JPH0413697Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field] This invention relates to a power supply circuit.

[Conventional technology]

A conventional example is shown in FIG. In FIG. 5, E is an AC power supply, DB is a rectifier circuit, L is a load, C ₁ and C ₂ are smoothing capacitors, and Sw is a changeover switch for selecting the input voltage to the load L. AC power supply E
As such, 100V and 200V are selectively used.

The operation of this power supply circuit is as follows.

At AC100V, the switch Sw is short-circuited, the capacitors C ₁ and C ₂ are each charged under a voltage of √2×100V≒141V, and a voltage of 2×141V=282V is applied to the load L. On the other hand, at AC200V, the switch
Sw is opened, and the series circuit of capacitors C ₁ and C ₂ is charged under a voltage of √2×200V≒282V, which becomes the voltage directly applied to the load L. In other words, at AC100V, double voltage rectification and smoothing is performed, and at AC200V
At this time, constant power is supplied to the load L by performing rectification and smoothing.

[Problem to be solved by the invention] Therefore, regardless of the voltage of the power source E, a rectified and smoothed voltage of 200V is always applied to the load L,
If the load L includes, for example, an inverter device that converts DC voltage into high frequency and supplies electric power, the stress applied to semiconductor components and the like included in the load L will also increase. Further, the stress (inrush current, etc.) applied to the switch Sw is large, and when a bidirectional thyristor, relay, etc. is used for this switch Sw, the reliability of the switch Sw becomes a problem.

The above problem occurs not only when 100V AC and 200V AC are used selectively, but also when the input voltage to the load L is changed (for example, 2
This problem also occurs when high voltage is applied in devices that perform step adjustment.

Therefore, as another conventional power supply circuit that supplies constant power to the load regardless of whether the power supply voltage of AC100V or AC200V is applied, the one shown in FIG. 6 can be considered. In Figure 6, E is AC100V or
AC200V AC power supply, DB is a rectifier circuit (diode bridge circuit) connected to AC power supply E, C is a smoothing capacitor connected to the output end of the rectifier circuit DB, S ₁ and S ₂ are connected in series with each other for smoothing. The first and second switch elements S 3 and S 4 are connected in parallel to the capacitor C, and the third switch element S ₃ and S ₄ are connected in series to each other and connected in parallel to the series connection circuit of the first and second switch elements S ₁ and S ₂ . and a fourth switch element, which constitute a full bridge inverter. L is the connection between the first and third switch elements S between the connection point a of the first and _second switch elements S ₁ and S ₂ and the connection point b of the third and fourth switch elements S 3 and S _{4 1} and _S3 are connected in parallel with a discharge lamp or other arbitrary load.

DK is a power supply detection circuit that detects the voltage of AC power supply E, IC is an inverter control circuit that controls on/off of switch elements S ₁ to S ₄ , and DT is a power supply detection circuit.
This is a duty control circuit that controls the output duty of the inverter control circuit IC based on the output of the DK.

In such a power supply circuit, the power supply voltage is 100V AC.
The power supply detection circuit DK detects whether it is AC200V or AC200V, and the duty control circuit DT sends a signal to the inverter control circuit IC according to the power supply voltage, thereby causing the full bridge inverter to perform switching operation according to the power supply voltage. It's summery. Specifically, this switching operation is performed in order to supply constant power to the load L.When the power supply voltage is AC100V,
The duty is increased as shown in FIG. 7a, and when the power supply voltage is 200 VAC, the duty is decreased as shown in FIG. 7b.

With this configuration, the power supplied to the load L can be made constant at 100V/200V AC, and the necessary value can be obtained for the peak-to-peak voltage. However, it is necessary to use the duty control circuit DT to change the length of the switch element on period to long or short depending on the power supply voltage.
is required, which complicates the configuration of the power supply circuit.

Further, as another conventional power supply circuit, the one shown in FIG. 8 can also be considered. This power supply circuit has a configuration in which the voltage of an AC power supply E is rectified by a diode bridge DB, and further smoothed by a smoothing capacitor C. Furthermore, a series connection circuit of a load L and a switch element Sw is connected in parallel with the smoothing capacitor C. A power supply detection circuit DK and a duty control circuit DT similar to those shown in FIG. 6 are connected to each other, and an on/off control circuit CR for controlling on/off of the switch element Sw is provided. The switch element Sw in this power supply circuit is controlled by duty control in the same way as the power supply circuit shown in Fig. 6, but a DC voltage is applied to the load L as shown in Fig. 9a and b. . Note that FIG. 9a shows a case where the power supply voltage is AC100V, and FIG. 9b shows a case where the power supply voltage is AC200V.

