JP2001308396A - Peltier element drive circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Peltier element drive circuit for controlling the temperature of a laser diode, which is smaller with less noise. SOLUTION: Two totem pole circuits are provided where constant-current source electrodes of first-polarity active element and second-polarity active element are connected between a high-voltage side constant voltage terminal and a low-voltage side constant voltage terminal, one being earth. A Peltier element is provided between the connection points of constant-current electrode, and the direction and value of electric current of the Peltier element is controlled based on the fact whether an input voltage is higher/lower than a half of the voltage of high-voltage side constant voltage terminal and low-voltage side constant voltage terminal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Peltier device driving circuit for supplying a current to a Peltier device for controlling an oscillation wavelength of a laser diode for converting an electric signal into an optical signal in an optical communication to be constant. The present invention relates to a Peltier element driving circuit capable of driving a Peltier element with a single power supply and generating a low noise level.

[0002] In Japan, a digital transmission method using electric signals, which was put into practical use in about 1965,
Around 1980, the analog transmission system became the main transmission system constituting a return line.

On the other hand, a digital transmission method using an optical signal is as follows.
At the same time that the digital transmission method using electric signals secured its position as the main transmission method,
In the latter half of the 980s, it became the dominant transmission system on the return line.

[0004] Since optical fiber cables are originally broadband, the optical digital transmission system has grown as a system suitable for a large-capacity transmission system in combination with an increase in the speed of an electric-optical conversion element or an optical-electrical conversion element. However, capacity increase by single wavelength transmission is approaching its limit.

On the other hand, with the arrival of the multimedia age,
With the recent rapid spread of the Internet, there is an urgent need to realize an optical digital transmission system having an even larger capacity.

A single-wavelength transmission system for transmitting a single-wavelength optical signal over a single optical fiber cable;
The development of the wavelength division multiplexing transmission system for multiplexing and transmitting optical signals of a plurality of wavelengths on one optical fiber cable has been carried out in parallel. In order to cope with the rapid expansion, the wavelength multiplex transmission system (generally called “WDM system”. “WDM” is an abbreviation that stands for “Wavelength Division Multplexing”). It depends.

Furthermore, in order to cope with a sudden increase in required transmission capacity, about 1,500 nanometers (“nano” is 10 ⁻⁹⁾
It is. ) It is necessary to multiplex wavelengths at wavelength intervals on the order of about 0.5 nanometers in a nearby wavelength range.

[0008] In general, the oscillation wavelength of a laser diode has the characteristic of changing with temperature, and its temperature coefficient is about 0.1 nanometer / ° C.

Therefore, when wavelength multiplexing is performed at wavelength intervals on the order of about 0.5 nanometer, it is necessary to suppress the temperature of the laser diode chip to a fluctuation of about 1 ° C.

In order to control the temperature of the laser diode to the extent described above, the chip of the laser diode is bonded to a ceramic plate that is in contact with the electrode on the heat absorption side of the Peltier element and is housed in the same package. Usually, the temperature of the laser diode is controlled by the direction and value of the flowing current. The current flowing through the Peltier device needs to be on the order of amperes.

Therefore, there is a possibility that a problem arises in that a drive circuit for supplying a current to the Peltier element becomes large and that noise is generated from the Peltier element itself and the drive circuit.
In this sense, it is important to commercialize a Peltier device drive circuit that can be reduced in size and generates a low noise level.

[0012]

2. Description of the Related Art FIG. 7 shows a conventional Peltier device driving circuit (part 1) in which a pulse width modulation (often referred to as a "PWM" system) controls heat absorption and heat generation of a Peltier device by controlling a duty ratio of a driving pulse. "PW
"M" is an abbreviation of "Pulse Width Modulation".

In FIG. 7, 1 is a Peltier element, 2 is a resistor connected in series with the Peltier element, 101 is an inverter for inverting the logic level of the drive pulse, and 102 to 10
5 is, for example, the logic level of the supplied pulse is “1”
The switch is opened when the logic level is "0" and short-circuited when the logic level of the supplied pulse is "0".

If the operation of the switch is defined as above, FIG. 7 shows a case where the logic level of the drive pulse is "1". That is, if the logical level of the drive pulse is "1", the logical level of the output of the inverter 101 is "0", so that the switches 103 and 104 are short-circuited and the switches 102 and 105 are open. In FIG. 7, a Peltier current flows in a direction indicated by a thin solid line arrow.

On the other hand, the logic level of the drive pulse is "0".
7, the logical level of the output of the inverter 101 becomes “1”, so that the switches 102 and 105 are short-circuited, and the switches 103 and 104 are opened.
, A Peltier current flows in a direction opposite to the direction indicated by the thin solid arrow.

The Peltier element is formed by joining a P-type semiconductor and a N-type semiconductor, which are basically made of bismuth tellurium, via metal electrodes. When a current flows from the N-type semiconductor to the P-type semiconductor, at the junction between the P-type semiconductor and the N-type semiconductor, the energy level of electrons transitions from a high state to a low state, and the vibration energy of the surrounding crystal lattice is reduced. Absorption increases the amount of heat absorbed and lowers the temperature.

On the other hand, when a current flows from the P-type semiconductor to the N-type semiconductor side, the energy level of electrons transitions from a low state to a high state at the junction and supplies vibration energy to the surrounding crystal lattice, so that the energy is absorbed. The amount of heat decreases and the temperature rises.

Therefore, according to the method of controlling the direction of the current of the Peltier element 1 by the drive pulse as described above,
When the duty ratio of the drive pulse is 50%, the increase / decrease in the amount of absorbed heat is balanced, and there is no change in the temperature of the junction. When the duty ratio of the drive pulse is increased / decreased from 50%, the temperature of the junction becomes the same. It rises or falls according to the increase or decrease.

By using the above characteristics of the Peltier element to stabilize the oscillation wavelength of the laser diode by controlling the duty ratio of the driving pulse by the output of the temperature sensor or the oscillation wavelength sensor of the laser diode. it can.

