JPS62135261A - Variable dc voltage generation circuit for apd - Google Patents

Abstract

PURPOSE:To dispense with the boosting transformer, the source of jamming to the preamplifier, and to miniaturize the unit by striking two (2) different phased pulse signals, the amplitude of either of which is made variable, and by rectifying these pulse signals one after another. CONSTITUTION:An oscillator 1 strikes two (2) different phased pulse signals, by which the switching operations are performed on transistors 2a and 2b respectively. The pulse signal on the collector side of a transistor 2a is varied by a control 4 and inputted to an alternate double rectification circuit 3 while the pulse signal on the collector side of a transistor 2b is directly inputted to the double rectification circuit 3. This alternate double rectification circuit 3 is composed of a series-connected diode 51-5N and capacitors 61-6N and 71-7N, in which the inputted pulse signals are rectified one after another to output the DC voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a method for controlling the direct current voltage applied to an APD (avalanche photodiode), which is one of the photoelectric conversion elements that converts an optical signal into an electrical signal in an optical receiver used in optical communication. AP generated
This relates to a D variable DC voltage generation circuit.

Conventional technology In addition to the low voltage DC power supply necessary for circuit operation, an appropriate high DC voltage 1APD required for APD operation must be applied to the optical receiver of an optical receiver using an APD. It won't happen. For this reason, the optical receiver requires at least two types of voltage: low voltage and high voltage. Therefore, the optical receiver generally has one high voltage supply terminal in addition to the low voltage supply terminal for the circuit. Alternatively, as shown in Fig. 3, there is a method of incorporating the DC-DC converter 11 into the optical receiver 1o in order to eliminate the high voltage supply terminal.The conventional high voltage generating circuit described above will be explained below as shown in Fig. Explain using.

In FIG. 3, the low voltage applied to the low voltage terminal 12 supplied to the optical receiver 10 is, for example, 5V.

A low DC voltage such as 12V or 2AV required for the circuit of the preamplifier 13 is supplied. From this low voltage, DC-DC
The high voltage required for the APD 14 is boosted by the converter 11 and applied to the cathode side of the APD 14 via 15 volumes. The multiplication factor of APD14 changes depending on the applied voltage,
Further, since the withstand voltage of the APD 14 varies greatly depending on the individual, it is necessary to appropriately adjust the voltage applied to the APD 14 using the volume 15. The optical input signal is A
The optical signal is optically amplified by the PDl 4, converted into an electrical signal, and the electrical signal corresponding to the strength of the optical input signal is amplified by the preamplifier 13 and output from both ends of the load resistor 16.

Problems to be Solved by the Invention - 4J: The 1dDc-DC converter consists of an oscillation circuit, a step-up transformer for amplifying the excavated voltage, and a rectifier circuit, and is structurally large and expensive. It is. Another drawback is the AC high voltage caused by the AC step-up transformer? Very often, noise caused by use is affected by the preamplifier and becomes interfering noise. Furthermore, in order to adjust the voltage by inserting a volume into the high voltage, the DC-DC converter has the problem that a certain amount of current is required to flow through the volume.

In view of the above-mentioned problems, the present invention has the following features: Since the current capacity flowing through the APD can be very small from several μA to several μA,
The present invention provides a variable DC voltage generation circuit for an APD that can obtain any desired DC high voltage without using the step-up transformer described above.

Means for Determining Problem KWI In order to achieve the above object, the present invention provides a pulse generation circuit that generates pulse signals of two different phases, and an amplitude variable circuit that has a function of fully varying the amplitude of the pulse signal of one phase. , a multiplier rectifier circuit formed of a plurality of diode groups, and a capacitor group, and formed to sequentially rectify the pulse signal to obtain a DC voltage.

Function The present invention does not use AC high voltage in the step-up transformer, so there is no source of interference to the preamplifier.
A high DC voltage for APD can be built into the optical receiver, and the voltage can be adjusted to any desired voltage. Furthermore, the circuit configuration is extremely compact and inexpensive.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 shows a variable DC voltage generation circuit for APD in one embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a pulse oscillator that generates pulse signals of two different phases, and is formed by, for example, an unstable multivibrator circuit using a TTL (transistor transistor logic) IC.

