JPH04281369A - Power supply - Google Patents

Abstract

PURPOSE:To realize step-up/step-down operation through a PWM inverter having simple structure by providing means for inverting the output of a DC power supply which also serves as a step-up/step-down means. CONSTITUTION:A transistor 2 is turned ON/OFF at high frequency while transistors 4, 5 are turned ON/OFF at low frequency. If the transistor 2 is turned ON when the transistor 4 is turned ON, energy is stored in a choke coil 3 by the output from a DC power supply 1 and when the transistor 2 is turned OFF, energy stored in the choke coil 3 is discharged through a parallel circuit of a discharge lamp 7 and a capacitor 6. If the transistor 2 is turned ON/OFF when the transistor 5 is turned ON, current flows in reverse direction. Consequently, a low frequency current having rectangular waveform containing a little high frequency ripple can be fed to the discharge lamp 7.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for converting direct current to alternating current, and more particularly to a power supply device for controlling the lighting of a discharge lamp such as a metal halide lamp as a load.

0002

2. Description of the Related Art A conventional power supply device generally has a configuration as shown in "Illumination Institute of Japan Journal, Vol. 72, No. 2, Page 19 (1988)." The configuration is shown below in Figure 8 and Figure 1.
This will be explained with reference to 0.

In FIG. 10, 31 is a DC power supply, 32,
33, 34, 35 are transistors which are switching elements;
36, 37, 38, 39 are diodes, 40 is a choke coil, 41 is a capacitor, transistors 32,
33, 34, 35 and diodes 36, 37, 38, 39
The choke coil 40 and the capacitor 41 constitute an inverter circuit. 42 is a discharge lamp which is a load of the inverter circuit.

[0004] The operation of the conventional device described above will be explained. Here, transistors 32, 33, 3 in FIG.
The on/off control signals inputted between the base emitters 5 and 34 correspond to D1, E1, F1, and G1 in FIG. 8, respectively. These on/off control signals turn transistor 35 or 34 on and off at a low frequency, and at the same time turn transistor 32 or 33 on and off at a high frequency. Such a control method is called PWM control (pulse width modulation control).

First, when the transistor 32 is turned on while the transistor 35 is on, a direct current is supplied from the positive terminal of the DC power supply 31 through the parallel circuit of the transistor 32, the choke coil 40, the discharge lamp 42, and the capacitor 41, and the transistor 35. A current flows through the path leading to the negative terminal of the power source 31. Furthermore, when the transistor 35 is on and the transistor 32 is off, the energy stored in the choke coil 40 is transferred from the choke coil 40 to the choke coil 40 via the parallel circuit of the discharge lamp 42 and the capacitor 41, the transistor 35, and the diode 38. It operates as a so-called step-down chopper circuit in which current flows in the return path. Therefore, each current becomes a direct current with a high frequency superimposed thereon. Most of the high frequency components of each current flow through the capacitor 41 connected in parallel to the discharge lamp 42, and the DC component and a small amount of high frequency component flow through the discharge lamp 42.

Next, when the transistor 33 is turned on while the transistor 34 is on, a signal is generated from the positive terminal of the DC power supply 31 through the parallel circuit of the transistor 33, the discharge lamp 42, and the capacitor 41, the choke coil 40, and the transistor 34. A current flows through a path leading to the negative terminal of the DC power supply 31. Furthermore, when the transistor 34 is on and the transistor 33 is off, the energy stored in the choke coil 40 causes the transistor 34, the diode 39, and the discharge lamp 42 to be
A current flows in a path returning to the choke coil 40 via the parallel circuit of the capacitor 41 and the capacitor 41 . Therefore, each current becomes a direct current with a high frequency superimposed thereon. The high frequency component of each current is connected to a capacitor 41 connected in parallel to the discharge lamp 42.
Most of the current flows into the discharge lamp 42, and a direct current component and a small amount of high frequency component flow into the discharge lamp 42. However, the current direction in this case is opposite to that when the transistor 35 is in the on state.

As described above, the lamp current flowing through the discharge lamp 42 becomes a low-frequency rectangular wave slightly containing high-frequency ripples.

In this way, the on/off of the switching element is controlled by P.
PW refers to the conversion circuit from DC to AC that is controlled by WM.
It is called M inverter.

[0009]

SUMMARY OF THE INVENTION Such a conventional power supply device is a step-down PWM inverter, and can only supply an effective value of AC output voltage to the load, which is lower than the output voltage of the DC power supply. Therefore, when the load requires an effective value of AC voltage higher than the output voltage of the DC power supply, a separate voltage boosting means is required between the DC power supply and the load. Therefore, there were problems in that the circuit configuration and control means became complicated, the number of parts increased, and the power supply device became larger. Furthermore, there is a problem in that the addition of the boosting means causes loss in the boosting means.

0010

[Means for Solving the Problems] The present invention is a PWM inverter type power supply device, which stores energy from a DC power source in an inductance element at a high frequency, and transfers the energy to a voltage higher than the voltage of the DC power source. This paper proposes a specific configuration of a power source that extracts low-frequency AC power with an effective voltage value and supplies it to a load such as a discharge lamp.