Moreover, it is easy to make the Peltier element drive circuit a single power supply circuit.

FIG. 9 schematically shows a method of controlling a Peltier current by a DC input voltage in a conventional Peltier device driving circuit (No. 2).

In FIG. 9, 1 is a Peltier element, 2 is a resistor connected in series to the Peltier element 1, 101 is an inverter for inverting the logic level of an input signal, and 106 is a logic for judging the value of the input voltage. A voltage determination circuit that outputs a signal of level “1” or “0”, 107 and 108 are current sources whose current is controlled by the value of the input voltage, and 109 and 110 are, for example, logic levels of supplied signals. This switch is opened when the signal is “1” and short-circuited when the logic level of the supplied signal is “0”.

If the operation of the switch is defined as described above, FIG. 9 shows a case where the logic level of the output of the voltage judgment circuit 106 is "1". That is, if the logic level of the output of the voltage determination circuit 106 is “1”, the logic level of the output of the inverter 101 is “0”.
Is short-circuited, and the switch 109 is opened. At this time, a Peltier current flows in the direction indicated by the thin solid arrow in FIG.

On the other hand, when the logic level of the output of the voltage judgment circuit 106 becomes "0", the logic level of the output of the inverter 101 becomes "1", so that the switch 109 is short-circuited and the switch 110 is opened. Therefore, the Peltier current flows in the direction opposite to the direction shown by the thin solid line arrow in FIG.

Therefore, depending on whether the input voltage is higher or lower than a predetermined voltage, one of the switches 109 or 110 is short-circuited, and the current source 107 or 1 is switched depending on the value of the input voltage.
By controlling the current 08, the amount of heat absorbed by the Peltier element can be controlled.

Then, the oscillation wavelength of the laser diode can be stabilized by controlling the value of the input voltage by the output of the temperature sensor or the oscillation wavelength sensor of the laser diode.

Further, since the Peltier current is controlled by the DC voltage, there is an advantage that the noise level generated by the Peltier element driving circuit is low.

[0028]

However, both the configuration of FIG. 7 and the configuration of FIG. 9 have problems.

First, the problem with the configuration shown in FIG. 7 is that the level of noise generated is extremely high because an ampere-order current is switched by pulse driving. That is, if the noise generated by the Peltier element driving circuit leaks into the circuit for processing data to be converted into light, it may cause a code error in the data. Is modulated by the noise, again causing a code error. In particular, the effect of noise is large in an electroabsorption optical modulator.

FIG. 8 is a diagram showing an outline of temperature control by a Peltier element in the electro-absorption modulator.

In FIG. 8, reference numeral 121 denotes a module of an electro-absorption modulator incorporating a Peltier element, 122 denotes a semiconductor chip constituting the electro-absorption modulator, and 123 denotes an electro-absorption effect formed in the semiconductor chip 122. Diode, 124 is a laser diode formed in the semiconductor chip 122, 125 is a Peltier element, the semiconductor chip 122 is monolithic, and is mounted on a ceramic substrate joined to the heat absorbing side electrode of the Peltier element 125. Die bonded.

Reference numeral 127 denotes a modulation signal source for processing data to be optically converted, and 128 denotes a laser diode drive current source ("L" in the figure) for supplying a drive current to the laser diode.
D drive current source ". "LD" stands for "Laser Di
ode is an abbreviation for the acronym. ).

The modulation operation in the electro-absorption modulator having the above configuration is as follows.

That is, the laser diode 124 is DC-driven by a laser diode drive current source 128, and supplies DC light to the diode 123 having an electric absorption effect via a waveguide in a bulk. .

On the other hand, data to be optically converted is supplied from the modulation signal source 127 to the diode 123 having an electric field absorption effect, which is a reverse bias element, and the diode 123 having the electric field absorption effect according to the logic level of the data. The intensity modulation is performed by shifting the wavelength of the DC light supplied from the laser diode 124.

Therefore, the diode 123 having the electric field absorption effect is extremely sensitive to an applied electric field, and may cause erroneous modulation, that is, a code error or deterioration of a modulation waveform, due to noise due to Peltier current switching. In addition, there is a possibility that a code error may occur due to leakage of noise due to Peltier current switching from the Peltier element driving circuit to the modulation signal source 127 or the laser diode driving current source 128.

Next, in the case of the configuration shown in FIG. 9, in order to use the Peltier element 1 connected to the ground via the resistor 2, two power supplies of a positive power supply V _CC and a negative power supply V _EE are required. .
As described many times, the drive current of the Peltier element is on the order of amperes, so that the need for two power supplies means an increase in the size of the Peltier element drive circuit.

[0038] Incidentally, the ground instead of the negative power supply V _EE, the voltage of the connection destination of the Peltier element 1 and the resistor 2 (1/2) V _CC
It seems that a single power supply can be used, but (1/2) V
_The circuit that generates _CC also needs to be configured with one power supply capable of flowing in and out of the Peltier current, and eventually becomes a circuit of two power supplies.

In view of the above problems, the present invention relates to a Peltier device driving circuit, and more particularly, to a Peltier device driving device capable of driving a Peltier device with a single power source and generating a low noise level. It is intended to provide a circuit.

[0040]

SUMMARY OF THE INVENTION The first invention, between a positive power supply (voltage = V _CC) and ground, a constant current characteristic of the first polarity of the active element and the second polarity of the active device Configuring two totem-pole circuits connected to terminals having a Peltier element between the connection points of the terminals having constant current characteristics,
DC voltage is supplied as the input voltage, and the input voltage is (1 /
2) When it is equal to V _CC , the four active elements constituting the two totem pole circuits are turned off. When the input voltage is higher than (（) V _CC , the positive power supply of the first totem pole circuit is turned off. The first polarity active element on the ground side of the second totem pole circuit and the second polarity active element on the ground side of the second totem pole circuit are made conductive, and the first polarity active element on the positive power supply side of the second totem pole circuit is turned on. the second polarity of the active element of the active element and the ground side of the first totem pole circuit interrupting state, when the input voltage is lower than (1/2) V _CC is the ground side of the first totem pole circuit The second active element of the second polarity and the active element of the first polarity on the positive power supply side of the second totem-pole circuit are made conductive, and the first polarity active element on the positive power supply side of the first totem-pole circuit is turned on. Ground for active element and second totem pole circuit The configuration of the Peltier element driving circuit for the second polarity of the active element of the cut-off state.

