JPH04368471A - Power source - Google Patents

Abstract

PURPOSE:To reduce power loss of a driving circuit of a switching element by maintaining an operating frequency of the element of a chopper constant during a period in which a momentary value of an input voltage of an AC power source is low. CONSTITUTION:In this circuit, an input voltage is detected by divided voltage of resistors R1, R2, and a DC voltage of a capacitor C3 is applied through a resistor R9. A rectified voltage of the divided sine wave is applied to a terminal 11 of an IC. Further, a voltage across a smoothing capacitor C1 is detected by a divided voltage of resistors R4, R5, and they are multiplied to decide a target waveform value of a peak value of a current flowing to a transistor(Tr) Q1. A current flowing to the Tr Q1 is detected by a voltage of a resistor R3. That is, as an input voltage is lowered during a period A of this circuit, a switching frequency is raised. However, since the target waveform of the peak value of the current flowing to the Tr Q1 is constant irrespective of the amplitude of the input voltage during a period B, rising of the frequency can be prevented.

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 using a chopper device that improves the input power factor by switching the input voltage from a commercial AC power source at a predetermined operating frequency using a switching element.

0002

[Prior Art] Conventionally, there has been a discharge lamp lighting device that inputs a DC voltage obtained by rectifying and smoothing an AC voltage from a commercial power source to an inverter device, converts it into a high frequency voltage by the inverter device, and supplies it to a discharge lamp, thereby lighting the discharge lamp at high frequency. Widely used. In this type of lighting device, the rectified output of the commercial AC voltage is smoothed so that the envelope of the high-frequency current supplied to the discharge lamp does not fluctuate with the commercial AC cycle. This is to substantially eliminate the arc phenomenon, improve the luminous efficiency of the discharge lamp, reduce the power consumption of the device, and eliminate flickering of light, thereby improving the performance of the lighting device.

However, when the commercial AC voltage is rectified and smoothed, the current flowing from the commercial power source into the smoothing capacitor flows only near the peak value of the commercial AC voltage, and the current flows only around the peak value of the commercial AC voltage. Since the current has a high value, the input power factor deteriorates. In addition, it contains many high-order harmonic current components with respect to the AC fundamental frequency, which has an adverse effect such as mixing high-frequency noise into other devices connected to the same AC power distribution system. Therefore, in order to increase the power factor of the input current, reduce harmonic components, and supply the inverter with a DC smoothed voltage that is as flat as possible, the following measures have been taken.

FIG. 7 is a circuit diagram of a conventional example. In this circuit, full-wave rectifier DB1 and smoothing capacitor C1
A step-up chopper CHP is inserted between the two. The DC voltage obtained at the smoothing capacitor C1 is converted into a high frequency voltage by the inverter device 1 and supplied to the load 2. The step-up chopper CHP has a choke L1 connected to the rectified output terminal of a full-wave rectifier DB1 via a switching transistor Q1, and a smoothing capacitor C1 connected to both ends of the transistor Q1 via a backflow blocking diode D1. It is configured. By switching the switching transistor Q1 at high frequency by the drive circuit 3, energy is accumulated in the choke L1 during the ON period of the transistor Q1, and the transistor Q
1, the self-induced electromotive force of the choke L1 is superimposed on the rectified output of the full-wave rectifier DB1 to charge the smoothing capacitor C1. As a result, the smoothing capacitor C1 is charged with a voltage higher than the peak voltage obtained at the rectified output terminal of the full-wave rectifier DB1. In this circuit system, the input current Iin from the commercial power supply Vs
has the advantage of almost no downtime,
Further, the input power factor is high, and harmonic components of the input current can be suppressed to a low level.

FIG. 8 shows a circuit configuration of a boost chopper CHP. The input voltage of the boost chopper CHP is set to V
0, a linearly increasing current flows through the inductor L1 during the on period of the transistor Q1. Assuming that the on-period of transistor Q1 is t0, the peak value of the current flowing through inductor L1 is as shown in FIG.
The result is t0×(V0/L1). In the drive circuit 3,
The voltage of the smoothing capacitor C1 is controlled by fixing the operating frequency of the transistor Q1 and controlling the on/off duty.