In order to solve the above problems, the power supply device of the present invention has a first loop that supplies energy from a DC power supply to an inductance element having an intermediate terminal at a high frequency by turning on and off a first switching element. The intermediate terminal of the inductance element is connected to one end of a parallel circuit of a load and a capacitor, and a second reverse blocking type which is turned on and off at a low frequency is connected between the other end of the parallel circuit and one end of the inductance element. A third switch element of a reverse blocking type that turns on and off at a low frequency with a phase opposite to that of the second switch element is provided between the other end of the parallel circuit and the other end of the inductance element. It has second and third loops that are connected and emit the energy of the inductance element.

Further, in the power supply device of the present invention, by turning on and off the first switching element, a DC power source is supplied at a high frequency through a series circuit of a reverse conduction type second switching element and the first rectifying element. a first loop supplying energy to an inductance element having an intermediate terminal; and a third loop of reverse conducting type.
a second loop for supplying energy to an inductance element having an intermediate terminal through a series circuit of a switch element and a second rectifier element, and a low A second and third switching element that is alternately turned on and off depending on the frequency is interposed, and when the second switching element is on, the inductance element, the second switching element, the parallel circuit, and the third
and a reverse conduction portion of the switch element, and a third loop that releases the energy of the inductance element.
A fourth loop comprising the inductance element, the third switch element, the parallel circuit, and a reverse conduction portion of the second switch element and releases the energy of the inductance element when the switch element is on. It is.

Further, the power supply device of the present invention has first and second switching elements that are alternately turned on and off at a low frequency between both ends of the parallel circuit of the load and the capacitor and both ends of the inductance element having an intermediate terminal. interposed, and when the first switch element is on, the inductance element, the first switch element, the parallel circuit, and the reverse conduction part of the second switch element are configured to dissipate the energy accumulated in the inductance element. When the second switch element is on, a first loop that emits light is formed by the inductance element, the second switch element, the parallel circuit, and a reverse conduction portion of the first switch element, and the discharge is accumulated in the inductance element. has a second loop that releases the energy that has been
a third loop that supplies energy from the DC power supply to the inductance element at a high frequency through a third switch element that turns on and off at a high frequency during the on-period of the first switch; It has a fourth loop that supplies energy from the DC power source to the inductance element at a high frequency via a fourth switching element that is turned on and off according to the frequency.

[0014]

[Operation] With the above-described configuration, the effective value of the voltage supplied to the load can be made higher or lower than the voltage of the DC power supply. In other words, the PWM inverter type power supply device itself can step up and down the voltage.

Furthermore, by connecting two reverse-blocking switch elements connected in series, which alternately turn on and off at low frequencies, to both ends of the inductance element having an intermediate terminal, short-circuiting of the DC power supply is prevented, and the inductance The energy of the element can be supplied to the load.

Furthermore, by connecting two reverse conduction type switching elements that alternately turn on and off at a low frequency between both ends of the parallel circuit of the load and capacitor and both ends of the inductance element having an intermediate terminal, The energy of the inductance element can be supplied to the load by utilizing the reverse conduction portion of the switch element.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a circuit diagram of a power supply device according to a first embodiment. In FIG. 1, 1 is a DC power supply, 2, 4, and 5 are transistors that are switching elements, 3 is a choke coil with an intermediate tap, and 6 is a capacitor. It constitutes an inverter circuit. 7 is a discharge lamp which is a load of the inverter circuit.

The operation of the first embodiment with the above configuration will now be described. Here, the on/off control signals inputted between the bases and emitters of transistors 2, 4, and 5 in FIG. 1 correspond to A1, B1, and C1 in FIG. 2, respectively. These on/off control signals turn transistor 2 on and off at a high frequency, and transistors 4 and 5 are alternately turned on and off at a low frequency.

First, when the transistor 2 is turned on while the transistor 4 is in an on state, a current flows through a path from the positive terminal of the DC power supply 1 to the negative terminal of the DC power supply 1 via the transistor 2 and the choke coil 3. Furthermore, when the transistor 2 is turned off while the transistor 4 is on, the energy stored in the choke coil 3 flows from the intermediate tap of the choke coil 3 through the parallel circuit of the discharge lamp 7 and the capacitor 6, and the transistor 4. It operates as a so-called inverted chopper circuit where the flow returns to one end on the L1 side. At this time, the direction of the current flowing through the discharge lamp 7 is assumed to be positive. Therefore, the current flowing through the parallel circuit of the discharge lamp 7 and the capacitor 6 becomes a positive DC current with a high frequency superimposed thereon. Most of the high frequency components of this current flow through the capacitor 6, and the DC component and a small amount of high frequency components flow through the discharge lamp 7. In addition, since the energy accumulated in the entire choke coil 3 during the on period of transistor 2 is released from the L1 side of the choke coil 3 during the off period of transistor 2, there is a large adverse reaction on the L2 side that may destroy transistors 2 and 5. No electromotive force is generated.

Next, when transistor 2 is turned on while transistor 5 is on, current flows from the positive terminal of DC power supply 1 through the transistor 2 and choke coil 3 to the negative terminal of DC power supply 1. . Furthermore, when the transistor 2 is turned off while the transistor 5 is on, the energy stored in the choke coil 3 is transferred from one end of the choke coil 3 on the L2 side to the choke coil through the parallel circuit of the transistor 5, the discharge lamp 7, and the capacitor 6. The flow returns to the middle tap of No.3. Therefore, the current flowing through the parallel circuit of the discharge lamp 7 and the capacitor 6 becomes a direct current with a high frequency superimposed thereon. Most of the high frequency components of this current flow through the capacitor 6, and the DC component and a small amount of high frequency components flow through the discharge lamp 7. However, the current direction in this case is opposite to that when the transistor 4 is in the on state, that is, the current flows in the negative direction. Also, during the ON period of transistor 2, choke coil 3
Since the energy accumulated as a whole is released from the L1 side of the choke coil 3 during the off period of the transistor 2, the L2
A large back electromotive force that would destroy the transistors 2 and 4 is not generated on the side.

