JPS609857Y2 - power supply - Google Patents

Description

[Detailed description of the invention] This invention relates to power supply devices for electronic equipment, etc., and is effective when applied to circuits that rectify AC power to obtain DC voltage. It is designed to supply a safe DC voltage that will not destroy the semiconductors inside the equipment even if the voltage fluctuates.

In general, when the AC power supply voltage fluctuates significantly with respect to the rated voltage, in conventional circuits that rectify the AC power supply voltage to supply DC voltage, a stabilization method is used to cope with fluctuations in the AC power supply voltage. The following methods are known.

First of all, there is the series regulator.

This method is fine as long as the fluctuation is small, but it has the drawback of not being efficient because a large amount of loss (margin) is set aside for large fluctuations.

The second type is a switching regulator, which first rectifies AC power and converts it to DC, and then operates in pulses at a relatively high frequency, but it requires pulse generation and a pulse transformer, and has a complicated configuration. Ta.

Third, there is the AC phase control method, which uses pulse generation (e.g. UJT, trigger diode, etc.)
It required a pulse transformer, a power transformer, and a diode bridge to operate these, resulting in a complex configuration.

The above-mentioned methods are not necessarily able to adequately cope with large fluctuations in the AC power supply.

In such cases, a transformer device such as a slider is used to adjust the power supply voltage supplied to the rectifier or the like by increasing or decreasing the voltage.

However, when compensating using a transformer device in this way, if the AC power supply voltage drops and the AC power supply voltage is boosted to cope with it, then while the AC power supply voltage has been operated for a while in the boosted state, the AC power supply voltage will conversely increase. The voltage may return to its original normal value or rise above it, increasing by the step-up ratio of the transformer, and high voltage may be applied inside the device.

This has caused semiconductors and parts to be destroyed.

Therefore, in the past, it was necessary to constantly monitor fluctuations in the AC power supply voltage.

However, even with monitoring, it is often not possible to respond immediately to fluctuations, often causing the above-mentioned drawbacks.

The present invention addresses the above-mentioned drawbacks and provides a power supply device that can supply a stable DC voltage even when the AC power supply voltage rises and falls significantly.

The present invention will be explained below with reference to FIGS. 1 to 5.

First of all, Fig. 1 is a circuit diagram showing an embodiment of the present invention. To describe this, 1 is an AC power supply, and a bridge type rectifier circuit consisting of diodes 2, 3, and 4.5 is connected to both ends of the AC power supply. There is.

A smoothing circuit 7 having a first capacitor 6 and a load circuit 8 are connected to the connection point a between the diodes 3 and 5, and the other ends of the capacitor 6 and the load circuit 8 are grounded to a reference potential.

Furthermore, voltage dividing resistors 9 and 10 are connected in series between the connection point a and the ground point, and the midpoint between these resistors is connected to one end of a Zener diode 11.

The other end of this Zener diode 11 is the first NP
Connected to the base of N transistor 12, the collector of this transistor 12 is grounded, and the emitter is connected to resistor 2.
0 to the -B power supply.

Further, the emitter is connected to the base of a second PNP transistor 13, and the emitter of this transistor 13 is grounded, and the collector is connected to the connection point between the diodes 2 and 4 via a second capacitor 14.

Furthermore, the collector of the transistor 13 is further connected to the diode 1.
5 to the ground, and also connected to the gate of the thyristor 17 via the diode 16.
The anode of is grounded and the cathode is connected to the connection point.

Note that a capacitor 18 and a resistor 19 are connected to the thyristor 17 in parallel.

Now, the operation of such a circuit will be explained with reference to FIGS. 3 and 4.

First, when the AC power supply 1 has a polarity voltage as shown in the figure, it passes from the ■ side of the power supply 1 through the diode 3, and then the capacitor 6.
The main current flows through the anode to the cathode of the thyristor 17, and the current flows through the diode 4 to the e side of the AC power supply 1.

The action of triggering the thyristor 17 for current to flow in this way is to flow from the emitter of the transistor 13 through the diode 3, through the capacitor 6, through the collector, through the capacitor 14, through the diode 4, and thus across the capacitor. A current flows through the diode 16 to the gate of the thyristor 17 due to the charge stored in the thyristor 14, and this is done when the magnitude of this current exceeds a predetermined current value.

This turns the thyristor 17 on.

Therefore, capacitor 6 is charged and this capacitor 6
A charging voltage (EB) across both ends of is supplied to the load circuit 8.