FIG. 10 shows the case where the input voltage of the step-up chopper CHP is high, and FIG. 11 shows the case where the input voltage of the step-up chopper CHP is low. (a) ON signal to transistor Q1, (b) current flowing through transistor Q1. ,
(c) The waveforms of the current flowing through the choke L1 and (d) the voltage across the transistor Q1 are shown. In this way, when the operating frequency of the transistor Q1 is fixed and the on/off duty is controlled, a rest period occurs in the current flowing through the chopper choke L1, and the length of the rest period depends on the magnitude of the input voltage. It changes accordingly. Note that if the transistor Q1 is turned on when there is no rest period and current is flowing through the choke L1, a steep current will flow through the transistor Q1, increasing stress. Therefore, it is necessary to turn on the transistor Q1 after the current flowing through the choke L1 disappears. In such a control method where the operating frequency is fixed, the use of choke L1 is not efficient, and
There is a problem in that a resonant voltage is generated at both ends of the transistor Q1 during the idle period due to the influence of stray capacitance, and the noise level becomes high.

FIG. 12 shows another control method for the boost chopper CHP. In this circuit, transistor Q1
The operating frequency is variable and the on/off duty is fixed. The drive circuit uses a general-purpose IC for a switching regulator (TDA4814A manufactured by Siemens), and detects that the current flowing through the chopper choke L1 disappears and turns on the transistor Q1. The operating principle of this circuit will be explained below. The input voltage is detected by the voltage division of resistors R1 and R2, and the voltage across the smoothing capacitor C1 is detected by the voltage division of resistors R4 and R5, and by multiplying these, the peak value of the current flowing through the transistor Q1 is calculated. Determining the target waveform value. And transistor Q1
The current flowing through the resistor R3 is detected. Therefore, when the same current as the target waveform value of the peak value flowing through the transistor Q1 flows through the transistor Q1, by turning off the transistor Q1, the transistor Q
1 is determined. If you control it like this,
The peak value of the current flowing through the transistor Q1 is a point on the same sine wave as the input voltage waveform. In addition, the transistor Q
1 is turned on by detecting the voltage of the secondary winding of choke L1, and when the current flowing through choke L1 disappears, the IC (TD
A4814A) receives a synchronizing signal, and transistor Q1
Turn on.

FIG. 13 shows the case where the input voltage of the boost chopper CHP is high, and FIG. 14 shows the case where the input voltage of the boost chopper CHP is low. (a) ON signal to transistor Q1, (b) current flowing through transistor Q1 ,
(c) The waveforms of the current flowing through the choke L1 and (d) the voltage across the transistor Q1 are shown. In this way, the operating frequency of transistor Q1 is made variable, and when the input voltage is high, the switching frequency is lowered as shown in Figure 13, and when the input voltage is low, the switching frequency is raised as shown in Figure 14. If you control it so that
There is no longer any rest period in the current flowing through the chopper choke L1.

[0009]

However, when performing variable frequency control as shown in FIG. 12, there are the following problems. As shown in Figure 14, as the input voltage decreases, the switching frequency increases, but when the input voltage is particularly low and approaches 0V, it is in a region that has little effect on the input power factor and current distortion. Despite this, there is a problem that the switching frequency of the chopper becomes high and the power loss in the drive circuit 3 for operating the transistor Q1 becomes large.

[0010] The present invention has been made in view of the above points, and its object is to perform switching in a chopper type power supply device by switching during a period when the input voltage from the commercial power source is below a predetermined voltage. The purpose is to reduce power loss.

[0011]

[Means for Solving the Problems] In order to solve the above problems, the power supply device of the present invention changes the operating frequency of the switching element according to the instantaneous value of the input voltage from the AC power supply. In a chopper device in which the envelope of the input current is sinusoidal, when the input voltage is below a predetermined voltage, means for making the operating frequency of the switching element constant, or
The device is characterized in that it includes means for stopping the switching operation.

[0012] Here, the predetermined voltage is preferably 0.37 times or less the peak value of the input voltage.

