SR10DB1 - Power Supply Microchip - Free user manual and instructions

Product Type	Inductorless Switching Power Supply Demoboard
Brand	Microchip (formerly Supertex)
Model	SR10DB1
Category	Power Supply
Input Voltage	90 VAC to 275 VAC
Input Frequency	50 Hz to 60 Hz
Output Voltage	6 V, 12 V, 24 V ±10% (fixed) or 6-28 V (adjustable via feedback divider)
Output Current	Up to 50 mA
No-load Input Power	As low as 20 mW
Efficiency	Up to 75%
Board Dimensions	88 mm x 28 mm
Topology	Capacitor-coupled switched shunt (CCSS)
Rectification	Selectable half-wave or full-wave via jumper
Configurability	Highly configurable with socketed components
Socketed Components	Yes, for easy substitution
Feedback Divider	On-board for adjustable output voltage
LED Drive Capability	Can be configured for constant-current LED drive
Overvoltage Protection	Yes, via external Zener diode
Safety Note	Do not connect earth-grounded loads without isolation transformer
Manual Availability	Free PDF download on notice-facile.com

Frequently Asked Questions - SR10DB1 Microchip

What is the input voltage range of the SR10DB1?

The SR10DB1 accepts an AC input voltage from 90 VAC to 275 VAC at 50-60 Hz.

How do I set the output voltage?

You can select fixed voltages of 6V, 12V, or 24V using a jumper on the V_OUT header. For adjustable output, set the jumper to ADJ and change R_FB1 resistor using the formula provided in the manual.

What is the maximum output current?

The maximum output current is up to 50 mA, depending on configuration and transient protection.

Can I use this board to drive LEDs?

Yes, the SR10 can be configured for constant-current LED drive by adding a current sense resistor (R_SNS) and setting the output voltage appropriately. Overvoltage protection is also available.

What are the board dimensions?

The board size is 88 mm x 28 mm.

Does the board require isolation?

Yes, the board is not galvanically isolated from the AC line. Do not connect earth-grounded loads or test equipment without an isolation transformer.

What protection features are included?

The board includes a fusible limiting resistor for transient protection, and can be configured with an overvoltage protection Zener for LED applications.

How do I measure input power accurately?

Because of high imaginary power, use an oscilloscope to multiply instantaneous voltage and current and average over an integer number of cycles. Alternatively, measure voltage after C_s to exclude its losses.

What value of C_s capacitor should I use for my output current?

Refer to the C_s table in the manual. For example, for 50 mA at 12V with full-wave rectification, a 2.2 μF ±10% capacitor provides sufficient current at 120VAC, but may exceed limits at 240VAC.

Are components replaceable?

Yes, many components are socketed, allowing easy substitution for different requirements.

USER MANUAL SR10DB1 Microchip

Inductorless Switching Power Supply Demoboard

Introduction:

The Supertex SR10 is an inductorless switching power supply controller intended for operation directly from a rectified 120/240VAC line. Due to the capacitor-coupled, switched shunt topology (CCSS), it exhibits low standby power and good efficiency while employing no magnetics nor high voltage electrolytic capacitors.

To meet a wide variety of applications, the SR10DB1 is highly configurable. Many components are socketed. Half or full-wave rectification is jumper-selectable. Output voltage is jumper-selectable to 3 fixed voltages or may be set anywhere in the range of 6 - 28V using an on-board feedback divider.

Specifications

Parameter Value
AC Input	90VAC to 275VAC50Hz to 60Hz
Output voltage	6V, 12V, 24V ±10%or 6-28V using divider
Output\ current1	up to 50mA
No-load input power1	as low as 20mW
Efficiency1	up to 75%
Actual board size 88mm x 28mm

Notes:
1. Dependent upon configuration and degree of transient protection.

Board Layout and Connection Diagram

AC Input (H and N)

Connect to the AC line. The 'H' terminal should be connected to the AC line hot conductor. The 'N' terminal should be connected to the AC line neutral conductor. When configured for half-wave rectification, the N terminal is connected to the DC output minus (−) terminal.

DC Output (+ and -)

Connect the load to these terminals. Do not connect earth-grounded loads or test equipment without using an isolation transformer on the AC line.

Output voltage is jumper-selectable at 6, 12, or 24V, or it may be set in the range of 6 - 28V using the R _FB feedback divider and setting the jumper to ADJ.

