JPS602675Y2 - discharge timer device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a discharge timer device that uses a time constant circuit including a constant current drive type comparator and a capacitor. The present invention relates to a method for obtaining a specified timer time and improving the temperature characteristics of the timer time.

FIG. 1 shows a conventional discharge timer device using a constant current type comparator.

In Figure 1, 1 is an AC power supply, 2 is a power switch, 3
is a transformer power supply, which includes a transformer 4, a diode 5, and a smoothing capacitor 6.

7 is a load A, and 8 is an integrated circuit including, for example, a plurality of constant current type comparators 9.10, whose input/output terminals a''-
h.

a and b are power supply terminals, 69g are reference terminals, C and f are input terminals, and e and h are output terminals.

In FIG. 1, input and output to the comparator 10 are omitted for ease of understanding.

11 and 12 are resistors, and a terminal d is connected to the intersection thereof to obtain a reference voltage Vrey.

13 is a time constant circuit, which includes a capacitor 14 and a discharge resistor 1.
5.

16 is a resistor, and 17 is a switch, which charges the time constant circuit when turned on and starts discharging when turned off.

18 is a load B, which is driven by the output terminal e of the comparator 9.

Next, the operation will be explained with reference to FIG.

First, close power switch 2.

At this time, the switch 18 is off, and assuming that the residual charge in the time constant circuit 13 is zero, the terminal C of the comparator 9 is at zero, so the output terminal e also falls to zero, and the load 818 is turned on.

Next, when the switch 17 is turned on at time t□, the voltage of the time constant circuit 13 becomes ▪ in FIG.

■ At the point where it rises like the waveform and passes the reference voltage Vrsf
.

> V rer, the comparator 9 is inverted and turned off, and the load B is turned off.

After that, the voltage V0 of the time constant circuit 13 is approximately the power supply voltage V.

Rise to 0.

Then, when the switch 17 is turned off at a certain time, the time constant circuit 13 is discharged with that point as the base point of time, and the timer is started.

Thereafter, at time t3, since V,<V,ef, the comparator 9 is turned on and the load 818 is activated again.

The time t2 to t3 is the timer setting time ts.

The above is the operation of a general discharge timer, and is shown as A mode.

Next, an explanation will be given of the operation when the power switch 2 in B mode is turned off and then turned on again, or when there is a momentary power outage of the AC power supply.

When the switch 17 is turned on at time t in FIG. 2, the time constant circuit 13 is charged.

The voltage rises as shown in the waveform, and the comparator 9 turns from on to off at the point where it passes voltage Vref.

Then, when the switch 17 is turned off after a certain period of time, the time constant circuit 13 starts discharging and the timer starts.

Then, when a power outage or the like occurs for a time Δt□ from the time finger to t8, the power supply voltage Vcc starts to gradually decrease from time t6 as a base point due to the effect of the smoothing capacitor 6, as shown by the broken line in the figure.

Then, when Δ has passed since time t6, ■.

. Ku■. Therefore, the voltage of the time constant circuit 13 is ■.

is the power supply voltage ■. be higher than Then the time constant circuit 13
A so-called leakage current flows from the terminal C to the comparator 9 through the terminal C, as shown in FIG.

As a result, the time constant circuit 1
3 voltage ■.

is rapidly decreasing■.

′ There is a problem. Then, when the power is re-energized at time t8, it should be ■.

What should be a waveform is a V(,' waveform, so the comparator 9 is turned on and the load B18 is activated over time, and the set time t8 becomes t8', which shortens it.

The reason for this is due to the configuration of the constant current comparator 8 made of an integrated circuit or the like shown in FIG.

19 is a constant current source, which includes diodes 20, 21, 22, resistors 23゜24, and transistors 25, 26, 27, 28.
The X line is the output.

The comparator 9 includes constant current source transistors 29 and 30 driven by the X line, differential amplifier transistors 31, 32, 33, and 34, and an amplification transistor 3.
5, 36, 37, 38 and input protection diodes 39 and 40 from input terminals C and d, and all current constant current type comparators have this structure.

By the way, the above-mentioned leakage phenomenon when a momentary power outage occurs in mode B in FIG. 2 can be explained by the leakage phenomenon in FIG. As a result, the current flows through the transistor 25 of the constant current source 19 through the terminal.

Note that when the power supply voltage (■eC) decreases and reaches (8) where the constant current source 19 stops operating, the outflow from the X line is blocked.

This state corresponds to the period from time t7 to t8 in FIG.

