Designing High-Performance Isolated DC/DC Power Stages with Discrete Components
2026/06/01
Accelerate your development with RECOM’s isolated power supply building blocks.
Table of Contents
- Introduction
- The Build vs. Buy Decision
- Key Power Supply Design Factors
- Key Components of an Isolated DC/DC Power Supply
- Transformer Driver Chip Selection Considerations
- Design, Integration, and Layout Considerations (Download/Login)
- Prototype Options, Long-Term Supply Chain, and Cost (Download/Login)
- Summary (Download/Login)
Introduction
Adding in-circuit isolated power just got more flexible. RECOM now offers its power supply components in discrete form as well as fully integrated modules. The “build vs buy” decision is always part of a complex power supply design: engineers must decide which systems or subsystems are available off the shelf and which require custom implementation using discrete components.
For over 50 years, RECOM has offered a broad selection of PC board-mounted isolated power supply modules. Now, with the addition of discrete versions, engineers gain greater flexibility to tailor solutions to their specific design requirements.
Isolated DC/DC power supplies are a mainstay of today’s complex electronics systems. Industrial automation, robotics, commercial communications, and other complex applications often include subsystems for communication, sensing, and control that operate at different voltage levels than the main DC rail. These subsystems frequently require galvanic isolation and benefit from precise, stable regulation within the circuit to ensure reliable performance. Traditionally, designers of these systems have had little choice but to include a pre-built module to satisfy this need.
The module approach offers the following advantages:
However, a discrete solution is a better option in higher volumes (typically above 50K units) or when facing critical and non-standard requirements. A custom design offers more options for input, output, and isolation, including multiple output options and greater PCB layout flexibility. This paper covers the key considerations required once the decision has been made to design your own isolated power section using RECOM’s discrete power supply components.
For over 50 years, RECOM has offered a broad selection of PC board-mounted isolated power supply modules. Now, with the addition of discrete versions, engineers gain greater flexibility to tailor solutions to their specific design requirements.
Isolated DC/DC power supplies are a mainstay of today’s complex electronics systems. Industrial automation, robotics, commercial communications, and other complex applications often include subsystems for communication, sensing, and control that operate at different voltage levels than the main DC rail. These subsystems frequently require galvanic isolation and benefit from precise, stable regulation within the circuit to ensure reliable performance. Traditionally, designers of these systems have had little choice but to include a pre-built module to satisfy this need.
The module approach offers the following advantages:
- Preassembled ready-to-use solution
- Reduced design-in time
- Full supporting documentation and certifications
- Lower TCO in smaller quantities
However, a discrete solution is a better option in higher volumes (typically above 50K units) or when facing critical and non-standard requirements. A custom design offers more options for input, output, and isolation, including multiple output options and greater PCB layout flexibility. This paper covers the key considerations required once the decision has been made to design your own isolated power section using RECOM’s discrete power supply components.
The Build vs. Buy Decision
Small isolated DC/DC power supplies are an important part of most complex designs. Isolation breaks ground loops, reducing system noise, and protects the whole application from system failure if a fault develops in a single subsystem. For example, sensor inputs are often isolated so that external voltages or electrical noise are not injected into the application. In addition, isolation may be a safety requirement to protect the user from electric shock should an input cable or sensor come in contact with a hazardous voltage.
Until recently, the most common design solution was a completely isolated supply module. However, modules occupy a fixed space, cost more in higher volumes generally above 50K units, and may require a secondary assembly operation. Now that RECOM offers its individual power ICs and SMD transformers in discrete form and a fast custom transformer design and manufacturing service, adding an isolated DC/DC supply directly into the design is a viable option.
The discrete approach gives engineers more PCB space, lower cost at higher volumes, and greater customization flexibility. Discrete solutions can deliver multiple output voltages, different voltage levels, and higher current capability, as well as PCB layout flexibility not possible with a pre-built module.
Until recently, the most common design solution was a completely isolated supply module. However, modules occupy a fixed space, cost more in higher volumes generally above 50K units, and may require a secondary assembly operation. Now that RECOM offers its individual power ICs and SMD transformers in discrete form and a fast custom transformer design and manufacturing service, adding an isolated DC/DC supply directly into the design is a viable option.
The discrete approach gives engineers more PCB space, lower cost at higher volumes, and greater customization flexibility. Discrete solutions can deliver multiple output voltages, different voltage levels, and higher current capability, as well as PCB layout flexibility not possible with a pre-built module.
Key Power Supply Design Factors
One of the first decisions is to select a power supply topology. Let’s explore the three most common choices: push-pull, full-bridge, and flyback.