Schematic

Bill of Materials

Designation	Description	Value	Rating	Mfg	PN
RLIM	Resistor, fusible	22Ω	2W	any	—
RBL	Resistor	4.7MΩ	1/4W	any	—
RFB1	Resistor	422kΩ	1/4W	any	—
RFB2	Resistor	68.1kΩ	1/4W	any	—
CS	Capacitor, film	220nF to 2.2μF	275VAC,X2	any	—
COUT	Capacitor, alum	220μF min	35V	any	—
CFB	Capacitor, ceramic NPO	470pF	6V	any	—
D1-4	Rectifier	—	1A, 50V	any	1N4001
DOUT	Rectifier	—	1A, 50V	any	1N4001
IC1	CCSS regulator	—	—	Supertex	SR10

Socketed Components

The SR10DB1 is provided with all components pre-installed. Other components may be substituted for the on-board components to meet other requirements.

Refer to the above schematic and BOM, and the drawing and photo on page 1 to determine the proper locations for the components.

Output Voltage

Fixed output voltages of 6V, 12V, or 24V may be selected by setting the appropriate jumper on the V_OUT header.

For other output voltages, the on-board resistive feedback divider may be used to provide any voltage in the range of 6 - 28V. To maintain a minimum 15 µ A through the feedback divider, only R_FB1 should be changed.

R _ FB 1 = R _ FB 2 ( V _ OUTV _ FB - 1) = 6 8. 1 kΩ ( V _ OUT1 . 2 5 V - 1)

Output Current ( C_s selection)

Output current is primarily dependent on input voltage, C_s value, and rectification (full or half). Given the minimum input voltage and choice of rectification, the minimum value of C_s

is given by the following equations. Don't forget to take tolerances into account. The SR10 is powered by V_OUT , so the available output current is reduced by the SR10's operating current (150μA nom, 200μA max). Current may also be reduced \~5% due to losses.

For standard capacitance values, see the table on page 4.

Full-wave:

C _ s ≥ I _ OUT4 f _ IN (V _ IN √ 2 - V _ OUT - 3 V _ D)

Half-wave:

C _ s ≥ I _ OUTf _ IN (2 V _ IN √ 2 - V _ OUT - 2 V _ D)

where: I_OUT is the maximum output current

f_IN is the AC line frequency

C_s is the series cap on the AC line

V_IN is the RMS AC line voltage

V_OUT is the DC output voltage

V_D is the diode forward voltage ( 700mV )

Limiting Resistor ( R_LIM )

The limiting resistor in series with the AC line is to protect against transients on the AC line. For safety reasons it fusible and is the most upstream component on the AC line. Higher values provide greater protection but at the expense of higher losses.

P _ LIM ≈ (V _ IN · 2 πf _ IN · C _ S) ^ 2 · R _ LIM

Output Capacitor ( C_OUT )

The output capacitor serves 2 functions - it supplies the load when the shunt is on, and helps absorb transients on the AC line. The supplied value may be lowered but at the expense of higher ripple voltage and increased output voltage during a transient.

Input Power Measurements

The high ratio between the imaginary and real power components makes power measurements difficult. To make accurate measurements of real power, the imaginary component may be eliminated by measuring input voltage after C_s . This excludes C_s losses, but AC rated film capacitors exhibit very low losses, so the error is minimal.

Since the PCB is laid out with R_LIM upstream of C_S for safety reasons, it must be relocated after C_S if R_LIM losses are to be included.

Do not connect earth-grounded instruments when operating off the AC line! Use either battery-powered equipment, high voltage differential probes, or an isolation transformer on the AC line. Note that many Variacs (variable transformers) do not provide isolation.

Ideally, R_BL should be removed. Its contribution to loss is approximately V_IN² / R_BL

Since the input current is not a perfect sine wave, real power cannot be obtained by simply multiplying RMS input current by RMS input voltage. One way to make correct measurements is by multiplying instantaneous current by instantaneous voltage on a time-point basis and taking the average over an integer number of 50/60Hz cycles. At low load currents the shunt turns off only occasionally, requiring a long time window for accurate power measurements.

is This measurement technique may be performed on most digital oscilloscopes. When taking the average, be sure to window the average over an integer number of cycles.