According to the first aspect, the input voltage becomes (1 /
2) When it is equal to V _CC , the four active elements constituting the two totem pole circuits are turned off. When the input voltage is higher than (（) V _CC , the positive power supply of the first totem pole circuit is turned off. The active element of the first polarity on the side and the active element of the second polarity on the ground side of the second totem pole circuit are made conductive, and when the input voltage is lower than (1/2) V _CC , The second polarity active element on the ground side of the totem pole circuit and the first polarity active element on the positive power supply side of the second totem pole circuit are brought into conduction.

Therefore, when the input voltage is equal to (1/2) V _CC , no current flows through the Peltier element disposed between the connection points of the active elements having the constant current characteristics of the two totem-pole circuits. When the input voltage is higher than (1/2) V _CC, the active element of the first polarity on the positive power supply side of the first totem pole circuit is activated from the active element of the second polarity on the ground side of the second totem pole circuit. A current flows to the element, and when the input voltage is lower than (1/2) V _CC , the active element having the first polarity on the positive power supply side of the second totem-pole circuit is grounded to the first totem-pole circuit. A current can flow toward the active element of the second polarity on the side. That is, currents in different directions can flow through the Peltier element depending on whether the input voltage is higher or lower than (1/2) V _{CC, and the} heat absorbed by the Peltier element can be controlled.

According to a second aspect, in the first aspect, a resistor is inserted in series with the Peltier element, a terminal voltage of the resistor is taken out, a first difference voltage from a reference voltage is generated, and A Peltier that controls the current of the Peltier element in the same manner as described above, depending on whether the second difference voltage is higher or lower than (１ ／) V _CC , 5 shows a configuration of an element driving circuit.

According to the second aspect, even if there is a variation or a change with time of the characteristics of the components constituting the Peltier device driving circuit of the first aspect, the influence of the variation or the change with time is offset. Therefore, the current of the Peltier device can be stabilized even if the characteristics of the components constituting the Peltier device drive circuit of the first invention vary or change with time.

[0045]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a plurality of embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention.

In FIG. 1, 1 is a Peltier element, 2
Is a resistance.

Reference numerals 3 to 6 denote operational amplifier circuits constituting a feedback amplifier circuit for generating a voltage corresponding to the difference voltage between the input voltage and (1/2) V _CC, and 7 denotes (1/2) V _CC The operational amplifier circuits constituting the generated amplifier, 8 and 9 are resistors and 10 which constitute a voltage dividing circuit for dividing the voltage V _{CC of the} positive power supply by half.
Reference numerals 13 to 13 denote resistors constituting a feedback amplifier circuit together with the operational amplifier circuit 3, 14 and 15 denote resistors constituting a feedback amplifier circuit together with the operational amplifier circuit 4, and 16 to 19 constitute a feedback amplifier circuit together with the operational amplifier circuit 5. Resistance, 20 and 21
Is a resistor that constitutes a feedback amplifier circuit together with the operational amplifier circuit 6. Then, the operational amplifier circuits 3 to 7 and the resistors 8 to 21 constitute a voltage discriminator that generates an output voltage according to the value of the input voltage.

Reference numerals 22 and 23 denote PNP junction transistors, 24 and 25 denote NPN junction transistors, 30
And 31 are PNP junction type transistors 22
, And 23 are resistors for determining the current of the NPN junction type transistors 24 and 25, respectively.

Here, the collector terminals of the PNP junction type transistor 22 and the NPN junction type transistor 24 are connected to each other, the emitter terminal of the PNP junction type transistor is connected to the positive power supply via the resistor 30, and the NPN junction type transistor 24 Since the emitter terminal is connected to the ground via the resistor 32, the PNP junction transistor 22 and the NPN junction transistor 24 form one totem pole circuit between the positive power supply and the ground. Similarly,
PNP-junction transistor 23 and NPN-junction transistor 25 connect another totem between the positive power supply and ground.
A pole circuit is configured. And two totems
A current driver for the Peltier element is constituted by the pole circuit.

In the configuration of FIG. 1, the input voltage is
It is supplied to the non-inverting input terminal of the feedback amplifier circuit centered on the operational amplifier circuit 3 via 0 and to the inverting input terminal of the feedback amplifier circuit centered on the operational amplifier circuit 3 via the resistor 18. .

The output of the feedback amplifier circuit centering on the operational amplifier circuit 3 is supplied to the inverting input terminal of the feedback amplifier circuit centering on the operational amplifier circuit 4 via the resistor 14, and the operational amplifier circuit 5 is centered. The output of the feedback amplifier circuit is supplied via a resistor 20 to an inverting input terminal of the feedback amplifier circuit centered on the operational amplifier circuit 4.

The operational amplifier circuit 7 is a voltage follower that directly connects the output terminal to the inverting input terminal.
A stable (1/2) V _CC is obtained from the voltage follower.

The output of the voltage follower is a resistor 1
2 is connected to the inverting input terminal of the feedback amplifier circuit centering on the operational amplifier circuit 3 via the resistor 16, and the non-inverting input terminal of the feedback amplifier circuit centering on the operational amplifier circuit 5 is connected via the resistor 16 to the operational amplifier circuit 4. And the non-inverting input terminal of the feedback amplifier circuit centering on the operational amplifier circuit 6 and the feedback amplifier circuit.

