Prepare for Power Consumption debugging and prepare for Power Consumption debugging

Prepare for Power Consumption debugging and prepare for Power Consumption debugging

Prepare for Power Consumption debugging

December 17, 2014

I. Basic Concepts

What is power consumption testing?

Power Consumption testing refers to measuring the current of each module in various power consumption states by using various tools (mainly oscilloscope, ammeter, and voltmeter), and then analyzing the measurement results, find out unreasonable modules, modify hardware or software, and then measure them to minimize the power consumption of the entire board and prolong the battery time.

Why do we use the current measurement method to represent power consumption?

Power is W = Pt = UIt, where W is power, P is power, t is time, U is voltage, I is current. When the voltage is stable, we can use the current to reflect the power. The unit of It can be viewed as Ah. The lithium battery capacity unit is generally mAh, that is, the mAh, for example, the cell phone battery is generally 1800 mAh, and the tablet is generally 3500 mAh. Why is mAh used to represent capacity? We know that the voltage value of the lithium battery is very small, usually between 3.7V and 4.2V, that is, 500mV. So we can take the mah battery here, if the battery is discharged at 400mA of the current, the battery can be used for 10 h. MAh can better reflect the battery time.

Ii. Purpose of Power Consumption debugging

1. Obtain the power consumption data of the device in various States to calculate the battery standby time;

2. Reduce the power consumption of the device, and ultimately reduce the residual heat and standby duration generated by the device;

3. detect problems and defects in hardware and software design in a timely manner, and observe the current fluctuation of the equipment to determine whether the equipment is stable;

4. It is not only a test but also a rare learning opportunity for technicians (just getting started;

Iii. testing tools that may be used

A) oscilloscope

This module uses a digital oscilloscope and a current probe to measure the current of each module. The data to be measured includes the maximum, minimum, and average values of various currents. The average value is the focus of Power Consumption debugging, while the maximum and minimum values are especially important for the stability of the entire board.

For example, the maximum current on the-board processor is 600mA, the minimum value is 100mA, and the average value is 200mA. The maximum value on the B-board is 400mA, the minimum value is 150mA, and the average value is 200mA, the two Board B must be more stable than the board, which is why the maximum and minimum values are added.

Note: If the average value of the measurement fluctuates too much, it is best to tune the time of each grid a little longer. In general, it is best to adjust the cycle of each grid to 400 ms for measuring video playback and game power consumption, in this way, the variation of the average value is smaller.

B) Multimeter

FLUK multimeter is easy to use. It is undoubtedly accurate in measuring current, voltage, and resistance. FLUK tables are generally used to measure power consumption during Shutdown and sleep.

It should be emphasized that the selected range should meet the requirements as much as possible. The smaller the range, the better, but the measured value cannot exceed the range.

It is used to measure the power consumption during sleep and shutdown. Because of the power consumption during sleep and shutdown, the error measured by the current probe of the oscilloscope is too large, while the current probe is running normally, the current probe value of the oscilloscope is relatively accurate.

C) Voltmeter

Used to measure the power supply of each module. For example, if the power supply voltage of the device is 3.3 V, the voltage should be 0 V when it enters sleep. If the measurement value is 0.8 V, it indicates that there is a leakage. This is a particularly important method to detect leakage of a module.

D) Steady pressure source

Do not use battery for Power Consumption debugging. It is best to use a steady pressure source and set the voltage to 4 V. This will eliminate the measurement error caused by the internal resistance of the battery.