As described above, the lamp current flowing through the discharge lamp 7 becomes a low frequency rectangular wave slightly containing high frequency ripples. The on/off control signals A1, B1 of transistors 2, 4, and 5 are obtained by omitting a slight high frequency ripple.
, C1, the lamp current waveform is shown as I0 in Figure 2.
It will be like 1. Further, the waveform of the current flowing from the choke coil 3 to the parallel circuit of the discharge lamp 7 and the capacitor 6 via the transistors 4 and 5 is
If it corresponds to the on/off control signals A1, B1, and C1, it will become as shown in I1 in FIG.

As described above, according to the power supply device of the first embodiment of the present invention, the operation in each half cycle of the inverter circuit, that is, the operation when transistor 4 or transistor 5 is on, is almost similar to that of an inverting chopper circuit. Since the operation is similar, the inverter circuit itself can step up and down the voltage. Thereby, even if the output voltage of the DC power supply is lower than the effective value of the AC voltage required by the load, the required voltage can be supplied to the load. For example, by using the power supply device of the first embodiment of the present invention, it is possible to light a discharge lamp such as a metal halide lamp from an automobile battery without using any other boosting means. Furthermore, since it is a buck-boost type, an appropriate voltage can be supplied to the load even when the load voltage needs to be changed significantly. For example, even in the case of a discharge lamp where the load voltage changes greatly, if the power supply device of the first embodiment of the present invention is used, it can be used even when the lamp voltage is extremely low immediately after starting the discharge lamp. It can also be used when the lamp voltage is high, such as during stable lighting.

Furthermore, according to the power supply device of the embodiment, it is possible to supply a low frequency rectangular wave current containing almost no high frequency ripple to the load, so it is possible to supply the load with a low frequency rectangular wave current containing almost no high frequency ripple. It is also possible to maintain stable operation. For example, even when the load is a high-pressure discharge lamp such as a metal halide lamp, it is possible to prevent the unstable discharge phenomenon called acoustic resonance that occurs when the high-pressure discharge lamp is lit at high frequencies, and the lamp can be lit stably. can be done.

Furthermore, according to the power supply device of the embodiment, since voltage is applied to the load by the back electromotive force of the choke coil 3, sufficient voltage can be supplied even when the load instantly requires high voltage. can do. For example, in the case of a load such as a discharge lamp, it is possible to sufficiently compensate for the restriking voltage that occurs between the electrodes of the discharge lamp when the direction of the lamp current is switched, so that the discharge lamp can be stably maintained without causing it to go out. can be turned on.

Further, according to the power supply device of the embodiment, PWM
The inverter can be configured with three switching elements, making the configuration simpler than that of conventional power supply devices, and thereby the control circuit for controlling on/off of the switching elements can also be simplified.

Further, according to the power supply device of the embodiment, since there is no need to separately provide a step-up/down means, the structure of the device can be simplified and the device can be made smaller.

Although both ends of the DC power supply 1 are connected to both ends of the choke coil 3 in the first embodiment of the present invention, both ends of the DC power supply 1 may be connected to a part of the choke coil 3.

Further, in the embodiment, the transistor 2, which is a switching element that turns on and off at high frequency, is connected to the positive terminal side of the DC power source 1, but it may be connected to the negative side of the DC power source 1.

Further, in the embodiment, a transistor is used as a switching element that turns on and off at low frequency, but other switching elements such as FET and thyristor may be used. However, F
In the case of a reverse conduction type switching element such as an ET, it is necessary to connect a diode in series with the switching element to prevent reverse conduction. Further, in this case, what is connected in series to the switching element is not a diode, but another rectifying element may be used.

Further, in the embodiment, a transistor is used as a switching element that is turned on and off at high frequency, but other switching elements such as an FET or a thyristor may be used.

Furthermore, in the embodiment, the DC power supply 1 was connected to both ends of the choke coil 3 via the transistor 2.
DC power supply 1 is connected to choke coil 3 via transistor 2
When connecting to the choke coil 3, it may be connected not only to both ends of the choke coil 3 but also to a part thereof.

Next, a second embodiment of the present invention will be explained based on the attached drawings. FIG. 3 is a circuit diagram of the power supply device of the second embodiment. The difference in configuration from the first embodiment is that a choke coil 8 is connected in series to a discharge lamp 7, which is a load. The difference in operation is that the choke coil 8 reduces high frequency components flowing into the discharge lamp 7.

As described above, according to the power supply device of the second embodiment of the present invention, the high frequency component of the current flowing through the load can be further reduced compared to the first embodiment, so that unstable operation due to the high frequency component can be avoided. The operation can be kept even more stable even under such a load. For example, even when the load is a high-pressure discharge lamp such as a metal halide lamp, the acoustic resonance phenomenon can be prevented and the lamp can be stably lit.

