore, when the discharge of the electric charge stored in the resonance capacitor is completed, the resonance operation is interrupted. Thereby, the DC power supply is short-circuited via the main reactor, the resonance reactor and the main switching element, and the main reactor stores electromagnetic energy.

Next, if the resonance operation command is output on condition that the power supply current of the DC power supply is within the range of the set value, an auxiliary pulse signal is output and the auxiliary switching signal is output before the main switching element is turned off. The device turns on. When the auxiliary switching element is turned on, both ends of the reversely charged resonance capacitor are connected to the main switching element via the resonance reactor, and the resonance operation is restarted. As a result, the reversely charged charge of the resonance capacitor is discharged through the auxiliary switching element, the main rectifier, and the resonance reactor, and the current flowing through the main switching element is reduced. Then, when the current flowing through the main switching element becomes substantially zero, the main switching element is turned off. After the main switching element is turned off, the recharging of the resonance capacitor is completed. However, the discharge of the electric charge stored in the resonance capacitor is stopped by the main switching element and the main rectifier, and the resonance operation stops. Thereby, the electromagnetic energy stored in the main reactor is supplied to the load via the rectifier circuit and the smoothing circuit. At this time, the output voltage of the resonance capacitor is clamped to the output voltage of the smoothing circuit. Thereafter, when the main switching element is turned on, the same resonance operation as described above is performed, and the resonance capacitor is reversely charged. The output voltage can be controlled by repeating such a resonance operation. At this time, if the conduction ratio of the main switching element is controlled according to the state of the load, the output voltage can be controlled according to the conduction ratio of the main switching element.

Further, since the auxiliary pulse signal is output only when the power supply current is within the range of the set value, the resonance operation and the non-resonance operation can be switched according to the state of the load. That is, when the power supply current is out of the range of the set value, if the auxiliary switching element is always turned off without generating the auxiliary pulse signal, the output voltage is controlled only by the operation of the main switching element to function as a non-resonant switch. Become. Furthermore, when the characteristic impedance of the resonance circuit is changed according to the magnitude of the power supply current, that is, when the reactor and the capacitor of the resonance circuit are changed, the zero current switching operation can always be performed, and under the optimum condition where the switching loss is minimized. The switching element can be operated.

Here, when performing the resonance operation using the main switching element and the auxiliary switching element, the condition for enabling the zero current switching operation is that the voltage of the resonance capacitor is Vc and the main switching element is ON. Assuming that the maximum peak current flowing is Ip and the characteristic impedance of the resonance circuit is Zn, these relationships are expressed by the following equations.

[0016]

From the above equation, the energy that must be stored when the resonance capacitor is reversely charged is the electromagnetic energy stored in the resonance reactor by the maximum peak current Ip. We need enough energy to cancel out. Therefore, it is necessary to select the constant of the resonance circuit so as to satisfy the above equation. However, if more energy than the energy sufficient to cancel the electromagnetic energy stored in the resonance reactor is stored in the resonance capacitor, the switching loss increases by the excess energy. In other words, if both sides of the above equation are always kept equal, the switching loss is minimized. Therefore, by changing the characteristic impedance of the resonance circuit according to the magnitude of the power supply current, a highly efficient resonance switching operation can be performed.

The point at which the resonance operation and the non-resonance operation are switched is that the switching loss of the main switching element in the non-resonance operation is compared with the total switching loss of the main switching element and the auxiliary rectifier element in the resonance operation. What is necessary is just to set so that the switching loss of the main switching element in the resonance operation exceeds the total switching loss of the main switching element and the auxiliary rectifier element in the resonance operation. If the resonance operation and the non-resonance operation are switched according to such a setting, DC / DC conversion can always be performed with high efficiency.

