JP3177240B2 - Power supply circuit - Google Patents

Description

The present invention can be used even when the power supply voltage fluctuates greatly and the power supply voltage may be lower than the voltage required for driving the switch, and The present invention relates to a power supply circuit suitable for miniaturization.

[Conventional technology]

As described in JP-A-1-251590, a power supply circuit for a discharge lamp includes a DC power supply as a power supply, a midpoint of a series circuit using two switch elements, and a series circuit of two capacitors. A load circuit composed of an inductance, a capacitor, and a discharge lamp is connected between the midpoint, and is generally called a half-bridge type discharge lamp lighting circuit.
An alternating current is supplied to the load circuit by alternately turning on and off the two switch elements, and by controlling the frequency of the alternating current to an appropriate value, the resonance state of the inductance and the capacitor of the load circuit is changed, and the preheating is performed. → Starting voltage generation → Transition to steady lighting, lighting the discharge lamp.

[Problems to be solved by the invention]

In the above prior art, a pulse transformer is used to drive the switch element. Therefore, if the turns ratio of the pulse transformer winding is set to an appropriate value, a sufficient drive voltage can be generated even if the power supply voltage decreases. On the other hand, the use of the above-mentioned pulse transformer causes problems such as an increase in the size of the device and an increase in cost, and a problem such as a hindrance to a higher frequency due to a leakage inductance and a hindrance to circuit integration.

SUMMARY OF THE INVENTION An object of the present invention is to provide a power supply circuit which is small and can obtain a stable driving voltage and has the advantages of using a pulse transformer, except for the problems of the prior art using a pulse transformer.

[Means for solving the problem]

The object is to provide a switch circuit connecting one ends of first and second switches, a DC power supply connected between the other end of the first switch and the other end of the second switch, A load circuit connected between a midpoint of the circuit and a high potential side or a low potential side of the DC power supply, or a midpoint of the first and second capacitor series circuits connected to the DC power supply; The first with the anode connected to the high potential side of the power supply
A rectifier, a third capacitor connected between the cathode of the first rectifier and the midpoint of the switch circuit, a second rectifier having an anode connected to the midpoint of the switch circuit, A fourth capacitor connected between the cathode of the rectifier and the high-potential side of the DC power supply; and a switch control circuit for controlling on / off of the first and second switches. The on / off control of the switch 2 supplies an alternating current to the load circuit, and the connection between the connection point between the second rectifier and the fourth capacitor and the low potential side of the DC power supply. The first and second switches are configured to obtain a voltage approximately twice as high as that of the DC power supply, and also function as a switch for boosting power and as a switch for supplying power to the load circuit. Is achieved by . That is, the drive of the switch element is performed using a semiconductor circuit, the control terminal of the switch element is connected to the middle point of the series circuit of the two drive switches, and the other end of the drive switch is connected to the drive DC power supply. Then, the switch element is controlled by turning on any of the driving switches. Further, since the voltage of the driving DC power supply is lower than the minimum voltage required for driving the switch element, the on-resistance when the switch element is turned on is increased, thereby preventing an increase in power loss. For this purpose, the power supply voltage is raised to create a driving DC power supply, and the necessary voltage is always secured.

[Action]

Since the power supply circuit of the present invention does not use a pulse transformer as described above, the size of the device can be reduced, and furthermore, semiconductor integration can be performed. Further, since the frequency can be increased, the size can be further reduced.

In addition, in order to boost DC voltage without using a transformer, it is necessary to turn on and off the boosting switch element, convert it to AC once, and boost it with a combination of a diode and a capacitor. This leads to an increase in points and causes an increase in cost. Therefore, a boost switch element,
By also using the main switch element for supplying power to the load circuit, the increase in circuit scale due to the addition of the booster circuit was suppressed. Further, by adopting a configuration in which an appropriate value of the boosting ratio can be selected according to the power supply voltage, useless power consumption is suppressed.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. First
FIG. 1 is a circuit diagram showing a first embodiment of a power supply circuit according to the present invention;
FIG. 2 is a circuit diagram showing a second embodiment of the present invention, FIG. 3 is a circuit diagram showing a third embodiment of the present invention, and FIG.
FIG. 5 is a circuit diagram showing a fifth embodiment of the present invention, FIG. 6 is a circuit diagram showing a sixth embodiment of the present invention,
FIG. 7 is a circuit diagram showing a seventh embodiment of the present invention, FIG. 8 is a circuit diagram showing an eighth embodiment of the present invention, and FIG. 9 is a circuit diagram showing one embodiment of a load circuit.

