JP3726636B2 - Power supply - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power supply device, and particularly to a power supply device having a high input power factor and a function of improving input current distortion.
[0002]
[Prior art]
Conventionally, for example, a power supply device as shown in FIG. 6 has been provided. This power supply device is connected to the AC power source E via the filter circuit 1 and connected to the rectifier DB composed of a diode bridge for rectifying the AC power source E, and connected to the rectifier DB via the impedance circuit 4 and outputs the output voltage of the rectifier DB. A half bridge that has a smoothing circuit 3 for smoothing and a series circuit of switching elements Q1 and Q2 such as FETs connected in parallel to the rectifier DB, converts the voltage smoothed by the smoothing circuit 3 into a high-frequency voltage and supplies it to a load Type inverter circuit 2 and a control circuit 20 for turning on / off switching elements Q1, Q2.
[0003]
The filter circuit 1 includes a capacitor C7, a transformer L3 as a common mode filter, and an inductor L4 as a normal mode filter, and blocks high frequency from the AC power source E.
[0004]
A small-capacitance capacitor C1 is connected between the output terminals of the rectifier DB, and the output voltage from the rectifier DB becomes a pulsating voltage.
[0005]
The impedance circuit 4 includes a series circuit of diodes D1 and D2, and a capacitor C2 connected in parallel to the diode D2. The cathode of the diode D1 is connected to the low potential side output terminal of the rectifier DB, and the anode of the diode D2 is The inverter circuit 2 is connected to the switching element Q2 on the low potential side. The impedance circuit 4 improves the input current harmonic distortion.
[0006]
The smoothing circuit 3 includes a capacitor C5 connected in parallel to the rectifier DB, a series circuit of an inductor L1 and a smoothing capacitor C3 and a diode D4 connected in parallel to the capacitor C5, and a cathode connected to a connection point of the capacitor C5 and the inductor L1. A diode D5 whose anode is connected to the connection point of the smoothing capacitor C3 and the diode D4, and a diode D3 whose anode is connected to the anode of the diode D5 and whose cathode is connected to the connection point of the switching elements Q1 and Q2 are provided. Yes. The connection point between the anode of the diode D4 and the capacitor C5 is connected to the low potential side output terminal of the rectifier DB via the impedance circuit 4 and is grounded, and the connection point between the inductor L1 and the capacitor C5 is the high point of the rectifier DB. It is connected to the potential side output terminal.
[0007]
Such a smoothing circuit 3 charges the smoothing capacitor C3 during a period in which the output voltage of the rectifier DB is larger than a predetermined value, and charges the smoothing capacitor C3 when the output voltage of the rectifier DB falls below a predetermined value. This is a partial smoothing circuit that discharges and smoothes the valley of the output voltage of the rectifier DB, and operates as a so-called step-down chopper circuit when the switching element Q2 is turned on / off. When the switching element Q2 is turned on, the AC power supply E, filter circuit 1, rectifier DB, inductor L1, smoothing capacitor C3, diode D3, switching element Q2, capacitor C2 or diode D2, diode D1, rectifier DB, filter circuit 1, AC A charging current flows through the smoothing capacitor C3 through the path of the power source E, and the smoothing capacitor C3 is charged. The charging operation to the smoothing capacitor C3 is performed only when the output voltage of the rectifier DB is higher than the voltage across the smoothing capacitor C3. The smoothing capacitor C3 is discharged when the output voltage of the rectifier DB is lower than the voltage across the smoothing capacitor C3. The electric charge is discharged from the smoothing capacitor C3 to the capacitor C5 via the diode D4 and accumulated in the capacitor C5. The generated electric charge acts as a power source supplied to the inverter circuit 2. As a result, the voltage Vdc across the capacitor C5 as the input power supply voltage of the inverter circuit 2 is valley-filled with the DC voltage of the smoothing capacitor C3 in the valley portion of the pulsating voltage obtained by full-wave rectifying the AC power supply voltage Vs of the AC power supply E. The so-called partially smoothed power supply voltage is obtained.