[0018]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a resonance type switching power supply in which the present invention is applied to a boosting power supply. In FIG. 1, a main reactor 12 is connected in series to a DC power supply 10, and the main reactor 12 includes a resonance reactor 14, a resonance capacitor 16, and a diode 18.
Is connected. A transistor 20 is connected in series to the resonance reactor 14, and a transistor 22 is connected in series to the resonance capacitor 16. The resonance reactor 14 and the transistor 20 are connected in parallel to the DC power supply 10 via the main reactor 12 and the resistor 24, and the resonance capacitor 16 and the transistor 22 are connected to the main reactor 12
And a resistor 24 connected in parallel to the DC power supply 10. A reverse current element diode 26 is connected in parallel to the transistor 20 forming the main switching element, and a reverse current element diode 28 is connected in parallel to the transistor 22 forming the auxiliary switching element. The resonance reactor 14 and the resonance capacitor 16 are connected in parallel via transistors 20 and 22 to form a resonance circuit. The constants of the resonance reactor 14 and the resonance capacitor 16 are determined so as to satisfy the equation (1) and the specified resonance frequency.

On the other hand, the diode 18 forms a rectifier circuit, and the cathode side of the diode 18 is connected to the capacitor 30 and the load 32. The capacitor 30 forms a smoothing circuit, and a voltage detection circuit 34 is provided at both ends of the capacitor 30. This voltage detection circuit 34 is connected to a conduction ratio creation circuit 36. The current ratio creating circuit 36 is connected to the bases of the transistors 20 and 22 via a switch timing circuit 38 and drivers 40 and 42. A current detection circuit 44 is provided at both ends of the resistor 24, and an output of the current detection circuit 44 is connected to a resonance switching circuit 46. Then, a resonance stop signal is input from the resonance switching circuit 46 to the driver 42.

The current ratio creating circuit 36 includes a voltage control circuit 362, a triangular wave oscillation circuit 364, a comparator 3
66. The voltage control circuit 362 obtains a deviation between the output voltage command value ED and the detection voltage ed of the voltage detection circuit 34, and constitutes a deviation signal generation circuit that outputs a signal for suppressing the deviation to zero to the comparator 366. Has become. The comparator 366 receives a triangular wave signal as a reference signal from the triangular wave oscillation circuit 364, compares the deviation signal from the voltage control circuit 362 with the triangular wave signal, and generates a pulse signal according to the comparison result. ing. This pulse signal is input to the switch timing circuit 38, and the pulse signal is converted into a main pulse signal and an auxiliary pulse signal by the switch timing circuit 38. That is, the comparator 366 and the switch timing circuit 38 constitute a main pulse signal generation circuit and an auxiliary pulse signal generation circuit.

As shown in FIG. 5, the switch timing circuit 38 includes a NAND circuit 382, a delay circuit 384 composed of R and C, and a buffer circuit 386. The switch timing circuit 38 includes a comparator 3
When a pulse signal as shown in FIG. 6A is inputted from 66, this pulse signal is branched, and one pulse signal is inputted as it is to the NAND circuit 382 and the other pulse signal is inputted to the delay circuit 384. Through the NAND circuit 38
2 is input to the buffer circuit 386. As a result, a main pulse signal delayed by a predetermined time Δt is output from the output terminal OUT1, and an auxiliary pulse signal as shown in FIG. 6D is output from the output terminal OUT2. The auxiliary pulse signal is turned off when the main pulse signal rises, and rises earlier by a time Δt than when the main pulse signal falls. This Δt is set to １ ／ of the resonance cycle. The main pulse signal is input to the driver 40, and the auxiliary pulse signal is input to the driver 42. The driver 40 is configured as a main drive circuit that drives the transistor 20 according to a main pulse signal. The driver 42 forms an auxiliary driving circuit that drives the transistor 22 in accordance with the auxiliary pulse signal, provided that the resonance stop signal is not input from the resonance switching circuit 46.

