We propose a stable control method for power conditioner within a high thrust operation zone on the oscillation-mode-map. First, we present observations of 20mN-class Hall thruster with oscillation-mode-map. We made an experimental and theoretical study of the thrust and electrical characteristics of the Hall thruster, and concluded that thrust, thrust efficiency and low frequency oscillation are clearly determined by the external control parameters, anode voltage, gas flow rate, and magnetic flux density. Second, we discuss how to control the power conditioners (PCs) to suppress the power consumption, especially when the operation or thruster conditions change temporally in the practical application. The new method will be a very important guideline for Hall thruster system design and operation, in particular making it easy to manage the power consumption in a satellite, using the PCs control. As a result of maximum performance experiments for 20mN-class Hall thruster, over 36% thrust efficiency of the Hall thruster was found to be sensitive to the anode voltage and applied magnetic flux density. A new power control method achieves the constant flow rate control method for controlling of the thrust. The benefits are light weight and low cost.