[0008]
The inverter circuit 2 includes a transformer T1 having a primary winding T1a connected between a connection point of the switching elements Q1 and Q2 and a connection point of the diodes D1 and D2 via a DC cut capacitor C4, and is a load. The series circuit of the discharge lamps La1 and La2 is connected in parallel to the secondary winding T1b of the transformer T1 via a DC cut capacitor C8. Further, a capacitor C6 is connected in parallel to the series circuit of the discharge lamps La1 and La2, and the resonance voltage generated at both ends of the capacitor C6 is supplied to the discharge lamps La1 and La2 as the output voltage of the inverter circuit 2.
[0009]
The circuit operation of the power supply device as described above will be described below.
[0010]
When the switching element Q1 is turned on, from the AC power source E, the filter circuit 1, the rectifier DB, the switching element Q1, the primary winding T1a of the transformer T1, the capacitor C4, the diode D1, the rectifier DB, the filter circuit 1, and the AC power source E Current flows through the path. When the switching element Q1 is turned off and the switching element Q2 is turned on, the transformer T1, the capacitor C4, and the capacitors C4, C4, C6, C8, the transformer T1, the capacitor C4, and the discharge lamp La1, La2 are used. A regenerative current flows through the path of C2, the built-in diode of the switching element Q2, and the transformer T1, and charges are accumulated in the capacitor C2. When the combined voltage of the charging voltage of the capacitor C2 and the output voltage of the rectifier DB (the voltage across the capacitor C1) exceeds the voltage Vdc across the capacitor C5, the charges of the capacitors C1 and C2 are charged into the capacitor C5 via the diode D1. The
[0011]
Then, using the capacitor C4 as a power source, a current flows through the path of the capacitor C4, the transformer T1, the switching element Q2, the capacitor C2, and the capacitor C4. When the charging voltage of the capacitor C2 becomes 0 V, the diode D2 is turned on. When the switching element Q2 is turned off and the switching element Q1 is turned on, a regenerative current flows through the path of the transformer T1, the built-in diode of the switching element Q1, the capacitor C5, the diode D2, the capacitor C4, and the transformer T1. Thereafter, a current flows through the path of the capacitor C5, the switching element Q1, the transformer T1, the capacitor C4, the capacitor C2, and the capacitor C5, the capacitor C2 is charged, and the combined voltage of the capacitor C1 and the capacitor C2 is generated across the capacitor C5. When the voltage Vdc is exceeded, the charges of the capacitors C1 and C2 are supplied as charge to the capacitor C5, and again the AC power supply E, the filter circuit 1, the rectifier DB, the switching element Q1, the transformer T1, the capacitor C4, the diode D1, and the rectifier DB. The input current flows through the path of the filter circuit 1 and the AC power source E. The above operation is repeated. That is, the charging and discharging of the capacitor C2 is repeated by the switching operation of the switching elements Q1 and Q2, and the diode D1 compares the combined voltage of the charging voltage of the capacitor C2 and the output voltage of the rectifier DB with the voltage Vdc across the capacitor C5. An input current is supplied from the AC power source E.
[0012]
By the way, the above-described power supply apparatus is configured such that the first detection circuit 5a that detects a voltage fluctuation in one cycle of the AC power supply voltage Vs from the both-ends voltage Vfe of the impedance circuit 4, and the AC from the both-ends voltage Vdc of the capacitor C5 of the smoothing circuit 3. The control circuit 20 includes a drive circuit 21 for turning on / off the switching elements Q1 and Q2 and a detection result of the second detection circuit 5b. The on-duty control circuit 22 that outputs a control signal for changing the on-duty of the first and second switching elements Q1 and Q2 to the drive circuit 21, and the switching elements Q1 and Q2 according to the detection result of the first detection circuit 5a Frequency control circuit 2 for outputting a control signal for changing the operating frequency of Q2 to the drive circuit 21 via the on-duty control circuit 22 It is provided with a door.
[0013]
The first detection circuit 5a includes a resistor R1 connected between the low potential side output terminal of the rectifier DB and the input terminal of the frequency control circuit 23, and the second detection circuit 5b includes the capacitor C5 of the smoothing circuit 3. And a resistor R2 connected between the connection point of the inductor L1 and the input end of the duty control circuit 22.
