R3 Series Fixed Input Voltage DC DC Converters

27th January 2020

The ultimate customer experience with the new R3 Series fixed input voltage DC/DC converters from MORNSUN

When considering using an industrial DC DC Converter R3 Series unit, the absolute essentials are; excellent performance, high quality, and cost-effectiveness.

MORNSUN’s first-generation fixed input voltage DC/DC converters met all 3 of the essential requirements. However, MORNSUN is not a company to rest on its laurels and delivered improvements on their first generation with the R2 series including, enhanced product reliability, lower cost through innovative technology and automated production procedures.

MORNSUN’s latest generation unit, the R3 Series, attempts to solve some of the industries’ wider challenges yet still maintaining the balance between performance and cost.

R3 Series - Mornsun DC DC Converters @ Relec Electronics Ltd 2020

The Industry Conundrum:

R3 Series Converter Performance vs Customer Experience

Low power (1 – 2 W) DC DC Converters are used extensively in bus communication systems and also to power isolated sensors. Traditionally these converters have been based around the Royer auto-self-excited push-pull circuit. Whilst simple and cheap to produce, it has many inherent defects including lack of short circuit protection, poor start up into highly capacitive loads and high standby power consumption. Figure 1 attempts to show the balances and constraints imposed by this topology.

MORNSUN’s R3 series fixed input voltage DC/DC converters use a brand new IC technology designed to resolve the conflict between achieving continuous short-circuit protection, capacitive load and start-up capability and in so doing has achieved a performance improvement across all three functions.

R3 Series -  technology with Mornuns' R3 Range @ Relec Electronics Ltd 2020

Output Short Circuit Protection (SCP) vs Large Capacitive Load

The lack of short circuit protection is a shortcoming of the Royer Circuit.  MORNSUN’s breakthrough with the R3 series fixed input DC DC Converter changes the operating mode of the push-pull circuit and allows operation with larger capacitive loads at the same time.

Large Capacitive Load vs Start-up

Extra capacitance often has to be added to the output of a DC DC Converter to reduce the effects of ripple and noise. However, a large capacitor can look like a short circuit to the converter when it starts, causing the converter to either hiccup or sometimes even fail. The Royer self-oscillation circuit has no soft start-up function and has a large transient input current at start-up, which may breakdown the internal switching components causing a short circuit or even the complete failure of the converter.  MORNSUN’s new technology allows converters to operate with a capacitance 10X that of older topologies.

High Efficiency at Full Load vs High Efficiency at Light Load & Low Standby Power Consumption

Traditionally customers have focused on the efficiency of converters at full load with less focus on the efficiency at light loads and standby power consumption. 
Many applications see a DC DC Converter having 3 operating modes.  Full load (de-rated in actual use), light load and no-load, of which the light load often accounts for the highest proportion of operating time.

R3 Series - Figure 3 Comparison of efficiency at light load (B0505) @ Relec Electronics Ltd 2020

Figure 3 Comparison of efficiency at light load (B0505)

This is especially important, if the system is battery-powered, where there are strict requirements for standby power consumption to improve battery life. Traditional Royer circuits have had no-load currents of the order of 15-30mA.  MORNSUN’s R3 series has reduced this figure down to <5mA

Stand-by power consumption: TheB0505S-1WR3’s standby power consumption is 25mW and no-load current is 5mA (see Figure 4). It is particularly suitable for energy-saving equipment that has a higher requirement for standby power consumption, e.g., portable equipment. 

Figure 4 Comparison of Typical No-load Current (B0505, unit: mA)

R3 Series - Figure 4 Comparison of Typical No-load Current (B0505, unit: mA) @ Relec Electronics Ltd 2020
Figure 4 Comparison of Typical No-load Current (B0505, unit: mA)

MORNSUN’s innovative engineers have introduced an independent oscillator instead of the Royer circuit and their own bespoke IC controller to the new R3 series.  These improvements in IC technology deliver the following significant advantages in short circuit protection, large capacitive loads, start-up performance and light load efficiency.

IC technology provides over-temperature protection (OTP).

