Realization circuit and realization method of constant current and constant power

Abstract

The invention discloses a realization circuit and a realization method of a constant current and a constant power. The realization method comprises the following steps of: sampling an output current of a load R0 to acquire an output current sampling value; inputting the current sampling value, a constant current set value and a constant power set value to an A / D sampling port of a controller; when the constant value set value is greater than or less than the output current sampling value, sending a control signal by the controller so as to control a PWM drive chip to increase or decrease a duty cycle of a PWM signal output by the PWM drive chip, thereby realizing the constant current on the load R0; or calculating a power sampling value on the load R0 by using the output current sampling value, when the constant power set value is greater than or less than the power sampling value, sending a control signal by the controller to control the PWM drive chip to increase or decrease the duty cycle of the PWM signal output by the PWM drive chip, thereby realizing the constant power on the load R0. According to the realization circuit and the realization method of the constant current and the constant power disclosed by the invention, a current sampling element, such as a diverter, a Hall sensor or a mutual inductor, is not needed; moreover, the realization circuit and the realization method have the advantages of simple structure of the circuit, low realization cost, and the like.

Description

technical field [0001] The invention relates to a control circuit, in particular to a circuit and method for realizing constant current and constant power by using a simple resistance method. Background technique [0002] Generally, electronic loads will collect current in the design of constant current (CC mode) or constant power (CP mode) to realize the closed-loop control of constant current and constant power. [0003] Such as figure 1 Shown is a schematic circuit diagram of an existing electronic load realizing constant current or constant power. By adjusting the resistance of the variable resistor R2 to change the given input current, the comparator U1 compares the given input current with the current feedback collected from the shunt S1, and continuously adjusts the on-off time of the transistor G1 to change The duty cycle makes the current meet the given requirements, and the same principle is used to achieve constant current or constant power, except that a voltag...

AI Technical Summary

Problems solved by technology

If resistive components are used for current sampling, it will bring losses, such as shunts. Although the shunts are all milliohm level, in the case of high current output, the power consumption of the shunt will not be small. It is a few watts (W), so sometimes it is difficult for a shunt to meet its own power derating requirements, so the shunts on the market are getting smaller and smaller, and the consequence of this is that the shunt must be matched with high amplification. Multiple chips are amplified, then the cost, sampling accuracy, and small-signal current sampling circuit will become the key and difficult factors affecting the design when the circuit board is manufactured.

Images