[0055] Here, when the resistance value of the resistor having the code by reference numeral of each resistor in alphabetical R (e.g., R ₁₀ is the resistance of resistor 10.), R ₁₁ /
By setting the _{R 10 = R 13 / R 12} , R 17 / R 16 = R 18 / R 19, a feedback amplifier circuit having a center and a feedback amplifier circuit around an operational amplifier circuit 3 an operational amplifier circuit 5 , And (input voltage − (）) V _cc ) × (R ₁₃ / R ₁₂ ), respectively.
And ((1/2) V _{CC -input} voltage) × (R ₁₉ / R ₁₈ )
Is output. Here, (R ₁₃ / R ₁₂ ) = (R ₁₉ / R ₁₈ )
, A symmetrical voltage can be obtained from the feedback amplifier circuit centered on the operational amplifier circuit 3 and the feedback amplifier circuit centered on the operational amplifier circuit 5. The output voltage of the feedback amplifier circuit centered on the operational amplifier circuit 3 is V ₃ , and the output voltage of the feedback amplifier circuit centered on the operational amplifier circuit 5 is V _3
5, and (R ₁₃ / R ₁₂ ) = (R ₁₉ / R ₁₈ ) = G.

On the other hand, R_Fifteen/ R₁₄= 1, R_{twenty one}/ R₂₀= 1
By setting, the feedback centering on the operational amplifier circuit 4
Amplifier circuit is 2 × (1/2) V_CC-V_Three= V_CC-V_ThreeOut
The feedback amplifier circuit centering on the operational amplifier circuit 6
× (1/2) V_CC-V_Three= V _CC-V_ThreeIs output. still,
The output voltage of the feedback amplifier circuit centered on the operational amplifier circuit 4
V_FourThe output of the feedback amplifier circuit centered on the operational amplifier circuit 6
Voltage to V₆And

The output of the feedback amplifier circuit centering on the operational amplifier circuit 3 is connected to the base terminal of the NPN junction transistor 25, and the output of the feedback amplifier circuit centering on the operational amplifier circuit 5 is connected to the base terminal of the NPN junction transistor 24. To the terminal
The output of the feedback amplifier circuit centering on the operational amplifier circuit 4 is PN
The output of the feedback amplification circuit centering on the operational amplifier circuit 6 is supplied to the base terminal of the P-junction transistor 23 and the base terminal of the P-junction transistor 23.

Now, consider the case where the input voltage is equal to (1/2) V _CC .

In this case, according to the above, V ₃ = 0 becomes N
V ₅ = 0 at the base terminal of the PN junction transistor 25
Is supplied to the base terminal of the NPN junction type transistor 24, V ₄ = V _CC is supplied to the base terminal of the PNP junction type transistor 22, and V ₆ = V _CC is supplied to the base terminal of the PNP junction type transistor 23.
Is supplied to the base terminal of

Therefore, when the input voltage is equal to (1/2) V _CC , all the four transistors constituting the two totem pole circuits in FIG. 1 are turned off,
No current flows through the Peltier element.

Next, consider the case where the input voltage is higher than (1/2) V _CC .

In this case, V ₃ = G (input voltage− (1
/ 2) Since V _CC ), V ₃ becomes a positive voltage, and V ₅ =
G - because it is ((1/2) V _CC input voltage) V ₅ becomes a negative voltage.

V ₄ = V _CC -G (input voltage- (1/1 /
_{2) V CC), V 6} = V CC + G ( input voltage - (1/2) V
_CC ).

Therefore, V ₄ is supplied to the base terminal P
NPN junction type transistor 25 NP junction transistor 22 and V ₃ is supplied to the base terminal can be conductive, NPN junction type transistor 24 and V ₆ which V ₅ is supplied to the base terminal is supplied to the base terminal PNP junction type transistor 23 is turned off.

Here, assuming that the base-emitter voltage when the PNP junction type transistor 22 and the NPN junction type transistor 25 are conductive is equal, by setting R ₃₀ = R ₃₃ , the PNP junction type transistor is set. The current of 22 and the current of NPN junction transistor 25 can be made equal, and this current flows through the Peltier element from left to right in FIG.

Finally, consider the case where the input voltage is lower than (1/2) V _CC .

In this case, V ₃ = G (input voltage− (1
/ 2) Since V _cc ), V ₃ becomes a negative voltage, and V ₅ =
G - because it is ((1/2) V _CC input voltage) V ₅ becomes a positive voltage.

Further, V ₄ = V _CC + G ((１ ／) V _{CC -input} voltage) and V ₆ = V _CC -G ((１ ／) V _CC -input voltage).

Therefore, V_FourIs supplied to the base terminal
NP junction type transistor 22 and V_ThreeSupplied to the base terminal
NPN junction type transistor 25 is turned off.
And V _FiveNPN junction type transformer supplied to the base terminal
Register 24 and V₆PNP junction supplied to base terminal
The type transistor 23 becomes conductive.

Here, assuming that the base-emitter voltage when the PNP junction type transistor 23 and the NPN junction type transistor 24 are conductive is equal, by setting R ₃₁ = R ₃₂ , the PNP junction type transistor is set. 23 and the current of the NPN junction type transistor 24 can be made equal, and this current flows through the Peltier element from the right side to the left side in FIG.

Therefore, with the configuration of FIG. 1, the direction of the current flowing through the Peltier element can be controlled according to the magnitude relationship between the input voltage and (1/2) V _CC , and the input voltage and (1/2) V _CC A current corresponding to the difference voltage of _CC can be passed through the Peltier element, and the amount of heat absorbed by the Peltier element can be controlled.

In the configuration shown in FIG. 1, the two totem-pole circuits for supplying a current on the order of amperes to the Peltier element need only be a single power supply, and the Peltier element drive circuit can be downsized.

Since a DC voltage is supplied as an input voltage, induced noise from other sources is suppressed, so that generated noise is limited to thermal noise in a resistor and an operational amplifier circuit, and the noise level is suppressed to a low level. It is possible to

The operational amplifier circuit 3 and the operational amplifier circuit 5 in the configuration of FIG. 1 require two power supplies to output a negative voltage. This is because a normal power supply for an electronic circuit having a small load current is used. This does not hinder miniaturization of the Peltier element driving circuit, and the configuration of FIG. 1 can be said to be a Peltier element driving circuit with a substantially single power supply.