In addition, in the case of the configuration shown in FIG. 8, when the AC voltage is 100 V, a complete DC voltage is applied to the load L as shown in FIG. Even if an intermittent voltage is applied to the load L as shown in b, it is possible to supply constant power to the load L at 100V/200V AC.

In any case, in the configuration shown in FIG. 8, the duty control circuit is similar to the case shown in FIG.
DT is required, making the circuit configuration complicated.

In addition, in the case of the configuration shown in Fig. 8, when the voltage applied to the load L is 100V AC, only about 140V is applied, so loads that require a high peak-to-peak value of voltage (for example, discharge lamps, etc.) ), problems such as difficulty in starting will arise.

In any case, if you use the conventional configuration as shown in Figure 6 or Figure 8, there is no need for a switching switch Sw compared to the conventional example in Figure 5, which switches the rectification and smoothing method at 100V/200V AC. Then,
Although it is possible to prevent the switch Sw from deteriorating due to inrush current, etc., the problem arises that the circuit configuration becomes complicated or the necessary peak-to-peak voltage cannot be obtained as described above.

The purpose of this invention is to provide a power supply circuit with a simple configuration, which has low stress on a changeover switch for selecting an input voltage to a load, and has high reliability.

[Means to solve the problem]

The power supply circuit of this invention includes a rectifier circuit connected to an AC power supply having a first power supply voltage or a second power supply voltage having a voltage value twice the first power supply voltage, and an output terminal of the rectifier circuit. a connected smoothing capacitor, a series connection circuit of first and second switch elements connected in parallel to this smoothing capacitor, and a series connection circuit of third and fourth switch elements connected in parallel to this series connection circuit. , said first
and a load interposed between a connection point between the second switch elements and a connection point between the third and fourth switch elements in a state where the first and third switch elements are connected in parallel; a state in which the first and fourth switch elements are turned on and the second and third switch elements are turned off; and a state in which the first and fourth switch elements are turned off and the second and third switch elements are turned off. A first control operation that alternately repeats the on state;
The second and third switch elements are kept OFF at the same operating frequency as during this first control operation and the length of the switch element ON period is substantially the same as during the first control operation. 1st and 4th
a control circuit that selectively controls two switch element control operations, a second control operation that alternately repeats a state in which the switch element is turned on and a state in which the first and fourth switch elements are turned off; It is determined whether the power supply voltage of the power supply is the first power supply voltage or the second power supply voltage, and the control operation of the two switch elements of the control circuit is performed when the power supply voltage of the AC power supply is the first power supply voltage. and a changeover switch that selects the first control operation and selects the second control operation when the power supply voltage of the AC power source is the second power supply voltage.

[Effect]

First, when the first power supply voltage is selected as the input voltage to the load, the first control operation is performed even at a frequency unrelated to the frequency of the AC power supply voltage, for example, a frequency of about several tens of KHz, The first and fourth switch elements are turned on and the second and third switch elements are turned off, so that a voltage is applied to the load in one direction via the first and fourth switch elements. The second and third switch elements are turned on, the first and fourth switch elements are turned off, and a voltage is applied to the load in the other direction via the second and third switch elements. will be repeated. In this case, the voltages in one direction and the other direction have the same absolute value.

Next, when the second power supply voltage is selected as the input voltage to the load, the second control operation is performed at the same frequency as above and with the switch element on period length being substantially the same as above. is performed, the second and third switch elements are held off, and the first
and a state in which the fourth switch element is turned on and voltage is applied to the load in one direction via the first and fourth switch elements, and a state in which the first and fourth switch elements are turned off and voltage is applied to the load in one direction. A state in which no voltage is applied is alternately repeated.

