White LED is usually a constant current DC source to maintain a constant brightness. The use of single lithium-ion battery for portable applications, white LED current source and the amount of voltage drop can be higher or lower than the battery voltage, which means that the white light needs time to raise the voltage of the battery. The best way to fulfill this request is to use the step-up DC-DC converters. This method can greatly improve efficiency, but the cost of rising costs and PCB area. Another update is to use the charge pump voltage battery, also called switched capacitor converter. This paper will examine in detail the operating principle of this device. Dell Inspiron 1470 battery Dell Inspiron 1470n battery
The basic principles of charge pump
Capacitor is used to store electrical charge or electrical energy, and time set for the default rate will be the release of the component.
If an ideal capacitor with an ideal voltage source VG dependents will be based on Dirac current pulse of charge stored function immediately. The total amount of stored charge calculated by the following ︰ Q = CVG
The real capacitor with equivalent series resistance (ESR) and equivalent series inductance (ESL), the two that will not affect the ability of the capacitor energy storage. However, they switched voltage converter capacitor overall conversion efficiency has a great influence. The equivalent circuit charging the capacitor, as shown, which switch RSW is the resistance. Load current path with a series inductance, through appropriate design of the layout device can reduce the series inductance. Dell Inspiron 14z battery Dell Inspiron 1570 battery
Once the circuit is energized, it will feature the exponential phase until it reaches a stable condition today. The limits of the parasitic capacitance of the peak load current, and increase the time of charge transfer. Therefore, the charge storage capacitor can not be performed immediately, which means that the initial voltage across the capacitor is zero. Charge pumps capacitors on the use of this feature, as indicated.
This method can be realized using the voltage times the pressure. Switching signal is usually 50% duty cycle, which usually produces the best efficiency of charge transfer. Let us learn more about the process of charge transfer and voltage converter capacitor parasitic how they affect their work.
The figure shows the voltage doubler capacitor switched steady state current and voltage waveforms. According to the principle of conservation of energy, the average input current is twice the current production. Dell Inspiron 1570n battery Dell Inspiron 15z battery
Initially, the load current flow to the C1. The initial value of load current depends on the initial voltage across the capacitor C1, C1 ESR and resistance switch. Load to C1, the charge current decreases exponentially. The charging time constant is the cycle of switching time, small time constant load will result in the peak current is increased. At that time, the output capacitor Cholder provide linear discharge of the battery charge current, the discharge is equal to:
In the second phase, C1 + connected to the output, the discharge current (the current size of the load current and past) C1 to flow through the load. At this stage, the output capacitor current IOUT in about 2. While the change in the course should be able to generate an output voltage IOUT ESRC_HOLD 2, the use of ceramic capacitors with low ESR made this change negligible. At this stage, Cholder linear power potential over the following dell inspiron 1525 battery dell inspiron 1526 battery
Higher switching frequency using a smaller output capacitor for the same ripple.
Voltage Charge pump output parasitic effects of lead than the increase in load current. In fact, there are always 2 IOUT RMS current flowing through C1 and the two switches (2Rsw), leading to lower power consumption ︰
In addition to these purely resistive losses, IOUT RMS current flowing through the switched capacitor C1 of equal strength, the energy created is short, because of low ESR ceramic capacitors, high frequency switching, the output drive and output voltage drop depends on the switch resistance. dell inspiron 1420 battery dell inspiron 1501 battery