Next, a third embodiment of the present invention will be explained based on the attached drawings. FIG. 4 is a circuit diagram of a power supply device according to a third embodiment. The difference in configuration from the first embodiment is that an igniter 9 for starting the discharge lamp is connected to both ends of the capacitor 6, and the primary side is connected to the igniter 9, and the secondary side is connected in series to the discharge lamp 7. Pulse transformer 10 to connect
This is because we have established the following.

The operation of the third embodiment with the above configuration will now be described. When starting the discharge lamp 7, the igniter 9 applies a pulse to the pulse transformer 10 using the voltage of the capacitor 6. The pulse voltage is stepped up by a pulse transformer 10 and applied to a discharge lamp 7 via a capacitor 6. As a result, the discharge lamp 7 is started.

As described above, according to the power supply device of the third embodiment of the present invention, the discharge lamp 7 can be started and restarted by the pulse transformer 10 even when the load is a high pressure discharge lamp that requires a high starting voltage. Can be done.

Furthermore, according to the power supply device of this embodiment, the high frequency components flowing into the discharge lamp 7 can be further reduced by the inductance on the secondary side of the pulse transformer 10 than in the first embodiment. Thereby, it is possible to prevent the acoustic resonance phenomenon of the discharge lamp 7, and it is possible to stably light the lamp.

Further, according to the power supply device of the embodiment, the impedance of the capacitor 6 is very small for high frequencies such as the starting pulse voltage, and the capacitor 6 can absorb the starting pulse voltage. The voltage can be applied to the discharge lamp 7 without dropping at the capacitor 6, and excessive voltage is not applied to other circuit elements, such as transistors 2, 4, and 5, thereby preventing failure of the circuit elements. be able to.

In the third embodiment of the present invention, the igniter 9 is operated using the voltage across the capacitor 6, but the voltage across the DC power supply 1 may be used, or the voltage from another power supply may be used. Alternatively, other means for obtaining voltage may be used.

Furthermore, in the embodiment, the capacitor 6 is connected in parallel to the series circuit between the secondary winding of the pulse transformer 10 and the discharge lamp 7, but the series circuit between the secondary winding of the pulse transformer 10 and the discharge lamp 7 A choke coil may be further connected in series, and a high frequency bypass capacitor 6 may be connected in parallel to this circuit. However, if the inductance value of the choke coil is large as it is,
Even if there is dielectric breakdown between the electrodes of the discharge lamp when the discharge lamp is started, the discharge lamp may not start reliably because the choke coil limits the current that is about to flow at the moment when the dielectric breakdown occurs between the electrodes. Therefore, in such a case, it is preferable to connect a capacitor for absorbing the pulse voltage to both ends of the series circuit between the secondary side of the pulse transformer and the discharge lamp. In this way, the high-frequency components of the lamp current are further reduced, and the discharge lamp can be started more reliably.

Next, a fourth embodiment of the present invention will be described based on the accompanying drawings. The configuration is the same as the first embodiment. The difference from the first embodiment is in the operation. On/off control signals input between the bases and emitters of transistors 2, 4, and 5 correspond to A2, B2, and C2 in FIG. 5, respectively. These on/off control signals turn transistor 2 on and off at a high frequency, and transistors 4 and 5 are alternately turned on and off at a low frequency. However, the on/off control signal A2 of transistor 2 is
This is different from the embodiment A1 in which the pulse widths are not equal, which is so-called unequal width PWM control. On the other hand, when the pulse width of A1 is equal as in the first embodiment, it is called equal width PWM.
It's called control. In the case of unequal width PWM control, the load current is large where the pulse width is wide, and conversely, the load current is small where the pulse width is narrow. By setting the on/off control signals for transistors 2, 4, and 5 as shown in FIG. 5, the load current becomes a sine wave.

As described above, according to the power supply device of the fourth embodiment of the present invention, when the direction of the load current is reversed, the current value becomes the smallest, so that the switching losses of the transistors 2, 4, and 5 are reduced. Therefore, the power supply device can be downsized.

Note that in the fourth embodiment of the present invention, the load current is made into a sine wave, but the ON/OFF state of transistors 2, 4, and 5 is
By setting the off control signal, the load current waveform can be changed to a trapezoidal waveform,
It is also possible to use any waveform such as a triangular wave or a sawtooth wave.

Next, a fifth embodiment of the present invention will be described based on the accompanying drawings. FIG. 6 is a circuit diagram of a power supply device according to a fifth embodiment. In FIG. 6, 11 is a DC power supply, 12, 14
, 15 is a FET which is a switching element, 13 is a choke coil having a center tap, 16 and 17 are diodes, 1
8 is a capacitor, and FETs 12, 14, 15, a choke coil 13, diodes 16, 17, and a capacitor 18 constitute an inverter circuit. 19 is a discharge lamp which is a load of the inverter circuit.

The operation of the embodiment with the above configuration will now be described. Here, the on/off control signals input between the gates and sources of FETs 12, 14, and 15 in FIG. 6 correspond to A1, B1, and C1 in FIG. 2, respectively. These on/off control signals turn FET 12 on and off at a high frequency, and alternately turn on and off FET 14 and FET 15 at a low frequency.