Driving LEDs

The SR10 can be configured to provide a constant-current output to drive LEDs. A current sense resistor ( R_SNS ) is used to convert LED current to the 1.25V feedback voltage required by the SR10.

Driving LEDs

When operated over a wide supply voltage range, a small C_OUT can result in overcharging at higher line voltages. It may take several cycles for the voltage to drop back down to the regulation threshold. This may cause visible flicker. The remedy is to increase C_OUT .

To protect against open LEDs, an overvoltage protection (OVP) circuit is employed. The OVP level is set by the value of the OVP Zener. R_B limits the current thru the Zener.

V _ OVP = V _ z + 1. 2 V

C_s Table

The following table is based on the previously provided equations for C_s . Actual output current may be less due to losses ( 5% less). AC line voltage is assumed to be 90 - 135VRMS @ 60Hz or 190 - 275VRMS @ 50Hz. Slashed cells exceed recommended operating conditions for peak shunt current at 85°C.

For universal 120V and 240V operation choose C_s based on 120VAC and make sure that operation at 240VAC does not fall in a slashed cell. The relevant cells are adjacent to each other. For example, if 50mA at 12V is needed and full rectification used, a C_s capacitor of 2.2µF ± 10% provides 53.8mA at 120VAC (90VAC low line). But at 240VAC, the cell to the right (240VAC column) is slashed, and universal operation is not possible. This assumes 120VAC low line is 90VAC and 240VAC high line is 275VAC. For other high/low voltages use the equations.

Output current capability (mA)

Cs	CsTol	6V Output 12V Output 24V Output
		Half Full Half Full Half Full
		120V 60Hz	240V 50Hz	120V 60Hz	240V 50Hz	120V 60Hz	240V 50Hz	120V 60Hz	240V 50Hz	120V 60Hz	240V 50Hz	120V 60Hz	240V 50Hz
220nF	10% 2	9 5.2 5.7	10.3 2.9	5.2 5.4	10.1 2.7	5.1 4.8	9.6
	20% 2	6 4.7 5.0	9.2 2.5	4.6 4.8 9	0.2 4.4	5 4.3 8.5
330nF	10% 4	4 7.9 8.5	15.5 4.3	7.8 8.1	15.1 4.1	7.6 7.2	14.4
	20%	3.9	7.0	7.6	13.8	3.8	6.9	7.2	13.4	3.6	6.8	6.4	12.8
470nF	10% 6	3 11.2 1	2.1 22.0	6.1 11.1	11.5 21.5	5 5.8 10.8	10.3 20.5
	20% 5	6 10.0 1	0.8 19.6	5.4 9.9 1	0.2 19.1	5.2 9.6	9.1 18.2
680nF	10% 9	1 16.2 1	7.5 31.9	8.9 16.0	16.6 31.2	8.4 15.7	14.9 29.7
	20% 8	1 14.4 1	5.6 28.4	7.9 14.3	14.8 27.7	7.5 13.9	13.2 26.4
1.0μF	10%	13.3	23.9	25.7	46.9	13.0	23.6	24.4	45.8	12.4	23.0	21.9	43.7
	20% 1	1.9 21.2	22.9 41.7	11.6 21	0 21.7	40.7 11.0	20.5 19	4 38.8
1.5μF	10%	20.0	35.8	38.6	70.4	19.5	35.4	36.7	68.7	18.6	34.6	32.8	65.5
	20%	17.8	31.8	34.3	62.5	17.4	31.4	32.6	61.1	16.5	30.7	29.1	58.2
2.2μF	10%	29.4	52.5	56.6	103.2	28.6	51.9	53.8	100.8	27.2	50.7	48.1	96.1
	20%	6.1 46.6	50.3 91.7	25.5 46.1	47.8	89.6 24.2	45.1 42.7	85.4

= Exceeds Recommended Operating Limits

Supertex inc. does not recommend the use of its products in life support applications, and will not knowingly sell them for use in such applications unless it receives an adequate "product liability indemnification insurance agreement." Supertex Inc. does not assume responsibility for use of devices described, and limits its liability to the replacement of the devices determined defective due to workmanship. No responsibility is assumed for possible omissions and inaccuracies. Circuitry and specifications are subject to change without notice. For the latest product specifications refer to the Supertex inc. (website: http://www.supertex.com)