The first embodiment shown in FIG. 1 shows an example in which the present invention is applied to a half-bridge type inverter, wherein 1 is a DC power supply, 2 and 3 are switches, 4 and 5 are capacitors,
6 is a load circuit, 7 and 9 are rectifiers for boosting, 8 and 10
Is a boosting capacitor, 11 is an output terminal, and 12 is a switch control circuit. The switches 2 and 3 are turned on and off alternately by the control signal of the switch control circuit 12. Therefore, the current flows from the positive side of DC power supply 1 → capacitor 4 →
The path of the load circuit 6 → the switch 3 → the negative side of the DC power supply 1 and the path of the positive side of the DC power supply 1 → switch 2 → the load circuit 6 → the capacitor 5 → the negative side of the DC power supply 1 alternately flow. Therefore, an alternating current flows through the load circuit 6. By the way, when the voltage of the DC power supply 1 is low,
If the voltage is lower than the voltage required to drive the driving circuits 3 and 3, the voltage is boosted by the following method, and the boosted voltage is used as the driving voltage. That is, at the same time as supplying the current to the load circuit 6, while the switch 3 is on, the positive side of the DC power supply 1 → the boosting rectifier 7 → the boosting capacitor 8
→ Switch 3 → A current flows through the path of the negative side of the DC power supply 1 to charge the boosting capacitor 8 with the power supply voltage. Then, when the switch 3 is turned off and the switch 2 is turned on, both ends of the boosting capacitor 8 are turned on. Since the low-voltage side terminal of the boosting capacitor 8 is raised to the power supply voltage while the power supply voltage is held between the terminals, the high-voltage side terminal of the boosting capacitor 8 is boosted to twice the power supply voltage. Further, since the boosting rectifier 7 is reverse-biased at this time, the boosting capacitor 10 is charged via the boosting rectifier 8. Therefore, a voltage about twice the power supply voltage is finally generated at the output terminal 11. Although one end of the boosting capacitor 10 is connected to the positive side of the DC power supply 1 in this embodiment, the same effect can be obtained by connecting it to the negative side.

In the second embodiment shown in FIG. 2, an example of application to a full-bridge inverter is shown. In the figure, switches 13 and 14 are different from each other in that the capacitors 4 and 5 are used in this embodiment in the first embodiment, and the same reference numerals indicate the same or equivalent parts as those in the first embodiment. . In the second embodiment, switches 2 and 14 are turned on / off by the same operation,
Switches 3 and 13 are turned on and off in the opposite operation. Therefore, the supply of the alternating current to the load circuit 6 is performed on the positive side of the DC power supply 1 → the switch 13 → the load circuit 6 → the switch 3
→ The path of the negative side of DC power supply 1 and the positive side of DC power supply 1 →
The current flows alternately through the path of the switch 2 → the load circuit 6 → the switch 14 → the negative side of the DC power supply 1. Other voltage boosting mechanisms are the same as in the first embodiment.
As described above, the present invention can be applied to a full-bridge inverter, and a voltage necessary for driving can be obtained.

In the full-bridge inverter, similar effects can be obtained even with the configuration as in the third embodiment shown in FIG. The procedure for supplying the alternating current to the load circuit 6 is the same as in the second embodiment. In FIG. 3, reference numeral 15 denotes a step-up rectifier, and reference numeral 16 denotes a step-up capacitor. The same reference numerals as in FIG. 2 denote the same or equivalent parts. While the switches 13 and 3 are turned on, the positive side of the DC power supply 1 → the switch 13
→ Boost rectifier 15 → Boost capacitor 16 → Switch 3 →
In the path of the negative side of the DC power supply 1, the boost capacitor
Charge 16 with power supply voltage. Subsequent operations are the same as in the second embodiment.

The first to third embodiments are examples in which a voltage approximately twice the power supply voltage is obtained. However, there may be cases where a higher boost ratio is required. The fourth embodiment shown in FIG. 4 is a circuit for obtaining a boost ratio of three times, in which reference numeral 17 denotes a boost rectifier, and reference numeral 18 denotes a boost capacitor. The process up to charging the boost capacitor 16 is the same as in the third embodiment. Then switch 2
When and 14 are turned on, the boosting capacitor 18 is charged with a voltage twice the power supply voltage via the boosting rectifier 17. When the switch 13 is turned on again, the boosting capacitor 18
Is boosted to the power supply voltage, the boosting capacitor 10 is charged through the boosting rectifier 9 with a voltage approximately three times the power supply voltage.