First, when the FET 14 is on, the FET
12 is turned on, F is connected from the positive terminal of the DC power supply 11.
ET12, L1 side of choke coil 13, FET14,
A current flows through the diode 16 in a path leading to the negative terminal of the DC power supply 11 . Furthermore, when the FET 12 is turned off while the FET 14 is on, the energy stored in the choke coil 13 causes the choke coil 13 to transfer the FET
14, a parallel circuit of the discharge lamp 19 and the capacitor 18, and a built-in diode of the FET 15, to operate a so-called inverted chopper circuit in which the flow returns to the choke coil 13. At this time, the direction of the current flowing through the discharge lamp 19 is assumed to be positive. Therefore, the current flowing through the parallel circuit of the discharge lamp 19 and the capacitor 18 becomes a positive DC current with a high frequency superimposed thereon. Most of the high frequency components of this current flow through the capacitor 18, and the DC component and a small amount of high frequency components flow through the discharge lamp 19. Here, the diode 17 is connected to prevent load short circuit. Furthermore, when the FET 12 is turned from on to off and the energy stored in the choke coil 13 is released, the magnetic flux is in the same direction on both the L1 and L2 sides of the choke coil 13, so the L2 side of the choke coil 13 is There is no obstruction to the flow of current.

Next, when the FET 15 is on, the FET
12 is turned on, F is connected from the positive terminal of the DC power supply 11.
ET12, L2 side of choke coil 13, FET15,
A current flows through the diode 17 in a path leading to the negative terminal of the DC power supply 11 . Furthermore, when the FET 12 is turned off while the FET 15 is on, the energy stored in the choke coil 13 causes the choke coil 13 to transfer the FET
15, the parallel circuit of the discharge lamp 19 and the capacitor 18, and the built-in diode of the FET 14, and then returns to the choke coil 13. Therefore, the current flowing through the parallel circuit of the discharge lamp 19 and the capacitor 18 becomes a direct current with a high frequency superimposed thereon. Most of the high frequency components of this current flow through the capacitor 18, and the DC component and a small amount of high frequency components flow through the discharge lamp 19. However, the current direction in this case is opposite to that when the FET 14 is in the on state, that is, the current flows in the negative direction. Here, the diode 16 is connected to prevent load short circuit. Furthermore, when the FET 12 is turned from on to off and the energy stored in the choke coil 13 is released, the magnetic flux is in the same direction on both the L1 and L2 sides of the choke coil 13, so the L1 side of the choke coil 13 is There is no obstruction to the flow of current.

As described above, the lamp current flowing through the discharge lamp 19 becomes a low frequency rectangular wave slightly containing high frequency ripples. Omitting the slight high frequency ripple,
On/off control signals A1, B for FET12, 14, 15
1, the lamp current waveform corresponding to C1 is I in Figure 2.
It will look like 01. In addition, FE from the choke coil 13
The waveform of the current flowing through the parallel circuit of the discharge lamp 19 and the capacitor 18 via T14 and T15 is the same as that of FET12 and T14.
, 15 on/off control signals A1, B1, C1, it becomes as shown in I1 in FIG.

As described above, according to the power supply device of the fifth embodiment of the present invention, the operation in each half cycle of the inverter circuit, that is, the operation when FET 14 or FET 15 is on, is almost the same as that of an inverting chopper circuit. Since it is an action, the first
Similarly to the embodiment, the inverter circuit itself can step up and down the voltage. Thereby, even if the output voltage of the DC power supply is lower than the effective value of the AC voltage required by the load, the required voltage can be supplied to the load. Furthermore, since it is a buck-boost type, an appropriate voltage can be supplied to the load even when the load voltage needs to be changed significantly.

Further, according to the power supply device of the embodiment, the FET 12 on the high voltage side and the FET 14 on the low voltage side or the FE on the high voltage side
Even if T12 and the low voltage side FET 15 are turned on at the same time, the L1 side and L2 side of the choke coil 13 turn on the FET 14, respectively.
Since it is connected in series with FET 15, no short circuit current will flow. This turns on/off FET14 and FET15.
Since there is no need to provide a dead time for the off signal, the configuration of the on/off control circuit can be simplified.

Furthermore, according to the power supply device of this embodiment, it is possible to supply a low frequency rectangular wave current containing almost no high frequency ripples to the load, so as in the first embodiment, unstable current due to high frequency components can be supplied to the load. Stable operation can be maintained even when the load is such that it moves.

Furthermore, according to the power supply device of the embodiment, voltage is applied to the load by the back electromotive force of the choke coil 13, so that when the load instantaneously requires a high voltage, as in the first embodiment, the voltage is applied to the load. Sufficient voltage can be supplied even in the case of

Further, according to the power supply device of the embodiment, the number of switch elements constituting the PWM inverter can be reduced to three, as in the first embodiment, and the configuration can be simpler than that of the conventional power supply device. Thereby, the control circuit for controlling the on/off of the switch element can also be made simple in configuration.

Further, according to the power supply device of the embodiment, since there is no need to separately provide a step-up/down means, the structure of the device can be simplified and the device can be made smaller.

Further, according to the power supply device of the embodiment, since the FET that turns on and off at low frequency is connected to the low voltage side and the FET that turns on and off at high frequency is connected to the high voltage side, the FET that turns on and off at low frequency is connected to the high voltage side.
Even if the source of the FET to be turned off is higher than the ground line by the forward voltage of the diode, by applying an on/off control signal between the gate and the ground line, it can be directly driven by the output signal of the signal circuit with the ground line as a reference. can do. Moreover, this allows the drive circuit of the low-voltage side FET to be downsized. Furthermore, even if noise is added to the on/off control signal of the FET on the low voltage side, only the voltage obtained by subtracting the forward voltage of the diode from the noise voltage is applied between the gate and source of the FET, making it difficult to cause malfunction. Can be done. Furthermore, F on the high pressure side
ET can be driven by a transformer, and since it is turned on and off at high frequency, the drive transformer can be made smaller. In other words, the drive circuit on the high voltage side can also be downsized.