[0013]

[Operation] As shown in Figure 6, the input current is 0 to θ0, π
The power factor is determined when there is a pause in the input current in the sections -θ0 to π+θ0 and 2π-θ0 to 2π. input voltage,
Letting the peak values of the input current be V0 and I0, respectively,

[0014]

[Math 1]

[0015]

[Math 2]

[0016]

[Math 3]

[0017]

[Equation 4] Generally, a value of 0.85 or more is called a high power factor, but considering a 10% margin due to characteristic variations, etc., 0.85×1.1
=0.935. Therefore, if ψ≧0.935, it can be said that the power factor is sufficiently high even if a rest angle occurs in the input current. therefore,

[0018]

[Math 5]

Therefore, θ0≦0.38. In other words,
A voltage below V0 · sin θ0 = 0.37×V0 can be treated as a high power factor even if no input current is applied and characteristic variations are included. The present invention focuses on the above principle, and when the input voltage is below a predetermined voltage (0.37 times the peak value of the input voltage), the operating frequency is kept constant and the on period of the switching element for the chopper is reduced. By increasing the length, the operating frequency is prevented from increasing. Furthermore, when the input voltage is below a predetermined voltage, even if the switching operation is stopped, a sufficient power factor improvement effect can be obtained, and the power loss in the switching element is reduced. The effect is even higher.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram of an embodiment of the present invention. The circuit configuration will be explained below. The commercial power supply Vs is connected to the AC input terminal of the full-wave rectifier DB1. Resistors R1 and R are connected to the DC output terminal of the full-wave rectifier DB1.
2 series circuits are connected in parallel, and a chopper choke L1 and a switching transistor Q1 are connected in parallel.
and a resistor R3 are connected in parallel. A smoothing capacitor C1 is connected to the series circuit of the transistor Q1 and the resistor R3 via a diode D1 for preventing backflow.
is connected. Resistor R4 is connected to capacitor C1.
, R5 are connected in parallel, and the DC input terminals of the inverter device 1 are connected in parallel. A load 2 is connected in parallel to the high frequency output terminal of the inverter device 1 . Secondary winding L2 of chopper choke L1
A resistor R6 is connected to the resistor R6, and the voltage generated at the resistor R6 is connected to the 14th terminal of a general-purpose IC (Siemens TDA4814A) for a switching regulator. The connection point of resistors R4 and R5 is connected to the 12th terminal of the above IC, as well as the resistor R7 and capacitor C2.
It is connected to the 13th terminal of the above IC via a parallel circuit. A capacitor C3 and a Zener diode Z are connected to the DC output terminal of the full-wave rectifier DB1 via a resistor R8.
A parallel circuit of D1 is connected. Capacitor C3
The voltage generated across the IC is applied between the first and third terminals of the IC. The connection point between resistors R1 and R2 is connected to the 11th terminal of the above IC, and the resistor R9
It is connected to the No. 3 terminal of the above IC via. The connection point between the transistor Q1 and the resistor R3 is connected to the No. 4 terminal of the above IC. Further, the second terminal of the above IC is connected to the gate of the transistor Q1. here,
The above IC (Siemens TDA4814A) is shown in Figure 12.
As shown in , it is composed of an operational amplifier OP, a multiplier MX, a comparator CP, an AND circuit &, a flip-flop FF, and other logic circuits.

The operation of this embodiment will be explained below. In this circuit, the input voltage is detected by voltage division between resistors R1 and R2, and by further adding the DC voltage of capacitor C3 through resistor R9 to this detected voltage,
As shown in FIG. 2, a rectified voltage with a valley-filled sine wave is applied to the 11th terminal of the above IC (TDA4814A manufactured by Siemens). Further, the voltage across the smoothing capacitor C1 is detected by the voltage division of the resistors R4 and R5, and by multiplying these, the target waveform value of the peak value of the current flowing through the transistor Q1 is determined. Then, the current flowing through the transistor Q1 is detected by the voltage of the resistor R3.

In such a circuit, during period A in FIG. 2, the higher the input voltage, the lower the switching frequency, and the lower the input voltage, the higher the switching frequency. However, in period B in Figure 2,
Regardless of the magnitude of the input voltage, the target waveform of the peak value of the current flowing through the transistor Q1 is constant. In other words, in the period B of FIG. 2, the lower the input voltage, the longer the on period of the transistor Q1 becomes, or the current value of the target waveform cannot be obtained. Therefore, in the B period, the lower the input voltage, the longer the on period of the transistor Q1 becomes, thereby preventing the operating frequency from increasing.

