JPH0970173A - Dc power unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the weight, size, and cost of a DC power unit and, at the same time, to improve the power factor of the power unit. SOLUTION: AC power inputted from an AC power source 1 flows to a negative common line from a positive hot line through a choke CH, capacitor C1, and transistor Q1 after the power is full-wave rectified by means of a diode bridge 2 and charges a capacitor C1. The current discharged from the capacitor C1 is supplied to a load 3 through a diode D1, the capacitor C1 and the choke CH. A switching control circuit(SWCC) 5 detects the voltage of the hot line and, while the instantaneous value of the detected voltage is higher than the DC-component voltage of the detected voltage, namely, during the charging cycle of the capacitor C1, outputs a driving signal which switches the transistor Q at a high speed. Therefore, the peak current of the AC power source 1 is remarkably reduced and the power factor of a DC power source is improved, because the control circuit 5 works as a choke input smoothing circuit even when the inductance of the choke CH is small, reduces ripples, and widens the conducting angle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC power supply device for rectifying and smoothing input AC power to supply DC power to a load, and more particularly to a smoothing circuit of the DC power supply device.

[0002]

2. Description of the Related Art In order to convert input AC (alternating current) power into DC (direct current) power and supply it to a load, full-wave rectification is generally performed by a diode bridge. Therefore, the ripple is reduced or eliminated through the smoothing circuit after the rectification. As a smoothing circuit for that purpose, a capacitor input type and a choke input type are well known.

FIG. 12 is a circuit diagram showing an example of a capacitor input type rectifying / smoothing circuit, which is a commercial 50 Hz or 60 H.
The AC power input from the z AC power supply 31 is full-wave rectified by the diode bridge 32, and the DC power smoothed by the smoothing capacitor C4 is output to the load 33. FIG.
FIG. 4 is a waveform diagram showing an example of voltage or current of each part when the load 33 is non-inductive, for example, a resistive load.

FIGS. 13A and 13B are waveform diagrams of the voltage (current is also the same) on the input side and the output side of the diode bridge 32 when the smoothing capacitor C4 is not connected. The voltage (current) input to the load 33 has a large ripple as shown in FIG. As shown in FIG. 12, the smoothing capacitor C4
, The voltage between the terminals, that is, the ripple of the voltage (current) input to the load 33 is greatly reduced as shown in FIG.

[0005]

However, since the frequency of the AC power source 31 which is a commercial power source is low, the capacity of the smoothing capacitor C4 must be set large in order to reduce the ripple, but the smoothing capacitor C4 is charged. The current flows only when the instantaneous value of the full-wave rectification voltage shown in FIG. 13B exceeds the instantaneous value of the voltage across the smoothing capacitor C4 shown in FIG. 13C. , The conduction angle is narrow when viewed in phase. Therefore, the reactive power increases and the effective power decreases.

Since a large capacity capacitor has to be charged with a small conduction angle, as shown in the waveform diagram of the AC current on the input side shown in FIG. 13D, the current flows to the load 33 in a short time. Since a large peak current, which is several times to more than ten times the average current value, flows, the power factor deteriorates, the life of the smoothing capacitor C4 is shortened, and high frequency noise occurs. Therefore, the instantaneous decrease in the power supply voltage of the AC power supply 31 and the high frequency noise adversely affect other devices connected to the same AC line.

Although not shown, the choke input type rectifying / smoothing circuit shown in FIG. 12 in which a choke coil is provided between the diode bridge 32 and the smoothing capacitor C4 has a lower output voltage with respect to the load than the capacitor input type. However, the inductive property of the choke coil and the decrease in the output voltage act in combination to widen the conduction angle, and the AC power supply 3
The peak current on the 1st side is reduced and the power factor is improved.

However, in this case as well, since the frequency of the AC power source 31 is low, the choke coil has an inductance of several mH or more (the smaller the required current value is, the larger it is) depending on the required current value of the load 33. Will be required. Therefore, there is a problem that the weight and size of the DC power supply device are increased and the cost is significantly increased.