In the fifth embodiment of the present invention, the FET 12, which is a switching element that turns on and off at high frequency, is connected to the positive terminal side of the DC power source 11, but it may be connected to the negative side of the DC power source 11. .

Further, in the embodiment, an FET is used as a switching element that turns on and off at low frequencies, but other switching elements such as a transistor or a thyristor may also be used. However, in the case of a reverse blocking type switching element such as a transistor or a thyristor, it is necessary to connect a diode in parallel to the switching element so that reverse conduction occurs. Further, in this case, what is connected in parallel to the switch element is not a diode, but another rectifier element.

Further, in the embodiment, an FET is used as a switching element that is turned on and off at high frequency, but other switching elements such as a transistor or a thyristor may be used.

Further, in the embodiment, a diode is used to prevent a load short circuit, but other rectifying elements may be used.

In addition, in the embodiment, only the discharge lamp 19, which is a load, is connected in parallel with the capacitor 18 for high frequency bypass, but as in the second embodiment, a choke coil for high frequency cut is connected in series with the discharge lamp 19. Alternatively, as in the third embodiment, a pulse transformer for starting the discharge lamp and for cutting off high frequency waves may be connected. In these cases, the same effects as in the second and third embodiments can be obtained.

Furthermore, in the embodiment, the current waveform flowing through the discharge lamp, which is the load, was made into a rectangular wave by performing equal width PWM control, but the current waveform flowing through the discharge lamp, which is the load, was made into a rectangular wave. The current waveform may be a sine wave. When a sine wave is used, FETs 12, 14, 1 are used as in the fourth embodiment.
5 can be reduced, and the power supply device can be downsized. Further, the waveform is not limited to a sine wave, but may be a trapezoidal wave, a triangular wave, a sawtooth wave, or the like.

Next, a sixth embodiment of the present invention will be explained based on the attached drawings. FIG. 7 is a circuit diagram of a power supply device according to a sixth embodiment. In FIG. 7, 21 is a DC power supply, 22 is a choke coil having an intermediate tap, 23, 24, 25, 2
6 is an FET which is a switch element, 27 is a capacitor, FETs 23, 24, 25, 26 and a choke coil 2.
2 and a capacitor 27 constitute an inverter circuit. 28 is a discharge lamp which is a load of the inverter circuit.

The operation of the embodiment with the above configuration will now be described. Here, the on/off control signals input between the gates and sources of FETs 23, 24, 26, and 25 in FIG. 7 correspond to D1, E1, F1, and G1 in FIG. 8, respectively. These on/off control signals control FET26 or 25.
turns on and off at a low frequency, and at the same time the transistor 23
Or 24 turns on and off at a high frequency.

First, when the FET 26 is on, the FET
23 is turned on, a current flows from the positive terminal of the DC power source 21 through the L1 side of the choke coil 22 and the FET 23 to the negative terminal of the DC power source 21. Also, when FET26 is on and FET23 is off,
Due to the energy stored in the choke coil 22, the power is transferred from the choke coil 22 to the built-in diode of the FET 25, the parallel circuit of the discharge lamp 28 and the capacitor 27, and the FET 26.
The flow returns to the choke coil 22 via the so-called inverted chopper circuit. At this time, the direction of the current flowing through the discharge lamp 28 is assumed to be positive. Therefore, the current flowing through the parallel circuit of the discharge lamp 28 and the capacitor 27 becomes a positive DC current with a high frequency superimposed thereon. Most of the high frequency components of this current flow through the capacitor 27, and the DC component and a small amount of high frequency components flow through the discharge lamp 28. Here, when the FET 23 changes from on to off and the energy stored in the choke coil 22 is released, the direction of the magnetic flux is the same on both the L1 side and the L2 side of the choke coil 22, so the L2 side of the choke coil 22 This does not impede the flow of current.

Next, when the FET 25 is on, the FET
24 is turned on, a current flows through a path from the positive terminal of the DC power supply 21 to the negative terminal of the DC power supply 21 via the L2 side of the choke coil 22 and the FET 24. Also, when FET25 is on and FET24 is off,
Due to the energy stored in the choke coil 22, the power is transferred from the choke coil 22 to the built-in diode of the FET 26, the parallel circuit of the discharge lamp 28 and the capacitor 27, and the FET 25.
, and returns to the choke coil 22. Therefore, the current flowing through the parallel circuit of the discharge lamp 28 and the capacitor 27 becomes a direct current with a high frequency superimposed thereon. Most of the high frequency components of this current flow through the capacitor 27, and the DC component and a small amount of high frequency components flow through the discharge lamp 28. However, the current direction in this case is FET2
6 is in the on state, that is, the current flows in the negative direction. Here, when the FET 24 changes from on to off and the energy stored in the choke coil 22 is released,
Since the choke coil 22 has the same direction of magnetic flux on both the L1 side and the L2 side, the L1 side of the choke coil 22
The flow of current is not obstructed by the sides.