Leakage current from terminal C is caused by transistor 2 of constant current source 19.
The operating current (drawing current) of No. 5 is the same ν.

Note that if the power supply does not include the smoothing capacitor 6 and the power supply voltage Vcc instantly becomes zero when a switch or the like is turned off, the above-mentioned problem does not occur.

This means that the constant current source 19 is turned off instantaneously, and the transistor 25
．． 26 is turned off.

Further, the transistors 29, 30, etc. are also reverse biased from the base to the emitter, and no current flows out.

In addition, the temperature characteristics of the conventional timer time are shown at T8 in Figure 4.
Shown as a characteristic.

This characteristic is the temperature characteristic of the capacitor 14 itself,
This is because when the temperature rises, leakage current and capacitance increase.

As explained above, the conventional discharge timer cannot provide satisfactory performance when there is a temporary stoppage of power supply or in terms of temperature characteristics.

The present invention solves all the drawbacks of the conventional device by inserting a single diode, thereby stabilizing the operating time.

The configuration of the present invention is shown in FIG.

The difference in FIG. 5 from the conventional FIG. 3 is that a diode 42 is inserted between the terminal C and the base of the transistor 31 in the direction shown in the figure, and the rest is exactly the same as FIG. 3.

Note that in the figure, the input protection diode 39, which is conventionally necessary, may be omitted.

This is because the input can be protected by the diode 42.

However, the diode 40 for input protection of terminal d is necessary.

Next, the operation will be explained.As a result of the leakage current being reliably blocked by the diode 42, even if the B mode of FIG. The discharge pressure is ■.

Since discharge is performed at a specified slope, the set time ts can be ensured.

Further, its temperature characteristics can be significantly improved compared to the conventional method, as shown by Tb in FIG.

The reason for this is that the capacitance of the capacitor 14 has a positive temperature characteristic and increases as the temperature rises (in the direction of increasing time), but conversely, the voltage across the diode 42 has a negative characteristic, that is, it decreases as the temperature rises. (in the direction of shorter time), so they cancel each other out.

In FIG. 5, the diode 42 is built into the integrated circuit 8 as a constant current type comparator.
The same result can be obtained even if this diode is removed from the integrated circuit 8 and inserted between the terminal C and the time constant circuit 13.

The discharge timer device of the present invention has the following great effects.

1 When a discharge timer device is configured using a constant current comparator driven by a constant current source by a power supply circuit including a smoothing capacitor, when a momentary power outage occurs in the AC power supply, a Although there was a discharge (leakage) current, by inserting a diode between the input terminal of the differential amplifier constituting the comparator and the time constant circuit, the time change due to the leakage current can be eliminated.

Furthermore, the temperature characteristics of the timer can be improved, and the input of the differential amplifier can be protected, which is a very significant effect.

In particular, in a discharge timer device using an aluminum electrolytic capacitor, the temperature characteristics match those of a diode so well that the temperature characteristics can be virtually ignored.

2. By incorporating the diode in the integrated circuit as a constant current type comparator used in the discharge timer device, it is possible to reduce the number of external components and improve the characteristics at low cost.

In this case, the base and emitter diodes for input protection of the transistors that constitute the differential amplifier connected to the diodes can be removed, simplifying the interior of the comparator, and allowing it to be used as a timer-specific integrated circuit at low cost and with high precision. There is.

[Brief explanation of drawings]

Figure 1 is a schematic electrical circuit diagram of a conventional discharge timer device;
3 is a conventional electric circuit diagram, FIG. 4 is a temperature characteristic diagram, and FIG. 5 is an electric circuit diagram of a discharge timer device according to an embodiment of the present invention. 3... Power supply circuit, 6... Smoothing capacitor, 8... Constant current comparator, 11, 12
...Resistance, 13...Time constant circuit, 14
...Capacitor, 18 ...Load, 42
······diode.

Claims (2)

[Scope of utility model registration request] (1) A power supply circuit including a smoothing capacitor, a constant current comparator driven in a multi-collector structure by a constant current source composed of an integrated circuit, and a capacitor that is charged when the switch is turned on and starts discharging when the switch is turned off. a time constant circuit, a reference voltage circuit that obtains a reference voltage by dividing a resistor, etc., and a load operated by the comparator,
A discharge timer device, wherein one input terminal of the comparator is connected to the reference voltage circuit, and the other input terminal is connected to a capacitor of the time constant circuit via a diode. (2) Comparators and diodes are part of a semiconductor integrated circuit.
A discharge timer device according to claim 1, which is constructed on a chip.