CN115395767A

CN115395767A - Infrared light source constant power control circuit

Info

Publication number: CN115395767A
Application number: CN202211150001.5A
Authority: CN
Inventors: 梁学军; 刘娜; 王巍; 赵康
Original assignee: Beijing SDL Technology Co Ltd
Current assignee: Beijing SDL Technology Co Ltd
Priority date: 2022-09-21
Filing date: 2022-09-21
Publication date: 2022-11-25

Abstract

The invention belongs to the technical field of infrared light source power input control. The embodiment of the invention discloses an infrared light source constant power control circuit, which comprises a multiplier, a transformer, a second capacitor, a first resistor, a second resistor, a Schottky diode and a PWM controller, wherein the multiplier is connected with the transformer; the PWM controller is arranged between the multiplier and the switching tube and converts a power analog signal input according to the multiplier into a PWM signal; the transformer is used for converting direct current voltage into alternating current in a direct-current inversion mode, a primary side of the transformer inputs a PWM signal, a first end of a secondary side of the transformer is connected with the anode of the Schottky diode, and a second end of the secondary side of the transformer is connected with the ground wire; the anode of the Schottky diode is connected with the secondary side of the transformer, and the cathode of the Schottky diode is connected with the first resistor and connected with the first capacitor C1 in parallel. The device can reduce the requirement on the input power VCC, eliminate the noise and ripple waves introduced by the power VCC, reduce energy consumption and stabilize output power.

Description

Infrared light source constant power control circuit

Technical Field

The invention belongs to the technical field of infrared light source power input control.

Background

Modern optical measurement instruments require increasingly high precision, detection limit and stability. The traditional light source driving generally adopts a constant voltage source for driving, and voltage is directly loaded at two ends of an infrared light source, so that the light source directly generates heat and emits light. In practice it has been found that light emission from a light source relies mostly on heat generation to produce light. The power of the infrared light source is relatively large, and the power identity equation in the whole system is as follows: the power P = Q1 of the constant voltage source VCC consumes heat power Pq + power Pd of the infrared light source; q1 works in the variable resistance area, and the multiplier outputs analog quantity to adjust the resistance of Q1. The power of the load is adjusted to be constant in the infrared D1. The power of the light source is continuously adjusted in practical application, and the redundant power is consumed by heat generated by the Q1. Thus, the system will emit a large amount of heat, requiring additional heat dissipation of Q1. Meanwhile, energy is wasted, the Q1 has high thermal power, is not utilized and is completely radiated in a heat form. Thirdly, the system must be a constant voltage source for the input power VCC, which is a high requirement. Fourth, VCC instability in the system directly affects output power stability.

Disclosure of Invention

In view of this, the embodiment of the present invention discloses a constant power control circuit for an infrared light source, which includes a multiplier, a transformer, a second capacitor, a first resistor, a second resistor, a schottky diode, and a PWM controller; the PWM controller is arranged between the multiplier and the switching tube and converts a power analog signal input according to the multiplier into a PWM signal; the transformer is used for converting direct current voltage into alternating current in a direct-current inversion mode, a primary side of the transformer inputs a PWM signal, a first end of a secondary side of the transformer is connected with the anode of the Schottky diode, and a second end of the secondary side of the transformer is connected with the ground wire; the anode of the Schottky diode is connected with the secondary side of the transformer, and the cathode of the Schottky diode is connected with the first resistor and connected with the first capacitor C1 in parallel.

In a specific embodiment of the invention, the device further comprises a third capacitor, and the third capacitor is connected with the secondary side of the transformer and the anode of the Schottky diode in parallel.

In a specific embodiment of the invention, the device further comprises a second capacitor and a second resistor, wherein the second capacitor and the second resistor are connected in series and then connected in parallel with the schottky diode; the positive pole of the Schottky diode is connected with the second capacitor, and the negative pole of the Schottky diode is connected with the second resistor.

The device can reduce the requirement on the input power VCC, eliminate the noise and ripple waves introduced by the power VCC, reduce energy consumption and stabilize output power.

Drawings

Fig. 1 is a diagram of a constant power control driven infrared light source.

Fig. 2 is a schematic diagram of the circuit principle of the embodiment.

Detailed Description

Example (whether or not there is a limitation in the specific type and value of the specific capacitive resistor)

A CPU: can be a single chip microcomputer.

PWM: pulse width modulation.

A PWM controller: the analog signal can be collected and converted into a PWM frequency and duty ratio output device, and the PWM frequency and duty ratio output device can also be realized by microprocessing.

A multiplier: and multiplying the two input analog signals, and outputting the calculated analog signals.

A transformer: realize the isolation effect of power, characteristics are: input power Pin = output power Pout.

The design of the invention aims to solve the problems, the transformer control is introduced into the driving system, the switching tube Q1 can work in a complete conducting area, the heat productivity is very small, the direct current voltage is directly inverted into alternating current by controlling the transformer, the alternating current is loaded on an infrared light source after being rectified, power consumption devices are not needed any more, and the power consumption is greatly reduced. And the input power supply does not have strict requirements any more, only the input power is required to be larger than the power of the load infrared light source, and constant voltage or constant current is not required.