Since the ratio of the first power supply voltage to the second power supply voltage is 1:2, the power supplied to the load is kept constant regardless of the above selection. Regardless of when the second power supply voltage is applied, when the first power supply voltage is applied, the first
The stress applied to the switch elements from 1 to 4 is relatively small.

Further, the control circuit and the changeover switch can be provided separately from the input circuit from the AC power supply to the load, and the stress placed on the control circuit and the changeover switch can be reduced. Depending on the circuit configuration, it is possible to reduce the stress to substantially zero.

Furthermore, since the operating frequency is the same during the first control operation and the second control operation, and the length of the switch element ON period is also approximately the same, the width of the switch element driving pulse is changed. There is no need for a circuit to turn on the switch element; in order to cope with the difference in the voltage of the AC power source, it is sufficient to simply provide a new switch that turns on or off the switch element. That is, there is no need for a configuration for changing the pulse width, such as in the duty control circuit in the conventional example, and the circuit configuration of the power supply circuit can be simplified.

〔Example〕

An embodiment of this invention will be explained based on FIG. In Figure 1, DB is a rectifier circuit (diode bridge circuit) connected to AC power supply E, C is a smoothing capacitor connected to the output terminal of rectifier circuit DB, and Q ₁ and Q ₂ are connected in series with each other. The first and second switch elements (transistors) Q ₃ and Q ₄ connected in parallel to the smoothing capacitor C are connected in series with each other to form a series connection circuit of the first and second switch elements Q ₁ and Q ₂ . the third connected in parallel to
and a fourth switch element (transistor), L
is between the connection point a between the first and second switch elements Q ₁ and Q ₂ and the connection point b between the third and fourth switch elements Q ₃ and Q ₄ . This is a discharge lamp or any other arbitrary load in which switch elements Q ₁ and Q ₃ are connected in parallel.

Moreover, D ₁ , D ₂ , D ₃ , D ₄ are each switch element Q ₁ ,
This is a feedback diode connected in parallel to Q ₂ , Q ₃ , and Q ₄ , and these diodes operate in an operating state equivalent to a heavy load state with a short reverse voltage application period in an inverter circuit composed of switch elements Q ₁ to Q ₄ . The purpose is to obtain a stable square wave output.

When the power supply E is AC100V, the first and fourth switch elements Q ₁ and Q ₄ are turned on and the second and third switch elements Q ₂ and Q ₃ are turned off, and the first
The first to fourth switch elements are arranged so that the fourth switch elements Q ₁ and Q ₄ are turned off and the second and third switch elements Q ₂ and Q ₃ are turned on, which are alternately repeated. The switch elements Q ₁ to _{Q 4} are configured to be controlled. At this time, the inverter circuit operates as a full bridge inverter circuit. This is the first control operation, and in both of the above states, the current flowing through the load L is in the opposite direction.

When the power supply E is AC200V, the first and fourth switch elements are kept off while the second and third switch elements Q ₂ and Q ₃ are kept off.
The configuration is such that a state in which the first and fourth switch elements Q ₁ and Q ₄ are turned on and a state in which the first and fourth switch elements Q ₁ and Q ₄ are turned off are alternately repeated.
This is the second control operation.

In this operation, the first and fourth switch elements
Instead of turning Q ₁ and Q ₄ on and off and keeping the second and third switch elements Q ₂ and Q ₃ off, the opposite may be done. In this case, in the configuration of the above-mentioned invention, if the second and third are replaced with the first and fourth, and the first and fourth are replaced with the second and third, there will be no contradiction in expression.

A specific example of the control circuit F that controls the above control operation is shown in FIG. In Figure 2, T ₁ is a transformer connected to power supply E, DB ₁ is a rectifier circuit (diode bridge circuit) connected to the output end of transformer T ₁ , and C ₃ is a smoothing capacitor connected in parallel to rectifier circuit DB ₁ . , Ry is a relay coil connected in parallel to capacitor _C3 , and _Sw1 is a normally closed relay switch that responds to relay coil Ry. Relay coil Ry is not excited when power source E is AC100V, and relay switch _Sw1 is in a short-circuited state. Relay coil Ry is excited when power supply E is AC200V, and opens relay switch _Sw1 .