Note that when the thyristor 17 is turned on, the charge in the capacitor 14 flows through the diode 15 and the anode and cathode of the thyristor 17 and is discharged. Until charging starts, the gate current of the thyristor 17 does not flow.

Furthermore, if the polarity of the AC voltage is reversed to that described above, the same explanation will be given by replacing diode 3 with 5 and diode 4 with 2 in the above description.

The waveform of the gate current of the thyristor 17 in the above operation is shown in FIG. 3a, and the waveform of the charging current of the capacitor 6 is shown in FIG.

Note that the Zener diode 11 is connected to the base of the transistor 12, and since the voltage applied to the resistor 10 exceeds a predetermined value, the Zener diode 11 becomes conductive, and the base voltage is applied to the transistor 12, resulting in a state of predetermined conductivity. is maintained.

In a circuit operating in this manner, when the voltage of the AC power supply 1 increases, the voltage applied to the resistor 10 increases beyond the reference value, so the base voltage of the transistor 12 increases and the conductive state changes.

Therefore, the conductivity of transistor 13 decreases.

(In other words, if the resistance value between the collector and emitter of the transistor 13 is r□, this r process becomes large.

) Therefore, the increase in the gate current of the thyristor 17, which is determined by r□ and the capacitance value C□ of the capacitor 14, slows down.

In other words, in steady state, since r□ is small, capacitor 1
4 was charged early, and the gate current was flowing through the diode 16 early, but as rl increases, the time constant determined by clxr increases, and the capacitor 14
As the charging of the thyristor 17 becomes slower, the increase in the gate current of the thyristor 17 becomes slower as shown in FIG.

Therefore, the time between ignition and extinction is shortened, and the charging time for the capacitor 6 is shortened.

Therefore, as shown in FIG. 4, the increase in charging of the capacitor 6 is suppressed, and the voltage of EB is controlled to an extremely low rate of increase compared to the rate of increase of the AC power supply, so that an excessive DC voltage is applied to the load circuit 8. can be prevented from joining.

In this way, even if the AC power supply voltage increases for some reason, the DC voltage applied to the load circuit 8 does not increase and can remain stable.

Furthermore, even when the AC power supply voltage drops, the DC voltage can be stabilized without dropping.

Therefore, damage to the semiconductors and components used in the load circuit 8 can be prevented.

In addition, the control method has low power loss. FIG. 2 is a circuit diagram showing another embodiment of the present invention.
The difference from FIG. 1 is that diodes 15 and 16 have been removed.

It will work even if the diodes 15 and 16 are omitted, but in this case, when the thyristor 17 turns on, its main current -I shunts the capacitor 14, so the waveform of the current is as shown in Figure 5a. FIG. 5 shows the original waveform of the charge of the capacitor 6 in this case.

In the embodiment described above, the -B power supply was used as the bias power supply for the transistors 12 and 13, but one end of the resistor 20 may be connected to the connection point S.

Furthermore, various other modifications can be considered based on the above explanation.

As described above, the present invention can supply a stable DC voltage against fluctuations in the AC power supply voltage, reliably prevent damage to semiconductors and other components, and is extremely practical.

[Brief explanation of drawings]

1 and 2 are circuit diagrams showing an embodiment of the power supply device of the present invention, and FIGS. 3 to 5 are current waveform diagrams of various parts for explaining the operation of the present invention. 2, 3.4.5... Diode constituting the rectifier circuit, 6... First capacitor, 7...
・Smoothing circuit, 12...First transistor, 1
3...Second transistor, 14...
Second capacitor, 17...thyristor.

Claims (1)

[Claims for Utility Model Registration] A diode bridge circuit that rectifies an alternating current voltage applied to first and second terminals by an alternating current power supply; a smoothing circuit connected between a third terminal and a reference potential; a voltage detection means for detecting the voltage of the smoothing circuit; and a voltage detection means for comparing the voltage of the smoothing circuit detected by the voltage detection means with a predetermined reference voltage. , the gate current is controlled by the time constant of a time constant circuit comprising an impedance control means whose impedance is controlled by this comparison, a capacitor connected to this impedance control means, and an impedance of this capacitor and the impedance control means. , comprising a thyristor whose cathode and anode current paths are connected between a fourth terminal of the diode bridge circuit and a reference potential in order to control the current flowing through the diode bridge circuit, and wherein the time constant is controlled by the impedance control means. A power supply circuit characterized in that the output voltage of the smoothing circuit is kept constant through control.