As described above, the lamp current flowing through the discharge lamp 28 becomes a low-frequency rectangular wave containing a slight high-frequency ripple. Omitting the slight high frequency ripple,
On/off control signal D for FET23, 24, 25, 26
1, E1, F1, and G1, the lamp current waveform is shown as I03 in FIG. Furthermore, the waveform of the current flowing from the choke coil 22 through the FETs 25 and 26 to the parallel circuit of the discharge lamp 28 and the capacitor 27 is FE
T23, 24, 25, 26 on/off control signal D1,
Corresponding to E1, F1, and G1 is similar to I1 in FIG. 2.

As described above, according to the power supply device of the sixth embodiment of the present invention, the operation in each half cycle of the inverter circuit, that is, the operation when FET 25 or FET 26 is on, is almost the same as that of an inverting chopper circuit. Since it is an action, the first
, the inverter circuit itself can step up and down the voltage as in the fifth embodiment. Thereby, even if the output voltage of the DC power supply is lower than the effective value of the AC voltage required by the load, the required voltage can be supplied to the load. Furthermore, since it is a buck-boost type, an appropriate voltage can be supplied to the load even when the load voltage needs to be changed significantly.

Further, according to the power supply device of the embodiment, since it is possible to supply a low frequency rectangular wave current containing almost no high frequency ripple to the load, it is possible to supply the load with a low frequency rectangular wave current containing almost no high frequency ripple. Stable operation can be maintained even in the case of a load that causes unstable operation.

Further, according to the power supply device of the embodiment, voltage is applied to the load by the back electromotive force of the choke coil 22, so that the load does not require instantaneous high voltage as in the first and fifth embodiments. Sufficient voltage can be supplied even in such cases.

Furthermore, according to the power supply device of the sixth embodiment,
Since there is no need to separately provide a voltage raising/lowering means, the configuration of the device can be simplified and the device can be downsized.

In the embodiment, an FET is used as a switching element that turns on and off at low frequencies, but other switching elements such as a transistor or a thyristor may also be used. However, in the case of a reverse blocking type switching element such as a transistor or a thyristor, it is necessary to connect a diode in parallel to the switching element so that reverse conduction occurs. Further, in this case, what is connected in parallel to the switch element is not a diode, but another rectifier element.

Further, in the sixth embodiment of the present invention, an FET is used as a switching element that turns on and off at high frequency, but other switching elements such as a transistor or a thyristor may also be used.

Further, in the sixth embodiment of the present invention, only the discharge lamp 28, which is a load, is connected in parallel with the high frequency bypass capacitor 27, but as in the second embodiment, a discharge lamp 28 is connected in series with the discharge lamp 28. A choke coil for high frequency cutting may be connected, or a pulse transformer for starting the discharge lamp and for high frequency cutting may be connected as in the third embodiment. In these cases, the same effects as in the second and third embodiments can be obtained.

Further, in the sixth embodiment, the current waveform flowing through the discharge lamp, which is the load, is made into a rectangular wave by performing equal width PWM control, but as in the fourth embodiment, the waveform of the current flowing through the discharge lamp, which is the load, is made into a rectangular wave.
M control may be performed to make the load current waveform a sine wave. However, in this case, the on/off control signals input between the gates and sources of FETs 23, 24, 26, and 25 correspond to D2, E2, F2, and G2 in FIG. 9, respectively. The load current at this time becomes I04 in FIG. When a sine wave is used, FETs 23, 24, 25,
26 switching loss can be reduced, and the power supply device can be downsized. Further, the waveform is not limited to a sine wave, but may be a trapezoidal wave, a triangular wave, a sawtooth wave, or the like.

In the first to sixth embodiments of the present invention, the load is a discharge lamp, but the load is not limited to a discharge lamp, but may be a resistive load or a motor load.

In the embodiment of the present invention, the DC power source may be a DC/DC converter, a rectified and smoothed alternating current, an automobile battery, or other sources.

Further, in the embodiment of the present invention, in order to control the output, means such as changing the pulse width of the switching element on the high frequency side or changing the on/off frequency of the switching element on the high frequency side are used. Bye.

In the embodiment of the present invention, when the load is a discharge lamp, in order to compensate for the restriking voltage that occurs between the electrodes of the lamp when the direction of the lamp current is switched, the high frequency side is set only at the beginning of switching. The pulse width of the switch element may be widened.

Furthermore, in the embodiment of the present invention, when the load has symmetrical characteristics, it is desirable that the inductances L1 and L2 of the choke coils have the same value, but as long as it is within the stable operating range of the load. It doesn't matter if there are some differences. Further, the difference between the two may be corrected by pulse width control.

Furthermore, in the embodiment of the present invention, when the load has asymmetrical characteristics, the inductance L1
, L2 may be intentionally set to be different. Further, even if the values of the inductances L1 and L2 are the same, an asymmetrical current may be caused to flow by controlling the pulse width.

[0081]

As is clear from the above embodiments, according to the present invention, it is possible to realize a buck-boost type power supply device using a PWM inverter system, and it is possible to operate a load with a large voltage fluctuation range. Further, since there is no need to separately provide a voltage raising/lowering means, the configuration of the device can be simplified and the device can be made smaller.

Furthermore, by connecting two reverse-blocking switch elements in series that alternately turn on and off at low frequencies to both ends of the inductance element having an intermediate terminal, short circuits of the DC power supply can be prevented and the necessary Voltage can be supplied to the load.