This circuit is commonly used, and its operation will not be explained here. Reference numeral 2 denotes a buffer circuit, into which pulse signals having a phase difference of 180° from the pulse oscillator 1 are input, and the respective transistors 2λ and 2b perform switching operations.

One point on the collector side of one transistor 2b can obtain a waveform up to the amplitude of a low voltage potential as shown in the second Na. For example, at a commonly used low voltage of 5V, a 5V pulse amplitude is -p can get. The other transistor 2a is connected to the collector side via the polygon 4 at a low voltage, and is outputted from the center of the volume 4. Therefore, the amplitude of the pulse at point b can be varied from 0V to 5V as shown in Figure 2. Using these pulse signals a and bl with different phases, the multiplier rectifier circuit 3
Enter. This multiplier rectifier circuit 3 includes a diode 61...5N connected in series, and a capacitor 61...
...6N, 71...7N, 8. To simplify the explanation, let us assume that the pulse amplitude at point a is 6V and the pulse amplitude at point b is -p, which is set to 3V by the volume control.The diode 61 conducts the pulse signal a'6 at the same time as the pulse amplitude is set to 3V by the volume control. Is the signal capacitor 71? b negative period of the pulse signal through? Clamp.

The cathode side of the diode 51 is connected to the s of the pulse signal a.
A pulse signal is further added to the vl reference via a capacitor 71. The waveform at this zero point is shown in FIG. 2C. As shown in FIG. 2C, pulse signals of <5V and 3V are added. Furthermore, the diode 62 rectifies the waveform C, and at the same time, the pulse signal a is clamped to the negative period of the pulse signal & through the capacitor 61' (i-, that is, d
At the point, especially as shown in waveform d, 8v'f! :6 as standard
The pulse signal of Vp-p is clamped.

In this way, the diodes and capacitors are sequentially connected to 180
°By alternately contacting pulse signals with different phases and grounding the other side of the capacitor 8 connected to the cathode side of the terminating diode 5N, a high DC voltage can be obtained from the cathode side of the terminating diode 5N. can. Figure 2 e
shows the waveform. The anode side of only the single diode 51 may be connected to the low voltage side of DC.

As described above, according to this embodiment, the multiplier rectifier circuit 3 includes 10 diodes and 10 capacitors. When used, it is possible to easily obtain variable DC high voltage from 25V to 60V. (However, in reality, the voltage decreases somewhat due to the forward voltage drop of the diode.) Furthermore, the buffer circuit 2, which is a part of this embodiment, can also be a TTL ICi. Furthermore, if only this buffer circuit 2 uses a DC voltage (for example, 24 V) that is separate from the circuit, a high voltage can be obtained more efficiently.

Effects of the Invention As described above, APDs have a very small current capacity, but require high voltage, so the present invention can produce a variable high voltage with an extremely simple circuit configuration. In addition, since the amplitude of the pulse signal is not increased, the source of noise caused by high AC voltage is extremely small, making it very effective in practice.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing a variable DC voltage generation circuit for APD in an embodiment of the present invention, Fig. 2 is a waveform diagram showing the operation of each part of Fig. 1, and Fig. 3 is a conventional high voltage generator. FIG. 1... Pulse oscillator, 2... Buffer circuit, 3... Multiplier rectifier circuit, 4... Volume, 51~5N... Diode , 61~
6N, 71-7N. 8... Capacitor. Name of agent: Patent attorney Toshio Nakao and one other person
Era - Calm d, xs tj Export 0 Ward 3 Figure L J-X f2 I Ujiga λ No E Optical reception country

Claims (1)

[Claims] A pulse generating circuit capable of extracting pulse signals of two different phases, an amplitude variable circuit having a function of varying the amplitude of the pulse signal of one of the phases, a plurality of diode groups and a plurality of capacitor groups are used to generate the pulse signals. A variable DC voltage generation circuit for an APD, comprising a multiplier rectifier circuit that can sequentially rectify signals to obtain a DC voltage.