By the way, the junction transistor cannot conduct unless a predetermined voltage is applied between the base and the emitter. This voltage is about 0.7 volt for a junction transistor using silicon. Therefore, if the voltage gain of the voltage discriminating unit in the configuration of FIG.
2) 0.7 volts above and below V _{CC is} a dead zone where the Peltier current does not change even if the input voltage changes. However, by setting the voltage gain of the voltage discriminator sufficiently larger than 1, the width of the dead zone with respect to the input voltage can be made sufficiently small.

FIG. 2 shows the relationship between the input voltage and the Peltier current in the configuration of FIG. 1. In particular, when the input voltage is (1/2) V
_The figure shows a case where the voltage is in the vicinity of the _CC , and shows that the width of the dead zone with respect to the input voltage depends on the voltage gain of the voltage discriminator.

FIG. 3 shows a second embodiment of the present invention.

In FIG. 3, 1 is a Peltier element, 2
Is a resistance.

Reference numerals 3 to 6 denote operational amplifier circuits which constitute a feedback amplifier circuit for generating a voltage corresponding to the difference voltage between the input voltage and (1/2) V _CC, and 7 denotes (1/2) V _CC The operational amplifier circuits constituting the generated amplifier, 8 and 9 are resistors and 10 which constitute a voltage dividing circuit for dividing the voltage V _{CC of the} positive power supply by half.
Reference numerals 13 to 13 denote resistors constituting a feedback amplifier circuit together with the operational amplifier circuit 3, 14 and 15 denote resistors constituting a feedback amplifier circuit together with the operational amplifier circuit 4, and 16 to 19 constitute a feedback amplifier circuit together with the operational amplifier circuit 5. Resistance, 20 and 21
Is a resistor that constitutes a feedback amplifier circuit together with the operational amplifier circuit 6. Then, the operational amplifier circuits 3 to 7 and the resistors 8 to 21 constitute a voltage discriminator that generates an output voltage according to the value of the input voltage.

Reference numerals 26 and 27 denote P-channel field-effect transistors, reference numerals 28 and 29 denote N-channel field-effect transistors, reference numerals 30 and 31 denote resistors for determining the currents of the P-channel field-effect transistors 26 and 27, respectively. 32 and 33 are resistors that determine the current of the N-channel field effect transistors 28 and 29, respectively.

Here, the drain terminals of the P-channel field-effect transistor 26 and the N-channel field-effect transistor 28 are connected to each other, and the source terminal of the P-channel field-effect transistor 26 is connected to the positive power supply via the resistor 30. , The source terminal of the N-channel field effect transistor 28 is connected to the ground via the resistor 32, so that the P-channel field-effect transistor 26 and the N-channel It constitutes a totem pole circuit. Similarly,
The P-channel field-effect transistor 27 and the N-channel field-effect transistor 29 constitute another totem-pole circuit between the positive power supply and the ground. And
A current driver for the Peltier element is constituted by the two totem pole circuits.

In the configuration of FIG. 3, the configuration of the voltage discriminating section is exactly the same as the configuration of the voltage discriminating section in the configuration of FIG. 1, so that the description of the configuration and operation will be omitted.

In the current driver, the PNP junction type transistor is replaced with a P-channel type field effect transistor.
The PN junction type transistor is replaced by an N-channel type field effect transistor. The difference from the configuration of FIG. 1 is that the dead zone of the Peltier current with respect to the input voltage is determined by the threshold voltage between the gate and the source. Therefore, a detailed description of the configuration and operation of the current driver is also omitted.

FIG. 4 shows a third embodiment of the present invention, in which negative feedback is applied to the configuration of FIG. 1 to stabilize the Peltier current.

In FIG. 4, 1 is a Peltier element, 2
Is a resistance.

Reference numerals 3 to 6 denote operational amplifier circuits which constitute a feedback amplifier circuit for generating a voltage corresponding to the difference voltage between the input voltage and (1/2) V _CC, and 7 denotes (1/2) V _CC The operational amplifier circuits constituting the generated amplifier, 8 and 9 are resistors and 10 which constitute a voltage dividing circuit for dividing the voltage V _{CC of the} positive power supply by half.
Reference numerals 13 to 13 denote resistors constituting a feedback amplifier circuit together with the operational amplifier circuit 3, 14 and 15 denote resistors constituting a feedback amplifier circuit together with the operational amplifier circuit 4, and 16 to 19 constitute a feedback amplifier circuit together with the operational amplifier circuit 5. Resistance, 20 and 21
Is a resistor that constitutes a feedback amplifier circuit together with the operational amplifier circuit 6. Then, the operational amplifier circuits 3 to 7 and the resistors 8 to 21 constitute a voltage discriminator that generates an output voltage according to the value of the input voltage.

Reference numerals 22 and 23 denote PNP junction transistors, 24 and 25 denote NPN junction transistors, 30
And 31 are PNP junction type transistors 22
, And 23 are resistors for determining the current of the NPN junction type transistors 24 and 25, respectively.

Here, the collector terminals of the PNP junction type transistor 22 and the NPN junction type transistor 24 are connected to each other, the emitter terminal of the PNP junction type transistor is connected to the positive power supply via the resistor 30, and the NPN junction type transistor 24 Since the emitter terminal is connected to the ground via the resistor 32, the PNP junction transistor 22 and the NPN junction transistor 24 form one totem pole circuit between the positive power supply and the ground. Similarly,
PNP-junction transistor 23 and NPN-junction transistor 25 connect another totem between the positive power supply and ground.
A pole circuit is configured. And two totems
A current driver for the Peltier element is constituted by the pole circuit.

