JPH0591731A - Switching power supply device - Google Patents

Abstract

PURPOSE:To obtain a switching power supply device which is compact and light, has a high power conversion efficiency, and can reduce cost at the time of mass-production by dividing and utilizing a control signal of a switch element of a DC/DC converter for a control signal of the switch element of a booster- type chopper circuit. CONSTITUTION:A switching power-supply device is constituted of a booster chopper and a DC/DC converter 4 and then an AC input is subjected to all-wave rectification by an all-wave rectifier 3 and then is input to a booster chopper part as a pulsating current. Then, after a control signal of a switch element 13 is synthesized by a signal of an input voltage monitoring circuit which is constituted of a resistor 9, a zener diode 10, and a transistor 11 and a NAND gate 8, a control signal to a switch element 6 of the booster chopper is supplied only before and after a zero-cross point of an input voltage waveform, thus enabling a power loss of the switch element 6 of the booster chopper to be small, a power conversion efficiency to be high, and at the same time an inductor 4 to be compact and light owing to drive at a same high frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high power factor type switching power supply device which inputs a single-phase AC power supply.

[0002]

2. Description of the Related Art Since the last 10 years, switching power supply devices have been widely used as power supplies for various devices because they are small and lightweight and have the advantage of cost reduction during mass production.
In an AC input switching power supply device, a ripple current is generally reduced by a capacitor input type smoothing circuit after rectification of an AC input, and is used as a DC input of a DC / DC converter. In the case of the capacitor input type smoothing circuit circuit, the input current waveform has a narrow conduction angle and a large peak current value as shown in FIG. For this reason, the effective value of the input current becomes large, and the AC input ratio is low at about 0.5 to 0.6, which is a drawback. On the other hand, since the effective value of the input current is large, it is necessary to thicken the wiring of the power supply line to the switching power supply, or to increase the capacity of the switch for the switching power supply of the distribution board (2 It causes various problems. This problem is particularly noticeable when a plurality of switching power supply devices are used together as a relatively medium / large capacity power supply device.

As a countermeasure against this, as shown in FIG. 4, an inductor 4 is provided between the full-wave rectifier 3 and the smoothing capacitor 7.
It is usually done to insert. In the case of this improvement measure, the input current waveform becomes as shown in FIG.
The current value is smaller than that of the capacitor input type smoothing circuit, and the AC input power factor can be improved to about 0.7 to 0.8, but the inductor is large in size, heavy and costly. It diminishes the major advantages of switching power supplies.

Therefore, in recent years, the active filter shown in FIG. 5 is often used for the purpose of improving the AC input power factor. When the active filter is used, the input current waveform is almost a sine wave as shown in FIG. 3 (k), and the AC input power factor is a value close to 1.

FIG. 5 shows an example of a switching power supply device with an active filter, and its operation will be described. The single-phase AC input is full-wave rectified by the full-wave rectifier 3 and becomes the input of the active filter. The main circuit of the active filter is composed of an inductor 4, a switch element 6, a diode 5 and a smoothing capacitor 7, which is a step-up chopper circuit. The current transformer 21 detects the input current i1 and the rectifier 2
After full-wave rectification in 2, the voltage is converted into a voltage by the resistor 23, while the output of the rectifier 3 is divided by the resistors 32 and 33 to obtain a voltage. Next, the difference between the voltage of the resistor 23 and the voltage divided by the resistors 32 and 33 is amplified by the amplifier 24. On the other hand, the amplifier 26 supplies the voltage of the smoothing capacitor 7 to the resistor 3
After the voltage is divided by 0 and 31, the difference from the reference voltage source 29 is amplified. The outputs of the amplifiers 24 and 26 are multiplied by a multiplier 25, further compared with a triangular wave by a comparator 28, converted into a PWM (pulse width modulation) signal, amplified by a drive circuit 27 (3), and then the switch element 6 is driven. To do.