Push-Pull
A push-pull supply is well-suited to lower voltages and higher current applications because push-pull transistors switch half the average current at the full input voltage. Conversion losses are lower than they are with other topologies because the input current is shared and full core magnetisation is utilised; therefore, push-pull is a highly efficient option. Because the IC design requires only two transistors, the IC cost is lower. However, the transformer requires a primary-side center-tap, so the transformer may be more expensive to manufacture.
Figure 1: Typical push-pull schematic
Figure 1: Typical push-pull schematic
Full-Bridge
The full-bridge primary IC requires four internal transistors, making it more costly than a push-pull IC. However, the full-bridge transformer does not require a primary-side center-tap. Therefore, it is less expensive, all other parameters being equal. Transformers typically cost more than driver ICs.
Figure 2: Typical full-bridge schematic
- Best for lower current, higher voltage (12V,15V, 24V)
- RECOM’s new driver chips: RVP001, RVP003, RVP003S, RVP005
Figure 2: Typical full-bridge schematic
Flyback
Key Components of an Isolated DC/DC Power Supply
All three topologies require three key components: a DC/DC transformer driver chip, a transformer, and a rectifier or rectifier/regulator. In functional terminology, a supply with a lower output than input voltage is called a buck converter. A supply that increases voltage is called a boost converter, and a supply that can perform both functions is referred to as a boost/buck converter.
The transformer driver chip sets the topology and essential operating parameters. It is an oscillator that creates an AC-like signal suitable for transformer/inductor management. The oscillating signal may be ground-referenced or floating.
The transformer determines the output voltage or voltages and provides an isolation barrier. To maintain separation, ground planes are not directly connected between the primary and secondary winding sides. Some circuit designs may bridge isolation using capacitors or resistors to manage high- or low-frequency isolation, or for ground-loop management.
The secondary IC is a rectifier or rectifier/regulator that converts the transformer’s alternating output into DC and, when needed, stabilizes the output voltage. Passive components in the isolated DC/DC supply include capacitors for signal conditioning and resistors for current limiting.
The transformer driver chip sets the topology and essential operating parameters. It is an oscillator that creates an AC-like signal suitable for transformer/inductor management. The oscillating signal may be ground-referenced or floating.
The transformer determines the output voltage or voltages and provides an isolation barrier. To maintain separation, ground planes are not directly connected between the primary and secondary winding sides. Some circuit designs may bridge isolation using capacitors or resistors to manage high- or low-frequency isolation, or for ground-loop management.
The secondary IC is a rectifier or rectifier/regulator that converts the transformer’s alternating output into DC and, when needed, stabilizes the output voltage. Passive components in the isolated DC/DC supply include capacitors for signal conditioning and resistors for current limiting.
Transformer Driver Chip Selection Considerations
RECOM offers transformer driver chips in all three topologies. The chips are used in RECOM’s line of DC/DC converter power modules and are therefore field-tested with a long track record of successful deployment.
The new RVP6501 is a logical successor and second source to the established 6501 push-pull transformer driver. While a 6501-type is a common choice for power supply design given its ubiquity and longevity, the new RVP6501 offers full compatibility with key improvements. The RECOM chip operates from a 2.8V to 6V supply and tolerates input transients up to 10V. It delivers a consistent 500mA across its entire operating range, outperforming the legacy 6501-type, which provides 300mA at 5V and only 150mA at 3.3V.
The RVP6501 features make-before-break switching and includes the ability to detect gate voltages. This feature adjusts the ...
Spotlight on the RVP6501
One of the most popular isolated DC/DC designs is based on the industry standard 6501 power IC. The chip has a long history and provides reliable operation, but it has some limitations. RECOM recently introduced an updated pin-compatible replacement part, the RVP6501, which improves on the legacy part.The new RVP6501 is a logical successor and second source to the established 6501 push-pull transformer driver. While a 6501-type is a common choice for power supply design given its ubiquity and longevity, the new RVP6501 offers full compatibility with key improvements. The RECOM chip operates from a 2.8V to 6V supply and tolerates input transients up to 10V. It delivers a consistent 500mA across its entire operating range, outperforming the legacy 6501-type, which provides 300mA at 5V and only 150mA at 3.3V.
| RECOM RVP6501 | Industry standard 6501 |
|---|---|
| New design | Older design introduced in 2012 |
| Short-circuit protection | No short-circuit protection |
| Actively prevents core saturation | Minimal core saturation mitigation |
| Over-temperature protection | No over-temperature protection |
| 500mA through the voltage range | 300mA at 5V and 150mA at 3.3V |
Table 1: Comparison of RVP6501 vs. industry standard 6501
The RVP6501 features make-before-break switching and includes the ability to detect gate voltages. This feature adjusts the ...
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RVP001
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RVP003
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RVP005
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RVP010
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RVP6501
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RVPW011
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RVPW014
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RVPW015
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RVPW016
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