On the other hand, as shown in FIG. 7, the resonance switching circuit 46 includes a filter circuit 462 and a reference value setting circuit 4.
64, a comparison circuit 466, and a stop signal generation circuit 468. The filter circuit 462 receives the power supply current detected by the current detection circuit 44 and outputs an average value thereof. The reference value setting circuit 464 outputs a signal indicating the average value of the power supply current for switching between the resonance operation and the non-resonance operation.

Here, when setting the reference value of the reference value setting circuit 464, the reference value is set according to the efficiency characteristics shown in FIG. The efficiency characteristics shown in FIG. 8 were obtained when the device shown in FIG. 1 was operated in resonance and non-resonance. In FIG. 8, the solid line indicates the characteristics when the device is operated in resonance, and the dotted line indicates the characteristics when the device is operated in non-resonance. When the device is operated in resonance, a loss accompanying the resonance operation is generated, so that the efficiency of the device is reduced at a low current value, in other words, at a low load. On the other hand, when the device is not operated in resonance, the switching loss increases rapidly as the power supply current increases and the current flowing through the switching element increases. For this reason, the efficiency of the device decreases at a large current value, in other words, at a high load. Therefore, if the non-resonant operation is performed at a low current value and the resonant operation is performed at a large current value, the device can always be operated in an efficient state. For this reason, in this embodiment, when the power supply current is about 10 A, the resonance switching point is set.

The comparison circuit 466 compares the output signal from the filter circuit 462 with the output signal from the reference value setting circuit 464, and outputs the comparison result to the stop signal generation circuit 468. The stop signal generating circuit 468 outputs a resonance stop signal assuming that the power supply current is out of the set value only when the average value of the power supply current is lower than the reference value, and outputs a resonance stop signal when the power supply current is within the set value range. The output of the stop signal is stopped. When the output of the resonance stop signal is stopped, a resonance operation command has been output from the resonance switching circuit 46 to the driver 42. That is, the resonance switching circuit 46 is configured as resonance operation command means.

Next, the operation of the apparatus shown in FIG. 1 will be described with reference to a time chart shown in FIG.

First, based on the output voltage command value ED and the detection voltage ed of the voltage detection circuit 34, a main pulse signal as shown in FIG. 9A and an auxiliary pulse signal as shown in FIG. When generated, at time t1, transistor 2
0 turns on and transistor 22 turns off. As a result, the DC power supply 10 is applied to the main reactor 12 and the resonance reactor 14, and the voltage of the resonance capacitor 16 is applied to the resonance reactor 14. Then, the charge charged in the resonance capacitor 16 is discharged via the resonance reactor 14, the transistor 20, and the diode 28, and a resonance current flows through the transistor 20. Then, the resonance capacitor 16 is reversely charged by the resonance current. At this time, the level of the voltage charged in the capacitor 16 is the same level as the DC voltage ed, and the current from the DC power supply 10 flows until the voltage value of the capacitor 16 becomes lower than the voltage value of the DC power supply 10. Does not flow to Before timing t1, power is supplied to the load 32 via the main reactor 12 and the diode 18, and no current flows through the reactor 14 and the transistor 20.
Is turned on, the transistor 20 can be turned on with zero current.

When the reverse charging of the capacitor 16 is completed by the discharging of the capacitor 16, the discharging of the charge reversely charged in the capacitor 16 starts to be started. However, the discharging of the charge is blocked by the diode 28 and the resonance operation is performed at the timing t2. Interrupted. At this time, the capacitor 16 is disconnected from the circuit while being reversely charged, and the resonance operation is interrupted.

