JPS6019687B2 - Time-voltage conversion circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a time-voltage conversion circuit, and more particularly to a time-voltage conversion circuit in which semiconductor elements of the time-voltage conversion circuit are constructed from monolithic ICs.

Conventionally, there is a method in which two capacitors are provided, the first capacitor is discharged for an appropriate period of time, and the second capacitor is charged depending on the amount of discharge. FIG. 1 shows an example of this. An example of such a circuit is the
No. 53743 is known. A resistor 2 is inserted as a collector resistor in the transistor 1, and a capacitor 3, a resistor 4, and a diode 5 are each connected in series and inserted between the collector and ground.

A diode 6 is connected in series to the output of the capacitor 3, and a capacitor 7 is further connected to perform predetermined charging. A transistor 8 whose bias voltage is the charging voltage of the capacitor 7 is connected to the capacitor 7 . An emitter resistor 9 is connected to the transistor 8,
The voltage drop that occurs across this resistor is extracted as an output.
2A shows the input signal waveform input to the transistor 1, and FIG. 2B shows the output signal waveform output from the transistor 8.

The capacitors 3 and 7 are charged in the direction shown in the figure, and the transistor 1 is turned on during the OFF period of the input signal, that is, the time T. While the transistor is on, the capacitor 3 is discharged through the diode 5 and the resistor 4. However, due to the parasitic effect, a diode 10 is connected between the anode of the diode 6 and the ground as shown in the figure. becomes. Therefore, the charge in the capacitor 3 is instantly discharged through the diode 10 and the transistor.Therefore, the amount of discharge in the capacitor 3 is not affected by the on time of the transistor 1, and the moment the input signal turns on (the transistor is off). The capacitor 7 is rapidly charged by the loop of the resistor 2, capacitor 3, and diode 6, and the charging voltage of the capacitor 7 becomes a voltage that is completely unaffected by the off-time of the input signal. When configuring a diode with a monolithic IC, the best configuration is to connect the collector terminal 22 and base terminal 21 of the NPN transistor structure shown in FIG. 3. When this configuration is adopted, the lowest potential of the monolithic IC Layer layer 0chi, Figure 3 Substrate layer 2
5, a structure is obtained in which a PN strike direction diode is connected to the collector layer 22, and a diode 10 is connected between the anode of the diode 6 in FIG. 1 and the ground.

As mentioned above, when a diode or discrete circuit is constructed with one monolithic IC, the diode 10 is connected to one end of the capacitor from the substrate layer, which has the lowest monolithic potential, due to parasitic effects, and the capacitor's Discharge occurs without passing through a discharge resistor, making it difficult to change the amount of discharge depending on the time.If the semiconductor device is constructed as a single monolithic device, even if there is a diode due to this parasitic effect, , a configuration is required in which the capacitor is discharged through a resistor.

SUMMARY OF THE INVENTION An object of the present invention is to provide a time-voltage conversion circuit that eliminates parasitic effects caused by diodes and exhibits good performance.

The present invention uses two capacitors, and connects a resistor in series with the first capacitor so that the discharge charge amount of the first capacitor changes with time, and sets the lowest potential of the discharge loop to the lowest potential of the monolithic IC. It is configured so that the potential layer voltage does not drop by more than the forward voltage drop of the diode, and when charging the second capacitor, most of the charging current flows through the diode connected in parallel with the discharging resistor of the first capacitor. The circuit configuration is such that it is not affected by the parasitic effects of a monolithic IC.

FIG. 4 is a circuit diagram showing an embodiment of the present invention. In FIG. 4, the same members as those used in FIG. 2 are given the same reference numerals. In FIG. 4, a monolithic IC 30 is composed of a transistor 1, a resistor 2, diodes 5 and 6, a transistor 8, and a resistor 9.

Furthermore, a conversion circuit is constructed using each of the capacitors 3 and 7 and the resistor 4 as external components. A pulse signal as shown in FIG. 3A is input to the base of the transistor, transistor 1 is turned on during the off time T of the pulse signal, and the charge in capacitor 3 is transferred through diode 10, resistor 4, and transistor 1. , is discharged with a time constant consisting of resistor 4 and capacitor 3.

At this time, the lowest potential of the discharge loop is at point A, which is a value lower than the lowest resistance potential OV of the power supply voltage by 0.7 V of the forward voltage of the diode 10. That is, the potential at point A is -0.7
It becomes V. Next, when the input signal is turned on, transistor 1 is turned off for a time of To-T, and during this time, capacitor 7
is charged in a loop consisting of resistor 2, diode 5, capacitor 3, and diode 6 with a time constant determined by resistor 2 and capacitors 3 and 7. In order to obtain an output voltage corresponding to the OFF time of the input signal, in this circuit, the value of the resistor 2 is set to be a value sufficiently subtracted by 4 times the value of the resistor 4.

The output of the capacitor 7 is connected to a resistor 9 in an emitter-follower configuration by a transistor 8, and the discharge resistance of the charge charged in the capacitor 7 is set to be sufficiently large, so that the output terminal as shown in FIG. An output voltage such as is generated.

That is, when the off time of the input signal is long, the amount of discharge of the capacitor 3 becomes large, and therefore the amount of charge of the capacitor 7 becomes large. As shown in FIG. 3, when the off time of the input signal is T, the output voltage has a value of V, as shown in FIG. 3B, and when ~(T2>T,), V2 (V2> V,)
As a result, an output voltage that responds to time can be obtained. According to the embodiments of the present invention, a monolithic IC can be constructed without being influenced by parasitic effects, so that reliability can be improved.

Further, since no new parts are required just by changing the circuit configuration, there is also an effect of cost reduction. As an application example, IC
A full-torra ignition system is most suitable and has a remarkable effect.
As is clear from the above, according to the present invention, it is possible to eliminate the influence of parasitic effects peculiar to a monolithic IC structure.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing a conventional time-voltage conversion circuit;
Figures A and B are waveform diagrams showing the input signal of the switching circuit and the output signal obtained by the embodiment of the present invention, and Figure 3 is a cross-sectional view showing the transistor structure and substrate structure in the molythic IC. FIG. 4 is a circuit diagram showing an embodiment of the present invention. 3, 7... Capacitor, 4... Resistor, 5, 6, 10
"""Diode. Figure 2 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. In a time-voltage conversion circuit that takes pulse waveforms with different on and off times as input signals and outputs an output signal that changes according to the change in time width of the signal;
a first capacitor that discharges a charge that is charged during one period of the on or off period of the input signal during the other period of the input signal; a diode connected in series to the first capacitor in order to discharge the accumulated charge in the first capacitor slowly at a predetermined time constant; A second capacitor is connected in series with the first capacitor during the other period of the input signal, charges the discharged charge of the first capacitor, and uses the charging voltage as an output signal. A time-voltage conversion circuit.