G is a constant voltage circuit connected to the rectifier circuit DB ₁ , H is an oscillation circuit connected to the constant voltage circuit G, FF is a clocked JK flip-flop, and N ₁ and N ₂ are two-stage NAND circuits that have the same two inputs, that is, an inverter ( Note) circuit, N ₃ and N ₄ are AND circuits, T ₂ and T ₃ are AND circuits respectively, transformers connected to the output terminals of N ₃ and N ₄ , q ₂ and q ₃ are secondary windings of transformer T ₂ These are connected between the bases and emitters of second and third switch elements (transistors) Q ₂ and Q ₃ , respectively. q ₁ and q ₄ are the output ends of the secondary winding of the transformer T ₃ , and these are connected between the base and emitter of the first and fourth switch elements (transistors) Q ₁ and Q ₄ , respectively.

The output terminal of the oscillation circuit H is a flip-flop.
It is connected to the clock terminal T of the FF and two input terminals of the NAND circuit _N1 , and the output terminal of the NAND circuit _N2 is connected to one input terminal of each of the two AND circuits _N3 and _N4 . The output terminal of the constant voltage circuit G is connected to the input terminals J and K of the flip-flop FF, and the output terminals Q, of the flip-flop FF are connected to each other by AND.
It is connected to the other input terminal of circuits N ₃ and N ₄ .

The relay switch _Sw1 is inserted into the output line of the AND circuit _N3 . Also, the load L in this case
is equivalent to pure resistance.

Since the input terminals J and K of the clocked JK flip-flop FF are always at a high level due to the output of the constant voltage circuit G, the output terminals Q and K are mutually inverted each time there is a clock input. Also, NAND circuit
The output of _N2 always goes high every time there is a clock input, that is, every time a clock pulse is output from the oscillation circuit H. Therefore, AND
In circuits N ₃ and N ₄ , one input terminal is always at high level each time a clock pulse is input, and the other input terminal is at low level when the previous state is high level, and when the previous state is low level. Flip to high level. Therefore, the outputs of AND circuits _N3 and _N4 are inverted to opposite levels each time a clock pulse is input. That is, AND circuits N ₃ , N ₄
The output voltages V ₃ and V ₄ are as shown in FIG.

At AC100V, relay coil Ry is not excited,
Relay switch Sw ₁ is in the on state. Therefore, both transformers T ₂ and T ₃ are driven, and each control output terminal q ₁ -q ₄ sends a control signal to the switch elements Q ₁ -Q ₄ . That is, the switch elements Q ₁ to _{Q 4} are controlled based on the first control operation described above, and the voltage E ₁ shown in FIG. 4A is applied to the load L. This voltage is a square wave alternating voltage with an amplitude of ±141V.

At AC200V, relay coil Ry is excited,
Relay switch Sw ₁ is turned off. Therefore,
Only the transformer _T3 is driven, and only the output terminals _q1 and _q4 send out control signals to the switch elements _Q1 and _Q4 .
Switch elements Q ₂ and Q ₃ are always off. That is, the switch elements _Q1 to _Q4 are controlled based on the second control operation described above, and the voltage _E2 shown in FIG. 4B is applied to the load L. This voltage has an amplitude of +
It is a square wave positive voltage of 282V.

Since the load L is equivalent to a pure resistance, the current and voltage are in phase, and the power consumed by the load L is equal to the voltage
It is proportional to the waveform area of E ₁ and ₂ . In other words, AC100V
The power consumption is the same at 200 VAC and at 200 VAC.

Furthermore, since the control circuit F and the relay switch _Sw1 operate with small signals, the stress applied to them can be suppressed to a sufficiently low level. Also, at AC100V, the voltage applied to load L is
It is 141V, which is half of AC200V, and therefore the current flowing through switch elements Q ₁ to Q ₄ is also small.
The stress placed on them can also be kept low, improving reliability and extending life.

Furthermore, as shown in Figure 4, since AC is applied to the load L at 100V AC and DC output is applied to the load L at 200V, switch elements Q ₂ , Q ₃ or Switch element Q ₁ ,
All you have to do is turn off the _Q4 pair, and it can be realized with a simple circuit configuration. That is, in this embodiment, the operating frequency is the same during the first control operation and the second control operation, and the length of the switch element ON period is also approximately the same, so that the switch element driving There is no need for a circuit to change the width of the pulse, and in order to cope with the difference in voltage of the AC power supply, it is only necessary to provide a new switch that turns the switch element on or off. In other words, the 6th
A configuration for changing the pulse width, such as the duty control circuit DT shown in the figure, is no longer necessary, and the circuit configuration of the power supply circuit is simplified.