FIG. 5 is a circuit diagram showing a fifth embodiment configured to obtain an arbitrary boost ratio. As the number of boost rectifiers and boost capacitors increases, a higher boost ratio can be obtained. In FIG. 5, reference numerals 21, 24 and 26 denote boost capacitors, and reference numerals 22, 23 and 25 denote boost rectifiers. The boosting mechanism repeats the operation of the fourth embodiment.

The sixth embodiment shown in FIG. 6 is an example in which the tripled output voltage obtained in the fourth embodiment is actually used as a switch driving power source. Reference numeral 27 denotes a drive circuit for the switches 2 and 3, 28
Is a drive circuit of the switches 13 and 14, and the drive circuits 27 and 28 are in accordance with an output signal of the switch control circuit 12,
A switch drive signal is generated based on a voltage about three times the power supply voltage, and switches 2, 3, 13 and 14 are driven.

The seventh embodiment shown in FIG. 7 is an application example in which the fluctuation range of the power supply voltage is so large that it is not possible to cope with it by preparing only one step-up ratio, 28 is a changeover switch, and 29 is a control circuit of the changeover switch. Is shown. Use of an unnecessarily high voltage leads to an increase in power loss, and in an extreme case, the breakdown may exceed the withstand voltage of the circuit element. Then, the output voltage is detected by the changeover switch control circuit 29, and the changeover switch 28 is automatically switched so that an appropriate voltage is obtained, thereby coping with a case where the power supply voltage fluctuates greatly.

The eighth embodiment shown in FIG. 8 further includes a voltage limiting circuit 30, which is an improvement of the seventh embodiment so as to cope with a sudden change in the power supply voltage.

FIG. 9 shows an embodiment of the load circuit 6, wherein 31 is a transformer, 32 is a choke coil, 33 is a capacitor, 34 is a discharge lamp having filaments 35 and 36, and 37 is a preheating capacitor. An alternating current flows through the primary side of the transformer 31 as described in the first embodiment or the second embodiment.
By appropriately controlling the on / off cycle of the switches 2, 3, 13, and 14, resonance is generated between the choke coil 32, the capacitor 33, and the preheating capacitor 37, and the filament
While preheating 35 and 36, a voltage is generated at both ends of the discharge lamp 34 to light it.

The load circuit may be a special discharge lamp lighting circuit other than a normal fluorescent lamp lighting circuit, for example, a special discharge lamp lighting circuit having a short distance between electrodes.

〔The invention's effect〕

As described above, the power supply circuit according to the present invention includes a switch circuit connecting one end of each of the first and second switches,
A DC power supply connected between the other end of the switch and the other end of the second switch, a midpoint of the switch circuit and a high potential side or a low potential side of the DC power supply, or a DC power supply connected to the DC power supply. A load circuit connected between the midpoints of the first and second capacitor series circuits, a first rectifier having an anode connected to the high potential side of the DC power supply, and a cathode of the first rectifier. A third terminal connected between the switch circuit and the middle point.
A second rectifier having an anode connected to the middle point of the switch circuit; a fourth capacitor connected between a cathode of the second rectifier and a high potential side of the DC power supply; A switch control circuit for controlling on / off of the first and second switches; supplying an alternating current to the load circuit by controlling on / off of the first and second switches; A connection point between a rectifier and the fourth capacitor and a low potential side of the DC power supply,
By obtaining a voltage approximately twice as high as that of the DC power supply, a stable drive voltage can be secured without using a transformer even if the power supply voltage fluctuates greatly, so that higher frequency and lower loss can be achieved. Since the circuit can be integrated into a semiconductor, the size can be further reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a power supply circuit according to the present invention, FIG. 2 is a circuit diagram showing a second embodiment of the present invention, and FIG. 3 is a circuit diagram showing a third embodiment of the present invention. FIG. 4 is a circuit diagram showing a fourth embodiment of the present invention, FIG. 5 is a circuit diagram showing a fifth embodiment of the present invention, FIG. 6 is a circuit diagram showing a sixth embodiment of the present invention, FIG. 7 is a circuit diagram showing a seventh embodiment of the present invention, FIG. 8 is a circuit diagram showing an eighth embodiment of the present invention, and FIG. 9 is a circuit diagram showing one embodiment of a load circuit. DESCRIPTION OF SYMBOLS 1 ... DC power supply 2 ... 1st switch 3 ... 2nd switch 4 ... 1st capacitor 5 ... 2nd capacitor 6 ... Load circuit 7 ... 1st rectifier 8 ... ... third capacitor 9 ... second rectifier, 10 ... fourth capacitor 12 ... switch control circuit 13 ... third switch 14 ... fourth switch 15 ... third rectifier 29 ... Changeover switch control circuit 30 …… Voltage limiting circuit