[0014]
Here, the voltage Vdc across the capacitor C5 of the smoothing circuit 3 is a valley of a pulsating voltage obtained by full-wave rectifying the AC power supply voltage Vs of the AC power supply E shown in FIG. The second detection circuit 5b detects the voltage fluctuation of the AC power supply voltage Vs from the voltage Vdc, and the duty control circuit 22 according to the voltage fluctuation. Changes the on-duty of the switching elements Q1, Q2 via the drive circuit 21.
[0015]
For example, as shown in FIG. 8 (a), when the amplitude of the AC power supply voltage Vs fluctuates large or small as shown by the dotted line from the reference indicated by the solid line in the figure, that is, when the effective value of the AC power supply voltage Vs fluctuates. The voltage Vdc fluctuates large or small as shown by the dotted line from the reference shown by the solid line in the figure according to the voltage fluctuation of the AC power supply voltage Vs as shown in FIG. When the voltage Vdc increases, the duty control circuit 22 of the control circuit 20 increases the degree of imbalance during the conduction period of the switching elements Q1 and Q2 to reduce the power supplied to the discharge lamps La1 and La2, and when the voltage Vdc decreases. Even when the on-duty of the switching elements Q1 and Q2 is controlled according to the fluctuation of the voltage Vdc so that the degree of imbalance in the conduction period is reduced and the supplied power is increased, the effective value of the AC power supply voltage Vs also fluctuates. Stable power is supplied to the discharge lamps La1 and La2.
[0016]
Further, as shown in FIG. 7B, the both-end voltage Vfe of the impedance circuit 4 is a peak portion of a pulsating voltage obtained by full-wave rectification of the AC power supply voltage Vs of the AC power supply E shown in FIG. Is output to the power source trough with a substantially triangular waveform. The first detection circuit 5a detects a voltage fluctuation near the zero cross of one cycle of the AC power supply voltage Vs from the voltage Vfe, and the frequency control circuit 23 switches the switching element via the drive circuit 21 according to the voltage fluctuation. The operating frequencies of Q1 and Q2 are changed. As a result, even when the voltage value of the voltage Vdc drops in the power source valley portion, the control circuit 20 causes the operating frequency of the switching elements Q1, Q2 to be higher than the operating frequency of the power source peak portion as the voltage value of the voltage Vfe increases. The input power factor can be increased without increasing or decreasing the input current (lamp current), and the inverter circuit 2 can be prevented from performing a phase advance operation.
[0017]
As described above, the conventional power supply device includes the duty control circuit 22 and the frequency control circuit 23 in the control circuit 20, and the first and second detection circuits 5a and 5b. And frequency control are combined to have an output fluctuation suppressing effect that suppresses output fluctuations with respect to voltage fluctuations of the AC power supply voltage Vs, and a phase advance operation suppressing effect in the power source troughs.
[0018]
[Problems to be solved by the invention]
However, when the on-duty is changed, the on-duty at the time of steady operation becomes unbalanced, the direct current component is superimposed on the discharge lamps La1 and La2, and the brightness decreases in the vicinity of the filaments serving as the anodes of the discharge lamps La1 and La2. There was a problem of causing a cataphoresis phenomenon.
[0019]
In order to prevent the occurrence of the cataphoresis phenomenon, it is considered effective to fix the on-duty to about 50% and prevent the DC component from being superimposed on the discharge lamps La1 and La2. However, if the on-duty is fixed, the output fluctuation suppressing effect against fluctuations in the AC power supply voltage Vs cannot be obtained.
[0020]
The present invention aims to solve the above-described problems, and provides a power supply apparatus that prevents the occurrence of a cataphoresis phenomenon, suppresses output fluctuation when the AC power supply voltage fluctuates, and suppresses the phase advance operation of the inverter circuit. To do.
