JP2010157032A - Overcurrent preventing circuit for light receiving module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide small-size, simple, and practical light receiving module circuit protection for protecting a light receiving module circuit from transient response caused by using a boosting circuit or the like. <P>SOLUTION: This light receiving module circuit where a reverse current prevention circuit is inserted between a cathode of a light receiving element and the boosting circuit, and are electrically interconnected in series, and a diode as an element having rectification is used as the reverse current prevention circuit, thereby constructing the light receiving module circuit establishing conditions such as miniaturization or electric power saving. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a circuit for protecting a photodetector used in an optoelectronic device from overcurrent.

  Currently, a light receiving element using a semiconductor is used as a photodetector for converting an optical signal into an electrical signal. Among them, photodiodes are often used as elements that satisfy the conditions such as low cost, stable supply, downsizing, long life, and power saving.

  Types of photodiodes include pn junction photodiodes (pn-PD), PIN structure photodiodes (PIN-PD), and avalanche photodiodes (APD). However, pn-PD is slower than PIN-PD and APD, and PIN-PD and APD are often used as photodiodes in current optoelectronic devices that require high-speed and high-sensitivity operation.

  The PIN-PD and APD are further excited by the collisional ionization of internal atoms by incident light from the light receiving portions under the state where carriers are excited by applying a reverse bias to both ends of the PIN-PD and APD. It takes advantage of the property that a large current flows as a result of being induced.

  Conventionally, a light receiving module circuit using a light receiving element such as PIN-PD or APD uses a sequential circuit having a large circuit scale such as a flip-flop circuit so as not to be damaged by a transient response generated when power is turned on. . However, there is a strong demand for miniaturization and power saving for an optoelectronic device using a light receiving module circuit, and a sequential circuit is often not mounted on such a device. As an alternative, in the case of APD, a booster circuit is used to amplify the output from the apparatus power supply in order to supply stable power for the light receiving element. In the case of PIN-PD, a surge protection circuit or the like is generally used to cope with a sudden voltage fluctuation.

  However, a booster circuit used for APD is generally composed of a switch composed of a diode and a transistor, and a capacitor. The power supply supplied to the light receiving element when the power is turned on corresponds to the time constant of the booster circuit. There will always be a delay. As a result, a forward bias (for example, about 1 V to 2 V) voltage is applied between the light receiving elements during the transient state time when the power is turned on, and a new transient response problem occurs in which a forward bias current exceeding an allowable amount is generated. This contributes to a change in characteristics of the light receiving module circuit and damage to elements used in the circuit. A similar phenomenon occurs when a protection circuit such as a surge protection circuit is used.

Patent Documents 1 to 3 disclose techniques related to stable operation of the light receiving module circuit. Patent Document 1 proposes a semiconductor light-receiving element that can efficiently convert incident light into a voltage. Patent Document 2 proposes a bias method for obtaining an output with an optimum multiplication factor regardless of the state of incident light. Has proposed an optical receiver circuit for preventing APD damage due to overvoltage.
JP 2008-198937 A JP-A-6-164501 JP-A-11-275755

  However, the techniques described in Patent Documents 1 and 2 are techniques for efficiently converting incident light to output, and do not solve the problems that occur in the light receiving module circuit due to the transient response as described above. Patent Document 3 describes a protection circuit that prevents damage to the APD due to an overvoltage in a transient response period. However, this is a protection circuit against a reverse bias overvoltage. It does not provide a circuit to protect. Accordingly, there remains a need for a means for protecting the light receiving module circuit from the transient response as described above.

  Therefore, if there is a small and simple circuit for protecting the light receiving module circuit from the transient response as described above, practical light receiving module circuit protection can be provided.

  The light receiving module circuit of the present invention is characterized in that a reverse current prevention circuit is inserted between the cathode of the light receiving element and the booster circuit and is electrically connected in series.

  Specifically, in the light receiving module circuit of the present invention, the light receiving element is an APD.

  In another aspect, the light receiving module circuit of the present invention is characterized in that a reverse current prevention circuit is inserted between the cathode of the PIN-PD and the surge protection circuit and electrically connected in series.

  The reverse current prevention circuit of the light receiving module circuit according to the present invention includes a diode.

  In the light receiving module circuit of the present invention, the cathode of the diode and the cathode of the light receiving element are electrically connected in series.

  The light receiving element module of the present invention is further characterized in that it can be used for various optoelectronic devices.

  By inserting a reverse current prevention circuit between the cathode of the light receiving element and the booster circuit and electrically connecting them in series, it is possible to effectively prevent the forward bias current from exceeding the allowable amount from flowing in the light receiving element during a transient response. Can do. Therefore, the TIA or the light receiving element is not damaged by an overcurrent due to a current outflow from the TIA to the light receiving element.

  Furthermore, by using an APD used for a general optoelectronic device as a light receiving element, the light receiving module circuit of the present invention can be applied to many existing and future developed optoelectronic devices.

  By inserting a reverse current prevention circuit between the cathode of the PIN-PD and the surge protection circuit and electrically connecting them in series, the forward bias current exceeding the allowable amount can be effectively passed to the light receiving element during a transient response. Can be prevented. Accordingly, an overcurrent caused by current outflow from the TIA to the light receiving element is prevented from damaging the TIA or the light receiving element. In addition, the protection effect against sudden voltage fluctuations by the surge protection circuit can be guaranteed at the same time.