As described above, the voltage across the smoothing capacitor 7 is made constant by the operation of the feedback control circuit for input voltage comparison, output voltage comparison, etc., and the AC input current waveform i1 is similar to the AC voltage waveform Vi. Therefore, the AC input current waveform becomes a sine wave, and the AC input power factor can be brought close to 1. FIG. 6 shows waveforms at various parts during active filter operation.

[0007]

As described above, in the conventional active filter circuit, the input current waveform can be made substantially similar to the input voltage waveform, but the current flowing through the switch element 6 is large and therefore the power loss of the switch element 6 is large. Inevitably, a heat radiation fin is required for the switch element 6, which causes a reduction in power conversion efficiency of the switching power supply device, an increase in external dimensions and weight, and a complicated control circuit for the active filter. There was also an important problem that the price of the switching power supply increased from a comprehensive viewpoint.

[0008]

OBJECTS OF THE INVENTION Following the purpose of making an AC input power factor close to a value of 1 in a conventional active filter, and solving various problems inherent in the above-mentioned conventional active filter, a small size, a light weight, and a low power consumption are obtained. An object of the present invention is to provide an improved switching power supply device with a built-in active filter, which has the advantages of a switching power supply device with high conversion efficiency and cost reduction during mass production.

[0009]

FIG. 1 shows an embodiment of a switching power supply device according to the present invention. In FIG. 1, the same components as those described in FIG. 5 are designated by the same reference numerals. FIG. 1 is composed of a step-up chopper (main part of an active filter, the same applies hereinafter) and a DC / DC converter (4). The AC input is full-wave rectified by the full-wave rectifier 3 to become pulsating direct current, which is input to the step-up chopper section. The control signal [Fig. 2 (C)] of the switch element 13 of the DC / DC converter is the resistance 9,
The signal of the input voltage monitoring circuit composed of the Zener diode 10 and the transistor 11 [Fig. 2 (b)] and the signal of the NAND gate 8 [Fig. 2 (d)] are synthesized [Fig. 2 (d)]. The control signal to the element 6 is supplied only before and after the zero cross point of the input voltage waveform.

Since the switch element 6 is driven only before and after the zero cross point of the input voltage, the current of the inductor 4 is as shown in FIG.
As shown in (e), the input voltage flows before and after the zero-cross point, and since the ON period of the switch element 6 is sufficiently long, it becomes a power supply of a magnitude sufficient for improving the AC input power factor, and the AC input power factor is improved. Achieve the purpose of. On the other hand, as described above, the switch element 6 is not driven around the peak value of the input voltage as shown in FIG. 2 (f), so that the current flowing through the switch element 6 of the conventional active filter is shown in FIG. 6 (P) and the present invention. As can be seen by comparing FIG. 2 (f), the current flowing through the switch element 6 of the boost chopper, the peak value of the current flowing through the switch element 6 of the boost chopper is low, and the pulse number is small.

As a result, the switch element 6 of the boost chopper
The power loss is small and the power conversion efficiency is high. Also,
Since the switch element 6 of the step-up chopper divides and uses the control signal of the DC / DC converter in the subsequent stage, the DC / DC converter
Since the inductor 4 is driven at the same high frequency as the converter, there is an advantage that the inductor 4 is small and lightweight. Furthermore, the control circuit of the step-up chopper (included in FIG. 1) can eliminate the drive circuit 27, the current transformer 21, and the full-wave rectifier 22 as compared with the control circuit of the conventional active filter (included in FIG. 5). As shown in FIG. 1, it has a simple circuit configuration, which greatly contributes to small size, light weight, cost reduction and further improvement in reliability.

[0012]

(5) According to the present invention, by simply adding a simple semiconductor circuit and a small inductor, there is a high input power factor, high power conversion efficiency, and a high possibility of cost reduction during mass production. A reliable switching power supply device can be provided. AC input power supply, which is widely used in industry
If the present invention is applied to a power source for computer peripherals, main body devices, etc., great results including energy saving effects can be achieved.

