LDO and DC-DC Simple Comparison and Selection

wangerxian

LDO and DC-DC Simple Comparison and Selection [Copy link]

1. LDO (low dropout regulator)
1. LDO: low dropout linear regulator, literally means linear;
2. Output current equals input current
3. Efficiency: equal to the ratio of output voltage to input voltage, the larger the input-output voltage difference, the lower the efficiency, on the contrary, the higher the efficiency, because the output current is roughly equal,
4. Type: fixed output, adjustable output
2. DC-DC
1. DC-DC: DC converted to DC
2. Efficiency: The efficiency is relatively high, up to 96% under heavy load and over 80% under light load.
3. Types: boost, buck, buck-boost, reverse structure
III. LDO and DC-DC selection
1. If the input and output voltages are close, LDO is more efficient than DC-DC. If the input and output voltage difference is large, DC-DC is more efficient
2. Cost: LDO is lower than DC-DC
3. Peripheral circuit: LDO is simpler than DC-DC
4. Noise/ripple: DC-DC is worse than LDO;
5. Maximum output current: LDO is generally several hundred mA, DC-DC is generally several A or even more

秦天qintian0303

The original poster is right. DCDC generally focuses on the impact of ripple on the system.

bioger

The landlord is right.

dwdsp

It is very clear, the only point is: input current = output current? For example, if the output is 5V10mA and the input is 10V, how many mA is it?

dwdsp

For example, LDO outputs 5V200mA (1W), and the input is 40V, is the current also 200mA (8W)?

maychang

dwdsp posted on 2022-7-16 12:12 It is very clear, the only point is: input current = output current? For example, if the output is 5V10mA and the input is 10V, how many mA is it?

"For example, if the output is 5V10mA and the input is 10V, how many mA is it?"

For linear regulator chips, the input current is slightly larger than the output current, and it can be approximately considered that the input current is equal to the output current.

maychang

dwdsp posted on 2022-7-16 12:18 For another example, LDO outputs 5V200mA (1W), inputs 40V, is the current also 200mA (8W)?

"For example, if an LDO outputs 5V200mA (1W) and inputs 40V, is the current also 200mA (8W)?"

Yes. This is also why linear regulators are quite inefficient. See the third sentence of the original poster.

maychang

dwdsp posted on 2022-7-16 12:18 For another example, LDO outputs 5V200mA (1W), inputs 40V, is the current also 200mA (8W)?

What the OP calls LDO actually refers to a linear regulator. LDO is a "low dropout linear regulator". Not all linear regulators are low dropout linear regulators, which means not all linear regulators are LDOs.

学无止境02

The original poster explained it very clearly. If the input voltage and output voltage are close, it is best to choose LDO; if the input voltage and output voltage are not very close, it is best to choose DC-DC

maychang

Endless Learning 02 Published on 2022-7-17 11:17 The host explained it very clearly. If the input voltage and output voltage are close, it is best to choose LDO; if the input voltage and output voltage are not very close, it is best to choose DC- ...

Linear regulators cannot step up voltages. Even if the output voltage is only required to be slightly higher than the input voltage, a linear regulator cannot be used.