Next, at timing t3, the transistor 22
Is turned on, both ends of the capacitor 16 are connected via the transistor 22, and the charge reversely charged in the capacitor 16 is discharged via the transistor 22, the diode 26 , and the reactor 14. As a result, a resonance current flows in the resonance circuit in a direction opposite to the previous direction, and the resonance operation is restarted. At this time, the main reactor 12
A current flows through the reactor 14 and the transistor 20, and electromagnetic energy is stored in the main reactor 12.
Thereafter, when the resonance current flows through the diode 26 , the transistor 20 is turned off at the timing t4, but the resonance current continues to flow through the diode 26 and the recharging of the capacitor 16 is continued. When the charging of the capacitor 16 is completed at the timing t5 by the resonance current, the charge recharged to the capacitor 16 starts to discharge again. However, the discharge of the charge is stopped by the diode 26, and the resonance operation stops. At this time, the energy stored in the main reactor 12 acts as a back electromotive force, and this back electromotive force is applied to the transistors 20 and 22 and the diode 18.
Is in the off state, the energy by the back electromotive force of the main reactor 12 is given to the diode 18, and this energy is rectified and supplied to the load 32.

As described above, the output voltage can be controlled by turning on / off the transistors 20 and 22 using the main pulse signal and the auxiliary pulse signal. At this time, from the timing t3 to the timing t5, the transistor 20 is turned off when the value of the current is zero, so that switching can be performed without switching loss.

Also, when the transistor 22 is turned off at the timing t1, the resonance operation is stopped, and the current flows through the diode 28 but does not flow through the transistor 22, so that there is no switching loss. Can be switched.

In the above-described embodiment, the timing for turning on the transistor 20 and the timing for turning off the transistor 22 have been described as the timing for generating the auxiliary pulse signal. However, the timing for turning off the transistor 22 is based on the capacitor 16. Any time between the completion of the recharging and the completion of the reverse charging, the suspension of the resonance operation and the restart of the resonance operation can be executed at any timing.

As described above, according to this embodiment, the output voltage is controlled by adjusting the conduction ratio of the main pulse signal according to the value of the detection voltage ed. However, the output voltage can be kept constant. In addition, since the resonance operation and the non-resonance operation are performed according to the value of the power supply current, efficient operation can be performed according to the state of the load.

Next, a second embodiment of the present invention will be described with reference to FIG.

In this embodiment, a resonance type switching power supply is applied to a power factor improving power supply, and a main reactor 12 is connected to an output side of a rectifier circuit 200 for rectifying an AC power supply line. Further, a transistor 50 as an impedance changing switching element is connected in parallel to both ends of the resonance reactor 14, and a driver 52 as an impedance changing drive circuit for driving the transistor 50 is provided. The voltage control circuit 36
2 is configured as an amplification factor generation unit, and a multiplier 368 is provided as a multiplication unit. Other configurations are the same as those in FIG.

The voltage control circuit 362 outputs a signal relating to an amplification factor for suppressing the deviation between the output voltage command ED and the detection voltage ed of the voltage detection circuit 34 to zero. The multiplier 368 multiplies the detection current of the current detection circuit 44 by the amplification coefficient from the voltage control circuit 362, and outputs a pulse signal corresponding to the multiplied value to the comparator 366. The comparator 366 is a multiplier 368
Is compared with the triangular wave signal from the triangular wave oscillation circuit 364, and a pulse signal corresponding to the comparison result is output to the switch timing circuit 38. The switch timing circuit 38 includes a comparator 366.
A main pulse signal and an auxiliary pulse signal are generated according to the pulse signals from the first and second transistors, and the respective pulse signals are output to the transistors 20 and 22 via the drivers 40 and 42. Each of the transistors 20 and 22 has its resonance operation and non-resonance operation controlled in accordance with the main pulse signal and the auxiliary pulse signal as in the above-described embodiment.

On the other hand, a resonance stop signal from the resonance switching circuit 46 is input to the driver 52. Driver 5
2 is a transistor 5 while the resonance stop signal is being input.
0, an on-pulse signal is output to both ends of the resonant reactor 14 when the power supply is in a non-resonant state.
0 is short-circuited. Therefore, when the device is switched from the resonance operation to the non-resonance operation, it is possible to prevent the output voltage from overshooting due to the inductance component of the resonance reactor 14.

