JPS5812244Y2 - Phase controlled power supply circuit - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a phase-controlled power supply circuit that is used in transformerless television receivers and the like, and uses a thyristor or the like as a rectifying element.

In general, transformerless systems that omit power transformers are often used in the power supply circuits of home appliances such as television receivers that use commercial power to reduce the weight and cost of the equipment.

Normally, commercial power supplies are accompanied by voltage fluctuations that cannot be ignored, so it is necessary for the power supply circuits used here to stabilize their output voltages.

This is because if the output voltage is not stabilized, stable operation of electronic circuits within the device cannot be expected, and failures are likely to occur if excessive voltage continues for a long time.

A typical power supply circuit for such applications is a phase-controlled power supply circuit using a thyristor as shown in FIG. 1, for example.

Regarding the circuit shown in FIG. 1, the inventor focused on the following points in arriving at the present invention, and first, the operation of the circuit will be explained.

That is, terminal T1. Output voltage V across T2.

is controlled by the length of the conduction phase of the thyristor (hereinafter abbreviated as SCR) 13.

That is, in the positive half cycle of the AC power supply 11, 5CR
If the timing at which 13 turns on is earlier, the output voltage will be V.

increases, and if the timing is delayed, the output voltage vo decreases.

Turn-on of the above 5CR13 is a programmable unijuction transistor (hereinafter abbreviated as PUT) 1
This is done by a trigger pulse derived from 5.

The trigger pulse generation conditions are that the voltages at the anode and gate of PUT15 are VA and VG, respectively, and the voltage between the anode and gate when PUT15 turns on is VT.
When R is assumed, ■A=VG+VTH (1).

That is, while VA<VG+VTH, PUT15 is off and the 5CR13 hetrica pulse is not applied.

However, the charging voltage of capacitor C1 increases and
When the formula is satisfied, PUT15 turns on at that moment,
Give a 5CR13 trigger pulse.

Here, the voltage VA is the resistance R2 and the capacitor C1.
The voltage VTH is determined by the time constant circuit consisting of the Zener diode 140 and the energy voltage of the Zener diode.
15 is unique.

Therefore, the voltage VAjVTR is the output voltage V of this power supply circuit.

Not affected by However, the voltage VG is
Since it is connected to the output terminal T1 via R6 and R6,
Output voltage V.

If the voltage vG changes, the voltage vG also changes. For example, if we consider the case where the output voltage drops, this voltage drop is caused by the resistance R
Voltage v through the resistor circuit consisting of 3 and R6 to R9
Decrease G.

Then, as is clear from equation (1), the voltage vA at which PUTl5 is turned on also decreases.

If this voltage vA decreases, the time required for the charging potential of the capacitor C1 to reach the voltage VA will be shortened.
The timing at which PUTl5 turns on is accelerated.

That is, the output voltage V.

If V were to decrease, the timing at which PUT15 would generate a trigger pulse would be earlier, which would extend the phase period during which 5CR13 turns on, causing the output voltage V to decrease.

operates to compensate for the decrease in

As mentioned above, the output voltage stabilization effect of this power supply circuit is
Output voltage V.

is done by negative feedback to the gate of PUTl5.

Here, the amount of change in the output voltage vo is defined as JVo, and this amount of change is Av.

If the amount of change in the voltage vG corresponding to , is JVG, then the ratio of the amount of change is, 4. VG/Δvo is approximately as follows.

The larger the AVG/Avo is, the stronger the negative feedback effect becomes, and the less the voltage fluctuation of the output voltage Vo becomes.

On the other hand, in the initial stage of operation of this power supply circuit, that is, the power switch 1
Let's consider the case when 2 is inserted.

Output voltage V before this switch 12 is turned on.

If is zero, it is equivalent to output terminals T1 and T2 being short-circuited.

Therefore, if the voltage VQ immediately after the switch 12 is turned on and the zener voltage of the east zener diode 14 are Vz, then the equation is approximately as follows.

By the way, in order to operate the 5CR13 reliably, a trigger pulse with a certain level of energy is required.

The energy of this trigger pulse is derived from the electrostatic energy stored in capacitor C1.

Therefore, the charging energy of capacitor C1 when PUTl 5 turns on, or 1/2C1VA!
should be as large as possible.

