JPH1187080A - Power source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the voltage across both ends of a capacitor from abnormally rising without detecting a condition of a load. SOLUTION: In a stationary mode, switching elements Q3 , Q4 are turned on/off synchronized with the frequency of an AC power source Ei, and switching elements Q1 , Q2 are turned on/off alternately at a high frequency. During this time, the on-period of the switching elements Q1 , Q2 are controlled so as to the voltage across hold both ends of a capacitor Ce to a reference voltage V11 . When the voltage across both ends of the capacitor Ce reaches a comparative voltage V2 higher than the reference voltage V11 , a nonstationary mode is selected by an action mode switching circuit MD, the switching elements Q1 , Q2 are turned on/off synchronized with the frequency of the AC power source Ei, and the switching elements Q3 , Q4 are tuned on/off at a high frequency. At no-load time, a reference voltage V12 higher than the reference voltage V11 and lower than the relative voltage V2 is selected.

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 charging a capacitor through a boost chopper circuit using an AC power supply as an input power supply and supplying power to a load using the capacitor as a power supply.

[0002]

2. Description of the Related Art Conventionally, a power supply device having a configuration shown in FIG. 4 has been proposed. This power supply device includes four switching elements Q _{1 to} Q ₄ forming a bridge circuit, and each arm of the bridge circuit is connected between both ends of a capacitor Ce. Each diode D ₁ to D ₄ in each of the switching elements Q ₁ to Q ₄ are connected in antiparallel. Here, the reverse current is antiparallel to the switching element Q ₁ to Q ₄ current flows through the orientation when on of the switching elements Q ₁ to Q ₄ a parallel to each of the switching elements Q ₁ to Q ₄ It means that the polarity is flowing. Further, a series circuit of a pair of diodes D ₅ and D ₆ which are rectifiers is connected between both ends of the capacitor Ce. Both diodes D _5, the series circuit of the D ₆ is connected in series circuit with anti-parallel each pair of switching elements Q ₁ to Q ₄ constituting each arm of the bridge circuit. An AC power source Ei is connected between the connection point of the diodes D ₁ and D _{2 and} the connection point of the diodes D ₅ and D _6.
Series circuit of the inductor L ₁ is connected to. further,
Between the connection point of each pair of switching elements Q _{1 to} Q ₄ constituting each arm of the bridge circuit (that is, between the connection point of switching elements Q ₁ and Q _{2 and} the connection point of switching elements Q ₃ and Q ₄ ) , the series circuit of the load circuit Z and the inductor L ₂ is connected.

In this power supply device, in a normal operation, each of the switching elements Q _{1 to} Q ₄ is controlled as shown in FIGS. FIGS. 5A and 6 show the control of the period during which one end of the AC power supply Ei on the connection point side of the diodes D ₅ and D ₆ is positive, and FIGS. 5B and 7 show the above-mentioned one end of the AC power supply Ei. Indicates the control of the period during which is negative. AC power supply E
The operation during the period when the polarity of i is different is that the operations of the switching elements Q ₁ and Q ₂ on the positive side and the negative side of each arm of the bridge-connected switching elements Q _{1 to} Q ₄ are interchanged. replaced the Q _1, the switching element Q _2, be read as a switching element Q ₃ and the switching element Q _4, since the other operations are substantially similar, mainly Fig. 5 (a) below, the control of FIG. 6 The operation will be described for the period during which the operation is performed.

In this period, the switching elements Q ₁ to Q ₁
The operation of the Q ₄ there are three state. That is, the state where the switching elements Q ₂ and Q ₃ are on,
_1, the state Q ₃ is turned on, all the switching elements Q ₁ to Q ₄ may have three states of the state is OFF, these states are repeated in the above order. Now, if what is the steady state, the period P ₁ switching element Q _2, Q ₃ is turned on, the capacitor Ce → switching element Q
₃ → Load circuit Z → Inductor L ₂ → Switching element Q
₂ → A path of capacitor Ce is formed. That is, current flows through the load circuit Z, and the input current from the AC power supply Ei flows, energy is stored in the inductor L _2. Further, when the voltage across the capacitor Ce is lower than the voltage of the AC power supply Ei is conductive and the diode D _5, the AC power supply Ei → diode D ₅ → switching element Q ₃ → load circuit Z → inductor L ₂ → inductor L ₁ → AC A current flows through the path of the power supply Ei.