Also in the case where the present invention is applied to a power factor improving power supply device, the efficiency of the device can be improved by performing a non-resonant operation at a low current and performing a resonant operation at a large current as in the above embodiment. As a result, a low-loss power factor improving power supply device is possible.

Next, a third embodiment of the present invention will be described with reference to FIG.

In this embodiment, the impedance of the resonance circuit is changed in accordance with the power supply current, and the other configurations are the same as those in FIG. 1. Therefore, the same components as those in FIG. The description thereof is omitted here.

More specifically, with the resonance frequency of the resonance circuit kept constant, only the characteristic impedance is set to three types: large current, medium current, and small current. Further, three types of resonance reactors 142, 144, 146 and three types of resonance capacitors 162, 164, 166 are provided. A bidirectional switch circuit 53 is connected between each of the reactors 142, 144, 146 and the transistor 20.
2, 534, 536 are inserted, and each resonance capacitor 162, 164, 166 and the transistor 22 are connected.
Bidirectional switch circuits 538, 540, 54
2 has been inserted. Each of the switch circuits 532 to 542 can be switched by a signal from the switching circuit 500. The switching circuit 500 is configured as selection command means for selecting a specified resonance reactor and a specified resonance capacitor according to the detection current of the current detection circuit 44. In the present embodiment, the reactor 142 at the time of a large current
And the capacitor 162 are selected, the reactor 144 and the capacitor 164 are selected at the time of a medium current, and the reactor 146 and the capacitor 166 are selected at the time of a small current. Only the selected reactor and the capacitor constitute a resonance circuit. In addition, each reactor 142, 14
4, 146, a transistor 600 is connected in parallel as an impedance change drive circuit. This transistor 600 is turned on in response to a resonance stop signal from the resonance switching circuit 46, short-circuits both ends of each of the reactors 142 to 146 at the time of non-resonance, and outputs the output voltage when the device switches from the resonance operation to the non-resonance operation. Overshoot is prevented from occurring.

In the above configuration, a main pulse signal and an auxiliary pulse signal as shown in FIG. 12 are generated in accordance with the output voltage command ED and the detection voltage ed of the voltage detection circuit 34, and the resonance operation by the transistor 20 and the transistor 22 is disabled. When the resonance operation is performed, the power supply current is detected by the current detection circuit 44. At this time, when the power supply current is large, the reactor 142 and the capacitor 162 are selected, and the characteristic impedance of the resonance circuit is reduced.
Thereby, the peak value of the resonance current can be increased. The reactor 144 and the capacitor 1
64 is selected to maintain the characteristic impedance of the resonant circuit at a moderate level. On the other hand, when the power supply current is small, the reactor 146 and the capacitor 166 are selected, and the characteristic impedance of the resonance circuit increases. Thus, the peak value of the resonance current is suppressed to a small value, and the loss due to the resonance current can be suppressed to a minimum.

In this embodiment, as in the above embodiments, the efficiency can be improved by executing a non-resonant operation at a low current and executing a resonant operation at a large current.

Further, in this embodiment, since the characteristic impedance of the resonance circuit is changed depending on the magnitude of the power supply current, no extra resonance current flows through the resonance circuit. Efficiency can be improved.

Further, in each of the above embodiments, the step-up type power supply device has been described. However, each of the above embodiments can be applied to a step-down type power supply device.

[0046]

As described above, according to the present invention,
Since the output voltage is controlled by controlling the conduction ratio of the current flowing through the switching element in accordance with the state of the load, the output voltage can be kept constant even when the load fluctuates, and the switching frequency can be kept high. Becomes possible,
This can contribute to downsizing of the device. Further, since the resonance operation and the non-resonance operation are performed in accordance with the state of the load, it is possible to contribute to an improvement in efficiency.

[0047]

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a resonant switching power supply device according to a first embodiment of the present invention.

FIG. 2 is a basic configuration diagram of a step-up power supply device.