Reference numerals 34 to 36 denote operational amplifier circuits, 37
Reference numerals 45 denote resistors, which constitute a feedback circuit unit.

Among them, the feedback amplifier circuit constituted by the operational amplifier circuit 34 and the resistors 37 to 40 is arranged to extract the terminal voltage of the resistor 2 in series with the Peltier element. Therefore, R ₃₇ / R ₃₈ = R ₃₉ / R ₄₀ is set.

[0091] operational amplifier 35 constituting a voltage follower, a terminal voltage or a reference voltage of the resistor 2 when the input voltage is equal to (1/2) V _CC is 0, the terminal voltage of the resistor 2 and the reference It is arranged for obtaining a voltage difference between the voltages and for inverting the polarity of the voltage difference.

Further, the operational amplifier circuit 36 and the resistors 42 to 4
The feedback amplifier circuit 5 is provided for obtaining a difference voltage between the input voltage and the difference voltage. Therefore, R ₄₂ /
R ₄₃ = R ₄₄ / R ₄₅ is set.

The configuration of FIG. 4 is obtained by adding a feedback circuit to the configuration of FIG. Therefore, the configuration and operation of the voltage discriminator and the current driver are omitted, and only the feedback circuit will be described.

In the feedback circuit section, the operational amplifier circuit 34
Since the absolute value of the voltage gain of the feedback amplifying circuit centered at is set to 1, the terminal voltage of the resistor 2 in series with the Peltier element can be taken out, and the feedback amplifying circuit centered on the operational amplifier circuit 34 The output is supplied to an inverting input terminal of an operational amplifier 35 constituting a voltage follower.

Since the ground voltage as a reference voltage is supplied to the non-inverting input terminal of the operational amplifier circuit 35 constituting the voltage follower, the operational amplifier circuit 35 constituting the voltage follower is connected to the terminal voltage of the resistor 2. It catches the fluctuation and inverts the polarity and outputs it.

A feedback amplifying circuit in which the output voltage of the operational amplifying circuit 35 constituting a voltage follower that captures the fluctuation of the terminal voltage of the resistor 2 is centered on the operational amplifying circuit 36 and the absolute value of the voltage gain is set to 1. And the input voltage is supplied to the inverting input terminal of a feedback amplifier circuit configured around the operational amplifier circuit 36 and having the absolute value of the voltage gain set to 1, so that the operational amplifier circuit 36 is The output of the feedback amplifier circuit is the difference voltage between the input voltage and the output of the operational amplifier circuit 35 forming the voltage follower, and the output of the feedback amplifier circuit centering on the operational amplifier circuit 36 is the terminal voltage of the resistor 2. Is a voltage that changes in the opposite direction to the change in

That is, by adding a feedback circuit unit to the configuration shown in FIG. 1, variations in the characteristics of the elements constituting the Peltier element, the voltage discriminating unit, and the current driving unit and changes in the Peltier current due to aging are suppressed. , The Peltier current can be stabilized.

FIG. 5 is an equivalent circuit of the configuration shown in FIG. 4 for analyzing the above description analytically.

In FIG. 5, 1 is a Peltier element, 2 is a resistor arranged in series with the Peltier element, 131 is a subtraction circuit, 132 is a forward amplification circuit (in the figure, simply indicated as "G"), 133 is a Peltier device driver, 1
Reference numeral 34 denotes a so-called β circuit (only “β” is shown in the figure).

The subtraction circuit 131 and the β circuit 134 correspond to the feedback circuit of FIG.
4 corresponds to the voltage discriminating unit of the configuration of FIG. 4, and the driver 133 corresponds to the current driving unit of the configuration of FIG.

The Peltier current is I _P , the terminal voltage of the resistor 2 is V _O , the input voltage is V _I , the gain of the forward amplifier is G, the transmission coefficient of the β circuit is β, and the resistance of the resistor 2 is Assuming that the value is R ₂ , V _O = G (V _I −βV _O ) and V _O = I _P R ₂ , so that I _O / V _I ≒ 1 / (βR ₂ ) is obtained within the range where G≫1 holds. obtain. That is, the Peltier current can be uniquely determined from the input voltage.

FIG. 6 shows a fourth embodiment of the present invention in which negative feedback is applied to the configuration of FIG. 3 to stabilize the Peltier current.

In FIG. 6, 1 is a Peltier element, 2
Is a resistance.

Reference numerals 3 to 6 denote operational amplifier circuits constituting a feedback amplifier circuit for generating a voltage corresponding to a difference voltage between the input voltage and (1/2) V _CC, and 7 denotes (1/2) V _CC The operational amplifier circuits constituting the generated amplifier, 8 and 9 are resistors and 10 which constitute a voltage dividing circuit for dividing the voltage V _{CC of the} positive power supply by half.
Reference numerals 13 to 13 denote resistors constituting a feedback amplifier circuit together with the operational amplifier circuit 3, 14 and 15 denote resistors constituting a feedback amplifier circuit together with the operational amplifier circuit 4, and 16 to 19 constitute a feedback amplifier circuit together with the operational amplifier circuit 5. Resistance, 20 and 21
Is a resistor that constitutes a feedback amplifier circuit together with the operational amplifier circuit 6. Then, the operational amplifier circuits 3 to 7 and the resistors 8 to 21 constitute a voltage discriminator that generates an output voltage according to the value of the input voltage.

26 and 27 are P-channel field-effect transistors, 28 and 29 are N-channel field-effect transistors, 30 and 31 are resistors for determining the currents of the P-channel field-effect transistors 26 and 27, respectively. 32 and 33 are resistors that determine the current of the N-channel field effect transistors 28 and 29, respectively.

Here, the drain terminals of the P-channel field-effect transistor 26 and the N-channel field-effect transistor 28 are connected to each other, and the source terminal of the P-channel field-effect transistor 26 is connected to the positive power supply via the resistor 30. , The source terminal of the N-channel field effect transistor 28 is connected to the ground via the resistor 32, so that the P-channel field-effect transistor 26 and the N-channel It constitutes a totem pole circuit. Similarly,
The P-channel field-effect transistor 27 and the N-channel field-effect transistor 29 constitute another totem-pole circuit between the positive power supply and the ground. And
A current driver for the Peltier element is constituted by the two totem pole circuits.