[0005] In period P ₂ switching elements Q _1, Q ₃ is turned on, current flows through a route of the alternating-current power supply Ei → diode D ₅ → the switching element Q ₁ → inductor L ₁ → AC power supply Ei, the inductor L ₁ Energy is stored. The route of the period P Within _second inductor L ₂ → diode D ₁ → switching element Q ₃ → load circuit Z → inductor L ₂ may be formed, by this route inductor L
₂ stored energy is released. That is, the periods P ₁ , P
_{In (2)} , the capacitor Ce operates as a power supply to operate as a step-down chopper circuit (second chopper circuit) for applying a voltage lower than the voltage across the capacitor Ce to the load circuit Z.

[0006] all periods P ₃ when the switching elements Q ₁ to Q ₄ is turned off, the AC power supply Ei → diode D ₅
→ Capacitor Ce → Diode D ₂ → Inductor L ₁ →
The path of the AC power supply Ei and the AC power supply Ei → diode D ₅
→ a path of the capacitor Ce → diode D ₄ → load circuit Z → inductor L ₂ → inductor L ₁ → AC power supply Ei is formed, the inductor L ₁ accumulated energy of the inductor L _1, L ₂ by this route is released, added voltage between the voltage and the voltage of the AC power source Ei developed across the L ₂ is applied to the capacitor Ce. That is, this power supply circuit also operates as a boost chopper circuit (first chopper circuit) that boosts the voltage between both ends of the capacitor Ce using the AC power supply Ei as a power supply.

[0007] As described above, mainly the capacitor Ce is discharged to the period P _1, and storing energy in the inductor L ₁ by mainly AC power source Ei is the period P _2, the period P
₃ is charged with the capacitor Ce so as to have a voltage higher than the voltage of the AC power supply Ei. In this way, it is possible to prevent an increase in input current distortion input current from the AC power supply Ei flow over the entire period P ₁ to P ₃ substantially. Further, a rectangular wave voltage synchronized with the voltage cycle of the AC power supply Ei is applied to the load circuit Z. As apparent from the above operation, by adjusting the on-period of the switching element Q ₁ in the period P _2, it is possible to control the input current amount from the AC power source i. Here, the AC power supply Ei is supplied through a high-frequency blocking filter (not shown) to prevent high-frequency noise from being mixed into the power supply line. Further, the increase in the input current distortion is suppressed by operating as the step-up chopper circuit as described above, but the capacitor Ce is operated by the operation as the step-down chopper circuit described above.
, The voltage applied to the load circuit Z can be reduced to an appropriate value.

[0008] As apparent from the above description, since the input current of the power supply device can be controlled mainly by the period P _2, the input by adjusting the length of the period P ₂ as indicated by a broken line in FIG. 8 The power can be controlled to some extent (FIG. 8A shows a period in which the one end of the AC power supply Ei is a positive electrode, and FIG. 8B shows a period in which the one end of the AC power supply Ei is a negative electrode. ). That is, if designed in accordance with the time of the rated operation of the load circuit Z, can be maintained at an appropriate value to the voltage across the capacitor Ce by adjusting the period P _2.

When the load circuit Z needs to change the applied voltage according to the operation state, it is necessary to change the voltage across the capacitor Ce in accordance with the operation state of the load circuit Z. For example, if the load circuit Z includes a high-pressure discharge lamp, the capacitor Ce is used before starting.
The voltage applied to the load circuit Z is increased by making the voltage between both ends higher than that at the time of rated lighting, thereby facilitating starting. Therefore, when the load circuit Z includes a high-pressure discharge lamp, the switching elements Q _{1 to} Q
It is possible to control _four .

This circuit includes a discharge lamp La which is a high pressure discharge lamp.
And a parallel circuit of a capacitor C ₂ to a load circuit Z and. Also detects the voltage polarity of the AC power supply Ei by polarity detector circuit PD, and is configured to switch the control procedure of the switching elements Q ₁ to Q ₄ according to the polarity switching circuit PC in accordance with the polarity of the detected AC power supply Ei . The voltage across the capacitor Ce is detected by the voltage detection circuit Vs, the detected voltage is sought is the difference between the reference voltage V _11, V ₁₂ in the error amplifier EA, a control circuit CN in the period P ₂ in accordance with the difference The switching elements Q ₁ and Q ₂ are controlled to adjust the length, and the voltage across the capacitor Ce is maintained at the reference voltages V ₁₁ and V ₁₂ . Here, the length of the period P ₂ is PWM circuit P provided in the second timing generating circuit T ₂
PWM control is performed by M. That is, the voltage detection circuit V
signal having a pulse width corresponding to the difference between the voltage and the reference voltage V _11, V ₁₂ detected by the s is given to the switching element Q ₁ to Q _4. Reference voltage V _11, V ₁₂ is set to 2 stages, it is selected by the changeover switch SW _1. Changeover switch SW ₁ is switched by the lighting discrimination circuit LD is load detecting means according to the lighting and non-lighting of the discharge lamp La. That is, by detecting the voltage between both ends of the discharge lamp La, the lighting determination circuit LD determines that the light is not lit when the detected voltage is higher than the specified value Vx, and determines that the light is lit if the detected voltage is equal to or less than the specified value Vx, as shown in FIG. , when not illuminated (when the voltage across the discharge lamp La is high) switches the changeover switch SW ₁ so as to select the reference voltage V ₁₂ of the higher.

