JPS6322148B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply device, and more particularly to a power supply device that supplies a DC voltage obtained by rectifying an AC power supply voltage to a DC load circuit having a back electromotive force.

In this type of power supply device, if the DC load circuit is equipped with a smoothing capacitor or is a DC motor, the DC load circuit will have a back electromotive force during operation, so it is rectified by a rectifier circuit. No AC load current flows through the AC power supply circuit until the pulsating voltage exceeds the reverse power. For this reason, there is a problem in that the waveform distortion of the AC load current becomes large and the power factor of the AC power supply circuit decreases. This power factor drop can be prevented by bringing the AC load current closer to the AC power supply voltage waveform. Therefore, an inductor is connected in series between the AC power supply and the rectifier circuit, so that the AC power supply voltage is closer to that of the DC load circuit. In a region smaller than the back electromotive force, the switching element is turned on and off, and when the switching element is on, a short-circuit current flows from the AC power supply to the inductor to accumulate energy, and when it is off, this energy is transferred to the DC load circuit via the rectifier circuit. I am trying to release it to

Figures 1 and 2 are specific examples of the power supply circuit in such a power supply device, and Figure 1 is a power supply circuit that rectifies the AC power supply voltage and supplies the same voltage to the DC load circuit. (hereinafter referred to as equal-voltage rectification power supply circuit), Figure 2 shows a power supply circuit (hereinafter referred to as voltage doubler voltage doubler) that rectifies the positive half cycle and negative half cycle of the AC power supply voltage and then adds them together to supply the DC load circuit. (referred to as a rectified power supply circuit). These two power supply circuits will be explained with reference to the operating waveform diagram in FIG.

In Figures 1 and 3, an AC power supply 1 generates an AC power supply voltage _Vs , which is rectified via an inductor 2 in a rectifier circuit 3 consisting of diodes _D1 to _D4 , and then rectified by a smoothing capacitor _Cd1. smoothed,
Supplied to load 4. In this circuit, the AC power supply voltage
In the region where the instantaneous value of V _s is smaller than the terminal voltage of smoothing capacitor C _d1 , the DC load current I _d for load 4
is supplied from the smoothing capacitor C _d1 , so no AC load current I _s flows through the AC power supply 1 . Since the AC load current I _s flows only in the region where the instantaneous value of the AC power supply voltage V _s exceeds the terminal voltage of the smoothing capacitor C _d1 , its waveform is pulse-like and contains many harmonic components, so the power factor is 60%. decreases to a certain degree. Therefore, diodes D ₅ and D ₆ are connected to the AC terminals of the rectifier circuit 3 to form a supplementary full-wave rectifier circuit together with the diodes D ₃ and D ₄ of the rectifier circuit, and the DC output terminal is turned on and off by the transistor T ₁ . Turn it off.
Based on the on/off signal C _h with a frequency higher than the frequency of the AC power supply, a period control signal V _sp is generated when the AC load current I _s is less than the reference value I _sp , I _so
During this period, a drive signal Drive is generated to turn on and off the transistor _T1 , causing a short circuit current to flow through the inductor 2, and even in a region where the AC power supply voltage _Vs is smaller than the voltage of the smoothing capacitor _Cd1 , the AC power supply 1
The power factor is improved by passing an AC load current _Is through.

In the case of Fig. 2, diodes D ₇ and D ₈ and capacitors C _d2 and C _d3 constitute a voltage doubler rectifier circuit, and diode D ₉ and transistor T ₂ and diode D ₁₀ and transistor T ₃ are connected to inductor 2 as described above. As in the case, a short circuit current is applied to improve the power factor.

In any power supply circuit, transistor
The on/off ratio (conductivity) Dc of T ₁ to _{T 3} is increased in direct proportion to the DC load current I _d flowing through the load 4, which becomes the standard for stopping the on/off operation of the transistors T ₁ to T ₃ . A high power factor can be obtained by controlling the AC load current limit values I _sp and I _so in proportion to the DC load current I _d . The load current circuit for load current detection includes:
A DC load current detection resistor R _d1 or R _d2 and an AC load current detection resistor R _s1 or R _s2 are connected.

An object of the present invention is to provide a power supply device equipped with a control circuit convenient for controlling switching elements such as transistors based on the magnitude of DC load current and AC load current in such a power supply circuit. There is a particular thing.

