JPS5910583Y2 - Photoconductor driving device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a photoconductor driving device, and particularly to an energizing power supply circuit for driving a photoconductor.

Photoconductors such as CdS are smaller, lighter, and more sensitive than light-receiving elements such as phototubes and transistors, and are therefore widely applied to detect finely modulated optical input signals.

A photoconductor such as CdS is driven by applying a constant DC voltage, and the output for a constant human optical signal increases in proportion to the magnitude of the applied voltage.

Therefore, in order to improve the detection sensitivity of the finely modulated optical input signal, it is sufficient to increase the DC voltage that energizes the photoconductor, but increasing the DC voltage inevitably increases the size of the power supply circuit.

A photodetection device using a photoconductor such as CdS as a light receiving element is applied to, for example, a blood flow signal or pulse signal detector in a blood pressure measuring device, so it needs to be small and lightweight.
A battery is used as a driving DC power source.

On the other hand, when detecting the above-mentioned blood flow signals, a photodetector using a photoconductor as a light-receiving element detects finely modulated light signals modulated by blood flow from the blood vessel wall, so it needs to be highly sensitive and In order to operate stably for a long period of time, low power consumption is required.

In view of the above, this idea aims to provide a drive device with high detection sensitivity and low power consumption even when driving a photoconductor such as CdS with a small-capacity DC power source such as a battery. The photoconductor is driven by converting a DC voltage into an intermittent pulse voltage using an intermittent oscillator, converting the intermittent pulse voltage into a DC voltage, and driving the photoconductor with the DC voltage.

This invention will be explained below with reference to the drawings.

In the figure, O is an oscillation circuit, and in the example, transistor Q
- An intermittent oscillation transformer T, a resistor R1, and a capacitor C1 constitute a well-known blocking oscillator.

E is a battery as a DC power source.

The direct current voltage of the battery E is converted into an intermittent pulse voltage by a blocking oscillation circuit O, and boosted by an intermittent oscillation transformer T.

A in the figure shows the output voltage waveform.

This boosted pulse voltage is applied to the intermittent oscillation transformer T.
The voltage is rectified and smoothed by a rectifier D2 and a capacitor C2 connected to the next side and converted into a direct current, and this converted voltage is applied to CdS(P) via a load resistor R2.

In the above structure, when light is incident on the CdS(P), the conductivity of the CdS changes depending on the intensity of the light, and an output voltage corresponding to the optical signal is obtained at the output point X.

In this case, in this design, CdS(p) changes the pulse voltage to D2
Since it is driven by a voltage that is rectified by C2, integrated by C2, and converted to DC, the power source impedance is high, and the output voltage generated at output point X due to the incidence of light can be driven by a low impedance DC power source such as a conventional battery. This means that a larger output voltage can be obtained for the same optical input signal than in the case where the optical input signal is the same.

In other words, when the CdS is driven by a DC power source such as a battery, the source impedance is low, so when light enters the CdS, the voltage at the output point X is the output voltage determined by the resistance ratio of the load resistance (R2) and the CdS. On the other hand, this device that drives CdS with intermittent pulse voltage has extremely high power source impedance, so at output point The voltage at output point Y fluctuates, and a voltage that is superimposed with this changing voltage is generated, so for the same optical input signal,
A large output signal can be obtained.

The table below shows the output voltage generated at the output point This shows actual measurement results.

Note that the input optical signal has a pulse width Q as shown in the figure.
．． lsec, pulse period Q. A 5 sec modulated optical input signal was used.

As is clear from the above measurement results, for the same applied voltage and the same optical input, this device provides approximately twice the output voltage, or in other words, approximately doubles the detection sensitivity. .

As described above, this invention converts DC voltage into intermittent pulse voltage, and converts this intermittent pulse voltage into DC and applies it to a photoconductor such as CdS to drive it, so the power source impedance is high and the detection sensitivity is high. The photoconductor driving device is improved in comparison with a conventional device driven by direct current voltage such as a battery, and because it is pulse driven, power consumption is low, so a photoconductor driving device that operates stably for a long period of time can be obtained.

In addition, since the detection sensitivity is improved, the power supply circuit can be simplified and the photodetection device can be made more compact compared to conventional methods that apply DC voltage from a battery or other source to obtain the same detection sensitivity. Become.

Furthermore, if the pulse voltage converted by the intermittent oscillation circuit is boosted as in the embodiment, a photoconductor driving device with high detection sensitivity can be obtained using a small DC power source such as a battery.

[Brief explanation of drawings]

The drawing is a circuit diagram showing an embodiment of this invention. E: battery, O: intermittent oscillation circuit (blocking oscillator),
D2: Rectifier, C2: Smoothing capacitor, R2: Load circuit, P: CdS (photoconductor).

Claims (1)

[Scope of utility model registration request] a rectifying and smoothing circuit consisting of a DC power supply, an intermittent oscillator that inputs the voltage of the DC power supply and converts it into an intermittent pulse voltage, and a rectifier and a capacitor for converting the pulse voltage output from the intermittent oscillator into DC; It consists of a series circuit of a photoconductor and a load resistor connected in parallel to the capacitor of the rectifying and smoothing circuit, and a DC voltage obtained from both ends of the capacitor is applied to the photoconductor as a driving voltage through the load resistor. A photoconductor driving device configured to apply an electric current to a photoconductor.