A Novel Capacitor Step

This paper presents a novel DC capacitor buck regulator circuit, the circuit without transformer, only by a few simple

Electronic component Composition. Output DC voltage over a wide range of arbitrary regulation, only to change the reference voltage components.

An overview of Electronic engineers are always in constant pursuit of reducing equipment size, optimal design, in order to minimize equipment costs. Among them, reducing the DC power supply as auxiliary

Power Supply Circuit part of the volume, is often one of the most difficult problems.

Ordinary linear DC power supply circuit efficiency is low, power transformer size and weight makes the cost higher.

Switching Power Supply Circuit structure is more complex, high cost and large power supply ripple, RFI and EMI interference is difficult to resolve.

Described below is a novel capacitor step-down DC regulated power supply circuits.

This circuit without Power Transformer , The structure is very simple, specifically: small size, light weight, low cost, fast dynamic response, stable and reliable, and efficient (90%) and so on.

2, capacitor step-down theory When a sinusoidal AC power U (such as 220V AC 50HZ) when applied to the capacitor circuit,

Capacitor Bipolar board charge, the electric field between the plates is a function of time. In other words: the capacitor voltage and current RMS and amplitude as follows Ohm's law.

That added some capacitors on the voltage amplitude, frequency is fixed, it will flow through a stable sinusoidal AC current ic. Capacitance smaller (larger capacitance), the greater the current flowing through the capacitor, the capacitor in series with an appropriate load, you can get a lower voltage source, can be rectified, filtered, regulated output.

Capacitor in the circuit is handling energy without consuming energy, the capacitor step-down circuit with high efficiency.

3, Block diagram Circuit consists of step-down capacitor, current limit, rectifier and voltage regulator shunt circuit.

1. Buck capacitor: the equivalent of general step-down transformer regulator circuit, direct access to AC power circuit, almost all of the AC power to withstand U, The Promise of the metal should be used membrane capacitance (METALLIZEDPOLYESTER FILM CAPAC

IT OR). 2. Limiting circuit: the power of the moment in the closed, U may be positive or negative half-cycle peak _ peak instantaneous current at this time would be great, so in the loop need a limiting resistor in series in order to ensure circuit safety.

3. Rectifier: half-wave rectification and full-wave rectifier, with the common DC power supply circuit of the same design requirements.

4. Regulated shunt: step-down circuit voltage, rms current I is stable, free from the impact of changes in the size of the load current, so voltage regulator circuit, to have shunt circuit, in response to the size of the load current change.

4, design examples of potential 1. Bridge full-wave rectifier voltage regulator:

Specifications: Output DC voltage of 12V, DC current of 300mA; input power 220V AC/50HZ electricity.

1) buck capacitor C1 of the options:

A. C1 capacitance choice: Capacitance value depends on the load current, load current I determined, available: C1 1/2 fU

Type of AC power when taking a negative U value of 10%, namely:

I = 300mA, U = 220V * (-10%) = 198V, f = 50HZ,

C1 0.3 (2 * 3.14156 * 50 * 198) = 4.82uF)

Large capacitor value only desirable, undesirable small, in this case capacitors C1 value 5uF.

B. Select voltage values: To consider the power supply is 10% of the cases, such as the electricity used in this example, C1 to choose 250VAC metal film capacitors.

C. instant impact-resistant current selection: Metal film capacitor internal resistance is very low, allowing capacitor energy in throughput when a large current flows through this current depends on the capacitance value and its du / dt value, this value by the capacitance of the structure , metal film type, lead the way decision.

Du / dt value and the capacitance values of the pressure, the higher the pressure, du / dt values of the larger products of different manufacturers du / dt value is also very different, such as the voltage is 250VAC capacitor's value 5uF metal film capacitor du / dt value is usually in the 3-30 to choose between.

In this case: C1 = 5uF, du / dt value of 3, then the current value of C1 instant impact resistance:

I = Cdu / dt = 5 * 3 = 15 (A)

2) the choice of the current limiting resistor R1:

First aim of the capacitance C1:

Xc = 1/2 fC = 1 / (2 * 3.1416 * 50 * 0.000005) = 636.36

The complex impedance: | Z | = 638.3 (R1 value to 47 )

Current valid values obtained: I = U / | Z | = 220/638.3344.7mA

Resistance to withstand the actual effective voltage value: UR = 344.7mA * 47 = 16.2V

Calculate the actual resistance to withstand the power: PR = 16.2V * 344.7mA = 5.58W (R1 use wirewound resistors, power take 7.5W)

3) shunt regulator circuit: Voltage regulator tube EB junction pipe ZD1 and T1, R3 component regulator circuit, T1, R2 component shunt circuit.

ZD1 use 11.3V the voltage regulator tube; R3 resistance to take 180 1/6W; T1 pipe to respond to changes in the size of the load current, load current can be varied from 0-300mA, T1 2W of the PNP control selected, the current magnification 200; R2 as the load current is small, the power-sharing part of the tube T1, R2 values 30 /3W.

2. Half-wave rectifier voltage regulator: Specifications: 24V DC voltage output of a group (such as the provision

Relay Work), a group of DC voltage 5V (such as micro-controllers for work or triac trigger current use), the output DC current of 60mA; input supply 220V/50HZ.

1) step-down capacitor C1 of the options:

A. The current flow through the capacitor C1 is about twice the load current, or 120mA, come:

C1 1/2 fU = 0.12 (2 * 3.14156 * 50 * 198) = 1.93 (uF)

C1 actual value 2uF.

B. Select voltage value of 250V AC metal film

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