[0021]
[Means for Solving the Problems]
To achieve the above object, the invention of claim 1 includes a rectifier that rectifies an AC power supply, a smoothing circuit that is connected to the rectifier via an impedance element and smoothes the output voltage of the rectifier, and at least one switching element. An inverter circuit that converts the voltage smoothed by the smoothing circuit into a high-frequency voltage and supplies the high-frequency voltage to the load; a control circuit that turns on and off the switching element; and a first that detects voltage fluctuation in one cycle of the AC power supply voltage And a second detection circuit that detects voltage fluctuations in the AC power supply voltage, The smoothing circuit has a smoothing capacitor and charges the smoothing capacitor during a period when the output voltage of the rectifier is larger than a predetermined value. When the output voltage of the rectifier falls below the predetermined value, the charge charged in the smoothing capacitor is discharged. A partial smoothing circuit for smoothing the valley of the output voltage of the rectifier, The control circuit keeps the on-duty of the switching element substantially constant and sets the operating frequency of the switching element. The first change rate is changed according to the detection result of the first detection circuit, the first change rate is changed according to the detection result of the second detection circuit, and the first change rate with respect to the second change rate is changed. The rate of change rate is made approximately equal to the rate of the smoothed portion voltage to the output voltage fluctuation width of the smoothing circuit in one cycle of the AC power supply voltage. By preventing the occurrence of cataphoresis by keeping the on-duty substantially constant, Also, The operating frequency of the switching element is changed according to the detection result of the first detection circuit. By making the ratio of the first rate of change to the second rate of change approximately equal to the ratio of the smoothed portion voltage to the output voltage fluctuation width of the smoothing circuit in one cycle of the AC power supply voltage, The phase advance operation of the inverter circuit can be suppressed. ,further, By changing the operating frequency of the switching element according to the detection result of the second detection circuit, output fluctuation when the AC power supply voltage fluctuates can be suppressed.
[0024]
Claim 2 The invention of claim 1's In the invention, the inverter circuit is a half-bridge type inverter circuit in which a series circuit of two switching elements is connected in parallel to a rectifier, and the control circuit sets the on-duty of each switching element to about 50%. As a feature, by making the on-duty of the switching element about 50%, the occurrence of the cataphoresis phenomenon can be prevented more reliably.
[0025]
Claim 3 The invention of claim 1 or 2 In the invention, the first detection circuit detects a voltage fluctuation of one cycle of the AC power supply voltage from the voltage across the impedance element. 1 or 2 The same effect as that of the present invention can be obtained.
[0026]
Claim 4 The invention of claim 1 to claim 1 3 In any one of the inventions, the second detection circuit detects a voltage fluctuation of the AC power supply voltage from a voltage across the smoothing circuit. 3 The same effect as any one of the inventions is achieved.
[0027]
Claim 5 The invention of claim 1 or 2 In the present invention, the first and second detection circuits divide the voltage applied between the output terminal of the smoothing circuit and the output terminal connected to the impedance element of the rectifier, and control the divided voltage. It is characterized by comprising a voltage dividing circuit that outputs to the circuit, and the first and second detection circuits are constituted by voltage dividing circuits having both functions, so that the input terminal of the control circuit is made one. The configuration can be simplified.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
Since the basic configuration in the present embodiment is the same as that of the conventional example, common portions are denoted by the same reference numerals, description thereof is omitted, and only the portions that characterize the present embodiment will be described in detail.
[0029]
As shown in FIGS. 1 and 2, the control circuit 10 according to the present embodiment corresponds to the detection results of the drive circuit 11 for turning on / off the switching elements Q1 and Q2 and the first and second detection circuits 5a and 5b. And a frequency control circuit 13 for outputting a control signal for changing the operating frequency of the first and second switching elements Q1, Q2 to the drive circuit 11, and the on-duty of the switching elements Q1, Q2 is kept substantially constant.
[0030]
The first detection circuit 5a detects a voltage fluctuation of one cycle of the AC power supply voltage Vs from the both-ends voltage Vfe of the impedance circuit 4 as in the conventional example, and increases when the voltage increases according to the detected voltage fluctuation. Conversely, the first modulation current, which decreases as the voltage decreases, is output to the frequency control circuit 13 of the control circuit 10. Similarly to the conventional example, the voltage Vfe is the minimum at the power supply peak and the maximum at the power supply valley, and accordingly, the first modulation current is also minimum at the power supply peak and maximum at the power supply valley.
