Power Supply

Instruments

Power is the backbone of any electronic system and the power supply is what feeds the system. Choosing the right supply can be the critical difference between a device working at optimum levels and one that may deliver inconsistent results.

In addition to Alternating Current (AC) to Direct Current (DC) power supplies, DC-to-DC converters are also available. If DC is already available in your system, a DC-to-DC converter may be a better design choice than AC.

Direct current power supplies are either unregulated or regulated.
Regulated supplies come in several options including linear, switched, and battery-based.

What is a Regulated Power Supply?

An electronic circuit that produces a stable DC voltage of fixed value across the load terminals irrespective of changes in the load is known as a regulated power supply.

  • The primary function is to convert AC power into a steady DC power.
  • Sometimes also called a linear power supply.
  • Ensures the output power at the load terminals remains constant even if the input power varies.

The regulated power supply receives AC power as input and generates a constant DC power as output.

A regulated power supply is an embedded circuit consisting of various blocks.

Block Diagram and Operation of Regulated Power Supply

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The regulated power supply consists of the following four major parts:

  1. Step-down transformer
  2. Rectifier circuit
  3. DC filter circuit
  4. Voltage regulator

Features of Regulated Power Supply

  • Efficiency ranging from 20% to 25%.
  • Relatively more reliable.
  • Less complex circuits and lighter weight.
  • Faster response.
  • Low cost and noise level.

Applications of Regulated Power Supplies

  • Mobile charging circuits
  • Testing circuits
  • Bench power supplies
  • Oscillators and amplifiers
  • Electronic computers
  • Automatic control systems

Direct Current Regulated Power Supplies

Scientech 4074 A Multiple DC Power Supply

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The Scientech 4074 is designed as a Constant Current (CC) and Constant Voltage (CV) source for use in laboratories, industries, and field testing.

  • Compact size, lightweight, and low power loss.
  • Provides DC output voltages for analog and digital testing.
  • Adjustable outputs: 0-30 V, 0 ±15 V dual tracking, and 5 V adjustable (4.8 – 6 V).
  • Current limit adjustable from 0–1A.
  • Overload indicated by LED and audible beep.
  • 3-digit display for voltage and 3½ digit display for current.
  • Low ripple, excellent line/load regulation, and protective circuits.

Features:
- Three floating, independent DC supply voltages.
- Constant Voltage and Constant Current operation.
- Selectable display for voltage & current.
- Adjustable current limiter.
- Excellent line & load regulation.

Scientech Triple Power Supply ST4071

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A versatile and reliable power source for electronics laboratories and educational settings.

  • Three independent outputs: 2 × 0-30 V / 500 mA & 5V / 1A.
  • Simultaneous positive and negative voltage supply.
  • Precise voltage and current control.
  • Robust construction with digital display.

Features:
- Constant Voltage and Constant Current operation.
- Short-circuit protection.
- Digital display for voltage and current.

Scientech 4078 DC Power Supply

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  • Designed as CC and CV source.
  • Adjustable 0-30 V output with coarse & fine controls.
  • Current limit adjustable up to 3A.
  • Overload protection with LED indication.
  • 3-digit LED display for voltage & current.

Product Features:
- Pre-regulator based design.
- Floating output.
- Selectable display for voltage & current.
- Low ripple voltage.
- Excellent line & load regulation.
- Large display.

Aplab L3202 LAB

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A versatile dual-channel power supply, delivering up to 30V / 2A per channel.

  • Precise voltage & current regulation.
  • Digital display with intuitive controls.
  • Built-in protection against overcurrent & overvoltage.
  • Compact, durable design suitable for labs, education, and industrial use.

Important Controls & Terms

Coarse & Fine Knob

  • Used for voltage adjustment.
  • Coarse knob: Brings voltage close to required value.
  • Fine knob: Precisely adjusts the voltage (e.g., from 3.0V to 3.3V).

Imax Knob

  • Sets the maximum output current (Imax).
  • Prevents excessive current flow, protecting sensitive components.

What does 30V/1A mean?

  • 30V → Maximum voltage output = 30 Volts.
  • 1A → Maximum current output = 1 Ampere.

    The power supply can deliver 30V max and 1A max to the circuit.

Dual Power Supply

A dual power supply provides two independent output voltages, usually +V and –V.

  • Enables bipolar supply for op-amps, audio amplifiers, etc.
  • Example: 0 – ±15V Tracking, meaning synchronized +15V and –15V outputs.

CV & CC Modes

  • CV (Constant Voltage):
  • Maintains stable voltage irrespective of load changes.

  • Used in applications needing a consistent voltage.

  • CC (Constant Current):

  • Maintains steady current irrespective of load changes.
  • Useful for LEDs, battery charging, and circuits needing fixed current.