[0011] As apparent from the above description, since both ends of the capacitor Ce is applied to the load circuit Z during the period P _1, the voltage across the capacitor Ce if the period P ₁ longer than during normal operation The period of application to the load circuit Z is lengthened, and starting the discharge lamp La becomes easier. Therefore, in order to control the period P ₁ in the control circuit CN, the reference voltages V ₃₁ and V ₃₂ applied to the first timing generation circuit T ₁
Switch SW ₂ according to the output of the lighting determination circuit LD.
Is switched with. Here, as shown in FIG. 11, the repetition period of the discharge lamp period P ₁ to P ₃ is lit for La and the time of non-lighting is not changed, by changing only the length of the period P _1, P ₂ (FIG. 11A shows the operation at the time of lighting, and FIG. 11B shows the operation at the time of non-lighting).

[0012]

By the way, the above-mentioned circuit
In the road configuration, the period P depends on whether the discharge lamp La is on or off.
₁, P_TwoChange, the lighting discrimination circuit LD is required
It has become. In such a lighting determination circuit LD,
The voltage between both ends of the discharge lamp La is detected as in
The configuration is such that the passing current of the discharge lamp La is detected. Ma
In addition, in the lighting determination circuit LD, the voltage or current generated in a short time is
Filter circuit (low-pass filter)
Data). Providing such a filter circuit
It is possible to distinguish between lighting and non-lighting without responding to instantaneous fluctuations
Voltage or current fluctuations
Time delay from the time when the judgment result is obtained
become. That is, the operation state of the load circuit Z has changed.
There will be a delay before the determination result is obtained later.

On the other hand, the discharge lamp La, which is the load circuit Z having the above-described circuit configuration, has a variable impedance.
When the lamp is not lit, the impedance is large, but immediately after starting, the impedance rapidly decreases. When the discharge lamp La is not lit, the period P ₁ is the steady operation as described above (at rated lighting) longer than, so that the voltage across the capacitor Ce is kept at a high voltage V ₁₂ than during steady operation Period P ₂
Is controlled, the operation characteristics are as shown in FIG. Further, the voltage across the capacitor Ce at the time of steady state operation from time P ₂ is controlled to be kept at the voltage V _11, made on the operating characteristics, such as in Figure 12.

However, immediately after the discharge lamp La is turned on, the output of the lighting discriminating circuit LD indicates that the lamp is not turned on. Therefore, the impedance of the load circuit Z suddenly decreases with the operating characteristics shown in FIG. since it becomes Z _1, even though the voltage across the capacitor Ce is Va if steady operation, so that the voltage across the capacitor Ce is increased to considerably higher Vb than the voltage Va. In addition, the current flowing through the load circuit Z rapidly increases due to the sudden decrease in the impedance. In other words, there is the great stress to the capacitor Ce and the switching element Q ₁ to Q ₄ is applied, a high breakdown voltage, there is a problem that leads to expensive and large become necessary component of a high capacity.

Further, when the impedance of the discharge lamp La during lighting is to have lighting failure in a low state as Z _1, in this case is operating in the operating characteristics of the FIG. 12, lower towards the reference voltage V ₁₁ is selected from being, it is necessary to change the reference voltage V ₁₂ of the higher for restarting,
Since the output of the discharge lamp lighting determination circuit from going out of La LD there is a time delay until they show unlit, there is a problem that there is a time delay before is switched to the higher reference voltage V ₁₂ of restarting is delayed.

