Since becoming more accustomed to designing electronic circuits, we often hear people saying things like, “I want to control the power supply for each part of the circuit to reduce power consumption” or “I want to protect the circuit from overcurrent and prevent product accidents”. But mounting circuits with transistors and shunt resistors requires higher design costs and longer verification times.
In this article, we will introduce a power management switch that easily controls and protects the power supply line.
A power management switch is an IC that is placed between the power supply and the load (LED / relay or external power supply output) to control the ON / OFF of the power supply line, shutting it off when an abnormality occurs in the circuit. The electronic circuit that turns this power line on and off is referred to as a “load switch”.
It’s a convenient IC for ON / OFF control, but some are equipped with a protection function that shuts off the energization, so the whole circuit won’t be damaged even if a large amount of current flows on the power supply line due to trouble in the circuit.
Power management switches include products that only have the load switch as an IC, as well as products that have an IC with a protection function added to the load switch. To avoid confusion in this article, both ICs are referred to as “power management switches”.
You can design ON / OF control and overcurrent cutoff functions using transistors and shunt resistors, however, the power management switch packages those electronic components internally.
The figure on the left is an example of the construction of a load switch circuit by combining electronic components. For the power management switch (the figure on the right), the circuit shown on the left is packaged in the IC.
Image reference: (left) Load switch | what is a transistor? | Electronics trivia | ROHM Co., Ltd., (right) 1ch small high side switch IC – BD2242G
Diagram of a circuit block that uses a power management switch. A power management switch is inserted between the power line and the load, and ON / OFF is controlled by the microcomputer.
Surface mount power management switch ROHM BD2242G. The power management switch is a surface mount IC, but if you use a conversion board, you can also use it on a breadboard or universal board.
This function turns the power supply to the load on and off using a microcontroller. This function is called a load switch.
In recent years, battery-equipped devices often cut off the energization of the parts of unused electronic circuits in order to reduce power consumption as much as possible. In such applications, power management switches that can produce space-saving and simple ON / OFF control circuits are utilized.
There are various potential scenarios where a large current could be generated due to a circuit abnormality, for example “short circuits in which a ceramic capacitor breaks due to the impact of dropping it” or “short circuits that occur due to poor contact when connecting or disconnecting the connector”.
If an abnormal current continues to flow, the operation will become unstable due to the drop in the voltage, causing heat generation in the electronic components and board, as well as smoke and fire.
The overcurrent protection function limits or stops the output when it detects an overcurrent condition. In addition, some power management switches detect if the power supply itself has become hot and cut off the power supply.
The soft start function prevents inrush current (a phenomenon in which a large current begins to flow the moment that the power is turned on).
The inrush current is generated by charging the capacitors (CL) in the circuit all at once the moment the switch is switched from OFF to ON.
Inrush current, which is a temporary short circuit, can cause a large voltage drop and adversely affect the circuit.
The inrush current can be suppressed by adding a capacitor (C2) (soft start function). Many power management switches have this soft start function built in, so you can easily take measures against inrush current without using an external capacitor.
Image reference: Load switch | What is a transistor? | Electronics trivia | RHOM Co., Ltd.
In addition to these functions, power management switches have various forms of protection, including “notifying the outside of the overcurrent state” and “over voltage protection / under voltage lock out”, making power management switches a versatile IC that can widely support the protection and control of power lines.
New power supply circuits are required to have various functions, such as break circuits that takes energy saving into consideration and safety protection features in the event of abnormalities.
Adding a break circuit will increase the scale of the circuit and may lead to cost increases. Using a power management switch not only makes it easy to implement protection functions, but also has many advantages, including low cost and improved reliability.
Various types of power management switches are available, depending on the breaking current and protection functions installed, so you should be able to find a suitable product for your applications.
The power management switch is a surface mount IC, but if you use a conversion board, it can also be used on a universal board or breadboard. It can also prevent expensive ICs from being damaged due to short-circuiting wiring or the reverse connection of the power supply, so why not use it in electronics kits as well?
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