[Basic Class] Based on XL6008E1 Boost Adjustable Power Supply Design +364498A

design process

First, I searched for relevant information about the C73012 chip, found its English information on Lichuang, downloaded it and read it. It is found that its internal pin diagram and internal circuit diagram are as follows:

Figure 1 Pin diagram

Figure 2 Internal circuit diagram

Here we combine the two pictures to draw the following conclusions:     First of all, it is clear that this is a power chip, which integrates a MOS switch tube, a PWM generator and a self-driving module.     FB is its feedback control terminal, which can realize feedback control. The internal feedback reference voltage is 1.25V, which needs to be very accurate. When the FB pin inputs a voltage of 1.25V, a stable operating point is formed.

VIN is the power input terminal. According to the data, the input voltage range is very large (Wide 3.6V to 32V Input Voltage Range), which is enough to meet the requirements of the question (input voltage 5~12V).     SW and GND are the source and drain pins of the MOS. When designing the circuit, you only need to replace these two pins with the switch tube.     The EN pin is the enable terminal, high level turns it on and low level turns it off.

So the chip is very simple.

Let's continue to look at the typical application circuit. Take the boost circuit as an example:

Figure 3 Boost circuit designed based on C73012 We know that the basic boost circuit is as follows:

Figure 4 boost circuit

Comparing the two circuit diagrams can verify our conjecture above: the MOS switch tube is integrated internally; SW and GND are the source and drain pins of the MOS; feedback control can be realized; there are PWM generation and self-driving modules. In addition to basic chopping, the principle of output voltage size also has the principle of feedback closed loop: the stable operating point of the circuit always meets the FB pin voltage of 1.25V. We can use this feature to design the output voltage range: by controlling the voltage division of the external resistor potentiometer on the FB pin, we can control the voltage on the output bus.

Figure 5 Voltage output scheme

As shown in the figure above, you only need to control the position of potentiometer R3 to control the Vout voltage. The formula for the output voltage is:

According to this formula, the relevant circuit parameters can be calculated. After determining the output voltage control scheme, the next step is to determine the circuit type, calculate the circuit parameters and select the device model. In addition, the data also provides another typical buck-boost circuit, which is actually an isolated flyback converter with a buck-boost function. The circuit schematic is as follows.

Figure 6 Flyback conversion circuit based on XL6008E1 Circuit structure selection: basic non-isolated DC chopper circuits include buck, boost, buck-boost, etc., and isolated types include flyback, forward, etc. The boost circuit is chosen here. The designed output voltage is adjustable from 5-15V, and the input voltage is provided by type-C with 5V. It can also be externally input with a wide range of DC voltage of 3.6V-10V.

Design the circuit diagram based on the above analysis.

Figure 7 Circuit schematic design

Check that there are no errors in the network and proceed with PCB layout. Circuit design description: Since the circuit adopts a boost structure, it can achieve a wide range of voltage boosting. Therefore, in theory, the inductor must be large enough and the capacitor must be large enough to store more electrical energy to achieve a substantial increase in electrical energy. However, the question only requires a voltage boost from 5V to 12V. The circuit design here has a maximum voltage boost of 15V. Therefore, in order to increase the power of the device and reduce the size of the device as much as possible, a larger inductor was not chosen here, but the current carrying capacity was chosen. The stronger C87568 inductor is enough for boosting the voltage from 5V to 15V; in addition, a red LED light is added to the circuit to indicate the circuit operating status; two 3V battery boxes are connected in series to provide a voltage of 6V The output provides a maximum power of 18W. In order to protect the dry battery, a 20V Schottky diode is added outside the battery box to prevent damage to the battery and accidents. When used here, it is still necessary to avoid connecting two power supplies at the same time. situation to prevent danger.

The circuit board supports three input methods:

1. Four dry batteries are input. When the current reaches 5A, the fuse operates to protect the battery and circuit. Therefore, when dry batteries are used as input, the maximum power input to the circuit is 30W.
3. 5V type-C input, convenient and fashionable interface, beautiful and elegant. This input side uses an 8V/3A self-restoring fuse to prevent the computer's USB output power from burning the computer motherboard when the computer is powered.
5. 3.6V-12V DC input, connected to a 16V/6A high-power fuse. If high-power output is required, this input interface can be used.

Supports port external wiring or USB output, and the output voltage of the two ports is equal. The PCB components and layout are as follows:

Figure 8 PCB diagram

Figure 9 3D preview

Summary: The title is "Boost adjustable power supply design based on XL6008E1". A multi-input and multi-output boost power supply is designed using the XL6008E1 chip, which supports four AA dry cell inputs, type-C 5V input, and external terminals. 3.6V-12V wide range input, the output voltage can be adjusted through the potentiometer, so that the output voltage can be converted between 5V-15V. It also supports USB output and provides an output wiring port. The overall design is beautiful and elegant, with diverse functions and flexible use. The functions can meet most low-power usage scenarios. When using, please note that although relevant protection is designed in the circuit, multiple power sources cannot be connected at the same time to prevent danger. However, they can be output at the same time. Please note that the output power cannot be too large.