The present invention has been made in view of the above points, and it is an object of the present invention to suppress the weight increase, the size increase, and the cost increase of a DC power supply device, and to improve the power factor.

[0010]

In order to achieve the above-mentioned object, the present invention provides a DC power supply device for full-wave rectifying AC input power with a diode bridge and smoothing with a smoothing capacitor to supply DC power to a load. Of the positive and negative lines connecting the output end of the bridge and the input end of the load,
One of them is used as a common line and the other is used as a hot line for the common line.

That is, a parallel circuit having a switching element for charging the smoothing capacitor and a diode for discharging the smoothing capacitor to a load, one end of which is connected to a common line, and the other end of the parallel circuit and the hot line When the absolute value of the detected voltage of the series circuit of the smoothing capacitor and the choke coil connected between and the hot line is detected is larger than the absolute value of the voltage of the direct current component excluding the ripple component from the detected voltage. And a switching control circuit for outputting a drive signal for opening and closing the switching element at high speed to the switching element.

Alternatively, a choke coil and a smoothing capacitor connected between the hot line and the common line,
A series circuit including a parallel circuit of a switching element for charging the smoothing capacitor and a diode for discharging the smoothing capacitor to a load, and the absolute value of the detected voltage is detected from the detected voltage by detecting the hot line voltage. When it is larger than the absolute value of the DC component voltage excluding the ripple component,
A switching control circuit that outputs a drive signal for opening and closing the switching element at high speed, a primary coil that inputs the drive signal that the switching control circuit outputs, and a secondary coil that is connected between the drive signal input terminals of the switching element. And a drive transformer consisting of.

Alternatively, a parallel circuit of a choke coil, a smoothing capacitor, a switching element for charging the smoothing capacitor, and a diode for discharging the smoothing capacitor to a load, connected between the hot line and the common line. And a series circuit consisting of and, for detecting the voltage of the hot line and switching the switching element at high speed when the absolute value of the detected voltage is greater than the absolute value of the DC component voltage, which is the detected voltage minus the ripple component. A CR including a switching control circuit that outputs a drive signal, a leak resistance connected between drive signal input terminals of a switching element, and a coupling capacitor that connects one end of the leak resistance and an output end of the drive signal of the switching control circuit. And a coupling circuit.

In the above DC power supply device, at least one small-capacity capacitor for bypassing high frequency noise may be provided between the hot line and the common line. Furthermore, the load may be a constant voltage DC / DC converter.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to the drawings. In the embodiments described below, a negative line is a common line, a positive line is a hot line, and a transistor is used as a switching element. FET (field effect transistor) or MO as a switching element
When using S-FET, the emitter of the transistor,
The base and collector can be read as source, gate, and drain, respectively.

FIG. 1 is a circuit diagram showing an example of the configuration of a first embodiment of a DC power supply device according to the present invention. A diode bridge 2 which constitutes a rectifying section and a choke coil CH which constitutes a smoothing section, respectively. , Smoothing capacitor C1,
It is composed of an NPN transistor Q1 and a parallel circuit 4 of a diode D1 and a switching control circuit (SWCC) 5.

The diode bridge 2 full-wave rectifies the AC power input from the AC power source 1 to convert it into DC power, and supplies it to the load 3 via the smoothing section. The negative output end of the diode bridge 2 and the negative input end of the load 3 are directly connected by a common line, and the positive output end of the diode bridge 2 and the positive input end of the load 3 are directly connected by a hot line.

One end of a series circuit of a choke coil CH and a smoothing capacitor C1 is connected to the hot line, and a parallel circuit 4 of a transistor Q1 and a diode D1 is provided between the other end of the series circuit and the common line. It is connected. A current flows in the diode D1 forming each of the parallel circuits 4 in a direction in which the smoothing capacitor C1 is discharged,
Since the emitter of the type transistor Q1 is connected to the common line and the collector thereof is connected to the negative terminal of the smoothing capacitor C1, a current flows in a direction to charge the smoothing capacitor C1 when its base is more positive than the common line.