[0031]
The frequency control circuit 13 of the control circuit 10 changes the operating frequency of the switching elements Q1 and Q2 at a first rate of change according to the detection result of the first detection circuit 5a based on the current value fluctuation of the first modulation current. . The first rate of change is a value obtained by dividing the fluctuation range of the operating frequency of the switching elements Q1 and Q2 by the fluctuation range of the voltage detected by the detection circuit 5a.
[0032]
By such a frequency control circuit 13, the operating frequency of the switching elements Q1 and Q2 is controlled to be low at the power source peak and high at the power source trough, thereby suppressing the phase advance operation of the inverter circuit at the power source trough. be able to.
[0033]
The second detection circuit 5b detects the voltage fluctuation of the AC power supply voltage Vs from the voltage Vdc across the smoothing circuit 3 as in the conventional example, and increases when the voltage increases according to the detected voltage fluctuation. A second modulation current that decreases as the voltage decreases is output to the frequency control circuit 13 of the control circuit 10.
[0034]
The frequency control circuit 13 of the control circuit 10 changes the operating frequency of the switching elements Q1, Q2 at a second rate of change according to the detection result of the second detection circuit 5b based on the current value fluctuation of the second modulation current. . Note that the second rate of change is a value obtained by dividing the fluctuation range of the operating frequency of the switching elements Q1 and Q2 by the fluctuation range of the voltage detected by the detection circuit 5b.
[0035]
The frequency control circuit 13 increases the operating frequency of the switching elements Q1 and Q2 by increasing the second modulation current when the amplitude of the AC power supply voltage Vs increases and the effective value increases, and the AC power supply E When the effective value becomes smaller due to the decrease in the amplitude of the switching element Q1, the operating frequency of the switching elements Q1 and Q2 is lowered by the decrease in the second modulation current to suppress the output fluctuation due to the fluctuation of the effective value of the AC power supply voltage Vs. Can do.
[0036]
Furthermore, the cataphoresis phenomenon can be prevented from occurring by making the on-duty constant at all times during the operation of the device. For example, the cataphoresis phenomenon can be prevented more reliably by setting the on-duty to about 50%. can do.
[0037]
By the way, as shown in FIG. 7B, the control circuit 20 of the conventional example has a maximum operating frequency at the power source valley when the fluctuation width of the voltage Vfe at the power source valley and the power source peak is Vs1. The phase advance operation at the power source trough portion is suppressed by increasing the operating frequency at the power source peak portion by the variation of Vs1.
[0038]
Here, simply changing the operating frequency of the switching elements Q1 and Q2 according to the respective fluctuations of the voltage Vdc and the voltage Vfe, as shown in FIG. 3, the maximum value of the voltage Vfe at the power source valley and the power source peak The difference Vs2 from the maximum value of the voltage Vdc at the portion is smaller than Vs1. As a result, the operating frequency at the power source valley can be increased from the operating frequency of the power source peak only by the fluctuation up to Vs2 smaller than Vs1, and the phase advance operation may not be sufficiently suppressed. .
[0039]
Therefore , The first change rate is made larger than the second change rate, and the operating frequency of the switching elements Q1, Q2 in the power source trough is increased. if, For example, as shown in FIG. 4, as shown in FIG. 4, the same effect as securing the difference in current value between the power supply valley and the power supply peak of the first modulation current flowing when Vs3 is increased to Vs3 corresponding to Vs1. Is obtained, and the phase advance operation can be sufficiently suppressed.
[0040]
Also, In this embodiment, The ratio of the first rate of change to the second rate of change is substantially equal to the ratio of the smoothed portion voltage to the output voltage fluctuation width of the smoothing circuit 3 in one cycle of the AC power supply voltage Vs. Have . Here, the output voltage fluctuation width of the smoothing circuit 3 in one cycle of the AC power supply voltage Vs is a difference between the maximum value and the minimum value of the voltage Vdc in one cycle of the AC power supply voltage Vs. The voltage of the smoothed portion is the minimum value at the power source trough of the voltage Vdc. For example, if the ratio of the voltage value (minimum value) of the power source valley to the maximum value of the voltage Vdc is n% and the first and second change rates are f1 and f2, respectively, f1: f2 = n: (100−n ) To set the first and second change rates. Thereby, the phase advance operation can be sufficiently suppressed.