Furthermore, by connecting two reverse conduction type switching elements that alternately turn on and off at a low frequency between both ends of the parallel circuit of the load and capacitor and both ends of the inductance element having an intermediate terminal, A necessary voltage can be supplied to the load by utilizing the reverse conduction portion of the switch element.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a power supply device according to a first and fourth embodiment of the present invention.

FIG. 2 shows on/off control signals for switch elements according to the first, second, third, and fifth embodiments of the present invention and conventional examples;
Waveform diagram of circuit current and lamp current

FIG. 3 is a circuit diagram of a power supply device according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram of a power supply device according to a third embodiment of the present invention.

FIG. 5 is a waveform diagram of the on/off control signal and lamp current of the switch element according to the fourth and fifth embodiments of the present invention.

[
FIG. 6 is a circuit diagram of a power supply device according to a fifth embodiment of the present invention

FIG. 7 is a circuit diagram of a power supply device according to a sixth embodiment of the present invention.

FIG. 8 is a waveform diagram of the on/off control signal and lamp current of the switch element according to the sixth embodiment of the present invention.

[Figure 9]
Waveform diagram of the on/off control signal and lamp current of the switch element according to the sixth embodiment of the present invention

[Fig. 10] Circuit diagram of a power supply device according to a conventional example

[Explanation of symbols]

1, 11, 21 DC power supply 2, 4, 5 Transistor 3, 8, 13, 22 Choke coil 6, 18, 27
Capacitor 7, 19, 28 Discharge lamp 9 Igniter 10 Pulse transformer 12, 14, 15, 23, 24, 25, 26 FET
16,17 diode

Claims (3)

[Claims] Claim 1: a DC power supply; a first switching element connected to one end of the DC power supply and turned on and off at a high frequency;
an inductance element having one end connected to a first switch element and the other end connected to the other end of the DC power supply, and having an intermediate terminal;
a series circuit consisting of a reverse blocking type second switching element and a reverse blocking type third switching element connected to both ends of the inductance element and turned on and off alternately at a low frequency; and one end connected to an intermediate terminal of the inductance element. and a load connected in parallel to this capacitor; The power supply, the first switch element, and the inductance element constitute a first closed circuit, and during the on period of the second switch element, a parallel circuit with the capacitor and the load, one winding of the inductance element, and the second closed circuit are formed. A second closed circuit is formed with the second switching element, and during the ON period of the third switching element, a parallel circuit with the capacitor and the load, the other winding of the inductance element, and the third switching element form a second closed circuit. A power supply device comprising a closed circuit according to No. 3. 2. A DC power supply; a first switching element connected to one end of the DC power supply and turned on and off at a high frequency;
an inductance element having an intermediate terminal and connecting the intermediate terminal to a first switching element; and a reverse conduction type inductance element connected between one end of the inductance element and the other end of the DC power supply and turned on and off at a low frequency. A series circuit of a second switching element and a first rectifying element, and a second switching element connected between the other end of the inductance element and the other end of the DC power supply, and turned on at a low frequency in opposite phase to the second switching element.・A series circuit of a reverse conduction type third switch element and a second rectifier element to be turned off, an intersection between the second switch element and the first rectifier element, and the third switch element and the second rectifier element. and a load connected in parallel to the capacitor, the DC power source and the first A first closed circuit is formed by the switching element, one winding of the inductance element, the second switching element, and the first rectifying element, and during the ON period of both the first switching element and the third switching element. A second closed circuit is configured by the DC power supply, the first switching element, the other winding of the inductance element, the third switching element, and the second rectifying element,
During the on-period of the second switch element, a parallel circuit with the capacitor and the load, the inductance element, the second switch element, and the reverse conduction portion of the third switch element are connected to the third switch element.
A closed circuit is formed during the ON period of the third switch element, and a fourth closed circuit is formed by the parallel circuit with the capacitor and the load, the inductance element, the third switch element, and the reverse conducting portion of the second switch element. A power supply device comprising a circuit. 3. A DC power supply, an inductance element having an intermediate terminal and connecting the intermediate terminal to one end of the DC power supply, and a reverse conduction type inductance element connected to one end of the inductance element and turned on and off at a low frequency. a second switch element of a reverse conduction type that is connected to the other end of the inductance element and turns on and off at a low frequency with an opposite phase to that of the first switch element; a capacitor connected between one end of the inductance element and the other end of the DC power supply, the second switching element being turned on and off at a high frequency during the on period of the second switching element; A third switch element is connected between the other end of the inductance element and the other end of the DC power supply and is turned off at a high frequency during the on period of the first switch element. a fourth switch element that is turned off during the off period of the first switch element; and a load connected in parallel to the capacitor; One of the windings of the inductance element and the third switch element constitute a first closed circuit, and during the ON period of the fourth switch element, the DC power supply and the other winding of the inductance element and the fourth switch element form a first closed circuit. constitutes a second closed circuit, and during the ON period of the first switch element, a parallel circuit with the capacitor and the load, a reverse conduction portion of the inductance element and the second switch element, and the first switch element form a second closed circuit. During the ON period of the second switch element, a parallel circuit with the capacitor and the load, the inductance element, the reverse conduction portion of the first switch element, and the second switch element form a fourth closed circuit. A power supply device comprising a closed circuit.