Reference numerals 34 to 36 denote operational amplifier circuits;
Reference numerals 45 denote resistors, which constitute a feedback circuit unit.

Among them, the feedback amplifier circuit constituted by the operational amplifier circuit 34 and the resistors 37 to 40 is arranged to extract the terminal voltage of the resistor 2 in series with the Peltier element. Therefore, assuming that the resistance values of the resistors 37 to 40 are R ₃₇ , R ₃₈ , R ₃₉ , and R ₄₀ , respectively, R ₃₇ / R ₃₈ = R ₃₉ / R
Set to ₄₀ .

Since the terminal voltage of the resistor 2 when the input voltage is equal to (1/2) V _CC, that is, the reference voltage is 0, the operational amplifier circuit 35 constituting the voltage follower is connected to the terminal voltage of the resistor 2 and the reference voltage. It is provided for obtaining a voltage difference between the voltages and for inverting the polarity of the difference voltage.

Further, the operational amplifier circuit 36 and the resistors 42 to 4
The feedback amplifier circuit 5 is provided for obtaining a difference voltage between the input voltage and the difference voltage. Therefore, R ₄₂ /
R ₄₃ = R ₄₄ / R ₄₅ is set.

As described above, the configuration of FIG. 6 is essentially the same as the configuration of FIG. 4, and therefore a further detailed description will be omitted.

The difference between the configurations shown in FIGS. 1 and 3 and between FIGS. 4 and 6 is that the configuration shown in FIGS. 1 and 4 uses a junction transistor in the current driver. , FIG.
6 only uses a field-effect transistor for the current driver, but it is desirable to generalize the junction-type transistor and the field-effect transistor.

The PNP junction type transistor and the P-channel type field effect transistor realize the transistor effect by moving holes (holes), and correspond in nature. That is, when the potential of the base, which is the control electrode of the PNP junction type transistor, increases and the potential difference between the base electrode and the emitter electrode decreases, the PNP junction type transistor is turned off, and the potential difference between the base electrode and the emitter electrode exceeds a predetermined level. When this happens, the PNP junction transistor becomes conductive, whereas when the potential of the gate, which is the control electrode of the P-channel field-effect transistor, increases and the potential difference between the gate and the source electrode decreases, the P-channel field-effect transistor turns on. The P-channel field-effect transistor is turned on when the potential difference between the gate electrode and the source electrode becomes more than a predetermined value.

When viewed from the outside, the collector electrode of the PNP junction transistor and the drain electrode of the P-channel field effect transistor both appear as a constant current source, and the emitter electrode of the PNP junction transistor and the source of the P-channel field effect transistor. The electrode looks like a constant voltage source when viewed from the outside.

On the other hand, the NPN junction type transistor and the N-channel type field effect transistor realize the transistor effect by the movement of electrons, and correspond in nature. That is, when the potential of the base, which is the control electrode of the NPN junction type transistor, decreases and the potential difference between the base electrode and the emitter electrode decreases, the NPN junction type transistor is cut off,
When the potential difference between the base electrode and the emitter electrode exceeds a predetermined value, the NPN junction type transistor becomes conductive, whereas the potential of the gate, which is the control electrode of the N-channel type field effect transistor, becomes lower and the potential between the gate and the source electrode becomes lower. When the potential difference between the gate electrode and the source electrode becomes smaller than a predetermined value, the N-channel field-effect transistor is turned off.

The collector electrode of the NPN junction type transistor and the drain electrode of the N channel type field effect transistor both appear as a constant current source when viewed from the outside, and the emitter electrode of the NPN junction type transistor and the source of the N channel type field effect transistor. The electrode looks like a constant voltage source when viewed from the outside.

Therefore, it can be said that both the junction type transistor and the field effect transistor are active elements having three electrodes of the control electrode, the constant current source electrode and the constant voltage electrode. Then, depending on whether to use the movement of holes or the movement of electrons, both the junction type transistor and the field effect transistor have an active element of the first polarity and an active element of the second polarity.

When generalized as described above, for example, FIG.
The configuration between the positive supply (voltage = V _CC) and ground, constitutes a first polarity of the active elements two totem-pole circuit connected to the constant current source electrode of the second polarity of the active device A Peltier element is arranged between the connection points of the constant current electrodes, and when the input voltage is equal to (1/2) V _CC , the four active elements forming the two totem pole circuits are cut off, and the input voltage is reduced. When the voltage is higher than (1/2) V _CC , the first polarity active element on the positive power supply side of the first totem pole circuit and the second polarity active element on the ground side of the second totem pole circuit are connected. The second totem-pole circuit has a first polarity active element on the positive power supply side and a first totem-pole circuit has a second polarity active element on the ground side in a cutoff state. When the voltage is lower than (1/2) V _CC , the first totem port The active element of the second polarity on the ground side of the ground circuit and the active element of the first polarity on the positive power supply side of the second totem pole circuit are made conductive, and the positive power supply side of the first totem pole circuit is turned on. It can be said that this is a configuration of a Peltier element drive circuit that turns off the active element of the first polarity and the active element of the second polarity on the ground side of the second totem-pole circuit.

[0119] In the above between ground and the "positive supply (voltage = V _CC), 2 single totem-connected constant current source electrode of the first polarity of the active element and the second polarity of the active device However, it is described that “a pole circuit is configured”. However, “the constant current source electrodes of the active element of the first polarity and the active element of the second polarity are connected between the ground and the negative power supply (voltage = −V _EE ). Even if "two connected totem-pole circuits are configured", the potential relationship in the totem-pole circuit is the same.