[0041]
As shown in FIG. 5, the first and second detection circuits 5a and 5b of the present embodiment include a high potential side output terminal of the smoothing circuit 3 and a low potential side output terminal connected to the impedance circuit 4 of the rectifier DB. The voltage dividing circuit 6 outputs the divided voltage to the frequency control circuit 13 of the control circuit 10.
[0042]
The voltage dividing circuit 6 includes a resistor 3 having one end connected to the connection point between the rectifier DB and the diode D1 of the impedance circuit 4, and a resistor 4 having one end connected to the connection point between the inductor L1 and the capacitor C5 of the smoothing circuit 3. The connection point of the resistors R3 and R4 is connected to the input terminal of the frequency control circuit 13 of the control circuit 10.
[0043]
This voltage dividing circuit 6 detects the voltage fluctuation of one cycle of the AC power supply voltage Vs and the voltage fluctuation of the AC power supply voltage Vs from the difference between the voltage Vdc and the voltage Vfe, and the difference between the voltage Vdc and the voltage Vfe. Is output to the frequency control circuit 13. As a result, the first and second modulation currents are output to the frequency control circuit 13 via the resistors R3 and R4, respectively. The frequency control circuit 13 receives the first and second modulation currents from one input terminal, and from the first and second modulation currents, the voltage fluctuation of one cycle of the AC power supply voltage Vs is the same as in the first embodiment. The operating frequency of the switching elements Q1, Q2 is changed according to the voltage fluctuation of the AC power supply voltage Vs.
[0044]
In the present embodiment, the first and second detection circuits 5a and 5b are composed of the voltage dividing circuit 6 having the respective functions, so that the input terminal of the frequency control circuit 13 of the control circuit 10 is integrated into one. The configuration can be simplified.
[0045]
Also in the present embodiment, as in the first embodiment, the ratio of the first rate of change to the second rate of change is a portion smoothed with respect to the output voltage fluctuation width of the smoothing circuit 3 in one cycle of the AC power supply voltage Vs. Is approximately equal to the voltage ratio of Have . Ie The resistance values of the resistors R3 and R4 of the voltage dividing circuit 6 are set so as to satisfy the relationship of f1: f2 = n: (100−n). ing .
[0046]
【The invention's effect】
The invention of claim 1 includes a rectifier that rectifies an AC power supply, a smoothing circuit that is connected to the rectifier via an impedance element and smoothes the output voltage of the rectifier, and at least one switching element, and is smoothed by the smoothing circuit. An inverter circuit for converting the converted voltage into a high-frequency voltage and supplying it to the load, a control circuit for turning on / off the switching element, a first detection circuit for detecting a voltage fluctuation in one cycle of the AC power supply voltage, and the AC power supply voltage A second detection circuit for detecting a voltage fluctuation of The smoothing circuit has a smoothing capacitor and charges the smoothing capacitor during a period when the output voltage of the rectifier is larger than a predetermined value. When the output voltage of the rectifier falls below the predetermined value, the charge charged in the smoothing capacitor is discharged. A partial smoothing circuit for smoothing the valley of the output voltage of the rectifier, The control circuit keeps the on-duty of the switching element substantially constant and sets the operating frequency of the switching element. The first change rate is changed according to the detection result of the first detection circuit, the first change rate is changed according to the detection result of the second detection circuit, and the first change rate with respect to the second change rate is changed. The rate of change rate is made approximately equal to the rate of the smoothed portion voltage to the output voltage fluctuation width of the smoothing circuit in one cycle of the AC power supply voltage. Therefore, by keeping the on-duty substantially constant, the occurrence of cataphoresis phenomenon is prevented, Also, The operating frequency of the switching element is changed according to the detection result of the first detection circuit. The ratio of the first rate of change to the second rate of change is approximately equal to the ratio of the voltage of the smoothed portion to the output voltage fluctuation width of the smoothing circuit in one cycle of the AC power supply voltage. Therefore, the phase advance operation of the inverter circuit can be suppressed. ,further, By changing the operating frequency of the switching element according to the detection result of the second detection circuit, there is an effect that output fluctuation when the AC power supply voltage fluctuates can be suppressed.