The fixed input voltage R3 series have built-in OTP. Once the temperature exceeds its rated value, the converter will automatically go into a dormant state to avoid damage and can automatically recover when the temperature drops to the set value, thus protecting both the converter and the equipment it is powering.

Evolution of the B0505 series and critical performance features

Specifications B0505S-1WR3 B0505S-1WR2 B0505S-1W
Ripple & noise (mV) ≤60 &75 ≤60 &75 ≤100 &100
Typ. efficiency at full load (100%) 83% 80% 70%
Typ. efficiency at light load (10%) 75% 55% 40%
Stand-by power consumption (W) 0.025 0.1 0.15
No-load current (mA) 5 20 31
Max. capacitive load (uF) 2400 220 220
Continuous SCP YES YES NO
Operating temperature -40°C-105°C -40°C -105°C -40°C -85°C
CE (peripheral circuit) CLASS B CLASS B CLASS A

Higher Reliability

The high reliability of the fixed input R2 series already had an excellent reputation, and the new R3 series takes this further. The R3 series is highly integrated which reduces the internal component count by over 40%.

The fixed input R3 series uses an independent oscillator rather than relying on the components’ inherent characteristics. This promotes higher yields in mass production and leads to a more reliable product.

Cost-Effective & Competitive Pricing

Thanks to MORNSUN’s IC technology, the R3 series reduces the number of components, simplifies the assembly process and saves assembly costs. All of which results in a more cost-effective solution and more value for money to the customer.

Backward Compatibility with R1, R2 & R3 Series

The R3 series is 100% compatible with MORNSUN’s previous fixed input voltage R1 and R2 series in terms of package sizing and pinning as well as those of leading competitive products. This means that the customers do not need to change PCB design when they replace or upgrade the system.

Backward Compatibility @ Relec Electronics Ltd 2020


MORNSUN takes innovation very seriously and is an essential part of its development program for the power industry and to bring improved customer experiences.

The use of independent oscillator IC technology leads the path in a new direction of innovation. The R3 series fixed input DC DC Converters have addressed many of the shortcomings of traditional low-cost components (short circuit protection, large capacitive loads, light load efficiency and over-temperature protection) whilst still reducing costs and maintaining short lead-times of typically less than 4 weeks).

Series Pwr
Vin  (VDC) Vo
No of Output Isolation  (VDC) Package Dimension  (mm)
A_S-1WR3 1 5 ±5,±9,±12,±15 2 1500 SIP 19.65*6.00*10.16
B_S-1WR3 1 5 3.3,5,9,12,15,24 1 1500 SIP 11.60*6.00*10.16
A_XT-1WR3 15 ±5,±9,±12,±15 21500SMT 15.24*11.40*7.25
B_XT-1WR3 153.3,5,9,12,15,24 11500SMT 13.20*11.40*7.25
B_LS-1WR3 1 5 5,9,12,15 1 1500 SIP 19.65*6.00*10.16
E_S-1WR3 1 5 ±5,,±9,±12,±15 2 3000 SIP 19.65*6.00*10.16
F_S-1WR3 1 5 5,9,12,15,24 1 3000 DIP 12.70*10.16*8.20
E_XT-1WR3 15 ±5,,±9,±12,±15 23000SMT15.24*11.40*7.25
F_XT-1WR3 15 5,9,12,15,24 13000SMT13.20*11.40*7.25
F_N-1WR3 1 5 5,9,12,15 1 1500 SIP 19.65*6.00*10.16
IB_LS-1WR3 1 5 5,9,12,15 1 1500 SIP 19.65*6.00*10.16
IB_S-W75R3 0.75 5 3.3,5,9,12,15 1 3000 SIP 11.60*6.00*10.16
IB_XT-W75R30.7553.3,5,9,12,15 11500SMT13.20*11.40*7.25
IF_S-1WR3 1 5 5,9,12,15 1 3000 SIP 19.65*6.00*10.16
IF_XT-W75R3 15 3.3,5,9,12,15 13000SMT 15.24*11.40*7.25

Relec Electronics has worked closely with our key suppliers for over 40 years, specialising in many industries; Automotive, Industrial & Defence.
We have a team of dedicated engineers ready to support you throughout the design process. We also carry stock of all standard modules and accessories for next day delivery.

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