Here, as a means for demonstrating the effect of the present invention, the loss values of the main switch element 6 in the conventional example and in the case of the present invention will be compared. 1. Conventional example Applies to FIGS. 5 and 6. The loss of the switch element 6 is neglected because the loss due to the leakage current of the switch element is small, and is set as the addition value of the conduction loss and the switching loss. Here, the conduction loss Wcond is

[Equation 1] Next, the switching loss is represented by switching loss WS = turn-on loss WON + turn-off loss WOff. The loss WON at turn-on is

[Equation 2] Here, the loss Woff at the time of turning off the internal capacitance of the switch element when CO: Vds = VO is

[Equation 3] Here, 1: Parasitic inductance such as vehicle allocation 2. The present invention applies to FIGS. 1 and 2. (6) The loss of the switch element 6 is neglected because the loss due to the leakage current of the switch element is small, and is set as the addition value of the conduction loss and the switching loss. Here, the conduction loss Wcond is

[Equation 4] Here, n is the number of times of switching in 1/4 cycle of the commercial frequency n <m D: Duty cycle (constant) Next, the switching loss is: switching loss WS = loss at turn-on WON + target
It is represented by a loss Woff during off-state. Turn-on loss Won is

[Equation 5] The turn-off loss Woff is

[Equation 6]

As a calculation example, for a switching power supply with an output capacity of 500 W, a certain numerical value is included in [Equation 1] ... [Equation 6], and the loss value is specifically calculated for the conventional example and the present invention. Let's compare. The main examples of the numerical values included are: fAC: 50Hz fS: 200KHz Vi: 100VAC Ii: 5A (7) As shown in the above example, the loss according to the present invention is reduced to about 28% of the loss in the conventional example. This means that when the switching power supply is used in an information processing apparatus, once it starts to operate, it is continuously operated for several years, so that the power saving effect during that time is quite significant.

[0015]

[Other Embodiments] In FIG. 1, instead of the single-phase AC and single-phase full-wave rectifiers, switching composed of a step-up chopper circuit and a DC / DC converter using three-phase AC and three-phase full-wave rectifiers. Power supply.

[Brief description of drawings]

FIG. 1 is an embodiment of a switching power supply device according to the present invention.

FIG. 2 is a waveform of each part of the switching power supply device according to the present invention.

[Figure 3] Various AC input current waveform diagrams

[Fig. 4] Example of improving AC input power factor

FIG. 5 shows an example of a conventional switching power supply device.

FIG. 6 is a waveform of each part of an example of a conventional switching power supply device (waveform of each part during active filter operation)

[Explanation of symbols]

 (8) 1 ... Single-phase AC power supply 2 ... Capacitor 3 ... Single-phase full-wave rectifier 4 ... Inductor 5 ... Diode 6 ... Active filter, step-up chopper switch element 7 ... Smoothing capacitor 8 ... Nand gate circuit 9 ... Resistance Container 10 Zener diode 11 Transistor 12 Transformer 13 Switch element of DC / DC converter 14 DC / DC converter drive circuit 15 DC / DC converter control circuit 16 Rectifying diode -Dode 17 ... Diode 18 ... Inductor 19 ... Smoothing capacitor 20 ... Control circuit of switch element 21 ... Current transformer 22 ... Single-phase full-wave rectifier 23 ... Resistor 24 ... Amplifier 25 ... Multiplier 26 ... Amplifier 27 ... Active filter drive circuit 28 ... Amplifier (9) 29 ... Reference voltage source 30 ... Resistor 31 ... Resistor 32 ... Resistor 33 ... Resistor

Claims (2)

[Claims] 1. A step-up chopper comprising a single-phase AC full-wave rectifier, a step-up chopper circuit connected to the output of the full-wave rectifier, and a DC / DC converter connected to the step-up chopper circuit. The switching power supply device is characterized in that the control signal of the switch element of the circuit uses the control signal of the switch element of the DC / DC converter in a divided manner. 2. The switching power supply device according to claim 1, wherein the switch element of the step-up chopper circuit is driven only for a certain period before and after the zero-cross point of the single-phase alternating current.