The switching control circuit 5 having the common terminal connected to the common line inputs the voltage of the hot line to the detection terminal, and the instantaneous value of the input detection voltage and the ripple obtained by further smoothing the detection voltage. Compared with the voltage of the DC component from which the component has been removed, a positive voltage having a frequency of several KHz to several hundred KHz, which is much higher than the frequency of the AC power source 1, only for a period in which the instantaneous value of the detected voltage is higher. A drive signal is output from its output terminal to the base of the transistor Q1 to open and close the transistor Q1 at high speed.

FIG. 2 is a waveform diagram showing an example of each instantaneous value of voltage and current in each part of the DC power supply device shown in FIG.
2 (A), (B) and (C) show the voltage of the output side when the input side of the diode bridge 2 is not connected to the smoothing section and the voltage of the hot line when the smoothing section is connected, respectively. It is a waveform diagram.

2D and 2E show waveform diagrams of the input side current of the diode bridge 2 and the charging current of the smoothing capacitor C1, respectively. Vd indicated by broken lines in FIGS. 2B and 2C is the voltage of each direct current component, and ΔV shown in FIG. 2C is the pp value of the ripple component.

The charging current of the smoothing capacitor C1 flowing in the choke coil CH is AC as shown in FIG.
Since the switching is performed at a frequency much higher than the frequency of the power source 1 or twice the frequency thereof (by full-wave rectification), it works as a choke input type even if its inductance is small, and Instead of the output voltage for 3 being slightly lowered, the conduction angle is widened as shown in FIG.

That is, during the charging period in which the instantaneous value of the voltage of the hot line is higher than the voltage between the terminals of the smoothing capacitor C1 with respect to the common line, the current for charging the smoothing capacitor C1 via the choke coil CH is higher than the frequency of the AC power source 1. Since the switching is performed at a much higher frequency, the inductance of the choke coil CH can be much smaller than that of a normal choke input type, and the size and weight can be reduced.

Further, the discharge current of the smoothing capacitor C1 is supplied to the load 3 via the choke coil CH and the diode D1, but since the choke coil CH has a small inductance, it has a frequency twice that of the AC power supply 1. There is almost no influence of the choke effect on the ripple component as the fundamental wave. Therefore, the same effect can be obtained by directly connecting the connection point between the choke coil CH and the smoothing capacitor C1 and the positive input terminal of the load 3.

The switching control circuit 5 operates with the DC component voltage obtained by removing the ripple component from the detection voltage (hot line voltage) input to the detection terminal as the power supply. Further, the small-capacity capacitor Cp for high frequency bypass, which is connected between the hot line and the common line as shown by the broken line, has a high frequency due to the switching of the charging current according to the drive signal shown in FIG. By bypassing noise, it is possible to prevent the AC power supply 1 and the load 3 from being adversely affected.

For example, as shown in FIG.
In the current of the C power source 1, high frequency noise due to switching of the charging current of the smoothing capacitor C1 by the transistor Q1 does not appear. The same applies to the current of the load 3 not shown.

FIG. 3 is a circuit diagram showing an example of the configuration of the second embodiment of the DC power supply device. The difference from the first embodiment shown in FIG. 1 is the output of the switching control circuit 5. Instead of directly connecting the terminal and the base of the transistor Q1, a drive transformer 6 in which the primary coil and the secondary coil are galvanically isolated is provided, and a drive signal is transmitted through the transformer 6. . The other same parts are designated by the same reference numerals and the description thereof will be omitted.

That is, the primary coil of the drive transformer 6 is between the output terminal of the switching control circuit 5 and the common line, and the secondary coil thereof is between the drive signal input terminals of the switching element, that is, between the base and emitter of the transistor Q1. When the output terminal of the switching control circuit 5 is positive with respect to the common line, the transistor Q1
The base of is set to be positive with respect to its emitter. (There is no problem even if the polarity of the secondary coil is reversed.)