The present invention has been made in view of the above circumstances, and has as its object to use, when a load whose impedance or applied voltage changes during operation is used, the change is immediately used for controlling the switching element. It is an object of the present invention to provide a power supply device capable of reflecting the information and avoiding inconvenience due to a delay in detection.

[0017]

According to a first aspect of the present invention, there is provided a first switching element including a series circuit of a first switching element and a first inductor connected between both ends of an AC power supply via a rectifying element. And a first chopper circuit for charging a capacitor by boosting the voltage of the AC power supply by using the stored energy of the first inductor by turning on and off at a frequency higher than the frequency of the AC power supply, and connected between both ends of the capacitor. A second switching element, which includes a series circuit of a second switching element, a second inductor, and a load circuit, is turned on and off at a frequency higher than the frequency of the AC power supply to reduce the voltage across the capacitor and apply the voltage to the load circuit. A second chopper circuit, and a third switching element connected between both ends of the AC power supply via the rectifying element. A third switching element including a series circuit of the second inductor and the load circuit, and turning on and off the third switching element at a frequency higher than the frequency of the AC power supply to charge the capacitor using the energy stored in the first and second inductors; A chopper circuit, a comparator for comparing the voltage between both ends of the capacitor with a prescribed comparison voltage, and a first circuit when the voltage across the capacitor is less than a prescribed comparison voltage.
An operation mode switching circuit for selecting a non-stationary mode for operating the third chopper circuit when the normal mode is selected for operating the chopper circuit and for operating the third chopper circuit at a voltage higher than the comparison voltage, and a voltage between both ends of the capacitor when the normal mode is selected. A steady mode control circuit that adjusts a period for storing energy in the first inductor from the AC power supply through the first or second switching element so as to reduce a difference from a reference voltage set lower than the comparison voltage; Load detecting means for detecting the presence or absence of a load circuit, providing the reference voltage in two stages, and selecting a higher reference voltage when there is no load. According to this configuration, since the switching between the steady mode and the non-steady mode is performed based on the change in the voltage across the capacitor, even when a load such as a discharge lamp whose applied voltage or impedance changes during operation is used. If the change in the operation affects the voltage across the capacitor, it is possible to respond by changing the control state of the switching element immediately without detecting the operation state of the load. Inconveniences, such as a rise in the number, can be prevented. Moreover, even if the load goes out when the load is a discharge lamp or the like, the reference voltage with respect to the voltage between both ends of the capacitor is immediately switched, so that the restart is facilitated.

According to a second aspect of the present invention, there are provided first to fourth switching elements constituting a bridge circuit, first to fourth diodes respectively connected in anti-parallel to each switching element, and first and second switching elements. A capacitor in which a series circuit of the switching element and a series circuit of the third and fourth switching elements are connected between both ends;
And a series circuit of fifth and sixth diodes connected in parallel to the series circuit of the first and second diodes, and a connection point between the connection point of the first and second diodes and the connection point of the fifth and sixth diodes. A series circuit of an AC power supply and a first inductor; a load circuit connected between a connection point of the first and second switching elements and a connection point of the third and fourth switching elements; and a second inductor And a series circuit with
A comparator for comparing the voltage between both ends of the capacitor with a prescribed comparison voltage, and a third and fourth circuit for turning on and off the first and second switching elements at a frequency higher than the frequency of the AC power supply when the voltage between both ends of the capacitor is less than the prescribed comparison voltage. A steady mode in which the fourth switching element is turned on and off at the frequency of the AC power supply is selected, and when the voltage across the capacitor is equal to or higher than a specified comparison voltage, the first and second switching elements are turned on and off at the frequency of the AC power supply. An operation mode switching circuit for selecting a non-stationary mode in which the fourth switching element is turned on and off at a frequency higher than the frequency of the AC power supply, and a voltage lower than the voltage across the capacitor and the comparison voltage when the steady mode is selected. The first or second switch from the AC power supply so as to reduce the difference from the reference voltage. A steady mode control circuit that adjusts a period during which energy is stored in the first inductor through the switching element; and a load detection unit that detects the presence or absence of the load circuit. The reference voltage is provided in two stages, and is high when there is no load. The other reference voltage is selected. According to this configuration, the mode is switched between the steady mode and the non-steady mode based on the change in the voltage across the capacitor.
Even if a load such as a discharge lamp whose applied voltage or impedance changes during operation is used, if the change in operation affects the voltage across the capacitor, the control state of the switching element is immediately changed. Thus, inconveniences such as an increase in the voltage across the capacitor can be prevented without detecting the operation state of the load. Moreover, even if the load goes out when the load is a discharge lamp or the like, the reference voltage with respect to the voltage between both ends of the capacitor is immediately switched, so that the restart is facilitated.