[0049]
Claim 2 The inverter circuit is a half-bridge type inverter circuit in which a series circuit of two switching elements is connected in parallel to a rectifier, and the control circuit sets the on-duty of each switching element to about 50%. Thus, there is an effect that the occurrence of the cataphoresis phenomenon can be prevented more reliably.
[0050]
Claim 3 Since the first detection circuit detects a voltage fluctuation in one cycle of the AC power supply voltage from the voltage across the impedance element, 1 or 2 The same effect as that of the present invention is achieved.
[0051]
Claim 4 Since the second detection circuit detects the voltage fluctuation of the AC power supply voltage from the voltage across the smoothing circuit, 3 The same effects as in any of the inventions are achieved.
[0052]
Claim 5 In the invention, the first and second detection circuits divide the voltage applied between the output terminal of the smoothing circuit and the output terminal connected to the impedance element of the rectifier, and control the divided voltage. Since the voltage dividing circuit for outputting to the circuit is used, there is an effect that the configuration of the apparatus can be simplified by using one input terminal of the control circuit.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a first embodiment.
FIG. 2 is a circuit diagram of the above.
FIG. 3 is an explanatory diagram for comparison operation as in the above.
[Fig. 4] Fig. 4 is a diagram for explaining another comparative operation.
FIG. 5 is a circuit diagram showing a second embodiment.
FIG. 6 is a circuit diagram showing a conventional example.
FIG. 7 is an operation explanatory diagram of the above.
FIG. 8 is another operation explanatory view of the above.
[Explanation of symbols]
1 Filter circuit
2 Inverter circuit
3 Smoothing circuit
4 Impedance circuit
5a First detection circuit
5b Second detection circuit
10 Control circuit
11 Drive circuit
13 Frequency control circuit
DB rectifier
E AC power supply

Claims (5)

A rectifier that rectifies the AC power supply, a smoothing circuit that is connected to the rectifier via an impedance element, smooths the output voltage of the rectifier, and has at least one switching element, and converts the voltage smoothed by the smoothing circuit into a high-frequency voltage. An inverter circuit for supplying the load to the load, a control circuit for turning on / off the switching element, a first detection circuit for detecting a voltage fluctuation in one cycle of the AC power supply voltage, and a first detecting circuit for detecting a voltage fluctuation in the AC power supply voltage The smoothing circuit has a smoothing capacitor, charges the smoothing capacitor during a period when the output voltage of the rectifier is greater than a predetermined value, and smoothes when the output voltage of the rectifier falls below the predetermined value. a partial smoothing circuit for smoothing the valley portion of the output voltage of the rectifier to discharge the electric charge charged in the capacitor, the control circuit Ondeyu switching element Maintaining the tee substantially constant, with varied first rate of change of the operating frequency of the switching element in accordance with the detection result of the first detection circuit, the second change rate according to the detection result of the second detecting circuit And the ratio of the first rate of change to the second rate of change is substantially equal to the ratio of the smoothed portion voltage to the output voltage fluctuation width of the smoothing circuit in one cycle of the AC power supply voltage. Power supply. The inverter circuit is a half-bridge inverter circuit in which a series circuit of two switching elements is connected in parallel to a rectifier, and the control circuit has an on-duty of each switching element of about 50%. The power supply device according to claim 1. First detection circuit, a power supply device according to claim 1, wherein sensing the voltage variation of one period of the AC power supply voltage from the voltage across the impedance element. The power supply apparatus according to any one of claims 1 to 3, wherein the second detection circuit detects a voltage fluctuation of the AC power supply voltage from a voltage across the smoothing circuit . The first and second detection circuits divide the voltage applied between the output terminal of the smoothing circuit and the output terminal connected to the impedance element of the rectifier, and output the divided voltage to the control circuit. 3. The power supply device according to claim 1, comprising a voltage dividing circuit .

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