FIG. 4 and FIG. 5 are circuit diagrams showing an example of the configurations of the third and fourth embodiments of the DC power supply device, and the points different from the second embodiment shown in FIG. That is, the arrangement order of the choke coil CH, the smoothing capacitor C1, and the parallel circuit 4 (of the transistor Q1 and the diode D1) forming the smoothing section connected between the hot line and the common line is changed.

That is, in the same manner as the first embodiment (FIG. 1), the choke coil CH, the smoothing capacitor C1, and the parallel circuit are arranged from the hot line to the common line, respectively, as in the first embodiment (FIG. 1). However, in the third embodiment (FIG. 4), the choke coil CH, the parallel circuit 4, and the smoothing capacitor C1 are in this order. In the fourth embodiment (FIG. 5), the parallel circuit 4 and The choke coil CH and the smoothing capacitor C1 are arranged in this order.

As described above, the output terminal of the switching control circuit 5 and the base of the transistor Q1 are not directly connected, but the drive transformer 6 is provided to insulate the output terminal and the base of the transistor Q1 from each other. Since it is not necessary to directly connect to each other, the same operation and effect can be obtained and the degree of freedom in design can be increased no matter how the arrangement order of the elements forming the smooth portion is changed.

FIG. 6 is a circuit diagram showing an example of the structure of the fifth embodiment of the DC power supply device. The difference from the fourth embodiment shown in FIG. 5 is that the NPN transistor Q1 is used.
Instead, a PNP type transistor Q2 is provided, and the other parts are the same. Even if the polarity of the transistor, which is a switching element, is reversed in this way, the same action and effect can be obtained as long as the current direction is the direction in which the smoothing capacitor C1 is charged.

The second operation described above with reference to FIGS.
The fifth to fifth embodiments are respectively according to the invention described in claim 2, and transmit the drive signal output from the switching control circuit 5 to the transistor Q1 or Q2 which is a switching element via the drive transformer 6. is there.

FIG. 7 is a circuit diagram showing an example of the configuration of the sixth embodiment of the DC power supply device. The difference from the second embodiment shown in FIG. 3 is that the primary coil and the secondary coil are different. A CR coupling circuit including a capacitor C2, which is a coupling capacitor whose input side and output side are also galvanically insulated, and a resistor R1, which is a leak resistance, instead of the drive transformer 6 whose coil is galvanically insulated. 7 is provided and the drive signal output from the switching control circuit 5 is transmitted to the transistor Q1 via the coupling circuit 7.

That is, as shown in FIG. 7, the transistor Q1 between the drive signal input terminals of the switching element is
Resistor R1 is connected between the base and emitter of
A capacitor C2 for blocking direct current is connected between the base side terminal of the switching control circuit 5 and the output terminal of the switching control circuit 5, and the time constant which is the product of the capacitance value of the capacitor C2 and the resistance value of the resistor R1 It is set to be larger than the reciprocal (cycle) of the frequency.

Therefore, the operation and effect are exactly the same as those of the drive transformer 6 used in the second embodiment (FIG. 3). In addition, in the seventh to ninth embodiments shown in FIGS. 8 to 10, respectively, the drive transformer 6 in the third to fifth embodiments shown in FIGS.
Since it is replaced with the coupling circuit 7, its operation and effect are exactly the same as in the sixth embodiment (FIG. 7), and the same parts are designated by the same reference numerals and their description is omitted. .

The sixth to ninth embodiments described with reference to FIGS. 7 to 10 are according to the invention described in claim 3, and the drive signal output from the switching control circuit 5 is CR-coupled. The signal is transmitted to the transistor Q1 which is a switching element via the circuit 7.

