D/A signal superposition feedback circuit

Abstract

The present invention relates to digital / analog signal superposition feedback circuit, and is applied to circuit of high strength gas discharge lamp electronic ballast, which comprises the following components: voltage sampling circuit, current sampling circuit, digital / analog conversion circuit, superposition follower circuit and microprocessor. The invention comprises the following steps: sampling circuit transmits signal of lamp voltage and current to microprocessor by multiply for calculating power; digital power signal output by microprocessor is converted into corresponding analog signal and transmitted to superposition follower circuit B; meanwhile sampled current signal gets into superposition follower circuit A; superposition follower circuit A and B output digital / analog superposition feedback signal together. Analog signal and digital signal of current and power of characterization lamp can be compensated mutually and output superposing, and characteristic demand of lamp starting and constant power output of after stable can be realized.

Description

Technical field [0001] The invention relates to a circuit in an electronic ballast, in particular to a circuit in an electronic ballast for a high-intensity gas discharge lamp. Background technique [0002] High-intensity gas discharge lamps have high efficiency and good color rendering, and have been widely used in various lighting occasions, and electronic ballasts that match them have also developed. The high-intensity gas discharge lamp has unique electrical characteristics. It can be divided into two working phases: the ignition phase and the steady-state phase. In the ignition phase, the lamp exhibits negative resistance characteristics, that is, during this period, the lamp current gradually decreases, the voltage gradually rises, and the power gradually increases; when the current and voltage reach the rated value, it enters the steady state stage. When the lamp shows a positive resistance characteristic, in this stage, the current and voltage are in a proportional relati...

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Problems solved by technology

In the starting stage, the lamp tube presents a negative resistance characteristic, that is, in this stage, the lamp current gradually decreases, the voltage gradually increases, and the power gradually increases; when both the current and voltage reach the rated value, it enters the steady state stage. During this period, the lamp tube presents positive resistance characteristics. In this stage, the current and voltage are in a proportional relationship, that is, they increase or decrease at the same time. However, there are also characteristic jumps in the lamp tube steady state stage, which requires the electronic ballast to be able to At the same time, it meets the load characteristic requirements of the starting phase and the steady state phase

[0003] The load characteristic of the high-intensity gas discharge lamp puts forward quite high requirements on the control part of the electronic ballast: in the ignition stage, the ballast provides a stable current to heat the gas in the lamp tube and raise the lamp voltage; In the steady-state stage, constant power control must be achieved, because the consistency of high-intensity gas discharge lamps is very poor, and the steady-state voltage and current of lamps from different manufacturers and batches often vary greatly, which will affect the quality of the lamps. Steady-state power, shorten lamp life

If a general-purpose PWM control chip is used, the characteristics of the two working stages cannot be satisfied at the same time, and if an MCU is used for control, due to the harsh working environment of the electronic ballast, the reliable and stable operation of the single-chip microcomputer cannot be guaranteed. The whole system crashes

Among the various high-intensity discharge lamp electronic ballasts currently on the market, the core control parts of mainstream products all use dedicated chips, and these dedicated chips all have defects in stability and functional integrity to varying degrees.

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