The invention utilizes the basic characteristics of the transformer, adjusts the output power of the transformer through the PWM controller, and leads the output power to reach the constant power by collecting the product of the voltage and the current of the load. The constant power system is loaded to two ends of the infrared light source, so that the infrared luminous power output is constant, and the constant light source is very important in the measurement of an optical instrument. Can improve the sensitivity of the instrument, the detection limit of the instrument and the like.

As shown in fig. 2, an embodiment of the present invention discloses an infrared light source constant power control circuit, which includes a transformer L1, a third capacitor C3, a second capacitor C2, a first capacitor C1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a schottky diode D1, and a PWM controller; wherein:

the first resistor R1 is used for sampling output power current, the third resistor R3 and the fourth resistor R4 are used for sampling output power voltage, and the multiplier calculates actual power according to the two sampling data.

The PWM controller is arranged between the multiplier and the switch tube Q1, converts a power analog signal input according to the multiplier into a PWM signal, controls the switch tube Q1 to convert a direct current power supply VCC into a variable signal through a transformer, and converts the signal change input into the primary coil into a magnetic field and couples the magnetic field to the secondary coil for output according to the transformer principle.

The transformer L1 is used for converting direct-current voltage into alternating current in a direct-current inversion mode, a primary side of the transformer L1 inputs a PWM signal, a first end of a secondary side of the transformer L is connected with the third capacitor C3 in parallel and connected with the anode of the Schottky diode D1, and a second end of the secondary side of the transformer L is connected with the ground wire.

The second capacitor C2 and the second resistor R2 are connected in series and then connected in parallel with the Schottky diode D1, the anode of the Schottky diode D1 is connected with the second capacitor C2, and the cathode of the Schottky diode D1 is connected with the second resistor R2.

The cathode of the schottky diode D1 is connected to the first resistor R1 and is connected in parallel to the first capacitor C1.

Assuming that the transformer adopts a primary coil and secondary coil with a turn ratio of 1:1, the voltage signal waveform at the point a is identical to the controlled signal waveform at the primary coil (without considering the loss of transformer coupling, which is the power loss of the primary coil coupled to the secondary coil), and the voltage signal waveform is filtered by a third capacitor C3 and converted into a standard sine wave at the point B. The schottky diode D1 functions as half-wave rectification, and only the positive half-axis signal of the sinusoidal signal can pass through. The second capacitor C2 and the second resistor R2 form an RC filter for filtering noise and ripple signals introduced by the VCC. The point C is a rectified signal waveform, and the rectified signal waveform is filtered by a first capacitor C1 to become a direct current signal. The PWM output signal is a switching signal, and the frequency and the duty ratio can be adjusted by the signal to achieve the constant output power.

In the design of the invention, because the switching tube Q1 works in two states and is not completely conducted, the resistance is 0; if the resistor is not completely closed, the resistor is infinite and does not emit a large amount of heat.

Compared with fig. 1, the output of the multiplier in fig. 1 is an analog quantity, and the excess power is consumed by adjusting the resistance of the switching tube Q1, so that the output power is constant. However, the system can emit a large amount of heat, and the switching tube Q1 needs to be subjected to heat dissipation treatment; meanwhile, the heat energy of the switching tube Q1 cannot be utilized, so that energy waste is caused.

The device of the invention reduces the requirement on the input power VCC due to the introduction of the work of the transformer, and the switching frequency and the duty ratio of the Q1 can be rapidly adjusted through the PWM controller, so that the constant of the power converted from VCC is achieved. The VCC requirement is reduced by requiring only power greater than the load power, thus not necessarily requiring the power supply VCC to be a constant voltage source. Meanwhile, the transformer is formed by coils, and has an isolation effect. The coil of the transformer can be regarded as an inductor, and an unstable signal of the input power supply VCC is filtered by the inductor. And the special RC filter structure formed by the second capacitor C2 and the second resistor R2 can further eliminate noise and ripples introduced by the power supply VCC, realize the stability of output power and reduce the dependence of a system on the stability of an input power supply.

Claims

1. The infrared light source constant power control circuit is characterized by comprising a multiplier, a transformer, a second capacitor, a first resistor, a second resistor, a Schottky diode and a PWM controller;

the PWM controller is arranged between the multiplier and the switching tube and converts a power analog signal input according to the multiplier into a PWM signal;

the transformer is used for converting direct current voltage into alternating current in a direct-current inversion mode, a primary side of the transformer inputs a PWM signal, a first end of a secondary side of the transformer is connected with the anode of the Schottky diode, and a second end of the secondary side of the transformer is connected with the ground wire;

the anode of the Schottky diode is connected with the secondary side of the transformer, and the cathode of the Schottky diode is connected with the first resistor and connected with the first capacitor C1 in parallel.

2. The infrared light source constant power control circuit as claimed in claim 1, further comprising a third capacitor connected in parallel with the secondary side of the transformer and the anode of the schottky diode.

3. The infrared light source constant power control circuit according to claim 1, further comprising a second capacitor and a second resistor, wherein the second capacitor and the second resistor are connected in series and then connected in parallel with the schottky diode;

the positive pole of the Schottky diode is connected with the second capacitor, and the negative pole of the Schottky diode is connected with the second resistor.