In the first to ninth embodiments described above, the conduction angle is increased as compared with the capacitor input type, and the AC
While having the characteristics of a choke input type that suppresses the peak current from the power source 1, the charging current of the smoothing capacitor C1 is switched at high speed to reduce the inductance of the choke coil, and it is small and lightweight, and the cost is low. Have

However, the DC power output from these DC power supply devices has the ripple component reduced or removed, but the output voltage with respect to the input voltage fluctuation of the AC power supply 1 and the fluctuation of the current flowing through the load 3. Has no constant voltage property. In addition, the common line and the hot line connected to the load 3 have an AC grounded on either side to the ground.
Since it is completely floating with respect to the power source 1, there is a risk of electric shock even if any line is touched.

Therefore, if the load 3 is a lighting lamp or the like in a TV studio, a stage for TV relay, a stadium, etc., in which only flicker due to a commercial frequency is a problem,
Since the constant voltage characteristic is hardly a problem and there is little risk of electric shock, the ripple is reduced by using a choke coil with a relatively small capacity in response to the large power demand, and the capacity of the smoothing capacitor is also reduced accordingly. The effect is extremely large.
As described above, although it is effective to some limited applications, it is dangerous to use it for many general applications as it is, and is not suitable for applications requiring constant voltage.

However, if a DC / DC converter having a constant voltage characteristic is connected as a load, there is no problem in terms of the constant voltage characteristic, and in particular, the input side and the output side are insulated from each other. , For example, if you connect a switching regulator, there is no danger of electric shock.

FIG. 11 is a circuit diagram showing an example of the configuration of a switching regulator which is a constant voltage DC / DC converter whose input and output sides to be combined as the load 3 are insulated from each other. Since the switching regulator shown in FIG. 11 is well known in its operation and effect,
Briefly explained.

DC input to the positive and negative terminals of the input side Vin
The electric power is a transistor (or FE) which is a switching element connected in series with the primary coil Np of the transformer 10.
T) Turned on and off at high speed by Q3. Transformer 1
The AC power induced in the secondary coil Ns of 0 is rectifier diode D2, commutation diode D3, choke coil CH.
c, the DC power is rectified and smoothed by the rectifying and smoothing circuit 11 including the smoothing capacitor C3, and the output side Vou
It is output from the positive and negative terminals of t.

The control circuit 12 which outputs the drive pulse to the transistor Q3 detects the voltage Vout of the DC power to be output, and raises the on-duty ratio of the drive pulse if it is lower than the preset output voltage, and raises the on-duty ratio if it is higher. By lowering, the control is performed so that the set output voltage is maintained even if the input voltage or the output current fluctuates.

Such a DC / DC converter is connected as the load 3, that is, the DC power supply device according to the present invention is connected to D
By using as a DC power source in combination with a C / DC converter and outputting the constant voltage DC power output by the DC / DC converter to a target device or apparatus, it is possible to safely handle a wide range of applications. .

In the embodiments described above, the negative line is the common line and the positive line is the hot line. On the contrary, the positive line is the common line and the negative line is the hot line. Even in such a case, it goes without saying that the present invention can be applied in exactly the same manner if the polarities of the smoothing capacitor C1 and the diode D1 and the directions of the currents flowing in the transistors Q1 or Q2 are reversed.

[0047]

As described above, the DC power supply device according to the present invention is small and lightweight, has a low cost, and has an improved power factor.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an example of a first embodiment of a DC power supply device according to the present invention.

FIG. 2 is a waveform diagram showing an example of voltage or current of each part of the DC power supply device shown in FIG.

FIG. 3 is a circuit diagram showing an example of a second embodiment of a DC power supply device according to the present invention.

FIG. 4 is a circuit diagram showing an example of a third embodiment of a DC power supply device.

FIG. 5 is a circuit diagram showing an example of a fourth embodiment of a DC power supply device.

FIG. 6 is a circuit diagram showing an example of a fifth embodiment of a DC power supply device.

FIG. 7 is a circuit diagram showing an example of a sixth embodiment of a DC power supply device.

FIG. 8 is a circuit diagram showing an example of a seventh embodiment of a DC power supply device.