Continued on the front page (51) Int.Cl. ⁷ Identification code FI H05B 41/24 H05B 41/24 KL

Claims (10)

(57) [Claims] A first switch connected to one end of each of the first and second switches; a second end connected to the second switch;
A DC power supply connected between the other ends of the switches, and a first and a second power supply connected to the midpoint of the switch circuit and the high potential side or the low potential side of the DC power supply, or the DC power supply.
A first rectifier having an anode connected to the high potential side of the DC power supply; a cathode of the first rectifier; and a midpoint of the switch circuit. A third capacitor connected between the first and second rectifiers, a second rectifier having an anode connected to the midpoint of the first rectifier and the third capacitor, a cathode of the second rectifier, and a high voltage of the DC power supply. A fourth capacitor connected between the first and second switches; and a switch control circuit for controlling on / off of the first and second switches, and controlling on / off of the first and second switches. Supplies an alternating current to the load circuit, and obtains a voltage approximately twice as high as the DC power supply between the connection point between the second rectifier and the fourth capacitor and the low potential side of the DC power supply. And the first and second switches described above. Power circuit switch is characterized in that also functions as a switch for power supply to function and the load circuit as a boost switch element. 2. The load circuit is connected between a midpoint of the switch circuit and a midpoint connecting one end of each of third and fourth switches, and the other end of the third switch is connected to the fourth end of the fourth switch. 2. The power supply circuit according to claim 1, wherein the DC power supply is connected between the other end of the switch, and the first to fourth switches are turned on and off. 3. The first rectifier has an anode connected to a connection point between the third switch and the fourth switch, and one end of the fourth capacitor opposite to the second rectifier connected to a high potential side of the DC power supply. The power supply circuit according to claim 1, wherein the power supply circuit is connected to a low potential side. 4. An end of the fourth capacitor opposite to the second rectifier is connected to a connection point between the third and fourth switches, and a connection point between the fourth capacitor and the second rectifier is connected to a third rectifier. An anode is connected, a fifth capacitor is connected between the cathode of the third rectifier and the high potential side or the low potential side of the DC power supply, and the first to fourth switches are turned on.
The off control supplies an alternating current to the load circuit, and a voltage approximately three times that of the DC power supply is applied between the middle point of the third rectifier and the fifth capacitor and the low potential side of the DC power supply. 4. The power supply circuit according to claim 3, wherein: 5. The rectifier according to claim 1, wherein a plurality of rectifiers are connected in series with the third rectifier in the same direction, and the cathode of the odd-numbered rectifier and the anode of the (odd-number-2) rectifier are connected to each other. A capacitor is connected between them, and this is sequentially repeated an arbitrary number of times. Finally, a series circuit of a rectifier and a capacitor is connected between the DC power supply to obtain a voltage of the number of capacitors. The power supply circuit according to claim 1, 3 or 4, wherein 6. The voltage of a magnification corresponding to the number of the capacitors is:
The power supply circuit according to claim 5, wherein the power supply circuit is used as a power supply for driving the first to fourth switches. 7. The power supply circuit according to claim 6, wherein said drive power supply selects one of voltages substantially equal to an integral multiple of said DC power supply. 8. The power supply circuit according to claim 6, wherein the driving power supply is limited so as not to exceed a predetermined voltage value. 9. The power supply circuit according to claim 1, wherein said load circuit is a lighting circuit for a discharge lamp. 10. The switch according to claim 1, wherein said switch is a boosting switch as a boosting circuit component for obtaining a drive voltage of the switch in a half-bridge type inverter or a full-bridge type inverter. Item 7. The power supply circuit according to any one of Items 4 to 6, or Item 6.