Description
Product Overview
The LM2577S + LM2596S Auto Step-Up/Down Voltage Regulator Module is a versatile buck-boost converter that combines two industry-standard switching regulators into one compact board. This module can automatically step up (boost) or step down (buck) an input voltage to a stable, user-defined output level, making it ideal for applications where the power source voltage fluctuates—such as solar panels, wind generators, or automotive systems .
Unlike standard voltage regulators that only step down (buck) or step up (boost), this module does both. If your input voltage is 24V and you need 12V, it bucks down; if your input is 5V and you need 12V, it boosts up. This automatic functionality ensures your output remains stable even as the input varies .
The module is built around the LM2596S (buck converter) and LM2577S (boost converter) ICs from Texas Instruments. It features Constant Current/Constant Voltage (CC/CV) control with dedicated indicator LEDs, making it particularly well-suited for battery charging applications—including lithium, lead-acid, nickel-cadmium, and nickel-metal hydride batteries . The onboard trimpots allow independent adjustment of output voltage (CV), constant current limit (CC), and the transition current at which the charging LED indicates completion .
With an input range of 4V to 35V and an adjustable output range of 1.25V to 25V (or up to 26V on some variants), this module is a practical choice for DIY power supplies, solar charge controllers, LED drivers, and battery charging systems .
Key Features
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Automatic Buck-Boost Operation: Automatically steps up (boosts) or steps down (bucks) input voltage (4-35V) to maintain a stable output between 1.25-25V, regardless of input fluctuations .
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CC/CV (Constant Current/Constant Voltage) Control: Enables precise battery charging with adjustable constant current (0-2A) and constant voltage, protecting batteries from overcharging .
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Dual-Chip Design: Combines LM2596S (step-down) and LM2577S (step-up) regulators for reliable performance in both operating modes .
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Three Adjustable Potentiometers: Independent trimpots for output voltage (CV), constant current limit (CC), and revolving light current (transition point from CC to CV mode) .
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Dual-Color Charging Status Indicators: Red LED indicates charging in progress/constant current mode; Blue LED indicates charging complete (constant voltage mode) .
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15W Output Power: Capable of delivering up to 15W under natural cooling; add a heatsink for operation beyond 15W .
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3A Maximum Output Current: Supports up to 3A output current (derate based on input-output voltage differential) .
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Wide Operating Temperature: Industrial grade rated from -40°C to +85°C; above 40°C ambient, reduce power or add a heatsink .
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Output Short Circuit Protection: Constant current protection activates during output short circuits .
Technical Specifications
| Parameter | Operating Value |
|---|---|
| Input Voltage | DC 4V – 35V |
| Output Voltage | 1.25V – 25V (continuously adjustable) |
| Output Current (Max) | 3A (derate based on power) |
| Constant Current Range | 0 – 2A (adjustable) |
| Output Power (Max) | 15W (natural cooling) |
| Minimum Voltage Differential | 2V |
| Conversion Efficiency | Up to 80% (higher with higher output voltages) |
| Switching Frequency | 52 kHz (LM2577S) / 150 kHz (LM2596S) |
| Operating Temperature | -40°C to +85°C |
| Full Load Temperature Rise | 45°C |
| Module Dimensions | 50mm × 37mm × 13mm |
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