When rewritten using equation (1), this energy is 1/
Since 2C1(VG+VTH)2 and t, c6° or more, the capacitor C
Possible methods include increasing the capacitance of 1 and increasing the voltage vG.

The former method of increasing capacitance is less effective as the capacitor C1 becomes larger and more expensive.

Therefore, the latter method of increasing the voltage vG can be said to be a better method.

As a means for increasing this voltage VG, according to equation (3), there are two possible methods: increasing the Zener voltage vz, and decreasing the resistor R3 and increasing the resistors R6 to R9.

The former means of increasing the Zener voltage vz is nothing but using a Zener diode 14 with a large Zener voltage.

However, Zener diodes with high Zener voltage generally have
Since the temperature coefficient of the Zener voltage is large, the use of such a Zener diode will deteriorate the temperature characteristics of the power supply circuit.

Furthermore, in order to maintain the Zener voltage vz stably, a certain amount of current must be allowed to flow through the Zener diode 14.

Therefore, increasing the Zener voltage Vz increases the power loss of the Zener diode 14.

Then, a large dog loss type Zener diode 14 must be used, which also becomes expensive.

Therefore, in order to increase the energy of the trigger pulse without increasing the product price, there is no better way than to decrease the resistor R3 and increase the resistors R6 to R9, as described above.

However, as mentioned above, by reducing the resistance R3, the resistance R6 becomes
As can be seen from equation (2), if R9 is increased,
△VG/△Vo becomes smaller.

In other words, increasing the energy of the trigger pulse and decreasing the voltage fluctuation rate of the power supply circuit include contradictory conditions.

As a practical matter, if this power supply circuit does not operate reliably after the switch 12 is turned on, it is useless.

Therefore, in conventional circuits, it is necessary to either sacrifice the voltage fluctuation rate to some extent or accept an increase in product price, and use an expensive high-voltage, high-loss, temperature-compensated Zener diode, or use a large-capacity capacitor C1. Furthermore, as shown in FIG. 2, an optical coupling element 16 is used as a negative feedback means.

This idea was made in view of the above circumstances, and the purpose is to provide a phase-controlled power supply circuit that ensures reliable circuit operation when the power switch is turned on, improves the voltage fluctuation rate, and can be realized at low cost. do.

An embodiment of this invention will be described below with reference to the drawings.

That is, as shown in FIG.
connected to the anode of 3.

The cathode of the 5CR13 is connected to one output terminal T1 of the power supply circuit, and the cathode of the 5CR13 is connected to the other output terminal T1 of the power supply circuit.
2 is connected to the other end of the AC power source 11.

The anode of the 5CRI 3 is connected to the cathode of a Zener diode 140 via a resistor R1, and the anode of the Zener diode 14 is connected to the other end of the AC power supply 11.

The cathode of the Zener diode 14 is connected to one end of the capacitor C1 via a resistor R2, and this capacitor C
The other end of AC power supply 11 is connected to the other end of AC power supply 11 .

A time constant circuit is formed by this resistor R2 and capacitor C1.

One end of the capacitor C1 has a PU as a trigger element.
The anode of T15 is connected.

The gate of this PUT 15 is connected to the cathode of the Zener diode 140 via a resistor R3, and the cathode of the PUT 15 is connected to the other end of the AC power source 11 via a resistor R4.

The gate of the PUT 15 is connected to the other end of the AC power supply 11 via a resistor RIO, forming a relaxation oscillation circuit.

The cathode of the PUT15 is connected to the gate of the 5CR13 via a capacitor C2, and the gate of the 5CR13 is connected to the cathode of the 5CR13 via a resistor R5.

The cathode of this 5CR13, that is, the power supply circuit output terminal T1
is connected to one end of a resistor R7, and the other end of the variable resistor R7 is connected to the other end of the AC power supply 11, ie, the output terminal T2 of the power supply circuit, via a resistor R8.

The variable resistor R7 is used to adjust the output voltage, and the anode of the diode 1T is connected to one end of the variable resistor R7.
The cathode of this diode 17 is connected to the gate of the PUT 15.

A smoothing capacitor C3 is connected between the cathode of the 5CR13 and the other end of the AC power supply 11, and the output terminal T
For example, a resistor RL is connected between T1 and T2 as a load.

The operation of the power supply circuit configured as described above is basically the same as that described in FIG. 1.