FIG. 3 is a circuit diagram of another embodiment of the present invention. In this embodiment, a capacitor C4 is connected in parallel to the output terminal of the full-wave rectifier DB1 to prevent high-frequency current from flowing through the full-wave rectifier DB1. When controlling as shown in the conventional example of FIG. 12 without the resistor R9 for filling the valley of the voltage applied to the No. 11 terminal of the above IC, as shown in FIG. 4, during the period when the input voltage is low, There is a problem that the voltage of the capacitor C4 becomes higher than the input voltage, and no input current flows during this period, resulting in poor input power factor and current distortion. On the other hand, in this embodiment, a resistor R9 is provided to fill in the valley of the voltage applied to the 11th terminal of the IC, so that the transistor Q1 is turned on during periods when the input voltage is low.
The period becomes longer, and the amount of charge discharged from the capacitor C4 increases. Therefore, the period during which the voltage of the capacitor C4 is higher than the input voltage is shorter than in the conventional example, and the input current rest period is shortened, which is advantageous in terms of input power factor and input current distortion.

FIG. 5 is a circuit diagram of another embodiment of the present invention. In this embodiment, a voltage obtained by dividing the voltage at the output end of the full-wave rectifier DB1 by resistors R10 and R11 is input to the buffer circuit IC1, and the gate of the transistor Q1 is connected to the buffer circuit IC1 via the anode and cathode of the diode D2. It is connected to the output of The other circuit configuration is the same as that of the conventional example shown in FIG. 12, and the valley-filling resistor R9 is omitted. When the input voltage becomes lower than a predetermined potential, the output of the buffer circuit IC1 becomes a low level, and the gate potential of the transistor Q1 is clamped to a low level via the diode D2, so the transistor Q1 is forcibly turned off. Ru. This prevents the switching frequency from increasing during periods when the input voltage is low.

[0025]

[Effects of the Invention] In the power supply device of the present invention, as described above,
During periods when the instantaneous value of the input voltage from the AC power supply is low, the operating frequency of the switching element of the chopper device is held constant to lengthen the on period of the switching element, or the switching element is forcibly turned off to prevent operation. Since the frequency is prevented from increasing, power loss in the drive circuit for operating the switching elements can be reduced, and the efficiency of the entire device can be improved.

[0026] In an embodiment in which a capacitor is connected in parallel to the output terminal of a full-wave rectifier that performs full-wave rectification of an AC power source, it is also possible to improve the input power factor and reduce harmonic distortion of the input current. It is something that can be done.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is an operational waveform diagram of an embodiment of the present invention.

FIG. 3 is a circuit diagram of another embodiment of the present invention.

FIG. 4 is an operational waveform diagram of another embodiment of the present invention.

FIG. 5 is a circuit diagram of another embodiment of the invention.

FIG. 6 is an operational waveform diagram of another embodiment of the present invention.

FIG. 7 is a circuit diagram of a conventional example.

FIG. 8 is a circuit diagram of a chopper device used in a conventional example.

FIG. 9 is an operation waveform diagram of a chopper device used in a conventional example.

FIG. 10 is an operational waveform diagram when the input voltage is high in the conventional example.

FIG. 11 is an operation waveform diagram when the input voltage of the conventional example is low.

FIG. 12 is a circuit diagram of another conventional example.

FIG. 13 is an operation waveform diagram of another conventional example when the input voltage is high.

FIG. 14 is an operation waveform diagram of another conventional example when the input voltage is low.

[Explanation of symbols]

Vs Commercial power supply DB1 Full wave rectifier L1 Choke for chopper Q1
Transistor D1 for switching
Diode C1 Smoothing capacitor 1 Inverter device 2 Load 3 Drive circuit

Claims (2)

[Claims] [Claim 1] Changing the operating frequency of the switching element according to the instantaneous value of the input voltage from the AC power supply,
What is claimed is: 1. A power supply device in a chopper device in which the envelope of an input current is sinusoidal, characterized in that the chopper device includes means for making the operating frequency of a switching element constant when the input voltage is below a predetermined voltage. [Claim 2] Changing the operating frequency of the switching element according to the instantaneous value of the input voltage from the AC power supply,
What is claimed is: 1. A power supply device in a chopper device in which the envelope of an input current is sinusoidal, comprising means for stopping a switching operation when the input voltage is below a predetermined voltage.