According to a third aspect of the present invention, in the second aspect of the present invention, a pair of switching elements connected in series between both ends of the capacitor via a series circuit of the load circuit and the second inductor are simultaneously turned on. Is set to be longer at the time of no load than at the time of the steady operation. According to this configuration, when a load such as a discharge lamp that needs to apply a higher voltage than at the time of steady operation is used at the time of starting, a period in which a voltage is applied from the capacitor to the load in a no-load state before starting is used. Since the length is longer than in the normal operation, the startability of the discharge lamp can be improved.

A fourth aspect of the present invention is a preferred embodiment in which the load circuit includes a discharge lamp in the first to third aspects of the present invention.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) This embodiment, as shown in FIG. 1, (corresponding to control circuit CN in the configuration of FIG. 9) stationary control circuit AT for controlling the switching element Q ₁ to Q ₄ during steady operation Separately , A non-stationary control circuit BT for turning on and off the switching elements Q _{1 to} Q ₄ in a procedure different from that in the normal operation
Is provided. In addition, the switching elements Q ₁ to Q _{1 in} either the steady control circuit AT or the non-steady control circuit BT.
Or controlling the Q ₄ are adapted to select the operating mode switching circuit MD based on the voltage across the capacitor Ce. The other basic configuration is the same as the configuration shown in FIG. 9, and members having the same functions are denoted by the same reference numerals.

An AC power supply Ei, which is a commercial power supply, switching elements Q _{1 to} Q ₄ , a capacitor Ce, an inductor L ₁ ,
The connection relationship between L ₂ and diodes D _{1 to} D ₆ is substantially the same as the configuration shown in FIG. As the load circuit Z be connected to one parallel circuit of a discharge lamp La and the capacitor C _2,
Capacitor C ₂ constitute a resonance circuit together with the inductor L _2. Further, the switching element Q ₁ to Q ₄ uses a MOSFET, the diode D ₁ to D ₄ are diverted parasitic diode of the MOSFET. These points are also similar to the configuration shown in FIG. Similarly to the configuration shown in FIG. 9, in the present embodiment, the switching elements Q ₁ to Q ₁
Q ₄ is controlled by the polarity switching circuit PC, the polarity detection circuit polarity switching circuit PC detects the polarity of the AC power supply Ei PD
The control procedure is switched according to the output of.

By the way, as described above, in this embodiment,
Has a stationary control circuit AT and an unsteady control circuit BT.
It is. Output of steady control circuit AT and unsteady control circuit BT
The operation mode switching circuit MD
Selected by. Off by operation mode switching circuit MD
The switching timing will be described later. During rated operation (steady state
During operation), keep the voltage across the capacitor Ce constant.
Sea urchin period P_TwoIs changed, and the structure shown in FIG. 9 is changed.
The voltage for detecting the voltage across the capacitor Ce in the same manner as
A detection circuit Vs is provided, and the detection is performed by the voltage detection circuit Vs.
The voltage Vce across the capacitor Ce and the reference voltage V₁₁, V₁₂
Is determined by the error amplifier EA.
The input voltage to the steady control circuit AT is changed according to the output of the EA.
Period P_TwoControl. That is, the capacitor C
The voltage Vce across the terminal e is set to the error amplifier EA.
Reference voltage V₁₁, V₁₂If lower than period P _TwoLonger, both
The terminal voltage Vce is equal to the reference voltage V₁₁, V₁₂If higher than period
P_TwoIs shortened, and this operation makes the capacitor C
The voltage Vce across e is kept constant.

On the other hand, in the non-stationary control circuit BT, the period P ₂ is fixedly set. A period P ₁ in the stationary control circuit AT and unsteady control circuit BT is kept constant at the same length. Incidentally, the mode switching circuit MD is controlled by the output of the comparator CP ₁ for comparing the magnitude relation between the voltage across Vce with the comparison voltage V ₂ of capacitor Ce detected by the voltage detection circuit _{Vs (> V 11, V 12} ), voltage across Vce of the capacitor Ce is the steady mode to a lower period than the comparison voltage V _2, the high period to control the mode switching circuit MD to select the non-stationary mode. Here, the reason the comparison voltage V ₂ is set higher than the reference voltage V _11, V _12, the comparison voltage V ₂ is the voltage that determines the switching point of the unsteady behavior and the steady operation, the reference voltage V ₁₁ ,
V ₁₂ is because determining the reference value of the control within a range of steady state operation.