Therefore, for the circuit shown in FIG. 3, the ratio △VG/△vo of the change △Vo in the output voltage to the change △VG in the gate voltage of PUT 15, which is related to the voltage fluctuation rate, and the trigger pulse when the switch 12 is turned on.・P related to energy
The gate voltage VG when the UT 15 is turned on will be explained.

First, JVG/JVo of the circuit shown in FIG. 3 is determined in the same way as formula (2) was determined.

What should be noted here is that from the output terminal T1 side to PUT1
In response to the negative feedback signal applied to the gate of 5, diode 1γ is top biased and therefore has almost no resistance valve.

That is, △VG/△v. is approximately, becomes.

Next, consider the voltage vG immediately after the power switch 12 is turned on.

In this case, the diode 1T is reverse biased until 5CR13 turns on and the output voltage rises to a certain extent, so the circuit of resistors R3 and RIO
It is separated from the circuits 6 to R8.

Therefore, the voltage vG immediately after the switch is turned on is approximately as follows, assuming that the Zener voltage of the Zener diode 14 is Vz.

From equations (4) and (5), J, VG/, J, V
o to be thicker (in order to make resistance R6 smaller and resistor R7
Even if +R8 is increased, the voltage V immediately after switch 12 is turned on
It turns out that G is not related.

Also, from equation (5), increasing the resistance RIO in order to increase the voltage vG means that AVo/□J, V
This also kills two birds with one stone by increasing o.

In other words, it is possible to secure the trigger pulse energy at the time of switching on and to improve the voltage fluctuation rate at the same time.

Moreover, the additional component required to obtain the above effect is a diode.
One piece is enough.

This diode has a small current flowing and a low reverse bias voltage, so it can be used with a very common and inexpensive small diode, such as an optical detection diode, so there is almost no increase in the price of the entire power supply circuit. good.

As described above, according to the phase-controlled weir power supply circuit according to this invention, a power supply circuit that ensures reliable operation when the power switch is turned on and improves the voltage fluctuation rate at the same time can be realized at low cost. It is easy to implement because there are few changes to the .

For example, when modifying the power supply circuit shown in Figure 1 to the power supply circuit shown in Figure 3, when assembling the printed wiring board, a diode 17 is inserted in place of the resistor R9, and the resistor RIO is connected to the pattern surface of the printed wiring board. You can solder it directly to the

Furthermore, since it is easy to secure the trigger pulse energy, it is possible to make the capacitor C1 of the time constant circuit smaller than in the conventional circuit (in this case, increase the resistor R2 as necessary), depending on the design. The overall price can be lower than that of conventional circuits.

In the above embodiments, a PUT is used as the trigger element, but this can also be realized by other trigger elements, such as a unijunction transistor (UJT) or a monostable multi-circuit.

Furthermore, the present invention may be applied to a circuit using other semiconductor switching elements instead of the SCR used in the above embodiments.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing a conventional phase-controlled weir power supply circuit;
The figure is a circuit diagram partially showing another example of the conventional circuit, and FIG. 3 is a circuit diagram illustrating an embodiment of the phase control weir power supply circuit according to the present invention. 11...AC power supply, 12...power switch, 13.
...5CR114... Zener diode, 15...
PUT (programmable unijunction transistor), 1T...diode, R1-R6t R8~
RIO...Resistor, R7...Variable resistor, R...Load resistance, 01-C3...Capacitor, T1. T2...
Terminal, 13...first thyristor, R1t14...
Clamp circuit, 15... second thyristor, R4t
c2t R5...Ignition means, R6-R8...Voltage fluctuation detection means.

Claims (1)

[Claims for Utility Model Registration] An input circuit to which an input voltage to be converted into a stabilized DC DC voltage is applied, an output circuit that provides this DC DC voltage, and a current path between the anode and cathode of the input circuit. a first thyristor provided between a circuit and the output circuit; a clamp circuit that clamps the input voltage to a predetermined voltage; a voltage clamped to a predetermined voltage level by the clamp circuit; a second thyristor fired by a potential difference with the integrated voltage; means for firing the first thyristor in response to firing of the second thyristor; A phase-controlled power supply circuit comprising: voltage fluctuation detection means applied to the gate of a thyristor; and a diode interposed and connected between the voltage fluctuation detection means and the gate of the second thyristor.