In order to achieve this object, the present invention generates an AC load current limit signal voltage from an on/off signal of a switching element that is controlled according to the magnitude of the DC load current, and generates an AC load current limit signal voltage. 1 of the AC power supply voltage depending on the magnitude of the signal voltage.
The present invention is characterized in that the control circuit is configured to control the on/off operation period of the switching element during the cycle.

The present invention exhibits particularly remarkable effects when applied to a power supply device using the voltage doubler rectifier power supply circuit shown in FIG. In the case of this voltage doubler rectifier power supply circuit, on/off driving of the switching element to flow a short-circuit current to the inductor is performed by a drive circuit with a reference potential set in the AC power supply circuit, as shown in Figure 2. The DC load current detection resistor R _d2 and the AC load current detection resistor R _s2 do not have a common potential.
Therefore, in order to control the conduction rate and on/off operation period of the switching element according to the magnitude of the DC load current, the control signal obtained based on the signal voltage from the DC load current detection resistor R _d2 is used as described above. A DC potential cutoff circuit is required when transmitting to the operating circuit.
According to the present invention, the control circuit in this case is such that an on/off signal for controlling the conduction rate of the switching element is created by a conduction rate control circuit in which a reference potential is set in the DC load circuit, and this on/off signal is is transmitted to the drive circuit on the AC power supply circuit side via a photocoupler or isolation transformer, and the on/off signal is again converted into an analog form AC load current limit signal voltage on the AC power supply circuit side to determine the on/off operation period. can be configured to control. Therefore, only one signal transmission circuit is required between the DC load circuit side and the AC power supply circuit side, and since the signal is transmitted in an on/off format, the transmission distortion is small and the circuit network is simplified. There is.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 4 shows an example of a voltage doubler rectifier power supply circuit type power supply device using a photocoupler as a signal transmission circuit means from a DC load circuit section to an AC power supply circuit section, and FIG. 5 shows its current and voltage waveforms. The voltage doubler rectifier power supply circuit is the same as that shown in FIG. In the DC load circuit section 5 of the control circuit, the magnitude of the terminal voltage of the DC load current detection resistor R _d2 is proportional to the DC load current I _d , and is amplified by the amplifier circuit 6 and averaged by the averaging circuit 7. This results in a DC load signal voltage Vid without pulsation.
Triangular wave voltage oscillation circuit 8 generates triangular wave voltage Vt. The comparator 9 compares the DC load signal voltage V _id and the triangular wave voltage V _t as shown in Fig.
An on/off signal _Ch for driving T ₂ and T ₃ on and off is generated as shown in FIG. 5B. As the DC load signal voltage V _id increases, the on period T _po of the on/off signal C _h becomes longer and the off period T _c becomes shorter, so the DC load current I _d and the conduction ratio D _c of the transistors T ₂ and T ₃ The relationship between the two is directly proportional as shown in Figure 6A. The output terminal of comparator 9 is photocoupler 1
0 light emitting diode D _l . In the AC power supply circuit section 11 of the control circuit, the output voltage of the phototransistor T _p of the photocoupler 10 is determined by the amplifier circuit 12.
Transistor after amplification with transistor T ₅
It is distributed to T ₆ and T ₇ and controls on/off the base currents of transistors T ₂ and T ₃ for flowing short circuit current. The on/off operation period of the transistors T ₂ and T ₃ is determined by detecting the magnitude of the AC load current I _s , and its reference value is set according to the magnitude of the DC load current I _d . The output voltage waveform of the phototransistor T _p of the photocoupler 10 is the voltage generated by the comparator 9.
This phototransistor has the same waveform as C _h .
If the output voltage of T _p turns on and off the transistor T ₄ of the analog conversion circuit 13 and charges and discharges the capacitor C ₁ via the resistors R ₁ , R ₂ and the diode D ₁₁ , then
An AC load current limiting signal voltage V _iso (negative half cycle) corresponding to the DC load current I _d is obtained in the capacitor C ₁ . By inverting the polarity of this value using the operational amplifier 14, a positive half-cycle AC load current limiting signal voltage V _isp can be obtained. conduction rate
The relationship between D _c and AC load current limiting signal voltages V _iso and V _isp is shown in Figure 6B. The terminal voltage of the AC load current detection resistor R _s2 is amplified by the amplifier circuit 15 to obtain the AC load current.
Obtain an AC load signal voltage _V is proportional to the magnitude of I _s . The period control circuit 16 includes comparators 17 and 18 and transistors T ₈ and T ₉ , and the comparators 17 and 18 change the AC load signal voltage V _is to the AC load current limit signal voltages V _iso and V as shown in FIG. _isp to obtain the period control signal V _sp shown in FIG. 5D. This period control signal
If the transistor _T9 is controlled by _Vsp through the transistor _T8 , and the base circuit of the transistor _T5 is controlled to be short-circuited, the on/off drive signal _Drive of the transistors _T2 and _T3 (the transistor _T5 's The base current) is as shown in Fig. 5(e).