With the above configuration, the voltage Vce across the capacitor Ce changes as shown in FIG. That is,
The voltage Vce across the capacitor Ce is kept constant (that is, the reference voltage V ₁₁ ) near the impedance of the discharge lamp La at the time of rated operation, and the smaller the impedance, the higher the voltage Vce between both ends (FIG. 2). .

Further, since the discharge lamp reference voltage V ₁₂ when the discharge lamp La is not lighted as before the start of the La is selected (in FIG. 2), the voltage across Vce of the capacitor Ce in impedance is large area When the impedance is kept constant at V ₁₂ and the impedance becomes small, the voltage V
ce will rise than the V _12. When the voltage across Vce of the capacitor Ce and the impedance of the discharge lamp La becomes even smaller to reach the comparison voltage V _2, the process proceeds to a non-steady operation from a steady operation (in FIG. 2). In this embodiment,
Because they were set equal to the period P ₁ in the steady operation and the unsteady operation, the voltage across Vce of the capacitor Ce at the time of the transition to non-steady operation from a steady operation (= V _2), the voltage obtained by the unsteady behavior And the voltage Vce across the capacitor Ce decreases. Therefore, the comparison voltage V
_The voltage Vce between both ends of the capacitor Ce is going to fall below 2, and the mode returns to the steady mode again, and the voltage Vce between both ends of the capacitor Ce is going to rise again. Thus, the voltage across Vce of the capacitor Ce is kept in the vicinity of the reference voltage V ₂ by the steady operation and the unsteady operation are alternately repeated.

[0027] As described above, since the switching control of the steady operation and the unsteady operation is selected by comparing the comparison voltage V ₂ and the voltage across Vce of the capacitor Ce, there is a time delay in the lighting determination circuit LD even, the voltage across Vce of the capacitor Ce is the never rises to the reference voltage V ₂ or more. As a result, it is possible to use a withstand voltage is relatively low small and inexpensive as circuit components such as capacitors Ce and switching elements Q ₁ to Q _4.
Further, since the steady operation and the unsteady operation are performed irrespective of the detection of lighting / non-lighting of the discharge lamp La, no special circuit is required as the lighting determination circuit LD.

[0028] (Embodiment 2) This embodiment, as shown in FIG. 3, a two-step period P ₁ in the stationary mode in response to addition to the configuration of the discharge lamp La or the lighting or non-lighting Embodiment 1 It is designed to be switched. That is, a part of the configuration shown in FIG. 9 is added to the configuration of the first embodiment. In the steady control circuit AT, the reference voltages V ₃₁ and V ₃₂ that determine the length of the period P ₁ are changed by the lighting determination circuit LD. Switching is performed according to the output. Specifically longer than the time of lighting the period P ₁ during a period the discharge lamp La is not lighted.

According to this configuration, the period P ₁ is extended before the discharge lamp La is started, and the reference voltage V during the period P ₂ is increased.
₁₂ is set higher than that during normal operation, the discharge lamp La
The high voltage required for starting can be applied to the motor. Also,
Since the load circuit Z after the start of the discharge lamp La is the voltage across Vce of the capacitor Ce even if rising of the output despite lighting determination circuit LD has become low impedance is delayed is not higher than the comparison voltage V _2, it is not necessary to use a high-voltage as a component such as a capacitor Ce and the switching elements Q ₁ to Q _4. Moreover, even if the rise of the output of the lighting determination circuit LD is delayed immediately after the start of the discharge lamp La, the voltage Vce across the capacitor Ce
Unsteady mode transition to, voltage across Vce than is kept comparison voltage V ₂ or less as possible from the steady mode based on. Other configurations and operations are the same as those of the first embodiment.