  Further, by using a diode, which is a rectifying element, in the reverse current prevention circuit, a light receiving module circuit that satisfies conditions such as downsizing and power saving can be constructed.

  Further, by electrically connecting the cathode of the diode and the cathode of the light receiving module circuit in series, it is possible to prevent a forward bias current from flowing due to the rectifying action of the diode.

  Further, the light receiving module circuit using the APD and the PIN-PD of the present invention can be obtained from a professional optoelectronic device such as an optoelectronic device in the existing optical communication field or the light control field, which will be developed in the future, or from a remote controller. The versatility can be enhanced by applying to a wide range of fields up to general optoelectronic devices such as instruments.

  Best modes for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 shows a block diagram of a light receiving module circuit of the present invention. The light receiving module circuit is applied to the boosting circuit 1, the light receiving element APD2, the transimpedance amplifier (TIA) 3 for amplifying and converting the reverse bias current generated in the APD 2 into a voltage, and driving the TIA 3 And an external power supply 4 and a diode 5 which are also used.

  The booster circuit 1 receives power supply from the external power supply 4 and generates a voltage (HV) necessary for the APD 2 to provide a reverse bias current to the TIA 4 when receiving light. The HV from the booster circuit is applied to the cathode side of the APD 2 and the APD 2 becomes operable. The anode of APD 2 is connected to TIA 3. The APD 2 is usually used in a region where a reverse voltage is applied between the anode and the cathode.

  Here, referring to FIG. 2, a circuit in the case where the diode 5 is not provided will be considered. In the APD 2 of FIG. 2, the power supply to the cathode side of the APD 2 is delayed by the time constant of the booster circuit 1 during a transient response when the power is turned on. Here, the voltage on the anode side of APD2 is V1, the voltage on the cathode side is V2, and the rising voltage of APD is VF (usually 0.6 to 1 V). FIG. 3 shows changes in V1 and V2 with respect to the time from power-on. As shown in the transient response period of FIG. 3, there is a period where VF ≦ V1−V2, and at this time, V1−V2 is about 1 to 2V. During this period, since V1-V2 exceeds the VF of APD2, a forward bias current flows through APD2. Since TIA3 is not designed for current outflow, characteristics are deteriorated or damaged, and APD2 is not designed for forward bias current. Therefore, forward bias current exceeding the allowable current value flows. Heat is generated, resulting in characteristic deterioration and damage.

  However, in the light receiving module circuit of the present invention shown in FIG. 1, a reverse current preventing diode 5 is inserted between the booster circuit 1 and the APD 2. Due to the rectifying effect of the diode 5, it is possible to prevent a forward bias current from being generated in the APD 2 during a transient response when the power is turned on, and to prevent damage to the light receiving module circuit of the present invention.

  FIG. 4 shows a block diagram of a light receiving module circuit of the present invention using PIN-PD 2-1 as a light receiving element, which is another embodiment of the present invention. In the present invention, the surge protection circuit 1-1 is disposed at the position of the booster circuit 1. Since the surge protection circuit 1-1 generally includes a capacitor, the voltage supply is delayed as described above. However, similarly to the above, the rectifying effect of the diode 5 prevents the forward bias current from being generated in the PIN-PD 2-1 during the transient response when the power is turned on, and prevents the light receiving module circuit of the present invention from being damaged. it can.

  The present invention is a light receiving module circuit that can be widely used from the fields of optical communication and light control to general applications, and can be used in various optoelectronic devices that require high sensitivity.

FIG. 1 is a block diagram showing a light receiving module circuit according to an embodiment of the present invention. FIG. 2 is a block diagram showing a conventional light receiving module circuit. FIG. 3 is a graph showing the voltage change until the steady state of the circuit of FIG. 2 after the power is turned on. FIG. 4 is a block diagram showing a light receiving module circuit according to another embodiment of the present invention.

Explanation of symbols

1 Booster circuit 1-1 Surge protection circuit 2 APD
2-1 PIN-PD
3 TIA
4 External power supply 5 Diode

Claims (6)

  In a light receiving module circuit in which a cathode of a light receiving element and a booster circuit are electrically connected in series, a reverse current prevention circuit is inserted between the cathode of the light receiving element and the booster circuit and electrically connected in series. A light receiving module circuit characterized by   2. The light receiving module circuit according to claim 1, wherein the light receiving element is an avalanche photodiode (APD).   In a light receiving module circuit in which a cathode of a PIN structure photodiode (PIN-PD) and a surge protection circuit are electrically connected in series, a reverse current prevention circuit is inserted between the cathode of the PIN-PD and the surge protection circuit. The light receiving module circuit is electrically connected in series.   4. The light receiving module circuit according to claim 1, wherein the reverse current prevention circuit includes a diode.   5. The light receiving module circuit according to claim 4, wherein a cathode of the diode and a cathode of the light receiving element are electrically connected in series.   An optoelectronic device using the light receiving module circuit according to claim 1.

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