New design method of battery charger

At present, lead-acid batteries are widely used in various power supply occasions. In order to give full play to the use of lead-acid batteries, the charger should fully charge the battery during the process of charging the battery, and prevent overcharging as much as possible to make it prolong life. Practice has proved that to ensure the service life of lead-acid batteries, it is very important to adopt the correct charging method. The batteries are often connected in series to form a battery pack to increase the output voltage. Correspondingly, it can be charged in series. However, due to the single capacity, terminal voltage and internal resistance of the battery, inconsistent problems will inevitably arise during the manufacturing and use process, resulting in that the battery pack is often unbalanced during the charging process, resulting in a serious service life of the battery pack shorten. This paper proposes a new charger design method. Three isolated outputs charge a single battery, and a new three-stage charging control method is used at the same time. 1 Charge theory The battery has three important working states in the work project: discharge state, charge state and floating charge state. When in the discharging state, the battery converts the stored chemical energy into electric energy to supply the load; the charging state is the state of energy saving after the battery is discharged. In this state, the electric energy is converted into chemical energy and stored; in the floating state, the battery maintains a certain amount The storage capacity of chemical energy must be maintained in the working state, and the energy storage of the battery in the floating charge state will not be lost due to self-discharge. The three states of discharging, charging and floating charging constitute a complete working cycle of the battery. Traditional chargers use a series charging method, and the current through each battery is the same. Although a three-stage charging method is adopted, the voltage that can be controlled during charging is only the series voltage of the battery pack, which is still accompanied by uneven and enlarged battery pack charging. The battery working condition curve is shown as in Fig. 1. Therefore, a new approach is adopted on this basis. 2Improved design method 2.1 The main circuit of the improved new charger main circuit, as shown in Figure 2. The front stage uses a soft-switching asymmetric half-bridge to achieve multiple isolated outputs, and uses its own parasitic parameters to achieve resonant zero-voltage soft switching to reduce switching losses and prevent leakage inductance from the transformer. Coming voltage spikes. The latter stage uses a mature and simple buck circuit topology to achieve step-down and use this to meet the requirements of three-stage charging. To realize the soft switching of the asymmetric half bridge, the parameter design of the asymmetric half bridge must meet the following two conditions, namely: where: Zn is the characteristic impedance; D is the duty cycle of the switching tube Q1; C is the switching tube Q1 And the parasitic capacitance of Q2; u0026omega;k is the resonant angular frequency; Lk is the primary leakage inductance of the transformer; I0 is the total load current; td is the dead time; n is the primary and secondary turns ratio of the transformer.