[0030]

According to the first aspect of the present invention, the first switching element includes a series circuit of a first switching element and a first inductor connected between both ends of the AC power supply via a rectifying element, and the first switching element is connected to the AC power supply. By turning on and off at a frequency higher than the frequency, the voltage of the AC power supply is boosted using the energy stored in the first inductor to charge the capacitor.
And a second switching element connected between both ends of the capacitor, a series circuit of a second inductor and a load circuit, and turning on and off the second switching element at a frequency higher than the frequency of the AC power supply. A second chopper circuit for stepping down a voltage between both ends of the capacitor and applying the voltage to a load circuit, a third switching element connected between both ends of the AC power supply via the rectifying element, and first and second inductors; A third switching element that includes a series circuit with the load circuit and turns on and off a third switching element at a frequency higher than the frequency of the AC power supply to charge a capacitor using energy stored in the first and second inductors;
A chopper circuit, a comparator for comparing the voltage between both ends of the capacitor with a specified comparison voltage, and a stationary mode for operating the first chopper circuit when the voltage between both ends of the capacitor is less than the specified comparison voltage. Third
An operation mode switching circuit for selecting an unsteady mode for operating the chopper circuit, and reducing a difference between a voltage across the capacitor and a reference voltage set lower than the comparison voltage when the steady mode is selected. A steady mode control circuit that adjusts a period during which energy is stored in the first inductor from the AC power supply through the first or second switching element, and load detection means that detects the presence or absence of a load circuit. In addition to providing two levels of voltage, it selects the higher reference voltage when there is no load, and switches between the steady mode and the non-steady mode based on the change in the voltage across the capacitor. Even if a load such as a discharge lamp with a variable impedance is used, the change in operation will affect the voltage across the capacitor In the case of a change in the degree, the control state of the switching element can be changed immediately to cope with it, and the advantage that the inconvenience such as a rise in the voltage across the capacitor can be prevented without detecting the operation state of the load. Moreover, even if the load goes out when the load is a discharge lamp or the like, the reference voltage with respect to the voltage between both ends of the capacitor is immediately switched, so that there is an advantage that the restart becomes easy.

According to a second aspect of the present invention, there are provided first to fourth switching elements forming a bridge circuit, first to fourth diodes respectively connected in anti-parallel to each switching element, and first and second switching elements. A capacitor in which a series circuit of the switching element and a series circuit of the third and fourth switching elements are connected between both ends;
And a series circuit of fifth and sixth diodes connected in parallel to the series circuit of the first and second diodes, and a connection point between the connection point of the first and second diodes and the connection point of the fifth and sixth diodes. A series circuit of an AC power supply and a first inductor; a load circuit connected between a connection point of the first and second switching elements and a connection point of the third and fourth switching elements; and a second inductor And a series circuit with
A comparator for comparing the voltage between both ends of the capacitor with a prescribed comparison voltage, and a third and fourth circuit for turning on and off the first and second switching elements at a frequency higher than the frequency of the AC power supply when the voltage between both ends of the capacitor is less than the prescribed comparison voltage. A steady mode in which the fourth switching element is turned on and off at the frequency of the AC power supply is selected, and when the voltage across the capacitor is equal to or higher than a specified comparison voltage, the first and second switching elements are turned on and off at the frequency of the AC power supply. An operation mode switching circuit for selecting a non-stationary mode in which the fourth switching element is turned on and off at a frequency higher than the frequency of the AC power supply, and a voltage lower than the voltage across the capacitor and the comparison voltage when the steady mode is selected. The first or second switch from the AC power supply so as to reduce the difference from the reference voltage. A steady mode control circuit that adjusts a period during which energy is stored in the first inductor through the switching element; and a load detection unit that detects the presence or absence of the load circuit. The reference voltage is provided in two stages, and is high when there is no load. Since the switching between the steady mode and the non-steady mode is performed based on the change in the voltage across the capacitor, a load such as a discharge lamp whose applied voltage or impedance changes during operation is selected. Even if it is used, if the change in the operation affects the voltage across the capacitor, it is possible to respond by changing the control state of the switching element immediately,
This has the advantage of preventing inconveniences such as an increase in the voltage across the capacitor without detecting the operating state of the load.Moreover, even if the load goes out when the load is a discharge lamp, the voltage across the capacitor can be reduced. Has an advantage that the reference voltage is immediately switched, so that the restart is easy.

According to a third aspect of the present invention, the load circuit and the second
The period during which the pair of switching elements connected in series between both ends of the capacitor are simultaneously turned on via a series circuit with the inductor is set so as to be longer at the time of no load than at the time of steady operation. When using a load such as a discharge lamp that requires a higher voltage to be applied at start-up than during steady-state operation, the period during which voltage is applied from the capacitor to the load in a no-load state before starting is longer than during steady-state operation. Since it becomes longer, there is an advantage that the startability of the discharge lamp can be improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment.

FIG. 2 is an operation explanatory view of the above.

FIG. 3 is a circuit diagram showing a second embodiment.

FIG. 4 is a circuit diagram showing a conventional example.