Further, the peak-to-peak values of the power and voltage supplied to the load L can also be made constant at 100V/200V AC.

Note that the following modifications of the above embodiment are also included in this invention.

A thyristor (SCR), gate turn-off thyristor (GTO), or other device is used instead of a transistor as the switch elements _Q1 to _Q4 .

A relay switch is used as a changeover switch for selecting the first and second control operations of the control circuit F.
A manual type instead of an automatic type like Sw ₁ .

The power supply E uses something other than a combination of 100V and 200V with a voltage ratio of 1:2.

Use a single power source E,
It is designed to adjust the input voltage to load L.

[Effect of idea]

According to the power supply circuit of this invention, it is possible to reduce the stress applied to the changeover switch for selecting the input voltage to the load, thereby improving its reliability.

Also, when the power supply voltage is low, AC is applied to the load, and when the power supply voltage is high, DC output is applied to the load, so when the power supply voltage is high, the second and third switch elements or the first and It is only necessary to keep the fourth pair of switch elements turned off, and it can be realized with a simple circuit configuration. In other words, the operating frequency is the same during the first control operation and the second control operation, and the length of the switch element ON period is also approximately the same, so the width of the switch element driving pulse is changed. There is no need for a circuit to turn on the switch element; in order to cope with the difference in the voltage of the AC power source, it is sufficient to simply provide a new switch that turns on or off the switch element. In other words, there is no need for a structure for changing the pulse width like the duty control circuit in the conventional example, and the circuit structure of the power supply circuit can be simplified.

Furthermore, the peak-to-peak values of the power and voltage supplied to the load can be made constant when the power supply voltage is high and low.

[Brief explanation of drawings]

Fig. 1 is an electric circuit diagram of an embodiment of this invention, Fig. 2 is an electric circuit diagram of a specific example of the control circuit of Fig. 1, Figs. 3 and 4 are voltage waveform diagrams,
Fig. 5 is an electric circuit diagram of a conventional example, Fig. 6 is an electric circuit diagram of another conventional example, Fig. 7 is a voltage waveform diagram corresponding to Fig. 6, and Fig. 8 is an electric circuit of yet another conventional example. 9 and 10 are electrical circuit diagrams corresponding to FIG. 8, respectively. E...AC power supply, DB...rectifier circuit, C...smoothing capacitor, _Q1 , _Q2 , _Q3 , _Q4 ...switch element, a, b...connection point, L...load, F... ...control circuit, Sw ₁ ...changeover switch.

Claims (1)

[Claims for Utility Model Registration] A rectifier circuit connected to an AC power supply having a first power supply voltage or a second power supply voltage having a voltage value twice the first power supply voltage, and an output terminal of this rectification circuit. a series connection circuit of a smoothing capacitor connected to the smoothing capacitor, a first and second switch element connected in parallel to this smoothing capacitor, and a series connection circuit of a third and fourth switch element connected in parallel to this series connection circuit. and a state where the first and third switch elements are connected in parallel between the connection point between the first and second switch elements and the connection point between the third and fourth switch elements. a connected load; a state in which the first and fourth switch elements are turned on and the second and third switch elements are turned off; and a state in which the first and fourth switch elements are turned off and the second and the second switch elements are turned off; a first control operation that alternately repeats a state in which the switch element No. 3 is turned on;
The second and third switch elements are kept OFF at the same operating frequency as during this first control operation and the length of the switch element ON period is substantially the same as during the first control operation. 1st and 4th
a control circuit that selectively controls two switch element control operations, a second control operation that alternately repeats a state in which the switch element is turned on and a state in which the first and fourth switch elements are turned off; It is determined whether the power supply voltage of the power supply is the first power supply voltage or the second power supply voltage, and the control operation of the two switch elements of the control circuit is performed when the power supply voltage of the AC power supply is the first power supply voltage. and a changeover switch that selects the first control operation and selects the second control operation when the power supply voltage of the AC power supply is the second power supply voltage.