FIG. 9 is a circuit diagram showing an example of an eighth embodiment of a DC power supply device.

FIG. 10 is a circuit diagram showing an example of a ninth embodiment of a DC power supply device.

FIG. 11: DC connected to a DC power supply according to the present invention
It is a circuit diagram which shows an example of a / DC converter.

FIG. 12 is a circuit diagram showing a conventional capacitor input type rectifying / smoothing circuit.

FIG. 13 is a waveform diagram showing an example of voltage or current in each part of the rectifying / smoothing circuit shown in FIG.

[Explanation of symbols]

 1: AC power supply 2: Diode bridge 3: Load 4: Parallel circuit 5: Switching control circuit 6: Drive transformer 7: CR coupling circuit C1: Smoothing capacitor C2: Capacitor (coupling capacitor) Cp: Small-capacity capacitor CH: Choke coil D1: Diode Q1, Q2: Transistor (switching element) R1: Resistance (leakage resistance)

Claims (5)

[Claims] 1. A DC power supply device for full-wave rectifying AC input power with a diode bridge and smoothing with a smoothing capacitor to supply DC power to a load, wherein a positive / negative connecting an output end of the diode bridge and an input end of the load. , One of which is a common line and the other is a hot line for the common line, one end of which is connected to the common line, and the switching element for charging the smoothing capacitor and the smoothing capacitor to the load. A parallel circuit with a diode for discharging, a series circuit of the smoothing capacitor and a choke coil connected between the other end of the parallel circuit and the hot line, and detecting the voltage of the hot line, The absolute value of the detected voltage is the absolute value of the voltage of the DC component, which is the detected voltage minus the ripple component. When large, the DC power supply apparatus, wherein a driving signal for opening and closing the switching element at a high speed is provided a switching control circuit for outputting to the switching element. 2. A DC power supply device for full-wave rectifying AC input power with a diode bridge and smoothing with a smoothing capacitor to supply DC power to a load, wherein a positive / negative connecting an output end of the diode bridge and an input end of the load. One of the lines is a common line and the other is a hot line for the common line, and is connected between the hot line and the common line,
A series circuit including a choke coil, the smoothing capacitor, a parallel circuit of a switching element for charging the smoothing capacitor, and a diode for discharging the smoothing capacitor to the load, and a voltage on the hot line are detected. Then, when the absolute value of the detected voltage is larger than the absolute value of the voltage of the direct current component obtained by removing the ripple component from the detected voltage, a switching control circuit that outputs a drive signal for opening and closing the switching element at high speed, A DC power supply device comprising: a primary coil for inputting a drive signal output from the switching control circuit; and a drive transformer including a secondary coil connected between drive signal input terminals of the switching element. 3. A DC power supply device for full-wave rectifying AC input power with a diode bridge and smoothing with a smoothing capacitor to supply DC power to a load, wherein a positive / negative connecting an output end of the diode bridge and an input end of the load. One of the lines is a common line and the other is a hot line for the common line, and is connected between the hot line and the common line,
A series circuit including a choke coil, the smoothing capacitor, a parallel circuit of a switching element for charging the smoothing capacitor, and a diode for discharging the smoothing capacitor to the load, and a voltage on the hot line are detected. Then, when the absolute value of the detected voltage is larger than the absolute value of the voltage of the direct current component obtained by removing the ripple component from the detected voltage, a switching control circuit that outputs a drive signal for opening and closing the switching element at high speed, A CR coupling circuit including a leak resistance connected between drive signal input terminals of the switching element and a coupling capacitor connecting one end of the leak resistance and an output end of the drive signal of the switching control circuit is provided. Characteristic DC power supply. 4. The DC power supply device according to claim 1, wherein a small-capacity capacitor for bypassing at least one high-frequency noise between the hot line and the common line. A DC power supply device characterized by being provided. 5. The DC power supply device according to claim 1, wherein the load is a constant voltage DC / DC converter.