FIG. 3 is a basic configuration diagram of a step-down power supply device.

FIG. 4 is a waveform chart for explaining the operation of the device shown in FIG. 2;

FIG. 5 is a specific configuration diagram of a switch timing circuit.

FIG. 6 is a waveform chart for explaining the operation of the switch timing circuit.

FIG. 7 is a specific configuration diagram of a resonance switching circuit.

FIG. 8 is a characteristic diagram showing a relationship between power supply current and efficiency.

FIG. 9 is a waveform chart for explaining the operation of the device shown in FIG. 1;

FIG. 10 is an overall configuration diagram of a power factor improving power supply device according to a second embodiment of the present invention.

FIG. 11 is an overall configuration diagram of a resonant switching power supply device according to a third embodiment of the present invention.

FIG. 12 is a waveform chart for explaining the operation of the device shown in FIG. 11;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 DC power supply 12 Main reactor 14 Resonance reactor 16 Resonance capacitor 18 Diode 20, 22 Transistor 26, 28 Diode 30 Capacitor 32 Load 34 Voltage detection circuit 36 Current ratio creation circuit 38 Switch timing circuit 40, 42 driver 44 Current detection circuit 46 Resonance switching circuit

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Tsunehiro Endo 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. Hitachi Research Laboratory (56) References JP-A-60-2026 (JP, A) JP-A-4 −372572 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H02M 3/155

Claims (4)

(57) [Claims] A main reactor connected in series to a DC power supply, a resonance reactor connected in parallel to the DC power supply through the main reactor, and a resonance reactor connected in parallel to the DC power supply through the main reactor. A resonance capacitor that forms a resonance circuit together with the resonance reactor, a main switching element connected in series with the resonance reactor, and a current flowing in the main switching element in parallel with the main switching element and having a reverse direction. A main rectifier that passes only current, an auxiliary switching element that is connected in series with the resonance capacitor, and an auxiliary rectifier that is connected in parallel with the auxiliary switching element and passes only a current in a direction opposite to a current flowing through the auxiliary switching element. An element, a rectifier circuit for rectifying a signal from the main reactor and guiding it to a load, and an output of the rectifier circuit A voltage detection circuit for detecting a voltage, a duty ratio creation circuit for determining a deviation between a detection voltage of the voltage detection circuit and an output voltage command value, and generating a pulse signal for suppressing the deviation to zero; A switch timing circuit for generating a main pulse signal for starting a resonance operation in accordance with a pulse signal generated by the rate creation circuit and an auxiliary pulse signal for restarting the resonance operation; and a main pulse signal for generating a main pulse signal generated by the switch timing circuit. A main drive circuit for driving a switching element, current detection means for detecting a power supply current of the DC power supply, and a resonance operation command for outputting a resonance operation command when a detection value of the current detection means is within a set value range Means, and an auxiliary pulse signal generated by the switch timing circuit on condition that the resonance operation command is received from the resonance operation command means. Thus the DC when the auxiliary switching element drive the other and an auxiliary drive circuit for stopping the drive of the auxiliary switching element - DC converter. 2. The DC-DC converter according to claim 1, wherein the duty ratio generating circuit obtains a deviation between a detection voltage of the voltage detection circuit and an output voltage command value, and suppresses the deviation to zero. DC-DC converter characterized by generating a pulse signal for use. 3. The DC-DC converter according to claim 1, wherein the switch timing circuit sets a timing at which the main switching element is turned off by the main pulse signal in accordance with the auxiliary pulse signal. A DC-DC converter, which is set after the device is turned on. 4. One of claims 1, 2 and 3
In the DC-DC converter according to the item, the impedance changing switching element connected in parallel to both ends of the resonance reactor, and the impedance change switching when the resonance operation command is output from the resonance operation command means A DC-DC converter comprising: a driver for turning off the element and turning on the switching element for impedance change during other non-resonances to short-circuit both ends of the reactor for resonance.