FIG. 5 is an operation explanatory view of the above.

FIG. 6 is an operation explanatory view of the above.

FIG. 7 is an operation explanatory diagram of the above.

FIG. 8 is an operation explanatory view of the above.

FIG. 9 is a circuit diagram showing an improved example.

FIG. 10 is an operation explanatory view of the above.

FIG. 11 is an operation explanatory diagram of the above.

FIG. 12 is an operation explanatory view of the above.

[Explanation of symbols]

AT stationary control circuit BT unsteady control circuit C ₂ capacitor Ce capacitor CP comparator D ₁ to D ₆ diodes EA error amplifier L _1, L ₂ inductor La discharge lamp MD operation mode switching circuit PC polarity switching circuit PD polarity detecting circuits Q ₁ ~ Q ₄ switching element SW ₁ , SW ₂ switch element Vs voltage detection circuit Z load circuit

Claims (4)

[Claims] An AC power supply includes a series circuit of a first switching element and a first inductor connected via a rectifying element between both ends of the AC power supply, and turns on and off the first switching element at a frequency higher than the frequency of the AC power supply. By the first
A first chopper circuit that boosts the voltage of an AC power supply using the stored energy of the inductor to charge a capacitor;
A second switching element connected between both ends of the capacitor, a series circuit of a second inductor and a load circuit, and a second switching element that is turned on and off at a frequency higher than the frequency of the AC power supply, thereby forming a voltage across the capacitor. A second chopper circuit for applying a voltage to the load circuit, and a third switching element connected between both ends of the AC power supply via the rectifying element, first and second inductors, and the load circuit. A third chopper circuit that includes a series circuit and charges a capacitor using stored energy in the first and second inductors by turning on and off a third switching element at a frequency higher than the frequency of the AC power supply; A comparator for comparing the voltage with a specified comparison voltage; and a comparator when the voltage across the capacitor is less than the specified comparison voltage. An operation mode switching circuit for selecting a non-stationary mode for operating the third chopper circuit when the normal mode is selected for operating the chopper circuit and for operating the third chopper circuit at a voltage higher than the comparison voltage, and a voltage between both ends of the capacitor when the normal mode is selected. A steady mode control circuit that adjusts a period for storing energy in the first inductor from the AC power supply through the first or second switching element so as to reduce a difference from a reference voltage set lower than the comparison voltage; And a load detecting means for detecting the presence or absence of a load circuit, providing the reference voltage in two stages, and selecting a higher reference voltage when there is no load. 2. The first to fourth elements constituting a bridge circuit.
, A first to a fourth diode respectively connected in anti-parallel to each switching element, a series circuit of the first and second switching elements, and a series circuit of the third and fourth switching elements. A capacitor connected between both ends, a series circuit of fifth and sixth diodes connected in parallel to a series circuit of the first and second diodes, a connection point of the first and second diodes, A series circuit of an AC power supply and a first inductor connected between a connection point of a sixth diode, a connection point of a first and a second switching element, and a connection point of a third and a fourth switching element; A series circuit of a load circuit connected to the second inductor and a second inductor, a comparator for comparing the voltage across the capacitor with a prescribed comparison voltage,
When the voltage between both ends of the capacitor is less than a prescribed comparison voltage, a steady mode in which the first and second switching elements are turned on and off at a frequency higher than the frequency of the AC power supply and the third and fourth switching elements are turned on and off at the frequency of the AC power supply. When the voltage across the capacitor is equal to or higher than a prescribed comparison voltage, the first and second switching elements are turned on and off at the frequency of the AC power supply, and the third and fourth switching elements are turned on and off at a frequency higher than the frequency of the AC power supply. An operation mode switching circuit for selecting an unsteady mode, and an AC power supply for reducing a difference between a voltage across the capacitor and a reference voltage set lower than the comparison voltage when the steady mode is selected. The period for storing energy in the first inductor through the first or second switching element is adjusted. And the steady mode control circuit, said a load detecting means for detecting the presence or absence of the load circuit, together with the reference voltage a two stage providing a power supply and selects the the higher reference voltage at the time of no load device. 3. A period in which a pair of switching elements connected in series between both ends of the capacitor through a series circuit of the load circuit and a second inductor is simultaneously turned on, the period during which no load is applied is longer than during normal operation. 3. The power supply according to claim 2, wherein the power supply is set to be longer. 4. The power supply device according to claim 1, wherein the load circuit includes a discharge lamp.