However, in this case, "the input voltage is (-1)
/ 2) When the voltage is higher than V _{EE, a} first polarity active element on the positive power supply side of the first totem pole circuit and a second polarity active element on the ground side of the second totem pole circuit can be conducted. The active element of the first polarity on the positive power supply side of the second totem-pole circuit and the active element of the second polarity on the ground side of the first totem-pole circuit are turned off, and the input voltage becomes (− 1/2) when the lower V _EE, conducting a first polarity of the active element of the positive power supply side of the ground side of the second polarity of the active element and a second totem pole circuit of the first totem pole circuit Enable the active element of the first polarity on the positive power supply side of the first totem-pole circuit and the active element of the second polarity on the ground side of the second totem-pole circuit. '' There is a need to.

Therefore, when the configuration of FIG. 1 is further generalized,
Two totem pole circuits in which the constant current source electrodes of the active element of the first polarity and the active element of the second polarity are connected between the high voltage side constant voltage terminal and the low voltage side constant voltage terminal, one of which is ground. And a Peltier element is arranged between the connection points of the constant current source electrodes. When the input voltage is equal to one half of the voltage of the high-side constant voltage terminal and the low-side constant voltage terminal, two totems
The four active elements that constitute the pole circuit are turned off,
When the input voltage is higher than 電 圧 of the voltage of the high-side constant voltage terminal and the low-side constant voltage terminal, the active element of the first polarity on the positive power supply side of the first totem pole circuit and the second totem pole
The second polarity active element on the ground side of the pole circuit is made conductive, and the first polarity active element on the positive power supply side of the second totem pole circuit and the first polarity active element on the ground side of the first totem pole circuit. The active element having two polarities is turned off, and the input voltage is １ ／ of the voltage of the high-voltage side constant voltage terminal and the low-voltage side constant voltage terminal.
When lower, the active element of the second polarity on the ground side of the first totem-pole circuit and the active element of the first polarity on the positive power supply side of the second totem-pole circuit are made conductive,
A Peltier device drive circuit that cuts off a first polarity active element on the positive power supply side of the first totem pole circuit and a second polarity active element on the ground side of the second totem pole circuit. It can be said that there is.

[0122]

According to the first invention, two totems
When the input voltage is equal to half the voltage of the high-side constant voltage terminal and the voltage of the low-side constant voltage terminal, the Peltier element arranged between the connection points of the active elements having the constant current characteristic of the pole circuit When the input voltage is higher than one half of the voltage of the high-side constant voltage terminal and the voltage of the low-side constant voltage terminal without flowing, the first totem pole circuit from the active element of the first polarity on the positive power supply side to the second A current to the active element of the second polarity on the earth side of the totem pole circuit of the above, and the input voltage is 1 / the voltage of the high voltage side constant voltage terminal and the voltage of the low voltage constant voltage terminal.
When the voltage is lower than 2, a current can flow from the first polarity active element on the positive power supply side of the second totem-pole circuit to the second polarity active element on the ground side of the first totem-pole circuit. it can. That is, currents in different directions can flow through the Peltier element depending on whether the input voltage is higher or lower than 1/2 of the voltage of the high-side constant voltage terminal and the voltage of the low-voltage combined constant terminal, and the absorption heat of the Peltier element is controlled. can do.

According to the second aspect of the present invention, even if the characteristics of the components constituting the Peltier device driving circuit of the first aspect of the present invention vary or change over time, the influence of the variation or change over time is offset. Therefore, the current of the Peltier device can be stabilized even if the characteristics of the components constituting the Peltier device drive circuit of the first invention vary or change with time.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of the present invention.

FIG. 2 shows a relationship between an input voltage and a Peltier current in the configuration of FIG.

FIG. 3 shows a second embodiment of the present invention.

FIG. 4 shows a third embodiment of the present invention.

FIG. 5 is an equivalent circuit of the configuration of FIG.

FIG. 6 shows a fourth embodiment of the present invention.

FIG. 7 shows a conventional Peltier device driving circuit (No. 1).

FIG. 8 is a diagram showing an outline of temperature control by a Peltier element in the electro-absorption modulator.

FIG. 9 shows a conventional Peltier device driving circuit (No. 2).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Peltier element 2 Resistance 3-7 Operational amplifier circuit 8-21 Resistance 22,23 PNP junction type transistor 24,25 NPN junction type transistor 26,27 P channel type field effect transistor 28,29 N channel type field effect transistor 30-33 Resistance 34-36 Operational amplifier circuit 37-45 Resistance

Claims (2)

[Claims] A constant current source electrode of an active element having a first polarity and a constant current source electrode of an active element having a second polarity are connected between a high voltage side constant voltage terminal and a low voltage side constant voltage terminal, one of which is ground. Two totem pole circuits are arranged, and a Peltier element is arranged between the connection points of the constant current source electrodes. When the input voltage is equal to one half of the voltage of the high voltage side constant voltage terminal and the low voltage side constant voltage terminal, 2 When the four active elements constituting the two totem-pole circuits are cut off, and the input voltage is higher than half the voltage of the high-side constant voltage terminal and the low-side constant voltage terminal, the positive of the first totem-pole circuit The active element of the first polarity on the power supply side and the second totem
The active element of the second polarity on the ground side of the pole circuit is made conductive, and when the input voltage is lower than half the voltage of the high-side constant voltage terminal and the low-side constant voltage terminal, the first totem-pole circuit A second polarity active element on the ground side and a second totem
A Peltier device drive circuit, wherein an active device having a first polarity on a positive power supply side of a pole circuit is made conductive. 2. The Peltier device driving circuit according to claim 1, wherein a resistor is inserted in series with the Peltier device, a terminal voltage of the resistor is taken out, and a first difference voltage from a reference voltage is generated. Generating a second difference voltage between the first difference voltage and the input voltage; determining whether the second difference voltage is higher or lower than 1/2 of the voltage of the high-side constant voltage terminal and the low-side constant voltage terminal; A Peltier element driving circuit, wherein a configuration for controlling the current of the Peltier element is added in the same manner as described above.