By doing the above, the conduction ratio D _c of the transistors T ₂ and T ₃ can be controlled according to the magnitude of the DC load current I _d , and the on/off operation period can be controlled depending on the DC load current I _d and the AC load. Since it can be controlled according to the magnitude of the current _Is , the power factor of the AC power supply circuit is improved. In addition, in the control circuit, one photocoupler 10 is used for signal transmission between the DC load circuit section 5 and the AC power supply circuit section 11.
Moreover, since the photocoupler 10 transmits ON/OFF signal waveforms, signal conversion distortion (transmission distortion) during signal transmission does not become a problem, and the circuit network becomes simple.

The above explanation has been given by taking a voltage doubler rectifier power supply circuit type power supply device as an example, but the control circuit of the present invention
It can also be used in combination with the equal voltage rectification power supply circuit shown in the figure.

As explained above, according to the present invention, an AC load current limiting signal voltage is generated from an on/off signal for controlling a switching element, which is generated according to the magnitude of a DC load current in order to cause a short circuit current to flow through an inductor. , the switching element is turned on and off by this AC load current limiting signal voltage and AC load signal voltage.
Since the off-operation period is controlled, the power factor of the AC power supply circuit can be improved. In the case of a voltage doubler rectifier power supply circuit type power supply device, one DC potential cutoff type signal transmission circuit means is used to transmit the on/off signal from the DC load circuit section to the AC power supply circuit section. Moreover, since the transmission signal is an on/off signal, there is less signal transmission distortion and the circuit network can be simplified.

[Brief explanation of the drawing]

1 and 2 are power supply circuit diagrams of a conventional power supply device, FIGS. 3A to 3F are waveform diagrams for explaining its operation, FIG. Figures A to E are waveform diagrams for explaining the operation.
Figures A and B are characteristic diagrams for explaining its operation. DESCRIPTION OF SYMBOLS 1... AC power supply, 2... Inductor, 3... Rectifier circuit, 4... Load, 5... DC load circuit section of the control circuit, 10... Photocoupler, 11... AC power supply circuit section of the control circuit, T ₁ ~ T ₃ ... Transistor for short circuit current, T ₉ ... Transistor for period control, _Ch
...On/off signal, V _isp , V _iso ...AC load current limit signal voltage, V _is ...AC load signal voltage, V _sp
...Period control signal.

Claims (1)

[Scope of Claims] 1. A power supply circuit that converts an AC voltage from an AC power source into a DC voltage by a rectifier circuit and supplies the DC power to a DC load circuit, and a power supply circuit connected in series between the AC power source and the rectifier circuit. a switching element that causes a short-circuit current with a frequency higher than a power supply frequency to flow from the AC power supply to the inductor; and a control circuit that controls an on/off ratio of the switching element based on the DC load current. In the power supply device, the control circuit includes circuit means for generating an AC load current limiting signal voltage according to a conduction rate of an on/off signal that controls a switching element;
A power supply device comprising: a period control circuit that controls an on/off operation period of the switching element during one cycle of an AC power supply voltage according to an AC load current and the AC load current limit signal voltage. 2. The power supply device according to claim 1, wherein the rectifier circuit is a voltage doubler rectifier circuit, and the on/off signal is transmitted to a switching element drive circuit via a DC potential cutoff circuit. . 3. The power supply device according to claim 2, wherein the DC potential cutoff circuit is a photocoupler.